Discovery successfully docked with the ISS at 18:52 Moscow time (14:52 GMT) Thursday.
A NASA expert assigned to the Mission Control in Korolyov, near Moscow, said experts had so far discovered three ceramic strips slightly protruding from the seams between thermal tiles in the space shuttle's heat shield.
Specialists will have to determine whether a space walk will be needed to repair the shield to avoid a tragedy during the space shuttle's re-entry to Earth's atmosphere. The protruding strips could cause the hull to overheat and disintegrate in the thick atmospheric layers.
In February 2003, a piece of foam insulation pierced a tiny hole in a wing during launch, causing Columbia to disintegrate during landing. All seven crew were lost.
Last year, two Discovery astronauts had to venture into space from the shuttle to remove a piece of gap-filling material protruding from the craft's underside before the spacecraft was allowed to return to Earth.
