Improving Ground Based Telescope Focus through Joint Parameter Estimation
AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING
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Space Surveillance Telescope SST is a Defense Advanced Research Projects Agency DARPA program designed to facilitate the detection of space debris in earths orbit. In order to achieve optimal performance, focusing of the telescope can be conducted by retrieving phase information in the image to determine the amount of defocus and then moving the mirrors axial to shift the focal point. One of its unique features is that operates with a mechanical shutter thats speed restricts the telescope to collecting long exposure imagery. Long exposure imagery less than 10ms consequently averages the atmosphere, which creates a point spread function PSF which can mimic one that contains fixed aberrations such as focus and spherical error. The average atmosphere masks the static aberrations of the telescope in the image affecting the ability to achieve an optimal focus. This paper will explore the joint estimation of the focus and the atmospheric seeing parameter. The Cramer-Rao lower bounds for variance are computed to facilitate an understanding of the joint estimation problem. These bounds will serve to demonstrate how the average atmospheric transfer function makes sensing a focus error more difficult in the presence of noise.
- Optical Detection and Detectors
- Unmanned Spacecraft