Slashdot Mirror
Geostationary GPS Satellite Galaxy 15 Out of Control
Bruce Perens writes "The Galaxy 15 commercial satellite has not responded to commands since solar flares fried its CPU in April, and it won't turn off. Intelsat controllers moved all commercial payloads to other birds except for WAAS, a system that adds accuracy to GPS for landing aircraft and finding wayward geocaches. Since the satellite runs in 'bent pipe' mode, amplifying wide bands of RF that are beamed up to it, it is likely to interfere with other satellites as it crosses their orbital slots on its way to an earth-sun Lagrange point, the natural final destination of a geostationary satellite without maneuvering power." (More below.)
Bruce continues: "The only payload that is still deliberately active on the satellite is its WAAS repeater. An attempt to overload the satellite and shut it down on May 3 caused a Notice to Airmen regarding the unavailability of WAAS for an hour. Unsaid is what will happen to WAAS, and for how long, when the satellite eventually loses its sun-pointing capability, expected later this year, and stops repeating the GPS correction signal. Other satellites can be moved into Galaxy 15's orbital slot, but it is yet unannounced whether the candidates bear the WAAS payload."
Here's a list of what AMC-11 is used for on Lyngsat.
Basically, if this wayward sat gets in the way, the average cable/DBS subscriber in the USA is going to wonder where half their digital channels went.
It should be mentioned that the stable libration points for geostationary satellites are earth-relative (105 deg west, 75 deg east) and are not the same as the Sun-Earth lagrange points (such as those occupied by SOHO and other observation satellites). If we could get spacecraft without maneuvering capability to perform that orbital transfer, we'd be much closer to living in a Star Trek-esque world.
"Open the pod by doors, Hal" > "I'm afraid I can't do that, Dave" sudo "Open the pod bay doors, Hal" > alright
It isn't GPS, it's WAAS. http://en.wikipedia.org/wiki/Wide_Area_Augmentation_System which is an "air navigation aid developed by the Federal Aviation Administration to augment the Global Positioning System (GPS), with the goal of improving its accuracy, integrity, and availability. Essentially, WAAS is intended to enable aircraft to rely on GPS for all phases of flight, including precision approaches to any airport within its coverage area."
You want to hit the satellite away from the direction it's orbiting in, so that it loses enough orbital velocity to descend into the top-most part of the atmosphere where drag will slow it down even further and pull it down.
This is a commercial communications satellite that hasnothing to do with the Global Positioning System
It is not a GPS satellite, in that it is not part of the constellation of satellites that provide position reference. However, as TFA and the other links say, this satellite is one of only two that operate the Wide Area Augmentation System. WAAS uses ground-based GPS receiving stations with known positions to generate a correction signal which increases the accuracy of GPS position fixes to less than 25ft within North America and surrounding areas. Without WAAS, plain GPS can have error in the hundreds of feet. Without the accuracy provided by WAAS, GPS navigation cannot be used for instrument flight approaches - one of the most critical, important, and common uses of GPS today. If this satellite fails, the WAAS system will remain operational throughout most of its original coverage area - but will almost certainly fall outside the reliability limits required for instrument flight certification. It will be a very serious problem for many commercial users of GPS, and possibly for some military applications as well.
I am a geek attorney, but not your geek attorney unless you've already retained me. This is not legal advice.
There are No GPS satellites in GEO. They have their own special orbits. The title is really, really wrong... http://en.wikipedia.org/wiki/Gps#Space_segment
Think before you type.
The YAL-1 doesn't "heat up and short out guidance systems", it and the NC-135 used a laser to burn through the missile's wall and causes a structural failure.
Really... massless particles can create pressure now?
Yes. Photons carry momentum despite having zero rest mass.
Light actually does have a pressure. It is incredibly small, but in enormous quantities (like the sun or lasers) it can be quite powerful. I believe something like Intensity / c is radiation pressure formula. Not sure though. But it definitely has pressure, without radiation pressure our creation of Bose Einstein condensates would totally fail. Photons may not have rest mass, but they have some momentum because matter is just a form of energy. E.^2=M.^2.*c.^4 Its not much, but enough of it has measurable effects. A good part of the time the pressure is converted to heat (like on earth, or in our metal cutting lasers).
Uh, YES. Reality is a fantastic thing, i would suggest learning more about it, it is an enriching experience. Or you could just go on being a dumb-ass making the world a harder place to live in because people that know things have to sit around and explain things to you like a five year old, or just accept you people attempting to influence the world around you without understanding the possible consequences of your actions.
Where is the mod rating for "scary"? Also,
Not to mention the fact that the Shuttle doesn't have the thrust necessary to put it into Geosync... heck, it can't even make it to GTO. VERY out of reach.
I guess thats all I have to say.
You really don't want to just pop one in orbit though. It'll leave one heck of a mess up there. It's not just debris, it's radioactive debris.
Not only that, but the blast itself will fry more satellites, which will have to be nuked in turn.
http://en.wikipedia.org/wiki/Operation_starfish_prime
mov ax, 4c00h
int 21h
WASS is used to provide corrections to upper atmospheric disturbances in the GPS signal. It works like this: you have a lot of beacons on ground, mostly close to the shore but pretty much everywhere in the country. These stations know *exactly* where they are, but they anyway measure their position via GPS. By looking at the difference between what GPS says and what they know, they calculate the effect of these atmospheric disturbances. These are uploaded to a central system and get in turn broadcasted via WASS. WASS signals get used mostly by air and maritime vehicles in the North America. Europe has something similar called EGNOS, that depending on the country it could be used with limited advantage on terrestrial measurements. In Germany for instance, the angle to EGNOS is about 20 degrees which makes it almost impossible to capture free-line-of-sight by anyone that is not airborne or in open waters. Now back to the issue. One WASS satellite is failing. There are two WASS satellites and we are fortunate that the one about to fail is not the most important one. This link has some nice images showing the coverage. Sorry for copy-pasting, it's my first post and don't know how to add tags yet. http://www.gpsworld.com/gnss-system/augmentation-assistance/news/failure-imminent-waas-geo-satellite-9841 The problem is that airspace people don't like single point of failure so having one satellite only is a yellow lamp. How this will affect air traffic is still to be seen. GPS accuracy is about 16m with a good view, and when traveling 200 mph during approach, this is not crucial if you ask me. Maritime is something different. You don't wanna sail in Sweden and hit an underground island because you are 10m too far left. For final approach to runway and landing WASS has never been an enabling technology, so business as usual. The US will either replace the satellite or bring the functionality to another one. Until then, people must know that WASS could be out for a few seconds every once in a while. Nothing new really. None of us here will probably feel anything particular happening in the sky.