ATTITUDE ESTIMATION FROM MAGNETOMETER AND EARTH-ALBEDO-CORRECTED COARSE SUN SENSOR MEASUREMENTS

摘要

A low cost, robust Attitude Determination System with good accuracy for small satellites can be achieved by using a combination of magnetometer and Coarse Sun Sensor. The Coarse Sun Sensor consists of solar cells placed on each of the six outside surfaces of the satellite. The main measurement error of the Coarse Sun Sensor occurs due to the Earth's albedo which can cause an angular deviation of more than 20 degrees. By modelling the albedo and applying state estimation methods for attitude determination the error can be reduced drastically to less than 1 degree, depending on the conditions. In the first part of this paper the development of the albedo model is presented. In the second part the Extended Kalman Filter used for attitude determination is described. The albedo model of the earth is created using existing reflectivity data. Polynomials to describe the albedo light vector received by a satellite in its orbit are derived. The total light vector and the magnetic field vector, taken from the IGRF model, are used by the Kalman Filter.