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Proceedings Paper

Absolute irradiance scale of the Moon for on-orbit calibration
Author(s): Thomas C. Stone; Hugh H. Kieffer
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Paper Abstract

The recognized need for on-orbit calibration of remote sensing imaging instruments drives the ROLO project effort to characterize the Moon for use as an absolute radiance source. For over 5 years the ground-based ROLO telescopes have acquired spatially-resolved lunar images in 23 VNIR (Moon diameter ≈500 pixels) and 9 SWIR (≈250 pixels) passbands at phase angles within ±90 degrees. A numerical model for lunar irradiance has been developed which fits hundreds of ROLO images in each band, corrected for atmospheric extinction and calibrated to absolute radiance, then integrated to irradiance. The band-coupled extinction algorithm uses absorption spectra of several gases and aerosols derived from MODTRAN to fit time-dependent component abundances to nightly observations of standard stars. The absolute radiance scale is based upon independent telescopic measurements of the star Vega. The fitting process yields uncertainties in lunar relative irradiance over small ranges of phase angle and the full range of lunar libration well under 0.5%. A larger source of uncertainty enters in the absolute solar spectral irradiance, especially in the SWIR, where solar models disagree by up to 6%. Results of ROLO model direct comparisons to spacecraft observations demonstrate the ability of the technique to track sensor responsivity drifts to sub-percent precision. Intercomparisons among instruments provide key insights into both calibration issues and the absolute scale for lunar irradiance.

Paper Details

Date Published: 24 September 2002
PDF: 11 pages
Proc. SPIE 4814, Earth Observing Systems VII, (24 September 2002); doi: 10.1117/12.451694
Show Author Affiliations
Thomas C. Stone, U.S. Geological Survey (United States)
Hugh H. Kieffer, U.S. Geological Survey (United States)


Published in SPIE Proceedings Vol. 4814:
Earth Observing Systems VII
William L. Barnes, Editor(s)

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