The Netherlands was responsible for two satellites:
Astronomical Satellite Netherlands (ANS), 1974-1976. Mapping UV and soft X-rays. The orbit was intended to be polar-circular at 500 km, but became elliptical.
Infra-Red Astronomical Satellite (IRAS), 1983. Mapping infrared 12-100 µm, at 900 km height.
After this period satellites became a multinational undertaking, mainly in ESA context.
However, small research experiments are incidentally piggy backing on bigger launches.