Effects of Self-Shadowing on Nonconservative Force Modeling for Mars-Orbiting Spacecraft

Modeling improvements of nonconservative forces affectingMars-orbiting spacecraft are presented in this study. Recent high-resolution gravity fields enable the recovery of smaller signals in the radio tracking data, previously obscured bymismodeled gravitational anomalies. In particular, the estimation of the atmospheric drag experienced by the spacecraft benefits from the new forcemodels.More precise calculations of the spacecraft cross-sectional areas entering the equations for the atmospheric drag anddirect solar radiation pressure are possible by accounting for the interplate self-shadowing of the spacecraft physicalmodel. The relevant surface areas can change by asmuch as 20% on average, and the effects can be very variable within one orbit ( 10%). The benefits of these updated models are assessed with two spacecraft, the Mars Odyssey and the Mars Reconnaissance Orbiter. The changes in the nonconservative forces can significantly impact the reconstructed spacecraft trajectory and the estimated model parameters depend on the spacecraft geometry and orbit. The atmospheric density estimated by theMarsOdyssey is much improved with self-shadowing applied to the solar radiation, but improvements to both the drag force and the solar radiation are important in this case of the Mars Reconnaissance Orbiter.