This particular one was seldom used in space; it was for planet landings. It scanned ahead in a narrow horizontal band, like a sea vessel's surface sweep. He'd planned only to use it as he transited Jupiter, to cut his course in near to the atmosphere, and it was only habit that had made him glance at it. The bright green line showed no peaks, but at the middle, and for a little way to each side, it was very slightly uneven.
He thought, It's just something in the system, out of adjustment. He looked at the forward sweep. There were no blips dead ahead. He moved the adjustments of the horizontal sweep, blurred the line, then brought it back to sharpness. Except in the middle. The blurriness there remained.
He opened a panel and punched automatic cross-checks, got a report that the instrument was in perfect order. He looked at the scope again. The blurred length had grown to either side. Clammy sweat began to form on his skin. He punched at the computers, set up a program that would curve the ship off its path, punched for safety verification, and activated the autopilot. He heard the drive's whine move higher, but felt no answering lateral acceleration. He punched for three G deceleration, working frantically to get strapped in. The drive shrieked but there was no tug at his body.
The blurred part of the green line was spreading.
He realized he was pressing against the side of his seat. That meant the ship was finally swerving. But he'd erased that program. And now, abruptly, deceleration hit him. He sagged forward against his straps, gasping for air. He heard a new whine as his seat automatically began to turn, pulling in the straps on one side, as it maneuvered to face him away from the deceleration. He was crushed sideways for a while, then the seat locked and he pressed hard against the back of it. This he could take, though he judged it was five or six G's. He labored for breath.
The deceleration cut off and he was in free fall. His screens and scopes were dark. The drive no longer whined. He thought, Something's got me. Something that can hide from radar, and control a ship from a distance like a fish on the end of a spear.
He tore at the straps, got free and leaped for the suit locker. He dressed in frantic haste, cycled the air lock ... and found himself on the surface of a planet.
He had been returned to Ganymede.
Panicked, he fled; then abruptly, where nothing had been, there was something solid in his path. He turned his face to avoid the impact and tried to get his arms in front of him. He crashed into something that did not yield. His arms slid around something, and without opening his eyes he knew the robot had him. He tried to fight, but his strength was pitiful. He relaxed and tried to think.
In his suit helmet radio the voice of the robot said, "We will put you to sleep now."