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Delta 2 Rocket Launches 50th GPS Satellite
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."
Its just you (and maybe some friends), no real pressure. Plus its an actual trek (ranges from in-city, to some caches are ones that need Scuba or moutain gear or whatever).
;-)
And with geocaching you've just got your GPS, a compass, and maybe a topographic map (if you can get one). None of this fancy cell phones with internet to tell you answers stuff
There is no god
Have you ever thought that conspiracy theories are a conspiracy to make you buy tin foil? I'd worry about why it itches!
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.
Uh, No. SA has been turned off since the Clinton administration and hasn't been turned back on. Ten feet or so is the best accuracy you're going to get without using differential gps.
We have our moments.
I'm not sure how much fuel is required to break orbit and send a satellite to the sun, but I'm pretty sure that an old GPS I satellite doesn't have it. It's easier just to slow the satellite down a bit so it burns up in the atmosphere as it falls to earth, which is what they do. Every US Air Force satellite that goes up nowadays has some sort of end-of-life plan.
First.. Space Junk.
GPS is launched into an orbit some 12,000 miles above the Earth's surface. That orbit has a grand total of about 50 satellites split into 6 different, non-overlapping planes and slightly different altitudes. There are very, very few satellites that go out that far and none have a circular orbit within a few hundred miles of the GPS satellites. Very, very little chance of a collision.
Also, from that height, the satellites lack enough fuel to deorbit or be sent into the sun. In 1992, my Univ of Colorado aerospace engineering lab went down to the control center and we had a nice tour. I asked the officer giving the brief if they intended to establish some sort of parking orbit for dying satellies as they get phased out. He indicated that it was something they would consider as the constellation gets built out.
Secondly..
Paying the bill.
GPS was encrypted from Day 1. The lower resolution receivers we use just are allowed to decrypt the satellites. It is very difficult to get the higher resolution channel.
The US government is perfectly willing to let the other countries contribute to the costs associated with running GPS.
But..
You might want to consider why the other countries are willing to spend billions on a redundant system rather than pay into GPS or use it for free.
When someone spend billions rather than use a free service, something is up.
The US military adamantly refuses to free any of the control of the system up. It is a US *military* asset. As such, it has military utility. They have completely thrown off the commercial channels in the past while engaging in military activities in a region by jiggering with the output to cause the locations to be off. (They can also turn off all the commercial channels on satellites flying over Afghanistan, then turn them back on before the reach the US, for example).
The rest of the world seems to have some qualms about handing the world's major navigation system to a single provider, for some reason.
I think he just hid his cache in the satellite before it went up. Darn, that is going to be hard to get.
"There is no teacher but the enemy."-Mazer Rackham
- 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.
2. The satellite launched was a Block IIR vehicle. Block IIR-M and IIF vehicles are still in a very low orbit (close to sea level..haven't been launched.)
3. We can't burn satellites in from semi-synchronous orbit (the GPS orbit) using today's technology. When they're disposed of we kick them away from the earth a couple of hundred kilometers. Orbital degradation is slight at semi-synchronous, but the satellites will interfere with each other in about 6,000 years. I hope we'll be able to clean it up before then.
4. GPS Signals arrive on two frequencies, L1 (L1 = 1575.42 MHz) and L2 (L2 = 1227.6 MHz). C/A code (which is FREE as in air to civil users) is modulated onto the L1 carrier signal. It has never been encrypted. It has been degraded (selective availability, the method of degradation, was turned off in 2000) but is now every bit as accurate as the military signal. The only significant advantage the military receivers have is the ability to correct for ionospheric defraction using both frequencies.
5. The major driver behind Galileo (EU GPS) is economics. Basically the US has a handle on a 12 billion dollar industry and the EU wants its share. They're expecting to charge money for the same service the US gives out for free! Somebody failed economics.
Feel free to respond with any questions, I'd love to answer them.