[meteorite-list] GRAIL Finish Prime Mission Ahead of Schedule

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 29 May 2012 14:27:18 -0700 (PDT)
Message-ID: <201205292127.q4TLRIHl016844_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.cfm?release=2012-146

NASA Lunar Spacecraft Finish Prime Mission Ahead of Schedule
Jet Propulsion Laboratory
May 29, 2012

PASADENA, Calif. -- A NASA mission to study the moon from crust to core
has completed its prime mission earlier than expected. The 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 10 a.m. PDT (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 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 to 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 of JPL, 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. JPL is a
division of the California Institute of Technology in Pasadena.

For more information about GRAIL, visit:
http://www.nasa.gov/grail .

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

Dwayne Brown 202-358-1726
NASA Headquarters, Washington
Dwayne.c.brown at nasa.gov

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

2012-146
Received on Tue 29 May 2012 05:27:18 PM PDT