TROPOMI: Solar backscatter satellite instrument for air quality and climate

TROPOMI is a nadir-viewing grating-based imaging spectrograph in the line of OMI and SCIAMACHY. TROPOMI is part of the ESA Candidate Core Explorer Mission proposal TRAQ and also of the CAMEO satellite proposed for the US NRC decadal study. A TROPOMI-like instrument is part of the ESA/EU Sentinel 4&5 pre-phase A studies. TROPOMI covers the OMI wavelengths of 270-490 nm to measure O3, NO2, HCHO, SO2 and aerosols and adds a NIR channel and a SWIR module. The NIR-channel (710-775 nm) is used for improved cloud detection and aerosol height distribution. The SWIR module (2305 - 2385 nm) measures CO and CH4 and forms a separate module because of its thermal requirements. TROPOMI is a non-scanning instrument with an OMI-like telescope but optimized to have smaller ground pixels (10 × 10 km²) and sufficient signal-to-noise for dark scenes (albedo 2 %). TROPOMI has the same wide swath as OMI (2600 km). In TRAQ's mid-inclination orbit, this allows up to 5 daytime observations over mid-latitude regions (Europe, North-America, China). The paper gives a description of the TROPOMI instrument and focuses on several important aspects of the design, for example the sun calibration and detector selection status.