Article Posted on : - Jan 02, 2012

Artist concept of GRAIL-B performing its lunar orbit insertion burn. Photo: NASA/JPL-Caltech

PASADENA, CALIFORNIA (BNS): The second of NASA's two Gravity Recovery And Interior Laboratory (GRAIL) spacecraft has successfully completed its planned main engine burn and is now in lunar orbit.

GRAIL-B achieved lunar orbit at 2:43 p.m. PST (5:43 p.m. EST) on Sunday and GRAIL-A successfully completed its burn Saturday at 2 p.m. PST (5 p.m. EST), NASA said.

The insertion maneuvers have placed the spacecraft into a near-polar, elliptical orbit with an orbital period of approximately 11.5 hours.

Over the coming weeks, the GRAIL team will execute a series of burns with each spacecraft to reduce their orbital period to less than two hours.

At the start of the science phase in March 2012, the two GRAILs will be in a near-polar, near-circular orbit with an altitude of about 55 kilometers.

During GRAIL's science mission, the two spacecraft will transmit radio signals precisely defining the distance between them. As they fly over areas of greater and lesser gravity caused by visible features such as mountains and craters, and masses hidden beneath the lunar surface, the distance between the two spacecraft will change slightly.

Scientists will translate this information into a high-resolution map of the moon's gravitational field. The data will allow scientists to understand what goes on below the lunar surface. This information will increase knowledge of how Earth and its rocky neighbors in the inner solar system developed.

Each spacecraft carries a small camera called GRAIL MoonKAM (Moon Knowledge Acquired by Middle school students) with the sole purpose of education and public outreach.