Image Signal Processing In Sub-Pixel Accuracy Star Trackers

Recent star tracker developments at JPL which utilize microprocessor-controlled large area imaging CCD arrays have included several novel techniques for maximizing the efficiency with which information can be extracted as well as corrected for electronic and opto/ mechanical distortions. Scanning algorithms which maximize the rate of obtaining target information, coupled with autonomous control of CCD and signal chain parameters, result from efficient task allocations between electronic hardware elements and operating software. Trade-offs between optical system and image processing software complexity allow sub-pixel star and image tracking using badly aberrated point spread functions by means of power series correction equations which define ideal image centroids from the aberrated image centroids. Star trackers employing these techniques currently under development at JPL are described.