On-orbit star tracker recalibration: A case study

Star trackers must be calibrated prior to flight so that they can make accurate measurements of star positions within the instrument field of view. This calibration is often performed in atmosphere and once the sensor is launched, it is not uncommon to observe a small shift in some of the calibration parameters. To maximize sensor performance, these parameter values must be corrected to better match the actual observations. In this paper, we explore the several practical strategies for on-orbit recalibration of star trackers. We consider both human-mediated batch-processing as well as autonomous, sequential algorithms. We base our results on orbital data from a number of Sinclair Interplanetary ST16 star trackers launched within the last year. Both approaches to on-orbit calibration can yield significant improvements both to sensor availability and geometric error.