Astronauts on the Space Station watch 16 sunrises and sunsets every day
Orbiting Earth at roughly 28,000 kilometers per hour, the International Space Station completes a full trip around the planet every 90 minutes. Because of this extreme speed, crew members experience a sunrise or sunset every 45 minutes, totaling 16 of each every 24 hours. Astronauts use set lighting schedules to maintain normal sleep rhythms.
The Mechanics of an Orbital Day
The International Space Station maintains an orbit in low Earth orbit, circling the planet at an altitude of roughly 400 kilometers above the surface. To remain in this stable orbit without falling back into the atmosphere or escaping into deep space, the station travels at a velocity of approximately 27,600 to 28,000 kilometers per hour. At this extreme speed, the orbital complex traverses the entire circumference of Earth in roughly 90 to 93 minutes.
Because the station circles the globe in an hour and a half, its environment alternates rapidly between direct sunlight and Earth's shadow. During each complete orbit, the station spends approximately 45 minutes in daylight followed by approximately 45 minutes in darkness. Across a standard 24-hour terrestrial day, this rapid cycle repeats approximately 15.5 to 16 times, meaning the crew witnesses a new sunrise and sunset roughly every 45 minutes.
Crossing the Terminator
From the vantage point of the space station, a sunrise or sunset is not the prolonged, gradual event experienced on the ground. Instead, the orbital laboratory rushes across the terminator line—the moving boundary dividing the illuminated day side of Earth from the dark night side. As the station crosses this line, the transition between intense sunlight and absolute orbital darkness happens in just a matter of seconds to a few minutes.
During these crossing periods, astronauts observing through windows like those in the Cupola module can see the layers of Earth's atmosphere illuminated in sharp cross-section. The thin blue line of the atmosphere glows vividly against the blackness of space as the Sun rises or dips beneath the planet's curved horizon, followed quickly by the emergence of city lights, auroras, or lightning flashes on the night side.