Slashdot is powered by your submissions, so send in your scoop

 


Forgot your password?
Close
typodupeerror
×
Space Technology

Satellite Glitch Rekindles GPS Concerns 101

Posted by samzenpus from the close-enough dept.
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."
This discussion has been archived. No new comments can be posted.

Satellite Glitch Rekindles GPS Concerns More

Satellite Glitch Rekindles GPS Concerns

Comments Filter:

  • Soloution? Pour more money into NASA!

    • Re:Soloution? (Score:5, Informative)

      by PeterBrett ( 780946 ) on Thursday June 18, 2009 @07:02AM (#28372135) Homepage

      Soloution? Pour more money into NASA!

      Um, the GPS constellation belongs to the USAF.

      • Um, the GPS constellation belongs to the USAF.

        Right, the extra money would obviously be so that NASA could battle the air force in space to take control of the GPS, at which point we'd dump even more money into NASA to fix the GPS.

  • Could it be related to this ? ;-)) (Score:5, Funny)

    by ls671 ( 1122017 ) * on Thursday June 18, 2009 @07:05AM (#28372169) Homepage

    Could it be related to this ? ;-))

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

    Hehe... ;-)

  • Followup on the story (Score:5, Funny)

    by BadAnalogyGuy ( 945258 ) <BadAnalogyGuy@gmail.com> on Thursday June 18, 2009 @07:06AM (#28372177)

    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 (Score:5, Informative)

      by morgan_greywolf ( 835522 ) on Thursday June 18, 2009 @07:27AM (#28372337) Homepage Journal

      Pretty much. Of course, any current problems with GPS are likely to be fixed once GPS III [globalsecurity.org] 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: (Score:2)

        by IflyRC ( 956454 )
        All part of SKYNET's plan....
  • 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: (Score:2, Interesting)

      by AlecC ( 512609 )

      "... 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? (Score:4, Interesting)

        by Richard_at_work ( 517087 ) on Thursday June 18, 2009 @08:08AM (#28372725)
        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.
        • As I recall GPS was developed to guide our ordinance and destroy theirs. Being able to find the local store is a secondary benefit. I also recall a time when every midshipman on every US Naval vessel was required to know how to use a sextant. Query: what happens if something knocks GPS out completely? One EMP can ruin your whole hemispheric constellation

      • Re: (Score:3, Informative)

        by Bakkster ( 1529253 )

        "... 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 tes

      • Re:What's The problem? (Score:4, Informative)

        by JohnnyComeLately ( 725958 ) on Thursday June 18, 2009 @12:31PM (#28376533) Homepage Journal
        RichardAtWork nailed most of the response, but the OP never cites an article. With Google, I found an article here [survapedia.com] 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 (Score:3, Insightful)

    by mikerubin ( 449692 ) on Thursday June 18, 2009 @07:13AM (#28372217)

    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: (Score:3, Informative)

      by Sporkinum ( 655143 )

      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: (Score:3, Informative)

        by Dare nMc ( 468959 )

        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 i

        • This is what I love about slashdot. I may know a little about a subject, but there is always an expert that can expand my knowledge. Thanks!

        • triangulate

          GPS uses trilateration, not triangulation.

        • Close, but no cigar:

          All receivers should be assuming you are on the surface of the earth. There are only two possible solutions with a three bird fix, and one is either way off the surface of the earth and/or moving at an improbable rate of speed. You need the fourth to get a lock, though, because you need to solve four things, not only the ambiguity of a three sphere intersection, but also the correct time.

          Once you have your receiver clock synched, though, you can run with three birds as long as you are

          • Re: (Score:3, Informative)

            by Dare nMc ( 468959 )

            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. Th

          • Re: (Score:2)

            by azrider ( 918631 )

            All receivers should be assuming you are on the surface of the earth.

            Ever been on an aircraft?

      • 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.

        Not even, since there are integral status/reliability bits in the GPS constellation download. The "faulty" satellite is marked as unusable (just as it has been since it was launched in March, because it's in testing), and will be ignored by receivers. There are more than sufficient other satellites to cover the sky, so... no problem.

    • After 8 years of field service I still use a road map and Google Maps. I just don't need another crutch

      I'll get off your lawn, shall I?

      • Re: (Score:2)

        by ArcherB ( 796902 )

        After 8 years of field service I still use a road map and Google Maps. I just don't need another crutch

        I'll get off your lawn, shall I?

        My GPS tells me that I'm on my own lawn!

    • We're all impressed, grandpa. I bet you can fix the axle on an ox-cart faster than anybody, too.

    • Re: (Score:2)

      by geekoid ( 135745 )

      GPS is only a crutch if you don't also use your brain and don't value your time.

      "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."
      hahahahahha..

    • This comment is mind-numbingly stupid.

      Do you walk to work because you refuse to use the "crutch" of a car, bicycle, or mass transit? Do you grow your own food because you refuse to use the "crutch" of modern agricultural practices? Do you refuse medicine because you refuse to use the "crutch" of modern sterile techniques? Do you live in a cave because you refuse to use the "crutch" provided by the building trades?

      GPS, calculators, google maps, the road map, and the car you're driving are all conven
      • What the hell?!

        Some people like to be self-reliant. It isn't ludditism. I know how to do simple math in my head. A lot of people don't. The girl at the store yesterday had to call a manager because I found a penny after she had typed in the amount I had given her. That is mind-numbingly stupid.

        If you can't see the benefit of being able to do simple math quickly in your own head in a world full of calculators then you are a retard.

        If you can't see the benefit of being able to navigate around town whe
        • So exactly which part of "assistive technologies designed to make hard work easy" did you not understand?

          I never stated that ignorance of simple math, or inability to find your way around your home town was a good thing. Refusing to use a GPS or a calculator out of hand because it's somehow "purer" and "less of a crutch" to do it yourself is ludditism, and is retarded.

    • Re:yet another justification (Score:4, Informative)

      by joggle ( 594025 ) on Thursday June 18, 2009 @11:23AM (#28375445) Homepage Journal

      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 [uscg.gov]

    • Yes, you're much better off being distracted by mapreading, or juggling Google Maps printouts (and trying to read their directions in 6-point fonts) than having the damn satnav read out clear instructions so you can keep your eyes on the road.
      I prefer giving up a bit of sense of direction/location, even using a suboptimal route to the nightmare that is manual navigation without a second person in the car.
      Also, the routes Google Maps generates aren't any better than those generated by a satnav.
      Checking the r

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

  • GPS will be just fine (Score:5, Insightful)

    by DaveInAustin ( 549058 ) on Thursday June 18, 2009 @07:27AM (#28372333) Homepage
    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: (Score:2, Insightful)

      by morgan_greywolf ( 835522 )

      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 (Score:5, Informative)

      by CosmicRabbit ( 1505129 ) <jppequenao@noSpAm.gmail.com> on Thursday June 18, 2009 @07:43AM (#28372457)
      Well, from TFA the problem seems to be the new L5 [wikipedia.org] 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.
      • They'll probably just adjust some software filters, or modulation settings to move the interference out a little bit. It sounds like a big issue, but will probably just required some firmware changes to alter the power spectral density at some points. The L5 is 3dB more powerful for right now, so they could also just decrease the power a bit to possibly counter-act the interference. There are all types of reasons that I can think of as to why the two may be interfering some other than just a basic, un-fi

      • Re: (Score:2)

        by Andy Dodd ( 701 )

        I find it hard to believe a new frequency would interfere with one of the existing ones.

        It makes a lot more sense that a software bug would degrade existing L1/L2 signals, or additional codes being broadcast on the L1/L2 frequencies would impact legacy signals on those frequencies.

        Probably some idiot journalist translated "satellite that adds L5 isn't performing as well on L1 and L2" to "L5 is causing problems on L1 and L2".

    • Re: (Score:2, Funny)

      by TeXMaster ( 593524 )

      Have you ever tested new code with new features and found some bugs?

      No, we only write perfect code.

    • That's why you do testing

      in production...

  • solution: (Score:3, Funny)

    by space_hippy ( 625619 ) on Thursday June 18, 2009 @07:44AM (#28372469)

    Buy an atlas.

  • My GPS is just being realistic when it tells me: "You're neither here nor there."

    • Re: (Score:2)

      by PhxBlue ( 562201 )

      My GPS is just being realistic when it tells me: "You're neither here nor there."

      But it knows exactly how fast you're moving. (Rimshot!)

  • Not as big of a deal as they're making it look (Score:5, Insightful)

    by Logical Zebra ( 1423045 ) on Thursday June 18, 2009 @08:43AM (#28373095)

    This is a problem with one satellite. ONE. The problem is with a brand new generation of satellite [foxnews.com] 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.

    • How do you know if the sky is falling or not?

      GPS is defective now. It's how we determine this sort of thing. :)

  • Did the glitch lead to a British warship going to Chinese territorial waters and be attacked by a drilling torpedo and then the Chinese MIG's getting shot down by SAMs coming from a stealth ship?
  • One thing to keep in mind... In North America, at least, the entire telephone/telecom/internet functionality relies on the GPS satellite system as its timing source. I work for a major North American phone/cellular/ISP service provider, and I can tell you that we have what's called a Bits Clock (which receives it's timing from a TimeSource box, which is fed via GPS signals) and without it, the entire communications system would begin to fail after about 30 days of no GPS service.

    This timing provision is

  • Do not worry left-side-of-the-pond-ers. Europe will step in [wikipedia.org] a 'save your asses' :-)

    • "Galileo, Galileo, Galileo, Galileo, Galileo figaro, here we GO-OH-OH-OH!!!!!"

      Well, if GPS is the king of sat-nav systems, then Galileo will certainly be the "Queen." ;-)

    • No quite the same as what we did for Europe [wikipedia.org] , but thanks, we'll take all the help we can get.

Slashdot Top Deals

Every successful person has had failures but repeated failure is no guarantee of eventual success.

Close