Design and preliminary test of a precision segment positioning actuator for the California Extremely Large Telescope primary mirror

Kenneth R. Lorell; Jean-Noel Aubrun; Robert R. Clappier; Ben Shelef; Gad Shelef

doi:10.1117/12.459974

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30 January 2003 Design and preliminary test of precision segment positioning actuator for the California Extremely Large Telescope primary mirror

Kenneth R. Lorell, Jean-Noel Aubrun, Robert R. Clappier, Ben Shelef, Gad Shelef

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Proceedings Volume 4840, Future Giant Telescopes; (2003) https://doi.org/10.1117/12.459974
Event: Astronomical Telescopes and Instrumentation, 2002, Waikoloa, Hawai'i, United States

Abstract

In order for the California Extremely Large Telescope (CELT) to achieve the required optical performance, each of its 1000 primary mirror segments must be positioned relative to adjacent segments with nanometer-level accuracy. This can be accomplished using three actuators for each segment to actively control the segment in tip, tilt, and piston. The Keck telescopes utilize a segmented primary mirror similar to CELT employing a highly successful actuator design. However, because of its size and the shear number of actuators (3000 vs. 108 for Keck), CELT will require a different design. Sensitivity to wind loads and structural vibrations, the large dynamic range, low operating power, and extremely reliable operation, all achieved at an affordable unit cost, are the most demanding design requirements. This paper examines four actuator concepts and presents a trade-off between them. The concept that best met the CELT requirements is described along with an analysis of its performance. The concept is based on techniques that achieve the required accuracy while providing a substantial amount of vibration attenuation and damping. A prototype actuator has been built to validate this concept. Preliminary tests confirm predicted behavior and future tests will establish a sound baseline for final design and production.

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Kenneth R. Lorell, Jean-Noel Aubrun, Robert R. Clappier, Ben Shelef, and Gad Shelef "Design and preliminary test of precision segment positioning actuator for the California Extremely Large Telescope primary mirror", Proc. SPIE 4840, Future Giant Telescopes, (30 January 2003); https://doi.org/10.1117/12.459974

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