The Pattern of the Space Station

It's a surprising fact to most people that I meet: you can actually see the International Space Station as it flies overhead with the naked eye.

When I have the chance to show it to people for the first time, they're amazed at how bright it appears. They're also amazed at how it appeared exactly at the time my ISS tracking app said it would.

The usual next question is: "When can we see it again?"

Why do we see the ISS?

OK, let's cover the basics: why are we able to see it as it flies over? 

Does it have giant lights shining back on Earth? No.

The reason we see it is because of its humongous solar panels reflecting light from the Sun. That reflected light shines back to Earth allowing us to spot it as it passes over.

How frequently can you see the ISS?

The ISS goes around the Earth 16 times per day. That means for any place on Earth, it will fly overhead 5 times per day. But this does not mean we see every one of those times it passes over. 

When We Can't See It

Sometimes it flies overhead in the daytime. We can't see those passes.

Sometimes it flies overhead in the middle of the night. You might think this would be a great time to see it. Ideal, even! But we can't because it is in the shadow of the Earth. The Sun's light can't reflect off the solar panels, and thus, we can't see it.

When We Can See It

Sometimes it flies overhead early in the morning before the Sun has risen. It's dark enough to see and its solar panels are able to reflect light. We can see it at this time.

Lastly, sometimes it flies overhead shortly after sunset. Like the dawn flyovers, it's dark enough to see and its solar panels can reflect the Sun's light. Not only can we see it at this time, but this is more convenient to see than those early morning passes.

Viewing Cycle

If you watch the ISS flyovers for a long enough period of time, you'll notice a pattern start to emerge. From my lived experience, here's how the pattern roughly shakes out:

• every dusk for about 3 weeks, we see the ISS flyovers
• for about 3 weeks, we don't see the ISS flyovers
• every dawn for about 3 weeks, we see the ISS flyovers

This cycle lasts about 2 months, then repeats itself.

Evening Visible Flyovers

For years I watched this 2-month cycle. Last year I finally started recording the dates that the evening flyovers began for Montreal:

• November 12 - December 5 (2024)
• January 11 - February 2 (2025)
• March 11 - April 1 (2025)

It's a small sample, but you can definitely see the pattern emerge. Every 2 months – or 6 times per year – we get an evening viewing cycle of the ISS.

As I write this in early May 2025, the next evening flyover cycle starts on May 8th. The app I use to track the station shows me flyovers 2 weeks in advance, so I'll update my findings when the data becomes available. But here's a rough guess of when we'll see evening flyovers for the rest of 2025:

• May 8 - May 30
• July 8 - July 30
• September 8 - September 30

Let's see how close I get.

The Death of the ISS in Context

There's no exact date set, but the International Space Station will be de-orbited in the next few years. The date has been pushed back several times, but some estimate say it will come down in 2030.

With this evening viewing cycle context, we can look at that 2030 date a little differently. Instead of saying it will be gone in 5 years, we can see how many evening viewing cycles remain:

We get 6 evening viewing cycles per year. Multiple that by 5 and only have 30 evening viewing cycles left.

That number now seems... more urgent. Put another way, each passing viewing cycle is now more than 3% of the total lifetime left of the station. 

Most attendees to my workshops have never seen the ISS flyover, even after 25 years of its existence. I feel this anxious desire to teach as many people as possible to see it as I hear the ISS clock count down.

Never seen it yourself? Today's a great day to learn how: