Spacecraft technicians dressed in clean room attire prepare to enclose NASA's Gravity Recovery and Interior Laboratory spacecraft in the Delta payload fairing.

At Space Launch Complex 17B on Cape Canaveral Air Force Station in Florida, spacecraft technicians dressed in clean room attire, known as "bunny" suits, prepare to enclose NASA's twin Gravity Recovery and Interior Laboratory spacecraft in the Delta payload fairing.

The fairing will protect the spacecraft from the impact of aerodynamic pressure and heating during ascent and will be jettisoned once the spacecraft is outside the Earth's atmosphere. Launch aboard a United Launch Alliance Delta II rocket from Pad 17B is scheduled for Sept. 8. The spacecraft 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. For more information, visit http://www.nasa.gov/grail. Photo credit: NASA/Jim Grossmann