NEW METHODS FOR ACCURATE THERMAL DISTURBANCE FORCE CALCULATION WITH APPLICATION TO PIONEER AND FLYBY ANOMALY

摘要

The exact modeling of external and internal perturbations becomes increasingly important for current and future space missions which have high requirements on disturbance knowledge. The simulation of perturbations which are caused by thermal effects are particularly challenging because the optical properties of spacecraft surfaces can change during the mission due to exposure to the space environment. At ZARM algorithms for the simulation and analysis of thermal perturbations have been developed. These codes include the simulation of the thermal recoil force (waste heat dissipation), Earth Albedo influence as well as Solar radiation pressure based on detailed finite element (FE) models of the craft. The results of thermal FE analysis and the geometry can be exported into disturbance algorithms where raytracing methods are applied to compute the resulting forces. As an example the computation of the thermal dissipation recoil force will be shown for the Pioneer 11 spacecraft in detail and the results will be evaluated with respect to the Pioneer anomaly. The main challenges of the thermal modeling process will be discussed. In addition, a short outlook on the influence of geometry-based disturbance modeling on the Flyby-anomaly will be given. The conducted analyses show that in particular for fundamental physics missions with high requirements on attitude and orbit knowledge (such as LISA, LISA pathfinder, MICROSCOPE) the exact modeling of thermal perturbations is a key issue for the calculation of accurate disturbance budgets.