Space

December 14, 2012

Twin NASA probes prepare for Dec. 17 mission-ending moon impact

Twin lunar-orbiting NASA spacecraft that have allowed scientists to learn more about the internal structure and composition of the moon are being prepared for their controlled descent and impact on a mountain near the moon’s north pole at about 2:28 p.m., PST, Dec. 17.

Ebb and Flow, the Gravity Recovery and Interior Laboratory (GRAIL) mission probes, are being sent purposely into the lunar surface because their low orbit and low fuel levels preclude further scientific operations. The duo’s successful prime and extended science missions generated the highest resolution gravity field map of any celestial body. The map will provide a better understanding of how Earth and other rocky planets in the solar system formed and evolved.

“It is going to be difficult to say goodbye,” said GRAIL principal investigator Maria Zuber of the Massachusetts Institute of Technology in Cambridge. “Our little robotic twins have been exemplary members of the GRAIL family, and planetary science has advanced in a major way because of their contributions.”

The mountain where the two spacecraft will make contact is located near a crater named Goldschmidt. Both spacecraft have been flying in formation around the moon since Jan. 1, 2012. They were named by elementary school students in Bozeman, Mont., who won a contest. The first probe to reach the moon, Ebb, also will be the first to go down, at 2:28:40 p.m. Flow will follow Ebb about 20 seconds later.

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.

Ebb and Flow will conduct one final experiment before their mission ends. They will fire their main engines until their propellant tanks are empty to determine precisely the amount of fuel remaining in their tanks. This will help NASA engineers validate fuel consumption computer models to improve predictions of fuel needs for future missions.

“Our lunar twins may be in the twilight of their operational lives, but one thing is for sure, they are going down swinging,” said GRAIL project manager David Lehman of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Even during the last half of their last orbit, we are going to do an engineering experiment that could help future missions operate more efficiently.”

Because the exact amount of fuel remaining aboard each spacecraft is unknown, mission navigators and engineers designed the depletion burn to allow the probes to descend gradually for several hours and skim the surface of the moon until the elevated terrain of the target mountain gets in their way.

The burn that will change the spacecrafts’ orbit and ensure the impact is scheduled to take place Friday morning.

“Such a unique end-of-mission scenario requires extensive and detailed mission planning and navigation,” said Lehman. “We’ve had our share of challenges during this mission and always come through in flying colors, but nobody I know around here has ever flown into a moon mountain before. It’ll be a first for us, that’s for sure.”

During their prime mission, from March through May, Ebb and Flow collected data while orbiting at an average altitude of 34 miles (55 kilometers). Their altitude was lowered to 14 miles (23 kilometers) for their extended mission, which began Aug. 30 and sometimes placed them within a few miles of the moon’s tallest surface features.

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 spacecraft.




All of this week's top headlines to your email every Friday.


 
 

 

Headlines July 25, 2014

News: VA reform bills stalled by partisan bickering - Plans for a comprehensive Veterans Affairs Department reform bill that appeared all but finished a month ago devolved into partisan bickering and funding fights July 24, casting doubt on the future of a deal.   Business: Airbus, Boeing, Lockheed announce bids on Danish fighter competition; Saab withdraws -...
 
 

News Briefs July 25, 2014

Marines investigate corporal who vanished in Iraq U.S. Marine Corp officers are launching a formal investigation into whether a Lebanese-American Marine deserted his unit in Iraq or later after returning to the United States. A spokesman for the 2nd Marine Expeditionary Force at Camp Lejeune said July 24 that Cpl. Wassef Ali Hassoun is being...
 
 
Air Force photograph by A1C Erin OíShea

U.S. Forces display military might at Farnborough

Air Force photograph by A1C Erin O’Shea Capt. Tom Meyers discusses the F-15E Strike Eagle’s capabilities with spectators July 17, 2014, at the Farnborough International Airshow in England. Public access was granted ...
 

 
raptors4

Raptors, Falcons fuel up in desert skies

Three U.S. Air Force F-22 Raptors assigned to the 325th Fighter Wing, Tyndall Air Force Base, Fla., fly alongside a KC-135 Stratotanker assigned to the 93rd Air Refueling Squadron, Fairchild AFB, Wash., during Red Flag 14-3, Ju...
 
 
lm-kmax

Lockheed Martin’s unmanned cargo helicopter team returns from deployment

After lifting more than 4.5 million pounds of cargo and conducting thousands of delivery missions for the U.S. Marine Corps, the Lockheed Martin and Kaman Aerospace Corporation K-MAX cargo unmanned aircraft system has returned ...
 
 
Air Force photograph by A1C Thomas Spangler

Sun sets on Red Flag 14-3

Air Force photograph by A1C Thomas Spangler The sun sets behind a row of F-16 Fighting Falcons during Red Flag 14-3, July 16, 2014, at Nellis Air Force Base, Nev. Red Flag provides a series of intense air-to-air combat scenario...
 




0 Comments


Be the first to comment!


Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>