 right|thumb|200px|oscar 2 oscar is an acronym for orbiting satellite carrying amateur radio. oscar series amateur radio satellites use amateur radio frequency allocations to facilitate communication between amateur radio stations. amsat was started by a group of amateur radio operators most of whom were working at or associated with nasa's goddard space center north of washington dc. 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 satellites in orbit act as repeaters, linear transponders or store and forward digital relays. the beginning of this project was very humble. the satellite had to be built in a very specific shape and weight in place of one of the weights used to balance the payload in the rocket stage. by nasa specification, it could not contain any propulsion system so as not to pose danger to the expensive payload the thor agena launch vehicle was carrying. throughout the years oscar 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. to date, over 70 oscars have been launched. ==satellites== ===oscar 1===  thumb|100px|right|ussr postal stamp depicting amateur radio satellites, rs-1 and rs-2 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. oscar 1 was the first satellite to be ejected as a secondary payload (discoverer 36) and subsequently enter a separate orbit. 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. ===oscar 10=== most of the components for oscar 10 were "off the shelf" and tested by group members. jan king led the project. solar cells were bought in batches of 10 or 20 from radio shack & tested for efficiency by group members (a. sergio torloni then a senior in high school) the most efficient cells were kept for the project, the rest were returned to radioshack. once ready, oscar 10 was mounted aboard a private plane & flown on a couple of occasions to evaluate its performance & reliability. special qsl cards were issued to those who participated in the airplane based flights. once it was found to be operative & reliable, the satellite was 
Amateur_radio_satellites