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1. Optimal Configuration of Omega-Kappa FF-SAR Processing for Specular and Non-Specular Targets in Altimetric Data: The Sentinel-6 Michael Freilich Study Case

Author

Samira Amraoui, Pietro Guccione, Thomas Moreau, Marta Alves, Ourania Altiparmaki, Charles Peureux, Lisa Recchia, Claire Maraldi, François Boy, and Craig Donlon

Subjects
fully focused SAR, altimetry, processing, optimization, Sentinel-6 Michael Freilich, Science
Abstract

In this study, the full-focusing (FF) algorithm is reviewed with the objective of optimizing it for processing data from different types of surfaces probed in altimetry. In particular, this work aims to provide a set of optimal FF processing parameters for the Sentinel-6 Michael Freilich (S6-MF) mission. The S6-MF satellite carries an advanced radar altimeter offering a wide range of potential FF-based applications which are just beginning to be explored and require prior optimization of this processing. In S6-MF, the Synthetic Aperture Radar (SAR) altimeter acquisitions are known to be aliased in the along-track direction. Depending on the target, aliasing can be tolerated or may be a severe impairment to provide the level of performance expected from FF processing. Another key aspect to consider in this optimization study is the unprecedented resolution of the FF processing, which results in a higher posting rate than the standard SAR processing. This work investigates the relationship between posting rate and noise levels and provides recommendations for optimal algorithm configurations in various scenarios, including transponder, open ocean, and specular targets like sea-ice and inland water scenes. The Omega–Kappa (WK) algorithm, which has demonstrated superior CPU efficiency compared to the back-projection (BP) algorithm, is considered for this study. But, unlike BP, it operates in the Doppler frequency domain, necessitating further precise spectral and time domain settings. Based on the results of this work, real case studies using S6-MF acquisitions are presented. We first compare S6-MF FF radargrams with Sentinel-1 (S1) images to showcase the potential of optimally configured FF processing. For highly specular surfaces such as sea-ice, distinct techniques are employed for lead signature identification. S1 relies on image-based lineic reconstruction, while S6-MF utilizes phase coherency of focalized pulses for lead detection. The study also delves into two-dimensional wave spectra derived from the amplitude modulation of image/radargrams, with a focus on a coastal example. This case is especially intriguing, as it vividly illustrates different sea states characterized by varying spectral peak positions over time.

Published
2024
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2. The ESA Permanent Facility for Altimetry Calibration in Crete: Advanced Services and the Latest Cal/Val Results

Author

Stelios P. Mertikas, Craig Donlon, Costas Kokolakis, Dimitrios Piretzidis, Robert Cullen, Pierre Féménias, Marco Fornari, Xenophon Frantzis, Achilles Tripolitsiotis, Jérôme Bouffard, Alessandro Di Bella, François Boy, and Jerome Saunier

Subjects
satellite altimetry, calibration, transponders, sea surface, Sentinel-6 MF, Sentinel-3, Science
Abstract

Two microwave transponders have been operating in west Crete and Gavdos to calibrate international satellite radar altimeters at the Ku-band. One has been continuously operating for about 8 years at the CDN1 Cal/Val site in the mountains of Crete, and the other at the GVD1 Cal/Val site on Gavdos since 11 October 2021. This ground infrastructure is also supported at present by four sea-surface Cal/Val sites operating, some of them for over 20 years, while two additional such Cal/Val sites are under construction. This ground infrastructure is part of the European Space Agency Permanent Facility for Altimetry Calibration (PFAC), and as of 2015, it has been producing continuously a time series of range biases for Sentinel-3A, Sentinel-3B, Sentinel-6 MF, Jason-2, Jason-3, and CryoSat-2. This work presents a thorough examination of the transponder Cal/Val responses to understand and determine absolute biases for all satellite altimeters overflying this ground infrastructure. The latest calibration results for the Jason-3, Copernicus Sentinel-3A and -3B, Sentinel-6 MF, and CryoSat-2 radar altimeters are described based on four sea-surface and two transponder Cal/Val sites of the PFAC in west Crete, Greece. Absolute biases for Jason-3, Sentinel-6 MF, Sentinel-3A, Sentinel-3B, and CryoSat-2 are close to a few mm, determined using various techniques, infrastructure, and settings.

Published
2024
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3. Towards Operational Fiducial Reference Measurement (FRM) Data for the Calibration and Validation of the Sentinel-3 Surface Topography Mission over Inland Waters, Sea Ice, and Land Ice

Author

Elodie Da Silva, Emma R. Woolliams, Nicolas Picot, Jean-Christophe Poisson, Henriette Skourup, Geir Moholdt, Sara Fleury, Sajedeh Behnia, Vincent Favier, Laurent Arnaud, Jérémie Aublanc, Valentin Fouqueau, Nicolas Taburet, Julien Renou, Hervé Yesou, Angelica Tarpanelli, Stefania Camici, Renée Mie Fredensborg Hansen, Karina Nielsen, Frédéric Vivier, François Boy, Roger Fjørtoft, Mathilde Cancet, Ramiro Ferrari, Ghislain Picard, Mohammad J. Tourian, Nicolaas Sneeuw, Eric Munesa, Michel Calzas, Adrien Paris, Emmanuel Le Meur, Antoine Rabatel, Guillaume Valladeau, Pascal Bonnefond, Sylvie Labroue, Ole Andersen, Mahmoud El Hajj, Filomena Catapano, and Pierre Féménias

Subjects
S3 land STM, uncertainties, FRM, sea ice thickness, inland water surface height, land ice height, Science
Abstract

The Copernicus Sentinel-3 Surface Topography Mission (STM) Land Altimetry provides valuable surface elevation information over inland waters, sea ice, and land ice, thanks to its synthetic aperture radar (SAR) altimeter and its orbit that covers high-latitude polar regions. To ensure that these measurements are reliable and to maximise the return on investment, adequate validation of the geophysical retrieval methods, processing algorithms, and corrections must be performed using independent observations. The EU-ESA project St3TART (started July 2021) aims to generalise the concept of Fiducial Reference Measurements (FRMs) for the Copernicus Sentinel-3 STM. This work has gathered existing data, made new observations during field campaigns, and ensured that these observations meet the criteria of FRM standards so that they can be used to validate Sentinel-3 STM Land Altimetry products operationally. A roadmap for the operational provision of the FRM, including the definition, consolidation, and identification of the most relevant and cost-effective methods and protocols to be maintained, supported, or implemented, has been developed. The roadmap includes guidelines for SI traceability, definitions of FRM measurement procedures, processing methods, and uncertainty budget estimations.

Published
2023
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4. Effects of Surface Wave Breaking Caused by Internal Solitary Waves in SAR Altimeter: Sentinel-3 Copernicus Products and Advanced New Products

Author

Adriana M. Santos-Ferreira, José C. B. da Silva, Jorge M. Magalhaes, Samira Amraoui, Thomas Moreau, Claire Maraldi, François Boy, Nicolas Picot, and Franck Borde

Subjects
internal solitary waves (ISWs), wave breaking, delay-Doppler altimeter, radar backscatter, altimetry, SAR, Science
Abstract

We address surface wave breaking caused by oceanic Internal Solitary Waves (ISWs) and how ISWs are manifested in the SAR altimeter onboard Sentinel-3A and -3B satellites by means of their effects in Significant Wave Height (SWH). Two different regions of the ocean are selected, namely the tropical Atlantic Ocean off the Amazon shelf and the Banda Sea in the Indian Ocean, where there are scenes of Sentinel-3 OLCI acquired simultaneously with an along-track SAR mode altimeter, which include signatures of large amplitude ISWs. New data of unfocused SAR (UF-SAR 20 Hz) and fully focused SAR (FF-SAR 160 Hz) modes are analyzed, which are retracked in full range and over a reduced range of bins (truncation carried out dynamically ten gates away from the estimated epoch position). At first order, in scales of 1–3 km, a strong decrease in the normalized radar cross section (NRCS) over the rough part of the ISWs is observed followed by a small increase in the smooth part relative to the unperturbed ocean background. A second order ISW signature, in scales of 20 km, is noted: the SWH is attenuated after the passage of an ISW, considering length scales of about 10 km before and after the ISW crest. The SWH signatures are unique in showing that the surface wave energy does not return to its unperturbed level after the passage of an ISW, admittedly because intense meter-scale wave breaking results in surface wave energy dissipation. Furthermore, Sentinel-2 MSI images are analyzed and provide insights into this same phenomenon: white-capping resulting in a radiance increase at all (visible) wavelengths. Modulation of breaking waves owing to ISWs is demonstrated by estimates of the fraction of breaking waves in the presence of internal waves.

Published
2022
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5. Ice Sheet Topography from a New CryoSat-2 SARIn Processing Chain, and Assessment by Comparison to ICESat-2 over Antarctica

Author

Jérémie Aublanc, Pierre Thibaut, Amandine Guillot, François Boy, and Nicolas Picot

Subjects
radar altimetry, SARIn altimetry, ice sheet remote sensing, Antarctic ice sheet, CryoSat-2, ICESat-2, Science
Abstract

In this study, we present a new level-2 processing chain dedicated to the CryoSat-2 Synthetic Aperture Radar Interferometric (SARIn) measurements acquired over ice sheets. Compared to the ESA ground segment processor, it includes revised methods to detect waveform leading edges and perform retracking at the Point of Closest Approach (POCA). CryoSat-2 SARIn mode surface height measurements retrieved from the newly developed processing chain are compared to ICESat-2 surface height measurements extracted from the ATL06 product. About 250,000 space–time nearly coincident observations are identified and examined over the Antarctic ice sheet, and over a one-year period. On average, the median elevation bias between both missions is about −18 cm, with CryoSat-2 underestimating the surface topography compared to ICESat-2. The Median Absolute Deviation (MAD) between CryoSat-2 and ICESat-2 elevation estimates is 46.5 cm. These performances were compared to those obtained with CryoSat-2 SARIn mode elevations from the ESA PDGS level-2 products (ICE Baseline-D processor). The MAD between CryoSat-2 and ICESat-2 elevation estimates is significantly reduced with the new processing developed, by about 42%. The improvement is more substantial over areas closer to the coast, where the topography is more complex and surface slope increases. In terms of perspectives, the impacts of surface roughness and volume scattering on the SARIn mode waveforms have to be further investigated. This is crucial to understand geographical variations of the elevation bias between CryoSat-2 and ICESat-2 and continue enhancing the SARIn mode level-2 processing.

Published
2021
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6. SKIM, a Candidate Satellite Mission Exploring Global Ocean Currents and Waves

Author

Fabrice Ardhuin, Peter Brandt, Lucile Gaultier, Craig Donlon, Alessandro Battaglia, François Boy, Tania Casal, Bertrand Chapron, Fabrice Collard, Sophie Cravatte, Jean-Marc Delouis, Erik De Witte, Gerald Dibarboure, Geir Engen, Harald Johnsen, Camille Lique, Paco Lopez-Dekker, Christophe Maes, Adrien Martin, Louis Marié, Dimitris Menemenlis, Frederic Nouguier, Charles Peureux, Pierre Rampal, Gerhard Ressler, Marie-Helene Rio, Bjorn Rommen, Jamie D. Shutler, Martin Suess, Michel Tsamados, Clement Ubelmann, Erik van Sebille, Martin van den Oever, and Detlef Stammer

Subjects
ocean current, tropics, Arctic, Doppler, altimetry, sea state, Science, General. Including nature conservation, geographical distribution, QH1-199.5
Abstract

The Sea surface KInematics Multiscale monitoring (SKIM) satellite mission is designed to explore ocean surface current and waves. This includes tropical currents, notably the poorly known patterns of divergence and their impact on the ocean heat budget, and monitoring of the emerging Arctic up to 82.5°N. SKIM will also make unprecedented direct measurements of strong currents, from boundary currents to the Antarctic circumpolar current, and their interaction with ocean waves with expected impacts on air-sea fluxes and extreme waves. For the first time, SKIM will directly measure the ocean surface current vector from space. The main instrument on SKIM is a Ka-band conically scanning, multi-beam Doppler radar altimeter/wave scatterometer that includes a state-of-the-art nadir beam comparable to the Poseidon-4 instrument on Sentinel 6. The well proven Doppler pulse-pair technique will give a surface drift velocity representative of the top meter of the ocean, after subtracting a large wave-induced contribution. Horizontal velocity components will be obtained with an accuracy better than 7 cm/s for horizontal wavelengths larger than 80 km and time resolutions larger than 15 days, with a mean revisit time of 4 days for of 99% of the global oceans. This will provide unique and innovative measurements that will further our understanding of the transports in the upper ocean layer, permanently distributing heat, carbon, plankton, and plastics. SKIM will also benefit from co-located measurements of water vapor, rain rate, sea ice concentration, and wind vectors provided by the European operational satellite MetOp-SG(B), allowing many joint analyses. SKIM is one of the two candidate satellite missions under development for ESA Earth Explorer 9. The other candidate is the Far infrared Radiation Understanding and Monitoring (FORUM). The final selection will be announced by September 2019, for a launch in the coming decade.

Published
2019
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7. S3MPC: Improvement on Inland Water Tracking and Water Level Monitoring from the OLTC Onboard Sentinel-3 Altimeters

Author

Nicolas Taburet, Lionel Zawadzki, Maxime Vayre, Denis Blumstein, Sophie Le Gac, François Boy, Matthias Raynal, Sylvie Labroue, Jean-François Crétaux, and Pierre Femenias

Subjects
altimetry, Sentinel-3, validation, SAR, inland waters, Open-Loop Tracking Command, Science
Abstract

The Sentinel-3A and Sentinel-3B satellites were launched, respectively, on 16 February 2016 and 25 April 2018 as part of the European Copernicus program. The Sentinel-3 Surface Topography Mission makes use of the altimeter instruments onboard Sentinel-3A and Sentinel-3B to provide elevation measurements not only of the ocean water level but also of the inland waters and ice caps. For the first time, the altimeters onboard Sentinel-3A and Sentinel-3B are operated in Synthetic Aperture Radar mode over all Earth surfaces. They also benefit from elevation priors (the Open-Loop Tracking Command) allowing them to precisely position their receiving window to track the backscattered signal from the inland water targets to be monitored rather than relying on the traditional Closed-Loop tracking mode. This paper makes use of the Sentinel-3A/Sentinel-3B tandem phase to assess the benefits of the Open-Loop tracking mode compared to Closed-Loop. Longer time series are also used to highlight the improvements in terms of the percentage of points over which the altimeter hooks on water surfaces and water surface height estimation brought by the switch of Sentinel-3A from the Closed-Loop to Open-Loop tracking mode as well as the successive Open-Loop Tracking Command updates. In particular, it is shown that from a Level-3 water level product service perspective, the increase in the number of water bodies with valid water surface height estimates is of the order of 25% in Open-Loop with respect to Closed-Loop with similar precision. It is also emphasized that the Open-Loop Tracking Command update onboard Sentinel-3A from v. 4.2 to v. 5.0 yielded a 30% increase in the number of water bodies over which valid water surface height could be estimated. Eventually, the importance of knowing whether a water target was associated with a fine-tuned Open-Loop Tracking Command or an interpolated one is stressed and the recommendation to provide such a flag in the Sentinel-3 Level2 Payload Data Ground Segment products is emitted.

Published
2020
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8. Calibrating the SAR SSH of Sentinel-3A and CryoSat-2 over the Corsica Facilities

Author

Pascal Bonnefond, Olivier Laurain, Pierre Exertier, François Boy, Thierry Guinle, Nicolas Picot, Sylvie Labroue, Matthias Raynal, Craig Donlon, Pierre Féménias, Tommaso Parrinello, and Salvatore Dinardo

Subjects
altimetry, SAR, calibration, validation, Science
Abstract

Initially developed to monitor the performance of TOPEX/Poseidon and to follow the Jason legacy satellite altimeters at Senetosa Cape, Corsica, this calibration/validation site has been extended to include a new location at Ajaccio. This addition enables the site to monitor Envisat and ERS missions, CryoSat-2 and, more recently, the SARAL/AltiKa mission and Sentinel-3A satellites. Sentinel-3A and CryoSat-2 carry altimeters that use a synthetic aperture radar (SAR) mode that is different to the conventional pulse-bandwidth limited altimeters often termed “low resolution mode” (LRM). The aim of this study is to characterize the sea surface height (SSH) bias of the new SAR altimeter instruments and to demonstrate the improvement of data quality close to the coast. Moreover, some passes of Sentinel-3A and CryoSat-2 overfly both Senetosa and Ajaccio with only a few seconds time difference, allowing us to evaluate the reliability and homogeneity of both ground sites in term of geodetic datum. The Sentinel-3A and CryoSat-2 SSH biases for the SAR mode are respectively +22 ± 7 mm and −73 ± 5 mm (for CryoSat-2 baseline C products). The results show that the stability of the SAR SSH bias time series is better than standard LRM altimetry. Moreover, compared to standard LRM data, for which the measurements closer than ~10 km from the coast were generally unusable, SAR mode altimeters provide measurements that are reliable at less than few hundred meters from the coast.

Published
2018
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11. Comparisons and water level analyses using Sentinel-6MF satellite altimetry data with 1D Mascaret and 2D Telemac models

Author

Sophie Ricci, Thanh Huy Nguyen, Sophie Le Gac, François Boy, Andrea Piacentini, Raquel Rodriquez-Suquet, Santiago Peña-Luque, quentin bonassies, and charlotte emery

Abstract

Remote sensing products provided by satellite missions, airborne and unmanned aerial vehicle (UAV) campaigns have tremendously developed over the last decade. They undoubtedly offer opportunities to improve our ability to monitor and forecast flooding. The observation of inland waters benefits from several altimetry missions that provide along-track water surface elevation observation from nadir (e.g. TOPEX/Poseidon, Jason, SARAL/AltiKa, Sentinel-6) or large-swath altimeters (e.g. SWOT launched in December 2022), as well as other radar/optical missions (Sentinel-1, Sentinel-2) that provide high-resolution water masks. The limitations of each type of sensor are potentially circumvented when data from different satellite sensors are combined; the fusion of multi-source data has thus become one of the mainstream research topics in the remote-sensing community nowadays. Such fusion can be achieved with data assimilation algorithms applied to hydrodynamics models, namely MASCARET-1D and TELEMAC-2D. The present work focuses on the validation of water surface height (WSH) data from Sentinel-6MF with respect to in-situ gauge data, UAV and 1D/2D-hydrodynamics model outputs as shown in Figure 1. This work participates in a global effort that aims at combining various remote sensing products to represent and forecast flooding. The study is carried out over a dry period in June 2022 and over a flood event that occurred in December 2021-January 2022 over the Garonne catchment near Marmande, in the southwest of France. The WSH of the river is retrieved from Sentinel-6MF high-resolution fully-focused SAR data with an algorithm that relies on the estimation of the river width and the positioning of the river center line. The impact of these a priori data is investigated and the Sentinel-6MF-derived WSH observations are compared to the WSH simulated with TELEMAC-2D. It should be noted that due to the defection of Sentinel-1B (one of the two satellites in the Sentinel-1 constellation) in mid-December 2021, this flood event is only partly observed by Sentinel-1A and that the additional data from Sentinel-6MF with a 10-day revisit period are of great use. This study shows that hydrodynamic simulations and satellite altimetry time-series compare particularly well during the dry period whereas flooding events are often underestimated by satellite altimetry data. We believe that the combined use of satellite altimetry, hydrodynamics model simulations and independent UAV-borne data is key to a better understanding of the processes involved in the Garonne river flow dynamics and flooding events. We also take advantage of this study to improve our Sentinel-6MF data processing techniques. Figure 1- Representation of water level height and flood extent with remote sensing data and hydrodynamic models.

Published
2023

12. Detection capabilities of a multi-satellite wide-swath altimetry conceptual mission

Author

Oscar Vergara, Gérald Dibarboure, Anaëlle Treboutte, Yannice Faugère, and François Boy

Abstract

The soon-to-be available swath altimetry observations from the SWOT mission are expected to drastically improve our capacity to observe fine-scale ocean processes (wavelengths shorter than 100 km). With its increased observing capacity and lower signal-to-noise (SNR) ratio in comparison to conventional nadir altimetry, this new technology is expected to deliver unprecedented high-resolution two-dimensional observations of the ocean surface circulation and surface water bodies. Benefiting from the technological maturity acquired during the preparation for SWOT, a new constellation concept composed of swath altimeters has been proposed to carry on the European operational observing system towards the end of the decade. In the present work, we focus on evaluating the ocean observing capabilities of a novel swath altimeter concept (WiSA – Wide Swath Altimeter). Using the observed surface wave field (SWH – Significant Wave Height) and the instrumental characteristics, we compute global estimates of the SNR. We observe an average global observability around 40 km wavelength over 50% of the global ocean, and 47 km on average over 80% of the globe. Little or no seasonality is observed in the SNR, related to the seasonal compensation of the two competing factors that contribute to the observability, namely the instrumental noise levels and the observed spectral slopes. The performance of recently developed data-driven filtering techniques is also evaluated, considerably increasing the purely instrumental observing capabilities. The results are also discussed from an operational perspective, considering the contribution of a constellation of swath altimeters over a mono-satellite mission.

Published
2023

13. Benefits of the Open-Loop Tracking Command (OLTC): Extending conventional nadir altimetry to inland waters monitoring

Author

Sophie Le Gac, Nicolas Picot, François Boy, Léa Lasson, and Denis Blumstein

Subjects
Atmospheric Science, Ocean observations, Data processing, 010504 meteorology & atmospheric sciences, Elevation, Aerospace Engineering, Astronomy and Astrophysics, 01 natural sciences, law.invention, Water level, Ocean surface topography, Geophysics, Space and Planetary Science, law, 0103 physical sciences, Nadir, General Earth and Planetary Sciences, Environmental science, Altimeter, Radar, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Remote sensing
Abstract

In the past 25 years, radar altimeters have been designed and operated primarily for ocean observation. However, over the past decade there has been a growing interest for altimetry measurements over inland waters. Studying lakes, reservoirs and rivers water level is of prime importance for the hydrology community to assess the Earth’s global resources of fresh water. Satellite altimetry is key to providing such global and continuous datasets of water surface height. Indeed, much progress has been made in altimeters capability to acquire quality measurements over inland waters. In this paper we present an overview of major technical evolutions of the tracking function of altimeters, from Jason-2/POS3 and SARAL/AltiKa to Jason-3/POS3B and Sentinel-3/SRAL and the improvements brought by the Open-Loop Tracking Command (OLTC) to extend the altimeter observation domain to inland waters. The OLTC is an on-board feature used to set the altimeter waveforms reception window, containing a priori elevation information built from a dedicated database of hydrological targets. This paper focuses on the use of OLTC for acquiring reliable water signal rather than discussing the accuracy of the retrieved height, which constitutes a further step in the altimeter data processing chain. We show how Jason-3 and Sentinel-3 altimetry missions are currently able to observe and monitor about 70,000 hydrological targets over the globe and how it is contributing in building a global dataset of inland waters level, in preparation for future missions such as Sentinel-6 and the Surface Water Ocean Topography mission (SWOT).

Published
2021

14. High-performance altimeter Doppler processing for measuring sea level height under varying sea state conditions

Author

Matthias Raynal, Nicolas Picot, Constantin Mavrocordatos, F. Demeestere, L. Phalippou, François Boy, E. Cadier, Franck Borde, P. Rieu, T. Moreau, Gérald Dibarboure, S. Labroue, J. Aublanc, and Pierre Thibaut

Subjects
Synthetic aperture radar, Atmospheric Science, Data processing, 010504 meteorology & atmospheric sciences, Aerospace Engineering, Astronomy and Astrophysics, Sea state, 01 natural sciences, law.invention, symbols.namesake, Geophysics, Space and Planetary Science, Surface wave, law, 0103 physical sciences, Nadir, symbols, General Earth and Planetary Sciences, Altimeter, Radar, 010303 astronomy & astrophysics, Doppler effect, Geology, 0105 earth and related environmental sciences, Remote sensing
Abstract

This paper describes an innovative method for processing nadir altimeter data acquired in Synthetic Aperture Radar (SAR) mode, enhancing the system performances over open ocean. Similarly to the current SAR data processing scheme, the so-called LR-RMC (Low Resolution with Range Migration Correction) method, originally designed by Phalippou and Demeester (2011), includes Doppler beam forming, Doppler shift correction and range correction. In LR-RMC, however, an alternative and less complex averaging (stacking) operation is used so that all the Doppler beams produced in a radar cycle (4 bursts of 64 beams for the open-burst Sentinel-3-mode altimeter) are incoherently combined to form a multi-beam echo. In that manner, contrarily to the narrow-band SAR technique, the LR-RMC processing enlarges the effective footprint to average out the effects of surface waves and particularly those from small sub-mesoscale structures (

Published
2021

15. Exploiting the Sentinel-3 tandem phase dataset and azimuth oversampling to better characterize the sensitivity of SAR altimeter sea surface height to long ocean waves

Author

François Boy, C. Maraldi, Matthias Raynal, Franck Borde, Craig Donlon, E. Cadier, S. Clerc, P. Rieu, and T. Moreau

Subjects
Atmospheric Science, 010504 meteorology & atmospheric sciences, Aerospace Engineering, Astronomy and Astrophysics, 01 natural sciences, Swell, Azimuth, Wavelength, Geophysics, Space and Planetary Science, Aliasing, 0103 physical sciences, Wind wave, General Earth and Planetary Sciences, Oversampling, Altimeter, 010303 astronomy & astrophysics, Spectral leakage, Geology, 0105 earth and related environmental sciences, Remote sensing
Abstract

Being the very first SAR mode altimeter tandem phase, the Sentinel-3 A/B tandem phase has provided an unprecedented opportunity to better characterize the sensitivity of SAR altimetry retrievals to high-frequency processes, such as long ocean waves. In this paper, we show that for some sea-state conditions, that are still to be precisely characterized, long ocean waves are responsible for high-frequency (spatial and temporal) coherent Sea Level Anomaly (SLA) signals. It is found that the peak wavelength corresponds to the dominant swell wavelength. Furthermore, the short time lag between S3-A and S3-B acquisitions allows performing cross-spectral analyses that reveal phase shifts consistent with waves travelling according to the wave dispersion relation. It is also demonstrated that the classical 20 Hz sampling frequency is insufficient to properly sample most swell-induced SLA signals and that aliasing can generate errors over the entire frequency spectrum, including at long wavelengths. These results advocate for the use of azimuth oversampling (40 Hz or 80 Hz). Low-pass filtering should be applied prior to any down-sampling to 20 Hz, in order to prevent long-wavelength errors induced by spectral leakage.

Published
2021

16. Ice Sheet Topography from a New CryoSat-2 SARIn Processing Chain, and Assessment by Comparison to ICESat-2 over Antarctica

Author

Nicolas Picot, Amandine Guillot, Pierre Thibaut, François Boy, and Jérémie Aublanc

Subjects
Synthetic aperture radar, CryoSat-2, geography, geography.geographical_feature_category, ice sheet remote sensing, Antarctic ice sheet, Science, Elevation, Mode (statistics), Geodesy, radar altimetry, ICESat-2, SARIn altimetry, Coincident, Surface roughness, General Earth and Planetary Sciences, Median absolute deviation, Ice sheet, Geology
Abstract

In this study, we present a new level-2 processing chain dedicated to the CryoSat-2 Synthetic Aperture Radar Interferometric (SARIn) measurements acquired over ice sheets. Compared to the ESA ground segment processor, it includes revised methods to detect waveform leading edges and perform retracking at the Point of Closest Approach (POCA). CryoSat-2 SARIn mode surface height measurements retrieved from the newly developed processing chain are compared to ICESat-2 surface height measurements extracted from the ATL06 product. About 250,000 space–time nearly coincident observations are identified and examined over the Antarctic ice sheet, and over a one-year period. On average, the median elevation bias between both missions is about −18 cm, with CryoSat-2 underestimating the surface topography compared to ICESat-2. The Median Absolute Deviation (MAD) between CryoSat-2 and ICESat-2 elevation estimates is 46.5 cm. These performances were compared to those obtained with CryoSat-2 SARIn mode elevations from the ESA PDGS level-2 products (ICE Baseline-D processor). The MAD between CryoSat-2 and ICESat-2 elevation estimates is significantly reduced with the new processing developed, by about 42%. The improvement is more substantial over areas closer to the coast, where the topography is more complex and surface slope increases. In terms of perspectives, the impacts of surface roughness and volume scattering on the SARIn mode waveforms have to be further investigated. This is crucial to understand geographical variations of the elevation bias between CryoSat-2 and ICESat-2 and continue enhancing the SARIn mode level-2 processing.

Published
2021
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17. Estimation of Lake Heights from Sentinel-3 Sar Mode Through Numerical Simulations

Author

François Boy, M. Boussaroque, C. Tison, and J.-F. Cretaux

Subjects
Ocean surface topography, Radar tracker, Mean squared error, Surface wave, Surface roughness, Mode (statistics), Inversion (meteorology), Altimeter, Geology, Remote sensing
Abstract

Altimetry missions provide very valuable measurements on hydrological bodies, although they have initially been built for ocean topography. The extension of their acquisition modes provides tens of thousands of lake and river observations thanks to recent OLTC table upgrades. The inversion of the waveforms is yet tricky because of mixed soil/water response, highly variable dynamics and surface roughness variations. In this paper, a physical retracking based on a priori simulation is proposed for Water Surface Height (WSH) estimation over lakes. The method is applied on Sentinel-3 SAR data. The results are illustrated and discussed over the Constance lake which is covered by three S3 tracks. Consistent estimations are obtained between the three with an unbiased RMSE better than 6cm. Extensive validation over Swiss lakes (19 tracks) has also been made leading to a median unbiased RMSE of 6cm.

Published
2021

18. Benefits of the 'Adaptive Retracking Solution' for the JASON-3 GDR-F Reprocessing Campaign

Author

A. Guerou, François Boy, F. Piras, C. Maraldi, Nicolas Picot, Gérald Dibarboure, F. Bignalet-Cazalet, H. Roinard, and Pierre Thibaut

Subjects
Computer science, media_common.quotation_subject, Quality (business), Environmental economics, media_common
Abstract

The purpose of this paper is to accompany the release of the Jason-3 GDR-F products delivered as part of the GDR-F reprocessing campaign and to explain its main benefits for the users of altimetry products. This reprocessing campaign has a twofold objective: improve the quality of the products and share common standards with Sentinel-6/Jason-CS. Illustrations of the different benefits for the users of altimetry products are provided.

Published
2021

19. The SARAL/AltiKa mission: A step forward to the future of altimetry

Author

Lionel Gourdeau, Pascal Bonnefond, Sara Fleury, David T. Sandwell, Jean-François Crétaux, Mei Ling Dabat, Ole Baltazar Andersen, Jacques Verron, Gérald Dibarboure, Denis Blumstein, Fabrice Ardhuin, François Boy, Karen M. Marks, Florent Garnier, Nadège Queruel, Laurent Brodeau, Suchandra Aich Bhowmick, Walter H. F. Smith, Muriel Berge-Nguyen, Edward D. Zaron, Observatoire de Paris, Université Paris sciences et lettres (PSL), Laboratoire d'Océanographie Physique et Spatiale (LOPS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), and Centre National d'Études Spatiales [Toulouse] (CNES)

Subjects
Atmospheric Science, 010504 meteorology & atmospheric sciences, Meteorology, Aerospace Engineering, 01 natural sciences, Reaction wheel, Footprint, 0103 physical sciences, Ka band, Altimeter, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Constellation, Horizontal resolution, Astronomy and Astrophysics, Ka-band, Geophysics, [SDU]Sciences of the Universe [physics], 13. Climate action, Space and Planetary Science, Satellite, Orbit (dynamics), General Earth and Planetary Sciences, Environmental science, Altimetry
Abstract

International audience; The CNES/ISRO altimetric satellite SARAL/AltiKa was launched in February 2013 and since then has provided useful data for various scientific and operational applications in oceanography, hydrology, cryospheric sciences and geodesy. However, a Reaction Wheel problem forced relaxation of the repeatability constraint on the satellite's orbit, which has been drifting slowly since July 2016. Beyond the expected contributions of this mission and its very good integration into the objectives of the constellation of altimetric satellites, it has become more and more apparent that specific contributions and innovations related to the main specification of SARAL/AltiKa, that is to say the use of the Ka-band, have clearly emerged. The advantages of the Ka-band are in short the reduction of ionosphere effects, the smaller footprint, the better horizontal resolution and the higher vertical resolution. A drawback of the Ka-band is the attenuation due to water/water vapor in case of rain and the resulting loss of data. The main objective of this paper is to highlight the specific advances of the Ka-band in different scientific and technical fields and to show why they are promising for the future and open the way to several missions or mission projects. Although unplanned initially, the fine coverage of the Drifting Phase brings some interesting openings especially for geodesy and hydrology applications.

Published
2021

20. Comparative Evaluation of Sea Ice Lead Detection Based on SAR Imagery and Altimeter Data

Author

Nicolas Picot, Nicolas Longepe, Franck Borde, Jean-Christophe Poisson, François Boy, Amandine Guillot, Pierre Thibaut, and Rodolphe Vadaine

Subjects
Synthetic aperture radar, Earth observation, Lead (sea ice), Detector, 0211 other engineering and technologies, 02 engineering and technology, Constant false alarm rate, Footprint, Nadir, General Earth and Planetary Sciences, Altimeter, Electrical and Electronic Engineering, Geology, 021101 geological & geomatics engineering, Remote sensing
Abstract

The detection of sea ice leads is a prerequisite for the estimation of ice freeboard and thickness from altimeter data. The classification of altimeter waveforms is generally performed using statistical parameters on the echo power or machine learning approaches directly on the waveforms. The validation and optimization of such algorithms can be carried out using a set of reference cases provided by Earth Observation images. In this paper, we first developed a new lead detector based on Sentinel-1 (S-1) synthetic aperture radar (SAR) images. A robust and consistent methodology for the joint assessment of Altimeter and SAR leads detector is then provided. We propose to fully account for the 2-D geometric problem when comparing the 1-D altimeter track and 2-D SAR image. The surface of the lead intersecting the altimeter footprint and its distance to nadir are considered here. Based on collocated Sentinel-3 (S-3) altimeter data and S-1 images, the performance of our S-3 lead detector is fully assessed. A new parameterization is found resulting in a better tradeoff between good detection and false alarm rate. A similar analysis is performed using AltiKa altimeter data, showing enhanced performance for S-3 altimeter data acquired in Delay-Doppler mode with reduced off-nadir returns.

Published
2019

21. New upgrades of Open-Loop Tracking Command (OLTC) tables of nadir altimeters in 2020 and benefits for inland waters users

Author

Simon Boitard, Pierre Féménias, Eric Munesa, Léo Grignon, Sophie Le Gac, Eric Jeansou, François Boy, Nicolas Picot, Denis Blumstein, and Mathilde Cancet

Subjects
Computer science, Nadir, Open-loop controller, Altimeter, Tracking (particle physics), Remote sensing
Abstract

Fresh water is an essential resource that requires a close monitoring and a constant preservation effort. The evolution of hydrological bodies water level constitutes a key indicator on the available quantity of fresh water in a given region. The limited extent of the in situ networks currently deployed has generated a growing interest in using space borne altimetry as a complementary data source to increase the coverage of emerged fresh water stocks and ensure a more global and continuous monitoring of their water surface height.A great effort has been carried out over the past decade to improve altimeters’ capability to acquire quality measurements over inland waters. In particular, the Open-Loop Tracking Command (OLTC), which consists in calibrating the altimeter signal acquisition window with a prior information on the overflown hydrological surface height, represents a major evolution of the tracking function. This tracking mode’s efficiency is such that it is now stated as operational mode for current Sentinel-3 and Jason-3 missions as well as the recently launched Sentinel-6A mission. The improvements brought to onboard tables contents in 2017 (Jason-3), 2018 (Sentinel-3B) and 2019 (Sentinel-3A) enhanced and confirmed the OLTC performances.In 2020, the onboard OLTC tables of the Jason-3, Sentinel-3A and Sentinel-3B missions have benefitted from further new major upgrades. The first version of the Sentinel-6A onboard OLTC tables holds the same content as Jason-3. The tracking command defined over Jason-3 and Sentinel-6A repeat cycle now accounts for more than 30,000 hydrological targets which represents five times more targets than in the previous version. For each Sentinel-3, the number of water body surface heights coded into the OLTC has been increased by a factor of 3 to 70,000. This further major step is made possible by the analysis and merging of the most recent digital elevation models (SRTM, MERIT and ALOS/PalSAR) and water bodies databases (HydroLakes, GRaND v1.3, SWBD, GSW). This methodology ensures coherency and consistent standards between all nadir altimetry missions and types of hydrological targets.A detailed description of the 2020 upgrades will be given as well as measurements validation results obtained since their upload. An overview of the global validation of Sentinel-6A measurements over hydrological targets will also be presented.These 2020 OLTC upgrades constitute a great asset for building a valuable and continuous record of the water surface height of worldwide lakes, rivers, reservoirs and wetlands. In addition, for a continuous improvement of the OLTC tracking mode, the users can check the content of the onboard OLTC tables over hydrological targets for both Sentinel-3 missions on the https://www.altimetry-hydro.eu/ web portal. When relevant, they can correct existing water surface heights or submit new targets.

Published
2021

22. Multidisciplinary team meetings in treatment of spinal muscular atrophy adult patients: a real-life observatory for innovative treatments

Author

Emmanuelle Salort-Campana, Guilhem Solé, Armelle Magot, Céline Tard, Jean-Baptiste Noury, Anthony Behin, Elisa De La Cruz, François Boyer, Claire Lefeuvre, Marion Masingue, Louise Debergé, Armelle Finet, Mélanie Brison, Marco Spinazzi, Antoine Pegat, Sabrina Sacconi, Edoardo Malfatti, Ariane Choumert, Rémi Bellance, Anne-Laure Bedat-Millet, Léonard Feasson, Carole Vuillerot, Agnès Jacquin-Piques, Maud Michaud, Yann Pereon, Tanya Stojkovic, Pascal Laforêt, Shahram Attarian, and Pascal Cintas

Subjects
Spinal muscular atrophy, SMA, Multidisciplinary team meeting, Clinical decision-making, Treatment, Medicine
Abstract

Abstract Background In 2017, a new treatment by nusinersen, an antisense oligonucleotide delivered by repeated intrathecal injections, became available for patients with spinal muscular atrophy (SMA), whereas clinical trials had mainly involved children. Since 2020, the oral, selective SMN2-splicing modifier risdiplam has been available with restrictions evolving with time. In this peculiar context of lack of data regarding adult patients, many questions were raised to define the indications of treatment and the appropriate follow-up in this population. To homogenize access to treatment in France, a national multidisciplinary team meeting dedicated to adult SMA patients, named SMA multidisciplinary team meeting, (SMDTs) was created in 2018. Our objective was to analyze the value of SMDTs in the decision-making process in SMA adult patients and to provide guidelines about treatment. Methods From October 2020 to September 2021, data extracted from the SMDT reports were collected. The primary outcome was the percentage of cases in which recommendations on validating treatment plans were given. The secondary outcomes were type of treatment requested, description of expectations regarding treatment and description of recommendations or follow-up and discontinuation. Data were analyzed using descriptive statistics. Comparisons between the type of treatment requested were performed using Mann–Whitney test or the Student t test for quantitative data and the Fisher’s exact test or the χ2 test for qualitative data. Results Cases of 107 patients were discussed at the SMDTs with a mean age of 35.3 (16–62). Forty-seven were SMA type 2, and 57 SMA type 3. Twelve cases were presented twice. Out of 122 presentations to the SMDTs, most of requests related to the initiation of a treatment (nusinersen (n = 46), risdiplam (n = 54), treatment without mentioning preferred choice (n = 5)) or a switch of treatment (n = 12). Risdiplam requests concerned significantly older patients (p = 0.002), mostly SMA type 2 (p

Published
2024
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23. Benefits of the Adaptive algorithm for retracking altimeter nadir echoes: results from simulations and CFOSAT/SWIM observations

Author

F. Piras, Danièle Hauser, Céline Tison, Laura Hermozo, Jean-Christophe Poisson, Annabelle Ollivier, François Boy, Cedric Tourain, Pierre Thibaut, Centre National d'Études Spatiales [Toulouse] (CNES), Collecte Localisation Satellites (CLS), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National d'Études Spatiales [Toulouse] (CNES), SPACE - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Centre National d'Etudes Spatiales - Direction Des Lanceurs. (CNES), and CNES

Subjects
010504 meteorology & atmospheric sciences, Computer science, 0211 other engineering and technologies, Inverse transform sampling, 02 engineering and technology, 01 natural sciences, law.invention, law, altimetry, 14. Life underwater, Altimeter, Electrical and Electronic Engineering, Radar, Point target, Physics::Atmospheric and Oceanic Physics, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 021101 geological & geomatics engineering, 0105 earth and related environmental sciences, Remote sensing, validation, Adaptive algorithm, [SDE.IE]Environmental Sciences/Environmental Engineering, CFOSAT, SWIM, Inversion (meteorology), ocean, retracking algorithm, 13. Climate action, Lookup table, General Earth and Planetary Sciences, nadir, Significant wave height, [SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing, radar
Abstract

The accuracy of sea surface parameters retrieved from altimeter missions is predominantly governed by the choice of the so-called ``retracking'' algorithm, i.e., the model and inversion method implemented to obtain the surface parameters from the backscattered waveform. For continuity reasons, the choice of space agencies is usually to apply the same retracker from one satellite mission to the other to ensure long-time homogeneous series. In this article, taking the opportunity of a new configuration of the nadir pointing measurements onboard the recently launched China France Oceanography Satellite (CFOSAT) with the Surface Waves Investigation and Monitoring (SWIM) instrument (Hauser et al., 2020), the retracking method was upgraded, by implementing a novel algorithm, called ``Adaptive'' retracker. It combines the improvements brought by Poisson et al., (2018) for the estimation of surface parameters from peaked waveforms over sea ice, improvements in the way the instrumental characteristics are considered in the model (mispointing, point target response) and a more accurate consideration of speckle statistics. In this article, we first show from simulations carried out in the instrumental configuration of SWIM that the Adaptive algorithm has better accuracy and performance than the classical MLE4 algorithm. Then, the geophysical parameters obtained with real data from SWIM are analyzed with comparisons to reference data sets (model and products from altimeters). We show that this new algorithm has several benefits with respect to the classical MLE4 method: no need of lookup tables to correct biases, significant noise reduction on all geophysical variables especially the significant wave height, and performance of inversion over a large set of echo shapes, resulting from standard oceanic scenes as well as highly specular conditions such as over bloom or sea ice.

Published
2020

24. Detection of Internal Solitary Waves with Conventional and Advanced SAR Altimetry Processing Methods: Preliminary Results

Author

Craig Donlon, Nicolas Picot, C. Maraldi, Adriana M. Santos-Ferreira, P. Rieu, Thomas Moreau, Jose C. B. da Silva, François Boy, and Franck Borde

Subjects
Synthetic aperture radar, Data processing, 010504 meteorology & atmospheric sciences, 0211 other engineering and technologies, 02 engineering and technology, 01 natural sciences, law.invention, Processing methods, Amplitude, law, Surface wave, Altimeter, Radar, Geology, Sea level, 021101 geological & geomatics engineering, 0105 earth and related environmental sciences, Remote sensing
Abstract

The Delay-Doppler altimeter data processing (commonly called SAR altimetry) is a mature technology offering many advantages in marine radar applications compared to conventional altimetry. Here we describe the potential of SAR altimetry (both unfocused and Fully Focused) for detecting and measuring Internal Solitary Wave (ISW) amplitudes in deep water regions. Analysis of ISW SAR altimeter signatures in the tropical ocean off the Amazon shelf are presented, since their large amplitude ISWs are known to exist. Preliminary results of the dependence of Sea Level Anomalies (SLA) associated to ISWs with respect to the differenced mean square slope variations along the waves' signatures are presented for the first time.

Published
2020

25. S3MPC: Improvement on Inland Water Tracking and Water Level Monitoring from the OLTC Onboard Sentinel-3 Altimeters

Author

Pierre Féménias, François Boy, Matthias Raynal, Jean-François Crétaux, Denis Blumstein, Lionel Zawadzki, Nicolas Taburet, S. Labroue, Maxime Vayre, and Sophie Le Gac

Subjects
Synthetic aperture radar, inland waters, 010504 meteorology & atmospheric sciences, Science, 0208 environmental biotechnology, 02 engineering and technology, Tracking (particle physics), 01 natural sciences, altimetry, Ground segment, Altimeter, 0105 earth and related environmental sciences, Remote sensing, validation, Payload, Elevation, Mode (statistics), Sentinel-3, SAR, Open-Loop Tracking Command, 020801 environmental engineering, Water level, General Earth and Planetary Sciences, Environmental science
Abstract

The Sentinel-3A and Sentinel-3B satellites were launched, respectively, on 16 February 2016 and 25 April 2018 as part of the European Copernicus program. The Sentinel-3 Surface Topography Mission makes use of the altimeter instruments onboard Sentinel-3A and Sentinel-3B to provide elevation measurements not only of the ocean water level but also of the inland waters and ice caps. For the first time, the altimeters onboard Sentinel-3A and Sentinel-3B are operated in Synthetic Aperture Radar mode over all Earth surfaces. They also benefit from elevation priors (the Open-Loop Tracking Command) allowing them to precisely position their receiving window to track the backscattered signal from the inland water targets to be monitored rather than relying on the traditional Closed-Loop tracking mode. This paper makes use of the Sentinel-3A/Sentinel-3B tandem phase to assess the benefits of the Open-Loop tracking mode compared to Closed-Loop. Longer time series are also used to highlight the improvements in terms of the percentage of points over which the altimeter hooks on water surfaces and water surface height estimation brought by the switch of Sentinel-3A from the Closed-Loop to Open-Loop tracking mode as well as the successive Open-Loop Tracking Command updates. In particular, it is shown that from a Level-3 water level product service perspective, the increase in the number of water bodies with valid water surface height estimates is of the order of 25% in Open-Loop with respect to Closed-Loop with similar precision. It is also emphasized that the Open-Loop Tracking Command update onboard Sentinel-3A from v. 4.2 to v. 5.0 yielded a 30% increase in the number of water bodies over which valid water surface height could be estimated. Eventually, the importance of knowing whether a water target was associated with a fine-tuned Open-Loop Tracking Command or an interpolated one is stressed and the recommendation to provide such a flag in the Sentinel-3 Level2 Payload Data Ground Segment products is emitted.

Published
2020

26. From conventional to Delay Doppler altimetry: A demonstration of continuity and improvements with the Cryosat-2 mission

Author

Matthias Raynal, T. Moreau, Nicolas Picot, S. Labroue, and François Boy

Subjects
Synthetic aperture radar, Atmospheric Science, 010504 meteorology & atmospheric sciences, Mode (statistics), Aerospace Engineering, Astronomy and Astrophysics, Sea state, 01 natural sciences, symbols.namesake, Geophysics, Signal-to-noise ratio, Space and Planetary Science, 0103 physical sciences, symbols, General Earth and Planetary Sciences, Satellite, Altimeter, Significant wave height, 010303 astronomy & astrophysics, Doppler effect, Geology, 0105 earth and related environmental sciences, Remote sensing
Abstract

Cryosat-2 is the first satellite that embarks an altimeter able to operate in several modes. Among them, the Synthetic Aperture Radar mode (SARM) also referred to as Delay Doppler mode is expected to improve the measurement resolution and precision. Based on a two year time series, this paper presents the SARM assessment over ocean. It demonstrates the seamless transition, below the centimeter level, between conventional pulse-limited and Delay Doppler altimetry at long wavelength for the sea level. Nevertheless, the SARM retrieved Significant Wave Height (SWH) is biased by 20 cm and depends on the sea state. This paper also confirms that, thanks to the better signal to noise ratio and along track resolution brought by the SARM, the small scales observability is significantly improved with respect to the Low Resolution Mode (LRM). The SARM Sea Level reveals a spectral slope never observed for wavelength below 30 km that is not yet explained. Further analyses at global scales using the Sentinel-3A dataset will certainly help to characterize the source of this signal.

Published
2018

27. Impact of long ocean waves on wave height retrieval from SAR altimetry data

Author

François Boy, T. Moreau, N. Tran, C. Tison, S. Le Gac, and J. Aublanc

Subjects
Atmospheric Science, 010504 meteorology & atmospheric sciences, 0211 other engineering and technologies, Aerospace Engineering, Astronomy and Astrophysics, 02 engineering and technology, Sea state, Sea-surface height, 01 natural sciences, Swell, law.invention, Geophysics, Space and Planetary Science, law, Wave height, Wind wave, General Earth and Planetary Sciences, Altimeter, Radar, Significant wave height, Geology, 021101 geological & geomatics engineering, 0105 earth and related environmental sciences, Remote sensing
Abstract

SAR altimetry is a new high-resolution operation mode exploited in new-generation altimeter missions, such as Sentinel-3. It takes advantage of its enhanced along-track resolution to make measurements of sea surface height variations in much greater detail than what can be achieved with conventional low resolution instruments (e.g. the Jason-3 altimeter). However, contrary to what is observed for conventional altimetry, long-wavelength ocean waves of a few hundred meters (swell and extreme wind waves) are no longer fully imaged in the instrument ground cells, and SAR waveforms have distorted shapes in such wave conditions. This affects the final retrieval of significant wave height (SWH). This paper analyzes the impact of long ocean waves on SAR-mode data by using both Cryosat-2 measurements and simulated data. Results from these two approaches are in good agreement and show that the estimated parameters from SAR-altimetry waveforms are particularly noisy under long-wave conditions and also biased when compared with conventional altimetry data. Additionally, we found evidence that these impacts are different between the two directions (along and cross-track directions) due to the asymmetry of the SAR-altimetry footprint. Simulations indicate that statistics of sea surface elevations within the SAR-altimetry footprint deviate from Gaussian behavior. The assumption commonly used for ocean retracking algorithms is therefore inaccurate. The sensitivity of SAR-mode altimetry data to long waves is a key issue for the ocean altimetry community, which is concerned to ensure the continuity of high-quality time series of the global sea-surface topography in future years. This is not only an issue for these new-generation radar altimeters (Sentinel-3 and Sentinel-6) but also for all innovative techniques or processing methodologies capable of providing higher spatial resolution of the ocean surface.

Published
2018

28. Evaluation of SAR altimetry over the antarctic ice sheet from CryoSat-2 acquisitions

Author

François Boy, Pierre Thibaut, J. Aublanc, Nicolas Picot, T. Moreau, and Frédérique Rémy

Subjects
Synthetic aperture radar, Atmospheric Science, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, Elevation, Aerospace Engineering, Antarctic ice sheet, Astronomy and Astrophysics, 010502 geochemistry & geophysics, 01 natural sciences, law.invention, Geophysics, Space and Planetary Science, Radar altimeter, law, Lake Vostok, General Earth and Planetary Sciences, Satellite, Altimeter, Ice sheet, Geology, 0105 earth and related environmental sciences, Remote sensing
Abstract

Since the 1990s and the launch of ERS-1, Earth’s polar regions have been near continuously monitored by satellite altimetry, improving substantially our knowledge of the ice sheet topography and its evolution. CryoSat-2 is the first satellite carrying on-board a new generation of radar altimeter able to operate in a Synthetic Aperture Radar (SAR) mode. In comparison with the Low Resolution Mode (LRM) used in conventional radar altimetry, SAR mode allows to reduce the along-track footprint from several kilometers to 300 m. In this paper we assess the SAR mode performance over the Antarctic ice sheet using sporadic CryoSat-2 acquisitions carried out in winter 2014 on dedicated zones (Lake Vostok and Adelie land). Level-1 data from two different algorithms are exploited: the CNES Cryosat-2 Processing Prototype (CPP) and the ESA Instrument Processing Facility (IPF). Firstly, results show that the estimated surface elevation from the SAR mode acquisitions over the flat surface of Lake Vostok is within the same order of magnitude as available DEMs. Mean bias is in the order of several centimeters, without any corrections accounting for the snowpack volume scattering. Secondly, the undertaken analyzes evidence that SAR altimetry has either no, or only small, sensitivity to the along-track slope-induced effect, while the across-track slope-induced effect is similar as LRM. Thirdly, SAR altimetry mode appears to be more performant than Pseudo-LRM over the steep slopes of the Antarctica margins. The precision of the estimated surface elevation is improved by 30%, and the processed waveforms are less noisy. Overall, this work demonstrates the improved measuring capability offered by SAR mode altimetry over the ice sheet surface compared to conventional altimetry.

Published
2018

29. CryoSat-2 SAR-Mode Over Oceans: Processing Methods, Global Assessment, and Benefits

Author

Jean-Damien Desjonquères, François Boy, Thomas Moreau, Nicolas Picot, and Matthias Raynal

Subjects
Synthetic aperture radar, 010504 meteorology & atmospheric sciences, 0211 other engineering and technologies, 02 engineering and technology, Geodesy, 01 natural sciences, Space-based radar, law.invention, Continuous-wave radar, Inverse synthetic aperture radar, Radar altimeter, law, Radar imaging, General Earth and Planetary Sciences, Altimeter, Electrical and Electronic Engineering, Radar, Geology, 021101 geological & geomatics engineering, 0105 earth and related environmental sciences, Remote sensing
Abstract

Inspired by the synthetic aperture radar (SAR) technique, a nadir radar altimeter concept called the “Delay/Doppler altimeter” or “SAR mode altimeter” provides better precision and resolution capabilities than conventional pulse-limited altimeters (i.e., low-resolution mode). This concept was initially carried on board the CryoSat-2 satellite, then used on Sentinel-3, initially for user requirements on ice or inland water monitoring. This paper addresses geophysical parameter retrieval from Delay/Doppler altimetry over ocean surfaces. For the inversion of geophysical parameters (sea surface height, significant wave height, and backscatter coefficient), we developed an inversion method based on the numerical computation of the radar power-return equation, including instrument design features, such as the range and azimuth impulse responses. To compare this technique with respect to conventional altimetry, we also generated reduced SAR (RDSAR) measurements from the same input data. Geophysical parameter retrieval from low- and high-resolution techniques was then performed for cross-comparison, demonstrating consistency for both techniques, but with a constant 3-cm bias. The proposed processing strategy was then validated using two years of CryoSat-2 data over oceans. The SAR mode provides significant benefits for the observation of small-scale signals (below 50 km) and performs as accurately as conventional altimetry for basin or global scales. The results demonstrate what is expected from the upcoming Sentinel-3 and Sentinel-6/Jason-CS missions.

Published
2017

30. Measuring ocean surface velocities with the KuROS and KaRADOC airborne near-nadir Doppler radars: a multi-scale analysis in preparation of the SKIM mission, Submitted to Ocean SCience, July 2019

Author

Louis, Marié, Collard, Fabrice, Frederic, Nouguier, Lucia, Pineau-Gouillou, Hauser, Danièle, François, Boy, Stéphane, Meric, Peureux, Charles, Goulwenn, Monnier, Bertrand, Chapron, Adrien, Martin, Pierre, Dubois, Donlon, Craig, Casal, Tânia, Ardhuin, Fabrice, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), OceanDataLab, SPACE - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Sorbonne Université (SU), Laboratoire d'Océanographie Physique et Spatiale (LOPS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA), and Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU]Sciences of the Universe [physics], Physics::Atmospheric and Oceanic Physics
Abstract

Surface currents are poorly known over most of the oceans. Satellite-borne Doppler Waves and Current Scatterom-eters (DWCS) can be used to fill this observation gap. The Sea surface KInematics Multiscale (SKIM) proposal, is the first satellite concept built on a DWCS design at near-nadir angles, and now one of the two candidates to become the 9th mission of the European Space Agency Earth Explorer program. As part of the detailed design and feasibility studies (phase A) funded by ESA, airborne measurements were carried out with both a Ku-Band and a Ka-Band Doppler radars looking at the sea surface at 5 near nadir-incidence in a real-aperture mode, i.e. in a geometry and mode similar to that of SKIM. The airborne radar KuROS was deployed to provide simultaneous measurements of the radar backscatter and Doppler velocity, in a side-looking configuration , with an horizontal resolution of about 5 to 10 m along the line of sight and integrated in the perpendicular direction over the real-aperture 3-dB footprint diameter (about 580 m). The KaRADOC system has a much narrower beam, with a circular footprint only 45 m in diameter. 10 The experiment took place in November 2018 off the French Atlantic coast, with sea states representative of the open ocean and a well known tide-dominated current regime. The data set is analyzed to explore the contribution of non-geophysical velocities to the measurement and how the geophysical part of the measured velocity combines wave-resolved and wave-averaged scales. We find that the measured Doppler velocity contains a characteristic wave phase speed, called here C 0 that is analogous to the Bragg phase speed of coastal High Frequency radars that use a grazing measurement geometry, with little 15 variations ∆ C associated to changes in sea state. The Ka-band measurements at an incidence of 12 • are 10% lower than the theoretical estimate C 0 2.4 m/s for typical oceanic conditions defined by a wind speed of 7 m/s and a significant wave height of 2 m. For Ku-band the measured data is 1 https://doi. 30% lower than the theoretical estimate 2.8 m/s. ∆ C is of the order of 0.2 m/s for a 1 m change in wave height, and cannot be confused with a 1 m/s change in tidal current. The actual measurement of the current velocity from an aircraft at 4 to 18 • incidence angle is, however, made difficult by uncertainties on the measurement geometry, which are much reduced in satellite measurements.

Published
2019

31. Measuring ocean surface velocities with the KuROS and KaRADOC airborne near-nadir Doppler radars: a multi-scale analysis in preparation of the SKIM mission

Author

Louis Marié, François Boy, Stephane Meric, Fabrice Collard, Tania Casal, Frederic Nouguier, Danièle Hauser, Craig Donlon, Bertrand Chapron, Lucia Pineau-Guillou, Goulven Monnier, Charles Peureux, Fabrice Ardhuin, Adrien Martin, Pierre Dubois, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), OceanDataLab, SPACE - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Sorbonne Université (SU), Laboratoire d'Océanographie Physique et Spatiale (LOPS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), European Space Research and Technology Centre (ESTEC), European Space Agency (ESA), and Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, 020206 networking & telecommunications, 02 engineering and technology, Sea state, Geodesy, Wind speed, law.invention, symbols.namesake, [SDU]Sciences of the Universe [physics], law, Wave height, 0202 electrical engineering, electronic engineering, information engineering, symbols, Nadir, 14. Life underwater, Radar, Phase velocity, Significant wave height, Doppler effect, Physics::Atmospheric and Oceanic Physics, Geology
Abstract

Surface currents are poorly known over most of the oceans. Satellite-borne Doppler Waves and Current Scatterometers (DWCS) can be used to fill this observation gap. The Sea surface KInematics Multiscale (SKIM) proposal, is the first satellite concept built on a DWCS design at near-nadir angles, and now one of the two candidates to become the 9th mission of the European Space Agency Earth Explorer program. As part of the detailed design and feasibility studies (phase A) funded by ESA, airborne measurements were carried out with both a Ku-Band and a Ka-Band Doppler radars looking at the sea surface at near nadir-incidence in a real-aperture mode, i.e. in a geometry and mode similar to that of SKIM. The airborne radar KuROS was deployed to provide simultaneous measurements of the radar backscatter and Doppler velocity, in a side-looking configuration, with an horizontal resolution of about 5 to 10m along the line of sight and integrated in the perpendicular direction over the real-aperture 1-way 3-dB footprint diameter (about 580m). The KaRADOC system has a much narrower beam and footprint that only about 45m in diameter. The experiment took place in November 2018 off the French Atlantic coast, with sea states representative of the open ocean and a well known tide-dominated current regime. The data set is analyzed to explore the contribution of non-geophysical velocities to the measurement and how the geophysical part of the measured velocity combines wave-resolved and wave-averaged scales. We find that the measured Doppler velocity contains a characteristic wave phase speed, called here C0 that is analogous to the Bragg phase speed of coastal High Frequency radars that use a grazing measurement geometry, with little variations ΔC associated to changes in sea state. The Ka-band measurements at an incidence of 12° are 10% lower than the theoretical estimate C0~2.4m/s for typical oceanic conditions defined by a wind speed of 7m/s and a significant wave height of 2m. For Ku-band the measured data is 30% lower than the theoretical estimate 2.8m/s. ΔC is of the order of 0.2m/s for a 1m change in wave height, and cannot be confused with a 1m/s change in tidal current. The actual measurement of the current velocity from an aircraft at 4 to 18° incidence angle is, however, made difficult by uncertainties on the measurement geometry, which are much reduced in satellite measurements.

Published
2019

32. Absolute Calibration of Sentinel-3A and Jason-3 Altimeters with Sea-Surface and Transponder Techniques in West Crete, Greece

Author

Georgios S. Vergos, Thierry Guinle, Demitris Galanakis, Constantin Mavrocordatos, Achilles Tripolitsiotis, Ilias N. Tziavos, François Boy, X. Frantzis, Pierre Féménias, Stelios P. Mertikas, and Craig Donlon

Subjects
Sea-surface, Sentinel-3A, Jason-3, Calibration, Validation, Altimeter, Geodesy, Transponder, Absolute calibration, Geology
Abstract

Summarization: This work presents the latest absolute and relative calibrations for the altimeters of the Sentinel-3A and Jason-3 at the Permanent Facility for Altimeter Calibration in west Crete, Greece. Results have been determined at first with the transponder at the CDN1 Cal/Val site on the mountains of west Crete using the ascending Sentinel-3A Pass No. 14 and the descending Jason-3 Pass No.18. Then, sea-surface calibration has been carried out with the descending Sentinel-3A Pass No. 335 and the ascending Jason-3 Pass No.109 based on the Cal/Val facility on Gavdos island. For Sentinel-3A results have been established for cycles 3–27 using Level 2 (Level 0 for transponder) and Non-Time Critical data. For Jason-3, cycles 5–80 and the S-GDR-D data have been worked with the transponder calibration, while for the results with sea-surface calibration, cycles 1–80 with the I-GDR-D data have been implemented. Sentinel-3A produces biases of the order of a few mm either with the transponder (+2.7 mm) or with the sea-surface calibration (7.3 mm and −4.4 mm). The altimeter of Jason-3 presents a range bias at +22.7 mm (No.18) with the transponder and −36.7 mm for the bias in sea-surface height, respectively. Finally, comparison of sea-surface heights observed by Sentinel-3A relative to Jason-3 demonstrates a difference of +4 cm within a period of ±3 days about 20 km south of Gavdos. Παρουσιάστηκε στο: International Review Workshop on Satellite Altimetry Calibration/Validation Activities and Applications

Published
2019

33. Validation of Jason-3 tracking modes over French rivers

Author

François Boy, Fabien Blarel, Denis Blumstein, Frédéric Frappart, Fernando Niño, Sylvain Biancamaria, Thomas Schaedele, Jean-Damien Desjonquères, Claire Pottier, Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales [Toulouse] (CNES), Géosciences Environnement Toulouse (GET), DCT/PS/TVI, GOHS, Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD), and Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
010504 meteorology & atmospheric sciences, 0208 environmental biotechnology, Soil Science, 02 engineering and technology, Tracking (particle physics), 01 natural sciences, law.invention, Rivers, law, Nadir, Altimeter, Computers in Earth Sciences, Radar, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, Digital elevation model, 0105 earth and related environmental sciences, Remote sensing, Open-LoopDEM tracking mode, [SDE.IE]Environmental Sciences/Environmental Engineering, Elevation, Mode (statistics), Geology, 020801 environmental engineering, Jason-3, Satellite, Open-Loop/DEM tracking mode, Altimetry
Abstract

International audience; Satellite nadir radar altimeters have been widely used to measure river and lake surface water elevations. They can now retrieve the elevations of some rivers

Published
2018

34. Satellite radar altimetry water elevations performance over a 200 m wide river: Evaluation over the Garonne River

Author

François Boy, Jean-Damien Desjonquères, Denis Blumstein, Sylvain Biancamaria, Frédéric Frappart, Aldo Sottolichio, Arnoldo Valle-Levinson, Vincent Marieu, A. S. Leleu, Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Centre National d'Études Spatiales [Toulouse] (CNES), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), and Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE)

Subjects
Atmospheric Science, Ground track, 010504 meteorology & atmospheric sciences, 0208 environmental biotechnology, Aerospace Engineering, 02 engineering and technology, 01 natural sciences, 14. Life underwater, Altimeter, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, 0105 earth and related environmental sciences, Remote sensing, geography, geography.geographical_feature_category, Mode (statistics), Elevation, Sampling (statistics), Astronomy and Astrophysics, Estuary, 020801 environmental engineering, Geophysics, 13. Climate action, Space and Planetary Science, General Earth and Planetary Sciences, Satellite, Nadir (topography), Geology
Abstract

For at least 20 years, nadir altimetry satellite missions have been successfully used to first monitor the surface elevation of oceans and, shortly after, of large rivers and lakes. For the last 5–10 years, few studies have demonstrated the possibility to also observe smaller water bodies than previously thought feasible (river smaller than 500 m wide and lake below 10 km2). The present study aims at quantifying the nadir altimetry performance over a medium river (200 m or lower wide) with a pluvio-nival regime in a temperate climate (the Garonne River, France). Three altimetry missions have been considered: ENVISAT (from 2002 to 2010), Jason-2 (from 2008 to 2014) and SARAL (from 2013 to 2014). Compared to nearby in situ gages, ENVISAT and Jason-2 observations over the lower Garonne River mainstream (110 km upstream of the estuary) have the smallest errors, with water elevation anomalies root mean square errors (RMSE) around 50 cm and 20 cm, respectively. The few ENVISAT upstream measurements have RMSE ranging from 80 cm to 160 cm. Over the estuary, ENVISAT and SARAL water elevation anomalies RMSE are around 30 cm and 10 cm, respectively. The most recent altimetry mission, SARAL, does not provide river elevation measurements for most satellite overflights of the river mainstream. The altimeter remains “locked” on the top of surrounding hilly areas and does not observe the steep-sided river valley, which could be 50–100 m lower. This phenomenon is also observed, for fewer dates, on Jason-2 and ENVISAT measurements. In these cases, the measurement is not “erroneous”, it just does not correspond to water elevation of the river that is covered by the satellite. ENVISAT is less prone to get ‘locked’ on the top of the topography due to some differences in the instrument measurement parameters, trading lower accuracy for more useful measurements. Such problems are specific to continental surfaces (or near the coasts), but are not observed over the open oceans, which are flatter. To overcome this issue, an experimental instrument operating mode, called the DIODE/DEM tracking mode, has been developed by CNES (Centre National d’Etudes Spatiales) and has been tested during few Jason-2 cycles and during the first SARAL/AltiKA cycle. This tracking mode “forces” the instrument to observe a target of interest, i.e. water bodies. The example of the Garonne River shows, for one SARAL ground track, the benefit of the DIODE/DEM tracking mode for a steep-sided river reach, which is not detected using the nominal instrument operating mode. Yet, this mode relies on ancillary datasets (a priori global DEM and global land/water mask), which are critical to obtain river valley observation. The ultimately computed elevations along the satellite tracks, loaded on board, should have an absolute vertical accuracy around 10 m (or better). This case also shows, when the instrument is correctly observing the river valley, that the altimeter can detect water bodies narrower than 100 m (like an artificial canal). In agreement with recent studies, this work shows that altimeter missions can provide useful water elevation measurements over a 200 m wide river with RMSE as low as 50 cm and 20 cm, for ENVISAT and Jason-2 respectively. The seasonal cycle can be observed with the temporal sampling of these missions (35 days and 10 days, respectively), but short term events, like flood events, are most of the time not observed. It also illustrates that altimeter capability to observe a river is highly dependent of the surrounding topography, the observation configuration, previous measurements and the instrument design. Therefore, it is not possible to generalize at global scale the minimum river width that could be seen by altimeters. This study analyzes, for the first time, the potential of the experimental DIODE/DEM tracking mode to observe steep-sided narrow river valleys, which are frequently missed with nominal tracking mode. For such case, using the DIODE/DEM mode could provide water elevation measurements, as long as the on board DEM is accurate enough. This mode should provide many more valid measurements over steep-sided rivers than currently observed.

Published
2017

35. Investigating Short-Wavelength Correlated Errors on Low-Resolution Mode Altimetry

Author

Gérald Dibarboure, P. Thibaut, Jean-Christophe Poisson, S. Labroue, François Boy, Y. Lasne, Nicolas Picot, and J. D. Desjonquères

Subjects
Footprint, Atmospheric Science, Wavelength, Altitude, Backscatter, Mode (statistics), Ocean Engineering, Sea-surface height, Altimeter, Geodesy, Geology, Sea level, Remote sensing
Abstract

The observation of ocean scales smaller than 100 km with low-resolution mode (LRM) altimetry products is degraded by the existence of a “hump artifact” visible on sea surface height (SSH) spectra. Through an analysis of simulations and actual data from multiple missions, this paper shows that the hump originates in a response to inhomogeneities in backscatter strength. Current retrackers cannot fit their Brown model properly because they were designed for a scene with homogeneous backscatter properties. The error is also smoothed along track because of the size and shape of the LRM disc-shaped footprint. Therefore, the hump is modulated by the altimeter design and altitude and by the retracker used. Because of the random nature of the phenomenon, a large majority of long topography segments (e.g., hundreds to thousands of kilometers) is affected. However, within these segments, a substantial fraction of the corruption is contained in small subsets of data (e.g., less than 10%). This paper shows that oceanography users interested in small-scale SSH signals can mitigate the hump corruption by using better editing and postprocessing algorithms on the 20-Hz rate of current products. Last, the thin stripe-shaped footprint of Cryosat-2’s synthetic aperture radar mode (SARM) is not affected by the hump artifact, thus improving the observation of topography features ranging from 30 to 100 km. The differences between SARM and pseudo-LRM sigma0 can also be used to detect major hump events on pseudo-LRM data, which might be an asset to design/validate a new generation of algorithms aimed at reducing the hump artifact on the existing LRM record.

Published
2014

36. A New Method of Precise Jason-2 Altimeter Calibration Using a Microwave Transponder

Author

Nicolas Picot, François Boy, W. Hausleitner, J. Weingrill, Stelios P. Mertikas, A. Daskalakis, J. D. Desjonquères, and Florian Moser

Subjects
Repeater, Oceanography, Geodesy, Signal, law.invention, Geography, Radar altimeter, law, Calibration, Waveform, Altimeter, Microwave, Remote sensing, Transponder
Abstract

This study presents a new method of precise altimeter absolute calibration using a dedicated microwave transponder, which acts as an altimeter signal repeater that can be deployed at any sub-track position both in coastal regions and inland. The Austrian Academy of Sciences operates an altimeter transponder at the Gavdos calibration/validation facility located beneath a Jason cross-over point. We discuss the capabilities and strengths of the transponder technique in general and in the particular case of a dedicated calibration campaign carried out in 2011. For the accomplishment of this campaign, including 26 ascending and descending Jason-2 passes, the onboard Poseidon-3 altimeter had to be switched to the DIODE/DEM mode for every overflight. Four different methods have been developed to analyze the transponder generated waveforms, provided by S-IGDR and S-GDR products, respectively. The resulting biases of the altimetric ranges have proven to be stable (3 mm rms) and agree to a large extent among the pr...

Published
2012

37. First quality assessment of the Cryosat-2 altimetric system over ocean

Author

Nicolas Picot, M. Urvoy, Michael Ablain, François Boy, and S. Labroue

Subjects
Atmospheric Science, Quality assessment, Mode (statistics), Mesoscale meteorology, Aerospace Engineering, Astronomy and Astrophysics, Standard deviation, Data set, Interferometry, Geophysics, Space and Planetary Science, General Earth and Planetary Sciences, Bathymetry, Altimeter, Geology, Remote sensing
Abstract

This paper presents the results of a Calval analysis performed for the Cryosat-2 mission over ocean. The data set used in this analysis consists of products generated by the Cryosat-2 Processor Prototype developed by CNES (Center National d’Etudes Spatiales). This data set has been analysed focusing on LRM (Low Resolution Mode) mode only. One major objective of this paper is to illustrate the potential of Cryosat-2 data over ocean, mainly for waves and Sea Level Anomaly applications. All the results indicate very good performances of the SIRAL (SAR/Interferometric Altimeter) altimeter over ocean. Crossover standard deviation is close to 6.5 cm over the analysed period (3 months) which is close to the Jason-2 and ENVISAT performance. All these results confirm that Cryosat’s altimeter can provide data almost as valuable as other flying altimetric missions, and that it has the potential to contribute to oceanography (e.g. multi-mission climate record, mesoscale monitoring in near real time) and to geodesy (e.g. mean sea surface, bathymetry).

Published
2012

38. Including antenna mispointing in a semi-analytical model for delay/Doppler altimetry

Author

François Boy, Corinne Mailhes, Jean-Yves Tourneret, Thomas Moreau, Abderrahim Halimi, Centre National d'Études Spatiales - CNES (FRANCE), Centre National de la Recherche Scientifique - CNRS (FRANCE), Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE), Université Toulouse III - Paul Sabatier - UT3 (FRANCE), Université Toulouse - Jean Jaurès - UT2J (FRANCE), Université Toulouse 1 Capitole - UT1 (FRANCE), Collecte Localisation Satellites - CLS (FRANCE), Laboratoire de recherche en télécommunications spatiales et aéronautiques - TéSA (FRANCE), Signal et Communications (IRIT-SC), Institut de recherche en informatique de Toulouse (IRIT), Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées, Télécommunications Spatiales et Aéronautiques - Telecommunications for Space ant Aeronautics (TéSA), Laboratoire de recherche coopératif dans les télécommunications spatiales et aéronautiques (TESA), CoMputational imagINg anD viSion (IRIT-MINDS), Institut National Polytechnique (Toulouse) (Toulouse INP), Centre National d'Études Spatiales [Toulouse] (CNES), Collecte Localisation Satellites (CLS), and Centre National d'Études Spatiales [Toulouse] (CNES)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)

Subjects
Least squares estimation, Cryosat, 010504 meteorology & atmospheric sciences, Computer science, 0211 other engineering and technologies, Réseaux et télécommunications, Antenna mispointing, 02 engineering and technology, 01 natural sciences, Least squares, Radiation pattern, Convolution, law.invention, symbols.namesake, [INFO.INFO-NI]Computer Science [cs]/Networking and Internet Architecture [cs.NI], law, Altimeter, Electrical and Electronic Engineering, Radar, Point target, Impulse response, SAR altimetry, 021101 geological & geomatics engineering, 0105 earth and related environmental sciences, Scattering, Delay/Doppler map, Geodesy, symbols, General Earth and Planetary Sciences, Antenna (radio), Altimetry, Doppler effect, Algorithm
Abstract

International audience; Delay/Doppler altimetry aims at reducing the measurementnoise and increasing the along-track resolution in comparison with conventional pulse limited altimetry. In a previous paper, we have proposed a semi-analytical model for delay/Doppler altimetry which considers some simplifications as the absence of mispointing antenna. This paper first proposes a new semi-analytical model for delay/Doppler altimetry. The proposed analytical expression for the flat surface impulse response considers antenna mispointing angles, a circular antenna pattern, no vertical speed effect and a uniform scattering. The two dimensional delay/Doppler map is obtained by a numerical computation of the convolution between the proposed analytical function, the probability density function of the heights of the specular scatterers and the time/frequency point target response of the radar. The approximations used to obtain the semi-analytical model are analyzed and the associated errors are quantified by analytical bounds for these errors. The second contribution of this paper concerns the estimation of the parameters associated with the multi-look semi-analytical model. Two estimation strategies based on the least squares procedure are proposed. The proposed model and algorithms are validated on both synthetic and real waveforms. The obtained results are very promising and show the accuracy of this generalized model with respect to the previous model assuming zero antenna mispointing.

Published
2015

39. A Semi-Analytical Model for Delay/Doppler Altimetry and Its Estimation Algorithm

Author

Abderrahim Halimi, Corinne Mailhes, François Boy, Jean-Yves Tourneret, Pierre Thibaut, Signal et Communications (IRIT-SC), Institut de recherche en informatique de Toulouse (IRIT), Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées, Institut National Polytechnique (Toulouse) (Toulouse INP), CoMputational imagINg anD viSion (IRIT-MINDS), Collecte Localisation Satellites (CLS), Centre National d'Études Spatiales [Toulouse] (CNES)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Centre National d'Études Spatiales [Toulouse] (CNES), Université Toulouse 1 Capitole (UT1)-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse 1 Capitole (UT1)-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National d'Études Spatiales [Toulouse] (CNES), Centre National d'Études Spatiales - CNES (FRANCE), Centre National de la Recherche Scientifique - CNRS (FRANCE), Institut Français de Recherche pour l'Exploitation de la MER - IFREMER (FRANCE), Institut National Polytechnique de Toulouse - INPT (FRANCE), Université Toulouse III - Paul Sabatier - UT3 (FRANCE), Université Toulouse - Jean Jaurès - UT2J (FRANCE), Université Toulouse 1 Capitole - UT1 (FRANCE), and Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)

Subjects
Synthetic aperture radar, Least squares estimation, Synthetic aperture radar (SAR) altimetry, Cryosat, Least squares (LS) estimation, Doppler radar, Least squares, Convolution, law.invention, [INFO.INFO-AI]Computer Science [cs]/Artificial Intelligence [cs.AI], [INFO.INFO-TS]Computer Science [cs]/Signal and Image Processing, law, Traitement du signal et de l'image, Electrical and Electronic Engineering, Radar, Impulse response, Mathematics, Estimation theory, [INFO.INFO-CV]Computer Science [cs]/Computer Vision and Pattern Recognition [cs.CV], Delay/Doppler, [INFO.INFO-GR]Computer Science [cs]/Graphics [cs.GR], Delay/Doppler (DD) map (DDM), Radar altimeter, [INFO.INFO-TI]Computer Science [cs]/Image Processing [eess.IV], General Earth and Planetary Sciences, Altimetry, Algorithm, [SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing
Abstract

International audience; The concept of delay/Doppler (DD) altimetry (DDA) has been under study since the mid-1990s, aiming at reducing the measurement noise and increasing the along-track resolution in comparison with the conventional pulse-limited altimetry. This paper introduces a new model for the mean backscattered power waveform acquired by a radar altimeter operating in synthetic aperture radar mode, as well as an associated least squares (LS) estimation algorithm. As in conventional altimetry (CA), the mean power can be expressed as the convolution of three terms: the flat surface impulse response (FSIR), the probability density function of the heights of the specular scatterers, and the time/frequency point target response of the radar. An important contribution of this paper is to derive an analytical formula for the FSIR associated with DDA. This analytical formula is obtained for a circular antenna pattern, no mispointing, no vertical speed effect, and a uniform scattering. The double convolution defining the mean echo power can then be computed numerically, resulting in a 2-D semi-analytical model called the DD map (DDM). This DDM depends on three altimetric parameters: the epoch, the sea surface wave height, and the amplitude. A multi-look model is obtained by summing all the reflected echoes from the same along-track surface location of interest after applying appropriate delay compensation (range migration) to align the DDM on the same reference. The second contribution of this paper concerns the estimation of the parameters associated with the multi-look semi-analytical model. An LS approach is investigated by means of the Levenberg-Marquardt algorithm. Simulations conducted on simulated altimetric waveforms allow the performance of the proposed estimation algorithm to be appreciated. The analysis of Cryosat-2 waveforms shows an improvement in parameter estimation when compared to the CA.

Published
2014

40. A Generalized Semi-Analytical model for delay/Doppler altimetry

Author

Jean-Yves Tourneret, François Boy, Corinne Mailhes, Abderrahim Halimi, Thomas Moreau, Centre National d'Études Spatiales - CNES (FRANCE), Centre National de la Recherche Scientifique - CNRS (FRANCE), Institut National Polytechnique de Toulouse - INPT (FRANCE), Université Toulouse III - Paul Sabatier - UT3 (FRANCE), Université Toulouse - Jean Jaurès - UT2J (FRANCE), Université Toulouse 1 Capitole - UT1 (FRANCE), Signal et Communications (IRIT-SC), Institut de recherche en informatique de Toulouse (IRIT), Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées, Institut National Polytechnique (Toulouse) (Toulouse INP), CoMputational imagINg anD viSion (IRIT-MINDS), Centre National d'Études Spatiales [Toulouse] (CNES), and Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)

Subjects
Least squares estimation, Computer science, 0211 other engineering and technologies, Antenna mispointing, 02 engineering and technology, Least squares, [INFO.INFO-AI]Computer Science [cs]/Artificial Intelligence [cs.AI], symbols.namesake, Traitement des images, [INFO.INFO-TS]Computer Science [cs]/Signal and Image Processing, 0202 electrical engineering, electronic engineering, information engineering, Waveform, Traitement du signal et de l'image, Altimeter, Synthèse d'image et réalité virtuelle, 021101 geological & geomatics engineering, Echo (computing), [INFO.INFO-CV]Computer Science [cs]/Computer Vision and Pattern Recognition [cs.CV], 020206 networking & telecommunications, Function (mathematics), Vision par ordinateur et reconnaissance de formes, Intelligence artificielle, Geodesy, [INFO.INFO-GR]Computer Science [cs]/Graphics [cs.GR], [INFO.INFO-TI]Computer Science [cs]/Image Processing [eess.IV], symbols, Antenna (radio), Doppler effect, Algorithm, Cryosat-2, Delay/Doppler altimetry
Abstract

International audience; This paper introduces a new model for delay/Doppler altimetry, taking into account the effect of antenna mispointing. After defining the proposed model, the effect of the antenna mispointing on the altimetric waveform is analyzed as a function of along-track and across-track angles. Two least squares approaches are investigated for estimating the parameters associated with the proposed model. The first algorithm estimates four parameters including the across-track mispointing (which affects the echo's shape). The second algorithm uses the mispointing angles provided by the star-trackers and estimates the three remaining parameters. The proposed model and algorithms are validated via simulations conducted on both synthetic and real data.

Published
2014

41. Parameter estimation for peaky altimetric waveforms

Author

François Boy, Corinne Mailhes, Pierre Thibaut, Abderrahim Halimi, J.-Y. Tourneret, Centre National d'Études Spatiales - CNES (FRANCE), Centre National de la Recherche Scientifique - CNRS (FRANCE), Institut National Polytechnique de Toulouse - INPT (FRANCE), Université Toulouse III - Paul Sabatier - UT3 (FRANCE), Collecte Localisation Satellites - CLS (FRANCE), Signal et Communications (IRIT-SC), Institut de recherche en informatique de Toulouse (IRIT), Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse - Jean Jaurès (UT2J)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Toulouse 1 Capitole (UT1), Université Fédérale Toulouse Midi-Pyrénées, Institut National Polytechnique (Toulouse) (Toulouse INP), Collecte Localisation Satellites (CLS), Centre National d'Études Spatiales [Toulouse] (CNES)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Centre National d'Études Spatiales [Toulouse] (CNES), and Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)

Subjects
010504 meteorology & atmospheric sciences, Brown model, Gaussian, 0211 other engineering and technologies, Coastal altimetry, 02 engineering and technology, Sea state, 01 natural sciences, Physics::Geophysics, symbols.namesake, Cramér-Rao bounds, Bias of an estimator, [INFO.INFO-TS]Computer Science [cs]/Signal and Image Processing, Traitement du signal et de l'image, 14. Life underwater, Electrical and Electronic Engineering, Cramér–Rao bounds, 021101 geological & geomatics engineering, 0105 earth and related environmental sciences, Remote sensing, Mathematics, Estimation theory, Estimator, Geodesy, Peaks, Amplitude, Parametric model, symbols, General Earth and Planetary Sciences, Cramér–Rao bound, [SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing, Maximum likelihood
Abstract

International audience; Much attention has been recently devoted to the analysis of coastal altimetric waveforms. When approaching the coast, altimetric waveforms are sometimes corrupted by peaks caused by high reflective areas inside the illuminated land surfaces or by the modification of the sea state close to the shoreline. This paper introduces a new parametric model for these peaky altimetric waveforms. This model assumes that the received altimetric waveform is the sum of a Brown echo and an asymmetric Gaussian peak. The asymmetric Gaussian peak is parameterized by a location, an amplitude, a width, and an asymmetry coefficient. A maximum-likelihood estimator is studied to estimate the Brown plus peak model parameters. The Cramér-Rao lower bounds of the model parameters are then derived providing minimum variances for any unbiased estimator, i.e., a reference in terms of estimation error. The performance of the proposed model and the resulting estimation strategy are evaluated via many simulations conducted on synthetic and real data. Results obtained in this paper show that the proposed model can be used to retrack efficiently standard oceanic Brown echoes as well as coastal echoes corrupted by symmetric or asymmetric Gaussian peaks. Thus, the Brown with Gaussian peak model is useful for analyzing altimetric easurements closer to the coast.

Published
2013

42. Limestone millstones: Facies, provenance and use of sandy to pure limestones in France

Author

Gilles Fronteau, François Boyer, Luc Jaccottey, Vincent Le Quellec, Stéphanie Lepareux-Couturier, Annabelle Milleville, Cécile Monchablon, Boris Robin, and Paul Picavet

Subjects
saddle quern, rotary quern, millstone, limestone, petrography, geomaterial, Archaeology, CC1-960
Abstract

Limestones are sedimentary rocks more commonly associated with building stones or sculptures than with millstones. Nevertheless, many examples of limestone saddle querns, rotary querns and millstones are spread across France, at times making up the bulk of the archaeological assemblages in various areas characterized by bedrocks rich of sedimentary stones. These limestone millstones are of different types, sources and geological origins: Eocene sandy or fossiliferous limestones, mainly from the various limestones layers from the Lutetian beds, Quaternary calcareous tufas, and fine Jurassic limestones. To explain the behaviour of these rocks, this study advances a classification of the rocks used for millstones, focused not only on the rock-type but mainly on the topological aspect of the stone surface. (empirical macroscopic surface roughness) This renders it possible to classify the rocks into categories by materials, rather than according to petrographic facies. The pure limestones in this study are essentially vacuolar, whereas sandy limestones or certain biodetritital limestones belong to either the granular rocks category, which also includes sandstones, or to the category of heterogeneous rocks. These limestones appear for the most part to have been used due to their availability. Moreover, they epitomise a very satisfactory compromise between their grinding properties and their ease of carving, even if the hardness of these limestones is lower than those of other rocks used as grindstone (basalts or sandstones).

Published
2020
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43. Eμ and 3′RR transcriptional enhancers of the IgH locus cooperate to promote c-myc–induced mature B-cell lymphomas

Author

Nour Ghazzaui, Hussein Issaoui, Mélissa Ferrad, Claire Carrion, Jeanne Cook-Moreau, Yves Denizot, and François Boyer

Subjects
Specialties of internal medicine, RC581-951
Abstract

Abstract: Numerous B-cell lymphomas feature translocations linking oncogenes to different locations in the immunoglobulin heavy chain (IgH) locus. During Burkitt lymphoma (BL), IgH breakpoints for c-myc translocation stand either close to JH segments or within switch regions. Transcription, accessibility, and remodeling of the IgH locus are under the control of the 2 potent cis-acting enhancer elements: Eμ and the 3′ regulatory region (3′RR). To ensure their respective contributions to oncogene deregulation in the context of the endogenous IgH locus, we studied transgenic mice harboring a knock-in of c-myc in various positions of the IgH locus (3′ to JH segments, 5′ to Cμ with Eμ deletion and Cα). The observed spectrum of tumors, kinetics of emergence, and transcriptome analysis provide strong evidence that both Eμ and 3′RR deregulate c-myc and cooperate together to promote B-cell lymphomagenesis. Transgenics mimicking endemic BL (with c-myc placed 3′ to JH segments) exhibited the highest rate of B-cell lymphoma emergence, the highest Ki67 index of proliferation, and the highest transcriptomic similarities to human BL. The 3′RR enhancer alone deregulated c-myc and initiated the development of BL-like lymphomas, suggesting that its targeting would be of therapeutic interest to reduce c-myc oncogenicity in vivo.

Published
2020
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44. IgH 3' regulatory region increases ectopic class switch recombination.

Author

Sandrine Le Noir, Amélie Bonaud, Bastien Hervé, Audrey Baylet, François Boyer, Sandrine Lecardeur, Zeliha Oruc, Christophe Sirac, and Michel Cogné

Subjects
Genetics, QH426-470
Abstract

DNA lesions inflicted by activation-induced deaminase (AID) instrumentally initiate the processes reshaping immunoglobulin genes in mature B-cells, from local somatic hypermutation (SHM) to junctions of distant breaks during class switch recombination (CSR). It remains incompletely understood how these divergent outcomes of AID attacks are differentially and temporally focused, with CSR strictly occurring in the Ig heavy chain (IgH) locus while SHM concentrates on rearranged V(D)J regions in the IgH and Ig light chain loci. In the IgH locus, disruption of either the 3'Regulatory Region (3'RR) super-enhancer or of switch (S) regions preceding constant genes, profoundly affects CSR. Reciprocally, we now examined if these elements are sufficient to induce CSR in a synthetic locus based on the Igκ locus backbone. Addition of a surrogate "core 3'RR" (c3'RR) and of a pair of transcribed and spliced Switch regions, together with a reporter system for "κ-CSR" yielded a switchable Igκ locus. While the c3'RR stimulated SHM at S regions, it also lowered the local SHM threshold necessary for switch recombination to occur. The 3'RR thus both helps recruit AID to initiate DNA lesions, but then also promotes their resolution through long-distance synapses and recombination following double-strand breaks.

Published
2021
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45. Bromodomain and extraterminal (BET) protein inhibition of IgG/IgE production in murine B cells is counter‐balanced by a strong Th2 bias

Author

Zeinab Dalloul, Marie Best, Pauline Chenuet, Iman Dalloul, Sandrine Le Noir, Dieudonnée Togbé, Mylène Gador, Bernhard Ryffel, Valerie FJ Quesniaux, Yolla El Makhour, François Boyer, Jean‐Claude Aldigier, Jeanne Cook‐Moreau, Nicolas Fazilleau, and Michel Cogné

Subjects
allergic inflammation, antibody class switching, bromodomain inhibition, immune response, Immunologic diseases. Allergy, RC581-607
Abstract

Abstract Objectives Inhibitors of bromodomain and extra terminal domain (BET) proteins are a new and growing class of anti‐cancer drugs, which decrease oncogene expression by targeting superenhancers. Antibody production is another physiological process relying on superenhancers, and it remains to be clarified whether potential immunomodulatory properties of BET inhibitors might impact humoral immunity and allergy. Methods We thus evaluated humoral immune responses and their Th2 context in vitro and in vivo in mice following treatment with the classical BET‐inhibitor JQ1. We quantified immunoglobulin (Ig) and antibody production by B cells either stimulated in vitro or obtained from immunised mice. JQ1 effects on class switching and activation‐induced deaminase loading were determined, together with modifications of B, T follicular helper (Tfh) and T helper 2 (Th2) populations. JQ1 was finally tested in B‐cell‐dependent models of immune disorders. Results Bromodomain and extra terminal domain inhibition reduced class switching, Ig expression on B cells and antibody secretion and was correlated with decreased numbers of Tfh cells. However, JQ1 strongly increased the proportion of GATA3+ Th2 cells and the secretion of corresponding cytokines. In a mouse allergic model of lung inflammation, JQ1 did not affect eosinophil infiltration or mucus production but enhanced Th2 cytokine production and aggravated clinical manifestations. Conclusion Altogether, BET inhibition thus interweaves intrinsic negative effects on B cells with a parallel complex reshaping of T‐cell polarisation which can increase type 2 cytokines and eventually promote B‐cell‐dependent immunopathology. These opposite and potentially hazardous immunomodulatory effects raise concerns for clinical use of BET inhibitors in patients with immune disorders.

Published
2021
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46. Locus suicide recombination actively occurs on the functionally rearranged IgH allele in B-cells from inflamed human lymphoid tissues.

Author

Iman Dalloul, François Boyer, Zeinab Dalloul, Amandine Pignarre, Gersende Caron, Thierry Fest, Fabrice Chatonnet, Céline Delaloy, Anne Durandy, Robin Jeannet, Emilie Lereclus, Hend Boutouil, Jean-Claude Aldigier, Sophie Péron, Sandrine Le Noir, Jeanne Cook-Moreau, and Michel Cogné

Subjects
Genetics, QH426-470
Abstract

B-cell activation yields abundant cell death in parallel to clonal amplification and remodeling of immunoglobulin (Ig) genes by activation-induced deaminase (AID). AID promotes affinity maturation of Ig variable regions and class switch recombination (CSR) in mature B lymphocytes. In the IgH locus, these processes are under control of the 3' regulatory region (3'RR) super-enhancer, a region demonstrated in the mouse to be both transcribed and itself targeted by AID-mediated recombination. Alternatively to CSR, IgH deletions joining Sμ to "like-switch" DNA repeats that flank the 3' super-enhancer can thus accomplish so-called "locus suicide recombination" (LSR) in mouse B-cells. Using an optimized LSR-seq high throughput method, we now show that AID-mediated LSR is evolutionarily conserved and also actively occurs in humans, providing an activation-induced cell death pathway in multiple conditions of B-cell activation. LSR either focuses on the functional IgH allele or is bi-allelic, and its signature is mainly detected when LSR is ongoing while it vanishes from fully differentiated plasma cells or from "resting" blood memory B-cells. Highly diversified breakpoints are distributed either within the upstream (3'RR1) or downstream (3'RR2) copies of the IgH 3' super-enhancer and all conditions activating CSR in vitro also seem to trigger LSR although TLR ligation appeared the most efficient. Molecular analysis of breakpoints and junctions confirms that LSR is AID-dependent and reveals junctional sequences somehow similar to CSR junctions but with increased usage of microhomologies.

Published
2019
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47. Gender as a Modifying Factor Influencing Myotonic Dystrophy Type 1 Phenotype Severity and Mortality: A Nationwide Multiple Databases Cross-Sectional Observational Study.

Author

Celine Dogan, Marie De Antonio, Dalil Hamroun, Hugo Varet, Marianne Fabbro, Felix Rougier, Khadija Amarof, Marie-Christine Arne Bes, Anne-Laure Bedat-Millet, Anthony Behin, Remi Bellance, Françoise Bouhour, Celia Boutte, François Boyer, Emmanuelle Campana-Salort, Françoise Chapon, Pascal Cintas, Claude Desnuelle, Romain Deschamps, Valerie Drouin-Garraud, Xavier Ferrer, Helene Gervais-Bernard, Karima Ghorab, Pascal Laforet, Armelle Magot, Laurent Magy, Dominique Menard, Marie-Christine Minot, Aleksandra Nadaj-Pakleza, Sybille Pellieux, Yann Pereon, Marguerite Preudhomme, Jean Pouget, Sabrina Sacconi, Guilhem Sole, Tanya Stojkovich, Vincent Tiffreau, Andoni Urtizberea, Christophe Vial, Fabien Zagnoli, Gilbert Caranhac, Claude Bourlier, Gerard Riviere, Alain Geille, Romain K Gherardi, Bruno Eymard, Jack Puymirat, Sandrine Katsahian, and Guillaume Bassez

Subjects
Medicine, Science
Abstract

Myotonic Dystrophy type 1 (DM1) is one of the most heterogeneous hereditary disease in terms of age of onset, clinical manifestations, and severity, challenging both medical management and clinical trials. The CTG expansion size is the main factor determining the age of onset although no factor can finely predict phenotype and prognosis. Differences between males and females have not been specifically reported. Our aim is to study gender impact on DM1 phenotype and severity.We first performed cross-sectional analysis of main multiorgan clinical parameters in 1409 adult DM1 patients (>18 y) from the DM-Scope nationwide registry and observed different patterns in males and females. Then, we assessed gender impact on social and economic domains using the AFM-Téléthon DM1 survey (n = 970), and morbidity and mortality using the French National Health Service Database (n = 3301).Men more frequently had (1) severe muscular disability with marked myotonia, muscle weakness, cardiac, and respiratory involvement; (2) developmental abnormalities with facial dysmorphism and cognitive impairment inferred from low educational levels and work in specialized environments; and (3) lonely life. Alternatively, women more frequently had cataracts, dysphagia, digestive tract dysfunction, incontinence, thyroid disorder and obesity. Most differences were out of proportion to those observed in the general population. Compared to women, males were more affected in their social and economic life. In addition, they were more frequently hospitalized for cardiac problems, and had a higher mortality rate.Gender is a previously unrecognized factor influencing DM1 clinical profile and severity of the disease, with worse socio-economic consequences of the disease and higher morbidity and mortality in males. Gender should be considered in the design of both stratified medical management and clinical trials.

Published
2016
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48. Altimetry for the future: Building on 25 years of progress

Author

Francesco d'Ovidio, Pierre Féménias, Sean Bruinsma, Felix Perosanz, Jerome Bouffard, S. Desai, Alexandre Couhert, Tatyana V. Belonenko, Sinead L. Farrell, Masafumi Kamachi, Rémi Laxenaire, Alexei V. Kouraev, M-Isabelle Pujol, Sandrine Mulet, Ciprian Spatar, Pablo Nilo Garcia, Loren Carrere, Vinca Rosmorduc, Michel Calzas, Marcello Passaro, Francesca Cirillo, Mathieu Hamon, Enrico Ser-Giacomi, Jida Wang, Raj Kumar, Stelios P. Mertikas, Luisella Giulicchi, Eric Jeansou, Benoit Legresy, Corinne Salaün, Donald Richardson, Martin Horwath, Sujit Basu, Rosemary Morrow, Jean-Damien Desjonquères, François Barlier, Cédric Brachet, Cécile Manfredi, Yves Morel, P. K. Gupta, Nicolas Taburet, Ferran Gibert, Anny Cazenave, Sung Yong Kim, Christopher Pearson, Lin Gilbert, Brian D. Dushaw, Johnny A. Johannessen, René Forsberg, Joël Dorandeu, Luciana Fenoglio, Denis Blumstein, C. K. Shum, Debadatta Swain, Stephan Paul, Valerii Vuglinskii, Marco Meloni, Hilary Wilson, Laurent Testut, Sebatian B. Simonsen, John Moyard, Fabien Léger, Andy Shaw, Abdolnabi Abdeh Kolahchi, Andrea Scozzari, Jan Even Øie Nilsen, Anna I. Bulczak, Valerio Poggiali, Rashmi Shah, John Wilkin, Steven Baker, Patrice Klein, Touati Benkouider, Claire Macintosh, Sarah T. Gille, Alexandre Guerin, Gilles Tavernier, Josh K. Willis, Jérôme Benveniste, Cedric Tourain, Emil V. Stanev, Praveen K. Thakur, Lionel Fichen, Céline Tison, Hans Ngodock, Shenfu Dong, Yuanyuan Jia, Sergey A. Lebedev, Nadia Ayoub, Constantin Mavrocordatos, Cédric H. David, Salvatore Dinardo, Yongjun Jia, Berguzar Oztunali Ozbahceci, Sara Fleury, Matthias Raynal, Yannice Faugère, Kathryn A. Kelly, Christian Schwatke, Craig Donlon, Etienne Poirier, Margaret Srinivasan, Remko Scharroo, Helena Antich, Barbara J. Ryan, Sergey V. Prants, Malcolm McMillan, Frédérique Rémy, David T. Sandwell, Annick Sylvestre-baron, Pascal Bonnefond, Fabien Blarel, Mounir Benkiran, Remi Tailleux, Marco Restano, Thierry Guinle, Stefano Vignudelli, Eric Leuliette, Madeleine Cahill, Ali Rami, Saulo Soares, Sophie Le Gac, Bàrbara Barceló-Llull, Claudia C. Carabajal, Veit Helm, Eva Alou-Font, Alejandro Blazquez, David Griffin, Habib B. Dieng, Prakash Chauhan, Albert Garcia-Mondejar, Christian Massari, Christopher J. Banks, Joana Fernandes, Blake A Walter, Nathalie Steunou, Karina Nielsen, Elena Zakharova, Bob Su, Stefania Camici, Frédérique Seyler, Fukai Peng, Denis L. Volkov, Wim Simons, Pieter Visser, Sophie Coutin-Faye, Lionel Gourdeau, Jesús Gómez-Enri, Andreas Schiller, Brian K. Arbic, Svetlana Karimova, Christine Gommenginger, Fanny Piras, Angélique Melet, Steve Coss, Meric Srokosz, Robert G. King, Frédéric Frappart, Fernando S. Paolo, Anna Klos, José Darrozes, Shannon Brown, Loreley Selene Lago, Susheel Adusumilli, Jay F. Shriver, Yves Quilfen, Martina Idžanović, Bernd Uebbing, Daniel Medeiros Moreira, Byron D. Tapley, R. Keith Raney, Frank G. Lemoine, Angelica Tarpanelli, Lara Díaz-Barroso, Jean-François Crétaux, Jean Tournadre, Tamlin M. Pavelsky, Sébastien Trilles, Carolina Nogueira Loddo, Léa Lasson, Stine Kildegaard Rose, Luc Lenain, Philip L. Woodworth, Marie-laure Frery, Saleh Abdalla, Bo Qiu, Stefan Hendricks, Mikhail A. Sokolovskiy, Antonio Sánchez-Román, Martin G. Scharffenberg, Per Knudsen, Andrew Shepherd, Michiel Otten, Sammie Buzzard, Philippe Schaeffer, Nicolas Picot, Luca Brocca, Michel Tsamados, Danielle De Staerke, Frederic Vivier, Nicole Bellefond, Jean-François Minster, Telmo Vieira, Brian D. Beckley, Stylianos Flampouris, Nadya Vinogradova Shiffer, Sergei Rudenko, Camille Noûs, Sabine Arnault, Frédéric Cyr, Liguang Jiang, Nicolas Bercher, Teresa K. Chereskin, Katsumi Takayama, Julienne Stroeve, Andrea Doglioli, Joanna Staneva, Stéphane Calmant, T. Moreau, Julien Le Sommer, David R. Donahue, Nadim Dayoub, Clement Ubelmann, Annie Richardson, Estelle Obligis, Laurent Brodeau, Catherine Prigent, Gérald Dibarboure, Simón Ruiz, LuAnne Thompson, Muriel Berge-Nguyen, Martina Ricko, Hugues Capdeville, Sammy Metref, Roshin P. Raj, Suchandra Aich Bhowmick, Andrey G. Kostianoy, Guillermina Paniagua, Mathilde Cancet, Eero Rinne, Sonia Ponce de León, Cédric Falco, Jianqiang Liu, Lucile Gaultier, Julia Gaudelli, Thierry Medina, Vadim Zinchenko, William Llovel, Eric P. Chassignet, Raymond Zaharia, Svetlana Y. Erofeeva, Lifeng Bao, Ole Baltazar Andersen, Emmanuel Cosme, Anna E. Hogg, Yohanes Budi Sulistioadi, Artur Gil, O. Laurain, Walter H. F. Smith, Ngan Tran, Pierre-Yves Le Traon, Laura Gomez-Navarro, Adrien Paris, Thomas W. K. Armitage, Alejandro Egido, Christopher Watson, João H. Bettencourt, Giuseppe Aulicino, Philippe Escudier, Fangfang Yao, Marco Fornari, Guoqi Han, Florent Lyard, Elisabeth Remy, Lotfi Aouf, Michele Scagliola, Martin Saraceno, Paolo Filippucci, Chao Wang, Zhongxiang Zhao, Juliette Lambin, Evan Mason, Ines Otosaka, Daniele Ciani, Raúl A. Guerrero, Ralf Bennartz, Michael Ablain, Fabrice Hernandez, Xiaoli Deng, John Lillibridge, Oscar Vergara, Marina Levy, Christine Drezen, Pierre Thibaut, Ronan Fablet, Bill Townsend, David Cotton, Sabrina Speich, Clara Lázaro, R. S. Nerem, Danièle Hauser, Pierre Exertier, Yuri Cotroneo, Henryk Dobslaw, Alessandro Di Bella, Karina von Schuckmann, Saskia Esselborn, Benjamin D. Gutknecht, Cecile Marie Margaretha Kittel, Rolf Koenig, Peter Bauer-Gottwein, Franck Borde, Alexander Braun, Christine Provost, Thomas Slater, Laiba Amarouche, Nikolai Maximenko, Raphael Schneider, Victor Zlotnicki, Jacques Verron, Sergei I. Badulin, Andreas Groh, Denise Dettmering, Mark R. Drinkwater, S. Cherchali, Marc Naeije, Fernando Niño, Alessio Domeneghetti, Kuo Hsin Tseng, François Boy, Rashmi Sharma, Laurent Soudarin, Peter A. E. M. Janssen, Robert Ricker, Frédéric Marin, Ananda Pascual, Eduard Makhoul Varona, Yongsheng Zhang, Pierrik Vuilleumier, Louise Sandberg Sørensen, Guillaume Dodet, Pascale Ferrage, Ramiro Ferrari, Yves Du Penhoat, Rodrigo Cauduro Dias de Paiva, S. Labroue, Camila Indira Artana, Joaquín Tintoré, David Brockley, Thierry Penduff, Paolo Cipollini, Augusto Getirana, Cecile Cheymol, Edward D. Zaron, Silvia Barbetta, Pierre Brasseur, Benoit Meyssignac, Matthias Becker, Kehan Yang, Juan Gabriel Fernández, Jean Paul Boy, European Centre for Medium-Range Weather Forecasts (ECMWF), Soil Conservation and Watershed Management Research Institute (SCWRMI), Agricultural Research, Education and Extension Organisation (AREEO ), Scripps Institution of Oceanography (SIO), University of California [San Diego] (UC San Diego), University of California-University of California, Space Applications Centre [Ahmedabad] (SAC), Indian Space Research Organisation (ISRO), Collecte Localisation Satellites (CLS), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National d'Études Spatiales [Toulouse] (CNES), National Space Institute [Lyngby] (DTU Space), Technical University of Denmark [Lyngby] (DTU), Institut Mediterrani d'Estudis Avancats (IMEDEA), Consejo Superior de Investigaciones Científicas [Madrid] (CSIC)-Universidad de las Islas Baleares (UIB), Météo France, Department of Earth and Environmental Sciences [Ann Arbor], University of Michigan [Ann Arbor], University of Michigan System-University of Michigan System, Jet Propulsion Laboratory (JPL), NASA-California Institute of Technology (CALTECH), Variabilité de l'Océan et de la Glace de mer (VOG), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU), Mercator Océan, Société Civile CNRS Ifremer IRD Météo-France SHOM, Universita degli studi di Napoli 'Parthenope' [Napoli], Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), P.P. Shirshov Institute of Oceanology (SIO), Russian Academy of Sciences [Moscow] (RAS), Department of Space and Climate Physics [UCL London], Mullard Space Science Laboratory (MSSL), University College of London [London] (UCL)-University College of London [London] (UCL), National Oceanography Centre (NOC), Institute of Geodesy and Geophysics [Wuhan], Chinese Academy of Sciences [Wuhan Branch], Istituto di Ricerca per la Protezione Idrogeologica [Perugia] (IRPI), Consiglio Nazionale delle Ricerche [Roma] (CNR), Géoazur (GEOAZUR 7329), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), DTU Environment, Department of Environmental Engineering, Technische Universität Darmstadt (TU Darmstadt), Centre National d'Études Spatiales [Toulouse] (CNES), St Petersburg State University (SPbU), Agence Spatiale Algérienne = Algerian Space Agency (ASAL), Vanderbilt University [Nashville], European Space Research Institute (ESRIN), European Space Agency (ESA), Centre for Marine Technology and Ocean Engineering (CENTEC), Instituto Superior Técnico, Universidade Técnica de Lisboa (IST), Systèmes de Référence Temps Espace (SYRTE), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), European Space Research and Technology Centre (ESTEC), Ecole et Observatoire des Sciences de la Terre (EOST), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), INSU Division Technique de l'INSU [Site de Brest], Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut des Géosciences de l’Environnement (IGE), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Queen's University [Kingston, Canada], OceanNext, Géosciences Environnement Toulouse (GET), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Institute of Oceanology, Polish Academy of Sciences (IO-PAN), Polska Akademia Nauk = Polish Academy of Sciences (PAN), Centre for Polar Observation and Modelling (CPOM), Natural Environment Research Council (NERC), Australian Institute of Marine Science [Townsville] (AIMS Townsville), Australian Institute of Marine Science (AIMS), NOVELTIS [Sté], Science Systems and Applications, Inc. [Hampton] (SSAI), International Space Science Institute [Bern] (ISSI), Center for Ocean-Atmospheric Prediction Studies (COAPS), Florida State University [Tallahassee] (FSU), Indian Institute of Remote Sensing (IIRS), Istituto di Science Marine (ISMAR ), Consiglio Nazionale delle Ricerche (CNR), European Centre for Space Applications and Telecommunications (ECSAT), Airbus Group [Germany], Airbus [France], School of Earth Sciences [Columbus], Ohio State University [Columbus] (OSU), Satellite Oceanographic Consultants Ltd (SATOC), Northwest Atlantic Fisheries Centre (NWAFC), Fisheries and Oceans Canada (DFO), Processus et interactions de fine échelle océanique (PROTEO), School of Engineering [Callaghan], University of Newcastle [Australia] (UoN), Deutsches Geodätisches Forschungsinstitut (DGFI-TUM), Technische Universität Munchen - Université Technique de Munich [Munich, Allemagne] (TUM), SOCIB Balearic Islands Coastal Ocean Observing and Forecasting System, German Research Centre for Geosciences - Helmholtz-Centre Potsdam (GFZ), Laboratoire d'Océanographie Physique et Spatiale (LOPS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), Department of Civil Chemical Environmental and Materials Engineering [Bologna] (DICAM), University of Bologna, NOAA Office of Satellite and Product Operations (OSPO), NOAA National Environmental Satellite, Data, and Information Service (NESDIS), National Oceanic and Atmospheric Administration (NOAA)-National Oceanic and Atmospheric Administration (NOAA), NOAA Atlantic Oceanographic and Meteorological Laboratory (AOML), National Oceanic and Atmospheric Administration (NOAA), Oregon State University (OSU), IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT), Département Mathematical and Electrical Engineering (IMT Atlantique - MEE), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Equipe Observations Signal & Environnement (Lab-STICC_OSE), Laboratoire des sciences et techniques de l'information, de la communication et de la connaissance (Lab-STICC), École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Université de Perpignan Via Domitia (UPVD), Department of Geographical Sciences [College Park], University of Maryland [College Park], University of Maryland System-University of Maryland System, Institut für Geodäsie und Geoinformationstechnik, Technische Universität Berlin (TU), Interdisciplinary Centre of Marine and Environmental Research [Matosinhos, Portugal] (CIIMAR), Universidade do Porto, Centro de Investigaciones del Mar y la Atmósfera (CIMA), Facultad de Ciencias Exactas y Naturales [Buenos Aires] (FCEyN), Universidad de Buenos Aires [Buenos Aires] (UBA)-Universidad de Buenos Aires [Buenos Aires] (UBA)-Consejo Nacional de Investigaciones Científicas y Técnicas [Buenos Aires] (CONICET), Institut für Planetare Geodäsie, Lohrmann-Observatorium, Technische Universität Dresden = Dresden University of Technology (TU Dresden), Universidad Nacional de Mar del Plata [Mar del Plata] (UNMdP), SPACE - LATMOS, Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Environmental Fluid Mechanics Laboratory [Daejeon] (EFML), Korea Advanced Institute of Science and Technology (KAIST), Ecole Normale Supérieure Paris-Saclay (ENS Paris Saclay), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA (UMR_8112)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY), Austral, Boréal et Carbone (ABC), Kansas State University, University of North Carolina [Chapel Hill] (UNC), University of North Carolina System (UNC), University of Tasmania [Hobart, Australia] (UTAS), Rutgers, The State University of New Jersey [New Brunswick] (RU), Rutgers University System (Rutgers), Institute of Arctic and Alpine Research (INSTAAR), University of Colorado [Boulder], Water Problems Institute (WPI), the Russian Academy of Sciences [Moscow, Russia] (RAS), Portland State University [Portland] (PSU), Applied Physics Laboratory [Seattle] (APL-UW), University of Washington [Seattle], Scripps Institution of Oceanography (SIO - UC San Diego), University of California (UC)-University of California (UC), Danmarks Tekniske Universitet = Technical University of Denmark (DTU), Météo-France Direction Interrégionale Sud-Est (DIRSE), Météo-France, Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Università degli Studi di Napoli 'Parthenope' = University of Naples (PARTHENOPE), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud]), Technische Universität Darmstadt - Technical University of Darmstadt (TU Darmstadt), Agence Spatiale Européenne = European Space Agency (ESA), University of Newcastle [Callaghan, Australia] (UoN), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), University of Bologna/Università di Bologna, IMT Atlantique (IMT Atlantique), École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-IMT Atlantique (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-IMT Atlantique (IMT Atlantique), Technical University of Berlin / Technische Universität Berlin (TU), Universidade do Porto = University of Porto, Consejo Nacional de Investigaciones Científicas y Técnicas [Buenos Aires] (CONICET)-Facultad de Ciencias Exactas y Naturales [Buenos Aires] (FCEyN), Universidad de Buenos Aires [Buenos Aires] (UBA)-Universidad de Buenos Aires [Buenos Aires] (UBA), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique et Atmosphères = Laboratory for Studies of Radiation and Matter in Astrophysics and Atmospheres (LERMA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-CY Cergy Paris Université (CY), Group on Earth Observations (GEO), Institute of Arctic Alpine Research [University of Colorado Boulder] (INSTAAR), Department of Water Resources, UT-I-ITC-WCC, Faculty of Geo-Information Science and Earth Observation, Abdalla S., Abdeh Kolahchi A., Ablain M., Adusumilli S., Aich Bhowmick S., Alou-Font E., Amarouche L., Andersen O.B., Antich H., Aouf L., Arbic B., Armitage T., Arnault S., Artana C., Aulicino G., Ayoub N., Badulin S., Baker S., Banks C., Bao L., Barbetta S., Barcelo-Llull B., Barlier F., Basu S., Bauer-Gottwein P., Becker M., Beckley B., Bellefond N., Belonenko T., Benkiran M., Benkouider T., Bennartz R., Benveniste J., Bercher N., Berge-Nguyen M., Bettencourt J., Blarel F., Blazquez A., Blumstein D., Bonnefond P., Borde F., Bouffard J., Boy F., Boy J.-P., Brachet C., Brasseur P., Braun A., Brocca L., Brockley D., Brodeau L., Brown S., Bruinsma S., Bulczak A., Buzzard S., Cahill M., Calmant S., Calzas M., Camici S., Cancet M., Capdeville H., Carabajal C.C., Carrere L., Cazenave A., Chassignet E.P., Chauhan P., Cherchali S., Chereskin T., Cheymol C., Ciani D., Cipollini P., Cirillo F., Cosme E., Coss S., Cotroneo Y., Cotton D., Couhert A., Coutin-Faye S., Cretaux J.-F., Cyr F., d'Ovidio F., Darrozes J., David C., Dayoub N., De Staerke D., Deng X., Desai S., Desjonqueres J.-D., Dettmering D., Di Bella A., Diaz-Barroso L., Dibarboure G., Dieng H.B., Dinardo S., Dobslaw H., Dodet G., Doglioli A., Domeneghetti A., Donahue D., Dong S., Donlon C., Dorandeu J., Drezen C., Drinkwater M., Du Penhoat Y., Dushaw B., Egido A., Erofeeva S., Escudier P., Esselborn S., Exertier P., Fablet R., Falco C., Farrell S.L., Faugere Y., Femenias P., Fenoglio L., Fernandes J., Fernandez J.G., Ferrage P., Ferrari R., Fichen L., Filippucci P., Flampouris S., Fleury S., Fornari M., Forsberg R., Frappart F., Frery M.-L., Garcia P., Garcia-Mondejar A., Gaudelli J., Gaultier L., Getirana A., Gibert F., Gil A., Gilbert L., Gille S., Giulicchi L., Gomez-Enri J., Gomez-Navarro L., Gommenginger C., Gourdeau L., Griffin D., Groh A., Guerin A., Guerrero R., Guinle T., Gupta P., Gutknecht B.D., Hamon M., Han G., Hauser D., Helm V., Hendricks S., Hernandez F., Hogg A., Horwath M., Idzanovic M., Janssen P., Jeansou E., Jia Y., Jiang L., Johannessen J.A., Kamachi M., Karimova S., Kelly K., Kim S.Y., King R., Kittel C.M.M., Klein P., Klos A., Knudsen P., Koenig R., Kostianoy A., Kouraev A., Kumar R., Labroue S., Lago L.S., Lambin J., Lasson L., Laurain O., Laxenaire R., Lazaro C., Le Gac S., Le Sommer J., Le Traon P.-Y., Lebedev S., Leger F., Legresy B., Lemoine F., Lenain L., Leuliette E., Levy M., Lillibridge J., Liu J., Llovel W., Lyard F., Macintosh C., Makhoul Varona E., Manfredi C., Marin F., Mason E., Massari C., Mavrocordatos C., Maximenko N., McMillan M., Medina T., Melet A., Meloni M., Mertikas S., Metref S., Meyssignac B., Minster J.-F., Moreau T., Moreira D., Morel Y., Morrow R., Moyard J., Mulet S., Naeije M., Nerem R.S., Ngodock H., Nielsen K., Nilsen J.E.O., Nino F., Nogueira Loddo C., Nous C., Obligis E., Otosaka I., Otten M., Oztunali Ozbahceci B., P. Raj R., Paiva R., Paniagua G., Paolo F., Paris A., Pascual A., Passaro M., Paul S., Pavelsky T., Pearson C., Penduff T., Peng F., Perosanz F., Picot N., Piras F., Poggiali V., Poirier E., Ponce de Leon S., Prants S., Prigent C., Provost C., Pujol M.-I., Qiu B., Quilfen Y., Rami A., Raney R.K., Raynal M., Remy E., Remy F., Restano M., Richardson A., Richardson D., Ricker R., Ricko M., Rinne E., Rose S.K., Rosmorduc V., Rudenko S., Ruiz S., Ryan B.J., Salaun C., Sanchez-Roman A., Sandberg Sorensen L., Sandwell D., Saraceno M., Scagliola M., Schaeffer P., Scharffenberg M.G., Scharroo R., Schiller A., Schneider R., Schwatke C., Scozzari A., Ser-giacomi E., Seyler F., Shah R., Sharma R., Shaw A., Shepherd A., Shriver J., Shum C.K., Simons W., Simonsen S.B., Slater T., Smith W., Soares S., Sokolovskiy M., Soudarin L., Spatar C., Speich S., Srinivasan M., Srokosz M., Stanev E., Staneva J., Steunou N., Stroeve J., Su B., Sulistioadi Y.B., Swain D., Sylvestre-baron A., Taburet N., Tailleux R., Takayama K., Tapley B., Tarpanelli A., Tavernier G., Testut L., Thakur P.K., Thibaut P., Thompson L., Tintore J., Tison C., Tourain C., Tournadre J., Townsend B., Tran N., Trilles S., Tsamados M., Tseng K.-H., Ubelmann C., Uebbing B., Vergara O., Verron J., Vieira T., Vignudelli S., Vinogradova Shiffer N., Visser P., Vivier F., Volkov D., von Schuckmann K., Vuglinskii V., Vuilleumier P., Walter B., Wang J., Wang C., Watson C., Wilkin J., Willis J., Wilson H., Woodworth P., Yang K., Yao F., Zaharia R., Zakharova E., Zaron E.D., Zhang Y., Zhao Z., Zinchenko V., Zlotnicki V., Technical University of Munich (TUM), European Space Agency, National Aeronautics and Space Administration (US), Centre National D'Etudes Spatiales (France), Laboratoire des Écoulements Géophysiques et Industriels [Grenoble] (LEGI), Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut national des sciences de l'Univers (INSU - CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Grenoble Alpes (UGA), Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Sorbonne Université (SU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Lab-STICC_IMTA_CID_TOMS, Université de Brest (UBO)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Université Bretagne Loire (UBL)-Centre National de la Recherche Scientifique (CNRS)-Université de Bretagne Sud (UBS)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Brest (UBO)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Université Bretagne Loire (UBL)-Centre National de la Recherche Scientifique (CNRS)-Université de Bretagne Sud (UBS)-École Nationale d'Ingénieurs de Brest (ENIB), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)

Subjects
Cryospheric science, Atmospheric Science, Earth observation, 010504 meteorology & atmospheric sciences, UT-Hybrid-D, Oceanography, 01 natural sciences, Cryospheric sciences, SDG 13 - Climate Action, Aerospace & Aeronautics, Cryosphere, Satellite altimetry, 010303 astronomy & astrophysics, ComputingMilieux_MISCELLANEOUS, Geodetic datum, ddc, Ocean surface topography, Geophysics, Section (archaeology), [SDE]Environmental Sciences, Astronomical and Space Sciences, Geology, Altimetria espacial, Coastal oceanography, Meteorology, Hidrologia, Aerospace Engineering, ITC-HYBRID, 0103 physical sciences, Geoid, Oceonografia, Sea level, SDG 14 - Life Below Water, 14. Life underwater, Altimeter, Criosfera, Life Below Water, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, 0105 earth and related environmental sciences, Mechanical Engineering, Hydrology, Astronomy and Astrophysics, Climate Action, Earth system science, [SDU]Sciences of the Universe [physics], 13. Climate action, Space and Planetary Science, ITC-ISI-JOURNAL-ARTICLE, General Earth and Planetary Sciences
Abstract

International Altimetry Team., In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the “Green” Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments’ development and satellite missions’ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion., At the forefront of this support, we must obviously mention the space agencies CNES, ESA and NASA which have played and still play a decisive role in the development and launch of several prominent altimetry missions from the outset. Other agencies such as DLR, EUMETSAT, ISRO, NOAA, NSOAS and organizations such as CMEMS, also contribute significantly to developments in all forms of altimetry.

49. De l’intérêt de l’étude climatique d’un bâtiment pour la conservation des collections

Author

Isabelle Colson and François Boyer

Subjects
conservation préventive, étude climatique, exploitation des données climatiques, prêt et climat, Fine Arts
Abstract

Nowadays any concerned person in charge for the long-term conservation of cultural heritage cannot ignore the climate control. The climatic study is one of the tools to achieve this goal: indeed, with an exploitation of data an interpretation and recommendations are associated which will be considered as many tracks to improve or maintain the climatic conditions. However in the field, in particular during a loan, a museum renovation or a climatic incident responsible for a deterioration of the collections, it appears gaps and ignorance on behalf of the institutions and their supervisions’ authority. Some reflexions are suggested to the institutions and their supervision to cure it gradually.

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