How long for a geostationary or geosync orbit to degrade?

[ravener]

If i put t a lump of steel with large solar panels on it in a geostationary orbit, when, if ever, will it reenter the atmosphere.

Are we talking in the order of thousands of years here? Millions?

We all know LEO objects orbits degrade relatively fast and require regular boosts to stay up, however atmosphere isn't a problem for geostationary craft, will solar winds and the moons gravity be enough to destabilize an orbit enough for it to reenter?

[legoheli]

For it reenter? A VERY long time. In fact I don't believe it would ever happen unless some gentle asteroid slowly and gently pushed the satellite onto a sub-80 km perigee. Solar winds and the Moons gravity does have an effect on the orbits of those satellites, yes, as do the tidal motion of the Earths oceans, but it is not something that will actually force the satellite out of orbit.

But for a satellite in geosynchronous to leave geosynchronous? That happens a lot. In fact i does require more or less constant stationkeeping maneuvers to maintain a geosynchonous orbit. Therefore, most geosynch satellites do not have a perfectly synchronous orbit, as that would use up their maneuvering reserves a lot. I am not sure about the tolerances, but once a satellite gets too far away from the original position, it will be maneuvered back, and once the fuel reserves are nearly depleted, it will be boosted out to a "graveyard orbit" slightly beyond geostationary.

I'm not sure if that answered you question, but hell it's the best I can do, haha.

[Nibb31]

It will take a while, which is why international law requires that GEO sats must be boosted to a graveyard orbit at their end of life.

If you were to leave it there forever, it becomes a hazardous debris in a very crowded and strategic location, which will make the entire global space industry very angry.

[Scotius]

So, we are creating another Kessler death zone just beyond geostationary orbit? Great Consider this: regardless how bad LKO might look, given a bit of time most space trash will eventually deorbit itself due to small but noticeable atmospheric drag. Beyond GEO? It will circle technically forever. Sure, there is a lot of space for junk to harmlessly float around, but it will only get worse as time passes.

[bsalis]

Like others have posted, I can't give an exact answer. My understanding is that Geo orbits, unlike LKO, are basically permanent.

Considering they are almost stationary, any traces of atmosphere up there are probably moving at much the same velocity.

Edited November 14, 2013 by bsalis

[K^2]

So, we are creating another Kessler death zone just beyond geostationary orbit? Great

I wouldn't worry about it too much. GEO is only useful with an equatorial orbit, so while we might end up putting enough junk there to eventually cascade, it won't create a death zone around the entire planet. All you'd have to do to get around it is launch along an inclined orbit.

[Tommygun]

Isn't there also a gravitational effect (at least partly caused by the Moon) that causes unpowered satellites to eventually start to clump together at certain points in an orbit?

[Yourself]

Isn't there also a gravitational effect (at least partly caused by the Moon) that causes unpowered satellites to eventually start to clump together at certain points in an orbit?

I think that's more to do with the fact that Earth isn't perfectly spherical.

[lajoswinkler]

For geostationary orbit... thousands of years would be nothing. Reentry might happen in hundreds of millions of years, possibly few billion if its surface is small enough and they're left alone.

SNAP-10A, USA satellite with a nuclear reactor onboard, is at 1300 km height and it will be there for around 4000 years.

[K^2]

Isn't there also a gravitational effect (at least partly caused by the Moon) that causes unpowered satellites to eventually start to clump together at certain points in an orbit?

Which isn't a problem either, since they would have almost zero relative velocity even if they collide.

SNAP-10A, USA satellite with a nuclear reactor onboard, is at 1300 km height and it will be there for around 4000 years.

And won't that surprise some feudal lord when it falls on his castle.

[rpayne88]

Instead of boosting them up to a graveyard orbit, why not drop their PE into LEO and place it in a decaying orbit? It shouldn't take that much DV from up there.

[K^2]

Instead of boosting them up to a graveyard orbit, why not drop their PE into LEO and place it in a decaying orbit? It shouldn't take that much DV from up there.

It would. More than 1km/s of dV.

[Nibb31]

It takes 4000m/s of dV to transfer from LEO (~200km) to GEO (35786km), and therefore the same amount to go back. In comparison, it doesn't take much to move from GEO to the graveyard orbit (>36000km).

[KerikBalm]

Couldn't you reduce that 4000 m/s a bit if you did some aerobraking? You don't need to go to a circular LEO, you just need your perapsis intersecting the upper atmosphere, a highly elliptical orbit should work

[Ralathon]

Couldn't you reduce that 4000 m/s a bit if you did some aerobraking? You don't need to go to a circular LEO, you just need your perapsis intersecting the upper atmosphere, a highly elliptical orbit should work

You could. For a hohmann transfer from GEO to LEO you need 4km/s total. But it's still about 1.5 km/s from GEO to a GEO-LEO transfer orbit. So still very expensive in terms of dV. it'd probably cost less dV to put the sat on a collision course with the moon.

[K^2]

it'd probably cost less dV to put the sat on a collision course with the moon.

It would. Less than 1.1km/s to Moon, almost 1.5km/s to skim the Earth's atmosphere. If we start having problems with graveyard orbit, somebody needs to propose this.

[goldenpeach]

I think this is the only place you can hear something like this: we don't have enough fuel to crash convert the satellite into a earth atmosphere analyzer?

Go to the mun instead!

Just after typing this, I realized that I instinctively typed "mun" instead of "moon"; maybe I play too much KSP

[PTNLemay]

It would. Less than 1.1km/s to Moon, almost 1.5km/s to skim the Earth's atmosphere. If we start having problems with graveyard orbit, somebody needs to propose this.

That's fascinating... I'd never thought of that.

In a semi-related question. I asked over here if there was something similar to the 70 Km limit in KSP, only in real life. http://forum.kerbalspaceprogram.com/threads/46318-Real-Life-atmospheric-limit The answer was that generally any orbit will decay, even GEOsync ones. I didn't realize that implied orbits lasting millions or billions of years. So I'd like to re-ask the question a bit more clearly... does anyone know how high an orbit you'd need to reach to have an approximate duration of say... 1000 years, or 100 years?

Someone in this thread said that at 1300 Km the object should last for 4000 years, so I take it the shorter durations will obviously be somewhere bellow that.