International Space Station

The International Space Station (ISS) is a space station in low Earth orbit (LEO). It is the product of the International Space Station program and is operated by five partner space agencies: NASA (United States), Roscosmos (Russia), ESA (Europe), JAXA (Japan), and CSA (Canada). It is the first space station built, maintained and crewed through international cooperation and the largest human spacecraft ever constructed. Since 2 November 2000, it has hosted the longest continuous presence of humans in space. Alongside Tiangong, it is one of the only two currently operational space stations.

The station orbits between 51.64° north and south, at about above Earth, below the Van Allen radiation belts and most space debris. Its orbit takes it at roughly every 93 minutes around Earth, times a day. Measuring (with solar arrays) by , and has a pressurised internal volume of 1,005 m<sup>3</sup> (35,491 ft<sup>3</sup>), comparable to a Boeing 747 airliner.

The station is a modular space station divided into two main sections: the Russian Orbital Segment (ROS), developed by Roscosmos, and the US Orbital Segment (USOS), built by NASA, ESA, JAXA, and CSA. The Integrated Truss Structure connects the station's vast system of solar panels and radiators to its 16 major pressurized modules. These modules support scientific research, crew habitation, storage, spacecraft control, and airlock operations. The ISS has eight docking and berthing ports for visiting spacecraft. In total, the station consists of 43 different modules and elements. Crews visit via the Soyuz and Crew Dragon spacecraft, and previously the Space Shuttle. Cargo supply craft include Progress, Cargo Dragon, Cygnus, Automated Transfer Vehicle, and HTV-X.

The ISS is the political product of the development of international cooperation in space throughout the space age. The station combines two previously planned crewed Earth-orbiting stations: the United States' Space Station Freedom and the Soviet Union's Mir-2. The first ISS module was launched in 1998, with major components delivered by Proton, Soyuz and Space Shuttle launch vehicles. Long-term occupancy began with the arrival of the Expedition 1 crew on 2 November 2000. Since then, the ISS has remained continuously inhabited for , the longest continuous human presence in space. , 290 individuals from 26 countries had visited the station.

Future plans for the ISS include the addition of at least one module, the Payload Power Thermal Module by Axiom Space, forming the commercial segment of the station. The station is expected to remain operational until the end of 2030, by which parts of it are to be used for Axiom Station and the Russian Orbital Service Station. After this the ISS is planned to be de-orbited using the US Deorbit Vehicle, but critique of this plan and the proposal of parking the station at a more stable higher orbit has gathered congressional support .

Conception

Purpose

The ISS was originally intended to be a laboratory, observatory, and factory while providing transportation, maintenance, and a low Earth orbit staging base for possible future missions to the Moon, Mars, and asteroids. However, not all of the uses envisioned in the initial memorandum of understanding between NASA and Roscosmos have been realised. In the 2010 United States National Space Policy, the ISS was given additional roles of serving commercial, diplomatic, and educational purposes.

Scientific research

The ISS provides a platform to conduct scientific research, with power, data, cooling, and crew available to support experiments. Small uncrewed spacecraft can also provide platforms for experiments, especially those involving zero gravity and exposure to space, but space stations offer a long-term environment where studies can be performed potentially for decades, with ready access by human researchers. Scientists on Earth have timely access to the data and can suggest experimental modifications to the crew. If follow-on experiments are necessary, the routinely scheduled launches of resupply craft allows new hardware to be launched with relative ease.

A notable ISS experiment is the Alpha Magnetic Spectrometer (AMS), which is intended to detect dark matter and answer other fundamental questions about the universe. According to NASA, the AMS is as important as the Hubble Space Telescope. It is docked on the station, and could not have been easily accommodated on a free flying satellite platform because of its power and bandwidth needs. On 3 April 2013, scientists reported that hints of dark matter may have been detected by the AMS. According to these scientists, "The first results from the space-borne Alpha Magnetic Spectrometer confirm an unexplained excess of high-energy positrons in Earth-bound cosmic rays".

The space environment is hostile to life. Unprotected presence in space results in exposure to intense radiation (consisting primarily of protons and other subatomic charged particles from the solar wind, in addition to cosmic rays), vacuum, extreme temperatures, and microgravity. Some simple forms of life called extremophiles, as well as small invertebrates called tardigrades, can survive in this environment in an extremely dry state through desiccation.

Medical research improves knowledge about the effects of long-term space exposure on the human body, including muscle atrophy, bone loss, and fluid shift. This data will be used to determine whether long-lasting human spaceflight and space colonisation is feasible. In 2006, data on bone loss and muscular atrophy suggested that there would be a significant risk of fractures and movement problems if astronauts landed on a planet after a lengthy interplanetary cruise, such as the six-month interval required to travel to Mars.

Medical studies are conducted aboard the ISS on behalf of the National Space Biomedical Research Institute (NSBRI). Prominent among these is the Advanced Diagnostic Ultrasound in Microgravity study in which astronauts perform ultrasound scans under the guidance of remote experts. The study considers the diagnosis and treatment of medical conditions in space. There is usually no physician on board the ISS and diagnosis of medical conditions is a challenge. It is anticipated that remotely guided ultrasound scans will have application on Earth in emergency and rural care situations where in-person access to a trained physician is difficult.

In August 2020, scientists reported that bacteria from Earth, particularly Deinococcus radiodurans bacteria, which is highly resistant to environmental hazards, were found to survive for three years in outer space, based on studies conducted on the International Space Station. These findings supported the notion of panspermia, the hypothesis that life exists throughout the Universe, distributed in various ways, including space dust, meteoroids, asteroids, comets, planetoids or contaminated spacecraft.

Remote sensing of the Earth, astronomy, and deep space research on the ISS have significantly increased during the 2010s after the completion of the US Orbital Segment in 2011. Throughout the more than 20 years of the ISS program, researchers aboard the ISS and on the ground have examined aerosols, ozone, lightning, and oxides in Earth's atmosphere, as well as the Sun, cosmic rays, cosmic dust, antimatter, and dark matter in the universe. Examples of Earth-viewing remote sensing experiments that have flown on the ISS are the Orbiting Carbon Observatory 3, ISS-RapidScat, ECOSTRESS, the Global Ecosystem Dynamics Investigation, and the Cloud Aerosol Transport System. ISS-based astronomy telescopes and experiments include SOLAR, the Neutron Star Interior Composition Explorer, the Calorimetric Electron Telescope, the Monitor of All-sky X-ray Image (MAXI), and the Alpha Magnetic Spectrometer.

Microgravity environment

thumb|[[Jessica Watkins and Bob Hines working on XROOTS, an experiment using the Veggie facility of the station testing soilless hydroponic and aeroponic plant growth]]

thumb|A comparison between the combustion of a candle on [[Earth (left) and in a free fall environment, such as that found on the ISS (right)]]

Researchers are investigating the effect of the station's near-weightless environment on the evolution, development, growth and internal processes of plants and animals. In response to some of the data, NASA wants to investigate microgravity's effects on the growth of three-dimensional, human-like tissues and the unusual protein crystals that can be formed in space. Other areas of interest include the effect of low gravity on combustion, through the study of the efficiency of burning and control of emissions and pollutants. These findings may improve knowledge about energy production and lead to economic and environmental benefits. Referring to the MARS-500 experiment, a crew isolation experiment conducted on Earth, ESA states, "Whereas the ISS is essential for answering questions concerning the possible impact of weightlessness, radiation and other space-specific factors, aspects such as the effect of long-term isolation and confinement can be more appropriately addressed via ground-based simulations". Sergey Krasnov, the head of human space flight programs for Russia's space agency, Roscosmos, in 2011 suggested a "shorter version" of MARS-500 may be carried out on the ISS.

In 2009, noting the value of the partnership framework itself, Sergey Krasnov wrote, "When compared with partners acting separately, partners developing complementary abilities and resources could give us much more assurance of the success and safety of space exploration. The ISS is helping further advance near-Earth space exploration and realisation of prospective programs of research and exploration of the Solar system, including the Moon and Mars." A crewed mission to Mars may be a multinational effort involving space agencies and countries outside the current ISS partnership. In 2010, ESA Director-General Jean-Jacques Dordain stated his agency was ready to propose to the other four partners that China, India, and South Korea be invited to join the ISS partnership. NASA chief Charles Bolden stated in February 2011, "Any mission to Mars is likely to be a global effort." Currently, US federal legislation prevents NASA co-operation with China on space projects without approval by the FBI and Congress.

Education and cultural outreach

thumb|Original [[Jules Verne manuscripts displayed by crew inside the Jules Verne ATV (Automated Transfer Vehicle)]]

The ISS crew provides opportunities for students on Earth by running student-developed experiments, making educational demonstrations, allowing for student participation in classroom versions of ISS experiments, and directly engaging students using radio, and email. ESA offers a wide range of free teaching materials that can be downloaded for use in classrooms. In one lesson, students can navigate a 3D model of the interior and exterior of the ISS, and face spontaneous challenges to solve in real time.

The Japanese Aerospace Exploration Agency (JAXA) aims to inspire children to "pursue craftsmanship" and to heighten their "awareness of the importance of life and their responsibilities in society". Through a series of education guides, students develop a deeper understanding of the past and near-term future of crewed space flight, as well as that of Earth and life. In the JAXA "Seeds in Space" experiments, the mutation effects of spaceflight on plant seeds aboard the ISS are explored by growing sunflower seeds that have flown on the ISS for about nine months. In the first phase of Kibō utilisation from 2008 to mid-2010, researchers from more than a dozen Japanese universities conducted experiments in diverse fields.

Cultural activities are another major objective of the ISS program. Tetsuo Tanaka, the director of JAXA's Space Environment and Utilization Center, has said: "There is something about space that touches even people who are not interested in science."

Amateur Radio on the ISS (ARISS) is a volunteer program that encourages students worldwide to pursue careers in science, technology, engineering, and mathematics, through amateur radio communications opportunities with the ISS crew. ARISS is an international working group, consisting of delegations from nine countries including several in Europe, as well as Japan, Russia, Canada, and the United States. In areas where radio equipment cannot be used, speakerphones connect students to ground stations which then connect the calls to the space station.

thumb|The first content made in space for Wikipedia, from November 2017. It is a voice recording of ESA astronaut [[Paolo Nespoli in which he introduces himself by stating his spaceflight history]]

First Orbit is a 2011 feature-length documentary film about Vostok 1, the first crewed space flight around the Earth. By matching the orbit of the ISS to that of Vostok 1 as closely as possible, in terms of ground path and time of day, documentary filmmaker Christopher Riley and ESA astronaut Paolo Nespoli were able to film the view that Yuri Gagarin saw on his pioneering orbital space flight. This new footage was cut together with the original Vostok 1 mission audio recordings sourced from the Russian State Archive. Nespoli is credited as the director of photography for this documentary film, as he recorded the majority of the footage himself during Expedition 26/27. The film was streamed in a global YouTube premiere in 2011 under a free licence through the website firstorbit.org.

In May 2013, commander Chris Hadfield shot a music video of David Bowie's "Space Oddity" on board the station, which was released on YouTube. It was the first music video filmed in space.

In November 2017, while participating in Expedition 52/53 on the ISS, Paolo Nespoli made two recordings of his spoken voice (one in English and the other in his native Italian), for use on Wikipedia articles. These were the first content made in space specifically for Wikipedia.

In November 2021, a virtual reality exhibit called The Infinite featuring life aboard the ISS was announced.

International co-operation

thumb|A Commemorative Plaque honouring Space Station Intergovernmental Agreement signed on 28 January 1998

Involving five space programs and fifteen countries, the International Space Station is the most politically and legally complex space exploration program in history.

Brazil was also invited to participate in the program, the only developing country to receive such an invitation. Under the agreement framework, Brazil was to provide six pieces of hardware, and in exchange, would receive ISS utilization rights. However, Brazil was unable to deliver any of the elements due to a lack of funding and political priority within the country. Brazil officially dropped out of the ISS program in 2007.

Following the 2022 Russian invasion of Ukraine, continued cooperation between Russia and other countries on the International Space Station has been put into question. Roscosmos Director General Dmitry Rogozin insinuated that Russian withdrawal could cause the International Space Station to de-orbit due to lack of reboost capabilities, writing in a series of tweets, "If you block cooperation with us, who will save the ISS from an unguided de-orbit to impact on the territory of the US or Europe? There's also the chance of impact of the 500-ton construction in India or China. Do you want to threaten them with such a prospect? The ISS doesn't fly over Russia, so all the risk is yours. Are you ready for it?" (This latter claim is untrue: the ISS flies over all parts of the Earth between 51.6 degrees latitude north and south, approximately the latitude of Saratov.) Rogozin later tweeted that normal relations between ISS partners could only be restored once sanctions have been lifted, and indicated that Roscosmos would submit proposals to the Russian government on ending cooperation. NASA stated that, if necessary, US corporation Northrop Grumman has offered a reboost capability that would keep the ISS in orbit.

On 26 July 2022, Yury Borisov, Rogozin's successor as head of Roscosmos, submitted to Russian President Putin plans for withdrawal from the program after 2024. However, Robyn Gatens, the NASA official in charge of the space station, responded that NASA had not received any formal notices from Roscosmos concerning withdrawal plans.

Participating countries

European Space Agency

Construction

Manufacturing

thumb|S3-S4 Truss being hoist to the payload transfer container inside the [[Space Systems Processing Facility|Space Station Processing Facility next to several other ISS modules (2007)]]

The International Space Station is a product of global collaboration, with its components manufactured across the world.

The modules of the Russian Orbital Segment, including Zarya and Zvezda, were produced at the Khrunichev State Research and Production Space Center in Moscow. Zvezda was initially manufactured in 1985 as a component for the Mir-2 space station, which was never launched.

Much of the US Orbital Segment, including the Destiny and Unity modules, the Integrated Truss Structure, and solar arrays, were built at NASA's Marshall Space Flight Center in Huntsville, Alabama and Michoud Assembly Facility in New Orleans.

The US Orbital Segment also hosts the Columbus module contributed by the European Space Agency and built in Germany, the Kibō module contributed by Japan and built at the Tsukuba Space Center and the Institute of Space and Astronautical Science, along with the Canadarm2 and Dextre, a joint Canadian-U.S. endeavor. All of these components were shipped to the SSPF for launch processing.

Assembly

right|thumb|upright=1.8|Animation of the [[assembly of the International Space Station]]

The assembly of the International Space Station, a major endeavour in space architecture, began in November 1998.

Modules in the Russian segment launched and docked autonomously, with the exception of Rassvet. Other modules and components were delivered by the Space Shuttle, which then had to be installed by astronauts either remotely using robotic arms or during spacewalks, more formally known as extra-vehicular activities (EVAs). By 5 June 2011 astronauts had made over 159 EVAs to add components to the station, totaling more than 1,000 hours in space.

thumb|Zarya and Unity, the first two modules of the ISS, pictured in May 2000

The beginning of the core of the ISS's tenure in orbit was the launch of the Russian-built Zarya module atop a Proton rocket on 20 November 1998. Zarya provided propulsion, attitude control, communications, and electrical power. Two weeks later on 4 December 1998, the American-made Unity was ferried aboard Space Shuttle Endeavour on STS-88 and joined with Zarya. Unity provided the connection between the Russian and US segments of the station and would provide ports to connect future modules and visiting spacecraft.

While the connection of two modules built on different continents by nations that were once bitter rivals was a significant milestone, these two initial modules lacked life-support systems and the ISS remained unmanned for the next two years. At the time, the Russian station Mir was still inhabited.

The turning point arrived in July 2000 with the launch of the Zvezda module. Equipped with living quarters and life-support systems, Zvezda enabled continuous human presence aboard the station. The first crew, Expedition 1, arrived that November aboard Soyuz TM-31.

The ISS grew steadily over the following years, with modules delivered by both Russian rockets and the Space Shuttle.

Expedition 1 arrived midway between the Space Shuttle flights of missions STS-92 and STS-97. These two flights each added segments of the station's Integrated Truss Structure, which provided the station with Ku band communications, additional attitude control needed for the additional mass of the USOS, and additional solar arrays. Over the next two years, the station continued to expand. A Soyuz-U rocket delivered the Pirs docking compartment. The Space Shuttles Discovery, Atlantis, and Endeavour delivered the American Destiny laboratory and Quest airlock, in addition to the station's main robot arm, the Canadarm2, and several more segments of the Integrated Truss Structure.

Tragedy struck in 2003 with the loss of the Space Shuttle Columbia, which grounded the rest of the Shuttle fleet, halting construction of the ISS.thumb|The ISS as seen from Space Shuttle Atlantis during [[STS-132, pictured in May 2010]]Assembly resumed in 2006 with the arrival of STS-115 with Atlantis, which delivered the station's second set of solar arrays. Several more truss segments and a third set of arrays were delivered on STS-116, STS-117, and STS-118. As a result of the major expansion of the station's power-generating capabilities, more modules could be accommodated, and the US Harmony module and Columbus European laboratory were added. These were soon followed by the first two components of the Japanese Kibō laboratory. In March 2009, STS-119 completed the Integrated Truss Structure with the installation of the fourth and final set of solar arrays. The final section of Kibō was delivered in July 2009 on STS-127, followed by the Russian Poisk module. The US Tranquility module was delivered in February 2010 during STS-130, alongside the Cupola, followed by the penultimate Russian module, Rassvet, in May 2010. Rassvet was delivered by Space Shuttle Atlantis on STS-132 in exchange for the Russian Proton delivery of the US-funded Zarya module in 1998. The last pressurised module of the USOS, Leonardo, was brought to the station in February 2011 on the final flight of Discovery, STS-133.

Russia's new primary research module Nauka docked in July 2021, along with the European Robotic Arm which can relocate itself to different parts of the Russian modules of the station. Russia's latest addition, the Prichal module, docked in November 2021.

As of June 2025, nasa.gov states that there are 43 different modules and elements installed on the ISS.

Structure

The ISS functions as a modular space station, enabling the addition or removal of modules from its structure for increased adaptability.

File:ISS blueprint.png|Blueprint of the ISS (as of 2018)

File:Iss after installation of all roll out solar arrays.jpg|Rendering of the ISS (as of 2023)

</gallery>

Below is a diagram of major station components. The Unity node joins directly to the Destiny laboratory; for clarity, they are shown apart. Similar cases are also seen in other parts of the structure.

Key to box background colors:

Pressurised component, accessible by the crew without using spacesuits
Docking/berthing port, pressurized when a visiting spacecraft is present
Airlock, to move people or material between pressurized and unpressurized environment
Unpressurised station superstructure
Unpressurised component
Temporarily defunct or non-commissioned component
Former, no longer installed component
Future, not yet installed component

</div>

Pressurised modules

Zarya

thumb|Zarya as seen by during [[STS-88]]

Zarya (), also known as the Functional Cargo Block (), was the inaugural component of the ISS. Launched in 1998, it initially served as the ISS's power source, storage, propulsion, and guidance system. As the station has grown, Zaryas role has transitioned primarily to storage, both internally and in its external fuel tanks.

A descendant of the TKS spacecraft used in the Salyut program, Zarya was built in Russia but is owned by the United States. Its name symbolizes the beginning of a new era of international space cooperation.

Unity

thumb|Unity as seen by during [[STS-88]]

Unity, also known as Node 1, is the inaugural U.S.-built component of the ISS. Serving as the connection between the Russian and U.S. segments, this cylindrical module features six Common Berthing Mechanism locations (forward, aft, port, starboard, zenith, and nadir) for attaching additional modules. Measuring in diameter and in length, Unity was constructed of steel by Boeing for NASA at the Marshall Space Flight Center in Huntsville, Alabama. It was the first of three connecting nodes – Unity, Harmony, and Tranquility – that forms the structural backbone of the U.S. segment of the ISS.

Zvezda

thumb|Zvezda as seen by during [[STS-106]]

Zvezda () launched in July 2000, is the core of the Russian Orbital Segment of the ISS. Initially providing essential living quarters and life-support systems, it enabled the first continuous human presence aboard the station. While additional modules have expanded the ISS's capabilities, Zvezda remains the command and control center for the Russian segment and it is where crews gather during emergencies.

A descendant of the Salyut program's DOS spacecraft, Zvezda was built by RKK Energia and launched atop a Proton rocket.

Destiny

thumb|The Destiny module being installed on the ISS

The Destiny laboratory is the primary research facility for U.S. experiments on the ISS. NASA's first permanent orbital research station since Skylab, the module was built by Boeing and launched aboard during STS-98. Attached to Unity over a period of five days in February 2001, Destiny has been a hub for scientific research ever since.

Within Destiny, astronauts conduct experiments in fields such as medicine, engineering, biotechnology, physics, materials science, and Earth science. Researchers worldwide benefit from these studies. The module also houses life-support systems, including the Oxygen Generating System.

Quest Joint Airlock

thumb|Quest Joint Airlock Module

The Quest Joint Airlock enables extravehicular activities (EVAs) using either the U.S. Extravehicular Mobility Unit (EMU) or the Russian Orlan space suit.

Before its installation, conducting EVAs from the ISS was challenging due to a variety of system and design differences. Only the Orlan suit could be used from the Transfer Chamber on the Zvezda module (which was not a purpose-built airlock) and the EMU could only be used from the airlock on a visiting Space Shuttle, which could not accommodate the Orlan.

Launched aboard during STS-104 in July 2001 and attached to the Unity module, Quest is a , structure built by Boeing. It houses the crew airlock for astronaut egress, an equipment airlock for suit storage, and has facilities to accommodate astronauts during their overnight pre-breathe procedures to prevent decompression sickness. Launched on 10 November 2009 attached to a modified Progress spacecraft, called Progress M-MIM2.

Poisk provides facilities to maintain Orlan spacesuits and is equipped with two inward-opening hatches, a design change from Mir, which encountered a dangerous situation caused by an outward-opening hatch that opened too quickly because of a small amount of air pressure remaining in the airlock. Since the departure of Pirs in 2021, it's become the sole airlock on the Russian segment.

Harmony

thumb|Harmony (center) shown connected to Columbus, Kibo, and Destiny. The dark [[Pressurized Mating Adapter|PMA-2 faces the camera. The nadir and zenith locations are open.]]

Harmony, or Node 2, is the central connecting hub of the US segment of the ISS, linking the U.S., European, and Japanese laboratory modules. It's also been called the "utility hub" of the ISS as it provides essential power, data, and life-support systems. The module also houses sleeping quarters for four crew members.

Launched on 23 October 2007 aboard on STS-120, Harmony was initially attached to the Unity before being relocated to its permanent position at the front of the Destiny laboratory on 14 November 2007. This expansion added significant living space to the ISS, marking a key milestone in the construction of the U.S. segment.

Tranquility

thumb|Tranquility in 2011

Tranquility, also known as Node 3, is a module of the ISS. It contains environmental control systems, life-support systems, a toilet, exercise equipment, and an observation cupola.

The European Space Agency and the Italian Space Agency had Tranquility manufactured by Thales Alenia Space. A ceremony on 20 November 2009 transferred ownership of the module to NASA. On 8 February 2010, NASA launched the module on the Space Shuttle's STS-130 mission.

Columbus

thumb|The Columbus module on the ISS

Columbus is a science laboratory that is part of the ISS and is the largest single contribution to the station made by the European Space Agency.

Like the Harmony and Tranquility modules, the Columbus laboratory was constructed in Turin, Italy by Thales Alenia Space. The functional equipment and software of the lab was designed by EADS in Bremen, Germany. It was also integrated in Bremen before being flown to the Kennedy Space Center in Florida in an Airbus Beluga jet. It was launched aboard Space Shuttle Atlantis on 7 February 2008, on flight STS-122. It is designed for ten years of operation. The module is controlled by the Columbus Control center, located at the German Space Operations Center, part of the German Aerospace Center in Oberpfaffenhofen near Munich, Germany.

The European Space Agency has spent €1.4 billion (about US$1.6 billion) on building Columbus, including the experiments it carries and the ground control infrastructure necessary to operate them.

Kibō

thumb|Kibō with its exposed facility on the right

, also known as the Japanese Experiment Module, is Japan's research facility on the ISS. It is the largest single module on the ISS, consisting of a pressurized lab, an exposed facility for conducting experiments in the space environment, two storage compartments, and a robotic arm. Attached to the Harmony module, Kibō was assembled in space over three Space Shuttle missions: STS-123, STS-124 and STS-127.

Cupola

thumb|The Cupola windows with shutters open

The Cupola is an ESA-built observatory module of the ISS. Its name derives from the Italian word ', which means "dome". Its seven windows are used to conduct experiments, dockings and observations of Earth. It was launched aboard Space Shuttle mission STS-130 on 8 February 2010 and attached to the Tranquility (Node 3) module. With the Cupola attached, ISS assembly reached 85 per cent completion. The Cupola central window has a diameter of .

Rassvet

thumb|Rassvet module with MLM-outfitting equipment (consisting of experiment airlock, RTOd radiators, and ERA workpost) at KSC

Rassvet (), also known as the Mini-Research Module 1 () and formerly known as the Docking Cargo Module is primarily used for cargo storage and as a docking port for visiting spacecraft on the Russian segment of the ISS. Rassvet replaced the cancelled Docking and Storage Module and used a design largely based on the Mir Docking Module built in 1995.

Rassvet was delivered in on 14 May 2010 on STS-132 in exchange for the Russian Proton delivery of the US-funded Zarya module in 1998. Rassvet was attached to Zarya shortly thereafter.

Leonardo

thumb|The Leonardo module hours after berthing

The Leonardo Permanent Multipurpose Module (PMM) was flown into space aboard the Space Shuttle Discovery on STS-133 on 24 February 2011 and installed on 1 March. Leonardo is primarily used for storage of spares, supplies and waste on the ISS, which was until then stored in many different places within the space station. It is also the personal hygiene area for the astronauts who live in the US Orbital Segment. The Leonardo PMM was a Multi-Purpose Logistics Module (MPLM) before 2011, but was modified into its current configuration. It was formerly one of two MPLM used for bringing cargo to and from the ISS with the Space Shuttle. The module was named for Italian polymath Leonardo da Vinci.

Bigelow Expandable Activity Module

thumb|Progression of the expansion of BEAM

The Bigelow Expandable Activity Module (BEAM) is an experimental expandable space station module developed by Bigelow Aerospace, under contract to NASA, for testing as a temporary module on the International Space Station (ISS) from 2016 to at least 2020. It arrived at the ISS on 10 April 2016, was berthed to the station on 16 April at Tranquility Node 3, and was expanded and pressurized on 28 May 2016. In December 2021, Bigelow Aerospace conveyed ownership of the module to NASA, as a result of Bigelow's cessation of activity.

International Docking Adapters

The International Docking Adapter (IDA) is a spacecraft docking system adapter developed to convert APAS-95 to the NASA Docking System (NDS). An IDA is placed on each of the ISS's two open Pressurized Mating Adapters (PMAs), both of which are connected to the Harmony module.

Two International Docking Adapters are currently installed aboard the Station. Originally, IDA-1 was planned to be installed on PMA-2, located at Harmonys forward port, and IDA-2 would be installed on PMA-3 at Harmonys zenith. After IDA 1 was destroyed in a launch incident, IDA-2 was installed on PMA-2 on 19 August 2016, while IDA-3 was later installed on PMA-3 on 21 August 2019.

Bishop Airlock Module

thumb|NanoRacks Bishop airlock module installed on the ISS

The NanoRacks Bishop Airlock Module is a commercially funded airlock module launched to the ISS on SpaceX CRS-21 on 6 December 2020. The module was built by NanoRacks, Thales Alenia Space, and Boeing. It will be used to deploy CubeSats, small satellites, and other external payloads for NASA, CASIS, and other commercial and governmental customers.

Nauka

thumb|upright|Nauka and Prichal docked to ISS

Nauka (), also known as the Multipurpose Laboratory Module, Upgrade (), is a Roscosmos-funded component of the ISS that was launched on 21 July 2021, 14:58 UTC. In the original ISS plans, Nauka was to use the location of the Docking and Stowage Module (DSM), but the DSM was later replaced by the Rassvet module and moved to Zaryas nadir port. Nauka was successfully docked to Zvezdas nadir port on 29 July 2021, 13:29 UTC, replacing the Pirs module.

It had a temporary docking adapter on its nadir port for crewed and uncrewed missions until Prichal arrival, where just before its arrival it was removed by a departing Progress spacecraft.

Prichal

Prichal () is a spherical module that serves as a docking hub for the Russian segment of the ISS. Launched in November 2021, Prichal provides additional docking ports for Soyuz and Progress spacecraft, as well as potential future modules. Prichal features six docking ports: forward, aft, port, starboard, zenith, and nadir. One of these ports, equipped with an active hybrid docking system, enabled it to dock with the Nauka module. The remaining five ports are passive hybrids, allowing for docking of Soyuz, Progress, and heavier modules, as well as future spacecraft with modified docking systems. As of 2024, the forward, aft, port and starboard docking ports remain covered. Prichal was initially intended to be an element of the now canceled Orbital Piloted Assembly and Experiment Complex.

Unpressurised elements

The ISS has a large number of external components that do not require pressurisation. The largest of these is the Integrated Truss Structure (ITS), to which the station's main solar arrays and thermal radiators are mounted. The ITS consists of ten separate segments forming a structure long. While these platforms allow experiments (including MISSE, the STP-H3 and the Robotic Refueling Mission) to be deployed and conducted in the vacuum of space by providing electricity and processing experimental data locally, their primary function is to store spare Orbital Replacement Units (ORUs). ORUs are parts that can be replaced when they fail or pass their design life, including pumps, storage tanks, antennas, and battery units. Such units are replaced either by astronauts during EVA or by robotic arms. Several shuttle missions were dedicated to the delivery of ORUs, including STS-129, STS-133 and STS-134. , only one other mode of transportation of ORUs had been usedthe Japanese cargo vessel HTV-2which delivered an FHRC and CTC-2 via its Exposed Pallet (EP).

There are also smaller exposure facilities mounted directly to laboratory modules; the Kibō Exposed Facility serves as an external "porch" for the Kibō complex, and a facility on the European Columbus laboratory provides power and data connections for experiments such as the European Technology Exposure Facility and the Atomic Clock Ensemble in Space. A remote sensing instrument, SAGE III-ISS, was delivered to the station in February 2017 aboard CRS-10, and the NICER experiment was delivered aboard CRS-11 in June 2017. The largest scientific payload externally mounted to the ISS is the Alpha Magnetic Spectrometer (AMS), a particle physics experiment launched on STS-134 in May 2011, and mounted externally on the ITS. The AMS measures cosmic rays to look for evidence of dark matter and antimatter.

The commercial Bartolomeo External Payload Hosting Platform, manufactured by Airbus, was launched on 6 March 2020 aboard CRS-20 and attached to the European Columbus module. It will provide an additional 12 external payload slots, supplementing the eight on the ExPRESS Logistics Carriers, ten on Kibō, and four on Columbus. The system is designed to be robotically serviced and will require no astronaut intervention. It is named after Christopher Columbus's younger brother.

MLM outfittings

In May 2010, equipment for Nauka was launched on STS-132 (as part of an agreement with NASA) and delivered by Space Shuttle Atlantis. Weighing 1.4 metric tons, the equipment was attached to the outside of Rassvet (MRM-1). It included a spare elbow joint for the European Robotic Arm (ERA) (which was launched with Nauka) and an ERA-portable workpost used during EVAs, as well as RTOd add-on heat radiator and internal hardware alongside the pressurized experiment airlock.

The RTOd radiator adds additional cooling capability to Nauka, which enables the module to host more scientific experiments. This process took several months. A portable work platform was also transferred over in August 2023 during VKD-60 spacewalk, which can attach to the end of the ERA to allow cosmonauts to "ride" on the end of the arm during spacewalks. However, even after several months of outfitting EVAs and RTOd heat radiator installation, six months later, the RTOd radiator malfunctioned before active use of Nauka (the purpose of RTOd installation is to radiate heat from Nauka experiments). The malfunction, a leak, rendered the RTOd radiator unusable for Nauka. This is the third ISS radiator leak after Soyuz MS-22 and Progress MS-21 radiator leaks. If a spare RTOd is not available, Nauka experiments will have to rely on Nauka's main launch radiator and the module could never be used to its full capacity.

Another MLM outfitting is a 4 segment external payload interface called means of attachment of large payloads (Sredstva Krepleniya Krupnogabaritnykh Obyektov, SKKO). Delivered in two parts to Nauka by Progress MS-18 (LCCS part) and Progress MS-21 (SCCCS part) as part of the module activation outfitting process. It was taken outside and installed on the ERA aft facing base point on Nauka during the VKD-55 spacewalk.

Robotic arms and cargo cranes

The Integrated Truss Structure (ITS) serves as a base for the station's primary remote manipulator system, the Mobile Servicing System (MSS), which is composed of three main components:

Canadarm2, the largest robotic arm on the ISS, has a mass of and is used to: dock and manipulate spacecraft and modules on the USOS; hold crew members and equipment in place during EVAs; and move Dextre to perform tasks.
Dextre is a robotic manipulator that has two arms and a rotating torso, with power tools, lights, and video for replacing orbital replacement units (ORUs) and performing other tasks requiring fine control.
The Mobile Base System (MBS) is a platform that rides on rails along the length of the station's main truss, which serves as a mobile base for Canadarm2 and Dextre, allowing the robotic arms to reach all parts of the USOS.

A grapple fixture was added to Zarya on STS-134 to enable Canadarm2 to inchworm itself onto the ROS. was launched on STS-124 and is attached to the Kibō Pressurised Module. The arm is similar to the Space Shuttle arm as it is permanently attached at one end and has a latching end effector for standard grapple fixtures at the other.

The European Robotic Arm, which will service the ROS, was launched alongside the Nauka module. The ROS does not require spacecraft or modules to be manipulated, as all spacecraft and modules dock automatically and may be discarded the same way. Crew use the two Strela () cargo cranes during EVAs for moving crew and equipment around the ROS. Each Strela crane has a mass of .

Former module

Pirs

Pirs (Russian: Пирс, lit. 'Pier') was launched on 14 September 2001, as ISS Assembly Mission 4R, on a Russian Soyuz-U rocket, using a modified Progress spacecraft, Progress M-SO1, as an upper stage. Pirs was undocked by Progress MS-16 on 26 July 2021, 10:56 UTC, and deorbited on the same day at 14:51 UTC to make room for the Nauka module to be attached to the space station. Prior to its departure, Pirs served as the primary Russian airlock on the station, being used to store and refurbish the Russian Orlan spacesuits.

Planned components

Axiom segment

thumb|Early rendering of the [[Axiom Orbital Segment, made prior to assembly plan changes, with now only one module, the Payload Power Thermal Module (PPTM), being planned to dock with the ISS]]

In January 2020, NASA awarded Axiom Space a contract to build a commercial module for the ISS. The contract is under the NextSTEP2 program. NASA negotiated with Axiom on a firm fixed-price contract basis to build and deliver the module, which will attach to the forward port of the space station's Harmony (Node 2) module. Although NASA only commissioned one module, Axiom planned to build an entire segment (Axiom Orbital Segment) consisting of five modules, including a node module, an orbital research and manufacturing facility, a crew habitat, and a "large-windowed Earth observatory". The Axiom segment was expected to greatly increase the capabilities and value of the space station, allowing for larger crews and private spaceflight by other organisations. Axiom planned to convert the segment into a stand-alone space station (Axiom Station) once the ISS is decommissioned, with the intention that this would act as a successor to the ISS. Canadarm2 is planned to continue its operations on Axiom Station after the retirement of ISS in 2030. In December 2024, Axiom Space revised their station assembly plans to require only one module to dock with the ISS before assembling Axiom Station in an independent orbit.

, Axiom Space expects to launch one module, the Payload Power Thermal Module (PPTM), to the ISS no earlier than 2027. PPTM is expected to remain at the ISS until the launch of Axiom's Habitat One (Hab-1) module about one year later, after which it will detach from the ISS to join with Hab-1. NASA plans to de-orbit ISS as soon as they have the "minimum capability" in orbit: "the USDV and at least one commercial station."

Cancelled components

Several modules developed or planned for the station were cancelled over the course of the ISS program. Reasons include budgetary constraints, the modules becoming unnecessary, and station redesigns after the 2003 Columbia disaster. The US Centrifuge Accommodations Module would have hosted science experiments in varying levels of artificial gravity. The US Habitation Module would have served as the station's living quarters. Instead, the living quarters are now spread throughout the station. The US Interim Control Module and ISS Propulsion Module would have replaced the functions of Zvezda in case of a launch failure. Two Russian Research Modules were planned for scientific research. They would have docked to a Russian Universal Docking Module. The Russian Science Power Platform would have supplied power to the Russian Orbital Segment independent of the ITS solar arrays.

Science Power Modules 1 and 2 (Repurposed Components)

Science Power Module 1 (SPM-1, also known as NEM-1) and Science Power Module 2 (SPM-2, also known as NEM-2) are modules that were originally planned to arrive at the ISS no earlier than 2024, and dock to the Prichal module, which is docked to the Nauka module. In April 2021, Roscosmos announced that NEM-1 would be repurposed to function as a core module of the proposed Russian Orbital Service Station (ROS), launching no earlier than 2027 and docking to the free-flying Nauka module. NEM-2 may be converted into another core "base" module, which would be launched in 2028. , NEM-1—now referred to simply as NEM—is expected to be launched to the ISS in 2029, where it will dock with the Universal Node module replacing Prichal prior to the separation of the ROS modules around 2030.

XBASE

In August 2016, Bigelow Aerospace negotiated an agreement with NASA to develop a full-size ground prototype Deep Space Habitation based on the B330 under the second phase of Next Space Technologies for Exploration Partnerships. The module was called the Expandable Bigelow Advanced Station Enhancement (XBASE), as Bigelow hoped to test the module by attaching it to the International Space Station. However, in March 2020, Bigelow laid off all 88 of its employees, and the company remains dormant and is considered defunct, making it appear unlikely that the XBASE module will ever be launched.

Nautilus-X Centrifuge Demonstration

A proposal was put forward in 2011 for a first in-space demonstration of a sufficiently scaled centrifuge for artificial partial-g gravity effects. It was designed to become a sleep module for the ISS crew. The project was cancelled in favour of other projects due to budget constraints.

Onboard systems

Life support

The critical systems are the atmosphere control system, the water supply system, the food supply facilities, the sanitation and hygiene equipment, and fire detection and suppression equipment. The Russian Orbital Segment's life-support systems are contained in the Zvezda service module. Some of these systems are supplemented by equipment in the USOS. The Nauka laboratory has a complete set of life-support systems.

Atmospheric control systems

thumb|upright=2|The interactions between the components of the ISS Environmental Control and Life-Support System (ECLSS)|alt=A flowchart diagram showing the components of the ISS life-support system.

The atmosphere on board the ISS is similar to that of Earth. Normal air pressure on the ISS is , the same as at sea level on Earth. While the crew would remain healthy at a lower pressure, some equipment is very pressure-sensitive. explicitly states on p. 11 that "NASA has recommended by detailed review that the inflight cabin atmosphere, outside the Earth's atmosphere, should continue to be 100 percent oxygen at 5 p.s.i.A." (c. 0.3 atm). FWIW, Andy Weir's 2021 SF novel Project Hail Mary claims that an Earth-like atmosphere is maintained in near-Earth space stations to simplify evacuation in case of emergency.-->

Earth-like atmospheric conditions have been maintained on all Russian and Soviet spacecraft, while American spacecraft used pure oxygen atmospheres at 5 psi (0.3 atm) after launch.

The Elektron system aboard Zvezda and a similar system in Destiny generate oxygen aboard the station. The crew has a backup option in the form of bottled oxygen and Solid Fuel Oxygen Generation (SFOG) canisters, a chemical oxygen generator system. Carbon dioxide is removed from the air by the Vozdukh system in Zvezda. Other by-products of human metabolism, such as methane from the intestines and ammonia from sweat, are removed by activated charcoal filters.

The US Orbital Segment (USOS) has redundant supplies of oxygen, from a pressurised storage tank on the Quest airlock module delivered in 2001, supplemented ten years later by ESA-built Advanced Closed-Loop System (ACLS) in the Tranquility module (Node 3), which produces by electrolysis. Hydrogen produced is combined with carbon dioxide from the cabin atmosphere and converted to water and methane.

Power and thermal control

Double-sided solar arrays provide electrical power to the ISS. These bifacial cells collect direct sunlight on one side and light reflected off from the Earth on the other, and are more efficient and operate at a lower temperature than single-sided cells commonly used on Earth.

The Russian segment of the station, like most spacecraft, uses 28 V low voltage DC from two rotating solar arrays mounted on Zvezda. The USOS uses 130–180 V DC from the USOS PV array. Power is stabilised and distributed at 160 V DC and converted to the user-required 124 V DC. The higher distribution voltage allows smaller, lighter conductors, at the expense of crew safety. The two station segments share power with converters.

The USOS solar arrays are arranged as four wing pairs, for a total production of 75 to 90 kilowatts.

The station originally used rechargeable nickel–hydrogen batteries () for continuous power during the 45 minutes of every 90-minute orbit that it is eclipsed by the Earth. The batteries are recharged on the day side of the orbit. They had a 6.5-year lifetime (over 37,000 charge/discharge cycles) and were regularly replaced over the anticipated 20-year life of the station. Starting in 2016, the nickel–hydrogen batteries were replaced by lithium-ion batteries, which are expected to last until the end of the ISS program.

The station's large solar panels generate a high potential voltage difference between the station and the ionosphere. This could cause arcing through insulating surfaces and sputtering of conductive surfaces as ions are accelerated by the spacecraft plasma sheath. To mitigate this, plasma contactor units create current paths between the station and the ambient space plasma.

thumb|upright=2.2|ISS External Active Thermal Control System (EATCS) diagram

The station's systems and experiments consume a large amount of electrical power, almost all of which is converted to heat. To keep the internal temperature within workable limits, a passive thermal control system (PTCS) is made of external surface materials, insulation such as MLI, and heat pipes. If the PTCS cannot keep up with the heat load, an External Active Thermal Control System (EATCS) maintains the temperature. The EATCS consists of an internal, non-toxic, water coolant loop used to cool and dehumidify the atmosphere, which transfers collected heat into an external liquid ammonia loop. From the heat exchangers, ammonia is pumped into external radiators that emit heat as infrared radiation, then the ammonia is cycled back to the station. The EATCS provides cooling for all the US pressurised modules, including Kibō and Columbus, as well as the main power distribution electronics of the S0, S1 and P1 trusses. It can reject up to 70 kW. This is much more than the 14 kW of the Early External Active Thermal Control System (EEATCS) via the Early Ammonia Servicer (EAS), which was launched on STS-105 and installed onto the P6 Truss.

Communications and computers

The ISS relies on various radio communication systems to provide telemetry and scientific data links between the station and mission control centers. Radio links are also used during rendezvous and docking procedures and for audio and video communication between crew members, flight controllers and family members. As a result, the ISS is equipped with internal and external communication systems used for different purposes. It also had the capability to utilize the Luch data relay satellite system, but was restored to operational status in 2011 and 2012 with the launch of Luch-5A and Luch-5B. Additionally, the Voskhod-M system provides internal telephone communications and VHF radio links to ground control.

The US Orbital Segment (USOS) makes use of two separate radio links: S band (audio, telemetry, commanding – located on the P1/S1 truss) and K<sub>u</sub> band (audio, video and data – located on the Z1 truss) systems. These transmissions are routed via the United States Tracking and Data Relay Satellite System (TDRSS) in geostationary orbit, allowing for almost continuous real-time communications with Christopher C. Kraft Jr. Mission Control Center (MCC-H) in Houston, Texas. Data channels for the Canadarm2, European Columbus laboratory and Japanese Kibō modules were originally also routed via the S band and K<sub>u</sub> band systems, with the European Data Relay System and a similar Japanese system intended to eventually complement the TDRSS in this role.

UHF radio is used by astronauts and cosmonauts conducting EVAs and other spacecraft that dock to or undock from the station.

The US Orbital Segment of the ISS is equipped with approximately 100 commercial off-the-shelf laptops running Windows or Linux. These devices are modified to use the station's 28V DC power system and with additional ventilation since heat generated by the devices can stagnate in the weightless environment. NASA prefers to keep a high commonality between laptops and spare parts are kept on the station so astronauts can repair laptops when needed.

The laptops are divided into two groups: the Portable Computer System (PCS) and Station Support Computers (SSC).

PCS laptops run Linux and are used for connecting to the station's primary Command & Control computer (C&C MDM), which runs on Debian Linux, a switch made from Windows in 2013 for reliability and flexibility. The primary computer supervises the critical systems that keep the station in orbit and supporting life. The primary computer experienced failures in 2001, 2007, and 2017. The 2017 failure required a spacewalk to replace external components.

SSC laptops are used for everything else on the station, including reviewing procedures, managing scientific experiments, communicating over e-mail or video chat, and for entertainment during downtime. NASA upgraded the system in 2019 and increased the speeds to 600 Mbit/s. ISS crew members have access to the internet.

Operations

Expeditions

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 Shuttle Columbia, 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. 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. With the arrival of crew on larger US commercial spacecraft beginning in 2020, crew size has been increased to seven, the number for which ISS was originally designed.

Oleg Kononenko of Roscosmos holds the record for the longest time spent in space and at the ISS, accumulating nearly 1,111 days in space over the course of five long-duration missions on the ISS (Expedition 17, 30/31, 44/45, 57/58/59 and 69/70/71). He also served as commander three times (Expedition 31, 58/59 and 70/71).

thumb|Chart of the number of ISS missions longer than 90 days, until 2020

Peggy Whitson of NASA and Axiom Space has spent the most time in space of any American, accumulating over 675 days in space during her time on Expeditions 5, 16, and 50/51/52 and Axiom Missions 2 and 4.

Private flights

As of June 2023, 13 individuals have paid for their own travel to visit the ISS. In news coverage, such travellers are often referred to as "space tourists"; however, many have objected to the term, as they typically undergo professional training and conduct scientific, educational, or outreach activities while on orbit. Accordingly, Roscosmos and NASA classify them as spaceflight participants.

Initially, privately funded access to the ISS was provided exclusively by Roscosmos through seats on Soyuz spacecraft, either during crew rotations or on dedicated missions. These seats were marketed by Space Adventures at prices of about US$40 million. NASA and the ESA initially criticised the practice, and NASA resisted training Dennis Tito, the first person to pay for an ISS stay.

Beginning in 2021, NASA also began authorizing commercially organized visits known as Private Astronaut Missions (PAMs). These flights are required to use a NASA-certified U.S. commercial vehicle and to include a mission commander who is a former NASA astronaut, responsible for spacecraft operations and oversight of the other spaceflight participants. The first PAM, Axiom Mission 1, launched in 2022 with one Axiom commander and three private passengers, followed in 2023 by Axiom Mission 2, with one private passenger and two astronauts from the Saudi Space Agency. As of 2025, NASA offers up to two PAM opportunities per year. In addition to private individuals, PAMs are frequently used by ESA and other national governments to fly astronauts for short-term missions.

Fleet operations

Various crewed and uncrewed spacecraft have supported the station's operations. Flights to the ISS have included 93 Progress, 73 Soyuz, 51 SpaceX Dragon, 37 Space Shuttle, 21 Cygnus, 10 HTV/HTV-X, 5 ATV, and 2 Boeing Starliner missions.

There are currently eight docking ports for visiting spacecraft, with four additional ports installed but not yet put into service:

Harmony forward (with PMA 2 & IDA 2)
Harmony zenith (with PMA 3 & IDA 3)
Harmony nadir (CBM port)
Unity nadir (CBM port)
Prichal aft
Prichal forward
Prichal nadir
Prichal port
Prichal starboard
Poisk zenith
Rassvet nadir
Zvezda aft

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, while zenith points away from it. Port is to the left and starboard 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.

Crewed

, a total of 294 individuals from 26 countries have visited the ISS, including both government-sponsored astronauts and privately funded spaceflight participants. The United States accounted for 172 of these visitors, followed by Russia with 65, Japan with 11, and Canada with 9. Italy had 6 visitors, France had 5 and Germany had 4. Saudi Arabia, Sweden, and the United Arab Emirates each had 2 individuals visit the ISS. One person has traveled to the ISS from each of the following countries: Belarus, Belgium, Brazil, Denmark, Hungary, India, Israel, Kazakhstan, Malaysia, the Netherlands, Poland, South Africa, South Korea, Spain, Turkey, and the United Kingdom.

List of current crew members

thumb|upright|Sergey Kud-Sverchkov, current commander

{| class="wikitable sortable" style="text-align:center;"

! Astronaut !! Role !! Agency

| Sergey Kud-Sverchkov || Commander || Roscosmos

| Sophie Adenot || Flight engineer || ESA

| Andrey Fedyaev || Flight engineer || Roscosmos

| Jack Hathaway || Flight engineer || NASA

| Jessica Meir || Flight engineer || NASA

| Sergei Mikayev || Flight engineer || Roscosmos

| Christopher Williams || Flight engineer || NASA

Uncrewed

Uncrewed spaceflights are primarily used to deliver cargo to the station including crew supplies, scientific investigations, spacewalk equipment, vehicle hardware, propellant, water, and gases. Cargo resupply missions have typically used Russian Progress spacecraft, the now-retired European ATV, the Japanese HTV, and American Dragon and Cygnus spacecraft. Additionally, several Russian modules have been launched on uncrewed rockets and autonomously docked with the station.

Currently docked/berthed

[[File:December 1, 2025 International Space Station Configuration.png|thumb|Rendering of the ISS and visiting vehicles . Live link at nasa.gov.]]

All dates are UTC. Departure dates are the earliest possible () and may change.

{| class="wikitable plainrowheaders" style="font-size:90%;"

|- style="text-align:center;"

! scope="col" colspan="2" | Mission

! scope="col" | Type

! scope="col" | Spacecraft

! scope="col" | Arrival

! scope="col" | Departure

! scope="col" | Port

| Soyuz MS-28

| style="background:#cfc" | Crewed

| Soyuz MS No. 753 Gyrfalcon

| 27 November 2025

| 26 July 2026

| Rassvet nadir

| Crew-12

| style="background:#cfc" | Crewed

| 14 February 2026

| September 2026

| Harmony zenith

| Progress MS-33

| style="background:lightblue" | Uncrewed

| Progress MS No. 463

| 24 March 2026

| September 2026

| Poisk zenith

| CRS NG-24

| style="background:lightblue" | Uncrewed

| Cygnus XL S.S. Steven R. Nagel

| 13 April 2026

| October 2026

| Unity nadir

| Progress MS-34

| style="background:lightblue" | Uncrewed

| Progress MS No. 464

| 25 April 2026

| November 2026

| Zvezda aft

Scheduled missions

All dates are UTC. Launch dates are the earliest possible () and may change.

{| class="wikitable plainrowheaders" style="font-size:90%;"

! scope="col" colspan="2" | Mission

! scope="col" | Type

! scope="col" | Spacecraft

! scope="col" | Launch date

! scope="col" | Launch vehicle

! scope="col" | Launch site

! scope="col" | Launch provider

! scope="col" | Docking/berthing port

| CRS SpX-34

| style="background:lightblue" | Uncrewed

| 15 May 2026

| Falcon 9 Block 5

| Cape Canaveral, SLC40

| SpaceX

| Harmony forward

| Soyuz MS-29

| style="background:#cfc" | Crewed

| Soyuz MS No. 759 Tigris

| 14 July 2026

| Soyuz2.1a

| Baikonur, Site 31/6

| RKTs Progress

| Prichal nadir

| Progress MS-35

| style="background:lightblue" | Uncrewed

| Progress MS No. 465

| 9 September 2026

| Soyuz2.1a

| Baikonur, Site 31/6

| RKTs Progress

| Poisk zenith

| Crew-13

| style="background:#cfc" | Crewed

| September 2026

| Falcon 9 Block 5

| Cape Canaveral, SLC40

| SpaceX

| Harmony

| CRS SpX-35

| style="background:lightblue" | Uncrewed

| Fall 2026

| Falcon 9 Block 5

| Cape Canaveral, SLC40

| SpaceX

| Harmony

| Progress MS-36

| style="background:lightblue" | Uncrewed

| Progress MS No. 466

| 24 November 2026

| Soyuz2.1a

| Baikonur, Site 31/6

| RKTs Progress

| Zvezda aft

| CRS NG-25

| style="background:lightblue" | Uncrewed

| Cygnus XL

| Winter 2026

| Falcon 9 Block 5

| Cape Canaveral, SLC40

| SpaceX

| Unity nadir

| Starliner-1

| style="background:lightblue" | Uncrewed

| 2026

| Atlas V N22

| Cape Canaveral, SLC-41

| ULA

| Harmony

| Progress MS-37

| style="background:lightblue" | Uncrewed

| Progress MS No. 467

| 2027

| Soyuz2.1a

| Baikonur, Site 31/6

| RKTs Progress

| Poisk zenith

Docking and berthing of spacecraft

thumb|The [[Progress M-14M resupply vehicle approaching the ISS in 2012. Nearly 100 unpiloted Progress spacecraft have delivered supplies during the lifetime of the station.]]

Russian spacecraft can autonomously rendezvous and dock with the station without human intervention. Once within about the spacecraft activates its Kurs docking navigation system, exchanging radio signals with the station's beacon to guide orbital manoeuvres. As it closes in, more accurate transceivers align the craft with the docking port and control the final approach. The crew supervises the procedure and can intervene using the TORU (Tele-robotically Operated Rendezvous Unit) system if required. Automated docking has been used by the Soviet program since 1967, with Kurs introduced on Mir in 1986 and refined since. Though costly to develop, its reliability and standardised components have delivered significant long-term savings.

The American SpaceX Dragon 2 cargo and crewed spacecraft can autonomously rendezvous and dock with the station without human intervention. However, on crewed Dragon missions, the astronauts have the capability to intervene and fly the vehicle manually.

thumb|Japan's [[Kounotori 4 berthing]]

Other automated cargo spacecraft typically use a semi-automated process when arriving and departing from the station. These spacecraft are instructed to approach and park near the station. Once the crew on board the station is ready, the spacecraft is commanded to come close to the station, so that it can be grappled by an astronaut using the Mobile Servicing System robotic arm. The final mating of the spacecraft to the station is achieved using the robotic arm (a process known as berthing). Spacecraft using this semi-automated process include the American Cygnus and the Japanese HTV-X. The now-retired American SpaceX Dragon 1, European ATV and Japanese HTV also used this process.

Launch and docking windows

Prior to a spacecraft's docking to the ISS, navigation and attitude control (GNC) is handed over to the ground control of the spacecraft's country of origin. GNC is set to allow the station to drift in space, rather than fire its thrusters or turn using gyroscopes. The solar panels of the station are turned edge-on to the incoming spacecraft, so residue from its thrusters does not damage the cells. Before its retirement, Shuttle launches were often given priority over Soyuz, with occasional priority given to Soyuz arrivals carrying crew and time-critical cargoes, such as biological experiment materials.

Repairs

thumb|upright=1.8|Spare parts are called [[orbital replacement unit|ORUs; some are externally stored on pallets called ELCs and ESPs.]]

thumb|While anchored on the end of the [[Orbiter Boom Sensor System during STS-120, astronaut Scott Parazynski performs makeshift repairs to a US solar array that was damaged during unfolding|alt=Two black and orange solar arrays, shown uneven and with a large tear visible. A crew member in a spacesuit, attached to the end of a robotic arm, holds a latticework between two solar sails.]]

thumb|[[Michael S. Hopkins|Mike Hopkins during a spacewalk]]

Orbital Replacement Units (ORUs) are spare parts that can be readily replaced when a unit either passes its design life or fails. Examples of ORUs are pumps, storage tanks, controller boxes, antennas, and battery units. Some units can be replaced using robotic arms. Most are stored outside the station, either on small pallets called ExPRESS Logistics Carriers (ELCs) or share larger platforms called External Stowage Platforms (ESPs) which also hold science experiments. Both kinds of pallets provide electricity for many parts that could be damaged by the cold of space and require heating. The larger logistics carriers also have local area network (LAN) connections for telemetry to connect experiments. A heavy emphasis on stocking the USOS with ORU's occurred around 2011, before the end of the NASA shuttle program, as its commercial replacements, Cygnus and Dragon, carry one tenth to one quarter the payload.

Unexpected problems and failures have impacted the station's assembly time-line and work schedules leading to periods of reduced capabilities and, in some cases, could have forced abandonment of the station for safety reasons. Serious problems include an air leak from the USOS in 2004, the venting of fumes from an Elektron oxygen generator in 2006, and the failure of the computers in the ROS in 2007 during STS-117 that left the station without thruster, Elektron, Vozdukh and other environmental control system operations. In the latter case, the root cause was found to be condensation inside electrical connectors leading to a short circuit.

During STS-120 in 2007 and following the relocation of the P6 truss and solar arrays, it was noted during unfurling that the solar array had torn and was not deploying properly. An EVA was carried out by Scott Parazynski, assisted by Douglas Wheelock. Extra precautions were taken to reduce the risk of electric shock, as the repairs were carried out with the solar array exposed to sunlight. The issues with the array were followed in the same year by problems with the starboard Solar Alpha Rotary Joint (SARJ), which rotates the arrays on the starboard side of the station. Excessive vibration and high-current spikes in the array drive motor were noted, resulting in a decision to substantially curtail motion of the starboard SARJ until the cause was understood. Inspections during EVAs on STS-120 and STS-123 showed extensive contamination from metallic shavings and debris in the large drive gear and confirmed damage to the large metallic bearing surfaces, so the joint was locked to prevent further damage. Repairs to the joints were carried out during STS-126 with lubrication and the replacement of 11 out of 12 trundle bearings on the joint.

In September 2008, damage to the S1 radiator was first noticed in Soyuz imagery. The problem was initially not thought to be serious. The imagery showed that the surface of one sub-panel had peeled back from the underlying central structure, possibly because of micro-meteoroid or debris impact. On 15 May 2009, the damaged radiator panel's ammonia tubing was mechanically shut off from the rest of the cooling system by the computer-controlled closure of a valve. The same valve was then used to vent the ammonia from the damaged panel, eliminating the possibility of an ammonia leak. The problem appeared to be in the ammonia pump module that circulates the ammonia cooling fluid. Several subsystems, including two of the four CMGs, were shut down.

Planned operations on the ISS were interrupted through a series of EVAs to address the cooling system issue. A first EVA on 7 August 2010, to replace the failed pump module, was not fully completed because of an ammonia leak in one of four quick-disconnects. A second EVA on 11 August removed the failed pump module. A third EVA was required to restore Loop A to normal functionality.

The USOS's cooling system is largely built by the US company Boeing, which is also the manufacturer of the failed pump. The loss of MBSU-1 limited the station to 75% of its normal power capacity, requiring minor limitations in normal operations until the problem could be addressed.

On 5 September 2012, in a second six-hour EVA, astronauts Sunita Williams and Akihiko Hoshide successfully replaced MBSU-1 and restored the ISS to 100% power.

On 24 December 2013, astronauts installed a new ammonia pump for the station's cooling system. The faulty cooling system had failed earlier in the month, halting many of the station's science experiments. Astronauts had to brave a "mini blizzard" of ammonia while installing the new pump. It was only the second Christmas Eve spacewalk in NASA history.

Mission control centers

The components of the ISS are operated and monitored by their respective space agencies at mission control centers across the globe, primarily the Christopher C. Kraft Jr. Mission Control Center in Houston and the RKA Mission Control Center (TsUP) in Moscow, with support from Tsukuba Space Center in Japan, Payload Operations and Integration Center in Huntsville, Alabama, U.S., Columbus Control Center in Munich, Germany and Mobile Servicing System Control at the Canadian Space Agency's headquarters in Saint-Hubert, Quebec.

Orbit, debris and visibility

Altitude and orbital inclination

The ISS is currently maintained in a nearly circular orbit with an eccentricity of 0.0002267 and at an inclination of 51.6 degrees to Earth's equator. This orbit was selected because it is the lowest inclination that can be directly reached by Russian Soyuz and Progress spacecraft launched from Baikonur Cosmodrome at 46° N latitude without overflying China or dropping spent rocket stages in inhabited areas. As a result, it makes more polar latitudes accessible and observable, for example the Chinese Space Station orbits more equatorial with an inclination of 41.47°. The ISS travels prograde (with Earth's rotation, west to east) at an average speed of , and completes orbits per day (93 minutes per orbit).