In two planned spacewalks, astronauts aboard the International Space Station (ISS) will install a new Canadian made Latching End Effector (LEE), or robotic hand, on the Canadarm2, replacing its ageing counterpart.
At a press conference last week, NASA and Canadian Space Agency (CSA) managers, detailed the two spacewalks needed to replace the LEE B on the Canadarm2.
After 16 years of use, the LEE’s on the ISS are showing their age. Three years ago space station manager began noticing “increasing motor current going to the” LEE’s on the Canadarm2. The system was designed to do this as it began to show wear. It was a signal though that maintenance was required.
In 2015 they conducted two spacewalks to lubricate the LEE’s. This helped for a couple of years, but last year the system starting showing the problem again and the decision was eventually made last fall to to replace both LEE’s on the Canadarm2.
In total, six LEE’s where built. Five are currently on the ISS, of which four are in use. A ground spare is being prepared to be sent to the ISS on a future resupply mission this year.
It should be noted that the LEE’s on the Canadaram2 are extensively used. The LEE on the Mobile Base System and Dextre by comparison, are sparingly used.
It was expected that the MDA built LEE’s would eventually show wear and tear. Last October, LEE A on the Canardarm2 was replaced. Now its LEE B’s turn.
LEE A was replaced with a LEE that was on the Mobile Base System and which had been sparingly used. Now LEE B will be replaced with a new LEE, the on-orbit spare, which has been sitting idly on the exterior of the ISS since it was brought up nine years ago.
Originally LEE B was planned to be replaced first, but LEE A began showing more wear and tear and was replaced first. LEE B is in better shape than LEE A and can be used from what will be its new home on the Mobile Base System where it is only occasionally used.
Tim Braithwaite, the CSA liaison office manager at NASA’s Johnson Space Center in Houston, said that while the new LEE has been sitting in the harsh environment of space for nine years, that they are confident it will work as expected. The on-orbit spare LEE has been kept “covered and heated.” Braithwaite noted that while the LEE’s were all built many years ago, that over the years they been “refining our ops techniques, how we use the arm, the way we run these mechanism.” The software has been updated over the years and they’ve become “a lot gentler” on the LEE’s now. One maintenance regimen which has proven effective in slowing down wear and tear, is lubricating the LEE’s.
Braithwaite also said that the LEE’s have “exceeded design expectations.”
NASA Expedition 54 Flight Engineer Mark Vande Hei and NASA Flight Engineer Scott Tingle will start preparing for the spacewalk tomorrow morning at 5:30 a.m. EST with an expected hatch opening at 7:10 a.m. EST. The first spacewalk should take about 6 1/2 hours. You can watch* the spacewalk live on SpaceQ.
The goal of the first spacewalk is to remove and replace LEE B. The second spacewalk scheduled for January 29th will see the astronauts securing the LEE B on the station’s Mobile Base System. The second spacewalk will once again be led by Flight Engineer Mark Vande Hei but he will be joined by Flight Engineer Norishige Kanai of the Japan Aerospace Exploration Agency (JAXA).
Later this year LEE A will be returned to Earth on SpaceX Dragon spacecraft where it will be refurbished at MDA’s Brampton robotic facility. It will then be sent back to orbit to act as the ISS’s on-orbit spare. There is no plan for LEE B to be refurbished since it will be used sparingly on the Mobile Base System and should operate as expected through the remaining lifespan of the ISS, which is currently set to be used through 2024.
* Note: The U.S. government shutdown late last week after the press conference took place. We have contacted the Canadian Space Agency and are currently waiting to hear back if the spacewalk will go ahead as planned, and if it will be broadcast live. As soon as we have answers to these questions we’ll update this article.