A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. Communications satellites are used for television, telephone, radio, internet, and military applications. Many communications satellites are in geostationary orbit 22,300 miles (35,900 km) above the equator, so that the satellite appears stationary at the same point in the sky; therefore the satellite dish antennas of ground stations can be aimed permanently at that spot and do not have to move to track the satellite. Others form satellite constellations in low Earth orbit, where antennas on the ground have to follow the position of the satellites and switch between satellites frequently.
The Titan IIIC was an expendable launch system used by the United States Air Force from 1965 until 1982. It was the first Titan booster to feature large solid rocket motors and was planned to be used as a launcher for the Dyna-Soar, though the spaceplane was cancelled before it could fly. The majority of the launcher's payloads were DoD satellites, for military communications and early warning, though one flight (ATS-6) was performed by NASA. The Titan IIIC was launched exclusively from Cape Canaveral while its sibling, the Titan IIID, was launched only from Vandenberg AFB.
Milstar is a constellation of military communications satellites in geosynchronous orbit, which are operated by the United States Space Force, and provide secure and jam-resistant worldwide communications to meet the requirements of the Armed Forces of the United States. Six spacecraft were launched between 1994 and 2003, of which only five were operational after launch; the third launch failed, both damaging the satellite and leaving it in an unusable orbit.
ATS-6 was a NASA experimental satellite, built by Fairchild Space and Electronics Division It has been called the world's first educational satellite as well as world's first experimental Direct Broadcast Satellite as part of the Satellite Instructional Television Experiment between NASA and Indian Space Research Organisation (ISRO). It was launched May 30, 1974, and decommissioned July 1979. At the time of launch, it was the most powerful telecommunication satellite in orbit. ATS-6 carried no fewer than 23 different experiments, and introduced several breakthroughs. It was the first 3-axis stabilized spacecraft in geostationary orbit. It was also the first to use experimentally with some success electric propulsion in geostationary orbit. It also carried several particle physics experiments, including the first heavy ion detector in geostationary orbit.
Advanced Extremely High Frequency (AEHF) is a constellation of communications satellites operated by the United States Space Force. They are used to relay secure communications for the United States Armed Forces, the British Armed Forces, the Canadian Armed Forces, the Netherlands Armed Forces and the Australian Defence Force. The system consists of six satellites in geostationary orbits. The final satellite was launched on 26 March 2020. AEHF is backward compatible with, and replaces, the older Milstar system and will operate at 44 GHz uplink and 20 GHz downlink. The AEHF system is a joint service communications system that provides survivable, global, secure, protected, and jam-resistant communications for high-priority military ground, sea and air assets.
The Lincoln Experimental Satellite series was designed and built by Lincoln Laboratory at Massachusetts Institute of Technology between 1965 and 1976, under USAF sponsorship, for testing devices and techniques for satellite communication.
Orbiting Vehicle or OV, originally designated SATAR, comprised five disparate series of standardized American satellites operated by the US Air Force, launched between 1965 and 1971. Forty seven satellites were built, of which forty three were launched and thirty seven reached orbit. With the exception of the OV3 series and OV4-3, they were launched as secondary payloads, using excess space on other missions. This resulted in extremely low launch costs and short proposal-to-orbit times. Typically, OV satellites carried scientific and/or technological experiments, 184 being successfully orbited through the lifespan of the program.
OSCAR IV 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.
Orbiting Vehicle 2-1, the first satellite of the second series of the United States Air Force's Orbiting Vehicle program, was an American life science research satellite. Its purpose was to determine the extent of the threat posed to astronauts by the Van Allen radiation belts. Launched 15 October 1965, the mission resulted in failure when the upper stage of OV2-1's Titan IIIC booster broke up.
Lincoln Experimental Satellite 1, also known as LES-1, was a communications satellite, the first of nine in the Lincoln Experimental Satellite program. Launched by the United States Air Force (USAF) on February 11, 1965, it pioneered many then-advanced technologies including active use of the military's SHF band to service hundreds of users. LES-1 did not have a successful operational life due to being placed in a suboptimal orbit, and it ceased transmissions in 1967. After 45 years of inactivity, LES-1 spontaneously resumed transmissions in 2012 making it one of the oldest zombie satellites.
Orbiting Vehicle 1-1, was the first satellite in the OV1 series of the United States Air Force's Orbiting Vehicle program. OV1-1 was an American Earth science research satellite designed to measure radiation, micrometeoroid density, and magnetic fields in orbit. Launched 21 January 1965, the mission resulted in failure when, after a successful launch of its Atlas booster, OV1-1's onboard Altair motor failed to fire.
Lincoln Experimental Satellite 2, also known as LES-2, was a communications satellite, the second of nine in the Lincoln Experimental Satellite. Launched by the United States Air Force (USAF) on 6 May 1965, it demonstrated many then-advanced technologies including active use of the military's SHF band to service hundreds of users.
Orbiting Vehicle 2-3, the second satellite of the second series of the United States Air Force's Orbiting Vehicle program, was an American solar astronomy, geomagnetic and particle science research satellite. Launched 22 December 1965 along with three other satellites, the mission resulted in failure when the spacecraft failed to separate from the upper stage of its Titan IIIC.
Lincoln Experimental Satellite 3, also known as LES-3, was a communications satellite, the third of nine in the Lincoln Experimental Satellite. Launched by the United States Air Force (USAF) on 21 Dec 1965, it was stranded in a Geostationary Transfer Orbit rather than its planned circular high orbit. Despite this, LES-3 returned good data on communications propagation in the UHF band.
The Initial Defense Communications Satellite Program or IDCSP was the first United States Department of Defense communications satellite constellation and the first stage of the Defense Communications Satellite Program (DCSP). Launched in five groups by Titan IIIC launch vehicles to near equatorial, subsynchronous orbits between 1966 and 1968, they were intended to be experimental testbeds. They were so successful that, by the time of the launch of the last set of eight satellites, the IDCSP was deemed operational and renamed Initial Defense Satellite Communications System or IDSCS. This system allowed real-time collection of battlefield intelligence during the Vietnam War. A total of 35 IDCSP satellites were launched, 27 successfully.
Orbiting Vehicle 2-5, the third and last satellite of the second series of the United States Air Force's Orbiting Vehicle program, was an American particle science and ionosphere research satellite. Launched 26 September 1968 along with three other satellites, OV2-5 became the first scientific satellite to operate at geosynchronous altitude.
Orbiting Vehicle 1-8, launched 14 July 1966, was the seventh satellite launched in the OV1 series of the United States Air Force's Orbiting Vehicle program. OV1-8 was designed to test the passive communications utility of an aluminum grid sphere versus a balloon satellite.
The Environmental Research Satellite program was a series of small satellites initially operated by the United States Air Force Office of Aerospace Research. Designed to be launched "piggyback" to other satellites during launch, detaching once in orbit, they were the smallest satellites launched to date—what would today be classified as microsatellites. 33 ERS satellites in six different series were launched between 1962 and 1971, conducting scientific research and serving as test beds to investigate the reliability of new spacecraft components.
Orbiting Vehicle 1-6 was launched via Titan IIIC rocket into orbit 2 November 1966 along with two other satellites in the United States Air Force's Orbiting Vehicle series on the first and only Manned Orbiting Laboratory test flight. The eighth satellite in the OV1 series to be launched, OV1-6 was designed to release a number of inflatable spheres, which would then be used in classified tracking experiments conducted on the ground. It is uncertain whether or not the satellite successfully released any of its spheres. OV1-6 reentered the Earth's atmosphere on 31 December 1966.
Orbiting Vehicle 1-11 was an American satellite launched 27 July 1967 to study a range of environmental conditions in the upper atmosphere. Part of the OV1 series of USAF satellites, using standardized designs and sent to orbit on decommissioned Atlas ICBMs to reduce development and launching costs, OV1-12 was launched with two other satellites in the series, OV1-12 and OV1-86, in the first triple launch of the program. The satellite was lost during launch when its onboard propulsion module failed.
