Hubert Yamada

The Gemini Near‐Infrared Imager (NIRI)

ABSTRACT This paper presents the basic design of the Gemini Near‐Infrared Imager (NIRI) and discusses its capabilities. NIRI offers three different pixel scales to match different operating modes of the Gemini telescope and allows polarimetric and spectroscopic observations. It is equipped with an infrared on‐instrument wave‐front sensor (OIWFS) to allow tip‐tilt and focus correction even in highly obscured regions. The science detector array is an Aladdin II InSb \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Concept and science of HiCIAO: High contrast instrument for the Subaru next generation adaptive optics

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Performance characterization of the HiCIAO instrument for the Subaru Telescope

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Design of the HiCIAO instrument for the Subaru Telescope

Direct exploration of exoplanets is one of the most exciting topics in astronomy. Our current efforts in this field are concentrated on the Subaru 8.2m telescope at Mauna Kea, Hawaii. Making use of the good observing site and the excellent image quality, the infrared coronagraph CIAO (Coronagraphic Imager with Adaptive Optics) has been used for various kinds of surveys, which is the first dedicated cold coronagraph on the 8-10m class telescopes. However, its contrast is limited by the low-order adaptive optics and a limited suppression of the halo speckle noise. HiCIAO is a new high-contrast instrument for the Subaru telescope. HiCIAO will be used in conjunction with the new adaptive optics system (188 actuators and/or its laser guide star - AO188/LGSAO188) at the Subaru infrared Nasmyth platform. It is designed as a flexible camera comprising several modules that can be configured into different modes of operation. The main modules are the AO module with its future extreme AO capability, the warm coronagraph module, and the cold infrared camera module. HiCIAO can combine coronagraphic techniques with either polarization or spectral simultaneous differential imaging modes. The basic concept of such differential imaging is to split up the image into two or more images, and then use either different planes of polarization or different spectral filter band-passes to produce a signal that distinguishes faint objects near a bright central object from scattered halo or residual speckles. In this contribution, we will outline the HiCIAO instrument, its science, and performance simulations. The optical and mechanical details are described by Hodapp et al. (2006)1. We also present a roadmap of Japanese facilities and future plans, including ASTRO-F (AKARI), SPICA, and JTPF, for extrasolar planet explorations.

Design and Commissioning of a Dual Visible/Near-IR Echelle Spectrograph for the AEOS Telescope

HiCIAO is a near-infrared, high contrast instrument which is specifically designed for searches and studies for extrasolar planets and proto-planetary/debris disks on the Subaru 8.2 m telescope. A coronagraph technique and three differential observing modes, i.e., a dual-beam simultaneous polarimetric differential imaging mode, quad-beam simultaneous spectral differential imaging mode, and angular differential imaging mode, are used to extract faint objects from the sea of speckle around bright stars. We describe the instrument performances verified in the laboratory and during the commissioning period. Readout noise with a correlated double sampling method is 15 e- using the Sidecar ASIC controller with the HAWAII-2RG detector array, and it is as low as 5 e- with a multiple sampling method. Strehl ratio obtained by HiCIAO on the sky combined with the 188-actuator adaptive optics system (AO188) is 0.4 and 0.7 in the H and K-band, respectively, with natural guide stars that have R ~ 5 and under median seeing conditions. Image distortion is correctable to 7 milli-arcsec level using the ACS data as a reference image. Examples of contrast performances in the observing modes are presented from data obtained during the commissioning period. An observation for HR 8799 in the angular differential imaging mode shows a clear detection of three known planets, demonstrating the high contrast capability of AO188+HiCIAO.

Gemini near-infrared imager (NIRI)

HiCIAO, the High-Contrast Coronographic Imager for Adaptive Optics, is a coronographic simultaneous differential imager for the Subaru Telescope Nasmyth focus. It is designed primarily to search for faint companions, brown dwarves and young giant planets, around nearby stars, but will also allow observations of disks around young stars and of emission line regions near other bright central sources. HiCIAO will work in conjunction with the new Subaru Telescope 188 actuator adaptive optics system. It is designed as a flexible, experimental instrument that will grow from the initial, simple coronographic system into more complex, innovative coronographic optics as these technologies become available. The main component of HiCIAO is an infrared camera optimized for spectral simultaneous differential imaging that uses a 2.5 μm HAWAII-2RG detector array operated by a Rockwell Sidecar ASIC.

Gemini near-infrared imager

The Institute for Astronomy has developed and recently installed a high-resolution cross-dispersed echelle spectrograph for use at one of the coudé foci of the AEOS 3.7-meter telescope, operated by the Air Force Space Command atop Mt. Haleakala on the island of Maui. The spectrograph features an optical arm for the wavelength range 0.5 - 1.0 μm and an infrared arm for the range 1.0 - 2.5 μm. We review the spectrograph design and present commissioning results obtained with both the visible and infrared arms. Both channels use a white-pupil collimator design to maximize grating efficiency and to limit the size of the camera optics. The visible arm of the spectrograph uses deep-depletion CCDs optimized for operation near 1.0 μm. The infrared detector is a 2048 x 2048 HgCdTe array (HAWAII-2) that has been developed by the Rockwell Science Center for this project. Both channels are equipped with slit-viewing cameras for object acquisition and control of a fast guiding tip-tilt mirror located at a pupil image in the spectrograph fore optics.

HiCIAO: A High‐contrast Instrument for the Next Generation Subaru Adaptive Optics

The NIRI for the Gemini North telescope is now undergoing acceptance testing. NIRI is the main near-IR facility camera on the Gemini North telescope and is designed to fully exploit the excellent characteristics of the site and the expected high performance o the telescope. NIRI offers 3 different pixel scales for wide-field, tip-tilt corrected and diffraction-limited imaging. It is equipped with a pupil imaging system to evaluate the telescope emissivity and to optimize the alignment of the instrument with the telescope. NIRI has an IR wavefront sensor so that tip-tilt and focus corrections can be obtained even in dark cloud regions or during daytime observing.

The University of Hawaii 2.2 Meter Fast Tip‐Tilt Secondary System

We discuss the main design features of the Gemini Near-IR Imager (NIRI) and its scientific capabilities. NIRI is designed to fully exploit the excellent image quality and low telescope emissivity expected from the Gemini telescope on Mauna Kea. It offers a range of pixel scales matched to different scientific objectives and has spectroscopic as well as polarimetric capabilities. One of its main design features is the use of a near-IR 2 X 2 Shack-Hartmann wavefront sensor for tip-tilt and focus control.

Gemini near-infrared imager (NIRI): a discussion of its design features and performance

HiCIAO (the High‐Contrast Instrument with Adaptive Optics) is a high‐contrast instrument for the 8.2‐meter Subaru Telescope. The instrument is a near‐infrared camera which benefits from a new adaptive optics (AO) system on the Subaru Telescope (AO188). The instrument realizes the high contrast with a help of AO188, a classical Lyot coronagraph, and three differential imaging techniques (polarimetric, spectral, and angular). Besides the differential imaging modes, HiCIAO also offers a normal imaging mode which covers 20″×20″ FOV with 0.″01 pixel−1 resolution, and a pupil viewing mode for a precise alignment of the Lyot stop on the pupil image. The expected contrasts are 105.5 at 1.″0 separation and 104 at 0.″1 separation from a central star in the spectral differential imaging mode. The instrument is currently in its commissioning phase after the first‐light observation in December 2008. This paper is an introductory review of the instrument.