Columbia’s astronauts wrapped up their third day in space early Sunday, completing another round of work with a variety of secondary experiments as their primary payload, the Chandra X-Ray Observatory, successfully passed another key milestone in its early days in orbit.

Commander Eileen Collins, Pilot Jeff Ashby and Mission Specialists Cady Coleman, Steve Hawley and Michel Tognini conducted experiments ranging from astronomical observations with an ultraviolet telescope to cell culture studies. Investigations also included testing new materials which may one day be used to fabricate sturdier solar arrays.

Hawley collected additional data for investigators from the Southwest Ultraviolet Imaging System (SWUIS), which he trained on the moon and Venus. Tognini and Coleman, meanwhile, monitored the operation of bioprocessing hardware collecting data from a number of biological and biomedical experiments. Tognini and Coleman reported that a series of hinges constructed from new lightweight materials unfurled successfully in a demonstration of technology expected to be applied to the development of solar panels for future spacecraft.

Last night, at 8:16 p.m., controllers at the Chandra X-Ray Observatory Operations Control Center in Cambridge, Massachusetts, reported a successful firing of the telescope’s liquid-fuel thrusters, the first of five such firings which will ultimately place Chandra in its proper scientific orbit. News of the successful maneuver was relayed to the astronauts by flight controllers in Mission Control. All of Chandra’s systems are functioning normally.

Midway through the astronauts’ workday, Tognini and Collins took time out to talk with the three cosmonauts aboard the Russian Space Station Mir in a ham radio hookup. Travelling some 7,700 miles apart, French astronaut Tognini offered greetings to his fellow countryman, Jean-Pierre Haignere, a European Space Agency astronaut who is in the homestretch of a six-month scientific research mission aboard Mir. Haignere, Commander Viktor Afanasayev and Flight Engineer Sergei Avdeyev are scheduled to land in their Soyuz capsule in Kazakhstan on August 28.

Collins reported to flight controllers late last night that a circuit breaker associated with an electrical bus on the Shuttle had popped open during a transient short seconds after launch. Although Columbia’s climb to orbit was unaffected by the short circuit, the breakers will be analyzed postflight to determine the exact cause of the problem.

Collins and Ashby also continued to provide investigators with data for a pair of experiments involving the study of exhaust vapors from the engines of space vehicles by firing reaction control system and orbital maneuvering system engines several times as Columbia passed over worldwide tracking network stations.

The astronauts will begin an eight-hour sleep period at 8:31 a.m. Central time this morning and will be awakened at 4:31 this afternoon to begin their fourth day in space. Columbia is flying smoothly, orbiting the Earth every 90 minutes at an altitude of 182 statute miles.

The next STS-93 status report will be issued late this afternoon following crew wake up, or as developments warrant. -end-

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