Page 13 - Curriculum Visions Dynamic Book

 This shows three geosynchronous satellites in orbit around the equator at 35,786 km altitude.
Each satellite has a direct line of sight over an area with a diametre of 18,000 km centreed on the equator. The Earth’s diametre is 21,000 km, so only a small area at each pole is not covered. Links across the world are made by sending signals between satellites.
dock To meet with and attach to another space vehicle.
equAtor The ring drawn around a body midway between the poles.
geosyncHronous orbit An orbit in which a satellite makes one circuit of the Earth in 24 hours.
rotAtion Spinning around an axis.
velocity A more precise word to describe how something is moving, because movement has both a magnitude (speed) and a direction.
Launches are often made toward the east. That makes use of the speed of rotation of the Earth (about 450 metres per second—m/s—at the equAtor and 400 m/s in the midlatitudes).
Launches are not made to the west because even more velocity would be needed from the spacecraft engines to overcome the rotational speed of the Earth.
Launches are sometimes made toward the North Pole or the South Pole to produce an orbit that includes both poles. Satellites in this orbit, for example, see the Earth sweep below them and are used for surveying the entire surface of the Earth.
If two spacecraft are intended to dock, as with a Space Shuttle and a space station, the second spacecraft is launched so that it will be well ahead of the path of the already orbiting craft. The relative speeds can then be adjusted not by firing motors so that one craft can chase the other but by changing altitude, since going to a higher altitude produces a lower velocity, and going lower results in a higher velocity. That saves on fuel.
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