Integrated modeling of jitter MTF due to random loads

Space borne astronomical telescopes are subjected to random dynamic disturbances from the host spacecraft that create line-of-sight (LoS) jitter errors, which decrease image quality. Special software tools and techniques have been developed to determine the degradation in image quality as measured by the modulation transfer function (MTF) and to identify regions of the telescope to be redesigned in order to minimize the LoS jitter response. A general purpose finite element program is used to find the natural frequencies and mode shapes of the telescope. Each of the optical surfaces for each mode shape is then decomposed into average rigid body motion and elastic deformation. Automated calculation of the LoS equations based on the optical prescription of the telescope provides the LoS response due to expected random loads. The percent contribution of each mode shape to the total LoS jitter is reported that helps pinpoint regions of the telescope structure to redesign. The LoS error due to the random input is then decomposed into drift and jitter components based on a specified sensor integration time. The random jitter is converted to a jitter MTF response function which may be used to modify the MTF function of the nominal optical system yielding the resulting optical system MTF in the operational random environment.