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NASA’s Lunar Crater Observation and Sensing Satellite mission (LCROSS) based on new analysis of available lunar data, has shifted the target crater from Cabeus A to Cabeus (proper).
The decision was based on continued evaluation of all available data and consultation/input from members of the LCROSS Science Team and the scientific community, including impact experts, ground and space based observers, and observations from Lunar Reconnaissance Orbiter (LRO), Lunar Prospector (LP), Chandrayaan-1 and JAXA’s Kaguya spacecraft. This decision was prompted by the current best understanding of hydrogen concentrations in the Cabeus region, including cross-correlation between the latest LRO results and LP data sets.
The general consensus of lunar experts led by the LCROSS science team is that Cabeus shows, with the greatest level of certainty, the highest hydrogen concentrations at the south pole. Further consideration of the most current terrain models provided by JAXA’s Kaguya spacecraft and the LRO Lunar Orbiter Laser Altimeter (LOLA) was important in the decision process.The models show a small valley in an otherwise tall Cabeus perimeter ridge, which will allow for sunlight to illuminate the ejecta cloud on Oct. 9, and much sooner than previously estimated for Cabeus. While the ejecta does have to fly to higher elevations to be observed by Earth assets, a shadow cast by a large hill along the Cabeus ridge, provides an excellent, high-contrast, back drop for ejecta and vapor measurements.
The LCROSS team concluded that Cabeus provided the best chance for meeting its mission goals. The team critically assessed and successfully advocated for the change with the Lunar Precursor Robotic Program (LPRP) office. The change in impact crater was factored into LCROSS’ most recent Trajectory Correction Maneuver, TCM7.
During the last days of the mission, the LCROSS team will continue to refine the exact point of impact within Cabeus crater to avoid rough spots, and to maximize solar illumination of the debris plume and Earth observations.
Image credit: B.Grieger, B.H. Foing & ESA/SMART-1/ AMIE team
The Cabeus crater is near the Moon’s south pole, and the bottom is permanently in shadow. See the shadow across the crater? As the Moon spins and orbits the Earth, that shadow never lifts, but instead moves around the crater floor like the hand of a celestial clock.
We know there is water all over the Moon in small quantities, but is there a lake of frozen water under the crater’s dusty floor? When LCROSS impacts, we may find out.
The above image was taken by SMART-1, an ambitious ESA spacecraft that orbited the Moon for nearly two years. Its ultimate fate? It too impacted the lunar surface in September 2006. While that impact wasn’t meant to hunt for water, it did kick up some dust, and made a flash bright enough to be detected from Earth. Its mission was a big success, and its demise was a harbinger for things to come on October 9.
Posted by: Soderman/NLSI Staff
Source: NASA & http://blogs.discovermagazine.com/badastronomy/2009/09/26/image-of-future-lcross-lunar-impact-site/
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Author/Curator: Greg Schmidt NASA Official: David Morrison Last Updated: November 24, 2009 + Contact NASA + Site Map |
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