Author Topic: Mars GPS system  (Read 20998 times)

Offline spacenut

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Mars GPS system
« on: 04/17/2015 01:47 PM »
In order to land cargo on Mars before humans arrive, wouldn't SpaceX need to put in place a Mars GPS system?  That way they can pick a spot to colonize, then have all the landers touch down near each other using the Mars GPS system, like their booster does to pick the spot to land.  If they do need this GPS system in place, would they use Falcon 9 or Falcon Heavy to launch the satelites to orbit Mars for the GPS system?  EM did say that Falcon Heavy would be used for Mars.  I'm assuming this is one way.

Offline Jim

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Re: Mars GPS system
« Reply #1 on: 04/17/2015 01:51 PM »
In order to land cargo on Mars before humans arrive, wouldn't SpaceX need to put in place a Mars GPS system?  That way they can pick a spot to colonize, then have all the landers touch down near each other using the Mars GPS system, like their booster does to pick the spot to land.  If they do need this GPS system in place, would they use Falcon 9 or Falcon Heavy to launch the satelites to orbit Mars for the GPS system?  EM did say that Falcon Heavy would be used for Mars.  I'm assuming this is one way.

Not required, see Apollo 12

Offline clongton

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Re: Mars GPS system
« Reply #2 on: 04/17/2015 02:01 PM »
Perhaps not to start, but to actually explore the surface I would think a gps constellation would be an asset.
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Offline Semmel

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Re: Mars GPS system
« Reply #3 on: 04/17/2015 02:50 PM »
I dont think so. You just need a small device, containing a clock and a startracker for the night and a sun tracker for the day. Its much more expensive than a GPS receiver but much cheaper than a GPS receiver and a GPS satellite constellation. The break even point is probably upwards some thousand of these devices. Not an issue for a long long time..

Offline baldusi

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Re: Mars GPS system
« Reply #4 on: 04/17/2015 02:58 PM »
I did a thread abut that: http://forum.nasaspaceflight.com/index.php?topic=29382.0
Go read it. Many issues are explained. But the gist is that GNSS like Galileo and GPS use a lot of surface based survey and tracking data.

Offline spacenut

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Re: Mars GPS system
« Reply #5 on: 04/17/2015 03:12 PM »
I thought for accuracy and having landers close together that a GPS system would work better.  You only need three for triangulation and they could be in a Mars GEO or GSO above the area you pre select.  More would be better in case of a failure.  Don't know what altitude that would be above Mars. 

Offline RonM

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Re: Mars GPS system
« Reply #6 on: 04/17/2015 03:48 PM »
In order to land cargo on Mars before humans arrive, wouldn't SpaceX need to put in place a Mars GPS system?  That way they can pick a spot to colonize, then have all the landers touch down near each other using the Mars GPS system, like their booster does to pick the spot to land.  If they do need this GPS system in place, would they use Falcon 9 or Falcon Heavy to launch the satelites to orbit Mars for the GPS system?  EM did say that Falcon Heavy would be used for Mars.  I'm assuming this is one way.

Not required, see Apollo 12

Yes, Apollo 12 proved it can be done.

If you need more accuracy to land on a specific pad, then radio beacons at the landing site will work.

Online llanitedave

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Re: Mars GPS system
« Reply #7 on: 04/17/2015 04:55 PM »
In order to land cargo on Mars before humans arrive, wouldn't SpaceX need to put in place a Mars GPS system?  That way they can pick a spot to colonize, then have all the landers touch down near each other using the Mars GPS system, like their booster does to pick the spot to land.  If they do need this GPS system in place, would they use Falcon 9 or Falcon Heavy to launch the satelites to orbit Mars for the GPS system?  EM did say that Falcon Heavy would be used for Mars.  I'm assuming this is one way.

Not required, see Apollo 12


Not to mention Apollo 15, 16, and 17.
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Offline nadreck

Re: Mars GPS system
« Reply #8 on: 04/17/2015 05:01 PM »
I still favour a concept that puts a constellation around Mars that supports the following:

1. 24/7 low latency Mars surface to Mars surface communications
2. 24/7 relay to/from Earth
3. GPS (yes it is not accurate for absolute surface position and altitude at first, but over time it helps build the datum needed for the accurate relief model of Mars and it still provides accurate relative position, particularly for surface vehicles)
4. Visual/IR/UV surface monitoring

I would put these in multiple planes a little over 1000km above the surface with significantly more density than needed and with tenders/spares since replacements will be a long time coming.
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline Sohl

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Re: Mars GPS system
« Reply #9 on: 04/17/2015 07:06 PM »
I still favour a concept that puts a constellation around Mars that supports the following:

1. 24/7 low latency Mars surface to Mars surface communications
2. 24/7 relay to/from Earth
3. GPS (yes it is not accurate for absolute surface position and altitude at first, but over time it helps build the datum needed for the accurate relief model of Mars and it still provides accurate relative position, particularly for surface vehicles)
4. Visual/IR/UV surface monitoring

I would put these in multiple planes a little over 1000km above the surface with significantly more density than needed and with tenders/spares since replacements will be a long time coming.

Would be nice!   8)

Especially if any of the current NASA orbiters used for Mars data relay fail.  I think most of us would like to see current robotic explorers still have a good pipeline for transmissions back to Earth.  The first couple of these new Mars datacomm sats could be used for contracted bandwidth to NASA.

Online guckyfan

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Re: Mars GPS system
« Reply #10 on: 04/17/2015 07:30 PM »
I would put these in multiple planes a little over 1000km above the surface with significantly more density than needed and with tenders/spares since replacements will be a long time coming.

Would be nice!   8)

Especially if any of the current NASA orbiters used for Mars data relay fail.  I think most of us would like to see current robotic explorers still have a good pipeline for transmissions back to Earth.  The first couple of these new Mars datacomm sats could be used for contracted bandwidth to NASA.

Yes, would be nice. However that sat constellation would likely use very different communication protocols than the Mars rovers. I have no idea how difficult or easy it would be to support them.


Offline nadreck

Re: Mars GPS system
« Reply #11 on: 04/17/2015 07:41 PM »
I would put these in multiple planes a little over 1000km above the surface with significantly more density than needed and with tenders/spares since replacements will be a long time coming.

Would be nice!   8)

Especially if any of the current NASA orbiters used for Mars data relay fail.  I think most of us would like to see current robotic explorers still have a good pipeline for transmissions back to Earth.  The first couple of these new Mars datacomm sats could be used for contracted bandwidth to NASA.

Yes, would be nice. However that sat constellation would likely use very different communication protocols than the Mars rovers. I have no idea how difficult or easy it would be to support them.

guckyfan, if you have read some of my other posts on this type of constellation, I see a tender for either each plane or every other plane, and that the satellite to satellite back bone would use the tender craft (which are much larger anyway) for Mars-Earth Relay. These craft might have the dedicated equipment to support legacy protocols and transport layers.

And just as a note to all. One of the advantages of this constellation will be to allow all future Mars craft/rovers/spacesuited gorillas to carry a device that is about as sophisticated (and costly) as a smartphone to take advantage of all of the services of the satellites. Spares could be afforded. In the longer run this will be a cost savings just on that basis, in the short run it simply ups the comms reliability.
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline notsorandom

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Re: Mars GPS system
« Reply #12 on: 04/17/2015 08:44 PM »
Us humans are actually pretty good at finding our way around without GPS. This planet was explored long before the first GPS satellites went up. Pretty much all the techniques we used before GPS can be used on Mars. Without GPS we have already been able to do some impressive things on Mars. MRO's imagery for example is very accurately placed and rectified. Also when both Phoenix and Curiosity were descending under parachute MRO was able to capture them.

Offline AncientU

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Re: Mars GPS system
« Reply #13 on: 04/17/2015 09:27 PM »
The thing we haven't done is land several spacecraft at/near the same location. 
One-off are considerably easier.
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Offline spacenut

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Re: Mars GPS system
« Reply #14 on: 04/17/2015 09:49 PM »
Yes, landing close together ISRU equipment, solar panels for to power them, earth excavation equipment, living units, food storage units, etc, could be a problem that I though GPS satelites in high Mars orbit could solve before sending humans.  Landing one rover in a general area by parachute is one thing, pin pointing a good landing spot is another.  They need to be close enough together to wire them up and transfer manufactured food, yet far enough apart the landing rockets don't put dust and dirt all over everything.  Landers could have engines mounted high on the sides to help with that since the cargo would be easier to unload from the bottom for returnable landers. 

I assume that the above non perishable ISRU equipment would be landed with minimum size landers not to take off again.  Empty fuel tanks would be used for manufactured fuel storage to be pumped to MCT's to return to earth and continually being made to fuel the next arriving MCT's.   MCT's could be human piloted so that isn't a problem choosing a landing site, but robotic equipment that stays would need to be located close together. 
« Last Edit: 04/17/2015 09:51 PM by spacenut »

Offline Jcc

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Re: Mars GPS system
« Reply #15 on: 04/17/2015 11:16 PM »
Two approaches can be used to do precious landings without GPS, radio beacons, and navigation by feature matching in imagery. i think both will be used, with feature matching of land forms used from high to medium altitude, then radio beacons and or visual beacons or other artificial navigational aids at low altitude.

Online Bob Shaw

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Re: Mars GPS system
« Reply #16 on: 04/17/2015 11:26 PM »
GPS-Light in the form of GPS derived location systems seem pretty elementary; you'd only need to integrate a couple of well-characterised ground locations into a local model to allow Cm-level location. Key to this would be linked timing systems, with perhaps some orbital assets - but you can navigate by the stars in orbit, anyway. I suspect that all this will fall off the back of laser comms systems in any case.

In short, for regular landings, highly precise control seems inevitable.
« Last Edit: 04/17/2015 11:30 PM by Bob Shaw »

Online Bob Shaw

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Re: Mars GPS system
« Reply #17 on: 04/17/2015 11:26 PM »
The thing we haven't done is land several spacecraft at/near the same location. 
One-off are considerably easier.

Apollo 12! And several Luna sample return missions.
« Last Edit: 04/17/2015 11:27 PM by Bob Shaw »

Offline Russel

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Re: Mars GPS system
« Reply #18 on: 04/18/2015 10:01 AM »
I agree. Precision navigation will become commonplace and the electronics to support this will shrink to the point where virtually any orbiting vehicle and ground station will provide a reference.

One thing I'd be curious to see is a small laser communications system landed on Deimos and Phobos. You can get accurate range finding on the back of the communications system (plus backup and storage of data).

So virtually anything on ground or in orbit can take a range off either or both moons. I'm not sure about the level of visibility but it couldn't be too bad.

Offline redliox

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Re: Mars GPS system
« Reply #19 on: 04/18/2015 10:31 AM »
I see GPS more as an optional asset; it's greatest use would be to crewed rovers making long-distance journeys, not so much to the first landing party.  I will say if a dedicated communication satellite gets delivered, giving it some GPS capability would be wise.  I wouldn't count on more than two satellites being set at best...

...however a cubesat network might make a workable GPS.  More than likely something small at Mars would need to devote it's time soaking up sun and staying alive, but it could manage a simple pinging setup more extensive equipment with the crew (on surface) could use to triangulate.  I.e., a bunch of twenty-first century Sputniks circle Mars for a simple GPS.  That might be the best to expect for the next quarter century in regards to Martian GPS.
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