More Spaceship Sightings
Beginning this week, the International Space Station
will make a series of eye-catching passes over North America.
He had caught a glimpse of the International Space Station (ISS).
"The station's T-shape was clearly visible," Beinert continued. "It was prettier to watch than seeing pictures because the colors were so vivid."
Above: On June 16th, Jim Young and Gary Grasdalen captured this picture of the ISS as it soared above JPL's Table Mountain Observatory in the Angeles National Forest. 
A typical sighting looks like this: A dim speck of light--the space station--appears near the horizon. It brightens rapidly as it glides overhead, leisurely crossing the sky in 3 to 6 minutes. You can't see details like solar panels with the unaided eye, but the station is nevertheless beautiful. At its best, it can outshine every star and planet except the sun and moon. More often it looks like an ordinary bright star--eye-catching because it moves.
When should you look?
Find out by visiting one of these three popular web sites: Chris Peat's Heavens Above, Science@NASA's J-Pass or NASA's SkyWatch. Each will ask for your zip code or city, and respond with a list of suggested spotting times. Predictions computed a few days ahead of time are usually accurate within a few minutes. However, they can change due to the slow decay of the space station's orbit and periodic reboosts to higher altitudes. Check frequently for updates.
Above: Local times in July when the station will appear brighter than a first-magnitude star over selected cities. In each case tabulated above, the ISS will emerge over the northwest horizon, slowly sail overhead (or nearly so), and disappear again in the southeast. Use one of these web sites to find sighting times for your hometown: Heavens Above, J-Pass or SkyWatch.
Sky watchers who see the ISS for the first time often remark that the station seems slow--much slower than meteors they've seen. In fact, the station moves rapidly: 17,000 mph as it circles the earth every 90 minutes. But that is slow compared to a typical meteor, which travels 100,000 mph and streaks across the sky in seconds.
In this case, slow is good. Because the ISS takes minutes to glide from horizon to horizon, it is possible to train a telescope on the station and track it.
Below: Canadian Dominic Cantin was outdoors on July 20, 2002, snapping pictures of Northern Lights when the ISS appeared. The streak in this 30-second exposure shows how far the station moves in half-a-minute.
"Hand-tracking is hard work," he cautions. "Carefully moving the telescope several degrees a second--mostly standing in positions reminiscent of yoga--burns quite a few calories, which you will notice afterwards." Amateurs who own computer-controlled "goto" telescopes can do the same thing with less effort using inexpensive satellite tracking software. (Go to your favorite search engine and type, e.g., "satellite tracking for telescopes.")
If you want to photograph the ISS through your telescope, Beinert recommends a digital video camera. Short exposures (1/30 of a second or less) "freeze" the moving spacecraft, nicely capturing its colors and outline. After the flyby you can examine your recording frame-by-frame and choose the frames that look best. "On your first try, it might be visible on only one or two frames of several thousand--but it's an amazing feeling, seeing your own images of this spaceship," he says.
Right: Beinert recorded this movie on March 31, 2001. The station's rolling motion is a result of changing perspective during the flyby; "the jitters" are a telltale sign of hand-tracking. [more]
Oh ... and don't forget to turn on the camera. "On one pass, I had tracked the station almost perfectly," laughs Beinert. "I couldn't wait to see the results; then I realized I had never started the exposure!"
Spellbound by the space station--it can happen to you, too. Just stroll outside on the right evening this month and take a look at what's flying over your backyard.
Editor's note: The space station passes over every continent except Antarctica. You can use the web sites mentioned in this article to discover ISS spotting times from any place in the world -- not only North America. Also, our story mentions that meteors move much faster than the space station. Meteors are also closer to Earth's surface--about 100 km high, compared to 400 km for the ISS.more information
NASA's Human Spaceflight -- (SpaceFlight.nasa.gov) Up-to-date information about the space shuttle and the International Space Station.
What makes the ISS shine? There are no bright lights on the outside of the space station. The ISS shines by reflecting sunlight, as much as 90% of the light that hits it. Much of the ship is light-colored. Even the awesome solar arrays, which must absorb sunlight to power the station, aren't completely black. Their reflectivity is near 35%.
Right: The brightly-lit International Space Station in April 2002. [more]
Watch Out for Spaceships -- (Science@NASA) If your neighbors hear you say this, they might laugh at you. But it's true: This is a good week to stand in your backyard and watch spaceships go by.
A New Star in the Sky -- (Science@NASA) Something in the heavens is growing brighter and it will soon become one of the more eye-catching stars in the night sky. No, it's not a supernova. It's the International Space Station!
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