NASA Lunar Spacecraft Complete Prime Mission Ahead of Schedule

May 29, 2012

Dwayne Brown
Headquarters, Washington
202-358-1726
dwayne.c.brown@nasa.gov

DC Agle
Jet Propulsion Laboratory, Pasadena, Calif.
818-393-9011
agle@jpl.nasa.gov

Caroline McCall
Massachusetts Institute of Technology, Cambridge
617-253-1682
cmccall5@mit.edu

RELEASE: 12-175

NASA LUNAR SPACECRAFT COMPLETE PRIME MISSION AHEAD OF SCHEDULE

WASHINGTON -- A NASA mission to study the moon from crust to core has
completed its prime mission earlier than expected. The mission team
of NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission,
with twin probes named Ebb and Flow, is now preparing for extended
science operations starting Aug. 30 and continuing through Dec. 3,
2012.

The GRAIL mission has gathered unprecedented detail about the internal
structure and evolution of the moon. This information will increase
our knowledge of how Earth and its rocky neighbors in the inner solar
system developed into the diverse worlds we see today.

Since March 8, the spacecraft have operated around the clock for 89
days. From an orbit that passes over the lunar poles, they have
collected data covering the entire surface three times. An instrument
called the Lunar Gravity Ranging System onboard each spacecraft
transmits radio signals that allow scientists to translate the data
into a high-resolution map of the moon's gravitational field. The
spacecraft returned their last data set of the prime mission today.
The instruments were turned off at 1 p.m. EDT when the spacecraft
were 37 miles (60 kilometers) above the Sea of Nectar.

"Many of the measurement objectives were achieved from analysis of
only half the primary mission data, which speaks volumes about the
skill and dedication of our science and engineering teams," said
Maria Zuber, principal investigator of GRAIL at the Massachusetts
Institute of Technology in Cambridge. "While there is a great deal of
work yet to be done to achieve the mission's science, it's energizing
to realize that what we traveled from Earth to the moon for is right
here in our hands."

"GRAIL delivered to Earth over 99.99 percent of the data that could
have been collected, which underscores the flawless performance of
the spacecraft, instrument and the Deep Space Network," said Zuber.

Both spacecraft instruments will be powered off until Aug. 30. The
spacecraft will have to endure a lunar eclipse on June 4. The eclipse
and the associated sudden changes in temperature and the
energy-sapping darkness that accompanies the phenomena were expected
and do not concern engineers about the spacecraft's health.

"Before launch, we planned for all of GRAIL's primary mission science
to occur between lunar eclipses," said David Lehman, project manager
of GRAIL from NASA's Jet Propulsion Laboratory (JPL) in Pasadena,
Calif. "But now that we have flown Ebb and Flow for a while, we
understand them and are confident they can survive these eclipses in
good shape."

The extended mission goal is to take an even closer look at the moon's
gravity field. To achieve this, GRAIL mission planners will halve
their current operating altitude flying at the lowest altitude that
can be safely maintained.

"Orbiting at an average altitude of 14 miles (23 kilometers) during
the extended mission, the GRAIL twins will be clearing some of the
moon's higher surface features by about 5 miles (8 kilometers)," said
Joe Beerer, GRAIL's mission manager. "If Ebb and Flow had feet, I
think by reflex they'd want to pull them up every time they fly over
a mountain."

Along with mission science, GRAIL's MoonKAM (Moon Knowledge Acquired
by Middle school students) education and public outreach program is
also extended. To date over 70,000 student images of the moon have
been obtained. The MoonKAM program is led by Sally Ride, America's
first woman in space, and her team at Sally Ride Science in
collaboration with undergraduate students at the University of
California in San Diego.

The GRAIL mission is managed by JPL for NASA's Science Mission
Directorate in Washington. The mission is part of the Discovery
Program managed at NASA's Marshall Space Flight Center in Huntsville,
Ala. NASA's Deep Space Network is an international network of
antennas that supports interplanetary spacecraft missions and radio
and radar astronomy observations for the exploration of the solar
system and the universe. The network also supports selected
Earth-orbiting missions. Lockheed Martin Space Systems in Denver
built the spacecraft.

For more information about GRAIL, visit:

http://www.nasa.gov/grail


-end-



To subscribe to the list, send a message to:
hqnews-subscribe@mediaservices.nasa.gov
To remove your address from the list, send a message to:
hqnews-unsubscribe@mediaservices.nasa.gov