Guiding a 50-foot-long robot arm with their own eyesight instead of a malfunctioning television camera, astronauts Jack R. Lousma and C. Gordon Fullerton today used the arm to move an 82-pound instrument freely from place to place in the cargo bay of the space shuttle Columbia.

"It's as close to perfect as it could be, the operation is real smooth," Lousma said as he crooked the arm and raised an instrument called the Plasma Diagnostics Package into space 25 feet above the open cargo bay doors. "If there's any surprises here, they're all pleasant. I am really impressed with that piece of machinery."

"That's great news and we were impressed, too," astronaut Sally Ride said from the Mission Control Center in Houston. "For your information, that PDP is getting super data out there, too."

Not only was today's exercise the first real test for the Canadian-built mechanical arm, the PDP beamed back to earth scientific information about the electrical disturbances left in the lower reaches of the earth's ionosphere by the 100-ton shuttle as it flies through it at five miles a second.

Looking like a tiny satellite at the end of the arm, the instrument also was measuring the electrical leakage of the shuttle itself. This information is needed to protect instruments and satellites on future shuttle flights from the electrical interference the DC9-sized shuttle will cause.

"I got the PDP out in the breeze right now," Lousma said as he televised the arm in a bent position against the bright blues of the Gulf of Mexico, the South Atlantic Ocean and the Caribbean Sea. "It's a spectacular sight as we move out over the Atlantic heading for the African continent."

Despite the useless television camera on the wrist of the mechanical arm, Lousma and Fullerton ran through the twice-postponed arm exercise with surprising ease today, maneuvering it with controls on a console in the cockpit.

Crooking the arm and using the elbow camera to help them guide the arm over the Plasma Diagnostics Package, the astronauts waited until the sun was overhead lighting up the payload bay so there were no confusing shadows in front of them. Then, Fullerton guided the grappling device into the drum-shaped instrument and fastened onto it with one clean motion.

Feeling well for the first time since he rocketed into space last Monday, Lousma sailed through his tasks so quickly that he and Fullerton were able to enjoy a leisurely lunch as they sped across the South Atlantic. The workaholic Lousma even found time to earth-gaze during lunch and talk about what he saw as the shuttle passed through sunset into nighttime.

"One of the most spectacular sights up here is moving into darkness," Lousma said. "You see a dark blue that fades into black but there's no real definition, it's kind of like going into nowhere. You don't see any stars at first and it's kind of a lonely feeling like you don't know where you're going."

Lousma stopped taking the Scopdex pills prescribed for his motion sickness but Fullerton began complaining about what he called a "full stomach." He was told to take a drug called Mylanta, a medication that contains a combination of antacids for the relief of gastric hyperacidity.

One thing Lousma and Fullerton didn't do today was use the arm to lift an instrument called the Induced Environment Contamination Monitor, an 80-pound drum that measures the tiny clouds of gas that enter the shuttle, which could contaminate future experiments carried in the cargo bay.

Though they grappled onto it with the arm, the astronauts did not attempt to raise this instrument out of the bay because it lies out of their sight and the range of the elbow camera. Flight directors told them to forget the lifting exercise because they might damage the arm and the instrument if they raised it without being able to use their wrist camera to see to maneuver it.