MODIFIED KALMAN FILTER BASED AUTONOMOUS ORBIT DETERMINATION USING HORIZON SCANNER MEASUREMENTS

With a pair of Horizon Scanners (HS) working as attitude sensors, four horizon points are obtained during each scan. A simplified non-linear model is developed for the horizon points using an appropriate choice of frame. The modified gain extended Kalman filter is used to estimat e the satellite position in the orbit reference frame based on the non -linear Horizon Scanner data. Through simulation studies it is shown t hat addition of one more scanner in the roll-yaw plane provides accura te estimates of the position. Under steady state conditions, simulatio n results show that estimates do not diverge even if there is a data b reak in the roll-yaw HS data. The achievable accuracies are of the ord er of 2 km with about 0.1 degrees(1 sigma) noise in the horizon points . Copyright (C) 1996 Elsevier Science Ltd.