ISS

By Anonymous

The International Space Station (ISS) is a space station (habitable artificial satellite) in low Earth orbit. The ISS programme is a joint project between five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA (Japan), ESA(Europe), and CSA (Canada). The ownership and use of the space station is established by intergovernmental treaties and agreements.

The ISS serves as a microgravity and space environment research laboratory in which crew members conduct experiments in biology, human biology, physics, astronomy, meteorology, and other fields. The station is suited for the testing of spacecraft systems and equipment required for missions to the Moon and Mars. The ISS maintains an orbit with an average altitude of 400 kilometres (250 mi) by means of reboost manoeuvres using the engines of the Zvezda module or visiting spacecraft. It circles the Earth in roughly 92 minutes and completes 15.5 orbits per day.

The station is divided into two sections, the Russian Orbital Segment (ROS), which is operated by Russia, and the United States Orbital Segment (USOS), which is shared by many nations. As of January 2018, operations of the US segment were funded until 2025. Roscosmos has endorsed the continued operation of ISS through 2024, but has proposed using elements of the Russian segment to construct a new Russian space station called OPSEK.

The first ISS component was launched in 1998, with the first long-term residents arriving on 2 November 2000. Since then, the station has been continuously occupied for 18 years and 285 days.This is the longest continuous human presence in low Earth orbit, having surpassed the previous record of 9 years and 357 days held by Mir. The latest major pressurised module was fitted in 2011, with an experimental inflatable space habitat added in 2016. As of December 2018, the station is expected to operate until 2030. Development and assembly of the station continues, with several major new Russian elements scheduled for launch starting in 2020. The ISS is the largest human-made body in low Earth orbit and can often be seen with the naked eyefrom Earth. The ISS consists of pressurised habitation modules, structural trusses, solar arrays, radiators, docking ports, experiment bays and robotic arms. Major ISS modules have been launched by Russian Proton and Soyuz rockets and US Space Shuttles.

Cost

The ISS has been described as the most expensive single item ever constructed. In 2010 the cost was expected to be $150 billion. This includes NASA's budget of $58.7 billion (inflation-unadjusted) for the station from 1985 to 2015 ($72.4 billion in 2010 dollars), Russia's $12 billion, Europe's $5 billion, Japan's $5 billion, Canada's $2 billion, and the cost of 36 shuttle flights to build the station; estimated at $1.4 billion each, or $50.4 billion in total. Assuming 20,000 person-days of use from 2000 to 2015 by two- to six-person crews, each person-day would cost $7.5 million, less than half the inflation-adjusted $19.6 million ($5.5 million before inflation) per person-day of Skylab.