December 27, 2011
Lunar Probes To Reach Destination Over The Weekend
Two spacecraft set to study the moon will enter our celestial neighbor's orbit over New Year's weekend.
NASA's twin lunar Gravity Recovery and Interior Laboratory (GRAIL) probes have been independently traveling to their destination since launching in September and will arrive 24 hours apart from each other.
"Both spacecraft have performed essentially flawlessly since launch, but one can never take anything for granted in this business," mission chief scientist Maria Zuber of the Massachusetts Institute of Technology said in a press release.
One of the probes will fire its engine to slow down so that it can be captured into orbit on New Year's Eve, while the other will follow the next day.
Engineers said the chances of the probes overshooting their target are slim since their trajectories have been exact.
The lunar mission will see the spacecraft spend the next couple of months flying in formation and chasing one another around the Moon until they are about 35 miles above the surface and 124 miles apart.
The plan for the GRAIL probes is to measure the uneven gravity field and determine what lies beneath the Moon's surface.
Previous missions have attempted to measure lunar gravity and have had little success.
As the probes circle the moon, regional changes in the lunar gravity field will cause them to speed up or slow down, changing the distance between them. Radio signals transmitted by the probes will measure the slight distance gaps, allowing scientists to map the gravity field.
Scientist can determine what lies below the surface by using the gravity information. This data could help them understand why the far side of the moon is more rugged than the side that faces Earth.
NASA will hold a meeting regarding the probe's journey on Wednesday, December 28th.
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