Space station orbit earth

Space station in Earth orbit: learn about the International Space Station, its modules, crew, and scientific experiments.

About this subject

The International Space Station (ISS) is the largest and most complex space cooperation project in history. Begun in 1998, the ISS orbits Earth at an average altitude of about 400 kilometers, traveling at approximately 28,000 km/h. Completing one orbit takes only 90 minutes, allowing astronauts to see 16 sunrises and sunsets each day. The modular structure houses microgravity research laboratories where experiments in biology, physics, materials science, and Earth observation are conducted, contributing to advances in medicine, agriculture, and technology.

Besides the ISS, other space stations have marked or still mark presence in orbit. The Russian Mir station operated from 1986 to 2001 as the first modular station. China completed assembly of its Tiangong space station in 2023, with three main modules and an expected operational lifetime of at least 10 years. Tiangong orbits at about 390 km altitude and hosts rotating crews for scientific and technological missions. These stations represent the human effort to maintain a continuous presence in space, driving exploration beyond low Earth orbit.

Maintaining the orbit of a space station is a critical process. Due to residual atmospheric drag at operational altitude, orbital velocity decays gradually, requiring periodic corrections using onboard thrusters or assistance from docked cargo vehicles such as Russian Progress or American Cygnus and Dragon spacecraft. These reboost maneuvers are scheduled to prevent uncontrolled reentry into the atmosphere. For the ISS, the decommissioning plan calls for controlled deactivation around 2031, targeting Point Nemo in the Pacific Ocean.

Interestingly, the ISS is visible from Earth with the naked eye as a fast-moving bright point, similar to an airplane but without blinking lights. Specialized websites and apps provide pass times over any location. The station is roughly the size of an American football field (109 meters in length) and has a mass of about 420 tons. To date, more than 250 astronauts from 20 countries have visited the ISS, which stands as a symbol of international cooperation in a hostile environment where survival depends on technology and teamwork.

Frequently Asked Questions

How fast does the International Space Station orbit Earth?

The ISS travels at about 28,000 km/h, completing one orbit every 90 minutes. This means it circles Earth approximately 16 times per day.

How many space stations are currently in orbit?

Two space stations are operational: the International Space Station (ISS), with multinational participation, and China's Tiangong space station. The Russian Mir station was decommissioned in 2001.

Can you see the space station from Earth?

Yes, the ISS is visible to the naked eye as a fast-moving bright point, typically during dawn or dusk. Apps and websites like Spot The Station provide pass times for any location.