A Bigger Pipe for Mars

[rogers_buck]

What would be an optimal constellation of communications satellites for Mars data relay? What type of orbits? Would GPS be a valuable feature for such satellites? Do we need to do something now to calibrate a future GPS system with the assets in place? What sort of minimal technology might be deployed for this purpose? Could something be cobbled together quickly for an Ion boost to Mars arriving in time to be usefull?<br />

 

[CalliArcale]

I believe there has been talk of creating some kind of Martian GPS. I'm not sure what the minimum constellation is, but you do need at least some spacecraft in something other than a polar orbit. That makes the current Martian constellation less than optimal -- they're all in polar orbits, the better to maximize their scanning capabilities. So the assets in place would not be ideal, although they could conceivably be made to act in concert with other spacecraft to become part of a GPS-like network.<br /><br />Could it be cobbled together in time to be useful? Well, that depends on one question -- useful for what? If you want to put a GPS receiver on the next Mars rover, I would say that it cannot be done in time, not without unacceptably delaying the rover. But if you want these for a manned expedition, then yes, it could certainly be done, as long as the money can be found. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[rogers_buck]

Thanks Calli, here's a timely story on SDC.<br /><br />http://www.space.com/spacenews/businessmonday_041115.html<br /><br />I guess I had something in mind along the lines of a GPS with a transponder/earth-relay. A few mods to an existing design, strap an Ion stage on it, and kick it out the door on a Pegasus sort of thing.<br /><br />An optical up/down link is an interesting development. <br /><br />

 

[najab]

><i>...but you do need at least some spacecraft in something other than a polar orbit...</i><p>Pardon my dumbness, but why?</p>

 

[rogers_buck]

The science orbits (Observer, MGS) are too low to be usefull communications satellites. Higher orbits imply longer periods. A polar orbit would take more time to come over the horizon than an equatorial orbit. <br /><br />I should add the communications passes are short because the science orbiters go ripping accross the sky...

 

[najab]

><i>The science orbits (Observer, MGS) are too low to be usefull communications satellites.</i><p>As far as positioning is concerned, a lower orbit isn't a real problem (other than the smaller visible arc) - besides, for purposes of argument we'll assume that the science satellites can be boosted to higher orbits once their main mission is over.<p>><i>A polar orbit would take more time to come over the horizon than an equatorial orbit. </i><p>A high polar orbit will come over the horizon just as often as a high equatorial orbit. Don't get caught up thinking that all polar orbits are sun synchronous. <img src="/images/icons/smile.gif" /><p>Also, an equatorial orbit limits the latitude range of your positioning system. One of the advantages that GLONASS has over GPS is that its satellites are in 'steeper' orbits and so the system works at the poles.<p>><i>I should add the communications passes are short because the science orbiters go ripping accross the sky.</i><p>This is a function of their low altitude, rather than their orbital plane.</p></p></p></p></p></p>

 

[najab]

><i>A high polar orbit will come over the horizon just as often as a high equatorial orbit.</i><p>Unless, of course, you're high enough to be nearly aresynchronous.</p>