Recent progress in the development of mid-infrared Medium Resolution Spectrometer (MRS) installed in SPICA/MCS

Mid-infrared Medium Resolution Spectrometer (MRS) is one of the key spectroscopic modules of Mid- Infrared Camera and Spectrometers (MCS) that will be onboard SPICA. MRS is an Echelle Grating spectrometer designed to observe a number of fine structure lines of ions and atoms, molecular lines, and band features stemming from solid particles and dust grains of the interstellar and circumstellar medium in the mid-infrared wavelength range. MRS consists of two channels; the shorter wavelength channel (MRS-S) covers the spectral range from 12.2 to 23.0 micron with a spectral resolution power of R̃1900-3000 and the longer wavelength channel (MRS-L) covers from 23.0 to 37.5 micron with R̃1100-1500 on the basis of the latest results of the optical design. The distinctive functions of the MRS are (1) a dichroic beam splitter equipped in the fore-optics, by which the same field of view is shared between the two channels, and (2) the small format image slicer as the integral field unit installed in each channel. These functions enable us to collect continuous 12-38 micron spectra of both the point-like and diffuse sources reliably with a single exposure pointed observation. In this paper, the specifications and the expected performance of the MRS are summarized on the basis of the latest results of the optical design. The latest progress in the development of the key technological elements, such as the Dichroic Beam Splitter and the Small Format Monolithic Slice Mirrors, are also reported.