Development status of the mid-infrared two-field camera and spectrograph MIMIZUKU for the TAO 6.5-m Telescope

Novel gratings for astronomical observations

“…We are developing a silicon grism with a grating lattice of sawtooth shape for the near to mid-infrared channel of the MIMIZUKU. The MIMIZUKU of the TAO Telescope has near to mid-infrared (2~5.3μm), mid-infrared (6.8~26μm) and mid to far infrared (24~38 μm) channels [16]. After several trial fabrications, we performed trial fabrication of silicon grism (24×24×t2.8, apex angle: 4.2°) by means of fly-cutting with a single-crystal diamond tool (UPC-T tool, A.L.M.T.…”

“…The reflector facet transmission (RFT) grating [12,13] is developed for the WFOS (Wide Field Optical Spectrograph) of the TMT [1,2], hybrid grism (direct vision grating) [12,13] is developed for the MOIRCS (Multi-Object InfraRed Camera and Spectrograph) of the Subaru Telescope [14], and an echelle grism with a volume binary (VB) grating is developed for the nuMOIRCS of the ULTIMATE Subaru [15]. We also introduce a silicon grism developed for the MIMIZUKU (Mid Infrared Multi-field Imager for gaZing at the UnKnown Universe) of the 6.5m TAO (the University of Tokyo, Atacama Observatory) Telescope in Chili [16] and a quasi-Bragg (QB) immersion grating [12,17]. The immersion grating has the big advantage for an astronomical spectrograph especially in the infrared wavelength since the size of a spectrograph can be dramatically reduced by using an immersion grating of silicon (n ~ 3.3) or germanium (n ~ 4.0) or a high index material.…”

The University of Tokyo Atacama Observatory 6.5m telescope: project overview and current status

“…Mid-Infrared Multi-field Imager for gaZing at the UnKnown Universe (MIMIZUKU) is a mid-infrared camera and spectrograph developed as the 1 st -generation mid-infrared instrument for the TAO 6.5-m telescope [14][15][16] [17] . It has capabilities of imaging and low-resolution (R<620) spectroscopy in a wide wavelength range from 2 to 38 microns with three optical channels, called NIR, MIR-S, and MIR-L. Their covering wavelengths are 2-5.3, 6.8-26, and 24-38 microns, respectively.…”

“…Such observation technique is effective for accurate calibration of the atmospheric transmittance because it can accurately compensate the temporal change of atmospheric transmittance, and it is expected that we can improve photometric accuracy to the order of one percent even in the wavelength regions with low atmospheric transmittance. This capability is also useful for spectroscopic observations in such low-transmittance bands like 2.7-and 20-micron bands [17] . These possibilities enable us to perform long-term infrared monitoring and obtain good quality spectroscopic data even from the ground.…”

Development of a flat calibration unit for accurate flat fielding in the mid-infrared region

“…To achieve high-precision long-term monitoring and rapid follow-up observations in the MIR region, we developed an MIR imager and spectrograph MIMIZUKU 5 – 10 for the University of Tokyo Atacama Observatory (TAO) 6.5-m telescope 11 – 15 MIMIZUKU has an optomechanical unit named Field Stacker (FS) 16 with two pick-off mirrors and a combining mirror, which enables simultaneous observations of two different sky regions.…”