‘We improve satellite applications by connecting science and society’

With the Partnerships for Space Instruments & Applications Preparatory Programme, the Netherlands is supporting technological breakthroughs and scientific cooperation in space research. The Expertise Network ‘Air Quality’ investigates how satellites may help to discover air quality over a street, harbor, or highway.

Ask Vrije Universiteit professor Sander Houweling what the holy grail in his field is and he answers firmly, "That we can measure air quality at street level. The best satellite measurements currently have details of seven-by-seven kilometers. In other words, the port of Rotterdam is only a few pixels wide. What exactly happens in the air above the port, highways, residential areas, or agricultural plots is not known.

How important is it to measure air quality so accurately? 'To answer that question, we first have to do it,' says Houweling. ‘Only when we have that data will we discover how valuable it is. First, for the safety of people, who may be affected by air pollution. Second, for policy makers, who decide on complex issues, such as the maximum allowable emission of nitrogen. And thirdly for the climate, which is also changing significantly due to locally produced greenhouse gases.'

NO2 emissions in 2019 observed by Tropomi. Source: EU/ESA/KNMI

Determining air quality at a resolution of one hundred meters. Houweling is taking up the challenge as coordinator of the Expertise Network ‘Better Measurement of Air Quality’. ‘Currently air quality research is fragmented across institutions such as the VU, WUR, TU Delft, TNO, KNMI and RIVM. With the Expertise Network we are joining forces. Together we can compete with major international institutes that are active in this field. As smaller parties, we can all benefit from this.’

When talking about air quality, one might think of China or India and cities that disappear under a thick blanket of smog. Yet the Expertise Network focuses primarily on the Netherlands. This is because the Dutch space industry has a great deal of experience in building satellite instruments for atmospheric research. In addition, the RIVM manages an extensive network of ground-based measuring stations, which makes it easy to test new methodologies based on satellite data.

'We start close to home, where we have the knowledge, experience and hardware to do our research well,' says Houweling. 'If the new techniques and models we develop turn out to work, we may apply them in other places around the world. That's the beauty of satellites: they measure air quality globally, day by day.'

Initially, the Expertise Network focuses on air quality models. These need to become so accurate that pollution in cities can be visualized at the exposure level. The technology needed to improve the models will be developed in the coming years at the universities and institutions of the Expertise Network. Possibly the spatial resolution of the available instruments is not enough to model that extreme level of detail well enough. In that case, new satellite measurement instruments are also being considered, which could observe even more accurately than the Dutch instrument Tropomi, on the European Sentinel-5P satellite, currently does.

'In the past, Dutch policy focused mainly on developing increasingly sophisticated instruments. But if you can't process the data from those instruments properly, that's becoming a bottleneck,' explains Houweling. As an Expertise Network we look at the whole chain, including how we may improve the use of satellite data.


The challenge for the Air Quality Expertise Network is therefore a scientific one, but certainly also a societal one. For this reason, in addition to universities and research institutes, stakeholders are also represented in the network. For example, the Lung Fund, De Waag and DCMR, the environmental agency for the Rijnmond region. In the Expertise Network we connect science with society. By involving stakeholders at an early stage, we increase the chance of developing technology that really benefits them.

Houweling hopes his network will demonstrate that even better air quality models can be of great value to people and society. As scientists and technicians, we are convinced that this is the case. But we still must prove it. And that is what we are going to do with our Expertise Network in the next 2.5 years.