OSCAR 3 (a.k.a. OSCAR III) is the third

amateur radio satellite An amateur radio satellite is an artificial satellite built and used by amateur radio operators. It forms part of the Amateur-satellite service. These satellites use amateur radio frequency allocations to facilitate communication between amat ...

launched by Project OSCAR into

Low Earth Orbit A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, with an altitude never mor ...

. OSCAR 3 was launched March 9, 1965 by a Thor-DM21 Agena D launcher from Vandenberg Air Force Base, Lompoc, California. The satellite, massing , was launched piggyback with seven United States Air Force satellites. Though the satellite's active life was limited to sixteen days due to battery failure, OSCAR 3 relayed 176 messages from 98 stations in North America and Europe during its 274 orbit life-time -- the first amateur satellite to relay signals from Earth. As of 2022, it is still in orbit.

Project OSCAR

Project OSCAR Inc. was started in 1960 by members of the TRW Radio Club of Redondo Beach, California as well as persons associated with

Foothill College Foothill College is a public community college in Los Altos Hills, California. It is part of the Foothill–De Anza Community College District. It was founded on January 15, 1957, and offers 79 Associate degree programs, 1 Bachelor's degree p ...

to investigate the possibility of putting an amateur satellite in orbit. Project OSCAR was responsible for the construction of the first Amateur Radio Satellites: OSCAR 1, launched from Vandenberg AFB in California on 12 December 1961, which transmitted a “HI” greeting in Morse Code for three weeks, the similar OSCAR 2, OSCAR 3, and

OSCAR 4 OSCAR IV ( OSCAR 4) was the fourth amateur radio satellite launched by Project OSCAR and the first targeted for Geostationary orbit on 12 December 1965. The satellite was launched piggyback with three United States Air Force satellites on a Titan I ...

Spacecraft

OSCAR 3 was a rectangular-prism-shaped satellite, in dimension. Unlike its predecessors, which could only transmit a morse code "HI" signal through their beacons, OSCAR 3 was a true communications satellite. Equipped with a

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, when the satellite received signals broadcast to it at 144.1

MHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...

, its translator converted them to 30 MHz for amplification, and then reconverted them to 145.9

for further amplification and retransmission. A

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of power was available for transmission; if more than one signal were received simultaneously, they shared the power in proportion to their signal strengths when received. OSCAR 3 also carried a beacon like OSCARs 1 and 2, though of lower power. Four quarter-wave antennas (two for input/output to the translator, one for the beacon, and one for telemetry to the ground) were mounted on the sides of the lightweight magnesium-lithium alloy satellite. The hull was covered with shiny aluminum foil tape to reflect the heat of the sun, and lack stripes were painted over the shiny aluminum to radiate heat away from OSCAR 3 during the times it orbited in the shadow of the earth. A large 18-

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battery powered the satellite, though the beacon was designed to continue functioning, supplied by power from solar cells and a rechargeable battery.

Mission and results

OSCAR 3 flew on the NRL Composite 5 mission, which lofted an unprecedented eight satellites on a single Thor Augmented Delta-Agena D rocket (including POPPY 4, an electronic signals intelligence (ELINT) surveillance package, GGSE-2, GGSE-3, Surcal 2B, SECOR 3, SOLRAD 7B, and Dodedcapole 1) on 9 March 1965 from Vandenberg Air Force Base Space Launch Complex 1, Pad 2. Though the satellite's active life was limited to sixteen days due to battery failure, OSCAR 3 relayed 176 messages from 98 stations in North America and Europe during its 274 orbit life-time. The two beacon transmitters continued operating for several months. OSCAR 3 was thus the first amateur communications satellite to relay voice contacts in the VHF 2 meter band, the first amateur satellite to operate from solar power and relay signals from Earth, and the first satellite to use beacon transmitters separate from the main communications system. As of 2022, OSCAR 3 is still in orbit, and its position can be tracked online.

References

{{DEFAULTSORT:OSCAR 3 Satellites orbiting Earth Amateur radio satellites Spacecraft launched in 1965