Gravity Recovery and Interior Laboratory - Overview

Overview

Maria Zuber of the Massachusetts Institute of Technology is GRAIL's principal investigator. NASA's Jet Propulsion Laboratory manages the project. As of August 5, 2011 (2011 -08-05), the program has cost US$496 million. Upon launch the spacecraft were named GRAIL A and GRAIL B and a contest was opened to school children to select names. Nearly 900 classrooms from 45 states, Puerto Rico and the District of Columbia, participated in the contest. The winning names, Ebb and Flow, were suggested by 4th grade students at Emily Dickinson Elementary School in Bozeman, Montana.

Each spacecraft transmits and receives telemetry from the other spacecraft and Earth-based facilities. By measuring the change in distance between the two spacecraft, the gravity field and geological structure of the Moon can be obtained. The two spacecraft are able to detect very small changes in the distance between one another. Changes in distance as small as one tenth of a micron—or half the diameter of a human hair—are detectable and measurable. The gravitational field of the Moon will be mapped in unprecedented detail.