If satellites are orbiting the Earth, how can they still work when they leave the area which they were supposed to broadcast to?
In: Technology
Either there are loads of them so one takes over as another leaves (gps uses this), or they don’t move relative to the earth (geo stationary – satellite communications use these)
There’s 2 possibilities.
First, they don’t. It’s called a geostationary orbit, which means that the satellite is so far up that the time it takes once around the earth is exactly the same it takes for the earth to spin once. In other words, it seems the satellite is standing still right above.
That only works around the equator, though. Since the satellite isn’t REALLY standing still, it has to go in an orbit, and it can only go in an orbit around the “whole” earth, not just orbit at a certain latitude. So if it was inclined, you’d see it go north-south (if you look up from the ground) as it orbits.
That the geostationary orbit is around the equator is also the reason why you have to point your sat dishes towards the south (if you’re in the north, to the north if you’re in the south) to receive the sat programs. The sat you’re aiming at is orbiting around the equator.
That works for most of the earth, it doens’t, though, if you’re close to the poles (and I mean really close, most of Canada and Sweden should still be good). Beyond that, sats are often put in a so called Molniya orbit. Look it up on Wikipedia if you’re interested. Basically the idea is here to put the sat into a very elliptical orbit that makes it be in the desired position for as long as possible. That way you can handle areas closer to the poles.
Short and sweet here
* There is an orbit called geostationary where satellite never leaves that spot (the satellite is far enough away from earth that the speed of the earth spinning is the same speed as the satellite) This keeps its position relative to earth the same.
* When one satellite flies ” out of the area ” another flies over to take over the job, Spacex’s star link is the perfect example of this.
There are basically two options:
Option 1: Geostationary orbit. Match the satellite’s orbit speed to the Earth’s rotation speed.
– Good: Works with a single satellite, receiver on Earth can be locked into a stable position.
– Bad: Satellite has to be pretty high up for this to work, which adds delays that are bad for anything that needs two-way data traffic (especially Internet).
Option 2: Constellation. Have a bunch of satellites covering the whole Earth. So many that, at any point on Earth, you have a clear line of sight to at least two satellites at any point in time. You can work out some geometry of satellite positions and orbits to achieve this with as few satellites as possible.
– Good: Satellites can be low, takes care of the delay problem.
– Bad: Having dozens of satellites is extremely expensive. If using a directional dish antenna, receiver needs to have a tracking mechanism to move the dish to keep it pointing at a satellite. Also needs cost and engineering complexity of either satellite-to-satellite data connections (mesh) or a worldwide network of ground stations.
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