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Proceedings Paper

Design and realization of ancillary control loops for the MMT adaptive optics system
Author(s): George Z. Angeli; Bruce C. Fitz-Patrick; Michael Lloyd-Hart
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Paper Abstract

The adaptive optics system of the Multiple Mirror Telescope is going to realize a high speed (1 kHz bandwidth) and high order (336 actuators) wavefront correction. However, to achieve the required 0.08 arcsec pointing stability the focal point of the Shack-Hartman wavefront sensor must be kept aligned to the Cassegrain focus better than 10 micrometers in spite of the non-common path tip/tilt error due to mechanical and thermal deformation of the telescope structure. The wave-front sensor must also be rotated with high precision to keep it aligned with the deformable secondary mirror in spite of the parallactic angle correction of the telescope. Our approach is to use a feed- forward loop to eliminate the adverse effect of deformation. A fast, deterministic field bus is applied to interconnect the actuators, sensors and computers. The bandwidth (500 kbs) and latency (less than 1 ms) of the DeviceNet serial bus is adequate to support our distributed control system. The field bus architecture simplifies and standardizes the control software as well as improves the reliability of the electronics by reducing the wiring.

Paper Details

Date Published: 2 August 2000
PDF: 10 pages
Proc. SPIE 4004, Telescope Structures, Enclosures, Controls, Assembly/Integration/Validation, and Commissioning, (2 August 2000); doi: 10.1117/12.393916
Show Author Affiliations
George Z. Angeli, Steward Observatory/Univ. of Arizona (United States)
Bruce C. Fitz-Patrick, Steward Observatory/Univ. of Arizona (United States)
Michael Lloyd-Hart, Steward Observatory/Univ. of Arizona (United States)

Published in SPIE Proceedings Vol. 4004:
Telescope Structures, Enclosures, Controls, Assembly/Integration/Validation, and Commissioning
Thomas A. Sebring; Torben Andersen, Editor(s)

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