NASA astronaut Nick Hague will install patches to the agency’s NICER (Neutron star Interior Composition Explorer) X-ray telescope on the International Space Station as part of a spacewalk scheduled for Jan. 16. Hague, along with astronaut Suni Williams, will also complete other tasks during the outing.

NICER will be the first NASA observatory repaired on-orbit since the last servicing mission for the Hubble Space Telescope in 2009.

Hague and other astronauts, including Don Pettit, who is also currently on the space station, rehearsed the NICER patch procedures in the NBL (Neutral Buoyancy Laboratory), a 6.2-million-gallon indoor pool at NASA’s Johnson Space Center in Houston, in 2024. 

“We use the NBL to mimic, as much as possible, the conditions astronauts will experience while preforming a task during a spacewalk,” said Lucas Widner, a flight controller at KBR and NASA Johnson who ran the NICER NBL sessions. “Most projects outside the station focus on maintenance and upgrades to components like solar panels. It’s been exciting for all of us to be part of getting a science mission back to normal operations.”

From its perch near the space station’s starboard solar array, NICER studies the X-ray sky, including erupting galaxies, black holes, superdense stellar remnants called neutron stars, and even comets in our solar system. 

But in May 2023, NICER developed a “light leak.” Sunlight began entering the telescope through several small, damaged areas in the telescope’s thin thermal shields. During the station’s daytime, the light reaches the X-ray detectors, saturating sensors and interfering with NICER’s measurements of cosmic objects. The mission team altered their daytime observing strategy to mitigate the effect. 

The team also developed a plan to cover the largest areas of damage using wedge-shaped patches. Hague will slide the patches into the telescope’s sunshades and lock them into place. 

“We designed the patches so they could be installed either robotically or by an astronaut,” said Steve Kenyon, NICER’s mechanical engineering lead at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “They’re installed using a tool called a T-handle that the astronauts are already familiar with.”

The NBL contains life-size mockups of sections of the space station. Under the supervision of a swarm of scuba divers, a pair of astronauts rehearse exiting and returning through an airlock, traversing the outside of the station, and completing tasks. 

For the NICER repair, the NBL team created a full-scale model of NICER and its surroundings near the starboard solar array. Hague, Pettit, and other astronauts practiced taking the patches out of their caddy, inserting them into the sunshades, locking them into place, and verifying they were secure. 

The task took just under an hour each time, which included the time astronauts needed to travel to NICER, set up their tools, survey the telescope for previously undetected damage, complete the repair, and clean up their tools. 

Practice runs also provided opportunities for the astronauts to troubleshoot how to position themselves so they could reach NICER without touching it too often and for flight controllers to identify safety concerns around the repair. 

Being fully submerged in a pool is not the same as being in space, of course, so some issues that arose were “pool-isms.” For example, astronauts sometimes drifted upward while preparing to install the patches in a way unlikely to happen in space. 

Members of the NICER team, including Kenyon and the mission’s principal investigator, Keith Gendreau at NASA Goddard, supported the NBL practice runs. They helped answer questions about the physical aspects of the telescope, as well as science questions from the astronauts and flight controllers. NICER is the leading source of science results on the space station. 

“It was awesome to watch the training sessions and be able to debrief with the astronauts afterward,” Gendreau said. “There isn’t usually a lot of crossover between astrophysics science missions and human spaceflight. NICER will be the first X-ray telescope serviced by astronauts. It’s been an exciting experience, and we’re all looking forward to the spacewalk where it will all come together.”

The NICER telescope is an Astrophysics Mission of Opportunity within NASA’s Explorers Program, which provides frequent flight opportunities for world-class scientific investigations from space utilizing innovative, streamlined, and efficient management approaches within the heliophysics and astrophysics science areas. NASA’s Space Technology Mission Directorate supported the SEXTANT component of the mission, demonstrating pulsar-based spacecraft navigation.

By Jeanette Kazmierczak
NASA’s Goddard Space Flight Center, Greenbelt, Md.

Media Contact:
Claire Andreoli
301-286-1940
claire.andreoli@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.

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