Ground station in the context of "Artificial satellite"

A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They 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 place satellites in orbit and formerly useful satellites that later become defunct.

Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotope thermoelectric generators (RTGs). Most satellites also have a method of communication to ground stations, called transponders. Many satellites use a standardized bus to save cost and work, the most popular of which are small CubeSats. Similar satellites can work together as groups, forming constellations. Because of the high launch cost to space, most satellites are designed to be as lightweight and robust as possible. Most communication satellites are radio relay stations in orbit and carry dozens of transponders, each with a bandwidth of tens of megahertz.

A satellite constellation is a group of artificial satellites working together as a system. Unlike a single satellite, a constellation can provide permanent global or near-global coverage, such that at any time everywhere on Earth at least one satellite is visible. Satellites are typically placed in sets of complementary orbital planes and connect to globally distributed ground stations. They may also use inter-satellite communication.

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:

• Ground (or Earth) stations, which provide radio interfaces with spacecraft
• Mission control (or operations) centers, from which spacecraft are managed
• Remote terminals, used by support personnel
• Spacecraft integration and test facilities
• Launch facilities
• Ground networks, which allow for communication between the other ground elements

These elements are present in nearly all space missions, whether commercial, military, or scientific. They may be located together or separated geographically, and they may be operated by different parties. Some elements may support multiple spacecraft simultaneously.

An orbital pass (or simply pass) is the period in which a spacecraft is above the local horizon, and thus available for line-of-sight communication with a given ground station, receiver, or relay satellite, or for visual sighting. The beginning of a pass is termed acquisition of signal (AOS); the end of a pass is termed loss of signal (LOS). The point at which a spacecraft comes closest to a ground observer is the time of closest approach (TCA).

Raisting Earth Station (German: Erdfunkstelle Raisting) is a satellite ground station near Raisting, Bavaria. The station was Germany's first commercial station for satellite communication and is still one of the largest ground stations in the world.

Royal Air Force Menwith Hill (RAF Menwith Hill) is a Royal Air Force station near Harrogate, North Yorkshire, England, which provides communications and intelligence support services to the United Kingdom and the United States. The site contains an extensive satellite ground station and is a communications intercept and missile warning site. It has been described as the largest electronic monitoring station in the world.

RAF Menwith Hill is owned by the Ministry of Defence (MoD), but made available to the US Department of Defense (DoD) under the NATO Status of Forces Agreement 1951 and other, undisclosed agreements between the US and British governments. His Majesty's Government (HMG) is entitled to possession of the site and retains control over its use and its facilities, though the administration of the base is the responsibility of the US authorities, with support provided by around 400 staff from Government Communications Headquarters (GCHQ), in addition to United States Air Force (USAF) and US National Security Agency (NSA) personnel. In 2014, the number of American personnel was reduced as part of a streamlining of operations due to improvements in technology.

The Iridium satellite constellation provides L band voice and data information coverage to satellite phones, satellite messenger communication devices and integrated transceivers. 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 (in 1988 protected by patents Motorola filed in their names) 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 constellation consists of 66 active satellites in orbit, required for global coverage, and additional spare satellites to serve in case of failure. Satellites are placed in low Earth orbit at a height of approximately 781 kilometres (485 mi) and inclination of 86.4°. The nearly polar orbit and communication between satellites via Ka band inter-satellite links provide global service availability (including both poles, oceans and airways), regardless of the position of ground stations and gateways.