Sentinels 4 and 5: Meeting the Needs of the Copernicus Programme

The Sentinel-4 (S4) mission, together with Sentinel-5 and the Sentinel-5 Precursor missions, is part of the Copernicus Space Component dedicated to atmospheric composition. The primary objective of the S4 mission is to provide hourly tropospheric composition data in support of the air quality applications of the Copernicus Atmosphere Monitoring Services. The S4 products include key air quality parameters such as tropospheric amounts of NO₂, O₃, SO₂, HCHO, CHOCHO, and aerosols.

The S4 instrument is a geostationary Ultra-violet Visible Near infrared spectrometer (S4/UVN) designed to measure Earth radiance and solar irradiance. Key features of the S4/UVN instrument are the spectral range from 305 nm to 500 nm with a spectral resolution of 0.5 nm, and from 750 nm to 775 nm with a spectral resolution of 0.12 nm, in combination with a low polarization sensitivity and a high radiometric accuracy. The instrument observes Europe with a revisit time of one hour. The spatial sampling distance varies across the geographic coverage area and takes a value of 8 km at the reference location at 45°N.

Two S4/UVN instruments will be embarked on the geostationary Meteosat Third Generation-Sounder (MTG-S) platforms. The Flight Acceptance Review of the first MTG-S satellite is expected to take place in the first quarter of 2021. The expected S4 mission lifetime spans 15 years.

ESA is responsible for the development of the S4/UVN instrument, the Level-1b Prototype Processor (L1bPP), and the Level-2 Operational Processor (L2OP). Instrument and L1bPP are built by a consortium led by Airbus Defence and Space. The L2OP is developed by a consortium led by DRL. EUMETSAT will operate the instrument and will process the mission data up to Level-2.

An overview of the mission and the implementations status will be presented.

ECMWF has been entrusted to operate the Copernicus Atmosphere Monitoring Service (CAMS) on behalf of the European Commission until the end of 2020. CAMS provides continuous data and information on atmospheric composition.  The global service combines a state-of-the art transport and chemistry model with satellite data from various sensors to provide global daily analyses and 5-day forecasts of 3-dimensional fields of atmospheric composition including ozone, carbon monoxide, nitrogen dioxide, sulphur dioxide and aerosols. More details about CAMS can be found on http://www.copernicus-atmosphere.eu.

Satellite retrievals from various European platforms are crucial for providing good analyses with the CAMS system. In this talk we describe the CAMS data assimilation system for chemically reactive gases and show examples from recent near-real time analyses and from a reanalysis of atmospheric composition produced with the CAMS system.

Since 2006, the European contribution to operational meteorological observations from polar orbit has been provided by the Meteorological Operational (MetOp) satellites, which is the space segment of the EUMETSAT Polar System (EPS). As part of the next generation EUMETSAT Polar System (EPS-SG), the MetOp Second Generation (MetOp-SG) satellites will provide continuity and enhancement of these observations in the 2020 – 2040 timeframe. MetOp-SG will consists of two series of satellites (“Satellite A” and “Satellite B”), with three satellites of each series.

The Sentinel-5 instrument will be provided to the MetOp Second Generation Programme by the Copernicus Programme to fly on board the MetOp-SG Satellite A series.

The Sentinel-5 mission objective is to monitor the composition of the atmosphere for the Copernicus Atmosphere Service. This service will provide coherent information on atmospheric variables in support of European policies and for the benefit of European citizens. Services proposed will cover air quality applications, air quality protocol monitoring, and climate protocol monitoring. Sentinel-5 is focused on air quality and composition-climate interaction. it  will  provide  daily analysis  of the atmosphere at various space and time scales, key information on  long  range  transport  of  atmospheric  pollutants, initial and boundary conditions  for  air  quality  models and sustained monitoring of green-house gases,  aerosols  and  reactive  gases.  Its main data products are O₃, NO₂, SO₂, HCHO, CO, CH₄ and aerosol optical depth.

The Sentinel-5 project will consist of a wide field high resolution imaging spectrometer covering Ultra-Violet, Visible, Near InfraRed and Short-Wave InfraRed spectral bands (270 – 2385 nm), together with the ground processor prototype. The concept relies on the integration of 5 spectrometers in push-broom configuration, covering a swath of approximately 2670 km. The instrument provides a ground resolution of 7.5 km at Nadir with a spectral resolution in the range 0.25 – 1 nm, depending on the spectral band.

This paper will present the Sentinel-5 instrument key design features and predicted performance, as well as an overview of associated key technology developments.

In the frame of the European Copernicus programme, two series of satellites are dedicated to the monitoring of atmospheric parameters: Sentinel-4 will focus on tropospheric constituents with relevance for European air quality with hourly temporal resolution; Sentinel-5 will observe atmospheric composition on a daily basis with full global coverage. The latter will have a precursor mission Sentinel-5p carrying a slightly simplified instrument.

The purpose of the Sentinel-5 mission is to provide long-term (2022-2040) global coverage of data on atmospheric composition. These will address the information needs of Copernicus services related to air quality, climate forcing and stratospheric ozone / surface UV irradiation.

The Sentinel-5 mission will be accomplished by flying spectrometers in the UV – visible – near infrared – short-wave infrared spectral regions (UVNS) on Eumetsat’s Metop-SG series of satellites, and utilising the relevant data from three other instruments on the same platforms, namely the infrared sounder IASI-NG, the multi-spectral imager Metimage and the polarisation imager 3MI.

The UVNS instrument will observe spectral features suitable for retrieval of O3, NO2, SO2, HCHO, CHOCHO, BrO, OClO and surface UV irradiation in the range 270-500nm, H2O and cloud in the range 685-773 nm, CH4 between 1590-1675 as well as 2305-2385 nm, and CO and H2O in the latter band. Aerosol information will be available in all spectral bands, in particular also at 755-773 nm. With a swath width of 2600 km, global coverage will be reached within a day at a spatial resolution of 7 km at nadir (except stratospheric ozone: ~50km). Spectral resolution will be between 0.25 and 1.0 nm.

The observation requirements at Level 1b have been consolidated. The instrument is currently in the detailed design phase and undergoing the preliminary design review.

The operational Level 2 data products have been defined. Accuracy requirements have been refined. The Level 2 processor prototype activity is to be started soon. EUMETSAT will be responsible for the operational processing and dissemination of the UVNS data products.

This paper will provide an overview of the main characteristics and status of the Sentinel-5 mission.

The Sentinel-4 (S4) mission focuses on monitoring of trace gas column densities and aerosols over Europe at high spatial resolution with an hourly revisit time, thereby covering the diurnal variation of atmospheric constituents.

In this article we present the Level 2 (L2) products being developed in the framework of the ESA S4 L2 project: O₃ total and tropospheric column, NO₂ total and tropospheric column, SO₂, HCHO, CHOCHO tropospheric columns, aerosol and cloud properties as well as surface reflectance.

The S4 L2 work comprises the development of bread-boarding algorithms, independent verification algorithms, prototype processors and ultimately the operational S4 L2 processors for the generation of state-of-science operational data products.