EARTH | Space instruments & demonstrators

EARTH | Space instruments & demonstrators

EARTH | Space instruments & demonstrators

EARTH | Space instruments & demonstrators

Artist's impression of Sentinel-5p with the TROPOMI instrument on board. Credit: ESA
Monolythic immersed grating produced at SRON
Tropomi SWIR Breadboard spectrometer
SWIR detector module thermal vacuum testing at SRON
SWIR spectrometer with SRON immersed grating and detector front-end electronics (courtesy SSTL)
TROPOMI instrument during integration at Airbus Defence and Space NL (courtesy ADSNL)
SCIAMACHY CO averaged over 2003-2012 (Borsdorff et al, 2017).

The Sentinel-5 precursor mission is a single-payload satellite in a low Earth orbit that provides daily global information at city-scale spatial resolution on concentrations of trace gases and aerosols important for air quality, climate, and the ozone layer. The payload of the mission is the TROPOspheric Monitoring Instrument (TROPOMI), which is jointly developed by The Netherlands and ESA.

TROPOMI is a pushbroom spectrometer with spectral bands in the UV, VIS, NIR and SWIR. It measures key atmospheric constituents, including ozone, nitrogen dioxide, carbon monoxide, sulfurdioxide, methane, formaldehyde, aerosols and clouds. TROPOMI builds upon the heritage of its predecessors SCIAMACHY and OMI, and further improves on their performances in particular with regard to its spatial resolution, with pixels of only 7x7 km2.

The Sentinel-5 precursor is the first in a series of atmospheric sentinels which will provide observations over the period 2018-2040.


Mission Objectives:

-    To better constrain the strength, evolution, and spatiotemporal variability of the sources of trace gases and aerosols impacting air quality and climate
-    To improve upon the attribution of climate forcing by a better understanding of the processes controlling the lifetime and distribution of methane, tropospheric ozone, and aerosols
-    To better estimate long-term trends in the troposphere related to air quality and climate from the regional to the global scale
-    To develop and improve air quality model processes and data assimilation in support of operational services including air quality forecasting and protocol monitoring


For TROPOMI, SRON has focused its activities on the SWIR spectrometer and its data products. SRON, together with TNO, developed compact immersed reflection gratings for TROPOMI. Diffraction takes place inside the silicon thereby reducing the spectrometer volume by almost a factor 40 (~n3). A dedicated breadboard programme was set-up at SRON to successfully demonstrate this new technology. Sentinel-5p is the first space mission to harbor immersed gratings.

In addition, SRON developed the SWIR detector read-out electronics and delivered a fully TV-characterised detector module to industry.

As part of its co-Principal Investigator activities, SRON defined the SWIR science and instrument requirements, supported industry during the development and building phase in making SWIR-related instrument trade-offs, and supported industry during the on-ground calibration.

We deduced the SWIR specific calibration key data from the on-ground calibration campaign and delivered the SWIR specific key data and in-flight calibration software. We have developed the algorithms to retrieve SWIR trace gas abundancies and delivered the operational retrieval software for the greenhouse gas methane (CH4) and the air pollutant carbon monoxide (CO). These data products are part of the mission deliverables of the EU’s Copernicus programme.

Our methane retrieval software uses the RemoTeC code, jointly developed by SRON and DLR, which has been extensively applied to GOSAT and OCO-2 data. For carbonmonoxide we developed a new retrieval approach (the Sicor code) accounting for low-altitude clouds using methane to provide the information on clouds. This approach was successfully applied to the full SCIAMACHY mission dataset. In addition to these operational products, we have developed the scientific HDO/H2O product for TROPOMI which provides valuable information on the hydrological cycle.


Tropomi is a partnership between Airbus Defense and Space, KNMI, SRON and TNO, commissioned by the NSO and ESA. Airbus Defense and Space is the main contractor for the construction phase. KNMI and SRON are responsible for the scientific management. TROPOMI is funded by the Ministry of Economic Affairs, the Ministry of Education, Culture and Science and also by the Ministry of Infrastructure and the Environment.