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Proceedings Paper

NOAA-20 VIIRS screen transmittance functions determined with both yaw maneuver and regular on-orbit data
Author(s): Ning Lei; Xiaoxiong Xiong
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Paper Abstract

The Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the NOAA-20 satellite regularly performs on-orbit radiometric calibration of its reflective solar bands (RSBs) through observations of an onboard sunlit solar diffuser (SD). The incident sunlight passes through an attenuation careen (the SD screen) and then scatters off the SD to provide a radiance source for the calibration. The on-orbit change of the SD bidirectional reflectance distribution function (BRDF), denoted as the H-factor, is determined by an onboard solar diffuser stability monitor (SDSM) whose eight SDSM detectors observe the sun through another attenuation screen (the SDSM screen) and the sunlit SD consecutively to measure the SD BRDF change. The products of the SD screen transmittance and the BRDF at the mission start for both the SDSM and RSBs and the SDSM screen transmittance were measured prelaunch. Large unrealistic undulations in the H-factor were seen when using the prelaunch screen transmittances. Shortly after the satellite launch, fifteen on-orbit yaw maneuvers were performed to further characterize the screens. Although significantly improved, the H-factor derived using the yaw maneuver data determined screens still has large unrealistic undulations, revealing that the solar azimuth angular step size of the yaw maneuvers is too large. In this paper, we add high quality regular on-orbit data to the yaw maneuver data to further improve the relative products and the relative SDSM screen transmittance. The H-factor time series derived from the newly determined screen transmittances is much smoother than that derived from using only the yaw maneuver data and thus improves considerably the radiometric calibration accuracy.

Paper Details

Date Published: 9 September 2019
PDF: 7 pages
Proc. SPIE 11127, Earth Observing Systems XXIV, 111271P (9 September 2019); doi: 10.1117/12.2529799
Show Author Affiliations
Ning Lei, Science Systems and Applications, Inc. (United States)
Xiaoxiong Xiong, NASA Goddard Space Flight Ctr. (United States)

Published in SPIE Proceedings Vol. 11127:
Earth Observing Systems XXIV
James J. Butler; Xiaoxiong (Jack) Xiong; Xingfa Gu, Editor(s)

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