Shuttle astronaut exercising. Astronaut Robert Curbeam exercising on an ergometer device onboard the Space Shuttle Atlantis. Astronauts in space must follow intensive daily exercise regimes. These are needed to reduce the muscle atrophy and loss of bone tissue that occurs in the weightless environment of space. This was during mission STS- 98 (7th-20th February 2001), which continued the construction of the International Space Station (ISS). The ISS is a joint effort between NASA, the European Space Agency, the Russian space agency, Canada, Japan and Brazil. It orbits at an altitude of 350 kilometres, has been manned since late 2000 and is scheduled for completion in 2004.