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Proceedings Paper

On-orbit characterization of a solar diffuser’s bidirectional reflectance factor using spacecraft maneuvers
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Paper Abstract

The MODerate Resolution Imaging Spectroradiometer (MODIS) uses an on-board solar diffuser (SD) panel made of Spectralon for the radiometric calibration of its 20 reflective solar bands (RSB). The spectral wavelengths of the RSB range from 0.41 to 2.1 micrometers. The on-orbit calibration coefficients are determined from the sensor s responses to the diffusely reflected solar illumination from the SD. This method requires an accurate pre-launch characterization of solar diffuser s bi-directional reflectance factors (BRF) that should cover the sensor s spectral range and illumination/viewing angles and accurate on-orbit monitoring of SD degradation over time. The MODIS SD panel s bi-directional reflectance factors were characterized prior to the sensor s final system integration (pre-launch by the instrument vendor using reference samples traceable to the NIST reflectance standards at a number of wavelengths and carefully selected combinations of the illumination/viewing angles. The measured BRF values were fitted into smooth surfaces and then interpolated for each of the MODIS reflective solar bands. In this paper, we describe an approach designed for the MODIS on-orbit characterization and validation of its SD BRF using multiple SD solar observations at several spacecraft yaw angels. This approach has been successfully applied to both the Terra and Aqua MODIS. This paper presents the algorithm used to derive the SD s relative BRF from observations during spacecraft yaws and compares the on-orbit results with corresponding pre-launch values.

Paper Details

Date Published: 10 November 2003
PDF: 9 pages
Proc. SPIE 5151, Earth Observing Systems VIII, (10 November 2003); doi: 10.1117/12.504802
Show Author Affiliations
Xiaoxiong Xiong, NASA Goddard Space Flight Ctr. (United States)
Junqiang Sun, Science Systems and Applications, Inc. (United States)
Joe Esposito, Science Systems and Applications, Inc. (United States)
Xiaojin Liu, Science Systems and Applications, Inc. (United States)
William L. Barnes, Univ. of Maryland, Baltimore County (United States)
B. Guenther, Univ. of Maryland, Baltimore County (United States)

Published in SPIE Proceedings Vol. 5151:
Earth Observing Systems VIII
William L. Barnes, Editor(s)

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