NASA is set to launch its long-awaited Lunar Reconnaissance Orbiter June 17, carrying synthetic aperture radar (SAR) similar to one that already is returning tantalizing data from its perch on India's Chandrayaan 1 lunar orbiter. The LRO and its piggyback Lunar Crater Observation and Sensing Satellite (LCROSS) impactor are ready to blast off on an Atlas V as early as 3:51 p.m. EDT, with subsequent windows at 4:01 p.m. and 4:11 p.m. EDT on June 17 and more opportunities on June 18. The search for water ice in permanently shaded craters at the moon's poles will be a principal objective of the mission.
LCROSS is set to plunge into one of them in the hope its debris plume will contain ice that can be detected by spectral analysis, and the Mini-RF radars on both Chandrayaan and LRO have the resolution needed to look for ice signatures in the craters from orbit.
Data from the Indian orbiter already has raised interest in the Peary crater near the lunar north pole, where radar returns from smaller craters in the floor of the 78-kilometer (48-mile) diameter feature might be from ice. "We have seen interesting areas, but we're not calibrated yet so we don't have quantative numbers so the analysis is ongoing," says Ben Bussey of the Johns Hopkins University Applied Physics Laboratory, the deputy principal investigator on both Mini-RF SARs, warning that it's too early yet to draw conclusions.
"We saw interesting radar properties inside those craters that we are analyzing," he says. "But we've seen similar properties in craters that are sunlit. That's why it's not a definitive one-magic-number-tells you it's ice."
Orbital properties will make analysis of Chandrayaan data from the south pole, where NASA is contemplating planting a lunar outpost that could use water ice as a resource, even trickier until more time has passed.
LRO artist's concept: NASA
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