The inspections and possible upgrades to protect the wiring will delay shuttle Endeavour's launch on an 11-day mission to map the Earth with radar, as well as a crucial preventative maintenance call to the Hubble Space Telescope that had been planned for mid-October.

Endeavour's radar-mapping mission, slated for launch on September 16, will be delayed 20 to 30 days, said Don McMonagle, the launch integration manager at Kennedy Space Center. The postponement would bump the mission into the time reserved for shuttle Discovery's servicing call to the Hubble Space Telescope. NASA worked in the mission to Hubble nine months earlier than planned to replace its positioning system, which is now operating without backups.

The delays, though, pale in comparison to what NASA could face if the orbiters have damaged wires, similar to what was found on shuttle Columbia. During its last launch on July 23, a short circuit five seconds after liftoff shut down the primary controllers for two of the shuttle's three hydrogen-burning main engines. The short was traced to a damaged wire in the shuttle's payload bay.

Columbia automatically switched to backup engine controllers and safely reached orbit. However, if a problem had shut down the backup controllers, the shuttle crew likely would have faced attempting NASA's first emergency landing.

On Thursday, McMonagle revealed that the Columbia crew was substantially closer to that scenario that originally realized. Another damaged wire was found in a tray of cables on the opposite side of the shuttle's payload bay. The 14-gauge wire, similar to what is found in a household light bulb, was about one-third of the way through its double wrapping of Kapton insulation.

"We had a close call," said McMonagle.

He quickly added, however, that the second wire still had sufficient insulation. "We were not on the verge of having a second short," he said.

The damaged wires are part of 300 miles of wiring that snake the left and right sides of the shuttle's 60-foot long cargo bay, connecting engines, sensors and computers to avionics and controllers in the shuttle's crew cabin.

The area where Columbia's wires were damaged is directly within range of technicians using work platforms during prelaunch preparations.

The damage is suspected to have occurred several years ago, when the tray of cables was last removed, said McMonagle. Endeavour has had similar work performed recently.

"It would be easy for some inadvertent damage to occur," said McMonagle. "Prudence would say that we should go back and take a look."

The suspect areas cannot be reached with the radar units anchored in Endeavour's cargo bay, so the equipment will be taken out and temporarily stored for inspections. Discovery's equipment for the Hubble servicing call arrived at the space center on Thursday and has not yet been installed.