European UVN satellite missions deliver global measurements for air quality and climate applications from Low Earth Orbit (LEO) satellites since over two decades. Currently we have in the morning data from GOME-2 on the three MetOp satellites and in the early afternoon data from OMI/Aura and TROPOMI/Sentinel-5 Precursor. The temporal barrier imposed by LEO satellites, providing only one daily observation, can be broken using Geostationary Equatorial Orbit (GEO) satellites. The Sentinel-4 (S4) mission on-board the MTG-S GEO satellite will focus on monitoring of trace gas column densities and aerosols over Europe with an hourly revisit time, thereby covering the diurnal variation of atmospheric constituents. We present the algorithm, verification, and processor work being performed as part of the ESA Sentinel-4 Level 2 (S4-L2) project responsible for developing the operational S4-L2 products: O3 total and tropospheric column, NO2 total and tropospheric column, SO2, HCHO, CHOCHO columns, aerosol and cloud properties as well as surface reflectance.

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 is an imaging spectrometer instruments covering wide spectral bands in the ultraviolet and visible wavelength range (305-500nm) and near infrared wavelength range (750-775 nm). S4 will observe key air quality parameters with a pronounced temporal variability by measuring NO2, O3, SO2, HCHO, CHOCHO, and aerosols over Europe with an hourly revisit time. 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. This paper will address the development status of the L1b Operational Processor (L1OPS) by EUMETSAT and the supporting L1b reference processor (L1RP) developed by ESA; In dedicated cases (e.g. CTI, Non-linearity signal loss, ...) the algorithms input from the S4 Industrial Prime have been used. The paper will also provide an overview of the status of the Level 2 processor developed by ESA for integration into the EUMETSAT MTG-S ground segment.

Sentinel-5 is an Earth Observation instrument to be flown on the Metop Second Generation (Metop-SG) satellites with the fundamental objective of monitoring atmospheric composition from polar orbit. The Sentinel-5 instrument consists of five spectrometers to measure the solar spectral radiance backscattered by the earth atmosphere in five bands within the UV (270nm) to SWIR (2385nm) spectral range. Data provided by Sentinel-5 will allow obtaining the distribution of important atmospheric constituents such as ozone, on a global daily basis and at a finer spatial resolution than its precursor instruments on the first generation of Metop satellites. The launch of the first Metop-SG satellite is foreseen for 2021. The Sentinel-5 instrument is being developed by Airbus DS under contract to the European Space Agency. The Sentinel-5 mission is part of the Space Component of the Copernicus programme, a joint initiative by ESA, EUMETSAT and the European Commission. The Preliminary Design Review (PDR) for the Sentinel-5 development was successfully completed in 2015. This paper provides a description of the Sentinel-5 instrument design and data calibration.