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Why don't we have a gps type satellite on the moon?  

Nate The Surveyor
5,000+ posts Registered

I was thinking putting three satellites on the moon would give you a small triangle and would give you some interesting information from a GPS point of view. It could augment our GPS system. And being on the moon, could provide 3 units, mounted together.
I'm just bringing it up.
Why, or why not?

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Posted : April 21, 2017 4:51 am


Posted : April 21, 2017 5:57 am
Mark Mayer
1,000+ posts Registered

Nate The Surveyor, post: 424683, member: 291 wrote: Why, or why not?

Probably a cost/benefit thing. Soft landing a unit on the moon would cost a lot more than orbiting one. In fact I'd guess it would cost more than orbiting a few dozen of them.

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Posted : April 21, 2017 7:32 am
Dan Patterson
1,000+ posts Registered

Also, I'm thinking your triangle would be incredibly small compared to the distance from the earth to the moon. Those three would essentially be the same as having just one given their relative proximity to each other vs the distance they are measuring.

Daniel J Patterson, PLS, PE

Posted : April 21, 2017 7:38 am
2,500+ posts Registered

The moon is on average 19 times the distance of the GPS satellite orbits.

So you have
-high cost of delivery and soft landing on moon
-weak signal unless you build it with high power transmitters (and big solar array, hard to deploy on landing)
-much more complicated calculations for position, involving moon's orbit and libration
to gain
-Little more benefit than one more satellite, because of the small angle between any number on moon. You might gain in resolving ambiguities, but not much in DOP.

Posted : April 21, 2017 8:49 am
2,500+ posts Registered

The moon is a bit too wobbly. "Fixed" points on the moon are not quite as "fixed" as would be optimal for any kind of ranging methods. Even with antennas spread around the edge of the visible side are not going to provide very good geometry, and would have to have their positions tracked as well if not better than the exiting orbiting sats. But as an augmentation to existing constellations? Have heard some pretty compelling ideas floated at past conferences (but no serious papers as yet). Now putting a persistent source of RF in very distant orbits (like out in the belt) could provide a very precise alignment augmentation (like VLBI). Existing VLBI sources (e.g. distant quasars) are too weak for small portable dish solutions to work.
Then there are things like gravitational "lens" effects around bodies like the moon that might boost distant sources. Still kind of a stretch.
But all that geekage aside.... I am sure that if/when there are developments on the moon and Mars that laterally provide persistent sources of RF, then some folks will figure out how to augment positioning and navigation using them... watch for a Kickstarter for the GavNav 2060... 😀

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Posted : April 21, 2017 3:43 pm
500+ posts Registered

Seems to be the type of question pondered up after partaking in a communal peace pipe with the local hill-billies.

Posted : April 21, 2017 4:06 pm
R.J. Schneider
1,000+ posts Registered

clearcut, post: 424806, member: 297 wrote: Seems to be the type of question pondered up after partaking in a communal peace pipe with the local hill-billies.

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Posted : April 21, 2017 4:17 pm
James Fleming
2,500+ posts Registered

Two words....moon people


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Posted : April 21, 2017 4:39 pm
250+ posts Registered

Posted : April 21, 2017 5:12 pm

James Fleming, post: 424815, member: 136 wrote: Two words....moon people



Posted : April 21, 2017 5:37 pm
2,500+ posts Registered

My brother asked me something similar a year ago. It was more along the line of obtaining better elevations probably thought of from the Big Bang episode where the geeks blasted a laser at a target on the moon and determined an expected distance.

I would prefer an array of photo satellites to see the whole moon at once. Same with mars and all the other planets. This originates from the Martian and the gaps in visibility from the lack of satellites. Does not help us until we really start mapping.

J. Thaddeus Eldredge, PLS, CFM
Eldredge Surveying & Engineering, LLC

Posted : April 21, 2017 6:06 pm
Chris Bouffard
100+ posts Registered

How about orbit, rotation and the revolving Earth? Not to mention that the moon is not on an equidistant orbit.

Posted : April 23, 2017 8:23 am

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