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

The first expedition

This legacy of achievement in global human endeavors began with the first crew’s arrival to the space station on Nov. 2, 2000. Expedition 1 crew members NASA astronaut William M. Shepherd and Russian Aviation and Space Agency, now Roscosmos, cosmonauts Yuri P. Gidzenko and Sergei K. Krikalev launched from the Baikonur Cosmodrome in Kazakhstan two days prior. After a 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 the life support and communications systems and working with three visiting space shuttle crews to continue the station’s assembly. The trio returned to Earth in March 2001 aboard space shuttle Discovery, after having turned the station over to the Expedition 2 crew. 

(Space)walking into history 

Assembly and maintenance of the International Space Station would not be possible without the skilled work of crew members performing intricate tasks, in bulky spacesuits, in the harsh environment of space. In addition to station upkeep, spacewalks provide a platform for testing and improving spacesuits and tools – critical information for future exploration of the Moon and Mars. Other spacewalks have included operations for scientific research. In Jan. 2025, for example, crew members collected samples for an investigation examining whether microorganisms have exited through station vents and can survive in space, to better inform spacecraft design that helps prevent human contamination of Mars and other destinations. 

More than 270 spacewalks dedicated to the space station have been accomplished in the last quarter century. Several made station and human spaceflight history: 

• May 1999: NASA astronaut Tamara Jernigan became the first woman to complete a spacewalk at the space station, in support of its construction. 

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

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

• First spacewalks by international partners included: 

• April 2001 – Canadian Space Agency astronaut Chris Hadfield 

• July 2005 – Japan Aerospace Exploration Agency astronaut Soichi Noguchi 

• Aug. 2006 – European Space Agency astronaut Thomas Reiter 

• Feb. 26, 2004: NASA astronaut Mike Foale and Russian cosmonaut Aleksandr Y. Kaleri complete the first spacewalk with no one inside the station.  

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

Orbiting laboratory welcomes first commercial crew 

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 lifted off from Kennedy Space Center in Florida the day before on NASA’s SpaceX Demo-2 test flight – the first launch of American astronauts from U.S. soil since the space shuttle’s retirement in 2011.  

The duo quickly integrated with the rest of the crew and participated in a number of scientific experiments, spacewalks, and public engagement events during their 62 days aboard station. Overall, the pair spent 64 days in orbit, completed 1,024 orbits around Earth, and contributed more than 100 hours of time to supporting the orbiting laboratory’s investigations before splashing down on Aug. 2.  

Successful completion 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 added research time and increased the opportunity for discovery aboard humanity’s testbed for exploration, including preparations for human exploration of the Moon and Mars. 

Frank Rubio’s record-breaking year in space  

On Sept. 27, 2023, NASA astronaut Frank Rubio returned to Earth after spending 371 days aboard the International Space Station—the longest single spaceflight by a U.S. astronaut in history. His mission surpassed the previous record of 355 days, set by NASA astronaut Mark Vande Hei, and provided scientists with an unprecedented look at how the human body adapts to more than a year in microgravity. 

Rubio’s record-setting mission supported six human research studies, including investigations into diet, exercise, and overall physiology and psychology. He was the first astronaut to test whether limited workout equipment could still maintain health and fitness, an important consideration for future spacecraft with tighter living quarters. He also contributed biological samples, surveys, and tests for NASA’s Spaceflight Standard Measures, a study that collects health data from astronauts 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, 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 groundwork for the next era of human exploration.  

A global foundation for growing a low Earth orbit economy 

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 takes primary responsibility for managing and running the station hardware it provides, as well as on-Earth construction, launch support, mission operations, communications, and research and technology facilities that support the station. 

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

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

 

To see Earth from space is to be forever changed by the view. Since Alan Shepard became the first American to lay eyes on our home planet from above, countless NASA astronauts have described feeling awed by the astonishing sight and a profound shift in perspective that followed.

This unique experience is known as the overview effect – a term coined in 1987 by space philosopher and author Frank White in a book of the same name. The phenomenon creates powerful changes in the way astronauts think about Earth and life and can be particularly strong for those who lived and worked aboard the International Space Station during its 25 years of continuous human presence. The orbiting laboratory’s cupola module, equipped with seven windows looking down on Earth, provides the perfect place for observation and reflection.

As Artemis II Mission Specialist Christina Koch explained:

“The overview effect is when you’re looking through the cupola and you see the Earth as it exists with the whole universe in the background. You see the thin blue line of the atmosphere, and then when you’re on the dark side of the Earth, you actually see this very thin green line that shows you where the atmosphere is. What you realize is every single person that you know is sustained and inside of that green line and everything else outside of it is completely inhospitable. You don’t see borders, you don’t see religious lines, you don’t see political boundaries. All you see is Earth and you see that we are way more alike than we are different.”

Koch’s Artemis II crewmate, NASA astronaut Victor Glover, said the overview effect’s potency is closely tied to the “sea level effect” – humanity’s shared experience on Earth. “You come back to sea level, and then you have a choice,” he explained. “Are you going to try to live your life a little differently? Are you going to really choose to be a member of this community of Earth?”

Many astronauts emphasize the importance of unity after experiencing the overview effect. “You see that it’s a single planet with a shared atmosphere. It’s our shared place in this universe,” said former NASA astronaut Bob Behnken. “I think that perspective, as we go through things like the pandemic or we see the challenges across our nation or across the world, we recognize that we all face them together.”

Seeing the Earth from space can also change their concept of home. Former NASA astronaut Nicole Stott recalls wanting to see her home state of Florida during her first mission to the International Space Station. “Finally, we were flying over Florida. I wanted to go to the window and see it, and then realized somewhere down the line that I wasn’t looking at Florida that same way anymore,” she said. “I still wanted to see Florida, but Florida had just become this special part of home, which is Earth. We’re all earthlings.”

For some astronauts, their perspective shift inspired them to make changes on the ground. “I think if you’re not a conservationist before you go to space, you’re at least partly a conservationist when you come back. Because when you see how thin that atmosphere is, that protective layer that we have here, you think, wow, we really have to take care of this because it does look so fragile from space,” said retired NASA astronaut Mike Foreman.

Others hope to share the overview effect with more people. “That perspective helps you grow. It has really inspired me to try to get more people this experience and to get a permanent foothold in the stars for our species,” said former NASA astronaut Jack Fischer. “I want to do everything I possibly can to help the human species, humanity as a whole, go further and grow and evolve like I know they’re capable of.”

Future crews to the orbiting laboratory can look forward to a similar experience. “In that instant, when you’re overwhelmed with that vista, when your eyes see nothing but the beauty of the Earth – every single crew member that I brought in [the cupola] for that exposure, cried,” said retired NASA astronaut T.J. Creamer. “It is heart stopping. It is soul pounding. It is breathtaking.”

For more astronaut perspectives from the International Space Station, watch “Down to Earth” on NASA+.

Brian Alpert’s path was always destined for the aerospace industry, but his journey turned toward NASA’s Johnson Space Center during his sophomore year in college. That was when Tricia Mack, who works in NASA’s Transportation Integration Office within the International Space Station Program, spoke to his aerospace seminar about planning spacewalks, training crews, and supporting operations from the Mission Control Center in Houston.

Alpert was inspired to join the agency and later earned a spot as an engineering co-op student at Johnson. “My first stop after new employee orientation was Tricia’s office,” he said.

Eighteen years later, Alpert is the cross-program integration deputy for NASA’s human landing system (HLS) – the mode of transportation that will take astronauts to the lunar surface as part of the Artemis campaign. In his role, Alpert is responsible for coordinating with other Artemis programs, like the Orion Program, on issue resolution, joint agreements, data exchanges, hardware integration, and reviews. He also co-leads the Exploration Atmospheres Issue Resolution Team, assessing risks to and impacts on space vehicle atmosphere, spacesuit pressure, and operational timelines for Artemis missions.

Alpert has enjoyed the opportunity to participate in several proposal reviews for Artemis program contracts as well. “NASA’s model of embracing public-private partnerships to achieve its strategic goals and objectives is exciting and will continue to expand opportunities in space,” he said.

He applies lessons learned and skills gained from his previous roles as a spacewalk crew instructor, flight controller, and systems engineer to his current work on HLS. “I hope to pass on to the next generation that skills and lessons you learn as a student or a young employee can and will help you in your future work,” he said.

Alpert’s prior NASA roles involved memorable experiences like working to address spacesuit and vehicle failures that occurred during a spacewalk on International Space Station Expedition 32. He was serving as the lead spacewalk systems flight controller in the Mission Control Center at the time and played a key role in getting NASA astronaut Suni Williams and JAXA (Japan Aerospace Exploration Agency) astronaut Aki Hoshide safely back aboard the space station. Since Williams and Hoshide did not complete the spacewalk’s primary objective – replacing a Main Bus Switching Unit – a backup spacewalk was scheduled several days later. Alpert was on console for that spacewalk, too.

“One important lesson that I have learned through my career to date is how exceptionally talented, passionate, and hard-working everyone is here at NASA,” he said. “Whenever work gets stressful or problems get hard, there are teams of people that have your back, are willing to problem-solve with you, and can bring another perspective to finding a solution that you may not have considered.” He added that his colleagues are the best part of his job. “As much as I love what we do at NASA, what really gets me excited to come to work is all the outstanding people I get to work with every day.”

Learning how to navigate change has been an important lesson for Alpert, as well. “NASA has been through a lot of change since I became a full-time employee in 2009,” he said. “Making sure that I have clear goals for myself, my work, and my team helps us all stay focused on the mission and the work at hand and helps us prioritize projects and tasks as questions or challenges inevitably arise.”

One challenge Alpert especially enjoys? Johnson’s annual Chili Cookoff. He has participated in many cookoffs as part of the Cosmic Chili team, noting that he often dons a Wolverine costume as part of the festive fun. He also welcomes a space trivia challenge – and a chance to add to his collection of trivia trophies.

NASA announced its newest class of astronaut candidates on Sept. 22, 2025, at the agency’s Johnson Space Center in Houston. After the welcome ceremony, the 10 highly qualified individuals rolled up their sleeves and prepared for the next step in their journey to the stars: nearly two years of training to become flight-eligible for missions to low Earth orbit, the Moon, and ultimately, Mars.

The training astronaut candidates complete is comprehensive and rigorous. They learn about NASA’s history and vision, and how astronauts advance the agency’s mission. They take classes on space health – gaining an understanding of radiation exposure, microgravity’s effects on the human body, space food and nutrition, and how to use the exercise equipment aboard the International Space Station. They also study first aid and practice providing medical care for crewmates. Each candidate will receive flight training, learning to pilot or improving their current piloting skills through the T-38 supersonic jet and other aviation platforms.

With NASA’s plans for the future of exploration, this class of astronauts may have opportunities to fly to low Earth orbit, or even beyond. Some may contribute to research and technology investigations taking place aboard the space station – which is about to celebrate 25 years of continuous human presence in space. Others may venture to the Moon to prepare for future Mars missions.   

To be ready for any destination, this class will complete both space station training and advanced preparation for deep space. These exercises allow astronaut candidates to work through problems and build relationships with their classmates while preparing them for space flights.

“Training was such an intense period that we got to know each other really well,” said NASA astronaut Anil Menon, who joined the agency as part of the 2021 class – astronaut group 23. “Now when we come together, there are these moments – like we might be handing off a capcom shift, or we might be flying a jet together – and in those moments, I feel like I know them so well that we know how to navigate all sorts of challenges together and just be our best selves as a team.”

Astronaut candidate training also teaches foundational skills that can be applied to any destination in space. The group will complete several dives in the Neutral Buoyancy Laboratory, simulating spacewalks in different environments and learning how to do maintenance tasks in microgravity with a full-scale underwater mockup of the International Space Station as their worksite. They will also train inside other mockups of space vehicles, learning emergency procedures, maintenance, and repair of spacecraft, along with how to contribute to future developmental programs.

Robotics training will prepare them to use the station’s Canadarm2 robotic arm. They will trek through the wilderness as part of their land and water survival training, and they will study geology in the classroom and in the field. The group will practice tasks in a variety of simulations, leveraging Johnson’s world-class facilities, virtual reality, and immersive technologies. Additionally, the class will work shifts in the Mission Control Center in Houston to experience a day in the life of the people who keep watch over the astronauts and vehicles.

Astronaut candidates who successfully complete the training program celebrate their achievement in a graduation ceremony, after which they are officially flight-eligible members of NASA’s astronaut corps. They will also receive office and ground support roles at Johnson while they await future flight assignments.

“I’ve been exposed to a lot of different parts of what we do at Johnson Space Center, working both with the current increment of supporting operations aboard the International Space Station, as well as supporting some development of the Orion spacecraft and Artemis II preparations,” said NASA astronaut Chris Birch, another member of astronaut group 23.

Many members of NASA’s active astronaut corps emphasize that the learning does not stop when astronaut candidate training ends. “You have the foundational training and you continue to build off of that,” said Deniz Burnham, adding that the hardest days can be the most educational. “You get to learn, you get to improve, and then you’re still getting the opportunity. It’s such a positively unique experience and environment, and you can’t help but be grateful.”

As NASA astronaut Frank Rubio, class mentor, told the group, “You’ll become part of a legacy of those who trained before you, continuing the adventure they started, and looking ahead to future human exploration.”