Become a fan of Slashdot on Facebook

 


Forgot your password?
Close
typodupeerror
×
Space United States Technology

Doubts About Future GPS Reliability 213

Posted by Zonk from the ground-control-to-major-tom dept.
loped_index writes "IT Week reports that the U.S. GPS system is in a delicate state, and that full coverage could be lost if older satellites fail faster than the current rate. From the article: 'The system relies on a network of satellites, which cannot be repaired once launched and have a limited lifespan. Sixteen of the present 28 satellites were built to last seven and a half years, but are now between eight and 14 years old. Twenty-four satellites are required for full coverage.'"
This discussion has been archived. No new comments can be posted.

Doubts About Future GPS Reliability More

Doubts About Future GPS Reliability

Comments Filter:

  • Oh dear (Score:4, Funny)

    by Britissippi ( 565742 ) on Friday October 14, 2005 @05:15PM (#13793955) Journal
    We'll never find them when they fall then..?

  • Always good to know... (Score:3, Funny)

    by Nom du Keyboard ( 633989 ) on Friday October 14, 2005 @05:15PM (#13793957)
    Always good to know I'll have something more to worry about this weekend. I was afraid I was going to run short.
  • I guess we shouldn't have jettisoned WBS [nist.gov] so quickly.

  • Well... (Score:3, Funny)

    by Sheetrock ( 152993 ) on Friday October 14, 2005 @05:17PM (#13793975) Homepage Journal
    Given that these things are about trying to figure out where you're going, we're close to the point where we don't need satellites for them anyway.

    When enough people have them, it'll be just as helpful to have the devices communicate with each other and work out amongst themselves where you're trying to go. Especially when you figure in the possibility of triangulating with cell towers.

    It's how the Internet works.

    • Re:Well... (Score:5, Insightful)

      by merreborn ( 853723 ) on Friday October 14, 2005 @05:27PM (#13794046) Journal
      we're close to the point where we don't need satellites

      That idea falls apart when you're in, say, the alps. Or the sahara. Or most of the planet.
      • Wasn't it the US Navy that started this whole GPS thing?
        Something about knowing where you are and where you're going...

      • Re:Well... (Score:2, Insightful)

        by Asetilean ( 540060 )
        And, last time I checked, it was looking kinda difficult to build stationary cell towers on the ocean, nevermind a pesky lack of demand...

        Plus, air traffic is now highly dependant on GPS and most cell antennas aren't aimed up at the sky.

        So, for imprecise civilian needs (tell me how to go from here to there), a cell tower based nav system might be fine. But GPS is capable of providing a whole lot more than that.
        • The Pacific ocean is 60060700 square miles. The cost of deploying GPS is about $3B, give or take a few orders of magnitude. Assuming that you would need 1 tower per square mile, you could spend $50 per tower - which might actually be possible for something just floating around transmitting a position beacon.

          Not necessarily impossible... just unlikely!
          • You might be able to BUILD them for $50 a piece. (Though even this is highly unlikely if it's a government project.) But you sure as hell couldn't distribute them across 60060700 square miles for $50 a pop. Forget about monitoring and maintaining them. Also, ground based transmission makes all sorts of other problems.

    • Re:Well... (Score:2, Interesting)

      by camt ( 162536 )
      When enough people have them, it'll be just as helpful to have the devices communicate with each other and work out amongst themselves where you're trying to go. Especially when you figure in the possibility of triangulating with cell towers.

      Except when there is no cell coverage (which is far from "full coverage") or where there aren't very many other people (tramping/geocaching through remote areas or national parks). Not to mention that would require all those devices to transmit as well as receive, incr
    • Especially when you figure in the possibility of triangulating with cell towers.

      The proper functioning of adjacent CDMA cell towers (i.e. Sprint, Verizon in the 1.8 GHz bands, and by US West in the 800 MHz bands) must be synchronized within 10 microseconds to support what is called "soft handoff" [rr.com].

      CDMA base stations use the GPS constellation to maintain synchronization. The satellites themselves need precise clock synchronization, and this is exported to GPS receivers.

    • Yeah, the thousands of cell towers that dot the pacific ocean really are a better way to navigate than an old 70's satellite system.

  • Well that sucks... (Score:2, Funny)

    by Anonymous Coward
    First the Internet, now this. :/

  • Yada yada (Score:5, Insightful)

    by Red Flayer ( 890720 ) on Friday October 14, 2005 @05:19PM (#13793984) Journal
    Is it just me, or does everyone else also realize we're still capable of launching new satellites into orbit?

    Is there a concern about current GPS-enabled devices reading signals from new satellites?

    I'd be shocked if there is not money available in the Pentagon Budget, or elswhere, for replacement of needed satellites. Then again, cutting funding of absolutely necessary programs is a great way to dodge real budget cuts... since there will need to be a "special appropriation" to cover the shortfall.

    • Re:Yada yada (Score:5, Informative)

      by Osiris Ani ( 230116 ) on Friday October 14, 2005 @05:27PM (#13794044)
      Indeed, I'm sure I remember reading something somewhere [slashdot.org] about the US government recently launching newer, more accurate GPS satellites. Of course, what we need these days is more alarmist rhetoric, so I suppose this is apropos.

    • Re:Yada yada (Score:5, Insightful)

      by Rakishi ( 759894 ) on Friday October 14, 2005 @05:32PM (#13794080)
      Yeah, why replace them when they're still working fine. That would be a waste of money, extra sats which age and provide little benefit. I mean, unless 5 fail in the time it takes to get a new one up there is no problem. Given that only 2 fail per year I don't see that happening anytime soon.

      I mean, come on look at this idiotic statement:
      'Bonnor said launches of new satellites are "only just keeping up" with current losses of around two satellites per year.'

      What they hell is the US supposed to do, send up more satellites than they lose and waste money keeping up sats when only 24 are needed (+ a few redundant ones)?
    • The concern is that 4 or 5 satellites will all fail in the same year. The current pace of only replacing 2 a year would cause gaps in the GPS coverage. Just because you allocate the funds doesn't mean you get to launch the replacement satellites tommorow to fix the problem. Not knowing much about satellite launch preparation I'm guessing it might take a month or two to get everything ready for launch.

      • Re:Yada yada (Score:4, Interesting)

        by GileadGreene ( 539584 ) on Friday October 14, 2005 @06:41PM (#13794527) Homepage
        The current replacement rate is designed to slowly phase out existing satellites before they hit their (statistical) expected end-of-life. It's not intended to cope with unexpected (i.e. low probability, such as 4 or 5 satellites dying at once) failures. Nor does it have to. The GPS constellation includes a number of "on-orbit spares" (i.e. spare satellites already in the GPS orbits), which can be used to ensure continuous availability in the face of an unexpected failure. AFAIK the typical scenario is something like:
        1. GPS satellite fails
        2. On-orbit spare is activated
        3. New satellite launched some months later becomes a spare
        4. Life goes on
        • Based on what you an others have said this entire article should be marked troll. The most interesting comment was that satellite failure isn't unexpected as the people who manage them get information on the health status of the satellites.

    • Working at the GPS hub (Score:5, Informative)

      by iamweezman ( 648494 ) on Friday October 14, 2005 @05:55PM (#13794239)
      As an active duty Air Force tech controller I work almost daily with the satellite operators that "fly" the GPS satellites. Some of their systems are more than antiquated, but still function with adequate redundancy built in. Although the lifespan might have been eclipsed the telemetry data recieved by the operators give them the state of health of the satellites which allows them to plan for future launches.

      In fact, a newer GPS satellite was just launched weeks ago. As stated before, the DOD has a special spot in their hearts for GPS. The GPS operators get treated extra special because of the US military's reliance on them. There are already plans in place for each satellite to be super-orbited when the time comes and for a new launch to follow.

      In other words, if the military isn't worried about it, neither should we be.

      • Absolutely (Score:5, Insightful)

        by Sycraft-fu ( 314770 ) on Friday October 14, 2005 @06:59PM (#13794661)
        People seem to forget that GPS is a military system, developed for military purposes. They opened it up for civilian use and that's wonderful, it's been a massive boon, but it was developed for the US Military alone. It is also the prime location system for just about all military units, from individual soliders up to large ships these days. While I'm sure the military COULD function without it, it would seriously screw things up.

        It's a strategic asset, and they aren't going to let it fail. If it was all private run, ok maybe then there'd be a worry that someone would decide to cut costs on it and let it slide, but it's the military's toy and there's no way in hell they are letting it fail.

        All the military implications aside, US commercial intrests rely very heavily on GPS these days and letting it fail would also not be in the economic intrest of the US government.
      • In other words, if the military isn't worried about it, neither should we be.

        I just love it when someone says, "I'm from the government. Trust me."

        Capturing Osama bin Laden and building a functioning democracy in Iraq are even greater priorities for the military than maintaining GPS operations. According to the Commander in Chief, things are going swimmingly on both of those fronts so if I follow this logic, if the military is not worried about Iraq or Osama, neither should we be.

        • Nice strawman, but your argument doesn't hold water.

          First, when did you discover their priority list? And second, just because George Bush is one of the biggest liars ever to disgrace the White House, and Donald Rumsfeld is by far the biggest liar ever to hold the Secretary of Defence chair DOES NOT mean the lies extend to our military. (It's really sad, when you think of it, that we can trust our Army to tell us the truth far more than we can trust our elected officials.)

          Anyway, it's very simple. It

          • I was too snide in my comments, and for that I owe the poster an apology.

            But my major point stands. The source is someone posting to slashdot, claiming privileged information that is not subject to independent verification, telling us to trust him because he's part of a government agency (specifically the military).

            Just because someone is a government functionary does not mean that I trust him when he makes claims based on evidence that's not available for scrutiny. I'm not saying that I lose sleep wor

  • oops (GPS goes out) (Score:4, Funny)

    by pmike_bauer ( 763028 ) on Friday October 14, 2005 @05:20PM (#13793986)
    Toto, I don't think we're in Kansas anymore.

  • There is only one solution... (Score:3, Funny)

    by Anonymous Coward on Friday October 14, 2005 @05:21PM (#13793992)
    We MUST hand over ALL CONTROL of the GPS system to the UN, to save it from destroying itself...
  • Everything dies, why is this news? GPS is an important and critical system, it will be maintained through new satellites.

  • I think I'm still OK (Score:5, Funny)

    by $RANDOMLUSER ( 804576 ) on Friday October 14, 2005 @05:22PM (#13794008)
    I use one of these [wikipedia.org] as my GPS.

  • Backup Satellites (Score:3, Informative)

    by g4n0n ( 659895 ) on Friday October 14, 2005 @05:23PM (#13794015)
    They fail to mention that there are a number of backup satellites sitting up there, waiting to go into the consellation if any fail.

  • May not be that important, really.... (Score:3, Funny)

    by ip_freely_2000 ( 577249 ) on Friday October 14, 2005 @05:24PM (#13794025)
    "Twenty-four satellites are required for full coverage

    As long as the satellites fail over someplace unimportant like Europe, why should we care?



    Please be gentle with my karma!
    • You're joking right?

      For those few that don't get it, the satellites aren't geostationary, so a failed satellite (once the minimum # is reached) will probably create a dead spot that moves around the planet, in which GPS service is degraded.
    • Please be gentle with my karma!

      My dogma ran over your karma.

      Wait..uh..I think I got that backwards...but you get the point.

  • No news here (Score:5, Insightful)

    by adsl ( 595429 ) on Friday October 14, 2005 @05:28PM (#13794056)
    If you put up satellites at a quicker rate then you have too much redunancy in the skies and too much junk in space. It's all a balance, as it should be. Another timely "This is why Europe should run everything" spin story. Be good if Europe invented something really new and useful, for American's to play with (for free)....

  • Why this scare tactic? (Score:3, Insightful)

    by rolfwind ( 528248 ) on Friday October 14, 2005 @05:28PM (#13794059)
    The US government/military has a humongous interest in keeping the system up - why be scared about it? It will keep plodding along.

    Or am I missing something here?

  • Ahh, yeah.... (Score:5, Insightful)

    by killtherat ( 177924 ) on Friday October 14, 2005 @05:30PM (#13794070)
    Given the military's dependence on GPS, do you think they would allow one second of interuption? And they use it on almost every corner of the globe. They would notice holes in service much sooner then you ever would.
    Call this article what it is, FUD to prop up EU's Galileo.
  • It sounds like they are already in the midst of replacing it - check out SpaceFlightNow [spaceflightnow.com]. The new series is going up with the next generation in the works. Maybe it's just a matter of keeping at or above the crucial 24 limit...?

  • Bush Administration Announces... (Score:3, Funny)

    by ENOENT ( 25325 ) on Friday October 14, 2005 @05:34PM (#13794100) Homepage Journal
    new "Faith-based" navigation system...

    Film at 11.

  • blind (Score:3)

    by -ryan ( 115102 ) on Friday October 14, 2005 @05:35PM (#13794102)
    the military lives by GPS these days, no GPS (or poor coverage) would almost halt military operations above the level of a patrol on foot with compass and map. but any infantryman will tell you, there's nothing more dangerous than a cherry ass Lt. with a map.

  • They're up longer BECAUSE they didn't fail (Score:5, Insightful)

    by MDMurphy ( 208495 ) on Friday October 14, 2005 @05:40PM (#13794137)
    It's not that the satellites were just left up there longer because they couldn't be replaced, it's because they've lasted longer than they were intended to. Kind of a "if it's not broke, don't fix it" philosophy.

    With redundant satellites and constant monitoring from the ground, it's possible to let one go until it fails, mark it as "bad" and replace it a little later.

    The article is wrong about 24 satellites being required for full coverage. A full set is 21 with 3 as spares.

    The article also implies that the satellites are failing at greater than planned rate, when the opposite is true.

    It's probably just a coincidence that the guy quoted in the article, Norman Bonnor, is a backer of the European counterpart to GPS: Galileo. It's not like he'd have an interest in bashing the GPS system to help further justify Galileo's funding?

    • Re:They're up longer BECAUSE they didn't fail (Score:4, Funny)

      by thewiz ( 24994 ) * on Friday October 14, 2005 @06:01PM (#13794270)
      It's not that the satellites were just left up there longer because they couldn't be replaced, it's because they've lasted longer than they were intended to. Kind of a "if it's not broke, don't fix it" philosophy.

      Actually, the military's philosophy is to over-engineer items like satellites to make sure they last awhile. If you don't believe me, read a couple of the military specifications (MIL-SPEC) manuals. There is a joke that goes:

      Q: What is an elephant?
      A: A mouse built to MIL-SPEC.

  • GPS Constellation status, with launch dates (Score:5, Informative)

    by Anonymous Coward on Friday October 14, 2005 @05:45PM (#13794176)
    From: ftp://tycho.usno.navy.mil/pub/gps/gpstd.txt [navy.mil]

    A. BLOCK II/IIA/IIR/IIR-M INDIVIDUAL SATELLITE STATUS

    SVN PRN
    15 15 Launched 01 OCT 1990; usable 15 OCT 1990; operating on Cs std
    24 24 Launched 04 JUL 1991; usable 30 AUG 1991; operating on Cs std
    25 25 Launched 23 FEB 1992; usable 24 MAR 1992; operating on Cs std
                        Scheduled unusable 20 Oct 0130 to 1330 UT for repositioning
                          maintenance (NANU 2005131/14 OCT)
    26 26 Launched 07 JUL 1992; usable 23 JUL 1992; operating on Rb std
    27 27 Launched 09 SEP 1992; usable 30 SEP 1992; operating on Rb std
    29 29 Launched 18 DEC 1992; usable 05 JAN 1993; operating on Rb std
    30 30 Launched 12 SEP 1996; usable 01 OCT 1996; operating on Rb std
    31 31 Launched 30 MAR 1993; usable 13 APR 1993; operating on Rb std
                        Unusable 14 Apr 1634 UT and will remain unusable until
                          further notice (NANU 2005055)
    32 01 Launched 22 NOV 1992; usable 11 DEC 1992; operating on Cs std
    33 03 Launched 28 MAR 1996; usable 09 APR 1996; operating on Cs std
    34 04 Launched 26 OCT 1993; usable 22 NOV 1993; operating on Rb std
    35 05 Launched 30 AUG 1993; usable 28 SEP 1993; operating on Cs std
    36 06 Launched 10 MAR 1994; usable 28 MAR 1994; operating on Rb std
    37 07 Launched 13 MAY 1993; usable 12 JUN 1993; operating on Rb std
    38 08 Launched 06 NOV 1997; usable 18 DEC 1997; operating on Cs std
    39 09 Launched 26 JUN 1993; usable 20 JUL 1993; operating on Cs std
    40 10 Launched 16 JUL 1996; usable 15 AUG 1996; operating on Cs std
    41 14 Launched 10 NOV 2000; usable 10 DEC 2000; operating on Rb std
    43 13 Launched 23 JUL 1997; usable 31 JAN 1998; operating on Rb std
    44 28 Launched 16 JUL 2000; usable 17 AUG 2000; operating on Rb std
    45 21 Launched 31 MAR 2003; usable 12 APR 2003; operating on Rb std
                        Unusable 13 Oct 0217 to 0905 UT due to repositioning
                          maintenance (NANUs 2005129, 2005130/13 OCT)
    46 11 Launched 07 OCT 1999; usable 03 JAN 2000; operating on Rb std
    47 22 Launched 21 DEC 2003; usable 12 JAN 2004; operating on Rb std
    51 20 Launched 11 MAY 2000; usable 01 JUN 2000; operating on Rb std
    53 17 Launched 26 SEP 2005
                        For more information about PRN17/SVN53, see:
                          http://www.spaceflightnow.com/delta/d313a/ [spaceflightnow.com]
    54 18 Launched 30 JAN 2001; usable 15 FEB 2001; operating on Rb std
    56 16 Launched 29 JAN 2003; usable 18 FEB 2003; operating on Rb std
    59 19 Launched 20 MAR 2004; usable 05 APR 2004; operating on Rb std
    60 23 Launched 23 JUN 2004; usable 09 JUL 2004; operating on Rb std
    61 02 Launched 06 NOV 2004; usable 22 NOV 2004; operating on Rb std

  • I would love to have a well paid job coming up with solutions to "difficult" problems like this. I'd give my employer the first solution for free:

    Launch new satelites that are compatible with the old system!

    then I would charge a fortune for all the other ideas once I had got them hooked. My god I can't believe anyone is even questioning this. It's a total no brainer. Have IQs dropped recently or is it just that all the money has been spent on other things?

  • not with the satellites you wish you had.
  • Since that article was written, they launched a new satellite, as the article mentions at the end. This is the first of the new series, currently in testing and scheduled to be launched as older satellites fail. When the article was written, it was a vaguely reasonable concern that they didn't yet have new satellites ready to send. Also, it's traditional to post stories on a topic in chronological order, so that they make sense.
  • I know that I'm not the oldest person here, but I've been using GPS since before all the satellites were up (~1992?).

    The main problem is that you need a larger view of the sky to see the minimum number of satellites (3-4) -- indoor reception was difficult because you were limited to seeing 1/2 of the sky.

    With fewer satellites, their geometry in the sky can become a problem -- if they are too close together, you'll get more measurement error (or, technically, GDOP [colorado.edu]).

    Back then, if you really needed a gps fix,

  • Such BS (Score:3, Insightful)

    by chadseld ( 761331 ) on Friday October 14, 2005 @06:36PM (#13794502)
    There is nothing to worry about, this article is inflammatory. Do you have any idea how many weapon systems rely GPS? I work in the defense industry, GPS is everywhere. When the current satellites start falling down, we will send up more. In fact, those plans to 'weaponize' space are mostly a reaction to the realization of how important the GPS system is. It is a single point of failure and must be protected. Do you really think the armed forces are going to let the system fail due to neglect?
  • Isn't 1/4 mile accuracy good enough for anybody?
  • ...the EU demands that the US cede control of the Global Positioning System.

  • The GPS system has built-in overkill. At any given time there are about a dozen satellites within view, and a receiver only requires four to work correctly (okay, theoretically only three if you have a clock). So even if we were to lose some of the satellites, GPS receivers would still work.

    There could be some degradation—using more than four satellites will give better accuracy. And a satellite on the horizon will give a weaker signal than one straight above, thus adding noise to the process and po

Slashdot Top Deals

He has not acquired a fortune; the fortune has acquired him. -- Bion

Close