Also, the faster the object is travelling, the more centripetal force is required to keep the object going round in a circle instead of shooting off in a straight line - but at the same time, the further the object is from the Earth, the less effect the Earth's gravity has on the object. So there's actually only a fairly thin band where gravity is sufficient to keep the object going round the Earth, but not crashing into it.
do geosynchronous satellites have to keep generating bits of thrust to keep their speed up & stay in the 36000Km orbit? Or once plonked there with the right initial nudge, do they stay there forever?
They stay put for a fair while - their orbit ends up decaying sometimes as has been previously stated elsewhere, because of the action of the moon's gravity, micro-meteorites, solar wind, and other such teeny-tiny forces that can have an effect over time. Hence they send up the Space Shuttle every so often to straighten out the orbits of the more expensive satellites. :-)
Not for refulling geosynchronous satellites though as the shuttle only goes up 300Km or so (Low Earth Orbit?). unless the satellite thought "ohh, need fuel", dropped to a lower orbit, picked up some gas & then nipped bak to higher orbit? EssoSpace division :)
must find the rather cute java app showing satellites orbits, can drag it around, rotate the earth, zoom in & out, highlist specific satellites. GPS satellites on that looked like a crowd of angry flies buzzing round the earth, with LEO satellites making a close to the surface sphere, the bunch of geostationary ones making a Saturnesque ring, and things like Chandra nipping well away from Earth then zooming back :) Way to waste hours wondering : http://science.nasa.gov/RealTime/jtrack/3d/JTrack3D.html
I say 'that's the best thing I've ever seen on the Internet' quite often, but honest to God I mean it in regards to this applet. I had no idea that anything so fucking amazing had been made.
I... I might have to enable Active Desktop and set this as my wallpaper. Oh God.
it *is* rather cool! Wish it did a lot more as well - imagine if it linked in a planetarium & the voyager & mariner & other probes and everything we've ever done in space ;)
A geosynchronous will generally be more stable than a low-Earth orbit because there isn't nearly as much of Earth's stray atmosphere floating around at that altitude. However, even at this distance there is matter floating around which has a slight effect on the orbit. There is also the gravitational pull of the Moon whill will gradually pull the satellite about in it's orbit, so geosynchronous do need to expend fuel to make course corrections too. I think ground stations sometimes need to make adjustments for sattelites that have drifted out of their original orbits too.
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must find the rather cute java app showing satellites orbits, can drag it around, rotate the earth, zoom in & out, highlist specific satellites. GPS satellites on that looked like a crowd of angry flies buzzing round the earth, with LEO satellites making a close to the surface sphere, the bunch of geostationary ones making a Saturnesque ring, and things like Chandra nipping well away from Earth then zooming back :)
Way to waste hours wondering : http://science.nasa.gov/RealTime/jtrack/3d/JTrack3D.html
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I say 'that's the best thing I've ever seen on the Internet' quite often, but honest to God I mean it in regards to this applet. I had no idea that anything so fucking amazing had been made.
I... I might have to enable Active Desktop and set this as my wallpaper. Oh God.
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Wish it did a lot more as well - imagine if it linked in a planetarium & the voyager & mariner & other probes and everything we've ever done in space ;)
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would be fun to set it to show spacecraft & satellites popping up (and disappearing :( as years go by
Sputnik, all alone...
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