Po1ar
Silver Cacher
Posts: 122
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Post by Po1ar on Feb 13, 2008 9:35:33 GMT -9
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Post by oleruns on Feb 13, 2008 10:17:13 GMT -9
Here is my guess – It would only work on one side to a limited degree. First, the software would have to be adapted to recognize the possibility that the unit would be on the moon. The satellites are in a geosynchronous orbit meaning that they stay in the same part of the sky relative to the earth, matching its rotation not the moons. (I love Star Trek where they put the ship in a geosynchronous orbit and the next scene the ship is doing laps around the planet.) But the satellites are in a known location. The moon’s location in its orbit is known so it would be possible. The signal is directed at the Earth but because the signal really would not degrade in space or in the nonexistent atmosphere, it may be able to be picked up. So, with that I would say with some major work, it could work on the sea of tranquility or my favorite – the sea of pain and get you to within a quarter mile or so. (just a guess)
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powmia
Silver Cacher
Caches Found/Hidden xxxx/x
Posts: 208
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Post by powmia on Feb 13, 2008 15:33:30 GMT -9
He wanted to know if a GPSr would work if you were on the moon? If I were on the moon it probably would not work. Mine never seems to work correctly when I really need it to be functioning perfectly. I don't believe the signal strength would be strong enough to extend to the moon surface. With the moon navigating around the earth one might not at all times have enough satellites to get a proper location fix. It would probably function properly upon reentry into the earth/satellite rotation area.
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Post by NorthWes on Feb 13, 2008 18:09:38 GMT -9
Hmmm... is your husband in the USAF's space systems command? I bet he already knows this answer... If the receiver was 'buff enough' to pick up the satellite signals and had the correct algorithms loaded in its memory chip to interpret them it'd work on the moon. Otherwise, if it didn't have programming set up to interpret the signals correctly (i.e. if it's an off the shelf GPS unit like we play with every day) it's gonna think it's really really really high up above sea level... and it's gonna give you wierd locations on the earth's surface. It's 'just' math that's being done inside the little receiver to 'multi'-triangulate the GPS satellite signals - but math that's set up for the earth's surface/elevations, not the moon's. Wow - signal should be good there - no trees or buildings - what a view! My two cents... and remember, I'm no rocket scientist either (but I have stayed at a Holiday Inn Express before!) This would be a fun one to post on the national geocaching.com forums! I'm sure the real experts (the manufacturers) would respond with a better answer...
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powmia
Silver Cacher
Caches Found/Hidden xxxx/x
Posts: 208
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Post by powmia on Feb 14, 2008 4:50:08 GMT -9
This would be a fun one to post on the national geocaching.com forums! I'm sure the real experts (the manufacturers) would respond with a better answer... Yes, but the novice replies are more entertaining and readable.
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Post by Malcore on Feb 14, 2008 13:45:16 GMT -9
I happen to watch a program on tv a few days ago about just how the system works. If I remember right heres how it works. Each satelite transmits a omni directonal signal so you would be able to get reception on the moon. Remember in space signal strength doen not degrade much in such a chort distance. But then it gets tricky. Remember that the gps calculates its posistion by calculating the time the signal takes to get to the gps from the individual satelites. Now this wouldn't be a problem if the gps was programed to take the distance from here to the moon into concideration. But It still wouldn't work corrrectly... Why? Because the system is designed to calculate a stationary point on earth relative to the moving satelites. Remember the moon is moving relitive to the earth AND the satelites. So as it is you would get a possition but it would be changing and say you were moving at about 2300 miles per hour, even if you were standing still on the moon. Most of this is just off the top of my head so im not sure how true most of it is. But it sure is fun thinking about how it would work. One last thing, Im sure if the people who designed the system wanted to, I bet they could do the programming to make it work correctly on the moon. Also, being that NASA has plains on going back to the moon, you never know, they may already be planning on doing just that.
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Post by Malcore on Feb 14, 2008 13:51:14 GMT -9
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powmia
Silver Cacher
Caches Found/Hidden xxxx/x
Posts: 208
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Post by powmia on Feb 14, 2008 15:16:51 GMT -9
HAY, I wonder if Groundspeak would let me put an earth cache (moon cache?) on the moon. As Rocky would say, "Go for it!".
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Post by NorthWes on Feb 14, 2008 15:26:49 GMT -9
This would be a fun one to post on the national geocaching.com forums! I'm sure the real experts (the manufacturers) would respond with a better answer... Yes, but the novice replies are more entertaining and readable. Frankly, the 'novice replies' are half the reason I read the geocaching.com forums!!! Of course, I'm much more sober-sided in my perusal of the GeocacheAlaska forums... Really! What else could you expect from a guy who caches with Standard Poodles? ;D
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Po1ar
Silver Cacher
Posts: 122
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Post by Po1ar on Feb 18, 2008 13:42:21 GMT -9
My husband says to say Thanks for all your input. ;D A GPSr without any modifications in software or hardware could not do the necessary calculations. However, it does seem possible to make it work with some sort of software change but leaving the hardware alone. One wonders if there might be something currently available for military or aerospace use. It would seem very likely. Thanks again guys! He really liked your answers. Northwes, my husband is not in the USAF Space program. He is just an information junkie. Sorry it took me SOOOO long to get back to you guys!!! Thanks Again!!!!
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Post by oleruns on Feb 18, 2008 22:29:28 GMT -9
One of the technologies tested by Deep space one and other spacecraft NASA have used is a system that uses a CCD to track the position of stars and orientate the craft in space. The system worked great and the spacecrafts were able to make adjustment autonomously without help from the ground. Another system they use is radio signals from other spacecraft with known positions and even quasars that emit radio signals to triangulate position. As for the military, GPS signals are easily jammed or altered, so I am sure they don’t rely on that technology much.
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Broccili
Bronze Cacher
Vehicle TB212QR "Powerstroke"
Posts: 67
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Post by Broccili on Apr 16, 2008 11:19:41 GMT -9
As for the military, GPS signals are easily jammed or altered, so I am sure they don’t rely on that technology much. Oh contrar monfrar. The signals can be jammed, but even that can be overcome. Do a search and read about mid-course guidance (Such as AGM-130), or the Joint Direct Attack Munition, or Small Diameter Bombs. Most modern military aircraft have GPS installed. Many a soldier have had the AN/PSN-11 (PLGR) in their hands to navigate. army-gps.robins.af.mil/Default.htm
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Post by NorthWes on Apr 16, 2008 14:28:54 GMT -9
Yeah - I've seen the kind of accuracy that's possible by the systems used to place indirect fires on target - most of which rely at one point or another on GPS observations to develop the firing solution. Whether it's a mortar platoon or an airstrike (or a cruise missile) that's being directed to target, a GPS is used as part of the mix. Military-spec GPS guidance allows the shooter to choose which window to direct the munition against... not just which building!
When the 'signal' was made accurate enough to make this geo-game possible, it wasn't completely retuned to bring civilian receivers in line with what the military receives from the satellite constellation.
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