Tomoyasu Yamamuro

The Infrared Camera (IRC) for AKARI–Design and Imaging Performance

The Infrared Camera (IRC) is one of two focal-plane instruments on the AKARI satellite. It is designed for wide-field deep imaging and low-resolution spectroscopy in the nearto mid-infrared (1.8–26.5 m) in the pointed observation mode of AKARI. The IRC is also operated in the survey mode to make an All-Sky Survey at 9 and 18 m. It comprises three channels. The NIR channel (1.8–5.5 m) employs a 512 412 InSb array, whereas both the MIR-S (4.6–13.4 m) and MIR-L (12.6–26.5 m) channels use 256 256 Si:As impurity band conduction arrays. Each of the three channels has a field-of-view of about 100 100, and they are operated simultaneously. The NIR and MIR-S share the same field-of-view by virtue of a beam splitter. The MIR-L observes the sky about 250 away from the NIR/MIR-S field-of-view. The IRC gives us deep insights into the formation and evolution of galaxies, the evolution of planetary disks, the process of star-formation, the properties of interstellar matter under various physical conditions, and the nature and evolution of solar system objects. The in-flight performance of the IRC has been confirmed to be in agreement with the pre-flight expectation. This paper summarizes the design and the in-flight operation and imaging performance of the IRC.

TRISPEC: A Simultaneous Optical and Near-Infrared Imager, Spectrograph, and Polarimeter

We present the design, construction, and performance of TRISPEC (Triple Range Imager and Spectrograph), a simultaneous optical and near-infrared imager, spectrograph, and polarimeter. This instrument splits the incoming light from a telescope into the three beams—one optical channel (0.45-0.90 μm) and two infrared channels (0.90-1.85 and 1.85-2.5 μm)—by means of two dichroic mirrors. It is capable of simultaneous three-band imaging or spectroscopy, with or without polarimetry. Low-resolution grisms (R ~ 70-360) cover a wide wavelength range of 0.46-2.5 μm, simultaneously. The instrument employs three arrays—one 512 × 512 SITe CCD and two 256 × 256 SBRC InSb arrays—to cover the three channels. It has been commissioned in the imaging, spectroscopic, and polarimetric modes on the United Kingdom Infrared Telescope, the University of Hawaii 2.2 m telescope, and the Okayama Astrophysical Observatory 1.88 m telescope since 1999 June.

Measurement of refractive indices of 20 optical materials at low temperatures

We build a refractometer capable of measuring refractive indices at low temperatures from visible to near-infrared wavelength. Refractive indices of 20 optical materials (three fluorides, 15 glasses, fused silica, and KRS-5) are measured at wavelengths of 365.0, 435.8, 546.1, 1014.0, 1529.6, 2122, and 3298 nm at temperatures of ~80, 120, 180, 240, and 293 K. The temperature dependences of the refractive indices are shown in a table and figures.

Multicolor imaging photometer for the MAGNUM project

We present the optical, mechanical and electronic design of MAGNUM-MIP. The MAGNUM project plans to carry out multi color monitoring observations for hundreds of AGNs over several years under remote and automated operation. MAGNUM- MIP has two channels that offer optical and IR broad-band imaging observations at the same time. The IR channel has a SBRC InSb 256 by 256 array which covers a wavelength range from 1 to 4 microns, and the optical channel uses a 1024 by 1024 SITE CCD which covers 0.35 micron to 1 micron. The two channels use the same optics and a beam splitter. We adopted a reflecting optical system in order to get good imaging quality over the wide wavelength range. Because the monitoring is expected to be carried out remotely for several years with minimum manual support and maintenance, the camera is designed to work with only semi-annual maintenance. It has a mechanical cooler, a low outgas design, and an automated vacuum system.

Image Slicer for the Subaru Telescope High Dispersion Spectrograph

We report on the design, manufacturing, and performance of the image slicer for the High Dispersion Spectrograph (HDS) on the Subaru Telescope. This instrument is a Bowen-Walraven type image slicer providing five 0.3 arcsec x 1.5 arcsec images with a resolving power of R= 110,000. The resulting resolving power and line profiles are investigated in detail, including estimates of the defocusing effect on the resolving power. The throughput in the wavelength range from 400 to 700 nm is higher than 80%, thereby improving the efficiency of the spectrograph by a factor of 1.8 for 0.7 arcsec seeing.

Infrared Doppler instrument (IRD) for the Subaru telescope to search for Earth-like planets around nearby M-dwarfs

We report the current status of the Infrared Doppler (IRD) instrument for the Subaru telescope, which aims at detecting Earth-like planets around nearby M darwfs via the radial velocity (RV) measurements. IRD is a fiber-fed, near infrared spectrometer which enables us to obtain high-resolution spectrum (R~70000) from 0.97 to 1.75 μm. We have been developing new technologies to achieve 1m/s RV measurement precision, including an original laser frequency comb as an extremely stable wavelength standard in the near infrared. To achieve ultimate thermal stability, very low thermal expansion ceramic is used for most of the optical components including the optical bench.

ISLE: a general purpose near-infrared imager and medium-resolution spectrograph for the 1.88-m telescope at Okayama Astrophysical Observatory

ISLE is a near-infrared (1.0-2.5μm) imager and spectrograph for the Cassegrain focus (f/18) of the 1.88 m telescope at Okayama Astrophysical Observatory. The detector is a HAWAII 1024 × 1024 HgCdTe Array, which covers 4.2 × 4.2 arcmin2 field of view with a pixel scale of 0.25 arcsec/pixel. ISLE also provides medium (R=300 - 4800) resolution long-slit (4 arcmin long spectroscopic capabilities using reflection gratings. A dedicated front-end electronics for the detector achieved a readout noise of 8 electrons by the conventional Fowler sampling, and a operation scheme that combined with a number of discarded readout greatly suppressed the reset anomaly. The measured limiting magnitudes were J=18.6 and K=17.7 (imaging of point sources at S/N=10 for 10 min. exposure).

ISLE: Near-Infrared Imager/Spectrograph for the 1.88m Telescope at Okayama Astrophysical Observatory

ISLE is a near-infrared imager and spectrograph for the Cassegrain focus (f/18) of the 1.88 m telescope at Okayama Astrophysical Observatory. It is upgraded instrument with a new detector, HAWAII-1 HgCdTe array and new optics. ISLE provides imaging capabilities which covers 4.2 × 4.2 arcmin2 field-of-view at 0.25 arc-sec/ pixel and long-slit (4 arcmin) spectroscopic capabilities at λ/Δλ = 1000 - 4000 using reflection gratings. The noise performance of the detector is excellent. The read noise of 2.5 electrons with 25 Fowler pairs has been achieved, that is one of the worlds lowest level among the instruments which use HAWAII-1 array as the detector. We discuss the technical performance of ISLE and examine the upgrade effectiveness.

MuSCAT: a multicolor simultaneous camera for studying atmospheres of transiting exoplanets

Abstract. We report a development of a multicolor simultaneous camera for the 188-cm telescope at Okayama Astrophysical Observatory in Japan. The instrument, named MuSCAT (Multicolor Simultaneous Camera for studying Atmospheres of Transiting exoplanets), has a capability of three-color simultaneous imaging in optical wavelengths where CCDs are sensitive. MuSCAT is equipped with three 1024 × 1024 pixel CCDs which can be controlled independently. The three CCDs detect lights in g2′ (400 to 550 nm), r2′ (550 to 700 nm), and zs,2 (820 to 920 nm) bands using Astrodon Photometrics Generation 2 Sloan filters. The field of view of MuSCAT is 6.1×6.1  arc min2 with the pixel scale of 0.358  arc sec/pixel. The principal purpose of MuSCAT is to perform high-precision multicolor transit photometry. For this purpose, MuSCAT has the capability of self-autoguiding which enables it to fix the positions of stellar images within ∼1 pixel. We demonstrate relative photometric precisions of 0.101%, 0.074%, and 0.076% in g2′, r2′, and zs,2 bands, respectively, for GJ 436 (magnitudes in g′=11.81, r′=10.08, and z′=8.66) with 30-s exposures. The achieved precisions meet our objective, and the instrument is ready for operation.

First Paschen alpha imaging from the ground: the first light of Atacama Near-Infrared Camera on the miniTAO 1m telescope

We have developed a near infrared camera called ANIR (Atacama Near InfraRed camera) for the University of Tokyo Atacama 1.0m telescope installed at the summit of Co. Chajnantor (5640m altitude) in northern Chile. The camera is based on a PACE HAWAII-2 array with an Offner relay optics for re-imaging, and field of view is 5. 3 × 5. 3 with pixel scale of 0. 31/pix. It is also capable of optical/infrared simultaneous imaging by inserting a dichroic mirror before the focal plane. The high altitude and extremely low water vapor (PWV=0.5mm) of the site enables us to perform observation of hydrogen Paschenα (Paα) emission line at 1.8751 μm. The first light observation was carried out in July 2009, and we have successfully obtained Paα images of the Galactic center using the N1875 narrow-band filter. This is the first success of Paα imaging of a Galactic object from a ground based telescope. System efficiencies for the broad-band filters are measured to be 15% at the J-band and 30% at Ks, while that of the N1875 narrow-band filter, corresponding to Paα; wavelength, varies from 8 to 15%, which may be caused by fluctuation of the atmospheric transmittance. ATRAN simulation suggests that this corresponds to PWV of 0.3 - 1.5mm, consistent with previous results of the site testing. Measured seeing size is median ~0. 8, corresponding to the real seeing value of 0. 6 - 0. 8. These results demonstrates the excellent capability of the site for infrared observations.