Major Harry Lightfoot, fighter pilot, felt a glow of satisfaction as he saw the light come on. He might not have reflexes fast enough to pilot the ship up here; he might not be able to survive the climb to intercept without the help of a lot of fancy equipment; but he was still necessary. He saw still one step ahead of this complex robot which had carried him up here. It was his human judgment and his ability to react correctly in an unpredictable situation which were needed to locate the warhead from among the cluster of decoys and destroy it. This was a job no merely logical machine could do. When all was said and done, the only purpose for the existence of this magnificent machine was to put him where he was now; in the same trajectory as the missile, and slightly behind it. Harry Lightfoot reached for a red-handled toggle switch at the top of the instrument panel, clicked it from AUTO to MANUAL, and changed his status from passenger to pilot. He had little enough time to work. He could not follow the missile down into the atmosphere; his ship would burn up. He must begin his pull-out at not less than two hundred miles altitude. That left him one hundred eighty-three seconds in which to locate and destroy the warhead. The screen in the center of his instrument panel could show a composite image of the space in front of his ship, based on data from a number of sensing elements and detectors. He switched on an infrared scanner. A collection of spots appeared on the screen, each spot indicating by its color the temperature of the object it represented. The infrared detector gave him no range information, of course. But if the autopilot had done its job well, the nearest fragment would be about ten miles away. Thus even if he set off the enemy warhead, he would be safe. At that range the ship would not suffer any structural damage from the heat, and he could be down on the ground and in a hospital before any radiation effects could become serious. He reflected quickly on the possible temperature range of the missile components. The missile had been launched from Central Asia, at night, in January. There was no reason to suppose that the warhead had been temperature-controlled during the pre-launch countdown. Thus it probably was at the ambient temperature of the launch site. If it had been fired in the open, that might be as low as minus 70 deg. F. Had it been fired from a shelter, that might be as high as 70 deg. F. To leave a safety margin, he decided to reject only those objects outside the range plus or minus 100 deg. F. There were two fragments at 500 deg. F. He rejected these as probably fragments of the engine. Six more exhibited a temperature of near minus 320 deg. F. These probably came from the liquid oxygen tanks. They could be rejected. That eliminated eight of the objects on the screen. He had nineteen to go. It would be a lot slower for the rest, too. * * * * *