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Dr. Christine Gommenginger
National Oceanography Centre (NOC); European Way, Southampton SO14 3ZH, UK

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Research Keywords & Expertise

0 Active and passive microwave remote sensing
0 Satellite oceanography of global, coastal and polar seas
0 Salinity from space
0 Ocean winds, waves and currents
0 New satellite sensors and missions

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Preprint content
Published: 04 March 2021
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Measurements of significant wave height from satellite altimeter missions are finding increasing application in investigations of wave climate, sea state variability and trends, in particular as the means to mitigate the general sparsity of in situ measurements. However, many questions remain over the suitability of altimeter data for the representation of extreme sea states and in particular applications that examine extremes in the coastal zone. In this paper, the limitations of altimeter data to estimate coastal Hs extremes (<10 km from shore) are investigated using the European Space Agency Sea State Climate Change Initiative (CCI) L2P altimeter data v1.1 product recently released. This Sea State CCI product provides near complete global coverage and a continuous record of 28 years. It is used here together with in situ data from moored wave buoys at a number of sites around the coast of the United States. The limitations of estimating extreme values based on satellite data are quantified and linked to several factors including the impact of data corruption nearshore, the influence of coastline morphology and local wave climate dynamics and the spatio-temporal sampling achieved by altimeters. The factors combine to lead to considerable underestimation of estimated Hs 10-yr return levels. Sensitivity to these factors is evaluated at specific sites, leading to recommendations about the use of satellite data to estimate extremes and their temporal evolution in coastal environments.

ACS Style

Ben Timmermans; Andrew Shaw; Chrsitine Gommenginger. Reliability of Extreme Significant Wave Height Estimation from Satellite Altimetry and In Situ Measurements in the Coastal Zone. 2021, 1 .

AMA Style

Ben Timmermans, Andrew Shaw, Chrsitine Gommenginger. Reliability of Extreme Significant Wave Height Estimation from Satellite Altimetry and In Situ Measurements in the Coastal Zone. . 2021; ():1.

Chicago/Turabian Style

Ben Timmermans; Andrew Shaw; Chrsitine Gommenginger. 2021. "Reliability of Extreme Significant Wave Height Estimation from Satellite Altimetry and In Situ Measurements in the Coastal Zone." , no. : 1.

Preprint content
Published: 04 March 2021
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Direct estimate of ocean surface motion sensed by the Doppler shift of the surface includes ocean surface current and a wind-wave induced artefact surface velocity (WASV). The Sentinel-1 (S1) C-band SAR mission includes direct ocean surface motion estimates as an operational Level-2 Ocean (OCN) Radial VeLocity (RVL) product. The existing operational RVL products suffer from significant uncorrected platform and instrument effects that presently prevent exploitation of the data. This paper proposes a simple method to calibrate and correct for these effects and evaluate the benefit of these corrections over 2.5 years S1A acquisition against ground truth measurements. A specific geometry for S1 has been chosen for S1-A over the HF radar (HFR) instrumented site in the German Bight. The 78 S1A snapshots end in 56 match-ups within 20 minutes of HFR measurements. HFR velocity fields were projected in the same radial direction as S1A. Land calibration corrects for constant snapshot biases of the operational products up to 2 m/s. Besides these constant biases there is persistent relative biases within snapshots between up to 0.4 m/s in addition to the TOPSAR uncorrected scalloping effect with an amplitude of 0.1 m/s. After calibration, corrected RVL are compared against HFR with various WASV correction. Applying WASV correction with a reduced 70% C-Dop model, gives the best results with a precision of 0.25 m/s and correlation in time of 0.9. This might be due to C-Dop amplitude in up/downwind being too strong for a coastal environment as encountered in the German Bight. Quadratic mean of all 78 S1A snapshots after all corrections applied exhibits coastal current jets in good agreement with bathymetry channels and is promising as a cheap way to infer local bathymetry channels.

ACS Style

Christine Gommenginger; Adrien C. H. Martin; Benjamin Jacob; Joanna Staneva. Multi-year assessment of ocean surface currents from Copernicus Sentinel-1 and HF radar in the German Bight. 2021, 1 .

AMA Style

Christine Gommenginger, Adrien C. H. Martin, Benjamin Jacob, Joanna Staneva. Multi-year assessment of ocean surface currents from Copernicus Sentinel-1 and HF radar in the German Bight. . 2021; ():1.

Chicago/Turabian Style

Christine Gommenginger; Adrien C. H. Martin; Benjamin Jacob; Joanna Staneva. 2021. "Multi-year assessment of ocean surface currents from Copernicus Sentinel-1 and HF radar in the German Bight." , no. : 1.

Preprint content
Published: 03 March 2021
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Global Navigation Satellite System-Reflectometry (GNSS-R) is an innovative and rapidly developing approach to Earth Observation that makes use of signals of opportunity from Global Navigation Satellite Systems, which have been reflected off the Earth’s surface. CYGNSS is a constellation of 8 satellites launched in 2016 which use GNSS-R technology for the remote sensing of ocean wind speed. The ESA ECOLOGY project aims to evaluate CYGNSS data which has recently undergone a series of improvements in the calibration approach. Using CYGNSS collections above the ocean surface, an assessment of Level-1 calibration is presented, alongside a performance evaluation of Level-2 wind speed products. L1 data collected by the individual satellites are shown to be generally well inter-calibrated and remarkably stable over time, a significant improvement over previous versions. However, some geographical biases are found, which appear to be linked to a number of factors including the transmitter-receiver pair considered, viewing geometry, and surface elevation. These findings provide a basis for further improvement of CYGNSS products and have wider applicability to improving calibration of GNSS-R sensors for remote sensing of the Earth.

ACS Style

Matthew Hammond; Giuseppe Foti; Christine Gommenginger; Meric Srokosz; Nicolas Floury. An Assessment of CYGNSS Ocean Wind Speed Products. 2021, 1 .

AMA Style

Matthew Hammond, Giuseppe Foti, Christine Gommenginger, Meric Srokosz, Nicolas Floury. An Assessment of CYGNSS Ocean Wind Speed Products. . 2021; ():1.

Chicago/Turabian Style

Matthew Hammond; Giuseppe Foti; Christine Gommenginger; Meric Srokosz; Nicolas Floury. 2021. "An Assessment of CYGNSS Ocean Wind Speed Products." , no. : 1.

Journal article
Published: 21 December 2020 in Journal of Marine Science and Engineering
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Measurements of significant wave height from satellite altimeter missions are finding increasing application in investigations of wave climate, sea state variability and trends, in particular as the means to mitigate the general sparsity of in situ measurements. However, many questions remain over the suitability of altimeter data for the representation of extreme sea states and applications in the coastal zone. In this paper, the limitations of altimeter data to estimate coastal Hs extremes (<10 km from shore) are investigated using the European Space Agency Sea State Climate Change Initiative L2P altimeter data v1.1 product recently released. This Sea State CCI product provides near complete global coverage and a continuous record of 28 years. It is used here together with in situ data from moored wave buoys at six sites around the coast of the United States. The limitations of estimating extreme values based on satellite data are quantified and linked to several factors including the impact of data corruption nearshore, the influence of coastline morphology and local wave climate dynamics, and the spatio-temporal sampling achieved by altimeters. The factors combine to lead to considerable underestimation of estimated Hs 10-yr return levels. Sensitivity to these factors is evaluated at specific sites, leading to recommendations about the use of satellite data to estimate extremes and their temporal evolution in coastal environments.

ACS Style

Ben Timmermans; Andrew Shaw; Christine Gommenginger. Reliability of Extreme Significant Wave Height Estimation from Satellite Altimetry and In Situ Measurements in the Coastal Zone. Journal of Marine Science and Engineering 2020, 8, 1039 .

AMA Style

Ben Timmermans, Andrew Shaw, Christine Gommenginger. Reliability of Extreme Significant Wave Height Estimation from Satellite Altimetry and In Situ Measurements in the Coastal Zone. Journal of Marine Science and Engineering. 2020; 8 (12):1039.

Chicago/Turabian Style

Ben Timmermans; Andrew Shaw; Christine Gommenginger. 2020. "Reliability of Extreme Significant Wave Height Estimation from Satellite Altimetry and In Situ Measurements in the Coastal Zone." Journal of Marine Science and Engineering 8, no. 12: 1039.

Letter
Published: 10 September 2020 in Remote Sensing
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The UK’s TechDemoSat-1 (TDS-1), launched 2014, has demonstrated the use of global positioning system (GPS) signals for monitoring ocean winds and sea ice. Here it is shown, for the first time, that Galileo and BeiDou signals detected by TDS-1 show similar promise. TDS-1 made seven raw data collections, recovering returns from Galileo and BeiDou, between November 2015 and March 2019. The retrieved open ocean delay Doppler maps (DDMs) are similar to those from GPS. Over sea ice, the Galileo DDMs show a distinctive triple peak. Analysis, adapted from that for GPS DDMs, gives Galileo’s signal-to-noise ratio (SNR), which is found to be inversely sensitive to wind speed, as for GPS. A Galileo track transiting from open ocean to sea ice shows a strong instantaneous SNR response. These results demonstrate the potential of future spaceborne constellations of GNSS-R (global navigation satellite system–reflectometry) instruments for exploiting signals from multiple systems: GPS, Galileo, and BeiDou.

ACS Style

Matthew Hammond; Giuseppe Foti; Jonathan Rawlinson; Christine Gommenginger; Meric Srokosz; Lucinda King; Martin Unwin; Josep Roselló. First Assessment of Geophysical Sensitivities from Spaceborne Galileo and BeiDou GNSS-Reflectometry Data Collected by the UK TechDemoSat-1 Mission. Remote Sensing 2020, 12, 2927 .

AMA Style

Matthew Hammond, Giuseppe Foti, Jonathan Rawlinson, Christine Gommenginger, Meric Srokosz, Lucinda King, Martin Unwin, Josep Roselló. First Assessment of Geophysical Sensitivities from Spaceborne Galileo and BeiDou GNSS-Reflectometry Data Collected by the UK TechDemoSat-1 Mission. Remote Sensing. 2020; 12 (18):2927.

Chicago/Turabian Style

Matthew Hammond; Giuseppe Foti; Jonathan Rawlinson; Christine Gommenginger; Meric Srokosz; Lucinda King; Martin Unwin; Josep Roselló. 2020. "First Assessment of Geophysical Sensitivities from Spaceborne Galileo and BeiDou GNSS-Reflectometry Data Collected by the UK TechDemoSat-1 Mission." Remote Sensing 12, no. 18: 2927.

Data description paper
Published: 02 September 2020 in Earth System Science Data
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Sea state data are of major importance for climate studies, marine engineering, safety at sea and coastal management. However, long-term sea state datasets are sparse and not always consistent, and sea state data users still mostly rely on numerical wave models for research and engineering applications. Facing the urgent need for a sea state climate data record, the Global Climate Observing System has listed “Sea State” as an Essential Climate Variable (ECV), fostering the launch in 2018 of the Sea State Climate Change Initiative (CCI). The CCI is a programme of the European Space Agency, whose objective is to realise the full potential of global Earth observation archives established by ESA and its member states in order to contribute to the ECV database. This paper presents the implementation of the first release of the Sea State CCI dataset, the implementation and benefits of a high-level denoising method, its validation against in situ measurements and numerical model outputs, and the future developments considered within the Sea State CCI project. The Sea State CCI dataset v1 is freely available on the ESA CCI website (http://cci.esa.int/data, last access: 25 August 2020) at ftp://anon-ftp.ceda.ac.uk/neodc/esacci/sea_state/data/v1.1_release/ (last access: 25 August 2020). Three products are available: a multi-mission along-track L2P product (http://dx.doi.org/10.5285/f91cd3ee7b6243d5b7d41b9beaf397e1, Piollé et al., 2020a), a daily merged multi mission along-track L3 product (http://dx.doi.org/10.5285/3ef6a5a66e9947d39b356251909dc12b, Piollé et al., 2020b) and a multi-mission monthly gridded L4 product (http://dx.doi.org/10.5285/47140d618dcc40309e1edbca7e773478, Piollé et al., 2020c).

ACS Style

Guillaume Dodet; Jean-François Piolle; Yves Quilfen; Saleh Abdalla; Mickaël Accensi; Fabrice Ardhuin; Ellis Ash; Jean-Raymond Bidlot; Christine Gommenginger; Gwendal Marechal; Marcello Passaro; Graham Quartly; Justin Stopa; Ben Timmermans; Ian Young; Paolo Cipollini; Craig Donlon. The Sea State CCI dataset v1: towards a sea state climate data record based on satellite observations. Earth System Science Data 2020, 12, 1929 -1951.

AMA Style

Guillaume Dodet, Jean-François Piolle, Yves Quilfen, Saleh Abdalla, Mickaël Accensi, Fabrice Ardhuin, Ellis Ash, Jean-Raymond Bidlot, Christine Gommenginger, Gwendal Marechal, Marcello Passaro, Graham Quartly, Justin Stopa, Ben Timmermans, Ian Young, Paolo Cipollini, Craig Donlon. The Sea State CCI dataset v1: towards a sea state climate data record based on satellite observations. Earth System Science Data. 2020; 12 (3):1929-1951.

Chicago/Turabian Style

Guillaume Dodet; Jean-François Piolle; Yves Quilfen; Saleh Abdalla; Mickaël Accensi; Fabrice Ardhuin; Ellis Ash; Jean-Raymond Bidlot; Christine Gommenginger; Gwendal Marechal; Marcello Passaro; Graham Quartly; Justin Stopa; Ben Timmermans; Ian Young; Paolo Cipollini; Craig Donlon. 2020. "The Sea State CCI dataset v1: towards a sea state climate data record based on satellite observations." Earth System Science Data 12, no. 3: 1929-1951.

Research letter
Published: 27 April 2020 in Geophysical Research Letters
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Long‐term changes in ocean surface waves are relevant to society and climate research. Significant wave height climatologies and trends over 1992‐2017 are intercompared in four recent high‐quality global datasets using a consistent methodology. For two products based on satellite altimetry, including one from the European Space Agency Climate Change Initiative for Sea State, regional differences in mean climatology are linked to low and high sea states. Trends from the altimetry products, and two reanalysis and hindcast datasets, show general similarity in spatial variation and magnitude but with major differences in equatorial regions and the Indian Ocean. Discrepancies between altimetry products likely arise from differences in calibration and quality control. However, multi‐decadal observations at two buoy stations also highlight issues with wave buoy data, raising questions about their unqualified use, and more fundamentally about uncertainty in all products.

ACS Style

B. W. Timmermans; C. P. Gommenginger; G. Dodet; J.‐R. Bidlot. Global Wave Height Trends and Variability from New Multimission Satellite Altimeter Products, Reanalyses, and Wave Buoys. Geophysical Research Letters 2020, 47, 1 .

AMA Style

B. W. Timmermans, C. P. Gommenginger, G. Dodet, J.‐R. Bidlot. Global Wave Height Trends and Variability from New Multimission Satellite Altimeter Products, Reanalyses, and Wave Buoys. Geophysical Research Letters. 2020; 47 (9):1.

Chicago/Turabian Style

B. W. Timmermans; C. P. Gommenginger; G. Dodet; J.‐R. Bidlot. 2020. "Global Wave Height Trends and Variability from New Multimission Satellite Altimeter Products, Reanalyses, and Wave Buoys." Geophysical Research Letters 47, no. 9: 1.

Preprint content
Published: 23 March 2020
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CryoSat’s ability to operate in different operating modes over water surfaces led to the first in-orbit evidence of the value of SAR-mode altimetry for oceanography, with the mission continuing to provide high-quality data and information not just over ice but also over the open ocean, polar waters and coastal regions. Approaching ten years in orbit, CryoSat routinely delivers a number of oceanographic products for global ocean applications. A dedicated operational CryoSat ocean processor (COP) has existed since April 2014 generating data products available in near real time (FDM/NOP), within ~3 days (IOP) and a geophysical ocean product (GOP) available within a month. An improved processing baseline was introduced in late 2017 and the same processing chain has now been applied to provide consistent ocean data products from the start of the mission. 
Within the ESA funded CryOcean-QCV project, the National Oceanography Centre (NOC) in the UK is responsible for routine quality control and validation of CryoSat Ocean Products. Activities include the production of daily and monthly reports containing global assessments and quality control of sea surface height anomaly (SSHA), significant wave height (SWH), backscatter coefficient (Sigma0) and wind speed, as well as a suite of validation protocols involving in situ data, model output and data from other satellite altimetry missions. This presentation will review some of the metrics and results obtained for CryoSat Ocean Products for SSHA, SWH and wind speed when assessed against data from tide gauges, wind and wave buoys, WaveWatch III wave model output, HF radar surface current data and comparisons with Jason-2 and Jason-3. Example metrics include SSHA along-track power spectra and the characterisation of offsets and variability regionally and in different sea states. 
In this presentation, we demonstrate the quality and scientific value of the CryoSat data in the open ocean where the altimeter operates mainly in conventional low-resolution-mode (LRM) but also over selected ocean regions where CryoSat operates in SAR-mode. 
Finally, scientific exploitation of the CryoSat data for oceanographic studies will be illustrated, focusing on CryoSat sea surface height anomalies. We will present examples of the benefits of CryoSat ocean products for oceanographic studies based on a dedicated Level 3 gridded product, featuring investigations of propagating ocean features (e.g. Rossby-type wave propagation) and their signatures in CryoSat in comparisons with data from other sources including SMOS, Sentinel 3A and 3B. 

ACS Style

Francisco Mir Calafat; Chris Banks; Helen Snaith; Christine Gommenginger; Andrew Shaw; Paolo Cipollini; Nadim Dayoub; Jérôme Bouffard; Marco Meloni. Evaluation and scientific exploitation of CryoSat ocean products for oceanographic studies. 2020, 1 .

AMA Style

Francisco Mir Calafat, Chris Banks, Helen Snaith, Christine Gommenginger, Andrew Shaw, Paolo Cipollini, Nadim Dayoub, Jérôme Bouffard, Marco Meloni. Evaluation and scientific exploitation of CryoSat ocean products for oceanographic studies. . 2020; ():1.

Chicago/Turabian Style

Francisco Mir Calafat; Chris Banks; Helen Snaith; Christine Gommenginger; Andrew Shaw; Paolo Cipollini; Nadim Dayoub; Jérôme Bouffard; Marco Meloni. 2020. "Evaluation and scientific exploitation of CryoSat ocean products for oceanographic studies." , no. : 1.

Preprint content
Published: 23 March 2020
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Accurate knowledge and understanding of the sea state and its variability is crucial to numerous oceanic and coastal engineering applications, but also to climate change and related impacts including coastal inundation from extreme weather and ice-shelf break-up. The increasing duration of the satellite altimeter record for sea state motivates a range of global analyses, including the examination of changes in ocean climate. For ocean surface waves in particular, the recent development and release of new products providing observations of altimeter-derived significant wave height make long term analyses fairly straightforward.

In this study, significant wave height climatologies and trends over 1992-2017 are intercompared in four recent high-quality global datasets using a consistent methodology. In particular, we make use of products presented by Ribal et al. (2019), and the recently released product developed through the European Space Agency Climate Change Initiative (CCI) for Sea State (Dodet et al. 2020, ESSD, in review). Regional differences in mean climatology are identified and linked to low and high sea states, while temporal trends from the altimetry products, and two reanalysis and hindcast datasets, show general similarity in spatial variation and magnitude but with major differences in equatorial regions and the Indian Ocean. Discrepancies between altimetry products likely arise from differences in calibration and quality control. However, multidecadal observations at buoy stations also highlight issues with wave buoy data, raising questions about their unqualified use, and more fundamentally about uncertainty in all sea state products. We discuss these results in the context of both the current state of knowledge of the changing wave climate, and the on-going development of CCI Sea State altimetry products.

ACS Style

Christine Gommenginger; Ben Timmermans; Guillaume Dodet; Jean-Raymond Bidlot. Global wave height trends and variability from new multi-mission satellite altimeter products, reanalyses and wave buoys. 2020, 1 .

AMA Style

Christine Gommenginger, Ben Timmermans, Guillaume Dodet, Jean-Raymond Bidlot. Global wave height trends and variability from new multi-mission satellite altimeter products, reanalyses and wave buoys. . 2020; ():1.

Chicago/Turabian Style

Christine Gommenginger; Ben Timmermans; Guillaume Dodet; Jean-Raymond Bidlot. 2020. "Global wave height trends and variability from new multi-mission satellite altimeter products, reanalyses and wave buoys." , no. : 1.

Preprint content
Published: 23 March 2020
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Global Navigation Satellite System-Reflectometry (GNSS-R) is an innovative and rapidly developing approach to Earth Observation that makes use of signals of opportunity from Global Navigation Satellite Systems, which have been reflected off the Earth’s surface. Using GNSS-R data collected by the UK TechDemoSat-1 (TDS-1) between 2014 and 2018, the National Oceanography Centre (NOC) has developed a GNSS-R wind speed retrieval algorithm called the Calibrated Bistatic Radar Equation (C-BRE), which now features updated data quality control mechanisms including flagging of radio frequency interference (RFI) and sea-ice detection based on the GNSS-R waveform. Here we present an assessment of the performance of the latest NOC GNSS-R ocean wind speed and sea-ice products (NOC C-BRE v1.0) using validation data from the ECMWF ERA-5 re-analysis model output. Results show the capability of spaceborne GNSS-R sensors for accurate wind speed retrieval and sea-ice detection. Additionally, ground-processed Galileo returns collected by TDS-1 are examined and the geophysical sensitivity of reflected Galileo data to surface parameters is investigated. Preliminary results demonstrate the feasibility of spaceborne GNSS-R instruments receiving a combination of GNSS signals transmitted by multiple navigation systems, which offers the opportunity for frequent, high-quality ocean wind and sea-ice retrievals at low relative cost. Other advancements in GNSS-R technology are represented by future mission concepts such as HydroGNSS, a proposed ESA Scout mission opportunity by SSTL offering support for enhanced retrieval capabilities exploiting dual polarisation, dual frequency, and coherent reflected signal reception.

ACS Style

Matthew Hammond; Giuseppe Foti; Christine Gommenginger; Meric Srokosz; Martin Unwin; Josep Rosello. NOC GNSS-R Global Ocean Wind Speed and Sea-Ice Products. 2020, 1 .

AMA Style

Matthew Hammond, Giuseppe Foti, Christine Gommenginger, Meric Srokosz, Martin Unwin, Josep Rosello. NOC GNSS-R Global Ocean Wind Speed and Sea-Ice Products. . 2020; ():1.

Chicago/Turabian Style

Matthew Hammond; Giuseppe Foti; Christine Gommenginger; Meric Srokosz; Martin Unwin; Josep Rosello. 2020. "NOC GNSS-R Global Ocean Wind Speed and Sea-Ice Products." , no. : 1.

Preprint content
Published: 23 March 2020
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SCOOP (SAR Altimetry Coastal & Open Ocean Performance) is a project funded under the ESA SEOM (Scientific Exploitation of Operational Missions) Programme Element, to characterise the expected performance of Sentinel-3 SRAL SAR mode altimeter products, and then to develop and evaluate enhancements to the baseline processing scheme in terms of improvements to ocean measurements. Another objective is to develop and evaluate an improved Wet Troposphere correction for Sentinel-3.

The SCOOP studies are based on two 2-year test data sets derived from CryoSat-2 FBR data, produced for 10 regions. The first Test Data Set was processed with algorithms equivalent to the Sentinel-3 baseline, and the second with algorithms expected to provide an improved performance.

We present results from the SCOOP project that demonstrate the excellent performance of SRAL at the coast in terms of measurement precision, with noise in Sea Surface Height 20Hz measurements of less than 5cm to within 5km of the coast.

We then report the development and testing of new processing approaches designed to improve performance, including, for L1B to L2:

  • Application of zero-padding
  • Application of intra-burst Hamming windowing
  • Exact beam forming in the azimuthal direction
  • Restriction of stack processing to within a specified range of look angles.
  • Along-track antenna compensation

 

And for L1B to L2

  • Application of alternative re-trackers for SAR and RDSAR.

 

Based on the results of this assessment, a second test data set was generated and we present an assessment of the performance of this second Test Data Set generated, and compare it to that of the original Test Data Set.

Regarding the WTC for Sentinel-3A, the correction from the on-board MWR has been assessed by means of comparison with independent data sets such as the GPM Microwave Imager (GMI), Jason-2, Jason-3 and Global Navigation Satellite Systems (GNSS) derived WTC at coastal stations. GNSS-derived path Delay Plus (GPD+) corrections have been derived for S3A. Results indicate good overall performance of S3A MWR and GPD+ WTC improvements over MWR-derived WTC, particularly in coastal and polar regions.

 

Based on the outcomes of this study we provide recommendations for improving SAR mode altimeter processing and priorities for future research.

ACS Style

David Cotton; Thomas Moreau; Mònica Roca; Christine Gommenginger; Mathilde Cancet; Luciana Fenoglio-Marc; Marc Naeije; M Joana Fernandes; Andrew Shaw; Marco Restano; Americo Ambrosio; Jérôme Benveniste. Improved Retrieval Methods for Sentinel-3 SAR Altimetry over Coastal and Open Ocean and recommendations for implementation: ESA SCOOP Project Results. 2020, 1 .

AMA Style

David Cotton, Thomas Moreau, Mònica Roca, Christine Gommenginger, Mathilde Cancet, Luciana Fenoglio-Marc, Marc Naeije, M Joana Fernandes, Andrew Shaw, Marco Restano, Americo Ambrosio, Jérôme Benveniste. Improved Retrieval Methods for Sentinel-3 SAR Altimetry over Coastal and Open Ocean and recommendations for implementation: ESA SCOOP Project Results. . 2020; ():1.

Chicago/Turabian Style

David Cotton; Thomas Moreau; Mònica Roca; Christine Gommenginger; Mathilde Cancet; Luciana Fenoglio-Marc; Marc Naeije; M Joana Fernandes; Andrew Shaw; Marco Restano; Americo Ambrosio; Jérôme Benveniste. 2020. "Improved Retrieval Methods for Sentinel-3 SAR Altimetry over Coastal and Open Ocean and recommendations for implementation: ESA SCOOP Project Results." , no. : 1.

Preprint content
Published: 06 February 2020
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Sea state data are of major importance for climate studies, marine engineering, safety at sea, and coastal management. However, long-term sea state datasets are sparse and not always consistent, and sea state data users still mostly rely on numerical wave models for research and engineering applications. Facing the urgent need for a sea state Climate Data Record, the Global Climate Observing System has listed Sea State as an Essential Climate Variable (ECV), fostering the launch in 2018 of the Sea State Climate Change Initiative (CCI). The CCI is a program of the European Space Agency, whose objective is to realize the full potential of global Earth Observation archives established by ESA and its member states in order to contribute to the ECV database. This paper presents the implementation of the first release of the Sea State CCI dataset, the implementation and benefits of a high-level denoising method, its validation against in-situ measurements and numerical model outputs, and the future developments considered within the Sea State CCI project. The Sea State CCI dataset v1 is freely available on the ESA CCI website (http://cci.esa.int/data) at ftp://anon-ftp.ceda.ac.uk/neodc/esacci/sea_state/data/v1.1_release/. Three products are available: a multi-mission along-track L2P product (https://doi.org/10.5285/f91cd3ee7b6243d5b7d41b9beaf397e1, Piollé et al., 2020a), a daily merged multi mission along-track L3 product (https://doi.org/10.5285/3ef6a5a66e9947d39b356251909dc12b, Piollé et al., 2020b) and a multi-mission monthly gridded L4 product (https://doi.org/10.5285/47140d618dcc40309e1edbca7e773478, Piollé et al., 2020c).

ACS Style

Guillaume Dodet; Jean-François Piolle; Yves Quilfen; Saleh Abdalla; Mickaël Accensi; Fabrice Ardhuin; Ellis Ash; Jean-Raymond Bidlot; Christine Gommenginger; Gwendal Marechal; Marcello Passaro; Graham Quartly; Justin Stopa; Ben Timmermans; Ian Young; Paolo Cipollini; Craig Donlon. The Sea State CCI dataset v1: towards a Sea State Climate Data Record based on satellite observations. 2020, 2020, 1 -28.

AMA Style

Guillaume Dodet, Jean-François Piolle, Yves Quilfen, Saleh Abdalla, Mickaël Accensi, Fabrice Ardhuin, Ellis Ash, Jean-Raymond Bidlot, Christine Gommenginger, Gwendal Marechal, Marcello Passaro, Graham Quartly, Justin Stopa, Ben Timmermans, Ian Young, Paolo Cipollini, Craig Donlon. The Sea State CCI dataset v1: towards a Sea State Climate Data Record based on satellite observations. . 2020; 2020 ():1-28.

Chicago/Turabian Style

Guillaume Dodet; Jean-François Piolle; Yves Quilfen; Saleh Abdalla; Mickaël Accensi; Fabrice Ardhuin; Ellis Ash; Jean-Raymond Bidlot; Christine Gommenginger; Gwendal Marechal; Marcello Passaro; Graham Quartly; Justin Stopa; Ben Timmermans; Ian Young; Paolo Cipollini; Craig Donlon. 2020. "The Sea State CCI dataset v1: towards a Sea State Climate Data Record based on satellite observations." 2020, no. : 1-28.

Journal article
Published: 17 August 2018 in IEEE Transactions on Geoscience and Remote Sensing
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ACS Style

Wenming Lin; Marcos Portabella; Giuseppe Foti; Ad Stoffelen; Christine Gommenginger; Yijun He. Toward the Generation of a Wind Geophysical Model Function for Spaceborne GNSS-R. IEEE Transactions on Geoscience and Remote Sensing 2018, 57, 655 -666.

AMA Style

Wenming Lin, Marcos Portabella, Giuseppe Foti, Ad Stoffelen, Christine Gommenginger, Yijun He. Toward the Generation of a Wind Geophysical Model Function for Spaceborne GNSS-R. IEEE Transactions on Geoscience and Remote Sensing. 2018; 57 (2):655-666.

Chicago/Turabian Style

Wenming Lin; Marcos Portabella; Giuseppe Foti; Ad Stoffelen; Christine Gommenginger; Yijun He. 2018. "Toward the Generation of a Wind Geophysical Model Function for Spaceborne GNSS-R." IEEE Transactions on Geoscience and Remote Sensing 57, no. 2: 655-666.

Article
Published: 26 December 2017 in Geophysical Research Letters
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We present the first examples of GNSS-Reflectometry observations of hurricanes using spaceborne data from the UK TechDemoSat-1 (TDS-1) mission. We confirm that GNSS-R signals can detect ocean condition changes in very high near-surface ocean wind associated with hurricanes. TDS-1 GNSS-R reflections were collocated with IBTrACS hurricane data, MetOp ASCAT A/B scatterometer winds and two re-analysis products. Clear variations of GNSS-R reflected power (σ0) are observed as reflections travel through hurricanes, in some cases up to and through the eye wall. The GNSS-R reflected power is tentatively inverted to estimate wind speed using the TDS-1 baseline wind retrieval algorithm developed for low to moderate winds. Despite this, TDS-1 GNSS-R winds through the hurricanes show closer agreement with IBTrACS estimates than winds provided by scatterometers and reanalyses. GNSS-R wind profiles show realistic spatial patterns and sharp gradients which are consistent with expected structures around the eye of tropical cyclones.

ACS Style

Giuseppe Foti; Christine Gommenginger; Meric Srokosz. First Spaceborne GNSS‐Reflectometry Observations of Hurricanes From the UK TechDemoSat‐1 Mission. Geophysical Research Letters 2017, 44, 1 .

AMA Style

Giuseppe Foti, Christine Gommenginger, Meric Srokosz. First Spaceborne GNSS‐Reflectometry Observations of Hurricanes From the UK TechDemoSat‐1 Mission. Geophysical Research Letters. 2017; 44 (24):1.

Chicago/Turabian Style

Giuseppe Foti; Christine Gommenginger; Meric Srokosz. 2017. "First Spaceborne GNSS‐Reflectometry Observations of Hurricanes From the UK TechDemoSat‐1 Mission." Geophysical Research Letters 44, no. 24: 1.

Journal article
Published: 31 May 2017 in IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
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An assessment of non-geophysical effects in spaceborne global navigation satellite system reflectometry (GNSS-R) data from the UK TechDemoSat-1 (TDS-1) mission is presented. TDS-1 was launched in July 2014 and provides the first new spaceborne GNSS-R data since the pioneering UK-disaster monitoring constellation experiment in 2003. Non-geophysical factors evaluated include ambient L-band noise, instrument operating mode, and platform-related parameters. The findings are particularly relevant to users of uncalibrated GNSS-R signals for the retrieval of geophysical properties of the Earth surface. Substantial attitude adjustments of the TDS-1 platform are occasionally found to occur that introduce large uncertainties in parts of the TDS-1 GNSS-R dataset, particularly for specular points located outside the main beam of the nadir antenna where even small attitude errors can lead to large inaccuracies in the geophysical inversion. Out of eclipse however, attitude adjustments typically remain smaller than 1.5°, with larger deviations of up to 10° affecting less than 5% of the overall sun-lit data. Global maps of L1 ambient noise are presented for both automatic and programmed gain modes of the receiver, revealing persistent L-band noise hotspots along the Equator that can reach up to 2.5 dB, most likely associated with surface reflection of signals from other GNSS transmitters and constellations. Sporadic high-power noise events observed in certain regions point to sources of human origin. Relevant conclusions of this study are that platform attitude knowledge is essential and that radiometric calibration of GNSS-R signals should be used whenever possible. Care should be taken when considering using noise measurements over the equatorial oceans for calibration purposes, as ambient noise and correlated noise in delay–Doppler maps both show more variation than might be expected over these regions.

ACS Style

Giuseppe Foti; Christine Gommenginger; Martin Unwin; Philip Jales; Jason Tye; Josep Rosello. An Assessment of Non-geophysical Effects in Spaceborne GNSS Reflectometry Data From the UK TechDemoSat-1 Mission. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 2017, 10, 3418 -3429.

AMA Style

Giuseppe Foti, Christine Gommenginger, Martin Unwin, Philip Jales, Jason Tye, Josep Rosello. An Assessment of Non-geophysical Effects in Spaceborne GNSS Reflectometry Data From the UK TechDemoSat-1 Mission. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. 2017; 10 (7):3418-3429.

Chicago/Turabian Style

Giuseppe Foti; Christine Gommenginger; Martin Unwin; Philip Jales; Jason Tye; Josep Rosello. 2017. "An Assessment of Non-geophysical Effects in Spaceborne GNSS Reflectometry Data From the UK TechDemoSat-1 Mission." IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 10, no. 7: 3418-3429.

Journal article
Published: 27 October 2016 in IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
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Global navigation satellite systems-reflectometry (GNSS-R) is an emerging technique that uses navigation opportunistic signals as a multistatic radar. Most GNSS systems operate at L-band, which is affected by the ionosphere. At present, there is only a GNSS-R space-borne scatterometer on board the UK TechDemoSat-1, but in late 2016, NASA will launch the CYGNSS constellation, and in 2019, ESA will carry out the GEROS experiment on board the International Space Station. In GNSS-R, reflected signals are typically processed in open loop using a short coherent integration time (∼1 ms), followed by long incoherent averaging (∼1000 times, ∼1 s) to increase the signal-to-noise ratio. In this study, the global ionospheric scintillation model is first used to evaluate the total electron content and the scintillation index S$_{4}$. The ionospheric scintillation impact is then evaluated as a degradation of the signal-to-noise ratio, which can be used to assess the altimetry and scatterometry performance degradation in a generic GNSS-R mission. Since ionospheric scintillations are mostly produced by a layer of electron density irregularities at ∼350 km height, underneath most LEO satellites, but closer to them than to the Earths surface, intensity scintillations occur especially in the GNSS transmitter-to-ground transect, therefore, the impact is very similar in conventional and interferometric GNSS-R. Using UK TechDemoSat-1 data, signal-to-noise ratio fluctuations are computed and geo-located, finding that they occur in the open ocean along ∼±20° from the geomagnetic equator where S$_{4}$ exhibits a maximum, and in low wind speed regions, where reflected signals contain a non-negligible coherent component.

ACS Style

Adriano Camps; Hyuk Park; Giuseppe Foti; Christine Gommenginger. Ionospheric Effects in GNSS-Reflectometry From Space. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 2016, 9, 5851 -5861.

AMA Style

Adriano Camps, Hyuk Park, Giuseppe Foti, Christine Gommenginger. Ionospheric Effects in GNSS-Reflectometry From Space. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. 2016; 9 (12):5851-5861.

Chicago/Turabian Style

Adriano Camps; Hyuk Park; Giuseppe Foti; Christine Gommenginger. 2016. "Ionospheric Effects in GNSS-Reflectometry From Space." IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 9, no. 12: 5851-5861.

Journal article
Published: 01 October 2016 in IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
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GEROS-ISS stands for GNSS REflectometry, radio occultation, and scatterometry onboard the International Space Station (ISS). It is a scientific experiment, successfully proposed to the European Space Agency in 2011. The experiment as the name indicates will be conducted on the ISS. The main focus of GEROS-ISS is the dedicated use of signals from the currently available Global Navigation Satellite Systems (GNSS) in L-band for remote sensing of the Earth with a focus to study climate change. Prime mission objectives are the determination of the altimetric sea surface height of the oceans and of the ocean surface mean square slope, which is related to sea roughness and wind speed. These geophysical parameters are derived using reflected GNSS signals (GNSS reflectometry, GNSS-R). Secondary mission goals include atmosphere/ionosphere sounding using refracted GNSS signals (radio occultation, GNSS-RO) and remote sensing of land surfaces using GNSS-R. The GEROS-ISS mission objectives and its design, the current status, and ongoing activities are reviewed and selected scientific and technical results of the GEROS-ISS preparation phase are described.

ACS Style

Jens Wickert; Estel Cardellach; Manuel Martin-Neira; Jorge Bandeiras; Laurent Bertino; Ole Baltazar Andersen; Adriano Camps; Nuno Catarino; Bertrand Chapron; Fran Fabra; Nicolas Floury; Giuseppe Foti; Christine Gommenginger; Jason Hatton; Per Høeg; Adrian Jaggi; Michael Kern; Tong Lee; Zhijin Li; Hyuk Park; Nazzareno Pierdicca; Gerhard Ressler; Antonio Rius; Josep Rosello; Jan Saynisch; Francois Soulat; C. K. Shum; Maximilian Semmling; Ana Sousa; Jiping Xie; Cinzia Zuffada. GEROS-ISS: GNSS REflectometry, Radio Occultation, and Scatterometry Onboard the International Space Station. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 2016, 9, 4552 -4581.

AMA Style

Jens Wickert, Estel Cardellach, Manuel Martin-Neira, Jorge Bandeiras, Laurent Bertino, Ole Baltazar Andersen, Adriano Camps, Nuno Catarino, Bertrand Chapron, Fran Fabra, Nicolas Floury, Giuseppe Foti, Christine Gommenginger, Jason Hatton, Per Høeg, Adrian Jaggi, Michael Kern, Tong Lee, Zhijin Li, Hyuk Park, Nazzareno Pierdicca, Gerhard Ressler, Antonio Rius, Josep Rosello, Jan Saynisch, Francois Soulat, C. K. Shum, Maximilian Semmling, Ana Sousa, Jiping Xie, Cinzia Zuffada. GEROS-ISS: GNSS REflectometry, Radio Occultation, and Scatterometry Onboard the International Space Station. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. 2016; 9 (10):4552-4581.

Chicago/Turabian Style

Jens Wickert; Estel Cardellach; Manuel Martin-Neira; Jorge Bandeiras; Laurent Bertino; Ole Baltazar Andersen; Adriano Camps; Nuno Catarino; Bertrand Chapron; Fran Fabra; Nicolas Floury; Giuseppe Foti; Christine Gommenginger; Jason Hatton; Per Høeg; Adrian Jaggi; Michael Kern; Tong Lee; Zhijin Li; Hyuk Park; Nazzareno Pierdicca; Gerhard Ressler; Antonio Rius; Josep Rosello; Jan Saynisch; Francois Soulat; C. K. Shum; Maximilian Semmling; Ana Sousa; Jiping Xie; Cinzia Zuffada. 2016. "GEROS-ISS: GNSS REflectometry, Radio Occultation, and Scatterometry Onboard the International Space Station." IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 9, no. 10: 4552-4581.

Journal article
Published: 28 September 2016 in IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
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GNSS-Reflectometry is a new technique that shows promise for many earth observation applications including remote sensing of oceans, land, and ice. A payload has been developed that is low size and power, and suitable for use on small satellites. The first flight of the SGR-ReSI GNSS Reflectometry Instrument is on the TechDemoSat-1 mission, launched in July 2014. The instrument has been operational since its commissioning in September 2014, and has been collecting delay Doppler maps routinely over many different surfaces. Preliminary work has been undertaken to develop and validate wind speed inversion algorithms against ASCAT measurements with promising results. Measurements over land and sea ice are also showing interesting geophysical characteristics This paper describes the instrument, early operations, data dissemination through the Measurement of Earth Reflected Radio-navigation Signals By Satellite (MERRByS) website and preliminary data assessments in preparation for further data exploitation.

ACS Style

Martin Unwin; Philip Jales; Jason Tye; Christine Gommenginger; Giuseppe Foti; Josep Rosello. Spaceborne GNSS-Reflectometry on TechDemoSat-1: Early Mission Operations and Exploitation. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 2016, 9, 4525 -4539.

AMA Style

Martin Unwin, Philip Jales, Jason Tye, Christine Gommenginger, Giuseppe Foti, Josep Rosello. Spaceborne GNSS-Reflectometry on TechDemoSat-1: Early Mission Operations and Exploitation. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. 2016; 9 (10):4525-4539.

Chicago/Turabian Style

Martin Unwin; Philip Jales; Jason Tye; Christine Gommenginger; Giuseppe Foti; Josep Rosello. 2016. "Spaceborne GNSS-Reflectometry on TechDemoSat-1: Early Mission Operations and Exploitation." IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 9, no. 10: 4525-4539.

Journal article
Published: 27 July 2016 in IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
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Global navigation satellite systems-reflectometry (GNSS-R) is an emerging remote sensing technique that makes use of navigation signals as signals of opportunity in a multistatic radar configuration, with as many transmitters as navigation satellites are in view. GNSS-R sensitivity to soil moisture has already been proven from ground-based and airborne experiments, but studies using space-borne data are still preliminary due to the limited amount of data, collocation, footprint heterogeneity, etc. This study presents a sensitivity study of TechDemoSat-1 GNSS-R data to soil moisture over different types of surfaces (i.e., vegetation covers) and for a wide range of soil moisture and normalized difference vegetation index (NDVI) values. Despite the scattering in the data, which can be largely attributed to the delay-Doppler maps peak variance, the temporal and spatial (footprint size) collocation mismatch with the SMOS soil moisture, and MODIS NDVI vegetation data, and land use data, experimental results for low NDVI values show a large sensitivity to soil moisture and a relatively good Pearson correlation coefficient. As the vegetation cover increases (NDVI increases) the reflectivity, the sensitivity to soil moisture and the Pearson correlation coefficient decreases, but it is still significant.

ACS Style

Adriano Camps; Hyuk Park; Miriam Pablos; Giuseppe Foti; Christine P. Gommenginger; Pang-Wei Liu; Jasmeet Judge. Sensitivity of GNSS-R Spaceborne Observations to Soil Moisture and Vegetation. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 2016, 9, 4730 -4742.

AMA Style

Adriano Camps, Hyuk Park, Miriam Pablos, Giuseppe Foti, Christine P. Gommenginger, Pang-Wei Liu, Jasmeet Judge. Sensitivity of GNSS-R Spaceborne Observations to Soil Moisture and Vegetation. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. 2016; 9 (10):4730-4742.

Chicago/Turabian Style

Adriano Camps; Hyuk Park; Miriam Pablos; Giuseppe Foti; Christine P. Gommenginger; Pang-Wei Liu; Jasmeet Judge. 2016. "Sensitivity of GNSS-R Spaceborne Observations to Soil Moisture and Vegetation." IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 9, no. 10: 4730-4742.

Technical note
Published: 08 July 2016 in Remote Sensing
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A conceptually simple formulation is proposed for a new empirical sea state bias (SSB) model using information retrieved entirely from altimetric data. Nonparametric regression techniques are used, based on penalized smoothing splines adjusted to each predictor and then combined by a Generalized Additive Model. In addition to the significant wave height (SWH) and wind speed (U10), a mediator parameter designed by the mean wave period derived from radar altimetry, has proven to improve the model performance in explaining some of the SSB variability, especially in swell ocean regions with medium-high SWH and low U10. A collinear analysis of scaled sea level anomalies (SLA) variance differences shows conformity between the proposed model and the established SSB models. The new formulation aims to be a fast, reliable and flexible SSB model, in line with the well-settled SSB corrections, depending exclusively on altimetric information. The suggested method is computationally efficient and capable of generating a stable model with a small training dataset, a useful feature for forthcoming missions.

ACS Style

Nelson Pires; M. Joana Fernandes; Christine Gommenginger; Remko Scharroo. A Conceptually Simple Modeling Approach for Jason-1 Sea State Bias Correction Based on 3 Parameters Exclusively Derived from Altimetric Information. Remote Sensing 2016, 8, 576 .

AMA Style

Nelson Pires, M. Joana Fernandes, Christine Gommenginger, Remko Scharroo. A Conceptually Simple Modeling Approach for Jason-1 Sea State Bias Correction Based on 3 Parameters Exclusively Derived from Altimetric Information. Remote Sensing. 2016; 8 (7):576.

Chicago/Turabian Style

Nelson Pires; M. Joana Fernandes; Christine Gommenginger; Remko Scharroo. 2016. "A Conceptually Simple Modeling Approach for Jason-1 Sea State Bias Correction Based on 3 Parameters Exclusively Derived from Altimetric Information." Remote Sensing 8, no. 7: 576.