Spotters Needed

In spite of radar, U.S. air defense still needs volunteer "spotters" like those who watched the skies from rooftops and lonely hills during World War II. Last week the Air Force estimated that an all-out war would call for 500,000 spotters to plug the unavoidable gaps in the U.S. radar network.

The trouble with radar is that it is subject to blind spots. Its waves go out in straight lines, like television waves; they cannot duck down behind buildings, hills or other obstacles, and they cannot follow the curvature of the earth (see diagram). So a radar station works best against high-flying airplanes. It can pick them up as far away as 150 miles, but if attacking bombers fly low, they can keep behind the bulge of the earth and get much closer before they are detected. With mountains or other obstacles to give them shelter, they are even harder to detect in time for effective warning.

It would be possible, of course, to space radar so close together that virtually all blind spots would be eliminated. But radar stations are complicated, expensive, and need up to 100 men each. To cover the U.S. with a gapless blanket of radar would cost more in money, electronics and men than the protection would be worth.

Spotters can neither see nor hear bombers at extreme altitudes, which is radar's job. The spotters will specialize on attackers trying to slip, perhaps at treetop level, through gaps between the radar stations. Such attacks, says the Air Force's Air Defense Command, are a very real danger. Once a group of bombers passes the radars that watch the coasts and northern border of the U.S., it might "get loose" in the interior. Unless it should blunder into the field of a radar, the defending jet fighters would not know where to look for it.

Volunteer spotters could do a great deal to forestall such an attack. Their telephoned reports, plotted on boards at "filter stations," would show with little delay where the invaders were heading.

Low-flying bombers are easy prey for fighters that can find them. If an enemy knows that an efficient spotting system is in operation, he is more likely to keep his bombers at extreme altitudes, where they can be tracked by radar.

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