Astronauts photographed the Soyuz from a window on the International Space Station while space shuttle Discovery was docked with the station. The blackness of space and Earth's horizon provide the backdrop for this image of the docked Soyuz 13 (foreground) and the Progress 22 resupply vehicle. Weather and television satellites are generally in this category. This allows the satellite to match the Earth's rotation and "hover" over the same spot at all times. Other objects are sent much farther into space and placed in what is called geosynchronous orbit. Most satellites around Earth are found in the LEO range. Satellites in low-Earth orbit, or LEO, stay within 500 miles (800 kilometers) and travel extremely fast-17,000 miles an hour (27,400 kilometers an hour) or more-to keep from being drawn back into Earth's atmosphere. These man-made objects circle Earth in orbits that range from as near as 150 miles (240 kilometers) to 22,500 miles (36,200 kilometers) away. These include Hubble and the ISS, the Russian Mir space station, the 27-satellite Global Positioning System, Iridium, GOES, Voyager, and hundreds of others that provide communications, broadcast television and radio signals, and help scientists predict weather, among many other purposes. Since then, some 2,500 satellites have been sent aloft. The Soviets launched the first, Sputnik 1, in October of 1957 just to prove they could. Satellitesįor half a century, humans have been putting satellites into orbit around Earth to serve a variety of functions. And there are millions of smaller, harder-to-track objects such as flecks of paint and bits of plastic. This celestial clutter includes everything from the International Space Station (ISS) and the Hubble Space Telescope to defunct satellites, rocket stages, or nuts and bolts left behind by astronauts. Space Surveillance Network uses radar to track more than 13,000 such items that are larger than four inches (ten centimeters). The skies above Earth are teeming with more than 8,000 manmade objects, large and small.
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