Lockheed Martin technicians determine the readiness of one of NASA's twin Gravity Recovery and Interior Laboratory lunar spacecraft.

At Astrotech Space Operation's payload processing facility in Titusville, Fla., Lockheed Martin technicians determine the readiness of one of NASA's twin Gravity Recovery and Interior Laboratory lunar spacecraft before the spacecraft are stacked in their launch configuration in preparation for transport to the launch pad.

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/Jim Grossmann