Twin GRAIL Probes Head to The Moon

NASA is headed back to the Moon!  Not with people, mind you, but with two very high tech spacecraft.  Yesterday morning, the GRAIL (Gravity Recovery and Interior Laboratory) mission successfully launched from Cape Canaveral atop a Delta 2 rocket.  The mission involves two nearly identical spacecraft, Grail-A and Grail-B, which are now headed, at a slow pace, to the Moon.

The Delta 2 rocket carrying the GRAIL spacecraft rises from Cape Canaveral (NASA).

The GRAIL mission is a fascinating one.  Its purpose is to construct a 'gravity map' of the Moon.  The 'gravity map' will tell scientists what parts of the Moon have a greater or weaker gravitational pull.  Knowing this information will not only reveal the make-up of the Moon's interior, but will help future spacecraft enter into more exact orbits, and aid in the landing of lunar probes.  As part of NASA's Discovery Program (promoting science missions on the cheap), costs were kept to a minimum, and that meant keeping the washing machine-sized spacecraft light on fuel.  The GRAIL craft will take nearly four months to reach the Moon - a trip that the Apollo missions made in three days.  As they approach the Moon, around New Year's Day, the spacecraft will maneuver into tandem orbits, and fly the duration of their mission in formation.  By keeping in constant radio contact with one another, and Earth based antennae, even the slightest perturbations in the crafts' orbits will be detectable.  The greater the disturbance of the orbit, the greater the gravitational pull any given point on the lunar surface is exerting on the spacecraft.  Voila, you've got a gravity map of the Moon.

Okay, so it isn't quite that simple, but that's the basic premise.  The actual maneuvering of the spacecraft into their exact orbits will be an unprecedented feat.  Two craft have never been put into tandem orbits like this around another planet, which is another reason the craft are taking their time to get to the Moon.  Small adjustments to the crafts' trajectories will be made over the coming months, so that when they reach lunar orbit, they will be ready for their formation flying.

An artist's rendition of the GRAIL spacecraft communicating with each other and the Earth (NASA/JPL).

Each GRAIL spacecraft will also be equipped with a MoonKAM (Moon Knowledge Acquired by Middle school students).  Students participating in the program will be able to pick out features on the lunar surface, and then photograph them using the cameras.  This is the first time NASA has launched an instrument with the express purpose of public outreach.

The successful launch of the GRAIL mission comes at a fortuitous time.  In the past three weeks there have been three major spacecraft launches; two by Russia, and one by China.  They all failed.  Not to mention the recent failure of a suborbital launch test by private space firm, Blue Origin.  I don't take pleasure in any of these failures, but it is nice to be reminded of NASA's dominance.  Even in the face of fickle funding, and sometimes waning public interest, NASA continues to succeed.  They employ some of the best engineers and scientists in the world, and NASA's budget is almost equal to the budgets of every other national space agency combined.  NASA leads in space science and in achieving amazing technological feats, and that isn't changing anytime soon.