NASA astronauts will use an S-band Antenna Subassembly that is already attached outside the space station to replace an S-band Antenna Subassembly. The S-band radio frequencies are used to send low-rate voice and data from the space station to flight controllers on the ground over a distance of more than 220 miles.
After 21 years of operation, the antenna recently ceased sending signals to Earth via NASA’s Tracking and Data Relay Satellite System. According to NASA spacewalk flight director Vincent LaCourt, mission managers discovered the problem in September.
“That timing allowed Tom and Kayla to go into our neutral buoyancy laboratory, or large pool where we practise spacewalks, and practise our exact spacewalk,” LaCourt explained.
In general, the loss of this antenna has little effect on space station operations. Maintaining antennas like this one, on the other hand, allows for redundancy in communications. Installing the spare, which has been sitting outside the station since 2010, will allow the backup system to continue. Other low-rate S-band systems and high-rate KU-band systems at the station relay video back and forth.
Marshburn will be on the end of the Canadarm2 robotic arm, which will be controlled from inside the space station by European Space Agency astronaut Matthias Maurer.
Marshburn will be extravehicular crew member 1 in the red-striped spacesuit, and Barron will be extravehicular crew member 2 in the unmarked suit. Barron is making his first spacewalk, and Marshburn is making his fifth.
Marshburn, Barron, and Maurer, along with NASA astronaut Raja Chari, docked at the space station on November 11 in their SpaceX Crew Dragon capsule.
The spacewalk on Tuesday is the 245th to assemble, maintain, and upgrade the space station, which has served as a continuous low-Earth orbit hub for humans for the past 21 years.
NASA Administrator Bill Nelson stated in a statement that he was disappointed “This irresponsible and destabilising action has outraged me. It is unthinkable that Russia would endanger not only the American and international partner NASA astronauts on the ISS, but also their own cosmonauts, given its long and illustrious history in human spaceflight. Their actions are reckless and dangerous, endangering the Chinese space station as well.”
While the debris field was initially dense, it has dispersed over time, according to Dana Weigel, NASA’s deputy manager of the International Space Station Program. The team in charge of planning the spacewalk used models and predictions to better understand the environment in which the NASA astronauts will be operating.
It has increased the risk to the spacewalkers by 7%, which “is not a large increase and is well within what we see with normal atmospheric fluctuations and the normal amount of debris that moves through,” according to Weigel. “What it really tells us is that EVA (extravehicular activity) has always been dangerous.”
This danger is posed by any debris that could penetrate the spacesuits or the space station itself. The pieces that could penetrate the spacesuits are much smaller than anything they can track, according to Weigel.
“It does imply penetration, but it does not imply catastrophic penetration,” Weigel explained. “There is a maximum size of penetration that can be tolerated. The suit has an emergency oxygen package that will keep it going for a while. When we talk about EVA risk, it’s usually around 1 in 2,700, which is the risk of having some size of a penetration over the course of the six and a half hour EVA.”
“Unfortunately,” Weigel said, “when you have a debris event like this and you get a lot of really small pieces scattered around, it just becomes part of the average environment.” “There is no specific directional aspect to the debris at some point. So they won’t do anything different during the spacewalk.”
The event did shuffle the task list for the spacewalk itself, and some “get-ahead” tasks, such as cable routing and releasing bolts on a spare nitrogen tank, have been removed, according to LaCourt. However, if there is time, the NASA astronauts will attend to a few matters that may prevent future spacewalks from being scheduled.
Overall, the team stated that they have been conservative in their decisions because some of these were made a few weeks ago before having all of the assessment data from the new debris. “We didn’t want to leave the crew out longer for items that we didn’t consider critical,” Weigel said, citing the increased risk and uncertainty caused by the new debris.
