NASA Jet Propulsion Laboratory (JPL) mission controllers announce that both spacecraft in the American space agency's Gravity Recovery And Interior Laboratory (GRAIL) have successfully completed the first flight path correction maneuvers in their long trek to the Moon.
Apollo astronauts made their way to Earth's natural satellite in about 3 days, having taken a direct route. But NASA chose to make a detour while sending GRAIL to lunar orbit, primarily because experts sought to save as much fuel as possible.
The mission launched aboard a Delta II delivery system, from Space Launch Complex 17B (SLC-17B) at the Cape Canaveral Air Force Station (CCAFS), in Florida. Takeoff took place at 1308 UTC, on September 10.
GRAIL-A and GRAIL-B are expected to enter lunar orbit on December 31, 2011 and January 1, 2012, respectively. They will spend more than three months on route, carrying out several more flight path corrections. Still, they will consume only a fraction of the fuel otherwise needed to go to the Moon.
“Both spacecraft are alive and with these burns, prove that they're kicking too, as expected. There is a lot of time and space between now and lunar orbit insertion, but everything is looking good,” JPL GRAIL project manager David Lehman explains.
The first correction maneuver was carried out on September 30, using the GRAIL-A spacecraft. The probe lost a total of 4 pounds (1.87 kilograms) of propellant, but managed to change its velocity by about 31.3 miles per hour (14 meters per second) in about 127 seconds.
On October 5, the GRAIL-B probe also carried out a course correction of its own, this time lasting about 234 seconds. This changed its velocity by about 56.1 miles per hour (25.1 meters per second).
The primary reason why so many differences exist in engine firing patterns is that experts want the probes spaced farther apart. This will ensure that they enter their planned orbits around the Moon, in the proper flight formation.
The purpose of the mission is to fly the two spacecraft in formation through multiple lunar orbits. As this happens, various areas will pull on the probes with varied strengths. By constantly measuring the distance between them, the instruments will be able to map the lunar interior.
The distribution of matter within the body itself is of special interest to experts, who say that this will give them fresh new insight into how the Moon came to its current appearance. “Our GRAIL twins have Earth in their rearview mirrors and the Moon in their sights,” Lehman concludes.
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