A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Satellites have a variety of uses, including communication relay, weather forecasting, navigation (GPS), broadcasting, scientific research, and Earth observation. Additional military uses are reconnaissance, early warning, signals intelligence and, potentially, weapon delivery. Other satellites include the final rocket stages that placed satellites in orbit and formerly useful satellites that are now defunct.
A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite, spacecraft are used for a variety of purposes, including communications, Earth observation, meteorology, navigation, space colonization, planetary exploration, and transportation of humans and cargo. All spacecraft except single-stage-to-orbit vehicles cannot get into space on their own, and require a launch vehicle.
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.
Iridium Communications Inc. is a publicly traded American company headquartered in McLean, Virginia. Iridium operates the Iridium satellite constellation, a system of 66 active satellites and nine in-orbit spares used for worldwide voice and data communication from handheld satellite phones, satellite messenger communication devices and integrated transceivers, as well as for two-way satellite messaging service from supported Android smartphones. The nearly polar orbit and communication between satellites via inter-satellite links provide global service availability.
Globalstar, Inc. is an American satellite communications company that operates a low Earth orbit (LEO) satellite constellation for satellite phone and low-speed data communications. The Globalstar second-generation constellation consists of 48 low Earth orbiting (LEO) satellites.
The U.S. Tracking and Data Relay Satellite System (TDRSS) is a network of American communications satellites and ground stations used by NASA for space communications. The system was designed to replace an existing network of ground stations that had supported all of NASA's crewed flight missions. The prime design goal was to increase the time spacecraft were in communication with the ground and improve the amount of data that could be transferred. Many Tracking and Data Relay Satellites were launched in the 1980s and 1990s with the Space Shuttle and made use of the Inertial Upper Stage, a two-stage solid rocket booster developed for the shuttle. Other TDRS were launched by Atlas IIa and Atlas V rockets.
Orbital Sciences Corporation was an American company specializing in the design, manufacture, and launch of small- and medium- class space and launch vehicle systems for commercial, military and other government customers. In 2014, Orbital merged with Alliant Techsystems to create a new company called Orbital ATK, Inc., which in turn was purchased by Northrop Grumman in 2018. The remnants of the former Orbital Sciences Corporation today are a subsidiary of Northrop Grumman, known as Northrop Grumman Innovation Systems.
Satellite Internet access is Internet access provided through communication satellites. Modern consumer grade satellite Internet service is typically provided to individual users through geostationary satellites that can offer relatively high data speeds, with newer satellites using Ku band to achieve downstream data speeds up to 506 Mbit/s. In addition, new satellite internet constellations are being developed in low-earth orbit to enable low-latency internet access from space.
A ground station, Earth station, or Earth terminal is a terrestrial radio station designed for extraplanetary telecommunication with spacecraft, or reception of radio waves from astronomical radio sources. Ground stations may be located either on the surface of the Earth, or in its atmosphere. Earth stations communicate with spacecraft by transmitting and receiving radio waves in the super high frequency (SHF) or extremely high frequency (EHF) bands. When a ground station successfully transmits radio waves to a spacecraft, it establishes a telecommunications link. A principal telecommunications device of the ground station is the parabolic antenna.
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 five are currently operational; the third launch failed, both damaging the satellite and leaving it in an unusable orbit.
The design of spacecraft covers a broad area, including the design of both robotic spacecraft, and spacecraft for human spaceflight.
ORBCOMM is an American company that offers industrial Internet of things (IoT) and machine to machine (M2M) communications hardware, software and services designed to track, monitor, and control fixed and mobile assets in markets including transportation, heavy equipment, maritime, oil and gas, utilities and government. The company provides hardware devices, modems, web applications, and data services delivered over multiple satellite and cellular networks.
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.
The Iridium satellite constellation provides L band voice and data information coverage to satellite phones, satellite messenger communication devices and integrated transceivers, as well as two-way satellite messaging service to supported Android smartphones, over the entire surface of Earth. Iridium Communications owns and operates the constellation, additionally selling equipment and access to its services. It was conceived by Bary Bertiger, Raymond J. Leopold and Ken Peterson in late 1987 and then developed by Motorola on a fixed-price contract from July 29, 1993, to November 1, 1998, when the system became operational and commercially available.
The European Data Relay System (EDRS) system is a European constellation of GEO satellites that relay information and data between satellites, spacecraft, UAVs, and ground stations. The first components were launched in 2016 and 2019.
The Laser Communications Relay Demonstration (LCRD) is a NASA mission that will test laser communication in space for extremely long distances, between Earth and geosynchronous orbit.
Starlink is a satellite internet constellation operated by SpaceX, providing satellite Internet access coverage to 50 countries. It also aims for global mobile phone service after 2023. SpaceX started launching Starlink satellites in 2019. As of February 2023, Starlink consists of over 3,580 mass-produced small satellites in low Earth orbit (LEO), which communicate with designated ground transceivers. In total, nearly 12,000 satellites are planned to be deployed, with a possible later extension to 42,000. SpaceX announced reaching more than one million subscribers in December 2022.
A ground segment consists of all the ground-based elements of a space system used by operators and support personnel, as opposed to the space segment and user segment. The ground segment enables management of a spacecraft, and distribution of payload data and telemetry among interested parties on the ground. The primary elements of a ground segment are:
Indian Data Relay Satellite System or IDRSS is a planned Indian constellation of Inter-satellite communications satellites. It is planned to initially comprise two satellites, CMS-04 & IDRSS-2 in geostationary orbit. It will facilitate relay of information between various Indian spacecraft, in-flight launch vehicle monitoring and assist Indian Human Spaceflight Programme.
O3b mPOWER is a communications satellite system currently under construction and deployment. The first two satellites were launched on 16 December 2022 and commercial service is expected to begin in Q3 2023. Owned and operated by SES, O3b mPOWER initially comprises 11 high-throughput and low-latency satellites in a medium Earth orbit (MEO), along with ground infrastructure and intelligent software, to provide multiple terabits of global broadband connectivity for applications including cellular backhaul to remote rural locations and simultaneous international IP trunking.
