Science Science for for South South Africa Africa
ISSN 1729-830X ISSN 1729-830X
Buil ding Mee rK AT: engine ering to the forefr ont
Volume 8 • Number 3 • 2012 Volume 3 • Number 2 • 2007 R29.95 R20
Use r requ irem ents : KAT contro l and monito ring From radio waves to the Big Bang: how doe s this hap pen ?
Radio frequency interference: shutting it out Managing complexity: systems engineering Hydrogen: a renewable resource Our changing climate: measuring history
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Building MeerKAT Tracy Cheetham explains the infrastructure required 10
Systems engineering – how to make a radio telescope work Richard Lord explains how to make the SKA work
KAT-7 control and monitoring: it’s all about the users The KAT-7 CAM team explain how to integrate control and monitoring
Radio frequency interference and radio astronomy: why the fuss? Richard Lord tells Quest why radio frequency interference can stop SKA from working
Contents Volume 8 • Number 3 • 2012
From theory to practice
Oleg Smirnov shows how radio telescopes provide astronomical data
Patsy Scholtz talks to Sarah Wild
How do we meaure historical temperature trends?
Kick starting the Congo Tim Jackson (in Africa Geographic) reports on ecotourism in this challenging region
Andries Kruger and Charlotte McBride look at the role of our weather stations
Communicating South Africa’s science triumph
Renewable energy: the role of hydrogen
A new tool for polar research Mike Lucas takes us aboard the SA Agulhus II
Jan Smit looks at hydrogen powered fuel cells
The Square Kilometer Array (SKA)
Quest provides a brief introduction
Bringing the SKA to Africa Willem Esterhuyse shows us how it is done
Fact file The mathematics of modelling. By Lindsay Magnus – p. 28
Diary of events
Back page science • Mathematics puzzle
The Itty Bitty Telescope (IBT): Tips for building a simple telescope How to build your own radio telescope
Quest 8(3) 2012 1
Science Science for for South South AfricA AfricA
ISSN 1729-830X ISSN 1729-830X
Building MeerK AT: engineering to the forefront
Volume 8 • Number 3 • 2012 Volume 3 • Number 2 • 2007 r29.95 r20
User requirements: KAT control and monitoring From radio waves to the Big Bang: how does this happen?
Radio frequency interference: shutting it out Managing complexity: systems engineering Hydrogen: a renewable resource Our changing climate: measuring history
Sc A c AAcdAedmeym yo fo fS c I eI eNNccee ooff SS o u u tt hh AAffrrI c I cA A
Images: SKA SA
SCIENCE FOR SOUTH AFRICA
Editor Dr Bridget Farham Editorial Board Roseanne Diab (University of KwaZulu-Natal) (Chair) Michael Cherry (South African Journal of Science) Anusuya Chinsamy-Turan (University of Cape Town) George Ellis (University of Cape Town) Kevin Govender (IAU OAD) Penny Vinjevold (Western Cape Education Department) Neil Eddy (Wynberg Boys High School) Peter Vale (University of Johannesburg) Correspondence and The Editor enquiries PO Box 663, Noordhoek 7979 Tel.: (021) 789 2331 Fax: 0866 718022 e-mail: firstname.lastname@example.org (For more information visit www.questinteractive.co.za) Advertising enquiries Barbara Spence Avenue Advertising PO Box 71308 Bryanston 2021 Tel.: (011) 463 7940 Fax: (011) 463 7939 Cell: 082 881 3454 e-mail: email@example.com Subscription enquiries Patrick Nemushungwa and back issues Tel.: (012) 349 6624 e-mail: Patrick@assaf.org.za Copyright © 2012 Academy of Science of South Africa
Published by the Academy of Science of South Africa (ASSAf) PO Box 72135, Lynnwood Ridge 0040, South Africa Permissions Fax: 0866 718022 e-mail: firstname.lastname@example.org Subscription rates (4 issues and postage) (For subscription form, other countries, see p. 56.)
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Design and layout Creating Ripples Graphic Design Illustrations James Whitelaw Printing Paradigm
2 Quest 8(3) 2012
Africa at the cutting edge O
n 25 May 2012 a crowded media briefing heard that South Africa had won the bid to host the majority share of the Square Kilometer Array, along with eight African partner countries and in partnership with Australia and New Zealand. It has taken nine years to secure this bid. Nine years of hard work by government, South Africa’s SKA team, partners across Africa and many participating scientists and students. All these people have made the SKA a reality for South Africa and eight other countries on the continent. Why is the SKA so important? You will learn in this issue of Quest that this vast array of radio telescopes will be harnessed to look back through space and time, to the very origins of the Universe. The SKA will help astronomers around the world answer some of the most important questions in science – how did the Universe begin? When did the Universe begin? What is dark matter? As these questions are addressed, even more questions will arise – this is the nature of science. But the main emphasis of this issue of Quest is that the SKA is not just about the ‘sexy’ mathematics and particle physics that astronomers and astrophysicists are involved in every day. Possibly the most important thing about winning the SKA bid is the way in which this project will involve scientists, civil, mechanical and electrical engineers, systems engineers, computer scientists and project managers. An enormous project such as this one requires input from people across many branches of the sciences – pure and applied. There are opportunities here that will ensure that South Africa and our partner countries are training and recruiting ever more varied arrays of people involved in different branches of science and engineering. The full science programme of the SKA will not start until 2024. The hope is that many of you reading this issue of Quest will see an opening in a branch of science and engineering that will take you to the cutting edge – to be part of discovering the very origins of our Universe. Naledi Pandor, Minister of Science and Technology Join Quest’s knowledge-sharing activities ■ Write letters for our regular Letters column – e-mail or fax your letter to The Editor. (Write QUEST LETTER in the subject line.) ■ Ask science and technology (S&T) questions for specialist members of the Academy of Science to answer in our regular Questions and Answers column – e-mail or fax your questions to The Editor. (Write QUEST QUESTION in the subject line.) ■ Inform readers in our regular Diary of Events column about science and technology events that you may be organising. (Write QUEST DIARY clearly on your e-mail or fax and provide full and accurate details.) ■ Contribute if you are a specialist with research to report. Ask the Editor for a copy of QUEST’s Call for Contributions (or find it at www.questsciencemagazine.co.za), and make arrangements to tell us your story. To contact the Editor, send an e-mail to: email@example.com or fax your communication to (021) 789 2233. Please give your full name and contact details. All material is strictly copyright and all rights are reserved. Reproduction without permission is forbidden. Every care is taken in compiling the contents of this publication, but we assume no responsibility for effects arising therefrom. The views expressed in this magazine are not necessarily those of the publisher.
South Africa’s Karoo SKA site.
The Square Kilometre Array (SKA) Africa has won a major victory for science on the continent and South Africa in particular – the SKA will take us to the cutting edge. Quest takes an overview. ‘We have an outstanding site for the SKA, as well as the people and the expertise to build and operate this mega-instrument.’ Dr Bernie Fanaroff, Director: SKA South Africa. Astronomy allows us to see back in time, because the light waves from very distant stars or galaxies take a long time to travel through space to our telescopes, so we see them as they were a very long time ago. Now astronomers want to build the most powerful telescope ever, to see back to before the first stars and galaxies formed. The Square Kilometre Array (SKA) will be a radio telescope – instead of seeing light waves, it will make pictures from radio waves. The majority of the SKA – the full dish array and the dense aperture array – will be built in Africa. The core, i.e. the region with the highest concentration of receivers, will be constructed in the Northern Cape Province, about 80 km from the town of Carnarvon (the same site on which the MeerKAT is being constructed). The sparse aperture array (low frequency array) will be built in Western Australia. South Africa has already demonstrated its excellent science and engineering skills by designing and starting to build the MeerKAT telescope – as a pathfinder to the SKA. The first seven dishes, KAT-7, are complete and have already produced their first pictures. MeerKAT is attracting great interest internationally – more than 500 international astronomers and 58 from Africa submitted proposals to do science with MeerKAT once it is complete. The technology being developed for MeerKAT is cutting-edge and the project is creating a large group of young scientists and engineers with world-class expertise in the technologies which will be crucial in the next 10 – 20 years, such
South Africa’s new Astronomy Geographic Advantage Act protects 12.5 million hectares in the Northern Cape as a radio astronomy reserve to ensure the future of radio astronomy in the region. Image: SKA
as very fast computing, very fast data transport, large networks of sensors, software radios and imaging algorithms. Since 2005, the African SKA Human Capital Development Programme has awarded close to 400 grants (2012) for studies in astronomy and engineering from undergraduate to post-doctoral level, while also investing in training programmes for technicians. Astronomy courses are being taught as a result of the SKA Africa project in Kenya, Mozambique, Madagascar and Mauritius (which has had a radio telescope for many years) and are soon to start in other countries. ❑ Adapted from www.ska.ac.za
The configuration of the SKA core and remote stations throughout Africa.Image: SKA
Quest 8(3) 2012 3
The KAT-7 array.
Image: Maik Wolleben
Bringing the Square On 25 May 2012 South Africa heard that the majority share of the Square Kilometre Array (SKA) would be built here. Willem Esterhuyse gives Quest the low-down.
he SKA SA radio astronomy site is situated in the Northern Cape near Carnarvon, about a seven-hour drive from Cape Town. The site can be reached by reasonable roads and an all-weather airstrip is being constructed close to the telescopes for easier access. The core of the MeerKAT site is at the following coordinates - 30°42’47.41”S, 21°26’38.00”E – a long way from anywhere. Radio telescopes need to be as far as possible from man-made electronics or machines that emit radio waves that will interfere with the faint radio signals coming from the distant Universe. And as SKA’s core function is to monitor these signals, interference should be at an absolute minimum. The Karoo site is also high and dry – equally important because The design of the Gregorian offset antenna. Image: SKA
4 Quest 8(3) 2012
moisture will also interfere with radio signals. The SKA SA radio astronomy site will be home to various different instruments – KAT-7, MeerKat and the SKA itself. KAT-7 KAT-7 is an array of seven dishes that have already been constructed. This is the world’s first radio telescope that is made up of composite antenna structures, built in fibre glass. These are mid-frequency or ‘pathfinder’ or demonstrator radio telescopes that will work alongside the SKA core site. They were completed in December 2010 and are now being commissioned. They were essentially an engineering prototype for the 64-dish array, but are also a useful instrument in their own right. KAT-7 has already delivered photographs of Centaurus A, a galaxy that is 14 million lights years away. KAT -7 was funded by the South African Department of Science and Technology (administered through the NRF) and was designed and constructed by the SKA SA team to act as a prototype interferometer
in building MeerKAT as part of the overall bid to host the SKA project in South Africa. MeerKAT MeerKAT is another radio telescope array that is designed for cuttingedge radio astronomy that will be composed of 64 dishes. It will be the largest and most sensitive radio telescope in the southern hemisphere until the SKA is completed in around 2024. MeerKAT will be an integral part of the SKA. Via MeerKAT, South Africa is playing a key role in design and technology developments for the SKA. MeerKAT will consist of 64 dishes of 13.5 m diameter each, with an offset Gregorian configuration. An offset dish configuration has been chosen because its unblocked aperture provides uncompromised optical performance and sensitivity, excellent imaging quality, and good rejection of unwanted radio frequency interference from satellites and terrestrial transmitters. The tender for the dishes was awarded in August 2012. MeerKAT itself will be delivered in two phases. The commissioning of
The remote, high, dry site in the Karoo.
Image: Rupert Spann
Kilometre Array to Africa and investigate the physics of enigmatic neutron stars. This radio pulsar timing survey will be led by Professor Matthew Bailes at the Swinburne Centre for Astrophysics and Supercomputing in Australia. n Another 5 000 hours to study the distant universe with MeerKAT. This ultra-deep survey of neutral hydrogen gas in the early universe will be led by Dr Sarah Blyth at the University of Cape Town in South Africa, Dr Benne Holwerda of the European Space Agency in the Netherlands, and Dr Andrew Baker of Rutgers University in the United States. The name of the survey will be ‘LADUMA’ – an acronym for Looking at the Distant Universe with the MeerKAT Array, but also a wellknown South African expression when a goal is scored in football. The Square Kilometre Array The SKA has been awarded jointly to South Africa and Australia – both being ideally suited to hosting the project and both having already made considerable investment to support their bids. The Australian SKA Pathfinder array in Western Australia is their equivalent to MeerKAT. Most SKA dishes in Phase I will be built in South Africa, combined with
MeerKAT. Further SKA dishes will be added to the ASKAP array in Australia, although we still need proof that Focal Plane Arrays (FPAs) are a feasible technology. In radio astronomy, focal plane arrays are arrays of receivers that are placed at the focus of a radio telescope. Traditional radio telescopes only have one receiver at the focus of the telescope.
All the dishes and the midfrequency (dense) aperture arrays for Phase II of the SKA will be built in South Africa, while the low frequency (sparse) aperture array antennas for Phases I and II will be built in Australia and New Zealand. Best returns for South Africa The above translates to the fact that the bulk (financial and scientific return) of the SKA project was awarded to South Africa. It is estimated that the dishes and dense aperture arrays will account for around 75% of the expenditure on SKA. However, South Africa has won the bid to host the SKA project in South Africa. The design, construction and commissioning will be overseen by an international project office, ▲ ▲
MeerKAT will take place in 2014 and 2015, with the array coming online for science operations in 2016. This phase will include all antennas, but only the first receiver will be fitted and a processing bandwidth of 750 MHz will be available. For the second phase, the remaining three receivers will be fitted and the processing bandwidth will be increased to at least 2 GHz, with a goal of 4 GHz. Five years before South Africa’s MeerKAT telescope becomes operational, more than 43 000 hours of observing time (adding up to about five years) have already been allocated to radio astronomers from Africa and around the world, who have applied for time to do research with this unique and world-leading instrument. The first round of time has been allocated to surveys of radio pulsars and hydrogen gas in the deep universe. The science objectives of the most highly rated projects also happen to be the prime science drivers for the first phase of the SKA telescope itself, confirming MeerKAT’s designation as an SKA precursor instrument. Observing time has been allocated as follows: n Nearly 8 000 hours to a proposal to test Einstein’s theory of gravity
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When KAT-7 and MeerKAT were positioned we hoped to win the SKA bid and so the best radio-astronomy site was reserved for SKA. The SKA team are in the process of working with the SKA Project Office to integrate MeerKAT with SKA Phase 1. Because there are specific science goals that need to be completed using MeerKAT, it is likely that MeerKAT will later be moved to fit in with SKA Phase 1, particularly since MeerKAT is pretty far advanced in its life cycle already. But, MeerKAT was developed with SKA high level specs in mind, so the proposed integration is feasible â€“ showing the importance of forward planning in such large projects. â?‘
The Australian SKA Pathfinder array in Western Australia. References http://ska.ac.za/ http://www.skatelescope.org/ http://en.wikipedia.org/wiki/Square_Kilometre_Array http://www.moneyweb.co.za/mw/content/en/moneyweb-economictrends?oid=570956&sn=2009%20Detail http://news.sciencemag.org/scienceinsider/2012/05/two-site-solutionsouth-africa.html
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which will (at least initially) be located at Jodrell bank in the UK. However, it is expected that the SKA SA team will have a key role in realising the SKA, especially as the site bid decision assumed the integration of MeerKAT into the SKA Phase 1. While this may prove to be a difficult exercise, the advantage is that South Africa will receive credit for MeerKAT as a direct SKA contribution.
Willem Esterhuyse has been the MeerKAT project manager since 2008. Before that he worked as Telescope Structure and Dome Project Manager on SALT and Telescope Structure Subsystem Manager at SKA SA. He is a graduate of Stellenbosch University, and has an M. Ing. degree. From 1996 to 2000 he designed mining equipment for Caterpillar. Karoo-born, he shares his love of the area with his wife and three daughters, spending free time in a 100-year-old Karoo house, restored by his wife.
Right: The upgraded Karoo substation.
Right below: Large transformers being delivered to the MeerKAT site. Image: SKA
MeerKAT is much more than theoretical astronomy. Tracy Cheetham gives Quest some idea of the infrastructure that is involved in this huge project.
for SKA staff and scientists n Civil works which includes earthworks, piling, sewers, pumping equipment, chlorination plants and sewer package treatment plants n Electrical works which includes the provision of transformers, minisubstations, ring-main units, 35 km of electrical cabling and optic fibre ducting between the site complex and each MeerKAT antenna. Construction of the civil works contract started in March this year and is expected to be finished by the end of March 2013. MeerKAT buildings MeerKAT will need new buildings and extensions to existing buildings
Power: the Karoo substation upgraded The Karoo substation that is 10 km outside Carnarvon is being upgraded from 5MVA to 10MVA capacity for MeerKAT. This work is divided into: n Supply, delivery, installation and acceptance of two new 5MVA transformers, and n civil works for the extension of the existing substation. The upgrade should be completed by
December 2012. Once completed, the substation will once again become the responsibility of Eskom. The existing power line that was constructed by the SKA SA will be switched over from 22kV and operated at 33kV once completed. This will provide for the full power requirement for MeerKAT. MeerKAT infrastructure will include roads, civil works, all-weather landing strip, electrical and fibre reticulation and construction camps. The contract to provide this includes bulk infrastructure: n The construction of 35 km of internal farm roads on the MeerKAT site between the site complex and each MeerKAT antenna n A new all-weather landing strip on site to enhance accessibility to site ▲ ▲
he infrastructure team of the SKA SA project is making excellent progress with the development of the Karoo MeerKAT site. Progress with power systems, as well as roads, civil works, landing strip, electrical and fibre reticulation and construction camps is on schedule. The clearing and grubbing of all internal roads has been completed and layering works has started. Test results have been received for the aggregate material, and the layering works have started for the all-weather landing strip. Trenching for the fibre and power reticulation has commenced and the first long-haul power cables have been laid.’ SKA newsletter. This excerpt from the SKA newsletter has a sense of excitement – and it is about more than the esoteric astronomy. The sheer scale of the project means that there are enormous numbers of people involved. The project has so far generated 164 local jobs in an area where work is scarce – with a wage bill of R2.4 million by the end of July. Putting together all this infrastructure involves civil engineers, electrical engineers, project managers and scientists and technicians of all types.
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Left Temporary contractors’ camps – a use for containers. Image: SKA Left below: MeerKat road construction in the barren Karoo landscape. Image: SKA
Karoo Array Telescope- (KAT-) 7 and MeerKAT will be housed in this building. The data generated on site will be sent from the array processor to the science and engineering office in Pinelands, Cape Town, using a longhaul fibre-optic link, which is already in place. This section of the building requires RFI shielding with effectiveness better than 100 dB between 70 MHz and 10 GHz and better than 80 dB between 10 GHz and 15 GHz. The shielding will include shielded doors and screened penetrations for power, cooling, fibre connections and interface plates for additional penetrations such as global positioning system cables. The hydrogen maser room, containing an extremely precise atomic clock, will be located in a separately partitioned room within the data rack area. An atomic clock is the most accurate time and frequency standard known and atomic clocks are used as the primary standards for international time distribution services, such as global positioning/navigation satellite systems (GPS). This type of clock is based on atomic physics and uses the microwave signal that electrons in atoms emit when they change energy levels.
The soil that will be excavated for the bunker will be used as a berm next to the site complex to improve shielding between the MeerKAT radio telescope and the site complex.
A trenching tool being used.
8 Quest 8(3) 2012
as the project progresses. There will be extensions to the existing dish assembly shed where the MeerKAT dishes will be assembled. A new pedestal integration shed, where the dish components will be integrated, is needed and the Karoo Array Processor building and its power facility need to be built. This is the building in which all on-site data processing is done. This building will be constructed 5 m underground in a bunker to protect the on-site radio telescope instruments from radio frequency interference (RFI) generated by equipment located in the centre. The underground construction is also to prevent the building from becoming too hot or too cold in the variable Karoo climate. All the centralised telescope equipment for the
Power supply The power facility next to the data centre will also be in a bunker. It will supply 640 kVA of power to the building. A project such as this obviously needs a continuous power supply and this is provided for through the provision of rotary uniterruptable power supplies (UPSs). The power supply design, as well as the distribution system and the building, will allow for growth up to 128 racks. The total maximum capacity of the power facility is 5 MVA but it will initially supply 2.5 MVA to KAT-7 and MeerKAT. Cooling
Cooling will be provided through a hot aisle/cold aisle concept and cold aisles will maintain a dry bulb temperature of between 18 °C and 27 °C. Hot aisle/cold aisle is a specific layout design for server racks and other computing equipment
The concept drawings for the MeerKAT antenna design.
in a data centre. The idea behind this concept is to conserve energy and lower cooling costs by managing air flow. At its simplest, a hot aisle/cold aisle design involves lining up server racks in alternating rows, with cold air intake facing one way and hot air exhausts facing the other way. The rows that are made up of rack fronts are called cold aisles and these usually face air conditioner output ducts. The rows that the heated exhausts pour into are calle hot aisles and usually face the air conditioner return ducts. The cooling capacity for each rack is 5 kW. Earthing, cabling and acoustics The earthing design and cabling strategy of the building and the power facility have been carefully designed – particularly because of the problem of radio frequency interference (RFI). A mesh screen has been included in the design of the power facility to prevent RFI leaking out over the top of the bunker walls. Environmental noise control was a particular factor in the design of the power facility and sound attenuators were installed on all air inlets and outlets of the mechanical plant rooms, as well as silencers for the generator exhausts, anti-vibration mountings for all vibration equipment, appropriately rated acoustic doors and noise-break panels in the cable trenches. The Karoo Array Processor Building and power facility are fitted with a fire-detection and suppression system, building management system and an access control and security system.
An artist’s impression of the site complex.
An artist’s impression of the Karoo Array processor building.
MeerKAT antenna foundations This contract includes the provision of 64 foundations for the MeerKAT positioners, and detailed designs are in progress. ❑ Tracy Cheetham is the General Manager: Karoo Astronomy Reserve Infrastructure and Site Operations. She qualified as an architect and has a a Master’s Degree in Sustainable Infrastructure and Environmental Engineering.
An artist’s impression of the Karoo Array processor building and its power facility.
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Systems engineering – Systems engineering is all about managing complexity. Richard Lord explains how this approach will make MeerKAT work.
he South African SKA organisation is using systems engineering to build the 64-antenna MeerKAT radio telescope.
Systems engineering techniques are used in complex projects: spacecraft design, computer chip design, robotics, software integration, and bridge building. Systems engineering uses a host of tools that include modelling and simulation, requirements analysis and scheduling to manage complexity. Image: Wikimedia Commons
Figure 1: An entire radio telescope system, showing the mission and operations functions, and the logistic support functions.
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Managing complexity What is systems engineering? The International Council on Systems Engineering (INCOSE) defines it as follows: ‘Systems engineering is an interdisciplinary approach to enable the realisation of successful systems. It focuses on defining customer needs and required functionality early in the development cycle, documenting requirements, then proceeding with design synthesis and system validation while considering the complete problem: n Operations n Performance n Testing n Manufacturing n Cost and schedule n Training and support n Disposal Systems engineering integrates all the disciplines and specialty groups into a team effort, forming a structured development process that proceeds from concept to production to operation. Systems engineering considers both the business and the technical needs of all customers with the goal of providing a quality product that meets the user needs.’ A systems engineer must understand the entire problem before attempting to solve it. A systems engineer looks at where the system is now, where it is going and what is going to happen once the project is completed. In other words, the system is understood in the context of its environment, and in the context of its entire life cycle, including maintenance, replacement, decommissioning and retirement. The field of systems engineering is too vast to cover completely in a short article. Instead, we will look at some of the key focus areas of the systems engineering approach. Definition of a system A radio telescope system is more than just a collection of antennas and computing hardware. Operators are needed to control and monitor the
how to make a radio telescope work
telescope and to record data that are given to the scientists. Maintainers are needed to repair faulty equipment and to service the telescope regularly. The telescope, together with its operators and maintainers, is often grouped as belonging to the mission and operations functions. The logistic support functions, which are also needed to operate and maintain the telescope, include items such as supplies, facilities, specialist equipment, as well as data and documents. The systems engineering approach requires proper documentation, so that the system can be maintained and supported long after the design and engineering teams have moved on to other projects. Figure 1 shows that a system consists of far more than simply the equipment that is needed to perform the mission.
Figure 3: XDM antenna standing at HartRAO, KAT-7 antennas in the Karoo, and artist’s impression of a MeerKAT antenna. Image: M Galard/HartRAO, Mark Wolleben/SKA SA, SKA SA
lower level. In the same way, all top-level requirements have to have lower-level requirements. Otherwise it is possible that some required functionality is not being implemented at a lower level. Concept exploration To arrive at the best solution for a particular problem, it is important to investigate all feasible alternatives before selecting a solution. As part of the systems engineering process, alternative designs are evaluated, based on performance, schedule, cost, risk and figures of merit. The engineering V-diagram One of the most important systems development models is captured in the engineering V-diagram, shown in Figure 2. ▲ ▲
Managing requirements The objective of any system is to satisfy the needs of the end user. For a
radio telescope such as MeerKAT, the most important users are the scientists. Capturing user requirements is an essential first step toward building a telescope that allows scientists to perform world-class research. User requirements are translated by systems engineers into system specifications, i.e. into requirements that engineers and subcontractors can understand. These requirements need to be measurable and verifiable. The requirements analysis process is an iterative process; some requirements are too costly or time-consuming to implement, and trade-offs have to be negotiated. Requirements need to be traceable – an important concept in systems engineering. You need to be able to trace lower-level requirements all the way to the top-level requirements. If you don’t do this, it is possible that there may be unnecessary development work going on at a
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Urban wisdom and systems engineering Would you tell me please, which way I ought to go from here? That depends a good deal on where you want to get to, said the cat. I don’t much care where, said Alice. Then it doesn’t matter which way you go, said the cat. Lewis Carroll, Alice in Wonderland
Figure 2: The engineering V-diagram – top-down design, bottom-up verification.
Figure 2 shows us: n A system consists of a multi-level hierarchy. Each level is a system in its own right. n The system design starts at the top level, and is further refined and developed at subsystem levels. n The system verification process starts at the lowest level. n During the integration process, emergent behaviour is verified at each system level. The process described by the V-diagram emphasises a requirementsdriven design and rigorous testing. The traceability of lower-level requirements to system-level requirements is important, because this ensures that nothing is done unnecessarily, and that everything necessary is done. Furthermore, all requirements are verified by corresponding acceptance tests.
item is produced, in the lab, where the item is assembled into the next higher level, and also on-site, after an item has been installed and integrated into the final system. Before the final system is handed over to the operational user, the systems engineers make sure that it meets the original user requirements.
Qualification and acceptance testing Qualification and acceptance testing is an integral part of the systems engineering process. Qualification testing verifies that the end-to-end design meets the given requirements, and it needs to be performed before an item is mass produced. Qualification units are not typically used in the final system, since they often undergo extreme testing, such as vibration testing, shock testing, ingress protection testing, etc. Acceptance testing is performed on all production items, and typically forms a subset of the qualification tests. Acceptance tests are usually performed at the factory, where the
Risk reduction Building a radio telescope in the Karoo is not without its challenges. Any system erected in the Karoo must be able to withstand dust, strong winds, lightning, and large variations in temperature. Infrastructure such as roads, power, water, sewage, accommodation, maintenance, support and operating facilities, etc. has to be established. In order to reduce both the project management risks as well as the technical risks, a number of development models were constructed. This is part of the systems engineering approach to developing complex systems. At the end of 2007, the Experimental Development Model
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Commissioning The objective of engineering verification is to verify that the system meets the system requirements. The commissioning process involves the characterisation and calibration of the instrument. Commissioning is also seen as the process that establishes the user system, i.e. it is the process that takes the engineering deliverable and refines it until it is a system that can be monitored and controlled by the operators.
The difference between the almost right word and the right word is really a large matter. Mark Twain, (1835-1910) Final Review is not necessarily the best time to discover the user requirements. Alexander’s 18th Law
(XDM) was completed at the Hartebeesthoek Radio Astronomy Observatory (HartRAO) (Figure 3). XDM is a single-antenna radio telescope with a diameter of 15 m. XDM not only addressed many technical risks, but also helped to build a coherent engineering team and to grow the systems engineering maturity of the SKA SA organisation. KAT-7 was developed immediately after the completion of the XDM, and it is the first interferometric radio telescope built in Africa. KAT-7 can be regarded as the Engineering Development Model (EDM) for MeerKAT. Its aims were to implement an operational system in the Karoo to learn how to operate and maintain a radio telescope on a remote site. ❑ Richard Lord completed his PhD in the field of radar remote sensing at the University of Cape Town in 2000. After completing postdoctoral research at the German Aerospace Centre in Munich, Germany, he returned to UCT where he worked as a Research Officer in the radar remote sensing group. He joined the SKA SA organisation in 2007, where he worked as a software specialist in the Computing Team during that year. In 2008 he joined the Systems Engineering Team, and is currently the project manager and systems engineer for KAT-7.
(Photo by Peter Macfarlane, SKA South Africa)
Have you ever wondered whatâ€™s out there? Thought of other planets orbiting the stars that you see in the night sky? Imagined billions of stars swirling through space in galaxies and clusters of galaxies and questioned how the stars and galaxies formed? Have you considered studying astrophysics at university? The Department of Astronomy at the University of Cape Town offers a vibrant undergraduate major in astrophysics with courses in modern astrophysics, observational and computational techniques, stellar astrophysics and extragalactic astronomy, with links to physics, applied mathematics and engineering. S T U DY A S T R O P H Y S I C S AT T H E U N I V E R S I T Y O F C A P E T O W N : D I S C O V E R T H E U N I V E R S E ! For more information visit the Department of Astronomy: www.ast.uct.ac.za
or email: firstname.lastname@example.org
ASTROPHYSICS, COSMOLOGY AND GRAVITY CENTRE
Commissioning scientists (fltr) Nadeem Ozeer, Maik Wolleben and Siphelele Blose in the MeerKAT control room at the Cape Town-based MeerKAT engineering office. Image: Nik van der Leek/SKA
KAT-7 control and monitoring: it’s all about the users KAT-7 doesn’t just work on its own in isolation. Its use requires a human interface. The KAT-7 CAM team explain how this has been put together. What is it? KAT-7 is an engineering prototype for the development of the MeerKAT telescope. Control and monitoring (CAM) is a sub-system of KAT-7. The CAM is a distributed computer-based system that integrates KAT-7 equipment, monitoring it for health and status and controlling it as required to perform observations and to provide a human interface for KAT-7. The human interface is used for different purposes by different role players. Scientists use it to operate KAT7, maintainers use it for fault detection and diagnosis, and engineers use it for testing. To put it in a different way: CAM is to KAT-7 almost what an operating system is to a computer. Apart from being a necessary part of KAT-7, the KAT-7 CAM is also an engineering prototype for the MeerKAT CAM subsystem and KAT-7 CAM is used to develop and evaluate technologies and concepts for MeerKAT.
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What does it do? The CAM has the following main functions: hardware control, monitoring and archiving, observation control and system control. Hardware control Real-time, closed-loop control is mostly implemented by computer-based hardware devices (here called devices). These devices implement TCP/IP stacks on small/embedded chips. Access to devices is protected through a proxy layer. The proxy layer is made up of software components that act as an interface between devices and the rest of the CAM system. Each device is exposed by a single proxy. Some devices can handle only a single connection, but the proxy provides multi-connection capability in that case. All engineering/support/system components/tools connect to proxies instead of device interfaces directly. This ‘protects’ the layers below the proxy
layer from unwanted or accidental manipulation. Proxies expose device commands to higher-level components to control. The proxy layer also ensures that the interface provided into the rest of the CAM system for all different hardware devices is consistent and uses exactly the same protocol and similar interface behaviour. Proxies may implement model logic and additional functionality or state handling for some devices – like the antenna controller and correlator. Monitoring and archiving Monitoring and archiving involve: n Sensor data monitoring and archiving n Health monitoring n Providing meta-data n Logging n Alarms monitoring and notifications n Integrated logistics system interaction. The CAM needs to monitor hardware, software and the
A diagram showing the CAM architecture.
of the captured signal data (like the temperature, humidity and pressure). Observation control The CAM allows scientists to schedule control tasks, using an observation control framework. The framework is based on schedule blocks and controlled resources. Scientists use Python scripts to control the system to do observations. Python is a general-purpose, interpreted high-level programming language that is designed to be readable.
If a scientist wants to observe a radio source, using two antennas, he or she creates a schedule block with those two antennas as controlled resources, and a reference to an observation script. Only one schedule block may use a specific controlled resource at a particular time. If the controlled resources are free (not allocated to another schedule block), then the schedule block can be activated. This causes the observation to be executed. Once the observation has run to completion, the resources are freed for use by other observations. Typical controlled resources are antennas and the correlator. Observations are scheduled for execution – put into a queue that is ordered, based on priority, required time of execution, etc. Using schedule blocks, observations can be scheduled either manually by the operator, or automatically by the CAM scheduler to execute the queued observations. System control The CAM software components are distributed over different nodes. Each
node runs a service, called a ‘node manager’, and the node manager launches the appropriate CAM components that run on that node as processes. A system controller automates and coordinates system startup and shutdown, using the ‘node manager’ services. Startup and shutdown is triggered by running a script. The start script launches the system controller as well as the components that it needs (logging component and a configuration server). The system controller coordinates startup and shutdown of CAM components via instructions to the ‘node managers’. Each ‘node manager’ controls the processes on its node by launching/stopping/(re)starting or killing components on its node as instructed by the CAM system controller or operator. The CAM uses alarms to trigger automated actions, like shutting down equipment when the cooling systems fail, or stowing the antennas when the wind becomes too strong to continue with observations. What is it made of? Architecture
The CAM is a distributed application, made up of software components, which is interfaced with client-server connection based communication via Ethernet LAN. The KATCP communication protocol is used to interconnect CAM software components, as well as connect CAM proxies to devices. KATCP is a message-based clientserver protocol on top of TCP/IP. A KATCP client connects to a KATCP server. The server exposes sensors ▲ ▲
environment, using sensors. There are 4 575 sensors in total. Physical sensors are used to monitor the environment as well as the performance of hardware, for example the temperature of the radio frequency (RF) feed of an antenna and the atmospheric humidity in the vicinity of the antennas. Software sensors are generated by software components, e.g. the disk usage of a server. Special software sensors aggregate other sensors, by applying a rule to their values. All sensors in the system are introspected at startup, and new sensors are automatically exposed, monitored and stored. Introspection means that CAM doesn’t have to know in advance which sensors are owned by the hardware it monitors – it discovers all sensors exposed by the hardware via their interfaces. Default sensor sampling is currently at 10s intervals, unless a different sampling strategy was defined. Proxies expose device sensors and log messages to ‘monitor’ components. Each ‘monitor’ component gathers the exposed sensors of specific devices. Sensor data are cached by the ‘monitor’ in memory and every 15 minutes these data are compressed to compressed CSV files and flushed to disk. About 13GB of sensor data are stored in the archive per month. Sensor data and log files stored in the archive are used for fault-finding, and to record the conditions under which observations are made. Alarms alert the user to conditions that may compromise KAT-7 equipment. A process evaluates the values of selected sensors, and generates alerts. Alerts include messages on a chat room, visual and audible indication by the graphical user interface (KatGUI), and an SMS sent to cell phones carried by support personnel. The CAM sends selected sensor values to the integrated logistic support system, which issues a work order in case of a failure, or triggers a preventive maintenance action for usage sensors (e.g. hours of operation). The CAM uses the sensor data it gathered to provide meta data (data about the captured signal data) for signal processing. For example, the metadata include information that is needed to process the captured signal data (such as where the antennas were pointing at every moment) as well as information about conditions that may be used in the interpretation
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Charles de Villiers, Rosly Renil and Ofaletse Mokone, members of the Cape Town CAM team.
(monitoring points) and requests (commands) to the client. The client can subscribe to the server for sensor updates. To use Twitter as an analogy, the client follows the server for sensor updates (tweets). The client can use the serverâ€™s requests to control the device that implements the server. Hardware: n Sensors and sensor transmitters n Embedded controllers n Servers n Operator workstations. An example of a sensor is the PT100 platinum resistance thermometer. Its resistance changes as the temperature changes. A transmitter is connected to the two wires of the sensor. The transmitter converts the resistance of the sensor to a 4-20mA current. An industrial IO module takes the analog current, digitises it, and makes the temperature available as a number via a Modbus message over TCP/IP on the network. The Modbus messages are converted to the KATCP communication protocol by a software component. Other devices, that interface with hardware, are embedded controllers that convert the sensor information to the KATCP communication protocol. Software components run on virtual machines, called nodes. Each virtual machine is hosted on a server. The Graphical User Interface (GUI) component runs on operator workstations, which are standard desktop computers. KAT-7 currently uses two iMACs with dual screens as well as LCD TV displays for webcams feeding the video from the Karoo to the control room in Cape Town. Software: Configuration and management components Each group of CAM servers (e.g. the server group in the Karoo, the server group in the lab, the server group used by the CAM team for development) has a single node
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defined as the head node and is coordinated by the KAT controller component running on the head node. Each server in the group runs a KAT node manager that manages the processes on that node as requested by the KAT controller component. The KAT configuration component provides the application program interface (API) to access system configuration from various sources and is used by the KAT controller to read the active system configuration and pass the subset of the configuration to each KAT node manager. The KAT node manager then launches the subset of the processes as received on that node and manages and monitors the processes on the node. The system configuration includes : n Definition of the nodes in the server group and which processes to launch on which node n Antenna configuration: including position and offsets, horizon masks, pointing models and noise diode models, wind stow parameters n Definition of the combination of real hardware devices, simulators and other software components that make up the active system n Software configuration. All these components adapt to the active system (i.e. alarms are only defined on the antennas that are included in that system configuration). Device proxies
The CAM proxy layer provides the core control and monitoring access layer for all hardware devices in the system. It protects hardware devices from direct access and exposes all device monitoring points (KATCP sensors) and commands (KATCP requests). It also pushes KATCP logs from hardware devices to the python logging framework. Other components access hardware devices exclusively through the proxy layer. Monitoring components Each node runs a KAT monitor component that gathers all sensors (monitoring points) from proxies and software components running on that node. Sensors are archived continuously by the KAT monitors at a configurable sensor strategy (sampling rate) or a default rate if no special strategy has been configured. The KAT monitor pushes sensor updates to the KAT store component, which stores the monitoring point.
Each KAT monitor component also implements aggregate sensors for the components it monitors per the system configuration and exposes those aggregate sensors in turn as KATCP sensors on its own KATCP interface. These are also pushed to KAT store for storage. The KAT store component provides the storage mechanism for all monitoring (and in future also logging data) as well as an API for accessing historic monitoring data and metadata. It stores monitoring points in a hierarchical structure per device proxy per sensor in compressed CSV files. KAT store indexes these in a PostgreSQL database for faster access and data extraction. The full CAM archive is stored on site and mirrored to Cape Town. The KAT aware component monitors the system and implements â€˜awarenessâ€™ in the form of alarms on critical failures as per the alarm definitions in the system configuration (including SMS and IRC chat notifications), it implements actions on critical alarms (e.g. shutting down servers when cooling is lost, or shutting down antennas when backup power does not kick in), and implements information exchange to the integrated logistics system for maintenance. The KAT logger component gathers all logs throughout the system and currently stores the logs to a human readable text file per process. The KAT store component may be extended to also cater for log storage in future. The KAT logger also provides the API for accessing current logs in a combined view or per process. Control components The KAT syscontroller manages control resources for observations by handling allocation and deallocation requests for resources. The KAT syscontroller will also manage configuration of and control over common components/devices. The KAT scheduler implements queue scheduling (where the operator orders the schedule blocks in the observation schedule) and support manual control. Automatic scheduling (automatic ordering and execution of schedule blocks) will be implemented. The KAT scheduler sends each schedule block to be executed to the KAT executor, which manages execution of the schedule block to completion or cancellation.
Schedule blocks and sub-arrays are stored in a PostgreSQL database. User interface components Various components and user interfaces to support engineering and commissioning are available for KAT-7 and the MeerKAT UI work will now focus on operator and observer interfaces and full support for remote operations. A web-based data archive search interface provides information on and access to download data files, while another web-based tool, sensor graph, provides user access to view, plot and download historic monitoring data. To support remote operations the CAM subsystem provides a KAT portal on site for access in the Karoo, as well as a KAT portal in Cape Town for remote access. The Cape Town portal pulls information from the Karoo and distributes it from Cape Town to support multiple remote users. Various user interfaces across numerous technologies have been implemented for KAT-7 and will now be reworked for MeerKAT, focusing on operators and observer interfaces, usability, consistent look and feel, etc. The existing user interfaces include: n Data archive browser – search and download data files n Sensor graph – search, plot, view and download historical sensor data n Operational displays: • Health and state displays • Alarms, logs and activity • Target/source catalogue displays • Antenna pointing and mode display • Weather displays • Sensor displays (including plotting of selected sensors and listing values of predefined groups of sensors) • Antenna control (stow/stop one/ all antenna(s)) • Node manager control (start/ stop/restart processes per node manager) • Build state / version display • Observation control display n Signal displays (science processing subsystem – including spectral plot, visibility magnitude, correlation phase displays) n Command line interface n On-line documentation – including version descriptions of deployed software, installation documentation and user help, developer documentation, specification and
design records. n IRC chat (with historic logs) n Homepage access with links to all documents, interfaces, access points of interest Figure 1 shows the health and antenna pointing screens of the KatGUI. The health screen is a map of sensors, and uses colours to distinguish failures and warnings from good health, It is used by operators to monitor the health of the system. The antenna pointing screen is used by operators to ensure that antennas are pointing where they should be. Figure 2 shows the user interface for the observation control. It is used by the operator to control execution of schedule blocks and to monitor availability of resources for observation. Figure 3 is a graph generated by the SensorGraph component. It plots the values of different sensors over time. It is used for fault finding and trend analysis. How it is made CAM development is driven by KAT-7 system requirements, as well as features requested by users to improve usability and reliability. Requirements are analysed and then followed by the design of the architecture needed to implement user requirements. Implementation of the design is primarily by coding in the Python programming language, followed by manual and automated testing to ensure quality. Unit tests are run regularly by a continuous build system. Software configuration control is achieved using Subversion, an open source version control system. Software is deployed on virtual machines. There are sets of virtual machines for development, testing and for the operational software in the Karoo. Releasing new versions of software to the KAT-7 operational system is done by creating a virtual machine for each node and deploying software components to the virtual machines. Creation of virtual machines and deployment are partly automated by scripts to reduce manual labour and the possibility of human error. Time is spent maintaining deployed software – fixing mistakes in the source code and making improvements suggested by users. ❑
Figure 1: KatGUI health and antenna pointing displays.
Figure 2: KatGUI observation control display.
Figure 3: SensorGraph.
The CAM team The CAM team currently consists of six computer science and engineering graduates. Developers are not required to have detailed knowledge of astronomy but experience in the Software Development Lifecycle and System Engineering is required, as well as solid programming skills. Some numbers: 3 servers hosting 5 virtual machines that run 21 software components that monitor 4 574 sensors
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Radio frequency interference and The radio telescope arrays that are to be build in the Karoo as part of MeerKAT and the SKA will be among the most sensitive telescopes ever built. Richard Lord explains the significance of radio frequency interference.
he Karoo Array Telescope (KAT) is an initiative of the South African government to further world-class scientific research. In the next few years, an array of 60 – 80 antennas will be built in the Karoo. This radio telescope array is called MeerKAT, and it will be among the most sensitive telescopes ever built. It is no secret that radio frequency interference (RFI) and radio astronomy are not the best of friends. However, the extent of their animosity is often suppressed or misunderstood.
Image of the NGC6251 galaxy obtained from the the VLA (Very Large Array). The image above is smothered by RFI, whereas the image below was cleaned using complex signal processing techniques. RFI severely limits the amount of information that can be extracted from recorded data. Image: http://www.vla.nrao.edu/
Karl Jansky’s antenna, designed to receive radio waves at a frequency of 20.5 MHz. It was mounted on a turntable that allowed it to rotate in any direction. Image: Wikimedia Commons
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The famous Jansky Karl Guthe Jansky was an American physicist and radio engineer who first discovered radio waves coming from the Milky Way in August 1931. He is regarded as one of the founding figures in radio astronomy. The non-SI unit used by radio astronomers for the strength of radio sources is the Jansky, defined as: 1 Jy is equivalent to 1.10-26 [W/m2/Hz] Where W=Watts Hz=Hertz Some of the strongest radio sources at 1 420 MHz are: n Our Sun: ~ 700 kJy n Virgo A: 201.81 Jy n Hercules A: 46.52 Jy n Hydra A: 42.37 Jy A drop in the ocean It is difficult to understand just how small a Jansky is. Let’s do a simple calculation. Imagine we had the luxury of pointing the 26 m HartRAO dish (assume 70% efficiency) in South Africa to one of the brightest radio sources out there, namely Virgo A. Now assume that we could do so for the entire lifetime of the dish, approximated to be 30 years. Every day, we would be able to receive radiation from Virgo A for a maximum of 12 hours (since the Earth rotates, the source would be hidden below the horizon for the other 12 hours). Furthermore, let’s assume we have an instantaneous collecting bandwidth of 256 MHz. Leaving out the maths of the
calculation (just trust me) the total energy collected over this timespan from Virgo A would be 25nWh – or 25 nanoWatt hours. To put this into perspective, a 100 W lightbulb, switched on for one second, uses a whoppping 28 milli-Watthours of energy – more than a million times what our 26 m dish recieves from Virgo A in 30 years. And just as an aside, radio astronomers are not really interested in these strong, well-researched sources. The sources they are interested in are in the milli-Jansky range, and for the SKA, in the microJansky range and less. Landing on the Moon One of NASA’s goals is to return humans to the moon by 2020. Will they carry cellphones? A typical cellphone has the following radiation characteristics: n Transmit power: 0.5 W n Bandwidth: 12 kHz (the GSM standard provides for a channel spacing of 200 kHz, with each channel having approximately a 12 kHz bandwidth) The distance from the Earth to the Moon is about 380 thousand kilometres. We can now calculate the approximate spectral power flux density (another way of saying RFI) as seen on Earth, assuming that the cellphone transmits isotropically, i.e. equally strongly in every direction (let’s look at the maths this time): In other words, a radiating Pt 4π R 2 B 0.5 = 4π (380 ⋅ 10 6 )2 ⋅ 12 ⋅ 10 3 scellphone =
= 2.3 ⋅ 10 −23 W / m 2 / Hz = 2 300 [ Jy ]
cellphone on the Moon will appear to be ten times brighter than Virgo A, which is already one of the brightest galactic sources out there. What about nylon chairs? Nylon chairs can accumulate static charge, leading to static discharges.
radio astronomy: why the fuss?
During the RFI measurement campaign in the Karoo, the RFI measurement system (which is much less sensitive than a radio telescope) picked up these static discharges, and the nylon chairs were subsequently replaced with canvas equivalents. Nylon chairs weren’t the only culprits. A portable gazebo, used to provide protection for vehicles, consisted of steel pipes strung together by a combination of metal chain and elastic cord that was threaded through the pipes. It was found that the contact of the links of the metal chain with the inside of the pipes and with each other caused RFI, especially when the wind made the frame shake. The gazebo had to be removed from the site.
The 26 m diameter dish at HartRAO.
Image: M Gaylard/HartRAO
So where do we go? It seems RFI is everywhere. Even the Antarctic isn’t immune from RFI from satellites. Then there are airplanes, criss-crossing the sky while radiating merrily. There are very, very few places left on Earth that are radio quiet. One such place is the Karoo. It is the (relative) lack of RFI, more than anything else, that has led to the decision to build a radio telescope array in such a deserted place. Not because there is no light-pollution from nearby cities (only optical telescopes care about light-pollution). Not because it is cheaper to build (due to the lack of roads, power lines and other infrastructure, it will be much more expensive). Not because we love the Karoo (we do, but it is not the reason). No, the reason is the (relative) lack of RFI. Virgo A, also called the Messier 87 galaxy.
Image: Hubble Telescope/Wikimedia Commons
amplifiers are saturated. 2. The receiver may not introduce any inter-modulation distortions. Therefore strong sources outside the bandwidth also need to be regulated. 3. The above two issues require RFI transmissions to be reduced, even if they cannot be removed entirely, i.e. even if they are still detected by
the radio telescope and (hopefully) flagged by the processing software. However, it is also feasible that some RFI transmissions can be avoided altogether, or shielded to levels below the radio telescope sensitivity. This should be the aim wherever possible. 4. The radio astronomy protected bands must remain completely ▲ ▲
Keeping it clean There are many reasons why it is important to devote so much effort to keeping the Karoo site as RFI-clean as possible, some of which are: 1. The receiver has to remain linear, i.e. there may not be any amplifier saturation. A strong RFI source, even if it only occupies a tiny fraction of the spectrum, will corrupt the data across the whole spectrum if the
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very difficult to achieve. The ITU recommendations give firm guidelines regarding the threshold levels of harmful RFI radiation. These levels depend on the sensitivity of the radio telescope, which is a function of the telescope’s noise temperature (Tsys), instantaneous bandwidth and total integration time. Any device emitting more than the recommended threshold should be sufficiently shielded. Wherever possible, the design should make use of natural attenuators, e.g. using mountains to shield antennas from equipment.
Drawing of a massive star collapsing to form a black hole. Energy released as jets along the axis of rotation forms a gamma ray burst that lasts from a few milliseconds to minutes. Image: National Science Foundation/Wikimedia Commons
Google Earth image of one of the sites in the Karoo where RFI measurements were conducted. Note the surrounding mountains, providing natural shielding against RFI.
A radiating cellphone on the Moon would appear to be the strongest radio source in the sky. Image: NASA
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RFI-free. They have been hardfought for, and any device emitting inside these bands, or producing harmonics or other non-intentional emissions inside these bands, must be removed or shielded. 5. The more RFI needs to be mitigated by the processing software, the more expensive the processing hardware becomes, and the more development time is needed for writing this software. Keeping the site RFI-clean is not a one-man show. It requires a consistent and concerted effort that spans many disciplines, for example: n Political (e.g. instituting a ‘Radio Quiet Zone’) n Infrastructure (e.g. power lines) n Ancillary equipment (e.g. shielding of buildings and other equipment) n Logistical (e.g. switching off cellphones and other radiating devices) n EMC (e.g. shielding noisy equipment, implementing good design principles, testing in anechoic chambers) n Monitoring and policing (e.g. illegal RFI sources need to be located and removed) n Lightning protection Threshold levels OK, so we shield everything that radiates. Although a noble idea, the required levels of shielding are often prohibitively expensive and
Epilogue One of the science drivers for MeerKAT is to observe new phenomena related to the transient radio sky, i.e. to discover sources that vary in brightness on time scales of seconds to years. Many of these transient events originate in processes involving ultramassive black holes in the centres of galaxies, distant supernova explosions near the edge of the observable universe, and gamma-ray bursts, the most energetic events in the cosmos. The stars linked to these events could be billions of light years away. This means the light from them took that many years to reach us. The Earth itself is about four billion years old, so some of these events occurred before our planet even existed, before the first microbes formed, before the oceans had formed. Is it not tragic then that these photons, after travelling for so many years through the universe, should fall prey to RFI in their last few milliseconds of existence, forever lost. Undetectable in a sea of man-made interference. ❑ Article based on a technical report prepared for the National Research Foundation. Richard Lord completed his PhD in the field of radar remote sensing at the University of Cape Town in 2000. After completing postdoctoral research at the German Aerospace Centre in Munich, Germany, he returned to UCT where he worked as a Research Officer in the radar remote sensing group. He joined the SKA SA organisation in 2007, where he worked as a software specialist in the Computing Team during that year. In 2008 he joined the Systems Engineering Team, and is currently the project manager and systems engineer for KAT-7.
IDC – financing South African innovation The IDC’s Venture Capital Strategic Business Unit (SBU) manages a R750 million fund providing equity funding to start-up companies for the development of globally unique South African Intellectual Property (IP) – this being the key criteria for any application.
Funding is provided in the form of ordinary shares and shareholder loans. There is no stipulated investment period, but the SBU’s objective is to achieve an exit opportunity within a reasonable time frame.
The funding provided by the SBU facilitates completion of the development, followed by the commercialisation of technology-rich products. These innovations and inventions most often stem from academic researchers who have developed their work to a point where they have a desire to become entrepreneurs; and innovators or inventors who want to move from tinkering with their ideas and prototypes in their backyards to fully commercialised businesses.
Through its investments, the Venture Capital SBU plays a proactive role in driving industrial development in South Africa, having a meaningful impact through the development of new entrepreneurs and shifting the focus from large companies to SMEs. This is achieved through sustainable development of more knowledge-intensive industries for long-term growth and job creation as prioritised in the Government’s New Growth Path (NGP). The unit continues to be a proactive, value-adding partner to its clients, capable of producing huge development returns to the benefit of South Africa’s economy and citizens.
The critical investment criterion for all Venture Capital projects is that the IP must be owned by the company and if not patentable, the product needs to provide a sustainable competitive advantage. The unit’s mandate allows for investment in projects across all industries, leading to sectoral growth and job creation. Recent South African inventions and innovations in the electronics, ICT, medical device and biotechnology sectors have proven particularly successful.
Funding for a project can reach a maximum of R40 million over several years, with the initial investment limited to R15 million. The IDC takes a minority shareholding of between 25% and 50% depending on the SBU’s valuation of the business and the amount of funding required. The start-ups stand to benefit from the further strategic support, guidance and advice provided through a partnership relationship with the IDC.
Telephone: 086 069 3888 Email: email@example.com To apply online for funding of R1 million or more go to www.idc.co.za
From theory to practice How do radio astronomers get the information that they need from radio telescopes? Oleg Smirnov explains.
Figure 1: A schematic representation of a telescope. A big primary mirror (in optical telescopes) or dish (in radio telescopes) collects incoming radiation, and focuses it on the detector at the centre.
roadly speaking, there are two kinds of radio astronomers (though of course some people manage to be a bit of both), and thus two ways to approach a radio telescope. Theoreticians use the telescope as a tool to explore the Universe, without needing to know too much about the tool’s inner workings. For the instrumentalists, the telescope itself is the whole point, and the challenge is to improve its capabilities (or even just to make it work in the first place!). For instrumentalists, the Square Kilometre Array (SKA) represents the ultimate challenge – but to understand why, we need to learn a little bit about how radio telescopes work in the first place. Why size matters Let’s look at optical telescopes first, because they’re much easier to understand. An optical telescope is essentially a digital camera with a very, very big lens. Instead of an actual lens, it uses mirrors (Figure 1) – mirrors serve exactly the same function, that of focusing incoming light on the detector – and huge mirrors are much more practical to manufacture than huge lenses. But why do they need to be so huge in the first place? The two keys to a telescope are aperture size and collecting area. Aperture size – the diameter of the mirror – determines resolution, i.e. the smallest detail that we can distinguish with the telescope. Collecting area – the surface area of the mirror/lens – determines
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Figure 2: The Arecibo dish – 305 m across. This dish was built in a natural crater, which means that it cannot be steered. Image: NAIC – Arecibo Observatory, a facility of the NSF
Figure 3: The Green Bank dish in West Virginia – the largest fully steerable dish at 110 m across. Image: Wikimedia commons
sensitivity, i.e. the faintest objects that we can observe. If you’ve ever compared photos taken with your phone (especially in low light) with
those from a professional camera, you can certainly appreciate the difference in both sensitivity and resolution – and it’s all down to the tiny lens on
were tens of metres across at most, and only had a single pixel for a detector. This made for a rather blurry picture of the Universe. For example, a 25 m dish observing radio at a wavelength of 21 cm (the famous ‘hydrogen line’) has a resolution, i.e. the finest detail that it can pick out, of about 0.5º – the size of the Moon – which is absolutely pathetic by the standards of optical telescopes. The 21 cm hydrogen line is visible evidence of the large amounts of neutral hydrogen gas filling the space between stars. In 1944 Dutch astronomers predicted that neutral hydrogen would emit radio waves at a wavelength of 21 cm, producing a spike or line in the electromagnetic spectrum. Observing the Doppler shift of the hydrogen line allows measurement of the relative speed of individual gas clouds moving through galaxies – giving important clues to galaxy formation. A key project for the SKA will be detection of the hydrogen line from early in the life of the Universe.
Aperture synthesis to the rescue Astronomers have long realised that a technique called interferometry offered a way to get a big jump in resolution. Interferometry relies on combining the radio or light waves received at two different locations, and measuring the resulting interference pattern. By carefully measuring the interference pattern, one could achieve an effective resolution that was determined by the distance between the two locations (called the baseline), which could be made much larger than the size of the individual lenses (or mirrors). Early experiments in this were conducted in the 1920s by A Michelson, but these were rather primitive – they could, for instance, be used to measure the size of a star, but not to make a direct image of it like a normal telescope could. It wasn’t until the late 1950s that Sir Martin Ryle and his group at Cambridge University developed a technique called aperture synthesis that used the principles of interferometry to combine multiple radio dishes into a single virtual telescope. A proper description of aperture synthesis requires some pretty advanced math, such as complex
Figure 4: Breaking the surface of the dish into segments. The operation of the telescope is mostly unaffected.
Figure 5: Each segment is replaced by some kind of electronic receiver. The incoming radiation still travels through free space (or air) before it reaches the dish (dotted green lines), but the path between the dish and the detector at the centre is now replaced by cables (solid green lines).
numbers and Fourier transforms, but it turns out that there’s a much simpler way to understand the process (for which I am indepted to Ron Ekers). For starters, let us imagine that we have somehow managed to build a radio telescope as per Figure 1 – kilometres (or even thousands of kilometres) across. The purple and green lines in Figure 1 show the path that radio waves take as they enter the telescope, reflect off the dish, and focus on the receiver. The important part – the thing that makes the telescope work in the first place – is that the distance that the reflected waves travel from each part of the dish to the detector is just right, so that they arrive at the receiver in focus (what we call in phase). In fact, the exact geometrical shape of the dish (and the position of the detector) is specifically designed to ensure this. Now, let’s break up the surface of the dish into little segments (Figure 4). As long as each segment still reflects radio waves back to the detector properly, not much will change. Next (Figure 5), we replace each segment
the phone versus the big lens on the camera. (It’s not really the actual number of megapixels – we could build a phone camera with more megapixels, but the pictures would not necessarily look better, as long as the lens is too small to take advantage of those extra pixels.) Because the light from the distant Universe is so incredibly faint by the time it reaches us, an optical telescope needs a really big mirror to catch enough of it. A measure that is closely related to sensitivity is speed. In principle, a telescope can compensate for low sensitivity by spending a longer time pointing at the same object in order to collect more signal (again like a camera, which requires a longer exposure in low light), but observing time is expensive, so speed is a handy measure. A telescope with 10 times the collecting area would be a hundred (102) times faster – it could reach the same sensitivity in 1/100th of the observation time needed by its 1/10-sized smaller brother. By nature, radio signals and visible light are very similar – both propagate as electromagnetic waves. They only seem so different to us because our eyes can see visible light and not radio signals. However, we can construct a telescope to ‘see’ radio using exactly the same principles. A metal dish reflects radio waves just as well as a polished mirror reflects visible light, and we can build radio detectors (called feeds) that serve the role of pixels. So Figure 1 could just as well be a radio telescope – and in fact, basic radio telescopes look exactly like that. There is one catch, though. The resolution of a telescope doesn’t just depend on its size, but on the ratio of wavelength to mirror size. The wavelength of visible light is about 390 – 750 nanometres, while radio waves range from millimetres to metres, i.e. anything from a thousand to millions time longer. This means that a radio dish on its own would need to be a thousand to a million times bigger than an optical telescope to achieve the same resolution (and so would its feeds –‘pixels’)! Clearly, a dish that’s thousands of kilometres across is utterly impractical to build. Early radio astronomers had to content themselves with dishes that
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Synthetic aperture With a technique called VLBI (very long baseline interferometry), radio dishes all over the world can be combined into a single synthetic aperture. This makes for baselines of thousands of kilometres, and resolutions of milliarcseconds, which is about onemillionth the apparent size of the Moon. With space-based VLBI, radio dishes carried by satellites are combined with dishes on the ground in order to form even longer baselines. Russia recently launched the Radioastron spacecraft which, with an orbit of 390 000 km at the apogee (i.e. its most distant point from the Earth), will allow for resolutions that are another thousand times higher. Optical astronomers cannot even dream of such staggeringly high resolution!
Figure 6: We put the detector on the ground, and add some extra lengths to the cables, precisely measured to make sure the signals still arrive in the same phase.
Figure 9: Image of the source IRC+10420. The lower resolution image on the left was taken with the UK’s MERLIN array and shows the shell of maser emission produced by an expanding shell of gas with a diameter about 200 times that of our own Solar System. The shell of gas was ejected from a supergiant star (10 times the mass of our sun) at the centre of the emission about 900 years ago. The corresponding EVN e-VLBI image (right) shows the much finer structure of the masers because of the higher resolution of the VLBI array. Image: Wikimedia commons Figure 7: We put the individual dish segments down on the ground as well, and again adjust all the cable lengths to compensate for the different signal travel time.
Figure 8: We replace the segments with dishes – the interferometer array is now complete.
with some kind of electronic receiver; and the path that the waves used to travel from the dish to the detector is now replaced by cables carrying the electronic signal. The detector is also replaced, by a special computer (called a correlator) that cleverly adds up the signals carried over the individual cables. As long as the cables are the right length, the signals will continue to arrive in phase, and the telescope will function as before. Now, cables are flexible, so there’s no point at all in keeping
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the correlator up there in front of the dish – we may as well lower it down to ground level. This may change the distances that the signal has to travel (perhaps we need longer cables), but we can compensate for this by adjusting the cable lengths precisely so that the signals still arrive at the correlator in perfect phase (Figure 6). If we’re doing that, we may as well mount the individual receiver segments down on the ground as well (Figure 7). This also changes the distance the signals travel before they hit the reciever segments, but we can also compensate for this by adjusting the cable lengths. It turns out that even this is not really necessary – instead of matching cable lengths, we can program the correlator to insert the appropriate phase delays into each signal line electronically. Finally, what can we use for the individual receivers? Well, we may as well use conventional small radio dishes, since they do such a good job of collecting signal (Figure 8). In effect, by spreading an array of small radio dishes over a large area, and combining their signals in the correlator, we have managed to make a virtual telescope with a ‘synthetic aperture’ that can easily be made thousands of kilometres across. In this way we can achieve incredibly high
resolution (see Figure 9 in the box). This is how a radio interferometer (also called an interferometer array, or often simply array) such as the SKA or MeerKAT functions. But wait a minute, you might say, if we start with an imaginary telescope dish thousands of kilometres across, and break it up into little pieces, surely we’re going to end up with a great many pieces, i.e. an array of thousands if not millions of dishes on the ground? Fortunately, it turns out that we don’t need anywhere near as many (although the full SKA will have thousands, see below) – we can get away with as few as, say, 14 (the WSRT array in the Netherlands), or even six (ATCA in Australia), thanks to a little help from our planet. As the Earth rotates, all our ground-based dishes rotate with it. If you’re sitting somewhere up on Alpha Centauri looking at our dishes with your own very powerful telescope, you’re going to see them rotate through a circle (or, more precisely, an ellipse) in the course of one Earth-day. By collecting the signal continuously during this period, we can have even a handful of dishes fill out a synthetic aperture. Fortunately, the Universe obliges us by remaining mostly still on such timescales, patiently waiting for us to build up our picture in such a ‘slow’ manner.
Interferometer elements Note that the elements of an interferometer do not necessarily have to be dishes. The SKA is actually three arrays in one, using three types of receivers – dishes, large (60 m wide) flat disk-shaped receivers composing the dense aperture array, and clusters of small upright receivers called the sparse aperture array. For this reason, the elements of an interferometer are often called stations, if we don’t want to be specific about receiver type. In this article we’ll keep on calling them dishes for simplicity, but everything we talk about also applies to aperture arrays.
Figure 10: Dish receivers.
Image: SKAOrganisation/Swinburn Astronomy Productions
Figure 11: The dense aperture array.
Image: SKAOrganisation/Swinburn Astronomy Productions
Why the SKA? With aperture synthesis, radio astronomers are clearly spoiled for resolution, and can already observe incredibly fine details of the Universe (Figure 9). So what is so groundbreaking about the SKA? Remember that there are two things that characterise a telescope – resolution and sensitivity – and that the latter depends on collecting area rather than aperture size. We may use VLBI to connect, say, ten 25 m radio dishes around the world to make a very large synthetic aperture with an incredibly high resolution, but the sensitivity of such an array is still determined by the combined surface area of the dishes – which in this case is about 490 m2 per dish, for a rather modest total of about 0.005 km2. So we may be able to distinguish very fine detail, but we’d still need to spend a lot of time collecting signal to reach a decent sensitivity. The SKA will have, you guessed it, a square kilometre of total collecting area 200 times more than our 10 x 25 m array for a speed increase of 2002 = 40 000 times! Another big advantage of the SKA is that, with its thousands of dishes, it will ‘fill’ a synthetic aperture pretty well immediately, even before the Earth-rotation trick kicks in. The SKA will thus be able to take highquality images in a very short time – what we call ‘snapshot’ observations – whereas small arrays require us to wait for hours while the Earth rotates them around into all the necessary configurations. Such capabilities will enable SKA to do groundbreaking new science. Why is it challenging? There are a number of reasons why interferometry is difficult. To begin with, the math required to process the signals and turn them into images is fairly advanced, and the computing power is very demanding. In fact, the SKA will require a world-class supercomputer just to process the huge amount of data it collects. ▲ ▲
Figure 12: The sparse aperture array.
Image: SKAOrganisation/Swinburn Astronomy Productions
The exception to this are fast-acting transient phenomena (i.e things that suddenly go bang). This is a very exciting branch of astronomy, but one that requires somewhat different observational techniques.
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Secondly, the kind of processing we need to do is very tricky, and this has to do with the very nature of aperture synthesis. Thirdly, the images we get from a radio interferometer are severely distorted to begin with. Some very clever processing has to be done in order to remove these effects. As radio telescopes get more sensitive, we’re beginning to pick up more and more subtle problems that we didn’t have to worry about with older, cruder instruments. At SKA sensitivities, our processing will have to be very clever indeed – a lot of it hasn’t even been invented yet – so we still have plenty of research to do. This is why it’s so important to build smaller pathfinder instruments (such as MeerKAT), followed by SKA Phase 1 (about 10% of the full SKA), before we get to the full SKA itself. We really need to learn to walk before we can run.
Worrying about distortions
b Figure 13a: What a single bright point-like object looks like to (a) an optical telescope, and (b) to a radio interferometer (MeerKAT, in this case). All the elaborate structure in (b), called sidelobes, is caused by gaps in the synthesised aperture. Image: Oleg Smirnov
There are two main distortions that we worry about. The first is caused by gaps in our ‘virtual telescope’. These were quietly introduced when we went from Figure 1 to Figure 8. Unfortunately, these gaps are almost unavoidable, since it’s practically impossible to build enough antennas to completely cover the area that a single giant dish would have covered. But why are gaps bad? Imagine that we point our telescope at a patch of sky that is completely empty,
apart for one bright point-like object. For an optical telescope, this could be an individual star. For a radio telescope, this could be a distant galaxy that is so far away that it is seen as essentially a single point. An optical telescope will see a single neat blob (Figure 13a) – and the bigger the telescope, the smaller the blob will be – which is just another way of saying that a bigger telescope has higher resolution. An image made from a radio interferometer, on the other hand, will show a blob surrounded by extra structure we call sidelobes (Figure 13b). The gaps in our aperture are exactly what causes the sidelobes in the first place. In fact, if we were to take a normal optical telescope and introduce ‘gaps’ into its mirror – say by covering bits of the mirror with masking tape – it would also produce images similar to Figure 13b. The same effect occurs when you get dirt or fingerprints on the lens of a regular camera – next time you notice your camera’s lens is dirty, take a picture of some bright lights, then clean the lens, take another picture, and carefully compare the results. When looking at just one object, as in Figure 13, this is not really a problem, but a typical image will contains hundreds to thousands of objects (Figure 14a). When seen through a radio interferometer, each object acquires its own set of sidelobes, and the image becomes something more like Figure 14b.
The Fourier transform The Fourier transform, developed in the 19th century by French mathematician Joseph Fourier, lies at the heart of all interferometry. This transform is a technique for representing any continuous signal by a sum of waves of different frequency, called Fourier components. If you’ve ever seen a spectrum analyser on a sound engineer’s console (or just on a particularly advanced stereo), you have essentially seen a Fourier transform at work. The set of Fourier components is, in some sense, completely equivalent to the original signal. If we can measure the Fourier components, we can perform an inverse transform to recover the exact original signal. Audio signals are one-dimensional, but an image of the sky can also be thought of as a signal – a two-dimensional (2D) one. A 2D Fourier transform turns it into a sum of 2D ‘spatial waves’, with large objects in the image associated with large (‘low-frequency’) waves, and small objects with small (‘highfrequency’) waves. Now here’s the interesting thing. If you were to somehow measure the signal on the surface of a telescope’s mirror (or in the lens aperture of a camera) – before it is focused on the detector – you would find a Fourier transform of whatever the telescope or camera is pointed at. When the mirror (or lens) then focuses this signal on the detector, it is actually, just by its very nature, performing an inverse Fourier transform. As you read this article, the optical system of your eyes is also continuously performing forward-and-inverse Fourier transforms, in order to form an image of the page on your retina. Fourier transforms are literally everywhere. Now remember that an interferometer works by connecting radio telescopes into a ‘synthetic aperture’, and measuring the signal in this aperture. This means that an interferometer actually measures the Fourier components corresponding to an image of the sky (rather than measuring an image of the sky directly). We can then do an inverse Fourier transform in software, and thus recover the original image. In some sense, an interferometer is like the ‘front half’ of a lens – with the rear half, the one responsible for the focusing, replaced by a computer that does inverse Fourier transforms.
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Image: Wikimedia Commons
Figure 14: (a) a typical patch of sky will contain hundreds to thousands of objects, if your telescope if sensitive enough to see them. When seen by a radio interferometer such as MeerKAT (b), the sidelobes of the brighter objects completely swamp the fainter objects. A process called deconvolution is required in order to get back to something resembling (a). What’s worse, instrumental errors during observations actually cause the interferometer to produce something more like image (c). These must first be carefully removed through a process known as calibration. Image: Oleg Smirnov
You can see that sidelobes from the brighter objects manage to completely contaminate all the faint detail (and it’s the faint detail that we’re most interested in – or why else would we be building telescopes with such high sensitivity?) It is possible to partially or fully remove sidelobes via a family of mathematical techniques broadly called deconvolution, but we still need to make a lot of progress on these. The second kind of distortion is produced by the Earth’s atmosphere, and also by electronics in the telescope itself. This causes delays and variation in the signal that is recorded at each antenna. Because of this, radio interferometry is really akin to lying on the bottom of an (indoor) swimming pool, and looking up through the water at a picture painted on the ceiling (Figure 15a), trying to make out the details – behind the glare of some really bright lights! The resulting image – before doing any processing – actually looks something like Figure 14c. The process of correcting for this distortion is called calibration, and we’ve become good enough at it so that (some of the time) we actually can go from Figure 14c to 14b to 14a. But by no means always. Quite often we can’t exploit the full sensitivity of the telescope simply because we haven’t figured out how to calibrate it well enough. Even so, calibration is relatively easy with our older, simpler interferometers. Large telescopes such as the SKA and its precursors present a whole new set of challenges. The difference can be roughly understood via the same swimming pool analogy. Older interferometers are either relatively small – tens of kilometres at most, VLBI being the exception – and/or have a very narrow field of view (by
which we mean the patch of sky that an interferometer observes at any one time). If the array is small compared to the ‘waves’ of our ‘swimming pool’, then each dish essentially looks up through the same bit of ‘wave’ (Figure 15b). If the array is big but the field of view is small, as in the case of VLBI, each dish looks up through a different wave, but is only affected by a tiny portion of it (Figure 15c). Both of these cases simplify calibration dramatically. The SKA, on the other hand, is a large array with a large field of view (Figure 15a), so each dish is affected by large sections of different waves. This is where calibration gets extremely tricky, and we still have a lot of work to do before we can say we’ve got the problem properly beaten. Conclusion There are many different reasons to be excited about the SKA. For theoreticians, it will provide muchneeded breakthroughs in many areas of astrophysics and cosmology – which the other articles in this issue talk about. For instrumentalists, it represents a fantastic mathematical, algorithmic and computational challenge, which is sure to keep us busy for years to come! ❑ Oleg Smirnov was born in Moscow, Russia. He studied theoretical mathematics at Moscow State University, then switched to optical astronomy for his PhD at the Russian Academy of Sciences. Having completed that, he switched again – to radio astronomy, and to the Dutch countryside – and spent the next 12 years at the Netherlands Institute for Radio Astronomy (ASTRON). In 2012 he moved to South Africa to take up the SKA Research Chair in Radio Astronomy Techniques and Technologies (RATT) at Rhodes University.
Figure 15a: To a large radio interferometer such as the SKA, looking up through Earth’s atmosphere is like looking up from the bottom of a swimming pool on a windy day.
Figure 15b: For a small interferometer the situation is a little easier, as every antenna looks up through almost the same part of a ‘wave’.
Figure 15c: Even a large interferometer has an easier time as long as its field of view is very narrow, so each antenna is only affected by a small part of each ‘wave’.
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The mathematics of modelling By Lindsay Magnus
The data in the figure show the measured spillover signal at five degree steps across the usual operating elevation range.
In this kind of model the value for an elevation of 43.5 would be the same as the value at 40, which was 14.75.
odels in mathematics are not people walking on a catwalk but rather a way of expressing some kind of predicted behaviour in mathematical terms. Astronomers and engineers use many kinds of models and in this article we will give a simple overview of how they can be used. Models can be created in different ways. The simplest is to first observe the system. Then, based on these observations, and your understanding of mathematics, choose an equation that you believe will allow you to predict the behaviour. If there are no equations that you can use then you have to go to the more complicated method of creating numerical models that use mathematical relationships to approximate the behaviour. Models as analytical equations or numerical methods Two examples are illustrated: n the spillover model, which is used to factor in the extra radiation that spills over the edges of a radio astronomy dish and adds to the total signal received n the pointing model that illustrates the corrections that need to be
given to the antenna system of the radio astronomy dish to make it point in the right direction. Spillover
The feed on a radio astronomy antenna gathers the radiation reflected from the dish surface. Depending on the position of the feed and the shape of its beam pattern it is possible for the feed to receive radiation from beyond the edge of the dish. This kind of signal is called spillover and is added to the desired signal at the feed. We want to know what this signal is so that it can be subtracted from the feed signal, leaving only the signal from the sky. In radio astronomy the very weak signals are represented as a temperature. The simplest way to think of this is the strength of signal you would get from a perfectly matched 50 ohm resistor heated to that temperature.
The problem is that there are no simple equations that can tell you what the level of spillover signal will be at different elevations. So what we do is measure the data at different elevations and use this to create the model. The maths
The simplest way to deal with these kind of data is to use a numerical method called interpolation. This method allows you to use the measured data points to infer what is happening in between each data point. We know, for example, the values at 40 degrees and 45 degrees elevation are 14.75K and 15K ,so we can now use interpolation to determine what we expect the value to be at 43.5 degrees. There are many different methods of interpolation, the two simplest being stepwise and linear interpolation. The model A stepwise model
Spillover from a radio astronomy dish.
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A stepwise model simply assumes that all the values in between are constant â€“ can you see why it is called a stepwise model?
A linear model
We can now use the equation for a straight line to calculate the values in between. Our two points are (x1,y1) = (40,14.75) and (x2,y2) = (45,15). From this we can calculate m = (y2– y1)/ (x2 – x1) = 0.05 and c = y – mx = 14.75 – (0.05) x 40 = 12.75. So from this we get the value at an elevation of 43.5 degrees to be: y = mx + c = 0.05 x 43.5 + 12.75 = 14.925K Pointing models An example of an analytical model is the system that is used to correct the direction in which the radio astronomy dishes point. Each dish is given two coordinates that are used to point the dish to the source in the sky. An example is given below. The data The observations were made for 100 sources and the results are shown in the middle figure on the right. The maths Although in this case it is possible to almost ‘see’ the relationship between the two data sets there are mathematical tools that will allow an objective determination of the relationship. For ease of description we will call the elevation that the antenna is instructed to point towards as the input and the actual measured elevation as the output. We can now say in mathematical terms that there exists a function that relates the input (x) to the output (y) or y = f (x) the problem here is to find the function. The function for a straight line is y = mx + c so the problem reduces to ‘what are the values for m and c that will allow us to take the required elevation angle (our intput (x)) and calculate the actual elevation angle (our output (y))’. The technique that we are going to use is called least squares regression. We will see shortly how this name arises. The purpose of our model is to predict what the output will be for any given input. We find this model by first defining the error expression, that is the difference between what the data give and what the model gives. So for each of our data points we can calculate the error term € = yi – (mxi + c). We still
To determine the pointing model to be used you must first make the observation. In this case you scan over a set of radio sources for which you know the exact positions in the sky. If the dish is correct then there will be no error in the pointing.
do not know the values for m and c. The error term € is the error for each data poin. In order the determine how all the data behave we first square the error term and add them all up for all our data: N–1 S = ∑. (yi – (mxi + c))2 i=0 This sum S is an indication of how well our model fits the data – the smaller S is, the better the model. We now need to find the values for m and c that will result in the smallest value of S. In mathematical terms we need to minimise S. Regression is the technique that is used to find the values for m and c that will minimise S. Can you see why it is called least squares regression?
In a linear model we assume that the data in between the points are on a linear or straight line.
The model There are many existing computer methods for performing this type of analysis. Below is section of Python code that will do the job for you: import numpy as np x = input_data # you would use your own data here y = output_data # you would use your own data here A = np.vstack([x, np.ones(len(x))]).T m, c = np.linalg.lstsq(A, y) This gives m to be 1.0 and c to be 2.99. We have modelled the data. That is, for any input elevation we can calculate the output elevation output = (1) x input + 2.99. ❑
An analysis of the data shows that there is a constant three degree offset in elevation for all the observations. Physically this means that when, for example, you instruct the dish control system to point the dish to an elevation of 30 degrees it actually points the dish three degrees above the point. This may be due to some installation default.
Lindsay Magnus is the commissioning manager for SKA SA.
A plot of the input data against the output data is often key to choosing the function f. In our case it looks like a straight line.
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The Itty Bitty Telescope (IBT):
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Fast facts about the IBT 1. It is a 12 GHz radio telescope. 2. It can detect frequencies in the range of 10.7 to 12.75 GHz. 3. It is not a radio telescope system that can be used for serious sky surveys. 4. It can detect the sun. 5. It can detect blackbody radiation such as 300K trees, buildings, people, when viewed against blank sky. 6. You must use it outside, or through a large window. Parts list and options for the IBT: All the dish parts are available from your local satellite supplier: 1. The dish with all the brackets and a Ku band LNB was around R230.00. 2. The satellite finder was also around R230.00. 3. 2 m of TV cable and a few F-type connectors cost about R10.00. Putting the dish together Remove the dish and its parts from the box and find the LNB arm mounting screws. Align the arm and attach with the screws, making sure to keep the button screws flush with the surface of the dish as shown in Figure 1. Attach the LNB coax cable to the LNB. The LNB is the block that sits in front of the dish (Figure 2). How you mount the dish will depend on your tripod. You want to be able to swivel the dish in azimuth and tip it in elevation. (Figure 3).
The detector The other important piece of the IBT is the detector. We use a simple satellite finder that technicians use to point a dish at a suitable satellite (Figure 4). With the cheap and midpriced meters, you will need to build a power supply. To assemble the power supply You will need 12 volts of DC power to operate a satellite finder. Hereâ€™s how to build a power supply (12 V) for the channel master tuning meter. 1. Cut off the end of a piece of coax cable (Figure 5). 2. Strip off about 5 cm of the white covering. Be careful not to cut through the silver wire braiding. 3. Comb and twist the silver wire braid shielding. 4. Remove the foil shield, exposing the white insulation. 5. Be careful not to score the white insulation. Cut off about 2.5 cm of the white insulation, exposing the copper wire. 6. Use a small wire nut to connect the silver braid shielding of the coax cable to the black, or ground, wire of the 9-volt battery connector. Use a small wire nut to connect the center wire of the coax cable to the red wire of the battery connector. 7. Using electrical tape, wrap from the insulation of the coax cable to the red and black leads of the 9-volt connector (Figure 6).
Q Practical Science
Tips for building and using a simple radio telescope 8. Insert batteries into the battery clip. Attach the battery clip to the 12-volt connector (Figure 7). 9. Attach the coax from the LNB to the TO LNB terminal on the satellite finder (Figure 8). 10. Attach the coax from the battery pack to the TO REC terminal on the satellite finder (Figure 9). You are done and ready to observe. Observing activities and ideas Activity 1
Turn your IBT to blank sky and adjust the gain to zero. Listen to the speaker or look at the meter. Now turn your IBT towards the ground and see/hear the difference. Blank sky is about 3K while the ground is about 300K. Activity 2
Now turn your IBT towards the Sun. Why isn’t the Sun, with all its enormous energy (temperature of 6 000K!) pinning the meter? It turns out that the IBT dish has a beam width of 3 degrees while the Sun appears to be only 0.5 degrees in our sky. Thus the area of the dish occupied by the sun is small and the signal appears weaker than the ground at 300K. Activity 3
Find the tree line and gaps between trees. The sensitivity of this IBT system is amazing and you can actually find the tops of trees and gaps between trees (if they are big enough). You could map the tree line using the angle of tilt of the antenna (altitude measured with an inexpensive angle finder available from hardware stores) and the azimuth found with a compass. Activity 4
Body temperature detection. As you’ve no doubt worked out, nearly anything with a temperature can be detected with a radio telescope and people are no exception. Having a temperature of 300K (37 ºC), your reading will be similar to the ground if you fill the beam. But you can have some fun with this... Try walking slowly past the telescope so the signal increases and then stabilises and then decreases; or try using just your
hand and make ‘music’. The first musical use of this radio-created music was the Theremin, played by waving your hands near antennas to vary pitch and amplitude – look it up on the web, it’s fascinating! Activity 5
Satellite detection. Many geo-stationary satellites are in orbit above the Earth and many transmit radio signals. Much of this we would consider radio noise or radio pollution. Doing this activity may help you understand radio noise pollution better and it is always exciting to find a satellite you can’t see. These satellites give off a signal that is very easy to detect and make you wonder why the satellite looks as though it has more energy than the Sun. Remember that the Sun is a broadband (extremely) transmitter whereas the satellite is a very narrow beam transmitter, so all its energy it given off in a very narrow band. Most of these satellites are in the Clarke belt (named after Arthur C. Clarke (author and engineer), who came up with the idea that you could create a geosynchronous orbit at a certain altitude above the Earth). For more information check the web at: www.heavens-above.com or many other sites. Most of these satellites orbit above the equator so work out where your celestial equator is by taking your latitude and subtracting it from 90 degrees. This is roughly the altitude to look for satellites. Remember that the orbit will be near the ground in the east and west and forms an arc through the altitude you calculated in the south. ❑
Figure 8 Credits The Itty Bitty Telescope was designed by Society of Amateur Radio Astronomy Members Kerry Smith and Chuck Forster. It has been incorporated into the NRAO Navigators Program—an outreach programme to promote radio astronomy and is used with permission here in Quest. Sue Ann Heatherly firstname.lastname@example.org Tom Crowley email@example.com Kerry Smith firstname.lastname@example.org Nadeem Oozeer email@example.com Lindsay Magnus firstname.lastname@example.org Originally http://www.gb.nrao.edu/ epo/ambassadors/ibtmanualshort.pdf adapted with permission.
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Research that can change the world
Impact is at the core of the CSIR's mandate. In improving its research focus and ensuring that it achieves maximum impact in industry and society, the organisation has identified six research impact areas: Energy - with the focus on alternative and renewable energy. Health - with the aim of improving health care delivery and addressing the burden of disease. Natural Environment - with an emphasis on protecting our environment and natural resources. Built Environment - with a focus on improved infrastructure and creation of sustainable human settlements. • Defence and security - contributing to national efforts to build a safer country. • Industry - in support of an efficient, competitive and responsive economic infrastructure. • • • •
Communicating South Africa’s science triumph Let’s face it – the story of the Square Kilometre Array (SKA) sounds a bit over the top, radical. At best, a good example of verbosity. Patsy Scholtz talks to science journalist, Sarah Wild.
he biggest science project on earth? The most ambitious global science and engineering quest? Detecting signals from the beginning of the universe? That was exactly what prompted Sarah Wild, science communicator, to write Searching African Skies: The Square Kilometre Array and South Africa’s Quest to Hear the Songs of the Stars. The SKA has all the ingredients that shaped Sarah’s life thus far. It is challenging as a project, exciting and fascinating. Making it digestible to the layman, however, poses a different challenge. How does one convey such a large volume of knowledge and the magnitude of possibilities slumbering within the SKA project and waiting to be unlocked without boring your audience to tears? Sarah chose to overcome this challenge by combining her seemingly erratic and contradictory background with exactly what she loves most – writing. Very little in her education and career suggested that she would become an integral catalyst in communicating South Africa’s spectacular science triumph. At school she studied English, Maths (higher grade), Physical Science, History, French and Afrikaans. Her subject choice at university is a random selection of what she loves most, leaving her with a BSc – ‘mainly because it was challenging’ – with majors in Physics, Electronics and English Literature. At Rhodes University her Dean suffered maddeningly each year when a time table needed to be organised, especially, when she decided to do a BSc (Hons) in English Literature. Becoming a science journalist was, according to Sarah, an accident. ‘I arrived in Johannesburg at the beginning of 2007 with no plan, no money and no idea about what I wanted to do. At a breakfast with friends, someone said, “Why don’t you try subbing?” He gave me the details of the deputy chief sub at Business Day.’ Her CV, although impressive, bore evidence of teaching Physics to matric learners, English Literature to university students, administrative duties at the university, spiced up with waitressing and bar-tending. Her first interview for sub editing went as follows: ‘I have no experience and you don’t know me, but you really want to’. She got the job, only to quit it a year later for a mad adventure of back-packing through Europe. On her return she did a stint of freelancing as feature writer and sub-editing before becoming a features editor/acting editor of the Sunday Times Magazine. She admits that this did not really suit her. ‘I spent most of my day researching celebrities. So when Peter Bruce, the editor of Business Day, offered me a job as the paper’s deputy news editor, I jumped at it.’ Since 2010, Sarah has gained her dream
job as science and technology correspondent, and subsequently moved on to science and technology editor at the same newspaper. The book on the SKA once again came about, and mainly to solve a challenge Sarah found particularly frustrating. ‘There was never enough space to tell the story of the SKA properly. Working on a newspaper, you have to fight the dual pressures of newspaper space and newsworthiness. Also, when you work for a newspaper, you are constrained by the style guidelines. I wanted to tell the story of this amazing project the way I wanted to and written in my style,’ she declares. SKA is a global science and engineering project to build the world’s largest radio telescope. It will have 50 times the sensitivity and 100 times the survey speed of current imaging instruments. South Africa won two-thirds of the bid to host the project, thereby providing Africa an opportunity to play an increasingly important role in the global knowledge economy. According to SKA Africa, the mega-telescope will be powerful and sensitive enough to observe radio signals from the immediate aftermath of the Big Bang. It will search for earth-like planets and potential life in the universe, test theories of gravity and examine the mystery of dark energy. A prime objective of the SKA is to probe the so-called ‘dark ages’, when the early universe was in a gaseous form before stars and galaxies were formed. Scientists are optimistic that the SKA will allow many new discoveries. Sarah describes herself as a science journalist. ‘In some guise or another, I will be writing (because I write better than I do anything else) about science and its exciting ideas for the rest of my life’, she says. Writing Searching African Skies was easy – ‘just me with my laptop, and transcribed interviews and the question: I have a platform, what do I really want to tell people?’ However, the most difficult part was the aftermath: one puts so much energy and effort into a project, and when it is finished, everything pales in comparison. The majority of the book was written in six weeks to coincide with the anticipated SKA decision deadline and in conjunction with a full-time day job, there was a great deal of pressure. ‘Once it was written, I wasn’t quite sure what to do with myself!’ Sarah loves her job. ‘Every day I sit at work and learn new things and speak to fascinating people – what more could I ask for?’ She gets to travel the country and the world looking at interesting innovation and things that will change lives, and then tells people about them, and why they are so exciting. ‘One day, I want to go to Antarctica to view the great South African science being done down there. That would be one of the greatest achievements of my career.’
Sarah Wild with the Minister of Science and Technology, Mrs Naledi Pandor. Image: ASSAf Her advice to prospective science writers is to obtain a background in science, coupled with the ability to explain complex ideas simply. Sarah is still overwhelmed by the support for her book from the government, colleagues and people in general. South Africans are intrigued by the project and want to know more about it. Her book is a way for them to understand what this project is about and why it is so exciting for South Africans. The SKA is a huge confidence boost for Africa, she says convincingly. It will show the world what we are capable of, technology spin-offs will eventually change the way that we live with its data-processing innovations, and it will discover things that we haven’t even imagined yet. Even better, South Africa’s fascination with the SKA project has liberated Sarah Wild and her thorough understanding of the project, from what she describes as being a ‘geek’ at parties where the unwritten rule is that ‘science’ should rather be left at home, to being ‘cool’. ❑ Patricia Scholtz is the Communication Manager at the Academy of Science of South Africa.
Sarah Wild is the author of Searching African Skies: The Square Kilometre Array and South Africa’s Quest to Hear the Songs of the Stars. Sarah is an award-winning science columnist and the science and technology editor at Business Day. The book is published by Jacana.
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How do we measure historical Andries Kruger and Charlotte McBride, from the South African Weather Service, explain.
limatologists have warned about global warming and the potential negative consequences of climate change for many decades. Climate change is caused by the ever-increasing release of greenhouse gases into the atmosphere. The release of greenhouse gases is not new, so climate change should also be seen in the historical climate records. But how do climatologists measure the changes in the climate, for example temperature, over time, and what factors should be considered in relation to any changes? What is the difference between weather and climate? Weather is what the atmosphere is doing at a specific time and place. Climate is the average weather for a region for at least 30 years.
This weather station is well placed to record the weather in a particular area.
Image: South African Weather Service
Cities trap heat because the materials that are used in construction trap heat.
Image: South African Weather Service
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Climatologists agree that as people release greenhouse gases, for example carbon dioxide and methane, into the atmosphere they have the ability to change the global climate. Examples of human activities that release greenhouse gases are burning fossil fuels for energy and transportation, and agriculture. The term ‘global warming’ is used to define the rise in the global mean temperature over more or less the last century-and-a-half. Climate change is known to have resulted from this global warming, as regional climates changed in response. Many climatologists have attempted to measure how the climate has changed over time in particular regions, looking particularly at temperature. In order to do this they looked at historical climate data collected by national meteorological services around the world. In South Africa we have been measuring the weather at some places for the last 150 years. This record of daily, and in more recent times hourly, values is what makes up a region’s climate record. How do climatologists at the South African Weather Service analyse historical climate data to look for patterns or trends, of which temperature is arguably the most important? To do this, climatologists need to take several factors into account – where was the temperature measured and what instruments were
temperature trends? used for these measurements? The data sets obtained also need to be checked for possible errors. Measuring surface temperature When you measure atmospheric temperature it is important to know that you are measuring a value that is representative of the wider environment around the weather station. There are many factors that might negatively influence your reading, for example nearby obstacles, such as trees and built structures. However, if these factors stay the same over time, e.g. the nearby structure was built before the establishment of the weather station, then trends can still be measured accurately. There are cases where buildings and roads have later been built close to the station and these can have an influence on your readings. Other changes that can influence your measurements could be linked to changes in instrumentation, an increase in vegetation or even a change in the ground cover. More distantly, built-up areas may have spread or become more dense over time. The photograph on the previous page shows a weather station which is well situated and not too close to structures or trees.
Determination of patterns or trends in the data Climatologists use statistics to determine the trends in the climate time series. They usually use linear regression to establish a trend line, but other methods are also used. Having found a trend, it is also important to establish whether the trend is statistically significant. This is to check whether the trend observed is evidence of a pattern in the data or whether the trend is due to chance. The 5% level is usually used and, if significant, will indicate that there was probably only a 5% chance that the pattern (trend) observed was random or due to chance. What are the temperature trends observed in South Africa? Climate change will not only show up as shifts in the long-term mean of the climate, but is also shown by an increase in the frequency and severity of extreme events. Temperature trends around the world are reported regularly in several scientific
Trend lines A trend line represents a trend or a long-term movement in a data set that shows whether the magnitudes (e.g. sale prices, population, etc.) have changed over time. In the graph below, the blue line represents actual sales, while the trend line shows the increase in sales over time.
A graph showing a trend line for vehicle sales.
Linear regression Linear regression is a mathematical technique that is used to model the relationship between a dependent variable (y) and one or more independent variables (x). If there is more than one independent variable this is called multiple regression.
This graph shows the results of a regression analysis.
journals. Examples are the Bulletin of the American Meteorological Society and the International Journal of Climatology. The graph on the next page shows the trends in the annual mean temperature of 27 South African weather stations, for the period 1961 – 2011. We can see clearly that there has been a statisticaly significant warming trend over the particular period. Consistent with the rise in the mean temperature, warm extremes have also become more frequent, while cold extremes have been decreasing.
Urban heat island effect The influence of a city with its buildings and road surfaces on atmospheric temperature is called the ‘urban heat island effect’. Climatologists need to be aware of the possible influence of urbanisation (expanding cities) on the climate records of many weather stations, since many of them are located in or near large urban areas. The urban heat island effect is shown by a difference between temperatures in a city and that in the surrounding countryside. The higher temperatures in the cities are mainly because of the manmade materials used for construction that are able to trap more heat than the soil and vegetation in the country. The effect is more noticeable early in the morning and also when there is little wind. Climatologists who study climate trends must ensure that these effects do not influence their analyses and lead them to make incorrect conclusions as to what is happening to the atmosphere at a particular place over time.
How do climatologists detect errors in the climate data? Most weather services employ quality control procedures that are able to identify errors in the data that come in from the weather station network. The procedures include checks for impossible values and changes in the readings over very short time periods, which are unlikely to be real. Additional checks can also include the comparison of the readings of a weather station with surrounding stations, to check whether the measurements are representative of the region in which the station is located. However, when you want to analyse trends (patterns in data), some additional checks are a good idea. These might include checking sudden changes of the long-term averages (or means) in the data series and comparing trends between weather stations close to one another. Eventually, when all unreliable weather stations have been removed from their study, as well as any unreliable data records from those stations that are retained, the trends can be calculated.
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Mean temperature anomaly for 27 selected South African weather stations from 1961 to 2011 (base period: 1961 to 1990), based on preliminary data. The black line represents the 5-year running mean and the red line the linear trend. Image: Blunden, J., and D. S. Arndt, Eds., 2012: State of the Climate in 2011. Bull. Amer. Meteor. Soc., 93 (7), S1-S264
The figure on the left, from an article published in the International Journal of Climatology, shows the regions over South Africa that have become more prone to hot temperature extremes. It is evident from regional studies that warming trends, as well as trends in extremes, are not uniform but differ substantially spatially.
Summary of regions of relatively stronger warming (with more hot extremes) in South Africa from 1962 - 2009. Image: Kruger, A. C. and S. S. Sekele. 2012. Trends in extreme temperature indices in South Africa: 1962 – 2009. International Journal of Climatology
An old climate record.
Image: South African Weather Service
Climatologists of the South African weather service at work. Image: South African Weather service
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Climate change studies from an historical perspective – the way ahead Most weather services, including the South African Weather Service, are increasing their efforts to rescue, preserve and quality control the climate data records with which they are entrusted. The World Meteorological Organization has introduced several initiatives over the years to assist with the rescue and analysis of historical climate records. We know that isolated extreme weather events are usually difficult, if not impossible, to link to either natural variations in the climate or human-induced climate change. However, it is becoming more and more clear that weather extremes are increasing, and climatologists need to find the causes of these events. But as Peterson, Stott and Herring state: ‘explaining the causes of specific extreme events in near-real time is severely stretching the current state of the science’. Usually, shortly after the occurrence of an extreme event, the public and media ask a weather service whether the event occurred because of climate change. In most cases these and similar questions are extremely difficult to answer. However, scientific thinking on this issue has moved on and now it is widely accepted that the causes of
As the climate changes and warms, droughts may become more frequent. Image: South African Weather Service
individual weather or climate events can be explained, provided proper account is taken of the uncertainties related to them. ❑ Andries Kruger is employed as a Chief Scientist: Climate Data Research and Analysis in the South African Weather Service. He does climate change and variability research, general climate publications, ad hoc scientific projects, climate information requests, drought monitoring, as well as the quality control of climate data. He obtained a PhD (Civil Engineering) degree in 2011 at the University of Stellenbosch. He has published extensively, and is the author of a South African Weather Service series of publications on the general climate of South Africa. Charlotte McBride is employed as the Unit Manager of the Climate Data Unit within the Climate Service Department at SAWS. Her work involves ensuring that data on the SAWS climate database are quality controlled. Other responsibilities include making sure that paper documents are archived correctly and that data contained in these documents is digitised and becomes part of the climate database records. She has a passion for science education and holds a Master’s degree in science education. She has been involved in promoting science through exhibitions such as SciFest Africa for many years. She has also compiled two SAWS publications on using weather and climate as topics to educate young learners. References Nature Publishing Group. Heavy weather. Nature, 2011; 477: 131–132, DOI:10.1038/477131. Peterson, Stott and Herring (eds.). Explaining Extreme Events of 2011 from a Climate Perspective, Bulletin of the American Meteorological Society. 2012; 93(7), 1041-1067, DOI:10.1175/BAMS -D-12-00021.1.
FACULTY OF APPLIED AND COMPUTER SCIENCES LONG-TERM PARTNERSHIP
VUT Vaal University of Technology
The diploma in Non-destructive Testing (NDT) is registered with the Department of Education. Two new laboratories have been completed in the past year and are fully equipped. In its endeavour to offer state-of-the-art NDT, the Department invites industries into a partnership that will include among others the following:
(a) Practical work that includes projects from industry. (b) Moderation of practical examination papers. (c) Commitment towards placing our students for inservice training. (d) Company visits by staff and students. (e) Part-time vacation jobs for students. (f) Membership of the NDT advisory board. For more information, please contact the below persons:
Dr I Sikakana Head: Non-destructive Testing Technology and Physics e-mail: email@example.com Prof B R Mabuza Executive Dean: Faculty of Applied and Computer Sciences e-mail: firstname.lastname@example.org
A city in Belarus, a remote part of eastern Europe. Even in these remote areas, we are completely dependent on electricity. Image: Wikimedia Commons
Jan Smit explains the way that hydrogen could be used to help to resolve the world’s energy crisis.
Renewable energy: The role of hydrogen T he world is facing an energy crisis. A crisis that will escalate unless serious efforts are made to relieve it. Let us start by first focusing on energy and the increasing need for energy in modern society. The primary source of energy on Earth is the Sun. All energy we use today comes from the Sun. Energy from the Sun makes waves in the sea, causes winds and rain, and makes plants grow, and plants produce food for animals and humans. Coal, oil and gas are fossil fuels that were deposited millions of years ago as a result of plant activity using the Sun’s energy. We have become dependent on fossil fuels such as coal and gas to produce electricity on a large scale, on petroleum products for transport and for the cultivation of land for grain and other food for humans and animals. An unwanted byproduct of electricity generation is pollution. Carbon dioxide, acid rain, soot and fine dust are pollutants that cause serious threats to the Earth’s ecology and to our future existence. There is therefore a serious need for largescale production of renewable energy
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– energy that does not pollute in its generation. Let us look briefly at modern society. Humans became adapted to the old world (roughly before 1750 when the Industrial Revolution started) over many centuries. People worked and slept according to the day-night cycles determined by the Sun. People used their own muscles to work. Wood, animal oil and plant products provided heat to cook food and to provide warmth in winter. Transport was slow, with ox wagons, horse and donkey carts and wind driven ships. Communication was limited to messengers on foot, smoke and light signals and letters. Since the start of the Industrial Revolution in about 1750 the basic sciences, mathematics, physics and chemistry have developed rapidly. Technological developments that were based on the principles, laws and methods of the basic sciences influenced nearly all parts of modern society. In the previous century and the first two decades of this century, technological developments accelerated and influenced all parts
of modern society. Our world has changed enormously. Consider communication by cellular telephones, the Internet, TV and the role of satellites in global communication. Food preservation by freezing, canning or addition of preservatives has made us largely independent of seasons and distance. Travel by aeroplanes and motor vehicles brings far-away destinations within easy reach in relatively short times. All the electric appliances in our households, such as stoves, electric lights, and water heating were unknown a century ago. Fridges, hair dryers and many more appliances can be added to the list. And don’t ignore developments in medicine and health care and their consequences. Focus for a moment on one aspect of these developments. Consider the question: How would life be if all of a sudden electricity should disappear? It is apparent that human dependence on energy has increased tremendously in the recent past. There are two alarm signals that cannot be ignored or the consequences for humankind and the environment
Hydrogen is a colourless gas that glows purple in its discharge state, seen here in a discharge tube. Image: Wikimedia Commons
Hydrogen is abundant on Earth: all water contains hydrogen. At standard temperature and pressure, hydrogen is colourless, odorless, tasteless, non-toxic, non-metallic and a highly combustible gas, with the molecular formula H2. Hydrogen gas is highly flammable and will burn in air. Pure hydrogen-oxygen flames emit ultraviolet light and are nearly invisible to the naked eye – seen below in the faint plume of the Space Shuttle main engine.
Figure 1: A demonstration model of a hydrogen fuel cell device to generate electricity. Image: North-West University
could be disastrous. First, fossil fuels are limited and will certainly become depleted or unaffordable in the near future at the present rate of utilisation. These sources are not renewable. Second, the growing human population consumes more and more energy. An obvious solution is to find alternative sources of clean renewable energy. One such source is hydrogen. It is the simplest element, the first one on the Periodic Table. When hydrogen gas combines with oxygen gas, energy is released. If the released energy is in the form of electricity, it can be utilised for many purposes. How can the hydrogen in water be utilised in such a way? Modern technology makes this possible. How?
The Space Shuttle main engine burnt hydrogen with oxygen, producing a nearly invisible flame at full thrust. Image: Wikimedia Commons
This method of electricity generation may, in future, make a significant contribution to the supply of clean, renewable energy. This demonstration model can be scaled up to generate considerable amounts of electric energy. Try to answer these questions before referring to the lists below. What are the main advantages and challenges of this method of electricity generation? Main advantages 1. The Sun’s energy is available in abundance in most parts of the world. In South Africa the average annual radiation is about 700 W/m2 at noon. 2. Hydrogen is also available in abundance in water, in seas, dams, lakes, rivers and in the atmosphere, clouds and mist. ▲ ▲
Using hydrogen and sunlight A solar panel converts the Sun’s energy to electricity (see Figure 1). The electricity dissociates water in its two elements, hydrogen and oxygen in a fuel cell that operates in a reverse mode. This process is called electrolysis and it takes place in an electrolyser. The fuel cell is a new technological device, which is currently being optimised. The oxygen produced during electrolysis is allowed to escape into the air. The hydrogen is captured and stored in a container until it is needed to produce electricity. This type of cell has an advantage over solar cells, which can generate electricity only when the Sun shines. This solar-generated electricity can be stored in batteries, but batteries are bulky, heavy and the storage capacity is limited. A lot of energy is
needed to build a battery and when its useful life is over the old battery contributes to pollution. The process of electricity generation by hydrogen is illustrated in the demonstration model of a fuel cell device pictured in Figure 1. The components of this hydrogen fuel cell are (from left to right): n First the solar panels. The panels convert solar energy to electric current. This current goes through the two connecting wires to the electrolyser (second component). n This second component, the electrolyser, has a thin membrane. Distilled water is fed by plastic tubes from a water reservoir (between the solar panel and the electrolyser) to the membrane. At the membrane, the water is dissociated by the current from the solar cells into hydrogen and oxygen (electrolysis). The oxygen escapes into the air and the hydrogen accumulates in the third component, a cylindrical reservoir. n In the reservoir water prevents the hydrogen from escaping into the air. The accumulated hydrogen is then fed into the fourth component, a hydrogen fuel cell. n In the fuel cell (fourth component), as a result of the working of the membrane in the cell, the hydrogen combines chemically with oxygen in the air to form water and electricity. The water is allowed to escape freely. n The electricity generated by this fuel cell is then used to drive a fan (far right). The fan is last of the five components of interest in this demonstration model.
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3. The energy generated by hydrogen fuel cells is clean. No environmental pollution results. The only interaction with the environment is the release of oxygen into the atmosphere. Exactly the same amount of oxygen is needed to recombine again with the hydrogen in the fuel cell where electricity is generated and water is released. It is thus a clean energy carrier for renewable energy. 4. An advantage of this method over solar cells (on their own) is that the hydrogen can be stored for use when the Sun does not shine. It is more practical and more economic than storage of solar-generated electric energy in batteries. Challenges 1. Fuel cell membranes are still in the research and development stage. More economic, more efficient, longer-lasting fuel cells and electrolysers with greater
capacity to generate electricity than those in use at present need to be developed. Research and development is already being done. The Department of Science and Technology (DST) is financing such research in South Africa. 2. Safe storage of large quantities of hydrogen is a challenge. At present the hydrogen is stored as gas. It is compressed by the generating cell to about 20 bar. Other methods of storage are continuously being researched. At the heart of this method of electricity generation is the fuel cell. How does a fuel cell work? Is there as difference between the electrolyser and fuel cell used in our demonstration? These and other relevant questions will be addressed in a future article. ❑
Acknowledgements The author wishes to acknowledge Mr Frikkie van der Merwe: Chemical Engineer, Involved in Research on Hydrogen Fuels Cells and Dr Dmitri Bessarabov, Director: DST Hydrogen Infrastructure Center of Competence. SAASTA, NRF and DST provided financial assistance.
Professor Jan Smit is Manager, Science Centre, NWU, Potchefstroom Campus.
Diary of events Q Shows and exhibitions Iziko Museum, Cape Town Location: South African Museum From: 8 – 31 December 2012 This exhibition, curated by Fritha Langerman, uses Rattus norvegicus, the brown rat, as a means to explore the representation of species within museums of natural history. Rather than a discrete display, R-A-T is an exhibition dispersed throughout the museum. Furtively making its way into disused corners and cabinets, this spread introduces the rat in relation to ranging themes, suggesting manners in which museum display impacts on the understanding of species. Enquiries: Fikiswa Matoti Tel. 021 481 3897 email email@example.com Iziko Planetarium, Cape Town Coming soon For the December/January school holidays! Sunshine Simon and the dark day One day Mister Sun didn’t come up! So Sunshine Simon, a brave little sheep, and his friend Robert were sent on a quest to fetch Mister Sun. Did they succeed? Join them on their adventure and find out! 8 December – 15 January Monday to Friday – 11:00, 12:00 and 15:00 (excluding 25 December) Saturday – 12:00 and 15:30 Sunday – 12:00 and 15:30 Especially for children aged 5 – 12 Do the Stars Influence Your Life? An examination into ancient beliefs and modern claims. Many people today believe that, somehow
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or other, the stars affect their lives. Astrology columns flourish in newspapers and magazines. Almost everyone knows what ‘star sign’ they were born under. Where did these beliefs originate and, more important, does astrology actually work? 1 October – 5 October Monday to Friday – 13:00 Suitable for teenagers and adults The Endless Horizon – Exploration through the ages In this presentation, we concentrate on the great ages of exploration and focus on explorers who typify each era, from the seafarers of old to the modern-day space explorers. We join Columbus, Dias, Da Gama and Cook on their sea voyages. We discuss, amongst others, Copernicus, Galileo, Newton, the flight of the Wright brothers and space exploration. This is a fascinating story of man’s reach beyond his known world! 10 December 2012 – 15 January 2013 Monday to Friday – 13:00 (excluding 25 December) Suitable for teenagers and adults
Talks, outings and events The Cape Bird Club Outings and talks Evening meetings are on the 2nd Thursday of every month at 20h00. We meet at The Nassau Centre, Groote Schuur High School, Palmyra Road, Newlands. Visitors and non-members are very welcome, tea and biscuits are served afterwards. Thursday 8 November: Adventures in search of nocturnal birds – John Carlyon Sun 21 October: Bergsig Estate in the Breedekloof Valley & Rawsonville Area. Booking
is essential. Lifts can be arranged. Contact Anne Gray at firstname.lastname@example.org or 021 712 1231. Tues 23 October: Cape Point Vineyards, Noordhoek. Leader Simon Fogarty on 021 701 6303 Co–ordinator Anne Gray on 083 311 1140 Sat 03 November: Rondevlei. Leader Merle Chalton on 021 686 8951 Tues 6 November: Silvermine Sunbird Centre. Co– ordinator Anne Gray on 083 311 1140 Sun 18 November: Porcupine Hills Guest Farm, Theewaterskloof. Leader & Co-ordinator Mike Saunders on 082 882 8688
Diarise World AIDS Day: 1 December 2012 World AIDS Day on 1 December brings together people from around the world to raise awareness about HIV/AIDS and demonstrate international solidarity in the face of the pandemic. The day is an opportunity for public and private partners to spread awareness about the status of the pandemic and encourage progress in HIV/ AIDS prevention, treatment and care in highprevalence countries and around the world. Between 2011-2015, World AIDS Days will have the theme of ‘Getting to zero: zero new HIV infections. Zero discrimination. Zero AIDSrelated deaths’. The World AIDS Campaign focus on ‘Zero AIDS-related deaths’ signifies a push towards greater access to treatment for all; a call for governments to act now. It is a call to honour promises like the Abuja declaration and for African governments to at least hit targets for domestic spending on health and HIV.
Leading minds in engineering
University of Pretoria’s students support the MeerKAT/SKA initiative
A pioneer in microelectronics research The Carl and Emily Fuchs Institute for Microelectronics (CEFIM) in the University of Pretoria’s Department of Electrical, Electronic and Computer (EEC) Engineering has pioneered microelectronics research (both at electron device level and at circuits/systems level) in South Africa over the past 30 years. It is the home of the Electronics and Microelectronics Research Group, where radio frequency (RF) and mm-Wave integrated circuit (IC) design has emerged prominently as a research focus area over the past 10 years.
SKA scholarships A project team from the University’s Department of EEC Engineering is among a number of young scientists and engineers who are involved in research relating to technologies and systems for the MeerKAT telescope, which forms part of the Square Kilometre Array (SKA) Project. Seven undergraduate and postgraduate students are supported through SKA scholarships. A PhD project seeks to integrate a differential low-noise ampliﬁer, using a SiGe technology node, which is aimed at delivering for sensitive SKA receivers. These projects of the Electronics and Microelectronics Research Group are under the leadership of Prof Saurabh Sinha, Director of CEFIM.
Because the telescope that is being developed as part of this project will be a radio telescope, making pictures from radio waves instead of light waves, research conducted in the University’s Department of EEC Engineering will be able to make an important research contribution to this world-class project.
Providing a cost-effective solution Due to the number of front-end receiver arrays anticipated for the SKA Project, the research team aims to develop an IC-based solution, which will be cost-effective. It is envisaged that the SKA Project will require tens of thousands of focal-plane arrays, where the total number of front-end receiver chipsets could range from hundreds to thousands. This calls for an integrated solution, which will reduce the cost of each receiver array. To validate the research ﬁndings, CEFIM is also equipped with on-wafer measurement capabilities, supported by vector network analysis capabilities up to 110 GHz. The research team therefore aims to address a number of innovative concepts relating to IC receivers in the nominal mid-band SKA RF range, such as ultra-low-noise ampliﬁer development, variable gain control, improved I/Q phase and amplitude mismatch, instrumentation or mixed-signal IC design and the identiﬁcation of model parameters inﬂuencing circuit performance.
Leading minds in engineering Universiteit van Pretoria • University of Pretoria • Yunibesithi ya Pretoria Privaatsak • Private Bag • Mokotla wa Posa X 20 • Hatﬁeld • 0028 Suid-Afrika • South Africa • Afrika Borwa Tel: +27 12 420 2164/3637 • Faks • Fax • Fekse: +27 12 362 5000
Departement Elektriese, Elektroniese en Rekenaar-Ingenieurswese Department of Electrical, Electronic and Computer Engineering Kgoro ya Boentšenere bja Mohlagase, Elektroniki le Khomphutha www.ee.up.ac.za
KICK-STARTING THE CONGO Ecotourism is almost non-existent in the Republic of Congo. According to the United Nations World Tourism Organisation, European tourists visit 170 other countries before venturing there. So it comes as something of a surprise to hear that Denis Sassou Nâ€™Guesso, the countryâ€™s president, recently declared that he wants to see 10 per cent of GDP generated from tourism revenue within the next five years. Can it be done? The answer may lie, in part, with developments at Odzala-Kokoua National Park. Scientific editor Tim Jackson reports. TEXT & PHOTOGRAPHS BY TIM JACKSON
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f tourism generates none of Congo’s revenue, how does the country survive? It’s all down to oil. In 2011, the black gold represented more than 90 per cent of exports and 85 per cent of revenues. Now, the president is looking to spread the country’s financial eggs among a few more baskets. Congo has three standout destinations that should appeal to visitors. These are its national parks: Conkouati-Douli on the coast, bordering Gabon, Nouabalé-Ndoki in the north and Odzala-Kokoua in the north-west. Until recently, none provided suitable facilities for visitors. Clearly, meeting the president’s demands will prove a real challenge. Odzala-Kokoua National Park offers a ray of hope. Driven largely by Henri Djombo, the country’s Minister
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of Forestry Economy, the sanctuary is currently seeing a rejuvenation in both management and visitor appeal that is aimed at kick-starting the tourist industry in the national parks. Odzala is the largest and oldest of the trio, sprawling across 13 500 square kilometres of pristine rainforest in the Congo Basin. Home to western lowland gorillas and forest elephants (both highly endangered), it also surrounds a number of bais – swampy, grassy clearings that are visited by the forest’s animals. The park’s change in fortunes can be attributed to the coming together of parallel forces that are driving both conservation and tourism forward in a unique way. One of the main catalysts in this process is the Leadership for Conservation in Africa (LCA), an organisation established by African businessmen primarily to link business
and conservation and to influence national and international leaders in their field to support investment in the development of the continent’s conservation- related resources. ‘For conservation to work we really have to get rid of this whole “begging bowl” approach and integrate business principles into it,’ says Chris Marais, CEO of LCA. It’s an approach the organisation has been applying across Africa to exped-ite conservation projects since 2006. ‘We do not manage parks, nor do we manage tourism operations. We facilitate the processes by getting the right people – the stakeholders – around the table and focusing their energy in one direction. Once the project gains a momentum of its own, we can move out.’ LCA’s goal is to set up a public– private partnership that will enable
in partnership with the Congolese government. ‘People often say money is the solution, but it’s not. Good, dependable management is the best tool for success,’ he explains. ‘There are examples of wprojects that have plenty of financial backing but where the situation in the park is still disastrous.’
t was initially at the request of the European Union (EU) that African Parks became involved in Odzala. Having supported the project financially for 20 years, the EU was concerned about the park’s lim-itations and outputs, and in 2010 its support programme, ECOFAC, parted ways with the Congolese government. African Parks stepped in to fill the void and today receives support through a national grant and from the Réseau des Aires Protégées d’Afrique
Above: Eastern black and white colobus – or guerezas – are common in Odzala-Kokoua National Park. These were photographed at the site of Wilderness Safari’s new camp. Odzala is considered to be one of the richest areas for primates in west–central Africa. Left: There is only one road inside Odzala, and that runs for just 33 kilometres. There-after, rivers such as the Lekoli provide the only means of access to the park’s interior for conservation staff. Previous spread: Odzala-Kokoua is Republic of Congo’s largest national park, with its forests providing a haven for some of Africa’s most iconic animals such as the forest elephant and western lowland gorilla.
its plans to be managed by an independent foundation. ‘After the inaugural meeting, we were approached by representatives from the Congolese government. “We want you in Congo,” they said.’ Marais went to see Minister Djombo and recommended that the first thing to do was to form a national LCA chapter. The who’s who of business were invited to take part. In this case, LCA’s primary objective was to use tourism as a tool to foster conservation and community development. However, the matter of sound park management was not far behind. ‘Management is the most fundamental requirement for making sure that a park works,’ confirms Peter Fearnhead, CEO of African Parks, an initiative that specialises in protected area administration across the continent and is now in charge of Odzala
Quest 8(3) 2012 45
Above: Odzala contains a great wealth of birds. Forest specials such as these green pigeons leave the shelter of the trees in the early morning and gather in enormous flocks to feed on mineral-rich clay along the riverbanks.
Centrale (RAPAC), the EU-funded entity that facilitates conservation in the Congo Basin. ‘We built a strong relationship with the EU through our project in Garamba in the Democratic Republic of Congo,’ says Fearnhead, ‘and we started discussions with the Congolese government.’
46 Quest 8(3) 2012
It was fortuitous that African Parks’ approach coincided with that of the LCA. Fearnhead explains, ‘LCA focused on tourism development inside Odzala. We concentrated on integrated management, which needs to be in place for tourism to be successful.’ The two organisations took up complementary roles in support of the government’s move to put Odzala firmly on the map. ‘It was very useful to work hand in hand with LCA,’ Fernhead adds. ‘We have a shared vision.’
nother important player in Odzala’s turnaround is undoubtedly LCA patron, successful businesswoman and philanthropist Sabine Plattner. Publicity-shy, she revealed the origin of her passion for Odzala in a rare interview with Africa Geographic’s Peter Borchert. ‘I grew up in forests, so I’m part of nature and I’ve always lived with animals,’ she said. ‘When I was 14 I saw a documentary about chimpanzees and human behaviour. I have always been keen on chimpanzees and gorillas and I think this is where it started.’ Since 1971 Plattner has made regular visits to explore Africa. ‘On one trip to Mala Mala Private Game Reserve [outside South Africa’s Kruger National Park], I realised I wanted to be in the bush, but I did not want to be a tourist in the bush. I lost interest in being driven around, I wanted to go deeper,’ she recollects. She became more and more interested in Africa in general, wanting to know what was happening and getting to grips with comments such as ‘The Africans will not make it’. Then in 1994, when other investors were fleeing South Africa, Plattner began investing in the country. In 2004, she listened to Marais’s embryonic ideas about LCA. ‘I saw a chance to
get into Africa and do something. At the first council meeting I agreed to become a patron in my own capacity. Then I started becoming involved in conservation across the continent because whatever charity I support, I donate money only if I’m involved.’ Today Plattner works very closely with LCA. ‘Now I am in Congo and I have this project at Odzala which brings a lot of difficulties, a lot of hardship and costs me a fortune personally – but I am committed,’ she says. Her real passion is forests, and she confesses that discussions about chopping down rainforests make her feel ‘radical’. ‘People sometimes ask, “What are your gorillas doing?” and I tell them, “I am not saving the gorillas, I am saving something of substance”. The bigger ecosystem must be protected to save the micro ecosystem. The gorillas have to be saved, but let others do that.’ If Odzala works, then her vision is to take this model throughout the Congo Basin to try to save the rainforest, or at least the main parts of it, through sensible and sensitive programmes. Plattner wants the local people to be committed to fighting for their forests. It’s a concept already incorporated in the mission of LCA which, in 2011, launched its ‘Vision 2020’, a drive to conserve 20 million hectares of Africa’s rainforest by the year 2020. To get the tourism infrastructure developed for Odzala, and to provide the local communities with work and education, she financed the building of a camp for operators Wilderness Safaris. She has pledged to help with money for the community too. ‘Luckily,’ she says, ‘there are not too many people; just 40 000 who live in three main commun-ities on the park’s borders.’
Odzala-Kokoua National Park Founded in 1935, Odzala-Kokoua is the oldest of the Republic of Congo’s three national parks. Area At 13 650 square kilometres, it is also the country’s largest national park. Vegetation Mainly rainforest, with 4 400 plant species recorded, including distinctive groves of Senegal date palms Phoenix reclinata. More than 100 saline clearings, called bais, form a hub of activity for many of the forest’s animals. Animal life The area has a reputation as a stronghold for the forest elephant and the western lowland gorilla, although elephants have suffered recently at the hands of poachers. Birdlife Recognised as an Important Bird Area, the park shelters more than 400 bird species. Management Since 1992 the European Union has actively supported conservation in Odzala through its ECOFAC programme (Ecosystèmes Forestiers – Afrique Centrale), in collaboration with the government of Congo. More recently, the EU has committed €5-million to African Parks to manage the sanctuary. African Parks also receives funding from RAPAC and WWF The Netherlands.
hris Roche from Wilderness Safaris agrees. ‘The forest belt in the north of the country is home to very few people,’ he says. ‘It’s definitely the forgotten Congo.’ With financial backing from Plattner’s Congo Conservation Company, the operator is set to run its new-found ecotourism venture in Odzala, starting this month. ‘The DRC has the “sensationalist Congo”, the old Belgian Congo, but the territory once called French Congo (Congo Brazzaville) doesn’t feature on anyone’s radar,’ Roche adds. For Wilder-ness Safaris, one of Africa’s largest safari operators, it certainly made sense to collaborate with Odzala. ‘We are proud
Quest 8(3) 2012 47
Below: The African forest buffalo Syncerus caffer nanus is actually a subspecies of the betterknown buffalo of African savannas. Forest buffaloes are only about half the size of their southern cousins, and their coats are distinctly reddishbrown in colour. Native to the equatorial forests found in central and western Africa, they are common in Odzala.
48 Quest 8(3) 2012
of the number of biomes we operate in and where we bring a measure of sustain- ability, but the one glaring gap in African conservation ecotourism is in the rainforests. If conserving rainforests is part of our agenda, where can we do that best?’ Odzala definitely fits the profile, although Roche admits that one of the biggest challenges facing his company is convincing people that there are two Congos. Market-ing Odzala as a new destination, putting it on the map, employing and training members of local communities – these are all standard practice for the business. Making ends meet, let alone contributing to the country’s tourism coffers, is going to need patience. Roche expects to lose money for the first couple of years. Establishing a new venture in Kenya, which has a thriving tourism industry, and setting up a similar operation in Congo are at different ends of the continuum. ‘All of the usual challenges are amplified,’ he says. ‘Odzala is a blank canvas, it could be the apogee of ecotourism to date, bringing together researchers, the conservation entity, diversity and the community. Hopefully it will prove the catalyst to get Congo working again.’ Together the organisations that
have laboured so diligently to make Odzala work hope to see their model replicated throughout the Congo Basin. In late 2010, all the elements came together to give rise to the Odzala Foundation, a unique public– private partnership whose board members include LCA, African Parks, RAPAC, the Congolese government and the local communities. ‘The Odzala model is already being rep- licated with the assistance of LCA and African Parks in Nouabalé-Ndoki, where the Wildlife Conservation Society [WCS] has been working for some 17 years,’ says Chris Marais. ‘There, they face the same sort of tourism development problems as Odzala does, even though WCS has un-doubtedly done a good job with conservation. We are helping it to work within a more public–private partnership context – and this is where Minister Djombo has the vision. He realises that this is what’s going to make it work, and is not trying to control everything.’ It seems that while the president’s de-mands for an increase in GDP from tourism may take some time to mature, the signs indicate that Congo is moving in the right direction. ❑ Text & photographs by Tim Jackson. First published by Africa Geographic www.africageographic.com
Rainforests There’s something magical about rainforests. Perhaps it’s that they featured in the world of our childhood, where Tarzan swung through the trees and Mowgli was taught life skills by his animal family. However, if you’re planning a visit to one, you’ll need more than a romantic memory to prepare you for these undeniably challenging destinations. Whether you’re going to a montane tropical rainforest in Rwanda, Congo or Uganda, or a lowland jungle in West Africa, the Amazon or South-east Asia, you can be sure that your destination will be difficult to get to, that it will contain many biting insects and animals that are often difficult to see (or even identify), and that conditions will be hot and humid. Three of our colleagues, with between them heaps of experience in exploring the world’s jungles, share their ‘absolutely essential’ tips to ensure that you’ll be able to cope with confidence in these shirt-clinging, at times impenetrable but always exhilarating environments.
Equipment n Check whether your destination has electricity, commun-ication facilities, etc. Communication can be problematic and cellphone reception unreliable, though local towns usually have the latter. It may be cheaper to pick up a local pay-as-you-go SIM card than cough up for exorbitant roaming rates. n Camera essentials: lens-cleaning cloths; silica gel sachets and a camera-sized plastic container for storage; spare batteries and memory cards; a lightweight carbon tripod, if used. n Moisture and cameras are lethal companions, so try to avoid changing lenses too often, and don’t change memory cards in the rain. n A torch. Tim Jackson’s ‘really small torch has incredible reach’. Check your local camping store to find a similar one.
The first-aid box n Antifungal powder to dry your feet. n Blister plasters. n Antiseptic cream or petroleum jelly to protect against chafed skin. n Mosquito repellent. n Anthisan cream for insect bites. n Eco-friendly soap.
Clothing n Rule number one: Pack lightly. Extra weight on your shoulders and back will make you sweat and irritate your skin. Carry only sufficient water/isotonic drink, your GPS or compass and map, binoculars, camera and the day’s essential supplies in a daypack. n Light wellies or water-resistant footwear for crossing streams; leather is unlikely to dry overnight. n UV-protective long-sleeved shirts and trousers (zippered for conversion into shorts, if possible) made of quick-dry nylon or rayon, preferably impregnated with citronella to ward off mosquitoes, and a head net. n Light, breathable underwear; cotton undergarments can chafe. n Wet socks are unavoidable, so bring as many pairs as possible. n Peaked caps keep your eyes shaded and your spectacles dry. Wide-brimmed hats protect you against the sun in open glades. n A poncho covers you, your pack and your camera. (Take it off once the rain stops, as your sweat will soak everything underneath it.) Alternatively, a rainjacket is light, though not all- encompassing; an umbrella gives good shelter for changing lenses. n A small, quick-dry towel. Christian Boix, who has spent many years organising tropical birding tours around the world, swears by his. ‘I use it to dry my face and arms, refresh at streams and to resuscitate myself when I’m hot and sweaty!’ n Africa aficionado Simon Espley swears by a lightweight scarf to ‘protect you from the sun and from cool evenings in the mountains’. n Disposable contact lenses, if needed. ‘The humidity and rain turn our bodies into spectacle-misting machines,’ says Boix.
Quest 8(3) 2012 49
A new ship for polar research South African research has a new ship. Mike Lucas tells us about the new polar research and supply ship, SA Agulhas II.
fter nearly 35 years of service, South Africa’s well-travelled and much-loved but aging polar research and supply vessel, SA Agulhas, was retired in April 2012 after its final voyage to Marion Island, 2000 km south towards the Southern Ocean. Affectionately known as ‘the little red taxi’ that rolled and plunged its way through the tempestuous Southern Ocean, SA Agulhas has been replaced by SA Agulhas II, a vastly more modern, larger and more powerful R1.3 billion state-of-the-art polar supply and research vessel. Built in Finland, the new ship was handed over to South Africa’s Department of Environmental Affairs (DEA) at the Rauma yard on 4 April 2012. She arrived at the V&A Waterfront, Cape Town on 3 May. SA Agulhas II is managed by Smit Amandla Marine (PTY) Ltd. SA Agulhas II is world-class, so how can such a ship and her price-tag be justified here? The answer to this question lies in our rich heritage as well as our geographical and historical ties to the Southern Ocean, Antarctica and the sub-Antarctic Prince Edward Islands, a South African maritime outpost. South Africa occupies an almost
50 Quest 8(3) 2012
unique geographical position as one of the three major ‘gateways’ to Antarctica, along with South America and Australia/New Zealand. South Africa is also an original signatory to the Antarctic Treaty, which was signed on 1 December 1959 and ratified in 1960. The treaty’s purpose is to set aside and protect Antarctica, its surrounding sub-Antarctic islands and the Southern Ocean (mostly south of 60°S) solely and permanently for peaceful purposes and for cooperative scientific research. One of the conditions of being part of this treaty is that we must maintain a base on Antarctica (SANAE IV) and engage in cooperative research activities. The South African National Antarctic Programme (SANAP) fulfills this role by maintaining a presence on Marion Island that includes managing Marion and Prince Edward Islands and the surrounding 200 km exclusive economic zone (EEZ) as South African territory. SANAE IV conducts various forms of cutting-edge research in the fields of astronomical, atmospheric, meteorological, geological and life sciences research throughout the year. An important meteorological station is also supported on Gough Island.
SANAP’s brief includes providing logistical support for oceanographic research and weather observations in the Southern Ocean, particularly in the context of marine living resources and climate change. The SA Agulhas II will serve as a mobile scientific research laboratory for oceanographic and biological research, while continuing in its predecessor’s role of deploying and collecting weather buoys as part of an international collaborative effort to provide a national and global weather prediction service. The new ship will also support the research base on Marion Island as well as servicing the South African meteorological station on Gough Island in the southern Atlantic Ocean, a UNESCO World Heritage Site that is leased to South Africa by Britain. The capability of the new SA Agulhas II is far superior to its predecessor. Capable of a maximum speed of 18 knots (using 40 tonnes of fuel a day), SA Agulhas II (134 m length x 22 m width x 7.7 m draft and 12 897 gross tonnage) has a range of 15 000 nautical miles (27 000 km) at 14 knots (using 14 - 25 tonnes of fuel a day) and can stay at sea for 90 days. The ship has considerably
Above: SA Agulhas II at its V & A Waterfront berth in Cape Town.
Image: Mike Lucas
Left: SA Agulhas II undergoing sea-trials during winter in the Baltic Sea.
Right: PELAGRA is a free-floating sediment trap developed at the National Oceanography Centre, UK. It can be programmed to sink to any depth to about 400 m or so where it captures sinking particles known as ‘marine snow’. Image: Mike Lucas
in South Africa helicopters that the ship carries, which are also used for cargo transport. As a floating science platform, the ship is almost unmatched, with eight permanent laboratories covering 800 m2 of floor space, and six portable and fully serviced 8.5metre container laboratories that can be secured beneath the heli-deck. A completely novel feature is the 2.4 x 2.4 m ‘moon pool’ – rather like a lift shaft – which extends from the ‘scientific environmental hanger’ down through three decks and through the ship’s hull. This allows large sampling instruments to be lowered into the ocean even when the ship is surrounded by ice, or in heavy weather when conventional over-theside instrument deployments are risky. Another innovative feature is a ‘drop keel’ carrying sensitive echo-sounders that can be lowered 3 m beneath the hull, where it is acoustically quiet, to track the ocean floor or to measure ocean currents and the presence of fish and other small organisms. In the large environmental hanger, winches with 6 000 m of steel conducting cable allow deep-water instruments to be lowered to the ocean floor to make real-time measurements of the
better ice-breaking capability (DNV Ice 10, PC 5) than the old SA Agulhas and is able to break through 1 m thick ice at 5 knots. It manages this because of its powerful diesel electric propulsion system (4 x 3 000 kW main engines) that delivers more than double the power of the old SA Agulhas, combined with a bow and underwater ice-knife design that allows it to operate even in winter sea ice conditions. Powerful bow and stern thrusters easily manoeuver the ship sideways or backwards and a computer-controlled dynamic positioning GPS system allows the ship to accurately maintain position, or be programmed to steam to any designated way-point. The ship carries up to 98 passengers (including 35 scientists) and 52 officers and crew in comfortable one-, two- and four-berth cabins, each with internet, satellite TV, bunk(s), day-chairs and desk(s). Passenger facilities include an internet-connected ‘business centre’, a serviced dining room, a number of lounges, numerous bars, a library, a lecture theatre, a gym, a hospital and even a sauna. Passengers and scientists can be transported ashore either by semirigid ski-boats, or in the two Oryx
A rosette of filled (24 x 20 litre) water-sampling bottles is hoisted on-board with a steel conducting cable. The orange instrument is an upward looking Acoustic Doppler Profiler (ADCP) that measures current velocities by tracking particle movements in the water. Image: Mike Lucas
Quest 8(3) 2012 51
Left: SeaGlider, developed at the University of Washington, USA, is a freely roving craft that can be deployed at sea for many weeks. Undulating from the surface to depths of about 500 m it travels slowly through the ocean and transmits data back to a lab at sea or on-shore via satellites. Image: University of Washington. Left below: A rosette of 24 x 20 litre water-sampling bottles stands on top of the trap-door access to the ‘moon pool’. The circular ‘docking head’ on top ensures the rosette can be carefully lowered through the hull below the ship. Image: Mike Lucas
The lecture theatre on SA Agulhas II.
Image: Mike Lucas
A well-equipped gym for passengers offsets the effects of too much good food! Image: Mike Lucas
52 Quest 8(3) 2012
physical properties of seawater (e.g. temperature, salinity, oxygen content), while also capturing water from any desired depth using electronically triggered closing bottles. Experiments and measurements using retrieved water samples can be made in the permanent on-board labs as well as in the portable container labs. The stern of the ship has a telescopic ‘A-frame’ that allows instruments, including nets and dredges, to be deployed, retrieved or towed from the stern. These capture biological specimens that allow biodiversity to be assessed, a good indicator of the ‘health of the oceans’. Remotely controlled or free-diving underwater vehicles (ROVs), including floats and ‘gliders’ that measure various ocean parameters, are also deployed from this position and later transmit recorded data back to the ship via satellites. Sea-bed sediments can also be sampled at depths down to 5 000 m using deep-corers – rather like pushing a piece of plastic rainwater drain-pipe into the ground. By examining sediment layering and preserved microscopic organisms called foraminifera, such cores can provide a ‘window’ into Earth’s past climate. Right at the top of the ship, perched above the ‘navigation bridge’ 24 m above sea-level, there is an enclosed observation tower that allows scientists to observe and record the numbers and movements of birds, seals and whales. Happily, Southern Ocean whale populations are recovering after the devastation caused by unregulated whaling activities over 60 years or so from the 1900s to 1965. One of the main functions of the ship is to re-supply SANAE and the other island bases. This is where the ship doubles up as a cargo vessel, with a capacity for 4 000 m3 of cargo – a volume equivalent to two
Olympic-sized swimming pools. The ship can also carry 2 600 tonnes of diesel for the bases, as well as 30 tonnes of lubricant and 250 tonnes of fresh water. To renew this supply, the ship makes its own fresh water from an on-board desalination plant. Equipment and materials can be lifted ashore with a crane on the foredeck capable of gently putting a 35 tonne load onto a 20 m high ice-shelf 25 m away. Alternatively, materials can be flown ashore by helicopters. The first short sea trials cruise to test key scientific equipment took place from 14 to 18 June 2012, mostly in False Bay. Apart from the usual teething problems, all the ship’s equipment performed well, allowing SA Agulhas II to go on a subsequent three week shake-down cruise down to the ice at nearly 60°S in July 2012, where the first oceanographic data were collected along the GoodHope monitoring line. As with any new ship, some teething problems remain that can, however, be resolved. The challenge now for DEA and SANAP is to effectively manage and accommodate the often conflicting demands of logistical support, supply and science on a multi-user ship. What is clear, however, is that SA Agulhas II will maintain South Africa’s leadership position over the next 20 – 30 years as a global player in Antarctica and the Southern Ocean. In doing so, it will provide a platform to educate and train the next generation of national and international polar research scientists. ❑ Associate Professor Mike Lucas is employed within the University of Cape Town’s Zoology Department. The ship-building project was led by Project Manager, Mr. Alan Robertson, Deputy Project Manager, Ms. Sharon ‘Shaz’ du Plessis and a team of specialist technical (Mr. Eric Walker), nautical (Captains David Hall and Freddie Ligthelm) and scientific advisors from DEA and a number of South African institutions.
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Books Q The magic of nature Adventure trails in Kirstenbosch. By Daphne Mackie. (Cape Town. Struik Nature. 2012.) What a magic book for children, young and old! Daphne Mackie has written an enchanting description of Cape Town’s beautiful garden, which is also quite unique in that most of the plants belong to the fynbos – the Cape’s great indigenous floral kingdom. Daphne Mackie takes children along five adventure trails shown on the map of Kirstenbosch. What they will see and discover as they follow these paths is simply and accurately described, supplemented with her beautiful illustrations and photographs. She has added little myths and anecdotal stories such as The Story of van Hunks – who causes the cloth on Table Mountain and The Tree of Life, from which all trees are descended. The animals that can be seen are not ignored and birds, mammals and insects also feature. No child’s (or adult’s) Christmas stocking this year should be without a copy of this lovely book. Next time I go to Kirstenbosch I will be accompanied by her book, to follow her five magic paths! (Review by Margaret Aldridge.) Indigenous knowledge systems Traditionally useful plants of Africa – their cultivation and use. By Phakamani m’Africa Xaba and Peter Croeser. (Cape Town. Cambridge University Press. 2012.) This is the fourth book in Cambridge University Press’s Indigenous Knowledge Library and is not only interesting in its own right, but provides a useful supplement to the indigenous knowledge systems required by the school curriculum. Africa is particularly rich in knowledge and folklore about plants, with its populations depending on plants for food, medicine, shelter and craftwork over the centuries. This knowledge base has built up and been handed down through the generations, now passing into written records. The most widespread early societies in Africa were hunter-gatherers, followed by nomadic pastoralists. Hunter-gatherers were constantly on the move and harvested all plant and animal food from the wild. Nomadic pastoralists were seasonal migrants, moving their domesticated animals from one area to another according to the availability of grazing, water and shelter. Agriculture first developed about 6 000 years ago – and subsistence farming started to become the dominant social system in Africa. All three of these early societies developed extensive knowledge of the wild plants around them. The plants were used for food, medicine, charms, essential crafts and shelter.
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The first section of the book looks at these early peoples in some detail, providing an excellent background to the development of indigenous knowledge systems. Three chapters concentrate on the plants used for food, plants used for crafts and plants used for medicine. The book then carries on to a really useful section on growing plants, which should stimulate a lot of interest in growing not only indigenous plants, but also plants used for food. The reference section covers biomes of Africa, plant and seed resources and information about botanical societies and research institutes. There is also a very useful guide to the plants mentioned in each chapter, as well as a glossary of terms. This is an excellent and inexpensive book that I would recommend for any classroom, library or bookcase. Conflicts Save me from the lion’s mouth: exposing humanwildlife conflict in Africa. By James Clarke. (Cape Town. Struik Nature. 2012.) A few days ago I saw a small article in the local newspaper about the potential loss of the Virunga National Park, home to some of the world’s last mountain gorillas. For some years now this park, in the eastern part of the DRC, has fallen foul of the conflict in the region, with rangers battling intruding rebels as well as poachers. Now it seems that the park is under an even greater threat – the potential for oil exploration beneath its soil. The DRC government openly state that if they decide that oil is more beneficial to the country than gorillas, the oil will win. This is an extreme example of how the desire – and need – to conserve animal species can come into conflict with the desires and needs of the populations who live around or among those animals. In Save me from the lion’s mouth, James Clarke talks about the far less well-known and publicised conflict between rural people who live on the edges or within the great parks of countries such as Kenya and Tanzania. The countries who host these parks are dependent on donor money from Europe and North America – and these same donors dictate policy, without regard for the welfare of the local people. It is no wonder that people in villages that are affected by marauding wildlife have little respect for the concept of ‘ecotourism’. James Clarke documents a growing resentment among rural communities close to game reserves who see no economic benefit accruing to them and warns that this may threaten the very existence of Africa’s game reserves. Clarke concludes, ‘Africa’s wildlife is a major world heritage but it must never be forgotten that the custodians are Africas.
Q Books Whatever the answers are to preserving Africa’s great landscapes and its wildlife, the answers must be found inside Africa’. Those overseas must listen, understand the issues and respond responsibly. Managing diversity Shaping Kruger: the dynamics of managing wildlife in Africa’s premier game park. By Mitch Reardon. (Cape Town. Struik Nature. 2012.) The Kruger National Park is made up of savanna – Africa’s newest environment. This newness makes it particularly vulnerable to shifts in micro and macro ecosystem processes, so the management of the wildlife and its environment within this ecosystem is particularly challenging. Mitch Reardon is a former wildlife ranger – in Namibia and South Africa – who has now turned wildlife photographer. In this book he documents the origins of the park and its animals. In particular he is at pains to explain how essential an understanding of the biology and life cycles of the different species is to their successful management. Each of the major mammal species is described in some detail, with in-depth discussion of their biology and interactions with other park animals, richly illustrated with Reardon’s photographs. This is a wonderful reference book, containing information on some of our major mammal species and on the Kruger National Park, in the past and in its current form. It is an enjoyable, well-written read. Looking for food security The Hungry Season: Feeding Southern Africa’s Cities. By Leonie Joubert, with photographs by Eric Miller. (Johannesburg. Picador Africa. 2012.) Leonie Joubert has done it again. She has taken a subject that people think is cut and dried – all you need to do is plant vegetable gardens, right? – and shown that there is much more to food security than a few veggies at the bottom of the garden. As in Boiling Point: People in a Changing Climate she has told the story of food security or its lack, through the voices of people. She and Eric Miller took the lives of eight people in eight southern African places to look at the complexity of food security in urban areas. This in itself is an unusual approach – most studies of food security concentrate on rural areas. Urban areas are assumed to be secure – after all, there are shops down the road. But, as anyone who has looked into food security in any depth will know, this is a complex subject that is not
simply about access to food. As Joubert so eloquently states, food has been a major driver of our technological development over the past 12 000 years. We are now largely free of the uncertainties of whether or not there will be enough food tomorrow. There are massive surpluses of food produced, we can store food for longer and ship it further. Much of what we today recognise as food, would be unrecognisable to our grandparents. It is food availability that has allowed our cities to grow so big, and ironically, what has now produced lack of food security among many living in those cities. And it is not just about lack of food security. Within this apparent abundance of food there is childhood stunting and malnutrition and the illnesses associated with a modern, Westernised diet. The book tackles the most important question – why, when southern Africa produces enough calories and nutrients to feed the region, are so many people living with hunger or the fear of hunger? This journey through eight people’s lives in eight different regions is an enlightening one. Perhaps if the right people read it we may progress some way towards addressing this fundamental question. Stirring controversy Extreme environment: how environmental exaggeration harms emerging economies. By Ivo Vegter. (Cape Town. Zebra Press. 2012.) I used to read Michael Crichton’s books avidly, until he wrote a novel that was essentially backing climate change denialists. This book has a similar feel. In this book Vegter claims that many of the environmental issues that are pertinent today, climate change and its consequences, the detrimental effects of shale gas exploitation (fracking), a general concern for the conservation of nature and natural environments, are flawed. Worse than this, environmetalists will make the poor poorer. He talks eloquently about the way that scientists, environmentalists and the media use data selectively and then goes on to do exactly that himself. We need a balanced approach to the need to conserve our environment and recognise where humankind has harmed it and looking after the needs of the economy, particularly in the developing world. But that does not mean ignoring real environmental harms, which in the end will damage everyone, rich and poor alike. Having said that, this book is essential reading for anyone concerned about the damage being done to our environment. It provides a superb insight into the mind of a denialist and the way that someone can manipulate information to a particular end.
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Back page science Q
Sunita Williams on spacewalk NASA astronaut Sunita Williams, Expedition 32 flight engineer, appears to touch the bright sun during the mission’s third session of extravehicular activity (EVA) on 5 September 2012.
association, and in chromatin structure and histone modification, according to the biologists. These all ultimately influence the activity of traditional genes. In an overview paper in Nature, members of the project consortium declared that 80% of the human genome has at least one ‘biochemical activity’ assigned to it in at least one cell type. In addition, 99% of this DNA lies relatively close to a place on the genome where this activity takes place, suggesting some level of participation. Source: World Science, http://www.world-science.net
Manufacturing crack-resistant lightweight components
During the spacewalk of 6 hours and 28 minutes, Williams and Japan Aerospace Exploration Agency astronaut Aki Hoshide (visible in the reflections of Williams’ helmet visor), flight engineer, completed the installation of a Main Bus Switching Unit (MBSU) that was hampered by a possible misalignment and damaged threads where a bolt must be replaced. They also installed a camera on the International Space Station’s robotic arm, Canadarm2. Image: NASA
Cold cracking in high-strength steel presents major quality assurance challenges for the automotive and machine-building industries, since cracks are difficult to predict – until now. A new process can determine as early as the design stage if critical conditions for such damage can be prevented. This lowers development times and costs.
predictable. ‘We are able to compute the probability of cold cracking as early as the design stage of a component, and immediately run through corrective measures as well,’ explains Frank Schweizer of the IWM. Source: Fraunhofer-Gesellschaft
Smart fabric sets off the alarm German researchers have developed a new kind of anti-theft system, based on a woven fabric that triggers an alarm when penetrated by intruders. The smart fabric enables the exact location of the break-in to be identified, and is significantly cheaper than other burglary detection systems. It is also suitable as an invisible means of protecting entire buildings. Thieves are unlikely to realise the significance of this fabric, which looks innocuous but in fact incorporates a fine web of conductive threads connected to a microcontroller that detects warning signals emitted when the fabric is cut and triggers an alarm. This system can be used to protect buildings, bank vaults, and trucks against even the most wily of intruders. Vehicles parked overnight at truck stops are particularly vulnerable to attacks by thieves who slit open the canvas tarp covering the trailer while the driver is asleep and make off with the cargo. If the tarp were made from the smart fabric, the driver in the bunk would be immediately alerted. Source: Fraunhofer-Gesellschaft
Most ‘junk’ DNA not junk, studies find Courtesy of Nature, The University of Washington and World Science staff Far from being junk, the vast majority of our DNA is active in at least one type of cell, according to biologists who made a vast set of new results public on 5 September 2012. The scientists, participating in a project called the Encyclopedia of DNA Elements (ENCODE), published the work in a set of 30 research papers in the journals Nature, Science and Genome Research. The traditional definition of a gene is a region of genetic code that provides the blueprint for production of a particular molecule, or protein, within the body. DNA that lies outside those regions was, in the early 2000s, considered ‘junk’ DNA with no known function. The view of large zones of DNA as useless has been changing in the past decade, however, and the new findings suggest that this idea may have to be abandoned. DNA formerly called ‘junk’ is involved in important activities such as transcription factor
Cold cracking in metal.
Cars, roof structures and bridges should become increasingly lighter, with the same stability, and thus save energy and materials. New high-strength steel is superbly suited for the needed lightweight design, because it can also withstand extremely heavy stresses. Yet these materials also betray a disadvantage: with increasing strength, their susceptibility to cold cracking rises when welded. These minuscule fractures might form as the welded joints cool off – typically at temperatures below 200°C. In a worst-case scenario, the welding seams would crack. For this reason, many industrial sectors are reluctant to employ these promising highstrength steels. Scientists at the Fraunhofer Institute for Mechanics of Materials (IWM) in Freiburg, in conjunction with the Chair of Joining and Welding Technology LFT at Brandenburg University of Technology (BTU) developed a new process for making cold cracking more
The Fraunhofer smart fabric alarm. Image: Fraunhofer-Gesellschaft
MIND-BOGGLING MATHS PUZZLE FOR Q uest READERS Q uest Maths Puzzle no. 22
Win a prize!
Place the numbers 2, 5, 6, and 8 in the boxes to make the equation true.
Send us your answer (fax, e-mail or snail-mail) together with your name and contact details by 15:00 on Friday, 2 November 2012. The first correct entry that we open will be the lucky winner. We’ll send you a cool Truly Scientific calculator! Mark your answer ‘Quest Maths Puzzle no. 22’ and send it to: Quest Maths Puzzle, Living Maths, P.O. Box 195, Bergvliet, 7864, Cape Town, South Africa. Fax: 0866 710 953. E-mail: email@example.com. For more on Living Maths, phone (083) 308 3883 and visit www.livingmaths.com.
Answer to Maths Puzzle no. 21: There are 20 possible first moves in a game of chess. The winner of Maths Puzzle no. 21 was Thoriso Letsopha.
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kids love chemistry Getting the next generations excited about chemistry is important for humankind’s future. That’s why we’ve created “Kids’ Lab” in 15 countries, where the young ones can learn about chemistry and science in a fun, hands-on way. Little students and test tubes finally getting along? At BASF, we create chemistry. www.basf.com/chemistry www.basf.co.za Tel: +27 11 203 2400
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