Astronauts Take Photos, Fire Gas Clouds : Atlantis: Crew captures nature’s light displays and completes another experiment after electron beam gun fails.

Atlantis’ astronauts photographed nature’s shimmering light displays and fired clouds of gas into space as the shuttle circled Earth for the fourth day Friday.

The crew of six men and one woman hastily rearranged its schedule after an electron beam gun used to create artificial auroras and radio waves failed to work properly.

The astronauts lighted up the night sky over the Southern Hemisphere 60 times, a spaceship first, before the gun became disabled Thursday by a blown battery fuse. They were able to fire the gun only twice to generate low-frequency radio waves that thousands of students worldwide had hoped to hear via special receivers.

Researchers held out little hope the gun could be fixed before the atmospheric research mission ends next week.

“We share your disappointment about the loss of the electron gun, but the rest of the experiments are yielding great results,” Mission Control messaged the crew.

The gun is among 13 scientific instruments in Atlantis’ cargo bay, all but one of which are examining the mid-to-upper atmosphere and solar energy.

“We hope it will stay routine and boring,” mission scientist Marsha Torr said. “The reason for this is the data product we will have on the atmosphere at the end . . . will be, we hope, very far from routine and boring. We believe it will be a base line people will reference for decades to come.”

Principal investigator Michael Gunson said his atmospheric mapping instrument noticed the polluting effects of last year’s eruption of Mt. Pinatubo in the Philippines.

“This is certainly a unique opportunity,” Gunson said. “It’s not often you get a chance to look at the composition of the atmosphere, even though it’s close to nine months after the eruption, and find out how particles are affected.”

The sole astronomical instrument--an ultraviolet telescope--resumed operation after ground controllers fixed a voltage problem. Principal investigator Stuart Bowyer said controllers essentially “wiggled the wires” through temperature changes that moved the contacts around.

The telescope observed an elliptical galaxy 41 million light years away and the Centaurus and Hydra constellations as Atlantis sailed through darkness 184 miles above Earth.

The four scientists aboard took turns operating a television camera that measures atmospheric light. Targets included natural auroras and blue clouds of xenon gas propelled into the area around the orbiter.

Researchers want to see whether neutral gases become charged when released into an already charged environment.

The scientists are especially interested in Earth’s ozone layer, which is being depleted by man-made chemicals. NASA reported last month that an ozone hole was expected to form over parts of North America and Europe later this year.

Ozone in the stratosphere protects Earth from cancer-causing ultraviolet rays.

Mission operations director Lee Briscoe said officials would decide today whether to keep Atlantis up until Thursday, a day longer than planned.