Surface error analysis for theuniversity of texas 7.6m telescope primary mirror

The techniques of modal control analysis derived by Creedon and Lindgren [1], an error analysis method proposed by Howell and Creedon [2], and various methods of finite element analysis are applied to a meniscus mirror of unusually large aspect ratio. The analyses predict the figure error for a set of characteristic error disturbances and correction strategies. Several arrangements of piston actuators are shown to be near optimum relative to the disturbance inputs considered, and in each case the related plots of modal coefficients, rms surface error, and the Howell and Creedon error analysis demonstrate the efficacy of the thin meniscus approach. In addition, the engineering approach to achieving a stable optical surface in this way is shown. Decomposing the distorted optical surface into modal terms gives it a natural order and allows the analyst to demonstrate that for some very harsh mechanical loads, relatively few modes are the chief contributors to the wavefront error. Therefore, by designing the active system for the control of the most significant modes, the mechanical engineering task becomes manageable.