The International Space Station Marks 25 Years of Continuous Human Presence 

On November 2, 2025, NASA honored 25 years of continuous human presence aboard the International Space Station. What began as a fragile framework of modules has become a springboard for international cooperation, advanced scientific research and technology demonstrations, the development of a low-Earth orbit economy, and NASA’s next big steps in exploration, including crewed missions to the Moon and Mars.

This legacy of achievement in global human endeavors began with the arrival of the first crew at the space station on November 2, 2000. Expedition 1 crew members, NASA astronaut William M. Shepherd and Russian Aeronautics and Space Agency, now Roscosmos, cosmonauts Yuri P. Gidzenko and Sergei K. Krikalev were launched from the Baikonur Cosmodrome in Kazakhstan two days ago. After successful docking, the crew transferred aboard the station and began bringing it to life. Their primary tasks during their four-month mission included installing and activating life support and communications systems and working with three visiting space shuttle crews to continue assembly of the station. The trio returned to Earth in March 2001 aboard the space shuttle Discovery, after handing over the station to the Expedition 2 crew.

The assembly and maintenance of the International Space Station would not be possible without the skilled work of crew members performing complex tasks, in bulky spacesuits, in the hostile environment of space. In addition to station maintenance, spacewalks provide a platform for testing and improving space suits and tools – critical information for future exploration of the Moon and Mars. Other spacewalks have included scientific research operations. In January 2025, for example, crew members collected samples for an investigation into whether microorganisms escaped through the station’s vents and could survive in space, to better inform the design of spacecraft that help prevent human contamination of Mars and other destinations.

More than 270 spacewalks dedicated to the space station have been carried out over the past quarter century. Several of them have marked the history of human space stations and flights:

• May 1999: NASA astronaut Tamara Jernigan becomes the first woman to perform a spacewalk to the space station, to support its construction.

• September 2000: Also during space station assembly, NASA astronaut Edward T. “Ed” Lu and Roscosmos cosmonaut Yuri I. Malenchenko performed the first U.S.-Russian spacewalk.

• March 10, 2001: NASA astronauts James Voss and Susan Helms set the record for the longest spacewalk in U.S. history, 8 hours and 56 minutes.

• The first spacewalks carried out by international partners included:

• April 2001 – Canadian Space Agency astronaut Chris Hadfield

• July 2005 – Soichi Noguchi, astronaut of the Japan Aerospace Exploration Agency

• August 2006 – European Space Agency astronaut Thomas Reiter

• February 26, 2004: NASA astronaut Mike Foale and Russian cosmonaut Aleksandr Y. Kaleri perform the first spacewalk without anyone inside the station.

• October 18, 2019: The first all-female spacewalk in history, led by NASA astronauts Christina Koch and Jessica Meir.

The International Space Station welcomed its first commercial crew members on May 31, 2020, when former NASA astronauts Robert Behnken and Douglas Hurley joined Expedition 63 Commander and NASA astronaut Chris Cassidy and Roscosmos cosmonauts Anatoly Ivanishin and Ivan Vagner aboard the orbiting laboratory.

Behnken and Hurley took off the day before from the Kennedy Space Center in Florida for NASA’s SpaceX Demo-2 test flight – the first launch of American astronauts from American soil since the retirement of the Space Shuttle in 2011.

The duo quickly integrated into the rest of the crew and participated in a number of scientific experiments, spacewalks and public engagement events during their 62 days aboard the station. In total, the pair spent 64 days in orbit, completed 1,024 orbits around Earth and contributed more than 100 hours to the orbiting laboratory’s research before crashing on August 2.

The success of the Demo-2 mission paved the way for regular SpaceX flights carrying astronauts to and from the space station. With another certified crew transportation system in place, the International Space Station program has extended research time and increased discovery opportunities aboard humanity’s testbed for exploration, including preparations for human exploration of the Moon and Mars.

On September 27, 2023, NASA astronaut Frank Rubio returned to Earth after spending 371 days aboard the International Space Station, the longest spaceflight by an American astronaut in history. Its mission surpassed the previous record of 355 days, set by NASA astronaut Mark Vande Hei, and provided scientists with unprecedented insight into how the human body adapts to more than a year in microgravity.

Rubio’s record-breaking mission supported six human research studies, including investigations into diet, exercise, and general physiology and psychology. He was the first astronaut to test whether limited training equipment could still maintain health and fitness, an important factor for future spacecraft with smaller living quarters. He also contributed biological samples, surveys and tests to NASA’s Spaceflight Standard Measures, a study that collects data on astronaut health to better understand how the body adapts to space, knowledge that helps prepare crews for the Artemis campaign to the Moon and future trips to Mars.

Alongside his fellow crew members, Rubio participated in dozens of investigations and technology demonstrations, ranging from growing tomato plants with hydroponic and aeroponic techniques to materials science experiments that advance spacecraft design.

Long-duration missions help inform future spaceflight and lay the foundation for the next era of human exploration.

The space station is one of the most ambitious international collaborations ever attempted. It brings together international flight crews, multiple launch vehicles, globally distributed launch and flight operations, training, engineering and development facilities, communications networks and the international scientific research community for the benefit of all humanity.

An international partnership of space agencies operates the elements of the orbiting laboratory: NASA, Roscosmos, ESA (European Space Agency), JAXA (Japan Aerospace Exploration Agency) and CSA (Canadian Space Agency). Each partner assumes primary responsibility for the management and operation of the station hardware it provides, as well as on-Earth construction, launch support, mission operations, communications, and the research and technology facilities that support the station.

At least 290 people representing 26 countries and five international partners have visited the orbiting laboratory during its 25 years of continuous human presence. Some of these visitors came to the station on private astronaut missions. These missions contribute to scientific, awareness and commercial activities. They also help demonstrate demand for future commercial space stations and are an important part of NASA’s strategy to enable a robust and competitive commercial economy in low Earth orbit.

The results of the international partnership created through the space station and its achievements illustrate how countries can work together to overcome complex challenges and achieve collaborative goals.