International Space Station

The International Space Station, or ISS, is the largest structure humans have ever built in space, a science laboratory the size of a football field that circles the Earth about 400 km up. It has been lived in without a break since November 2000, making it one of the longest continuous human presences anywhere off the planet.

Quick facts

• Assembly began: 1998, with the first long-duration crew arriving in November 2000.
• Partners: five space agencies, NASA (United States), Roscosmos (Russia), ESA (Europe), JAXA (Japan), and CSA (Canada).
• Orbit: roughly 400 km high, tilted 51.6 degrees, circling the Earth about 16 times a day.
• Size: around 109 m (357 ft) end to end, with solar arrays spanning a football field.
• Crew: usually about seven astronauts and cosmonauts at a time.

How it was built

The station was carried up piece by piece over more than a decade and bolted together in orbit, mostly by Space Shuttle and Russian rockets. It is a connected set of pressurized modules where crews live and work, attached to a long truss that holds huge solar panels for power. Because it travels so fast, it laps the planet roughly every 90 minutes, so astronauts aboard see about sixteen sunrises and sunsets each day.

Why it matters

The ISS is a research lab where the main experiment is often the human body itself, helping scientists learn how people can live and work in space long enough to reach the Moon and Mars. Crews run thousands of experiments in biology, physics, and materials science that depend on weightlessness, and they test the life-support and spacewalking techniques future missions will need. Just as important, the station is a rare example of former rivals, especially the United States and Russia, cooperating peacefully for decades, a partnership written across the sky.