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."

Comments

Re:Title is wrong, not GPS

[mpoulton]

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.

Re:Light pressure

[mmontour]

Really... massless particles can create pressure now?

Yes. Photons carry momentum despite having zero rest mass.

Re:Light pressure

[The Hatchet]

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.