Sentinel-3 is part of a series of Sentinel satellites responsible for taking care of a continuous ‘health check’ of the Earth planet under the umbrella of the Copernicus program. The Copernicus program will launch four Sentinel-3 satellites (from A to D) to achieve this goal from 2016 to 2030s. EUMETSAT’s ground segment is responsible for the processing of the Sentinel-3 altimetry data in the marine environment: open ocean, coastal zones and sea level into the...

This study will report on results from two parallel sea state bias correction model investigations. Ongoing verification of sea level measurements from the Sentinel-6 Michael Freilich mission suggests the possibility of systematic range bias and noise due to the use of preliminary sea state bias correction models based on tandem comparisons with Jason-3 altimeter data. New C- and Ku-band sea state bias models built using Side-B altimeter data from S-6 will be presented including an...

Satellite altimetry continues to revolutionize ocean science, enabling precise observations of geocentric sea level with near-global coverage. However, altimetry has traditionally been challenged in the coastal zone (within 20 km of land) due to the presence of land in the altimeter and radiometer footprint. As the oceans further encroach on coastal communities, a more detailed understanding of the physical processes impacting sea-level variability as it propagates landward is needed. State-of-the-art satellite altimeters have the potential...

Satellite observations can help in the retrieval of constituents in shallow waters. Noise contamination, however, makes smaller constituents irretrievable and large sources of error. Throughout shallow areas, the constituent’s relevancy changes. For example, near an amphidromic point where M2 relevance drops, so does the potential of satellite contribution for improving its accuracy. Moreover, shallow waters are generally influenced by many constituents (>100). Accurately retrieving all these constituents with satellite radar altimeter data alone is not...

OSTST community feeds climate community with altimetry data of increasing quality. Number of missions and observations increase, uncertainties are better characterized and historical missions are reprocessed to benefit from recent standards. Among the users, the IPCC (International Panel on Climate Change) is about to close its sixth assessment cycle, in which the IPCC have produced the Sixth Assessment Report (AR6) with contributions from its three Working Groups, three Special Reports, and a Synthesis Report. In...

Overview of the SARAL/AltiKa mission

Status of the CRISTAL mission

The wave spectrum is a representation of the state of the ocean surface from which many parameters can be deduced: significant wave height, peak parameters of dominant waves, directional parameters, etc... For more than 30 years, Synthetic Aperture Radars allow their routine montoring far from the coast in all surface conditions (through clouds and despite night), where buoys cannot be deployed. These measurements benefit from scientific efforts that now make it a reliable measurement technique....

With global mean sea level rising because of climate change, Copernicus Sentinel-6 is the radar altimetry reference mission to extend the legacy of sea-surface height measurements until at least 2030. The satellite carries a Poseidon-4 radar altimeter and a microwave radiometer. The analysis of the altimeter data relies on highly-accurate knowledge of the orbital position, in particular in the radial component, with errors below 1.5 cm. For this reason, Sentinel-6 carries several instruments, e.g. Laser...

Mesoscale eddies are ubiquitous structures in the ocean. As mesoscale eddies can trap and transport water within their cores over long distances, they have been investigated globally since the availability of altimetry maps. Mesoscale eddies are first detected in the sea surface, and then tracked in time and space. Several methods of detection and tracking have been developed, most of them propose to describe the evolution of mesoscale eddies with an association in individual trajectories,...

Operating in Ka band, SARAL/AltiKa is more sensitive to liquid water in the atmosphere which can drastically attenuate the signal even for moderate events (eg light rain) and impact the retrieval of geophysical parameters. This turned out not to pose any problem regarding data availability thanks to the instrument's link budget margins. The operational products come with a rain flag based on the pre-launch work of Tournardre et al. (2009), which was finely tuned during...

Given the major role of the Atlantic Ocean in the climate system, it is essential to characterize the temporal and spatial variations of its heat content. The 4DATLANTIC-OHC Project (https://eo4society.esa.int/projects/4datlantic-ohc/) aims at developing and testing space geodetic methods to estimate the local ocean heat content (OHC) changes over the Atlantic Ocean from satellite altimetry and gravimetry. The strategy developed in the frame of the ESA MOHeaCAN Project (https://eo4society.esa.int/projects/moheacan/) is pursued and refined at local scales...

Serial correlation in sequences of radar pulse echoes backscattered from the ocean surface is an important factor in the design of satellite altimeters and in the exploitation of their measurements. Previous investigations considered serial correlation in the random fluctuations in echo power called speckle noise [Egido and Smith 2018]. This study takes a new and different approach, examining the complex degree of coherence. If ocean echoes behave statistically as expected of backscatter from a homogeneously...

At the interface between New-Caledonia and the Pacific Ocean, the Noumea Lagoon is an example of a dynamically complex coastal zone, that challenges the present and future altimetry mission. In this area, the SSH evolution is still an unresolved issue as sea level from altimetry and coastal tide gauge, and vertical land movements from GNSS, do not provide consistent information on long term trends (Aucan et al. 2017; Martínez-Asensio et al. 2019). This could be...

The primary focus of this presentation is results from the radiometric evaluation of the TriG Precise Orbit Determination (POD) Global Positioning System (GPS) receiver onboard the Sentinel-6 Michael Freilich (MF) mission. We assess various tracking metrics, data noise, and precise orbit determination performance, and compare them to those from the Jason-3 IGOR+ GPS receiver. We also present results from the evaluation of our GPS-based POD solutions using independent metrics such as withheld satellite laser ranging...

Sea ice thickness is an important variable for sea ice monitoring and climate projections. Although observations of ice extent and concentration have been available since late 1978, the same is not true for ice thickness. Because of the high interannual variability of the ice pack, climate trends in thickness and volume can only be observed over long time series. The earliest measurements of sea ice thickness (as multi-year averages for ERS-1 and ERS-2) were published...

The CryoSat-2 mission is designed to determine fluctuations in the mass of the Earth’s land and the marine ice fields. Its primary payload is a radar altimeter that operates in different modes optimised depending on the kind of surface: Low resolution mode (LRM), SAR mode (SAR) and SAR interferometric mode (SARIn). This instrument is named SIRAL: SAR Interferometric Radar Altimeter. Transponders are commonly used to calibrate absolute range from conventional altimeter waveforms because of its...

The variability of sea surface height (SSH) is controlled by processes that span a broad range of spatial and temporal scales. At mesoscales and large submesoscales (300--15 km), the SSH spectrum is expected to be consistent with quasi-geostrophic (QG) turbulence theory and to be characterized by a quasi-linear spectral slope, with variance decaying toward higher wavenumbers. In contrast, at scales ranging from hundreds of meters to a few meters, SSH variability is dominated by surface...

We present a new Arctic sea level dataset (https://doi.org/10.24400/527896/a01-2020.001) based on the optimal interpolation of three satellite radar altimetry missions. A dedicated processing is applied on measurements from SARAL/AltiKa, CryoSat-2 and Sentinel-3A to identify radar echoes coming from leads in the ice covered regions of the Arctic Ocean. After a data editing and application of instrumental, environmental and geophysical corrections tailored for the Arctic Ocean, these echoes are combined with open ocean echoes through an...

Through different projects, the Center for Topographic studies for the Ocean and Hydrosphere (CTOH) contributes largely to advances in coastal altimetry and to its use in coastal applications. It has developed the X-TRACK software dedicated to the reprocessing of coastal altimetry data. X-TRACK is now a mature sea level product distributed worldwide by AVISO+ (https://www.aviso.altimetry.fr), cited in many scientific publications. It consists in long time-series of SLA from most altimetry missions, processed homogeneously, but also...

We describe design of the new 1/6° (mesoscale) resolution daily global Blended Ocean Surface Current (BOSC) product (analysis depths: 20 cm and 15m). This quasi-realtime data-informed product will eventually be available through NOAA CoastWatch for applications ranging from climate and weather analysis and forecasting to fisheries, marine debris, and coastal engineering. Looking forward, BOSC is designed to complement velocity observations from future Doppler satellite scatterometry. BOSC currents are constructed by summing gradient currents derived from...

Here we present a global sea level reconstruction from 1992 to 2021. Each mass contribution (Greenland, Antarctica, Glaciers, Terrestrial Water Storage, GIA) to both relative (S) and absolute sea level (N) and vertical land movement (U = N - S) and the halo- and thermosteric contribution is defined monthly in an equal-area grid (r ~ 45km). This allows for reconstructing both secular and seasonal sea level changes at any location of the globe. Each contributions...

Sea surface temperature (SST) variability is controlled both by ocean processes such as advection, Ekman transport, and mixing, and by surface heat flux driven by atmospheric variations. Quantifying the relative strength of ocean and atmospheric forcing from observations previously has been explored by analyzing local heat budgets. Here, we use an observationally constrained local metric that quantifies the relative influence of ocean and atmospheric forcing from surface observations using a feedback framework. We use monthly...

The Sentinel. 6 satellite has a new platform, with a very different geometry from the preceding missions like Jason 1,2,3. The main difference is that the solar array panel is now fixed on the satellite body, and the satellite has a fixed attitude in the local orbital frame (with small rotations for geodetical pointing and ground velocity alignment). As a consequence the sun direction relative to the panels has important variations along one orbit. On...

A first attempt was made to quantify the impact of the assimilation of Surface Water Ocean Topography (SWOT) swath altimeter data in a global 1/12° high resolution analysis and forecasting system through a series of Observing System Simulation Experiments (OSSEs). The impact of assimilating data from SWOT and three nadir altimeters was quantified by estimating analysis and forecast error variances for sea surface height (SSH). Wave-number spectra and coherence analyses of SSH errors were also...