Astro APS - The Next Generation Hi-Rel Star Tracker Based on Active Pixel Sensor Technology

Abstract

Star trackers are opto-electronic sensors used on-board of satellites for the autonomous inertial attitude determination. During the last years star trackers became more and more important in the field of the attitude and orbit control system (AOCS) sensors. State of the art high performance star trackers are based on charge coupled device (CCD) detectors. The active pixel sensor (APS) technology, introduced in the early 90-ties, allows now the beneficial replacement of the CCD detectors with respect to performance, reliability, power, mass and cost. The European Space Agency and the German National Space Agency recognized the large potential of the APS technology for star tracker system improvements and kicked off several pre-development and technology projects. The Jena-Optronik GmbH as one of the leading European companies in star tracker design and manufacturing awarded in 2003 ESA contracts for the pre-development of the AlphaBus APS based star tracker and for the development of very robust software algorithms to support the special features of the APS technology. AlphaBus is the European high power geo-stationary telecom platform. In the frame of the pre-development project an engineering model of the APS star tracker has been manufactured in order to demonstrate the key performance parameters. The Jena-Optronik GmbH received a project from the German National Space Agency to improve and optimize the APS technology particularly for star tracker applications. Within this program the Thin Film on CMOS (TFC) technology is studied and prototypes of APS detectors are manufactured and tested with respect to performance and space environment. The paper describes the design philosophy of the APS based star tracker as the next generation of high reliability autonomous attitude determination sensors. Special emphasis will be taken on the hardware and software implementation of the selected APS detector.