An instrument capable of imaging the field of NO2 in various open-air situations has been designed, manufactured, and tested. It is an improved version of the NO2 camera relying on an AOTF (acousto-optical tunable filter) which has demonstrated, amongst other things, its capability to quantify the NO2 released by power plant smokestacks. The improved version which is presented has a larger field of view, a higher frame rate, and better spectral registration performance. The working principle of the instrument has been preserved: by driving the AOTF with the appropriate acoustic frequency, a spectral image of the scene captured by the camera is recorded at a particular wavelength. The recording of a number of spectral images allows to form an hypercube: two spatial dimensions, and a spectral one. While the earlier instrument was relying on a handful of wavelengths to quantify the slant column density of NO2 observed in each pixel line of sight, the new instrument can now record "continuous" portions of the visible-light spectrum, typically between 440, and 460nm, where the NO2 exhibits some of its largest absorption lines. When the target is stable, like the air observed above a city skyline, the NO2 camera has enough time to build a large hypercube, and the spectrum measured in each pixel can be processed by the DOAS (differential optical absorption spectroscopy) method. This approach is better suited when NO2 is expected across the entire scene, not just in the plume of a smokestack for instance. The new instrument will be presented, and results of measurements performed in an urban context will be shown. The performance of the NO2 camera will be discussed based on the results of an intercomparison with the MAX-DOAS of Uccle, Brussels, and other air quality stations. @en

On 13 October 2017 the European Sentinel 5 Precursor was successfully launched, with on board the TROPOMI (TROPOspheric Monitoring Instrument). TROPOMI is an imaging spectrometer developed by The Netherlands and ESA for monitoring the atmospheric composition, for air quality climate and ozone layer monitoring. The launch of TROPOMI marks the start of operational atmospheric composition measurements from space within the European Copernicus programme, the largest Earth observation programme in the world. After one month of instrument checkout, the first light of TROPOMI was received in November 2017. During the commissioning phase the TROPOMI instrument settings were optimized. This included an increase in the spatial sampling from 7x7 to 3.5x7 km2(across track x along track), for most of the TROPOMI spectral bands. The S5P commissioning phase was completed half a year after launch and on 30 April 2018 the routine operations were started. The first batch of data products was publicly released on 11 July 2018. By the time of the AGU fall meeting, almost all the data products must have been released. TROPOMI has provided very exciting results during its first year in orbit. Very remarkable are the plumes of short-lived gases like NO2, which can extend several tens of kilometers from the source. These plumes were predicted by air quality models; however it requires the spatial resolution of TROPOMI to see them from space. Also, the CO maps have attracted a lot of attention. Because of the high sensitivity for the entire vertical column, both the sources as well as the transport of CO are clearly visible in the TROPOMI data. The high spatial resolution of the TROPOMI data also poses new challenges. More than for the previous satellite sensors, the need for accurate modelling of the surface reflectance becomes clear. Also, the 3D effects of clouds are now more prominent. All these aspects are also important for the upcoming geostationary missions within the CEOS air quality constellation. In this presentation an overview will be given of the status of the mission, including the in-orbit calibration and the data products. Specific results will be highlighted that illustrate the new capabilities of TROPOMI and also the challenges that need to be addressed in future updates of the data products.@en