"Paul Mc" wrote in message
ups.com...
I'm no expert on gravitational or radiological issues but have
considerable experience in marketing commercial satellites and so was
wondering what comunications possibilities this idea might afford. As I
non-expert I have difficulty envisaging its 'orbit' when viewed from
the Earth or the Moon (being used to simple concepts like
geo-stationary or LEO.

I also thought it a worthy subject for discussion within cam.misc, but
it seems to have been diappeared from there already.

The Lagrange points are positions where the gravitational fields of two
bodies effectively cancel. For the moon, there are five such points, named
L1 to L5. The moon's Lagrange point L1 is about 36,000 miles from the moon
(or about 203,000 miles from earth) on a straight line connecting earth and
moon. A satellite positioned at moon L1 would therefore orbit the earth
along with the moon every 27.322 days (orbit tilted about 28.7 degress to
the equator this year). Radio signals would take about 1.3 seconds to
cover the distance, one way.

The other Lagrange points are L2 (on the same line but about 36,000 miles
behind the moon), L3 (on the same line but about 239,000 miles behind the
earth) and L4/L5 (on lines 60 degrees ahead/behind the first line and both
about 239,000 miles away).