NASA scientists have observed a sensor glitch with a James Webb Space Telescope's key instrument. The US space agency and its partners are investigating the issue.The glitch was discovered during a routine performance monitoring and calibration of all 17 observing modes of the next-generation Telescope.
Calibration is performed by comparing the brightness of standard stars that have been well-catalogued by other observatories to what Webb's MIRI was receiving.Mission officials noticed a discrepancy in the data. They zeroed it on a mode of MIRI's Medium Resolution Spectroscopy (MRS).
They found that the mode is receiving less sensor "throughput" less than the expected amount of light at the longest wavelengths. No risk was seen for MIRI imaging and the instrument, NASA officials said.
"Analysis of MIRI's Medium Resolution Spectroscopy (MRS) mode revealed that at the longest wavelengths, the throughput, or the amount of light that is ultimately registered by MIRI's sensors, has decreased since commissioning last year," they wrote in a mission update.
"No effect has been seen for MIRI imaging, and there is no risk to the instrument. All other observation modes within MIRI and each of Webb's other scientific instruments remain unaffected," they added.
The $10 billion Webb telescope, is an international programme led by NASA, European Space Agency and the Canadian Space Agency.
Together with its partners, NASA said it is "developing a systematic plan to approach, analyse, and then explore the issue".Meanwhile, the Webb team will continue MIRI observations as planned. They will gather all relevant ground test and flight data to fully assess MRS performance.
Further test observations will be taken to completely characterise the nature of the issue using this particular mode of observation."The team continues to investigate the cause, identify risks, and explore mitigations that would potentially improve performance. One possible mitigation strategy includes taking slightly longer exposures at the affected wavelengths to increase the signal to noise," the team said.
This is not the first time that MIRI has faced down a glitch with the MRS. The instrument had a stuck grating wheel for a few months between August and November 2022, but MIRI was still able to observe in other modes.
Launched on December 25, 2021, the powerful telescope has been offering scientists unprecedented views into the universe beyond our planet. The telescope's actual aim is to solve mysteries in our solar system, look beyond distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it.