As part of the Copernicus long-term scenario, ESA is planning the development of the Sentinel-1 Next Generation (NG) mission. It’s main goal is to ensure the C-band data continuity beyond the next decade (2030) in support of the operational Copernicus services that are routinely using Sentinel-1 data. In addition, the enhanced capabilities of Sentinel-1 NG compared to Sentinel-1, will support novel imaging capabilities and enable further development and improvement of operational applications.
The Sentinel-1 NG mission addresses three cross-cutting categories of requirements. These are:
1. Continuity which are requirements linked to the continuation of current observations in order to establish long and reliable time series of measurements. The compatibility of different sources and data streams has to be ensured across time and space.
2. Enhanced continuity which are requirements for improvements in current observations in terms of accuracy, quality in general, and temporal and spatial resolution.
3. Observation gaps which are requirements corresponding to parameters not yet observed by Copernicus. These are not necessarily the observations to be provided with the highest priority. Some of them cannot be provided by instruments embarked on satellites given the current state of knowledge, others could be secured through international collaboration and data exchange rather than committing limited resources to satellite mission developments.
The primary goal of Sentinel-1 NG is to ensure the continuity of Copernicus and other important services that rely on Sentinel-1 as a primary source of information to deliver the service. Continuity in this context is defined as the continuity of services and applications. In addition to ensuring continuity of services, the S1 NG mission and satellites shall also address the enhanced continuity of current services as well as possible new areas of development or evolution of services responding to the evolving capabilities of the user community.
Sentinel-1 NG will directly address the information needs of numerous services including inter alia:
- The nascent European Ground Motion Service (EGMS) which is now part of the Copernicus Land Monitoring Service’s product portfolio. EGMS is a service that aims to provide consistent, regular, standardized, harmonized and reliable information regarding natural and anthropogenic ground motion phenomena over Europe and across national borders, with millimeter accuracy.
- The Copernicus Emergency Management Service (EMS) providing enhanced continuity and improved geospatial information to assess the impact of natural and man-made disasters all over the world.
- The Copernicus Land Monitoring Service (CLMS) where Sentinel-1 NG is expected to support enhanced continuity and service evolution are the many applications centred on land cover mapping and soil moisture information.
- Maritime Safety and Security including continuity with respect to existing Maritime Surveillance Services for oil spill detection and new capabilities to support vessel monitoring leveraging the higher resolution and wide swath of Sentinel-1 NG.
- Monitoring of the Arctic seas through enhanced continuity in monitoring ice and the change of ice over time, supporting transport and human activities with key environmental information for safety and environmental protections purposes and security applications.
As can be seen above Sentinel-1 NG represents a multi-purpose SAR mission whose design is required to support multiple applications and services. The driving mission requirements are the combination of higher resolution, wider swath and more frequent coverage with respect to the current generation of Sentinels. As an example a spatial resolution of 5m x 5m is being targeted compared to the 20m x 5m typical of the interferometric wide swath mode of Sentinel-1.
The technical concept of Sentinel-1 NG is currently being studied by European industry within the context of a Phase-AB1 study. Special consideration is given to the compatibility of the mission with the current Sentinel-1 and future ROSE-L constellation with harmonised coverage, e.g. on another node of the same orbital plane or observing the same ground area few seconds apart (typically 60 seconds or less).

The Copernicus Sentinel-2 Next Generation (NG) mission will be the new European reference multi-spectral imaging mission supporting Copernicus Services related to land, coastal areas, climate change, emergency management, and security. In continuity with Sentinel-2, Sentinel-2 NG will be a workhorse for the Earth Observation (EO) and geospatial scientific communities, as well as a crucial data provider for the Copernicus EO downstream market.

Scheduled for launch in the early 2030s, the Sentinel-2 NG space segment and its mission specific ground segment will ensure enhanced continuity of service to the current Sentinel-2 data in order to meet new and emerging user needs. This will be achieved thanks to the enhanced observational capabilities of the Advanced Multi-Spectral Imager (AMSI), allowing a higher spatial resolution while concurrently maintaining (as a minimum) the same image quality and accommodating a larger number of spectral bands compared to Sentinel-2. A lower revisit time compared to the current generation of Sentinel-2 is also being targeted in response to the users’ request. During pre-Phase 0 and Phase 0, ESA – together with the Sentinel-2 NG Ad Hoc Expert Group (AHEG) – defined a baseline set of spectral bands for potential implementation in AMSI. These spectral bands reflect specific requirements expressed by the user community, the relevant Copernicus services and the Sentinel-2 NG AHEG. Next to the current Sentinel-2 MSI heritage bands, some new and additional bands that can enable new applications or enhance existing ones are being considered. Complementarity and coordination with other Copernicus missions expected to fly in the same time frame as Sentinel-2 NG (e.g. CHIME, LSTM, Sentinel-3 NG) is being strongly pursued. Moreover, synergies with the future NASA/USGS Landsat Next mission are being considered.

In addition to the multispectral bands, the user requirement analysis showed that some applications may benefit from the availability of a very high resolution (VHR) or panchromatic (PAN) band. Although the addition of a PAN band onboard the Sentinel-2 NG satellite has been discarded from the Phase 0 study, the inclusion of VHR data, i.e. with a spatial sampling distance below 2.5 m, within the Sentinel-2 NG overall mission architecture is being considered as a relevant feature. Specific user and mission requirements to pave the way for a combined use of AMSI measurements and VHR data are currently being identified.

The Sentinel-3 Mission provides an essential satellite altimetry data set for the Copernicus services over the global ocean, coastal zones, sea and land ice and inland waters in support of a large number of end user applications. Four Sentinel-3 satellites (two currently on orbit and two replacements to be launched in the coming years) operating in a sun-synchronous near polar orbit provide an unprecedented and unbroken time series of satellite altimetry measurements from 2016-2035.

Considering the User needs expressed by the European Commission and inputs from an independent Mission Advisory Group are documented in the S3-NG-T Mission Requirements Document. The aim of the Copernicus Next Generation Sentinel-3 Topography (S3NG-T) Mission is to guarantee baseline continuity of existing Copernicus Sentinel-3 nadir-altimeter measurements in the 2030-2050 time-frame while enhancing measurement performance.

The primary objectives of the S3NG-T mission are to:

PRI-OBJ-1. Guarantee continuity of Sentinel-3 topography measurements for the 2030-2050 time frame with performance at least equivalent to Sentinel-3 in-flight performance (‘baseline mission’).
PRI-OBJ-2. Respond to evolving user requirements and improve sampling, coverage and revisit of the Copernicus Next Generation Topography Constellation (S3NG-T and Sentinel-6NG) to "≤ 50" km and "≤ 5" days in support of Copernicus User Needs.
PRI-OBJ-3. Enhance sampling coverage, revisit and performance for Hydrology Water Surface Elevation measurements in support of Copernicus Services.
PRI-OBJ-4. Respond to evolving user requirements and enhance topography Level-2 product measurement performance.

The secondary objectives of the S3NG-T mission are to:

SEC-OBJ-1. Provide directional wave spectrum products that address evolving Copernicus user needs.
SEC-OBJ-2. Provide new products (e.g. sea surface height gradients and river reach averaged gradients, river width and water area. that address evolving Copernicus user needs.

A coordinated constellation of spacecraft is required to provide enhanced continuity to the Sentinel-3 Mission to meet sampling at "≤ 5" days, "≤ 50" km (25 km wavelength) between 81.5 degrees north and south of the equator - regardless of the satellite technologies employed. Such a constellation requires a reference that allows satellite to be used in synergy with each other to satisfy User needs without bias discrepancies. For the S3NG-T mission, it is assumed that a reference satellite mission (e.g. Copernicus Sentinel-6/NG) will be available in orbit that is designed for this purpose providing a common reference measurement for all S3NG-T satellites and with excellent knowledge of measurement stability. Additional third party altimeter missions may also provide additional data although their launch or access to their data cannot be guaranteed.

Continuity of Sentinel-3 measurements can be guaranteed using a number of different technical solutions with potential enhancements in terms of coverage, sampling, calibration stability, system complexity and size amongst others. The best implementation approach for the S3NG-T mission shall be based on "fitness for purpose to provide enhanced continuity to Sentinel-3 topography measurements" determined by compliance to mission requirements, maturity of technical heritage, technical feasibility/readiness, scientific readiness and maturity, development schedule, risk, cost and programmatic arrangements. Based on the S3NG-T Phase-0 activities and other studies conducted by ESA over the last 5 years the most likely scenarios to implement S3NG-T include the following:

• Scenario-1: Replacement of Sentinel-3C and Sentinel-3D using a constellation of 2-n nadir-pointing altimeters.
• Scenario-2: Implementation of 2..n swath altimeter including a nadir altimeter.
• Scenario-3: A hybrid approach including both nadir pointing altimeter and swath altimeter satellites

This paper will review the current status of the S3NG-T Mission following the completion of Phase-0 studies and on-going Phase A/B1 studies at ESA.

Sustained observations in the visible and infrared domain are one of the pillars of the Copernicus Programme. The vast amount of data collected by the current Sentinel-3 optical payloads, i.e. the Ocean and Land Colour Imager (OLCI) and the Sea and Land Surface Temperature Radiometer (SLSTR), provide crucial input to a number of Services including the Marine Service (CMEMS) and Land Monitoring Service (CLMS)
To ensure continuity of service for Copernicus, the next generation (NG) of the Copernicus Space Component (CSC) of the Sentinel-3 mission is foreseen to be launched in the 2032 time horizon. The Next Generation of Sentinel-3 Optical (Sentinel-3 NG Optical) will address the evolution of the optical payloads OLCI and SLSTR , while the radar payload will be addressed by a different mission (Sentinel-3 and Sentinel6 NG Topography).
The Sentinel-3 NG Optical will aim at the delivery of crucial observations both over oceans and over land . In the oceanic domain these observations are needed to constrain and drive global and local ocean assimilation models and coupled ocean/atmosphere assimilation models. For this, Sentinel-3 Optical NG will deliver as primary mission objectives:
• Continuity of sea colour data, at least at the level of the quality of the current generation of Sentinel-3 OLCI
• Continuity of sea surface temperature, at least at the level of the quality of the current generation of Sentinel-3 SLSTR
Observations of moderate resolution and wide swath from this mission will also provide information needed to derive global land products and feed the related services with data. These are:
• Continuity of land surface colour at least at the level of quality of the current generation of Sentinel-3 OLCI
• Continuity of land surface temperature at least at the level of quality of the current generation of Sentinel-3 SLSTR
• Continuity of vegetation products, based on synergetic measurements from optical instruments at least at the level of quality of the current generation of Sentinel-3

Ensuring continuity goes hand in hand with the technical evolution of the OLCI and SLSTR instruments, in order to improve the products; this in turn leads to enhanced services or new services, and also enables R&D into new applications. In this presentation we will review the key scientific and service requirements of the mission, illustrate the advanced technical concepts that are currently being evaluated as part of Phase 0 of the mission development, and discuss some of the expected applications.

As part of the Copernicus component of the European Union (EU) Space Programme, the European Space Agency (ESA) and EUMETSAT are preparing for the expansion of the Copernicus Space Infrastructure with new observation capabilities for monitoring greenhouse gas emissions, marine and polar areas. This includes in particular the development of an Anthropogenic CO2 Monitoring mission (CO2M), a Polar Ice and Snow Topography Mission (CRISTAL), and a Polar Ice and Ocean Imaging Microwave Radiometer Mission (CIMR).
Through a Contribution Agreement with the European Union, EUMETSAT was entrusted to contribute to the development of those three missions, taking up a different role for each of them.
EUMETSAT contributes to the development of a significant part of the CO2M ground segment and is responsible for the routine operations of the Anthropogenic CO2 Monitoring mission (CO2M). EUMETSAT will undertake the day-to-day routine satellite operations of CO2M and the continuous processing, monitoring, validation and, where needed, vicarious calibration of the payload data-products and their operational dissemination to users. ESA is contributing with the development of the space-segment and the remaining CO2M ground segment elements. ESA will also perform the satellite in-orbit verification activities and operate the satellites in this phase.
In the case of CRISTAL, when the mission is confirmed by the European Commission, EUMETSAT will be responsible for the deployment of data processing chains for global ocean products, including their validation aspects, in synergy with Sentinel-3/-6. This includes L1 and L2, as well as L2P/L3 products over global ocean.
In the case of CIMR, also subject to confirmation from the Commission, EUMETSAT will be responsible for the deployment of data processing chains for generating L2 products over the global ocean, in order to support marine and weather applications, extracting the associated geophysical parameters, in synergy with other relevant missions operated by EUMETSAT
This presentation provides an overview of the main logical elements of the CO2M operational ground segment. In particular, we provide an overview of the key parameters and products, which can be expected from CO2M and point to specific challenges for a future operational CO2 monitoring system.
In addition, the presentation addresses the activities within EUMETSAT in preparation for the potential CRISTAL and CIMR missions.