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Crampton’s interest in spectroscopy and instrumentation

everything we wanted into GMOS and at the same

was first aroused by Jack Heard, the University

time not weigh more than two tonnes. We also needed

of Toronto professor who supervised his doctoral

to have a flexure control system. If you have something

research. In 1967, the freshly minted Ph.D. came to

the size of a Smart® car hanging off the end of the

what was then known as the Dominion Astrophysical

telescope, and you move it around, it will flex.”

Observatory outside of Victoria, B.C., intending, as he now wryly recalls, “to stay only for a few years!”

Based on the experience with CFHT, the HIA team knew there were big returns (and challenges) to be

Still there in 1994, at what became the Herzberg Institute

had by having the telescope and instruments stable

of Astrophysics, Crampton and his instrument group

and precise enough to capture spectra that required

found themselves with two challenging tasks: designing

all-night, or even multi-night exposures. This would

and building the optical assembly and wavefront

allow Gemini not only to provide more precise

sensors for two Gemini multi-object spectrographs

measurements than other observatories, as in radial

(one GMOS for each telescope) and designing and

velocities of Milky Way stars, but also to see very

building the ALTitude conjugate Adaptive optics for

deeply into the universe.

the InfraRed (Altair), the adaptive optics system for Gemini North. The HIA group got the jobs because

The challenges were especially great for the GMOS

of its track record or, as Crampton put it, “because we

team, Crampton said. This is because the Gemini

had heritage in both those instruments.”

telescopes were designed for the near-infrared portion of the spectrum while GMOS operates in the visible.

Along with the Observatoire de Paris, HIA had pioneered

The resulting instrument allowed a maximum field of

an innovative multi-object spectrograph (MOS) for the

view seven arcminutes in diameter compared to, for

3.6-meter Canada-France-Hawai‘i telescope (CFHT). It

example, Keck’s 20 arcminutes.

allowed users to capture the spectra of hundreds of objects simultaneously. Crampton and his colleagues

In an e-mail headed “GMOS vs. the World” sent

had also designed and built PUEO (Probing the

almost seven years ago to fellow astronomers Matt

Universe with Enhanced Optics, also the name of a

Mountain and Jean-René Roy, Crampton mused about

sharp-eyed endemic Hawaiian owl), an adaptive optics

why GMOS deserved the caché of a forefront scientific

system for CFHT, which was cutting-edge technology

instrument:

at that time. “First telescope – spectrograph combination that acts as a The Altair system was HIA’s task alone, while GMOS

complete system to exploit large 8-m aperture and improved

was a collaborative effort with the University of

image sharpness. Instruments for large telescopes are challenging

Durham and The Royal Observatory in Edinburgh.

because they must be correspondingly larger while at the same

For GMOS, Crampton was the Canadian principal

time more precise…. GMOS accomplishes this through carefully

investigator working with the overall project manager,

engineered design of the structure and its many mechanisms, as

Rick Munowinski (also at HIA). “I’d describe myself

well as continually compensating for variations due to changes

largely as a cheerleader for Altair,” he said.

in temperature and orientation of the instrument as the telescope moves. The entire GMOS system (optics, mechanics, software,

Faced with building two major instrument systems

detectors) was designed to take advantage of the best images that

with roughly the same delivery dates, the HIA group

the Gemini telescope produces.”

had expanded to almost 50, including students, and with the important addition of professional engineers.

The HIA instrument chief is especially proud of his

“I remember being blown away by those guys,” he

team’s contributions in four areas: optical coating, mask-

said. “They’d say, we do this and it’s going to move by

making, a multi-tasking component officially known as

a couple of microns. And by golly, they were right.”

the Integral Field Unit, and “active optics” as distinct from adaptive optics.

Having such engineering expertise was crucial in

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scaling up from the CFHT MOS system to GMOS,

The optical coating aspect underlines the cutting-edge

Crampton said. “The big challenge was how to get

research and development that was routine in GMOS.

GeminiFocus

Issue 38 - June 2009  
Issue 38 - June 2009  

GeminiFocus

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