For the relocation, Expedition 15 Flight Engineer Clay Anderson was at the controls of the station's robotic arm. Expedition 15 commander Fyodor Yurchikhin worked with the docking systems. Flight Engineer Oleg Kotov backed up both men.
Intensive preparations for the move began Monday. PMA-3 was undocked at 8:18 a.m. EDT and docked to Unity's lower port at 9:07.
During unberthing operations, fault alarms were seen on two occasions, first in one bolt after it had reached zero load and then intermittently in three bolts. After two delays to study the situation, the crew was told to continue with the unberthing.
PMA-3 was moved to the nadir port to prepare for the arrival of Node 2, the Harmony module, on the STS-120 flight of Discovery in October. Canadarm2 could not reach the end of Harmony if the node were installed on the nadir port.
After Discovery leaves the station, the arm will be used to remove PMA-2 from the end of Destiny and install it on the end of Harmony. Harmony will be moved to the front of Destiny, where PMA-2, at the forward end, will be ready to welcome shuttles again.
Harmony will provide docking ports for the European Space Agency's Columbus laboratory and the Japanese Space Agency's Kibo experiment module.
PMA-3 was delivered to the station by Discovery on its STS-92 flight in October 2000. It was installed during a spacewalk by Jeff Wisoff and Michael Lopez-Alegria. Koichi Wakata used Discovery's robotic arm to grapple PMA-3, remove it from the cargo bay and install it on Unity's nadir port.
Endeavour on STS-97 docked to PMA-3 in December 2000 with the P6 Truss. Atlantis used it when it brought the U.S. laboratory Destiny to the station on STS-98 in February 2001.
During the STS-102 mission of Discovery it was moved to the port side of Unity during a spacewalk by Susan Helms and Jim Voss. That cleared the nadir port for use by the Multi-Purpose Logistic Module, the Italian-built, U.S.-funded pressurized cargo carrier.
PMAs allow a visiting spacecraft or another module to be attached to the station. PMA-1 was launched with Unity, and links the node to the Zarya module. PMA-2 also was launched with Unity, and was moved to the forward end of Destiny, where shuttles now dock, during the STS-98 mission.