Small is beautiful: this could be the motto for ESA’s PROBA satellites. Not only are they small and cheap to produce, but they have the dual function of testing technological developments and also offer an opportunity for scientists to send experimental and new scientific missions into space. It has been more than ten years since the first PROBA was launched and the concept continues with more missions ahead and more demonstrations in several domains.
More background information can be found on: http://www.esa.int/esaMI/Proba/index.html