Astronomy-grade cameras with robust performance and heritage in the space environment have long been costly, substantially limiting capacity for space-based astronomy and creating a resource barrier to access. Additionally, ultraviolet observations have historically been limited by the low-sensitivity of most sensors in this wavelength range. The LUVCam program is designed to address both issues, providing a high-performance, low-cost, UV/optical camera system sufficiently capable to support a wide-array of space-based astronomy missions. LUVCam features a large format, low-noise, large pixel, and high quantum efficiency, commercial-off-the-shelf backside illuminated CMOS sensor, packaged with custom built readout electronics and thermomechanical structure. LUVCam is ITAR-free, and cheap to fabricate, opening up new opportunities for access to space telescopes. LUVCam has reached TRL 6, and has passed qualification testing for operation in low-earth orbit, with competitive performance from 200-900 nm. LUVCam is manifested for multiple near-term orbital missions, including a technology demonstration CubeSat, and a UV transient astronomy SmallSat.
We present an optical design of a slicer-based integral-field spectrograph for GIRMOS. The performance budget of subsystems is discussed, and then the performance of the end-to-end design is evaluated to ensure compliance with overall requirements.
The MMT Adaptive optics exoPlanet characterization System (MAPS) is an exoplanet characterization program that encompasses instrument development, observational science, and education. The instrument we are developing for the 6.5m MMT observatory is multi-faceted, including a refurbished 336-actuator adaptive secondary mirror (ASM); two pyramid wavefront sensors (PyWFS's); a 1-kHz adaptive optics (AO) control loop; a high-resolution and long-wavelength upgrade to the Arizona infraRed Imager and Echelle Spectrograph (ARIES); and a new-AO-optimized upgrade to the MMT-sensitive polarimeter (MMT-Pol). With the completed MAPS instrument, we will execute a 60-night science program to characterize the atmospheric composition and dynamics of ~50-100 planets around other stars. The project is approaching first light, anticipated for Summer/Fall of 2022. With the electrical and optical tests complete and passing the review milestone for the ASM’s development, it is currently being tuned. The PyWFS's are being built and integrated in their respective labs: the visible-light PyWFS at the University of Arizona (UA), and the infrared PyWFS at the University of Toronto (UT). The top-level AO control software is being developed at UA, with an on-sky calibration algorithm being developed at UT. ARIES development continues at UA, and MMT-Pol development is at the University of Minnesota. The science and education programs are in planning and preparation. We will present the design and development of the entire MAPS instrument and project, including an overview of lab results and next steps.
The MMTO Adaptive optics exoPlanet characterization System (MAPS) is an ongoing upgrade to the 6.5-meter MMT Observatory on Mount Hopkins in Arizona. MAPS includes an upgraded adaptive secondary mirror (ASM), upgrades to the ARIES spectrograph, and a new AO system containing both an optical and near-infrared (NIR; 0.9-1.8 μm) pyramid wavefront sensor (PyWFS). The NIR PyWFS will utilize an IR-optimized double pyramid coupled with a SAPHIRA detector: a low-read noise electron Avalanche Photodiode (eAPD) array. This NIR PyWFS will improve MAPS’s sky coverage by an order of magnitude by allowing redder guide stars (e.g. K & M-dwarfs or highly obscured stars in the Galactic plane) to be used. To date, the custom designed cryogenic SAPHIRA camera has been fully characterized and can reach sub-electron read noise at high avalanche gain. In order to test the performance of the camera in a closed-loop environment prior to delivery to the observatory, an AO testbed was designed and constructed. In addition to testing the SAPHIRA’s performance, the testbed will be used to test and further develop the proposed on-sky calibration procedure for MMTO’s ASM. We will report on the anticipated performance improvements from our NIR PyWFS, the SAPHIRA’s closed-loop performance on our testbed, and the status of our ASM calibration procedure.
Grating-based spectrographs suffer from smile and keystone distortion, which are problematic for hyperspectral data applications. Due to this, spectral lines will appear curved and roughly parabola-shaped. Smile and keystone need to be measured and corrected for accurate spectral and spatial calibration. In this paper, we present a novel method to accurately identify and correct curved spectral lines in an image of a spectrum, using a clustering algorithm we developed specifically for grating spectrographs, inspired by K-means clustering. Our algorithm will be used for calibrating a multi-object spectrograph (MOS) based on a digital micromirror device (DMD). For each spectral line in a spectrum image, our algorithm automatically finds the equation of the parabola which models it. Firstly, the positions of spectral peaks are identified by fitting Gaussian functions to the spectrum image. The peaks are then grouped into a given number of parabola-shaped clusters: each peak is iteratively assigned to the nearest parabola-shaped cluster, such that the orthogonal distances from the parabola are minimized. Smile can then be measured from the parabolas, and keystone as well if a marked slit is used. Our method has been verified on real-world data from a long-slit grating spectrograph with sub-pixel error, and on simulated data from a DMD-based MOS. Compared to traditional approaches, our method can measure distortions automatically and accurately while making use of more spectral lines. With a precise model and measurement of distortion, a corrected hyperspectral data cube can be created, which can be applied for real-time data processing.
The multi-object spectrograph (MOS) has been the benchmark for the current generation of astronomical spectrographs, valued for its ability to acquire the spectra of hundreds of objects simultaneously. In the last two decades, the digital micromirror device (DMD) has shown potential in becoming the central component of the MOS, being used as a programmable slit array. We have designed a seeing-limited DMD-based MOS covering a spectral range of 0.4 to 0.7 μm, with a field of view (FOV) of 10.5’ ×13.98’ and a spectral resolution of R ∼ 1000. This DMD-MOS employs all-spherical refractive optics, and a volume phase holographic (VPH) grism as the dispersive element for high throughput. In this paper, we present the optical design and optimization process of this DMD-MOS, as well as a preliminary wavelength calibration procedure for hyperspectral data reduction. Using simulated data of the DMD-MOS, a procedure was developed to measure hyperspectral imaging distortion and to construct pixel-to-wavelength mappings on the detector. An investigation into the relationships between DMD micromirrors and detector pixels was conducted. This DMD-MOS will be placed on a 0.5 m diameter telescope as an exploratory study for future DMD-based MOS systems.
The Gemini Infrared Multi-Object Spectrograph (GIRMOS) is an adaptive optics-fed multi-object integral field spectrograph with a parallel imaging capability. The instrument is composed of four separate but identical spectrographs, giving it the ability to observe four objects simultaneously. Each slicer-based integral field spectrograph offers capabilities over three different fields of view (FOVs) and spatial sampling scales: 1.0”x1.0”, 2.1”x2.1” and 4.2”x4.2” out of a 2’ diameter field-of-regard, associated with samplings of 25 mas (mode 1), 50 mas (mode 2) and 100 mas (mode 3), respectively. Spectral resolutions of R=3000 and R=8000 are available in Y, J, H and K bands from 0.95 to 2.4 µm. To achieve spatial sampling requirements, the integral field unit (IFU) is designed as a 42-slices advanced image slicer. In this paper, the preliminary optical design and performances of the GIRMOS image slicer are presented, as well as the first diamond-turned prototype. The design is optimized for both optical performance and manufacturability by opting for a staircase arrangement that delivers diffraction-limited image quality while minimizing slice width losses due to diamond turning. Stray light and slice diffraction effects are also taken into account and reported.
We present the detailed performance of the preliminary end-to-end optical design of GIRMOS that is designed to take advantage of the multi-object adaptive optics corrected field at the Gemini North telescope. GIRMOS’s optical design consists of object selection pick-offs, adaptive optics, and four identical Integral-Field Spectrographs (IFSes), which employ image slicers to arrange the integral field along a slit. Each IFS can image the individual FOV of 1.0x1.0”, 2.0x2.0”, 4.0x4.0” over a 2’ diameter field-of-regard at different spatial sampling. The pick-offs can also be configured in close-packed arrangement to image a single field. Spectral resolutions of R~3000 and 8000 are available in 0.95-2.4 μm.
The Gemini Infrared Multi-Object Spectrograph (GIRMOS) is an adaptive optics-fed multi-object integral field spectrograph with a parallel imaging capability. GIRMOS implements multi-object adaptive optics (MOAO) for each of its spectrographs by taking advantage of the infrastructure offered by Gemini upcoming wide-field AO facility at Manua Kea. The instrument offers the ability to observe four objects simultaneously within the Gemini-North AO (GNAO) system’s field-of-regard or a single object by tiling the four fields that feed light to four separate spectrographs. Each integral field spectrograph has an independent set of selectable spatial scales (0.025", 0.05", and 0.1" /spaxel) and spectral resolution (R 3,000 and 8,000) within an operating band of 0.95 2.4µm. These spatial scales correspond to indvidual spectrograph fields of view of 1x1", 2X2" , and 4x4", respectively. GIRMOS’s imager offers Nyquist sampling of the diffraction limit in H-band over a 85x85" imaging field. The imager can function in a parallel data acquisition mode with just minor vignetting spectroscopic pick- offs when they are deployed.
MAPS, MMT Adaptive optics exoPlanet characterization System, is the upgrade of the adaptive optics system for 6.5-m MMT. It is an NSF MSIP-funded project that includes developing an adaptive-secondary mirror, visible and near-infrared pyramid wavefront sensors, and the upgrade of Arizona infrared imager and echelle spectrograph (ARIES) and MMT High Precision Imaging Polarimeter (MMTPol) science cameras. This paper will present the design and development of the visible pyramid wavefront sensor, VPWFS. It consists of an acquisition camera, a fast-steering tip-tilt modulation mirror, a pyramid, a pupil imaging triplet lens, and a low noise and high-speed frame rate based CCID75 camera. We will report on hardware and software, present the laboratory characterization results of individual subsystems, and outline the on-sky commissioning plan.
In this paper we discuss the mechanical design of the GIRMOS Cryostat. GIRMOS is an adaptive optics fed multi-object Integral-Field Spectrograph with a parallel imaging capability and will be installed at the Gemini North Observatory. This instrument includes four separate identical spectrograph channels arranged symmetrically around the central axis of the instrument which provide it its multiplexing capability. Each spectrograph channel starts off at the object selection mechanism. The object selection mechanism contains four motorized fold mirror assemblies which scan the incoming light from the telescope to look at four separate objects simultaneously or combine their efforts to look at a single object in a tiled mode. Each of the four individual beams from the object selection system are then directed into the instrument dewar via separate entrance windows. Within the dewar each IFS beam moves through an anamorphic relay, an optical image slicer assembly and eventually makes it to a Spectrograph unit. All of these assemblies are located on a single cold bench within the dewar. The instrument imager is located along the central axis of the dewar and is housed in the cold bench as well. In this paper we will provide some details regarding the Cryostat design, the mechanical packaging of the IFS and imager along with some of the thermal load mitigation techniques employed. We will also discuss some key performance requirements that were expected from the Cryostat and the design choices we made in order to achieve them.
We discuss the preliminary end-to-end optical design of an infrared multi-object integral-field spectrograph (GIRMOS) that is designed to take advantage of the multi-object adaptive optics corrected field at the Gemini telescope. GIRMOS’s optical design consists of object selection pick-offs, an adaptive optics (AO) system, and four identical Integral-Field Spectrographs (IFSes), which employ an image slicer to arrange the integral field along a slit. Each IFS can pick off the individual FOV of 1.0x1.0”, 2.0x2.0”, 4.0x4.0” over a 2’ diameter field-of-regard, at a spatial sampling of 25mas, 50mas, and 100mas, respectively. The pick-offs can also be configured in close-packed arrangement to image a single field. Spectral resolutions of R~3000 and 8000 are available in Y, J, H, and K-bands from 0.95 to 2.4μm.
We are upgrading and refurbishing the first-generation adaptive-secondary mirror (ASM)-based AO system on the 6.5-m MMT in Arizona, in an NSF MSIP-funded program that will create a unique facility specialized for exoplanet characterization. This update includes a third-generation ASM with embedded electronics for low power consumption, two pyramid wavefront sensors (optical and near-IR), and an upgraded ARIES science camera for high-resolution spectroscopy (HRS) from 1-5 μm and MMT-POL science camera for sensitive polarization mapping. Digital electronics have been incorporated into each of the 336 actuators, simplifying hub-level electronics and reducing the total power to 300 W, down from 1800 W in the legacy system — reducing cooling requirements from active coolant to passive ambient cooling. An improved internal control law allows for electronic damping and a faster response. The dual pyramid wavefront sensors allow for a choice between optical or IR wavefront sensing depending on guide star magnitude, color, and extinction. The HRS upgrade to ARIES enables crosscorrelation of molecular templates to extract atmospheric parameters of exoplanets. The combination of these upgrades creates a workhorse instrument for exoplanet characterization via AO and HRS to separate planets from their host stars, with broad wavelength coverage and polarization to probe a range of molecular species in exoplanet atmospheres.
The Gemini Infrared Multi-Object Spectrograph (GIRMOS) is a powerful new instrument being built to facility- class standards for the Gemini telescope. It takes advantage of the latest developments in adaptive optics and integral field spectrographs. GIRMOS will carry out simultaneous high-angular-resolution, spatially-resolved infrared (1 - 2.4 µm) spectroscopy of four objects within a two-arcminute field-of-regard by taking advantage of multi-object adaptive optics. This capability does not currently exist anywhere in the world and therefore offers significant scientific gains over a very broad range of topics in astronomical research. For example, current programs for high redshift galaxies are pushing the limits of what is possible with infrared spectroscopy at 8 -10- meter class facilities by requiring up to several nights of observing time per target. Therefore, the observation of multiple objects simultaneously with adaptive optics is absolutely necessary to make effective use of telescope time and obtain statistically significant samples for high redshift science. With an expected commissioning date of 2023, GIRMOS’s capabilities will also make it a key followup instrument for the James Webb Space Telescope when it is launched in 2021, as well as a true scientific and technical pathfinder for future Thirty Meter Telescope (TMT) multi-object spectroscopic instrumentation. In this paper, we will present an overview of this instrument’s capabilities and overall architecture. We also highlight how this instrument lays the ground work for a future TMT early-light instrument.
KEYWORDS: Adaptive optics, Wavefront sensors, Prisms, Stars, Wavefronts, Near infrared, Monte Carlo methods, Modulation, Electron multiplying charge coupled devices, Sensors
There are long existing limitations of the sky coverage of astronomical Adaptive Optics (AO) systems that use natural guide stars (NGSs) as reference sources. In this work, we present numerical simulations and lab test results of an optical NGS pyramid wavefront sensor (PWFS) for the MMT AO system. The potential increase of sky coverage benefits from the gain in sensitivity of the PWFS in a closed-loop NIR AO system compared with the optical Shack-Hartmann wavefront sensor (SHWFS). The upgraded MMT AO WFS system will use IR avalanche photodiode (APD) array with extremely low readout noise (at sub-electron level), run at a high frame rate (over 1kHz), and cover the wavelength range from 0.85-1.8 μm. This upgraded system will access a larger portion of the sky by looking at fainter, redder reference stars. We use ”yao” simulation to show the expected limiting magnitude gain of NIR PWFS compared with the existing optical SHWFS. The sky coverage will increase by 11 times at the Galactic plane and by 6 times at the North Galactic Pole when compared to traditional optical WFSs. This novel WFS will also enable observations of the dust obscured plane of the Galaxy, where the optical light of most stars is more extincted. We demonstrate the basic lab test with a set of double roof prisms. We evaluate the overall performance of the PWFS on our lab AO bench, present captured micro-pupil images and do wavefront reconstruction. We will upgrade to SAPHIRA and pyramid prism for later lab test. We plan to implement this system at MMT and carry out on-sky tests in Spring 2019.
We discuss the optical design of an infrared multi-object integral-field spectrograph (IRMOS) that is designed to take advantage of the multi-object adaptive optics corrected field at the Gemini telescope. The IRMOS is designed for the Gemini Telescope, so we call this instrument GIRMOS. The GIRMOS has four identical Integral-Field Spectrographs (IFSes), which employ a unique slicer design to arrange the integral field along a slit to obtain two-dimensional spectroscopy. Each IFS can pick off the individual fields of view of 1.0x1.0”, 2.1x2.1”, 4.2x4.2” over a 2’ diameter fieldof- regard, at the spatial sampling scales of 25mas, 50mas, and 100mas, respectively. Spectral resolutions of R~3000 and 8000 are available in J, H, and K-bands from 1.0 to 2.4μm. The primary design constraints are associated with diffractive effects from the grating and spectrograph camera.
We will be upgrading the MMT Observatory’s (MMTO) Adaptive Optics (AO) system with a novel Pyramid Wavefront Sensor (PWFS). Our camera will utilize Leonardo’s SAPHIRA, a low-read-noise electron Avalanche Photodiode (eAPD) array. By observing natural guide stars in the near-infrared, we will improve the sky coverage at the MMTO by an order of magnitude. We have developed a compact cryostat that utilizes Sunpower’s CryoTel MT cryocooler to reduce the SAPHIRA’s dark current and thermal background radiation. Our camera’s cooling performance and cryocooler induced vibrations have been quantified and the results are presented here. Upon characterizing the laboratory performance of our camera at various reverse-bias voltages, this instrument will be integrated with MMTO’s adaptive optics system. The successful implementation of this wavefront sensor will pave the way for future applications using this technology in AO systems of extremely large telescopes.
We report the optical design of an infrared (0.85-1.8 μm) pyramid wavefront sensor (IRPWFS) that is designed for the 6.5m MMT on telescope adaptive optics system using the latest developments in low-noise infrared avalanche photodiode arrays. The comparison between the pyramid and the double-roof prism based wavefront sensors and the evaluation of their micro pupils’ quality are presented. According to our analysis, the use of two double-roof prisms with achromatic materials produces the competitive performance when compared to the traditional pyramid prism, which is difficult to manufacture. The final micro pupils on the image plane have the residual errors of pupil position, chromatism, and distortion within 1/10 pixel over the 2×2 arcsecond field of view, which meet the original design goals.
We discuss the optical design of an infrared multi-object spectrograph (MOS) concept that is designed to take advantage of the multi-conjugate adaptive optics (MCAO) corrected field at the Gemini South telescope. This design employs a unique, cryogenic MEMS-based focal plane mask to select target objects for spectroscopy by utilizing the Micro-Shutter Array (MSA) technology originally developed for the Near Infrared Spectrometer (NIRSpec) of the James Webb Space Telescope (JWST). The optical design is based on all spherical refractive optics, which serves both imaging and spectroscopic modes across the wavelength range of 0.9−2.5 μm. The optical system consists of a reimaging system, MSA, collimator, volume phase holographic (VPH) grisms, and spectrograph camera optics. The VPH grisms, which are VPH gratings sandwiched between two prisms, provide high dispersing efficiencies, and a set of several VPH grisms provide the broad spectral coverage at high throughputs. The imaging mode is implemented by removing the MSA and the dispersing unit out of the beam. We optimize both the imaging and spectrographic modes simultaneously, while paying special attention to the performance of the pupil imaging at the cold stop. Our current design provides a 1' ♦ 1' and a 0.5' ♦ 1' field of views for imaging and spectroscopic modes, respectively, on a 2048 × 2048 pixel HAWAII-2RG detector array. The spectrograph’s slit width and spectral resolving power are 0.18'' and 3,000, respectively, and spectra of up to 100 objects can be obtained simultaneously. We present the overall results of simulated performance using optical model we designed.
The Rapid Transient Surveyor (RTS) is a proposed rapid-response, high-cadence adaptive optics (AO) facility for the UH 2.2-m telescope on Maunakea. RTS will uniquely address the need for high-acuity and sensitive near-infrared spectral follow-up observations of tens of thousands of objects in mere months by combining an excellent observing site, unmatched robotic observational efficiency, and an AO system that significantly increases both sensitivity and spatial resolving power. We will initially use RTS to obtain the infrared spectra of ∼4,000 Type Ia supernovae identified by the Asteroid Terrestrial-Impact Last Alert System over a two year period that will be crucial to precisely measuring distances and mapping the distribution of dark matter in the z < 0.1 universe. RTS will comprise an upgraded version of the Robo-AO laser AO system and will respond quickly to target-of-opportunity events, minimizing the time between discovery and characterization. RTS will acquire simultaneous-multicolor images with an acuity of 0.07–0.10" across the entire visible spectrum (20% i′-band Strehl in median conditions) and <0.16" in the near infrared, and will detect companions at 0.5" at contrast ratio of ∼500. The system will include a high-efficiency prism integral field unit spectrograph: R = 70-140 over a total bandpass of 840–1830nm with an 8.7" by 6.0" field of view (0.15" spaxels). The AO correction boosts the infrared point-source sensitivity of the spectrograph against the sky background by a factor of seven for faint targets, giving the UH 2.2-m the H-band sensitivity of a 5.7-m telescope without AO.
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.
Maximizing the grating efficiency is a key goal for the first light instrument IRIS (Infrared Imaging Spectrograph)
currently being designed to sample the diffraction limit of the TMT (Thirty Meter Telescope). Volume Phase
Holographic (VPH) gratings have been shown to offer extremely high efficiencies that approach 100% for high line
frequencies (i.e., 600 to 6000l/mm), which has been applicable for astronomical optical spectrographs. However, VPH
gratings have been less exploited in the near-infrared, particularly for gratings that have lower line frequencies. Given
their potential to offer high throughputs and low scattered light, VPH gratings are being explored for IRIS as a potential
dispersing element in the spectrograph. Our team has procured near-infrared gratings from two separate vendors. We
have two gratings with the specifications needed for IRIS current design: 1.51-1.82μm (H-band) to produce a spectral
resolution of 4000 and 1.19-1.37μm (J-band) to produce a spectral resolution of 8000. The center wavelengths for each
grating are 1.629μm and 1.27μm, and the groove densities are 177l/mm and 440l/mm for H-band R=4000 and J-band
R=8000, respectively. We directly measure the efficiencies in the lab and find that the peak efficiencies of these two
types of gratings are quite good with a peak efficiency of ~88% at the Bragg angle in both TM and TE modes at H-band,
and 90.23% in TM mode, 79.91% in TE mode at J-band for the best vendor. We determine the drop in efficiency off the
Bragg angle, with a 20-23% decrease in efficiency at H-band when 2.5° deviation from the Bragg angle, and 25%-28%
decrease at J-band when 5° deviation from the Bragg angle.
We present the efficiency of near-infrared reflective ruled diffraction gratings designed for the InfraRed Imaging
Spectrograph (IRIS). IRIS is a first light, integral field spectrograph and imager for the Thirty Meter Telescope
(TMT) and narrow field infrared adaptive optics system (NFIRAOS). IRIS will operate across the near-infrared
encompassing the ZYJHK bands (~0.84 - 2.4μm) with multiple spectral resolutions. We present our experimental
setup and analysis of the efficiency of selected reflective diffraction gratings. These measurements are used as a
comparison sample against selected candidate Volume Phase Holographic (VPH) gratings (see Chen et al., this
conference). We investigate the efficiencies of five ruled gratings designed for IRIS from two separate vendors.
Three of the gratings accept a bandpass of 1.19-1.37μm (J band) with ideal spectral resolutions of R=4000 and
R=8000, groove densities of 249 and 516 lines/mm, and blaze angles of 9.86° and 20.54° respectively. The other
two gratings accept a bandpass of 1.51-1.82μm (H Band) with an ideal spectral resolution of R=4000, groove
density of 141 lines/mm, and blaze angle of 9.86°. The fraction of flux in each diffraction mode was compared to
both a pure reflection mirror as well as the sum of the flux measured in all observable modes. We measure the
efficiencies off blaze angle for all gratings and the efficiencies between the polarization transverse magnetic (TM)
and transverse electric (TE) states. The peak reflective efficiencies are 98.90 ± 3.36% (TM) and 84.99 ± 2.74%
(TM) for the H-band R=4000 and J-band R=4000 respectively. The peak reflective efficiency for the J-band R=8000
grating is 78.78 ± 2.54% (TE). We find that these ruled gratings do not exhibit a wide dependency on incident angle
within ±3°. Our best-manufactured gratings were found to exhibit a dependency on the polarization state of the
incident beam with a ~10-20% deviation, consistent with the theoretical efficiency predictions. This work will
significantly contribute to the selection of the final grating type and vendor for the IRIS optical system, and are also
pertinent to current and future near-infrared astronomical spectrographs.
The inductively coupled plasma atomic emission spectrometry (ICP-AES) has always attracted great interest and is widely used for routine elemental analysis. While one drawback of this technique is the fact that conventional Czerny- Turner spectrographs in combination with CCD cameras are very limited either in terms of spectral resolution or in terms of simultaneously detectable spectral range. A cross-dispersion system with echelle grating and prism has therefore been developed, and the spectral image is directed by large area charge coupled device (CCD). This configuration meets the needs of atomic emission spectroscopy well, since it has many benefits including high resolving power, spectral coverage, high sensitivity, and high optical throughput. While, because the limitation of the development of detectors, it is difficult to complete wide spectral coverage measurement. Due to the improvements in optical design, this system can detect the wide spectral coverage from 180nm to 900nm simply by rotating the prism, and these two ranges are 180nm- 260nm and 210nm-900nm, with a high resolution 0.009nm@200nm. The detection of different elements only needs to choose appropriate wavelength coverage, thus lots of elements can be analyzed within quite short time. The novel optical design of this instrument is presented in this paper and its merits are discussed. The optical spectral resolution and the precision of wavelength calibration are found to be satisfactory and within design goals. Experiments show that the ICPAES with echelle spectrometer is available to detect multiple elements within a short time correctly, and the wavelength precision is better than 0.01nm.
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