Autonomous Satellite Navigation Using Observations of Starlight Atmospheric Refraction

Abstract

Performance results are presented for an autonomous navigator using refraction measurements of starlight passing through the upper atmosphere. To obtain a realistic performance indication, a full-state simulation was developed comprising a truth model with an 8 × 8 gravity field, lunar and solar perturbations, atmospheric drag, real star distributions, and the effect of atmospheric density variations on the measurements. Some data on actual observations of refraction by the satellite HEAO-2 are presented to show the variability in density within ± 20° latitude. The navigation portion of the simulation is capable of handling gravity fields up to degree 4 and order 4, and utilizes the extended Kalman filter to estimate satellite position and velocity.