Workers in the Payload Changeout Room at launch pad 39A, ride a platform toward the forward cargo bay area of Space Shuttle Endeavour to search for an oxygen leak. During the course of their work a platform struck the shuttle's robot arm. Photo: NASA

Engineers installing an access platform in the shuttle Endeavour's cargo bay for work to repair an oxygen leak inadvertently hit the ship's 50-foot-long robot arm today, tearing the fragile space crane's protective thermal insulation. Whether any other, possibly more serious, damage occurred is not yet known. The issue will be discussed at a management review Wednesday.

Endeavour's countdown to an early Monday launch was called off Sunday night when engineers discovered one of two systems that feed oxygen into the shuttle's crew cabin was leaking. The leak is believed to be in the shuttle's midbody, just below the floor of the ship's cargo bay, forward of the aft end of the shuttle's space station docking module.

The docking module is mounted in the front of the payload bay. Just behind it - or below it, when the shuttle is vertical at the launch pad - is the primary payload for mission STS-113, the 45-foot-long, 14.5-ton P1 solar array truss segment bound for the international space station.

To gain access to the area where the oxygen leak is believed to be, engineers opened Endeavour's cargo bay doors and worked today to install a cargo access platform, or CAP, between the aft end of the docking module and the forward face of P1. Standing on this platform, workers can remove payload bay floor blankets to gain access the suspect oxygen line plumbing.

As the platform was being maneuvered into place today, it came in contact with the shuttle's 50-foot-long robot arm, just above its shoulder joint. The arm's protective insulation was torn, but no other signs of obvious damage are apparent.

"In trying to get access to look at the (oxygen) line there, the platform did make contact with a very small area of some of the thermal blankets on robot arm," said NASA spokeswoman Lisa Malone. "We don't know yet if it's strictly cosmetic or anything beyond that."

The Canadian-built robot arm is crucial for Endeavour's mission. To install the P1 truss on the station, the shuttle arm must pull the segment from the cargo bay and then hand it off to the station's Canadarm2 space crane.

There may be nothing wrong with the shuttle arm other than the torn insulation, which can be fixed relatively easily. If so, and if engineers can repair the oxygen leak in short order, Endeavour could be ready for launch by Monday evening. While engineers are confident about fixing the oxygen leak, the arm incident is a wild card.

NASA managers will discuss the status of the oxygen line repair work and what, if anything, might need to be done about the robot arm at a meeting Wednesday. But there is little actual work that can be done on the fragile arm, which cannot support its own weight in Earth's gravity, in the vertical orientation.

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