Big Voice from Space

The radio voice of U.S. space probe Pioneer V grew painfully feeble last week.

This was not surprising: the voice came from a five-watt transmitter 8,000,000 miles away from the earth. Britain's 250-ft. radio telescope at Jodrell Bank could still hear the signal, but the U.S. station at South Point. Hawaii had to strain its 60-ft. ear. So the time had finally come to shoot the works--by switching on the probe's 150-watt transmitter.

In a Teletype-lined room at Space Technology Laboratories in El Segundo. Calif, gathered a group of tense men. There was a chance that the big transmitter might malfunction and that in its failure it might silence completely its five-watt companion, leaving Pioneer V with no voice at all. Before being sent into space, the big transmitter had been tested rigorously. It had been shaken, spun, heated and cooled. It had survived all such tortures, but no test on earth could duplicate the hostile environment of space.

For nearly two months in its trip through space, the transmitter had been soaked in a vacuum higher than can be reached in any earthly laboratory, while powerful radiations riddled it through and through.

No one could guess the effects of this ordeal. And no one had ever tried to turn on a transmitter 8,000,000miles away.

Space Technology Laboratories gave the first order, and up from Jodrell Bank flashed a preliminary signal. Traveling at the speed of light. 186.300 miles per second, it took 43 seconds to reach Pioneer V.

The probe's receiver heard it. responded dutifully by allowing a half-strength electric current to flow through the filaments of the big transmitter's tubes. After this initial warmup, the apparatus was rested for six hours to recharge the batteries.

Then a second signal commanded the probe to send full current through the tubes. Both tests were successful, a fact reported to earth by the barely audible voice of the five-watt transmitter.

So far, so good. The California lab told Jodrell Bank to give the final commands; then it listened to the proceedings over an open-voice channel. At intervals of one minute, not long enough to get a response from 8,000,000 miles away. Jodrell sent orders speeding into space. First it told Pioneer V to switch half-power current through the filaments of the 150-watt transmitter. Then it called for full-power current. Then it gave the payoff order: to turn on the high plate voltage that would actually start the big transmitter. Eighty-six seconds after the final command left the earth, the signal strength from Pioneer V increased twentyfold. The big boy was on the line, calling loud and clear from Pioneer V as the probe continued on its lonely journey.

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