The International Space Station (ISS) is a space laboratory in low-Earth orbit (LEO), which is the site of continuous manned missions and was built through a multinational collaboration. Launched in 1998, the project is a joint effort of five major space agencies: the United States (NASA), Russia (Roscosmos), the European Space Agency (ESA), Japan (JAXA) and Canada (CSA). The station is a platform for scientific research, technology development and international cooperation.

Establishment and History

The International Space Station (ISS) was planned in the late 20th century to increase international cooperation in space exploration and construction began in 1998. The foundations of the project were laid in 1984 when US President Ronald Reagan proposed a space station named “Freedom”, while the Soviet Union was simultaneously developing the “Mir-2” project. Following the end of the Cold War, the two projects were merged in 1993 in an agreement between the United States and Russia, forming the basis of the ISS, a multinational initiative. The first module, the Russian-built Zarya, was launched by a Proton-K rocket from Baikonur Spaceport in Kazakhstan on November 20, 1998, followed by the American-built Unity module on December 4, 1998. On November 2, 2000, Expedition 1 mission sent the first permanent manned crew to the station and since then, the station has been conducting uninterrupted manned missions. In the 2000s, modules such as the European Space Agency's Columbus, Japan's Kibo, Canada's Canadarm2 and Russia's Nauka were integrated into the station. With the expansion of this modular structure, the ISS has become a platform for scientific experiments, technology testing and international space cooperation.

Planning and Start-up Process

Initial Idea: In 1984, a space station called “Freedom” was proposed by US President Ronald Reagan, while the Soviet Union was developing the “Mir-2” project.
International Consensus: With the end of the Cold War, the United States and Russia agreed to cooperate in space in 1993.
International Participation: In 1998, the ISS project was officially launched in partnership with NASA, Roscosmos, ESA, JAXA and CSA.

The International Space Station (ISS) is a multinational space exploration project. In 1984, US President Ronald Reagan called for the construction of a space station in Earth orbit. In 1993, with the inclusion of Russia in the project, the station concept gained an international structure. On January 29, 1998, a total of 15 countries, including the United States, Russia, Japan, Canada, Japan, Japan, Canada and various European countries, signed an Intergovernmental Agreement establishing the legal basis for the ISS.

The station's first module, a Functional Cargo Block named Zarya, was launched by a Russian Proton rocket on November 20, 1998. This was followed in December 1998 by the docking of the US-built Unity docking module to Zarya, launched by the Space Shuttle. Between 1998 and 2011, a total of 42 assembly flights (37 on the Space Shuttle and 5 on Proton/Soyuz rockets) assembled the main components of the ISS in orbit.

On November 2, 2000, the first permanent crew (Expedition-1 crew) arrived on the ISS and since then the station has been conducting continuous manned missions. Throughout the 2000s, science modules such as Destiny from the United States, Zvezda from Russia, Columbus from the European Space Agency (ESA) and Kibo from the Japanese Space Agency (JAXA) were integrated into the station, increasing its operational capacity. In 2011, with the last Space Shuttle mission, major assembly work was completed and the ISS reached its basic structure.

The ISS is a space platform for continuous manned missions, and as of 2024, it hosted more than 270 astronauts and cosmonauts from 22 different countries. Previously, the record in this field belonged to the Soviet Union's Mir Space Station.

^{The International Space Station's solar panels and external support girder structure are seen against the Earth background in this photo taken by the Space Shuttle Endeavour. The Tranquility module and Cupola observation window were integrated into the station during this mission. (Source}^:^NASA⁾

Technical and Structural Features

The International Space Station (ISS) has a modular structure consisting of pressurized living modules, an integrated truss system and large solar panels. The station consists of two main sections: The Russian Orbital Section (ROS), which includes modules built by Russia, and the US Orbital Section (USOS), which consists of modules developed by the United States, Europe, Japan and Canada.

The main component of ROS is the Zvezda service module, which houses life support systems and propulsion control systems. In addition, the Nauka laboratory module, which was added in 2021, and the Pirs, Poisk, Rassvet and Prichal connectivity modules are also included in ROS.

On the USOS side, there are various modules developed by different countries. The Unity, Harmony and Tranquility link modules and the Destiny research module developed by the United States; the Columbus laboratory module developed by the European Space Agency; the three-part Kibo (JEM) laboratory complex developed by the Japanese Space Agency; and the Cupola observation module are among the main components of this section. In addition, the Quest airlock module is used for spacewalks (EVA).

^{Drawing of the International Space Station with all of the parts labeled.}^(Source:^NASA⁾

The integrated truss system on the exterior of the ISS carries the solar panel fins and radiators that provide the station's stability and energy needs. A total of eight solar panel fins generate approximately 75 to 90 kilowatts of electrical power and are connected to the station's electrical system via cables more than 8 kilometers long.

U.S. Elements

Unity Module
Destiny Laboratory Module
External Stowage Platform-1
External Stowage Platform-2
External Stowage Platform-3
Harmony Module
EXPRESS Logistics Carrier-1
EXPRESS Logistics Carrier-2
Tranquility Module
Cupola
EXPRESS Logistics Carrier-4
Alpha Magnetic Spectrometer-2
EXPRESS Logistics Carrier-3
Bigelow Expandable Activity Module
NanoRacks Bishop Airlock

International Elements

Zarya Module
Zvezda Service Module
Canadarm2 Robotic Arm
Pirs Docking Compartment
Mobile Base System
Columbus Laboratory Module
Japanese Logistics Module
Dextre
Kibo Laboratory Module
Japanese Exposed Facility
Poisk Mini-Research Module
Rassvet Mini-Research Module
Permanent Multipurpose Module
Nauka Multipurpose Laboratory Module
Prichal Docking Module

Truss Segments/Solar Arrays

Zenith-1 (Z1) Truss
Port-6 (P6) Truss
Starboard-0 (S0) Truss
S1 Truss
P1 Truss
P3/P4 Truss
P5 Truss Spacer
S3/S4 Truss
S5 Truss Spacer
S6 Truss Spacer
Roll-Out Solar Arrays 2B/4B
Roll-Out Solar Arrays 3A/4A
Roll-Out Solar Arrays 1A/1B

^{Japanese Test Module Kibo, (Source:}^NASA⁾

The station configuration includes a variety of docking ports, allowing up to eight vehicles to dock simultaneously. These ports enable docking of spacecraft such as Soyuz crew vehicles, Progress cargo ships, SpaceX Crew Dragon and Cargo Dragon, Northrop Grumman Cygnus, Japan's HTV.

The overall dimensions of the ISS are given as an end-to-end length of about 109 meters (including solar panels) and a total mass of about 420 tons. The length of the integrated lattice structure is about 94 meters and the span of the solar panels is about 73 meters.

International Space Station Size and Mass

Pressurized Module Length: 218 feet (67 meters) along the main axis
Truss Length: 310 feet (94 meters)
Solar Panel Length: 239 feet (73 meters) across both longitudinally aligned panels
Mass: 925.335 pounds (419.725 kilograms)
Habitable Volume: 13,696 cubic feet (388 cubic meters) excluding visitor vehicles
Pressurized Volume: 35,491 cubic feet (1,005 cubic meters)
Power Generation: 8 solar panels provide 75 to 90 kilowatts of power
Lines of Computer Code: approximately 1.5 million

The pressurized internal volume of the station is about 1,000 m³ and the crew habitat volume is about 388 m³. The station's internal environment is kept under a pressure of 1 atmosphere with 79% nitrogen and 21% oxygen, similar to the Earth's atmosphere at sea level.

^{Bigelow Extensible Activity Module (BEAM), (Source:}^NASA⁾

This image shows the Bigelow Expandable Activity Module (BEAM) attached to the Tranquility module. BEAM is an experimental habitat that is lower in mass and volume compared to metal habitats and can increase the efficiency of cargo shipments, reducing the number of launches needed and overall mission costs.

The station houses thermal and environmental control, life support systems, propulsion and navigation control computers, and communications systems. For example, the water recycling system within the ECLSS (Environmental Control and Life Support System) recovers about 65% of the water consumed by astronauts, reducing the amount of water that needs to be sourced from external sources.

More than 50 computers on the station continuously monitor environmental parameters such as pressure and temperature by monitoring data from over 350,000 sensors. The Canadian-developed Canadarm2 robotic arm and the Dextre robotic system are involved in the transportation of modules, installation of experimental platforms and external maintenance.

With these technical equipment and structural features, the ISS is one of the largest artificial satellites orbiting the Earth. Under favorable observation conditions, it can be observed with the naked eye from the Earth's surface.

^{Japanese Open Plant, (Source:}^NASA⁾

This image shows Japan's Exposed Facility attached to the Kibo laboratory module while the International Space Station orbits over the South Pacific Ocean. Japan's Open Facility is located outside Kibo, where experiments are conducted in the vacuum of space for a variety of research, including Earth observations, technology demonstrations and materials physics.

Structural

The ISS is modular, consisting of pressurized modules developed by different countries, a supporting exoskeleton system and large solar panels. With a total length of about 109 meters and a mass of about 420 tons, the station offers a habitable internal volume of 388 cubic meters. It moves in orbit at a speed of about 28,000 kilometers per hour, completing a revolution around the Earth in about 90 minutes.

Technical

1. Orbit Characteristics

Orbit Type: Low Earth Orbit (LEO)

Altitude: Average 408 kilometers (periodically readjusted)

Inclination Angle: Approximately 51.6 degrees

Orbit Duration: One full revolution around the Earth in 92 minutes

Orbital Speed: Approx. 27,600 km/h (7.66 km/s)

2. Physical Structure

Total Length: Approx. 109 meters

Width: Total 73 meters including solar panels

Height: Approx. 20 meters

Total Mass: Approximately 420,000 kilograms (420 tons)

Habitable Volume: 388 cubic meters (NASA data)

Number of Internal Pressurized Modules: 16 (US, European, Japanese and Russian-made modules)

3. Energy and Electricity

Energy Source: Solar panels

Total Solar Panel Area: Approximately 2,500 square meters

Electric Power Generated: 84-120 kilowatts (depending on solar radiation)

Energy Storage: Rechargeable nickel-hydrogen batteries (replaced by lithium-ion batteries from 2020)

4. Life Support Systems

Crew Capacity: Usually 6 astronauts (maximum up to 10)

Ventilation and Atmosphere: Oxygen nitrogen mixture - similar to Earth's atmosphere

Waste Management: Water recycling systems; water from urine and sweat can be reused

Carbon Dioxide Removal: Electrically assisted chemical systems

Food and Water: Provided by regular cargo vehicles, partially supplemented by recycling

5. Communication and Control

Main Communication Systems: NASA's TDRSS (Tracking and Data Relay Satellite System) via

Secondary Systems: UHF and S-band radio communications

Flight Control: Conducted simultaneously by NASA Johnson Space Center in Houston and Roscosmos control center in Moscow

6. Modules and Hardware

US Division: Destiny Lab, Unity and Tranquility modules

European Division: Columbus Laboratory Module (ESA)

Japan Division: Kibo Laboratory and external experiment platform (JAXA)

Russian Division: Zvezda, Zarya, Nauka modules

Ports: Pressurized Mating Adapter (PMA), International Docking Adapter (IDA)

7. Robotic Systems

Canadarm2: Robotic arm provided by Canada, used for module docking and maintenance

Dextre: Precision robotic maintenance tool

ERA (European Robotic Arm): Added in 2021, integrated into Russian Nauka module

8. Cargo and Transportation

Cargo Spacecraft:

NASA: SpaceX Dragon, Northrop Grumman Cygnus

Japan: HTV (H-II Transfer Vehicle)

Russia: Progress

Europe: ATV (Advanced Transfer Vehicle, now out of service)

Resupply Frequency: New supplies and food shipments every 4-6 months on average

9. Launch and Assembly

First Module Launch: Zarya (Russian-built), November 20, 1998

Completion Progress: Main skeleton completed by 2011, new modules still being added.

Total Number of Launches: More than 40 major transportation missions (Space Shuttle, Proton, Falcon 9, etc.)

First Launch Information

First Launch

Date: November 20, 1998

Launched Module: Zarya (Functional Cargo Block - FGB)

Launch Vehicle: Proton-K rocket

Launch Site: Baikonur Spaceport, Kazakhstan

Manufacturer: Roscosmos (Russia), but the module was financially funded by the United States

Mission Purpose: Zarya was designed to provide power generation for the ISS and to house the first guidance system.

Second Launch and First American Module

Date: December 4, 1998

Module: Unity (Node 1) - US-built link node module

Launch Vehicle: Space Shuttle Endeavour (STS-88 mission)

Note: With this launch, Zarya and Unity were joined in orbit, completing the first structural assembly of the ISS.

First Manned Mission

Date: November 2, 2000

Crew: Expedition 1 mission - William Shepherd (NASA), Yuri Gidzenko and Sergei Krikalev (Roscosmos)

Vehicle: Soyuz TM-31

Significance: With this mission, the station became permanently manned. Since then, the ISS has never been empty.

Next Major Milestones

2001: Canada's robotic arm Canadarm2 is assembled.

2008: ESA's Columbus module and JAXA's Kibo laboratory were added.

2011: The last Space Shuttle mission (STS-135, Atlantis) carried a module to the ISS.

2021: Russia's Nauka (Science) module was added.

^{Roll-Out Solar Panels 3A/4A, (Source:}^NASA⁾

This image shows spacewalkers Thomas Pesquet of ESA (European Space Agency) and Akihiko Hoshide of JAXA (Japan Aerospace Exploration Agency) installing the 4A channel for the roll-out solar panel installation on the International Space Station's P4 (Port) truss.

General Station Information

The International Space Station is larger than a six-bedroom house, with six bedrooms, two bathrooms, a gym and a window with 360-degree views.
An international partnership of five space agencies from 15 countries operates the International Space Station.
An international crew of seven live and work aboard while traveling at five miles per second, orbiting the Earth about every 90 minutes.
To reduce the loss of muscle and bone mass in the human body in microgravity, astronauts exercise at least two hours a day.
The solar panel wingspan (356 feet, 109 meters) is longer than the world's largest passenger plane, the Airbus A380 (262 feet, 80 meters).
The end-to-end length of the space station is 109 meters, which is one yard shorter than the length of an American football field, including the end zones.
Eight spaceships can be docked to the space station at the same time.
Four different cargo spacecraft carry science, cargo and supplies: Northrop Grumman's Cygnus, SpaceX's Dragon, JAXA's HTV and the Russian Progress.
More than 20 different research payloads can be housed outside the station at the same time. These include Earth sensing equipment, materials science payloads, particle physics experiments like the Alpha Magnetic Spectrometer-02 and more.
The space station covers the distance to the Moon and back in about a day.
The Water Recovery System reduces the crew's reliance on water from the cargo spacecraft by 65 percent - from about a gallon a day to a third of a gallon.
Orbiting software monitors about 350,000 sensors to ensure the health and safety of the station and crew.
The space station's internal pressure volume is equal to that of a Boeing 747 airplane.
More than 50 computers control the systems on the space station.
More than 3 million lines of software code on the ground support more than 1.5 million lines of flight software code.

^{Nauka Multipurpose Laboratory Module, (Source:}^NASA⁾

This image shows Russia's Nauka multipurpose laboratory module as the International Space Station flew into an orbital sunset 422 kilometers above North America. Nauka, which means “science” in Russian, is a 43-meter-long, 23-ton module that serves as a new science facility in the Roscosmos section of the International Space Station.

^{Roskosmos (Source:}^NASA⁾

This image shows Roscosmos' Prichal docking module attached to the Nauka multipurpose laboratory module. Prichal, named after the Russian word for scaffolding, has five docking ports to dock Russian spacecraft and provide fuel transfer capability to the Nauka multipurpose laboratory module.

Scientific Research

The ISS is home to a variety of scientific research carried out in a microgravity environment. This research is conducted in areas such as biology, physics, chemistry, medicine and materials science. Experiments on the effects of long-duration spaceflight on human health, drug development processes and the testing of life support systems in space are also being conducted.

Participating Countries and Cooperation Structure

The ISS is designed and operated in partnership with five space agencies. The main partners are NASA (United States of America), Roscosmos (Russia), ESA (European Space Agency), JAXA (Japan Space Agency) and CSA (Canadian Space Agency). The 1998 intergovernmental agreements define the rights and responsibilities for the design, development, operation and use of the station. Each partner assumes ownership and maintenance responsibility for the modules and systems it provides, while operational tasks and financial obligations are shared according to contribution rates.

The cooperation structure is based on a system of shared responsibility and barter. For example, NASA manages the overall integration and command and control system of the US Structural Division, while Roscosmos is responsible for the control of the Russian segment and altitude-raising maneuvers. ESA, JAXA and CSA operate the systems they contribute to through their own control centers. ESA's Columbus module is operated from the Columbus Control Center in Germany, while JAXA's Kibo module is operated from its headquarters in Tsukuba, Japan. Canada's robotic systems are operated in coordination with NASA.

The use of station resources is shared among the partners according to specific ratios. Approximately 76.6% of the common areas on the ISS (crew working time, electrical power, data communications, etc.) are allocated to NASA, 12.8% to JAXA, 8.3% to ESA and 2.3% to CSA. Similarly, the Columbus laboratory is 51% owned by ESA and the rest by NASA and Canada; the Kibo laboratory is 51% owned by JAXA and the rest by NASA and Canada. These proportions are proportional to the financial and hardware contributions of each agency.

The station's operations are run under an international management model. Two primary flight control centers provide 24/7 operational support: One at NASA's Johnson Space Center in Houston, USA, and the other at Roscosmos Flight Control Center in Korolyov, Russia. In addition, support control centers in Tsukuba, Japan, at the Columbus Control Center near Munich, Germany, and in Montreal, Canada, handle the operations of the respective contribution systems. All operations are coordinated through structures such as the Multilateral Coordination Board (MCB).

^{Space Station Remote Manipulator System (SSRMS), astronaut David A. Wolf, (Source:}^NASA⁾

In this image, astronaut David A. Wolf, STS-112 mission specialist, attaches to a foot holder on the Space Station Remote Manipulator System (SSRMS), or Canadarm2, as he participates in the mission's first off-board activity (EVA) session.

The transportation of personnel and cargo to the station is provided in cooperation with the project partners. Until 2011, NASA's Space Shuttle vehicles were used for assembly and logistics missions. Today, Russia's Soyuz spacecraft and SpaceX's Crew Dragon are used for manned flights. For cargo transportation, Russian Progress vehicles, SpaceX's Dragon cargo vehicles, Northrop Grumman's Cygnus vehicle, and Japan's HTV (H-II Transfer Vehicle) and Europe's ATV (Automated Transfer Vehicle) systems have been used in the past. So far, four different manned vehicles and five different automated resupply vehicles have visited the ISS.

Scientific Objectives and Conducted Research

The main purpose of the ISS is to provide data for scientific and technological studies by enabling long-term research in microgravity. Experiments that are difficult or impossible to perform on the Earth's surface can be carried out in the station's weightless environment. In this way, data is obtained in various fields such as physics, chemistry, materials science, biology, human physiology and earth sciences. As an orbital laboratory, the station provides a platform for observing the effects of long-term human presence in space, studying material and fluid behavior under space conditions, and testing technologies for future missions to the Moon and Mars. In particular, within the scope of human health research, the biological effects of long-term space missions are evaluated by monitoring physiological effects such as loss of bone and muscle mass and immune system changes observed in astronauts. These data generate information that will contribute to the understanding of health problems such as osteoporosis and muscle atrophy on Earth.

^{Destiny Laboratory Module, NASA astronauts Susan Helms and James Voss, (Source:}^NASA⁾

In this image, NASA astronauts Susan Helms and James Voss look out the window of the Destiny laboratory module. The US Destiny laboratory module is the primary research laboratory for US payloads and supports a wide range of experiments and studies that contribute to the health, safety and quality of life of people around the world.

The scientific activities carried out on the ISS can be categorized under several main headings:

Human Health and Long-Term Spaceflight: The effects of microgravity on human physiology are being investigated in multiple ways. For example, studies are being conducted on processes such as the decrease in bone mineral density, kidney stone formation, changes in the circulatory and immune systems, and sleep-wake cycles. The findings from these studies are being used for both space medicine and clinical applications on Earth. In addition, in a study conducted by NASA (The Twins Experiment), the genetic and physiological effects of long-term space conditions were examined by comparing an astronaut (Scott Kelly) with his identical twin living on Earth after a one-year stay on the ISS.

Materials Science and Physical Processes: Microgravity conditions allow physical processes such as surface tension of liquids, heat transfer and combustion to be studied without the influence of gravity. For example, data on combustion dynamics have been collected by studying the shape, behavior and propagation of fire in space. These findings have been evaluated in terms of fire safety and energy efficiency. In addition, experiments on the growth of semiconductor crystals and protein crystals in microgravity have provided data that could contribute to the development of purer materials and certain drugs.

Biology and Biotechnology: Many experiments on the growth of plants in the space environment (e.g., growing lettuce with the VEGGIE experiments), microbial behavior and cell biology have been conducted on the ISS. By studying the effects of weightlessness on living systems, information is obtained on topics such as food production, closed ecosystem management and radiation protection during long-term space travel. DNA sequencing experiments conducted directly on the station have provided important findings for space biotechnology.

Astrophysics and Earth Sciences: The ISS is used as an observation platform as well as a laboratory. Large experimental instruments, such as the station's externally mounted Alpha Magnetic Spectrometer (AMS-02), contribute to particle physics and cosmology by detecting cosmic rays and dark matter signatures. In addition, high-resolution cameras and sensors on the ISS continuously monitor the Earth, collecting data on climate change, the ozone layer, forest fires and natural disasters. For example, EarthCARE and similar devices externally mounted on Europe's Columbus module have been used to study atmospheric and cloud dynamics.

ISS Scientific Outputs: As of 2020, the number of experiments conducted on the ISS was reported to be close to 3,000, involving researchers from more than 108 countries. By 2023, the number of peer-reviewed scientific publications based on ISS research was reported to be around 3,700. These include protein crystallization experiments for cancer treatments, the synthesis of new alloys, the effects of space radiation on genetics, and advanced water purification technologies. For example, advanced water recycling systems and air filtration devices tested on the ISS have contributed to water purification technologies on Earth. Furthermore, robotic systems and AI-powered operations developed and tested on the station have advanced satellite repair and spacecraft maintenance concepts.

In addition to scientific research, the ISS has also conducted educational activities aimed at encouraging younger generations in science and engineering. The crew broadcast live to schools on Earth via multilingual educational links, and student experiments from many countries were conducted aboard the station. All these activities enable the ISS to serve as “humanity's common home in space”.

^{International Space Station: Humanity’s Lab in Space (Narrated by Adam Savage), (Kaynak:}^NASA⁾

International Cooperation

The ISS has so far been visited by more than 240 astronauts and cosmonauts. The station is a platform that symbolizes international cooperation and provides an environment where crews from different countries work together and carry out scientific projects. This cooperation emphasizes the importance of working towards peaceful and common goals in space exploration.

Financing and Management Model

The ISS project is a high-cost undertaking due to its scale. The total cost of designing, building and operating the station is estimated to have exceeded USD 150 billion as of 2010. Most of this cost was borne by NASA, the station's largest partner (NASA expenditure between 1985 and 2015: $58.7 billion; about $90 billion in 2021 dollars). Russia's contributions and operating expenditures up to 1998 amounted to around $12 billion, ESA member states contributed $5 billion, Japan $5 billion and Canada $2 billion. In addition, the cost of the 36 Space Shuttle flights to assemble the station between 1998 and 2011 (an average of $1.4 billion each) is estimated to have totaled about $50 billion. The ISS is therefore recognized as one of the most expensive man-made objects in history.

Each partner made its financial contribution largely as an “in-kind contribution” through the hardware and services it provided. For example, ESA contributed to the project by developing the Columbus module and ATV cargo vehicles; Japan contributed the Kibo module and HTV resupply vehicles. In return for these contributions, the respective partners received a share of experiment time and resource utilization rights at the station (for example, ESA has 51% of the rights to use the experiments in the Columbus module). Canada developed advanced robotic systems (Canadarm2 and Dextre) and in return received a say in the station's operations and the right to participate in crew flights. The financing was done through an exchange of equipment and services, rather than a dollar-for-dollar transfer of funds. However, the United States continues to bear a significant share of the station's joint operating costs; NASA allocates approximately $3-4 billion each year to ISS operations and maintenance. This amounts to about one-third of NASA's human spaceflight budget.

Station Management Model

The ISS has a multi-layered governance structure that defines the authority and responsibilities of the five partners. At the highest level, the Multilateral Coordination Board and related working groups between the space agencies of the partner countries coordinate the station's long-term planning and policy decisions. Day-to-day operations are managed through two main flight control centers based at NASA (Houston) and Roscosmos (Moscow). Flight control teams from these centers monitor the station's orbital position, system status, energy management and crew activities in real time. In addition, ESA's control centers in Germany, JAXA's in Japan and CSA's in Canada are responsible for the operation of their own modules and experiments and are in constant communication with Houston and Moscow.

Commercialization and Private Sector Involvement

Commercialization and private sector involvement have been encouraged in recent years to reduce the operating costs and increase the efficiency of the ISS. In 2005, the US Congress declared the US share of the station a National Laboratory, expanding its use for commercial and academic research. In this context, the non-profit organization ISS National Lab organizes non-NASA research and enables private companies to take advantage of the station's facilities. In addition, NASA has started to purchase cargo and crew transportation services from private companies: Since 2012, companies such as SpaceX and Northrop Grumman have operated regular cargo flights to the ISS, and from 2020, SpaceX Crew Dragon vehicles will deliver US astronauts to the station. This public-private partnership model reduces NASA's operational burden and enables the development of commercial space activities in low Earth orbit.

Maintenance and Upgrades

After more than 20 years of continuous use, some of the ISS's systems are showing signs of aging. To maintain the structural integrity of the station and replace aging equipment, the partners are implementing regular maintenance flights and software/upgrade packages. In 2019-2020, small cracks and air leaks detected in the Russian Zvezda module were isolated and repaired by engineers. This emphasized the importance of proactive maintenance to extend the station's lifetime. Starting in 2017, next-generation lithium-ion batteries were installed to replace the old batteries, and by 2021, the first new solar panel reinforcements (iROSA) will be added to the existing panels to maintain power generation capacity. All partners are working closely together technically and financially to ensure the safe and efficient operation of the ISS.

Station Visitors

^{Visits to the International Space Station, (Source:}^NASA⁾

More than 23 people representing 280 countries and five international partners visited the International Space Station. This image shows the distribution of visitors in the world.

ISS Visitor Country Distribution:

United States – 169 visitors
Russia – 63 visitors
Japan – 11 visitors
Canada – 9 visitors
Italy – 6 visitors
France – 4 visitors
Germany – 4 visitors
Belarus – 1 visitor
Belgium – 1 visitor
Brazil – 1 visitor
Denmark – 1 visitor
Great Britain – 1 visitor
Israel – 1 visitor
Kazakhstan – 1 visitor
Malaysia – 1 visitor
Netherlands – 1 visitor
André Kuipers – 2 visits
Saudi Arabia – 2 visitors
South Africa – 1 visitor
South Korea – 1 visitor
Spain – 1 visitor
Sweden – 2 visitors
Türkiye – 1 visitor (Alper Gezeravci)
United Arab Emirates – 2 visitors

Current Situation and Future Plans

The Operational Life and Future Plans of ISIS

The operational life of ISIS is planned to be extended by 2030. In this process, it is aimed to use the station more actively by the private sector and to support commercial space activities. Furthermore, the experiences and technologies obtained in ISS will serve as the basis for future space missions to more distant destinations such as the Moon and Mars.

ISS continues its active use in 2020’s. As of 2023, the station typically has a crew of 7 (NASASA's SpaceX Crew Dragon vehicle put into service, with permanent crew members from 6’ to 7’). Periodically, crew and cargo services continue regularly. In recent years, astronauts from new countries such as the United Arab Emirates and Saudi Arabia have also served on the ISS and international participation has diversified. For example, an UAE astronaut in 2023’ stayed in the station for 6 months, and later in the same year, Turkey's first astronaut is scheduled to be sent to the ISS on a short-term science mission. In addition, commercial visiting missions such as Axiom-1 (2022), which were attended by private sector astronauts, were carried out and significant improvements were made in terms of commercial and tourist use of ISS.

^{Mission Weather Lock, NASA astronaut Mike Hopkins, (Source:}^NASA⁾

In this image, NASA astronaut Mike Hopkins was viewed outside of the Quest airlock, where spacewalks were performed with Spacecraft Non-Mobility Units (EMU) or space suits. Quest Airlock consists of an end-to-end connection compartment and two compartments or locks that are attached with the cover. Provides systems for equipment lock, space suit maintenance and renovation. The crew lock provides a safe exit and entrance for astronauts who are on spacewalks.

The Term and Future of ISS

The original term of office of ISIS has been extended several times. Initially projected to close at 2016’, this period was extended to 2020’ye, then 2024’.At the beginning of 2022, the U. S. government officially announced the station's operations until 2030’ Following this, other major partners made similar commitments and announced that they would remain in the program until 2030’ in Europe (ESA), Japan (JAXA) and Canada (CSA). The Russian Federation has decided to continue its ISP partnership for a certain period of time despite the political tensions caused by the Ukraine crisis. Roscosmos has previously reported its intention to withdraw by the end of 2024, confirming that it will extend this period to at least 2028’ in July 2022’. Russia plans to focus on its new space station project (ROSS) after 2028. Thus, ISS is projected to continue to be operated with international cooperation up to 2030’ and the 2020’s will be ready to take over the mission at the end.

When the Term of Duty of ISSU is over

When the ISP task ended, detailed planning was made by the partner agencies on its fate. According to current plans, it is aimed that the station will be removed from orbit in a controlled manner towards the end of 2030 and reduced to a point far from human settlement in the Pacific Ocean. This region is the southern Greater Ocean region, also used in the past for controlled destruction of spacecraft and known as “Nemo Point”. NASA and other partners are developing the technical infrastructure necessary for the safe, burning destruction of the station in the atmosphere. The U. S. has allocated $2023 in the 180 million budget for a special towing spacecraft design called the “Deorbit Vehicle”. This tool will clamp to the ISS when the time comes, directing the station with its propellant motors to the atmosphere input in a controlled manner. In addition, Progress cargo vehicles of Russia are among the options to be used for support in this process. As planned, the ISS will be destroyed by being dropped into the ocean at the end of its mission period, thus completing its service without creating a debris problem in orbit.

ISS Post Period and New Space Stations Projects

New space station projects are taking shape for the post-ISS era. NASA has agreements with companies such as Axiom Space, Northrop Grumman, Blue Origin to develop fully commercial operating space stations in low-Earth orbit. From 2025’, Axiom Space plans to add its own commercial modules to ISSe and convert them into an independent station after the retirement of ISS. Projects such as Orbital Reef station, developed under the leadership of Blue Origin, are considered as new platforms to be operated by the private sector in 2030’s. Russia is preparing to build a completely self-controlled station called Russian Orbital Service Station (ROSS); the first module is aimed at launching in 2027’ and the core part up to 2030’. China, independent of ISS, built and operated its own multimodal space station, Tiangong, in 2021-2022.

Lessons from the ISS and Future Space Stations

Experience from the International Space Station (ISS) project has provided an important foundation for future space stations. ISS has shown that countries from different cultures and technological infrastructures can collaborate long-term in space. Thanks to this collaboration, astronauts have gained experience of living in space for a long time, numerous scientific experiments have been carried out and new discoveries have been made. The planned retirement of the ISP marks the beginning of a new era in space exploration, although it is the end of the current period. The next generation of space stations, which will come into play in the coming years, will take over the legacy of ISS and provide platforms for research and exploration. The ISS project is a concrete example of international cooperation and coming together for a common goal in space. The knowledge and technology gained will enable sustainable existence in Earth orbit and manned journeys into the depths of the Solar System.

International Space Station (ISS)