GRAIL

The GRAIL mission is set to launch on September 8, 2011 to the moon! GRAIL will help scientists obtain high resolution map of moon's gravitational field [1]. This mission will deploy two spacecrafts in the same orbit around the moon, moving toward and away from each other. Measuring the changes in their relative velocity is the key to obtaining moon's high resolution gravitational map. The same technique was used for the GRACE mission, in orbit since 2002, for measuring the gravitational field of the Earth [3].

"NASA's Twin GRAIL Spacecraft Are Ready For Launch

These images show the various stages of pre-launch preparations of NASA's twin GRAIL spacecraft at Space Launch Complex 17B on Cape Canaveral Air Force Station in Florida. Image credit: NASA/JPL-Caltech." [2]


References:
[1] http://www.nasa.gov/mission_pages/grail/main/index.html
[2] http://www.nasa.gov/mission_pages/grail/multimedia/collage20110907.html
[2] http://science.nasa.gov/missions/grace/