The U.S. space agency, NASA, says hail from a passing thunderstorm has damaged the external fuel tank of the space shuttle Atlantis.
NASA officials in Florida say the incident occurred late Monday while the Atlantis was being prepared for a March 15 launch. They say the fuel tank is being inspected to assess the damage and to determine how to fix it.
A six-person crew is to take part in the March launch. During the mission, the Atlantis will carry a new solar module for the space station - an orbital project headed by the United States and Russia in partnership with 15 other countries.
NASA officials say the astronauts plan to conduct three spacewalks to install the new solar panels, and to carry out other station construction tasks during the mission.
This will be the fifth shuttle flight since the spacecraft Columbia disintegrated on re-entry in 2003, killing all seven astronauts aboard. NASA grounded the shuttle fleet until 2005 while it investigated the accident.