Shane Jacobson

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

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.

Performance characterization of the HiCIAO instrument for the Subaru 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.

2Kx2K molecular beam epitaxy HgCdTe detectors for the James Webb Space Telescope NIRCam instrument

The NIRCam instrument will fly ten of Rockwell Scientific’s infrared molecular beam epitaxy HgCdTe 2048x2048 element detector arrays, each the largest available with current technology, for a total of 40 Megapixels. The instrument will have two varieties of MBE HgCdTe, a SWIR detector with λco = 2.5 μm, for the shortwave channel of NIRCam (0.6-2.3 μm); and a MWIR detector with λco = 5.3 μm, for the longwave channel of NIRCam (2.4-5.0 μm). Demonstrated mean detector dark currents less than 0.01 electrons per second per pixel at operating temperatures below 42 K for the MWIR and below 80 K for the SWIR, combined with quantum efficiency in excess of 80 percent and read noise below 6 electrons rms, make these detector arrays by far the most sensitive SWIR and MWIR devices in the world today. The unique advantages of molecular beam epitaxy as well as FPA data on noise, dark current, quantum efficiency, and other performance metrics will be discussed. In addition, the focal plane assembly package designs will be presented and discussed.

HIGH-SPEED IMAGING AND WAVEFRONT SENSING WITH AN INFRARED AVALANCHE PHOTODIODE ARRAY

Infrared avalanche photodiode arrays represent a panacea for many branches of astronomy by enabling extremely low-noise, high-speed and even photon-counting measurements at near-infrared wavelengths. We recently demonstrated the use of an early engineering-grade infrared avalanche photodiode array that achieves a correlated double sampling read noise of 0.73 e- in the lab, and a total noise of 2.52 e- on sky, and supports simultaneous high-speed imaging and tip-tilt wavefront sensing with the Robo-AO visible-light laser adaptive optics system at the Palomar Observatory 1.5-m telescope. We report here on the improved image quality achieved simultaneously at visible and infrared wavelengths by using the array as part of an image stabilization control-loop with adaptive-optics sharpened guide stars. We also discuss a newly enabled survey of nearby late M-dwarf multiplicity as well as future uses of this technology in other adaptive optics and high-contrast imaging applications.

Next-generation performance of SAPHIRA HgCdTe APDs

We present the measured characteristics of the most recent iteration of SAPHIRA HgCdTe APD arrays, and with suppressed glow show them to be capable of a baseline dark current of 0:03e-/s. Under high bias voltages the device also reaches avalanche gains greater than 500. The application of a high temperature anneal during production shows great improvements to cosmetic performance and moves the SAPHIRA much closer to being science grade arrays. We also discuss investigations into photon counting and ongoing telescope deployments of the SAPHIRA with UH-IfA.

Design of the HiCIAO instrument for the Subaru Telescope

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.

HgCdTe APD-based linear-mode photon counting components and ladar receivers

Linear mode photon counting (LMPC) provides significant advantages in comparison with Geiger Mode (GM) Photon Counting including absence of after-pulsing, nanosecond pulse to pulse temporal resolution and robust operation in the present of high density obscurants or variable reflectivity objects. For this reason Raytheon has developed and previously reported on unique linear mode photon counting components and modules based on combining advanced APDs and advanced high gain circuits. By using HgCdTe APDs we enable Poisson number preserving photon counting. A metric of photon counting technology is dark count rate and detection probability. In this paper we report on a performance breakthrough resulting from improvement in design, process and readout operation enabling >10x reduction in dark counts rate to ~10,000 cps and >104x reduction in surface dark current enabling long 10 ms integration times. Our analysis of key dark current contributors suggest that substantial further reduction in DCR to ~ 1/sec or less can be achieved by optimizing wavelength, operating voltage and temperature.

Commissioning of the infrared imaging survey (IRIS) system

The Infrared Imaging System (IRIS) is a 0.8m telescope and a 1024×1024 pixels camera (IRISCAM) with a HAWAII-1 detector array. IRIS is located at the Cerro Armazones Observatory in Chile that is operated by the Ruhr University Bochum jointly with the Universidad Católica del Norte in Antofagasta. It will be used primarily to survey star-forming regions for variability. Our goal is to discover young stellar objects undergoing accretion instabilities or rotational modulation of star spots, eclipsing binaries, and variable reflection nebulae. The telescope and the infrared camera are completed and first light was achieved in May of 2010. IRIS is currently being tested and characterized, before the longterm monitoring project will commence.

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

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.

Performance of the first HAWAII 4RG-15 arrays in the laboratory and at the telescope

The primary goal of the HAWAII 4RG-15 (H4RG-15) development is to provide a 16 megapixel 4096x4096 format at significantly reduced price per pixel while maintaining the superb low background performance of the HAWAII 2RG (H2RG). The H4RG-15 design incorporates several new features, notably clocked reference output and interleaved reference pixel readout, that promise to significantly improve noise performance while the reduction in pixel pitch from 18 to 15 microns should improve transimpedance gain although at the expense of some degradation in full well and crosstalk. During the Phase-1 development, Teledyne has produced and screen tested six hybrid arrays. In preparation for Phase-2, the most promising of these are being extensively characterized in the University of Hawaii’s (UH) ULBCam test facility originally developed for the JWST H2RG program. The end-to-end performance of the most promising array has been directly established through astronomical imaging observations at the UH 88-inch telescope on Mauna Kea. We report the performance of these Phase-1 H4RG-15s within the context of established H2RG performance for key parameters (primarily CDS read noise), also highlighting the improvements from the new readout modes.