Terrain-relative planetary orbit determination

Abstract

This paper presents an approach to visual navigation for a spacecraft during planetary orbit. Spacecraft orbital parameters are determined autonomously by registration to terrain. To accomplish this, individual camera images are registered to pre-existing maps to determine spacecraft latitude and longitude. Using knowledge of orbital dynamics, the time history of sensed latitudes and longitudes is fit to a physically realizable trajectory. Outlier measurements are rejected using robust estimation techniques. Simulation results using data from the Lunar Reconnaissance Orbiter show that method determines the orbit semi-major axis with an average error less than 6km for a 500km altitude lunar orbit.