Ground station

A ground station, earth station, or earth terminal is a terrestrial radio station designed for extraplanetary telecommunication with spacecraft (constituting part of the ground segment of the spacecraft system), 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 or extremely high frequency bands (e.g., microwaves). When a ground station successfully transmits radio waves to a spacecraft (or vice versa), it establishes a telecommunications link. A principal telecommunications device of the ground station is the parabolic antenna.

Ground stations may have either a fixed or itinerant position. Article 1 § III of the ITU Radio Regulations describes various types of stationary and mobile ground stations, and their interrelationships.

Specialized satellite earth stations are used to telecommunicate with satellites—chiefly communications satellites. Other ground stations communicate with manned space stations or unmanned space probes. A ground station that primarily receives telemetry data, or that follows a satellite not in geostationary orbit, is called a tracking station.

EarthStation 5

Earth Station 5 (ES5) was a peer-to-peer network active between 2003 and 2005, operated by a company of the same name. The user client application also shared this name. Earth Station 5 was notable for its strong, if overstated, emphasis on user anonymity, and for its bold advocacy of piracy and copyright infringement. ES5's highly antagonistic position toward copyright advocacy and enforcement organizations garnered the group significant attention and peaked with an ES5 press release announcing a "declaration of war" against the Motion Picture Association of America. ES5 claimed to operate out of the Jenin in the Palestinian Authority-controlled West Bank, a region where they argued that copyright laws were unenforceable. Investigative journalism cast serious doubts on the company's Palestinian origin as well as many of its other claims. To this day, much about the company and its leadership remains uncertain or unknown.

Peer-to-peer services

Earth Station 5 was based around a peer-to-peer (P2P) file sharing service and a standalone Earth Station 5 file-sharing client. Initial versions of the software could only share or download files by using the ES5 network.