Friday, February 13, 2009

Mini-SAR imaging radar on the Chandrayaan-1

In carefully threading through the much anticipated and voluminous abstracts and presentations listed on the program for next month's Lunar & Planetary Science Conference XL (2009), as one might expect, there is much new from investigators for Japan's Kaguya and India's Chandrayaan 1 lunar orbiter missions, and much else besides.

Veteran PI Paul Spudis is the natural lead author of Abstract 1098, The Mini-SAR imaging radar on the Chandrayaan-1 Mission to the Moon, a presentation listed on the first of two full sessions devoted to science from those two missions along with China's Chang'E 1.

Because the abstracts for the presentations, posters and "print-only" studies are now on-line, we proceed with our own presentation of selected highlights from the conference schedule, hoping to draw your attention to this, the 40th annual LPSC since 1969 alone with the good science we anticipate will be unveiled there.

Chandrayaan's Mini-SAR is primarily an American contribution to India's mission, with contributed oversight from the LPS Institute itself, Johns Hopkins' Applied Physics Laboratory, the National Radio Astronomical Observatory (NRAO) in Socorro, NASM in Washington, DC, the University of Hawaii at Honolulu, ISRO and JPL.

"The possible existence of ice in the polar cold traps of the Moon continues to be debated. Clementine conducted a bistatic radar experiment in 1994, which supported the idea of an ice deposit within Shackleton crater near the south pole. However this result generated controversy and there is still disagreement whether the observed polarization anomalies are due to ice."

"However there is little argument related to the discovery by Lunar Prospector of enhanced hydrogen levels in the polar regions. The question is whether this hydrogen is in the form of water ice (or hydrogen). By determining the backscatter properties inside the dark areas near the poles we will constrain the nature and occurrence of water ice deposits on the Moon."

"While no remote measurement can definitively answer the question of whether ice exists at the lunar poles, an orbiting SAR provides the most robust method of obtaining a positive indication of ice deposits. With an orbital SAR, ALL areas on the Moon can be seen. The 6° inclination of the Moon’s orbital plane around the Earth means that large areas of permanent shadow that might contain water ice can never be seen from Earth and all polar areas that can be seen from Earth are viewed at high incidence angles, which reduces the coherent backscatter predicted for ice deposits. However all permanently shadowed regions will be imaged multiple times by an orbiting radar with incidence angles favorable for determining their scattering properties."

"Mini-SAR uses S-band (2380 MHz), has an illumination incidence angle of 35°, and image strips have spatial resolution of 75 meters per pixel. During the observation opportunities given to the instrument, it will image in SAR mode both poles every 2-hr orbit, covering both polar regions in a single 28-day mapping window."

Read LPSC XL #1098 HERE.

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