Contingency Plans for MESSENGER's Mercury Orbit Insertion Maneuver

Abstract

MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) will be the first spacecraft to orbit the planet Mercury when it begins its one-year Mercury orbital mission phase next year. On 18 March 2011 MESSENGER will perform the critical 862 m/s Mercury orbit insertion (MOI) maneuver. This paper summarizes strategies for recovering MESSENGER’s science mission in the event of an aborted or anomalous MOI maneuver. If 70% or more of the MOI burn is completed, MESSENGER will be captured into a high Mercury orbit. One or two maneuvers would then be required to achieve the planned 82.5inclination, 12.0-hour orbit, and all science objectives can be met for most of these cases. If less than 70% of the MOI burn is completed, MESSENGER would remain in a heliocentric orbit, and a recovery maneuver must occur either 10 to 14 days after the 18 March 2011 MOI attempt, or approximately one Mercury year (87.97 days) later in June 2011. For these heliocentric trajectories, solutions were found by which the spacecraft returns to Mercury after either one Mercury year or multiple (Earth) years (subsequent to completing one more or one less revolution of the Sun than Mercury). None of the successful return solutions exceeds the 7-year maximum preferred return time to Mercury.