GRAIL (Gravity Recovery and Interior Laboratory)
The Gravity Recovery and Interior Laboratory, or GRAIL, mission is a part of NASA's Discovery Program. It is scheduled to launch in 2011. GRAIL will fly twin spacecraft in tandem orbits around the moon for several months to measure its gravity field in unprecedented detail. The mission also will answer longstanding questions about Earth's moon and provide scientists a better understanding of how Earth and other rocky planets in the solar system formed.