Return to Mercury: An Overview of the MESSENGER Spacecraft Thermal Control System Design and Up-to-Date Flight Performance

Launched on August 3, 2004, MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) will be the first spacecraft to orbit the planet Mercury. Designed and built by The Johns Hopkins University Applied Physics Laboratory in conjunction with the Carnegie Institution of Washington, MESSENGER will study Mercury during a 1-year orbital phase that will begin in March 2011. Currently the spacecraft is in the middle of a 7-year cruise phase that so far has included a flyby of the Earth (August 2005), two flybys of Venus (October 2006 and June 2007), and the first of three flybys of Mercury (January 2008). The January 2008 Mercury flyby marked the first spacecraft visit since Mariner 10 (1975) and made MESSENGER the first spacecraft to encounter Mercury when near the planet's perihelion. This paper will provide an overview of the thermal design challenges for both the cruise and orbital phases, the solutions implemented to resolve those challenges, and the flight temperature and power data that verify the performance of the thermal control subsystem over the mission to date.