Sorry, you need to enable JavaScript to visit this website.

MCST Banner Image

Cross-calibration of the Oceansat-2 Ocean Colour Monitor (OCM) with Terra and Aqua MODIS

TitleCross-calibration of the Oceansat-2 Ocean Colour Monitor (OCM) with Terra and Aqua MODIS
Publication TypePresentation
Year of Publication2016
AuthorsAngal, A., J. Brinkmann, S. A. Kumar, and X. Xiong
ProceedingsProc. of SPIE Earth Observing Missions and Sensors: Development, Implementation, and Characterization IV
MCST ConferenceProc. of SPIE Earth Observing Missions and Sensors: Development, Implementation, and Characterization IV
Volume9881
Abstract

The Ocean Colour Monitor (OCM) sensor on-board the Oceansat-2 spacecraft has been operational since its launch
in September, 2009. The Oceansat 2 OCM primary design goal is to provide continuity to Oceansat-1 OCM to
obtain information regarding various ocean-colour variables. OCM acquires Earth scene measurements in eight
multi-spectral bands in the range from 402 to 885 nm. The MODIS sensor on the Terra and Aqua spacecraft has
been successfully operating for over a decade collecting measurements of the earth’s land, ocean surface and
atmosphere. The MODIS spectral bands, designed for land and ocean applications, cover the spectral range from
412 to 869 nm. This study focuses on comparing the radiometric calibration stability of OCM using near-
simultaneous TOA measurements with Terra and Aqua MODIS acquired over the Libya 4 target. Same-day scene-
pairs from all three sensors (OCM, Terra and Aqua MODIS) between August, 2014 and September, 2015 were
chosen for this analysis. On a given day, the OCM overpass is approximately an hour after the Terra overpass and an
hour before the Aqua overpass. Due to the orbital differences between Terra and Aqua, MODIS images the Libya 4
site at different scan-angles on a given day. Some of the high-gain ocean bands for MODIS tend to saturate while
viewing the bright Libya 4 target, but bands 8-10 (412 nm – 486 nm) provide an unsaturated response and are used
for comparison with the spectrally similar OCM bands. All the standard corrections such as bidirectional reflectance
factor (BRDF), relative spectral response mismatch, and impact for atmospheric water-vapor are applied to obtain
the reflectance differences between OCM and the two MODIS instruments. Furthermore, OCM is used as a transfer
radiometer to obtain the calibration differences between Terra and Aqua MODIS reflective solar bands.

DOI10.1117/12.2224046