The Infra-Red Sounder (IRS) instrument is the primary payload of the Meteosat Third Generation Sounder satellite (MTG-S). The main objective of the MTG sounding mission is to enhance Numerical Weather Prediction (NWP) capabilities at regional and global scales, through the provision of Atmospheric Motion Vectors (AMV) with higher vertical resolution and frequent information on temperature and water vapour profiles. Additionally, layer-by-layer analysis of the atmosphere will offer greater insight into its complex chemical composition and support atmospheric gas tracing applications, such as air quality and pollution monitoring. The MTG-S satellite and the IRS instrument are being developed under the responsibility of OHB System (Germany), with TAS (France) as MTG’s mission prime contractor and ESA/EUMETSAT as end customers.

The IRS will be the first European hyperspectral sounding instrument in geostationary orbit and will be capable of scanning a full Earth’s disc (over Europe and Africa) every hour with a spatial resolution of 4 x 4 km² at nadir, covering roughly 640 x 640 km² per stare every 10 seconds. The design of the instrument is based on an imaging Fourier Transform Infrared Spectrometer (FTIR) and will deliver hyperspectral sounding information in two infrared bands: LWIR (700 - 1210 cm-1) and MWIR (1600 - 2175 cm-1), with a spectral channel interval of 0.625 cm-1. The instrument incorporates two IR detectors of 160 x 160 pixels each, which leads to a total of 51,200 delivered interferograms per stare. The recorded interferograms will undergo pre-correction and data compression before being sent to ground. Once the data is received on-ground, the Level 1 ground processing algorithms will convert the measured interferograms into radiometrically and spectrally corrected spectra.

Applications benefiting from the Level 1 science data provided by the IRS instrument are manifold and await to be fully explored. For example, by delivering frequent four-dimensional information on humidity, temperature, and wind profiles, the IRS will significantly enhance regional and global NWP, thus improving early detection (and warning) of rapidly developing atmospheric instability like severe convective storms. The spectral range of the IRS will also allow to estimate and monitor the concentration of atmospheric trace gases like ozone and carbon monoxide, leading to enhanced information for air pollution forecasting. Moreover, through information on the composition and density of volcanic ash clouds, ash fallout prediction models will be refined.

The first flight model of the instrument (IRS PFM) is currently in its AIT phase that will culminate with an optical performance test in vacuum starting in Q2 2022. The instrument verification follows a proto-flight approach, including tests successfully carried out on several development models (i.e. STM, Flat-EM and Core Spectrometer) and the achievement of the final qualification on the PFM. The first MTG-S satellite launch is planned by end 2023/early 2024.

This paper will provide a detailed overview of:
• the objectives and capabilities of the MTG sounding mission
• the design and development status of the IRS instrument
• the Level 1 science data provided by the IRS instrument and its expected performance

The Copernicus missions Sentinel-4 (S4) and Sentinel-5 (S5) will carry out atmospheric composition observations on an operational long-term basis to serve the needs of the Copernicus Atmosphere Monitoring Service (CAMS) and the Copernicus Climate Change Service (C3S).

Building on the heritage from instruments such as GOME, SCIAMACHY, GOME-2, and OMI, S4 and S5 are imaging spectrometer instruments covering wide spectral bands in the UV, visible, near infrared, and (S5 only) the short wave infrared domain. S4 will monitor key air quality parameters with a pronounced temporal variability by observing NO2, O3, SO2, HCHO, CHOCHO, and aerosols over Europe with an hourly revisit time. In addition to the S4 target species, S5 will observe CO, CH4, and stratospheric O3. S5 will provide composition data with global coverage on a daily basis serving climate, air quality, and ozone/surface UV applications.

A series of two S4 instruments will be embarked on the geostationary Meteosat Third Generation-Sounder (MTG-S) satellites. S4 establishes the European component of a constellation of geostationary instruments with a strong air quality focus, together with the NASA mission TEMPO and the Korean mission GEMS.

The presentation will provide an overview of the S4 and S5 missions and the related science and applications.

EUMETSAT has provided the user community with more than three decades worth of satellite data, starting with the geostationary missions of the Meteosat First Generation, and since 2002 with the Meteosat Second Generation (MSG) series satellites.

EUMETSAT is currently developing the future geostationary program, the Meteosat Third Generation (MTG). The MTG system will host a more advanced 16-channel VIS/IR Flexible Combined Imager (FCI) as well as a Lightning Imager (LI) on its geostationary imaging platform (MTG-I), whereas the sounding platform (MTG-S) will host the MTG InfraRed Sounder (IRS) and the Copernicus Sentinel-4 ultraviolet/near-infrared (UVN) sounding missions. The launch of the first two satellites MTG-I1 and MTG-S1 hosting the imaging and sounding instruments is foreseen in late 2022 and in early 2024, respectively.

The presentation will give an overview of the MTG system design, the system architecture, its observation missions, and some of the main improvements over Meteosat Second Generation (MSG) in terms of new missions and expected product performance.

More specifically, a brief status update will be provided on the Telemetry, Tracking & Commanding Facility (TTCF) and the Mission Operations Facility (MOF). Regarding data processing, the presentation will discuss the status up to launch and commissioning of the Instrument Data Processing Facility for both MTG-I and MTG-S (IDPF-I and IDPF-S, respectively) which process the mission data from Level 0 to Level 1, as well as the Level-2 Processing Facility (L2PF). The L2PF is also split in MTG-I and MTG-S parts in functionalities and deliveries.

Regarding the MTG system overall activities, the operations preparations are well underway and the so called system freeze is expected in June 2022. The stability of the LEOP Ground Segment has already been demonstrated, with solid operational knowledge of the LEOP contractor.

System Integration Verification Validation (IVV) are well underway, with System Version V1.0 completed. Operational Scenario Validation has started in December 2021. As a highlight of the system validation activities, it can be mentioned the successful full system end-to-end test (4 runs of 41 hours) involving Satellite Application Facilities (SAF) which was completed already in July 2021.