TROPOspheric Monitoring Instrument (TROPOMI)

Here, below: IntroductionMission objectivesHeritage, Instrument descriptionAtmospheric composition productsList of TROPOMI data productsMore information?. This WebPage is mostly  based on Veefkind et al. (2012), and ESA & KNMI TROPOMI websites (see below).

Introduction

The TROPOspheric Monitoring Instrument (TROPOMI) is the single sensor on board of the Copernicus Sentinel-5 Precursor satellite. The Sentinel-5 Precursor (S5p) is the first of the atmospheric composition Sentinels (i.e. long-time series of operational satellite missions supporting the Copernicus programme), launched in 2017, for a nominal lifetime of 7 years. Sentinel-5 Precursor, is a gap-filler and a preparatory programme covering products and applications for Sentinel-5. The S5P mission will fill the gap between the end of the OMI and SCIAMACHY exploitation and the Sentinel-5 mission.

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Last look at Sentinel-5P (Credits: ESA–Stephane Corvaja, 2017) (Source: http://blogs.esa.int/eolaunches/2017/10/03/last-look-at-sentinel-5p/).

Mission objectives

The TROPOMI science objectives (Van Weele et al., 2008) are:
1. To better constrain the strength, evolution, and spatio-temporal variability of the sources of trace gases and aerosols impacting air quality and climate.
2. To improve upon the attribution of climate forcing by a better understanding of the processes controlling the lifetime and distribution of CH4 – Methane, tropospheric O3 – Ozone, and aerosols.
3. To better estimate long-term trends in the troposphere related to air quality and climate from the regional to the global scale.
4. To develop and improve air quality model processes and data assimilation in support of operational services including air quality forecasting and protocol monitoring.

TROPOMI is then expected to provide accurate and timely observations of key atmospheric species, for services on air quality, climate forcing (including non-CO2 – Carbon dioxide emissions), UV and the O3 – Ozone layer. The daily global observations will be used for improving air quality forecasts as well as for monitoring the concentrations of atmospheric constituents. Trend monitoring is very important to verify that policies implemented to control emissions to the atmosphere are effective. In addition, TROPOMI will also contribute to services on volcanic ash for aviation safety, warnings for high levels of UV radiation that can cause skin damage, and to numerical weather prediction.

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TROPOMI on fuelling stand. (ESA) (Source: http://blogs.esa.int/eolaunches/2017/09/20/sentinel-5p-lifted-onto-fuelling-stand/).

With its global coverage and open data policy, the mission is an essential contribution for providing critical information to services and decision makers to improve the life and atmospheric composition of European citizens, and our knowledge of important chemical and dynamical processes in the atmosphere.

The Royal Netherlands Meteorological institute (KNMI), via Dr. Pepijn Veefkind as Principal Investigator (PI), & the Netherlands Space institute (SRON) as co-PI are responsible for processing TROPOMI’s raw data and retrieving geophysical variables.  The Dutch space industry has set a new standard for satellite instruments. Without TROPOMI, there would be a gap of several years when it comes to monitoring gasses in the troposphere (the lowest part of the atmosphere and the air that we live in). Dutch climate researchers have signaled this problem, taking the initiative to build TROPOMI.

The TROPOMI project was commissioned by the Netherlands Space Office (NSO) and is financed by the ministries of Economic Affairs, Infrastructure and Environment and Education, Culture and Science, as well as the European Space Agency (ESA). ESA is leading the development of a satellite system encompassing the spacecraft, accommodation of the TROPOMI payload, a basic ground segment and the launch and in-orbit commissioning. The TROPOMI instrument was designed and built on the instruction of the Dutch government and ESA. Airbus Defence and Space Nederland are the main contractor for TROPOMI. TNO is responsible for the optomechanical design. The development of TROPOMI data products is a joint project partnered by institutes from The Netherlands, Germany, Great Britain and Finland.

TROPOMILifting
Carefully lifting the fuelled satellite onto the launch adapter (ESA) (Source: http://blogs.esa.int/eolaunches/2017/09/29/satellite-now-on-launch-adapter/).

Heritage

This mission is a result of a great team work: the Netherlands has been designing and building satellite atmospheric sensors, such as those carried on ERS and Envisat, since the 1990s. Building on this technical heritage, TROPOMI is the most advanced multi-spectral imaging spectrometer to date (2017).

TROPOMI succeeds the current Ozone Monitoring Instrument (OMI) (Levelt et al., 2006) and past SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY (SCIAMACHY) (Bovensmann et al., 1999). It should be then followed by the operational Sentinel-5 mission starting after 2020. In addition, the early afternoon observations of TROPOMI have strong synergy with the morning observations of Global Ozone Monitoring Experiment 2 (GOME-2). Although GOME-2 has a lower spatial resolution and doesn’t have the SWIR spectral range, the combination of TROPOMI and GOME-2 allows observing diurnal variations, as successfully shown with the OMI-SCIAMACHY combination (Boersma et al., 2008).

The combination of TROPOMI and GOME-2 is a first step toward higher temporally resolved observations over Europe starting in 2019-2020 with the Sentinel-4 mission on the geostationary Meteosat Third Generation (MTG) sounder platform (Ingmann et al., 2012). In addition to the GOME-2 synergy, there is also a synergy between TROPOMI and the American Soumi National Polar-orbiting Partnership (NPP) satellite. Identified synergies include the use of the Visible/Infrared Imager Radiometer Suite (VIIRS) for high spatially resolved cloud information and Ozone Monitoring and Profiling Suite (OMPS) for high vertically resolved stratospheric O3 – Ozone profiles. It is planned to fly the S5P mission within approximately 5 min of NPP, thus building upon the successes of the “A-Train” constellation of Earth observation satellites (L’Ecuyer & Jiang, 2010).

Instrument description

TROPOMI measures the Solar light in the ultraviolet and visible (270–500 nm), near-infrared (675–775 nm) and shortwave infrared (2305–2385 nm) spectral bands. The spectral resolution lies in the range of 0.25-0.55 nm. With a spatial resolution as high as 7 km × 3.5 km and in a nadir pointing observation mode, it has the potential to detect air pollution over individual mega-cities. This is considerably smaller than its predecessor, OMI, which has a pixel size of around 24 km x 13 km, and certainly much smaller than GOME-2 (80 km x 40 km) and SCIAMACHY (200 km x 30 km). The smaller pixel size means air quality can likely be resolved on the scale of mega-cities and distinguish different industrial areas. The daily-global coverage is ensured by a swath width of 2600 km. This also means a significant higher number of measurements to be delivered to scientists: while OMI acquires approximately 1 million spectra per day, TROPOMI will deliver around 20 times more! With TROPOMI, a new era of challenges regarding big data and the processing capability is then open. It has a minimum lifetime of 7 years.

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TROPOMI vs. OMI, GOME-2 and SCIAMACHY pixel sizes. Image made by my friend and colleague Jonathan Izett (Source: https://www.tudelft.nl/en/2017/citg/grs/what-makes-tropomi-special/)

The instrument images a strip of the Earth on a two dimensional detector for a period of 1 s during which the satellite moves by about 7 km. This strip has dimensions of approximately 2600 km in the direction across the track of the satellite and 7 km in the along track direction. After the 1 second measurement a new measurement is started, thus the instrument scans the Earth as the satellite moves. The two dimensions of the detector are used to detect the different ground pixels in the across track direction and for the different wavelengths. The light is separated in the different wavelengths using grating spectrometers. TROPOMI has four different detectors for the different spectral bands.

The payload mass is 200 kg.

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TROPOMI measurement principle. The dark-gray ground pixel is imaged on the two-dimensional detector as a spectrum. All ground pixels in the 2600 km wide swath are simultaneously measured (Veefkind et al., 2012)

As compared to the OMI instrument, TROPOMI has extended the wavelength range with bands in the Near InfraRed (NIR) and in the SHort-Wave InfraRed (SWIR). The primary objective of the NIR band is to perform a better cloud correction of trace gas retrievals. The deeper oxygen A band (758–770 nm) contains significantly more information on clouds, including cloud pressure and cloud fraction, compared to the weak O2–O2 band (460–485 nm) that is used for this purpose in OMI. The SWIR band at 2.3 um has been added for observations of CO – Carbon monoxide and CH4 – Methane. Furthermore, improvements in signal-to-noises are of  factor of 2-5 compared to OMI and SCIAMACHY (Veefkind et al., 2012).

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Spectral ranges for TROPOMI and the heritage instruments OMI, SCIAMACHY and GOME (Veefkind et al., 2012).

Atmospheric composition products

TOPOMI instrument is expected to deliver information about a wide range of pollutants gases such as NO2 – Nitrogen dioxide, O3 – Ozone, HCHO – Formaldehyde, SO2 – Sulphur dioxide, and CO – Carbon monoxide, the important green-house gas CH4 – Methane  and aerosol particles. Effective cloud parameters will be also monitored.

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Sentinel-5 Precursor – Copernicus Atmosphere Mission in Polar Orbit (Source: talk from Dr. Pieternel Levelt, Air quality and satellites, Urban Air Quality Symposium, Delft, the Netherlands, 2017.02.17).

List of TROPOMI data products

The TROPOMI Level 2 data products are generated within the Copernicus ground system and are listed in the table below. There are three different data streams: the near-real-time (NRT) stream, the Off-line stream and the Reprocessing stream. NRT data are available within 3 hours after data acquisition and intended for users that need quick access to the data. NRT data may be incomplete and may not have the full data quality. Most data users should use the off-line data, available within a few days after acquisition, or the latest version of reprocessed data. The data products contain information on the data quality for each TROPOMI ground pixel.

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List of S5P/TROPOMI Level 2 Products.

 

More information?

See the video interview of Dr. Pepijn Veefkind, TROPOMI principal investigator (PI) here, and the written interview here.

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Interviews with Dr. Pepijn Veefkind, TROPOMI principal investigator (PI) here, and the written interview here.
  • Tropomi.eu website maintained by KNMI R&D Satellite Observations here
  • Public TROPOMI website maintained by the Netherlands here
  • European Space Agency (ESA) Sentinel-5 Precursor / TROPOMI website here
  • ESA Sentinel-5 Precursor launch campaign blog here
  • ESA Sentinel-5 Precursor fact sheet here
  • Veefkind et al., 2012: Veefkind, J. P., Aben, E. A. A., McMullan, K., Forster, H., de Vries, J., Otter, G., … Visser, H.: TROPOMI on the ESA Sentinel-5 Precursor: A GMES mission for global observations of the atmospheric composition for climate, air quality and ozone layer applications. Remote Sensing of Environment, 120(SI), 70-83. DOI: 10.1016/j.rse.2011.09.027, 2012.
  • Ingmann, P., Veihelmann, B., Langen, J., Lamarre, D., Stark, H., and Courrèges-Lacoste, G. B.: Requirements for the GMES Atmosphere Service and ESA’s implementation concept: Sentinels-4/-5 and -5p, Remote Sens. Environ., 120, 58–69, doi:10.1016/j.rse.2012.01.023, 2012.
  • NO2 – Nitrogen dioxide WebPage here
  • Aerosols WebPage here
  • CO – Carbon monoxide WebPage here
  • CH4 – Methane WebPage here