Development of the Arcsecond Pico Star Tracker (APST)

The second generation star tracker estimates pointing knowledge of the satellite without a-priori knowledge. But star trackers are larger in size, heavier, power hungry and expensive for nanosatellite missions. The Arcsecond Pico Star Tracker (APST) is designed based on the limitations of nanosatellite and estimated to provide pointing knowledge in an arcsecond. The APST is planned to be operated in SNUSAT-2, earth observing nanosatellite. This paper describes the requirements of APST, trade-off for the selection of image sensor, optics, and baffle design. In addition, survey of algorithms for star trackers, and comparison of the specifications of APST with other Pico star trackers are detailed. The Field of View estimation shows that 17° and 22° is suitable for APST and it reduces stray light problems. In order to achieve the sky coverage of 100%, the FOV of 17° and 22° should able to detect the 5.85 and 5.35 visual magnitude of stars respectively. It is validated by estimating Signal to Noise Ratio of APST and night sky test results. The maximum earth stray light angle is estimated to be 68° and miniaturized baffle is designed with the exclusion angle of 27°