Satellite Internet Frequently Asked Questions

What is a Geostationary Satellite ?

A geostationary satellite is a satellite that is in a fixed position relative to the earth. Kind of like your cars' driver's side mirror is in a fixed position relative to the rest of your car. If you turn left or right or even in a circle the mirror stays in it's fixed position relative to the rest of the vehicle.  A GeoSat follows the same premise, only on a larger scale and it uses physics to do so. First the how, then then why. I'm going to keep the math to a minimum.

Ever noticed that if you drop something it falls to the ground? So did the experts at NASA, and they got concerned because they didn't want satellites dropping out of the sky. It's embarrassing and expensive. So they had to try and find the point where the satellite would maintain enough speed to keep it from falling to earth while staying in a fixed spot over the equator.

Why do it this way ?

Because satellites (like your car) only have a limited amount of gas or propulsion fuel. Unlike your car, when they run out of energy, that's it. They can no longer maneuver. If they're too close to the earth they fall into the atmosphere slowly but inevitably. If they're too far out they simply slowly drift away into space. So the idea was to put them at a place where the speed of the satellite is sufficient to keep it from falling to earth yet have a rotation of one day. This keeps the satellite in it's position. A combination of forces trying to equal out to a stable area.

22,300 miles over the equator there is a whole belt of satellites zooming along. This area is named after Sir Dr. Arthur C. Clarke, the science-fiction novelist. It is frequently referred to as "Clarke's Constellation" Because it was he, back in 1947, who postulated the idea of using satellites for point-to-point-to-point radio communication.

Why a fixed position ?  Why line of sight (LOS) ?

Satellites are expensive. If you can have one covering a large area it is more cost effective than having two or three. In addition, we on earth do not want to keep trying to find satellites every day and having to adjust the antennas we use. So we keep them at fixed positions. So once we are locked in and pointed at the satellite we do not have to worry about tracking it across the sky. It's that simple. There are other reasons as well, but those are the most important ones.
Now to the question regarding "Line of Sight": if you think about it, you will realize that from where you are standing right now, you can see some things that are farther away from you than other things. This is frequently because they are taller. They have more "altitude". For instance, you can see the top of a water tower long before you can see the pumping station underneath it. So we know that the greater the height, the farther away you can "see" something.

Geostationary satellites are at fixed positions at an altitude of 22,300 miles from Earth. They can "see" (and be seen from) a huge area of land and ocean, and this area they can "see" is called the "footprint". They are also frequently located over the equator. You can imagine what the foot print looks like by holding a flashlight at a fixed distance from a basketball and turning the light on. The closer you get, the smaller the footprint.

Now if you hold the flash light at a fixed distance from the centerline or "equator" of the basketball AND aim it at the upper half you will see that the "footprint" elongates and gets much larger on one side, extending itself by half again. And turning from a simple circle, into an oval. That's why a lot of birds are "parked" in orbit over the equator. There is a consequence to this large footprint though. Radio waves travel at the speed of light, or about 186,000 miles per second. So any traffic from you to the satellite has to go 22,300 miles up, go through the satellite, and be retransmitted 22,300 miles back down.

The net effect is that it adds about a minimum of 240 milliseconds (ms) to the round trip. This is from an ideal position as close to the satellite as possible, which is probably in the ocean at the equator. And remember, that if you send for a web page both the request and the response have to travel these distances in addition to any ground distance. A more realistic expectation is a response of about 500 - 1000ms.

1000ms (milliseconds) equals one second. The satellite internet systems currently available run about a half second delay because of the distances involved. To an average web surfer this means about one half a second MINIMUM, between the time you click a link and the time you start to see a change take place. On a practical level it's probably closer to 3/4 of a second response time (750ms). Unfortunately, if you're heavy into internet multiplayer gaming, then we're pretty much done here. You can go elsewhere because a 750ms plus response time is unplayable. Why?

Imagine you are driving a racecar. Now imagine it's about three-quarters of a second delay (750ms) between the time you try to steer left, and the time the racecar starts to respond. You see the problem. It's like driving on ice and is simply not useable for many internet games that require fast reflexes. Some flight games may be useable, because they don't need as fast a response. However, popular first person shooters like Quake III and Tribes 2 and Counter-Strike are almost unplayable. If, on the other hand, you're not as big into gaming and are in an area not serviced by DSL or cable then Internet via Satellite may be just the thing for you.