Scientists can use this information to create models of climate change. Learn more about NASA's earth science missions. Satellites help scientists study space. They can provide much more data than instruments on Earth can.
Satellites can see into space better than telescopes on Earth's surface because Earth's atmosphere doesn't interfere with the view from satellites. Many of these satellites are operated by NASA and other countries' scientific organizations.
Satellites that face toward space have many different jobs. Some watch for dangerous rays coming from the sun. 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.
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.
During the northern summer, when the nights are the shortest, the time that a satellite in a low-Earth-orbit like the ISS can remain illuminated by the sun can extend throughout the night - a situation that can never be attained during other times of the year.
Because the ISS circles the Earth about every 90 minutes on average, this means that it's possible to see it not just on one singular pass, but for several consecutive passes.
Moreover, because the ISS revolves around the Earth in an orbit that is inclined In the first case we'll call it a "Type I" pass , the ISS initially appears over toward the southwestern part of the sky and then sweeps over toward the northeast. About seven or eight hours later, it becomes possible to see a second type of pass we'll call it "Type II" , but this time with the ISS initially appearing over toward the northwestern part of the sky and sweeping over toward the southeast.
Type I passes will initially be visible in the morning hours, prior to sunrise. By early July, Type I passes will be visible during the evening hours, just after sunset, while Type II passes will be occurring in the early morning. However, since October many thousands of artificial human-made satellites have been placed in orbits around the Earth. To stay in orbit, a satellite has to travel at a very high velocity, which depends on the height. So, typically, for a circular orbit at a height of km above the Earth's surface, a speed of 7.
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.
In general, the higher the orbit, the longer the satellite can stay in orbit. At lower altitudes, a satellite runs into traces of Earth's atmosphere, which creates drag. The drag causes the orbit to decay until the satellite falls back into the atmosphere and burns up. At higher altitudes, where the vacuum of space is nearly complete, there is almost no drag and a satellite like the moon can stay in orbit for centuries.
A launch window is a particular period during which it will be easier to place the satellite in the orbit necessary to perform its intended function. With the space shuttle, an extremely important factor in choosing the launch window was the need to bring down the astronauts safely if something went wrong. The astronauts had to be able to reach a safe landing area with rescue personnel standing by. For other types of flights, including interplanetary exploration, the launch window must permit the flight to take the most efficient course to its very distant destination.
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