Posted by Courtney E. Howard

CAPE CANAVERAL, Fla., 10 Sept. 2011. NASA officials launched its twin lunar Gravity Recovery and Interior Laboratory (GRAIL) spacecraft from Cape Canaveral Air Force Station, Fla., today at 9:08 a.m. EDT to study the moon in detail. GRAIL-A is expected to reach the moon on New Year's Eve 2011, whereas GRAIL-B is scheduled to arrive New Year's Day 2012. The two solar-powered spacecraft will fly in tandem orbits around the moon to measure its gravity field, helping to answer longstanding questions about the moon and how Earth and other rocky planets in the solar system formed.

The spacecraft launched aboard a United Launch Alliance Delta II rocket. GRAIL mission controllers acquired a signal from GRAIL-A at 10:29 a.m., and from GRAIL-B eight minutes later. Telemetry data from both spacecraft indicates their solar panels are deployed and operating as expected.

"Our GRAIL twins have Earth in their rearview mirrors and the moon in their sights," explains David Lehman, GRAIL project manager at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. "The mission team is ready to test, analyze, and fine tune our spacecraft over the next three-and-a-half months on our journey to lunar orbit."

The distance from Earth to the moon, in a straight line, is roughly 250,000 miles (402,336 kilometers). NASA's Apollo moon crews needed approximately three days to cover that distance; yet, each spacecraft will take approximately 3.5 months and cover more than 2.5 million miles (4 million kilometers) to arrive. This low-energy trajectory results in the longer travel time. The size of the launch vehicle allows more time for spacecraft check-out and time to update plans for lunar operations. The science collection phase for GRAIL is expected to last 82 days.

"GRAIL will take lunar exploration to a new level, providing an unprecedented characterization of the moon's interior that will advance understanding of how the moon formed and evolved," says Maria Zuber, GRAIL principal investigator from the Massachusetts Institute of Technology in Cambridge, Mass.

JPL manages the GRAIL mission, which is part of the Discovery Program managed at NASA's Marshall Space Flight Center in Huntsville, Ala. Lockheed Martin Space Systems in Denver built the spacecraft. Launch management for the mission is the responsibility of NASA's Launch Services Program at the Kennedy Space Center, Florida.