[meteorite-list] NASA's Moon Twins Going Their Own Way (GRAIL)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 6 Oct 2011 14:18:57 -0700 (PDT)
Message-ID: <201110062118.p96LIv1e009894_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.cfm?release=2011-314

NASA's Moon Twins Going Their Own Way
Jet Propulsion Laboratory
October 06, 2011

PASADENA, Calif. - NASA's Gravity Recovery And Interior Laboratory
(GRAIL)-B spacecraft successfully executed its first flight path
correction maneuver Wednesday, Oct. 5. The rocket burn helped refine the
spacecraft's trajectory as it travels from Earth to the moon and
provides separation between itself and its mirror twin, GRAIL-A. The
first burn for GRAIL-A occurred on Sept. 30.

"Both spacecraft are alive and with these burns, prove that they're
kicking too, as expected," said David Lehman, GRAIL project manager at
NASA's Jet Propulsion Laboratory in Pasadena, Calif. "There is a lot of
time and space between now and lunar orbit insertion, but everything is
looking good."

GRAIL-B's rocket burn took place on Oct. 5 at 11 a.m. PDT (2 p.m. EDT).
The spacecraft's main engine burned for 234 seconds and imparted a
velocity change of 56.1 mph (25.1 meters per second) while expending 8.2
pounds (3.7 kilograms) of propellant. GRAIL-A's burn on Sept. 30 also
took place at 11 a.m. PDT. It lasted 127 seconds and imparted a 31.3 mph
(14 meters per second) velocity change on the spacecraft while expending
4 pounds (1.87 kilograms) of propellant.

These burns are designed to begin distancing GRAIL-A and GRAIL-B's
arrival times at the moon by approximately one day and to insert them
onto the desired lunar approach paths.

The straight-line distance from Earth to the moon is about 250,000 miles
(402,336 kilometers). It took NASA's Apollo moon crews about three days
to cover that distance. Each of the GRAIL twins is taking about 30 times
that long and covering more than 2.5 million miles (4 million
kilometers) to get there. This low-energy, high-cruise time trajectory
is beneficial for mission planners and controllers, as it allows more
time for spacecraft checkout. The path also provides a vital component
of the spacecraft's single science instrument, the Ultra Stable
Oscillator, to be continuously powered for several months, allowing it
to reach a stable operating temperature long before beginning the
collection of science measurements in lunar orbit.

GRAIL-A will enter lunar orbit on New Year's Eve, and GRAIL-B will
follow the next day. When science collection begins, the spacecraft will
transmit radio signals precisely defining the distance between them as
they orbit the moon. Regional gravitational differences on the moon are
expected to expand and contract that distance. GRAIL scientists will use
these accurate measurements to define the moon's gravity field. The data
will allow mission scientists to understand what goes on below the
surface of our natural satellite.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the GRAIL
mission. The Massachusetts Institute of Technology, Cambridge, is home
to the mission's principal investigator, Maria Zuber. The GRAIL mission
is part of the Discovery Program managed at NASA's Marshall Space Flight
Center in Huntsville, Ala. Lockheed Martin Space Systems, Denver, built
the spacecraft. Launch management for the mission is the responsibility
of NASA's Launch Services Program at the Kennedy Space Center in
Florida. JPL is a division of the California Institute of Technology in
Pasadena.

More information about GRAIL is online at: http://www.nasa.gov/grail and
http://grail.nasa.gov .

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
Cmcall5 at mit.edu

2011-314
Received on Thu 06 Oct 2011 05:18:57 PM PDT