We present an extensive dataset of groundbased, balloon and satellite data on NO2, aerosols, and ozone obtained from two campaigns during May-June 2005 and September 2006. The data are available through the Aura Validation Data Center website for use in validation efforts. In this paper we describe the available data, and the methods and instruments used, including a novel instrument, namely the RIVM NO2 lidar. We show that NO2 from maxdoas compares well with in situ. We show that different maxdoas instruments, operating simultaneously during the campaign, give very similar results. We also provide unique information on the spatial homogeneity and the vertical and temporal variability of NO2. In addition, we show that there is good agreement between tropospheric NO2 from OMI and maxdoas, and also between total NO2
from OMI and direct-sun DOAS. We also regard observations of the aerosol optical thickness (AOT). Values derived with three groundbased instruments are shown to correspond well with each other, and with aerosol optical thicknesses observed by OMI.