A method of monitoring the figure of the primary mirror of the University of Texas 7.6-m telescope is under study, in which slope errors are determined by reflection of laser beams from small flat mirrors cemented to the back of the thin meniscus primary mirror. The method requires calibration against a stellar image wavefront sensor but does not require continuous presence of the stellar image for operation. The method will be described, together with an error analysis. An optimum distribution of test points will be shown based on finite element and modal structural analyses of the mirror blank. A discussion of possible operational errors attributable to the laser system, based on similar experience at the University of Arizona - Smithsonian MMT Observatory, will be given.
Robert G. Tull,
Brenda W. Young,
"Primary Mirror Figure Control By Laser Autocollimation", Proc. SPIE 0444, Advanced Technology Optical Telescopes II, (3 November 1983); doi: 10.1117/12.937982; https://doi.org/10.1117/12.937982