TheInternational Space Station programme is tied together by a complex set of legal, political and financial agreements between the fifteen nations involved in the project, governing ownership of the various components, rights to crewing and utilisation, and responsibilities for crew rotation and resupply of theInternational Space Station. It was conceived in September 1993 by theUnited States andRussia after 1980s plans for separate American (Freedom) and Soviet (Mir-2) space stations failed due to budgetary reasons.[2] These agreements tie together the five space agencies and their respective International Space Station programmes and govern how they interact with each other on a daily basis to maintain station operations, from traffic control of spacecraft to and from the station, to utilisation of space and crew time. In March 2010, the International Space Station Program Managers from each of the five partner agencies were presented withAviation Week'sLaureate Award in the Space category,[3] and the ISS programme was awarded the 2009Collier Trophy.
As thespace race drew to a close in the early 1970s, the US andUSSR began to contemplate a variety of potential collaborations in outer space. This culminated in the 1975Apollo-Soyuz Test Project, the first docking of spacecraft from two different spacefaring nations. The ASTP was considered a success, and further joint missions were also contemplated.
One such concept was International Skylab, which proposed launching the backupSkylab B space station for a mission that would see multiple visits by bothApollo andSoyuz crew vehicles.[4] More ambitious was the Skylab-Salyut Space Laboratory, which proposed docking the Skylab B to a SovietSalyut space station. Falling budgets and risingCold War tensions in the late 1970s saw these concepts fall by the wayside, along with another plan to have theSpace Shuttle dock with a Salyut space station.[5]
In the early 1980s,NASA planned to launch a modular space station calledFreedom as a counterpart to the Salyut andMir space stations. In 1984 the ESA was invited to participate in Space StationFreedom, and the ESA approved the Columbus laboratory by 1987.[6] TheJapanese Experiment Module (JEM), orKibō, was announced in 1985, as part of theFreedom space station in response to a NASA request in 1982.
In early 1985, science ministers from theEuropean Space Agency (ESA) countries approved theColumbus programme, the most ambitious effort in space undertaken by that organization at the time. The plan spearheaded by Germany and Italy included a module which would be attached toFreedom, and with the capability to evolve into a full-fledged European orbital outpost before the end of the century.[7]
Increasing costs threw these plans into doubt in the early 1990s. Congress was unwilling to provide enough money to build and operateFreedom, and demanded NASA increase international participation to defray the rising costs or they would cancel the entire project outright.[8]
Simultaneously, the USSR was conducting planning for theMir-2 space station, and had begun constructing modules for the new station by the mid-1980s. However thecollapse of the Soviet Union required these plans to be greatly downscaled, and soon Mir-2 was in danger of never being launched at all.[9] With both space station projects in jeopardy, American and Russian officials met and proposed they be combined.[10]
In September 1993, American Vice-PresidentAl Gore and Russian Prime MinisterViktor Chernomyrdin announced plans for a new space station, which eventually became the International Space Station.[11] They also agreed, in preparation for this new project, that the United States would be involved in the Mir programme, including American Shuttles docking, in theShuttle–Mir programme.[12]
A commemorative plaque honouring Space Station Intergovernmental Agreement signed on January 29, 1998
The legal structure that regulates the station is multi-layered. The primary layer establishing obligations and rights between the ISS partners is the Space Station Intergovernmental Agreement (IGA), aninternational treaty signed on January 28, 1998 by fifteen governments involved in the space station project. The ISS consists of Canada, Japan, the Russian Federation, the United States, and eleven Member States of the European Space Agency (Belgium, Denmark, France, Germany, Italy, The Netherlands, Norway, Spain, Sweden, Switzerland and the United Kingdom).[13] Article 1 outlines its purpose:
This Agreement is a long term international co-operative framework on the basis of genuine partnership, for the detailed design, development, operation, and utilization of a permanently inhabited civil Space Station for peaceful purposes, in accordance with international law.[14]
The IGA sets the stage for a second layer of agreements between the partners referred to as 'Memoranda of Understanding' (MOUs), of which four exist between NASA and each of the four other partners. There are no MOUs between ESA, Roskosmos, CSA and JAXA because NASA is the designatedmanager of the ISS. The MOUs are used to describe the roles and responsibilities of the partners in more detail.
A third layer consists of bartered contractual agreements or the trading of the partners' rights and duties, including the 2005 commercial framework agreement between NASA andRoscosmos that sets forth the terms and conditions under which NASA purchases seats on Soyuz crew transporters and cargo capacity on uncrewedProgress transporters.
A fourth legal layer of agreements implements and supplements the four MOUs further. Notably among them is the ISS code of conduct made in 2000, setting outcriminal jurisdiction, anti-harassment and certain other behavior rules for ISS crewmembers.[15]
Zarya andUnity were entered for the first time on 10 December 1998.
Soyuz TM-31 being prepared to bring the first resident crew to the station in October 2000
Each permanent crew is given an expedition number. Expeditions run up to six months, from launch until undocking, an 'increment' covers the same time period, but includes cargo spacecraft and all activities. Expeditions 1 to 6 consisted of three-person crews. After the destruction of NASA's Space ShuttleColumbia, Expeditions 7 to 12 were reduced to two-person "caretaker" crews who could maintain the station, because a larger crew could not be fully resupplied by the small Russian Progress cargo spacecraft.[16] After the Shuttle fleet returned to flight, three person crews also returned to the ISS beginning with Expedition 13. As the Shuttle flights expanded the station, crew sizes also expanded, eventually reaching six around 2010.[17][18] With the arrival of crew on larger UScommercial spacecraft beginning in 2020,[19] crew size has been increased to seven, the number for which ISS was originally designed.[20][21]
Travellers who pay for their own passage into space are termedspaceflight participants by Roscosmos and NASA, and are sometimes referred to as "space tourists", a term they generally dislike.[a] As of June 2023[update], thirteen space tourists have visited the ISS; nine were transported to the ISS on Russian Soyuz spacecraft, and four were transported on AmericanSpaceX Dragon 2 spacecraft. For one-tourist missions, when professional crews change over in numbers not divisible by the three seats in a Soyuz, and a short-stay crewmember is not sent, the spare seat is sold by MirCorp through Space Adventures. Space tourism was halted in 2011 when the Space Shuttle was retired and the station's crew size was reduced to six, as the partners relied on Russian transport seats for access to the station. Soyuz flight schedules increased after 2013, allowing five Soyuz flights (15 seats) with only two expeditions (12 seats) required.[29] The remaining seats were to be sold for around US$40 million each to members of the public who could pass a medical exam. ESA and NASA criticised private spaceflight at the beginning of the ISS, and NASA initially resisted trainingDennis Tito, the first person to pay for his own passage to the ISS.[b]
Anousheh Ansari became the first self-funded woman to fly to the ISS as well as the first Iranian in space. Officials reported that her education and experience made her much more than a tourist, and her performance in training had been "excellent."[30] She did Russian and European studies involving medicine and microbiology during her 10-day stay. The 2009 documentarySpace Tourists follows her journey to the station, where she fulfilled "an age-old dream of man: to leave our planet as a 'normal person' and travel into outer space."[31]
In 2008, spaceflight participantRichard Garriott placed ageocache aboard the ISS during his flight.[32] This is the first non-terrestrial geocache in history.[33] At the same time, theImmortality Drive, an electronic record of eight digitised humanDNA sequences, was placed aboard the ISS.[34]
Various crewed and uncrewed spacecraft have supported the station's operations. Flights to the ISS have included 93 Progress,[c] 72 Soyuz, 50SpaceX Dragon[d] 37 Space Shuttle, 21Cygnus, 9HTV, 5ATV, and 2Boeing Starliner missions.[42]
There are currently eight docking ports for visiting spacecraft, with four additional ports installed but not yet put into service:[43]
Forward ports are at the front of the station in its usual orientation and direction of travel.Aft is the opposite, at the rear.Nadir points toward Earth, whilezenith points away from it.Port is to the left andstarboard to the right when one's feet are toward Earth and one is facing forward, in the direction of travel.
Cargo spacecraft that will perform an orbital re-boost of the station will typically dock at an aft, forward or nadir-facing port.
As of 31 July 2025[ref], 290 people from 27 countries had visited the space station, many of them multiple times. The United States sent 170 people, Russia sent 64, 11 were Japanese, nine were Canadian, six were Italian, four were French, four were German, two from the United Arab Emirates, Hungary and Saudi Arabia and one each from Belgium, Brazil, Denmark, Israel, Kazakhstan, Malaysia, the Netherlands, India, Turkey, Sweden, Belarus, South Africa, Poland, South Korea, Spain, Sweden, and the United Kingdom.[44]
Uncrewed spaceflights to theInternational Space Station (ISS) are made primarily to deliver cargo, however several Russian modules have also docked to the outpost following uncrewed launches. Resupply missions typically use the RussianProgress spacecrafts, i.e,Progress-M (Standard and Modified),Progress-M1 andProgress MS series vehicles, EuropeanAutomated Transfer Vehicles, JapaneseKounotori vehicles, and the AmericanDragon 1 and2 vehicles andCygnus (Standard, Enhanced and XL series) spacecraft. The primary docking system for Progress spacecraft is the automatedKurs system, with the manualTORU system as a backup. ATVs also use Kurs, however they are not equipped with TORU. The other spacecraft — the JapaneseHTVs andHTV-Xs, theSpaceX Dragon (under CRS phase 1) and the Northrop Grumman[45] Cygnus vehicles — rendezvous with the station before being grappled usingCanadarm2 and berthed at thenadir port of theHarmony orUnity module for one to two months. Progress, Cygnus and ATV can remain docked for up to six months.[46][47] Under CRS phase 2, SpaceX Cargo Dragon docks autonomously at IDA-2 or 3 as the case may be.Dream Chaser Cargo System is also planned to resupply ISS in future. As of September 2025,Progress spacecraft have flown most of the uncrewed missions to the ISS.
AstronautScott Parazynski ofSTS-120 conducted a 7-hour, 19-minute spacewalk to repair (essentially sew) a damaged solar panel which helps supply power to the International Space Station. NASA considered the spacewalk dangerous with potential risk of electrical shock.Since construction started, the International Space Station programme has had to deal with several maintenance issues, unexpected problems and failures. These incidents have affected theassembly timeline, led to periods of reduced capabilities of the station and in some cases could have forced the crew to abandon the space station for safety reasons, had these problems not been resolved.
The components of the ISS are operated and monitored by their respective space agencies atmission control centres across the globe.
The two primary control centres are:
Roscosmos'RKA Mission Control Center atKorolyov, Russia — manages the maintaining of the station, controls launches of the crewed missions, guides launches from Baikonur Cosmodrome
They are supported by several more specialized control centres:
JAXA's JEM Control Center and HTV Control Center atTsukuba Space Center (TKSC) inIbaraki, Japan – responsible for operating theKibō laboratory complex and all flights of theHTV cargo spacecraft, respectively[48]
This article needs to beupdated. Please help update this article to reflect recent events or newly available information.(July 2022)
Primary contributing nations
Formerly contracted nations
The politics of theInternational Space Station have been affected by superpower rivalries, international treaties, and funding arrangements. TheCold War was an early factor, overtaken in recent years by the United States' distrust of China. The station has an international crew, with the use of their time, and that of equipment on the station, being governed by treaties between participant nations.
There is no fixed percentage of ownership for the whole space station. Rather, Article 5 of the IGA sets forth thateach partner shall retain jurisdiction and control over the elements it registers and over personnel in or on the Space Station who are its nationals.[49] Therefore, for each ISS module only one partner retains sole ownership. Still, the agreements to use the space station facilities are more complex.
Crew time, electrical power and rights to purchase supporting services (such as data upload & download and communications) are divided 76.6% for NASA, 12.8% for JAXA, 8.3% for ESA, and 2.3% for CSA.[51][52][53]
The heads of the ISS agencies from Canada, Europe, Japan, Russia and the United States meet in Tokyo to review ISS cooperation.
FormerNASA AdministratorMichael D. Griffin says the International Space Station has a role to play as NASA moves forward with a new focus for the crewed space programme, which is to go out beyond Earth orbit for purposes of human exploration and scientific discovery. "The International Space Station is now a stepping stone on the way, rather than being the end of the line", Griffin said.[54] Griffin has said that station crews will not only continue to learn how to live and work in space, but also will learn how to build hardware that can survive and function for the years required to make the round-trip voyage from Earth to Mars.[54]
Despite this view, however, in an internal e-mail leaked to the press on August 18, 2008 from Griffin to NASA managers,[55][56][57] Griffin apparently communicated his belief that the current US administration had made no viable plan for US crews to participate in the ISS beyond 2011, and that theOffice of Management and Budget (OMB) andOffice of Science and Technology Policy (OSTP) were actually seeking its demise.[56] The e-mail appeared to suggest that Griffin believed the only reasonable solution was to extend the operation of theSpace Shuttle beyond 2010, but noted that Executive Policy (i.e. theWhite House) was firm that there would be no extension of the Space Shuttle retirement date, and thus no US capability to launch crews into orbit until theOrion spacecraft would become operational in 2020 as part of theConstellation programme. He did not see purchase of Russian launches for NASA crews as politically viable following the2008 South Ossetia war, and hoped the incomingBarack Obama administration would resolve the issue in 2009 by extending Space Shuttle operations beyond 2010.
A solicitation issued by NASAJSC indicates NASA's intent to purchase from Roscosmos "a minimum of 3 Soyuz seats up to a maximum of 24 seats beginning in the Spring of 2012" to provide ISS crew transportation.[58][59]
On September 7, 2008, NASA released a statement regarding the leaked email, in which Griffin said:
The leaked internal email fails to provide the contextual framework for my remarks, and my support for the administration's policies. Administration policy is to retire the shuttle in 2010 and purchase crew transport from Russia until Ares and Orion are available. The administration continues to support our request for anINKSNA exemption. Administration policy continues to be that we will take no action to preclude continued operation of the International Space Station past 2016. I strongly support these administration policies, as do OSTP and OMB.
On October 15, 2008, President Bush signed the NASA Authorization Act of 2008, giving NASA funding for one additional mission to "deliver science experiments to the station".[61][62][63][64] The Act allows for an additional Space Shuttle flight,STS-134, to the ISS to install theAlpha Magnetic Spectrometer, which was previously cancelled.[65]
President of the United States Barack Obama has supported the continued operation of the station, and supported the NASA Authorization Act of 2008.[65] Obama's plan for space exploration includes finishing the station and completion of the US programmes related to theOrion spacecraft.[66]
On 12 April 2021, at a meeting with Russian PresidentVladimir Putin, then-Deputy Prime MinisterYury Borisov announced he had decided that Russia might withdraw from the ISS programme in 2025.[67][68] According to Russian authorities, the timeframe of the station's operations has expired and its condition leaves much to be desired.[67] On 26 July 2022, Borisov, who had become head of Roscosmos, submitted to Putin his plans for withdrawal from the programme after 2024.[69] However, Robyn Gatens, the NASA official in charge of space station operations, responded that NASA had not received any formal notices from Roscosmos concerning withdrawal plans.[70] On 21 September 2022, Borisov stated that Russia was "highly likely" to continue to participate in the ISS programme until 2028.[71]
Originally the ISS was planned to be a 15-year mission.[72]Therefore, an end of mission had been worked on,[73] but was several times postponed due to the success and support for the operation of the station.[74] As a result, the oldest modules of the ISS have been in orbit for more than 20 years, with their reliability having decreased.[73] It has been proposed to use funds elsewhere instead, for example for a return to the Moon.[74] According to theOuter Space Treaty, the parties are legally responsible for all spacecraft or modules they launch.[75] Anunmaintained station would pose anorbital andre-entry hazard.
Russia has stated that it plans to pull out of the ISS program after 2025.[76] However, Russian modules will provideorbital station-keeping until 2028.[73]
The US planned in 2009 to deorbit the ISS in 2016.[74] But on 30 September 2015, Boeing's contract with NASA as prime contractor for the ISS was extended to 30 September 2020. Part of Boeing's services under the contract related to extending the station's primary structural hardware past 2020 to the end of 2028.[77] In July 2018, the Space Frontier Act of 2018 was intended to extend operations of the ISS to 2030. This bill was unanimously approved in the Senate, but failed to pass in the U.S. House.[78][79] In September 2018, the Leading Human Spaceflight Act was introduced with the intent to extend operations of the ISS to 2030, and was confirmed in December 2018.[80][81][82] Congress later passed similar provisions in itsCHIPS and Science Act, signed into law by U.S. PresidentJoe Biden on 9 August 2022.[83][84]
China has reportedly expressed interest in the project, especially if it would be able to work with theRussian Federal Space Agency. Due to national security concerns, the United States Congress passed a law prohibiting contact between US and Chinese space programmes.[86] As of 2019[update], China is not involved in the International Space Station.[87] In addition to national security concerns, United States objections include China's human rights record and issues surrounding technology transfer.[88][89]The heads of both the South Korean and Indian space agencies announced at the first plenary session of the 2009International Astronautical Congress on 12 October that their nations intend to join the ISS programme. The talks began in 2010, and were not successful. The heads of agency also expressed support for extending ISS lifetime.[90] European countries not a part of the International Space Station programme will be allowed access to the station in a three-year trial period,ESA officials say.[91] TheIndian Space Research Organisation has made it clear that it will not join the ISS and will instead build its own space station.[92]
The ISS has been described as themost expensive single item ever constructed.[93] As of 2010, the total cost was US$150 billion. This includesNASA's budget of $58.7 billion ($89.73 billion in 2021 dollars) for the station from 1985 to 2015, 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 man-days of use from 2000 to 2015 by two- to six-person crews, each man-day would cost $7.5 million, less than half the inflation-adjusted $19.6 million ($5.5 million before inflation) per man-day ofSkylab.[94]
One of the most ambitious ISS modules to date, theCentrifuge Accommodations Module, has been cancelled due to the prohibitive costs NASA faces in simply completing the ISS. As a result, the research done on the ISS is generally limited to experiments which do not require any specialized apparatus. For example, in the first half of 2007, ISS research dealt primarily with human biological responses to being in space, covering topics likekidney stones,circadian rhythm, and the effects ofcosmic rays on thenervous system.[98][99][100]
Other critics have attacked the ISS on some technical design grounds:
Jeff Foust argued that the ISS requires too much maintenance, especially by risky, expensiveEVAs.[101] The magazineThe American Enterprise reports, for instance, that ISS astronauts "now spend 85 percent of their time on construction and maintenance" alone.[citation needed]
The Astronomical Society of the Pacific has mentioned that its orbit is rather highly inclined, which makes Russian launches cheaper, but US launches more expensive.[102]
Critics[who?] also say that NASA is often casually credited with "spin-offs" (such asVelcro and portable computers) that were developed independently for other reasons.[103] NASA maintains a list of spin-offs from the construction of the ISS, as well as from work performed on the ISS.[104][105]
In response to some of these criticisms, advocates ofhuman space exploration say that criticism of the ISS programme is short-sighted, and that crewed space research and exploration have produced billions of dollars' worth of tangible benefits to people on Earth. Jerome Schnee estimated that the indirect economic return from spin-offs of human space exploration has been many times the initial public investment.[106] A review of the claims by the Federation of American Scientists argued that NASA's rate of return from spin-offs is actually "astoundingly bad", except for aeronautics work that has led to aircraft sales.[107]
It is therefore debatable whether the ISS, as distinct from the wider space programme, is a major contributor to society. Some advocates[who?] argue that apart from its scientific value, it is an important example of international cooperation.[108] Others[who?] claim that the ISS is an asset that, if properly leveraged, could allow more economical crewed Lunar and Mars missions.[109]
^ESA director Jörg Feustel-Büechl said in 2001 that Russia had no right to send 'amateurs' to the ISS. A 'stand-off' occurred at the Johnson Space Center between CommanderTalgat Musabayev and NASA managerRobert Cabana who refused to train Dennis Tito, a member of Musabayev's crew along withYuri Baturin. Musabayev argued that Tito had trained 700 hours in the last year and was as qualified as any NASA astronaut, and refused to allow his crew to be trained on the USOS without Tito. Cabana would not allow training to begin, and the commander returned with his crew to their hotel.
^Including the modified DC-1, M-MIM2 and M-UM module transports
^abcdThe Prichal aft, forward, port and starboard ports still have their protective covers in place and have yet to be used since the module originally docked at the station.
^Morring, Frank (July 27, 2012)."ISS Research Hampered By Crew Availability".Aviation Week. Archived fromthe original on May 1, 2013. RetrievedJuly 30, 2012.A commercial capability would allow the station's crew to grow from six to seven by providing a four-seat vehicle for emergency departures in addition to the three-seat Russian Soyuz capsules in use today.
^Hoversten, Paul (April 2011)."Assembly (Nearly) Complete".Air & Space.Smithsonian Institution.Archived from the original on June 7, 2023. RetrievedMay 8, 2011.In fact, we're designed on the U.S. side to take four crew. The ISS design is actually for seven. We operate with six because first, we can get all our work done with six, and second, we don't have a vehicle that allows us to fly a seventh crew member. Our requirement for the new vehicles being designed is for four seats. So I don't expect us to go down in crew size. I would expect us to increase it.
^Cook, John; Aksamentov, Valery; Hoffman, Thomas; Bruner, Wes (September 2011).ISS Interface Mechanisms and their Heritage(PDF). AIAA Space. Houston, Texas:Boeing.Archived(PDF) from the original on August 10, 2023. RetrievedMarch 31, 2015.Docking is when one incoming spacecraft rendezvous with another spacecraft and flies a controlled collision trajectory in such a manner so as to align and mesh the interface mechanisms. The spacecraft docking mechanisms typically enter what is called soft capture, followed by a load attenuation phase, and then the hard docked position which establishes an air-tight structural connection between spacecraft. Berthing, by contrast, is when an incoming spacecraft is grappled by a robotic arm and its interface mechanism is placed in close proximity of the stationary interface mechanism. Then typically there is a capture process, coarse alignment and fine alignment and then structural attachment.
^Dobrovidova, Olga (April 20, 2021). "Russia mulls withdrawing from the International Space Station after 2024".Science. American Association for the Advancement of Science (AAAS).doi:10.1126/science.abj1005.ISSN0036-8075.S2CID235542488.
^Lafleur, Claude (March 8, 2010)."Costs of US piloted programs".The Space Review.Archived from the original on August 1, 2023. RetrievedFebruary 18, 2012. See author correction in comments.
^James J. Secosky; George Musser (1996)."Up, Up, and Away". Astronomical Society of the Pacific. Archived fromthe original on August 8, 2011. RetrievedSeptember 10, 2006.
