[meteorite-list] LADEE Satellite to Continue Gathering Data Up to Planned Lunar Impact

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 4 Apr 2014 15:34:22 -0700 (PDT)
Message-ID: <201404042234.s34MYMDq009118_at_zagami.jpl.nasa.gov>

April 3, 2014
     
NASA Satellite to Continue Gathering Data Up to Planned Lunar Impact

NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft is
gradually lowering its orbital altitude to continue making science
observations prior to its planned impact on the moon's surface on or before
April 21.

Ground controllers at NASA's Ames Research Center in Moffett Field, Calif.,
are maneuvering the spacecraft to fly approximately 1 to 2 miles (2 to 3
kilometers) above the lunar surface to gather science measurements at the
lowest altitude possible.

A final maneuver will ensure LADEE's trajectory will impact the far side of
the moon, which is not in view of Earth or near any previous lunar mission
landings. Ground controllers have little room for error with LADEE's
navigation system, and at these low orbital altitudes, a small error could
mean the difference between continuing to orbit above the lunar surface and
impacting it. Because of this, the team does not intend to target a specific
impact location on the moon's surface.

"The moon's gravity field is so lumpy, and the terrain is so highly variable
with crater ridges and valleys that frequent maneuvers are required or the
LADEE spacecraft will impact the moon's surface," said Butler Hine, LADEE
project manager at Ames. "Even if we perform all maneuvers perfectly, there's
still a chance LADEE could impact the moon sometime before April 21, which is
when we expect LADEE's orbit to naturally decay after using all the fuel
onboard."

Until mid-April, ground controllers will continue to fire the LADEE altitude
control thrusters once a week to keep the observatory in its target orbit. On
April 11, LADEE will perform its final orbital maintenance maneuver before
the total lunar eclipse on April 15, when Earth's shadow passes over the
Moon. This eclipse, which will last approximately four hours, exposes the
spacecraft to conditions at the limits of what it was designed to withstand.

"If LADEE survives the eclipse, we will have nearly a week of additional
science at low altitudes before impact," said Rick Elphic, LADEE project
scientist at Ames. "For a short mission like LADEE, even a few days count for
a lot - this is a very exciting time in the mission."

After the eclipse, ground controllers will determine how well the spacecraft
is functioning. If it is healthy, LADEE will continue to acquire and transmit
science data, as longs as its altitude and contact with ground controllers
allow.

"We're very eager to see how LADEE handles the prolonged exposure to the
intense cold of this eclipse, and we've used flight data to predict that most
of the spacecraft should be fine," said Hine. "However, the eclipse will
really put the spacecraft design through an extreme test, especially the
propulsion system."

Launched in September 2013, from NASA's Wallops Flight Facility on Wallops
Island, Va., the vending-machine size spacecraft has been orbiting the moon
since Oct. 6. On Nov. 10, LADEE began gathering science data, and on Nov. 20,
the spacecraft entered its science orbit around the moon's equator. LADEE has
been in extended mission operations following a highly successful 100-day
primary science phase.

"Because the LADEE team has flawlessly performed every maintenance maneuver,
they've been able to keep the spacecraft flying in its proper orbit and have
enabled this amazing mission extension and science to continue up until the
very end," said Joan Salute, LADEE program executive at NASA Headquarters in
Washington.

LADEE's three science payload instruments have been working to unravel the
mysteries of the moon's atmosphere, acquiring more than 700,000 measurements.
In its previous orbit, LADEE's closest approach to the lunar surface was
between 12.5 and 31 miles (20 and 50 kilometers), and its farthest was
between 47 and 93 miles (75 and 150 kilometers) - a unique position that
allows the spacecraft to frequently pass from lunar day to lunar night every
two hours. This vantage provides data on the full range of changes and
processes occurring within the moon's tenuous atmosphere.

Scientists hope this data will help answer a long-standing question: Was
lunar dust, electrically charged by sunlight, responsible for the pre-sunrise
glow detected during several Apollo missions above the lunar horizon? LADEE
also is gathering detailed information about the structure and composition of
the thin lunar atmosphere. A thorough understanding of these characteristics
of our nearest celestial neighbor will help researchers understand other
bodies in the solar system, such as large asteroids, Mercury, and the moons
of outer planets.

NASA's Science Mission Directorate in Washington funds the LADEE mission.
Ames manages the overall mission and serves as a base for mission operations
and real-time control of the probe. NASA's Goddard Space Flight Center in
Greenbelt, Md., catalogues and distributes data to a science team located
across the country and manages the science instruments. NASA's Marshall Space
Flight Center in Huntsville, Ala., manages LADEE within the Lunar Quest
Program Office.

For more information about the LADEE mission, visit:

http://www.nasa.gov/ladee

-end-

Dwayne Brown
Headquarters, Washington
202-358-1752
dwayne.c.brown at nasa.gov

Rachel Hoover
Ames Research Center, Moffett Field, Calif.
650-930-6149
rachel.hoover at nasa.gov
Received on Fri 04 Apr 2014 06:34:22 PM PDT