Last Thursday, on October 5, two NASA astronauts, Randy Bresnik and Mark Vande Hei, performed service action to help keep Canadarm2 operational.
Even if Canadarm2 usually works perfectly and supports astronauts inside International Space Station in their work, sometimes it fails. Delivered to ISS in 2001 during STS-100 inside trunk of Endeavour Space Shuttle remains attached to the Station for last 16 years without any serious problems.
Being part of Mobile Servicing System (MSS) Space Station Remote Manipulator System (SSRMS), known as Canadarm2, is one of the crucial instruments installed outside the ISS. It is necessary for undocking and docking of cargo spacecrafts, during scientific experiment and most of the service actions of the ISS. It was designed as upgraded version of Canadarm, robotic arm installed at Space Shuttles by Canadian Space Agency.
Unfortunately recently one of LEE latches used for both securing Canadarm2 on rail system attached to ISS and for grabbing cargo failed on August 22, 2017. Issue was in fact predicted by results of analysis of the telemetry data. Both latches were under observation by ground control center, as their best times far beyond. NASA decided to perform EVA to replace failed part and bring Canadarm2 to life in October.
Station Commander Randy Bresnik and Flight Engineer Mark Vande Hei left Quest airlock at 12:05 UTC on October 5, 2017 and left ISS 402 km over Egypt. Main objective was replacing LEE-A latch from the end of Canadarm2 were cargo is usually attached. Duo reached Canadarm2 and begun replacing LEE-A module. They removed insulation and loosened all six bolts securing part. After replacing module they re-attach insulation after securing bolts and returned with faulty part to Quest airlock after 6 hours 55 minutes.
To make Canadarm2 fully operational it is necessary to relube LEE-A, what is planned for October 10, 2017 again by Randy Bresnik and Mark Vande Hei. This spacewalk will be followed by another planned to be performed by Randy Bresnik and Joe Acaba on October 18, 2017 when duo will conduct ordinary maintenance tasks and replace two cameras outside the Station. Replacing LEE-B latch is planned for the end of 2017 or even later, for 2018.