Communications with Curiosity during Solar Conjunction

This study examines the methodology for operating and communicating with NASA's Mars Science Laboratory (MSL) Curiosity Rover during the 2019 solar conjunction. For MSL, solar conjunction occurs when the viewing angle between the Sun and Mars from Earth's perspective falls below 3 degrees, which occurs roughly every two Earth years and lasts for about two weeks. This presents a challenge for engineers operating a vehicle on Mars because the degraded signal to noise ratio disrupts data flow between Earth and the spacecraft. As a result, operators designate a command moratorium in which no commands are sent to the rover and instead design long-term plans that are uplinked weeks in advance (rather than the nominal case of daily uplinks). Coordinating communications with the rover leading up to and following conjunction requires negotiations with several orbiters, another lander, and the Deep Space Network (DSN) - each with their own set of constraints. It is the Strategic Comm Planning Team's job to oversee this coordination, which acts as a baseline for the conjunction planning cadence. In the 2019 conjunction, MSL's Comm team faced additional complications such as the arrival of two new spacecraft at Mars - NASA's InSight (NSY) and the ESA-Roscosmos ExoMars Trace Gas Orbiter (TGO). The team also utilized a set of new, complex planning tools that were developed to handle the intricate incorporation of these new spacecraft into the Mars relay environment, but which had never before been used for conjunction communication planning. Although experience with previous conjunctions provides guidance, each conjunction period presents unique challenges and finding the optimal solution each time is one of the hardest challenges that the Comm team faces.