OSCAR 4

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

OSCAR 4 with exterior panels removed
Mission type	Communications
Operator	Project OSCAR / DoD
COSPAR ID	1965-108C
SATCAT no.	01902
Spacecraft properties
Launch mass	18.1 kilograms (40 lb)
Start of mission
Launch date	21 December 1965 (1965-12-21)
Rocket	Titan IIIC 3C-8
Launch site	Cape Canaveral LC-41
End of mission
Decay date	12 April 1976 (1976-04-12)
Orbital parameters
Reference system	Geocentric
Regime	Geostationary (planned); Geostationary transfer orbit (actual)
Eccentricity	0.71843
Perigee altitude	162 kilometers (101 mi)
Apogee altitude	33,561 kilometers (20,854 mi)
Inclination	26.80 degrees
Period	587.4 minutes
Epoch	20 December 1965
OSCAR ← OSCAR 3 OSCAR 5 →

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 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]

Spacecraft

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]

Mission

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]

Legacy

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]