How do satellites orbiting the earth avoid colliding with each other?

Question

There are thousands of satellites in near-space orbit. How do they not hit each other? Is there a navigational database to track them? Can satellites change their orbit in order to prevent foreseen collision? How is the orbit originally decided?
How do satellites avoid space debris?

Answer 1

How do they not hit each other: near earth space is huge, there is a lot of *space* inbetween satellites.

Is there a database: yes, it is run by NORAD (or what was formerly called NORAD), and there are other space-faring countries that keep their own databases. NORAD tracks 1000s of objects continually.

Can satellites change their orbits: most can, some cannot. If the satellite is important (expensive) enough to stay in orbit for many years, they usually put small maneuvering rockets on those satellites for course correction. The grossest example of this is a Huges comm satellite that did not get placed in the correct orbit (in the mid-90s). They used their maneuvering rockets to change to a highly elliptical orbit, and they just kept on extending the eccentricity of that orbit so much that they reached the moon. Once the satellite reached the moon's pull, it looped around the moon, and they made some precise course corrections, so when it finished that "orbit" of the earth (with the moon loop included), they were back to where they wanted to be. Then they lowered the eccentricty of the eliptical orbits back down to a geosync circular orbit and operated as the comm sat it was meant to be. This whole process took months, but it worked.

How is an orbit decided? almost never based on what else is up there. It is always decided on the reason for sending it up in the first place. For communication (TV, telephone, radio), it is put where it is needed for the comm links to be provided. For science (earth mapping, weather, observation) it is placed in an orbit and inclination that best suits the science experiment. There are even some comm satellites at the same equivalent longitude (same apparent position) in the sky (but operating on different frequencies). Even so, if you actually went up there and looked, they would be 10s of miles apart from each other.

How to avoid debris? For some of the larger tracked objects NORAD warns the satellite operator when a collision is imminent so they can take action to change an orbit, or shut down temporarily. Sometimes collisions happen. The shuttles have been hit a few times by particles smaller than can be tracked (by NORAD). Mostly though, space is huge, and the chances of collision are very small -- they just "play the odds".

.

Answer 2

There is a lot of room around the earth, so it is unlikely that a satellite would hit another satellite in orbit. Also, since many satellites are geosynchronous, this means that they will stay in the same position above the earth; also decreasing the chances of satellites hitting each other.
The orbit of the satellite is decided by physics and mathematics, to determine the point above the earth where the satellite will be geosynchronous.
As to your last question, satellites don't avoid space debris, as far as I know. I believe that was a problem with the Hubble Telescope in the past.

Answer 3

There's a LOT of room out there, and it's in 3 dimensions. Each satellite's orbit is pretty unique. Not only would the satellite have to be at the exact same altitude as another satellite, its orbit would have to intersect another satellite's orbit at precisely the right second. Considering these satellites are moving at over 6 miles per second, it's like trying to hit a bullet with another bullet, except bullets don't travel as fast.

Answer 4

they are at different altitudes, different orbital angles, and they are preplanned that way so as not to interfer wit h each other. avoiding space debris is pretty much hit or miss, reasearch was done on several older sats and returned to earth by the early shuttles, and they looked like they were made of swiss cheese and used for shotgun practice small flecks of dust can almost destroy a sat if it is hit hard enough. total penetration is indeed easy, skins on the units are not made too thick.

Answer 5

What a great question! Am sure there is no definitive answer other than ; the risk and chance those whom launch are going to take. There is so much space up there, the odds are slim and none of a collision. If we scattered a few hundred ants randomly on earth, would they ever collide ?

Answer 6

Mostly they don't encounter each other. Space in orbit is very big.

Answer 7

simple. each one has its own orbit and there are big distances between 'em.

Answer 8

first of all theres alot of room out there and they all move about the same rate so there good.

Answer 9

They have really smart people working at NASA. Some of them are rocket scientists.