Mid-InfRAred Camera w/o LEns (MIRACLE) is a focal plane instrument for the future JAXA/ESA infrared
astronomical mission, SPICA. MIRACLE is designed for wide field imaging (5' × 5') and low-resolution spectroscopic
observations (R~100) over a wide spectral range in the mid-infrared wavelengths (5-38μm). Thanks
to the SPICA's large aperture (3-m class) and cold (<6K) telescope, MIRACLE has a better sensitivity than
JWST/MIRI at the wavelength over 20μm (3.5 μJy at 20μm, R=5, S/N=5, 3600 seconds) and its wider field
of view (FOV) provides a faster mapping speed in its full spectral range for point sources. Confocal off-axis
reflective imaging system provides a wide FOV with diffraction limited image quality over wide spectral range.
MIRACLE consists of two channels: MIRACLE-S and MIRACLE-L, which are optimized for 5-26μm and 20-
38μm, respectively. Each of them consists of a fore-optics and a rear-optics, each of which has a pupil position
equipped with a filter wheel and a grating wheel, respectively. A field stop wheel, which provides optimal slits in
the spectroscopic mode and a wide FOV in the imaging mode, is installed at the focal plane of the fore-optics.
A large format array detector (Si:As 2K×2K for MIRACLE-S and Si:Sb 1K×1K for MIRACLE-L) is installed at
the focal plane of the rear-optics in order to achieve Nyquist sampling of the point spread function. Contiguous
wavelength coverage is considered in choice of the filter bands from the experiences in the Spitzer and AKARI
observations. We will present the results of conceptual design study including sensitivity analysis.