An often unglamorous, yet critical, part of most millimeter/submillimeter astronomical instruments is cryogenic temperature monitoring and control. Depending on the operating wavelength of the instrument and detector technology, this could be stable temperatures in the Kelvin range for millimeter heterodyne systems to 100 mK temperatures at sub-micro-Kelvin stability as for many submillimeter bolometer systems. Here we describe a project of the HARDWARE.astronomy initiative to build a low-cost open-source temperature monitoring and control system. The HARDWARE.astronomy Housekeeping Box, or H.aHk Box (pronounced “hack box”) is developed primarily by undergraduates and employs existing open-source devices (e.g Arduino, Raspberry Pi) to reduce costs while also limiting the complexity of the development. The H.aHk Box features a chassis with a control computer and ten expansion slots that can be filled with a variety of expansion cards. These cards include initially an AC 4-wire temperature monitor and PID control cards. Future work will develop 2-wire temperature monitors, stepper motor controller, and high-power supply. The base-system will also be able to interface with other house-keeping systems over USB, serial port and ethernet. The first deployment of the H.aHk Box will be for the ZEUS-2 submillimeter grating spectrometer. All designs, firmware, software and parts list will be published online allowing for other projects to adopt the system and create custom expansion cards as needed. Here we describe the design (including mechanical, electrical, firmware, and software components) and initial performance of the H.aHk Box system with initial AC/DC 4-wire and PID cards.
KEYWORDS: Mirrors, Manufacturing, Surface roughness, Telescopes, Etching, Surface finishing, Short wave infrared radiation, Received signal strength, Temperature metrology, Optical simulations
The Fred Young Submillimeter Telescope (FYST) is a 6-meter diameter telescope with a surface accuracy of 10.7 microns, operating at submillimeter to millimeter wavelengths (100 GHz – 1.5 THz). It will be located at 5600 meters elevation on Cerro Chajnantor in the Atacama desert of northern Chile overlooking the ALMA site. Its novel optical “crossed-Dragone” design will deliver a high-throughput, wide field-of-view telescope capable of mapping the sky very rapidly and efficiently. This paper discusses the mirror panel production and its contribution to the overall half wave front error of the telescope. The first half details the panel manufacturing precision. The effect of panel production quality on the beam shape and beam quality is presented. The second half of the paper looks at the local surface roughness of a mirror panel. Surface roughness data for a machined panel with an etched surface are presented. Some non-ideal surface features for an etched panel are discussed.
The Fred Young Submillimeter Telescope (FYST) is a 6-meter diameter telescope currently being built by the CCAT-prime project that will observe at millimeter and submillimeter wavelengths. It will deliver a total wavefront error of less than 22 microns at the focal plane. The optics follow a modified crossed-Dragone configuration, yielding a 7.8° field of view across a ~2 meter diameter focal plane. The telescope will be located at 5600 meters on Cerro Chajnantor in the Atacama Desert. The demands of first-generation and future instruments significantly drove the design of the telescope. The telescope layout consists of multiple instrument bays, which provide the capacity to house a total of 11 tons of focal plane instrumentation across 23 square meters of floor space. The Yoke Traverse is divided into telescope servo, instrument electronics, and process spaces, and can support an additional 8 tons of instrument equipment. We discuss the final design and fabrication status of FYST.
We report on the CCAT-prime Project, including the science program, the Fred Young Submillimeter Telescope (FYST), its instrumentation, and the schedule. FYST is a 6-m telescope sited at 5600 m elevation near the summit of Cerro Chajnantor in northern Chile. The site, together with its very large field-of-view optics, and high surface accuracy, low-emissivity surface enables pursuit of low surface brightness science over large fields. Our science goals include: tracing the formation and evolution of star forming galaxies from the epoch of reionization to the cosmic peak of star formation activity through wide-field, broad-band [CII] line imaging and dust continuum surveys; constraining thermodynamics and feedback in galaxy clusters through the Sunyaev-Zel’dovich effects on the CMB; improving constraints on primordial gravitational waves through precision removal of polarization foregrounds; and tracing local star formation processes through velocity-resolved spectroscopy at 15” spatial resolution over 110 scales in the Galaxy. These goals are realized through sensitive wide-field surveys. Our main instruments are Prime-Cam, a large FoV direct detection imager and CHAI, a multi-beam submillimeter heterodyne spectrometer. We have also built Mod-Cam which serves as a Prime-Cam test facility and/or first light camera. Prime-Cam has seven instrument modules, four now under construction: three polarimetric cameras (at 280, 350, and 850 GHz) and a 210-420 GHz Fabry-Perot imaging spectrometer, EoR-Spec. CHAI will have 128 pixels covering important lines in the short submillimeter windows. The CCAT-prime team is an international group of universities, led by Cornell University. FYST is being designed and built by CPI Vertex Antennentechnik, GmbH, Germany with first light expected in 2024.
The Advanced L-band Phased Array Camera for Astronomy (ALPACA) will be a fully cryogenic phased array feed instrument operating from 1.3-1.7 GHz, providing an unmatched combination of sensitivity, wide bandwidth, and large instantaneous field of view. The instrument was originally targeted for installation at the Arecibo Radio Telescope but the tragic loss of the Gregorian platform in 2020 has led to a proposal to deploy ALPACA at the prime focus of the Green Bank Telescope. Here, we will report on the design and implementation of the antenna array, cryogenic vacuum vessel, signal transport and the digital back end.
This paper, originally published on 13 December 2020, was replaced with a corrected/revised version on 2 February 2021. If you downloaded the original PDF but are unable to access the revision, please contact SPIE Digital Library Customer Service for assistance.
The Cerro Chajnantor Atacama Telescope prime (CCAT-p) Observatory is a widefield, 6 meter aperture submillimeter telescope. Prime-Cam will be a powerful, first light camera for CCAT-p with imagers working at several wavelengths and a spectroscopic instrument aimed at intensity mapping during the epoch of reionization.
We present the design of an instrument module in Prime-Cam, operating at 350 microns — the shortest wavelength on the instrument, and the most novel for astronomical surveys, taking full advantage of the atmospheric transparency at the high 5600 meter CCAT-p siting on Cerro Chajnantor. This instrument module will provide unprecedented broadband intensity and polarization measurement capabilities to address pressing astrophysical questions regarding galaxy formation, Big Bang cosmology, and star formation within our own Galaxy. We present the overall optical and mechanical design for the module, and laboratory characterization of the 860-GHz KID array.
*[email protected] Optical design study for an 850 GHz commissioning camera module for CCAT-prime Doug Henke*a, Doug Johnstonea,b, Lewis B.G. Kneea, Scott Chapmanc, Colin Rossc, Michel Fichd, Thomas Nikolae, Steve K. Choif, Michael D. Niemackf,g, Stephen C. Parshleyf, Gordon J. Staceyf, Eve Vavagiakisf aNRC Herzberg Astronomy and Astrophysics Research Centre, Victoria, BC V9E 2E7, Canada; bDept. of Physics and Astronomy, Univ. of Victoria, Victoria, BC V8W 2Y2, Canada; cDept. of Physics and Atmospheric Science, Dalhousie Univ., Halifax, NS B3H 4R2, Canada; dDept. of Physics and Astronomy, Univ. of Waterloo, Waterloo, ON N2L 3G1, Canada; eCornell Center for Astrophysics and Planetary Science, Cornell Univ., Ithaca, NY 14853, USA; fDept. of Astronomy, Cornell Univ., Ithaca, NY 14853, USA; gDept. of Physics, Cornell Univ., Ithaca, NY 14853, USA ABSTRACT The CCAT-prime telescope, also known as the Fred Young Submillimeter Telescope (FYST), has an unblocked 6-m aperture designed for an extraordinarily wide field-of-view to be used in cosmological and galactic studies. Located at 5600 m near ALMA, the site has extremely dry conditions which make it particularly suited for observations at shorter sub-mm wavelengths. These attributes make CCAT-prime a potential platform for the next generation “Stage IV” cosmic microwave background experiment to conduct cosmology surveys of the extragalactic sky. CCAT-prime is also ideal for polarization studies within the galaxy and time-domain observations of nearby protostars. Prime-Cam is the wide-field, first-light instrument for CCAT-prime which, when complete, will contain seven instrument modules, including cameras and spectrometers, spanning mm through sub-mm wavelengths. Not all receiver modules are currently funded—including the 350 mm (~850 GHz) camera module that motivates the extraordinary high site of CCAT-p. Recognizing that an 850 GHz commissioning camera may be needed within the next 1–2 years, an optical design study was initiated where we purposely chose to reduce the scope, cost, and complexity while still preserving diffraction-limited optics, allowing for early science until the more powerful wide field science-grade camera module replaced it. In order to minimize the cost and scope of an 850 GHz commissioning camera, the optics plan for reuse of existing detectors (ACT MBAC TES detectors or BLAST-TNG MKIDs) and interface with the existing instrument module cartridge planned for Prime-Cam. Further simplifications include restricting the field-of-view and utilizing on-axis HDPE lenses without an anti-reflection layer. Discussion of optimal detector array F-lambda scaling, analysis of power loading, and feed horn coupling efficiency is included.
We describe a system being developed for measuring the shapes of the mirrors of the Fred Young Submillimeter Telescope (FYST), now under construction for the CCAT Observatory. “Holographic” antenna-measuring techniques are an efficient and accurate way of measuring the surfaces of large millimeter-wave telescopes and they have the advantage of measuring the wave-front errors of the whole system under operational conditions, e.g. at night on an exposed site. Applying this to FYST, however, presents significant challenges because of the high accuracy needed, the fact that the telescope consists of two large off-axis mirrors, and a requirement that measurements can be made without personnel present. We use a high-frequency (~300GHz) source which is relatively close to the telescope aperture (<1/100th of the Fresnel distance) to minimize atmospheric effects. The main receiver is in the receiver cabin and can be moved under remote control to different positions, so that the wave-front errors in different parts of the focal plane can be measured. A second receiver placed on the yoke provides a phase reference. The signals are combined in a digital cross-correlation spectrometer. Scanning the telescope provides a map of the complex beam pattern. The surface errors are found by inference, i.e. we make models of the reflectors with errors and calculate the patterns expected, and then iterate to find the best match to the data. To do this we have developed a fast and accurate method for calculating the patterns using the Kirchhoff-Fresnel formulation. This paper presents details of the design and outlines the results from simulations of the measurement and inference process. These indicate that a measurement accuracy of ~3μm rms is achievable.
The Simons Observatory (SO) is a new experiment that aims to measure the cosmic microwave background (CMB) in temperature and polarization. SO will measure the polarized sky over a large range of microwave frequencies and angular scales using a combination of small (~0.5 m) and large (~6 m) aperture telescopes and will be located in the Atacama Desert in Chile. This work is part of a series of papers studying calibration, sensitivity, and systematic errors for SO. In this paper, we discuss current efforts to model optical systematic effects, how these have been used to guide the design of the SO instrument, and how these studies can be used to inform instrument design of future experiments like CMB-S4. While optical systematics studies are underway for both the small aperture and large aperture telescopes, we limit the focus of this paper to the more mature large aperture telescope design for which our studies include: pointing errors, optical distortions, beam ellipticity, cross-polar response, instrumental polarization rotation and various forms of sidelobe pickup.
The Simons Observatory (SO) will make precision temperature and polarization measurements of the cosmic
microwave background (CMB) using a series of telescopes which will cover angular scales between 1 arcminute
and tens of degrees, contain over 40,000 detectors, and sample frequencies between 27 and 270 GHz. SO will
consist of a six-meter-aperture telescope coupled to over 20,000 detectors along with an array of half-meter
aperture refractive cameras, coupled to an additional 20,000+ detectors. The unique combination of large and
small apertures in a single CMB observatory, which will be located in the Atacama Desert at an altitude of
5190 m, will allow us to sample a wide range of angular scales over a common survey area. SO will measure
fundamental cosmological parameters of our universe, find high redshift clusters via the Sunyaev-Zeldovich effect,
constrain properties of neutrinos, and seek signatures of dark matter through gravitational lensing. The complex
set of technical and science requirements for this experiment has led to innovative instrumentation solutions
which we will discuss. The large aperture telescope will couple to a cryogenic receiver that is 2.4 m in diameter
and over 2 m long, creating a number of interesting technical challenges. Concurrently, we are designing an array
of half-meter-aperture cryogenic cameras which also have compelling design challenges. We will give an overview
of the drivers for and designs of the SO telescopes and the cryogenic cameras that will house the cold optical
components and detector arrays.
We present the novel design of microfabricated, silicon-substrate based mirrors for use in cryogenic Fabry-Perot Interferometers (FPIs) for the mid-IR to sub-mm/mm wavelength regime. One side of the silicon substrate will have a double-layer metamaterial anti-reflection coating (ARC) anisotropically etched into it and the other side will be metalized with a re ective mesh pattern. The double-layer ARC ensures a re ectance of less than 1% at the surface substrate over the FPI bandwidth. This low reflectance is required to achieve broadband capability and to mitigate contaminating resonances from the silicon surface. Two silicon substrates with their metalized surfaces facing each other and held parallel with an adjustable separation will compose the FPI. To create an FPI with nearly uniform finesse over the FPI bandwidth, we use a combination of inductive and capacitive gold meshes evaporated onto the silicon substrate. We also consider the use of niobium as a superconducting reflective mesh for long wavelengths to eliminate ohmic losses at each reflection in the resonating cavity of the FPI and thereby increase overall transmission. We develop these silicon-substrate based FPIs for use in ground (e.g. CCAT-prime), air (e.g. HIRMES), and future space-based telescopes (e.g. the Origins Space Telescope concept). Such FPIs are well suited for spectroscopic imaging with the upcoming large IR/sub-mm/mm TES bolometer detector arrays. Here we present the fabrication and performance of multi-layer, plasma-etched, silicon metamaterial ARC, as well as models of the mirrors and FPIs.
CCAT-prime will be a 6-meter aperture telescope operating from sub-mm to mm wavelengths, located at 5600 meters elevation on Cerro Chajnantor in the Atacama Desert in Chile. Its novel crossed-Dragone optical design will deliver a high throughput, wide field of view capable of illuminating much larger arrays of sub-mm and mm detectors than can existing telescopes. We present an overview of the motivation and design of Prime-Cam, a first-light instrument for CCAT-prime. Prime-Cam will house seven instrument modules in a 1.8 meter diameter cryostat, cooled by a dilution refrigerator. The optical elements will consist of silicon lenses, and the instrument modules can be individually optimized for particular science goals. The current design enables both broad- band, dual-polarization measurements and narrow-band, Fabry-Perot spectroscopic imaging using multichroic transition-edge sensor (TES) bolometers operating between 190 and 450 GHz. It also includes broadband kinetic induction detectors (KIDs) operating at 860 GHz. This wide range of frequencies will allow excellent characterization and removal of galactic foregrounds, which will enable precision measurements of the sub-mm and mm sky. Prime-Cam will be used to constrain cosmology via the Sunyaev-Zeldovich effects, map the intensity of [CII] 158 μm emission from the Epoch of Reionization, measure Cosmic Microwave Background polarization and foregrounds, and characterize the star formation history over a wide range of redshifts. More information about CCAT-prime can be found at www.ccatobservatory.org.
We present the detailed science case, and brief descriptions of the telescope design, site, and first light instrument plans for a new ultra-wide field submillimeter observatory, CCAT-prime, that we are constructing at a 5600 m elevation site on Cerro Chajnantor in northern Chile. Our science goals are to study star and galaxy formation from the epoch of reionization to the present, investigate the growth of structure in the Universe, improve the precision of B-mode CMB measurements, and investigate the interstellar medium and star formation in the Galaxy and nearby galaxies through spectroscopic, polarimetric, and broadband surveys at wavelengths from 200 m to 2 mm. These goals are realized with our two first light instruments, a large field-of-view (FoV) bolometer-based imager called Prime-Cam (that has both camera and an imaging spectrometer modules), and a multi-beam submillimeter heterodyne spectrometer, CHAI. CCAT-prime will have very high surface accuracy and very low system emissivity, so that combined with its wide FoV at the unsurpassed CCAT site our telescope/instrumentation combination is ideally suited to pursue this science. The CCAT-prime telescope is being designed and built by Vertex Antennentechnik GmbH. We expect to achieve first light in the spring of 2021.
A common optical design for a coma-corrected, 6-meter aperture, crossed-Dragone telescope has been adopted for the CCAT-prime telescope of CCAT Observatory, Inc., and for the Large Aperture Telescope of the Simons Observatory. Both are to be built in the high altitude Atacama Desert in Chile for submillimeter and millimeter wavelength observations, respectively. The design delivers a high throughput, relatively flat focal plane, with a field of view 7.8 degrees in diameter for 3 mm wavelengths, and the ability to illuminate >100k diffraction-limited beams for < 1 mm wavelengths. The optics consist of offset reflecting primary and secondary surfaces arranged in such a way as to satisfy the Mizuguchi-Dragone criterion, suppressing first-order astigmatism and maintaining high polarization purity. The surface shapes are perturbed from their standard conic forms in order to correct coma aberrations. We discuss the optical design, performance, and tolerancing sensitivity. More information about CCAT-prime can be found at ccatobservatory.org and about Simons Observatory at simonsobservatory.org.
The CCAT-prime telescope is a 6-meter aperture, crossed-Dragone telescope, designed for millimeter and sub-millimeter wavelength observations. It will be located at an altitude of 5600 meters, just below the summit of Cerro Chajnantor in the high Atacama region of Chile. The telescope’s unobscured optics deliver a field of view of almost 8 degrees over a large, flat focal plane, enabling it to accommodate current and future instrumentation fielding <100k diffraction-limited beams for wavelengths less than a millimeter. The mount is a novel design with the aluminum-tiled mirrors nested inside the telescope structure. The elevation housing has an integrated shutter that can enclose the mirrors, protecting them from inclement weather. The telescope is designed to co-host multiple instruments over its nominal 15 year lifetime. It will be operated remotely, requiring minimum maintenance and on-site activities due to the harsh working conditions on the mountain. The design utilizes nickel-iron alloy (Invar) and carbon-fiber-reinforced polymer (CFRP) materials in the mirror support structure, achieving a relatively temperature-insensitive mount. We discuss requirements, specifications, critical design elements, and the expected performance of the CCAT-prime telescope. The telescope is being built by CCAT Observatory, Inc., a corporation formed by an international partnership of universities. More information about CCAT and the CCAT-prime telescope can be found at www.ccatobservatory.org.
This paper presents the current concept design for ALPACA (Advanced L-Band Phased Array Camera for Arecibo) an L-Band cryo-phased array instrument proposed for the 305 m radio telescope of Arecibo. It includes the cryogenically cooled front-end with 160 low noise amplifiers, a RF-over-fiber signal transport and a digital beam former with an instantaneous bandwidth of 312.5 MHz per channel. The camera will digitally form 40 simultaneous beams inside the available field of view of the Arecibo telescope optics, with an expected system temperature goal of 30 K.
This paper presents the results of the optical design tradeoff study that result in a reduction in complexity, size and cost of the structure for the sub-millimeter 25 m class CCAT telescope. Four optical configurations are presented; dual reflector Cassegrain and Gregorian options, and Gregorian Nasmyth and quasi-Nasmyth options. All configurations are shown to have diffraction limited performance.
We describe the Short Wavelength Camera (SWCam) for the CCAT observatory including the primary science drivers, the coupling of the science drivers to the instrument requirements, the resulting implementation of the design, and its performance expectations at first light. CCAT is a 25 m submillimeter telescope planned to operate at 5600 meters, near the summit of Cerro Chajnantor in the Atacama Desert in northern Chile. CCAT is designed to give a total wave front error of 12.5 μm rms, so that combined with its high and exceptionally dry site, the facility will provide unsurpassed point source sensitivity deep into the short submillimeter bands to wavelengths as short as the 200 μm telluric window. The SWCam system consists of 7 sub-cameras that address 4 different telluric windows: 4 subcameras at 350 μm, 1 at 450 μm, 1 at 850 μm, and 1 at 2 mm wavelength. Each sub-camera has a 6’ diameter field of view, so that the total instantaneous field of view for SWCam is equivalent to a 16’ diameter circle. Each focal plane is populated with near unit filling factor arrays of Lumped Element Kinetic Inductance Detectors (LEKIDs) with pixels scaled to subtend an solid angle of (λ/D)2 on the sky. The total pixel count is 57,160. We expect background limited performance at each wavelength, and to be able to map < 35(°)2 of sky to 5 σ on the confusion noise at each wavelength per year with this first light instrument. Our primary science goal is to resolve the Cosmic Far-IR Background (CIRB) in our four colors so that we may explore the star and galaxy formation history of the Universe extending to within 500 million years of the Big Bang. CCAT's large and high-accuracy aperture, its fast slewing speed, use of instruments with large format arrays, and being located at a superb site enables mapping speeds of up to three orders of magnitude larger than contemporary or near future facilities and makes it uniquely sensitive, especially in the short submm bands.
We have developed a fully cryogenically cooled, 19-element phased array feed (PAF), prototype camera for the
Arecibo Radio Telescope. The 19 PAF elements are dual polarized dipoles over a ground plane, and they sit
behind a 70 cm diameter vacuum window transparent to RF.
The CCAT observatory is a 25-m class Gregorian telescope designed for submillimeter observations that will be deployed at Cerro Chajnantor (~5600 m) in the high Atacama Desert region of Chile. The Short Wavelength Camera (SWCam) for CCAT is an integral part of the observatory, enabling the study of star formation at high and low redshifts. SWCam will be a facility instrument, available at first light and operating in the telluric windows at wavelengths of 350, 450, and 850 μm. In order to trace the large curvature of the CCAT focal plane, and to suit the available instrument space, SWCam is divided into seven sub-cameras, each configured to a particular telluric window. A fully refractive optical design in each sub-camera will produce diffraction-limited images. The material of choice for the optical elements is silicon, due to its excellent transmission in the submillimeter and its high index of refraction, enabling thin lenses of a given power. The cryostat’s vacuum windows double as the sub-cameras’ field lenses and are ~30 cm in diameter. The other lenses are mounted at 4 K. The sub-cameras will share a single cryostat providing thermal intercepts at 80, 15, 4, 1 and 0.1 K, with cooling provided by pulse tube cryocoolers and a dilution refrigerator. The use of the intermediate temperature stage at 15 K minimizes the load at 4 K and reduces operating costs. We discuss our design requirements, specifications, key elements and expected performance of the optical, thermal and mechanical design for the short wavelength camera for CCAT.
Low-loss lenses are required for submillimeter astronomical applications, such as instrumentation for CCAT, a 25 m diameter telescope to be built at an elevation of 18,400 ft in Chile. Silicon is a leading candidate for dielectric lenses due to its low transmission loss and high index of refraction; however, the latter can lead to large reflection losses. Additionally, large diameter lenses (up to 40 cm), with substantial curvature present a challenge for fabrication of antireflection coatings. Three anti-reflection coatings are considered: a deposited dielectric coating of Parylene C, fine mesh structures cut with a dicing saw, and thin etched silicon layers (fabricated with deep reactive ion etching) for bonding to lenses. Modeling, laboratory measurements, and practicalities of fabrication for the three coatings are presented and compared. Measurements of the Parylene C anti-reflection coating were found to be consistent with previous studies and can be expected to result in a 6% transmission loss for each interface from 0.787 to 0.908 THz. The thin etched silicon layers and fine mesh structure anti-reflection coatings were designed and fabricated on test silicon wafers and found to have reflection losses less than 1% at each interface from 0.787 to 0.908 THz. The thin etched silicon layers are our preferred method because of high transmission efficiency while having an intrinsically faster fabrication time than fine structures cut with dicing saws, though much work remains to adapt the etched approach to curved surfaces and optics < 4" in diameter unlike the diced coatings.
We have designed and evaluated a Miniature Cryogenic Scanning Fabry-Perot (MCSF) interferometer which can be
inserted into the optical path of a mid-IR camera to observe fine structure lines in the 25-40 μm wavelength regime. The
MCSF uses free standing metal meshes as its filters and can scan over a length of ~2 mm. The short wavelength range in
which the MCSF will be used requires very tight fabrication tolerances to maintain the parallelism of the meshes to
within 0.15 μm and to obviate the need for dynamic parallelizing adjusters. A monolithic notch flexure design delivers
these properties and minimizes the number of moving parts, maximizing reliability. The scanning mechanism includes a
cryogenic stepper motor that drives a miniature fine-adjustment screw via a worm gear assembly. This allows for a step
resolution of 1 step ~ 14 nm when operating in full step mode. Finite Element Analysis of the MCSF’s monolithic
flexure guided the design and confirmed that the MCSF will remain within required limits over the course of operation.
We developed the MCSF for use in the mid-IR camera FORCAST on the 2.5 meter SOFIA telescope.
We have built a new long-slit grating spectrometer (ZEUS-2) for observations in the submillimeter wavelength regime (200-650 μm). ZEUS-2 is optimized for observations of redshifted far-infrared spectral lines from galaxies in the early Universe. The spectrometer employs three transition-edge sensed bolometer arrays, allowing for simultaneous observations of multiple lines in several telluric windows. Here we will discuss the optical, mechanical, and thermal requirements of ZEUS-2 and their subsequent design and performance. The entire instrument is cooled using a pulse tube cryocooler and an adiabatic demagnetization refrigerator. The cryogen-free approach enables remote control of the cooling system and allows for deployment of ZEUS-2 to telescope sites where access is limited. The compact and lightweight design is also within the size and weight constraints of several submm telescopes, making ZEUS-2 deployable at a variety of sites. ZEUS-2 completed a successful engineering run at the CSO on Mauna Kea in May 2012, and we plan to have our science-grade array system deployed on the APEX telescope in Chile for a science run in the fall of 2012.
We have recently commissioned the 2nd generation redshift(z) and Early Universe Spectrometer (ZEUS-2) at the Caltech
Submillimeter Observatory. ZEUS-2 is a long-slit grating spectrometer (R~1000) for observations in the submillimeter
wavelength regime that is optimized for observations of redshifted far-infrared spectral lines from galaxies in the early
universe. Here we report on the design and first light performance of the first TES bolometer array installed in ZEUS-2.
This array features 280 pixels each 1.26 mm square and arranged to provide ~35 pixel spectra at ~8 spatial positions on
the sky. A 1/4-wavelength back short of 100 micron and gold mesh absorber matching the impedance of free space
provides near 90% quantum efficiency for the 350 and 450 micron telluric windows. Array readout is done using SQUID
multiplexers and the Multichannel Electronics. We will also report on the progress to install two additional arrays tuned
to provide similar performance across the remaining telluric windows between 200-850 microns.
ZEUS-2, the second generation (z)Redshift and Early Universe Spectrometer, like its predecessor is a moderate
resolution (R~1000) long-slit, echelle grating spectrometer optimized for the detection of faint, broad lines from distant
galaxies. It is designed for studying star-formation across cosmic time. ZEUS-2 employs three TES bolometer arrays
(555 pixels total) to deliver simultaneous, multi-beam spectra in up to 4 submillimeter windows. The NIST Boulder-built
arrays operate at ~100mK and are readout via SQUID multiplexers and the Multi-Channel Electronics from the
University of British Columbia. The instrument is cooled via a pulse-tube cooler and two-stage ADR. Various filter
configurations give ZEUS-2 access to 7 different telluric windows from 200 to 850 micron enabling the simultaneous
mapping of lines from extended sources or the simultaneous detection of the 158 micron [CII] line and the [NII] 122 or
205 micron lines from z = 1-2 galaxies. ZEUS-2 is designed for use on the CSO, APEX and possibly JCMT.
We report the performance of Triplespec from commissioning observations on the 200-inch Hale Telescope
at Palomar Observatory. Triplespec is one of a set of three near-infrared, cross-dispersed spectrographs
covering wavelengths from 1 - 2.4 microns simultaneously at a resolution of ~2700. At Palomar, Triplespec
uses a 1×30 arcsecond slit. Triplespec will be used for a variety of scientific observations, including
moderate to high redshift galaxies, star formation, and low mass stars and brown dwarfs. When used in
conjunction with an externally dispersed interferometer, Triplespec will also detect and characterize
extrasolar planets.
The TEDI (TripleSpec Exoplanet Discovery Instrument) will be the first instrument fielded specifically for finding low-mass
stellar companions. The instrument is a near infra-red interferometric spectrometer used as a radial velocimeter.
TEDI joins Externally Dispersed Interferometery (EDI) with an efficient, medium-resolution, near IR (0.9 - 2.4 micron)
echelle spectrometer, TripleSpec, at the Palomar 200 telescope. We describe the instrument and its radial velocimetry
demonstration program to observe cool stars.
The redshift (z) and Early Universe Spectrometer (ZEUS) is an echelle grating spectrometer designed to study the history of star formation in the Universe from about 2 billion years after the Big Bang to the present by observing submillimeter and far-infrared spectral lines from distant dusty galaxies. ZEUS has moderate resolving power (R~1000), and large spectral coverage so as to optimize extragalactic point source sensitivity in the telluric submillimeter (350, 450, and 610 um) windows. When completed, ZEUS will have a 4 x 64-element array of TES PUD bolometers delivering an instantaneous 64-element spectrum for each of 4 spatial positions on the sky. ZEUS is designed for use on the 15 m JCMT telescope on Mauna Kea. We also plan to use it on the 12 m APEX telescope at the Chajnantor site in northern Chile. Our scientific goals include (1) investigating star formation in the early Universe by measuring the redshifted fine-structure lines from distant (z ~1 to 4) (proto-) galaxies, (2) measuring the redshifts of optically obscured submillimeter galaxies by detecting their bright 158 um [CII] line emission, and (3) investigating the properties of starburst and ultraluminous galaxies in the local Universe by observing their [CI] and mid-J CO rotational line emission.
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