The MESSENGER Spacecraft Power Subsystem Thermal Design and Early Mission Performance

Abstract

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, launched on August 3, 2004, is a NASA spacecraft that will orbit the planet Mercury for a one-year mission. The spacecraft launch mass limitation, combined with the large solar distance variations, impose severe requirements on the spacecraft power and thermal subsystems. The spacecraft is three-axis stabilized. A sunshade protects the spacecraft from the high intensity solar flux. The attitude control maintains the sunshade pointed to the Sun. The solar panels, which are outside the thermal shield, are designed to survive normal Sun incidence at 0.3 AU. The solar panels consist of alternating rows of triple junction cells placed between Optical Solar Reflectors (OSRs). Solar panels thermal control is performed by tilting the panels with increasing solar flux. To minimize the mass of the spacecraft, the structure is made of composite materials. Spacecraft electronic boxes that are high power dissipaters are designed with special thermal vias that conduct the heat directly to diode heat pipes, which transport the heat of the box to thermal radiator panels on the side of the spacecraft behind the sunshade. The MESSENGER spacecraft is on a trajectory to enter Mercury orbit in 2011. The spacecraft is performing as designed.