The Copernicus Imaging Microwave Radiometer (CIMR) is one of the six Copernicus Expansion Missions currently being implemented by the European Space Agency and the European Commission. CIMR will provide low-frequency, high spatial resolution microwave imaging radiometry measurements with high radiometric fidelity. To address Copernicus user needs, derived Level-1 and Level2 data products will have global coverage and sub-daily revisit in the polar regions and adjacent seas. The mission is specifically designed to provide measurement evidence in support of developing, implementing, and monitoring the impact of the European Integrated Policy for the Arctic which is changing rapidly due to climate change and Arctic amplification. This paper presents an overview of the CIMR mission implementation (now in Phase C/D) and reports the latest scientific simulation developments.

The Copernicus Imaging Microwave Radiometer (CIMR) is one of the six Copernicus Expansion Missions currently being implemented by the European Space Agency and the European Commission. The mission is specifically designed to provide measurement evidence in support of developing, implementing, and monitoring the impact of the European Integrated Policy for the Arctic. CIMR provides microwave imaging radiometry measurements at low frequency (L-, C-, X-, K- and Ka-band) with relatively high spatial resolution and high radiometric fidelity. In this paper, the current plan for the design, development and validation of the ESA CIMR Level-2 products is described.

The Copernicus Imaging Microwave Radiometer (CIMR) is one of the six Copernicus Expansion Missions currently being implemented by the European Space Agency and the European Commission. The mission is specifically designed to provide measurement evidence in support of developing, implementing, and monitoring the impact of the European Integrated Policy for the Arctic. The Arctic region is changing more rapidly than anywhere else in the world due to climate change and Arctic amplification. CIMR provides microwave imaging radiometry measurements at low-frequency (L-,C-,X-, K- and Ka-band) with relatively high spatial resolution and high radiometric fidelity. To address Copernicus user needs, derived Level-1 and Level2 data products will have global coverage and sub-daily revisit in the polar regions and adjacent seas. This paper presents an overview of key mission requirements [11] that underpin the CIMR mission implementation (now in Phase C/D). Two satellites are now in preparation (CIMR-A and CIMR-B) to be launched sequentially separated by ~7 years starting in 2028/29.

The Copernicus Imaging Microwave Radiometer (CIMR) mission is one of the six Copernicus Expansion (CopEx) Missions [1], that are part of the Copernicus Space Component being implemented by the European Space Agency (ESA) and the European Commission (COM). The mission responds to Copernicus User needs embodied in Mission Requirements [3] by providing high-spatial resolution low-frequency microwave imaging radiometry measurements and derived products. Continuous global coverage every day with sub-daily revisit in the polar regions and adjacent seas is necessary to address Copernicus user needs. The primary mission requirements [3] are to acquire global observations to address Sea Ice Concentration (SIC) and Sea Surface Temperature (SST) with secondary requirements covering a very wide number of parameters related to EU Arctic Policy. For more information about Mission requirement see [2] and [3].The mission can be considered a "game changer" for global and polar region observations, thanks to features such as•All weather, day/night imaging capability;•multi-frequency (L to Ka), simultaneous acquisitions;•Unrivaled spatial resolution (5…<60km);•Excellent radiometric accuracy/resolution and stability;•Global coverage, "no hole at the pole", sub-daily (6h) revisit.The paper provides and overview of the Project and System implementation following the successful System and Instrument Preliminary Design Review (PDR) held on October 2022.

Copernicus [http://www.copernicus.eu/] is a European system for monitoring the Earth in support of European policy. It includes Earth Observation satellites (notably the Sentinel series developed by ESA) that form part of the Copernicus Space Component of the European Space Agency (ESA) and the European Commission (COM). The Copernicus Imaging Microwave Radiometer (CIMR) mission is one of six Copernicus Expansion (CopEx) Missions that address emerging and urgent needs for new types of observations and will have a particular focus on monitoring Polar regions.The primary mission objectives of CIMR [2] are to measure Sea Ice Concentration (SIC) and Sea Ice Extent (SIE) at a spatial resolution of 5 km and Sea Surface Temperature (SST) at a spatial resolution of 15 km with a focus on sub-daily coverage of Polar Regions and daily coverage of Adjacent Seas. In addition, CIMR has to ensure European operational continuity of L-band measurement capability in synergy with other missions (e.g. MetOp-SG) to enhance monitoring of the Polar Regions and Adjacent Seas.Following the successful System and Instrument Preliminary Design Review (PDR) held on October 2022, this paper focusses on the CIMR Instrument architecture and performance. For more details on the CIMR mission [2] and CIMR project, please consult [3] and [4], respectively.

The Copernicus programme [1] is a European system for monitoring the Earth in support of European policy as developed by the European Commission (COM). It includes Earth Observation (EO) satellites (notably the Sentinel series developed by the European Space Agency (ESA)) that form part of the Copernicus Space Component (CSC). The Copernicus Imaging Microwave Radiometer (CIMR) mission [2] is one of six Copernicus Expansion (CopEx) Missions [3] that address emerging and urgent needs for new types of global coverage observations with a particular focus on monitoring Polar regions.

The Copernicus Sentinel-3 mission is part of the first generation of Copernicus satellites and was set out to deliver operationally high quality measurements over ocean, land, and atmosphere. The European Space Agency (ESA) is now studying concepts for the Next Generation Sentinel-3 Topography (S3NG-T) mission that would launch in the 2032+ time period. In order to meet the primary objectives of the S3NG-T mission requirement document a complex analysis of river and lake targets is required to size the satellite mass memory and downlink system. We have adopted a different approach that derives a non-conservative mask of water density that defines a more useful user friendly approach to specifying where river and lake targets are located. Within this work, the design and construction of our water density maps as well as application examples are discussed. The results prove an easy-to-apply methodology to create global surface water density maps using high-resolution water body maps. The work further illustrates different use cases to optimize data sizing considering constraints such as global coverage, river width, and total data volume.

The main payload of the Sentinel-6 Michael Freilich (S6-MF) is the Poseidon-4 Ku- and C-band Radar Altimeter launched Nov 18th2020 was developed to continue the ocean surface topography reference data record that commenced in 1992 (TOPEX/Poseidon), was followed by Jason-1 (2001), Jason-2 (2008) and Jason-3 (2016). The satellite has been developed to, as a minimum, meet in-orbit performances of the Jason-2 and adopts, for the first time, requirements concerning estimated Global Mean Sea Level (GMSL) drift and stability. The design of S6 has also taken into account the in-orbit performances of the CryoSat-2/Sentinel-3 missions and their altimeter designs. Integrated into the design is the capability to allow for further on-ground processing enhancements that now demonstrate focused processing capabilities that can be performed globally for evolving future applications. This paper provides an overview of the key performances of the mission at the end of its commissioning and tandem phase with Jason-3, that has also allowed for the first time the characterization of both nominal and redundant chains of the altimeter. It is now demonstrated that the mission meets all its commissioning objectives and all mission level requirements are met, though long-term estimates of GMSL stability requires a longer time series of around 3 years. The Poseidon-4 design and its performances has provided the basis for future missions, such as CRISTAL and potentially for the Sentinel-3 and 6 Next Generation systems.

This article describes the Copernicus Sentinel-6 satellite mission and early in-orbit results. The mission is designed to address the needs of the European Copernicus programme for precision sea level, near-real-time measurements of sea surface height, significant wave height, and other products tailored to operational services in the climate, ocean, meteorology and hydrology domains. It is designed to provide enhanced continuity to the very stable time series of mean sea level measurements and ocean sea state started in 1992 by the TOPEX/Poseidon (T/P) mission and follow-on Jason-1, Jason-2 and Jason-3 satellite missions. The mission is implemented through a unique international partnership with contributions from NASA, NOAA, ESA, EUMETSAT, and the European Union (EU). It includes two satellites that will fly sequentially (separated in time by 5 years). The first satellite, named Sentinel-6 Michael Freilich (S6-MF), launched from Vandenburg Air Force Base, USA on 21stNovember 2020. The main payload is the Poseidon-4 dual frequency (C/Ku-band) nadir-pointing radar altimeter providing synthetic aperture radar (SAR) processing in Ku-band to improve the signal through better along-track sampling and reduced measurement noise. The altimeter has an innovative interleaved mode enabling radar data processing on two parallel chains, one with the SAR enhancements and the other furnishing a “Low Resolution Mode” that is fully backward-compatible with the historical TOPEX/Poseidon and Jason measurements, so that complete inter-calibration between the state-of-the-art data and the historical record can be assured. Early in-orbit performance data are presented.

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.

The Copernicus Imaging Microwave Radiometer (CIMR) is one of the Copernicus High Priority Candidate mission recently approved at the ESA (European Space Agency) Ministerial Council 2019 as a reply to climate policy set by the European Commission in cooperation with ESA. CIMR is a conically scanning multi-frequency radiometer that will deploy a wide-swath with world global coverage with particular attention to the Arctic and Antarctic regions. CIMR measurements will be made using a forward scan arc followed by a second measurement using a backward scan arc. This paper will provide an overall system view of the mission in particular discussing main technical challenges. The mission is being developed in the frame of Copernicus ESA-EU partnership.

The Sentinel-3 (S3) mission is developed as part of the Copernicus Space Component (CSC) Programme to fulfil the space-based observation requirements in response to European policy priorities with a particular emphasis on the Copernicus core services as identified by the Commission.

The GlobCurrent project (http://www.globcurrent.org) aimed to: (i) advance the quantitative estimation of ocean surface currents from satellite sensor synergy; and (ii) demonstrate impact in user-led scientific, operational and commercial applications that, in turn, would improve and strengthen the uptake of satellite measurements. It is often demonstrated that sharp gradients in the sea surface temperature (SST) and current fields and the ocean surface chlorophyll-a distribution are spatially correlated with the sea surface roughness anomaly fields at small spatial scales, in the sub-mesocale (1-10 km) to the mesoscale (30-80 km). The 2-dimensional structures manifested in the satellite observations represent evidence of the upper ocean dynamics. Whereas the quasi geostrophic assumption is valid for the upper ocean dynamics at the larger scale (> 100 km), possible triggering mechanisms for the expressions at the mesoscale-to-submesoscale may include spiraling tracers of inertial motion and the interaction of the wind-driven Ekman layer with the quasi-geostrophic current field. This latter, in turn, produces bands of downwelling (convergence) and upwelling (divergence) near fronts. A regular utilization of the sensor synergy approach with the combination of Sentinel-3, Sentinel-2 and Sentinel-l together with other satellite missions will provide a highly valuable data set for further research and development to better relate the 2-dimensional surface expressions and the upper ocean dynamics.

The Sentinel-3 mission forms part of the Copernicus Space Component. Its main objectives are to measure sea-surface topography, sea- and land-surface temperature and ocean- and land-surface colour in support of ocean forecasting systems, and for environmental and climate monitoring. The series of Sentinel-3 satellites will ensure global, frequent and near-real time ocean, ice and land monitoring, with the provision of observation data in routine, long term (up to 20 years of operations) and continuous fashion, with a consistent quality and a high level of reliability and availability. The Sentinel-3 mission addresses these requirements by implementing and operating the following instruments, building on experience and heritage from the ERS and ENVISAT missions: •A dual frequency, delay-Doppler Synthetic Aperture Radar Altimeter (SRAL) instrument supported by a dual frequency passive microwave radiometer (MWR) for wet-tropospheric correction, and a Precise Orbit Determination package. This combined package provides measurements of sea-surface height and topography measurements over sea ice, ice sheets, rivers and lakes. •A highly sensitive Ocean and Land Colour Imager (OLCI) delivering multichannel wide-swath optical measurements for ocean and land surfaces. With 21 bands, compared to the 15 on Envisat's MERIS, a design optimised to minimise sun-glint and, a resolution of 300 m over all surfaces, OLCI marks a new generation of measurements over the ocean and land. The swath of OCLI and nadir SLSTR fully overlap. •A dual-view Sea and Land Surface Temperature Radiometer (SLSTR) delivering accurate surface ocean, land, and ice temperature, with an accuracy better than 0.3 K. SLSTR measures in 9 spectral channels and two additional bands optimised for fire monitoring. SLSTR has a spatial resolution in the visible and shortwave infrared channels of 500 m and 1 km in the thermal infrared channels.

The Sentinel-3 (S3) mission is developed as part of the Copernicus Space Component (CSC) Programme to fulfil the space-based observation requirements in response to European policy priorities with a particular emphasis on the Copernicus core services as identified by the Commission. The Sentinel-3 main objectives are to measure sea-surface topography, sea- and land-surface temperature and ocean- and land-surface colour in support of ocean forecasting systems, and for environmental and climate monitoring. A series of Sentinel-3 satellites will ensure global, frequent and near-real time ocean, ice and land monitoring, with the provision of observation data in routine, long term (up to 20 years of operations) and continuous fashion, with a consistent quality and a high level of reliability and availability. Sentinel-3 carries an Ocean and Land Colour Instrument (OLCI), a Sea and Land Surface Temperature Radiometer (SLSTR), a SAR Radar altimeter (SRAL) supported by a Microwave Radiometer (MWR) and a suite of orbit determination instruments. A full description of Sentinel-3 can be found in [Donlon et al (2012)]. The paper will focus on S3 optical payloads described in Nieke et al (2015) and Coppo et al (2015).

The Copernicus Programme, being Europe's Earth Observation and Environment Monitoring Programme led by the European Union, aims to provide, on a sustainable basis, reliable and timely services related to environmental and security issues. The Copernicus Programme uses multiple source data and comprises a service component, a space infrastructure component and an in-situ component. The objective of the Copernicus Space Component (CSC) Programme is to fulfil the space-based observation requirements in response to European policy priorities with a particular emphasis on the Copernicus core services as identified by the European Commission. It aims at developing a fully operational capability in view of feeding Copernicus services with satellite data. The CSC Programme also aims at the operational provision of satellite data for other European and national services. The main data source for the CSC Programme are the Sentinels, dedicated missions providing continuity to past or present data sets. In addition, the CSC Programme covers the development and operations of a Data Access Layer, the Coordinated Data access System (CDS), aiming at providing Copernicus Services also with satellite data from other missions (by ESA, National, EUMETSAT and other Third Party Missions) that are of relevance to the overall space component of Copernicus.

The overall process commonly referred to as Ocean Acidification (OA) is nowadays gathering increasing attention for its profound impact at scientific and socio-economic level. To date, the majority of the scientific studies into the potential impacts of OA have focused on models and in situ datasets. Satellite remote sensing technology have yet to be fully exploited and could play a significant role by providing synoptic and frequent measurements for investigating OA processes on global scales. Within this context, the purpose of the ESA “Pathfinders-OA” project is to quantitatively and routinely estimate surface ocean pH by means of satellite observations in several ocean regions. Satellite Ocean Colour, Sea Surface Temperature and Sea Surface Salinity data (with an emphasis on the latter) will be exploited. A proper merging of these different datasets will allow to compute at least two independent proxies among the seawater carbonate system parameters and therefore obtain the best educated guess of the surface ocean pH. Preliminary results of the anomaly and variability of the ocean pH maps are presented.

The series of Global Monitoring for Environment and Security (GMES) Sentinel satellites will continue and extend the European heritage of ENVISAT to provide data to numerous user communities. Sentinel-3 is being developed to support GMES Ocean and global Land monitoring services. Two Sentinel-3 satellites are in development with a first launch in 2014 and the second satellite expected approximately 18 months after the first. This paper provides an overview of the Sentinel-3 Mission.

A preliminary attempt of deriving a purely satellite-based Temperature-Salinity (T-S) diagram is presented, with the overall aim of assessing to what extent is possible, and in which geographical areas, to identify and trace water masses by satellite. This has been performed by using recent SMOS and Aquarius satellite SSS products in conjunction with spaceborne SST data. A baseline T-S diagram is arranged from climatology data, differentiating 7 ocean zones and mapping them into the T-S domain. Therefore, a comparison with satellite data is carried out, highlighting, for this preliminary test, which are the most challenging zones and where, in turn, they mutually agree in a reasonable way.

Satellite measurements of global sea surface temperature (SST) distribution are increasingly recognised to have great importance for understanding changes in the world's climate, as well as for operational forecasting of the oceans and atmosphere. If satellite-derived SSTs are to provide the basis of an essential climate variable (ECV) it is necessary to establish methods for independently verifying their quality. Previously the validation of satellite SST products has been performed by comparison with sea temperatures measured by contact thermometers on the hulls of moored or drifting buoys or of ships. Such sensors operate below the sea surface, within the top few metres of the water column, recording what is now referred to [1] as SSTdepth. Infrared radiometers on satellites measure the temperature of the surface skin of the ocean, referred to as SSTskin. However, significant uncertainties are introduced when validation is based on comparisons between SSTdepthand SSTskinbecause the sea temperature is not uniform across the skin and the upper few metres, especially but not only because of diurnal variability. Such uncertainties can be eliminated by using in situ SSTskinmeasurements as the basis for a satellite SST validation approach which genuinely compares like with like. This paper describes the principles and results of such a system which has now been in place for five years. It has been used to validate SST measurements from the Advanced Along Track Scanning Radiometer (AATSR) on Envisat. Within the collaborative approach developed by the Group for High Resolution SST (GHRSST, [1]) for merging of complementary data from different satellites, the primary role of AATSR data is to provide a reference for bias adjustment of other data. Precise validation of AATSR measurements is therefore essential for maintaining the quality of other GHRSST products.

The Advanced Along Track Scanning Radiometer is an imaging radiometer on board ESA's Envisat satellite. The primary mission aim for AATSR is the measurement of sea surface temperature (SST), on a global scale, to the degrees of accuracy and precision required for climate change research (better than 0.3K ± 1 sigma). Since the launch of Envisat, on 1st March 2002, AATSR has been producing excellent data, with images of high quality in the thermal, near infrared and visible wavelength regions. An intensive validation programme has been underway to assess whether AATSR SST data meet their stringent accuracy requirements. There have been a number of activities for SST validation using, for example, SST data from buoys, global SST analysis fields and SST measurements from high-precision radiometers on research vessels and ships of opportunity. Initial assessment indicates that the AATSR SST shows a global mean deviation of better than 0.3K with respect to in situ observations, with significantly higher levels of accuracy under certain conditions, thereby meeting its performance objectives.