Sixteen Sunrises in a 90-Minute Orbit: How the ISS Keeps Time in Space

The ISS orbits Earth roughly every 92 minutes at about 28,000 km/h, completing around 15–16 orbits per day. From the cupola, crew see about sixteen sunrises and sunsets daily, but that cycle is a window view, not a crew day; onboard time runs on UTC and is supported by LED lighting to align sleep and wakefulness. During high-beta-angle periods the station can stay in sunlight for days, so the “sixteen sunrises” figure is an average, not a constant.