Hybrid Geomagnetic Attitude and Orbit Estimation Using Time-Differential Feedback

This paper introduces a novel filter for hybrid attitude and orbit estimation of spacecrafts with geomagnetic measurements and its time-differential information. Geomagnetic measurements can be used for simultaneous attitude and orbit estimation of spacecrafts. In practice, the attitude estimation from a single magnetometer is achieved by fusing the magnetometer readings and their time derivatives together. The orbit will also be estimated according to the relationship between the geomagnetic model and spacecraft coordinates in the Earth geodetic frame. However, the magnetic time derivatives have not participated in estimating the orbit elements. According to the mathematical structures of the geomagnetic models, the time-differential feedback can effectively enhance the estimation of the velocity and thus will provide better performance for the position loop. This paper first introduces such direct feedback and formulates a new filter with better characteristics. The simulation study of a medium Earth orbit (MEO) Nadir-pointing satellite mission shows that the proposed filter achieves faster convergence and lower estimation errors.