Apache Point Observatory 3.5m User's Committee Meeting January 13, 2003 Attending: Bruce Gillespie, Ed Turner, Michael Strauss, Alan Uomoto, Jon Holtzman, Jon Morse, Al Harper, Don York, Bruce Balick, Mike Shull Absent: Chris Stubbs, Rene Walterbos On Monday and Tuesday evenings of last week, members of the ARC community (roughly 15 people in each meeting) met in a pair of 2-hour meetings during the AAS meeting in Seattle. The primary focus of those meetings (and indeed, the current meeting) was a discussion of the various projects suggested to receive CIF funds this year, and how we might prioritize these projects. Bruce Gillespie will distribute minutes from last week's meeting. There are seven major projects which were considered; here is the jist of the discussion: The JHU/Chicago Near-IR spectrograph An NSF proposal for this has been submitted, which, if successful, would help pay for the building of this instrument. The instrument will be built at JHU, by Alan Uomoto and his team. Its ownership would then be transferred to Chicago, as part of the deal by which JHU got telescope time from Chicago. If the NSF proposal is unsuccessful, this instrument becomes quite a bit more expensive for ARC, because CIF funds could be required to make up any shortfall. The NIC-FPS The basic instrument is being built with funds from the University of Colorado as part of their buy-in to the 3.5m telescope. They have submitted a proposal to the NSF, largely to buy a large suite of filters. The CIF funds would be to get a z filter (not included in the NSF proposal) plus spare filters, plus a final payment on the detector. Echelle upgrade The instrument is currently read-noise limited for faint-object spectroscopy. Don York plans to submit an NSF proposal for a really low-read-noise chip, which assumes a cost-sharing with ARC, whereby the CIF would pay for the detector (and the NSF would pay for the manpower, electronics, etc). The estimated cost of such a chip is $130K, of which $30K may be supplied by George Wallerstein. UW multi-band imager This instrument would use dichroics to image in four broad bands simultaneously. It would have a field of view of order 5 arcminutes. The CIF funds would support the UW technical staff who would build it. "New top end" This refers to a series of improvements to the primary, secondary and tertiary mirror supports to improve image quality, both by removing slow-term drifts in collimation, and removing higher-speed harmonic image motion. A related issue is to put in the hardware to allow fast (tip-tilt) guiding at the secondary or tertiary. Recovery of DIS UV sensitivity We have long known that the coatings of the optics of DIS do not transmit below roughly 3800A. To fix this would cost of order $25K-50K. Telescope engineering projects/maintenance/improvements There is a long list of maintenance items that Jon Davis has compiled, concerning the smooth operation of the telescope, and the prevention of catastrophic failures (like the failure of the telescope drives last month). The main items are to improve the robustness of: The telescope drives The enclosure shutters The enclosure rotator system In addition, there are a number of CIF projects from previous years that are not quite complete, and which should be completed in 2003: Baffling NIC-FPS detector upgrade Observing software upgrade Echelle slit guide camera upgrade Finishing optics upgrade for DIS While everyone agreed that everything on this list was meritorious, and we would love to have everything, we would prefer to put our resources to being successful on a small number (2-3) of the items above, rather than spreading ourselves thinly, and making slow progress on all of the above. Even if we were in the happy position of having funds for all of the above, we would be limited by personnel (i.e., many of the key people would have important responsibilities for more than one item in the above list). We spent much of this meeting in a discussion of the balance between instrumentation, and work on the telescope. Ed Turner emphasized that when he first came on as director, everyone agreed that the telescope needed attention and that was more important than instrumentation for the short term. The telescope performance is dramatically improved since then, and the concensus has been that more resources should be put towards instrumentation. Having said that, it is clear that the telescope is the limiting factor in image quality on at least some nights (for imaging programs), and it would be very good to improve on that. A full characterization of the image quality problems is needed. We know that the telescope collimation does occasionally jump, and an on-going Shack-Hartmann monitoring project is trying to figure out what is going on. It was not clear to all of us whether this was the full story behind the degraded images on the best-seeing nights, or whether there was more going on as well. Al Harper reported that he has often seen images (with GRIM) in which stars appear double; he thought this might be due to oscillations in the primary mirror support. This last really sounded like something was broken, and fixing it belongs in a different category from a general program of telescope improvements to fix the image quality. We all agreed that further progress on image quality will require one or more dedicated people to investigate the problem(s). In the meantime, it would be very useful to have a summary of: -All known and possible problems affecting image quality (wind-shake? Primary mirror support? Not enough tension in the secondary truss? Catastrophic slippage giving rise to double images? Focus instability? High-speed vibrations caused by the drives?) -What is currently known (and not known) about their contribution to the error budget. -What we need to do to get more information about these things. Without this in hand, it is difficult to make decisions of the relative importance of these different items. Bruce Gillespie emphasized that we need to have this discussion of priorities, in the context of what the ARC institutions actually want to do scientifically. For example, do we want to tool ourselves up as a telescope optimized as a time-domain instrument, able to respond quickly to synoptic opportunities? Or do we want to emphasize superb image quality? An all-purpose observatory? This ended the discussion (for this meeting) of this important question. DIS optics: In the last day or two, a problem in the manufacture of the new optics for the DIS (red side) was found; it will have to be sent back to the manufacturers. The blue side is fine, and the new blue-side optics will be installed over the next week or so. Last month's meeting minutes are approved. Next meeting on Monday, February 3 at 11:30 AM East Coast Time. APO APO APO APO APO Apache Point Observatory 3.5m APO APO APO APO APO This is message 650 in the apo35-general archive. You can find APO the archive on http://www.astro.princeton.edu/APO/apo35-general/INDEX.html APO To join/leave the list, send mail to apo35-request@astro.princeton.edu APO To post a message, mail it to apo35-general@astro.princeton.edu APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO