Geometric distortion and astrometric calibration of the JWST MIRI Medium Resolution Spectrometer

Understand

The Medium-Resolution integral field Spectrometer (MRS) of MIRI on board JWST performs spectroscopy between 5 and 28~$\mu$m.

• The optics of the MRS introduce substantial distortion, and this needs to be rectified in order to reconstruct the observed astrophysical scene.
• We use data from the JWST/MIRI commissioning and cycle 1 calibration phase, to derive the MRS geometric distortion and astrometric solution, a critical step in the calibration of MRS data.
• These solutions come in the form of transform matrices that map the detector pixels to spatial coordinates of a local MRS coordinate system called $\alpha$/$\beta$, to the global JWST observatory coordinates V2/V3.