Poster Session 4, Thursday, October  6, 11:00–12:40

Poster 48

Shading effects induced by optical buoys for system vicarious calibration

In light of system vicarious calibration (SVC) activities undertaken by Copernicus and EUMETSAT for Sentinel-3/OLCI, this study presents a direct comparison between Shading Effects (SE) induced by the Marine Optical BuoY (MOBY) and the Buoy for the acquisition of a long-term optical time series (BOUSSOLE). SE simulations are performed for oligotrophic water conditions at 412, 560, and 667 nm, using the MOX Monte Carlo code to model the in-water radiance field and the Finite Element Method (FEM) to model the sky radiance. When considering the same environmental conditions, the results difference is only due to the buoy structure and the radiometers field-of-view. In favourable cases where the Relative Azimuth Angle (RAA) between the sun and the sensors arm is lower than 90° (sun head), and the Sun Zenith Angle (SZA) is between 10° and 50°, MOBY SE tends to be below 1%. BOUSSOLE SE also tends to be lower than 1% at 560 nm, but slightly larger perturbations (generally up to 2%, yet in some cases larger) are observed at 412 and 667 nm. SE significantly increases in the unfavourable case when RAA approaches 180° or more (with structure between the sensors and the sun SE can exceed 50%). Notable is that the compact MOBY structure limits RAA values most affected by SE to a smaller range than BOUSSOLE. The work additionally demonstrates how the applied methods for SE analysis permit an evaluation of the effect of Bidirectional Radiance Distribution Function on SVC field data without additional computing cost.

Tamito Kajiyama, AEQUORA LDA, [email protected]

Davide D’Alimonte, AEQUORA LDA, [email protected] 

Barbara Bulgarelli, Joint Research Centre of the European Commission, [email protected] 

Constant Mazeran, SOLVO, [email protected]

Gianluigi Liberti, Consiglio Nazionale delle Ricerche, Istituto di Scienze Marine, [email protected] 

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