Optimized mirror supports, active primary mirrors and adaptivesecondaries for the Optical Very Large Array (OVLA),

摘要

Abstract: This article first deals with general aspects of optimizing mirror supports. A wide variety of support topologies have been optimized by Nelson et al for unobscured entrance pupils. Optical forces and locations of point supports have been calculated here for annular pupils. Efficient topologies introducing a small amount of defocusing are also proposed for unobscured and annular pupils. Support efficiencies are given for each topology. Wavefront errors are estimated in the case of a defective cell, in order to specify tolerances on forces and geometries. The OVLA active optics is then discussed. The very thin, meniscus-shaped primary will be actively supported by 29 actuators and 3 fixed points. Actuator locations and forces have been calculated to minimize the mirror deflection under its own weight but also to allow a good control of astigmatism. We finally present a study of a concave adaptive secondary for the OVLA telescopes. As an initial result, we propose a defocus adaptive corrector with a variable thickness distribution. Conditions of use are defined, and performances are evaluated.!13