APPLYING EXPERIENCE FROM MERCURY ENCOUNTERS TO MESSENGER'S MERCURY ORBITAL MISSION

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission is the seventh in NASA's Discovery Program series. The spacecraft was launched in August 2004 and began an interplanetary cruise that culminated in insertion into orbit about Mercury in March 2011 for a nominal one-year scientific investigation. The cruise phase included six planetary gravity-assist flybys and eighteen propulsive events, which included five large deep-space maneuvers, one in two parts, and twelve smaller trajectory-correction burns. From the approach to the first Mercury flyby through orbital insertion about the innermost planet, an interval that spanned over three years, solar sailing was employed successfully for trajectory correction. This paper describes the navigation performance achieved for the three Mercury flybys and how experiences gained during the mission cruise phase have been applied to support Mercury orbit insertion and maintenance operations during the Mercury orbital phase of the MESSENGER mission.