Jan. 24, 2025

NASA’s NICER Continues Science Operations Post Repair

NASA crew aboard the International Space Station installed patches to the agency’s NICER (Neutron star Interior Composition Explorer) mission during a spacewalk on Jan. 16. NICER, an X-ray telescope perched near the station’s starboard solar array, resumed science operations later the same day.

The patches cover areas of NICER’s thermal shields where damage was discovered in May 2023. These thin filters block sunlight while allowing X-rays to pass through. After the discovery, the NICER team restricted their observations during the station’s daytime to avoid overwhelming the mission’s sensitive detectors. Nighttime observations were unaffected, and the team was able to continue collecting data for the science community to make groundbreaking measurements using the instrument’s full capabilities.

The repair went according to plan. Data since collected shows the detectors behind the patched areas are performing better than before during station night, and the overall level of sunlight inside NICER during the daytime is reduced substantially.

While NICER experiences less interference from sunlight than before, after analyzing initial data, the team has determined the telescope still experiences more interference than expected. The installed patches cover areas of known damage identified using astronomical observations and from photos taken by both external robotic cameras and astronauts inside the space station. Measurements collected since the repair and close-up, high-resolution photos obtained during the spacewalk are providing new information that may point the way toward further daytime data collection.

In the meantime, NICER continues operations with its full measurement capabilities during orbit night to enable further trailblazing discoveries in time domain and multimessenger astrophysics.

Media contact: Alise Fisher, NASA Headquarters / Claire Andreoli, NASA Goddard

June 8, 2023

Sunlight ‘Leak’ Impacting NASA’s NICER Telescope, Science Continues

On Tuesday, May 22, NASA’s NICER (Neutron Star Interior Composition Explorer), an X-ray telescope on the International Space Station, developed a “light leak,” in which unwanted sunlight enters the instrument. While analyzing incoming data since then, the team identified an impact to daytime observations. Nighttime observations seem to be unaffected.

The team suspects that at least one of the thin thermal shields on NICER’s 56 X-ray Concentrators has been damaged, allowing sunlight to reach its sensitive detectors.

To mitigate the effects on measurements, the NICER team has limited daytime observations to objects far away from the Sun’s position in the sky. The team has also updated commands to NICER that automatically lower its sensitivity during the orbital day to reduce the effects from sunlight contamination. The team is evaluating these changes and assessing additional measures to reduce the impact on science observations.

To date, more than 300 scientific papers have used NICER observations, and the team is confident that NICER will continue to produce world-class science.

Media contact: Alise Fisher, NASA Headquarters / Claire Andreoli, NASA Goddard

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.