The first satellites at the beginning of the space age were small satellites. Primarily because of the fact that the launch capacity was small. Later on the launchers and satellites grew, and today a lot of big missions with a high complexity are in space. These missions serve the science, the military and defense, commercial and operational users as well as public and private interests. Today’s technology allows the supplement of the big missions by small satellite missions. By exploring new technologies and methods small satellites can prepare new experiments and technologies for big missions or solve complementary questions. Small satellites have several advantages, e. g. extremely smaller budgets, shorter development and manufacturing time, more dedicated mission objectives, smaller user communities, implementation of new technologies with higher risks.