Laying down tracks: DSN planning for Cassini's final mission phase

Abstract

The Cassini Mission is in the final years of its second extension, the Cassini Solstice Mission (CSM). Nine months prior to the end-of-mission, the spacecraft will embark on its final mission phase, the F-ring and Proximal Orbits (FRPO). These orbits will bring the spacecraft closer to Saturn than ever before, allowing for the collection of some of the most unprecedented, imperative, and profuse science of the entire mission. A key challenge during this phase is identifying viable spacecraft downlink opportunities given the reduced orbital period and the temporal ‘balancing act’ that must be maintained between science data acquisition, orbit trim maneuvers (OTMs), orbital geometry, other missions' events, and Deep Space Network (DSN) downtimes. This paper describes the development of the DSN straw-man for the FRPO phase of the Cassini mission, starting with the constraints identified from the above sources, then the process followed to select DSN passes given those constraints, and finally the products produced to summarize the selected passes and verify their compliance with the constraints. Ultimately, the DSN straw-man included 286 selected passes, of which only 44 had conflicts with constraints.