Monday, December 05, 2005
This is a closeup of part of yesterdays image showing two geostationary satellite orbign at just the right distance above Earth to take 24 hours to orbit Earth - the same rate the the Earth rotates, so the satellite appears stationary over the Earth. I don't know what these two satellites are doing, but typically they are communications satellites, weather satellites, Satellite TV satellites and spy satellites. The term "Geostationary" refers to a subset of "Geosynchronous" satellites that have nearly zero inclination so that they hover over one spot on the surface. If a geosynchronous satellite has an inclined orbit, it will move north and south during a days time. If the orbit isn't perfectly circular, it will wobble east and west (and the combination of the two make them follow a figure 8 path over one days time). If the object orbits just a little high, it will lag behind the surface below and drift westward, and likewise, if it is below the right altitude, it was drift ahead of the rotating Earth and move eastward. Science Fiction author Arthur C. Clarke was the first to suggest such an orbit and hint at its potential usefullness.