With the intent of mapping its gravity, twin satellites are due to go into orbit around the Moon this weekend. Lead scientist Dr Maria Zuber is expecting some dramatic discoveries. The duos were launched from Cape Canaveral, Florida, last September, and have taken a long twisting out to their destination.
Grail will map the small variations in gravity athwart the Moon. This weekend's loom to the Moon will bring them in above the South Pole. The Grail twins will make their measurements by transportation out a carefully calibrated tracking down of each other. Each satellite will carry out a roughly 40-minute engine burn to slow itself and take up an indirect orbit around the 3,500km-wide sphere.