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Proceedings Paper

Design of a solar diffuser for on-orbit calibration of the Clouds and the Earth's Radiant Energy System (CERES) instruments
Author(s): Mark A. Folkman; Peter J. Jarecke; Ted R. Hedman; John S. Yun; Robert Benjamin Lee
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Paper Abstract

Stability of the solar constant makes the Sun an attractive on-orbit calibration source for radiometers operating at visible and near IR wavelengths. Direct viewing of the Sun provides a radiance or irradiance that is significantly above the dynamic range of most earth observing system (EOS) radiometers, thereby requiring attenuated viewing of the Sun. To provide radiometric repeatability, the attenuator used must be stable over time at all in-band wavelengths, uniformly flood the radiometer aperture and field of view, and be invariant over the range of solar viewing angles. The Earth Radiation Budget Experiment (ERBE) radiometers flown in the mid-1980s carried a mirror attenuator mosaic (MAM) to attenuate the solar energy. This device, consisting of specularly reflective, closely packed concave hemispheres with a black mask covering the area between the spheres, was successfully used to calibrate the ERBE shortwave (0.3 to 3.5 micrometers ) and total (0.3 to > 50 micrometers ) radiometer channels. For CERES, the calibration accuracy requirements have been tightened (+/- 1% shortwave, +/- 0.5% total channel, end-of-life, 1 (sigma) ). While the stability and uniformity demonstrated by the ERBE MAM are sufficient for CERES, the variation with solar incidence angle is not. Improvements to the ERBE design have been made for CERES and sample MAMs have been fabricated and tested. The results of this study as well as the features and details of the MAM design are addressed.

Paper Details

Date Published: 25 August 1993
PDF: 10 pages
Proc. SPIE 1939, Sensor Systems for the Early Earth Observing System Platforms, (25 August 1993); doi: 10.1117/12.152858
Show Author Affiliations
Mark A. Folkman, TRW Space & Electronics Group (United States)
Peter J. Jarecke, TRW Space & Electronics Group (United States)
Ted R. Hedman, TRW Space & Electronics Group (United States)
John S. Yun, TRW Space & Electronics Group (United States)
Robert Benjamin Lee, NASA Langley Research Ctr. (United States)


Published in SPIE Proceedings Vol. 1939:
Sensor Systems for the Early Earth Observing System Platforms
William L. Barnes, Editor(s)

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