How long before we need dedicated Martian com sats?

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willpittenger

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Currently, we use orbiters with other duties as communication relays. However, as the workloads of those satellites increase and the amount of data collected that is being relayed increases, eventually there becomes a point when the mission designers have to choose between getting things done and relaying that data. Besides, a polar orbit is not ideal for a communications relay. <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>
 
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h2ouniverse

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Exomars in 2013 is going to need that one of the US-martian orbiters serves as a com relay.<br /><br />So it's occuring soon.
 
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docm

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Any bets before manned missions at least a few GPS-type satellites are put in Mars orbit to aid navigation (rovers etc.)? <div class="Discussion_UserSignature"> </div>
 
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j05h

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Guaranteed need for GPS/relay sats before crews arrive. They provide a huge risk-reduction and improved data-gathering for very modest investment (esp. when sending a crew later)...<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>
 
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willpittenger

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A year ago I listed three key elements that I felt must be in place for manned missions: a GPS system with comparable accuracy in 3 dimensions to the GPS system we have here and communications satellites that double as weather observation sats. <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>
 
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holmec

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IMHO the time is now. But to get that realization through to a budget.....well that where miracles happen and hell freezes over. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>
 
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cbased

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You need a lot of satellites to cover the whole planet. So I guess IF the decision to have GPS on Mars will be made it will be a solution that only partially covers Mars' surface - probably the most likely area for human landing.
 
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holmec

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<blockquote><font class="small">In reply to:</font><hr /><p>You need a lot of satellites to cover the whole planet<p><hr /></p></p></blockquote><br /><br />Mars is smaller than the Earth, so hopefully that would mean less satellites than Earth. Also you may get away with a scaled down version of GPS system which may bring down the the number of satellites as well. <br /><br />Another aspect is that since Martian atmosphere is thinner than Earth's does it not take less power to transmit from orbit to the ground? So the satellites could be less powerful and hopefully that would translate into lighter satellites. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>
 
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holmec

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I would like to say that a GPS like system not only benefits manned missions, but also future robotic rovers. Hear on earth in the 90's, I think, someone experimented with making an autonomous tractor to work on a field. I would expect future rovers with GPS to be more autonomous than Spirit and Opportunity. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>
 
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docm

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Sounds like a job for micro/mini-sats. <div class="Discussion_UserSignature"> </div>
 
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willpittenger

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Would it be pratical to send the various GPS sats out attached to a mother craft that would dispense the into the correct orbits? <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>
 
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willpittenger

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Modern harvesting equipment (everything from the tractors to sprayers to combines) practically are autonomous. You only need to actually drive them to the field. After that, sit back and enjoy the ride. The driver at that point is only really needed as a safety precaution. <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>
 
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PistolPete

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<blockquote><font class="small">In reply to:</font><hr /><p>Mars is smaller than the Earth, so hopefully that would mean less satellites than Earth. Also you may get away with a scaled down version of GPS system which may bring down the the number of satellites as well.<p><hr /></p></p></blockquote><br />Current GPS systems need to see at least 3-4 satellites to get a decent fix. Even at 1/3 the size I would still say that you would need about a dozen of them even for Mars. GPS is also based on time, so turning GPS satellites into microsats depends on how small you can make an atomic clock.<br /><br />Comm sats on the other hand only require three in a Martian Clark orbit. <div class="Discussion_UserSignature"> <p> </p><p><em>So, again we are defeated. This victory belongs to the farmers, not us.</em></p><p><strong>-Kambei Shimada from the movie Seven Samurai</strong></p> </div>
 
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willpittenger

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Unfortunately, if the comm sats are also your weather units, you need more to cover the entire surface -- even if you ignore the polar regions. The problem is for Weather, you need overlap of what they see on the ground. It doesn't make sense to restrict the forecasters to oblique angles.<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p>Martian Clark orbit.<p><hr /></p></p></blockquote><br />Is that the same distance from Mars (roughly) as it is 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>
 
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dragon04

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<font color="yellow">Would it be pratical to send the various GPS sats out attached to a mother craft that would dispense the into the correct orbits?</font><br /><br />That's not a bad idea at all. <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>
 
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3488

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Hi willpittenger.<br /><br />Mars Aerostationary Orbit is 17,075 KM above a point on the equator, (radius of 20,475<br />KM from centre of Mars) as against 35,700 KM for Earth Geostationary Orbit (radius of <br />42,200 KM from centre of Earth).<br /><br /><img src="/images/icons/laugh.gif" /> <img src="/images/icons/laugh.gif" /> <img src="/images/icons/laugh.gif" /> Happy Christmas everyone. <img src="/images/icons/laugh.gif" /> <img src="/images/icons/laugh.gif" /> <img src="/images/icons/laugh.gif" /><br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>
 
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thalion

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^<br />Arrgh! Scooped me by five minutes! <img src="/images/icons/wink.gif" /><br /><br /><i>Is that the same distance from Mars (roughly) as it is here? </i><br /><br />Martian "GEO" is about 6.04 planet radii out, or about 20,476 km. For the record, this would also be a good station to observe Deimos, as it's less than 3,000 km inside its orbit. <br />
 
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3488

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Thanks Thalion, your figures agree with mine. Good to see someone else post an <br />answer to the same question, that is similar to mine <img src="/images/icons/smile.gif" /> .<br /><br />I like your idea regarding Deimos. I had not thought of that one (would have come to me later on <br />probably though). <img src="/images/icons/crazy.gif" /><br /><br /><img src="/images/icons/laugh.gif" /> <img src="/images/icons/laugh.gif" /> <img src="/images/icons/laugh.gif" /> Happy Christmas everyone. <img src="/images/icons/laugh.gif" /> <img src="/images/icons/laugh.gif" /> <img src="/images/icons/laugh.gif" /><br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>
 
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3488

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Hi willpittenger,<br /><br />Remember Mars has only 11% of the mass of the Earth, so despite the slightly longer rotational <br />period than Earth, approx by 37 minutes, the Aerostationary point will be <br />very much closer in. <br /><br /><img src="/images/icons/laugh.gif" /> <img src="/images/icons/laugh.gif" /> <img src="/images/icons/laugh.gif" /> Happy Boxing Day everyone. <img src="/images/icons/laugh.gif" /> <img src="/images/icons/laugh.gif" /> <img src="/images/icons/laugh.gif" /><br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>
 
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richalex

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<blockquote><font class="small">In reply to:</font><hr /><p>GPS is also based on time, so turning GPS satellites into microsats depends on how small you can make an atomic clock.<p><hr /></p></p></blockquote>That small.
 
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PistolPete

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Damn, that's tiny!<br /><br />Yup, that would do it, right about that size right there. The next obstacle would be building transmitters tiny enough, yet powerful enough to be useful. Because it would need to transmit a fairly powerful signal the size of the antenna can only be so small. The antenna could be collapsed for transport, but it would still mean that there is a bare minimum size for one of these sats. Whittling it down to a smallsat (100-500kg) would be easy, trying to cram it into a microsat (10-100kg) might be pushing it a little bit. <div class="Discussion_UserSignature"> <p> </p><p><em>So, again we are defeated. This victory belongs to the farmers, not us.</em></p><p><strong>-Kambei Shimada from the movie Seven Samurai</strong></p> </div>
 
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holmec

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<blockquote><font class="small">In reply to:</font><hr /><p>The antenna could be collapsed for transport, but it would still mean that there is a bare minimum size for one of these sats<p><hr /></p></p></blockquote><br /><br />Well, since all you need in an antenna is wire, you could redesign them to be lighter. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>
 
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windnwar

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Just so long as you don't end up with the antenna's failing to deploy properly like what happened with Galileo's antenna during the Jupiter mission. I'd imagine a micro sat wouldn't have a backup transmitter like Galileo had. <div class="Discussion_UserSignature"> <p> </p><p><font size="2" color="#0000ff">""Only two things are infinite, the universe and human stupidity, and I'm not sure about the former." --Albert Einstein"</font></p> </div>
 
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samkent

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GPS and radio relay in one sat is one function too many. At least three sats have to be in view to give a position. So which one does the radio relay? That forces all the sats to keep one antenna pointed at earth. <br />Even with GPS the rovers still have to deal with rocks and craters and sand traps. A position fix of 100 meters is good enough at this point. They don't move that fast. If you need a better fix one of the optical sats can hone in at less cost. Three sats in high orbit can photo the entire planet with overlap in one Mars day. They don't have to be stationary above any on point. Data relay is much easyer also.<br /><br />For positioning:<br />A better, lower cost solution would be the old style LORAN system. When Man gets there he can set up two fixed transmitters some distance apart. The receiver does the rest.
 
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