Aerospace newsroom

A glossary for following ISS news

News about the station keeps repeating a dozen terms that are rarely explained. These are the ones you will see most often in the headlines above:

Docking and berthing

A spacecraft docks when it joins the station under its own power, as Crew Dragon and Soyuz do. It is berthed when the station's robotic arm captures it and places it on a port: that is how the Cygnus cargo ship arrives.

Expedition

Each period of occupation carries an expedition number. It changes when one crew leaves and the next takes over, and command is handed over in a short ceremony on board.

Spacewalk (EVA)

Extravehicular activity: one or two astronauts go outside in pressurised suits, usually to install equipment or fix faults. It typically lasts six to seven hours.

Reboost

The station slowly loses altitude through drag from the residual atmosphere. Every so often the engines of a docked spacecraft push it a few kilometres higher. After a manoeuvre like that, pass predictions shift slightly.

Debris avoidance manoeuvre

An engine burn to move the station away from a piece of space debris whose path comes too close. It is decided only a few hours in advance.

Cargo ships

Uncrewed spacecraft that bring food, water, experiments and fuel: cargo Dragon, Cygnus and Russia's Progress, among others. When their mission ends, some return with samples and others burn up on re-entry.

TLE

Two lines of text with the orbital parameters published by tracking organisations. It is what this site, like most trackers, uses to work out where the station will pass.

Deorbit

The controlled retirement of the station at the end of its service life, planned for around 2030: a dedicated spacecraft will lower it so that whatever does not burn up falls into an uninhabited area of the Pacific.

If a story leaves you with questions, the guides above explain in more depth how the station is resupplied and what will happen when it is retired.