First, we must get our satellite above the atmosphere. Air resistance from even the very thin atmosphere found at a height of 100 km would quickly slow a satellite down and make it fall back down to Earth. Even a height of 300 km (the lowest possible for a satellite) is on the boundary of the atmosphere and satellites at that height often need the occasional extra kick to keep their speed sufficiently high to continue orbiting. |
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Secondly, by the time the satellite reaches orbital height, it must have a sideways speed high enough to keep it in orbit. Otherwise it will just fall back down again!
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