The International Space Station (ISS) is an internationally developed research facility that is being assembled in low Earth orbit. On-orbit construction of the station began in 1998 and is scheduled for completion by late 2011. The station is expected to remain in operation until at least 2015, and likely 2020. With a greater mass than that of any previous space station, the ISS can be seen from Earth with the naked eye, and is by far the largest artificial satellite that has ever orbited Earth. The ISS serves as a research laboratory that has a microgravity environment in which crews conduct experiments in biology, chemistry, human biology, physics, astronomy and meteorology. The station has a unique environment for the testing of the spacecraft systems that will be required for missions to the Moon and Mars. The ISS is operated by Expedition crews, with the station programme maintaining an uninterrupted human presence in space since the launch of Expedition 1 on 31 October 2000.
The station is 51m in length and 109m in width. She is travelling at an average speed of 27 743.8 km/h and completes an orbit of the earth every 91 minutes. She orbits at about 425km above the earth.