Off to the Moon

September 12, 2011 — Forget about going back to the future. NASA is finally going back to the moon. More than 30 years after Neil Armstrong became the first man to step on the moon, NASA is finally going back to study the moon in unprecedented detail. But man won’t be inside the twin aircraft that will determine the structure of the lunar interior, from crust to core, and advance understanding of the thermal evolution of the moon. After launches on Thursday and Friday were postponed because of upper-level high winds and time needed to review propulsion system data, NASA's twin GRAIL spacecraft left Saturday morning for the moon aboard the most powerful Delta rocket in NASA’s inventory. The lunar orbiters are nestled inside the top of a United Launch Alliance Delta II 7920H-10C rocket. “Our GRAIL twins have Earth in their rearview mirrors and the moon in their sights," said David Lehman, GRAIL project manager at NASA's Jet Propulsion Laboratory. "The mission team is ready to test, analyze and fine-tune our spacecraft over the next three-and-a-half months on our journey to lunar orbit." The straight-line distance from Earth to the moon is approximately 250,000 miles. NASA's Apollo moon crews needed approximately three days to cover that distance. However, each spacecraft will take approximately 3-1/2 months and cover more than 2.5 million miles to arrive. This low-energy trajectory results in the longer travel time. The GRAIL mission will place two spacecraft into the same orbit around the moon. As they fly over areas of greater and lesser gravity, caused both by visible features such as mountains and craters and by masses hidden beneath the lunar surface, they will move slightly toward and away from each other. An instrument aboard each spacecraft will measure the changes in their relative velocity very precisely, and scientists will translate this information into a high-resolution map of the moon's gravitational field. The two GRAIL spacecraft are near-twins, each about the size of a washing machine, with minor differences resulting from the need for one specific spacecraft to follow the other as they circle the moon. GRAIL-A is scheduled to reach the moon on Dec. 31, 2011, while GRAIL-B will arrive on Jan. 1, 2012. The science payload on each spacecraft is the Lunar Gravity Ranging System, which will measure changes in the distance between the two spacecraft down to a few microns — about the diameter of a red blood cell. Each spacecraft will also carry a set of cameras for MoonKAM, marking the first time a NASA planetary mission has carried instruments expressly for an education and public outreach project. "If there was ever any doubt that Florida's Space Coast would continue to be open for business, that thought was drowned out by the roar of today's GRAIL launch," said NASA Administrator Charles Bolden. "GRAIL and many other exciting upcoming missions make clear that NASA is taking its next big leap into deep space exploration, and the space industry continues to provide the jobs and workers needed to support this critical effort."

NASA's GRAIL spacecraft successfully launched from Cape Canaveral Air Force Station, Florida, at 9:08 local on September 10, 2011. Image credit: NASA/JPL-Caltech/Thom Baur, United Launch Alliance As depicted above, GRAIL-A and GRAIL-B will work together to study the lunar interior, from crust to core, and to advance understanding of the moon’s thermal evolution. Credit: NASA/JPL-Caltech/Thom Baur, United Launch Alliance These images show the various stages of pre-launch preparations of NASA's twin GRAIL spacecraft at Space Launch Complex 17B on Cape Canaveral Air Force Station in Florida. Image credit: NASA/JPL-Caltech

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