Radiometric Validation of Sentinel-3AB by the WATERHYPERNET

RUDDICK, K.; KUUSK, J.; ANSKO, I.; BECK, M.; BIALEK, A.; BRANDO, V.; CATTRIJSSE, A.; CONCHA, J.; CORIZZI, A.; DE VIS, P.; DOGLIOTTI, A. I.; DOXARAN, D.; ETAL.

Encuentro; 7th Sentinel-3 Validation Team Meeting 2022; 2022

The WATERHYPERNET network of hyperspectral radiometers is being developed for radiometric validation of satellite missions. The network will provide water reflectance data for all visible and near infrared bands of all optical imaging missions, including Sentinel-3A&B&C&D, Sentinel-2 A&B&C&D, PROBA-V, MODIS-AQUA&TERRA, VIIRS, Landsat-8, Pléiades, CHRIS-PROBA, MSG-SEVIRI, PlanetDove,PRISMA … ENMAP, PACE, CHIME, SBG, MTG and ... any future optical missions, including nanosatellites. This network follows closely the AERONET-OC federation concept [Zibordi et al, 2009]but uses hyperspectral radiometers. Two instrument systems have been developed: a) the PANTHYR system [Vansteenwegen et al, 2019] consists of one radiance and one irradiance TRIOS/RAMSES sensor, a mature high performance radiometer b) the prototype HYPSTAR® system, based on a newly designed hyperspectral radiometer with a single spectrometer and both radiance and irradiance fore-optics and an integrated camera. Both systems including a pointing robot, data acquisition computer and 2G/3G/4G data transmission, and are or can be supplemented with GPS, inclinometer, rain sensor and camera auxiliary sensors. The measurement method is based on the abovewater method of [Mobley, 1999 and 2015], but allows additional scenarios for different viewing zenith and azimuth configurations.Both systems provide measurements every 20-30 mins for validation of all visible and near infrared Sentinel-3AB bands (400nm to 900nm inclusive).The first PANTHYR systems have been deployed in the Italian Adriatic Sea (September 2019 - present) and the Belgian North Sea (December 2019 - August 2020 and September 2021 - present). The first HYPSTAR® systems have been deployed in the Blankaart reservoir (Belgium), Etang de Berre (France), Adriatic Sea (Italy), La Plata Estuary (Argentina), Gironde estuary (France) and Lake Garda (Italy) as well as at land-based sites. Two more PANTHYR and five more HYPSTAR®deployments are planned for 2022Q4 with further international expansion in 2023. This presentation will provide results from these deployments, comparing matchups with Sentinel-3A and -3B, illustrating the usefulness for validation of Sentinel-3 and outlining the next steps as regards hardware improvements, measurement method refinements, radiometer calibration and characterisation and quantification of the in situ measurement uncertainties.