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WIYN Project Review: October 1994 (1Dec94)
(from KPNO, NOAO Newsletter No. 40, 1 December 1994)

Commissioning of the WIYN Observatory continues to unfold smoothly, as
the Project begins the transition from telescope commissioning to instrument
commissioning.

The main optics systems continue to function quite well and routinely
produce the best images on Kitt Peak. Whenever the telescope is operated at
night, delivered image quality measurements are made at approximately
80^o elevation in the R band. For short (10 sec and less) exposures, image
sizes are typically in the 0.6"-0.7" FWHM range. About 10% of the time,
image sizes of 0.5" FWHM or less are measured. The image quality of
longer exposures is still limited by open-loop tracking accuracy, but image
sizes of 0.8" FWHM or smaller are often achieved over 60-120 s exposures.
At present, the number of measurements is insufficient to assess the
statistical significance of these image sizes. However, image quality
measurements are being made 3-4 days per week, so a statistically
meaningful determination should be available for publication in the next
NOAO Newsletter.

Image quality degradation at lower elevation appears to be consistent with
known atmospheric effects, such as differential atmospheric refraction, and
errors in the current open loop telescope focus lookup tables. These latter
errors are not unexpected, since these lookup tables do not yet reflect the
nightly thermal contraction of the telescope. Very simple closed loop lookup
tables that are tied to telescope temperature will be implemented shortly. A
more sophisticated closed loop focus adjustment based on measuring the
actual focus in real time will be implemented in the Instrument Adaptor
Subsystem next spring.

As mentioned above, long exposure image quality continues to be limited by
telescope tracking. Although telescope pointing has been improved to
approximately 5" RMS over the whole sky, non-random errors in the current
pointing model lead to position dependent open loop tracking errors which
can be as high as 1"/min in some parts of the sky. However, by 15
November, an improved pointing model as well as closed loop guiding
should be implemented.

The MOS Nasymth port Wide Field Corrector (WFC) lenses were finally
accepted in September. The lenses slightly exceed their original polishing
specification. They are currently being AR coated by Continental Optical
and are due back in Tucson in late November. The lenses will then be
assembled into their cell and installed at the Observatory. Once the WFC is
installed, the 1^o diameter field-of-view will be characterized
photographically to assess the magnitude of residual optical aberrations and
field distortions. The latter measurement is crucial for achieving accurate
fiber positioning by MOS/Hydra.

Unfortunately, since final MOS/Hydra installation and commissioning cannot
begin until these measurements are made and WFC installation is now
several months behind schedule, it now appears that MOS/Hydra will not be
available for science operations until at least mid-May 1995.

The WIYN Imager is making steady progress and should be available for
shared-risk science operations by mid-March 1995. Deploying the Imager
requires completing and commissioning three components: the Instrument
Adaptor Subsystem (IAS), the Filter/Shutter Assembly (FSA), and the CCD
detector system. The permanent IAS, which encompasses all the hardware
for guiding, wavefront curvature sensing, and closed loop focusing on the
WIYN Imager Nasymth port, is now scheduled for telescope installation in
late February 1995 and commissioning completion by mid-March 1995. In
August, Indiana University delivered a substitute IAS, which consists of a
duplicate of the IAS outer shell and a single axis stage. A ICCD borrowed
from KPNO has been mounted on this stage. This substitute IAS will allow
the Project to start
commissioning the FSA and the CCD detector system immediately. It will
also be used as a closed loop guiding testbed. In September, the FSA was
delivered to Indiana University. The FSA is currently being commissioned
and interfaced to the Harcon CCD control software.

As discussed elsewhere in this Newsletter, the initial WIYN Imager CCD
detector will not be a KPNO Mini-Mosaic with 15 um pixels as originally
planned but a thinned STIS 2048 X 2048 pixel device with 21 um (0.197")
pixels.

The University of Wisconsin Controls Group (UWCG) continues to work
towards completing delivery of the control system and to support WIYN
commissioning activities. Closed loop guiding remains the most significant
undelivered capability at this writing but should be implemented by
December 1994. Commissioning activities being supported include tuning
main axis servo performance, diagnosing control system bugs revealed
during commissioning operations, finishing documentation delivery, and
transitioning the day-to-day maintenance of the control system to the KPNO
based operations staff. This is expected to be completed by the end of 1994.

Work continues on the WIYN control system graphical user interfaces
(GUIs). UWCG supplied several engineering GUIs which are being used
routinely by the WIYN and UWCG staff to diagnose control system
problems. Several of the operations GUIs being implemented by the KPNO
Mountain Programming Group are now in use during normal night-time
operations. This GUI effort is scheduled to be completed in early 1995.

The WIYN Observatory was officially dedicated on 15 October under
memorable weather conditions. In the weeks leading up to this event, the
WIYN Project staff spent many days cleaning up and organizing the
Observatory, an effort which has already had great benefit for the Project
beyond the Dedication event itself.

The telescope is now routinely used 3-4 nights a week and it is anticipated
that this will increase to 5-6 nights per week by the end of the year. To
support this increase in night-time activities, the WIYN Project has trained a
second Observing Technician, Bridget Watts.

In recognition of the complex nature of this new facility, the WIYN Board
approved the allocation of one week per month during the first year of
science operations for engineering activities. This extended engineering time
will be used for normal facility maintenance as well as to resolve problems
that arise during the rest of the month. These nights will be allocated to
specific consortium members and returned to the designated institution if no
engineering is required or engineering tasks are completed early.

The current major project scheduling milestones are: (1) complete closed
loop guiding implementation by 15 November; (2) install WFC and begin
photographic assessment of the wide-field by 1 December; (3) complete
Imager commissioning, including IAS, FSA, and CCD detector
commissioning by 15 March; (4) begin shared risk Imager operations by 1
April; (5) finish MOS/Hydra commissioning and begin shared risk
MOS/Hydra operations by 15 May.

Dave Silva

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