Nov 30, 2000

A New Star in Space



A New Star in the Sky


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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December 1, 2000 -- When the space shuttle Endeavour (STS-97) blasted off for an encounter with the International Space Station (ISS) last night, it carried aloft a 17-ton package of immense solar arrays and associated hardware -- the heaviest and largest station elements flown to date. Once deployed, this first set of solar panels will measure 240 feet tip-to-tip, a wingspan greater than that of a 777 jumbo jetliner.


The arrays will quintuple the amount of electrical power available on the station, paving the way for delivery of the first research laboratory, the U.S. Destiny module, on STS-98 in January.

They will also make the station bigger and easier to see from Earth.

Right: The space shuttle Endeavour left Earth on Nov. 30, 2000 for a rendezvous with the ISS. The dazzling nighttime launch was a fitting prelude to a mission that will make the International Space Station one of the brightest star-like objects in the sky.

"Even before the solar panels were added, I was able to see the ISS streak by during a recent pass over California," says astronomer Tony Phillips. "It was nearly as bright as a first magnitude star when I spotted it. That's eye-catching! It's only going to get easier to see as the station grows larger. "

It's possible to see the space station from Earth because it reflects sunlight. How bright the station looks when it passes overhead will depend on its orientation with respect to you and to the Sun. After the STS-97 assembly mission, the space station will rival the bright star Sirius (or perhaps even Venus) when the angles are favorable for a bright reflection. But, when the station is not aligned optimally, it will seem no brighter than a modest 2nd or 3rd magnitude object.




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Normally, the best times to see the ISS are within an hour or two before sunrise or after sunset. During those times your sky will be dark (barring urban light pollution) but the high-flying ISS can still be sunlit. In the evening the station will look brightest just before entering the Earth's shadow and suddenly "disappearing" partway across the sky. Early in the morning the ISS can abruptly "appear" as it emerges from Earth's shadow.

The ISS orbits the Earth roughly every 90 minutes, or about 16 times a day. To get the correct picture, take a look at a typical globe of the Earth. Imagine the Station orbiting about ¼-inch above the globe's surface. That's a good representation of the low Earth orbit that the ISS and Space Shuttle travel. Since no significant forces are acting on the ISS other than the Earth's gravity, the geometric plane of the Station's orbit does not change. However, the orbit of ISS is not synchronized with the rotation of the Earth. Hence the ISS travels over a different swath of the Earth's surface on each revolution as the Earth rotates under it. Also, the station will not be in the same spot in its orbit, and therefore overhead, each time the orbit swath passes over your location. All of this combines to mean that you will not see the ISS at the same time every night or morning.


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The orbit of the ISS is inclined 51.6 degrees to the equator. This is because the Russian components of the station are launched from the Baikonur Cosmodrome in Kazakhstan. When launching a spacecraft, the most fuel efficient orbit is one that has an inclination equal to that of the launch site, and the gain of an additional boost from the Earth's rotation means most launches are toward the East. The greatest rotational boost is at the equator, where the Earth's surface is traveling about 1,000 mph. That's why the United States chose one of its southernmost points, Florida, for its primary launch site.

Above: The lighter blue area is where the Space Station can be seen from the ground.

At the higher latitude of Kazakhstan the Earth's surface is not traveling as fast, but the lesser speed imparted is not as large a fuel factor as launching to a lower inclination orbit would be. So the ISS has a higher inclination orbit than the typical orbit of the Space Shuttle launched from Kennedy Space Center in Florida. But all of this is great news for us observers on Earth, because the higher inclination means the ISS can be seen from a much larger area of our planet.

Again, using the globe, you can see that there is an "ascending" half of ISS's orbit, as it moves from south to north, and a "descending" half as the ISS moves from north to south. This will determine the direction you see the ISS travel across your sky. If you see the Station on an ascending pass, it will be traveling in a generally southwest to northeast direction. On a descending pass, it will appear from the northwest and travel toward the southeast. And, if the geometry is just right, you may see the Station apparently travel almost due west to east. Unfortunately, if you live at a latitude greater than about 60 degrees, you will not be able to see ISS at all since it never rises above your horizon.


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Science@NASA's Liftoff to Space Exploration website offers two programs that can help you find the space station. First is J-TRACK. This program shows you the location of ISS (and over 600 other satellites) at any given time. You can see where ISS is in its orbit right now!


The other program is J-PASS. Just enter your latitude and longitude, the name of a nearby large city, or your zip code if you live in the U.S., and J-PASS will tell you when ISS will be visible at your location. It will also tell you where to look in your sky and, how long it will be visible, and about how bright it will be.

Above: Patrick Meyer, author of JPASS, and its sister program JTRACK, describes the program and how to use it. Click on the image to view a RealVideo movie. (Go to RealNetworks for a free player, if you need it.)

Since ISS can be very bright, even those of you who suffer from urban light pollution may be able to view it. So visit our Liftoff site and find out when ISS will be visible over your home. Then join the millions of people around the world looking at this new star in the sky!


Web Links


Where is the International Space Station?" -- helps users identify the orbiting Space Station and determine in advance when it will pass over their hometowns. Created by NASA/Marshall's Liftoff to Space Exploration

SkyWatch -- another online program designed to help stargazers track the ISS. This one is from, NASA's International Space Station home page

J-Pass 2.0 -- from Liftoff to Space Exploration

J-Pass E-Mail Generator -- from Liftoff to Space Exploration

Water on the Space Station -- The first Science@NASA article in this series about the practical challenges of extended living in space. This article looks at how water will be conserved and recycled on the Space Station -- including the crew's own urine!

Breathing easy on the Space Station -- The second Science@NASA article in this series about the practical challenges of extended living in space. The systems and methods used to ensure safe, breathable air for the crew are examined in this article.

Microscopic stowaways on the Space Station -- The third Science@NASA article in this series about the practical challenges of extended living in space. 

International Space Station -- NASA's Web page for the International Space Station

Advanced Life Support Web Page -- from the Johnson Space Flight Center

Environmental Control and Life Support Systems -- describes the life support systems being developed at Marshall Space Flight Center


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For lesson plans and educational activities related to breaking science news, please visit Thursday's Classroom Author: John M. Horack
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Curator: Bryan Walls
Media Relations: Steve Roy
Responsible NASA official: John M. Horack