The largest spacecraft ever built can be seen orbiting our planet in a low Earth orbit with our very own eyes in the night sky – it is the International Space Station (ISS). Maintained at an orbital altitude of between 205 to 255 miles, the ISS completes around 15.7 orbits per day. The habitable satellite, whose first component of its modular structure was rocketed into space in 1998, weighs in at approximately 45,000kg and has a length of around 73 metres, a width of just over 100 metres and a height of 20 metres.
The artificial satellite serves as a microgravity and space environment research laboratory for its crew members where experiments encompassing the disciplines of biology through to astronomy and meteorology are conducted. Situated in orbit for the testing of spacecraft and equipment required for missions to Mars and the Moon, the ISS has been occupied for just over 12 years. While the ISS is capable of holding a capacity of six astronauts, there are sometimes just three crew members on board. The ISS programme is jointly owned by five space agencies: the Russian Federal Space Agency, JAXA, ESA, CSA and NASA. It should be in operation until at least 2020.
Answered by science journalist Gemma Lavender