Technicians finish toasting shuttle tiles

Workers use banks of heat lamps to dry out Atlantis

(CNN) -- The space shuttle Atlantis is all dried out and has a new waterproof coat. The shuttle's mission was pushed back from June 14 to June 20 -- at the earliest -- because of soggy thermal tiles.

Atlantis was caught in a rare desert downpour after landing at Edwards Air Force Base in the Mojave Desert on February 20. Shuttles often are rained on while sitting on the launch pad in Florida, but waterproofing protects the tiles.

The waterproofing burns off during the shuttle's fiery re-entry into Earth's atmosphere, leaving the tile-encrusted spacecraft vulnerable to the elements after landing.

"We've had wet orbiters before," said NASA spokesman Joel Wells. "But our typical tile-drying efforts have been enough."

Not this time.

Atlantis had to be baked under dozens of heat lamps to cook off the moisture. Technicians finished work on the orbiter over the weekend.

Water on the tiles could freeze as the shuttle reaches orbit, and could cause the tiles to come off. The 22,000 heat protection tiles shield the shuttle from the 3,000-degree Fahrenheit temperatures encountered during reentry into Earth's atmosphere for landing.

NASA still hasn't set a firm launch date for Atlantis, saying the orbiter will go up no earlier than June 20 at about 1:45 p.m. EDT.

The mission may have to be revamped to include some repair work on the international space station's new Canadian-built robot arm.

During tests by space station crew members, Russian commander Yury Usachev and U.S. astronauts Jim Voss and Susan Helms, a backup electronics box near the arm's elbow failed to work properly.

The shuttle currently is scheduled to deliver a new U.S.-built airlock to Alpha. The station's robot arm was to be used to help attach the airlock.

On June 8, Usachev and Voss will conduct an "internal spacewalk." The pair will work inside the space station, but with the hatch open, to move a docking mechanism in the Zvezda module to prepare for the arrival of a Russian docking module later this summer.

The spacewalk may be expanded to include work on the robot arm if ground controllers can't correct the problem.