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ORIGINAL RESEARCH article

Front. Remote Sens.
Sec. Multi- and Hyper-Spectral Imaging
Volume 5 - 2024 | doi: 10.3389/frsen.2024.1347520
This article is part of the Research Topic Optical Radiometry and Satellite Validation View all 22 articles

WATERHYPERNET: A prototype network of automated in situ measurements of hyperspectral water reflectance for satellite validation and water quality monitoring

Provisionally accepted
Kevin Ruddick Kevin Ruddick 1*Vittorio E. Brando Vittorio E. Brando 2Alexandre Corizzi Alexandre Corizzi 3Ana I. Dogliotti Ana I. Dogliotti 4David Doxaran David Doxaran 3Clémence Goyens Clémence Goyens 1Joel Kuusk Joel Kuusk 5Quinten Vanhellemont Quinten Vanhellemont 1Dieter Vansteenwegen Dieter Vansteenwegen 6Agnieszka Bialek Agnieszka Bialek 7Pieter De Vis Pieter De Vis 7Héloïse Lavigne Héloïse Lavigne 1Matthew Beck Matthew Beck 1Kenneth Flight Kenneth Flight 5Anabel Gammaru Anabel Gammaru 1Luis Gonzalez Vilas Luis Gonzalez Vilas 2Kaspars Laizans Kaspars Laizans 5Francesca Ortenzio Francesca Ortenzio 1Pablo Perna Pablo Perna 4Estefania Piegari Estefania Piegari 4Lucas Rubinstein Lucas Rubinstein 4Morven Sinclair Morven Sinclair 7Dimitry Van Der Zande Dimitry Van Der Zande 1
  • 1 Royal Belgian Institute of Natural Sciences, Brussels, Belgium
  • 2 Consiglio Nazionale delle Ricerche (CNR-ISMAR), Rome, Sicily, Italy
  • 3 Laboratoire Océanographique de Villefranche, Sorbonne Université (SU/LOV), Villefranche-sur-Mer, France
  • 4 Instituto de Astronomía y Física del Espacio, Consejo Nacional de Investigaciones Científicas y Técnicas (IAFE, CONICET/UBA), Buenos Aires, Buenos Aires, Argentina
  • 5 University of Tartu, Tartu, Tartu County, Estonia
  • 6 Flanders Marine Institute, Ostend, Belgium
  • 7 National Physical Laboratory, Teddington, United Kingdom

The final, formatted version of the article will be published soon.

    This paper describes a prototype network of automated in situ measurements of hyperspectral water reflectance suitable for satellite validation and water quality monitoring. Radiometric validation of satellite-derived water reflectance is essential to ensure that only reliable data, e.g. for estimating water quality parameters such as chlorophyll a concentration, reach end-users. Analysis of the differences between satellite and in situ water reflectance measurements, particularly unmasked outliers, can provide recommendations on where satellite data processing algorithms need to be improved. In a massively multi-mission context, including Newspace constellations, hyperspectral missions and missions with broad spectral bands not designed for "water colour", the advantage of hyperspectral over multispectral in situ measurements is clear. Two hyperspectral measurement systems, PANTHYR (based on the mature TRIOS/RAMSES radiometer) and HYPSTAR® (a newly designed radiometer), have been integrated here in the WATERHYPERNET network with SI-traceable calibration and characterisation. The systems have common data acquisition protocol, data processing and quality control. The choice of validation site and viewing geometry and installation considerations are described in detail. Three demonstration cases are described: 1. PANTHYR data from two sites are used to validate Sentinel-2/MSI (A&B); 2. HYPSTAR® data at six sites are used to validate Sentinel-3/OLCI (A&B); 3. PANTHYR and HYPSTAR® data in Belgian North Sea waters are used to monitor phytoplankton parameters, including Phaeocystis globosa, over two 5 month periods. Conclusions are drawn regarding the quality of Sentinel-2/MSI and Sentinel-3/OLCI data, including indications where improvements could be made. For example, a positive bias is found for ACOLITE_DSF processing of Sentinel-2 in clear waters (Acqua Alta) and clues are provided on how to improve this processing. The utility of these in situ measurements, even without accompanying hyperspectral satellite data, is demonstrated for phytoplankton monitoring.The future evolution of the WATERHYPERNET network is outlined, including geographical expansion, improvements to hardware reliability and to the measurement method (including uncertainty estimation) and plans for daily distribution of near real-time data.

    Keywords: Water colour, Satellite validation, Hyperspectral reflectance, In situ measurements, Phytoplankton

    Received: 30 Nov 2023; Accepted: 10 Jun 2024.

    Copyright: © 2024 Ruddick, Brando, Corizzi, Dogliotti, Doxaran, Goyens, Kuusk, Vanhellemont, Vansteenwegen, Bialek, De Vis, Lavigne, Beck, Flight, Gammaru, Gonzalez Vilas, Laizans, Ortenzio, Perna, Piegari, Rubinstein, Sinclair and Van Der Zande. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Kevin Ruddick, Royal Belgian Institute of Natural Sciences, Brussels, Belgium

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