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Satellite Glitch Rekindles GPS Concerns
coondoggie writes "News today that the Air Force is investigating signal problems with its latest Global Positioning System satellite is likely to rekindle the flames of a congressional report last month that said the current GPS coverage may not be so ubiquitous in the future.
The Air Force stated that routine early orbit checkout procedures determined that the signals from the Lockheed-built GPS IIR-2 (M), which was launched in March, were inconsistent with the performance of other GPS IIR-M satellites.
The Air Force said it has identified several parameters in the GPS IIR-20 (M)'s navigation message that can be corrected to bring the satellite into compliance with current GPS Performance Standards."
Soloution? Pour more money into NASA!
Um, the GPS constellation belongs to the USAF.
Pirate Party UK
Pretty much. Of course, any current problems with GPS are likely to be fixed once GPS III is up and running. It will combine land-based positioners with satellites that have 500 times the transmitter power. Of course, that 'not so ubiquitous' factor is still there as GPS III will allow the U.S. military to shut down GPS to selected geographic areas at will to all but sanctioned receivers. ;)
My blog
Well, from TFA the problem seems to be the new L5 frequency, which is "interfering with other signals from the satellite and reducing their accuracy"
This is a little more serious than just some glitches in the software. It's a basic design problem.
Heck, I work for a GPS company and don't rely on GPS for navigation (we do high-precision applications, not navigation so I don't feel too hypocritical about it). However, this isn't because I don't trust GPS but because I prefer to have a good situational awareness of where I am and where I'm going.
I have tried using GPS navigation in rental cars for fun but usually their directions aren't as good as Google maps directions and have led me down a dead-end street once late at night.
The best compromise I've seen so far between maintaining a good idea of what's going on and using GPS is Google maps on the G1. You simply map out your directions before you start driving and then you have the choice of enabling the GPS to see where you are on the route or leaving it disabled if you like. Either way you can still zoom in on the map, check street view, etc without needing to spread out a huge map (or having to print out directions before you take off).
Note: I wouldn't use this story as a justification for not using GPS. The Air Force likes to maintain a 95% reliability of the constellation remaining fully operational each year (meaning that in the lower 48 that you will get a good position fix virtually all the time). They are worried that in the future they can only estimate an 80% chance of the system staying fully operational. The system would still work even if they don't have 31 satellites working. The minimum number of satellites needed in the constellation to provide good position fixes virtually all the time is 24 (4 good satellites in 6 orbital planes). They have additional satellites up there that are either at their end of life or backup satellites that are ready to take the position of another that becomes disabled. See this PDF if you want all the details: http://www.navcen.uscg.gov/GPS/geninfo/2008SPSPerformanceStandardFINAL.pdf
The satellites are not identical by any means. Rockwell built the originals and they were rock solid R&D birds. SVN3 was nearly 13 years old when I (and the crew I was on duty with) turned off the payload back in the early 90s. I used to joke with the Rockwell engineers that if requirements could be stopped, a Block 1 payload/chassis, with Block 2 electrical system would last decades (plural). Instead, we've got L1, L2, M-Code, L-5, NUDET territary sensors, and there's some boxes that only 3 letters now know about... Too much crap on something that's basically just transmitting, "HERE I AM!! (at this time)"