A fleeting problem with the arm's shoulder joint had prompted NASA managers to consider postponing the Atlantis flight until September.

But the crane-like device in recent weeks has been working as advertised, and NASA engineers have devised a plan that would enable the arm to operate even if the shoulder joint problem were to crop up again.

"They feel like they have a high degree of confidence that they understand the problem and know how to deal with it," said Kyle Herring, a spokesman for NASA's Johnson Space Center in Houston, Texas.

Atlantis and a crew of five astronauts now are scheduled to blast off July 12 on a mission to mount the airlock to the station, where it will serve as a staging area for spacewalking work to be conducted by resident outpost crews.

The station's 57.7-foot (15.5-meter) robot arm will be used to pluck the airlock from the shuttle's cargo bay and then install it on the starboard side of the U.S. Unity module.

Shorter shuttle robot arms -- which have been used to carry out all station construction to date -- are too short to perform the airlock installation job.

The problem with the arm's shoulder joint, consequently, raised fears that the crane could fail during the Atlantis flight, leaving the airlock stranded in the midst of the installation job.

Engineers, however, now have traced the problem to a suspect computer chip within a shoulder joint electronics unit. The fix: A software patch that essentially will bypass the chip and enable the arm to operate even if the shoulder joint problem recurs.

Herring said the patch is to be beamed up to the station next week. In the meantime, the station crew on Thursday will carry out a second dress rehearsal for the airlock installation job.

An initial dry run was conducted last Thursday and the arm's shoulder joint worked without problems during that test.

NASA mission managers, meanwhile, are facing a mid-July deadline for launching Atlantis.

The flight cannot be launched between July 17 and August 4. The station during that time will be flying in an orbit that would expose a docked shuttle to high temperatures that could foul its docking mechanism as well as cargo within its payload bay.

Shuttle Discovery remains scheduled to launch Aug. 5 on a mission to ferry a new crew to the station and return to Earth with its current tenants: Yuri Usachev, Susan Helms and Jim Voss.

Onboard the station since early March, Usachev, Helms and Voss already are facing an extra month in space. Consequently, NASA managers likely would opt to postpone the Atlantis flight until September if the upcoming launch is delayed beyond the mid-July deadline.