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Front. Mar. Sci. | doi: 10.3389/fmars.2018.00437

ProVal: A new autonomous profiling float for high quality radiometric measurements

  • 1Sorbonne Université, CNRS, Laboratoire d’Océanographie de Villefanche, LOV, France
  • 2ACRI-ST, 260 route du Pin Montard, France
  • 3Remote Sensing and Satellite Research Group (RSSRG), Curtin University, Australia
  • 4UMR7093 Laboratoire d'océanographie de Villefranche (LOV), France
  • 5School of Marine Sciences, University of Maine, United States
  • 6Dalhousie University, Canada

An efficient system to produce in situ high quality radiometric measurements is compulsory to rigorously perform the vicarious calibration of satellite sensors dedicated to Ocean Color Radiometry (OCR) and to validate their derived products. This requirement is especially needed during the early stages of an OCR satellite activity or for remote areas poorly covered by oceanographic cruises with possible bio-optical anomalies. Taking advantage of Argo’s profiling float, we present a new autonomous profiling float dedicated to in situ radiometric measurements. The float is based on the Provor CTS5 (manufacturer NKE) with an added novel two protruding arm design allowing for sensor redundancies, shading mitigation and near-surface data. Equipped with two identical radiometers on each arm that measure downward irradiance and upwelling radiance at seven wavelengths, the ProVal float generates both redundant radiometric profiles as well as an estimate of Remote Sensing Reflectance. Results from 449 profiles sampled obtained in the NW Mediterranean Sea and in the Indian sector of the Southern Ocean are presented to illustrate the ProVal float technical maturity. Analysis of the behavior of the profiling float, including tilting and ascent speeds, is presented. The vertical stability of the ProVal exhibits 85% of surface data of the Mediterranean Sea with a tilt smaller than 10 degrees. This percentage is 45% in the Southern Ocean due to rougher seas. Redundant sensors provide a characterization of the relative drift between sensors over the deployment which is found to be less than 0.15% per month over a year. Post-cruise calibration of a recovered float revealed no significant drift. As an example of the utility of ProVal floats, a match-up of Remote Sensing Reflectance measured with the European Space Agency Ocean and Land Color Imager (OLCI onboard Sentinel-3A & 3B) is shown. It follows that profiling floats, such as ProVal, could provide a significant contribution to an upcoming global System Vicarious Calibration of space-based radiometers.

Keywords: Autonomous profiling floats, remote sensing reflectance, Ocean Color, Validation, System Vicarious Calibration, Mediterranean Sea, Radiometric measurement, Austral ocean

Received: 16 Jul 2018; Accepted: 30 Oct 2018.

Edited by:

Gilles Reverdin, Centre national de la recherche scientifique (CNRS), France

Reviewed by:

Christoph Waldmann, University of Bremen, Germany
Shinya Kouketsu, Japan Agency for Marine-Earth Science and Technology, Japan  

Copyright: © 2018 Leymarie, Penkerc'h, Vellucci, Lerebourg, Antoine, Boss, Lewis, D'Ortenzio and CLAUSTRE. 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) and the copyright owner(s) 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: Dr. Edouard Leymarie, Sorbonne Université, CNRS, Laboratoire d’Océanographie de Villefanche, LOV, F-06230 Villefranche-sur-mer, France, leymarie@obs-vlfr.fr