Orbiter

Orbiter is a term used in spaceflight and computing with several related meanings. In spaceflight, an orbiter is a spacecraft designed to operate in orbit around a celestial body, conducting observations, experiments, or deployment of satellites while remaining on orbit. Orbiter spacecraft may serve as scientific platforms, communication relays, or testbeds for propulsion, guidance, and life-support systems.

In the context of the NASA Space Shuttle program, the term orbiter refers to the reusable winged spacecraft that carried crews and cargo to low Earth orbit. The program fielded several orbiters over its lifetime. Enterprise was a test vehicle used for approach-and-landing tests and never flew in space. Discovery, Atlantis, and Endeavour were the operational orbiters that conducted the majority of missions, while Challenger (lost in 1986) and Columbia (lost in 2003) were also orbiters within the fleet. Each orbiter was designed to launch on a Shuttle Carrier Aircraft, mate with a large external tank and solid rocket boosters, and return to Earth for refurbishment.

Orbiter is also the name of a popular freeware space flight simulator for Windows, commonly referred to simply as Orbiter. The program models orbital mechanics, spacecraft control, and re-entry physics, allowing users to fly various vessels through the solar system. First released in the late 1990s, it has an active community that develops add-ons, vessels, and missions, enabling a wide range of simulated scenarios.

See also: spacecraft, satellite, orbital mechanics, spaceflight simulation.