ROSETTA NAVIGATION AT COMET CHURYUMOV-GERASIMENKO

On August 6, 2014, the European Space Agency's Rosetta mission arrived at comet Churyumov-Gerasimenko to mark a new era in comet exploration. After a series of orbits which took it progressively closer to the nucleus, the Philae lander was released from the Rosetta orbiter and touched down on the surface of the comet on November 12, 2014. Navigation of Rosetta, including the landing of Philae, was especially challenging due to several factors, including the use of terrain-relative optical navigation, the central body being a highly irregularly shaped object with unknown mass distribution, and an unknown coma environment. The responsibility for mission design and navigation of Rosetta resides with the Flight Dynamics group at the European Space Operations Center; through a collaborative arrangement, navigation specialists at the Jet Propulsion Laboratory also performed a parallel effort to reconstruct the spacecraft's orbit from approach through the Philae landing. In this paper, we describe JPL's methods and results in determining the orbit of Rosetta and the Philae lander.