Wind deformation of the Subaru primary mirror

Tomio Kanzawa; Masami Yutani; Tomio Kurakami; Fumihiro Uraguchi

doi:10.1117/12.457986

4 February 2003 Wind deformation of the Subaru primary mirror

Tomio Kanzawa, Masami Yutani, Tomio Kurakami, Fumihiro Uraguchi

Proceedings Volume 4837, Large Ground-based Telescopes; (2003) https://doi.org/10.1117/12.457986
Event: Astronomical Telescopes and Instrumentation, 2002, Waikoloa, Hawai'i, United States

Abstract

I will report on the deformation of the Subaru Telescope primary mirror surface due to wind pressure. The 261 actuators, controlled precisely down to 0.01 N level, together with 3 fixed points maintains the optical figure of the primary mirror. The extra-force exerted by wind pressure, however, pushes the actuator pistons to cause their displacement while not affecting the fixed points. This results in an overall deformation of the primary mirror, which we measured. We first measured the difference in the actuator force of the sensors with and without wind pressure, i.e., with the dome shutter opened and closed. The force were then converted to the displacement of the 261 actuator pistons. The experiment was made under the wind speed of 5m/s with the telescope pointing toward the wind at elevations 30 and 60 degrees. The deformation pattern at EL=30 was triangular with three fixed points protruding, while that at EL=60 was saddle with the left and right pushed back. The value of deformation was ~2um. The patterns were interpreted that the wind pushes the entire mirror surface at EL=30 while it lifts the bottom part up at EL=60.

Citation Download Citation

Tomio Kanzawa, Masami Yutani, Tomio Kurakami, and Fumihiro Uraguchi "Wind deformation of the Subaru primary mirror", Proc. SPIE 4837, Large Ground-based Telescopes, (4 February 2003); https://doi.org/10.1117/12.457986

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