ISS Marks 16 Years in Orbit: Sunrises Every 90 Minutes, Sleep Struggles, and Crew Traditions

It’s hard to picture, but up there on the International Space Station the day flips over a dozen times a day. In fact, the crew watches a sunrise roughly every ninety minutes – that’s sixteen times in a single Earth day. Sixteen years ago the first long‑duration crew stepped aboard, and today the rhythm of those rapid dawns is still the backdrop for every routine.

Because the station whirls around Earth at about 28,000 km/h, the sun never stays down for long. The lights in the cupola glow amber, then fade to deep night, only to blaze again in a flash. For the astronauts, this means their internal clocks get a very polite reminder that “time” up there is a little…different.

Most crew members try to lock into a 90‑minute sleep‑wake cycle that matches the orbital period. They strap into sleeping bags, dim the interior lights, and hope the gentle hum of fans will lull them. It’s not always smooth; sometimes the brain rebels, especially after a busy day of experiments, EVA prep, or a surprise video call from home.

One of the quirks that survived the years is the little prayer or moment of gratitude that astronauts slip into before they drift off. Whether it’s a quiet thank‑you for a safe launch, a whisper for a loved one’s birthday, or a simple “peace” before a night‑shift, these rituals help anchor the human side of an otherwise high‑tech environment.

Speaking of birthdays, just a few weeks ago a crew member celebrated his 42nd birthday while orbiting at 408 km. The station’s commander coordinated a mini‑party: a sealed bag of his favorite trail mix, a prerecorded message from his family playing on the station’s tablet, and a tiny cake‑shaped protein bar. The candles were imagined, of course, but the smiles were real.

All of this underscores a bigger point: even as the ISS reaches its 16th anniversary, it remains a place where human habits – sunrise coffee, bedtime prayers, birthday cheers – adapt to a new cosmic schedule. Scientists keep a close eye on the crew’s circadian rhythms, tweaking lighting and schedule cues to keep health metrics in the green. The goal? To make life in space feel, as much as possible, like life back on the planet we left behind.

So the next time you glance up at the sunrise and think, “That’ll be back tomorrow,” remember: up there, it’s already tomorrow – twice over.