John Canfield

Design and development of NIRSPEC: a near-infrared echelle spectrograph for the Keck II telescope

The design and development of NIRSPEC, a near-IR echelle spectrograph for the Keck II 10-meter telescope is described. This instrument is a large, facility-class vacuum-cryogenic spectrometer with a resolving power of R equals 25,000 for a 0.4 inch slit. It employs diamond-machined metal optics and state-of-the-art IR array detectors for high throughput, together with powerful user-friendly software for ease of use.

Low-noise readout using active reset for CMOS APS

Pixel reset noise sets the fundamental detection limit on photodiode based CMOS image sensors. Reset noise in standard active pixel sensor (APS) is well understood and is of order kT/C. In this paper we present a new technique for resetting photodiodes, called active reset, which reduces reset noise without adding lag. Active reset can be applied to standard APS. Active reset uses bandlimiting and capacitive feedback to reduce reset noise. This paper discusses the operation of an active reset pixel, and presents an analysis of lag and noise. Measured results from a 6 transistor per pixel 0.35 micrometers CMOS implementation are presented. Measured results show that reset noise can be reduced to less than kT/18C using active reset. We find that theory simulation and measured results all match closely.

The Infrared Imaging Spectrograph (IRIS) for TMT: instrument overview

We present an overview of the design of IRIS, an infrared (0.84 - 2.4 micron) integral field spectrograph and imaging camera for the Thirty Meter Telescope (TMT). With extremely low wavefront error (<30 nm) and on-board wavefront sensors, IRIS will take advantage of the high angular resolution of the narrow field infrared adaptive optics system (NFIRAOS) to dissect the sky at the diffraction limit of the 30-meter aperture. With a primary spectral resolution of 4000 and spatial sampling starting at 4 milliarcseconds, the instrument will create an unparalleled ability to explore high redshift galaxies, the Galactic center, star forming regions and virtually any astrophysical object. This paper summarizes the entire design and basic capabilities. Among the design innovations is the combination of lenslet and slicer integral field units, new 4Kx4k detectors, extremely precise atmospheric dispersion correction, infrared wavefront sensors, and a very large vacuum cryogenic system.

The integral field spectrograph for the Gemini planet imager

The Gemini Planet Imager (GPI) is a complex optical system designed to directly detect the self-emission of young planets within two arcseconds of their host stars. After suppressing the starlight with an advanced AO system and apodized coronagraph, the dominant residual contamination in the focal plane are speckles from the atmosphere and optical surfaces. Since speckles are diffractive in nature their positions in the field are strongly wavelength dependent, while an actual companion planet will remain at fixed separation. By comparing multiple images at different wavelengths taken simultaneously, we can freeze the speckle pattern and extract the planet light adding an order of magnitude of contrast. To achieve a bandpass of 20%, sufficient to perform speckle suppression, and to observe the entire two arcsecond field of view at diffraction limited sampling, we designed and built an integral field spectrograph with extremely low wavefront error and almost no chromatic aberration. The spectrograph is fully cryogenic and operates in the wavelength range 1 to 2.4 microns with five selectable filters. A prism is used to produce a spectral resolution of 45 in the primary detection band and maintain high throughput. Based on the OSIRIS spectrograph at Keck, we selected to use a lenslet-based spectrograph to achieve an rms wavefront error of approximately 25 nm. Over 36,000 spectra are taken simultaneously and reassembled into image cubes that have roughly 192x192 spatial elements and contain between 11 and 20 spectral channels. The primary dispersion prism can be replaced with a Wollaston prism for dual polarization measurements. The spectrograph also has a pupil-viewing mode for alignment and calibration.

UCLA double-beam infrared camera system

This paper describes a new infrared imaging system being developed at UCLA for use on both the Lick Observatory 3-m telescope and the W.M. Keck 10-m telescope. The instrument has a relatively wide field of view on each telescope and is intended for infrared surveys and deep imaging. To enhance efficiency, the new instrument incorporates a dichroic beam splitter to provide two simultaneous imaging systems, one short-wave (SW) from 1 - 2.5 micrometers and one long-wave (LW) from 2 - 5 micrometers . Each wavelength channel is independently optimized. The SW channel contains a Rockwell NICMOS3 256 X 256 HgCdTe array and the LW channel has an SBRC 256 X 256 InSb array. The thermal design employs a closed cycle cooler. A control and data acquisition system based on transputers and high speed analog electronics is being developed to handle the high data rates.

An ultralow-noise high-speed CMOS linescan sensor for scientific and industrial applications

This paper describes a 2048x1 linear image sensor implemented in a 0.35 μm 4M1P CMOS process that uses a low fixed pattern noise capacitive transimpedance amplifier (LFPN CTIA) pixel architecture. The pixel also includes circuitry for reducing 1/f noise, correlated double sampling, electronic shuttering, and a horizontal anti-blooming drain. High speed non-destructive readout of the sensor is achieved by using a hierarchical readout structure with two output ports. Using a JTAG interface the sensor can be programmed to operate in multiple readout modes. In the fastest readout mode, ROI, the sensor achieves 90Mpixel/sec (43.4Klines/sec) with 14e- RMS read noise. In the lowest noise mode, MRDI, with 13x oversampling of each pixel the sensor achieves 2.7Klines/sec with 1.2e- RMS read noise.

An overview of the NIRSPEC upgrade for the Keck II telescope

NIRSPEC is a 1-5 um echelle spectrograph in use on the Keck II Telescope since 1999. The spectrograph is capable of both moderate (R=λ/▵λ~2000) and high (R~25,000) resolution observations and has been a workhorse instrument across many astronomical fields, from planetary science to extragalactic observations. In the latter half of 2018, we will upgrade NIRSPEC to improve the sensitivity and stability of the instrument and increase its lifetime. The major components of the upgrade include replacing the spectrometer and slit-viewing camera detectors with Teledyne H2RG arrays and replacing all transputer-based electronics. We present detailed design, testing, and analysis of the upgraded instrument, including the finalized optomechanical design of the new 1-5 μm slit-viewing camera, detector characterization of the science and Engineering A grade arrays, electronics systems, and updated software design. The optomechanical design of the slit-viewing camera and replacement detector head assembly have both been assembled and cold-tested in our lab. We also show results from the GigE interface to the SAM/ASIC boards to control the H2RG. The upgrade will continue NIRSPEC’s legacy as a powerful near-infrared spectrograph behind one of the world’s most scientifically productive telescopes.