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Proceedings Paper

Technique for visible calibration of future GOES sensors by solar viewing through a perforated screen
Author(s): James C. Bremer; Guojun Si
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Paper Abstract

Future GOES missions, augmented by the addition of very stable visible calibration, could measure long-term changes in the earth's albedo. Direct sunlight can be viewed through a plate perforated by small holes, attenuating the radiance at the center of the solar image by both blockage and diffraction. Attenuation by a factor of 50,000 produces a full-aperture, end-to-end calibration source with radiance comparable to a high-albedo target. Since its radiance depends only upon geometry, the perforated plate technique avoids the materials degradation problems inherent to calibration techniques based on reflection or refraction. Our analysis indicates that a plate with 50 micrometers holes spaced 4.9 mm apart in a hexagonal array has the potential to satisfy the requirement for a source stable to < 1 percent over a 5-year GOES mission. Some randomization of the hole positions may be desirable to suppress interference effects. We have made preliminary measurements of the large- scale angular structure of a simulated solar image viewed through a perforated screen, and have demonstrated their agreement with out theoretical predictions.

Paper Details

Date Published: 18 October 1996
PDF: 12 pages
Proc. SPIE 2812, GOES-8 and Beyond, (18 October 1996); doi: 10.1117/12.254107
Show Author Affiliations
James C. Bremer, Swales and Associates, Inc. (United States)
Guojun Si, Swales and Associates, Inc. (United States)

Published in SPIE Proceedings Vol. 2812:
GOES-8 and Beyond
Edward R. Washwell, Editor(s)

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