A hail storm left hundreds of divots on space shuttle Atlantis' external fuel tank, and NASA managers weren't sure Tuesday if the damage was severe enough to postpone next month's launch.
The storm Monday evening passed over the launch pad where Atlantis was being prepared for a March 15 launch, NASA spokesman Bill Johnson said.
"Right now, the big deal is how many divots? How deep are they? Can they be repaired at the pad? Can they not be repaired at the pad?" Johnson said.
NASA officials were weighing their options. They could make repairs to the external tank on the launch pad using an enormous crane, or they could move the space shuttle back into its Vehicle Assembly Building to fix the divots. NASA also has another external fuel tank at Kennedy Space Center that is being readied for a mission in June.
The damage is concentrated in the upper third of the enormous external tank, a section which holds liquid oxygen propellant.
The shuttle's launch window extends into late March. Russia plans to launch a Soyuz vehicle to the international space station in early April.
Coincidentally, NASA managers on Tuesday began a two-day meeting at the Kennedy Space Center to determine whether there were any problems that would prevent Atlantis from launching as planned.
In 1999, hail from a storm made 650 divots in space shuttle Discovery's external tank, forcing NASA to delay a launch and return the spacecraft to the Vehicle Assembly Building. Hail also hit the external tank of space shuttle Atlantis in 1990, causing minor damage.
The insulating foam on the external tank is of special concern to NASA since foam flew off space shuttle Columbia during lift off in 2003 and struck the orbiter. The damage allowed fiery gases to penetrate Columbia during re-entry, breaking up the craft and killing its seven astronauts.
NASA redesigned the external tank, removing large amounts of foam, before last year's three successful shuttle missions. The space agency plans another design change to the tank before the shuttle program ends in 2010.
During their 11 days in space, Atlantis' astronauts will deliver a 35,000-pound addition, the heaviest ever, along with a new pair of solar arrays. Crew members will unfurl the solar arrays, fold up an old pair and conduct at least three spacewalks.