How do satellites stay where we put them?

Answer 1

Cigar Me was close when he mentioned firing the thrusters to maintain the satellite's orbit. Satellites generally don't stay where we put them.

The Earth's gravity is the most dominant force acting on a satellite. Since the center of the Earth is stationary relative to the satellite, there is no net work done and force of gravity maintains a constant, never changing orbit. However, there's a lot of other forces acting on satellites that cause their orbits to drift.

The Earth bulges around the equator due to a soft molten layer and centripetal acceleration (the Earth spins like a centrifuge). The extra mass around the equator changes the satellite's orbit over time (this can be a good thing - with a 98.6 degree angle between the satellite's orbit plane and the equatorial plane, the satellite's orbit plane rotates at the same rate that the Earth orbits the Sun. In other words, you can set up an orbit where the satellite always crosses the equator in a northerly direction at sunrise and always crosses the equator in a southerly direction at sunset - or if you want pictures with no shadows, you can set up your orbit so it always crosses the equator in a northerly direction at noon.)

The atmosphere slowly tapers off the further away from Earth you get, so low altitude satellites still experience atmospheric drag. They eventually fall back to Earth and usually (but not always) burn up during re-entry. To keep a low altitude spacecraft, such as the International Space Station, in orbit, you have to periodically re-raise the orbit by firing the thrusters (this is why resuming space shuttle flights is so critical - the space shuttles, along with some Russian spacecraft, supply fuel for the thrusters to the ISS).

High altitude satellites, such geosynchronous communications satellites, are beyond the furthest reaches of the atmosphere and will never fall back to Earth. However, they, like all satellites, are still affected by the Sun's gravity and the Moon's gravity. That pulls them out of their assigned orbits. Once again, the thrusters are used to correct the satellite's orbit to keep it in its assigned position.

Answer 2

No, no, NO! It's nothing to do with centifugal (or centripetal force)!!!!!

The satellite is in free fall just like anything else that is subjected to the Earth's gravity. Satellites never fall into the Earth because Earth is round and curves. The Earth curves approximately 5 meters downward for every 8000 meters along its horizon. In order for a satellite to successfully orbit the Earth, it must travel a horizontal distance of 8000 meters before falling a vertical distance of 5 meters.

Your question asks how do satellites STAY where we put them... well they don't really, they travel round and round the earth all day long, maybe as fast as every 90 minutes. However, there is a special case where a satellite will travel around the Earth in exactly the same time as it takes the Earth to rotate (~24hrs) and so if you look up from the same place on the surface, it would always appear to be in the same position in the sky. This is called Geosynchronous orbit and is used for thinks like satellite TV (your TV dish always points in the same direction, right? It's always pointing at the satellite.)

Answer 3

If you fill a bucket with water and swing it over your head, the water will stay in the bucket even when it's upside down. This is because the centrifugal force of the rotating bucket is greater than the force of gravity at the top of the arc.

A satellite works in a similar way. Earth's gravity pulls the satellite down, but the centrifugal force of its own movement pulls the satellite away from the Earth. In an elliptical orbit, these two forces are always exactly balanced, so the satellite does not fall.

Lower orbits are faster, because the force of gravity is stronger closer to the earth, and you need more centrifugal force to overcome it. Using rockets, it is possible for a satellite to move from one orbit to another.

Answer 4

If you fill a bucket with water and swing it over your head, the water will stay in the bucket even when it's upside down. This is because the centrifugal force of the rotating bucket is greater than the force of gravity at the top of the arc.

A satellite works in a similar way. Earth's gravity pulls the satellite down, but the centrifugal force of its own movement pulls the satellite away from the Earth. In an elliptical orbit, these two forces are always exactly balanced, so the satellite does not fall.

Lower orbits are faster, because the force of gravity is stronger closer to the earth, and you need more centrifugal force to overcome it. Using rockets, it is possible for a satellite to move from one orbit to another.

Answer 5

To stay over the same spot on earth, a geostationary satellite also has to be directly above the equator. Otherwise, from the earth the satellite would appear to move in a north-south line every day. We call that "orbiting in the equatorial plane."

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Answer 6

The geocentric satellites are moving at the same rate of velocity as the Earth.

Answer 7

The same thing that keeps the earth going around the sun. A very delicate balance of gravity and centrifugal force. The distance from the earth dictates how fast it has to travel according to its mass and the pull of the gravity.

Answer 8

the difintion of a satellite is a orbiting body either man made or natural so they don't stay where we put them, they float around in space as they are meant to

Answer 9

Its all about falling. When you throw a ball it will travel in away from you it travels in a arc back to the earth. If you could throw it fast enough the arc it makes as it falls back down would match the curvature of the earth and just keep falling.

Answer 10

They are launched and end up in geosynchronous orbit (the point at which they are relatively stable between earth's gravitational pull and outer space).

I believe that, occasionally, they have to utilize small jet bursts to adjust their positioning and height to maintain the orbit.

When they've outlived their usefulness, they're allowed to fall back to earth and burn up, or they continue to float as "space junk."