Everett M. Irwin

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

The HAWAII Infrared Detector Arrays: testing and astronomical characterization of prototype and science-grade devices

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The University of Hawaii NICMOS-3 near-infrared camera

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KSPEC -- A NEAR-INFRARED CROSS-DISPERSED SPECTROGRAPH

Abstract Two generations of prototypes of a HgCdTe infrared detector array with 1024 × 1024 pixels developed by the Rockwell International Science Center have been tested in the new Quick Infrared Camera (QUIRC) and an upgraded version of KSPEC a cross-dispersed near-infrared spectrograph, on the University of Hawaii 2.2 m telescope. The HAWAII (HgCdTe Astronomical Wide Area Infrared Imager) prototype devices achieved very good performance. The read-noise in correlated double sampling (CDS) is between 10 and 15 e − rms, depending on the conditions of the operations and the way read-noise is computed. The quantum efficiency in H and K is above 50%. The full-well capacity is above 10 5 e − at 0.5 V applied detector bias and is, in our system, limited by the dynamic range of the A/D converter. The residual excess dark-current problem known from NICMOS-3 devices (Hodapp et al., 1992) [PASP, 104, 441] is not fully resolved. However, it appears less serious in our first HAWAII prototype devices. Using KSPEC, operation under low background conditions has been tested. At an operating temperature of 65 K, and using up to 128 samples of multi-sampling, a read-noise of − and a dark current −1 /min has been demonstrated. Tests of fast sub-array reads for wavefront sensing were conducted using QUIRC. For a sub-array frame repeat time of 11 ms, a read-noise of 6 e − has been demonstrated. An engineering-grade second-generation HAWAII device with reliable hybridization is now in routine operation in KSPEC. The first science-grade HAWAII device has now been installed in the QUIRC camera and is in routine operation. Steven Beckwith

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

The UH Near Infrared Camera is equipped with a NICMOS-3 HgCdTe detector array sensitive from -1 to 2.5 microns and produced by the Rockwell International Science Center for the Near Infrared Camera and Multi Object Spectrometer Project (NICMOS). In our camera, the NICMOS-3 array operates with 53 electrons read-noise in double correlated sampling mode. A dark current below 1 electron per second at an operating temperature of 60 K has been achieved. The device works linearly within 1% up to 250000 electrons (2/3 full-well) at 1.0 V bias. Techniques for further reduction in read-noise and dark current are discussed. The only significant remaining problem is a residual excess dark current, remaining from previous exposure of the device.

Gemini near-infrared imager (NIRI)

KSPEC (K-Band Spectrograph) is an infrared spectrograph designed primarily for spectroscopy in the 2.0 - 2.5 micron region. It offers two different optical configurations. The first is a cross-dispersed echelle mode designed to cover the atmospheric windows from 1 - 2.5 microns in one spectral frame of 256 X 256 format on a NICMOS-3 HgCdTe detector array. This configuration of the spectrograph provides medium spectral resolution (lambda/delta-lambda ~500) for spectral classification work, emission-line detection, and redshift measurements. Alternatively, KSPEC can be equipped with a different spectrograph camera, giving a long-slit, single-order spectrum from 2.05 - 2.35 microns. The instrument uses a second NICMOS-3 infrared detector array for slit-viewing, to facilitate the acquisition of optically invisible objects, to document the slit position and to monitorit during long spectroscopic integrations. KSPEC does not contain any moving components, making it a very reliable, relatively low-cost instrument that is easy to use.

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.

Astronomical characterization results of 1024 x 1024 HgCdTe HAWAII detector arrays

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.

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

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.

Design of the near-infrared camera for the Gemini telescope

The first prototype of a HgCdTe infrared detector array with 1024 X 1024 pixels developed by the Rockwell International Science Center has been tested in a new infrared camera at the UH 2.2 m telescope, the 0.6 m telescope, and the CFHT. At the 2.2 m tests were conducted both at f/31, where images of very high resolution were obtained using tip-tilt correction, and at f/10 for a wide field of view. At the CFHT both wide field imaging (f/8) and adaptive optics work was done. The HAWAII (HgCdTe astronomical wide area infrared imager) prototype device achieved very good performance. In the camera system, a double correlated readnoise of 15 e- rms was achieved. The dark current at 1 V bias could be confirmed to be below 1 e-, even though the device was operated above 77 K. The quantum efficiency is slightly below 50% and shows the wavy pattern characteristic of LPE-grown HgCdTe. The full well capacity is above 105 e- at 1 V bias, limited in our system by the dynamic range of the A/D converter. Data reduction is practically identical to what is used for NICMOS3 256 X 256 devices. Combined integration times of more than 1 hour have been used and demonstrate that the HAWAII devices are suitable for very deep imaging. The residual excess dark current problem known from NICMOS3 devices is not fully resolved. However, it appears less serious in our first HAWAII prototype device.