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 22,236 miles (35,785 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.
Ultra high frequency (UHF) is the ITU designation for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter. Radio waves with frequencies above the UHF band fall into the super-high frequency (SHF) or microwave frequency range. Lower frequency signals fall into the VHF or lower bands. UHF radio waves propagate mainly by line of sight; they are blocked by hills and large buildings although the transmission through building walls is strong enough for indoor reception. They are used for television broadcasting, cell phones, satellite communication including GPS, personal radio services including Wi-Fi and Bluetooth, walkie-talkies, cordless phones, satellite phones, and numerous other applications.
Skynet is a family of military communications satellites, now operated by Babcock International on behalf of the United Kingdom's Ministry of Defence (MOD). They provide strategic and tactical communication services to the branches of the British Armed Forces, the British intelligence agencies, some UK government departments and agencies, and to allied governments. Since 2015 when Skynet coverage was extended eastward, and in conjunction with an Anik G1 satellite module over America, Skynet offers near global coverage.
The Joint Tactical Radio System (JTRS) aimed to replace existing radios in the American military with a single set of software-defined radios that could have new frequencies and modes (“waveforms”) added via upload, instead of requiring multiple radio types in ground vehicles, and using circuit board swaps in order to upgrade. JTRS has seen cost overruns and full program restructurings, along with cancellation of some parts of the program.
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.
The Mobile User Objective System (MUOS) is a United States Space Force narrowband military communications satellite system that supports a worldwide, multi-service population of users in the ultra high frequency (UHF) band. The system provides increased communications capabilities to newer, smaller terminals while still supporting interoperability with legacy terminals. MUOS is designed to support users who require greater mobility, higher bit rates and improved operational availability. The MUOS was declared fully operational for use in 2019.
The Wideband Global SATCOM system (WGS) is a high capacity United States Space Force satellite communications system planned for use in partnership by the United States Department of Defense (DoD), Canadian Department of National Defence (DND) and the Australian Department of Defence. The system is composed of the Space Segment satellites, the Terminal Segment users and the Control Segment operators.
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.
FLTSATCOM-3 or (FSC-3) was the third vehicle in the Navy's FLTSATCOM communications satellite constellation, which were used by the United States Navy for communications between aircraft, ships, submarines and ground stations. Fltsatcom 3 provided 28 5-kHz and 11 20-kHz communications channels simultaneously in the UHF band. The UHF up-link was in the 290 to 320 MHz range while down-link was in the 240 to 320 MHz range. A number of channels were reserved for high priority communications by the United States Air Force. These were ground to air communications between SAC aircraft, the E-3A airborne warning and control system and elements of the presidential command structure. FSC-3's life officially ended in September 1995.
USA-233, or Wideband Global SATCOM 4 (WGS-4) is a United States military communications satellite operated by the United States Air Force as part of the Wideband Global SATCOM program, launched in 2012. The fourth Wideband Global SATCOM satellite, it is the first WGS Block II satellite to be launched. It is stationed at 88.5° East in geostationary orbit.
USA-66, also known as GPS IIA-1, GPS II-10 and GPS SVN-23, was an American navigation satellite which formed part of the Global Positioning System. It was the first of nineteen Block IIA GPS satellites to be launched, and was the oldest GPS satellite still in operation until its decommissioning on 25 January 2016.
USA-83, also known as GPS IIA-5, GPS II-14 and GPS SVN-26, is an American navigation satellite which forms part of the Global Positioning System. It was the fifth of nineteen Block IIA GPS satellites to be launched.
USA-92, also known as GPS IIA-12, GPS II-21, GPS SVN-39, and NAVSTAR 39, is an American navigation satellite which forms part of the Global Positioning System. It was the twelfth of nineteen Block IIA GPS satellites to be launched.
USA-94, also known as GPS IIA-13, GPS II-22 and GPS SVN-35, was an American navigation satellite which formed part of the Global Positioning System. It was the thirteenth of nineteen Block IIA GPS satellites to be launched.
USA-96, also known as GPS IIA-14, GPS II-23 and GPS SVN-34, is an American navigation satellite which is part of the Global Positioning System. It was 14 of 19 Block IIA GPS satellites to be launched, and the last one to be retired.
USA-126, also known as GPS IIA-17, GPS II-26 and GPS SVN-40, is an American navigation satellite which forms part of the Global Positioning System. It was the seventeenth of nineteen Block IIA GPS satellites to be launched.
USA-135, also known as GPS IIA-19, GPS II-28 and GPS SVN-38, is an American navigation satellite which forms part of the Global Positioning System. It was the last of nineteen Block IIA GPS satellites to be launched.
The Boeing 601 is a retired communications satellite bus designed in 1985 and introduced in 1987 by Hughes Space and Communications Company. The series was extremely popular in the 1990s, with more than 84 purchased by customers globally. The more advanced 601HP derivative was introduced in 1995. Hughes, and the 601 platforms, were acquired by Boeing in 2000.
X band or SHF Satellite Communication is widely used by military forces for beyond line of sight communications. X band is used because it provides a compromise between the characteristics of different frequency bands which is particularly suited to the needs of military users. The characteristics include interference and rain resilience, terminal size, data rates, remote coverage and whether it is reserved for governmental use.
Mobile-satellite service is – according to Article 1.25 of the International Telecommunication Union's Radio Regulations – "A radiocommunication service
