NASA has announced that their twin space probes, Ebb and Flow, which have been orbiting the moon since January 1 of this year, will and their missions and are being prepared for their controlled descent and impact near the moon’s north pole at roughly 2:30 PM PST Monday, December 17, 2012.
The twin satellites, named Ebb and Flow, are part of the Gravity Recovery and Interior Laboratory (GRAIL) mission. The space probes are being sent to the lunar surface because of low fuel levels, and their degrading orbit limits any further scientific research.
The satellite’s primary mission was to generate a high-resolution gravity field map of the Earth’s moon, so that we may have a better understanding of how Earth and other planets in the solar system were formed and have evolved over the years.
“It is going to be difficult to say goodbye.” Said Grail principal investigator Maria Zuber of MIT. “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 impact the moon is located near the moon’s north pole near a crater named Goldschmidt.
But before they end their mission, the satellites will conduct one final experiment. NASA will fire their main engines until all fuel is expended, helping NASA engineers determine the precise amount of fuel remaining in their fuel tanks, as well as validating fuel consumption computer models, so as to improve predictions of future fuel needs on space 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 in engineering experiment that could help future missions operate more efficiently.”
“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 will be a first for us, that’s for sure.”
Because the exact amount of fuel remaining on board each spacecraft is not known, NASA engineers designed the depletion burn allowing the program to descend gradually over several hours time, just skimming the service of the moon until the elevated terrain of the mountain gets in their way.
What follows is a video animation of the twin space probes final flight path. The animations were created from data obtained by NASA’s Lunar Reconnaissance Program.
Article by Jim Donahue