OSCAR IV (a.k.a. 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 IIIC launch vehicle. Due to a booster failure, OSCAR 4 was placed in an unplanned and largely unusable Geostationary transfer orbit.

OSCAR 4 interior AMSAT.jpg
OSCAR 4 with exterior panels removed
Mission typeCommunications
OperatorProject OSCAR / DoD
COSPAR ID1965-108C
SATCAT no.01902
Spacecraft properties
Launch mass18.1 kilograms (40 lb)
Start of mission
Launch date21 December 1965 (1965-12-21)
RocketTitan IIIC 3C-8
Launch siteCape Canaveral LC-41
End of mission
Decay date12 April 1976 (12 April 1976)
Orbital parameters
Reference systemGeocentric
RegimeGeostationary (planned); Geostationary transfer orbit (actual)
Perigee altitude162 kilometers (101 mi)
Apogee altitude33,561 kilometers (20,854 mi)
Inclination26.80 degrees
Period587.4 minutes
Epoch20 December 1965

Project OSCAREdit

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 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,[1] launched from Vandenberg AFB in California on 12 December 1961, which transmitted a “HI” greeting in Morse Code for three weeks,[2] OSCAR 2, and OSCAR 3.[1]


OSCAR 4 massed 15 kilograms (33 lb) and was a regular tetrahedron with edges 48 centimetres (19 in) long. It had four independent monopole antennae and contained a tracking beacon transmitter and a communications repeater. It was powered by a solar cell array and batteries.[3] The satellite marked the first attempt for a High Earth Orbit (HEO) or GeoStationary Earth Orbit (GEO) amateur radio satellite, later categorized by AMSAT as Phase 3 and Phase 4. Improvements from prior OSCAR satellites included a higher power (3 Watt) 10 kHz wide linear transponder (144 MHz uplink and 432 MHz downlink), due to the higher planned orbit.[4]


Titan 3C launch 22 Dec 1965

OSCAR 4, along with LES-3, LES-4, and OV2-3, was launched on the third Titan IIIC test flight[5] on 22 December 1965 at 14:00:01 UT from Cape Canaveral LC41[6] just one second behind schedule. From an initial parking orbit of 194 kilometres (121 mi), the Titan's Transtage boosted into a transfer orbit pending a final burn to circularize its orbit. However, this final burn, scheduled for T+6:03:04 after liftoff,[5] never occurred due to a leaking valve in the booster's attitude control system.[7]: 422  OSCAR 4, LES-3 and LES-4, were released from the Transtage, albeit much later than intended, likely by the booster's backup timer;[5] OV2-3 remained attached and did not operate.[7]

The satellite remained in operation for 85 days, until 16 March 1966, and re-entered Earth's atmosphere on 12 April 1976.[8]


In 1969, AMSAT-NA was founded by radio amateurs working at NASA's Goddard Space Flight Center and the Baltimore-Washington DC region, to continue the efforts begun by Project OSCAR. Its first project was to coordinate the launch of Australis-OSCAR 5, constructed by students at the University of Melbourne.[4]


  1. ^ a b Rogerio Atem de Carvalho; Jaime Estela; Martin Langer, eds. (2020). Nanosatellites: Space and Ground Technologies, Operations and Economics. Glasgow: John Wiley & Sons, Ltd. p. 496. ISBN 978-1-119-04203-7. OCLC 1126347525.
  2. ^ "OSCAR 1". NASA Space Science Data Coordinated Archive. Retrieved 26 November 2020.
  3. ^ "OSCAR 4". NASA Space Science Data Coordinated Archive. Retrieved 26 November 2020.
  4. ^ a b Baker, Keith; Jansson, Dick (23 May 1994). "Space Satellites from the World's Garage -- The Story of AMSAT". Archived from the original on 5 October 2006. Retrieved 15 February 2013.
  5. ^ a b c "Titan 3 Transtage Malfunctions, Fails to Achieve Circular Orbit". Aviation Week and Space Technology. New York: McGraw Hill Publishing Company. 27 December 1965. p. 27. Retrieved 24 November 2020.
  6. ^ McDowell, Jonathan. "Launch Log". Jonathan's Space Report. Retrieved November 26, 2020.
  7. ^ a b Powell, Joel W.; Richards, G.R. (1987). "The Orbiting Vehicle Series of Satellites". Journal of the British Interplanetary Society. Vol. 40. London: British Interplanetary Society. p. 422.
  8. ^ "OSCAR 4". Gunter's Space Page. 31 December 1999. Retrieved 26 November 2020.

  This article incorporates public domain material from websites or documents of the National Aeronautics and Space Administration.