The ISS, Earth and moon as seen by space shuttle Atlantis in 2011. (Image courtesy NASA)

On Nov. 2, NASA and the world marked 20 years of continuous human occupation of the International Space Station (ISS).

The ISS has been an international endeavor since the very start when NASA astronaut William Shepherd launched to the ISS with Russian cosmonauts Yuri Gidzenko and Sergei Krikalev from the Baikonur Cosmodrome in Kazakhstan. This crew is known as Expedition 1 and was the first to live on the ISS.

The design and manufacture of the ISS has also been an international collaboration, with modules from the U.S., Russia, Japan and the European Union. Canadarm2, the 17-meter-long robotic manipulator arm that has been instrumental in the assembly of the ISS’s 16 pressurized modules, was contributed by Canada. Canadarm2 also captures some of the resupply spacecraft that fly to the ISS.

While Canadarm2 has done the heavy lifting, the bulk of station assembly and maintenance has been done by spacewalking humans. Astronauts have performed around 230 spacewalks and have spent well over 1,000 hours on construction, repair and maintenance of the ISS.

More than 240 people from 19 countries have visited the ISS over the last 20 years. Some have been lucky enough to visit on multiple occasions. The most recent group of four astronauts launched to the station on Nov. 15. They departed Earth on board a SpaceX Crew Dragon capsule and will join the Expedition 64 crew when they reach the ISS.

The main mission of the ISS is research. More than 4,200 investigators from over 100 countries have conducted thousands of experiments with the help of the ISS crew over the last 20 years.

The ISS is visible on a regular basis. When it flies over, it is one of the brightest objects in the night sky and can be easily seen from even the most light-polluted location. Go to to learn when the next ISS pass will be.

When you observe the station, realize that you are seeing a marvel of human ingenuity and engineering. The ISS travels around the Earth at 17,500 mph at an altitude of 250 miles. That fast-moving point on the sky is also the current home of seven remarkable people.

Wave to them as they fly overhead.

The Weekly Roundup: The Morning Sky

Mercury is still visible in the early morning eastern sky, but it is rapidly moving behind the sun from our perspective. On Dec. 19, Mercury will line up on the exact opposite side of the sun from the Earth. We call this point in Mercury’s orbit Superior Conjunction. Mercury completes one orbit around the sun every 87.97 days. Venus shines brightly well above Mercury in the east before dawn.

The Evening Sky

Jupiter and Saturn are a striking pair in the south after sunset. The gibbous moon will appear below Mars high in the south east on the evening of Nov. 25. Mars sits almost exactly in between Neptune (toward the west) and Uranus (toward the east). You can see Uranus through binoculars, but you’ll need a telescope to spot Neptune. At 2.7 billion miles away, Neptune is the most distant planet in the solar system. Uranus is 1 billion miles closer to Earth and therefore brighter.

Dan Price is a NASA/JPL Solar System Ambassador and informal educator. He leads the Night Sky Tours at Josephine Sculpture Park. Have a question about astronomy or space science? Send an email to and it might be featured in a future column.

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