Word: surveyor
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Three times the JPL controllers ordered Surveyor's verniers to fire, hoping to jar the sticky valve shut. The leakage slowed but did not stop. Within an hour, helium pressure had dropped from 5,000 lbs. to 3,000 lbs. per sq. in. Dejectedly, some JPL scientists suggested that it would be best to fire Surveyor's retrorocket immediately, placing the craft in high earth orbit. It would be preferable to have a live spacecraft in orbit, they argued, than a dead one on the surface of the moon...
Others kept working. Using computers, engineers calculated the rate at which the helium leak would decrease as pressure dropped. At Hughes Aircraft (Surveyor's designer and builder) and at a JPL test site, propulsion experts hurriedly put duplicate vernier engines through tests to determine their performance with low helium pressures. Feeding the results into computers, JPL scientists took less than 40 hours to work out a new and complex lunar landing sequence...
Then they put it to the crucial test of action. First they fired Surveyor's vernier engines for 33 seconds to consume more fuel and reduce the craft's landing weight. New instructions were radioed to Surveyor's memory bank and programmed into ground-based computers. As a result, the craft's main retrorocket began firing at a height of 26 miles above the lunar surface, instead of the originally planned 52 miles. It shut off at an altitude of only 4,400 ft., instead of 40,000 ft., after braking Surveyor...
...Distant Orders. Tilted at a 20° angle on the side of a small crater, Surveyor almost immediately began transmitting high-quality photographs of the surrounding landscape, including a shot of its own footpad covered by lunar soil kicked up by the landing. On orders from distant Pasadena, it again briefly fired its verniers while its cameras peered at the surface to observe blast effects...
...Finally, Surveyor displayed its pièce de résistance, lowering a goldplated, square "jewel box" to the surface. From six radioactive sources in the box, alpha particles bombarded a small area (4 sq. in.) of the lunar surface. Inside the box, delicate sensors recorded the number and velocities of alpha particles rebounding from the surface material and relayed them to earth via Surveyor's radio. By analyzing the pattern of the rebound particles, scientists hope to be able definitely to identify compounds and elements in the lunar soil. "If the experiment succeeds, it will mark the first...