Tracking algorithm for star sensors using CMOS devices

This paper presents an original tracking algorithm designed for star trackers adopting CMOS sensing devices. It compensates the effects of higher noise than in Charge Couple Devices (CCDs) by taking advantage of CMOS sensors capability to manage regional shutter time on small windows surrounding each viewed star. This capability allows acquired star frames to have different number of detected stars depending on the local value of the shutter time. In these conditions, sensor accuracy is equal to the temporal average of single frame accuracy. A comparative analysis of star sensitivity and sensor noise has been carried out considering both CMOS and CCD technologies. This analysis has estimated the value of the limiting detectable star brightness for different shutter times. Finally, attitude accuracy has been evaluated for each photodetector type and algorithm.