Satellite autonomous navigation and orbit determination using magnetometers

A near-earth (less than 1000 km altitude) satellite autonomous navigation and orbit determination method that uses measurements of the Earth´s magnetic field is presented. An orbit state vector composed of six Keplerian elements enables the estimation of the instantaneous orbital elements by a relatively simple extended Kalman filter algorithm. The satellite position and velocity are computed as functions of the estimated orbital elements. The basic algorithm uses a measurement of the magnetic-field magnitude. This algorithm is thus independent of attitude information. Simulation tests yielded an accurate Keplerian element estimation and a few kilometers of position estimation error. More complicated algorithms which estimate drag and/or utilize attitude information were tested. The basic algorithm was successfully applied to Earth Radiation Budget Satellite data, and a modified version of this algorithm was applied to Gamma Ray Observatory magnetometer readings to yield orbital elements, position, and velocity estimation. In both cases of real satellite navigation, the position was estimated within a few tens of kilometers