G15 troubles

[B.J.]

Not to shoot down (pun intended) another idea, but here is the way the orbital mechanics work. You can't change the laws of physics...

If you add energy to the satellites orbit (in other words, increase its orbital speed relative to the Earth), the satellite will gain altitude but still be in orbit. The reverse is true as well - if you decrease the orbital speed, the satellite will fall to a lower (and smaller radius) orbit. Since the radius is smaller the orbit is actually faster in completing one orbit (even though you decreased orbital speed to get to the new orbit).

So, to "bounce it out of the orbit towards the sun", you would have to add enough energy (increase the speed) of the orbit to a point that the satellite was out of geostationary orbit and then continue until the orbit was out of the gravity well of the Earth (hyperbolic trajectory relative to the Earth). The problem with that is you are still in an orbit 1AU distant from the Sun (the same as Earth's orbit).

Therefore you would have to start decreasing your orbital energy relative to the Sun to a point that the lowest part of the orbit now starts decreasing and the satellite gets closer to the Sun. The closest we've gotten a spacecraft to the Sun is the Messenger probe about to go into orbit around Mercury and that took multiple planetary flybys to reduce speed. This is because of how much energy it takes to reduce orbital velocity. The Sun's gravity well is very very large but we are in an orbit already and therefore you have to null-out that orbital velocity before something would fall "towards the Sun."

I know you were trying to start a conversation with your comment - so how's that for starters from the physics side? When geostationary satellites have warp drives, then we can talk about aiming for the Sun!

Andy

Just to add confusion, two things. First, readers might look at Escape velocity - Wikipedia, the free encyclopedia@@AMEPARAM@@/wiki/File:Newton_Cannon.svg" class="image"><img alt="" src="http://upload.wikimedia.org/wikipedia/commons/thumb/7/73/Newton_Cannon.svg/220px-Newton_Cannon.svg.png"@@AMEPARAM@@commons/thumb/7/73/Newton_Cannon.svg/220px-Newton_Cannon.svg.png which discusses escape velocity. The main implication here is that I think the discussion above assume that the added energy was tangential to the orbit, ie in the direction of travel, and that for small additions of energy, you are just turning a circular orbit into an elliptical orbit, and you're still in orbit. Escape velocity is usually thought of in terms of being directly away from the earth, ie perpendicular to the orbital motion. While I understand what is being said above, I intuitively think that you can attain a perpindicular component of the velocity that you can escape, orbit, so that in reality you are no longer in orbit. The above url refers to escape using a parallel burn having a parabolic shape rather than elliptical shape. Of course it's been decades since I've had to think about such things.

But the real reason for my reply here, with the partial intention of adding confusion , only because adding confusion often makes us think, is that while I think the above is worded properly, however I'm not sure that the reader gets the implications, not with respect to going to the sun, but with respect to the

if you decrease the orbital speed, the satellite will fall to a lower (and smaller radius) orbit. Since the radius is smaller the orbit is actually faster in completing one orbit (even though you decreased orbital speed to get to the new orbit).

part. This is often used as a discussion starter because it seems logically backward in that by doing a parallel burn to slow an orbital object, you are really increasing it's speed. Or said another way, if a low earth orbit object like the shuttle decays in orbit due to friction with whatever atmosphere might be up there, the friction slowing it actually speeds it up, because it's lowering it's orbit. Ie the actual speed of an object that has been lowered into a lower orbit is faster. For example, a TVRO sat is going about 6860 mph, while the ISS that's only 230 miles out is going about 17,600 mph. So when you slow these things down, they actually speed up.

Actually, if NASA wants to decrease the orbital radius, it requires two burns, one to slow the ship down. This causes the ship to go into an elliptical orbit, ie when it slows down, it starts to fall a bit towards earth, but then speeds up due to gravity's acceleration, and when it gets to the lower protion of the elliptical orbit it has enough speed to bring it back out to the original point where the burn took place. To get the ship into a lower circular orbit, they need to do a second burn down when it is at the lowest point of the ellipse, the second burn again decreasing the speed to the point where the ship has the velocity associated with a circular orbit, thus two burns to slow the ship down have actually sped up the ship. While the 2 burn thing makes sense, it's still a mind bender (for me at least) relative to how a natural decay due to friction works, but I THINK that it's pretty much the same principle, since the friction slows the ship down so that the orbit's a bit elliptical, and then slows it even more at the lower part of the ellipse, keeping the orbit near circular as the friction lowers the orbit and speeds up.

Anyway, sorry for getting off topic once again, but this bumping the sat out of orbit thing reminded me of the friction speeds up the sat quandry.

 

[Dishman Dan]

Just to add confusion...
But the real reason for my reply here, with the partial intention of adding confusion , only because adding confusion often makes us think, is that while I think the above is worded properly, however I'm not sure that the reader gets the implications, not with respect to going to the sun, but with respect to the part.

That is what exactly what I was thinking???

I guess that I am just a end user of some kind of TV signals and not a rocket scientist. Some of you guys really know alot of the nuts and volts of things!!!

Hey B.J.,
Just messing with a partial quote from your post, I hope that you do not take it serious.

 

[raj2001]

Typical FoxNews. They can't even get the headline correct. The satellite didn't "spin".

Read the byline. It is a space.com story.

 

[alk3997]

The main implication here is that I think the discussion above assume that the added energy was tangential to the orbit, ie in the direction of travel, and that for small additions of energy, you are just turning a circular orbit into an elliptical orbit, and you're still in orbit. Escape velocity is usually thought of in terms of being directly away from the earth, ie perpendicular to the orbital motion...

Good explanation. I was trying to wrap my head around taking an object already in a high orbit around one body and then accellerating it to escape the first body (Earth) but then being caught by the second one (the Sun) but wanting to go into a shorter period orbit around that second body. I'll have to go look at the Mariner 10 trajectory (although I'm not sure if they used a LEO parking orbit).

I would bet that if we were truly trying this, using a lunar flyby might provide a more efficient method.

 

[photoman76]

Read the byline. It is a space.com story.

I know it's from space.com. The story is fine. But the headline was all FoxNews. Don't they read the story before making up a headline? "Spin" does not even appear in the story.
The original headline at space.com was "Out-of-Control Satellite Threatens Other Nearby Spacecraft".
http://www.space.com/news/out-of-control-satellite-threatens-others-sn-100503.html

 

[JimmyMcGee]

I know it's from space.com. The story is fine. But the headline was all FoxNews. Don't they read the story before making up a headline? "Spin" does not even appear in the story.
The original headline at space.com was "Out-of-Control Satellite Threatens Other Nearby Spacecraft".
SPACE.com -- Out-of-Control Satellite Threatens Other Nearby Spacecraft

Well yeah but to "low education" readers "out-of-control" in regards to Satellite mean spin. Otherwise its not "Out-of-control" they aren't rocket surgeons here.

 

[roho]

Elvis is watching it.. all is well.

 

[tracker1998]

Very interesting topic for someone like myself that doesn't know much about this stuff.
Reading with interest as I gather this is not a thing that happens too often?
Glad to be on the best site to see how this "plays out". Great info, theories and knowledge!
"Reading and learning on the sideline", tracker.

 

[k1wy-bill]

G 15 shut down fails

http://www.space.com/news/zombiesat-galaxy-15-shutdown-fails-sn-100505.html

 

[B.J.]

Very interesting topic for someone like myself that doesn't know much about this stuff.
Reading with interest as I gather this is not a thing that happens too often?
.....

I'm not positive about this, but you keep reading about the sat operators needing to keep enough fuel on these sats so that when the sat has reached an end of it's life span, it can be kicked into a higher orbit to a so called sat graveyard.

In the past, when I'd read about kicking the sats into a higher graveyard orbit, I was assuming that this so called "graveyard" was one of the so called Lagrangian points, which I think are 60 deg either side of the moon at lunar orbit distances, but this didn't make sense, because those points are WAY out there, and it would probably take millions of years for sats to get out there, if they ever would actually drift in that direction, so I was really unsure what was being done when they were kicking the sats to higher orbit.
When I learned about these so called libration points, the problem with using THOSE points as a graveyard, is that they are still at the orbital height of the other geosync sats, and as we've seen, unless placed there intentionally, they're still moving around into the vicinity of all the other sats, so it's not really a safe graveyard, and if placed there, it's not safe for the sats in the 105 slot.
MOST of the old TV sats that have died are in orbits that are a few hunderd miles higher than the geosync orbital distance, and these sats will apparently continue to move around the earth forever, as you can't have a stable spot at a higher altitude than the geosync altitude, so I'm assuming that this graveyard orbit is really just a layer out just a bit further, above the geosync band, and not a stable spot where they put sats. As mentioned above, if they just give an over the hill sat a single burn to put it in a higher orbit though, it's orbit will just become eliptical, the low end of which will still be at the distance at which the burn took place, so to actually get it at the higher altitude, they really need to do two burns, unless they figure that an elliptical orbit will not be a danger, and will eventually decay to a point where it is completely outside the geosync distance.
Anyway this has been an interesting topic, and I've learned a lot from it. Too bad they weren't able kill the transponders on G15, but I guess that the problems it causes will be a continuing education to all of us, including the sat owners and the FCC, etc. It will be interesting to see what happens, and what they do to minimize interferrence.

 

[nelson61]

http://www.space.com/news/zombiesat-galaxy-15-shutdown-fails-sn-100505.html

Good article. I had a broken link and had to go to space.com to retrieve it.

 

[digiblur]

Good article. I had a broken link and had to go to space.com to retrieve it.

Fixed the broken link

 

[tvropro]

G-15 the bird that won't give up What a mess.

 

[alk3997]

I'm not positive about this, but you keep reading about the sat operators needing to keep enough fuel on these sats so that when the sat has reached an end of it's life span, it can be kicked into a higher orbit to a so called sat graveyard.

...

Yes, the idea was that 300km above geostationary orbit would be a perfect place to park satellites. From what I've read recently, the reason for the 300km was that this was high enough that pressure from the solar wind and gravitational forces (lunar probably) were not enough to ever push these satellites back down to geostationary. The long term (hundreds of years) charts show oscillations in altitude that never reach geostationary.

One of the Insats (India) looks like its apogee made it to graveyard but its perigee is just slightly above geostationary. That satellite will continue to be a concern for geostationary.

The bottom line is that each geostationary spot is a precious resource - precious because only those slots can make money and because there are so few of the slots. So operators have incentive to make sure their satellites are disposed of properly.

The libration points discussed in the articles really are best thought of as a valley with a car that has no brakes and a little friction. Each time the car goes down the valley it gets slightly less up the hill until it comes back down towards the valley and goes up the other side.

So even if Galaxy 15 makes it to the libration point, it is still going to be oscillating around that point for many years. And with each swing, the satellite operators for the functioning birds are going to have to make sure they are prepared.

Andy

 

[alk3997]

Elvis is watching it.. all is well.

I thought Elvis was on Mars eating rovers? When did he move?

 

[B.J.]

Yes, the idea was that 300km above geostationary orbit would be a perfect place to park satellites. From what I've read recently, the reason for the 300km was that this was high enough that pressure from the solar wind and gravitational forces (lunar probably) were not enough to ever push these satellites back down to geostationary. The long term (hundreds of years) charts show oscillations in altitude that never reach geostationary.

I've heard this as well. I've read posts from people who have said that these deep space sats actually drift away from the earth rather than decay into the earth. I just tried running a 45 year simulation with Kelso's trakstar though, and it shows sats that were kicked up a couple hundred miles slowly sinking back closer to the geosync altitude, however I don't think there is any way a small program like that can possibly handle all the perturbations a sat would likely experience, I doubt that it even considers the moon's attraction. Anyway, I don't know if deep space objects drift away or not, but you have to wonder why they kick the sats out rather than in. Ie if they eventually drift back then that would really mess up the Clarke belt at some point, whereas kicking them inward would never be a problem, except for getting the sats there in the first place. So I'm really wondering if in fact geosync sats might actually drift away, and that's why they park them higher??? But whichever, you're right, that it would be hundreds of years before they got back to the Clarke belt.

One of the Insats (India) looks like its apogee made it to graveyard but its perigee is just slightly above geostationary. That satellite will continue to be a concern for geostationary.

Sounds like they only did a single burn. It would be interesting to see what the tracking programs predict for that one. Do you know what sat it was? When I did the 55 year run on Westar1 using Trackstar, it showed an interesting sine wave behavior, whereas as it's position progressed around the earth, the distance from the earth varied, possibly for the same reason that there are the libration spots. And it also seemed like at times the orbits became more circular. You have to wonder how an orbit that starts out elliptical might change the predicted decay.

I just thought of another interesting experiment. I posted above that I had downloaded all the historical Keps from GOES-6 . It might be interesting to run the OLD keps from 10 or 15 years ago, but run them for the current time, and compare this to the current keps for the current time. It might give an indication of just how good the prediction programs actually are, and also give an idea of whether the sat is drifting away or decaying toward the earth.

 

[alk3997]

...

I just thought of another interesting experiment. I posted above that I had downloaded all the historical Keps from GOES-6 . It might be interesting to run the OLD keps from 10 or 15 years ago, but run them for the current time, and compare this to the current keps for the current time. It might give an indication of just how good the prediction programs actually are, and also give an idea of whether the sat is drifting away or decaying toward the earth.

Try page 376 & 377 of:
2005ESASP.587..373J Page 377

(it's actually only 5-6 pages long but the page numbers are from the overall journal)

I believe it was Insat IIB.

Andy

 

[Krapola]

G-15 the bird that won't give up What a mess.

What, no "fun" for you any more?

 

[photoman76]

What, no "fun" for you any more?

Is there any hope of getting control of Galaxy 15 or turning it off after it passes through AMC 11's box?

 

[qwert1515]

According to the article I think they plan on trying again after it moves away from the other C-Band satellites.
(Maybe they can try sending higher powered "shut down" signals)

In a Tuesday statement in response to Space News inquiries, Intelsat said it is researching other ways to shut down Galaxy 15 once the satellite has passed through the AMC-11 position and enters — for a limited period of time — a stretch of orbital terrain unoccupied by other C-band spacecraft.

"We do not have an additional specific technical attempt identified at this time," Intelsat said in the statement. "But we will not give up, and expect to have other options to pursue at that time. We are now cooperating with other operators and customers to minimize potential service disruptions caused by interference."