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The WIYN Telescope Update (1Mar94)
(from KPNO, NOAO Newsletter No. 37, 1 March 1994)

During the last few months the WIYN Project achieved several important
milestones as we near the end of the construction phase.  Major
components of the control system have been completed and installed by
the University of Wisconsin Controls Group.  The telescope mount is now
able to slew and track under computer control and tests of the control
system and mount are underway using a finder telescope attached to the
optical support structure.  Glitches in the servo system are being
quickly resolved by the Controls Group and the early indication is that
the telescope will perform well.

The NOAO WIYN mirror group completed the laboratory assembly of the
active mirror support system, and then connected the mirror to the
supports and installed the whole assembly under the optical tower for
testing.  Interferometric tests using the same null lens used for
polishing demonstrated that the redesigned active axial supports
perform extremely well when pointed towards the zenith, the only
orientation we can test.  The rms figure of the finished, supported
mirror is 0.04 waves (at 6328 A), producing images with a mere 0.033"
FWHM, about a factor of 4 better than specified for the mirror
operating in the telescope under varying thermal conditions and
elevation angles.  The support system and mirror cell were shipped to
Kitt Peak in early February.  The mirror will be aluminized in the 4-m
vacuum chamber, and the cell will be "fit" to the telescope structure
before the primary mirror is installed.

Work on the secondary mirror was completed by Contraves, U.S.A. in
Pittsburgh, and the mirror has been shipped back to NOAO for
installation in the mirror cell.  The surface figure of the mirror is
0.030 waves RMS and meets WIYN's secondary mirror image error budget of
0.05 arcsecond.

Work also continues on the tertiary mirror cell and supports.  The
rotator assembly that mounts the tertiary mirror on the primary mirror
cell is complete and ready to be installed.

Requirements for the telescope control system graphical user interface
(GUI) have been completed.  NOAO has undertaken to write the GUI
software as part of the control system hand- off from the UW Controls
Group.  NOAO involvement at this phase will help assure that the WIYN
GUI is reasonably consistent with those at other NOAO telescopes, and
that operators and observers will find WIYN operations to be familiar.

Thermal testing of the enclosure is underway using the KPNO 10 micron
infrared camera and thermocouple probes throughout the structure.  In
nighttime tests with the dome vents opened up, the air temperature
within the telescope chamber tracked the outside temperature to 0.13
degree C RMS.  Surface temperatures within the chamber generally
tracked the air except for those surfaces exposed to the night sky
which cooled below the air temperature.  Reflective coatings will be
used to control surfaces where this is a problem.  No major sources of
heat were apparent in the telescope chamber even while the telescope
and dome drives were operating.

We expect the commissioning phase for the WIYN Project to begin in May
after completion of the optics installation and other major telescope
systems.  During commissioning the performance of the telescope will be
brought up to the levels specified in the project Scientific and
Technical Requirements.  Commissioning of instruments on WIYN (Hydra
and the WIYN Imager) will occur during late summer and fall, and WIYN
operations are expected to begin early in 1995.
                                                                                Matt Johns, Caty Pilachowski, Dave Silva

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