aiming for the moon...or satellite

[GammaMambo]

so how many fully intact satellite fall into the earth's atmosphere?

they make it such a simple and ordinary task of shooting down this one on thursday, but really, what are the odds?

a bet is on.

 

okay so...the bet is off...the satellite will enter our atmosphere with grace, i'm sure...if it even does.

the big deal is that skylab is the last satellite to crash into our atmosphere as they so eloquently put it.

or was it.

well, anywho, skylab was 100 tons and this satellite is 2.5 tons.

not to say size matters, but...well.

[iNow]

Hey there mammagambo... I was distracted by your avatar momentarily, and I seem to have missed your point. Can you help a guy, one who seems to have temporarily lost blood flow to his cranium resulting from visual stimuli, to understand where skylab comes into all of this?

[Pangloss]

I think he must be talking about the planned shoot-down of the US spy sat by the US Navy.

 

I believe a number of other satellites have re-entered the atmosphere since Skylab. Mir comes to mind, for example, but I'm sure there have been many. I don't know what the odds are for them hitting it, but that information may not be known outside of security-cleared folks at the moment, although I'm sure industry analysts have a fair notion. We're really just going to have to wait and see if they hit it or not.

 

Of course, I would hit it.

 

 

 

(sorry -- that was a long way to go for a very small joke, wasn't it?)

[D H]

Per the 1967 UN Space Treaty, countries that launch satellites are required to pay for damages done to aircraft or the Earth by falling satellites. Note that I said countries, not companies. This is already an issue with private satellite ventures: What country takes on the liability when a multinational company performs the launch and another multinat owns and operates the satellite? This will become an even bigger issue when/if commercialized space efforts take off.

 

Countries are also supposed to (but not required to) "play nice" in space. Part of playing nice is carrying enough fuel on a LEO satellite to make it ends its life with a controlled re-entry -- i.e., in the middle of some ocean. Most LEO satellites do carry that suicidal dose of fuel. However, bad things sometimes happen, as is the case with the vehicle to be "shot down" on Thursday.

 

Playing nice in geosynchronous orbit means carrying enough extra fuel to move a GEO satellite to a graveyard orbit at the end of its life. Most GEO satellites do not carry their dose of suicide fuel. Using every bit of fuel for orbit maintenance extends the life of the vehicle by months or years. Only about a third of GEO satellites "play nice".

 

GEO now has quite a bit of uncontrolled junk flying through it. When a GEO satellite runs out of fuel without moving to a graveyard orbit, it does not remain perfectly geostationary. Solar radiation pressure, Earth's non-spherical gravity field, and third body effects (Moon and Sun primarily) change the orbit slightly. This makes dead GEO satellites a hazard to every functional vehicle up there. I won't be surprised if someday soon we lose a big chunk of TV broadcasts because of a collision in GEO.

 

This Parliamentary Office of Science and Technology note is a bit dated, but is well-written and provides some very nice charts and tables on amount of stuff in orbit, orbit lifetimes, Earth impacts, and the Space Treaty.