The Messenger Spacecraft Solar Array Design and Early Mission Performance

The MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft was launched in 2004 and will be inserted into Mercury orbit in March 2011 for one year of orbital operation. The large solar distance variations from 1 AU near Earth to 0.3 AU near Mercury impose severe requirements on the solar array design. The solar cell strings were placed between Optical Solar Reflector (OSR) mirrors with a cell to OSR ratio of 1:2 to reduce the panel absorbance. Thermal control is performed by tilting the panels away from normal incidence with increased solar intensity. To minimize the development cost and risk to the program schedule, the approach taken was to avoid the development of new materials and processes but rather to extend the use of existing proven materials and processes. Extensive cell characterization and panel testing were performed successfully to demonstrate meeting the worst-case predicted environments during the mission