Cassini Attitude Control Configuration for Huygens Probe Release

Abstract

The Cassini spacecraft, including the Orbiter and Huygens Probe, is the largest and most complex interplanetary spacecraft ever built to explore the Saturnian system and undertake a series of ambitious and unique scientific observations of planet Saturn, its largest moon, Titan, and other Cronian (= Saturnian, just like Jovian) satellites. The Huygens Probe, manufactured by the European Space Agency, successfully separated from Cassini on December 24, 2004 during the third flyby of Titan. Three weeks later, the probe landed successfully on a predetermined landing site on the surface of Titan. This important event by itself marked the landing of a man made probe on the farthest celestial body from our planet to date, not to mention the vast, invaluable scientific data from the early Earth-like environment of Titan relayed to Earth by the probe through Cassini. All of this was only possible because of the accurate separation of the Huygens Probe from Cassini; in fact, this successful separation event and the postseparation health and safety of both vehicles were crucial to the entire Cassini-Huygens mission. This paper describes the dynamics and attitude control challenges associated with the design of the Probe release sequence, and how these challenges were overcome in order to not only meet but exceed all the functional requirements. The simulation and test methodologies to ensure a robust Probe release event are also discussed. Finally, the engineering flight data of the orbiter before and after Probe separation are reviewed leading to the reconstruction of attitude control functionalities of the orbiter, along with the post-separation kinematics and dynamics of both the orbiter and probe.