The Muztage-Ata One-point-nine-three-meter Synergy Telescope (MOST) is a novel equatorial telescope currently being constructed in China. Spectroscopy of bi-Channel with UlTra-wide band and high flUx for MOST (SCUTUM) serves as one of the first-light instruments and adopts a modified FOSC type design with two channels. The design incorporates a shared catadioptric collimator followed by separate refraction cameras in each channel, where in between filters and grisms are inserted into the optical path through two rotating wheel units. The instrument converts the F/8 beam from the telescope to a nearly F/4.3 beam. The spectroscopy of SCUTUM can be performed in the wavelength range 310-1000nm in one exposure, offering various choices of grisms and slits with resolution ranging from 250 to 7500. The theoretical monochromatic RMS spot sizes are expected to be between 0.04′′ and 0.26′′. To optimize total throughput, SCUTUM employs high-efficiency optical elements, coatings, and sensitivity-enhanced detectors within its operational band. The overall transmission from the collimator to the detector is anticipated to exceed 20% at 330nm and surpass 40% at wavelengths above 355nm when operating in R≤3000 mode. The designed weight of this instrument amounts to approximately 280kg. The instrument is currently planned to be assembled in the Institute laboratory in September and to be commissioned on MOST in 2025.
The Next Generation Palomar Spectrograph (NGPS) is a high-throughput medium-resolution broadband spectrograph developed for the Hale telescope. It consists of four spectroscopic channels, where ultraviolet channel covers the region [310-436] nm and delivers a resolving power about 4000 with 0.5 arcsec focal plane sampling at the center wavelength 370 nm. The spectrometer operates in the dome under wide temperature range from -10 degrees to 30 degrees, and temperature variation is around 3 degrees per night. One of the goals of NGPS is to achieve excellent image quality and extremely high stability over a wide temperature range. It is indeed a challenge due to limited selection of optical materials in the ultraviolet waveband. This article introduces different camera concept for the ultraviolet channel of NGPS. The Schmidt reflective camera was finally adopted after evaluation of their performance.
We present the current design of WFOS, a wide-field UV/optical (0.31-1.0 µm) imaging spectrograph planned for first-light on the TMT International Observatory 30 m telescope. WFOS is optimized for high sensitivity across the entire optical waveband for low-to-moderate resolution (R ∼ 1500-5000) long-slit and multi-slit spectroscopy of very faint targets over a contiguous field of view of 8′ .3×3 ′ .0 at the f/15 Nasmyth focus of TMT. A key design goal for WFOS is stability and repeatability in all observing modes, made possible by its gravity-invariant opto-mechanical structure, with a vertical rotation axis and all reconfigurable components moving only in planes defined by tiered optical benches parallel to the Nasmyth platform. WFOS’s optics include a linear ADC correcting a 9′ diameter field, including both the science FoV and 4 patrolling acquisition, guiding, and wavefront sensing camera systems; a novel 2-mirror reflective collimator allowing the science FoV to be centered on the telescope optical axis; a dichroic beamsplitter dividing the collimated beam into 2 wavelength-optimized spectrometer channels (blue: 0.31-0.56 µm; red: 0.54-1.04 µm); selectable transmissive dispersers (VPH and/or VBG) with remotely configurable grating tilt (angle of incidence) and camera articulation that enable optimization of diffraction efficiency and wavelength coverage in each channel; all-refractive, wavelength-optimized f/2 spectrograph cameras, and UV/blue and red-optimized detector systems. The predicted instrumental through put of WFOS for spectroscopy averages > 56% over the full 0.31-1 µm range, from the ADC to the detector. When combined with the 30 m TMT aperture, WFOS will realize a factor of ∼20 gain in sensitivity compared to the current state of the art on 8-10 m-class telescopes.
A kind of swing micro-mirror structure for gravitational wave observatory in space is presented in this paper. Harmonic response analysis and random vibration analysis are carried out. The analysis results show that the mechanism is able to bear the effect of the load during launch and has high dynamic stiffness.
IMSP is the versatile first-light instrument under construction for the 4m telescope in China. The special feature of IMSP is the multimode operation modes and high-efficiency. Direct imaging mode is designed to work in a synchronous multi-color bands covering from 360 to 1700 nm using two dichroic mirrors with a 3’x3’ field of view (FOV). Long-slit spectrograph mode supports two spectral resolutions operation modes (R=1000 and 5000) via different combination of Volume Phase Holographic Prisms to cover the whole spectrum in visible. High resolution spectrograph mode (R=30000-60000) with wavelength range from 380 to 800 nm is reserved using fiber link system connected from Nasmyth foci to the enviroment controled room. The IMSP is planned to strart commssion at the end of 2021. In this paper, the lastest status of IMSP development will be given, including the final optical design and the integration of each sub-system.
TMT’s wide field optical spectrograph is a multi-object, first-light instrument with broad continuous wavelength coverage (0.310 – 1.0 m) at a moderate spectral resolution of R = 5000. The international WFOS design team has recently completed the downselect of two design approaches: a slicer-based monolithic architecture and a fiber-based modular concept. We present here the end-to-end conceptual design for the fiber-based optical spectrograph. Included are the front-end focal reduction optics for coupling light into the fibers, the spectrograph collimator and camera optics, and the dispersive architecture for each color channel. The highly multiplexed fiber-WFOS presents a unique design challenge in keeping costs for the modular spectrographs low while maintaining performance gains afforded by the TMT, and in particular the TMT plus ground-layer adaptive optics (GLAO). A full performance analysis including predicted spectral resolution and throughput is presented for the design.
The Wide Field Optical Spectrometer (WFOS) is a seeing limited, multi-object spectrograph and first light instrument for the Thirty Meter Telescope (TMT) scheduled for first observations in 2027. The spectrograph will deliver a minimum resolution of R~5,000 over a simultaneous wavelength range of 310 nm to 1,000 nm with a multiplexing goal of between 20 and 700 targets. The WFOS team consisting of partners in China, India, Japan, and the United States has completed a trade study of two competing concepts intended to meet the design requirements derived from the WFOS detailed science case. The first of these design concepts is a traditional slit mask instrument capable of delivering R~1,000 for up to 100 simultaneous targets using 1 x 7 arc second slits, and a novel focal plane slicing method for R~5,000 on up to 20 simultaneous targets can be achieved by reformatting the 1 arc-second wide slits into three 0.3 arc-second slits projected next to each other in the spatial direction. The second concept under consideration is a highly multiplexed fiber based system utilizing a robotic fiber positioning system at the focal plane containing 700 individual collectors, and a cluster of up to 12 replicated spectrographs with a minimum resolution of R~5,000 over the full pass band. Each collecting element will contain a bundle of 19 fibers coupled to micro-lens arrays that allow for contiguous coverage of targets and adaptation of the f/15 telescope beam to f/3.2 for feeding the fiber system. This report describes the baseline WFOS design, provides an overview of the two trade study concepts, and the process used to down-select between the two options. Also included is a risk assessment regarding the known technical challenges in the selected design concept.
The LAMOST completed its first five years of operation in June 2017, and 9 million low resolution spectra are obtained. The spectrographs have been upgraded in 2017, and the resolution can reach up to 7500(with 2/3 slit). In the midresolution mode, the wavelength can cover 495nm-535nm(blue band) and 630nm-680nm(red band). The LAMOST will carry out the middle resolution spectroscopic survey in September 2018, and 3 million middle resolution spectra will be obtained. This paper describes the requirements, optical design and mechanical design of the LAMOST-MRS (the LAMOST middle resolution spectrograph)
The design and performance of a three-channel image and long-slit spectrograph for the new 4-m telescope in China are described. The direct imaging covers a 3 arcmin by 3 arcmin field of view and a large wavelength range 370-1,600 nm, it has two optical channels and one near infrared channel with different filters. The spectrograph with a long slit is to provide two observing modes including the following spectral resolutions: R1000 and R5000. For dispersing optical elements it use volume-phased holographic grisms (VPHG) at each of the spectroscopic modes to simplify the camera system. The low resolution mode (R1000) is provided by consecutive observations with the spectral ranges: 360-860 nm, however it adopts only one VPHG for the first light. The spectral range of medium resolution mode (R5000) is 460- 750nm, it is constrained with the use of a 4k × 4k CCD detector of 15 μm pixel size. Peak efficient in the spectrograph are achieved to be higher than 50% in different resolution mode.
Design a best light-weighting collimator to conform to the requirements of opto-mechanical design. Good surface accuracy is our aim, based on a less mass. The ratio of diameter to thickness, the type, size and thickness of pocket, the thickness of the mirror, the support size and position, the thickness of the wall and so on is concerned. Besides, comparing two kinds material is also discussed. In addition, we consider the situation that the orientation vary in support plane. Use the orthogonal table to analyze these elements, and find the better methods. According to the analysis in ANSYS, the collimator mass can reduce to 103 kg, below 159 kg; the ratio of light-weight can reach 70%; the peak-valley value is below 100 nm, that meets the request of below 200 nm.
High accuracy radial velocity measurement isn’t only one of the most important methods for detecting earth-like
Exoplanets, but also one of the main developing fields of astronomical observation technologies in future. Externally
dispersed interferometry (EDI) generates a kind of particular interference spectrum through combining a fixed-delay
interferometer with a medium-resolution spectrograph. It effectively enhances radial velocity measuring accuracy by
several times. Another further study on multi-delay interferometry was gradually developed after observation success
with only a fixed-delay, and its relative instrumentation makes more impressive performance in near Infrared band.
Multi-delay is capable of giving wider coverage from low to high frequency in Fourier field so that gives a higher
accuracy in radial velocity measurement. To study on this new technology and verify its feasibility at Guo Shoujing
telescope (LAMOST), an experimental instrumentation with single fixed-delay named MESSI has been built and tested
at our lab. Another experimental study on multi-delay spectral interferometry given here is being done as well. Basically,
this multi-delay experimental system is designed in according to the similar instrument named TEDI at Palomar
observatory and the preliminary test result of MESSI. Due to existence of LAMOST spectrograph at lab, a multi-delay
interferometer design actually dominates our work. It’s generally composed of three parts, respectively science optics,
phase-stabilizing optics and delay-calibrating optics. To switch different fixed delays smoothly during observation, the
delay-calibrating optics is possibly useful to get high repeatability during switching motion through polychromatic
interferometry. Although this metrology is based on white light interferometry in theory, it’s different that integrates all
of interference signals independently obtained by different monochromatic light in order to avoid dispersion error caused
by broad band in big optical path difference (OPD).
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