NASA changes its Moon crash target

Published in The Hindu on September 29, 2009

LCROSS_6097f
The Lunar Crater Remote Observation and Sensing Satellite (LCROSS) will now plough into Cabeus, a 100-kilometre-wide crater and not Cabeus A, which was the earlier target on October 9, 2009. — Photo: New Mexico State University/ Marshall Space Flight Center

The National Aeronautics and Space Administration (NASA) has made a last-minute change in the target location where the Lunar Crater Remote Observation and Sensing Satellite (LCROSS) will send its spent upper-stage Centaur to crash on October 9 on the Moon in its search for water.

According to the journal Nature, the new target location is Cabeus, a 100-kilometer-wide crater, and not Cabeus A.

Cabeus A was earlier chosen based on a set of conditions, including the high concentration of hydrogen, maturity of the crater, and finally and most importantly, the visibility from earth as the debris plume rises after the impact.

The change in the site of impact was made as evidence from instruments aboard the Lunar Reconnaissance Orbiter, launched with LCROSS, showed significant differences between craters where water may be present.

The neutron-counting instrument had apparently provided evidence of hydrogen in different craters. Compared to Cabeus A, the Cabeus appeared to have an excess of hydrogen, a possible indicator of ice.

“The Cabeus region seems to be one of the places that could be the wettest, so we’d like to go there,” Jennifer Heldmann, the LCROSS observation campaign coordinator at NASA’s Ames Research Center in Moffett Field, California, was quoted as saying in Nature journal.

The data returned by LRO provided startling evidence that “water could be locked in a deep freeze within permanently shadowed polar craters.”

The change in the target site will make viewing the impact from earth a little difficult as Cabeus is deeper than Cabeus A. Observation of the impact plume from earth can happen only if the plume rises much higher.

“It’s not a big burden,” Nancy Chanover was quoted as saying in Nature. Dr. Chanover is an astronomer at New Mexico State University in Las Cruces, and is leading an effort to deduce the composition of the plume through an analysis of its ballistics.

Apart from watching the plume from earth, a ‘shepherding spacecraft,’ following the spent upper-stage Centaur after four minutes, will record the plume till it crashes the site itself.

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