Tropomi is a spectrometer sensing ultraviolet, visible, near and short-wavelength infrared to monitor ozone, methane, formaldehyde, aerosol, carbon monoxide, NO2 and SO2 in the atmosphere. It extends the capabilities of the OMI from the Aura satellite and the SCIAMACHY instrument from Envisat. Tropomi will be taking measurements every second covering an area of approximately 2600 km wide and 7 km long in a resolution of 7 x 7 km. Light will be separated into different wavelengths using grating spectrometers and then measured with four different detectors for respective spectral bands. The UV spectrometer has a spectral range of 270-320 nm, the visible light spectrometer has a range of 310-500 nm, NIR has a range of 675-775 nm, and SWIR has a range of 2305-2385 nm. The instrument is split into four major blocks: UV-VIS-NIR spectrometers and a calibration block, SWIR spectrometer with its optics, instrument control unit and a cooling block. The total mass of Tropomi will be 200 kg with a power consumption of 170 watts on average and a data output of 140 Gbit per orbit. The instrument was built by a joint venture between the Netherlands Space Office, Royal Netherlands Meteorological Institute, Netherlands Institute for Space Research, Netherlands Organisation for Applied Scientific Research and :nl:Airbus Defence and Space Netherlands|Airbus Defence and Space Netherlands. The SWIR spectrometer was designed and built by the Optical Payloads Group of Surrey Satellites ; it employs an immersed grating design in which light impinges upon an etched grating from within a high-index substrate. The reduced wavelength within the refractive medium permits an efficient, space-saving design. The SWIR grating was provided by SRON, who also provided the Front-End Electronics. The SWIR spectrometer receives light from the main instrument via an intermediate pupil, and directs this - via a telescope - towards a slit which defines the along-track footprint of the instrument on the ground. Light from the slit is re-collimated, diffracted by the immersed-grating at high-order and finally imaged onto a two-dimensional detector by a high aperture relay lens. The SWIR detector has 256 elements in the across-track direction and 1024 elements in the spectral direction ; it is operated cold. The SWIR spectrometer optics are mounted on a cooled optical bench and the instrument is insulated by a multiple-layer insulation blanket. The SWIR instrument was aligned, focussed and characterised at the Mullard Space Science laboratory thermal vacuum facility in Surrey, UK. The Tropospheric Monitoring Instrument provides the most detailed methane emissions monitoring available. It has a resolution of about 50 square kilometres.
History
The first large contract for Sentinel-5P was signed in July 2009 for Tropomi instrument between the European Space Agency and Dutch Ministry of Economic Affairs which contributed million. On 8 December 2011, ESA selected Astrium UK as a prime contractor for the satellite, signing contract worth million. Construction of the satellite itself was completed in May 2014, and integration with its primary instrument has been completed successfully. From design to launch Tropomi cost million. The satellite was launched by Eurockot Launch Services onboard Rokot. The launch was originally planned for late 2014, but had been postponed multiple times, before occurring on 13 October 2017 at 09:27 UTC from Plesetsk Cosmodrome Site 133. Sentinel-5P successfully reached its final orbit 79 minutes after lift-off from the Plesetsk cosmodrome.
The Tropomi instrument on the 5P satellite, showed substantial reductions in nitrogen dioxide amounts over Chinese cities between late-January and February 2020. These were linked to China's response to the coronavirus pandemic which greatly reduced industrial and other polluting activities.
