FEM-based High-fidelity Solar Radiation Pressure Analysis

In medium-Earth-orbit, geostationary, and deep space missions, the effects of solar radiation pressure (SRP) on the motion of a spacecraft are dominant relative to other perturbations. Recently, several spacecraft have actively used SRP torque for attitude control, and the importance of calculating the SRP torque accurately is increasing. The present paper introduces a newly developed SRP analysis tool called the FEM radiation analysis tool (FRAT). This tool uses an element-based ray tracing strategy, and each element is assigned different optical parameters derived from its material properties. This tool calculates the SRP applied to each mesh element taking shadows into consideration. In the present paper, the accuracy of this calculation is evaluated using flight data of the HAYABUSA 2 asteroid exploration spacecraft. Then, two application examples in which FRAT has played an important role are presented. The first example involves HAYABUSA 2, the attitude of which has been stabilized by actively using the SRP. In the second example, the shape of the sail of IKAROS, a solar sail spacecraft, was estimated using FRAT in order to reproduce the flight data.