OSCAR (Orbiting Satellite for Communication by Amateur Radio) is a long-running series of small satellites built and operated by radio 'hams' around the world. OSCARs have no fixed design but are lightweight (typically about 30 kilograms) and generally launched free of charge, when space is available, as secondary payloads on rockets carrying much heavier, primary payloads. OSCAR 1 was launched by the American Department of Defense. In 1969, the Amateur Radio Satellite Corporation (AMSAT) was set up to coordinate work on the OSCAR series.