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Near-nadir scan overlap in Earth observations from VIIRS and MODIS
Author(s): Slawomir Blonski; Changyong Cao
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Paper Abstract

Satellite multi-detector cross-track scanners, such as MODIS (Moderate Resolution Imaging Spectroradiometer) and VIIRS (Visible-Infrared Imaging Radiometer Suite), require synchronization of optical and orbital characteristics to avoid gaps in Earth coverage between scans. Prelaunch tests have revealed that such scan-to-scan gaps will occur near nadir in VIIRS observations from the future JPSS-1 (Joint Polar Satellite System) and JPSS-2 satellites. Our analysis of VIIRS geolocation products shows that the gaps do not occur for the instrument currently on orbit onboard the S-NPP (Suomi National Polar-orbiting Partnership) spacecraft. When the same analysis is applied to the MODIS data products, it reveals that small, near-nadir gaps exist in MODIS observations from both Aqua and Terra satellites. Although magnitude of the MODIS scan overlap gaps (up to 100 m for Terra and 25/175 m for Aqua) is quite small in comparison to the 1-km pixels, it is rather significant for the bands with the 250-m and 500-m pixels. Despite the size of the gaps, it appears that their effects on scientific analyses (e.g., NDVI) have not been reported since launch of the MODIS instruments. Because the gaps currently predicted for the JPSS-1 and -2 VIIRS are similar in size to the ones occurring for MODIS, one can expect that their effects on science data will be similarly negligible. A model that uses S-NPP orbit data as well as the S-NPP VIIRS telescope’s focal length and scan rate predicts the overlap that agrees very well with the analysis of the geolocation data. For JPSS-1/-2 VIIRS focal length and scan rate, the model predicts scan overlap gaps of more than 100 m. With a shorter focal length and a faster scan rate than for the JPSS-1/-2 VIIRS, the scan overlap gaps are expected to be avoided altogether for VIIRS on the future JPSS-3 and -4 satellites.

Paper Details

Date Published: 29 September 2017
PDF: 11 pages
Proc. SPIE 10423, Sensors, Systems, and Next-Generation Satellites XXI, 1042312 (29 September 2017); doi: 10.1117/12.2278440
Show Author Affiliations
Slawomir Blonski, Earth Resources Technology, Inc. (United States)
Changyong Cao, STAR/NESDIS, National Oceanic and Atmospheric Administration (United States)


Published in SPIE Proceedings Vol. 10423:
Sensors, Systems, and Next-Generation Satellites XXI
Steven P. Neeck; Jean-Loup Bézy; Toshiyoshi Kimura, Editor(s)

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