Validation of Sentinel-2 Surface Reflectance over water and land sites by measurements from HYPERNETS

RUDDICK, K.; DOGLIOTTI, A.I.; ET AL.

Encuentro; 6th Sentinel-2 Validation Team Meeting 2023; 2023

HYPERNETS hasestablished a network of validation sites with autonomous radiometer systemsmeasuringhyperspectral water and land surface reflectancefor validation ofsatellite missions.Spaceborneoptical imaging missions such as Sentinel-2 and Sentinel-3 are used routinelyto provide data for environmental monitoring of water and land surfaces viaproducts such as chlorophyll and suspended particulate matter concentrations inwater and Fraction of photosynthetically active radiation absorbed byvegetation (FAPAR) and Land cover over land.Validation of the intermediatewater and land surface reflectance products is needed to ensure reliability ofall suchderived satellite data products and identify any problems in sensorcalibration, atmospheric correction or quality masking.A newradiometer, the HYPSTAR®,has beendesigned and deployed at diverse water and land sites aroundthe world to provide hyperspectral resolution(3nm FWHM for the range380-1100nm, 10nm FWHM for 1100-1700nm). Further water sites have beeninstrumented with the PANTHYR system based on the TRIOS/RAMSES hyperspectralradiometer (10 nm FWHM for the range 400-900 nm).The HYPERNETSnetwork is now acquiring continuous time series of water and land surfacereflectance for a number of validation sites and representsa core source of insitu measurements for the radiometric validation of Sentinel-2 over a range ofsurface and atmospheric conditions. The results ofcomparisons of Sentinel-2 water and land surface reflectance within situmeasurements will be presented here, indicating the performance that can beexpected from the Sentinel-2 products as well as some difficult conditionswhere improvements could be focussed.