# Would a Lagrange point sat see much of the Lunar far side?

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#### willpittenger

##### Guest
Suppose we put a satellite into either the Earth-Moon L4 or L5 point. How much of the far side of the Moon could that satellite see? For that matter, if we put a satellite at L2, how much of the Earth could that satellite see? <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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#### docm

##### Guest
L4/5: less than we do, half or less, and at a greater distance.<br /><br />L2: the dark side of Earth, sometimes overlaid by the moon. <div class="Discussion_UserSignature"> </div>

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#### willpittenger

##### Guest
<blockquote><font class="small">In reply to:</font><hr /><p>L4/5: less than we do, half or less, and at a greater distance.<p><hr /></p></p></blockquote><br />Huh? We don't see any of the far side of the Moon. So how can the sat see less? All it has to do is serve as a communication 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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#### docm

##### Guest
<font color="yellow">We don't see any of the far side of the Moon</font><br /><br />The Dark Side <br /><br />All by way of Earthshine for at least part of its orbit. <div class="Discussion_UserSignature"> </div>

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#### docm

##### Guest
I know, but I just had to tweak him. <div class="Discussion_UserSignature"> </div>

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#### brellis

##### Guest
It'd be great to have 24/7 cameras at LaGrange points, so we can watch "As the World Turns" for real <img src="/images/icons/cool.gif" /> <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

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#### willpittenger

##### Guest
Why? I went back and double checked both of my previous posts. I got the terms right each time. If you don't want to answer the question, just say so rather than being a smart ass. <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

##### Guest
I would figure that if you put a communications sat at the L2, L4, and L5 points and had them relay signals back and forth to one another and Earth, then you could get about as much coverage of the Moon as a three-sat GEO comm-sat system on Earth gets. <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

##### Guest
Finally. Someone who doesn't see this thread as a place to put their jokes. <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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#### brellis

##### Guest
What is the time delay for L-points versus GEO? <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

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#### comga

##### Guest
Earth, Moon, and EML-4 or EML-5 form equilateral triangles. The distance to the moon is the same as from Earth. You see the moon from sixty degrees off the almost-fixed Earth-Moon line. That means you see another sixty degrees "around the limb" as seen from Earth. Combining the views from EML-4 and ELM-5 allows you to see two thirds of the "far side" of the Moon. <br /><br />ELM-1 has the same line of sight as the Earth, but at a closer distance so less of the Moon is seen. EML-2 would see some of the "far side" but would be out of communications with the Earth, unless a large halo orbit could be established. Anyone know how larger a halo orbit can get and still be stable?

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#### bobw

##### Guest
I think his head is going to explode soon. <div class="Discussion_UserSignature"> </div>

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#### brellis

##### Guest
<img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p><font size="2" color="#ff0000"><em><strong>I'm a recovering optimist - things could be better.</strong></em></font> </p> </div>

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