AITC News
Published in the RSAA Lunations
Vol1 Issue23 1–31 December 2021
I should begin by thanking Rob Sharp for his Earth Observation piece last month, because it sets the scene nicely for some of the new directions we’re exploring downstairs in the detector labs. The most promising of these relates to the OzFuel mission, for which a Conversation article was just published by the team. You might like to read it – after reading this of course.
The AITC ‘Detector Program’ – not a new thing but recently bestowed with a capital ‘D’ and ‘P’, thus making it official – encompasses all of the joy and heartache associated with optical sensor arrays, their integration into instruments, their control and their characterisation. It’s a cross-disciplinary game, spanning solid state physics, electronics, cryogenics, vacuum engineering, mechanical engineering, software and optics. Perhaps it’s not surprising, then, that there aren’t many groups in the world building these systems, and hopefully it’s clear why the wider AITC engineering team is quite good at it. That said, we shouldn’t rest on our laurels: Continued success in this field depends on maintaining the expertise and access to new technologies that has buoyed the program of late. The AITC’s flagship instrument projects also present flagship problems that require a tactical approach.
Some of you may recall the establishment of a distinct ‘Detector & Electronics’ group back in 2018, along with an ambitious goal to put an infrared wide-field photometer called Emu on the International Space Station by 2021. This in turn gave birth to the ‘Rosella’ detector controller project, with the goal of reformatting burly laboratory detector readout electronics into something suitable for small satellites. While Emu itself hasn’t flown yet (we should have chosen a different bird), the core technology in Rosella (a better choice of bird) has allowed us to pursue the space-based remote sensing applications detailed in Rob’s November update. It’s my hope that this will position us to contribute to large space astronomy missions in the long-run.
But back to detectors themselves: Whether you see them as magical portals between photonic and data realms, or misbehaving and expensive metal sandwiches (for me it’s a bit of both), one can’t deny their importance in astronomy. Indeed, the recent Astralis consortium R&D workshop saw several talks where statements like “it all comes down to the detectors”, or “detectors are the main limiting factor”, or “detectors represent a risk unless…” were made.
No pressure, then.
It’s no secret that astronomical detector technology – particularly at infrared wavelengths – is a by-product of substantial post-WW2 US military spending; perfecting detector manufacturing processes is, after all, an expensive game. For better or worse, many astronomical discoveries have ridden on the coat tails of these investments. But what about the future? This is where meaningful engagement with the emergence of new technologies becomes important, especially as commercial R&D ‘business models’ take on new forms.
This philosophy is exemplified by the AITC’s ongoing relationship with commercial detector manufacturer Leonardo MW in the UK, which has seen the first ever samples of a large-format (1 megapixel) avalanche photodiode (APD) array delivered to our labs for testing and evaluation. These devices are extremely sensitive to short-wave infrared light, are virtually noise-free, and were developed with low-background astronomy in mind. Interestingly, they were funded not by the defence sector but jointly by the University of Hawaii Institute for Astronomy and NASA, at a level that we Australians can only dream of. This is all the more reason to keep the wheels of international collaboration and industry engagement well oiled.
Rapid development, deployment and demonstration of new sensors is just one way that AITC instrumentation can be given the edge in the coming years, not least because we have both the builders and end users of instruments right here on our pretty little hill.
But as disruptive as new detector technologies may be, there’s no escaping the exponential increase in the number of pixels that the next generation of optical instruments will bring. This creates new challenges for the downstream electronics and data processing systems, which must be bigger and faster without sacrificing performance. You can’t buy them at Jaycar either (although someone should probably check). For this reason we have an active detector control electronics agenda that aims to, among other things, reduce the risk of having nothing to plug our misbehaving metal sandwiches into in future. A small part of this puzzle is the approaching rollout of ESO ‘New General Controllers’ (NGCs) across the AAT, starting with Veloce and AAOmega in 2022, followed by HERMES and others. We’re also working with ESO on the design of the upgraded ‘NGCII’ system, which aims to future-proof ESO observatory instruments and, we hope, those closer to home as well.
Upgraded facilities are also on the horizon with work on the Space Detector Test Facility well underway, funded by the ACT government. Once complete, we’ll be able to measure absolute infrared detector quantum efficiency to a few percent. Alexey Grigoriev can regale you with tales of just how difficult this has proven to be, but also how the solution might be a $5 bit of hot metal (probably available from Jaycar).
With all this talk about the future, I should return to the present (good advice for anyone I think) and acknowledge the tireless efforts of Annino Vaccarella and Brian Taylor leading technical activities on true bread-and-butter projects like the DIRAC camera (4 m DAG telescope, Turkey) and additional Veloce cameras (AAT), all of which are being assembled in the labs right now. Mike Ellis is providing invaluable electronics support as ever, recently impressing us all by turning around a prototype camera module for the Pyxis project in the blink of an eye, lest we miss a free ride on a Falcon 9 rocket in the New Year. Of course, work continues on the behemoths that are GMTIFS and MAVIS too.
Ok, at this point I’ll admit I’m feeling a bit like a main sequence star, forging on only because the pressure to wrap this article up is perfectly balanced by a reluctance to think of a wry closing remark.
Perhaps a bold claim will do: By the time I’m asked to write another one of these, we should have two more projects out the detector lab doors, upgraded detector controllers at the AAT, and at least one detector electronics system in orbit.
At least now if you see me running away from Michelle you’ll know there have been some delays.
Jamie Gilbert
Figure1: Annino Assembles the Leonardo large-format APD test system
