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Proceedings Paper

Comparison of MODIS and VIIRS solar diffuser stability monitor performance
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Paper Abstract

Launched in December 1999 and May 2002, Terra and Aqua MODIS have successfully operated for more than 12 and 10 years, respectively. MODIS reflective solar bands (RSB) are calibrated on-orbit by a solar diffuser (SD). Its on-orbit degradation, or the change in its bi-directional reflectance factor (BRF), is tracked by a solar diffuser stability monitor (SDSM). The MODIS SDSM makes alternate observations of direct sunlight through an attenuation screen (Sun view) and of sunlight reflected diffusely off the SD (SD view) during each SDSM calibration event. The MODIS SDSM has 9 detectors, covering wavelengths from 0.41 to 0.94 μm. Due to a design error in MODIS SDSM sub-system (identified post-launch), relatively large ripples were noticed in its Sun view responses. As a result, an alternative approach was developed by the MODIS calibration team to minimize the uncertainty in determining the SD on-orbit degradation. The first VIIRS, on-board the Suomi NPP spacecraft, was successfully launched in October 2011. It carries a MODIS-like SD and SDSM system for its RSB on-orbit calibration. Its design was improved based on lessons learned from MODIS. Operationally, the VIIRS SDSM is used more frequently than MODIS. VIIRS SDSM collects data using 8 individual detectors, covering a similar wavelength range as MODIS. This paper provides an overview of MODIS and VIIRS SDSM design features, their on-orbit operations, and calibration strategies. It illustrates their on-orbit performance in terms of on-orbit changes in SDSM detector on-orbit responses and on-orbit degradations of their SD. Results show that on-orbit changes of both MODIS and VIIRS SD BRF and SDSM response have similar wavelength dependency: the SD degradation is faster at shorter visible wavelengths while the decrease of SDSM detector responses (gains) is greater at longer near-infrared wavelengths.

Paper Details

Date Published: 1 July 2013
PDF: 8 pages
Proc. SPIE 8528, Earth Observing Missions and Sensors: Development, Implementation, and Characterization II, 852809 (1 July 2013); doi: 10.1117/12.977567
Show Author Affiliations
Xiaoxiong Xiong, NASA Goddard Space Flight Ctr. (United States)
Jon Fulbright, Sigma Space Corp. (United States)
Amit Angal, Science Systems and Applications, Inc. (United States)
Junqiang Sun, Sigma Space Corp. (United States)
Zhipeng Wang, Sigma Space Corp. (United States)

Published in SPIE Proceedings Vol. 8528:
Earth Observing Missions and Sensors: Development, Implementation, and Characterization II
Haruhisa Shimoda; Xiaoxiong Xiong; Changyong Cao; Xingfa Gu; Choen Kim; A. S. Kiran Kumar, Editor(s)

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