The International Space Station Celebrates 25 Years in Space

NASA recently celebrated the 25th anniversary of the International Space Station (ISS) with a space-to-Earth call between the 7-person Expedition 70 crew and outgoing NASA Associate Administrator, Bob Cabana, and ISS Program Manager, Joel Montalbano. On December 6, 1998, the U.S.-built Unity module and the Russian-built Zarya module were mated in the Space Shuttle Endeavour cargo bay, as Endeavour was responsible for launching Unity into orbit that same day, with Zarya having waited in orbit after being launched on November 20 from Kazakhstan.

“I cannot believe it was 25 years ago today that we grappled Zarya and joined it with the Unity node,” said Cabana during the call from NASA Headquarters in Washington, D.C. “Absolutely amazing.”

While this milestone marks 25 years since the first two ISS modules were attached, it would be another two years until the ISS had a crew, Expedition 1, which arrived at the ISS in November 2000 and stayed until March 2001, beginning an uninterrupted human presence on the ISS that continues today. During the two-year period between the first mating and Expedition 1, the Russian-built Zvedza module was attached to the Unity and Zarya modules on July 26, 2000, after launching from Kazakhstan two weeks earlier. Assembly of the large modules of the ISS would continue until 2021 when the Roscosmos-funded Nauka module was attached in July 2021.

Now in its final configuration, the ISS is approximately the size of an American gridiron football field consisting of 8 solar arrays that provide the station’s power while maintaining an average altitude of 400 kilometers (250 miles). Its massive size consists of a pressurized module length along the major axis of 67 meters (218 feet), a truss (primary body) length of 94 meters (310 feet), a solar array length (measured along the truss) of 73 meters (239 feet), and a total mass of 419,725 kilograms (925,335 pounds).

Artist rendition of the ISS compared to an American gridiron football field. (Credit: NASA)
Image of the ISS taken by SpaceX Crew-2 mission on November 8, 2021 after it successfully undocked from the ISS Harmony module. (Credit: NASA)

Ever since the 3-person Expedition 1 crew first took command of the ISS, a total of 273 individuals from 21 countries have visited the orbiting laboratory and have been comprised of trained astronauts and private visitors. From most visitors to least, the following visitor countries include the United States, Russia, Japan, Canada, Italy, France, Germany, Saudi Arabia, United Arab Emirates, Belgium, Brazil, Denmark, Great Britain, Israel, Kazakhstan, Malaysia, Netherlands, South Africa, South Korea, Spain, and Sweden.

“One of my favorite aspects of the International Space Station is the international part of it,” said NASA Astronaut and Expedition 70 Flight Engineer, Jasmin Moghbeli, during the call. “We each bring our unique perspectives, not just from our different nationalities, but also our different backgrounds. I think we’re definitely strengthened by the international partnership. It’s just like gaining redundancy when you have multiple partners working together. It’s stronger and more resilient to any sort of problems or obstacles that come our way and so it definitely makes us stronger. And I think that’s why we have had the International Space Station up here for 25 years now.”

Image of all five space station partner nations being represented during Expedition 20. From left to right: Flight Engineer Roman Romanenko (Russia); Flight Engineer Koichi Wakata (Japan); Flight Engineer Frank De Winne (Belgium); Flight Engineer Michael Barratt (United States); Flight Engineer Bob Thirsk (Canada); Flight Engineer Tim Kopra (United States), and Commander Gennady Padalka (Russia). (Credit: NASA)

Along with the vast international participation, the ISS has conducted more than 2,500 research experiments from scientific researchers in more than 108 nations across a myriad of industries, including biology and biotechnology, Earth and space science, educational activities, human research, physical science, and technology. This also includes 20 different research experiments having been conducted on the outside of the ISS, as well. Currently, Expedition 70 has conducted just over 200 experiments since the start of its mission in September 2023.

NASA astronaut Kayla Barron examining plants for the Veggie PONDS experiment during Expedition 66/67. (Credit: NASA)

Despite the vast scientific and technological achievements accomplished on the ISS, all good things must come to an end, as the massive orbiting laboratory is planned to be deorbited in January 2031. This is when NASA will allow burn up in the Earth’s atmosphere and fall into Point Nemo in the middle of the Pacific Ocean, also known as the “spacecraft cemetery” and is the most distant oceanic point from any land on Earth.

As we celebrate the 25th anniversary of the ISS, we look forward to its final years of service to science, technology, and humanity, along with celebrating its 30th anniversary in 2028!

As always, keep doing science & keep looking up!