Great plans for the future!

[Dimkin]

Hey all!
I've got this big idea and I want to try it, but:
1. I don't know if it's even possible.
2. I don't know what skills I have to master to be able to do it.

So, the idea is that I want to deploy GPS-like network on moon, for this purpose I want to put N satellites on moon on geostationary planes to cover it 100%.
So, is it even possible to houl the satellites all the way from earth to the moon and deploy them there?
And what skill I have to master to do it?
Thanks

 

[astrosammy]

I recommend the SkyLink Sat that comes with Kulch's Energy Project.
You could launch some of them with a Nova rocket (that comes with sputnik's velcro rockets) .
Geostationary is impossible on Moon, Polar Orbits are better

 

[pattersoncr]

Geostationary (would they be Lunar-stationary?) satellites don't really work on the moon. Given the moon's very low rotation rate, you probably wouldn't be able to get a big enough orbit to give you the required orbital period (28days or so) and still be inside the moon's sphere of influence. You'd be better off placing a larger number of satellites in a lower orbit. This is actually how the GPS satellites are set up, they are not geostationary.

 

[Dimkin]

If I drop them on low orbit how can I calculate where to drop them that every single minute there is influence of at least 3 of them?

 

[astrosammy]

I think the best way is to place 4 satellites in a high but still stable Orbit (2000km or so), that way you have a satellite at 0°, 90°, 180° and 270° of the orbit. Now you could make 4 groups of satellites, each having 4 satellites placed like described above. Now each group has another equatorial Inclination, a group at 90°, another at 45°, the next at 0°, and the last at -45°. I think this way you'll even have 6 to 8 satellites in range.

 

[pattersoncr]

The GPS satellite "constellation" (what a great word) consists of 24 satellites. The satellites are arranged in six different orbital planes. Each plane has a 55deg inclination (with different LANs) with four satellites equally spaced around each plane.

This page explains in more detail:
http://www.kowoma.de/en/gps/orbits.htm

 

[martins]

An animation discussing visibility:

 

[Urwumpe]

even more important than pure visibility is also that the satellites are not too close together when seen from ground. Otherwise, the accuracy of the calculation drops.

 

[pattersoncr]

even more important than pure visibility is also that the satellites are not too close together when seen from ground. Otherwise, the accuracy of the calculation drops.

That's what having all the satellites at the same inclination but different LAN does for you. They all end up widely separated.

 

[Urwumpe]

That's what having all the satellites at the same inclination but different LAN does for you. They all end up widely separated.

Yes, but the trick is to achieve this at any place in your coverage area. different LAN alone does not do that, you also need the right orbit period for the angles.

 

[pattersoncr]

Yes, but the trick is to achieve this at any place in your coverage area. different LAN alone does not do that, you also need the right orbit period for the angles.

How so? This speaks to a question I already had. The GPS satellites hava a period of 1/2 a sideral day. What is the advantage of that? Don't you just need the periods of all the satellites to be the same?

Dimkin,
I hope I'm not taking your thread too far off course.

 

[tblaxland]

How so? This speaks to a question I already had. The GPS satellites hava a period of 1/2 a sideral day. What is the advantage of that? Don't you just need the periods of all the satellites to be the same?

I have read somewhere that a non-uniform pattern of orbits actually yields better accuracy a slight expense of visibility. The advantage of having a half sidereal period orbit is predictable repeating ground tracks.

Here is the document I was thinking of:
http://www.aero.org/publications/crosslink/summer2002/03.html

 

[HiPotOk1978]

I recommend the SkyLink Sat that comes with Kulch's Energy Project.
You could launch some of them with a Nova rocket (that comes with sputnik's velcro rockets) .
Geostationary is impossible on Moon, Polar Orbits are better

I am still trying to get my farside comm sat idea to fly... One thing I love about the moon a little dV goes a long way.... sadly if your trying for EXTREAME precision, it can also hurt you

 

[Dimkin]

Well, accuracy can be acheved with small low power burns.
For the GPS system, thanks all for lots of information, I've decided to dig a bit unto it before I will start the deploying, and while I'm at it I'll have time to learn some fundamentals I don't know yet.
And if we're already talking a bit offtopic: Can anyone point out a good tutorial of how to fly and land deltaglider IV inside Earth atmosphere?

 

[HiPotOk1978]

I was talking with my wife about the problems with navigating on the moon and lack of a proper GPS system. I started describing a system of placing a series of satellies in orbit right over the moons equator and after i babbled for a few minutes, she said one word... 'http://en.wikipedia.org/wiki/Sextant'

I figured that you could do it with the stars that you see but if you wanted a more modern approach, a series of satellites in orbit where you could always see at least one of them could provide a navigational aid similar to what we do on Earth. Link provides good reading for naviation. Not sure why it would not apply to any body in the solar system. You just need the proper charts