Engineers describe every space mission as a system made of segments. The three most common are the space segment, the ground segment and the launch segment. Knowing these terms helps when reading contracts, requirements or tenders, because responsibilities are usually split along these lines.
How ECSS defines the segments
The European Cooperation for Space Standardization (ECSS), whose standards are used across European space projects, defines a space system as a system that contains at least a space, a ground or a launch segment. Its glossary defines:
- Space segment: the part of a space system placed in space to fulfil the space mission objectives.
- Ground segment: the part of a space system located on ground which monitors and controls the space segment elements.
- Launch segment: the part of a space system which is used to transport space segment elements into space.
What belongs to the launch segment
According to ECSS, a launch segment is composed of a launcher system with its specific launch complex, supported by a launch range. It also includes the integrated launcher and the facilities needed to manufacture, test and deliver launcher elements. A launcher itself consists of further elements such as stages, engines and the upper part.
In practice, the launch segment therefore covers:
- The rocket, including its stages, engines, upper stage and payload fairing.
- The launch pad and launch complex, such as Launch Complex 39A shown on the cover image.
- The launch range, which tracks the flight and protects the public. See our article on launch range safety.
- The facilities for manufacturing, testing and preparing the launcher.
The space segment
The space segment is what operates in orbit: satellites, landers, rovers or space stations. It includes both the payload that performs the mission and the platform, or bus, that supplies power, attitude control and communications.
The ground segment
The ground segment includes ground stations, antennas, mission control centres and data processing. Our article on satellite ground systems explains how these networks work.
Why the split matters for customers
For a satellite operator, the launch segment is usually bought as a service from a launch provider. The interfaces between the segments, such as the payload adapter between satellite and rocket or the frequencies between satellite and ground stations, are where most of the coordination work happens.
Sources
Cover image: Aerial view of Launch Complex 39A at NASA's Kennedy Space Center, January 2021. Credit: NASA/Ben Smegelsky (KSC-20210113-PH-JBS01_0201), public domain.