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."

Comments

Re:Soloution?

[PeterBrett]

Soloution? Pour more money into NASA!

Um, the GPS constellation belongs to the USAF.

Could it be related to this ? ;-))

[ls671]

Could it be related to this ? ;-))

http://idle.slashdot.org/article.pl?sid=09/06/12/1713237

Hehe... ;-)

Followup on the story

[BadAnalogyGuy]

According to Air Force officials, the previous story was incorrect and the GPS are working properly. The person responsible for the false story has been apprehended and will face a military tribunal. These are not the droids you are looking for.

Move along.

Re:Followup on the story

[morgan_greywolf]

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. ;)

yet another justification

[mikerubin]

for me not using GPS, at least in day-today driving. After 8 years of field service I still use a road map and Google Maps. I just don't need another crutch (ie: calculator).
Yes, I know a map of the Atlantic won't help if I drop the compass overboard but that kind of detail isn't necessary if you are just trying to find dry land.

Re:yet another justification

[joggle]

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

GPS will be just fine

[DaveInAustin]

A brand new GPS satellite has some bugs they are finding during testing, therefore GPS won't work as well in the future? Stop with the panic folks. Have you ever tested new code with new features and found some bugs? That's why you do testing.

Re:GPS will be just fine

[CosmicRabbit]

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.

solution:

[space_hippy]

Buy an atlas.

Re:What's The problem?

[Richard_at_work]

No, they are not exact replicas of the original constellation members, but they can be placed into a compatible mode to fit into the standard GPS constellation. What is happening in this story is simply that mode being callibrated. As more and more updated satellites are placed into orbit, the GPS system can be upgraded by turning on new features.

Re:Soloution?

[bberens]

I think it's bad form to call NASA a bloated behemoth while giving the US military a pass. Most military research and development has been privatized and yet it doesn't seem to be particularly non-bloated.

Not as big of a deal as they're making it look

[Logical Zebra]

This is a problem with one satellite. ONE. The problem is with a brand new generation of satellite created by Lockheed Martin. Boeing is also producing new-generation GPS satellites. It stands to reason that the first of any new production run might have a glitch or two that didn't show up in developmental testing. (I'm not defending their shoddy testing procedures, mind you.) The remaining next-generation satellites haven't been completed yet, so it's probably safe to assume that these glitches will be fixed before launch.

The sky is not falling, and GPS will still be around.

Re:What's The problem?

[JohnnyComeLately]

RichardAtWork nailed most of the response, but the OP never cites an article. With Google, I found an article here that explains it's L-5 that's causing the problems. L-5 is being turned on so they have first rights to the new frequency and to meet the deadline associated. GPS still works fine on L1 and L2. I have a feeling there might be some co-site interference that is the issue, although I'd think simple RF issues would have been caught in testing.

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)"