Calibration and Validation
SENTINEL-3 calibration and validation (cal/val) activities are essential to the quality of the mission. Data quality will be assessed through determination of the radiometric, spatial, spectral and geometric fidelity of the satellite sensor and the accuracy of geophysical products. Three phases of cal/val are foreseen for SENTINEL-3:
Dedicated SENTINEL-3 calibration tasks include:
Dedicated SENTINEL-3 validation tasks include:
In addition, the cal/val component of the SENTINEL-3 mission includes maintenance and evolution of prototype ground processors, generation of all pre-launch auxiliary data sets needed for Level-1 and Level-2 processing and the definition and planning of in situ campaigns to be conducted during the commissioning phase. SENTINEL-3 cal/val plans will be reviewed and updated on a regular basis as required by the mission. In particular, a PDGS re-processing capability will support calibration and validation activities as well as potential tuning of algorithms and product evolution.
The responsibilities for the 3 SENTINEL-3 cal/val specific phases will be split as follows:
SLSTR Calibration and Validation Overview
For the majority of channels, SLSTR is a self-calibrating instrument (based on the approach successfully implemented in the (A)ATSR series of instruments). Notably, the F1 and F2 Fire channels are not self-calibrating as the upper dynamic range of these channels exceeds that of the on-board black bodies. F1 and F2 will require vicarious adjustments using reference radiance sources on ground. The on-board calibration system involves the use of two highly stable Black Body (BB) reference targets (for the thermal channels) maintained at different temperatures above and below the range of earth targets (but optimised for SST retrievals), and a diffusely reflecting target (VISCAL) that is illuminated once per orbit (for the VIS-SWIR channels). Traceability to international standards is maintained through the on-ground characterisation, on-board calibration sources and pre-launch calibration. The validation process for geolocation is similar to OLCI with the use of SPS and GPP. Due to the scanning mechanism, pre-launch characterisation of scanner and mirror performance is essential. For Level-2 SST and LST products, the main purpose is to validate the products using a variety of reference data.