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Proceedings Paper

Characterization of MODIS SD screen vignetting function using observations from spacecraft yaw maneuvers
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Paper Abstract

The MODIS reflective solar bands (RSB) include both the low-gain and high-gain spectral bands depending on their specific applications. MODIS RSBs are calibrated on-orbit by an on-board solar diffuser. In order to avoid detector response saturation when calibrating the high-gain bands, an optional attenuation screen, made of a metal plate with pinhole arrays, is placed in front of the SD panel. Since no pre-launch system-level characterization was made for the SD screen (SDS) vignetting function (VF), a series of spacecraft (Terra and Aqua) yaw maneuvers were carried out to perform on-orbit characterization of the VF. Assuming that the low-gain bands and the high-gain bands have the same VF, the current VF was derived from yaw observations using the MODIS low-gain bands through taking the ratio of their SD responses with and without the SDS in place. In this study, we attempt to characterize the SDS VF directly using detector responses of individual high-gain bands with the SDS in place only. The corresponding SD responses without the SDS, not available from measurements due to saturation, are calculated using detector gains, the SD bi-directional reflectance factor (BRF), and the view geometry that matches the yaw observations with the SDS in place. Results and discussions are focused on the band dependent and detector dependent features of the SDS VF, and their potential impact on the RSB calibration.

Paper Details

Date Published: 21 August 2009
PDF: 12 pages
Proc. SPIE 7452, Earth Observing Systems XIV, 745217 (21 August 2009); doi: 10.1117/12.824656
Show Author Affiliations
Zhipeng Wang, Science Systems and Applications, Inc. (United States)
Xiaoxiong Xiong, NASA Goddard Space Flight Ctr. (United States)

Published in SPIE Proceedings Vol. 7452:
Earth Observing Systems XIV
James J. Butler; Xiaoxiong Xiong; Xingfa Gu, Editor(s)

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