
A large satellite appears to be falling apart in geostationary orbit - robin_reala
https://arstechnica.com/science/2017/07/a-large-satellite-appears-to-be-falling-apart-in-geostationary-orbit/
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rasz
>"The AMC-9 could have been attacked by something"

Are we sure its a real satellite? and real news?

New Cloverfield franchise film is coming out in October:
[https://en.wikipedia.org/wiki/God_Particle_(film)](https://en.wikipedia.org/wiki/God_Particle_\(film\))

J. J. Abrams and his company Bad Robot is known for doing this type of
guerrilla marketing (
[http://cloverfield.wikia.com/wiki/Viral](http://cloverfield.wikia.com/wiki/Viral)
), they did it for both original Cloverfield and for 10 Cloverfield Lane. It
included fake YT news clips, fake websites for fake satellite/oil/power
companies, fake press releases, the whole nine yards.

Fake satellite:
[http://cloverfield.wikia.com/wiki/ChimpanzIII](http://cloverfield.wikia.com/wiki/ChimpanzIII)

ExoAnalytic was founded in 2008, the same time Abrams ran his first viral
campaign for the Cloverfield.

More about the tangled lore and extent of the viral marketing:
[https://www.youtube.com/watch?v=FtaCF87_d0c](https://www.youtube.com/watch?v=FtaCF87_d0c)

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Animats
Cleaning up geosync orbit is going to be tough.

There's a proposal to remove small objects from low earth orbit by shining an
10KW or so earth-based laser at them for a few hours. This exerts enough light
pressure to drop their orbit deeper into the atmosphere, where they slow
further, re-enter, and burn up. That's probably the most cost-effective
approach proposed so far. Now that solid-state lasers in the 50KW range are
available, this looks like a viable option.

~~~
planteen
How does an Earth based laser bring something closer to Earth with radiatipn
pressure rather than pushing it further away? And how does that work in GEO?
The typical disposal method there is to go up to a graveyard orbit, not down
to the atmosphere. The atmosphere is very far away from GEO. You are looking
at 35,000 km in GEO while the ISS is skimming the atmosphere in LEO at 400 km.

~~~
Terr_
> How does an Earth based laser bring something closer to Earth with radiatipn
> pressure rather than pushing it further away?

It changes the _shape_ of the orbit. Shooting sideways is hard (more
atmosphere) but pushing it away from the center of the earth works too: The
orbit becomes less circular and more elliptical. While the higher point
(apogee) is further away than before, the lowest point (perigee) is closer.

Lower the perigee enough, and the satellite starts grazing the atmosphere.
That's what really bleeds off energy, and causes the orbit to shrink overall.

> And how does that work in GEO?

I'm not sure. At that distance you can't rely on the same subtle
destabilization, nor really hit it from any angle but "below".

~~~
kobeya
> The orbit becomes less circular and more elliptical. While the higher point
> (apogee) is further away than before, the lowest point (perigee) is closer.

Orbital dynamics is complicated and I admit I could be wrong here, but I'm
pretty sure this is incorrect. If you push radially outward from a circular
orbit, it should raise the apogee but keep the perigee the same.

I could see this working if you exert a radially outward force on an object in
an elliptical orbit that is already coming in from apogee to perigee, because
relative to the object's radial velocity that would actually be a braking
maneuver. Is that what you meant?

~~~
freeman478
No if you raise the apogee without giving the object any additional speed, the
perigee will be lower.

~~~
kobeya
You did give the object additional speed.

~~~
ScottBurson
No, you've deflected it in a direction perpendicular to the one it's moving
in; turning it slightly away from the Earth, initially, but not speeding it
up. This will increase the eccentricity of the orbit.

~~~
kobeya
If x is the direction of travel at the moment of impact, Vx remains the same
but it gains Vy. Total V increases.

~~~
eyko
It depends on the angle at which you hit the debris with the laser, as well as
the shape of the debris.

The idea is, generally, to hit the debris at an angle as it approaches you
(bottom front of you may)[1]. Depending on the shape of the object as well as
the material of the surface, you'll be able to transfer enough momentum to
actually slow it down as well as nudge it further (loss of mass?) out into a
new orbit with a low enough perigee.

It's obviously not easy to predict the new orbit because debris comes in very
different shapes, and of many different materials.

Also, because there's a transfer of energy, the part of its original Vx is
lost in the process (the laser is deflected at an angle). There's no loss of
total Vx (sum of laser Vx and debris Vx) however.

1: See figure 3 in page 6 of this pdf (the laser at an angle).
[https://arxiv.org/pdf/1004.0390](https://arxiv.org/pdf/1004.0390)

~~~
kobeya
I understand, but this subthread was about what happens when you hit it when
it is directly overhead, pushing it outward.

~~~
eyko
That seems unlikely, but even in that case you'll achieve a lower perigee.
It's also extremely unlikely that it would happen - hitting debris when it's
directly overhead, yes, but hitting it on a surface that's perpendicular to
the laser, like a letter T, probably not.

But assuming we do hit it like a T, the two things happen: loss of mass (laser
ablation) and transfer of momentum. Vy will increase but Vx remains constant.
The debris is moving in a straight line - that speed doesn't increase, but now
it's moving at a different orbit so, relative to its previous orbit, Vx will
appear to have reduced (but it hasn't).

But I'm definitely not an expert in orbital mechanics so don't quote me on
that.

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mirimir
OK, I see that AMC-9 is flashing at a more-or-less regular rate, throughout
the video clip. But other geostationary satellites in the field, such as the
four bright ones near the beginning of the clip, don't flash. This is because
AMC-9 is spinning, right? Some flat surface, perhaps the PV array, is
reflecting more of the sun's light.

I'm guessing that some of the attitude-control thrusters malfunctioned. Maybe
that's what rendered the satellite unresponsive.

But in any case, excessive rotation could fragment the satellite. From the
observed rotation rate and the size of the satellite, one could estimate a
range of relative fragment velocities. And if one knew the video's angular
field of view, one could estimate observed relative fragment velocities. I
don't know that, but they seem smaller than velocity differences between AMC-9
and other geostationary satellites.

~~~
nthcolumn
[https://www.ses.com/our-coverage/satellites/315](https://www.ses.com/our-
coverage/satellites/315)

So at that rate how fast is it spinning? Says it is fairly large satellite -
car sized?

~~~
mrpjdog
It's how fast it is spinning yes but it there could be multiple surfaces that
reflect more brightly.

I actually work at a telescope where we're in the business of tracking
satellites. Its boring work, but it's good as a summer job, and the professor
it's under has me working on much cooler projects. I'll have to find the
ephemerides of the sat and point out scope there.

~~~
mirimir
True. And with multiple reflective surfaces, intensities would probably
differ. I can see some of that in the clip. I also get the sense that it's
tumbling on at least two axes. The light curve would be instructive.

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Tepix
The relative speeds of pretty much all objects that are in GEO orbit is
probably very small - after all they all started out orbiting the earth in the
same direction at the same speed. Shouldn't this make collecting debris much,
much easier? Navigating within the orbit could be done using electric
propulsion. Of course such an undertaking would still be very expensive given
that once you have collected a bunch of debris you need to deorbit it.

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empath75
When people talk about how crowded geostationary orbit is, keep in mind, that
the surface area of a sphere 86,000 km above the earth is about 30 times
larger than the surface area of the earth itself.

~~~
function_seven
That’s relevant for geosynchronous orbits, but for geostationary, the
circumference is 7 times longer than the equator’s distance.

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wglass
"space weather problem" ?

~~~
knz
[https://en.m.wikipedia.org/wiki/Space_weather](https://en.m.wikipedia.org/wiki/Space_weather)

I assume electronics that are failing due to shielding that has failed?

~~~
tmsldd
It looks like structural fault.. two possibilities here: a) debris collision
and, b) hardware fault during maneuvering (e.g. Fuel tank explosion, solar
panel or antena detachement). The later I think is more likely to happen
towards the end of the life of the hardware.. which seems to be the case.. but
in other hand we could expect a cloud of smaller debris floating around..

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ge96
That video is cool

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yummmuy
If only we knew the details ...

