The shutdown of an orientation control gyroscope aboard the international space station will not impact the planned launch of the shuttle Discovery in May, officials said today, even though only two of the lab's four gyros will be operating when the orbiter arrives.

Station program manager Bill Gerstenmaier also said the loss of control moment gyroscope No. 2 early Wednesday would not prevent Discovery's crew from making worst-case repairs to the orbiter after docking if the ship's heat shield tiles or wing leading edge panels were damaged during launch.

If such repairs were actually needed, the shuttle might have to be re-oriented using the ship's robot arm to give spacewalking repairmen access to hard-to-reach areas. While that would be more difficult with just two operational gyros, Gerstenmaier said station stability could be maintained using Russian rocket thrusters instead.

And in any case, a new CMG will be installed during Discovery's visit to replace one that failed in 2002, once again giving the station three operational gyros. When CMG-2's faulty circuit breaker eventually is replaced, the lab complex will once again have four operational CMGs.

Gerstenmaier said flight planners are studying the timelines for the three shuttle spacewalks to determine if it might be possible for Discovery astronauts Stephen Robinson and Soichi Noguchi to install a fresh remote power control module during one of their excursions.

Mike Fincke, who spent six months aboard the station last year, installed the unit that failed Wednesday during a spacewalk last summer. He said today it would probably take Robinson and Noguchi about an hour to complete the swap out if time was available.

But the Discovery spacewalk timelines already are tight, training time is short and it appears more likely the space station's crew will be asked to replace the unit during a spacewalk after Discovery departs.

Gerstenmaier said the power control module has 17 channels and that a suspect transitor believed to be susceptible to failures in identical devices used throughout the station apparently caused the gyro circuit to trip open Wednesday. An identical failure knocked CMG-2 off line last year, requiring Fincke and Expedition 9 commander Gennady Padalka to replace the unit.

Gerstenmaier said engineers are developing a new design to eliminate the transistor problem and that in the meantime, he viewed the most recent failure as a relatively minor glitch.

Overall, he said, the space station is in good shape for Discovery's return to flight in mid May. Over the past few days, engineers have been troubleshooting recurring problems with the station's Russian Elektron oxygen generator. But Gerstenmaier said even if the unit failed today and could not be restarted, enough stored air is available to support Discovery's launching and to support both crews in a "safe haven" mode if shuttle damage forced NASA to launch a rescue mission.

As of today, with the Elektron in operation, the station has enough air to support both crews for at least 45 days, which NASA says is long enough to get another shuttle to the station in an emergency. A total Elektron failure in the immediate future would cut into those reserves, but Gerstenmaier said enough would be available for safe haven.