A Super AnTennA for Deep Space in SarDinia

by Giuseppe Nucera

The Sardinia Deep Space Antenna (SDSA) managed by the Italian Space Agency, ASI, is evolving to support humans on future interplanetary missions to the Moon and Mars

The SDSA enhancement process now under way will secure novel functions that will enable astronauts flying on interplanetary missions to communicate with their loved ones on Earth while ensuring privacy, or allow the direct acquisition of data generated by distant technologies from lunar bases, just to mention a few.

The SDSA represents the deep space configuration of the Sardinia Radio Telescope (SRT), which is among the largest ones in Europe with its 64-meter dish. Located in San Basilio, 30 km North of Cagliari, the telescope was built in 2012 by INAF (National Institute of Astrophysics) in partnership with the Italian Space Agency (ASI), the Sardinia Region and the Ministry of Education and Universities and Research (MIUR). The SDSA shares with the SRT a part of the infrastructure but has its own control center to communicate with spacecraft and provide navigation services. On top of its radio astronomy research activities to capture radio signals emitted by celestial bodies, a good portion of the Center's observational time is dedicated to space activities and radio science.

The SDSA was first deployed in 2017 to track the Cassini probe, a NASA-ESA-ASI mission, in its final stage when diving into Saturn's atmosphere. The ability to pick up even the faintest signal from interplanetary spacecraft is the SDSA's key feature that led it to be included in Nasa's Deep Space Network (DSN), a multi-mission system of antennas located around the world to monitor all space missions. Internationally known as DSN69, the Italian antenna was deployed, under the management of the Italian Space Agency (ASI) and in cooperation with NASA's Jet Propulsion Laboratory, to track the Mars landing of the InSight lander at the end of 2018.

"The size of the SDSA allows for incredible levels of performance, which is an invaluable feature for missions’ special operations, in emergency conditions and when necessary to ensure antenna redundancy capabilities," said Viviano Salvatore, Head of the Site, ASI.

Italy’s super antenna can support the DSN at topical moments, while the other antennas carry out a routine monitoring of operational missions.

The Sardina Deep Space Antenna, which is also used for national and ESA missions, is now going through an upgrade that will provide Italy with greater Deep Space Ground Capability, that is the ability to monitor from Earth future missions heading towards distant worlds.

The evolution rests primarily on the expansion to other frequency bands: the current X-band downlinks will be coupled by K-band downlinks in the near-Earth region, i.e. within two million kilometers of the Earth thus including the Moon, too. Beyond that distance, in the Deep Space region, the new Ka-band receive capability will be added and thus near and Deep Space transmit capability will be ensured.

The use of new bands will provide increased capacity to acquire data, with throughput increasing from about ten to 150/500 megabits per second. "This new level of performance takes into account the evolution of space missions: in the future, astronauts traveling to Mars will need to contact the control center but also their family, their doctor and share sensitive information in a secure fashion."

By upgrading technologies more data will be collected and transmitted more securely. However, the new frontiers of deep space pose a problem: the farther you go, the weaker the signal becomes. This is where the SDSA can be of great avail by tracking a spacecraft even with very low on-board communication power. This is also due to the antenna pointing that has switched from an open loop system to a feedback system.

"Once a probe signal is acquired, the SDSA adjusts its pointing locking onto the signal to improve its reception. It is a crucial capability in case of a very low received power," said Viviano.

Italy’s super antenna will become indispensable for acquiring large amounts of data from future lunar bases and sites, as well as signals from small CubeSat satellites and very low-power equipment placed on the lunar surface, especially if stable communication networks are not available.

To support the development of the SDSA, the Italian Space Agency, ASI, is setting up a new facility at Selargius, the SDSA Research Center. It is designed to support station operations and research activities related to space telecommunications and mission science content, providing suitable scientific and logistical support to university researchers engaged in the Antenna.

Do you remember the impact of NASA's DART probe against the asteroid?

Images taken by LiciaCube, the Italian Space Agency’s nanosatellite, have reached Earth, after a journey of 12 million kilometers, thanks to a special network the U.S. agency has designed to pick up signals in Deep Space: the Deep Space Network (DSN).

It’s the largest and most sensitive scientific telecommunications system in the world. It consists of three facilities spaced equidistant from each other – approximately 120 degrees apart in longitude –in California, Spain and Australia. Their strategic placement permits constant monitoring as our planet rotates thus ensuring that any spacecraft are always visible to at least one of the three giant antennas.

'Interplanetary surveillance' pursues many goals: monitoring the health and activities of a spacecraft; determining its position and speed accurately; and performing scientific investigations. By relying on the Deep Space Network, robotic explorers venturing beyond Earth do not need their own specialized space communications network.

The Network's highly sophisticated technology amplifies and decodes even the faintest signals picked up by interplanetary spacecraft, which are degraded by background radio noise emitted by celestial bodies in the Universe. The data is then processed by NASA's Jet Propulsion Laboratory and provided to mission science teams.

The precursor to the Deep Space Network was born in 1958 when three portable radio stations were deployed in Nigeria, Singapore and California to monitor and track the launch of Explorer 1, the first U.S. satellite.