Second GRAIL probe above lunar surface.
Launched last September, the GRAIL lunar probes have finally arrived at the Moon and successfully entered orbit. GRAIL-A fired its thruster on Sunday, and 24 hours later, GRAIL-B joined its partner to circle the Moon. Over the next coupe of months, the two spacecraft will use minute bursts of thrust to align themselves into a stable orbit of 55 kilometers above the surface.
Once in their stable orbit, the two probes will maintain a communications link with each other, and measure the disturbances in altitude and separation of spacecraft to help probe the gravity field of the Moon, helping scientists to understand more about the Moon's interior.
Students in 5th through 8th grades are participating in this exploration. Each probe includes a GRAIL MoonKAM (Moon Knowledge Acquired by Middle school students). The cameras will receive requests from students across the country, and the returned images will be studied by students in their science classes.