The James Webb Space Telescope is experiencing an issue with one of its instruments, the Near Infrared Imager and Slitless Spectrograph, or NIRISS. The instrument is currently offline with no indication of when it will be back online, but engineers are working to address the issue and the telescope hardware remains safe.
As alarming as that might sound, it is not uncommon for such issues to crop up, especially in space telescopes. As performing physical maintenance on space telescopes is extremely difficult, software troubleshooting is done in a slow and careful way to prevent any damage from occurring. That’s why you’ll see instruments on space telescopes like Hubble or the Swift Observatory going into safe mode to protect themselves whenever an issue arises.
In the case of James Webb, the problem with the NIRISS instrument was due to a communication delay. “On Sunday, Jan. 15, the James Webb Space Telescope’s Near Infrared Imager and Slitless Spectrograph (NIRISS) experienced a communications delay within the instrument, causing its flight software to time out,” NASA wrote in a statement. “The instrument is currently unavailable for science observations while NASA and the Canadian Space Agency (CSA) work together to determine and correct the root cause of the delay.”
NIRISS sits alongside a sensor called the Fine Guidance Sensor or FGS which allows the telescope to point at its targets accurately. NIRISS can work as both a camera and a spectrograph and has a special feature called an aperture mask which allows it to block out light from particularly bright sources to better see dimmer sources around them. The instrument is used for tasks like detecting and examining exoplanets and for looking at distant galaxies.
The planned scientific observations which were scheduled to use NIRISS will now be rescheduled, according to NASA.
This comes on the heels of another issue with Webb which occurred in December 2022. A software issue in the attitude control system caused some instruments to enter safe mode on December 7, with science observations being paused. That was fixed by December 20, when all science operations resumed.
