片坐 宏一

MIMIZUKU is the first-generation mid-infrared instrument for the TAO 6.5-m telescope. It has three internal optical channels to cover a wide wavelength range from 2 to 38 mu m. Of the three channels, the NIR channel is responsible for observations in the shortest wavelength range, shorter than 5.3 mu m. The performance of the NIR channel is evaluated in the laboratory. Through the tests, we confirm the followings: 1) the detector (HAWAII-1RG with 5.3-mu m cutoff) likely achieves similar to 80% quantum efficiency; 2) imaging performance is sufficient to achieve seeing-limit spatial resolution; 3) system efficiencies in imaging modes are 2.4-31%; and 4) the system efficiencies in spectroscopic modes is 5-18%. These results suggest that the optical performance of the NIR channel is achieved as expected from characteristics of the optical components. However, calculations of the background levels and on-sky sensitivity based on these results suggest that neutral density (ND) filters are needed to avoid saturation in L'- and M'-band observations and that the ND filters and the entrance window, made of chemical-vapor-deposition (CVD) diamond, significantly degrade the sensitivity in these bands. This means that the use of different window materials and improvements of the detector readout speed are required to achieve both near-infrared and long-wavelength mid-infrared (>30 mu m) observations.

We have developed a prototype half-wave plate (HWP) based polarization modulator (PMU) for Cosmic Microwave Background polarization measurement experiments. We built a 1/10 scaled PMU that consists of a 50 mm diameter five-layer achromatic HWP with a moth-eye broadband anti-reflection sub-wavelength structure mounted on a superconducting magnetic bearing. The entire system has cooled below 20 K in a cryostat chamber that has two millimeter-wave transparent windows. A coherent source and the diode detector are placed outside of the cryostat and the millimeter-wave goes through the PMU in the cryostat. We have measured the modulated signal by the PMU, analyzed the spectral signatures, and extracted the modulation efficiency over the frequency coverage of 34-161 GHz. We identified the peaks in the optical data, which are synchronous to the rotational frequency. We also identified the peaks that are originated from the resonance frequency of the levitating system. We also recovered the modulation efficiency as a function of the incident electromagnetic frequency and the data agrees to the predicted curves within uncertainties of the input parameters, i.e.The indices of refraction, thickness, and angle alignment. Finally, we discuss the implication of the results when this is applied to the LiteBIRD low-frequency telescope.

We report the estimation of the heat dissipation on a levitating rotor over superconducting magnetic bearing operating below 10 K. The continuously rotating mechanism is one of key devices to support the rotation of a sapphire half wave plate (HWP) in a polarization modulator of a LiteBIRD satellite. Due to the system requirement, the HWP must be kept at a cryogenic temperature while it is spinning. In order to minimize the frictional energy loss, we employ a superconducting magnetic bearing (SMB) and AC synchronous motor, which enables a contactless rotational mechanism. While we can minimize the frictional heat loss, there exists an energy loss due to the magnetic friction. As a result, it is essential to build a thermal model an estimation of heat dissipation to this contactless rotor is important to predict how much the HWP temperature rises during its rotation. For an estimation of heat dissipation, we conduct an experiment in order to establish the thermal simulation model equivalent to the flight model in size. Each thermal contact conductance between the rotor and the cryogenic rotor holder is also estimated through the experiment data. From the data, we only can know the difference in the rotor temperature before and after the rotor rotation. We monitor the transient temperature profile of grippers after the rotor is gripped by them. The rotational time is related to the total heat dissipation on the rotor because the heat dissipation is attributed to two kinds of energy losses: a magnetic hysteresis and induced eddy currents on metal parts of the rotor. Finally, we make a comparison between the thermal model and the experimental result and estimate the allowable heat dissipation to keep the HWP temperature lower than 20K.

We present the design and thermal characteristics of a levitating rotor in a superconducting magnetic bearing (SMB) system that is designed for a polarization modulator of a cosmic microwave background (CMB) polarization experiment. Thermal characteristics of the levitating rotor in the SMB are important to reduce the detector noise. We have constructed two types of SMB systems that both employ a NdFeB permanent magnet as a rotor and a YBCO superconductor array as a stator. One is the 1/6 scale prototype model and the other one is the flight representative full-scale prototype. In order to build a thermal model of the SMB system, we estimate thermal properties of a NdFeB magnet based on the measured data using the 1/6 scale prototype model. The thermal model is expanded to the full-scale prototype, and we obtained the requirement of heat loads from the SMB system is to be less than 1 mW. We also measured the thermal conductivity between the levitating rotor and a holder mechanism, which is the thermal path when the rotor is held in place at the time of field cooling. The measured conductivity is 1.34 mW/K, which is almost same as the 1/6 scale prototype model.

The Mid-Infrared Multi-field Imager for gaZing at the UnKnown Universe (MIMIZUKU) is a mid-infrared camera and spectrograph developed as a first-generation instrument on the University of Tokyo Atacama Observatory (TAO) 6.5-m telescope. MIMIZUKU covers a wide wavelength range from 2 to 38 pm and has a unique optical device called Field Stacker which realizes accurate calibration of variable atmospheric transmittance with a few percent accuracy. By utilizing these capabilities, MIMIZUKU realizes mid-infrared long-term monitoring, which has not been challenged well.MIMIZUKU has three optical channels, called NIR, MIR-S, and MIR-L, to realize the wide wavelength coverage. The MIR-S channel, which covers 6.8-26 pm, has been completed by now. We are planning to perform engineering observations with this channel at the Subaru telescope before the completion of the TAO 6.5-m telescope. In this paper, we report the results of the laboratory tests to evaluate the optical and detector performances of the MIR-S channel. As a result, we confirmed a pixel scale of 0.12 arcsec/pix and a vignetting free field of view of 2.10 x1.18. The instrument throughputs for imaging modes are measured to be 20-30%. Those for N- and Q-band spectroscopy modes are 17 and 5%, respectively. As for the detector performance, we derived the quantum efficiency to be 40-50% in the mid-infrared wavelength region and measured the readout noise to be 3000-6000 electrons, which are larger than the spec value. It was found that this large readout noise degrades the sensitivity of MIMIZUKU by a factor of two.

With the imminent launch of the JWST, the field of thermal-infrared (TIR) astronomy will enjoy a revolution. It is easy to imagine that all areas of infrared (IR) astronomy will be greatly advanced, but perhaps impossible to conceive of the new vistas that will be opened. To allow both follow-up JWST observations and a continuance of work started on the ground-based 8m's, we continue to plan the science cases and instrument design for a TIR imager and spectrometer for early operation on the TMT. We present the current status of our science cases and the instrumentation plans, harnessing expertise across the TMT partnership. This instrument will be proposed by the MICHI team as a second-generation instrument in any upcoming calls for proposals.

We present our design and development of a polarization modulator unit (PMU) for LiteBIRD space mission. LiteBIRD is a next generation cosmic microwave background (CMB) polarization satellite to measure the primordial B-mode. The science goal of LiteBIRD is to measure the tensor-to-scalar ratio with the sensitivity of delta r < 10(-3) The baseline design of LiteBIRD is to employ the PMU based on a continuous rotating half-wave plate (HWP) at a telescope aperture with a diameter of 400 mm. It is an essential for LiteBIRD to achieve the science goal because it significantly reduces detector noise and systematic uncertainties. The LiteBIRD PMU consists of a multi-layered sapphire as a broadband achromatic HWP and a mechanism to continuously rotate it at 88 rpm. The whole system is maintained at below 10K to minimize the thermal emission from the HWP. In this paper, we discuss the current development status of the broadband achromatic HWP and the cryogenic rotation mechanism.

The Herbig Ae star HD 169142 is one of the objects that show complex structure, such as multiple (innermost, middle, and outer) disks, gaps, and unresolved sources. We made N-band (8-13 mu m) observations of HD 169142 with the Cooled Mid-Infrared Camera and Spectrometer on the 8.2 m Subaru Telescope. The images are spatially resolved out to an similar to 1 '' radius in all the observed bands. We made a simple disk model composed of an unresolved central source (representing the innermost disk/halo) and the ring at a radius r similar to 25 au (corresponding to the. inner wall or edge of a middle disk at similar to 25-40 au). The radial intensity profile within the central region (less than or similar to 0.'' 3 or less than or similar to 40 au) is well reproduced by the model. Furthermore, we subtracted the model image from the observed one to search for additional structures. In the model-subtracted images, we found an unresolved west. source separated by 17.0 +/- 2.9 au in the direction of position angle. 260 degrees +/- 5 degrees from the original emission peak, which is supposed to correspond to the position of the central star, and a bright east. arc located at r similar to 60 au. The west. source is different from the L'-band unresolved source recently found in coronagraphic observations. It could be a structure related to planet formation in the disk, such as a circumplanetary disk or clumpy disk structure. The east. arc corresponds to the inner wall or edge of the outer disk.

We propose an all-silicon multi-layer interference filter composed solely of silicon with sub-wavelength structure (SWS) in order to realize high performance optical filters operating in the THz frequency region with robustness against cryogenic thermal cycling and mechanical damage. We demonstrate fabrication of a three-layer prototype using well-established common micro-electro-mechanical systems (MEMS) technologies as a first step toward developing practical filters. The measured transmittance of the three-layer filter agrees well with the theoretical transmittances calculated by a simple thin-film calculation with effective refractive indices as well as a rigorous coupled-wave analysis simulation. We experimentally show that SWS layers can work as homogeneous thin-film interference layers with effective refractive indices even if there are multiple SWS layers in a filter.

SPICA (Space Infrared Telescope for Cosmology and Astrophysics) is an astronomical mission optimized for mid- and far-infrared astronomy with a cryogenically cooled 3-m class telescope, envisioned for launch in early 2020s. Mid-infrared Camera and Spectrometer (MCS) is a focal plane instrument for SPICA with imaging and spectroscopic observing capabilities in the mid-infrared wavelength range of 5 - 38µm. MCS consists of two relay optical modules and following four scientific optical modules of WFC (Wide Field Camera 5 × 5 field of view, f/11.7 and f/4.2 cameras), LRS (Low Resolution Spectrometer 2.5 long slits, prism dispersers, f/5.0 and f/1.7 cameras, spectral resolving power R ~ 50 - 100), MRS (Mid Resolution Spectrometer echelles, integral field units by image slicer, f/3.3 and f/1.9 cameras, R ~ 1100-3000) and HRS (High Resolution Spectrometer immersed echelles, f/6.0 and f/3.6 cameras, R ~ 20000-30000). Here, we present optical design and expected optical performance of MCS. Most parts of MCS optics adopt off-axis reflective system for covering the wide wavelength range of 5-38µm without chromatic aberration and minimizing problems due to changes in shapes and refractive indices of materials from room temperature to cryogenic temperature. In order to achieve the high specification requirements of wide field of view, small F-number and large spectral resolving power with compact size, we employed the paraxial and aberration analysis of off-axial optical systems (Araki 2005 [1]) which is a design method using free-form surfaces for compact reflective optics such as head mount displays. As a result, we have successfully designed compact reflective optics for MCS with as-built performance of diffraction-limited image resolution.

We report a thermal analysis of a polarization modulator unit (PMU) for use in a space-borne cosmic microwave background (CMB) project. A measurement of the CMB polarization allows us to probe the physics of early universe, and that is the best method to test the cosmic inflation experimentally. One of the key instruments for this science is to use a half wave plate (HWP) based polarization modulator. The HWP is required to rotate continuously at about 1 Hz below 10 K to minimize its own thermal emission to a detector system. The rotating HWP system at the cryogenic environment can be realized by using a superconducting magnetic bearing (SMB) without significant heat dissipation by mechanical friction. While the SMB achieves the smooth rotation due to the contactless bearing, an estimation of a levitating HWP temperature becomes a challenge. We manufactured a one-eighth scale prototype model of PMU and built a thermal model. We verified our thermal model with the experimental data. We forecasted the projected thermal performance of PMU for a full-scale model based on the thermal model. From this analysis, we discuss the design requirement toward constructing the full-scale model for use in a space environment such as a future CMB satellite mission, LiteBIRD.

We present the vibrational characteristics of a levitating rotor in a superconducting magnetic bearing (SMB) system operating at below 10 K. We develop a polarization modulator that requires a continuously rotating optical element, called half-wave plate (HWP), for a cosmic microwave background polarization experiment. The HWP has to operate at the temperature below 10 K, and thus an SMB provides a smooth rotation of the HWP at the cryogenic temperature of about 10 K with minimal heat dissipation. In order to understand the potential interference to the cosmological observations due to the vibration of the HWP, it is essential to characterize the vibrational properties of the levitating rotor of the SMB. We constructed a prototype model that consists of an SMB with an array of high temperature superconductors, YBCO, and a permanent magnet ring, NdFeB. The rotor position is monitored by a laser displacement gauge, and a cryogenic Hall sensor via the magnetic field. In this presentation, we present the measurement results of the vibration characteristics using our prototype SMB system. We characterize the vibrational properties as the spring constant and the damping, and discuss the projected performance of this technology toward the use in future space missions.

We report measurement of the internal attenuation coefficient, alpha(att), of a bulk high-resistivity cadmium zinc telluride (CdZnTe) single crystal at wavelength, lambda = 0.84-26 mu m, to the unprecedentedly low level of alpha(att) similar to 0.001 cm(-1). This measurement reveals the spectral behavior for small attenuation in the infrared transparent region between the electronic and lattice absorptions. This result is essential for application of CdZnTe as an infrared transmitting material. Comparing the attenuation spectrum with model spectra obtained on the basis of Mie theory, we find that sub-micrometer-sized Te particles (inclusions) with a number density of approximately 10(7.5-9) cm(-3) are the principal source of the small attenuation observed at lambda = 0.9-13 mu m. In addition, we determine alpha(att) = (7.7 +/- 1.9) x 10(-4) cm(-1) at lambda = 10.6 mu m, which is valuable for CO2 laser applications. Higher transparency can be achieved by reducing the number of inclusions rather than the number of precipitates. This study also demonstrates that high-accuracy measurement of CdZnTe infrared transmittance is a useful approach to investigating the number density of sub-micrometer-sized Te particles that cannot be identified via infrared microscopy.

This paper demonstrates a cryogenic deformable mirror (DM) with 1020 actuators based on micro-electrical mechanical systems (MEMS) technology. Cryogenic space-borne infrared telescopes can experience a wavefront error due to a figure error of their mirror surface, which makes the imaging performance worse. For on-orbit wavefront correction as one solution, we developed aMEMS-processed electro-static DM with a special surrounding structure for use under the cryogenic temperature. We conducted a laboratory demonstration of its operation in three cooling cycles between 5 K and 295 K. Using a laser interferometer, we detected the deformation corresponding to the applied voltages under the cryogenic temperature for the first time. The relationship between voltages and displacements was qualitatively expressed by the quadratic function, which is assumed based on the principle of electro-static DMs. We also found that it had a high operating repeatability of a few nm root-meansquare and no significant hysteresis. Using the measured values of repeatability, we simulated the improvement of the point spread function (PSF) by wavefront correction with our DM. These results show that our developed DM is effective in improving imaging performance and PSF contrast of space-borne infrared telescopes. (C) 2017 Optical Society of America

We have carried out numerical analysis of mechanical properties of a superconducting magnetic bearing (SMB). A contactless bearing operating at below 10 K with low rotational energy loss is an attractive feature to be used as a rotational mechanism of a polarization modulator for a cosmic microwave background experiment. In such application, a rotor diameter of about 400 mm forces us to employ a segmented magnet. As a result, there is inevitable spatial gap between the segments. In order to understand the path towards the design optimizations, 2D and 3D FEM analyses were carried out to examine fundamental characteristics of the SMBs for a polarization modulator. Two axial flux type SMBs were dealt with in the analysis: (a) the SMB with axially magnetized permanent magnets (PMs), and (b) the SMB with radially magnetized PMs and steel components for magnetic flux paths. Magnetic flux lines and density distributions, electromagnetic force characteristics, spring constants, etc. were compared among some variations of the SMBs. From the numerical analysis results, it is discussed what type, configuration and design of SMBs are more suitable for a polarization modulator.

We present the design and mechanical performances of a magnetically coupled gear mechanism to drive a levitating rotor magnet of a superconducting magnetic bearing (SMB). The SMB consists of a ring-shaped high-temperature superconducting array (YBCO) and a ring-shaped permanent magnet. This rotational system is designed to operate below 10 K, and thus the design philosophy is to minimize any potential source of heat dissipation. While an SMB provides only a functionality of namely a bearing, it requires a mechanism to drive a rotational motion. We introduce a simple implementation of a magnetically coupled gears between a stator and a rotor. This enables to achieve enough torque to drive a levitating rotor without slip at the rotation frequency of about 1 Hz below 10 K. The rotational variation between the rotor and the drive gear is synchronised within sigma = 0. 019 Hz. The development of this mechanism is a part of the program to develop a testbed in order to evaluate a prototype half-wave plate based polarization modulator for future space missions. The successful development allows this modulator to be a candidate for an instrument to probe the cosmic inflation by measuring the cosmic microwave background polarization. (C) 2016 Elsevier B.V. All rights reserved.

We present the design and the mechanical and thermal performances of a prototype rotational mechanism using a superconducting magnetic bearing (SMB) for a space compatible polarization modulator. The rotational mechanism consists of an SMB with an optical encoder and a three-grip mechanism that holds a levitating rotor until a high-temperature superconducting array (YBCO) cools down below its critical temperature. After the successful operation of a grip mechanism, the rotor magnet levitates at 10-16 K, and we conduct spin-down measurements. We estimate the heat dissipation from the rotor rotation and an optical encoder. From the mechanical and thermal performances of the prototype rotation mechanism, we did not find the potential no-go results from this SMB technology for use in a future space mission. The development of this rotational mechanism is targeting for use of a polarization modulator for a space mission to probe the comic inflation by measuring the cosmic microwave background polarization.

Using all-sky maps obtained from the Cosmic Background Explorer/Diffuse Infrared Background Experiment (DIRBE) at 3.5 and 4.9 mu m, we present a reanalysis of diffuse sky emissions such as zodiacal light (ZL), diffuse Galactic light (DGL), integrated starlight (ISL), and isotropic residual emission including the extragalactic background light (EBL). Our new analysis, which includes an improved estimate of ISL using the Wide-field Infrared Survey Explorer data, enabled us to find the DGL signal in a direct linear correlation between diffuse near-infrared and 100 mu m emission at high Galactic latitudes (vertical bar b vertical bar > 35 degrees). At 3.5 mu m, the high-latitude DGL result is comparable to the low-latitude value derived from the previous DIRBE analysis. In comparison with models of the DGL spectrum assuming a size distribution of dust grains composed of amorphous silicate, graphite, and polycyclic aromatic hydrocarbon (PAH), the measured DGL values at 3.5 and 4.9 mu m constrain the mass fraction of PAH particles in the total dust species to be more than similar to 2%. This was consistent with the results of Spitzer/IRAC toward the lower Galactic latitude regions. The derived residual emission of 8.9 +/- 3.4 nWm(-2) sr(-1) at 3.5 mu m is marginally consistent with the level of integrated galaxy light and the EBL constraints from the gamma-ray observations. The residual emission at 4.9 mu m is not significantly detected due to the large uncertainty in the ZL subtraction, the same as in previous studies. Combined with our reanalysis of the DIRBE data at 1.25 and 2.2 mu m, the residual emission in the near-infrared exhibits the Rayleigh-Jeans spectrum.

MIMIZUKU is the first-generation mid-infrared instrument for the university of Tokyo Atacama Observatory (TAO) 6.5-m telescope. MIMIZUKU provides imaging and spectroscopic monitoring capabilities in a wide wavelength range from 2 to 38 mu m, including unique bands like 2.7-m and 30-m band. Recently, we decided to add spectroscopic functions, KL-band mode (lambda= 2.1-4.0 tm; R = lambda/Delta lambda similar to 210) and 2.7-m band mode (lambda= 2.4-2.95 mu m; R similar to 620), and continuous spectroscopic coverage from 2.1 to 26 m is realized by this update. Their optical designing is completed, and fabrications of optical elements are ongoing. As recent progress, we also report the completion of the cryogenic system and optics. The cryogenic system has been updated by changing materials and structures of thermal links, and the temperatures of the optical bench and detector mounting stages finally achieved required temperatures. Their stability against instrument attitude is also confirmed through an inclination test. As for the optics, its gold-plated mirrors have been recovered from galvanic corrosion by refabrication and reconstruction. Enough image quality and stability are confirmed by room-temperature tests. MIMIZUKU is intended to be completed in this autumn, and commissioning at the Subaru telescope and scientific operations on the TAO telescope are planned in 2017 and around 2019, respectively. In this paper, these development activities and future prospects of MIMIZUKU are reported.

A cold chopper is a key device for next generation mid-infrared instruments such as TMT/MICHI. It should achieve fast and accurate position switching with a large chopping throw at cryogenic temperature. To satisfy the requirements, voice coil motors using superconducting MgB2 wire have been developed. We have made a first prototype of the VCM and carried out its performance measurements such as a transition temperature, transfer functions, and power dissipation in the laboratory. The results are almost consistent with the expectations and the calculations, but some show significant inconsistency. We have also made a next prototype which is small to fit the size of the MICHI chopper. This will be installed to a developing mid-infrared instrument MIMIZUKU and used for actual observations.

We have carried out a trial production of the large-format (n=11) image slicer unit for a possible future mid-infrared instrument on the TMT aiming to verify its technical feasibility. The key elements in our trial production are the monolithic large-format slice mirrors and the monolithic large-format pupil mirrors. The results of our trial production of those key elements based on the ultra high-precision cutting techniques and the assembly of the large-format image slicer unit are presented in this paper.

Using all-sky maps obtained with COBE/DIRBE, we reanalyzed the diffuse sky brightness at 1.25 and 2.2 mu m, which consists of zodiacal light, diffuse Galactic light (DGL), integrated starlight (ISL), and isotropic emission including the extragalactic background light. Our new analysis including an improved estimate of the DGL and the ISL with the 2MASS data showed that deviations of the isotropic emission from isotropy were less than 10% in the entire sky at high Galactic latitude (vertical bar b vertical bar > 35 degrees). We derived the DGL to 100 mu m brightness ratios of similar to 4.79 and similar to 1.49 n W m(-2) MJy(-1) at 1.25 and 2.2 mu m, respectively. The result of our analysis revealed a significantly large isotropic component at 1.25 and 2.2 mu m with intensities of 60.15 +/- 16.14 and 27.68 +/- 6.21 n W m(-2) sr(-1), respectively. This intensity is larger than the integrated galaxy light, upper limits from gamma-ray observation, and potential contribution from exotic sources (i.e., Population III stars, intrahalo light, direct collapse black holes, and dark stars). We therefore conclude that the excess light may originate from the local universe: the Milky Way and/or the solar system.

An immersion grating composed of a transmissive material with a high refractive index (n > 2) is a powerful device for high-resolution spectroscopy in the infrared region. Although the original idea is attributed to Fraunhofer about 200 years ago, an immersion grating with high diffraction efficiency has never been realized due to the difficulty in processing infrared crystals that are mostly brittle. While anisotropic etching is one successful method for fabricating a fine groove pattern on Si crystal, machining is necessary for realizing the ideal groove shape on any kind of infrared crystal. In this paper, we report the realization of the first, to the best of our knowledge, machined immersion grating made of single-crystal CdZnTe with a high diffraction efficiency that is almost identical to that theoretically predicted by rigorous coupled-wave analysis. (C) 2015 Optical Society of America

The Space Infrared Telescope for Cosmology and Astrophysics (SPICA) is an astronomical mission optimized for mid-and far-infrared astronomy, envisioned for launch in the 2020s. The Mid-infrared Camera and Spectrometer (MCS) is a model instrument that covers the 5-38 mu m wavelength range and enables imaging and spectroscopic observations via four modules named WFC-S, WFC-L, HRS, and MRS. Both of the wide field camera (WFC) modules have a 5-arcmin square field of view (FOV) but cover di r erent wavelength ranges; WFC for the short wavelength region (WFC-S) covers 5 to 24 mu m, whereas WFC for the long wavelength region (WFC-L) covers 18 to 38 mu m. The High Resolution Spectrometer (HRS) covers the 12-18 mu m range with a resolving power of 22,000-30,000, and the Mid Resolution Spectrometer (MRS) performs integral filed units spectroscopy with a 12'' by 8'' FOV. MRS simultaneously covers the 12-38 mu m range with a moderate resolving power of 720-2000. Here, we report sensitivity estimates from a detailed modeling process involving the instrument itself, the telescope, environmental conditions, and the system error budgets. We show that the WFC-S and HRS modules require an adaptive system to correct for telescope pointing error. In particular, band pass fi lters (BPFs) longer than 26 mu m should be developed.

We imaged circumstellar disks around 22 Herbig Ae/Be stars at 25 mu m using Subaru/COMICS and Gemini/T-ReCS. Our sample consists of an equal number of objects from each of the two categories defined by Meeus et al.; 11 group I (flaring disk) and II (flat disk) sources. We find that group I sources tend to show more extended emission than group II sources. Previous studies have shown that the continuous disk is difficult to resolve with 8 m class telescopes in the Q band due to the strong emission from the unresolved innermost region of the disk. This indicates that the resolved Q-band sources require a hole or gap in the disk material distribution to suppress the contribution from the innermost region of the disk. As many group I sources are resolved at 25 mu m, we suggest that many, but not all, group I Herbig Ae/Be disks have a hole or gap and are (pre-) transitional disks. On the other hand, the unresolved nature of many group II sources at 25 mu m supports the idea that group II disks have a continuous flat disk geometry. It has been inferred that group I disks may evolve into group II through the settling of dust grains into the mid-plane of the protoplanetary disk. However, considering the growing evidence for the presence of a hole or gap in the disk of group I sources, such an evolutionary scenario is unlikely. The difference between groups I and II may reflect different evolutionary pathways of protoplanetary disks.

Investigations of the point spread functions (PSFs) and flux calibrations for stacking analysis have been performed with the far-infrared (wavelength range of 60 to 140 mu m) all-sky maps taken by the Far-Infrared Surveyor (FIS) on board the AKARI satellite. The PSFs are investigated by stacking the maps at the positions of standard stars with their fluxes of 0.02-10 Jy. The derived full widths at the half maximum (FWHMs) of the PSFs are similar to 60 '' at 65 and 90 mu m and similar to 90 '' at 140 mu m, which are much smaller than those of the previous all-sky maps obtained with the Infrared Astronomical Satellite IRAS (similar to 6'). Any flux dependence in the PSFs is not seen on the investigated flux range. By performing the flux calibrations, we found that absolute photometry for faint sources can be carried out with constant calibration factors, which range from 0.6 to 0.8. After applying the calibration factors, the photometric accuracies for the stacked sources in the 65, 90, and 140 mu m bands are 9%, 3%, and 21%, respectively, even below the detection limits of the survey. No systematic dependence between the observed flux and model flux is found. These results indicate that the FIS map is a useful dataset for the stacking analyses of faint sources at far-infrared wavelengths.

We present the concept, design, fabrication, and evaluation of a new deformable mirror (DM), which is latchable, compact, and designed to be applicable for cryogenic environments. The main body of a prototype DM was fabricated from a monolithic cuboid of aluminum using wire electrical discharge machining (EDM). A flexible structure was constructed inside the block by 3-dimensionally crossed hollowing using the EDM. The prototype has 6 x 6 channels, and its volume is 27 mm x 27 mm x 30 mm. The mirror was formed on the surface of the aluminum block using a high-precision NC lathe. The surface figure of the mirror was evaluated and 34 nm rms was obtained. The evaluated surface roughness for the center and off-center areas of the mirror was 9.2 nm rms and 7.6 nm rms, respectively Screws set at the back of the block deform the mirror via springs and the internal flexible structure. We present our first demonstration of deformation of the mirror carried out at ambient temperature. The relationship between the displacement of the screws and the deformation of the mirror was evaluated. Consequently, a linear relationship was confirmed, and no significant hysteresis was found. The application of such mirrors to telescopes used for various different objectives is discussed. We conclude that a DM based on our concept can be used for wavefront correction of space-borne telescopes, especially in the infrared wavelength region.

The MIMIZUKU is the first-generation mid-infrared instrument for the TAO 6.5-m telescope. It challenges to prove the origin of dust and the formation of planets with its unique capabilities, wide wavelength coverage and precise calibration capability. The wide wavelength coverage (2-38 mu m) is achieved by three switchable cameras, NIR, MIR-S, and MIR-L. The specifications of the cameras are revised. A 5 mu m-cutoff HAWAII-1RG is decided to be installed in the NIR camera. The optical design of the MIR-L camera is modified to avoid detector saturation. Its final F-number is extended from 5.2 to 10.5. With these modifications, the field of view of the NIR and MIR-L camera becomes 1.2' x 1.2' and 31 '' x 31 '', respectively. The sensitivity of each camera is estimated based on the revised specifications. The precise calibration is achieved by the "Field Stacker" mechanism, which enables the simultaneous observation of the target and the calibration object in different fields. The up-and-down motion of the cryostat (similar to 1 t), critical for the Field Stacker, is confirmed to have enough speed (4 mm/s) and position accuracy (similar to 50 mu m). A control panel for the Field Stacker is completed, and its controllers are successfully installed. The current specifications and the development status are reported.

SPICA (Space Infrared Telescope for Cosmology and Astrophysics) is an astronomical mission optimized for mid-and far-infrared astronomy with a 3-m class telescope which is cryogenically cooled to be less than 6 K. The SPICA mechanical cooling system is indispensable for the mission but, generates micro-vibrations which could affect to the pointing stability performances. Activities to be undertaken during a risk mitigation phase (RMP) include consolidation of micro-vibration control design for the satellite, as well as a number of breadboarding activities centered on technologies that are critical to the success of the mission. This paper presents the RMP activity results on the micro-vibration control design.

We have carried out the trial production of small format (n=5) image slicer aiming to obtain the technical verification of the Integral Field Unit (IFU) that can be equipped to the next generation infrared instruments such as TMT/MICHI and SPICA/SMI. Our goal is to achieve stable pseudo slit image with high efficiency. Here we report the results of the assembly of the image slicer unit and the non-cryogenic evaluation system of the pseudo slit image quality in the infrared.

We report the restraint deformation and the corrosion protection of gold deposited aluminum mirrors for mid-infrared instruments. To evaluate the deformation of the aluminum mirrors by thermal shrinkage, monitoring measurement of the surface of a mirror has been carried out in the cooling cycles from the room temperature to 100 K. The result showed that the effect of the deformation was reduced to one fourth if the mirror was screwed with spring washers.We have explored an effective way to prevent the mirror from being galvanically corroded. A number of samples have been prepared by changing the coating conditions, such as inserting an insulation layer, making a multi-layer and over-coating water blocking layer, or carrying out precision cleaning before coating. Precision cleaning before the deposition and protecting coat with SiO over the gold layer seemed to be effective in blocking corrosion of the aluminum. The SiO over-coated mirror has survived the cooling test for the mid-infrared use and approximately 1 percent decrease in the reflectance has been detected at 6-25 microns compared to gold deposited mirror without coating.

Context. Little is known about the properties of the warm (T-dust greater than or similar to 150 K) debris disk material located close to the central star, which has a more direct link to the formation of terrestrial planets than does the low-temperature debris dust that has been detected to date.Aims. To discover new warm debris disk candidates that show large 18 mu m excess and estimate the fraction of stars with excess based on the AKARI/IRC Mid-Infrared All-Sky Survey data.Methods. We searched for point sources detected in the AKARI/IRC All-Sky Survey, which show a positional match with A-M dwarf stars in the Tycho-2 Spectral Type Catalogue and exhibit excess emission at 18 mu m compared to what is expected from the K-S magnitude in the 2MASS catalogue.Results. We find 24 warm debris candidates including 8 new candidates among A-K stars. The apparent debris disk frequency is estimated to be 2.8 +/- 0.6%. We also find that A stars and solar-type FGK stars have different characteristics of the inner component of the identified debris disk candidates. While debris disks around A stars are cooler and consistent with steady-state evolutionary model of debris disks, those around FGK stars tend to be warmer and cannot be explained by the steady-state model.

Mid-Infrared Camera and Spectrometers (MCS) is one of the Focal-Plane Instruments proposed for the SPICA mission in the pre-project phase. SPICA MCS is equipped with two spectrometers with different spectral resolution powers (R=Λ/δΛ); medium-resolution spectrometer (MRS) which covers 12-38μm with R≈1100-3000, and high-resolution spectrometer (HRS) which covers either 12-18μm with R≈30000. MCS is also equipped with Wide Field Camera (WFC), which is capable of performing multi-objects grism spectroscopy in addition to the imaging observation. A small slit aperture for low-resolution slit spectroscopy is planned to be placed just next to the field of view (FOV) aperture for imaging and slit-less spectroscopic observation. MCS covers an important part of the core spectral range of SPICA and, complementary with SAFARI (SpicA FAR-infrared Instrument), can do crucial observations for a number of key science cases to revolutionize our understanding of the lifecycle of dust in the universe. In this article, the latest design specification and the expected performance of the SPICA/MCS are introduced. Key science cases that should be targetted by SPICA/MCS have been discussed by the MCS science working group. Among such science cases, some of those related to dust science are briefly intriduced.

An image slicer is highly in demand for an integral field unit (IFU) spectrograph of the next generation infrared telescopes. This paper reports the results of the trial production of three key optical elements for a small format (number of slice; n=5) image slicer, i.e. monolithic slice mirrors, monolithic pupil mirrors and monolithic pseudo slit mirrors. We have demonstrated that sufficiently high processing accuracy and mirror surface accuracy for infrared observations are achieved for each optical element based on our super precision cutting techniques.

We present the characterization and calibration of the slow-scan observation mode of the Infrared Camera (IRC) aboard AKARI. The IRC Slow-scan observations were operated at the S9W (9 mu m) and Ll8W (18 mu m) bands. We developed a toolkit for data reduction of the IRC Slow-scan observations. We introduced a "self-pointing reconstruction" method to improve the positional accuracy to as good as 1 ''. The sizes of the point spread functions were derived to be similar to 6 '' at the S9W band and similar to 7 '' at the Ll8W bands in full width at half maximum. Flux calibrations were achieved with observations of 3 and 4 infrared standard stars at the S9W and Ll8W bands, respectively. The flux uncertainties are estimated to be better than 20% from comparisons with the AKARI IRC PSC and the WISE preliminary catalog.

We report Herschel and AKARI photometric observations at far-infrared (FIR) wavelengths of the debris disk around the F3V star HD 15407A, in which the presence of an extremely large amount of warm dust (similar to 500-600 K) has been suggested by mid-infrared (MIR) photometry and spectroscopy. The observed flux densities of the debris disk at 60-160 mu m are clearly above the photospheric level of the star, suggesting excess emission at FIR as well as at MIR wavelengths previously reported. The observed FIR excess emission is consistent with the continuum level extrapolated from the MIR excess, suggesting that it originates in the inner warm debris dust and cold dust (similar to 50-130 K) is absent in the outer region of the disk. The absence of cold dust does not support a late-heavy-bombardment-like event as the origin of the large amount of warm debris dust around HD 15047A.

The disk around the Herbig Ae star HD 169142 was imaged and resolved at 18.8 and 24.5 mu m using Subaru/COMICS. We interpret the observations using a two-dimensional radiative transfermodel and find evidence for the presence of a large gap. The mid-infrared images trace dust that is emitted at the onset of a strong rise in the spectral energy distribution (SED) at 20 mu m, and are therefore very sensitive to the location and characteristics of the inner wall of the outer disk and its dust. We determine the location of the wall to be 23(-5)(+3) AU from the star. An extra component of hot dust must exist close to the star. We find that a hydrostatic optically thick inner disk does not produce enough flux in the near-infrared, and an optically thin, geometrically thick component is our solution to fit the SED. Considering the recent findings of gaps and holes in a number of Herbig Ae/Be group I disks, we suggest that such disk structures may be common in group I sources. Classification as group I should be considered a strong case for classification as a transitional disk, though improved imaging surveys are needed to support this speculation.

We report an intriguing debris disk toward the F3V star HD 15407A in which an extremely large amount of warm fine dust (similar to 10(-7)M(circle dot)) is detected. The dust temperature is derived as similar to 500-600 K and the location of the debris dust is estimated as 0.6-1.0 AU from the central star, a terrestrial planet region. The fractional luminosity of the debris disk is similar to 0.005, which is much larger than those predicted by steady-state models of the debris disk produced by planetesimal collisions. The mid-infrared spectrum obtained by Spitzer indicates the presence of abundant mu m-sized silica dust, suggesting that the dust comes from the surface layer of differentiated large rocky bodies and might be trapped around the star.

We have evaluated on-sky performances of a mid-infrared camera MAX38 (Mid-infrared Astronomical eXploerer) on the miniTAO 1-meter telescope. A Strehl ratio at the N-band is estimated to be 0.7-0.8, and it reaches to 0.9 at the 37.7 micron, indicating that diffraction limited angular resolution is almost achieved at the wavelength range from 8 to 38 micron. System efficiencies at the N and the Q-band are estimated with photometry of standard stars. The sensitivity at the 30 micron cannot be exactly estimated because there are no standard stars bright enough. We use the sky brightness instead. The estimated efficiencies at the 8.9, 18.7, and 31.7 micron are 4%, 3%, 15%, respectively. One-sigma sensitivity in 1 sec integration of each filter is also evaluated. These give good agreements with the designed values. Preliminary scientific results are briefly reported.

We present the Prototype-testbed for Infrared Optics and Coronagraphs (PINOCO) which is a large, multi-purpose cryogenic chamber. At present, the priority for PINOCO is to evaluate binary pupil mask coronagraphs in the mid-infrared wavelength region, which are planned to be adopted for the SPICA coronagraph instrument. In addition, various other experiments are possible using PINOCO: testing diverse high dynamic-range techniques, mirrors, active optics, infrared detectors, filters and spectral dispersion devices, the mechanics of the instruments, measurement of material properties, and so on. PINOCO provides a work space of 1m x 1m x 0.3m, of which inside is cooled to <5K. Flexible access to the work surface is possible by removing detachable plates at the four sides and on the top of the chamber. At the interface to the exterior, PINOCO is currently equipped with an optical window, electric connectors, and an interferometer stage. PINOCO is cooled by two GM-cycle cryo-coolers, so no cryogen is needed. A cooling test of PINOCO was successfully completed.

TAO (The University of Tokyo Atacama Observatory) is planned to be constructed at the summit of Co. Chajnantor (5640 m altitude) in Chile. MIMIZUKU (Mid-Infrared Multi-field Imager for gaZing at the UnKnown Universe) is a mid-infrared imager (Field of View: 1'x1'-2'x2') and spectrometer (Delta lambda/lambda: 60-230) for the 6.5-m TAO telescope, covering the wavelength range of 2-38 mu m. The MIMIZUKU has a unique equipment called Field Stacker (FS) which enables the simultaneous observation of target and reference object. The simultaneity is expected to improve photometric accuracy and to realize long-term monitoring observations. The development status of the MIMIZUKU is reported in this paper. The FS and the cryostat of the MIMIZUKU have been fabricated and under testing. The cold optics (550 mmx750 mmx2 floors) with 28 mirrors has been constructed. The mirrors were aligned with the positional precision of 0.1 mm and the angular precision of 0.1 deg. The evaluated optical performance is that the diffraction-limited image at lambda > 8 mu m and the enough compact image (r <2 pix=0.22 '') at lambda similar to 2 mu m can be obtained. In the cold optics, the drive systems with backlash-less gears are employed and work well even in cryogenic environment. The grisms made with silicon and germanium have been fabricated by ultraprecision cutting. It was found that their surface roughness, grating constant, and blaze angle almost measure upto the designed values.

SPICA (Space Infrared Telescope for Cosmology and Astrophysics) is an astronomical mission optimized for mid-and far-infrared astronomy, envisioned for launch in early 2020s. The core wavelength coverage of this mission is 5 to 200 micron. Mid-infrared Camera and Spectrometer (MCS) will provide imaging and spectroscopic observing capabilities in the mid-infrared region with 4 modules. WFC (Wide Field Camera) has two 5 arcminutes square field of view and covers the wavelength range from 5 to 38 micron. MRS (Mid Resolution Spectrometer) has integral field units by image slicer and covers the wavelength range from 12.2 to 37.5 micron simultaneously using dichroic filter and two sets of spectrometers. HRS (High Resolution Spectrometer) covers the wavelength range from 12 to 18 micron with resolving power 20000 to 30000, and it has optional short wavelength channel which covers from 4 to 8 micron with resolving power 30000. LRS (Low Resolution Spectrometer) adopts prism disperser and covers the wavelength range from 5 to 38 micron with resolving power 50 to 100. Here, we present detailed specifications of MCS, optical design, and estimated performance on orbit.

We present the current status of the development of the SPICA Coronagraph Instrument (SCI). SPICA is a next-generation 3-meter class infrared telescope, which will be launched in 2022. SCI is high-contrast imaging, spectroscopic instrument mainly for direct detection and spectroscopy of extra-solar planets in the near-to-mid infrared wavelengths to characterize their atmospheres, physical parameters and evolutionary scenarios. SCI is now under the international review process. In this paper, we present a science case of SCI. The main targets of SCI, not only for direct imaging but also for spectroscopy, are young to matured giant planets. We will also show that some of known exoplanets by ground-based direct detection are good targets for SCI, and a number of direct detection planets that are suitable for SCI will be significantly increased in the next decade. Second, a general design of SCI and a key technology including a new high-throughput binary mask coronagraph, will be presented. Furthermore, we will show that SCI is potentially capable of achieving 10(-6) contrast by a PSF subtraction method, even with a telescope pointing error. This contrast enhancement will be important to characterize low-mass and cool planets.

A mid-infrared (MIR) imager and spectrometer is being investigated for possible construction in the early operation of the Thirty Meter Telescope (TMT). Combined with the MIR adaptive optics (AO) system (MIRAO), the instrument will afford similar to 15 times higher sensitivity and similar to 4 times better spatial resolution (0.07") at 10 mu m compared to 8m-class telescopes. Additionally, through exploiting the large collection area of the TMT, the high-dispersion spectroscopy mode will be unrivaled by other ground-and space-based facilities. These combined capabilities offer the possibility for breakthrough science, as well as 'workhorse' observing modes of imaging and low/moderate spectral resolution. In this paper we summarize the primary science drivers that are guiding the instrument design.

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 R similar to 1900-3000 and the longer wavelength channel (MRS-L) covers from 23.0 to 37.5 micron with R similar to 1100-1500 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.