The highest priority objectives of the flight were the installation, activation and checkout of the Canadarm2 robotic arm on the station. The arm - manufactured by MDA Space Missions under contract of the Canadian Space Agency and NASA, went into operation on 28 April 2001. It was critical to the capability to continue assembly of the International Space Station. The arm was also necessary to attach a new airlock to the station on the subsequent shuttle flight, mission STS-104. The final component of the Canadarm is the Mobile Base System (MBS), which was installed on board the station during the STS-111 flight.