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Couldn't a rover use an AM radio direction finder to determine it's exact distance from the mars habitat?
If the rover and the hab both have clocks set to the same time, couldn't the hab send out three signals on the hour, each signal ten seconds apart, the rover's direction finder should be able to locate the direction the signals are coming from and measure the time difference to determine it's distance from the hab?
If the rover has a map of the surface and knows where the hab is located (they should since that is where they departed from) the crew could then find their location.
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Hmm, thought about it and one problem is that the signal would not travel in a straight line toward the rover but bounce back and forth from the atmosphere and ground thus traveling much farther and giving the wrong distance.
I think the direction finder part would work well though.
Maybe a system that combines information received from a heading gyro and something that measures the amount of wheel rotation? It could all be combined by a computer program to determine position.
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Zubrin suggests celestial navigation. It is very low tech and therfore very robust. Just whip out the 'ol sextant.
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Hmm, thought about it and one problem is that the signal would not travel in a straight line toward the rover but bounce back and forth from the atmosphere and ground thus traveling much farther and giving the wrong distance.
I think the direction finder part would work well though.
Maybe a system that combines information received from a heading gyro and something that measures the amount of wheel rotation? It could all be combined by a computer program to determine position.
You could use an ADF (automatic direction finder) system just like Earth-based aircraft use. It is an old system but it does have the advantage of working over-the-horizion. However, as far as I know, all it provides is a bearing to the station and does not provide a distance measurement.
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The earth has a system of 24 satellites to provide global positioning to GPS devices on the earth. Are you saying we should do the same over mars? I do not think the cost is worth the benefit.
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Hmm, thought about it and one problem is that the signal would not travel in a straight line toward the rover but bounce back and forth from the atmosphere and ground thus traveling much farther and giving the wrong distance.
I think the direction finder part would work well though.
Maybe a system that combines information received from a heading gyro and something that measures the amount of wheel rotation? It could all be combined by a computer program to determine position.
You could use an ADF (automatic direction finder) system just like Earth-based aircraft use. It is an old system but it does have the advantage of working over-the-horizion. However, as far as I know, all it provides is a bearing to the station and does not provide a distance measurement.
In the link, as I thought, it says the ADF reflects the radio waves off earth's ionosphere. Now I'm not sure, but I don't think that Mars has the same thing, so this may not work, at least not on the same frequency.
http://www.newton.dep.anl.gov/askasci/a … tm]Martian Ionosphere
Anyone?
On the GPS issue: Why not every satellite we send up to Mars in the future be equipped with basic technology. At first, the APS (ahem) can actually acknowledge it's "customers" on the ground because there will not be an excessive amount of traffic of "users" using the system. So the satellites can communicate with whoever is on the ground, reducing the number of satellites needed, I think. They don't fill the same role as the GPS beacons, which are just simple beacons.
And another possibility: why not a series of ground-based beacons/weather stations which might have been constructed anyway? Assuming a antenna height of 2 m, the distance to the horizon is 3.7 km If you use a 3 m antenna, the distance increases to 4.5 km. If there's no problem with stretching yourself really thin, the distance can even be 8km between beacons (so you can see both but they can't see eachother). This is also assuming you don't take advantages of natural topography.
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I wrote about this a long time ago http://www.newmars.com/forums/viewtopic.php?t=3451]here
But to sum it all up again, I think the problems with navigation are overblown. With good maps, and a internal navigation system, it should be fairly difficult to impossible to get lost on Mars. Certianly a full blown GPS system is overkill. Just practice the same orientering skills we do on Earth.
He who refuses to do arithmetic is doomed to talk nonsense.
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Agreed that it is over kill but the benefits would be for exact position of mineral resources and of possible rescue times to rover crews if need to be reduced, rather than following the rover tracks to them.
But a much simpler system is very practical if we are setting up a network communications by satellites for future crews with each probe we will send over the next 20 plus years.
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There will be a good beacon, and repeater at Home Base.
Another 2 beacons would give 3 angles, 3 distance differences, to fix the position.
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A good fix might be obtained by only using 2 transmit
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Any beacon would only work as long as the vehicle is in line of sight which on mars, I'm guessing, is about 15-20 miles. Once over the horizon they are useless.
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On Earth VLF (very low frequency) ground waves travel long distances. Some even penetrate under sea water for submarine communication.
Mars will also have http://www.ee.duke.edu/~cummer/reprints … pdf]ground wave propagation.
With several stations, position could be calculater from http://lectureonline.cl.msu.edu/~mmp/ka … terference patterns
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On Earth VLF (very low frequency) ground waves travel long distances. Some even penetrate under sea water for submarine communication.
Mars will also have http://www.ee.duke.edu/~cummer/reprints … p.pdf]over the horozion radio propagation modes.
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Low frequency (AM) radio waves bounce off of the atmosphere and land so as they move around a planet they travel much farther than they would if they went in a straight line. I don't believe you can get a distance and position reading off of it other than to know what direction the signal came from.
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Considering that Mars is one third the size of Earth, I can't imagine we would need a constellation of 24 satillites to get the job done.
I'd suggest a smaller constellation of about 12 multipurpose GPS/Communications/Weather/Opical satillites.
"Yes, I was going to give this astronaut selection my best shot, I was determined when the NASA proctologist looked up my ass, he would see pipes so dazzling he would ask the nurse to get his sunglasses."
---Shuttle Astronaut Mike Mullane
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Whenever I talk about humans on mars it's only as far as the mars direct plan. Others here want massive human populations on mars from the first landing. So launching many GPS satellites for mars is not necessary in my opinion while others think it is a necessary first step.
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Whenever I talk about humans on mars it's only as far as the mars direct plan. Others here want massive human populations on mars from the first landing. So launching many GPS satellites for mars is not necessary in my opinion while others think it is a necessary first step.
I wouldn't assume massive populations, but I would assume coutinuous habitation, continous operations, and cycling of crews. It would help landers as well.
But thats why I'd imbed it into a series of multipurpose orbiters, the other data gathered more than justifies the cost, and the infrastructure will be there when were ready for it.
"Yes, I was going to give this astronaut selection my best shot, I was determined when the NASA proctologist looked up my ass, he would see pipes so dazzling he would ask the nurse to get his sunglasses."
---Shuttle Astronaut Mike Mullane
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There was an article on the web just the other day that talked about a GPS like system for Mars using I think four or five multipurpose satellites. They would also serve as the backbone of Mars's internet, which would be its communications backbone.
-- RobS
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By the time Mars explorers arrive, there will be a functional http://www.google.com/search?q=mars+gps … =utf-8]GPS.
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Just by monitoring http://www.msss.com/mer_mission/finding_mer/]doppler from the rover,
some positional information could be deduced.
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Comparing angle with quasars gives http://mars.jpl.nasa.gov/mer/mission/comm_nav.html]1 KM accuracy.
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Only one satellite could precisely determine location ?
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