In the latest version of APT (2020.4), the MIRI Coronagraphic Observation APT Template now includes the capability to obtain a background observation separate from the primary target. Specifically, users can request a nearby background image for each coronagraphic filter/mask combination. No additional target acquisition is required for the background observations and, once observed, this background image will be associated with the primary observations, enabling it to be used in standard pipeline processing.

Thermal emission from the telescope, zodiacal dust, or other galactic sources may make it advantageous to acquire a background measurement independent from the primary coronagraphic image. Observers should carefully assess their MIRI science programs to determine whether dedicated background observations are needed to successfully accomplish their science objectives. Accurate background subtraction is especially needed to perform reference PSF subtraction and artifacts from background mismatch will be particularly deleterious for science targets with extended structure, such as debris disk and host galaxies associated with active galactic nuclei.

For more information on the MIRI coronagraph and the observation template, see JDox.