The U.S. space agency NASA says the shuttle Atlantis will remain grounded until at least June 8 while technicians repair storm damage to the orbiter's external fuel tank. As we hear from VOA's David McAlary, mission managers say replacing the tank with an undamaged one would delay the launch even longer.

NASA says technicians have repaired 350 out of more than 2,600 dents in the shuttle's external fuel tank caused during a late February hail storm. Atlantis was attached to the tank on the launch pad undergoing preparations for a March liftoff, so the tank damage required their rollback to the hangar.

The pits occurred in the tank's hard foam external casing, an insulation layer that prevents the frigid liquid hydrogen and oxygen inside from causing ice to form on the outside of the tank.

The bigger pits must be filled with poured or sprayed foam, while shallower ones can be smoothed by sanding.

Shuttle program manager Wayne Hale says disconnecting the old fuel tank from Atlantis and attaching a new one would delay launch until June 19, while keeping the existing tank bolted on would allow a June 8 takeoff at the earliest if repairs proceed smoothly. "They [the two dates] are becoming close in schedule, but the consideration is [that], of course, we would like to avoid the work taking the orbiter back to the orbiter processing facility and all of the effort that is involved in switching tanks. So as long as we are on a good path to repair the hail-damaged tank, we should stay with it."

Atlantis will be the first shuttle this year to continue construction of the International Space Station. Its cargo is a new set of solar arrays for the starboard side of the research outpost.

The NASA official in charge of space operations, William Gerstenmaier says the technique for pouring or spraying foam into the deeper external fuel tank divots is a standard application procedure. He says similar repairs have bonded well for previous flights and expects no foam shedding during Atlantis' launch of the kind that struck and doomed the shuttle Columbia in 2003.

"We have flown this type of repair before and it is not totally outside of our experience base. The teams have reviewed the data and showed that this repair technique is pretty viable from an overall assurance that the tank will not shed foam," he said.

The integrity of the shuttle external fuel tank foam has been a NASA priority since the Columbia disaster, when the piece that broke away during launch punctured a wing. Seven astronauts died during re-entry when atmospheric gases superheated by friction with the shuttle entered the wing and destroyed it.

Shuttle manager Hale says that despite the delay in Atlantis' takeoff, there is a possibility that four shuttles can fly to the space station this year. He has said previously that the postponement will not set back the goal of completing station assembly by 2010, the year President Bush has ordered the aging shuttle fleet to be retired.