CCD Stellar Attitude Sensor System for Spacecraft

The objective of the proposed program i to develop an improved compact celestial attitude sensor system to meet the advanced needs of space-based laser altimetry techniques for earth, lunar and planetary mapping missions. The system will also be used (and tested) in support of topographic measurements of the earth from NASA's high altitude aircraft which incorporate autonomous laser altimetry. Sub arc second measurement of a spacecraft's attitude will be accomplished in near real time through use of a star tracker which utilizes a CCD array sensor and array processing techniques to locate and identify 10 to 20 stars per image. A unique parameterization and error minimization for multi-star celestial attitude determination will provide for increased attitude precision compared to present star trackers. The algorithm will also be self-correcting for temperature related changes in the star sensor system (primarily focal length changes) and provide correction for residual distortions in the optical system. The final system will provide a compact, rugged, cost-effective solution to spacecraft and aircraft laser altimeter attitude determination.