R: [amsat-bb] Some P4 moon landing ideas :-)

["i8cvs" <domenico.i8cvs@xxxxxx>]

Hi Ed  AL7EB,

In addition,because of the lunar libration the earth as seen from the moon
is not exacly a fixed point in the lunar sky but it moves some +5 degrees to
 - 4 degrees

Because of  libration the  earth as seen from the moon changes his position
and in one month the earth describes a pattern like the numbar 8 with the
above +5 to - 5 degrees elevation changes.

If the antenna on the moon is a low gain one it is only necessary  precisely
stearing it one time forever at the center of the above pattern or at the
center of the above 8

This is the case of the helix  for 2300 MHz used  during the Apollo mission
on the moon but the groung station where using some monster dishes on the
earth stations.

If you think for example to put a 60 cm 10 GHz dish on the moon in direction
of the earth you have to precisely stearing the dish and in addition you
must track the earth from the moon because the -3 dB lobe of the above dish
is 3.5 degrees only wich is less than the angular changes of the earth
position as seen from the moon due to libration in one month.

I dont see any technical good reason by  wich a lunar based station is more
convenient than a satellite to relay communications by a transponders and
this can be easily demontrated by calculations of the uplink and downlink
path loss, EIRP needs,antenna gain needs and receiver noise floor needed.

For radio ham activity of coarse it would be very useful to have a microvave
beacon on the moon because it  would be used  to precisely track the moon on
moonbounce EME from 2.3 MHz ad up.

When the Apollo 2300 MHz signal was still available from the moon some years
ago it was used by many EME stations for precise traking purposes and this
was very useful and it really make sense.

73" de i8CVS Domenico


----- Original Message -----
From: Edward R. Cole <al7eb@ptialaska.net>
To: <amsat-bb@AMSAT.Org>
Sent: Monday, July 01, 2002 11:00 PM
Subject: RE: [amsat-bb] Some P4 moon landing ideas :-)


>
> >I'd like to see a concept in which a lunar-based relay would be more
> >advantageous than a satellite.  The Moon is about 8 times further away
than
> >AO-40 at apogee (~18 dB more path loss).
> >
> >Ken Ernandes, N2WWD
>
> Yep!  And the high gain antenna will need precise stearing to stay looking
> at the Earth.  I more probable project might be just a lunar-based
> repeater...for use by the Astronauts to talk back to Lunar Base One from
> their rover!  No particular advantage for Earth-based hams, though!
>
> Ed, AL7EB
>
> ----
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