Washington, Aug 26 (IANS): NASA's discovery mission programme - GRAIL - is making final launch preparations for its Sept 8 launch from Cape Canaveral Air Force Station in Florida, the space agency announced Thursday.

The Gravity Recovery And Interior Laboratory twin spacecraft are tasked for a nine-month mission to explore Earth's nearest neighbour 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, Xinhua reported.

The spacecraft twins, GRAIL A and B, will fly a circuitous route to lunar orbit taking 3.5 months and covering approximately 2.6 million miles (4.2 million km) for GRAIL-A, and 2.7 million miles (4.3 million km) for GRAIL-B.

"GRAIL will unlock lunar mysteries and help us understand how the moon, Earth and other rocky planets evolved as well," said Maria Zuber, GRAIL principal investigator from the Massachusetts Institute of Technology.

GRAIL's launch period opens Sept 8 and extends through Oct 19.