Antenna Pointing from Angus Bay to Earth
For moon to Earth communications it should not be necessary to
track the motion
of the earth in the lunar sky with an antenna. Since the earth
travels about within an 8-degree region of the lunar sky, once an
antenna has been pointed at this region it will not need to be
moved again. The half power beamwidth for even very high gain
antennas is larger than 8 degrees. (For example, 35 to 40 element
yagi antennas for 70 cm, with a gain of 20 to 21 dBi, have beamwidths
of about 18 degrees.) Only for a combination of frequencies higher
than about 10 GHz and parabolic dishes larger than about 4 meters
(half power beam width of 10 degrees) will it be necessary to track
the earth with an antenna. A Laser
communication system would fall into this category of needing to
track the earth.
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Updated Thu, May 14, 1998.