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NASA EPOXI Mission Earth Flyby Imagery: Lunar Calibration: HRI IR Results

Status Report From: University of Maryland
Posted: Monday, December 31, 2007

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3 Images

Caption: The December 2007 Earth gravity assist provided a unique opportunity for us to calibrate our instruments using the Moon. In particular, the Moon is very useful because it fills the entire field of view of the spectrometer. As planned, we smeared our exposures while scanning across the Moon. The results show that our spacecraft pointing and commanding was spot on.

For the first time, either on the ground or in space, we now have uniform data at all wavelengths covering over 90% of the IR detector. We also made measurements which will allow us to cross-calibrate our instruments with telescopic data and, in the very near future, with a wealth of lunar measurements from new orbiting spacecraft. These data will significantly improve the science from EPOCh observations of Earth and the DIXI flyby of comet Hartley 2, as well as from Deep Impact's prime mission to comet Tempel 1. The EPOXI lunar calibration was very successful and nearly three years after launch it sure is nice to get new data from an old friend!

Technical Details: The top image does not appear to be all that exciting or beautiful, but is the critical measurement made during the 2007 Earth Flyby. We blurred the Moon at three different rates and then stitched the results together to make a "flat-field" -- a record of the instrument response to a uniform light source.

The middle and bottom images show the IR data reconstructed as images of the Moon at 1.5um. These are very comparable to the VIS images (same resolution as MRI). The longer wavelength thermal IR was as we expected mostly saturated except at our shortest exposures (the little image "1005000").

Image Credit: NASA/JPL-Caltech/UMD/GSFC

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