The two squirrel monkeys and two dozen rats accompanying seven astronauts today turned the interior of the $1 billion Spacelab being carried by the space shuttle Challenger into something resembling an orbiting zoo.

Hundreds and perhaps thousands of animal food and waste particles were floating in Spacelab's cabin. Crew members in masks were trying to clean up the mess while coping with 15 scientific experiments in the European-built laboratory.

Feeding and cleaning up after the monkeys and rats became as much of a chore for the crew as getting faulty circuit breakers to close and balking experiments to work.

"Be advised," Challenger Commander Robert F. Overmyer told the Mission Control Center in Houston after inspecting Spacelab, "that we have the same problem with the monkey cages as we have with the rat cages."

The "problem" was with the way the animals were getting their food and water.

One rat had to be hand-fed a gelatin bar to get water into him, and each time physician-astronaut William E. Thornton tried to press food bars into the cages, the bars would crumble and a cloud of tiny particles would pour into the cabin and scatter.

"I'm not exaggerating," Thornton told Mission Control, "but there are food particles flooding out of every crack in those cages. I don't see any way we can stop this except if we had a seal over the entire cage."

Monkey and rat feces also leaked out of the cages, forcing Thornton to put on a smock and a mask.

At one point, Thornton and physicists Don Lind and Taylor W. Wang donned masks to protect themselves from contamination.

"We have recommended that the men in the module Spacelab wear surgical masks every time the cages are handled," Flight Director William Reeve said tonight.

"We have no serious concerns about this but we are taking precautions like using vacuum cleaners to get rid of that stuff and placing plastic bags over some of the cracks in the cages."

The five scientists in the seven-member crew also had to cope with two experiments that refused to work. A French-built camera to survey hot stars in distant galaxies for 17 hours could not be deployed into free space because an airlock hatch failed to open. Circuit breakers kept popping open in an experiment Wang was running.

"We don't know why the airlock hatch won't open," Flight Director Gary Coen said. "We may try it again near the end of the mission and there is even a slight chance the mission could be extended one day if we think we can get that airlock hatch to open."

Wang's experiment is a test to see how drops of fluids behave in weightless space.

By 7 tonight, Wang was talking at length with his colleague, Eugene Trinh, to see if they could troubleshoot their way into starting the experiment.

"Be very gentle with those circuit breakers," Trinh said from Houston's Johnson Space Center.

"You have never seen anybody so gentle with circuit breakers," Wang replied.

Despite their troubles the crew was performing as if nothing was bothering them.

At least nine of the 15 experiments were up and running even better than hoped, the monkeys and rats were described as "real clean and real happy" and Challenger itself was flying almost effortlessly around the world every 90 minutes.

"Challenger once again is proving to be a magnificent flying machine," Flight Director Reeve said. "All we have on board is some nuisance problems."

Spectacular television pictures of the Northern and Southern lights were beamed down as the space shuttle flew near the North and South poles.

Cosmic rays striking the Earth's magnetosphere at this time of year apparently produce extraordinary electrical lights at the extreme ends of both hemispheres. No two light shows seen today appeared to be the same, as they sent flickering and glowing rainbows almost completely across the screen. "I wish you could be up here," physicist-astronaut Lind said as he photographed the Aurora Australialis. "We've had some marvelous auroras. The streaks of light we're seeing are really spectacular stuff."

Almost nothing was heard today from Challenger Pilot Frederick D. Gregory, a native of Washington and the first black astronaut to handle shuttle controls.

Gregory is in Challenger's cockpit where he talks to Mission Control on a separate radio frequency from the scientist crew members. He is also the leader of the "Silver Team" working the night shift on the round-the-clock Spacelab mission.