[Thread abduction]
If the earth’s rotational period has been altered (say, by a giant earthquake), doesn’t that mean that the previous distance used for geosynchronous orbit is now wrong? Does a “drift” exist that would necessitate either moving or replacing the existing satellites to get them in a truly synchronous orbit?
I am speaking of a hypothetical situation large enough to cause a non-trivial change in the earth’s rotational period… let’s say an increase or decrease of a second per day. I’m thinking the recent earthquake probably wasn’t big enough to make much difference, correct me if I’m wrong.
Well, satalites in geosynchronous orbits make slight adjustments to maintain their orbit anyway. The geosynchronous orbit would be slightly different but my WAG is that satalites that are currently orbiting will be able to achieve the new orbit negating the need to put up new satalites.
I’ve read that it added a very slight wobble to the Earth’s orbit.
Regarding the satellites if there were a rotational period change, a quick scribble suggests that a 1% increase in period would require about a 0.5% increase in orbit distance to compensate; about 250km. Without this correction the satellites would appear to travel backwards around the world at a ground speed of about 16km/h (using the old hour). I’m afraid I don’t know whether the satellites’ propulsion systems are set up to do this, but since you’re in space, one correction is pretty much like another, assuming you don’t mind waiting a bit longer. You’d also have to deal with the fact that after correcting, geostationary satellites probably wouldn’t be above their old position, but working out the extent of this effect is beyond me.
Er, make that “appear to travel forwards around the world, i.e. ahead of the earth’s rotation”.