The International Space Station

7 min read

Key facts

Size	About 356 feet end to end, about a football field
Mass	About 925,000 pounds
Orbit height	About 250 miles
Speed	About 17,500 mph
Time for one orbit	About 90 minutes, roughly 16 orbits a day
Crewed continuously since	November 2, 2000
Usual crew	About 7 people
Partners	NASA, Roscosmos, ESA, JAXA and the Canadian Space Agency
Planned retirement	Around 2030, then a controlled reentry

In short

The ISS is the largest structure people have built in space, about the length of a football field.
It circles Earth about every 90 minutes at roughly 250 miles up.
People have lived aboard without a break since November 2, 2000.
From the ground it looks like a very bright, steady point gliding across the sky, with no blinking lights.
NASA plans to retire it around 2030 and steer it into a remote part of the Pacific Ocean.

A home and laboratory in orbit

The International Space Station is a joint project of five space agencies: NASA of the United States, Roscosmos of Russia, the European Space Agency, Japan's JAXA and the Canadian Space Agency. Its first piece launched in 1998, and astronauts and robots assembled the rest over more than a decade.

It has pressurized modules for living and working, a robotic arm, and large solar arrays. End to end, including the solar panels, it spans about 356 feet. Inside, the livable space is roughly that of a six-bedroom house.

Orbit and speed

The station flies about 250 miles above Earth at around 17,500 mph. At that speed it laps the planet roughly every 90 minutes, so the crew sees about 16 sunrises and 16 sunsets a day.

Crews float not because there is no gravity up there, but because the station and everything inside it are falling around Earth together. This continuous free fall is called microgravity. A trace of air still slows the station, so it fires engines now and then to raise its orbit.

Life and work aboard

People have lived on the ISS continuously since November 2, 2000, when the first long-duration crew arrived. More than 280 people from over 20 countries have visited. A typical crew is about seven, staying around six months.

Astronauts exercise about two hours a day to slow the loss of bone and muscle. They run experiments in biology, medicine, materials and physics that are hard or impossible on the ground, from growing crystals to studying how flames behave without gravity. Crews and supplies arrive on Russian Soyuz and Progress craft and on American commercial spacecraft such as SpaceX's Dragon.

How to spot the ISS

The ISS is often the brightest thing in the night sky after the Moon and Venus. It has no light of its own; it shines because its large solar panels reflect sunlight while the ground below is already dark. That is why it is visible only for an hour or two after sunset or before sunrise.

Look for a bright, steady white point moving smoothly across the sky, usually from the west toward the east. It does not blink and has no colored lights, which is how you tell it from an airplane. A pass lasts up to about six minutes. Sometimes it fades out partway across the sky as it slips into Earth's shadow.

To know when to look, use NASA's Spot the Station service or a satellite-tracking app. They give the start time, direction, highest point in degrees above the horizon, and duration. Passes that climb above about 40 degrees are the brightest. No equipment is needed; binoculars help but are not necessary.

Retirement around 2030

The station's oldest modules have been in space for more than 25 years, and parts are aging. The partners plan to keep the ISS working until around 2030.

After that, NASA intends to use a special deorbit vehicle, being built by SpaceX, to guide the station down into a remote area of the South Pacific, far from shipping lanes. Most of it will burn up in the atmosphere. NASA plans to rely on commercial space stations for research in low Earth orbit after the ISS, while China already operates its own station, Tiangong.