Washington, May 25 (IANS): NASA engineers are set to prepare the International Space Station (ISS) for the future arrival of US commercial crew and cargo vehicles.

On May 27, robotics flight controllers at NASA's Johnson Space Centre in Houston will detach the large Permanent Multipurpose Module (PMM), used as a supply depot on the orbital laboratory, from the Earth-facing port of the Unity module and robotically relocate it to the forward port of the Tranquility module.

This move will clear the Unity port for its conversion into the spare berthing location for US cargo spacecraft.

The Earth-facing port on Harmony is the primary docking location.

"Harmony's space-facing port currently is the spare berthing location for cargo vehicles, so this move frees that location to be used in conjunction with Harmony's forward port as the arrival locations for commercial crew spacecraft," the US space agency said in a statement.

Expedition 43 commander Terry Virts and flight engineer Scott Kelly of NASA will supervise the unbolting of the module from Unity and its final attachment to Tranquility.

NASA is in the process of re-configuring the station to create primary and back up docking ports for US commercial crew spacecraft currently in development by Boeing and SpaceX.

The move will once again transport astronauts from US soil to the space station and back beginning in 2017.

The primary and backup docking ports also will be reconfigured for US commercial spacecraft delivering research, supplies and cargo for the crew.