Amateur radio satellite

An amateur radio satellite is an artificial satellite built and used by amateur radio operators for use in the Amateur-satellite service. These satellites use amateur radio frequency allocations to facilitate communication between amateur radio stations.

Many amateur-satellites receive an OSCAR designation, which is an acronym for Orbiting Satellite Carrying Amateur Radio. The designation is assigned by AMSAT, an organization which promotes the development and launch of amateur radio satellites. Because of the prevalence of this designation, amateur radio satellites are often referred to as OSCARs.

These satellites can be used for free by licensed amateur radio operators for voice (FM, SSB) and data communications (AX.25, packet radio, APRS). Currently, over 5 fully operational amateur-satellites in orbit act as repeaters, linear transponders or store and forward digital relays.

Throughout the years, amateur-satellites have helped make breakthroughs in the science of satellite communications. A few advancements include the launch of the first satellite voice transponder (OSCAR 3) and the development of highly advanced digital "store-and-forward" messaging transponder techniques.

The first amateur satellite, simply named OSCAR 1, was launched on December 12, 1961, barely four years after the launch of world's first satellite, Sputnik I. The beginning of this project was very humble. The satellite had to be built in a very specific shape and weight, so it could be used in place of one of the weights necessary for balancing the payload in the rocket stage. OSCAR 1 was the first satellite to be ejected as a secondary payload (with Discoverer 36 as the primary) and subsequently enter a separate orbit. The satellite carried no on-board propulsion and the orbit decayed quickly. Despite being in orbit for only 22 days, OSCAR 1 was an immediate success with over 570 amateur radio operators in 28 countries forwarding observations to Project OSCAR.

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