May 30, 2012
GRAIL Mission Complete, Powers Down Kicking Off New Mission In August
Lee Rannals for RedOrbit.com
The spacecraft have been operating around the clock for 89 days since March 8, collecting data covering the entire surface three times.
GRAIL used an instrument called the Lunar Gravity Ranging System onboard each spacecraft to transmit radio signals that allow scientists to translate the data into a high-resolution map of the moon's gravitational field.
The primary mission ended this week as the twin probes sent in their last data set while orbiting 37 miles above the Sea of Nectar.
"Many of the measurement objectives were achieved from analysis of only half the primary mission data, which speaks volumes about the skill and dedication of our science and engineering teams," Maria Zuber, principal investigator of GRAIL at the Massachusetts Institute of Technology in Cambridge, said in a press release.
"While there is a great deal of work yet to be done to achieve the mission's science, it's energizing to realize that what we traveled from Earth to the moon for is right here in our hands."
He said GRAIL was able to deliver over 99.99 percent of the data that could have been collected, marking the twin probes' performances as flawless.
Both of the spacecraft instruments will be powered off until August 30, when they will start their extended science operations that will last through December 3, 2012.
The power down and mission completion took place just before next week's lunar eclipse, which the scientists at NASA say they anticipated.
"Before launch, we planned for all of GRAIL's primary mission science to occur between lunar eclipses," David Lehman, project manager of GRAIL from NASA's Jet Propulsion Laboratory, said in the press release. "But now that we have flown Ebb and Flow for a while, we understand them and are confident they can survive these eclipses in good shape."
The extended mission starting off in August will see that GRAIL takes a closer look at the moon's gravity field by halving the current altitude the twin probes are flying at.
"Orbiting at an average altitude of 14 miles (23 kilometers) during the extended mission, the GRAIL twins will be clearing some of the moon's higher surface features by about 5 miles (8 kilometers)," Joe Beerer, GRAIL's mission manager, said in a statement. "If Ebb and Flow had feet, I think by reflex they'd want to pull them up every time they fly over a mountain."
Now that the mission has been extended, so will GRAIL's reach into the education field through its MoonKAM education and public outreach program. Over 70,000 student images of the moon have been obtained through GRAIL so far.