CAPE CANAVERAL, Fla. -- NASA engineers moved the payload for the Space Shuttle Discovery onto the launch pad late Thursday night and early Friday morning.

Discovery will carry the Leonardo Module filled with spare parts to the International Space Station. The shuttle is scheduled to blast off April 5.

Engineers will conduct more tests over the weekend to see if a helium valve that failed last week needs to be repaired. If repairs are needed, it could mean Discovery will have to be rolled back to the Vehicle Assembly Building.