SARCalNet is an initiative of the SAR subgroup of the Working Group on Calibration and Validation (WGCV) of the Committee on Earth Observation Satellites (CEOS). Development of SARCalNet began in 2020, based upon a longstanding and existing target database of calibration targets contributed to this same group. When fully implemented, SARCalNet will provide a pre-defined set of information about SAR calibration targets, both natural and artificial, to facilitate joint calibration and performance evaluations between sensors as well as post-launch Cal/Val of any operating SAR sensor data operating at typical SAR frequencies and polarizations. When possible, SARCalNet will also provide access to the calibration data sets that were used to either calibrate or monitor calibration and performance of specific sensors.

The Copernicus Sentinel-1 Next Generation (S-1 NG) mission will ensure the continuity of C-band Synthetic Aperture Radar (SAR) data for the next decade, and broaden the spectrum of potential applications and services of the current Sentinel-1 mission by means of advanced capabilities and improved performance. DLR, within the consortium led by TAS-I, has supported both the Phase 0 and the Phase A/B1 of the S-1 NG mission study, funded by the ESA. The activity focused on the definition of the mission concept and of the SAR instrument architecture. A description of the performed analysis and its main outcomes is reported.

Measuring the Doppler Centroid Anomaly (DCA) of Single Look Complex (SLC) SAR data is a powerful resource to estimate Ocean Surface Radial Velocity (OCN-RVL). The Sentinel-1 Ocean Surface Radial Velocity (S-1 OCN RVL) product derived from Interferometric Wide Swath (IW) Terrain Observation with Progressive Scan (TOPS) mode data was designed to increase both accuracy and resolution compared to the previously available ENVISAT-ASAR product. However, while theoretically better, the S-1 OCN RVL products available on the ESA Copernicus open access hub in practice have been plagued by strong processing artifacts manifesting as discontinuities within sub-swaths and bursts of the IW data. Moreover, the available S-1 OCN RVL products are also uncalibrated due to obvious non-zero velocities over land areas. Simon Fraser University (SFU) is working with the European Space Agency (ESA) to improve the ocean surface velocity estimation from Sentinel-1 IW TOPS SLC data. We propose a novel algorithm for S-1 IW TOPS SLC based Dopler Centroid Anomaly data that robustly exploits the continuity constraints for the Doppler signature surface across bursts and sub-swaths to generate a smooth and enhanced Ocean Surface Radial Velocity product. To assess the validity of our approach we perform a cross comparison with ocean surface radial velocity products derived from RADARSAT-2 Moving Object Detection Experiment (MODEX-1). A total of twelve co-incident acquisitions for Sentinel-1 IW TOPS and RADARSAT-2 Modex-1 mode at six different sites across the world were collected for this purpose. Here, we present a preliminary result for a data collection over Bay of Fundy on 6th July 2020. Our proposed method produces a continuous ocean radial velocity map that is both free of discontinuities and quantitatively agrees more closely with the simultaneous corresponding RS-2 ATI and DCA based maps compared to the existing S-1 OCN RVL product.

This paper presents an overview of the planned Copernicus Sentinel-1 Next Generation (NG) mission, which will provide enhanced C-band data continuity through the next decade (2030s) in support of operational Copernicus services that are routinely using Sentinel-1 data. In this context, we consider novel imaging capabilities in view of addressing challenging mission requirements, and existing and evolving applications. The recently completed Phase A/B1 studies focused on the definition of novel SAR system concepts and the related analysis of key SAR performance parameters in view of achieving the envisaged performance enhancements. As part of the studies, pre-development activities for critical SAR technologies were implemented to ensure the required technology readiness. The studies concluded that the use of phased array antenna systems is the most suitable approach for the implementation of the Sentinel-1NG mission. The planar SAR antenna concept would enable the implementation of a multi-channel High Resolution Wide Swath (HRWS) SAR system using ScanSAR modes exploiting digital beamforming techniques, such as Scan On Receive (SCORE) and Multiple Azimuth Phase Center System (MAPS). In addition, the multi-azimuth channel HRWS concept would provide an Along-Track Interferometry (ATI) capability for an improved estimation of the radial velocity of ocean surface currents and ocean-going vessels. In addition, the Phase A/B1 studies comprised the analysis of potential SAR concepts regarding their performance characteristics in view of supporting the planned ESA Earth Explorer bistatic Harmony SAR mission.

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.

This paper provides an overview of the Copernicus L-band SAR mission referred to as ROSE-L (Radar Observing System for Europe at L-band).In particular, the paper provides an overview of the ROSE-L spacecraft and focuses on the ROSE-L SAR instrument architecture, performance and critical technology developments.The current status of the instrument activities (project is in Phase C) will be presented, highlighting the main achievements and challenges.

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.

Monitoring ocean surface parameters plays an important role in assessing climate change as well as in disaster and ocean traffic management. Ocean surface radial velocity estimation using various SAR sensors has been successfully demonstrated in the past both with Along Track Interferometry (ATI) and Doppler Centroid Anomaly (DCA) techniques. Simon Fraser University (SFU) with the kind support of European Space Agency (ESA), German Space Agency (DLR) and Defence Research and Development Center (DRDC)-Ottawa have conducted a study to compare ATI and DCA techniques for RADARSAT-2 Moving Object Detection Experiment (RS-2 Modex-1) datasets; and then further to cross-analyze these results with other SAR sensor radial velocity products for the same test sites simultaneously (i.e. TerraSAR-X (TSX)/Tandem-X (TDX) ATI and Sentinel-1 DCA products). The study has been motivated by previously observed challenges faced in the DCA analyses for the Sentinel-1 Terrain Observation with Progressive Scan (TOPS) mode, manifesting as discontinuities within sub-swaths for the derived radial velocity; evaluating ATI as an alternative technique. Here, we are presenting ATI and DCA results for RS-2 Modex-1 ScanSAR data for one of the datasets collected over the Agulhas current. The ScanSAR datasets were focused into SLCs with a full aperture approach. ATI products were derived using conventional interferometric techniques for the fore and aft SLC channels. Corresponding DCA products were derived for a single SLC channel with a variant of Madsen‘s method using the same interferometric techniques for the original but de-whitened SLC channel and an appropriately azimuth shifted copy of this. The casting of both ATI and DCA into the same interferometric framework rendering both measurements as an interferometric phase simplifies a quantitative “apples to apples” comparison of sensitivity and noise levels for both techniques. For RS-2 Modex 1 ScanSAR data we were able to produce high resolution ATI ocean surface velocity maps of 160 m x 160 m spatial resolution (ground range), while to achieve DCA products with comparable phase noise levels required us to lower final resolution significantly to about 1.5 km x 1.5 km (ground range). Results were cross validated with Ocean Surface Current Analyses Real-time (OSCAR) data for the radial surface velocity and with historical AIS data for vessel velocities. The presented is a first sample of future detailed analysis results from coincident acquisitions for 14 different sites worldwide with RS-2 Modex-1, TSX/TDX ATI and S-1 TOPS mode to provide a fully quantitative suitability assessment of ATI and DCA method based on a comprehensive inter method and cross sensor comparison.

The Copernicus Sentinel-1 mission ensures continuity of C-band SAR observations for Europe. The routine operations of the constellation are on-going and performed at full mission capacity. The mission is characterized by large-scale and repetitive observations, systematic production and 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. The paper addresses the mission status, the Sentinel-1 observation scenario, the impact on the COVID-19 crisis, and an overview on the recent mission performance aspects. It also presents the mission perspective for the years to come, in particular preliminary information on the new concept of a Sentinel-1 satellite in stand-by in orbit. In a second part, the paper addresses the improvements in system robustness and performance for the Sentinel-1C/-1D units. 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.

This paper provides an overview of the Copernicus L-band SAR mission referred to as ROSE-L (Radar Observation System for Europe at L-band), which ESA has started to implement (currently in Phase B2). In particular, we discuss the ROSE-L system and instrument design focusing on the envisaged SAR modes and their key performance parameters, and critical novel technology developments. Furthermore, we outline the approach for the implementation of the split-spectrum technique at SAR instrument level, which is required for the Ionosphere phase correction to ensure high-quality SAR interferometry data.

SAR Mission developers are facing several challenges to meet their requirements such as the choice of frequencies when it is not multi-frequencies requirements, trade-off between conflicting requirements, architecture that can meet the INSAR requirements and with the new development of micro-SAR, the choice between fast implementation of low-cost short life SAR versus slow implementation of expensive long-life SAR. This paper provides an overview and explains those challenges considering the environment context. It serves as an introduction to the other papers in the session.

ROSE-L (Radar Observing System for Europe) is a future L-band SAR system developed in the frame of the ESA Copernicus Program. It will consist of two monostatic satellites in constellation. “ROSE-L Tandem” is a concept to extend this system by a third satellite. This third satellite will fly in close formation with one of the two monostatic ones to create a bi-static, single-pass SAR interferometer. The main applications of the system are tomographic observations of forest and ice as well as the generation of a global Digital Elevation Model (DEM). A joint DLR-ESA study was conducted to determine the technical impact on the ROSE-L satellite design. This paper describes the necessary add-ons for such a bistatic extension. Starting from high-level requirements for tomography and DEM generation, additional system requirements are derived, a basic observation scenario with the needed formations and amount of fuel is introduced and the necessity and feasibility of phase synchronization via a dedicated RF-sync link between the satellites is assessed.

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.

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.

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.

This paper provides an overview of the Copernicus SAR missions, namely Sentinel-1, ROSE-L and Sentinel-1 Next Generation (NG). In particular, we discuss the Sentinel-1 SAR performance and enabling techniques for SAR interferometry (InSAR). Further, we describe the key characteristics of the ROSE-L SAR instrument. For the Sentinel-1 NG mission, we discuss potential SAR performance enhancements and novel imaging capabilities. In addition, we present different SAR system concepts and results of the preliminary mission analysis, addressing coverage and revisit time. Finally, we discuss the ESA Earth Explorer BIOMASS P-band SAR mission and its SAR instrument.

We present a new perspective on Earth's land surface, providing a normalised microwave backscatter map from spaceborne Synthetic Aperture Radar (SAR) observations. The Sentinel-1 Global Backscatter Model (S1GBM) describes Earth for the period 2016-17 by the mean C-band radar cross section in VV- and VH-polarisation at a 10 m sampling. We processed 0.5 million Sentinel-1 scenes totalling 1.1 PB and performed semi-automatic quality curation and backscatter harmonisation related to orbit geometry effects. The overall mosaic quality excels (the few) existing datasets, with minimised imprinting from orbit discontinuities and successful angle normalisation in large parts of the world. Regions covered by only one or two Sentinel-1 orbits remain challenging, owing to insufficient angular variation and not yet perfect sub-swath thermal noise correction. Supporting the design and verification of upcoming radar sensors, the obtained S1GBM data potentially also serve land cover classification and determination of vegetation and soil states. Here, we demonstrate, as an example of its potential use, the mapping of permanent water bodies and evaluate against the Global Surface Water benchmark.

The Copernicus Sentinel-1 mission is implemented through a constellation of two C-band SAR satellites in near-polar, dawn-dusk orbit at 693km altitude, to provide data continuity of previous ERS and ENVISAT missions. Following Sentinel-1A and Sentinel-1B successful launches in 2014 and 2016, Sentinel-1C and -1D models are in development and will provide operational continuity to the mission. This paper addresses the improvements in system robustness and performance, the Automatic Identification System (AIS) instrument to augment the SAR payload data for ship marine traffic applications, and 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.