The SCA instrument is a C-band wind scatterometer, which forms part of the EUMETSAT Polar System Second Generation (EPS-SG) mission. Fully space qualified in December 2022, in January 2023 it has been delivered for integration on one of the two MetOp-SG satellites. The paper presents an overview on the SCA Instrument space qualification results, the thereof predicted in-orbit mission performance and ongoing satellite test results.

This paper describes the definition, manufacturing and testing of the antenna breadboard demonstrator intended for the MetOp-SG SCAtterometer Instrument. The breadboard is a dual polarization array antenna composed of separate radiating panels for H and V polarizations, respectively. The panels with the supporting structures are undergoing a test campaign that comprises thermal cycling, vibration, thermoelastic and RF tests.

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

ESA is developing the Sentinel-1 European Radar Observatory, a constellation of two polar orbiting satellites that provide C-band SAR products for operational applications. The Sentinel-1 mission has been designed to comply with stringent radiometric stability and accuracy requirements. To ensure these requirements are achieved, the mission relies on an efficient and robust strategy for in-flight calibration. This consists of (a) pulse-coded Internal Calibration pulses that achieve leakage cancellation and robust estimation and separation of different types of leakage signals and (b) an Antenna Model that estimates very accurately the antenna radiation patterns based on the instrument configuration and pre-launch measurements. Usage of calibration data and the Antenna Model supports maintaining the long-term absolute radiometric accuracy and enables a graceful degradation of performance in the event of unrecoverable failures of individual transmit/receive modules. During the commissioning phase, calibration also relies on precise external calibration transponders and measurements with notch patterns over the rainforest and transponders for accurate pointing determination.

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. In contrast to SAR systems already existing in C-band like ASAR/ENVISAT or RADARSAT-2, high demands on the radiometric stability and accuracy are made for Sentinel-1. The mission depends on the method of calibrating the entire Sentinel-1 system in an efficient way. This paper describes the strategy and provides a plan of all activities required for in-flight calibration of Sentinel-1.

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. In contrast to SAR systems already existing in C-band like ASAR/ENVISAT or RADARSAT-2, high demands on the radiometric stability and accuracy are made for Sentinel-1. The mission depends on the method of calibrating the entire Sentinel-1 system in an efficient way. This paper describes the strategy and provides a plan of all activities required for in-flight calibration of Sentinel-1.

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. In contrast to SAR systems already existing in C-band like ASAR/ENVISAT or RADARSAT-2, high demands on the radiometric accuracy are made for Sentinel-1. This paper provides an overview of the main features of GMES Sentinel-1 System, a C-band Synthetic Aperture Radar Observatory for Earth Observation. The main system requirements are presented as drivers for the design of system, satellite and operations. The major design challenges as well as the most critical development aspects are outlined, mainly focusing on the Space Segment components.

The Sentinel-1 satellite carries on board a C-band Synthetic Aperture Radar built from 560 active radiating waveguide arrays. The 280 horizontally polarised waveguide arrays and the 280 vertically polarised waveguide arrays are arranged as dual-polarised pairs in suficient proximity to allow for grating lobe free electronic steering of the S-1 SAR antenna in the elevation plane. Each waveguide array is connected to a transmit-receive module (TRM) feeding or receiving signals via their common antenna port. The SAR instrument has an internal RF Characterisation mode exploiting the phase shifting capabilities of the TRMs, that allows monitoring of the individual excitations of each waveguide array in both Tx and Rx. The present paper reports on a novel Pulse Coded Calibration (PCC) scheme, that whilst maintaining some salient features of the Hadamard based PCC, also allows to optimise the antenna active return losses. A low active return loss is beneficial to minimise the RF stress of the TRM output circuitry and improves the accuracy of the RF Characterisation itself. (4 pages)

An efficient and highly accurate network model for analysing and synthesising large but finite slotted waveguides (SWGs) is presented. The network model is tailored for arrays of linear end-fed narrow wall inclined slots. The network model accurately predicts, as function of frequency, the key electrical antenna parameters such as antenna-radiation pattern (beamwidth, inner and spurious sidelobes down to the -40 dB level, main beam squint), waveguide loss, power dissipated in the load and return loss. The network model explicitly takes mechanical tolerances into account. The model is based upon S-parameter measurements of a number of test-SWGs. The network model has been proven to be scalable from X-band to S-band waveguides and can be extrapolated to slot parameters far beyond the range of the slots of the test-SWGs. The comparison between predicted and measured results has shown that the network model is highly accurate, providing a significant improvement over full wave commercial tools in terms of prediction of the antenna parameters of interest as well as in computational speed.

The EU-ESA Global Monitoring for Environment and Security (GMES) program calls for a number of different Satellites called Sentinels to be launched within the next 6 years. The first among these are the two Sentinel-1 polar orbiting sun-synchronous satellites which each carries onboard a C-band Synthetic Aperture Radar (C-SAR).

In the framework of the EU/ESA co-funded Copernicus program, ESA is undertaking the development of a series of five Sentinel missions with the objective to provide routinely Earth observation data for the implementation of operational Copernicus and national services. The Copernicus services comprise mapping and forecasting activities for Land, Marine, Atmosphere, Emergency, Security, and Climate Change monitoring. 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 for TOPS image burst-synchronization are discussed.

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 in-orbit calibration aspects for the Sentinel-1 mission. It provides an overview of the calibration requirements, and a potential technical concept for the implementation.