Astronauts Akihiko Hoshide of JAXA and Thomas Pesquet of ESA switched their spacesuits to battery power at 1215 GMT on 12 September to begin their spacewalk from the Quest airlock. During the mission the astronauts had to install a “mod kit” at the base of the 4A solar array wing on the P4 truss. This kit comprised of a set of struts that will serve as a support bracket in preparation for installation of the next set of ISS Roll-Out Solar Arrays (iROSA) as NASA continues augmenting six of the eight existing power channels of the space station. Once this modification was complete on the P4 truss, the astronauts turned their attention to replacing the old FPP (Floating Potential Probe) on P6 truss with a new FPMU (Floating Potential Measurement Unit) which measures the electrical charging potential of the arrays and associated surfaces. Once installed the new FPMU was then powered up successfully.
The astronauts returned to the Quest airlock and the mission was concluded at 1909 GMT, after six hours and 54 minutes. This was the fourth EVA for Hoshide and the sixth for Pesquet. This was US EVA-77 and the 244th spacewalk in support of assembly and maintenance of the 20 year old space station.