The International Space Station (ISS) is a research facility in low Earth orbit, orbiting at an altitude between 320 km (199 mi) to 345 km (214 mi). As of May 2007, the International Space Station consists of four small rooms, known as "pressurized modules" in engineering parlance, and has a living capacity for three astronauts. The station is scheduled to be completed as of 2010, and will include a total of 10 pressurized modules, alongside a Soyuz spacecraft functioning as a lifeboat and a large unpressurized truss structure for solar panels.
Currently, the International Space Station is the only permanently manned facility in orbit. It was created as a way for five space agencies to share the high costs of launching and maintaining an in-orbit facility. The five agencies participating in the ISS project are NASA (United States), Roskosmos (Russia), JAXA (Japan), CSA (Canada), and the ESA (European Union). By the time the station is completed in 2010, the entire project will have cost around $100 billion USD or more. The International Space Station has been in orbit since 1998 but only occupied since 2000. It has already had 124 distinct visitors, including five paying space tourists, who paid $20 million US Dollars (USD) each to visit the station.
The first module of the International Space Station, Zarya (meaning "dawn" in Russian), was launched in 1998, and orbited autonomously for almost two years due to delays in constructing Zvezda ("star" in Russian), a service module with sleeping space for two astronauts. Zvezda also contains a shower and toilet, exercise equipment, a galley for food preparation, and is the largest module on the ISS, by a small margin. Shortly after Zarya was launched, the American Unity Module was attached to it. True to its name, Unity functions as a connecting node between other modules, and is sometimes referred to as Node 1. The final module currently in orbit is the US-built Destiny Laboratory Module, where scientific research is conducted.
From late 2007 to 2010, six additional modules are to be launched: Node 2, the Columbus Laboratory Module (European), Japanese Experiment Module, Multipurpose Laboratory Module (Russian), Node 3, and the Docking Cargo Module. The goal is for the space station to be completed by 2010. Most of the modules have a projected operating lifespan of 15 years, so the first module may need replacing or discarding in 2013, but the majority of the station should remain operational through 2020.