Even with gravity, if the intended satellite goes too fast, it will eventually fly away. On the other hand, if the satellite goes too slowly, gravity will pull it back to Earth. At the correct orbital velocity, gravity exactly balances the satellite's inertia, pulling down toward Earth's center just enough to keep the path of the satellite curving like Earth's curved surface, rather than flying off in a straight line.
The orbital velocity of the satellite depends on its altitude above Earth. The nearer to Earth, the faster the required orbital velocity. At an altitude of miles kilometers , the required orbital velocity is a little more than 17, mph about 27, kph. To maintain an orbit that is 22, miles 35, kilometers above Earth, the satellite must orbit at a speed of about 7, mph 11, kph.
That orbital speed and distance permit the satellite to make one revolution in 24 hours. Since Earth also rotates once in 24 hours, a satellite at 22, miles altitude stays in a fixed position relative to a point on Earth's surface. Because the satellite stays right over the same spot all the time, this kind of orbit is called "geostationary. Access the image Objects that travel around a planet are called satellites.
Each complete journey a satellite makes around the planet is called an orbit. Our Earth has one natural satellite — the Moon. Some explore asteroids and comets. Some fly close to or orbit other planets, looking for evidence of water on Mars or capturing pictures of Saturn's rings.
The Hubble Space Telescope orbits around Earth once every 95 minutes, at about 5 miles per second. It takes pictures of planets, stars, galaxies and black holes. Scientists have learned a lot from Hubble's pictures. It is considered by some to be the most valuable satellite ever built. The largest satellite is the International Space Station. It is the size of a soccer field. It is so big that scientists had to send up pieces of it to be assembled in space. The ISS is the only satellite that has people living on board, providing a home for a rotating crew of six astronauts from different countries.
They do experiments and study what happens to people when they live in space. Scientists will use lessons from the space station to get astronauts ready for future space travel. If thousands of satellites have been launched but only a portion of them are currently functioning, what happened to the rest? Many satellites have a working life of years. When a satellite wears out and stops working, it sometimes falls back toward earth and burns up in the earth's atmosphere.
Other satellites continue to orbit the earth, joining the category of orbiting objects known as space debris, or space junk. Space debris includes obsolete satellites whose work is finished and thousands of fragments of space materials.
These objects come from exploding rockets, accidentally dropped tools, or pieces of unneeded equipment. These bits of space junk are satellites too, as they are in orbit around the earth, but they can be hazardous to working satellites and spacecraft traveling in and through Earth's orbit. Sometimes, the International Space Station has to be moved to avoid impact with chunks of space debris. These days, when a new satellite is launched, its engineers are required to have a plan for the end of its working life: either it will be returned to the earth or sent far out into space into "graveyard orbit," away from the busy community of working satellites.
Image: NASA Since that time, the number of satellites and their complexity has continued to increase. Different Kinds of Satellites When it comes to satellites, it's all about the orbit. The Uses of Satellites Satellites are used for many purposes. Communication Communication satellites allow television, radio, internet and telephone signals to be sent live anywhere in the world.
Image courtesy Explain That Stuff Communication satellites allow video conferencing for businesses and classrooms. Navigation GPS is made up of ground stations, satellites, and receivers. Image: NASA. Safety First responders rely on satellites as they help people in trouble. Space Science Satellites help scientists study space. Fun Facts About Satellites Vanguard-1 is the oldest man-made satellite still in orbit. It has orbited Earth for 62 years, and is expected to continue to do so for nearly another two centuries.
They are much less expensive than large satellites and can share launchers to get them up into orbit. CubeSats can measure space weather, take pictures of the earth, and monitor radiation - but they are smaller than a football.
What do space satellites have to do with endangered species? Satellites provide clear migration images that scientists can use to help protect threatened animals from drought, habitat loss, and poachers. Spacecraft Cemetery - image: NASA Large satellites like space stations and other spacecraft returning to Earth might not entirely burn up before reaching the ground. Spacecraft operators can make sure that any debris falls into an area far from where anyone lives.
This designated area in the Pacific Ocean is called the Spacecraft Cemetery. Some satellites are launched and operated by governments and scientific organizations.
Others belong to private companies and students. Could you launch a satellite someday? And in fact most satellites -- especially the bits of debris -- are too faint to be seen with the unaided eye.
But depending on who's counting, several hundred can be spotted with the unaided eye. These are the satellites that are large enough typically more than 20 feet in length and low enough to miles above Earth to be most readily seen a sunlight reflects off them.
On-orbit construction of the station began in , and is scheduled to be complete by , with operations continuing until around More than four times as large as the defunct Russian Mir space station, the completed International Space Station will ultimately have a mass of about 1,, pounds tons and will measure feet across and feet long, with almost an acre of solar panels to provide electrical power to six state-of-the-art laboratories.
Presently circling the Earth at an average altitude of mi km and at a speed of 17, mi 27, km per hour, it completes Because of its size and configuration of highly reflective solar panels , the space station is now, by far, the brightest man-made object currently in orbit around the Earth. On favorable passes, the space station can appear as bright as the planet Venus, at magnitude Some have made estimates as bright as magnitude -5 or -6 for the station smaller numbers represent brighter objects on this astronomers scale.
And as a bonus, sunlight glinting directly off the solar panels can sometimes make the ISS appear to briefly "flare" in brilliance to as bright as magnitude -8; more than 16 times brighter than Venus!
Along with the ISS, you can also look for China's Tiangong-1 space laboratory, which has hosted visiting crews on Shenzhou spacecraft in recent years. Also visible to the naked eye is the Hubble Space Telescope. But they could potential be visible under the best observing conditions.
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