[meteorite-list] Rocket Burn Sets Stage for Dynamic Moon Duos' Lunar Impact

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Sat, 15 Dec 2012 19:17:34 -0800 (PST)
Message-ID: <201212160317.qBG3HYJv015559_at_zagami.jpl.nasa.gov>


Rocket Burn Sets Stage for Dynamic Moon Duos' Lunar Impact
Jet Propulsion Laboratory
December 14, 2012

Mission status update

PASADENA, Calif. - The lunar twins of NASA's Gravity Recovery
and Interior Laboratory (GRAIL) mission have each completed a rocket burn
that has sealed their fate. The burns modified the orbit of the formation-flying
spacecraft. Over the next three days, this new orbit will carry the twins
lower and lower over the moon's surface. On Monday afternoon, Dec. 17,
at about 2:28 p.m. PST (5:28 p.m. EST), their moon-skimming will conclude
when a portion of the lunar surface - an unnamed mountain near the natural
satellite's north pole - rises higher than their orbital altitude.

The maneuvers began at 7:07 a.m. PST (10:07 a.m. EST) today when the Ebb spacecraft
fired its main engines for 55.8 seconds, changing its orbital velocity
by 10.3 mph (4.6 meters per second). Sixteen seconds later, still at 7:07
a.m. PST, the Flow spacecraft began its maneuver, executing a burn 55.4
seconds in duration with a resulting change in orbital velocity of 10.3
mph (4.6 meters per second). The spacecraft were named Ebb and Flow by
elementary school students in Bozeman, Mont., who won a nationwide contest.

Ebb and Flow are being sent purposely into the lunar surface because their
low orbit and low fuel levels preclude further scientific operations.

"NASA wanted to rule out any possibility of our twins hitting the surface anywhere
near any of the historic lunar exploration sites like the Apollo landing
sites or where the Russian Luna probes touched down," said David Lehman,
GRAIL project manager at NASA's Jet Propulsion Laboratory in Pasadena,
Calif. "Our navigators calculated the odds before this maneuver as about
seven in a million. Now, after these two successful rocket firings, there
is zero chance."

The unnamed mountain where the two spacecraft will make
contact is on the moon's nearside, near its north pole, in the vicinity
of a crater named Goldschmidt. Both spacecraft will hit the surface at
3,760 mph (1.7 kilometers per second). No imagery of the impact is expected,
because the region will be in shadow at the time.

Both spacecraft have been orbiting the moon since Jan. 1, 2012. The duo's
successful primary mission yielded the highest-resolution gravity field map of
any celestial body. Future gravity field models developed from data collected
during the extended mission will be of even higher resolution. The map will
provide a better understanding of how the moon, Earth and other rocky planets
in the solar system formed and evolved.

JPL manages the GRAIL mission 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. Lockheed Martin Space Systems in Denver built the

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

D.C. 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

Sarah McDonnell 617-253-8923
Massachusetts Institute of Technology, Cambridge
s_mcd at mit.edu

Received on Sat 15 Dec 2012 10:17:34 PM PST

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