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Delta 2 Rocket Launches 50th GPS Satellite

Posted by timothy on from the more-to-choose-from dept.

wetshoe writes "This CNN article reports that 'the 50th U.S. Global Positioning Satellite has lifted off aboard a Boeing Delta 2 rocket.' It was sent into space to replace an aging GPS satellite. One more reason why geocaching is so much fun."

14 of 188 comments (clear)

  1. Re:Geocaching by Anonymous Coward · · Score: 5, Insightful

    I find it funny that someone carrying a GPS would decry a cell phone user getting answers. How about dropping the GPS and using a compass and topo map ONLY?

  2. Kudos to the US by ergo98 · · Score: 5, Insightful

    I'm well aware that the EU has plans of a GPS type system, however it does seem a bit unfair that the United States foots the bill for virtually the entire world's navigation system. While the system is primarily there for military means, the US could have encrypted the system from day one to avoid non-military use (which is what many other nations would do), or have offered decryption codes to US organizations to give them a competitive advantage. Instead they've offered it free of charge worldwide, even turning selective availability off so that geocaching adventure is even less of an adventure. Perhaps there's an insidius underlying motive (for example getting the world hooked on GPS while keeping their finger on the conceptual power button), but overall it's a praiseworthy thing they've done.

    1. Re:Kudos to the US by gnuman99 · · Score: 3, Insightful

      Maybe because the US can manipulate it? If a rogue nation's army is trying to get to point A using GPS, the US might direct it to trap B instead :)

    2. Re:Kudos to the US by grotgrot · · Score: 2, Insightful

      The US has gone to great lengths to try and stop Europe and Russia from deploying their own systems. They have never explicitly stated the reasons, but most observers come up with defense and control. I'll thank the US the day they stop trying to prevent others from deploying their own systems.

    3. Re:Kudos to the US by pe1rxq · · Score: 4, Insightful

      Actually Russia already has its own system... (From the cold war era) called glonas.

      Jeroen

      --
      Secure messaging: http://quickmsg.vreeken.net/
    4. Re:Kudos to the US by grotgrot · · Score: 3, Insightful

      Yes (it has two s' - Glonass). My point wasn't that other sources (Europe, Russia) have their own, but that the US has been very proactive in trying to prevent widespread use of them. The aviation press has a lot of information about this.

      I have no issue with the US campaigning to prevent widespread use of the other systems, but I am not going to turn around and thank the US for being so magnanimous when in fact they are advancing their own agenda.

    5. Re:Kudos to the US by Anonymous Coward · · Score: 1, Insightful
      afaik the public signal is about 12 feet, but in practice i've seen 4 or 5 feet.

      Those numbers are based on statistics. No one should give an accuracy with out the rest of the story. You need to state the % confidence.

      For example: within 5 m 95% of the time and within 10 m 99% of the time. Most the stats for receiver will list these.

    6. Re:Kudos to the US by Anonymous Coward · · Score: 1, Insightful
      Close enough, but the clocks in most GPS receivers aren't good enough (not atomic clocks), so you need one more satellite than you listed to solve for time.

      Estimated orbits are transmitted as you said. They are called broadcast ephemeris. They are basically predictions made by ground stations, which are relayed by the satellites. The accuracy is poor as you guess, but good enough for most things.

      It's very simple at first, but once you get into GPS seriously, it gets much more complex again. Sure CA code pseudorange solutions like you talk about are simple, but there are far more complex ways to process GPS signals. For example, it's possible with a fixed station to get sub-millimeter accuracy.

    7. Re:Kudos to the US by Nimey · · Score: 2, Insightful

      I hereby declare war on (over)use of the word "kudos".

      --
      Hail Eris, full of mischief...

      E pluribus sanguinem
  3. Re:OFF TOPIC? by Eevee · · Score: 4, Insightful

    It's off topic because it's a GPS launch, not a recon sat launch.

    It's also more than a bit stupid because a Delta II isn't a heavy SLV (space launch vehicle) and a GPS satellite weighs a significant chunck of the possible lauch weight. (The article didn't say what model GPS sat was launched, but assuming it was the newest model, the IIF, then the Delta II couldn't handle two of them, let alone one of the NRO's monster satellites.) If I can look up the sat weight (3758 lbs) and the Delta II lauch capacity (4971 for the configuration used) in under five minutes, then he can look it up too.

  4. er? by EMH_Mark3 · · Score: 4, Insightful

    Geocaching is fun because they replace old GPS satellites with new ones? wtf?

    --
    Burn the land and boil the sea, you can't take the sky from me
  5. Re:Geocaching by Staos · · Score: 1, Insightful

    Have you ever been caching? GPSrs are not nearly that accurate. In a wooded area, there can be as much as a 150 foot error. Add that to tricky hides and rough terrain, it's not as simple as you think.

    --
    In Soviet russia, only old Koreans profit from pictures of Natalie Portman stored on Beowulf Clusters.
  6. Re:Some math by Y2K+is+bogus · · Score: 4, Insightful

    Umm, you aren't counting right.

    That's the 50th satellite launched. That means $105m * 50 over the entire life of the GPS project.

    IIRC, there are only 26 operating satellites, give or take.

    Honestly though, do you believe the gov pays $105m for each satellite in orbit? There are plenty of ways for them to get their money back.

  7. Re:space junk? by nautical9 · · Score: 5, Insightful
    Personally, I've never understood the folks who are worried about space junk/clutter. Consider:
    • it's three dimensional space (different sat's orbit at different altitudes)
    • the imaginary "surface area" for any given orbital altitude is much larger than that of the Earth (and the Earth is really incredibly large, especially when you include the 70% that's the oceans, and the fact a typical satellite or other "space junk" is smaller than a yugo).
    • that all sats' orbits will decay over time, either inward or outward (and really, any sat with a normal decay rate typically won't be around longer than 10 years, sometimes all it takes is a few days or weeks if they can intentionally alter its speed). It's actually quite hard (ie. takes a lot of small course corrections) to keep a sat in perfect orbit.
    • that it's really expensive to put stuff up there, so as a result there really isn't that much physical man-made junk currently in orbit.
    When you visit a site that tracks the orbits of various satellites, it can appear to a layman that there's a whole bunch of stuff up there, but that's usually because each sat is shown as a big blinking dot over a tiny map of the earth. If viewed to scale, of course that dot wouldn't be visible until you zoomed the map in to where you could see cars on the street.

    The only problem is that the space junk can be traveling a few hundred mph relative to each other, so it can make for some pretty spectacular collisions should it ever happen (and its been speculated that certain impressions and chips in the Hubble, for example, were caused by "paint chips", although I'd speculate it's just comet dust or other natural space debris).

    But really, the odds of two bigger-than-a-breadbox man-made objects colliding in orbit has to be astronomically small (forgive the pun). I just don't get what the big fuss is about.