The Copernicus Sentinel-5 Precursor (Sentinel-5P or S5P) satellite mission is one of the European Space Agency's (ESA) new mission family - Sentinels, and it is a joint initiative between the Kingdom of the Netherlands and the ESA. The sole payload on Sentinel-5P is the TROPOspheric Monitoring Instrument (TROPOMI), which is a nadir-viewing 108 degree Field-of-View push-broom grating hyperspectral spectrometer, covering the wavelength of ultraviolet-visible (UV-VIS, 270nm to 495nm), near infrared (NIR, 675nm to 775nm), and shortwave infrared (SWIR, 2305nm-2385nm). Sentinel-5P is the first of the Atmospheric Composition Sentinels and provides measurements of ozone, NO2, SO2, CH4, CO, formaldehyde, aerosols and clouds at high spatial, temporal and spectral resolutions. Spatial resolution is 5.5 km along-track and 3.5 km across-track at nadir. S5P is in a sun-synchronous orbit with an ascending node of ~13:30 which provides daily global coverage of the sun-lit Earth. Data are archived in enhanced netCDF-4 format. Beginning August 6th in 2019, S5P implemented along-track high spatial resolution (~5.5km at nadir). The near-real-time (NRT) data are generally available within three hours of measurement as required by the Land Atmosphere NRT Capability Earth Observing System (LANCE). Data granules are in five-minute intervals of an orbit, rather than a full orbit as provided for the standard products. NRT data are only archived for five days and not considered to be science-quality data. The data are intended for rapid turnaround assessments, for rigorous scientific analyses users should use the standard Version 3 product.

The TROPOMI retrieval of total and tropospheric NO2, is based on the DOMINO approach, a DOAS retrieval, a pre-calculated air-mass factor (AMF) look-up table, and a data assimilation/chemistry transport model for the separation of the stratospheric and tropospheric contributions to the NO2 column. It also includes many retrieval developments of the European Quality Assurance for Essential Climate Variables (QA4ECV) project. The Version 3 algorithm uses a new AMF lookup table based on Monki calculations (Monte-Carlo radiative transfer model with full sphericity and polarization). This AMF lookup table is used both in NRT and OFFL processing. Version 3 also: fixes the monotonic relationship between O2–O2 cloud pressure and O2-O2 cloud height; Adds additional features for better error characterization and additional lower-troposphere column results (useful for emission inversions). The additional variables in Version 3 increase the output file size by 30 MB (5%).