Philae Attitude Determination through Nonlinear Optimal Identification of Solar Arrays Telemetry

In Rosetta lander Philae, the ability to increase the on-comet power production gives the chance to maintain the system alive, as well as the opportunity to accomplish scientific experiments during the Long Term Science (LTS) phase. This can be accomplished if the lander operates at solar incidence angles that maximize the total power produced by the solar arrays. However, due to strict mass limitations, the lander lacks of systems for attitude determination. In this work, a method based on system identification and parameter estimation has been developed to reconstruct the Sun orbit relative to Philae in on-comet conditions. The objective is to find the azimuth and elevation angles of the Sun as a function of time, which is done by post-processing the telemetry data acquired few hours after landing. This allows us to design the optimal rotation of Philae to maximize the power produced, and thus the scientific return.