'Zombie' Satellite Returns To Life

realperseus writes "The American telecommunications satellite Galaxy 15 has been brought under control after spending most of the year traversing the sky and wreaking havoc upon its neighbors. The satellite is currently at 98.5 degrees west longitude (from 133 west). An emergency patch was successfully uploaded, ensuring that the conditions which caused it to 'go rogue' will not occur again. Once diagnosis and testing have been completed, Intelsat plans to move the satellite back to 133 west."

Comments

133 west

[circletimessquare]

aka 133t status

Drat

[JustOK]

Drat! Foiled again.

Technically...

[mandark1967]

It wasn't a Zombie satellite. Zombies remain dead. Plus, it didn't incessantly transmit the message, "BRAINS! It's what's for dinner!"

Re:Technically...

[Anonymous Coward]

But the satellite is now UNdead! Doesn't that make it MORE of a zombie?

Re:Traversing the sky?

[locofungus]

If it was perturbed into a slightly lower orbit then it would orbit the Earth in less than 24hrs. If it ended up in a slightly higher orbit then it would orbit the Earth in slightly more than 24 hrs.

I don't want to commit to which way this satellite has gone (because I'm bound to get it backwards) but it's now about 2 hours displaced from where it should have been. That's an error in its orbit of about 0.02% or about 20 seconds per day.

Tim.

Nuke it from the ground

[Stele]

It's the only way to be sure.

Amsat-OSCAR 7

[Gordonjcp]

It's worth comparing it with the venerable AO-7 satellite, which was launched in 1974 and eventually "died" when its battery failed dead short in 1981. A little over ten years later, the failed battery failed again, this time going *open* circuit and allowing the satellite to run entirely off its solar panels. So, while the satellite is illuminated by the Sun it works fairly reliably. You need to keep the power down, because it has a linear transponder so the more power you put in the more comes out - until you exceed the tiny amount produced by the solar cells. It works, though, and people communicate across the world on it every day.

Nice story submission!

[swordgeek]

Seriously, three short lines which clearly convey the entire summary of the story, contains lots of links to both story and background, AND doesn't contain terrible typos! Also, geeky and interesting. This is what slashdot needs more of.

Re:Does this mean

[v1]

So does Intelsat have to give the insurance money back now? Or does it take more than a year to process this kind of claim anyway?

They were delayed due to problems scheduling an appointment for an adjustment agent to take a look at the satellite.

Just like that?

[Thapa]

What impresses me most is that you can just upload patches to orbiting satellites. Sounds like a party for the next DEFCON...

Re:Just like that?

[Cylix]

Not too long ago the norm was actually for transponders to simply be open.

Meaning if you had a means to send a signal to a particular frequency it would be easy to bounce from that transponder and relay back down. Now, if the NOC (or SOC really) caught an open transponder being used as a relay they would eventually shut it down if you were not paying for the air time.

This became a big deal during the initial war in Iraq as there were a good deal of hijack broadcasts spewing forth from across the sea. In response, they eventually began shutting down transponders until they were scheduled to be used. Either out of interest or trying to lock a particular bird I would find them at random times.

Somehow I doubt the mechanisms used on the old satellites were more obscurity then security to prevent updates.

Windoze on Board?

[Identita]

"We have placed Galaxy 15 in safe mode, and at this time, we are pleased to report it no longer poses any threat of satellite interference to either neighboring satellites or customer services," Intelsat officials announced." Unknown to anyone, the last shuttle launch had a secret space walk in order to hit CTRL-ALT-DEL on the sat's terminal.

Triaxiality

[mangu]

Except for two stable points at 75 and 255 degrees east longitude, any geostationary satellite suffers an East-West (or West-East) perturbation due to the earth not being a perfect sphere. This is called "triaxiality" by experts in the field.

The result is that without correcting maneuvers the satellite longitudinal position oscillates around those two stable points, even if the orbit is exactly at the geostationary altitude.

Re:Triaxiality

[mangu]

I have worked with geostationary satellite control for over twenty years, so I know a bit about this. The masses on the earth aren't distributed evenly, the higher density of the rock in some parts pull the satellite to the east or the west.

You are right in that the perturbation caused by the moon is several orders of magnitude larger than the one caused by this slight longitudinal asymmetry. It's only for satellites that are either in geostationary orbit or in 12 hour period orbits that this effect becomes significant.

For other orbits the pull in one direction is compensated by a pull in the opposite direction when the satellite comes around the earth. For geostationary orbits, however, the perturbation is always in the same direction, because the satellite is always in the same position with respect to the mass asymmetry, so the effect adds up in time.

Typically a geostationary satellite needs correcting East-West maneuvers every couple of weeks or so. These maneuvers consume about 10% of the total fuel budget for station keeping, inclination maneuvers consume the other 90%. This goes to show how stronger the perturbations caused by the sun, moon, and earth's ellipsoid shape, which cause the inclination of the orbit to increase, are compared to the triaxial density asymmetry.

Re:Traversing the sky?

[TheRaven64]

Corollary one: Any object in orbit around a body with mass has an external force applied to it.

Corollary two: Any object in the solar system is part of an n-body problem and has lots of external forces applied to it.