# Talk:Comm satellites

Gary is the primary contact on this. But, Let the ideas flow...

okay, first, from the point of view of the moon, the earth is in a lunar 'geo-stationary' orbital position.
Since most of the data probably needs to go there, It makes some sense to put a largish dish on the surface with the power generating infrastructure to blaze away with high bandwidth comms. (comm distance 384,402km)

The second stationary point would be the L1 Lagrange point. Located 58,000 km above the lunar surface. It's not stable, but a small engine can keep it from wandering to far. The comm range to the earth is still an additional 334000 km

A third 'Position' would be at or around the L2 point. The L2 point is about 65000 km above the surface of the far side of the moon. An orbit around the L2 point can probably be large enough so that a satellite could 'see' around the moon directly to the earth. The position of such a satellite would make a low-lain or tracking antenna system.

The L4 or L5 points are as far from the moon as the earth is, and only add

For polar and limb access, a more conventional constellation will be required. Low lunar orbits are not very stable because of the gravitational lumpiness. High orbits are similarly perturbed by the earth (and sun) gravitational relations.

Another design parameter is that the higher the orbit, the more area covered but the longer distance the radios have to talk.

While we are at it, a large data rate satellite is a large satellite wih large solar arrays to generate the required power. Since it probably needs some sort of station-keeping, a plasma (ion, Hall, MPD, etc.) engine is probably a good idea.

Notes:

Earth moon Distance 384403 km E-M L1 Distance 58080 km E-M L2 Distance 64598 km

So here are some questions:

What comm system should be used - Range (sat altitude req) - Power (consumed and transmitted) - antenna (gain or omni) - data rate (hd video or slow telemetry)

Where are the points of interest on the surface ? - if the poles are primary, could some polar orbits solve all the coverage problems ?

These will drive the satellite designs and orbital altitudes

Comments, additions etc ?

-gar 2/15