MAY 24 LOOKING FOR ARTIFICIAL SATELLITES Skywatching is typically about looking for natural objects and phenomena, but there are now a host of interesting targets orbiting Earth that anyone can spot, from the space shuttle to the International Space Station to satellites that can briefly outshine the brightest stars.
Satellites are visible because they reflect sunlight. A satellite entering the Earth's shadow immediately vanishes from view and pursues an unseen path until it again emerges into full sunlight. For that reason, there are certain times and locations that offer the best viewing.
To see these "moving stars," go out during twilight, roughly 45 to 90 minutes after sunset, or 45 to 90 minutes before sunrise.
The International Space Station and the space shuttles are by far the brightest satellites. Orbiting the Earth at an average altitude of 240 miles, they can appear to move as fast as a high-flying airliner, sometimes taking just three to four minutes to cross the sky. They can easily be confused with aircraft lights, though at their brightest they sometimes appear to rival Jupiter in brilliance.
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 | Crowded Sky: These paths represent just a handful of the more than 10,000 satellites orbiting Earth.
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| A typical satellite can traverse much of the sky in 15 minutes or less. This graphic shows an example of how Starry Night software plots satellites on your computer and provides color images or animations.
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With a little scanning during twilight, you should not have to wait more than 15 minutes before you see one of the nearly 10,000 satellites now in orbit around Earth. While most are too faint to be seen with the unaided eye, a few hundred are large enough -- over 20 feet in length (6 meters) and low enough -- 100 to 500 miles (160-800 kilometers) above Earth -- to be seen.
In the past several years, a new fleet of satellites has been put into Earth orbit that can flare to incredible brilliance. The Iridium communication satellites, whose silver-coated Teflon antenna arrays mimic near-perfect mirrors, can cause a dazzling glint of reflected sunlight from their orbits 492 miles up. The flares range in brightness from merely a bright star to, in the most extreme case, 100 times brighter than Venus.
In fact, it is even possible to see some flares during the daytime, if you know exactly where to look!
To see the brief flares, you will first have to know your exact latitude, longitude and local time zone. Then, you'll need tracking information, provided at that web site Heavens Above, which is hosted by the German Aerospace Center (also known as "DLR" - Deutsches Zentrum Für Luft - Und Raumfahrt). There, you can also obtain interesting satellite viewing tips as well as access the very latest predictions on spotting numerous other orbiting satellites, such as the Hubble Space Telescope, a space shuttle or the International Space Station.
NASA also provides Space Station and shuttle sighting data for scores of cities around the world, at this site.
Starry Night Software
Plot satellites (or anything else in space) with this award-winning software.
Main Spacewatch Page
Sky calendar, Moon phases, and more backyard astronomy tips and news.
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.
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