Short-term orbital effects of radiation pressure on the Lunar Reconnaissance Orbiter

Abstract

Precision orbit determination for geodetic applications requires force models even for small perturbations. Radiation from the Sun and Moon is a significant source of perturbation in lunar orbits and inadequate modeling of radiation pressure (RP) can lead to large position errors. This paper describes the short-term effect of RP on the Lunar Reconnaissance Orbiter (LRO), which has a position knowledge requirement of 50 m to 100 m in total and below 1 m radially. We compared models of varying complexity to determine the benefits and computational cost of high-accuracy RP modeling. We found that (1) the accelerations differ greatly depending on the Sun position, (2) only a paneled spacecraft model can account properly for changing orientation and geometry of LRO, and (3) a constant-albedo model is sufficient for lunar radiation, which is dominated by the thermal component. A spherical harmonics model for lunar albedo increases computational cost with little gain in the attained accuracy. If RP is neglected, the along-track position errors can be as large as 1100 m and the radial error varies periodically with an amplitude of up to 24 m, highlighting the importance of adequate force modeling to meet LRO's orbit determination requirements.