Abstract
The spectral resolution requirements for in situ remote sensing reflectanceRRS measurements aiming at supporting satellite ocean color validation and System Vicarious Calibration (SVC) were investigated. The study, conducted using sample hyperspectral RRS from different water types, focused on the visible spectral bands of the ocean land color imager (OLCI) and of the Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) satellite sensors. Allowing for a ±0.5% maximum difference between in situ and satellite derived RRS solely due to the spectral band characteristics of the in situ radiometer, a spectral resolution of 1 nm for SVC of PACE is needed in oligotrophic waters. Requirements decrease to 3 nm for SVC of OLCI. In the case of validation activities, which exhibit less stringent uncertainty requirements with respect to SVC, a maximum difference of ±1% between in situ and satellite derived data indicates the need for a spectral resolution of 3 nm for both OLCI and PACE in oligotrophic waters. Conversely, spectral resolutions of 6 nm for PACE and 9 nm for OLCI appear to satisfy validation activities in optically complex waters.
Highlights
Satellite ocean color radiometric products, such as the water-leaving radiance, L, or the W related remote sensing-reflectance, R, are the fundamental quantities used to generate geoRS physical data products
Because of the higher resolution of the satellite sensor bands, the same analysis performed for PACE-like bands exhibits larger values of ε than those determined for Ocean Land Color Imager (OLCI) in the spectral regions with large changes in the slope of R
Accounting for the results from the analyses presented in the previous section and of findings from the discussion topics included spectral resolution and sampling interval requirements for in situ hyperspectral data supporting satellite ocean color validation and system vicarious calibration (SVC) applications are summarized assuming strict uncertainty thresholds
Summary
Satellite ocean color radiometric products, such as the water-leaving radiance, L , or the W related remote sensing-reflectance, R , are the fundamental quantities used to generate geoRS physical data products (e.g., chlorophyll concentration, Chla). A source of uncertainty, which causes systematic differences between in situ and satellite radiometric data, but is controllable by instrument design, is the diversity of spectral characteristics of in situ and satellite ocean color sensors due to the different widths, shapes and center-wavelengths of corresponding spectral bands. This uncertainty can be minimized through the application of corrections (i.e., band-shifting) obtained by modeling the spectral dependence of radiometric quantities such as R [3,4].
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