MSL Relay Coordination and Tactical Planning in the Era of InSight, MAVEN, and TGO

Abstract

This study examines an approach for optimizing the scheduling of regular relay communications between the Mars Science Laboratory (MSL) rover and the non-sun-synchronous Mars orbiters MAVEN and TGO as well as the impacts of the approaching InSight landing on MSL relay and tactical planning. Rover operations require knowledge of recently executed activities, termed decisional data, in order to inform tactical activity planning. As a result, timely and routine data return is critical for nominal rover operations. Mars orbiters are used as relay assets to achieve such timeliness. They also provide greater overall rover data throughput considering their larger data transfer capacity between Mars and Earth. Relay opportunities and their performance are thus tightly coupled to MSL's operations efficiency and science return. With InSight landing only 600 kilometers away and at the same longitude as MSL, orbiter view periods will be shared between the missions, resulting in fewer relay opportunities for MSL. The introduction of MAVEN and TGO as relay assets helps to alleviate this, but the orbit geometries of these spacecraft introduce their own challenges. Unlike sun-synchronous orbiters MRO and ODY, the timing of MAVEN and TGO overflights walks sol-to-sol, resulting in seasonal variations that preclude their usability. The overflights may occur too early in the sol to enable science activities or too late in the sol to be decisional for the subsequent planning cycle. Moreover, the highly elliptical orbit of MAVEN results in much longer view periods as well as intervals of lower or higher data volume return. With the introduction of InSight, MAVEN, and TGO, the MSL mission undertook a design effort in order to define new overflight selection criteria and identify the impact to operational efficiency. Instead of selecting all usable relay opportunities, as was the case with just MRO and ODY, this new paradigm requires deconflicting and down-selecting from available overflights. The overflight selection algorithm presented in this study selects based on key overflight metrics such as timing, the predicted data volume return, and the latency between the relay and data arrival to Earth. The relative priority of each of these metrics is scenario-specific; thus, the algorithm is flexible and configurable for when mission priorities evolve. Additionally, operational constraints and considerations such as human factors are applied. The resulting tactical planning timeline post-InSight landing suggests comparable operational efficiency to the pre-InSight era but yields more variation in the timing of the planning shifts, adding strain on the MSL planning team.