NOAO Abstracts for SPIE Meeting in March
WIYN Active Optics - A Platform for Adaptive Optics
Authors:
A. Code, C. Claver, L. Goble, G. Jacoby, D. Sawyer
Abstract:
The WIYN 3.5 meter telescope is sited on the south west ridge of Kitt
Peak yielding excellent atmospheric seeing conditions. As such, the
telescope and enclosure design was directed towards exploiting this
feature. The primary mirror was spun cast and figured by the Steward
Observatory Mirror Lab. and the secondary mirror by Contraves. In both
cases the performance exceeded the design specifications. The borosilicate
primary is actively temperature controlled to approximately 0.2 to 0.5 C
below the ambient air temperature. The telescope structure is also
temperature controlled and the enclosure is opened to the outside on
all sides, while all heat sources are vented to ducts carrying air down
wind of the facility. The primary mirror is actively controlled for low
order aberrations by 66 axial actuators which are adjusted open loop via
force matrix lookup tables and closed loop via real time wavefront
curvature sensing measurements. The active optics also include real time
collimation and focus control. The telescope drive and guider are capable
of providing tracking to a few hundreths of a second of arc. By employing
active telescope control at this level, it is possible to maintain
telescope and local wavefront distortion to a level where atmospheric
effects dominate the image quality. Since a significant fraction of the
power in the atmospheric disturbances is contained in image motion the
first step in adaptive optics control will be simple tip tilt. Studies
of higher order AO systems are being carried out, as well as tests
characterizing the telescope and site, and will continue in an attempt to
establish long term variances.
[NOAO at the SPIE Meeting in
March]
National Optical Astronomy Observatories, 950 North Cherry Avenue,
P.O. Box 26732, Tucson, Arizona 85726 Phone: (520) 318-8000
Posted: 02Mar1998