Tuesday, December 27, 2011

NASA gives update on mission to moon

NASA announced Monday that it is entering a new stage of a mission intended to place a pair of probes around Earth’s nearest neighbor and only satellite.

NASA officials said Monday mission controllers are preparing for the twin spaceships, named Grail-A and Grail-B, to enter the moon’s orbit on New Year’s Eve. The pair of probes are tasked with measuring the uneven gravity field of the moon and determine what lies beneath — straight down to the core.

NASA’s twin lunar Gravity Recovery and Interior Laboratory (GRAIL) probes were launched from Cape Canaveral Air Force Station on September 10, 2011. GRAIL-A is scheduled to arrive in lunar orbit beginning on Saturday, December 31, and GRAIL-B on Sunday, January 1. On New Year’s Eve, the pair of probes will fire their engine to slow down so that it could be captured into orbit. This move will be repeated by the other the following day.

Once in orbit, the pair will spend two months following each other around the moon. Scientists back on Earth will measure the varying distance between the pair of spaceships to calculate the lunar gravity field.

Speaking Monday, the team expressed confidence that the mission will continue to perform flawlessly, adding that they expect to gather an unprecedented amount of data from the mission.

“Both spacecraft have performed essentially flawlessly since launch, but one can never take anything for granted in this business,” said mission chief scientist Maria Zuber of the Massachusetts Institute of Technology.

Engineers said the chances of the probes overshooting are slim since their trajectories have been precise. Getting struck by a cosmic ray may prevent the completion of the engine burn and they won’t get boosted into the right orbit.

The straight-line distance from Earth to the moon is about 250,000 miles. It took NASA’s Apollo moon crews about three days to cover that distance. Each of the GRAIL twins is taking about 30 times that long and covering more than 2.5 million miles to get there. This low-energy, high-cruise time trajectory is beneficial for mission planners and controllers, as it allows more time for spacecraft checkout. NASA said the path would allow the program to save money and increase the chances of a successful mission.

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