A cable that connects an astronaut to the spacecraft during an extravehicular activity. From a space shuttle, an astronaut embarking on a space walk will first reach outside the secure air lock to pull in the safety tether and attach it to a ring on his or her spacesuit. A ring at the other end of the tether slides on a line leading through the cargo bay into space. If there is some distance to go, as when retrieving a satellite, the astronaut unhooks the tether and uses a manned manoeuvring unit (MMU).