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Proceedings Paper

Hobby-Eberly Telescope segment alignment maintenance system
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Paper Abstract

A sensing and control system for maintaining the optical alignment of the ninety-one 1-meter diameter hexagonal segments forming the Hobby-Eberly Telescope (HET) primary mirror array has been developed by NASA - Marshall Space Flight Center (Huntsville, AL) and Blue Line Engineering (Colorado Springs, CO) and implemented. This Segment Alignment Maintenance System (SAMS) employs 480 edge sensors to measure the relative shear motion between each segment edge pair and compute individual segment tip, tilt and piston position errors. Error information is sent to the HET primary mirror control system, which then corrects the physical position of each segment every 90 seconds. On-site installation of the SAMS sensors, ancillary electronics and software was completed in September 2001. Since that time, SAMS has undergone engineering testing. The system has operated almost nightly, improving HET's overall operational capability and image quality performance. SAMS has not yet, however, demonstrated performance at the specified levels for tip, tilt, piston and Global Radius of Curvature (GRoC) maintenance. Additional systems development and in situ calibration are expected to bring SAMS to completion and improved operation performance by the end of this year.

Paper Details

Date Published: 4 February 2003
PDF: 9 pages
Proc. SPIE 4837, Large Ground-based Telescopes, (4 February 2003); doi: 10.1117/12.458006
Show Author Affiliations
Mark T. Adams, McDonald Observatory/Univ. of Texas at Austin (United States)
Povilas Palunas, McDonald Observatory/Univ. of Texas at Austin (United States)
John A. Booth, McDonald Observatory/Univ. of Texas at Austin (United States)
James R. Fowler, McDonald Observatory/Univ. of Texas at Austin (United States)
Marsha J. Wolf, McDonald Observatory/Univ. of Texas at Austin (United States)
Gregory H. Ames, Blue Line Engineering Co. (United States)
John M. Rakoczy, NASA Marshall Space Flight Ctr. (United States)
Edward E. Montgomery, NASA Marshall Space Flight Ctr. (United States)


Published in SPIE Proceedings Vol. 4837:
Large Ground-based Telescopes
Jacobus M. Oschmann; Larry M. Stepp, Editor(s)

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