GRAIL’s twin spacecraft are tasked for a nine-month mission to explore Earth’s nearest neighbor in unprecedented detail. They will determine the structure of the lunar interior from crust to core and advance our understanding of the thermal evolution of the moon.
The spacecraft twins, GRAIL-A and GRAIL-B, will fly aboard a Delta II rocket launched from Florida. The twins’ circuitous route to lunar orbit will take 3.5 months and cover approximately 2.6 million miles (4.2 million kilometers) for GRAIL-A, and 2.7 million miles (4.3 million kilometers) for GRAIL-B.
In lunar orbit, the spacecraft will transmit radio signals precisely defining the distance between them. Regional gravitational differences on the moon are expected to expand and contract that distance.
GRAIL scientists will use these accurate measurements to define the moon’s gravity field. The data will allow mission scientists to understand what goes on below the surface of our natural satellite.
The launch will also be streamed live, with a chat available, on http://www.ustream.tv/nasajpl2 .