GPS sats for Mars

[willpittenger]

Eventually, our exploration of Mars will require something equivilent to GPS.<br /><br />* Would you use existing GPS (or comparable) designs? Or build something new?<br />* How would you get them there? In one big cruise stage? Or one cruise stage per sat?<br />* Would you put science instruments on them so they could do double duty?<br /><br />I assume we would need the same number of sats that we use here. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[qso1]

I'd utilize improved existing designs to the extent possible. If this is something that is going to happen beyond 20 years from now. I'd use whatever technology has replaced GPS by then. Even if its still called GPS.<br /><br />A few sats per stage with several stages to put the system in place. This is the best of both approaches. One sat per stage would involve additional costs in having each sat requiring a launcher etc.<br /><br />Putting all sats on one stage would involve potential loss of all sats in the event of a malfunction resulting in mission loss.<br /><br />I would definetily put any science instruments I could. Always try to get the most bang for the buck if possible.<br /><br />A Mars GPS system should be equipped with all basic necessities for a Mars constellation of satellites. Weather monitoring being one example. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[qso1]

Good points. Initially, as few as 3 plus 1 backup would be needed in areosynchronous orbit to provide service to emerging outposts on Mars. Earthly GPS does not operate in a geosynchronous orbit but a Mars GPS could, by way of advancing technology and probably should operate in a synchronous orbit. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[holmec]

Its an excellent idea, since we are not going to stop sending landers and robots to mars.<br /><br />I would try to remake them into small sats, get other space agencies on it and make it an international one. Then I would probably put as many as possible in each shot. Maybe two or three shots should do the trick (of course I'm just talking off the top of my head).<br /><br />Somthing like that should make it easier for a robotic plane on Mars to operate. It may prove to be of some value in just landing a lander, I think landings now are somewhat in the blind as far as where the device is....hence Beagle. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[wdobner]

A GPS style system for Mars seems like a very good idea. The lack of a magnetic field would certainly seem to hinder navigation over long distances and I believe would reduce most navigation to dead reckoning based on local landmarks, inertial navigation, or some variant of celestial position fixing. <br /><br />If a Martian Positioning System (areopositioning? arespositioning?) is to use roughly the same technology as the Global Positioning System you'd need to have more than three or four satellites, especially if they were in a synchronous orbit. With only 4 satellites you'd potentially end up with situations where one MPS satellite would be at zenith, one shadowed by the bulk of the planet, and the other two very close to the horizon. The worst thing is that you'd have all satellites on one plane, which I believe would lead to poor accuracy. And with the two satellites close to the horizon you'd either lose the signals of both satellites if you, say, dropped into a crater, and any roughly vertical surface behind your reciever would reflect the signals thereby creating a multipath problem which would also negatively effect accuracy. <br /><br />To make an MPS system work you'd need to guarantee that at least 3 or 4 satellites would be above the horizon and in different parts of the sky during the time in which a probe (or, optimistically, an exploration team) was trying to take a reading. Preferably you'd have two satellites near, but not at zenith, and two more around 20 to 30 degrees above the horizon, with no satellites sharing the same quadrant of the sky. That sort of arrangement would yield the most accurate results, and if you're using the system for a daily or even less frequent updates of an inertial navigation system accuracy would most definitely count for a lot. I don't know the orbital mechanics, but it'd seem to me somewhat unlikely that even in a relatively high martian orbit these satellites would converge in the same patch of sky over our

 

[nyarlathotep]

"I'd utilize improved existing designs to the extent possible. If this is something that is going to happen beyond 20 years from now. I'd use whatever technology has replaced GPS by then. Even if its still called GPS. "<br /><br />Given the deficit, it's entirely more likely to be called Galileo 2.

 

[qso1]

Because of the time that such a system might be expected to be deployed. I made a general assumption on capabilities and number of satellites. But even if one deploys 12 satellites, that could be accomplished at 3 per LV or 4 per LV. So if it takes 12 to do it, not that much trouble IMO.<br /><br />My thinking was more towards clean slate design, minimal satellites as possible. Thinking along TDRSS lines. The current GPS IIRC is deployed much lower than synchronous orbit (11,000 miles?) which is one reason a larger number of them is required. I don't know for certain if Areosynchronous orbit has the same circumstance as geo, but I would think it would. Just a different altitude.<br /><br />I would think a compromise between a Transit and GPS could be done but as I am not up on detailed specs as to what they can do, I can't say for sure. But basically a GPS type system around Mars is doable as I see it. The specs to be determined by when and how many are deployed and what the objectives will be upon deployment. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[wdobner]

<i>Because of the time that such a system might be expected to be deployed. I made a general assumption on capabilities and number of satellites. But even if one deploys 12 satellites, that could be accomplished at 3 per LV or 4 per LV. So if it takes 12 to do it, not that much trouble IMO.</i><br /><br />Yes, I kind of meant to say that. The nice thing with three or four satellites in each of the orbital planes is that you can have the Earth-Mars transfer stage haul the three or four MPS birds to Mars and then insert them in the proper inclination orbit. I'd imagine you could go so far as to have the transfer stage place the MPS satellites in their slots within that plane. Three or four launches of perhaps something like a Delta IVH boosting an upper stage and transfer stage with three or four MPS satellites would be expensive. However, I'd imagine in the long run an effective GPS-like navigation system around Mars would pay for itself through more reliable probe deployments and perhaps the ability to launch simpler rovers which don't have to sight stars for a position fix or use very accurate INS systems to navigate.<br /><br /><i>My thinking was more towards clean slate design, minimal satellites as possible. Thinking along TDRSS lines. The current GPS IIRC is deployed much lower than synchronous orbit (11,000 miles?) which is one reason a larger number of them is required. I don't know for certain if Areosynchronous orbit has the same circumstance as geo, but I would think it would. Just a different altitude.</i><br /><br />I think you're right, I believe the GPS satellites are some 12,000 miles up. However, from what I can see that's more than high enough to cover nearly all of a given hemisphere below the satellite. Most of the time when I fire up my GPS unit I have at least 6 of the 24 GPS satellites over my head, and a few times I've had more than 10 on the reciever (right now it's saying 8), so a high orbit, even if it's only half that of a synchronous orbi

 

[willpittenger]

<blockquote><font class="small">In reply to:</font><hr /><p>A Mars GPS system should be equipped with all basic necessities for a Mars constellation of satellites. Weather monitoring being one example.<p><hr /></p></p></blockquote><br />Actually, I would put the weather systems into geostationary sats that would double as communication birds. MRO makes a good relay system for now, but half the time, it is out of sight. Besides, any moving bird would require constant reaiming of the ground antennas. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[qso1]

There will be some kind of trade offs regardless how its done. The trick is finding the optimal set of capabilities for a given mission. I'd think that a satellite constellation would be done if it appears were about to send humans on a regular or even semi regular basis.<br /><br />BTW, both you and wdobner have some very good ideas here. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>