U.S. Planet

For nearly 3 1/2 days the delicate radio signal came bravely down from space. At last it faltered. The Jet Propulsion Laboratory's 85-ft. antenna at Goldstone Dry Lake, Calif, changed to a special filter and held the signal for a few minutes more. A receiver of General Electric's at Schenectady, N.Y. heard the signal intermittently for about an hour longer. Then it faded out. Some 410,000 miles away in outer space, Pioneer IV, the U.S.'s first man-made planet, wheeled on around the sun, but now silent forever.

The new planet, a gold-plated fiberglass cone weighing 13.4 Ibs., did not compare in weight with the 796-lb. Lunik that the Russians put into solar orbit early in January, but its instruments apparently worked much better. The signal from its tiny transmitter was so strong that the 250-ft. radio telescope at Jodrell Bank, England could have followed it 4,000,000 miles into space if its batteries had lasted. The Russians reported that they lost their Lunik's signal (which no one else had followed) at 370,000 miles.

The U.S.'s feat had taken a lot of trying. Two earlier space probes were failures and two were qualified successes, reaching 71,000-and 63,000-mile altitudes before falling back to earth. Last week's shoot, bossed by the National Aeronautics and Space Administration, worked almost exactly as planned. The launching vehicle was a Chrysler-built Army Jupiter beefed up with extra fuel for extra range. Mounted on its massive shoulders were 15 small, solid-fuel rockets arranged to fire in three stages (see diagram). Perched on the nose of the final rocket was the gilded cone itself, Pioneer IV.

Dark Coasting. For two nights Pioneer IV was held on its pad, once because of low clouds, and once because a radio instrument failed to function. On the third night the bird lifted off only 4 seconds late. The Jupiter fired for 182 seconds. As it passed through a high veil of cloud, a bluish ring formed around its orange tail flame like a ring around the moon. After 55 seconds of dark coasting, a faint light bloomed in the sky as the second-stage rockets fired. Then Pioneer IV disappeared.

Soon after the last of its light was lost among the stars, instruments and computers indicated that the flight would be a success. Top speed achieved (24,700 m.p.h.) was slightly less than planned (24,985 m.p.h.), but it was still 200 m.p.h. more than was needed to escape from the earth. All instruments were working perfectly.

Most important were two Geiger tubes, one of them unshielded, the other wrapped in sheet lead about 1/8 in. thick. Devised by Professor James Van Allen of State University of Iowa, they watched the double belt of radiation that bears Van Allen's name. The naked tube reported all radiation that hit it, while the shielded tube reported only radiation strong enough to penetrate its shield. By comparing the tubes' reports with each other, Van Allen hopes to learn more about the character and origin of the radiation belts.

Slowdown. As the gilded cone climbed through the earth's weakening gravitational field, it slowed down. Nineteen hours after launch, it was 190,000 miles from the earth's surface and moving at 4,700 m.p.h. Forty-one hours after launch, it passed the moon's orbit and plunged into translunar space, still moving at 4,525 m.p.h.

Pioneer IV's solar orbit is slightly more elliptical than the earth's, which it will approximately cross twice a year for generations unknown. But NASA Director Keith Glennan was not inclined to rest on his new laurels. Said he: "We count the weights of our space payloads in tens of pounds, while the Russians count theirs in the hundreds of pounds."

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