Integration of Spacecraft Telemetry into Navigation Operations for the Cassini-Huygens Mission

The Cassini orbiter is the largest and most complex interplanetary spacecraft ever built. Since attaining orbit around Saturn in the summer of 2004, Cassini, along with its Huygens probe, have been continually improving our understanding of Saturn, its satellites, its enigmatic rings system, and of the solar system. One of the hallmarks of the CassiniHuygens Project is the close working relationship between the many teams required to operate such a sophisticated spacecraft. Their ingenuity has enabled them to find new and different ways to improve their processes during Cassini’s prime 4-year orbital tour. This paper will discuss the relationship between Cassini’s Navigation and Spacecraft Teams and the work required to properly configure Cassini’s telemetry system for Navigation. A detailed explanation of how the Navigation Team utilizes spacecraft telemetry and analysis demonstrating the benefits will also be provided. Finally, telemetry requirements for Navigation for future missions will be addressed. I. Introduction Since the summer of 2004, the Cassini spacecraft orbiting Saturn has been working around the clock collecting historic science data and returning it to Earth. The science results have been well documented in papers, journals, mass media, and websites. What is not as extensively documented is the creativity and adaptability of the Cassini Project flight team members to continually improve the manner in which they operate the spacecraft. There are many teams within a project such as Cassini, each with specific responsibilities vital to the success of the mission, and each who must forge close working relationships. This paper will discuss in particular the relationship between the navigation team & the spacecraft operations team, especially the Attitude & Articulation Control Subsystem (AACS), and how continual collaboration between the two teams dramatically improved the spacecraft’s performance and the process by which the spacecraft is flown. Much of the joint effort between the two teams has been spent addressing AACS’s growing concern for the health and safety of the Reaction Wheel Assembly (RWA). A major source of the improvement for Navigation operations was extensive reconfiguration of the AACS telemetry. Examples of how the Navigation team makes the most of the AACS telemetry and its advantages are highlighted. Finally, based on the experience gained from Cassini, telemetry configuration requirements to better serve Navigation’s needs for future missions are offered.