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There and back again!

A.S.Ganesh
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Last week, we saw how submarines use sonar for navigation: a simple technique that utilises the propagation of sound underwater to find out the relative positions of other objects. Sound waves emitted from the submarines are reflected from these objects, enabling the submarine to detect and calculate the position and distance.

It doesn’t take long to extrapolate this very idea on to a larger canvas. What if we use a similar technique for communication? Would we be able to bounce off something in order to create a reliable secure wireless communication system? If I was able to think of that, surely some of the brighter minds of yesteryear would have gone a step further.

An idea, once it takes form, often turns out to be an obsession. Post-World War II, many efforts were made in the field of radio espionage and one of them would lead to the Communication Moon Relay project. Also known as Moon Relay or Operation Moon Bounce, the United States Naval Research Laboratory (NRL) under the auspices of the United States Navy carried out this telecommunication project.

Using the moon as a natural communications satellite and a technique known as EME (Earth-Moon-Earth) communications, the bulk of this project took place in the 1950s. By 1951, NRL was able to demonstrate that the moon reflected radio energy that was far more coherent than predicted. As a result, a passive moon circuit that could transmit data at a rate and fidelity accurate enough for radio communication was constructed once the necessary transmitter and receiver technologies were developed.

NRL became the first to transmit and return human voice through outer space in 1954. By 1955 they were successful in demonstrating transcontinental satellite communication. In 1959, the world’s first operational communications satellite was placed in operation, communicating between Washington, DC, and Hawaii. When the Chief of Naval Operations sent a message to the Commander-in-Chief of the Pacific fleet, the system was officially inaugurated on January 28, 1960.

In the 1960s, with the advent of artificial satellite communication systems, the Moon Relay system went out of favour. Even though the project was short-lived, it allowed astronomers to examine the moon when in positions not conducive to radio transmissions and laid the foundations for the artificial systems that stemmed from it.

Earlier this month, NASA tested new methods of space communication by beaming an image of Mona Lisa on to the moon. An experiment in laser communication, scientists sent the image to the Lunar Reconnaissance Orbiter (LRO) and achieved, for the first time, laser communication at planetary distances. The image, divided into an array of pixels – each corresponding to a shade of gray, was transmitted by a laser pulse to the satellite, where it was pieced together and sent back through radio waves. Allowing for natural disturbances, and employing Reed-Solomon error-correction coding system, the scientists were able to obtain a near-perfect transmission of the portrait.

Up till now, radio waves have been predominantly used to communicate with satellites. This experiment, and more expected to come on these lines, are considering lasers for the same. Lasers can transmit more date at a faster rate than radio signals and hence are being contemplated as an alternative. Whatever it takes, the process is simple; it’s just about being there and back again!

Beaming with excitement? Write to ganesh.a.s@thehindu.co.in to know more about the ideas in science that excite you (do include your name, class and school!).

The public demonstration of Operation Moon Bounce was carried out on this day in 1960. This is a picture of the USS Hancock (CV-19) with ship officers & crew spelling out “Moon Relay”, the image that was transmitted from Honolulu, Hawaii to Washington, D.C. via the moon!


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