Suddenly a bell began to ring in front of Roger. Without hesitation he adjusted a dial that brought the radar scanner into focus. When the screen remained blank, he made a second adjustment, and then a third and fourth, until the bright white flash of a meteor was seen on the scanner. He quickly grabbed two knobs, one in each hand, and twisted them to move two thin, plotting lines, one horizontal and one vertical, across the surface of the scanner. Setting the vertical line, he fingered a tabulating machine with his right hand, as he adjusted the second line with his left, thus cross-fixing the meteor. Then he turned his whole attention to the tabulator, ripped off the answer with lightning moves of his fingers and began talking rapidly into the microphone.
"Radar bridge to control deck! Alien body bearing zero-one-five, one-point-seven degrees over plane of the ecliptic. On intersecting orbit. Change course two degrees, hold for fifteen seconds, then resume original heading. Will compensate for change nearer destination!"
Roger watched the scanner a moment longer. When the rumbling blast of the steering jets sounded in the chamber and the meteor flash shifted on the scanner screen, he returned to the problem in his hand.
Seven minutes later he turned to Strong and handed him the answer.
"Present position by dead reckoning is northwest quadrant of Mars, chart O, area thirty-nine, sir," he announced confidently.
"I was unable to get a sight on Alpha Centauri"
Strong tried to mask his surprise, but a lifted eyebrow gave him away. "And how did you arrive at this conclusion, Manning?"
"I was unable to get a sight on Alpha Centauri due to the present position of Jupiter, sir," replied Roger easily. "So I took a fix on Earth, allowed for its rotational speed around the sun and took the cross-fix with Regulus as ordered in the problem. Of course, I included all the other factors of the speed and heading of our ship. That was routine."
Strong accepted the answer with a curt nod, motioning for Roger to continue. It would not do, thought Strong, to let Manning know that he was the first cadet in thirty-nine years to make the correct selection of Earth in working up the fix with Regulus, and still have the presence of mind to plot a meteor without so much as a half-degree error. Of course the problem varied with each cadet, but it remained essentially the same.