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

[Ron Baalke]

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