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. ;)

Re:Followup on the story

[digitig]

Well, if you don't like it, you're free to build and deploy your own damned GPS system. Don't have hundreds of billions of dollars to spare? Don't have a national interest in precision, real-time mapping? Then shut the hell up.

You called?

Re:Followup on the story

[morgan_greywolf]

I never said I was complaining about it (see the smiley at the end), but if I were, I'd have every right to since, as a U.S. citizen and tax payer, they are using my hard-earned tax dollars to build it.

I can fully understand why the military would use this approach, and I actually agree with the capability so long as it isn't abused. Unfortunately, I'm intimately familiar with my government. :(

Re:Followup on the story

[digitig]

Yeah, cuz it's not like Galileo was purposefully designed to be easy to jam in the event of hostilities..... oh wait......:

Any satnav system is going to be easy to jam. I used to know somebody who had a cottage industry manufacturing GPS jammers for the UK military; commercialised they would have been cheap enough to drop as chaff. The only issue with Galileo is that it and GPS can be jammed independently.

The US did not want to lose the ability to themselves use accurate [Global navigation satellite system] while denying enemies the use of accurate GNSS. Some US officials became especially concerned when Chinese interest in Galileo was reported.

This is what led to some US officials to go as far as threatening to potentially shoot down Galileo satellites in the event of a conflict.

Even before Galileo was announced -- and certainly before the Chinese became interested -- the US DoD announced that in a conflict any ground stations for such a system would be "valid military targets, even if on friendly soil". So that bit about setting up your own satnav system also needed to have the rider "and you are confident that you can take on the US military and win".

What's The problem?

[GreenTech11]

Really, what is the problem with this, at least they found out something was wrong before they accidentally blew something up. Most satellites are getting on a bit, so that there are tech issues shouldn't be worrying, and this is an endorsement of the ability of people to pick up the problem in the first place.

Re:What's The problem?

[AlecC]

"... which was launched in March". That is not "getting on a bit" - it says that replacements are not fully-functioning copies of the originals, which is worrying.

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:What's The problem?

[Bakkster]

"... which was launched in March". That is not "getting on a bit" - it says that replacements are not fully-functioning copies of the originals, which is worrying.

"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"
In other words, a small workaround is needed, but the satellite will be just fine. If you only knew how often this happened in engineering.
"The degraded signals are accurate only to about 20 feet, versus about two feet for typical GPS signals, the article stated."
Sure, this should have been picked up in testing, but it's not like testing something like this is easy. The accuracy needed to detect something of this magnitude is pretty staggering.

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)"

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

[Sporkinum]

It's not that it doesn't work, it's just that if your GPS happens to be getting a time signal from that one particular satellite, the accuracy might be degraded. The article said +- 20 ft. That's not a big deal. It may be if you were using the GPS to land a plane though. A GPS only needs 3 time signals to triangulate, but can be more accurate if it can see more signals.

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

Re:yet another justification

[Dare nMc]

A GPS only needs 3 time signals to triangulate,

it can continue to track with 3 time signals (since it can rule out some incorrect solutions, based on a physical movement constraint), but can only triangulate with a minimum of 4 inputs. 3 points works in a 2d (IE draw circles on a paper) sense, GPS are calculating intersections of 3d Orbs. It is also possible for terrestrial GPS to assume your the solution located on the surface of earth. Technically a GPS only needs some 4th bit of info, since you are always moving in relation to the satellites, it is possible to use that movement to fine tune your position over time, but most handheld GPS's don't have that bit of calculus and require at least 4 satellites, then assume a maximum movement if you drop to 3.

Re:yet another justification

[Dare nMc]

A false solution way off the earth, but not all of them. If you imagine 2 spheres interacting where the satellites are both straight above you at very close distance, you end up with possible solutions being in one big elliptical arc, a good portion being away from the earth. When you add in a third source, they must intersect in at least 2 locations. But because the satellites are very close together your most likely at 4 intersection points, 2 will be in deep space, 2 will be in the earths sphere. The further apart the centers of the spheres the more circular the solution from 2 satellites, the less likely multiple solutions. So if you got good solutions from satellites on opposite ends of the earth, then 3 is good, you won't get that unless your really high though.

Of course that is all assuming a perfect measurement, add in a little uncertainty in the time dimension (all of your distances are going to be a slightly different moments in time, but within a few microSeconds) and with the closeness of the GPS satellites (relative to your location) your 4th source is a absolute requirement.

As you say, a little ground based info goes a long ways, partially because it is from such a different direction and distance, its accuracy can even be less.

Copyright Violation

[jimand]

Doesn't "re-kindling" violate one of Amazon's copyrights?

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

[morgan_greywolf]

Have you ever tested new code with new features and found some bugs? That's why you do testing.

Can someone please explain this to Microsoft? In words they can understand? :-P

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.

Re:GPS will be just fine

[jamesh]

Can someone please explain this to Microsoft? In words they can understand?

If you don't work for Microsoft, no explanation is necessary. If you do work for Microsoft, no explanation is possible.

(with apologies to whoever I paraphrased)

Re:GPS will be just fine

[digitig]

I work at Microsoft, we just ship, ship and ship. What is this testing you speak of?

It's what you do to the installed software, to make sure the user has paid for it.

solution:

[space_hippy]

Buy an atlas.

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.

Re:Soloution?

[Anonymous Coward]

What the hell does space tourism has to do with ANYTHING? It's a STUPID idea and will only be available for the super-rich, and will make the owners of their company super-rich.

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:Soloution?

[RenderSeven]

There are also a lot of military R&D programs that are lean, DARPA in particular. They are dubiously famous among contractors for pushing slim margins, compressing schedules, adding features, and generally insisting on maximizing their bang for their buck. Some of their programs may seem silly but many are based on improving military cost-effectiveness and ROI. The latter obviously dont get the same media coverage.

Re:Soloution?

[TooMuchToDo]

Air travel was once only for the rich as well. The wealthy typically underwrite new/cutting edge services/technologies/etc, eventually bringing down their cost.

Re:Soloution?

[SkyDude]

.....and generally insisting on maximizing their bang for their buck.

One might think they're part of the dreaded private sector with that mindset.