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When at last he reached the long-range ante
Poole had approached it from the rear; he had been careful not to go in front of the shallow parabolic reflector, lest Betty interrupt the beam and cause a momentary, but a
Beneath that small metal plate lay the cause of the trouble. The plate was secured by four locknuts, and as the entire AE-35 unit had been designed for easy replacement, Poole did not anticipate any problems.
It was obvious, however, that he could not do the job while he remained in the space pod. Not only was it risky to maneuver so close to the delicate, and even spidery, framework of the ante
All this he reported carefully to Bowman, who double-checked every stage in the operation before it was carried out. Though this was a simple, routine job, nothing could be taken for granted in space, and no detail must be overlooked. In extravehicular activities, there was no such thing as a "minor" mistake.
He received the O.K. for the procedure, and parked the pod some twenty feet away from the base of the ante
Then he checked the systems of his pressure suit, and, when he was quite satisfied, bled the air out of the pod. As Betty's atmosphere hissed away into the vacuum of space, a cloud of ice crystals formed briefly around him, and the stars were momentarily dimmed.
There was one thing more to do before he left the pod. He switched over from manual to remote operation, putting Betty now under control of Hal. It was a standard safety precaution; though he was still secured to Betty by an immensely strong spring-loaded cord little thicker than cotton, even the best safety lines had been known to fail. He would look a fool if he needed his vehicle – and was unable to call it to his assistance by passing instructions to Hal.
The door of the pod swung open, and he drifted slowly out into the silence of space, his safety line unreeling behind him. Take things easy – never move quickly – stop and think – these were the rules for extravehicular activity. If one obeyed them, there was never any trouble.
He grabbed one of Betty's external handholds, and removed the spare AE-35 unit from the carry-pouch where it had been stowed, kangaroo fashion. He did not stop to collect any of the pod's collection of tools, most of which were not designed for use by human bands. All the adjustable wrenches and keys he was likely to need were already attached to the belt of his suit.
With a gentle push, he launched himself toward the gimbaled mounting of the big dish that loomed like a giant saucer between him and the Sun. His own double shadow, thrown by Betty's spotlights, danced across the convex surface in fantastic patterns as he drifted down the twin beams. But here and there, he was surprised to notice, the rear of the great radio mirror sparkled with dazzlingly brilliant pinpoints of light.
He puzzled over these for the few seconds of his silent approach, then realized what they were. During the voyage, the reflector must have been penetrated many times by micrometeors; he was seeing the sunlight blazing through the tiny craters. They were all far too small to have affected the system's performance appreciably.
As he was moving very slowly, he broke the gentle impact with his outstretched arm, and grabbed hold of the ante
There was one minor problem; he was standing – or floating – in his own light, and it was hard to see the AE-35 unit in the shadow he cast. So he ordered Hal to swing the spots off to one side, and after a little experimenting got a more uniform illumination from secondary light reflected off the back of the ante
For a few seconds, he studied the small metal hatch with its four wire-secured locking nuts. Then, muttering to himself, "Tampering by unauthorized perso
The four nuts came off without any trouble, and Poole stowed them carefully away in a convenient pouch. (One day, somebody had predicted, Earth would have a ring like Saturn's, composed entirely of lost bolts, fasteners, and even tools that had escaped from careless orbital construction workers.) The metal cover was a little sticky, and for a moment he was afraid it might have cold-welded into place; but after a few taps it came loose, and he secured it to the ante
Now he could see the electronic circuitry of the AE-35 unit. It was in the form of a thin slab, about the size of a postcard, gripped by a slot just large enough to hold it. The unit was secured in place by two locking bars, and had a small handle so that it could be easily removed.
But it was still operating, feeding the ante
To avoid this particular hazard, it was only necessary to cut off power to the control system; then the ante
"Hal," Poole called over the radio circuit, "I am about to remove the unit. Switch off all control power to the ante
"Ante
"Here goes. I'm pulling the unit out now."
The card slipped out of its slot with no difficulty; it did not jam, and none of the dozens of sliding contacts stuck. Within a minute, the spare was in place.
But Poole was taking no chances. He pushed himself gently away from the ante
"Power on," answered Hal. The ante
"Carry out fault prediction tests."
Now microscopic pulses would be bouncing through the complex circuitry of the unit, probing for possible failures, testing the myriads of components to see that they all lay within their specified tolerances. This had been done, of course, a score of times before the unit had ever left the factory; but that was two years ago, and more than half a billion miles away. It was often impossible to see how solid-state electronic components could fail; yet they did.