The Payoff Was Perfection

The ungainly gadget carried no human passengers. But as it eased its complex cargo to a soft landing on the moon's Ocean of Storms last week, the U.S. spacecraft, Surveyor I, moved man himself closer than ever to a landing on his nearest planetary neighbor. In an exercise of textbook perfection, Surveyor settled down only a few miles from its planned target; its TV camera panned across the lunar landscape and high-quality pictures streamed back to earth. For a program that had languished for years in exasperating delay, expanding expenses and mounting criticism, the very first payoff was perfection.

For the scientists at the Jet Propulsion Laboratory control center in Pasadena, the difficult task of nursing Surveyor to a point 60 miles above the moon's surface was far less harrowing than the final phase of the trip. For in the long moments of the last drop, Surveyor's own computers and radar were issuing the necessary orders. And back on earth, 230,930 miles away, the craft's creators could do no more--no more than pray that their design and pre-launch calculations were all correct.

Cushioning the Jolt. They were, Small vernier rockets near each of the craft's three legs fired to stabilize the spacecraft in a base-down attitude. When the radar sensed that Surveyor was precisely 52 miles above the moon, it fired a powerful, solid-fuel retrorocket that slowed the craft from 5,840 m.p.h. to only 267 m.p.h. in 40 seconds.

At a lunar altitude of 25,000 ft., the retrorocket was jettisoned and the vernier rockets took over the job of further reducing speed, stabilizing and gently guiding Surveyor along the proper trajectory toward its impact point. When it was 13 ft. above the lunar surface and descending at 3.3 m.p.h., the 620-lb. Surveyor shut down its verniers and fell the remaining distance. It struck the moon no harder than a parachutist hits the earth. And even this relatively small jolt was cushioned by hydraulic shock absorbers and crushable aluminum pads under Surveyor's legs and body.

As telemetry confirmed that the landing was proceeding according to plan, scientists and spectators at the JPL control center first stared in apparent disbelief. They were well aware that the Russians had failed at least four times before landing an instrument package intact on the moon and that the first seven of the ten planned Surveyor shots had been designated "engineering flights"--a tacit admission that U.S. scientists expected many failures before a successful soft landing was achieved. But when telemetry continued after impact--evidence that Surveyor had survived the landing--disbelief gave way to wild cheering. Half an hour later, on radioed command, the craft's television camera began to take its first pictures.

Pictures by Earthlight. One after another, the pictures showed that Surveyor was standing on a broad, relatively level plain littered with pebbles as small as one-eighth of an inch in diameter and rocks that were more than a foot across. The terrain was pocked by an occasional small crater, and one picture clearly showed a hump on the horizon that is believed to be either a crater rim or a low hill. A view of one of Surveyor's feet showed that its impact had dented the surface a few inches, indicating to some scientists that the site had the consistency of a terrestrial ocean beach.

To learn more about the lunar surface, JPL scientists decided to fire the small attitude-control thrusters located near the bottom of each of Surveyor's three legs, less than a foot above the surface. Seven different times, the thrusters fired jets of nitrogen into the lunar soil while Surveyor's camera shot pictures of the area near its feet. The pictures showed no clouds of dust--another indication that the lunar surface is firmly packed. By week's end, as the sun rose toward its apex in the lunar sky, shortening shadows and making it more difficult to distinguish lunar objects, Surveyor had already taken and transmitted more than 2,000 pictures. Because Surveyor landed in the morning of the two-week lunar daytime, period, its TV camera should be able to operate for about twelve days, powered by batteries that will be constantly recharged by solar cells. By shooting the reflections from a mirror that can rotate 360DEG and tilt up and down, the fixed camera can televise views from Surveyor's feet to above the horizon a mile away. As the lunar night descends, the batteries should remain charged long enough for the camera to take a picture of the lunar landscape, faintly illuminated by earthlight.

Shuffling the Standings. After a plague of misfortune and mismanagement had put it three years behind schedule, the Surveyor success was doubly sweet. Equipment broke down during tests and had to be redesigned. The second-stage Centaur--the first liquid-hydrogen rocket--had several mishaps and had flown only one completely successful mission before last week's shot. Summarizing the program, the House Space Committee characterized it as "one of the least orderly and most poorly executed NASA projects."

Yet last week, the clouds over Surveyor all seemed to dissipate. The Atlas-Centaur rocket that hurled Surveyor toward the moon was only one second late in leaving the pad; it followed a near-perfect trajectory that would have placed Surveyor only 250 miles from its target on the moon. The mid-course correction was so accurate that Surveyor actually scored an effective bull's-eye. Only one "glitch" marred the performance: one of Surveyor's two antennas failed to extend fully after the craft left the earth's atmosphere. But even this problem corrected itself. When Surveyor hit the moon, the modest jolt snapped the antenna into place.

With its impressive performance, Surveyor has once again shuffled the standings in the space race. After Luna 9's lunar landing and Luna 10's lunar orbiting, the Russians seemed clearly ahead. But Luna 9's landing method, which involved the ejection of a well-protected instrument package just before the carrier rocket hit hard on the moon, would probably be fatal to human passengers. Surveyor, on the other hand, employed a soft touchdown technique similar to the one that will be used to land Apollo's Lunar Excursion Module with its two astronauts. Its success was welcome assurance that the U.S.'s man-on-the-moon program is proceeding according to plan.

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