Moon GPS

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awuj2

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Moon Polar Positioning and Meteoroid Impact Assessment System - what do you think?<br /><br />In 1995 American satellite based Global Positioning System became fully operational. <br />It actually carries two sets of instrumentation - first for positioning signal emission (as everybody knows) and second – for nuclear detonation detection (NUDET, as they call it).<br />It is global and easy-to-use. There is even a rival system – Russian GLONASS (but not so nicely working), and an European one is being built (GALILEO).<br />The technology is ready and mature, why don’t we use it for something more? <br /><br />1)Why do we need this?<br /><br />A last three nations seriously plan to land humans on the Moon: China, Japan and the United States (there is no clear information about Russia). It is difficult to say which of them will be first (USA?), but it actually does not matter much. The real problem would be to build and maintain a lunar base, with continual human presence. To do so we need proven human-rated spacecrafts (CEV?), heavy-lift rockets, Earth-Moon transition systems, Moon-landing and ascending vehicles, habitation modules. All of that is doable (albeit costly), but: <br /> a)It is very difficult (if possible at all!) to precise maneuver a spacecraft (especially with no humans onboard) far from the Earth, without knowing its exact position. <br /> b)Moon has no atmosphere, so there is no shield defending it from asteroids (or meteoroids). That impacts are currently the only cause for any geological changes there, and actually pose the biggest threat for future station (or other moon-based infrastructure).<br /> c)It is possible to establish a communication link to Earth, but only from one side of the Moon (that facing Earth). A lunar base on its dark side can not have a direct link to Earth at all! <br />Why cannot we solve all of that problems with one good system, based on existing technology?<br /> <br />2)Mission<br />That system should be able to pr
 
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shadowsound

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I agree it is a key component that would spur greater expansion of the space exploration and development of the moon.<br /><br />Along with it a integrated communications system. and possibly land sat mapping system.<br /><br />By adding a 24/7 communications system with the Earth you have a leap forward in research capability.<br /><br />A company with the capability to build it is Loral. They built the Globalstar system of around 50 plus satellite for several billion dollars . Small satellite built with high capacity even at the time. whose design would be able to be updated with modern tech. Putting up clusters at a time enhances upgradable as the older ones are removed from service or upgraded on orbit.<br /><br />Once in place it decreases the needed cost of all other missions in research and development. <br /><br />The cheaper the cost; the more that are done, and the more money the launch industry makes. This make it cheaper still for solar research and development.<br /><br />It provide a standard mapping reference configuration. all virtual and read maps using the same mapping reference configuration. Like that one earth. thus allowing a standard reference that can be submitted to to the bureau of standards.<br /><br />I've been talk, pushing, and waiting for such for a number of years. <br /><br />Ive heard rumor and inuendoes for the ast year but noting solid about a program.<br /><br />If need be it could be farmed out as a commercial profit venture program for a company.
 
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willpittenger

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<blockquote><font class="small">In reply to:</font><hr /><p>In 1995 American satellite based Global Positioning System became fully operational.<p><hr /></p></p></blockquote><br />It was at least partially operational before that. In the first Gulf War, we gave the military civilian model GPS devices because the Military spec units were not available in suffficient quanities. This forced the Pentagon to turn off GPS encryption. (The encryption causes civilian models to be less accurate.) 1995 sounds like about when GPS encryption was turned off permenantly. (Some encryption options may remain in case of war with a GPS equipped adversary. Read Tom Clancy's <i>Executive Orders</i> for what happens.) <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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A GPS-like system was one of my pre-requisists for a manned mission to Mars. Strangely enough, when I asked how the satelittes should be sent to Mars, some claimed that only 3-4 units would be required. Personally, I figure the number is much higher -- at least for Mars. The Moon is smaller. That means it has more Horizon curvature. That might reduce the number somewhat, but still not to 3-4. <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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bpfeifer

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In reality, you don't need to provede GPS coverage for the intire moon. To start with, you only need to cover the area surrounding your first lunar base. Then over time you can expand the system as activities warrent. <div class="Discussion_UserSignature"> Brian J. Pfeifer http://sabletower.wordpress.com<br /> The Dogsoldier Codex http://www.lulu.com/sabletower<br /> </div>
 
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rocketman5000

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that might be difficult to only provide partial coverage because typically GPS satelittes are not in a syncronous orbit. minimum number of satelittes required should be easy to calculate if the required orbit is known. using lines tangent to the surface of the moon (using mean radius) estimate the number needed to completely cover the surface. Then add one more. Receiveing only two satelittes would only locate you within one of two locations north or south of lunar equator. (assuming equatorial orbits of GPS satelittes)<br /><br />Anyone know what orbit altitude a typical lunar GPS sat would to maintain? Course my above explaination assumes a smooth surface, so its not a perfect explaination.
 
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shadowsound

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The point is that you limit yourself if you cover only a piece initially. The idea is to make the whole lunar globe available. <br /><br />It should allow a vehicle to move about the Lunar globe autonomously to be given a location and it maneuver itself to that position. It should allow an immediate link to the Earth for remote control or download of sensory data. It should allow broad band communications relay for any spacecraft the enters within its sphere. It should allow immediate imaging of a lunar or orbital location above or below it at emergency notice.<br /><br />It is a public resource that allows the immediate expansion of human and robotic activities.<br /><br />It is an enabling infrastructure that reduces the cost of Lunar operations <br /><br />By placing surface receivers on the lunar surface you can track and provide communications or the rest of the solar system without the perturbations of the earths atmosphere. <br /><br />Astronomical devices can be far larges and the worry about loss of tracking do to loss of momentum wheels or gyroscope problems. Repair by lunar maintenance cost is reduced. <br /><br />The Watcher <br /><br /><br /><br />
 
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spacester

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Nice thread. I've been trying to talk lunar bandwidth here for ages with little effect, so I don't think folks here are going to embrace your lunar GPS. Don't worry, it's not your fault.<br /><br />It IS a bit grandiose, though. Myself, at the moment I'd settle for just one cast-off comsat that could be replenished on orbit and live out its days in lunar orbit. That would be just the thing to get it started, of course. In fact the whole strategy ought to be to have the com capability always stay one step ahead of surface activity.<br /><br />The thing is, if you're on the near side, you've got line of sight comms to Earth. But unless you've got a big transmitter, your bandwidth is going to be too small to carry out robust telepresence, for example. <br /><br />So what is needed is at least one lunar comsat to act as a relay. My thinking is that if you put a GEO bird at medium lunar orbit, you would get at least periodic bursts of high bandwidth. Coverage would be limited, but the orbit would be chosen to work for the initial private efforts on the moon. And given the initial capability, clever com guys could maximize the resource.<br /><br />Knowing their prospective comm capability, even with these limits, lunar telepresence based business plans would be able to move forward.<br /><br />Having said all that, having global coverage right away would be awesome, and is a fabulous idea if you can pull it off.<br /><br /> <div class="Discussion_UserSignature"> </div>
 
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mrmorris

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For a heckuva good lunar GPS, you need three satellites. Or actually four, but the fourth wouldn't really be part of the GPS constellation.<br /><br />Put the three GPS/comm satellites in lunar equatorial orbit -- each 120-degrees from each other (i.e. the three satellites evenly separated in the same orbit) at the most stable altitude possible. This will ensure that two will always be in sight of any position on the moon. This won't provide GPS yet, but it's a good start and *does* provide excellent communications capability.<br /><br />The fourth satellite isn't part of the constellation... it's more of a minelayer. It will be sent into an <b>extremely</b> low lunar orbit. It will be essentially a railgun launcher with an onboard storage of scores of very small transponders. As the satellite orbits the moon, it will 'fire' the transponders at various angles (always retrograde) at a velocity sufficient for them to de-orbit. Each transponder will mass just a couple of kilograms. They will be surrounded by an inflatable 'beach ball' as landing system. In vacuum, one of the small CO2 cartridged like is used for paintball guns would inflate such a ball handily. Once landed (and after they stop rolling), the deflation system will be set up to maximize chances that the transponder will end up with its solar cell 'upright'. Failing that -- you might design the devices as a disk with solar cells top *and* bottom (expecting to always write one off).<br /><br />So eventually your 'minelayer' will have dispersed a few score (or a couple hundred -- depending on how small they can be made) transponders about the surface of the moon. At this point, the satellites will query and pinpoint all of the transponders that survived our insertion scheme. Once this is complete, our 'lost' astronauts will have two satellites in the sky visible to them, and the satellites will have scores of transponders in known locations about the moon to help them pinpoint exactly where you are in
 
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spacester

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Nice! The surface transponder network makes sense, it's a question of deployment.<br /><br />For three lunar GPS/comsats, I didn't quite parse your description - all 3 in equatorial orbit? Inclination goes up to 90 degrees and then it's retrograde. I confused.<br /><br />IIRC, 3 birds can't get you full global coverage. <br /><br />I'm thinking that if your fleet numbers 3, you simply put them in inclinations of zero and polar and somewhere near 45 deg. They may or may not have the same altitude and thus orbital period. This simple concept would then be tweaked to optimize for the actual operations to be supported (customers).<br /><br />I wonder what the trade-offs are on the surface transponders in terms of getting the thing elevated above the surface and the additional mass/complexity needed to do that. Perhaps it ends up on top of the beach ball and that's good enough. Perhaps it's worth building towers.<br /><br />My vision is more along the lines of deploying transponders with surface rovers, pathfinder explorers used as precursors to development of whatever stripe. Scientific scouts that leave behind a cookie crumb comm network during their travels, science supporting development. <div class="Discussion_UserSignature"> </div>
 
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mrmorris

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<font color="yellow">"For three lunar GPS/comsats, I didn't quite parse your description - all 3 in equatorial orbit? "</font><br /><br />Yes -- all three in equatorial orbit. There's 360-degrees in the orbital path. If the three are equally spaced, they'll be at 120-degrees separation from each other. Looking back at my post, I said two will be in the sky at all times -- that was a mistype. One will always be overhead at all times, and each of the three should be able to communicate with the other two.<br /><br /><font color="yellow">"I wonder what the trade-offs are on the surface transponders in terms of getting the thing elevated above the surface..."</font><br /><br />I don't understand why you want them elevated. The transponders are responding to the satellite, not the astronauts. Given that -- they don't need elevation... the satellite has that in spades.
 
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shadowsound

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Say that the ball is not a perfect sphere, but that it is like a golf ball, pock marked with focusing indentations with a blister cover that includes the mylar subreflector and rf connections in it. the rest of the surface is photo receptive that gathers energy to be stored.<br />The electronics is tethered bungy like in the center. Using the connections a eletrical, and RF transponders connections.<br />Setting at rest it gathers the communications from multiple sources and transmits to reciever sources.<br /><br />It monitors the frequency range of the orbital satellites and transmits to the optimal reception receiver region. This could be up to the number of satellites in view.<br /><br />It doesn't matter what side it finally rests on it will optimize itself.<br /><br />The problem though is that given too many it can become a source of RF polution. Each one would have to optimze itself after in position with a unique location number. Size of the balls would depend on how great the transmit power and frequency range would have to be. <br /><br />Deployment low orbiting craft that accellerats them out the back of the craft up to one hundred percent 180 degrees out from the deploying crafts flight path and velocity relative to the lunar surface. This places them in a zero delta v relative to the surface. This allows it to drop relative to mass to the gravitational pull and hight above the surface. The ballistic arc can be calculated for deployment, and least impact damage.
 
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shadowsound

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If were going to do it as a mind game scenario why not go hog wild with the imagination, and spend those virtual dollars like water.<br /><br />Aside from the GPS cluster about the moon we add another layer or rather a network to it.<br /><br />Lunar equatorial synchronous orbiting satellites about the Moon for the GPS comm bird to communicate with continuously. These transmit to a series of molniya orbiting comm bird about the earth three to four sets like the Sirius satellite system that provides together a multiple transmitter, multiple receiver, network of laser comm satellites. <br /><br />They would transmit from multiple sources to multiple receivers on multiple spectral frequencies with code hopping to provide security. if you needed it after that.<br /><br />by transmitting on multiple paths you increase your effective bandwidth. and provide redundancy for error correction. <br /><br />I call it Hydra. cut off one head and it continues to live via the other heads until you replace the damaged one.<br /><br />This gives a survivability in a major sunspot storm.<br /><br /><br />
 
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bpfeifer

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"Lunar equatorial synchronous orbiting satellites about the Moon"<br /><br />Is it even feasible to place lunarsyncronous satellites in orbit? Considering how slowly the moon rotates, wouldn't that put the satellite in a rediculously high orbit? <div class="Discussion_UserSignature"> Brian J. Pfeifer http://sabletower.wordpress.com<br /> The Dogsoldier Codex http://www.lulu.com/sabletower<br /> </div>
 
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mrmorris

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<font color="yellow">"The problem though is that given too many it can become a source of RF polution."</font><br /><br />A transponder doesn't continuously transmit -- that would take ***much*** more energy. Transponders re<b>spond</b> when <b>trans</b>mitted to. They simply send a quick blip to say something like "Here I am... transponder number XB14J6729".<br /><br /><font color="yellow">"Each one would have to optimze itself after in position with a unique location number."</font><br /><br />It's the nature of transponders to have unique identifiers. They're used for automated toll booths (i.e. each car has a unique transponder for their account), locating fleet vehicles and tracking high-value shipments. Transponders are already used to track things in this fashion from thousands of miles away.<br /><br /><font color="yellow">"Deployment low orbiting craft that accellerats them out the back of the craft up to one hundred percent 180 degrees out from the deploying crafts flight path and velocity relative to the lunar surface. This places them in a zero delta v relative to the surface."</font><br /><br />Yes.... this is basically what I said initially. Except that achieving zero <b>velocity</b> relative to the surface is not feasible (<b>not</b> delta-v, which is change in velocity). A railgun which could provide that much accelleration even to relatively tiny payloads is simply not reasonable. However, if the satellite is already in a very low orbit -- even one low enough to be unstable itself (we only need it to make one pass, maybe two before impact anyway) -- it can certainly provide enough retrograde acceleration to the transponders to make *their* orbits unstable. After all -- we don't need the transponders to be precisely distributed. We simply need a bunch of them scattered about the moon's surface to provide the ability to triangulate relative positions.
 
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mrmorris

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<font color="yellow">"...wouldn't that put the satellite in a rediculously high orbit? </font><br /><br />Correct -- lunarsyncronous orbit is not feasible.
 
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willpittenger

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Actually, your house is in such an orbit around the moon. However, you might want to work on a public relations spin to counteract the physical spin you have to put up with.<br /><br />Other lunar synchronous orbits are possible, but the object would orbit the Earth as much as the Moon. <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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mrmorris

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<font color="yellow">"Actually, your house is in such an orbit around the moon."</font><br /><br />No. It's not. The moon is tidally locked, such that only one face points towards earth in its orbit around the planet. This is not a lunar synchronous orbit. <br /><br />A geosynchronous orbit is one high enough (~35,786 km) such that the velocity of the satellite (~3.07 km/sec) exactly matches the rotation of the planet Earth. An orbit around the moon which produced a similar match of altitude and speed would be so far out that the satellite in question would have exceeded escape velocity for the moon.<br /><br /><font color="yellow">"Other lunar synchronous orbits are possible..."</font><br /><br />No -- there are no such animals. The closest thing to a lunar synchronous orbit would be the Earth-Moon Lagrange points.
 
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shadowsound

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Am I wrong in that you are thinking of geostationary vice synchronized with the equator yet still rotating above the same surface path this may be equatorial or Polar. <br /><br />Anything else would make the satellite orbit like the space stations path over the earth in a circular orbit, or an elliptical orbit.<br /><br />The GPS of our present system is a non-synchronous system of multiple shells. they will never have orbit location that will coincide. IE Crash.
 
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mrmorris

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<font color="yellow">"Please rethink your arguments."</font><br /><br />You made two statements:<br /><br /><font color="orange">"Actually, your house is in such an orbit around the moon."</font><br /><br />and<br /><br /><font color="orange">"Other lunar synchronous orbits are possible, but the object would orbit the Earth as much as the Moon."</font><br /><br />Both of these statements are <b>false</b>. A synchronous orbit has a very specific meaning. The Earth is <b>not</b> in a synchronous orbit around the moon. There are <b>no</b> lunar synchronous orbits that 'would orbit the Earth as much as the Moon'.<br /><br />I'm well aware of the portion of my post that you consider to be 'proving your points' (specifically the second one). You can place satellites in L1, L2, L4 and L5 and they will stay in that position with only minor corrections required. Because the moon is tidally locked with respect to the Earth and the satellites are fixed with respect to the positions of the Earth/Moon -- they will mimic an LSO (in marked contrast to a satellite at the Sun-Earth Lagrange points which would <b>not</b> mimic a satellite in GEO). However, this is ***not*** synonymous with a lunar synchronous orbit. In fact -- satellites in these positions won't orbit the moon <b>at all</b>. I will now reword the second statement you made such that it is correct.<br /><br /><i>"It's possible to place an object at one of the lunar lagrange points to achieve results similar to a lunar synchronous orbit, but the object would not be 'orbiting' the moon at all but would rather be orbiting around the Earth in a fixed position relative to the moon."</i><br /><br />But I'm sure that's what you really meant to say.
 
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mrmorris

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I'm not able to parse this statement and understand what you're asking: <br /><br /><font color="yellow">"Am I wrong in that you are thinking of geostationary vice synchronized with the equator yet still rotating above the same surface path this may be equatorial or Polar. "</font><br /><br />You said here: <font color="orange">"Lunar equatorial synchronous orbiting satellites about the Moon for the GPS comm bird to communicate with continuously."</font><br /><br />Then bpfeifer asked here: <font color="orange">"Is it even feasible to place lunarsyncronous satellites in orbit?"</font><br /><br />Then I answered bpfeifer here: <font color="orange">"Correct -- lunarsyncronous orbit is not feasible."</font><br /><br />What I am stating is that there is no such thing as a "lunar equatorial synchronous orbit". If you're asking me a different question, I don't know what that question is.
 
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shadowsound

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The molniya is a bit different in that it is in a highly eccentric synchronized orbit. in the case of the Sirius satellites, and I gather Russian satellites, it is optimized to provide maximum orbit in apogee and minimum in perigee. A plot on subsurface sill show it as a lopsided figure 8 the larger part over the northern latitudes and a smaller over the southern latitudes.<br /><br />It provides for maximum line of site for sub satellite RF reception. <br /><br />By providing for several satellite systems half optimized for the norther hemisphere and half for the southern. you have maximum planetary coverage
 
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shadowsound

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So what your saying is that you can never orbit continuously about the Lunar Equator, or polar axis.<br /><br />In that case are you saying that the moons uneven mass and tidal locked orbit prevents passing over the same location on the lunar surface one orbit to the next?<br /><br />Http://www.braeunig.us/space/orbmech.htm<br /> <br />if not maybe we have a difference in semantics.<br /><br />I located a very good web site that people
 
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mrmorris

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<font color="yellow">"So what your saying is that you can never orbit continuously about the Lunar Equator, or polar axis."</font><br /><br />No. Apparently what I'm saying is that you have no idea what a synchronous orbit is. The confusion arises in that I didn't <b>realize</b> until your latest post that this is what I was saying.<br /><br />A synchronous orbit is one that is <b>synced</b> with the rotation of the body it's orbiting, such that it is *always* directly over the same portion of it. Synchronous orbits can only be equatorial orbits. <b>Geosynchronous</b> orbits (which is to say synchronous orbits for the planet Earth) have an orbital period of 24 hours. Lunar Synchronous orbits would have an orbital period of two weeks. This is not feasible.<br /><br />At the URL that you so kindly provided, there is a link called Types of Orbits which neatly explains GEO:<br /><br /><i>"Geosynchronous orbits (GEO) are circular orbits around the Earth having a period of 24 hours. A geosynchronous orbit with an inclination of zero degrees is called a geostationary orbit. A spacecraft in a geostationary orbit appears to hang motionless above one position on the Earth's equator. For this reason, they are ideal for some types of communication and meteorological satellites."</i><br /><br /><font color="yellow">"if not maybe we have a difference in semantics."</font><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.
 
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