In a message dated 1/12/2007 7:22:19 AM GMT Standard Time, w7lrd@comcast.net writes:
Hello Amsat'ers Is it possible or practical to have a communications satellite at the L1 or L2 points. 73 Bob W7LRD Seattle
Hello Bob.
I finally got around to looking at The Langrangian points referred to in your mail. - Thanks for that pointer, it's a really interesting piece of physics. Good fun looking it all up.
At a first 'pass' it would appear that maintaining a satellite at the L1 and L2 points would require some station keeping, hence fuel. They would give excellent coverage from 56,000km / 200,000km respectively. Tracking the one held between the sun and earth would give really simple tracking. Start by pointing at the sun and then move around a little to peak the signals. - Of course the disadvantage is that instead of cold sky you would have all the Sun noise. The L2 point is only visible at night...so may be a bit 'antisocial' for practical use. - I wonder how the eclipse works out there?
The ones I found most interesting were the L4 and L5 points. Areas of space where satellites are held in a stable position by gravitational forces alone without needing any fuel. Big problem there is the distance. At 60 degrees ahead and behind the earths orbital position would make the path loss huge. Also, apparently, those areas tend to gather space dust, rocks etc. Probably a bit of a risk for collision albeit at low relative velocity.
Very thought provoking
73
David G0MRF
From Wikipedia:
The Lagrangian points also Lagrange point, L-point, or _libration_ (http://en.wikipedia.org/wiki/Libration) point), are the five positions in _interplanetary space_ (http://en.wikipedia.org/wiki/Interplanetary_space) where a small object affected only by _gravity_ (http://en.wikipedia.org/wiki/Gravity) can theoretically be stationary relative to two larger objects (such as a _satellite_ (http://en.wikipedia.org/wiki/Satellite) with respect to the _Earth_ (http://en.wikipedia.org/wiki/Earth) and _Moon_ (http://en.wikipedia.org/wiki/Moon) ). The Lagrange Points mark positions where the combined gravitational pull of the two large masses provides precisely the _centripetal_ (http://en.wikipedia.org/wiki/Centripetal) force required to rotate with them