During a spacewalk on Jan. 23, 2018, Expedition 54 flight engineers Mark Vande Hei and Scott Tingle replaced a Latching End Effector (LEE-B) on the Canadarm2 robotic arm. An issue preventing the LEE from transitioning to an operational state on one of two redundant sets of communications strings was detected. The spacewalking crew demated and remated the connectors and ground teams were able to power up the arm to an operational state on its secondary communications string leaving the arm operational but without a redundant communications string.
After extensive troubleshooting by teams from NASA and the Canadian Space Agency (CSA), the decision was made by space station managers to use the scheduled Jan. 29 spacewalk to reinstall the LEE removed on the Jan. 23 spacewalk to restore fully redundant capability to the robotic arm. CSA and its robotics specialists are continuing diagnostics over the weekend to gain additional insight. If data is obtained that could be used to solve the issue, Monday’s spacewalk could be postponed.