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June 1962 Radio-Electronics
 [Table of Contents]
Wax nostalgic about and learn from the history of early electronics.
See articles from Radio-Electronics,
published 1930-1988. All copyrights hereby acknowledged.
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 Hugo Gernsback wrote in his June 1962 issue
of Radio-Electronics magazine editorial "Earth Signals on the Moon" editorial
that, "Within the next few years - certainly before 1970 - men will have landed
on the moon, opening up a vast new world." That was a year after
John F.
Kennedy made his famous "man on the moon" speech. As he was wont to do, Mr. Gernsback
accurately predicted the series of events that would lead up to the first manned
moon landing. He mentions the need for automation to achieve a controlled, soft
landing on the lunar surface because of the time lag for radio communications between
the Earth and the moon - a little more than a second each way - which is not fast
enough for a remotely controlled landing of an unmanned craft. He also addresses
the necessity for accommodating the Doppler frequency shift due to relative motion,
and line-of-sight communication being shorter on the moon for lack of a signal-refracting
atmosphere to lengthen the effective distance to the horizon. Fortunately, NASA
and its contractors had plenty of smart people working the problem, so we did, indeed,
"land[ing] a man on the Moon and return[ing] him safely to the Earth," before 1970.
Earth Signals on the Moon
By Hugo Gernsback
... Coming Communications Problems Between Earth and Moon ...
Within the next few years - certainly before 1970 - men will have landed on the
moon, opening up a vast new world.
However, before humans actually visit the moon, they will have been preceded
by electronically equipped robots, specifically designed to pre-explore the moon's
inhospitable environment. Many moon-landing vehicles and machines already have been
designed, and prototypes built. These robot explorers will make "soft" landings
on the lunar surface, after having been propelled by rocket over the 238,000 miles
separating the moon from earth. Guided entirely by electronics and telemetric control,
not everyone of the early lunar flights can be expected to turn out smoothly. There
probably will be mislandings - not all moonshots will be successful, any more than
all our first earth satellites succeeded. But we may be certain that before 1970
we will have succeeded in setting down a number of lunar robots that will make later
manned landings reasonably safe.
One of the difficult problems in precise moon landings - possibly solved theoretically
by now - is the time lag of telemetering the robots from earth. It takes 1.2 seconds
for light or radio waves to span the 238,000 miles between earth and moon in one
direction. Even if you could follow a rocket's flight to the moon via telescope,
it would be impossible actually to see the last important 50 or so feet of the descent.
Because light from the moon takes 1.2 seconds to reach the earth observer, he of
course could not see the approach to landing till 1.2 seconds later. It would therefore
be a most difficult operation to land a rocket robot telemetrically from earth.
There are, however, better and more precise means to soft-land lunar robots.
Let us mention only one. The principles we used during World War II in the electronically
operated proximity fuze - or similar ones - can conceivably operate the robot's
retro-rockets, independent of earth telemetry. These means will be certain and automatic
for all landing purposes. Once the robot equipment has arrived safely and intact
on the moon, earth scientists can take over certain operations via telemetry. Because
in all likelihood, the robot must be able to move over small distances for orientation
and exploring purposes, it will be equipped with a TV camera so that earth observers
can see the machine's immediate environment. Other vital information sent via radio
for the benefit of physicists, geologists and astronomers would be transmitted automatically
by the robot's exploratory instruments.
While we have made innumerable radio contacts with the moon since 1946,* bouncing
signals off its surface successfully, there will be some future problems which cannot
be solved with certainty until we actually get to the moon.
Because lunar robot receivers must of necessity be exceedingly sensitive, interference
from earth transmitters to the special moon-beamed signals intended to operate the
moon robots will become critical.
Consider that the moon always turns its same side to the earth. It is known today
that all frequencies (even broadcast waves) penetrate our atmosphere to a certain
degree. But frequencies, from the vhf range down to centimeter waves, probably reach
the moon in various intensities from earth transmitters "visible" to the moon. As
the earth turns, many earth transmitters will contact the moon once in 24 hours.
Note also the inevitable Doppler effect of the rapidly spinning earth - 1,000
miles an hour at the Equator - when it transmits vital signals to a moon robot.
This complicates reception.
Earth signals will come in strongest on the moon robot's instruments when the
earth station is exactly opposite to it. They will become progressively weaker as
the earth transmitter nears a 90° angle vis-a-vis the receiver on the moon.
This is because the radio waves now must pierce the vast horizontal mass of the
earth's atmosphere, against the former 150 miles or so when the moon is overhead.
To circumvent this, we require a number of transmitters located at different points
on the earth, all connected in a radio network, if we intend to maintain 24-hour
uninterrupted communication with moon robots.
Another completely unsolved problem is future radio communication on the moon.
Because of its small diameter, the moon's horizon is much nearer than that on earth.
The moon having no Heaviside layer, radio communication can reach only as far as
the horizon, some 2 miles, if the transmitter and receiver are 10 feet above the
ground.† We know nothing of the ground composition of the moon - whether
it is conductive or riot. Hence we cannot know until we get to it if we can communicate
through ground-wave conduction as we do on earth. If we can, the problem of radioing
to any distance and to the far side of the moon will become simple and inexpensive.
If not, we must set up a cumbersome and expensive radio relay system.
-H.G
* The author first predicted echo radio signals from the moon in his former magazine,
Radio News, in the article "Can We Radio the Planets?" in the February, 1927 issue.
In January, 1946, the US Signal Corps first established two-way radio contact with
the moon in 2.4 seconds, as predicted by the author 19 years before. (His forecast
time had been 2.5 seconds. an error of 1/10 second.)
† See also "Radio On the Moon," Radio-Electronics July, 1959, and "Lunar
Radio and TV Traffic," December, 1961.
Posted May 27, 2024
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