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Proceedings Paper

Spatial Input Response Of Active Cavity Radiometers Are Shown To Obey Cosine Law Over Input Angles Extending Beyond The Earth Limb
Author(s): R. J. Hesser; S. L. Carman; R. I. Gilje
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Paper Abstract

The requirement to verify that the Earth Radiation Budget Experiment (ERBE) radiation measurement instruments respond accurately to input radiation over large input angles is discussed in this paper. The use of active cavity radiometers (ACRs) in the reference and the ERBE flight instruments, with fields of view ranging between 50 and 145 deg conical angle, required considerable development and analysis to ensure that the radiometers were designed properly. Ray trace analyses, laser experiments in both visible and infrared regimes, test data of the instrument when subjected to distributed irradiance calibration sources and, finally, a cosine response test on the overall instrument, are also discussed. Cosine response is demonstrated within the included field of view with these large acceptance angles, while zero input response is verified for sources emanating outside the nominal cut-off angles for each sensor. The use of reflecting field-of-view limiters reduces the sensitivity of thermal input from the instrument front end, but enhances the stray radiation. These instruments are shown to be insensitive to stray radiation caused by the radiometric design. This paper describes the angular response analyses, tests, and associated hardware that enables the prospective users of the ERBE instruments to con-fidently measure earth radiation for input acceptance angles extending beyond the earth limb, without having to be concerned with solar or lunar stray radiation effects outside the acceptance angles.

Paper Details

Date Published: 22 September 1983
PDF: 8 pages
Proc. SPIE 0416, Applications of Optical Metrology: Techniques and Measurements II, (22 September 1983); doi: 10.1117/12.935937
Show Author Affiliations
R. J. Hesser, TRW Inc. (United States)
S. L. Carman, TRW Inc. (United States)
R. I. Gilje, TRW Inc. (United States)


Published in SPIE Proceedings Vol. 0416:
Applications of Optical Metrology: Techniques and Measurements II
Jar Jueh Lee, Editor(s)

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