GRAIL-A Spacecraft Arrives at the Moon [HD]

The first of two NASA spacecraft to study the moon
in unprecedented detail has entered lunar orbit.

NASA's Gravity Recovery And Interior Laboratory (GRAIL)-A spacecraft
successfully completed its planned main engine burn at 2 p.m. PST (5
p.m. EST) today. As of 3 p.m. PST (6 p.m. EST), GRAIL-A is in a
56-mile (90-kilometer) by 5,197-mile (8,363-kilometer) orbit around
the moon that takes approximately 11.5 hours to complete.

"My resolution for the new year is to unlock lunar mysteries and
understand how the moon, Earth and other rocky planets evolved," said
Maria Zuber, GRAIL principal investigator at the Massachusetts
Institute of Technology in Cambridge. "Now, with GRAIL-A successfully
placed in orbit around the moon, we are one step closer to achieving
that goal."

The next mission milestone occurs tomorrow when GRAIL-A's mirror twin,
GRAIL-B, performs its own main engine burn to place it in lunar
orbit. At 3 p.m. PST (6 p.m. EST) today, GRAIL-B was 30,018 miles
(48,309 kilometers) from the moon and closing at a rate of 896 mph
(1,442 kph). GRAIL-B's insertion burn is scheduled to begin tomorrow
at 2:05 p.m. PST (5:05 p.m. EST) and will last about 39 minutes.

"With GRAIL-A in lunar orbit we are halfway home," said David Lehman,
GRAIL project manager at NASA's Jet Propulsion Laboratory (JPL) in
Pasadena, Calif. "Tomorrow may be New Year's everywhere else, but
it's another work day around the moon and here at JPL for the GRAIL
team."

Once both spacecraft are confirmed in orbit and operating, science
work will begin in March. The spacecraft will transmit radio signals
precisely defining the distance between them as they orbit the moon
in formation. As they fly over areas of greater and lesser gravity
caused by both visible features, such as mountains and craters, and
masses hidden beneath the lunar surface, the distance between the two
spacecraft will change slightly.

Scientists will translate this information into a high-resolution map
of the moon's gravitational field. The data will allow scientists to
understand what goes on below the lunar surface. This information
will increase knowledge of how Earth and its rocky neighbors in the
inner solar system developed into the diverse worlds we see today.

JPL manages the GRAIL mission for NASA's Science Mission Directorate
at the agency's headquarters in Washington. The GRAIL mission 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.

For more information about GRAIL, visit:

http://www.nasa.gov/grail