The Copernicus Programme is a joint European initiative developed by the European Commission (EC) and the European Space Agency (ESA) to provide accurate, up-to-date, and comprehensive Earth observation data for environmental monitoring, climate change analysis, disaster management, and security. The Copernicus program comprises a series of dedicated satellite missions i.e., the Sentinels spanning a wide range of the electromagnetic spectrum with different sensing techniques.Sentinel-1 [1] is the radar imaging component of Copernicus. It is a two-satellites constellation placed in the same orbit and spaced 180º apart. The Sentinels are providing systematically data to the Copernicus service component and scientific users.The Copernicus operational services are covering key operational applications tailored to support the definition and monitoring of European policies such as:–Observation of the marine environment and sea-ice monitoring–Surveillance of maritime transport zones–Land surface mapping, e.g., vegetation cover and surface deformation,–Polar environment monitoring (e.g., ice shelves and glaciers)–Climate Change–Emergency Response and ManagementThe Sentinel-1 first generation comprises four satellite units developed in two batches. The first two (A and B) have been already launched and two recurrent (C&D) ones planned for launch ensuring continuity of measurement throughout the 2020’s. Sentinel-1C and D will overlap with other Copernicus SAR mission in development like ROSE-L [2] and the Sentinel-1 Next Generation [3].In this paper we discuss the status and evolution of the Sentinel-1 first generation.

This paper addresses the planned Copernicus Sentinel-1 Next Generation (NG) mission, which will provide enhanced C-band data continuity novel imaging capabilities beyond the next decade (2030) in support of operational Copernicus services that are routinely using Sentinel-1 data. We discuss potential SAR system concepts and their launcher compatibility along with key SAR instrument design parameters and their envisaged performance enhancements.In this context, we consider novel imaging capabilities in view of addressing challenging mission requirements, and existing and evolving applications.Furthermore, we consider modular and incremental observation concepts, involving NewSpace smallSat SAR constellations to complement Sentinel-1 NG C-band SAR acquisitions. In addition, we discuss the planned embarkation of the Automatic Identification System (AIS) payload in support of maritime surveillance.

The Sentinel-1 mission represented an unprecedented source of SAR imagery, on which Copernicus and other providers conveniently leveraged to build a continuously expanding catalogue of operational services. In the next two decades, the family of SAR instruments under the Copernicus umbrella will feature additional wavelength diversity, with the ROSE-L mission providing operational illumination in L-band, and will introduce with the next generation Sentinel-1 (Sentinel-1 NG) a significant step ahead in terms of imaging quality and coverage performance, while carefully guaranteeing data and service continuity with the current generation. The massive volumes of data in space, time, polarizations and frequencies are expected on one hand to significantly enhance the applications and services already in place and on the other to open the way to new mapping and monitoring solutions in land, water and cryosphere domains. This paper will address such new perspectives.

The Copernicus Sentinel-1 mission ensures continuity of C-band SAR observations for Europe. The mission is characterized by large-scale and repetitive observations, systematic production and a free and open data policy. Sentinel-1 data are routinely used by Copernicus and many operational services, as well as in the scientific and commercial domain. Sentinel-1 is based on a constellation of two SAR satellites, Sentinel-1A and Sentinel-1B that have been launched from Kourou on a Soyuz rocket on 3rd April 2014 and 25th April 2016 respectively. At the time of finalising this paper (31 May 2022), the operations of Sentinel-1B have been interrupted due to an anomaly on the satellite power sub-system, that occurred on 23 December 2021. This is a major anomaly that will probably result in a permanent loss of the satellite. Detailed investigations are close to completion, and unfortunately, all attempts to bring back the faulty power unit to nominal operations have failed. The paper provides some details on the Sentinel-1B power anomaly and on the mitigation actions performed at mission level to compensate, to some extent, the lack of Sentinel-1B data.

This paper addresses the planned Copernicus Sentinel-1 Next Generation (NG) mission, which will provide enhanced C-band data continuity beyond the next decade (2030) in support of operational Copernicus services that are routinely using Sentinel-1 data. In particular, it discusses the envisaged SAR performance enhancements and novel imaging capabilities. It focusses on potential SAR system concepts comprising the definition of SAR instrument designs and the analysis of their performance, the launcher compatibility, and pre-development activities for critical technologies. In addition, it discusses the planned embarkation of the Automated Identification System (AIS) payload and the novel VHF Data Exchange System (VDES) in support of maritime surveillance. The Sentinel-1 Next Generation will consider modular and incremental observation concepts, involving NewSpace smallSat SAR constellations to complement Sentinel-1 NG C-band SAR acquisitions.

This paper addresses the planned Copernicus Sentinel-1 Next Generation (NG) mission, which will provide enhanced C-band data continuity beyond the next decade (2030) in support of operational Copernicus services that are routinely using Sentinel-1 data. In particular, we discuss potential SAR and SAR interferometry (InSAR) performance enhancements and novel imaging capabilities for vessel detection and velocity estimation for vessels and ocean surface currents, respectively. In addition, we present results of the preliminary mission analysis, addressing the coverage, revisit time, and repeat-orbit interval for SAR interferometry. Further, we discuss different SAR system concepts, which were considered during the feasibility study phase.

In this paper we provide an overview of the evolution of the Copernicus SAR Space Component: the Sentinel-1 Space Segment, including the Spacecraft development status, the ROSE- L mission development status and the approach for the development of Sentinel-1 Next Generation mission. In particular, we discuss the objectives and implementation approaches and related challenges for the evolution.

In the last ten years, ESA's Earth Observation (EO) program has been based on three main pillars, i.e. Copernicus, Meteorology and Earth Science Explorer and on some crosscutting activities covering international cooperation and preservation of historical data. In the framework of the Copernicus program, the Sentinel-1 mission is the workhorse for acquiring systematically and providing routinely a large volume of C-band SAR data to the Copernicus services and the global scientific and commercial user community. As part of the Copernicus expansion, ESA completed the study phase for an L-band SAR mission (ROSE-L) last October 2019 and issued the corresponding Request for Proposal for the development of two spacecraft. On the other hand, the availability of high-resolution X-band data is ensured through national European SAR missions, such as TerraSAR-X, Cosmo-SkyMed and PAZ, which are referred to as Copernicus Contributing Missions. L-band SAR data are required for applications, such as surface deformation mapping, monitoring of cryosphere dynamics, sea-ice classification and land cover mapping, among others. As such, L-band data provide complementary information to C- and X-band data. Besides ESA's ROSE-L, Germany is perusing the implementation of the proposed Tandem-L mission, at national level. Recently, disruptive NewSpace smallSat SAR companies have emerged on the EO market. This has triggered discussions on whether or to what extent smallSats can eventually replace or complement large institutional SAR missions. In this paper we provide the overview of the evolution of the Copernicus SAR Space Component: the Sentinel-1 Space Segment and the Spacecraft development status, the ROSE-L development approach and we also discuss the challenges for the evolution. its objectives and implementation, the systematic data acquisition strategy including coverage and revisit frequency, and the end-to-end SAR performance

In the last ten years, ESA's Earth Observation (EO) program has been based on three main pillars, i.e. Copernicus, Meteorology and Earth Science Explorer and on some crosscutting activities covering international cooperation and preservation of historical data.In the framework of the Copernicus program, the Sentinel-1 mission is the workhorse for acquiring systematically and providing routinely a large volume of C-band SAR data to the Copernicus services and the global scientific and commercial user community.On the other hand, the availability of high-resolution X-band data is ensured through national European SAR missions, such as TerraSAR-X, Cosmo-SkyMed and Paz, which are referred to as Copernicus Contributing Missions.L-band SAR data are required for applications, such as surface deformation mapping, monitoring of cryosphere dynamics, sea-ice classification and land cover mapping, among others. As such, L-band data provide complementary information to C- and X-band data.As part of the Copernicus expansion, ESA has initiated the study phase for an L-band SAR mission (ROSE-L). At national level, Germany is perusing the implementation of the proposed Tandem-L mission.Recently, disruptive NewSpace smallSat SAR companies have emerged on the EO market. This has triggered discussions on whether or to what extent smallSats can eventually replace or complement large institutional SAR missions.In this paper we provide the overview of the evolution of the Copernicus Sentinel-1 Space Segment and the Spacecraft development status and we also discuss the challenges for the evolution of the Copernicus SAR Space Component, based upon a review of the Sentinel-1 mission, i.e. its objectives and implementation, the systematic data acquisition strategy including coverage and revisit frequency, and the end-to-end SAR performance.

The paper provides the overview of the evolution of the Copernicus Sentinel-l Space Segment and the Spacecraft development status. Following the successful launch and in-orbit Commissioning of Sentinel-1A in 2014 and Sentinel-1B in 2016, ESA is currently developing the Sentinel-1C and -1D models. The paper addresses the improvements in system robustness and performance. In addition, it discusses the main characteristics of the Automatic Identification System (AIS) instrument to augment the SAR payload data for ship marine traffic applications and the Optical Communication Payload (OCP) for payload data downlink via inter-satellite laser-link with the European Data Relay System (EDRS). Finally, it will address the novel solutions to make Sentinel-1C and Sentinel-1D design fully compliant with the latest Space Debris code-of-conduct and the required casualty risks at re-entry.

Sentinel-1A and Sentinel-1B have been launched from Kourou on a Soyuz rocket on 3rd April 2014 and 25 April 2016 respectively. Data opening was made early October 2014 for Sentinel-1A and end-September 2016 for Sentinel-1B. At the time of writing this paper, the so-called mission operational qualification phase is on-going, with a gradual increase of the capacity of the overall system, including the use of the European Data Relay Satellite System (EDRS). The Full Operation Capacity (FOC) of the mission will be reached indicatively by Q2 2017. The paper provides high-level information on the on-going mission operations. It describes at high level the system operations, incl. ground segment operational activities, as well as some user data access statistics. It presents few examples of mission results achieved since the operations of Sentinel-1A, in some key application domains.

The paper provides an overview of the evolution of the Copernicus Sentinel-1 mission, which is part of the Copernicus European Earth Observation program. Following the successful launch and in-orbit Commissioning of Sentinel-1A in 2014 and Sentinel-1B in 2016, ESA is currently developing the Sentinel-1 C and D models. The paper addresses the expected improvements in system robustness and performance. In addition, it discusses the main characteristics of the Automatic Identification System (AIS) instrument to augment the SAR payload data for ship marine traffic applications and the Optical Communication Payload (OCP) for payload data downlink via inter-satellite laser-link with the European Data Relay System (EDRS). Finally, the design of Sentinel-1C and Sentinel-1D incorporates novel solutions that will make both satellites fully compliant with the latest Space Debris code-of-conduct and the required casualty risks at re-entry.

Sentinel-1A, the first component of the Copernicus Space Segment developed by the European Space Agency, was launched on 3 April 2014. It was commissioned in orbit during the following months leading to a In-Orbit Commissioning Review in September 2014. The launch of the identical Sentinel-1B is planned in April 2016, two years after Sentinel-1A with which will complete the Copernicus Sentinel-1 constellation. After launch, the LEOP Phase is expected to last three days where all subsystems and the SAR instrument will be checked. It will immediately be followed by the four-month Commissioning Phase that will include the in-orbit Calibration and Characterisation, and the verification of the satellite, in order to deliver a full functional and well performing satellite to the mission operations. This paper will present the LEOP and Commissioning activities already completed, and the status of Sentinel-1B Calibration, Characterisation and Verification activities of the Commissioning in place.

Sentinel-1A has been launched from Kourou on a Soyuz rocket on 3rd April 2014. The second satellite Sentinel-1B is planned to be launched first half of 2016. The In-Orbit Commissioning phase was completed on 23 September 2014, followed by the so-called operational qualification phase (ramp-up). This ramp-up operations phase is a phase during which the capacity of the overall system, including the ground segment operations, is progressively increased, together with the gradual release of the operationally qualified products. The ramp-up phase is being completed at the time of writing this paper (end May 2015); at this stage the routine operations are starting. The Full Operation Capacity (FOC) of the mission will be reached once the In-Orbit Commissioning phase of Sentinel-1B and the subsequent constellation operational qualification phase will have been completed, indicatively by end 2016. The paper provides high-level information on the ongoing mission operations, at the time of the ramp-up phase completion. It described at high level the system operations, incl. ground segment operational activities, as well as some user data access statistics. It presents few examples of mission results achieved during the first year of Sentinel-1A in orbit, in some key application domains.

The paper provides an overview of the Copernicus Sentinel-1 system capabilities and applications. In particular, the characteristics of the Sentinel-1 SAR imaging modes and their key performance parameters are described. In addition, the Sentinel-1 SAR interferometry (InSAR) capabilities, especially for TOPS InSAR and the strategy for maintaining the orbital baseline as well as the requirements for TOPS image co-registration are discussed.

The Copernicus Sentinel-1 Earth Radar Observatory, a mission funded by the European Union and developed by ESA, is a constellation of two C-band radar satellites. The satellites have been conceived to be a continuous and reliable source of C-band SAR imagery for operational applications such as mapping of global landmasses, coastal zones and monitoring of shipping routes. The Sentinel-1 satellites are built by an industrial consortium led by Thales Alenia Space Italia as Prime Contractor and with AIRBUS Defence and Space as SAR Instrument Contractor. The paper describes the general satellite architecture, AIT flow and the satellite key performances. It provides also an overview on the CSAR Instrument, its development status and prelaunch SAR performance prediction.

Sentinel-1A, the first component of the Copernicus Space Segment developed by the European Space Agency, has been launched 3 April 2014. The LEOP Phase is expected to last three days where all subsystems and the SAR instrument will be checked. It is immediately followed by the three-month Commissioning Phase that will include the in-orbit Calibration and Characterisation, and the verification of the satellite, in order to deliver a full functional and well performing satellite to the mission operations. This paper will present the LEOP and Commissioning activities in progress, and the status of Calibration, Characterisation and Verification activities of the Commissioning in place.

The paper provides an overview of the GMES Sentinel-1 system characteristics including the SAR imaging modes and their key performance parameters, the SAR interferometry capabilities, and the specifics of related attitude and orbit control modes (i.e., roll steering mode and zero-Doppler steering mode). Furthermore, the paper outlines the planned Sentinel-1 commissioning phase activities related to the in-orbit SAR system end-to-end performance verification and calibration.

This paper provides an overview of the main features of GMES SENTINEL-1 Satellite System, a C-band Synthetic Aperture Radar Satellite for Earth Observation. The main system requirements are presented as drivers for the design of satellite and operations. The paper will include a description of the satellite general architecture, the decomposition into modules and a description of all functional subsystems. In addition, the major design challenges, the most critical developments, the main performances and operational concepts are outlined.

The ESA Sentinels constitute the first series of operational satellites responding to the Earth Observation needs of the EU-ESA Global Monitoring for Environment and Security (GMES) programme. The GMES space component relies on existing and planned space assets as well as on new complementary developments by ESA. This paper describes the Sentinel-1 mission, an imaging synthetic aperture radar (SAR) satellite constellation at C-band. It provides an overview of the mission requirements, its applications and the technical concept for the system.

The paper describes the C-SAR instrument for the GMES Sentinel-1 mission. After a brief introduction of the Sentinel-1 instrument requirements a design description of the overall C-SAR instrument as well as of its major subsystems (i.e. the SAR Antenna Subsystem (SAS) and the SES Electronic Subsystem (SES)), is given. The paper concludes with an overview on the predicted instrument performance.

The TerraSAR-L system, currently in Phase B definition carried out by a European/Canadian consortium lead by EADS Astrium Ltd., provides ESA with its most powerful radar imaging programme to date. Key mission characteristics are a 5-year mission lifetime, global coverage from a 14-day repeat 635-km orbit, more than 20 minutes per orbit of SAR data acquisition in L-band, in both right-looking (nominal) and left-looking configurations, and a launch in late 2008. TerraSAR-L first mission priority is serving commercial applications focused on agriculture, forestry and marine applications. Joint products from TerraSAR-L and the German national programme TerraSAR-X use the complementary properties of the backscattering in L and X bands for high levels of classification performance necessary for crop monitoring, forest inventory and cartographic maps of different thematic content and scale. Scientific and institutional applications are defined focused on solid Earth monitoring relying on differential interferometry. L-band penetration of vegetation cover facilitates these applications also over vegetated surfaces. The high coherence of L-band assists the monitoring of ice sheet and glacier dynamics. Sea ice classification is supported with full polarimetric measurements. Large-scale land cover change detection, global forest biomass estimation, permafrost monitoring, wetland inventory, soil moisture retrieval and flood monitoring are also supported. A dedicated Wave Mode provides measurements of directional ocean surface wave spectra. Additionally for single-pass interferometry and generation of a global DEM, a complementary cartwheel system with different micro satellite constellations flying in close formation with TerraSAR-L has been investigated. The spacecraft is built around an active phased array antenna and provides full polarimetric capabilities, maximum bandwidth within the 85 MHz allocation for Earth observation in L-band, and repeat-pass ScanSAR interferometry. The platform is based on a novel Snapdragon configuration. The TerraSAR-L Ground Segment provides the operational link between the spacecraft, the TerraSAR Exploitation and Service Infrastructure and the users. A high-performance modular architecture is designed to fulfil the high requirements on throughput, quality and accessibility of data, as well as the reuse of existing infrastructure elements and the interoperability with other missions, especially with the companion TerraSAR-X Ground Segment

This paper presents the main characteristics of the advanced synthetic aperture radar (ASAR) instrument on board ENVISAT, ASAR products, the challenges in the ASAR calibration and product validation, the methodology used to perform the sensor performance monitoring and product calibration based on the special ASAR features and dedicated calibration sites and finally a summary on the product quality status will also be provided.

This paper presents the approach for the in-flight calibration of the ENVISAT-1 ASAR and the verification of the ground processing facility PF-ASAR during the commissioning phase. The philosophy presented is a logical progression from the experience gained during calibration of the ERS SARs. The ASAR has a comprehensive internal calibration loop, which is described distinctly from the external calibration and characterisation. The antenna patterns of the various beams have been fully measured during on-ground flight-model testing and have been used for initial performance predictions. In-flight characterisation of the main beams is performed over the South American rainforest. As for ERS, absolute gain calibration is achieved using three fixed and one transportable precision calibration transponders situated in the Netherlands. These transponders are also capable of recording the azimuth beam patterns and supporting the external characterisation mode of ASAR.