Performance Analysis of a Stellar-Inertial System for Spacecraft Autonomous Attitude Determination Based on MEMS and CMOS Technology

This paper deals with the performance analysis and preliminary design of an integrated system for autonomous attitude state determination of spacecrafts based on the fusion of MEMS (Micro-Electro-Mechanical-System) gyros with an advanced CMOS-based star sensor. In the integration scheme the star sensor is used as aiding sensor. Sensor data fusion is performed by means of Kalman filtering, following a detailed analysis of star trackers and gyros measurement errors. As a consequence, the integrated system performances are estimated by covariance propagation. In particular, the steady state error covariance for different inertial and stellar sensor typologies and aiding sensor update intervals is numerically analysed, in order to evaluate different sensor configurations considering the performances of sensors available in the market. Analysis results will help in selecting the star sensor data rate and the updating frequency to be used for the inertial sensor aiding. The study is performed considering the following sensor physical parameters: gyros drift rate, resolution and bias stability; star sensor sensitivity, detection limit, field-of-view and instantaneous field of view; star catalogue size and coverage. The above parameters are modelled with reference to state-of-art MEMS gyros and MOS and CMOS-based star sensors. Results show that stellar-inertial sensors for coarse/medium (0.01°) and high (<0.001°) attitude accuracy applications can be obtained by integrating, respectively, MEMS silicon vibrating gyros with CMOS-based star sensor and fyber optic gyros with MOS-based star sensors. Finally, preliminary analysis also shows that integrated systems with mass of about 2 kg and power consumption lower than 15 W can be realised, that are adequate for microsatellite applications. Copyright © 2003 by the International Astronautical Federation. All rights reserved.