I received my PhD degree in 1992 in theoretical physics at the University of Groningen. Since 1997 I am employed as senior scientist at the Royal Netherlands Meteorological Institute (KNMI). My research focusses on the composition of the atmosphere, specializing on atmospheric chemistry modeling, chemical data assimilation and satellite observations of trace gases in the atmosphere. I am strongly involved in the Copernicus Atmosphere Monitoring Service (CAMS) and the coordinator of the CAMS validation contract. I am product lead for the NO2 product of the TROPOMI spectrometer instrument on the Sentinel-5P satellite.