NASA GRAIL Probes To Crash Into Moon
December 13, 2012

NASA’s GRAIL Probes Prepare To Crash Into Moon On Monday

[ Watch the Video: Last Flight For GRAIL's Twin Spacecraft]

Lee Rannals for - Your Universe Online

After a year run, NASA is preparing to end the twin lunar-orbiting GRAIL probes' mission with a bang — into the Moon, that is.

NASA said that the twin spacecraft are being prepared for their controlled descent and impact on a mountain near the moon's north pole next Monday at 2:28 p.m. Pacific time.

The Gravity Recovery and Interior Laboratory (GRAIL) mission probes, Ebb and Flow, are being crashed into the lunar surface because their low orbit and low fuel levels preclude any further scientific operations, NASA said.

The twin spacecraft have allowed scientists to learn more about the internal structure and composition of the moon.

Monday will mark the end of the successful prime and extended missions that helped generate the highest-resolution gravity field map of any celestial body. The map will help 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," GRAIL principal investigator Maria Zuber of the Massachusetts Institute of Technology (MIT) in Cambridge, said in a statement. "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 twin probes will crash land into a mountain located near a crater named Goldschmidt. Both spacecraft have been flying in formation around the moon since January 1 of this year.

Ebb and Flow will make impact with the moon at 3,760 miles per hour. NASA said that no imagery of the impact is expected because the point of impact will be in the shadowy part of the Moon.

For their final task, the twin probes will be firing off their main engines until their propellant tanks are empty to determine exactly how much fuel remained in their tanks. This will help NASA 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, California.

"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."

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.

"Such a unique end-of-mission scenario requires extensive and detailed mission planning and navigation," Lehman said in the release. "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."