Satellites provide a perspective of the Earth that cannot be matched by ground-based technology. In the early days of the Space Age, satellites served little purpose beyond demonstrating that they were in orbit. Decades of experience and technological advancement have yielded sophisticated craft that perform multiple essential missions for militaries, government agencies, and companies around the world.
Ground stations are an essential but often overlooked segment of space infrastructure. Ground stations connect satellites to terrestrial networks and collect satellite information ranging from tracking and telemetry to imagery and scientific data. The stations also upload information to spacecraft, including command and control data, software upgrades, and other mission-critical instructions. Employees at some ground stations process, analyze, and distribute satellite-based data, products, and services.
Ground station infrastructure is a key component of space systems providing command control, tracking, and telemetry services for launch vehicles, satellites, and other platforms. Worldwide tracking systems operated by government agencies support launch command and control. In addition, space situational awareness systems like the U.S. Space Surveillance Network track space debris and assist with collision avoidance.
Ground station infrastructure provides command, control, tracking, and telemetry systems for launch vehicles, satellites, and other platforms. Worldwide tracking systems operated by government agencies support launch command and control. Satellite ground stations are operated either by commercial or government entities; their components include the large satellite receivers used to transmit and receive signals to and from satellites on orbit for the purpose of communication, navigation, or data transfer.
As geostationary (GSO) satellites remain in an essentially fixed position relative to the ground at all times, they can communicate with fixed ground stations continually. Medium Earth orbit (MEO) and low Earth orbit (LEO) satellites appear to “fly by” overhead and have a shorter communication window for a given station, from ten minutes for a LEO satellite to two hours or more for a MEO satellite. Satellites in highly elliptical orbits may be in communication with a fixed ground station for up to eight hours.
Satellites in use have four basic applications: communications, remote sensing, navigation, positioning and timing, and scientific experimentation (generally using a suite of sensors with variations of some or all of the other types). The sidebar describes the various satellite orbits.