MIRI LRS Mosaics

The low-resolution spectroscopy mode for JWST’s Mid-Infrared Instrument (MIRI) offers a mosaicking option for coverage of larger fields of view (FOV) that extend beyond a single pointing.

Mosaics for low-resolution spectroscopy mode

Mosaics for an LRS observation can be implemented in the Astronomer's Proposal Tool (APT) using the JWST APT MIRI Low Resolution Spectroscopy template. These mosaics provide coverage of larger fields of view (FOV) that extend beyond a single pointing. Mosaics are only supported for observations with the LRS slit; the LRS slitless mode is dedicated to single-pointing time-series observations. 

A pointing pattern can be defined in the Mosaic Properties tab in the observations form. Here, the pattern is defined in rows, columns, and percentage overlap between the pointings. Note that a similar strategy can be achieved by selecting the MAPPING option for the Dither strategy, and specifying the pattern steps in spatial and spectral directions, in arcseconds. The two can also be combined to execute a dither pattern at each mosaic pointing location, if specific spatial sampling of the target is required.

Users are encouraged to always check the defined pattern using the APT Aladin visualization functionality, which shows the slit footprints superimposed on the target.

The user should also consider using the MIRI Medium-Resolution Spectrometer (MRS), which provides integral field spectroscopy (IFU) at higher spectral resolution than the LRS (from ~5 to 28.5 µm, albeit without continuous spectral coverage).

1  Bold italics font style is used to indicate parameters, parameter values, and/or special requirements that are set in the APT GUI.


JWST Astronomers Proposal Tool Overview


JWST APT Mosaic Planning



Latest updates