NASA scientists hope to uncover more of the Moon’s structure, which will help us on Earth to learn more about our past and future—along with the evolution of other rocky planets orbiting the Sun and other stars (what are called extrasolar planets, or exoplanets).

The GRAIL mission, part of NASA’s Discovery Program, will be managed by NASA’s Jet Propulsion Laboratory and its principal investigator is Maria Zuber of the Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology (MIT). Additional information about Zuber is found at: http://web.mit.edu/newsoffice/2003/zuber-0612.html.

Lockheed Martin Space Systems, Denver, Colorado, will build the spacecraft. Both spacecraft will be launched by one launch vehicle.

GRAIL is a part of the United States’ goal of returning astronauts to the Moon by 2020 and permanently establishing a scientific and exploratory presence on our closest neighbor in space.

NASA’s Discovery program is found on the Web at: http://discovery.nasa.gov/.

An illustration of the GRAIL spacecraft is found at: http://jpl.nasa.gov/images/grail/grail.jpg.

The December 11, 2007 NASA press release “New NASA Mission to Reveal Moon's Internal Structure and Evolution” is found at: http://www.nasa.gov/home/hqnews/2007/dec/HQ_07274_Grail_Mission.html.

[Authors note from reader's comment:

From the NASA Headquarters' website , [quote, with BOLD inserted for emphasis]: "Scientists will use the gravity field information from the two satellites to X-ray the moon from crust to core to reveal the moon's subsurface structures and, indirectly, its thermal history."

From SpaceRef.com website, [quote, with BOLD]: "The lunar mission will use two identical spacecraft orbiting the moon in a low, polar orbit. The spacecraft are based on the flight-proven XSS-11 technology demonstration satellite developed for the Air Force Research Laboratory. They will use Ka-band ranging instruments to send signals between one another, and then relay the data back to Earth to be analyzed. Scientists will examine the minute differences in distance the signals traveled between spacecraft. This will give unprecedented insight into the gravitational changes over the entire moon."

From MoonDaily.com website [with BOLD]:"The lunar mission will use two identical spacecraft orbiting the moon in a low, polar orbit. The spacecraft are based on the flight-proven XSS-11 technology demonstration satellite developed for the Air Force Research Laboratory. They will use Ka-band ranging instruments to send signals between one another, and then relay the data back to Earth to be analyzed. Scientists will examine the minute differences in distance the signals traveled between spacecraft. This will give unprecedented insight into the gravitational changes over the entire moon."

Author: Ka-band is a specific band within microwave radiation. I opted to say x-ray, instead of Ka-band, because I felt NASA was a better authority on the subject than those stating Ka-band.  Ka-band could very well be used for the mission, instead of x-rays.

The reader commented, saying that it uses "radio tracking". I haven't seen any reference to radio waves being used--but it [radio tracking] may indeed be the sensing mechanism of choice for the mission. If the reader would supply verification of "radio tracking" I would be glad to include this information in the article. In the meantime, I will investigate further, and update the article as need be.

Possibly, the article should state, until I learn more: "The twin spacecraft will measure the Moon, from core to surface, with very sensitive tracking instruments." --Atkins]

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