Effect of Dimensional Stability of Composites on Optical Performances of Space Telescopes

Abstract

To achieve high-resolution images from satellites, the dimensional-stability effect of telescope structure on optical performance should be considered in the operating environment. In this paper, the dimensional stability of composite telescope structure and optical performance degradation resulting from its dimensional instability have been evaluated under operating conditions. Dimensional-stability evaluation of the composite structure was achieved by a combination of precise deformation measurement and finite-element analysis of the composite-structure model. Thermal deformation of composites was measured by interferometer, and a brand-new dilatometer using an optical-scale sensor was developed for outgassing deformation measurement. The thermal/outgassing deformation of the telescope structure was interpreted as despace of the two-mirror Cassegrain telescope, and the optical-performance change resulting from despace was calculated in terms of the module transfer function (MTF) value. The MTF value change and image simulation based on the MTF value were shown for each case: original, thermal-deformed, and outgassing-deformed telescopes.