In the first of three planned spacewalks, NASA astronauts Randy Bresnik and Mark Vande Hei will go outside the International Space Station to repair the ISS main robotic appendage.

The three spacewalks have been scheduled with the purpose of tinkering around the ISS. Bresnik will take the lead in all three of these expeditions. Repair and maintenance work is required from time to time, as is the addition of new elements. Now, efforts will focus on the robotic arm, informally known as Canadarm2.

Officially called the Space Station Remote Manipulator System (SSRMS), Canadarm2 is part of the Mobile Servicing System (MSS), and it is one of the most crucial tools on the ISS. Much like the name implies, it is a snake-like robotic arm which can extend up to nearly 60 feet (18 meters) into space. The Canadarm2 was instrumental during the early days of the ISS when large pieces of equipment had to be moved and installed. Nowadays, it is used for routine inspections outside the ISS and to latch and dock incoming cargo spacecraft.

Canadarm2 riding the Mobile Base System along the Mobile Transporter railway, running the length of the station’s main truss. Credits: NASA.

Astronauts will replace one of the two Latching End Effectors on Canadarm2, lubricate the new component and replace cameras at two locations on the station’s truss. The Latching End Effectors, or LEEs, have been steadily deteriorating. They’re complex devices, incorporating sensors, electronics, and a camera, so reparations are not an easy feat. Initially, NASA planned to repair the LEE which seemed most degraded, but the other one stopped working, which moved it to the top of the priority list. The other one is also set for repairs, but that has been postponed for January.

As I am writing this (and sneaking a peak on NASA’s livestream), the astronauts are suiting up and conducting final preparations. By the time you read this, they will probably be outside, working on Canadarm2.

Five days from now, on October 10th, Bresnik and Vande Hei will do another spacewalk to lubricate the new LEE and then replace a camera on the outside of the station. Another five days later, October 15th, Bresnik will be joined by NASA astronaut Joe Acaba for a third spacewalk on to do more lubrication and another camera replacement.

All the three spacewalks of October are slated to begin at 8:05 am EDT (8:05 pm SST), but it is possible to start earlier if the astronauts are moving ahead of schedule.