On Apr. 21, 2023, the James Webb Space Telescope team shared that one of the MIRI (Mid-Infrared Instrument) observing modes, called Medium-Resolution Spectroscopy (MRS), showed a reduction in the amount of light registered by MIRI’s detectors. Initial analysis of MIRI’s imaging mode did not show a similar effect. However, as part of the team’s investigation into the issue, additional monitoring observations were taken with MIRI imaging. Combined with earlier data, these new calibrations have revealed a reduced signal for MIRI imaging at the longer wavelengths.
This change does not substantially impact MIRI’s science capabilities but will have an impact on the exposure times needed for MIRI imaging.
There is no risk to the instrument, and the effect on imaging is less than the effect in MRS. The team is investigating the cause of this issue. Regular monitoring observations are being taken to continue measuring the response, and the team is providing updated guidance to Webb’s user community to correct for this change. MIRI’s third observing mode, Low-Resolution Spectroscopy, is currently performing normally, and the investigation of MIRI’s fourth mode, Coronographic Imaging, has not yet concluded.
The Webb team has also enacted a plan for long-term monitoring, and are exploring potential mitigations. The observatory is in good health, and each of Webb’s other scientific instruments are unaffected.
For more information, visit the Space Telescope Science Institute.