Celebrating 25 Years of Human Presence on the International Space Station
On November 2, 2025, NASA celebrated a significant milestone: a quarter-century of continuous human presence aboard the International Space Station (ISS). What started as a delicate assembly of modules has transformed into a symbol of global collaboration, a hub for advanced scientific research, a platform for technology demonstrations, and a foundation for the emerging low Earth orbit economy. This milestone also marks a stepping stone towards NASA’s upcoming missions to the Moon and Mars.
A Legacy of Global Human Endeavors
The journey began with the first crew’s arrival at the ISS on November 2, 2000. This historic event set the stage for what would become a testament to international cooperation in space exploration. The inaugural crew included NASA astronaut William M. Shepherd and Russian cosmonauts Yuri P. Gidzenko and Sergei K. Krikalev. They embarked on their mission from the Baikonur Cosmodrome in Kazakhstan, docking with the ISS two days later. Their mission was crucial in activating the station’s life support and communication systems and integrating with three visiting space shuttle crews to progress the station’s assembly. After four months, the crew returned to Earth aboard space shuttle Discovery, handing over the station to the Expedition 2 crew.
The Role of Spacewalks in ISS Maintenance and Exploration
The ISS’s assembly and upkeep rely on the skilled efforts of astronauts performing complex tasks, often while wearing cumbersome spacesuits in the harsh environment of space. Spacewalks, or extravehicular activities (EVAs), are not only vital for station maintenance but also for testing spacesuits and tools that will be essential for future missions to the Moon and Mars. Recent spacewalks have included scientific operations, such as the January 2025 mission where astronauts collected samples to study whether microorganisms can survive the vacuum of space, providing valuable insights into how spacecraft design can prevent human contamination of other celestial bodies like Mars.
In the past 25 years, over 270 spacewalks have been conducted for the ISS. Notable milestones include:
- May 1999: NASA astronaut Tamara Jernigan became the first woman to perform a spacewalk at the ISS during its construction.
- September 2000: The first U.S.-Russian collaborative spacewalk was conducted by NASA astronaut Edward T. "Ed" Lu and Russian cosmonaut Yuri I. Malenchenko.
- March 10, 2001: NASA astronauts James Voss and Susan Helms set a record for the longest spacewalk in U.S. history at 8 hours and 56 minutes.
- April 2001: Canadian Space Agency astronaut Chris Hadfield completed his first spacewalk.
- July 2005: Japan Aerospace Exploration Agency astronaut Soichi Noguchi made his debut spacewalk.
- August 2006: European Space Agency astronaut Thomas Reiter participated in his first spacewalk.
- February 26, 2004: NASA astronaut Mike Foale and Russian cosmonaut Aleksandr Y. Kaleri completed the first spacewalk without anyone inside the station.
- October 18, 2019: NASA astronauts Christina Koch and Jessica Meir conducted the first all-female spacewalk.
Commercial Collaborations and the Future of Spaceflight
On May 31, 2020, the ISS welcomed its first commercial crew members, former NASA astronauts Robert Behnken and Douglas Hurley. They joined Expedition 63 Commander Chris Cassidy and Russian cosmonauts Anatoly Ivanishin and Ivan Vagner. This marked a new era in space exploration where commercial partnerships play a crucial role. Behnken and Hurley launched from Kennedy Space Center in Florida aboard NASA’s SpaceX Demo-2 test flight, signifying the first launch of American astronauts from U.S. soil since the space shuttle program concluded in 2011.
During their 62-day mission on the ISS, Behnken and Hurley engaged in numerous scientific experiments, participated in spacewalks, and communicated with the public about their experiences. Their mission completed 1,024 orbits around Earth and significantly contributed to the station’s ongoing research. The successful conclusion of the Demo-2 mission paved the way for regular SpaceX flights, which has increased research opportunities and supports preparations for human exploration of the Moon and Mars.
Record-Breaking Missions and Scientific Contributions
On September 27, 2023, NASA astronaut Frank Rubio returned to Earth after a record-breaking 371 days aboard the ISS, making it the longest single spaceflight by a U.S. astronaut. This mission surpassed the previous record of 355 days set by astronaut Mark Vande Hei and provided researchers with invaluable data on how the human body adapts to extended periods in microgravity.
Rubio’s mission contributed to six human research studies focusing on diet, exercise, physiology, and psychology. His work involved testing limited workout equipment to maintain health and fitness, a crucial consideration for future missions with confined living quarters. Additionally, Rubio provided biological samples and data for NASA’s Spaceflight Standard Measures, a study aimed at understanding how the human body adapts to space, which is critical for the Artemis campaign to the Moon and future Mars missions.
A Testament to International Collaboration
The ISS stands as one of the most ambitious international collaborations in history, bringing together flight crews from around the world, multiple launch vehicles, and a global network of operations and research facilities. This partnership includes NASA, Roscosmos, ESA (European Space Agency), JAXA (Japan Aerospace Exploration Agency), and CSA (Canadian Space Agency). Each partner is responsible for managing their respective contributions to the station, including hardware, mission operations, and research capabilities.
Over its 25 years, the ISS has hosted over 290 individuals from 26 countries, making it a true symbol of international cooperation. Some visitors have participated in private astronaut missions, enhancing scientific, outreach, and commercial activities. These missions demonstrate the growing demand for commercial space stations and play a crucial role in NASA’s strategy to foster a competitive commercial economy in low Earth orbit.
The achievements of the ISS and its international partnership illustrate how countries can collaborate to overcome complex challenges and achieve shared goals for the benefit of all humanity. This legacy will continue to inspire future generations as we embark on new journeys to explore the Moon, Mars, and beyond.
For more information, visit NASA’s official International Space Station page.
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