IAU day 4: Radar from WWII to the outer solar system

Posted by Korey Haynes
on Sunday, August 9, 2015

Original radar plot of what was later realized to be the attacking Japanese fleet on the morning of the attack on Pearl Harbor, recorded by Privates Joseph Lockard and George Elliot of the U.S. Army Air Corps.
I'm still nominally at the International Astronomical Union meeting here in Honolulu. But most of the astronomers have taken a break for the weekend, leaving me to amuse myself for some of the time.

This morning, I hopped a bus over to Pearl Harbor to view the memorial of the USS Arizona, one of the battleships struck and sunk on December 7, 1941, in the attack on Pearl Harbor that toppled the United States into World War II. Walking over the sunken battleship and the men entombed there to this day is a powerful experience, one I won't forget.

But I couldn't help but pick out the astronomy angle in the collection of information about that fateful day. It's a well-known story, but one I'd still like to share. On the morning of December 7, Privates Joseph L. Lockard and George Elliot were manning the Opana radar station on Oahu, north of Pearl Harbor, when, at 7:02 a.m., they saw a strong signal. At this time, Lockard and Elliot should have been off-duty; military command had deemed the hours of 4-7 a.m. as those when the enemy was most likely to attack, so the men only saw the signal at all because the bus to take them to their breakfast was running late. It should also be pointed out that while technically operational, the Opana station was still considered a training post. Despite both of these factors, the men adhered to their duty and stayed to report the signal. Alas, on the other end of the communications chain at the Information Center, the specialists had signed off on time. A single man, Lieutenant Kermit A. Tyler, was left to respond, and he reasoned that the privates' signal was in fact a group of American bombers due in at 8 a.m. from California along a similar approach, and so he told them not to worry about it. Between lack of familiarity with the new radar technology and security concerns about relating the size of the bomber fleet over radio, the fact that the Opana signal represented a fleet much larger than six bombers was never communicated.

Treating the signal as a training exercise (and having by now missed their breakfast bus anyway), the servicemen plotted the signal until 7:40, when they lost it in the noise as its progenitor approached the island. The men secured their station and headed off to breakfast, finding out only when they arrived of the ongoing attack, which had started at 7:48. They immediately drove back and helped man the radar for the rest of the day.

At the time, radar was still a brand new invention, and while the military was aware that the technology held potential, they had not fully integrated a radar alert system into their air defense. The tale is one of frustration, but commanders chose to see this very particular outcome of the day as a victory. It was the implementation and integration of the technology that had failed, not the technology itself or any man involved that morning, and indeed Lockard and Elliot were commended for their attention and service. It was no individual's fault that no system existed to interpret the warning and pass it up the chain of command. Even Tyler, who essentially ignored warning of the attack, was cleared of any wrongdoing because he had never received training for the post he held that morning. Given the information available to him, he made the call he thought completely correct. While the result was devastating, the fact that men had seen the signal was proof of radar's power and utility in the war in which America suddenly found itself. Radar quickly became a staple of aviation technology.

While the word has long since been absorbed into standard English usage, "radar" entered the world as an acronym: RAdio Detection And Ranging. Like sonar does with sound waves, radar is the process of bouncing waves of electromagnetic radiation, specifically radio waves, off of objects. By measuring how long it takes the signal to come back and the strength of that signal, scientists can tell how far away an object is and even what it is made of. Popularized and researched precisely because of the military value highlighted by the above story, radar has broad applications, including astronomy. Arecibo in Puerto Rico and Goldstone in California are the most commonly used stations for radar astronomy from Earth, and have been used to map the Moon, study asteroids, and determine exact distances to the other planets in the solar system. Scientists have also used radar carried on spacecraft to map or probe surface features on the solar system's inner and outer worlds. 

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