GRAIL | Gravity Recovery and Interior Laboratory

JPL
Engineers have conducted a fuel tank check of one of NASA's GRAIL mission spacecraft (Gravity Recovery and Interior Laboratory)"
http://www.jpl.nasa.gov/news/news.cfm?release=2010-249
GRAIL Spacecraft Takes Shape
The GRAIL mission will fly twin spacecraft (spacecraft "A" and "B") in tandem orbits around the moon for several months to measure its gravity field in unprecedented detail.
http://www.physorg.com/news199635110.html
GRAIL | Gravity Recovery and Interior Laboratory
Map the structure of the crust & lithosphere.
Understand the Moon’s asymmetric thermal evolution.
Determine the subsurface structure of impact basins and the origin of mascons.
Ascertain the temporal evolution of crustal brecciation and magmatism.
Constrain deep interior structure from tides.
Place limits on the size of the possible inner core."
http://moon.mit.edu/objectives.html