MSTI3 star tracker attitude determination and estimation algorithm

Abstract

The third Miniature Sensor Technology Integration (MSTI) spacecraft was successfully launched from Vandenberg AFB on 17 May 96. Its mission is infrared Earth mapping and missile tracking. A second objective is to demonstrate that this type of mission can be successfully performed on a reduced schedule and budget. MSTI3 is 3-axis stabilized, and has an attitude knowledge requirement of 0.01° (0.17 mrad), 1 sigma. A star tracker, a Sun sensor, and rateintegrating gyros provide the attitude reference. Integrated Systems, Inc. (ISI) developed and implemented an attitude determination algorithm which meets the above requirements. The algorithm performs a star pattern recognition based on reported separation angles between the stars. It then checks the reported star magnitudes against the matched star pattern as a secondary identifier. These algorithms were tested extensively in three ways: non-real-time workstation simulations, realtime simulations using the flight processor, and finally, outdoor night-sky tests. This paper describes the stellar acquisition, attitude determination and estimation algorithm of the MSTI3 spacecraft. The MSTI spacecraft were built by Phillips Laboratory at Edwards Air Force Base. Integrated Systems is responsible for all of the Attitude Determination and Control System (ABACS) algorithms, as well as the entire flight software for MSTI3, and the previous MSTIs.