Human WorldSpace

How to spot ISS in your sky

A blue, sparse background with a white line crossing the sky, near a medium-bright star.
View at EarthSky Community Photos. | Robert Watcher in Seaforth, Ontario, Canada captured this cool image on May 17, 2021. He wrote: “A perfect night to capture the International Space Station. We had the trajectory down pat for moving through my frame during the middle part of its 6-minute crossing. Although I had no clue that tonight it would pass right through the view of the North Star (Polaris) – the white static star in the middle that all stars rotate around during the night – so that was pretty special.” Very special indeed. Thank you, Robert!

A bird? A plane? A space station!

The International Space Station (ISS) has been orbiting our planet since 1998. From most locations on Earth, assuming you have clear night skies, you can see ISS for yourself. It looks like a bright star moving quickly from horizon to horizon to us on Earth. As suddenly as it appears, it disappears.

But how do you know when to see ISS pass overhead from your location?

NASA has a great tool to help – the Spot the Station program lets you sign up to receive alerts to let you know when ISS will be visible from your location – anywhere in the world. Plus, there’s a map-based feature to track when to look for the station as it flies over you in your night sky. You can also sign up for alerts via email or text message. Typically, alerts are sent out a few times each month when the station’s orbit is near your location.

Visit the Spot the Station website to sign up, and see a list of upcoming sighting opportunities.

How to spot ISS

If you sign up for NASA’s Spot the Station service, notices will be sent to you only when ISS will be clearly visible from your location for at least a couple of minutes. The notices contain information on which direction to look for ISS in your night sky. Not sure about your directions? Just note where the sun sets. You know it sets generally westward. From there, you can easily find the direction where the station will appear (for example, in the southwest or northwest).

Via NASA’s service, the height at which the station will appear in your sky is given in degrees. Remember, 90 degrees is directly over your head. Any number less than 90 degrees will mean that the station will appear somewhere between the horizon and the overhead mark.

Want a way to measure degrees on the sky’s dome? Make a fist, and stretch out your arm. Your fist at arm’s length is equal to about 10 degrees. Then, just use the appropriate number of fist-lengths to find the location marker, e.g., four fist-lengths from the horizon would be equal to about 40 degrees.

The station is bright! It’s hard to miss if you’re looking in the correct direction.

Jupiter, Saturn, the moon, and a streak - the ISS - in a twilight sky, above a sururban neighborhood.
View at EarthSky Community Photos. | Matt Lantz in Aledo, Texas caught this image on the evening of November 19, 2020. See the streak? It’s the International Space Station. Matt wrote: “Was waiting to pick up my daughter from soccer practice and managed to catch the ISS as it passed right by the moon, Jupiter, and Saturn all right next to each other. Pretty cool!” Thank you, Matt!

Two decades of human occupation

The first module of ISS was launched into space in 1998 and the initial construction of the station took about two years to complete. Human occupation of the station began on November 2, 2000. Since that time, ISS has been continuously occupied.

ISS serves as both an orbiting laboratory and a port for international spacecraft. It orbits at approximately 220 miles (350 km) above the Earth and it travels at an average speed of 17,227 miles (27,724 km) per hour. It makes multiple orbits around the Earth every day.

The primary partnering countries involved in operating ISS include the United States, Canada, Japan, several European countries, and Russia. China is currently building its own space station, called Tiangong, and launched the first module in 2021.

One note. Those who live north of 51.6 degrees latitude (for example, in Alaska) will likely have to visit the Spot the Station website directly. That’s because notifications in this region would be rare.

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A white space station with eight golden panels on both sides floats above the blue Earth.
The International Space Station (seen here in 2018) has been continuously occupied by astronauts since 2000. Image via NASA/ HowStuffWorks.

Bottom line: Learn to watch the International Space Station moving above your location.

Posted 
July 16, 2021
 in 
Human World

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