Moon GPS

[shadowsound]

Much of how I respond is based on past experience.<br /><br />Most of my experience is in the following areas:<br />Satellite ground terminals operations and maintenance for satellite communications Heavy fixed, medium movable and tactical terminals and associated equipment (9 years)<br /><br />Wide-band operations and maintenance support of satellite operations connectivity, and recording of data including back-haul for NASA shuttle. commanding of Elliptical satellites (7 years)<br /><br />Satellite operations and control of various Geostationary and molniya satellites using liquid and ion thrusters.<br /><br />I am not an orbital analyst or an engineer. I have sat and monitored many satellites 24/7 for three years and sweat through performing numerous spacecraft maneuvers, and anomalies including eclipses and ion storms.<br /><br />The Watcher<br /><br />

 

[shadowsound]

No. Apparently what I'm saying is that you have no idea what a synchronous orbit is.<br /><br />A Geostationary orbit around the Earth is a geosynchronous orbit but a geosynchronous orbit may not be a geostationary orbit. IE a polar synchronous orbit is 90 deg tilted from the earths ecliptic plane but will pass over the same sub satellite locations on the earths surface continuously. it just means that it will in a given period of time follow the same track and intersect the same latitude and longitudes over the period of time. It is synchronized with it.<br /><br />You can only argue semantics when dealing with words or phrases that have multiple meanings. You're simply using the phrase 'lunar synchronous orbit' incorrectly. <br /><br />If I didn't make my meaning clear I meant to say the the satellites I indicated would be synchronized in the direction of the lunar rotations with zero inclination. In a circular orbit. If this is not possible do to the gravitational anomalies of the lunar structure . As it passes through the Gravitational hills of the lunar surface it would increase and decrease in velocity and in doing so its orbit would vary in height, and graph either more elliptical or somewhat uneven.<br /><br />The same thing happens to Geostationary satellites. They rest in a orbit area above the earth that has uneven gravity do to the ocean crust and core. We kept the satellite in a mathematically defined area of space called a box. A Box that requires the craft to be moved periodically that allow it to drift from one side to the other. Because of the gravity hills bias it will always drift relative to it. If the maneuver were not done it would drift outside the box and into that of the next satellites. this is a legal no no and the company could be fined for doing so. When the satellite is just at the end of its life expectancy it will be maneuvered to a grave yard area where it will not cause any problems if it drifts and bumps into any other objects IE dead

 

[trailrider]

I'm probably oversimplifyling this, but if you need very precise selenopositioning and continuous data relay from very scattered locations on the lunar surface, somebody will have to bite the bullet and orbit enough satellites around the moon to give you continuous coverage. Might have to rely partially on surface relay sites. Don't forget some of those mountains rise quite high above MLS (Mean Lunar Surface). I suspect for awhile the relay and location functions will be relatively short-ranged and line-of-site will work fine...just like we did with VHF repeaters on the mountain tops in various western states for communications with a central base.<br /><br />Ad Luna! Ad Ares! Ad Astra!

 

[willpittenger]

Actually, a very good strategy was discussed in this reply to this thread. My only complaint is the lack of polar coverage. <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>

 

[willpittenger]

The more I think about it, the more I like this solution for both the Moon and Mars. However, it has one huge drawback that would be very important on the Moon: No polar coverage. Scientests currently want to check out some polar craters that might have water ice. Such water might be better than making it from Regolith or bringing from elsewhere (asteroids, comets, Earth, etc). To not have polar coverage on the Moon would be a real pain in the neck. <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>

 

[shadowsound]

A multi shell series of satellites Polar in one orbiatal shell and equotial in the other. the polar satellite would each pass within range of teh either the north or soutern pole<br /><br />if you shine a set of flashlights on a ball you see where the beam patterns overlap where the sun doesn't directly shine you have a loss of comunications. yo have to have overlapping beam patterns. Try it with a basket ball and you'll see why.<br /><br />also there is a very major distinctions between the Moon and Mars. The atmosphere. Mars is comparable to the earth in the sense. the atsmosphere will attenuate the signal of a satellite. The fewer you have the more area it needs to cover. This brings in other typs of loss beside free space, there is atsospheic and water it has any and finally dust storms. <br /><br />the closer to the edge of the beam pattern the lower the rf power recieved on either end. greater beam loss. The satelite has a greater amount of amplifier gain and a large antenna it can compensat Some but is makes it more expensive. Mars if much farther from the sun than the Earth, and receives much les solar power per square foot of solar array. <br /><br />it doen't matter how size your beam width is past the masimum view anlgle. Anything that misses the lunar surface is free space loss.<br /><br />No polar coverage.<br /><br />You would have a problem with lower latitude locations within deep craters. it deals with the look angle of the signal. The azimuth and elevation of any given satellite may not allow a clear shot.<br /><br /><br /><br />Globalstar, Sirius, and Iridium have the same problem within cities and mountains. Satellites are line of sight. no see no talk. For permanent locations within such locations repeaters are needed. sometimes old technologies are best.

 

[mrmorris]

<font color="yellow">"...a polar synchronous orbit is 90 deg tilted from the earths ecliptic plane but will pass over the same sub satellite locations on the earths surface continuously. it just means that it will in a given period of time follow the same track and intersect the same latitude and longitudes over the period of time. It is synchronized with it. "</font><br /><br />I must admit that I'm not familiar with an orbit that has this characteristic. I almost mentioned a polar sun-synchronous orbit in my previous post, except that sun-synced orbits have no meaning for a lunar satellite (that I can think of). A sun-synchronous orbit will pass the equator and each latitude at the same local solar time each day, but not latitude *and* longitude. The orbital plane rotates about a degree per day to keep up with the Earth's rotation about the sun. Do you have any references for a geosynchronous polar orbit -- I can't locate it via Google.<br /><br /><font color="yellow">"If I didn't make my meaning clear I meant to say the the satellites I indicated would be synchronized in the direction of the lunar rotations with zero inclination."</font><br /><br />They would be synchronized with what? Geosynchronous (geostationary) orbits are synced with the orbit of the Earth. Sun-synchronous orbits are synced with the earth's solar orbital period. I don't think that you are arguing that a lunar synchronous (stationary) orbit is possible. I don't think that you'll disagree that a sun-synchronus lunar orbit would be useful (assuming it is even possible). So what specifically is it that the orbit is being synced with?

 

[mrmorris]

<font color="yellow">"However, it has one huge drawback that would be very important on the Moon: No polar coverage."</font><br /><br />A satellite in equatorial orbit *will* be able to have line-of sight to an entire hemisphere. Granted, as you get closer to the poles, the LOS becomes less direct and more tangental, with a corresponding loss in accuracy.<br /><br />So let's add a rider to the idea. Along with the three satellites and the scattered transponders, put two ground-based high-power transmitters at the poles. Position them on the highest conventient location around and place them on towers (lunar gravity -- no wind -- towers should be reasonably easy). Since we're at the poles and have good access to solar power -- these need not be the low-powered transponders we scattered about the rest of the surface. They can transmit continuously in the same fashion as the satellites. They would add a good bit of accuracy to much of the lunar GPS system (obviously providing the least help at the equators).

 

[rocketman5000]

If you start to put all of these transponders on the surface of the moon throwing RF around you'll kill one of the major justifications of long term habitation of the moon; radio astronomy

 

[shadowsound]

I haven't figure out how to change the color of the text yet even after reading the FAQ. <br /><br />First<br /><br />--Interspersed--<br /><br />"...a polar geo synchronous orbit is 90 deg tilted from the earths ecliptic plane<br /><br /><br />-- this should have read that the polar synchronous orbit is inclined 90 deg to the Earths equatorial orbit. --<br /><br /><br /><br />"I must admit that I'm not familiar with an orbit that has this characteristic." "A sun-synchronous orbit will pass the equator and each latitude at the same local solar time each day, but not latitude *and* longitude."<br /><br /><br />Your right in my usage of the term in this instance.. <br /><br />--I should have said Earth's equatorial plane. <br /><br />However tying the term Ecliptic plane to the sun and not applying it to the Earth is incorrect. the earth is tilted on its axis to the sun by about 23° 27’ per Wiki reference. the moon is inclined to the Earths semi-major axis by 10 degrees. the Earth has its own ecliptic plane as does the moon.--<br /><br />http://en.wikipedia.org/wiki/Axial_tilt<br /><br /> <br /><br /><br />http://www.swri.org/9what/releases/2000/incline.htm<br /><br />Second<br />"If I didn't make my meaning clear I meant to say the the satellites I indicated would be synchronized in the direction of the lunar rotations with zero inclination." <br />--Snip--<br />They would be synchronized with what? <br /><br />--It will synchronize its orbital period and its rotational path above the geosurface which is synchronized to the Earths rotation.<br /><br />Take a hypothetical rod that runs from a geostationary satellite at the equator and pivots at the earth's center. keeping the rod at zero inclination to the Earths equatorial plane rotate the earth a 24hour period. You will have sliced the Earth perfectly in half.<br /><br /> Now take the same period of tim

 

[mrmorris]

<font color="yellow">"...all of these transponders on the surface of the moon throwing RF around..."</font><br /><br />Already mentioned and responded to. Transponders don't broadcast continuously -- they only respond when transmitted to. They would not be continuously emitting RF noise. Also -- the transponders would all be transmitting on a *very* narrow frequency range. Part of the RT problem with Earth-generated noise is that it's across all parts of the RF spectrum. The transponders could be set to a very 'uninteresting' RF range for radiotelescopes and/or one that was simply accounted for and ignored.<br /><br />Also -- we can reduce the noise even further. Unlike the Earth-based GPS, a lunar one would *not* have millions of anonymous users at any given time. GPS satellites on earth transmit continuously and GPS receivers simply receive. There is no 2-way communication. The lunar system could be more query-response oriented. The GPS 'receiver' could transmit a position request on demand to the satellite. The satellite only *then* queries the transponders in the area around the querying reciever -- performs triangulation calculations, and then transmits a response to the querying receiver. Beyond the RF noise reduction, this would also seriously reduce power requirements for the transponders and for the GPS satellites themselves.

 

[rocketman5000]

I was refering to your polar towers, but if you modified the architecture of the systems as mentioned in the post immediately above I believe that would be a workable solution.

 

[shadowsound]

An interesting idea but you want all calculations , location made at the querying source. Not at the GPS transmitter. The GPS satellite knows where it is and what time it is, relative to all the others but not where a querying source might be. Each of the ground based transcievers would have to have a time reference source for this to work. that makes it very complex and costly.<br /><br /><br /><br />Another is that it would take a great deal of these sources vice the few orbiting satellites. <br /><br /><br />The personal receivers are already designed the research and development done to a fairly refined state. <br /><br />Don't redevelop the boat just modify it to suit the needs.<br /><br />Check out the link.<br /><br />http://www.go.ednet.ns.ca/~larry/gps/gps_talk.html<br /><br />http://www.nist.gov/public_affairs/releases/mercury_atomic_clock.htm

 

[mrmorris]

<font color="yellow">"The GPS satellite knows where it is and what time it is, relative to all the others but not where a querying source might be."</font><br /><br />GPS receivers on Earth don't <b>talk</b> to the satellite, so there's no way it would know where they are. In the system I described -- since the 'receiver' actually queries the satellite -- it would be able to use the RF to backtrack and locate the source with reason accuracy (a couple hundred meters at least) before even invoking GPS-style calculations. If it's not feasible for the satellite to query the nearby transponders directly and return the results to the receiver, then it could certainly 'ping' them and tell them to transmit such that the ground-based receiver would be able to pick the signals up from the transponders directly.<br /><br /><font color="yellow">"Each of the ground based transcievers would have to have a time reference source for this to work. that makes it very complex and costly. "</font><br /><br />Yep. It'd be devastating if each of the transponders had to have their own Chip-Scale Atomic Clock.<br /><br /><font color="yellow">"Another is that it would take a great deal of these sources vice the few orbiting satellites. "</font><br /><br />Yep -- scores -- possibly hundreds of them. Each massing about 1/500th or less of a satellite, costing about a thousandth of a satellite, having no propellant costs, and providing massive redundancy. Silly idea.<br /><br /><font color="yellow">"Don't redevelop the boat just modify it to suit the needs."</font><br /><br />Of course. A system designed to support millions of people on Earth is obviously perfectly suited as-is to support a few dozen astronauts & rovers on the moon. Redesign? Nah -- just ship it.

 

[willpittenger]

<blockquote><font class="small">In reply to:</font><hr /><p>I haven't figure out how to change the color of the text yet even after reading the FAQ.<p><hr /></p></p></blockquote><br />Look at the last 8 tags in Can I use HTML in my posts?. <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>

 

[mrmorris]

<font color="yellow">"However tying the term Ecliptic plane to the sun and not applying it to the Earth is incorrect. "</font><br /><br />I don't believe I've done that. If you're providing data for general information... OK. <br /><br />When I mention an equatorial orbit while referring to a satellite, I mean the equator *of* the body it is orbiting. I would assume most people (at least most of the arguably small fraction of the population who would be discussing equatorial orbits) would do this as a general rule.<br /><br /><font color="yellow">"Take a hypothetical rod that runs from a geostationary satellite at the equator and pivots at the earth's center. keeping the rod at zero inclination to the Earths equatorial plane rotate the earth a 24hour period..."</font><br /><br />OK -- all I'm seeing here is satellite -- 24-hour period -- Earth. Everything in the example you gave seems to involve an earth-orbiting satellite. You've been talking about <font color="orange">lunar</font>synchronous orbits and you argued that I was incorrect when I stated there is no such thing. Specifically:<br /><br />You: <font color="orange">"Lunar equatorial synchronous orbiting satellites about the Moon for the GPS comm bird to communicate with continuously."</font><br /><br />Me: <font color="yellow">"What I am stating is that there is no such thing as a "lunar equatorial synchronous orbit". "</font><br /><br />You: <font color="orange"> "So what your saying is that you can never orbit continuously about the Lunar Equator, or polar axis."</font><br /><br />One last time: what lunar equatorial orbit are you saying is possible that will synchronize with the moon? I understand Earth and sun-syncronous orbits. You can't be talking about a 24-hour orbit around the moon -- it'd be too far out, it wouldn't be <b>lunar</b> synchronous and I don't see a value-add to it anyway. It would simply mean that the satellite would always

 

[MeteorWayne]

"GPS receivers on Earth don't talk to the satellite"<br /><br />This is a great point. On earth there are hundreds of thousands of GPS receivers, so the thransmitters need to be on all the time. For at least a few decades, there might be one or two receivers, so a "pinging " arrangement to activate the network when needed can really save on resources. If there are hyndreds of receivers scattered across the surface, then the complexity might outweigh the savings, but that's certainly at least a century away. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[willpittenger]

I figure each satellite would also have a much smaller (and robust) power system. We may never know what happened to MGS, but since a power failure is one possibility, perhaps solar cells arranged in a sphere like the old Telstar might work better. <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>

 

[j05h]

<i>> This is a great point. On earth there are hundreds of thousands of GPS receivers... </i><br /><br />That needs to be balanced against scalability. A sudden change in approach, for instance "net landers" or a group of balloons, could saturate such a system. Whatever positioning/comm sats fly should be somewhat reconfigurable about data and transmission. <br /><br />Could actual GPS satellites (on a different freq) be used for the Moon or Mars? Could Iridium satellites perform similiar functions, with built-in comms? For Mars all these ideas have power issues. Comments?<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[shadowsound]

OK I guess I just confused the matter by adding the synchronous to the reference. Equatorial orbit. So leave the word off it. Lunar Equatorial orbit it is. <img src="/images/icons/smile.gif" /><br /><br /><font color="yellow">One last time: what lunar equatorial orbit are you saying is possible that will synchronize with the moon? I understand Earth and sun-synchronous orbits. You can't be talking about a 24-hour orbit around the moon -- it'd be too far out, it wouldn't be lunar synchronous and I don't see a value-add to it anyway. It would simply mean that the satellite would always follow the same path across Earth when it passed between the Earth and moon. </font><br /><br />What I was talking about was a permanent communications infrastructure that would service the entire moon and orbit above it. It would have to be able toe provide communications also for manned and unmanned spacecraft to and from the Moon and Earth.<br /><br />What I was proposing was a highly robust line of sight system with a high degree of security and redundancy to keep it running with multiple failures. <br /><br />This separate from the GPS / communications system that would service the lunar orbit and ground users, from the communications path between the earth and the moon.<br /><br />The distance from the Earth to Moon varies because of the moons elliptical orbit. Even with using laser beams as communications carriers it will take a lot of power to cover that distance and keep the orbitals receiving hardware fairly low in power usage.<br />Perigee 363,300 km <br />Mean 384,400 km <br />Apogee 405,500 km <br /><br />http://www.freemars.org/jeff/planets/Luna/Luna.htm<br /><br />http://en.wikipedia.org/wiki/Moon

 

[shadowsound]

<font color="yellow">That needs to be balanced against scalability. A sudden change in approach, for instance "net landers" or a group of balloons, could saturate such a system. Whatever positioning/comsats fly should be somewhat reconfigurable about data and transmission.</font><br /><br />For the difference between the mars and Moon GPS/Comm satellites I don't know. It would have to have some legacy capability with existing ground assets.<br /><br />The satellite being like the Iridium satellite for Mars while more complicated would be better than one that simply provide a bent pipe configuration. I would say that it would have to have a tracking and data relay setup (TDRS) with satellite to satellite relay capability and GPS if possible in one system. It may require separate systems.<br /><br />http://nssdc.gsfc.nasa.gov/multi/tdrs.html<br /><br />http://www.gmat.unsw.edu.au/snap/gps/gps_survey/chap2/222sats.htm<br /><br /><br />

 

[mrmorris]

<font color="yellow">"Lunar Equatorial orbit it is. "</font><br /><br />s'cool. I have <b>zero</b> concerns about a lunar equatorial orbit... or a lunar polar orbit... or any inclination in-between. It's only when synchronization comes into play that my WTF flag is raised (given the moon's 28-day rotation).<br /><br /><font color="yellow">"What I was proposing was a highly robust line of sight system with a high degree of security and redundancy to keep it running with multiple failures. "</font><br /><br />Minitial post was regarding three satellites in equatorial orbit -- which would provide LOS to just about any point on the surface (terrain features might block som locations very close to the poles. <i>Looking back at that post for reference, I see that I made a stupid terminology faux-pas indicating that the three should be at 120-degrees <b>inclination</b> from each other, when what I meant was that the three should be equally spaced in the orbit (i.e. each opposed by 120-degrees from the other two satellites in the same orbit). I've edited the post to avoid confusing anyone new entering the thread.</i> Until and unless the population of the moon rises into tens of thousands of people, these three will *certainly* be able to do double-duty as comm satellites. If you have ten people that you need to get from one side of a river to another... the solution of choice is <b>not</b> to build the Golden Gate Bridge... no matter how pretty it would look.

 

[shadowsound]

<font color="yellow">Until and unless the population of the moon rises into tens of thousands of people, these three will *certainly* be able to do double-duty as comm satellites.</font><br /><br />If we are intent on fostering commercialization of the lunar resources we will need to encourage it by having as robust of network prepositioned as possible in place that will allow a large spectrum of users. <br /><br />The communications and navigational systems are common use resources like the telephone and highways here on earth. <br /><br />Without one or the other you stifle the development of modern commerce. Think of third world countries until roads, them rails, and Finally cellphone systems are introduced. Each stage of this fosters activity. <br /><br />About seven to eight years ago Loral put up a series of communications satellite that offered services to Africa. before the use of a cell phone Internet network would have been impossible.<br /><br />Now a person in remote areas that had never seen a phone in their life. Can talk and email and run businesses with people around the world.<br /><br />It is a key component in development of the moon and from their Mars or the rest of the Solar System.<br /><br /><br />We want to foster commercial enterprise that will also encompass research capability rather than just individual research projects. It can be a coalition of several commercial groups that are subsidized by guarantees by The United Nations, or the International Monetary Fund. The loans must be paid back when the commercial sale of services begin but amortized over a long enough period that it will not cause the commercial venture to fail, or the builders to default on their loans. No default should be a built in clause. <br /><br />The money which is spent on earth to build and launch these networks are not lost in space, but fosters employment and entrepreneurship for further development.

 

[shadowsound]

<font color="red"> I made a few changes to this after original posting it. Some of you may get this via email and not see the changes on the first.</font><br /><br /><font color="yellow">Until and unless the population of the moon rises into tens of thousands of people, these three will *certainly* be able to do double-duty as comm satellites. </font><br /><br />If we are intent on fostering commercialization of the lunar resources we will need to encourage it by having as robust of network prepositioned as possible in place that will allow a large spectrum of users. <br /><br />The communications and navigational systems are common use resources like the telephone and highways here on earth. <br /><br />Without one or the other you stifle the development of modern commerce. Think of third world countries until roads, then rails, and Finally cellphone systems are introduced. Each stage of this fosters activity. <br /><br />About seven to eight years ago Loral put up a series of communications satellite that offered services to Africa. before the use of a cell phone Internet network would have been impossible. <br /><br />Now a person in remote areas that had never seen a phone in their life. Can talk and email and run businesses with people around the world. <br /><br />It is a key component in development of the moon and from their Mars or the rest of the Solar System. <br /><br /><br />We want to foster commercial enterprise that will also encompass research capability rather than just individual research projects. It can be a coalition of several commercial groups that are subsidized by guarantees by The United Nations, or the International Monetary Fund. The loans must be paid back when the commercial sale of services begin but amortized over a long enough period that it will not cause the commercial venture to fail, or the builders to default on their loans. No default should be a built in clause. <br /><br />The money which is spent on earth to build and launc

 

[shadowsound]

<font color="red">As you can see I finally figure out what they were saying.<br /><br />Thanks for the help</font><img src="/images/icons/smile.gif" /><br /><br />Look at the last 8 tags in Can I use HTML in my posts?. <br />