Minutes of APO 3.5m User's Committee Phone Conference Monday, May 12, 1997 Attending: Tom Harrison (standing in for Walterbos), Alan Uomoto, Bruce Gillespie, Ed Turner (Chair), Michael Strauss (taking minutes), Chris Stubbs, Jeff Secker (arriving late). Ed Kibblewhite, standing in for Hobbs, did not attend. Agenda: Current status of Three-year Plan Current status of DIS. Optical counterparts to Gamma-ray bursts; what shall we do with targets of opportunity? The Future of DSC Upcoming negotiations with WSMR Three Year Plan Stubbs: new Primary Mirror Support system is in, and seems to rectify the major problems with the old system. It is now stable as it stands, although there is still some work to be done. Some aspects of the installation could have gone better; management of the effort might have been better. One of the issues that has come up is collimation. Focus has become much sharper; as you go out of focus, things degrade much more rapidly, a sign of poor collimation. We need a proper method of collimating the telescope. Gillespie: With the old system, there were probably several tenths of arcsecond image degradation due to mirror support wobbling, especially at 2 airmasses and above. Poor weather has meant that we have not yet fully tested this system on the sky. In particular, the automatic focus change with airmass probably needs to be recalibrated with new system. Next big thing: New guider with 1K thinned chip, 4 times the field of view of the present system. This should make quite a difference; we hope to be able to pick up a guide star anywhere in the sky at arbitrary position angle. This upgrade is planned for June, during a 5-night engineering run. A big shutdown for the entire month of August (monsoon season) is planned for a wide range of engineering tasks. The engineers are asking for a ten-day extension of this into September. Note that we do not have resources for KPNO-like shutdowns, wherein large numbers of people are swarming over the telescope, fixing many things simultaneously. A question to the committee: how painful is this shutdown likely to be, and in particular, how difficult would it be to see it extended significantly? Turner will be out at the site at the end of the week to talk to people about the schedule for the shutdown. Alan says that this seems a too long shutdown, given that long shutdown periods tend to be a bit inefficient. In any case, we need to see what would actually be done during those ten days, and see what the efficiencies are. Turner et al will discuss this, and send a note about this to the user's committee at the end of the week. DIS Walterbos has sent around an e-mail about current status of DIS. Excerpts follow: >The readnoise on the red side of DIS is much higher than it was before, >between 22 and 30 electrons, rather than 15. Even in a recent Halpha >imaging run the data were READnoise limited. It will be next to impossible >to be skynoise limited in spectroscopic mode. Even at the nominal 15 e >this may be the case, but that is still a factor up to two better S/N for >same integration time. >The issue is, will DIS chips be replaced, and when? Given the need for >funding for the secondary, we fear that we may be stuck with DIS in its >current mode for another couple of years; this would eliminate much of >gain obtained by the throughput advantage after re-alum. for the red side. >Clearly, replacing the chips would be the best solution and might avoid >a long hunt to fix problems with a very old chip. However, the time scale >for this replacement is the crucial issue. Uomoto: The high read noise is probably an electronics problems; it would require roughly 2 weeks of a skilled electronics technician's time (who is familiar with the electronics of this system) to diagnose and fix this. Gillespie: There are several possible people who could work on this: Richard Luccinio, Jim Gunn (when he's down at APO for the Sloan camera), or the new electronics technician who is being hired to replace Brinkmann (who has moved over to SDSS). It has long been a hope to use Sloan electronics for the DIS. Uomoto is building the ability to generate Sloan electronics for CCDs in his lab. Hope to get Advanced Camera chips into the DIS some time in the next year, or perhaps some Loral-like 2Kx4K chips from Stubbs. Walterbos has also indicated interest in wider slits, up to 4", for spectroscopy of diffuse objects. Slits are ~$1600 each. We have 1.5" and 2" slits in progress. If these turn out well, we can ask the same outfit to make 4" slits as well. Walterbos (via Harrison) will tell us exactly what he needs. Very high-dispersion gratings: Not yet converged on exactly what we want here. These cost ~$5-6K each. Bruce Balick is very enthusiastic, as are a number of people at UW. Another possibility is to use the echelle for the same science (i.e., take out the cross-disperser, and operate the echelle in long-slit mode in a single order with an order-sorting filter). Of course, the echelle is not in operation yet, while DIS is. Stubbs: There now exist CCDs with read noise less than 1 electron. If we were to have one of these on the echelle, this would be an instrument competitive with high-res instruments on much larger telescope, even Keck. These chips have 15 micron pixels; that could be really exciting. We had some discussion about whether the possibility of getting such a chip would be worth delaying the echelle for. Medium-resolution gratings: when these come in, we probably do not want to be in the position of having to switch gratings (between medium, and low) in the middle of the night, as this is a non-trivial task. Thus people applying for DIS time will need to indicate which resolution they would prefer, and Ed Turner, as scheduler, will have more work putting together programs that do not require a switch of grating in the middle of the night. Target of Opportunity Programs Turner: On Friday morning, Beppo-SAX found a gamma-ray burst with a good position; an optical counterpart has been found. Over the weekend, Turner tried to organize people to observe with APO. This organizational effort worked, in that people were agreeable to using the telescope for these observations. However, it took a huge amount of Turner's time, and and in the end, the weather was poor; no observations were made. Ideas are being floated around how to use APO to observe these objects synoptically. How do we set up a system to exploit the flexibility of our telescope to follow these very exciting objects? There will be a proposal written soon for this. Harrison: We should definitely put together a multi-institution proposal to follow-up these things up. There are people at each of the institutions have a particular interest in these things. XTE is also interested in following these things up, and generating good positions, so we may get as much as 10 of these a year. It is difficult to plan, because we don't know enough about these objects yet to know how they vary. Whatever we do, we have to avoid wasting telescope time. We need up front a description of how this will work, and who is in charge of making sure the data are taken. We need a target of opportunity plan, that all observers will know about. Stubbs and Margon will draft a policy document for how this should be done; we'll discuss this when we have that in front of us. Gillespie: look at what HST does for target of opportunity problems. DSC Gillespie: Will DSC be available for third quarter? Fermilab people have a last set of observations that they want to use it for. Stubbs: drift-scan capabilities with SPICAM have not been fully tested on sky yet. DSC will not be available as a backup for SPICAM in 3Q; it will not be kept cold all the time. WSMR Gillespie and Turner will meet with the WSMR folks on Thursday to discuss details of agreements with the observatory. We plan to ask them to pay a base fee per quarter, just to be involved. Also, they tend to give details of their observing needs only a few days in advance. Negotiations on how much advance warning is needed. We need to clarify policies to the user's community. There is a possibility that a vBNS link capability will exist between APO and essentially all APO sites (other than Washington State) which might improve throughput over the internet by a factor of as much of 5! Craig Loomis has taken over from Jim Fowler as an interim systems manager for the mountain, until someone can be hired permanently for the position. Last month's meeting approved. Next meeting is June 9, 1997. 12:30 EDT APO APO APO APO APO Apache Point Observatory 3.5m APO APO APO APO APO This is message 143 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