Hybrid Geomagnetic Attitude and Orbit Estimation Using Time-Differential Feedback

Abstract

This paper introduces a novel filter for hybrid attitude and orbit estimation of spacecraft using geomagnetic measurements and their time-differential information. Geomagnetic measurements can be used to simultaneously estimate attitude and orbit 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 can also be estimated using the relationship between the geomagnetic model and spacecraft coordinates in the Earth geodetic frame. However, the magnetic time derivatives have not been utilized in estimating the orbit elements. According to the mathematical structures of the geomagnetic models, the time-differential feedback can effectively enhance estimation of the velocity and can therefore provide better performance for the position loop. This paper first introduces 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.