GRAIL Will 'Dissect' the Moon Starting in 2012

NASA officials are eager to see their latest mission blast off to space. If all goes according to current plans, the two space probes making up the agency's Gravity Recovery and Interior Laboratory will reach the Moon by New Year's Eve, and start conducting scientific studies in March 2012.

The main goal of the GRAIL mission is to study the lunar interior, while compiling a map of its gravity field. This is a very important part of figuring out how matter is distributed inside Earth's satellite.

Once this is determined, the data will be fed in a computer simulation that will create a model of the Moon's interior. In turn, those datasets will be used to gain a deeper understanding of how the object formed in the early and violent days of the solar system.

In order to achieve this objective, experts decided to opt for a two-probe setup, similar to the NASA Solar Terrestrial Relations Observatory (STEREO) mission. Both spacecraft will take off aboard the same rocket, and will take about 3-and-a-half months to reach the Moon.

Usually, when an orbiter is placed on a direct orbit to the Moon, it takes about 3 days to get there. However, the $496-million mission was kept at such a low cost by taking on a different type of route.

NASA selected an orbit that will take the two space probes through the Sun-Earth Lagrange Point 1. By doing so, mission controllers managed to preserve large amounts of fuel, extending the science phase of the mission proportionally.

The duo will fly above the lunar surface in formation, in varying orbits. As they move over each area, differences in material distribution inside the Moon will exert a heavier or lighter gravitational pull on one of the probes.

As this happens, the distance between the two will be slightly modified, but more than enough for the mission's ultra-sensitive science suite to pick up and analyze. In this manner, NASA wants to cover the entire surface of the satellite, producing the most detailed and precise gravity map to date.

The average distance between GRAIL-A and GRAIL-B will vary depending on the orbits they occupy, within 75 to 225 miles (121 to 362 kilometers), Space reports.

“GRAIL, simply put, is a journey to the center of the moon. We will learn more about the interior of the moon with Grail than all previous lunar missions combined,” NASA Science Mission Directorate associate administrator Ed Weiler told reporters yesterday, September 6.

“We don't really have a good feel for lunar gravity. That can be very critical for future landing of robotic spacecraft, or even human spacecraft,” the agency official added.

GRAIL will take off from the Cape Canaveral Air Force Station's (CCAFS) Space Launch Complex 17B (SLC-17B), aboard a Delta II 7920H-10 delivery system. The spacecraft are scheduled to begin their science mission in March 2012, but the date depends on the success of the testing phase.

According to experts, there are only two, 1-second launch windows available for the planned September 8 launch date, at 8:37 am and 9:16 am EDT (1237 and 1337 GMT), respectively. The overall launch window runs until October 19.

The mission “will unlock lunar mysteries and help us understand how the Moon, Earth and other rocky planets evolved as well,” Massachusetts Institute of Technology professor Maria Zuber, the principal investigator of the GRAIL mission, said in a recent statement.