SRON’s Earth programme

Watchful eyes over our planet

The Earth’s climate is changing because of man-made greenhouse gas emissions. Carbon dioxide and methane are the two main contributors to the enhanced greenhouse effect. Where are those gases emitted? Where do they go from there? How will these processes of emission and absorption be influenced in a changing climate? What is the role of various types of aerosols? We try to answer these scientific questions and address public health concerns such as air pollution.

So research of the Earth’s atmosphere is vitally important for society. As watchful eyes over the earth, Earth observation satellites provide detailed information from which scientists deduce the global distribution of sources and sinks of greenhouse and air-polluting gases. With the Dutch/ESA TROPOMI instrument on board the Sentinel-5 Precursor mission we have one of the most advanced space instruments for atmospheric composition measurements at our disposal.

Next to greenhouse gases aerosols – microscopically small, particles such as volcanic ash, sea salt, dust and soot – play a significant yet poorly known role both in climate and air quality. According to the IPCC 2013 the impact of aerosols constitutes one of the largest uncertainties in anthropogenic radiative forcing and consequently in predicting the Earth’s future climate. Moreover, aerosols directly influence human health. The main missing information is the detailed information on the optical and microphysical properties of aerosols and their distribution. The novel spectral modulation technology applied in the SPEX family of instrument prototypes developed at SRON features unprecedented polarimetric accuracy. This improved accuracy is needed to quantify the essential aerosol properties (optical thickness, absorption, size and type) with the accuracy needed to significantly advance our knowledge on the role of aerosols in climate change and air quality.

The Earth programme is headed by dr. Aaldert van Amerongen and consists of the Earth science group attached to the programme and instrument scientists assigned on a long-term basis to the programme. Engineers are assigned to the programme on a project basis. The science group consists currently of about 20 persons, including permanent and temporary scientific staff and PhD students.

The Earth programme covers SRON’s activities for Earth-system science. Observing the Earth from space has a big advantage as compared to ground-based observations. It provides time series of measurements with global and homogeneous coverage. This has led to initiatives for international space research programmes in which Earth observation provides essential diagnostic tools for improving our understanding of the Earth.

SRON’s Earth programme focuses on atmospheric measurements addressing the global carbon cycle (in particular the trace gases CH4, CO2, and CO) and aerosols, and the interpretation of the data in terms of processes fundamental for climate and air quality. Our activities cover contributions to the full project cycle of space-borne Earth observation:

  • specification of science and high-level observation requirements
  • development of enabling technologies and prototypes for future instruments
  • scientific support to the industrial instrument development
  • safeguarding the science requirements and calibration
  • retrieval of the geophysical data products (trace gas concentrations and aerosol microphysical and optical properties) from the measurements
  • scientific exploitation of the data products using atmospheric models and inversions.

The aim is to improve our understanding of planet Earth and the challenges we are faced with, like climate change and air quality.


The international Earth observation community has expressed a clear need for observations with higher spatial and temporal resolution. The European Commission has responded with H2020 calls for new highly-miniaturized optical instrument concepts, to be deployed alongside the large long-term ESA/EC Sentinel series. In addition, the changing political national landscape implies that relatively large national instrument contributions such as SCIAMACHY and TROPOMI are not likely to happen again in the next decade. This calls for a partial revision of our strategy. The institute will, in collaboration with industry, focus on scientific performance assessment and prototyping of new instrument concepts, including characterisation and calibration. We will pursue options for dedicated measurements with (constellations of) small satellites. Our ambition is to put Dutch industry, supported by SRON, in a position where it can win international contracts for space instruments to advance Earth observation. SRON will benefit because of its involvement in the future mission, doing calibrations and developing and exploiting data products for science and society.

The TROPOMI instrument during integration at Airbus Defence and Space Netherlands (courtesy ADS-NL)
The SPEX-airborne aerosol instrument on board of the NASA ER-2 high-altitude ER-2 research plane
Integration of the TROPOMI instrument with the Sentinel-5P satellite (courtesy Airbus Defence and Space, Stevenage)