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WIYN Progress Continues (1Sep95) (from KPNO, NOAO Newsletter No. 43, September 1995) The WIYN Project achieved a major milestone on 15 July with the commencement of official science operations. The first three night block was devoted to the NOAO WIYN queue observing program, with Di Harmer as the WIYN Queue Observer. This was immediately followed by the first University block, a five night run for Bob Zinn and Sidney Barnes (Yale University). Although these runs were hampered by monsoon conditions typical of mid-summer in Tucson, all involved were very happy to finally make this transition. Early observers have been constrained to using the Imager, but as discussed below, MOS/Hydra is expected to be released for shared risk observations in mid-August. The telescope continues to deliver excellent images with the median Delivered Image Quality since June 1994 being 0.9" FWHM for the standard, benchmark 10-15 s R-band exposures. We have confirmed that under median seeing conditions, closed-loop guiding does not degrade the benchmark DIQ, and we achieve 0.7"-0.8" FWHM for long (15-20 min) exposures routinely. The biggest component of DIQ degradation remains rapid thermal contraction of the telescope, but by early September a closed-loop system for measuring telescope temperature and adjusting the telescope focus should be in place. We did experience a period of exceptional seeing in June. For five nights, the DIQ was 0.5"-0.6" FWHM with periods of 0.4" FWHM seeing. Purely by coincidence, a CCD with 15mm (0.15") pixels was being checked out at WIYN during this period, so we were still able to sample the PSF under these conditions. As noted in previous reports, the WIYN DIQ is mostly tracking atmospheric seeing when the active optics systems are working nominally. Thus, this period in June was a time of very stable atmospheric conditions. We continue gradually to improve telescope pointing. After improving the mechanical mounting of our azimuth encoders and fine-tuning our pointing model, the current "raw" all-sky telescope pointing accuracy is roughly 10" RMS. This is comparable to the current Mayall 4-m performance but much larger than the original goal of 2" RMS all-sky, as well as being larger than that of other modern telescopes (e.g., ARC which reports 2"-3" RMS all-sky pointing accuracy). Modeling of recent pointing data suggests that pointing accuracy of 6"-8" RMS all-sky may be achievable by further fine-tuning of the pointing model. Pushing below that range seems unlikely with the current friction encoders, which appear to drift mechanically with time. Possible replacement encoder systems are currently being investigated. We are also making progress in reducing telescope windshake. Test analog circuitry, which implements velocity and acceleration feedback into the elevation axis servo control system, has been installed and tuned. Comparison between encoder feedback errors and image motion errors shows that under windy conditions these errors are now following each other much more closely than in the past; i.e., motions in the image plane correspond in time and direction to position errors detected by the encoders. Image plane errors are still larger in magnitude than encoder errors but nonetheless smaller than they were under the baseline servo system. These results are encouraging, but more development and testing are required. This effort will be pursued during regularly scheduled T&E blocks this fall. We have deferred further investigation of the telescope "breakaway" problem at wind gusts above 20 m/s until later this year. In practice, this problem does not significantly affect observing efficiency since even on windy nights, normal operations are possible by closing the dome vents and pointing more than 30o out of the wind. In contrast, the installation of the closed-loop telescope temperature/focus correction system has higher priority, since that currently affects every observation every night. The Imager continues to perform well. Our Ha filters are scheduled for delivery in mid-August. Software for automating focus sequences should be installed by mid-September. An Arcon-IRAF User's Guide will be available as a Web page soon (see the WIYN Observatory link on the NOAO homepage at http://www.noao.edu). MOS/Hydra is scheduled to be released for shared risk operations on 18 August. For the release to happen on schedule, the Hydra commissioning team must accomplish three major tasks: achieve the specified fiber positioning accuracy of 0.2" RMS, release revised user documentation, and verify that the final version of the released software is robust and debugged. To facilitate the completion of these tasks, NOAO is allocating some of its July and August observing time to MOS/Hydra commissioning. Hydra commissioning will also be top priority during the normal WIYN T&E block in early August. The Instrument Adaptor Subsystem (IAS) achieved two major milestones since the last report: internal wiring was completed and the low-level control system code was implemented successfully in the lab. The IAS is scheduled to be shipped to WIYN in early August. Specifications for the mid-level and high-level control system interfaces have been completed and approved. Implementation of these interfaces should begin in late August. We hope to start night-time IAS commissioning in early October. Current control system activity is focused on cleaning up the various control system software interfaces and procedural documentation. This has delayed the implementation of the IAS interfaces and the closed-loop telescope temperature/focus compensation but will result in more efficient and robust telescope operations as well as easier maintenance. As part of this effort, we are verifying that the entire software system can be easily compiled and that it is all under version control. Although Science Operations have officially begun, further telescope and instrument performance tuning is still desirable and will likely continue for at least a year. To facilitate these activities, during the first year of Operations, the WIYN Project will be taking seven nights each month centered on full moon for "testing and engineering" (T&E). Activities during the first few T&E runs will include further pointing and servo performance testing, Hydra commissioning, control system upgrades and maintenance, and IAS commissioning. The next Project report should highlight early IAS commissioning progress as well as the first three months of science operations. Dave Silva
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