spacetoday.net: Second GRAIL spacecraft arrives in lunar orbit

Posted: Sun, Jan 1, 2012, 8:55 PM ET (0155 GMT)
GRAIL-B orbit insertion illustration (NASA)

Just over a day after the first of two NASA spacecraft went into orbit around the Moon, its twin successfully entered lunar orbit. The Gravity Recovery And Interior Laboratory (GRAIL) B spacecraft inserted itself into an elliptical lunar orbit at 5:43 pm EST (2143 GMT) Sunday after a 37-minute engine burn. GRAIL-B entered orbit just over 24 hours after GRAIL-A entered orbit around the Moon. The two spacecraft will circularize their orbits at an altitude of 55 kilometers by March, when the science mission begins. The two spacecraft will use radio signals to map the Moon's gravity, allowing scientists to better understand the lunar interior.