LPNHE on Wednesday: Euclid and LSST

Wednesday morning was the end of my time at LPNHE, so I went and talked to as many key figures as I could. Nicolas and I quickly went over things we owed each other in the near future for the SkyMapper SN survey, and then he had to run. Never write down your debts, especially not if you’re the debtor! he laughed as I made a to-do list.

Pierre Astier told me more about the design for Euclid, the flagship ESA dark energy mission, not entirely unlike WFIRST (or whatever they’re calling SNAP/JDEM these days). It’ll be a ~1-meter space telescope, with a set of filters for near-infrared work on high-redshift galaxies and a grism for slitless spectroscopy. Since there are no slits to select single objects, the dispersed spectral orders for all objects in the field can mix and overlap in the focal plane; I remember a talk from a wide-field meeting in Baltimore last year, on a clever method to untangle different orders using coded masking of parts of the focal plane. The mission will have weak lensing and baryon oscillation components (see this astrobite), but as yet no supernova survey is planned, so Pierre is looking into it. The short answer is that it doesn’t look good unless more attention is given to calibration, both by characterizing the filters before the spacecraft launches and by taking calibration data periodically during the mission. For an expensive space mission like this, and with the world’s calibration experts on tap at LPNHE, it really shouldn’t be a source of drama.

Pierre Antilogus gave me a tour of the hardware labs for the LSST effort in Paris. Power dissipation requirements for the enormous LSST camera mean they have to keep the camera as compact as possible, avoiding lengthy cables with large resistances; they’re actually keeping the electronics in the cryogenically cooled dewar with the detector itself. Magnetic couplings in the drive train for the enormous filter wheel reduce friction, hence risk of mechanical failure. To speed up the design process, the readout electronics are using FPGAs; different configurations can be auditioned to reduce the risk of crosstalk (a potentially significant source of bogus detections in science images, as we’ve been finding out with SkyMapper lately). Overall they’re doing some very impressive engineering work, but I’m quite content to leave it to the experts!

We then talked about the future of astronomy, especially in the US with perennially shrinking budgets (hear that, Congress? you should all think more about awesome), and how LSST influenced strategies for success in that constrained funding landscape. I haven’t yet read the recent NSF Portfolio Review, but my rough understanding of the bottom line is that the US astronomy community could either afford to keep its public-access observatories (like Kitt Peak) open, or fund graduate students, but not both. Since there’s no sense in having telescopes if there’s no one to analyze the data, NSF chose to close its public observatories. This means the playing field could soon be even more heavily dominated by large, rich institutions like Caltech and the University of California (“the 1%” in academic terms?), who have their own, privately-funded, restricted-access large telescopes.

Cosmology forms a huge chunk of LSST’s science case, but I’m personally more interested in spectroscopy of rare transients that LSST will find. So are many other people, which might create some anxiety about Europe and ESO (who still have their public-access telescopes) dominating the transient spectroscopy scene; many US transient astronomers could be left out in the cold. We might be able to cope with this shifting ground by growing membership in consortia of smaller institutions, to buy out threatened telescopes and dedicate them to transient follow-up using money from NSF grants and, increasingly, private sources. Building a new telescope is a lengthy, trouble-prone process, so if we could save reliable workhorse telescopes like the Mayall 4-m from being mothballed, we could get a lot more good science from them.

One last useful thing I learned is that there are foreign exchange programs for scientists! Sounds like there’s a pot of money set aside for travel between France and Australia which I didn’t know about. I’ll see whether that’s something I can take advantage of.

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About Richard

I'm an American scientist who is building a new life in Australia. This space will contain words about science and math, but also philosophy, policy, literature, my travels, occasional rants, all sorts of things I find strange and awesome. The views expressed in this blog do not necessarily reflect the opinions of my employer at the time (currently University of Sydney), though personally, I think they should.
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