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CAPE CANAVERAL, Fla. -- A Lockheed Martin technician in Astrotech Space Operation's payload processing facility in Titusville, Fla., tests the solar arrays on NASA's Gravity Recovery and Interior Laboratory-A, or GRAIL-A, spacecraft to ensure that they will function as planned during the mission. The electrical power subsystem on each of GRAIL's twin spacecraft includes two solar arrays and a lithium ion battery. Each solar array is capable of producing no less than 700 watts. They will be deployed shortly after separation from the launch vehicle and remain fixed throughout the mission. GRAIL will fly in tandem orbits around the moon for several months to measure its gravity field. GRAIL's primary science objectives are to determine the structure of the lunar interior, from crust to core, and to advance understanding of the thermal evolution of the moon. Launch aboard a United Launch Alliance Delta II rocket from Space Launch Complex 17B on Cape Canaveral Air Force Station is scheduled for Sept. 8. For more information, visit http://www.nasa.gov/grail. Photo credit: NASA/Frankie Martin