Robust Attitude Determination for Spacecraft with Magnetic Sensors

Abstract

This paper presents a new attitude determination algorithm for a spacecraft in low earth orbits using magnetic sensors and rate sensors (e.g. quartz rate sensor gyros) for generic missions including earth observations. The algorithm is applicable to mainly a three-axis spacecraft, including when it is tumbling just after the separation from a launch vehicle or due to some anomaly. The advantage of the proposed approach is that it does not require additional attitude sensors such as sun sensors. First, an attitude determination algorithm using only magnetic sensors is introduced presuming that the attitude change during the measurement period is very small. Then the algorithm is extended to combine magnetic sensors with rate sensors, where both the three-axis attitude and rate sensor biases are estimated. The estimation error is statistically analyzed. Numerical examples are given to validate the proposed algorithm and its accuracy evaluation.