Rarefied Aerothermodynamics of Mars Odyssey

Abstract

On January 11 of 2002, Mars Odyssey successfully completed the aerobraking phase of the mission, becoming the second successful planetary mission designed specifically to utilize aerobraking as a primary means of achieving its mission objectives. Direct simulation Monte Carlo and free‐molecular analyses were used to provide aerothermodynamic characteristics of the spacecraft for mission planning, flight operations, and atmospheric reconstruction. The results of these analyses were used to develop an aerodynamic database that was used for numerous trajectory simulations both prior to and during aerobraking operations, and to reconstruct atmospheric density profiles during each pass. The aerodynamic database was also used together with data obtained from on‐board accelerometers to reconstruct the spacecraft attitudes throughout each aerobraking pass. The reconstructed spacecraft attitudes are in good agreement with those determined by independent on‐board inertial measurements for all aerobraking passes. The differences in the pitch attitudes are significantly less than the preflight uncertainties of ±2.9%. The differences in the yaw attitudes are influenced by zonal winds. When latitudinal gradients of density are small, the differences in the yaw attitudes are significantly less than the preflight uncertainties. Direct simulation Monte Carlo simulations were also performed to provide aerodynamic heating inputs for detailed thermal analyses of the Odyssey solar panels. Predictions of solar panel temperatures compared well with those from thermocouple measurements obtained during aerobraking.