The Giant Magellan Telescope Integral Field Spectrograph: Preliminary Design Review.

Published in the RSAA Lunations
Vol1 Issue52 1–30 June 2024

The week of 22nd July 2024, Mount Stromlo will be hosting the review panel charged with assessing the Preliminary Design Study for the Giant Magellan Telescope Integral Field Spectrograph (GMTIFS). GMTIFS is one of three major instrument/systems being designed for the GMT here in Australia alongside the Laser Tomograph Adaptive optics system also here at ANU, and the MANIFEST multi-object fibre feed under development at Macquarie University.
 
The project has been going for a while. It’s currently on its 3rd (possibly 4th, depending on when you start the clock) RSAA director and 6th baby (of which two are mine). This time has also seen me buy a house (twice, although we could only afford to keep one at a time), get married (once), create small children (twice), and take up dragon boat racing (ongoing).

So, what is a Preliminary Design Study? Large projects like GMTIFS (currently estimated to a final cost of $35M US dollars on delivery) follow a well-established development path. A Conceptual Design Study first roughs out the concepts, checks there are no showstoppers and establishes a clear user need for the instrument. GMT ran seven instruments in a cooperative down select process finishing in 2012 with GMTIFS selected as one of the first-generation instruments (first science will be with the G-CLEF high resolution spectrograph – GMTIFS needs the AO system in operation otherwise we horribly oversample even the excellent 0.5 arcsecond natural seeing).
 
The next stage is Preliminary Design. Here we develop all the concepts in considerably more detail. Particular attention is paid to how the parts fit together, both within the instrument and in how they connect (physically, electrically, emotionally, economically, etc.) with the outside world. A significant element of this stage is paying attention to the development and interaction of “design requirements” and “interface compliance”. Getting these elements right means you are building the right thing and that it’s going to operate properly. Getting it right at the scale of ELT instrumentation projects has required the AITC team to adopt a number of new approaches to engineering and engineering management. To this end - working alongside the ESO/MAVIS and Subaru/Ultimate teams - we’ve developed an engineering management framework that has been successful enough that a number of our partner organisations have adopted our methodologies.
 
A major outcome of the Preliminary Design Study is the first proper end-to-end cost and schedule estimate for what an instrument is going to take. The review panel’s report will be significant in recommending the project continue to Critical and then Final Design (with long-lead time items ordered, metal cut, glass polished, and detectors cooled during both these later stages). To that end it is important to select an expert review panel with skills across all the key disciplines.

The review panel is selected by GMT, not by GMTIFS, although there is of course consultation (and right of veto). These experts will be at the Observatory for the week of 22nd July, but we are only keeping them locked in the review from 9 am to 1 pm and so I’d like to take the opportunity below to introduce our visitors and encourage you to engage with them while they are here. Some know ANU well, and some will not have been here before. I’m sure very few of them bite so please engage with them and find out about the wider instrumentation community within GMT and beyond.
 
GMTIFS PDR review panel:
 
Brian McLeod – SAO/Harvard - Brian will be the review panel Chair. Based at the Smithsonian Astrophysical Observatory (SAO), Brian has a long history with astronomy instrumentation, particularly in the infrared. He is currently leading development of the acquisition and guiding system for GMT and heavily involved in the recent demonstration of the phasing solution for the seven-segment primary mirror.
 
Gabor Furesz – MIT – Gabor is an expert in astronomical spectroscopy of almost all flavours at optical to infrared wavelengths with experience on major ground and space-based sensor systems. We’re told he likes to look deep into the instrument design, and so it’s a good job we have a lot of depth after over a decade.
 
Helen McGregor – Macquarie-AAO – Helen is the mechanical engineering group lead and a veteran of delivering many astronomical instruments for a range of major telescopes.
 
Greg Mace – U.Texas at Austin - Greg is also Principal Investigator for the GMTNIRS high resolution JHKLM (l = 1-5 mm) spectrograph for GMT. GMTNIRS is an innovative instrument, using the same silicon emersion grating technology the GMTNIRS team has deployed with IGRINS/IGRINS-II on the Gemini telescopes. Greg will present GMTNIRS at RSAA on Friday afternoon.
 
Simon Morris – U.Durham – Simon cannot join us in person for the review this time, and so will dial in via zoom. Simon was chair of the Conceptual Design review panel for GMTIFS and so his longer-term view of the bigger picture will be invaluable.
 
William Podgorski – Harvard CfA – William leads the Systems Engineering group at the CfA, and has a long history of ground and space-based instrumentation for Astronomy. He is heavily engaged in the design/delivery of a number of GMT instruments including the G-Clef high resolution spectrograph, the GMACS multi object spectrograph, and the Active Guiding system (along with Brian McLeod) for GMT - which we will need to point all these instruments in the correct directions.
 
Julia Scharwaechter – NoirLabs/Gemini-North – Julia will be well known to anyone who has been here at RSAA for a while since, as a fresh-faced postdoc, she was one of the first to undertake science with WiFeS on the 2.3 m (working with Peter McGregor and Mike Dopita). Julia works on black holes and AGN feedback, and has extensive experience with NIFS (and critically, with AO IFS operations on a large telescope) on Gemini-North.
 
The GMT instrument team will be represented in person by:
 
Rafael Milan-Gabet – Rafael is the GMT instrument program manager, but also has a long history in interferometry, having worked on the original Keck Observatory interferometry program.
 
Aline Souza – Aline is the instrument program systems engineer. Systems Engineering is best characterised as the job of making sure the random musings of the scientists are actually translated (and are indeed translatable) into metal that can be cut, glass that can be polished and power supplies that deliver the correct phase of juice etc.
 
William Schoenell – William is the GMT software program manager. William will be staying with us at Stromlo for four weeks after the review under the RSAA distinguished visitors program. Both GMTIFS and the Laser Tomograph AO team will work with William to ensure our operationally challenging instruments concepts are properly integrated into the GMT observatory operations framework from the start.
 
So, do please engage with our review team when you see them and keep your fingers crossed for the GMTIFS review! I’m afraid the review is a closed door affair, not open to a general audience, but we’re always happy to answer questions and show off the protoype hardware.
 
Rob Sharp & the GMTIFS team 

Figure 1: The internal workings of the GMTIFS instrument are shown from different viewpoints. The central optical table, cooled to 100 ± 0.1 K, supportsthe cryogenic optical components. The foreoptics (yellow) hosts an atmospheric dispersion corrector and the cold-stop needed to reject stray thermal radiation. The Integral Field Spectrograph (red) half fills the lower chamber. The Imager (blue) is essential for source acquisition and AO calibration as well as taking spectacular AO assisted images. The On-Instrument WaveFront Sensor (purple) is in the centre of the table and provides prevision offset control at the 1 milli-arcsec level.