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Old 02-05-2013, 05:19 AM   #1
rixwrites
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Communication satellites and junk orbit

Hi,
How long do communication satellites last, and once they are out of power what happens to them? Are they moved into junk orbit, and if so is that a preprogrammed action or initiated from some sort of ground control. Or do they fall to earth/burn up. Is 100 years in orbit reasonable to assume - just orbit, not necessarily powered. Could a satellite maintain orbit for that long? What facilities can launch communication satellites? Can it be done in a non-government facility? Could an amateur radio satellite be launched privately somewhere/somehow, and if so, what would be needed to do that?
Thank you for your expert time.
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Old 02-05-2013, 05:42 AM   #2
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I know that older satelites were not designed to come out of orbit when their useful life expired. Lots of these old satelites are still circling, and there is concern that some of them may remain there as junk indefinitely. Some of them will fall and burn up, so I think there is a lot of variation. Some of the newer satelites are designed with avoiding space debris in mind and are equiped to drop down from orbit or break out of orbit and go higher.

I'm not sure how private companies like SpaceX work (whether it is under the close supervision of NASA or not), but currently they do launch things that are taken to the international space station, so why not a communications satelite? There has been a certain move toward comercialization of space recently with the elimination of the shuttle program.

(All of these details are courtesy of my daughter who had space development as her debate topic last year.)
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Old 02-05-2013, 09:24 AM   #3
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Orbit duration is largely a matter of altitude. The higher the orbit the longer it will last. Many communication satellites are geostationary and will never come down in any reasonable amount of time.

Communication satellites used to carry data where latency is important must be in low Earth orbit, which means their orbits degrade relatively quickly and thus they need to expend fuel every once in a while to compensate for the tiny amount of drag from the very thin atmosphere up there.

I don't know how long they last on average, but any new satellite is required to have the capability to either safely re-enter the atmosphere (i.e. largely burn up) or boost itself up into a graveyard orbit.

I'm sure 100 years would be trivial for a geostationary satellite. I think there is no chance a LEO satellite would last that long. To maintain a LEO orbit, the satellite needs to be almost completely functional. It needs power, fuel, attitude control, and navigation. Solar panels and computer chips degrade in space and nobody puts 100 years of fuel into a satellite that will likely be obsolete in 20.

Small satellites can be launched by ICBMs actually. The Russians and USA have both used old ICBMs to do this. The Russians have even launched them from ships and submarines. Only nation states have ICBMs though. There are several private space companies currently working on launching satellites.

Cheap, small satellites would be launched either by the Russians aboard an ICBM, or aboard something like a Pegasus. http://en.wikipedia.org/wiki/Pegasus_(rocket)
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Old 02-05-2013, 11:00 AM   #4
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This is a dramatic article about how the Iridium satellites used for satellite phone service were about to be "decommissioned" (what a euphemism for throwing away many millions of dollars of perfectly operating orbiting space hardware):
http://www.computerworld.com/s/artic...ecommissioning
This article tells "the rest of the story:"
http://gigaom.com/2012/08/27/how-iri...pacex-and-won/

You asked about amateur radio satellites - there have been several:
http://en.wikipedia.org/wiki/Amsat
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Old 02-05-2013, 05:04 PM   #5
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Thanks. I will check out those links. My supposition is that in 100 years there is no satellite communication because no one maintained what was there, or launched anything new. Except, of course, that hidden in graveyard orbit is a microsatellite constellation that can be activited, and using attitude control from the ground is re-orbited and the constellation provides near global coverage. I think the constellation would have to be geostationary array, but not sure about the mother. And.... in my future there are ham operators that can then send a message to... say... europe from the US using this reactivated satellite. I know I've gotta fudge the science a bit here, but would like it to be as plausible as I can.
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Old 02-06-2013, 04:06 AM   #6
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rixwrites: I think any satellite in geosynchronous orbit will be a big, fancy one rather than one designed to bounce amateur radio because GSO requires boosting the satellite over 22,000 miles up rather than 200 or so. I would think a more plausible scenario would be for an old, formerly state of the art communications satellite to be shut down due to severely degraded performance, and then hacked by someone on the ground who is able to make good use of it despite its limitations. Reasonable limitations causing the owners to discard it would be a drastic reduction in bandwidth caused by the loss of solar panel efficiency or loss of signal processing chips in most of the signal pathways.
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Old 02-06-2013, 05:09 AM   #7
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Spice Chai: thanks very much for the info. I am going to abuse your generosity further, if you are willing. My plan was to have a satellite purposely hidden and waiting reactivation. It doesn't have to be an array or geostationary, or big or small. I just came up with that based on what I'd read. As part of my complicated solve-the-riddle plot device, the equations for a keplerian orbit are discovered, allowing someone on the ground to determine where this hidden satellite is and reactivate it. And they have the means to move it out of graveyard orbit (not actually necessary, just a plot thingy). But the only viable technology able to receive a message is ham radio. So the uplink doesn't necessarily need to be amateur radio, although I'd like it to be. More importantly is that the signal would be trans-continental and picked up by ham operators x-USA. So my actual question is about the power source. If there were such a satellite that was discarded because of power degradation, would it still, after 100 years, have enough power to relay radio signals back to earth? And should it be solar power or nuclear? And would it need to actually be reactivated? Or re-orbited? And you are the bee's knees for giving me your time. thank you.
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Old 02-06-2013, 05:25 AM   #8
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BenBradley: thanks for those links to spaceX and iridium. They were very helpful. Maybe I can call my imaginary company spaceY.
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Old 02-06-2013, 05:28 AM   #9
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PlainsPen: tell your daughter thanks.
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Old 02-06-2013, 05:34 AM   #10
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this open up a whole new possibility, use junks to do something useful on earth. love to see someone succeed in this.
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Old 02-06-2013, 06:31 AM   #11
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But I did see Telstar pass overhead one time back in the sixties.

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Old 02-07-2013, 03:42 AM   #12
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No problem at all, rixwrites. It's fun to talk about one of my favorite subjects.

There would be no need to move it out of a junk orbit, and this would probably not even be possible. I believe satellites in a junk orbit always have their fuel tanks vented to prevent detonation when they are eventually impacted by space debris. A junk orbit is just one that is up and away from other satellites and high enough that the atmosphere won't cause enough drag to result in it re-entering any time soon.

I don't know much about specific radio technologies or radio bands, but I suspect a really sensible way to contact a satellite would be just the method you describe, but with an old satellite dish for an antenna. The dish needs to be pointed at the satellite, so you need to know it's approximate location in the sky, which would provide some good plot points and details for the characters to futz over. Using this kind of parabolic dish would make the signal appear much stronger to the satellite (and conversely weaker to anyone else if your characters are trying to hide their signal at all).

If it's not in a geostationary orbit, they will have to follow the satellite across the sky, which might provide good futzing for them, or it might interfere with your plot. If it does, an alternative would be for the comm sat to actually be a satellite TV broadcaster. Regular old satellite TV equipment would pick up the signal, the location could be looked up in old manuals, and the satellite will already be in a geostationary orbit (and thus not need a graveyard orbit).

Solar panels slowly produce less and less power due to exposure to the intense radiation in orbit. I think it would be safe to say that this satellite still produces enough power to weakly power one of its transmitters, or maybe to trickle charge its battery and thus produce a few minutes of communication time a day. Whichever is better for your plot. It would have been retired because it didn't operate reliably, or it couldn't generate enough power to run all the transmitters or maybe it was just too old and slow and a much better satellite (that didn't survive as long) was launched to replace it.

All civilian satellites are definitely solar powered. The only nuclear satellites are government experiments, or government deep space probes. (Believe it or not the Soviets actually orbited a complete nuclear reactor and then accidentally smeared it across Canada. Canada sent them a bill for the clean up.)

An alternative if you want a low Earth orbit would be the Iridium network. There are tons of those things up there, and there are a lot of publicly available details, so you could include a lot of that for delicious texture. They can be communicated with via satellite phone hardware. http://en.wikipedia.org/wiki/Iridium...te)#Satellites

No satellite is ever told "stop listening to signals from the Earth", so they are always listening, even after they've been officially deactivated. Deactivation primarily means boosting them up or down into a less used orbit (to minimize risk of collision), venting out the fuel, and turning off the transmitters (to free up bandwidth). There is really no reason to turn anything else off.

I should also point out that I don't have any special knowledge in this field - I'm not in the industry or anything. I just read a lot about space.
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Old 02-07-2013, 06:20 AM   #13
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By the way, ham operators can talk to Europe without a satellite right now on the shortwave bands. I doubt that has any impact on your story, but it's pretty neat that with a modest antenna and radio package you can bounce your signal all over the world and talk to people in foreign lands.
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