Flight engineers will soon conduct the only spacewalk of the STS-135 shuttle mission, marking the last such walk of the US space shuttle programme.

Expedition 28 flight engineers Mike Fossum and Ron Garan will conduct the 6.5-hour mission in order to conduct important tasks, including the retrieval of a failed pump module from an external stowage platform.

They will also transfer the robotic refuelling mission experiment from the shuttle bay to the special purpose dexterous manipulator, designated by Dextre, and deploy components of the Materials International space station experiment 8.

Space shuttle Atlantis lifted off for the final time on 8 July and is scheduled to return to Earth on 20 July.