Astronauts on a Mission: Fixing NASA’s X-ray Telescope in Space!

NASA astronaut Nick Hague is set to affix patches to the organization’s NICER (Neutron star Interior Composition Explorer) X-ray telescope on the International Space Station as part of a spacewalk planned for January 16. During this outing, Hague, alongside astronaut Suni Williams, will also perform additional duties.

NICER will mark the first NASA observatory to undergo repairs in orbit since the last servicing mission for the Hubble Space Telescope in 2009.

Hague and fellow astronauts, including Don Pettit—who is also presently on the space station—practiced the NICER patch techniques in the NBL (Neutral Buoyancy Laboratory), which is a 6.2-million-gallon indoor swimming facility at NASA’s Johnson Space Center in Houston, throughout 2024.

“We utilize the NBL to replicate, as closely as possible, the conditions that astronauts will encounter while performing a task during a spacewalk,” remarked Lucas Widner, a flight controller at KBR and NASA Johnson who supervised the NICER NBL sessions. “Most projects outside the station concentrate on maintenance and upgrades to parts like solar panels. It has been thrilling for all of us to partake in restoring a scientific mission to standard operations.”

Positioned adjacent to the station’s starboard solar array, NICER examines the X-ray sky, including explosive galaxies, black holes, superdense stellar remnants known as neutron stars, and even comets within our solar system.

However, in May 2023, NICER encountered a “light leak.” Sunlight started to penetrate the telescope through multiple small, damaged sections in the telescope’s fragile thermal shields. During daylight hours at the station, the light accesses the X-ray detectors, overwhelming sensors and disrupting NICER’s observations of cosmic entities. The mission team revised their daytime observing tactics to alleviate the impact.

The team also devised a strategy to cover the most extensive damaged areas with wedge-shaped patches. Hague will slide these patches into the telescope’s sunshades and secure them.

“The patches were designed for installation by either robotic means or by an astronaut,” explained Steve Kenyon, the mechanical engineering lead for NICER at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “They are installed with a tool known as a T-handle, which the astronauts are already acquainted with.”

The NBL features life-sized replicas of sections of the space station. Under the oversight of several scuba divers, a duo of astronauts rehearses exiting and re-entering through an airlock, navigating the exterior of the station, and executing tasks.

For the NICER maintenance, the NBL team constructed a full-scale replica of NICER and its vicinity close to the starboard solar array. Hague, Pettit, and other astronauts trained in retrieving the patches from their caddy, inserting them into the sunshades, securing them, and confirming they were in place.

The endeavor took just under an hour each instance, which encompassed the time astronauts required to travel to NICER, prepare their tools, inspect the telescope for previously unseen damage, carry out the repair, and tidy up their tools.

Rehearsal sessions also allowed astronauts to troubleshoot how to position themselves for reaching NICER while minimizing contact, alongside enabling flight controllers to pinpoint safety issues surrounding the repair.

Being entirely submerged in a pool does not equate to being in space, naturally, so some issues that emerged were “pool-isms.” For instance, astronauts occasionally drifted upward while getting ready to install the patches, a scenario unlikely to occur in space.

Members of the NICER team, including Kenyon and the mission’s principal investigator, Keith Gendreau at NASA Goddard, provided support during the NBL training runs. They facilitated answers to questions regarding the physical characteristics of the telescope, as well as scientific inquiries from the astronauts and flight directors. NICER serves as the primary source of scientific results aboard the space station.

“It was incredible to observe the training sessions and to debrief with the astronauts afterward,” Gendreau said. “Typically, there isn’t much overlap between astrophysics science missions and human space travel. NICER will be the first X-ray telescope serviced by astronauts. It has been a thrilling experience, and we are all eagerly anticipating the spacewalk where it will all come together.”

The NICER telescope represents an Astrophysics Mission of Opportunity within NASA’s Explorers Program, which offers frequent flight chances for distinguished scientific inquiries from space utilizing innovative, streamlined, and efficient management techniques within the heliophysics and astrophysics science fields. NASA’s Space Technology Mission Directorate supported the SEXTANT component of the mission, which demonstrated pulsar-based spacecraft navigation.