Help! Artificial satellites working principle, anyone?? Presentation tomorrow, worried!!?

Question

Got a presentation tomorrow, wiki isn't helping. Tried search engines too, no good.
Can anyone find me a link to a good website which explains satellites working principle???
Will be grateful

Answer 1

Wherever they orbit, or if they are in deep space (orbiting around the sun), or if they are out of the solar system, all satellites have these things in common:

1. They have a mechanical "bus" that hold everything together

2. They all have some kind of power source (solar panels, RTGs, and/or batteries) and power management system. The power management system usually operates 2 separate redundant systems in case one fails (2 sets of batteries, 2 sets of power cables, 2 sets of battery chargers, etc.)

3. They all have some kind of attitude control system to control the direction the body of the satellite is pointed. It may be reaction wheels, torque rods, small rocket engines, or some combination of all three. If the primary source of attitude control is small rocket engines then enough fuel has to be brought along in tanks, also. Attitude control systems also contain star-sensors or earth-sensors, to use as references.

4. They all have some kind of flight control system (central computer) that controls everything else. This is also a redundant system.

5. They all have some kind of communication system to communicate system operations (telemetry) and either scientific data or commercial comm data (TV signals, radio signals).

5a. In the case of a scientific satellite, there may only be one main antenna for transmission with redundant transmitters that can be switched into the antenna. There may be a low-gain and a high-gain antenna for redundancy. There will be redundant receivers. Transmission time-per-day for both science data and engineering telemetry is shared and scheduled by the ground controllers. In the case of the ISS and shuttle, there are separate antennas, transmitters, and receivers for almost every function (that's highly redundant, but safer because it's for human spaceflight).

5b. For comm. satellites, there are many transponders (transmitter-receiver pairs) that operate autonomously, taking power from the satellite power system. They receive TV/radio signals from a few ground transmitters and rebroadcast the signal onto a wide-field antenna so it covers the 1/3 of the earth that it "sees".

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Answer 2

The wiki page explanes it well. Basically the idea is the use of high speed (at least 17,000 mph)speed and gravity to achieve a balance called orbit. Orbit usually last about 90 minutes for low Earth orbit and geosychronous satellites which appear to remain over the same spot on Earth are a great deal farther out in space.



http://en.wikipedia.org/wiki/Satellite

Answer 3

This site tells how orbits work--and how Isaac Newton worked out the basic principles:
http://spaceplace.jpl.nasa.gov/en/kids/orbits1.shtml

In addition:
Try nasa.gov (their education sections)
Also try space.com and livescience.com-both are legit sites and might have what you're looking for