Since March 8th, NASA's Gravity Recovery and Interior Laboratory (GRAIL) mission has studied the moon from crust to core using its twin lunar probes, Ebb and Flow, flying in polar orbits and collecting three complete sets of data. On Tuesday, May 29th, NASA announced that GRAIL had completed its prime mission ahead of schedule. The GRAIL team is now preparing for extended science operations which will begin August 30th and continue through December 3rd.
The GRAIL mission has gathered unprecedented detail about the internal structure and evolution of the moon. This information will increase our knowledge of how Earth and its rocky neighbors in the inner solar system developed into the diverse worlds we see today.
An instrument called the Lunar Gravity Ranging System onboard each spacecraft transmits radio signals that allow scientists to translate the data into a high-resolution map of the moon's gravitational field. The spacecraft returned their last data set of the prime mission today. The instruments were turned off on Tuesday at 1 PM EDT / 10 AM PDT, when the two spacecraft were 37 miles (60 kilometers) above the Sea of Nectar.
Both spacecraft instruments will be powered back on August 30th. The spacecraft will have to endure a lunar eclipse on June 4, as well as the associated sudden changes in temperature and the energy-sapping darkness that accompanies the phenomena were expected and do not concern engineers about the spacecraft's health.
The extended mission goal is to take an even closer look at the moon's gravity field. To achieve this, GRAIL mission planners will halve their current operating altitude to the lowest altitude that can be safely maintained, averaging 14 miles (23 kilometers) during the extended mission. And the probes will be clearing some of the moon's higher surface features by about 5 miles (8 kilometers).
And now, the mission particulars...
The GRAIL mission is managed by JPL 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. NASA's Deep Space Network is an international network of antennas that supports interplanetary spacecraft missions and radio and radar astronomy observations for the exploration of the solar system and the universe. The network also supports selected Earth-orbiting missions. Lockheed Martin Space Systems in Denver built the spacecraft. JPL is a division of the California Institute of Technology in Pasadena.
For more information about GRAIL, visit: www.nasa.gov/grail .
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