New reference files for the MIRI Low-Resolution Spectrometer (LRS) slit and slitless modes are now available in CRDS pmap versions jwst_1174.pmap and later.

These updates affect the wavelength and photometric calibration, and the aperture correction. The wavelength calibration of the LRS slit has changed the most, with a shift to the blue, up to about 50 nm at 6 microns and decreasing to nearly zero at the red end of the spectral range (see Figure 1). The LRS slitless wavelength calibration has not changed. For both LRS slit and slitless data, the wavelength calibration is good to +/- 20 nm for sources in the nominal pointing positions.

For LRS slit and slitless, the photometric correction is now based on deeper exposures and thus has improved the signal-to-noise ratio at all wavelengths. Smoothing the photometric correction at the longest wavelengths has further improved the signal-to-noise ratio. The new aperture correction is based on empirical data for standard stars.

Automatic reprocessing of all MIRI LRS data is underway and will take between 3 to 6 weeks. Please use the MAST subscription service to receive notifications of when the data has been reprocessed. Users can also reprocess their own data using jwst_1174.pmap or later.

STScI encourages JWST users with any additional questions to contact the MIRI team via the JWST Help Desk. Not only will this action generate a personal response, but it will help the MIRI team to better understand issues users are running into. To keep up-to-date with new reference file deliveries, please sign up for the reference file mailing lists.