Performance Verification of the EXtreme PREcision Spectrograph
Ryan T. Blackman, Debra A. Fischer, Colby A. Jurgenson, David Sawyer, Tyler M. McCracken, Andrew E. Szymkowiak, Ryan R. Petersburg, J. M. Joel Ong, John M. Brew… 展开作者
Ryan T. Blackman, Debra A. Fischer, Colby A. Jurgenson, David Sawyer, Tyler M. McCracken, Andrew E. Szymkowiak, Ryan R. Petersburg, J. M. Joel Ong, John M. Brewer, Lily L. Zhao, Christopher Leet, Lars A. Buchhave, René Tronsgaard, Joe Llama, Travis Sawyer, Allen B. Davis, Samuel H. C. Cabot, Michael Shao, Russell Trahan, Bijan Nemati, Matteo Genoni, Giorgio Pariani, Marco Riva, Rafael A. Probst, Ronald Holzwarth, Tilo Steinmetz, Paul Fournier, Rafal Pawluczyk
The EXtreme PREcision Spectrograph (EXPRES) is a new Doppler spectrograph designed to reach a radial velocity measurement precision sufficient to detect Earth-like exoplanets orbiting nearby, bright stars. We report on extensive laboratory testing and on-sky observations to quantitatively assess the instrumental radial velocity measurement precision of EXPRES, with a focused discussion of individual terms in the instrument error budget. We find that EXPRES can reach a single-measurement instrument calibration precision better than 10 cm/s, not including photon noise from stellar observations. We also report on the performance of the various environmental, mechanical, and optical subsystems of EXPRES, assessing any contributions to radial velocity error. For atmospheric and telescope related effects, this includes the fast tip-tilt guiding system, atmospheric dispersion compensation, and the chromatic exposure meter. For instrument calibration, this includes the laser frequency comb (LFC), flat-field light source, CCD detector, and effects in the optical fibers. Modal noise is mitigated to a negligible level via a chaotic fiber agitator, which is especially important for wavelength calibration with the LFC. Regarding detector effects, we empirically assess the impact on radial velocity precision due to pixel-position non-uniformities (PPNU) and charge transfer inefficiency (CTI). EXPRES has begun its science survey to discover exoplanets orbiting G-dwarf and K-dwarf stars, in addition to transit spectroscopy and measurements of the Rossiter-McLaughlin effect.
MagAO-X system is a new adaptive optics for the Magellan Clay 6.5m telescope. MagAO-X has been designed to provide extreme adaptive optics (ExAO) performance in the visible. VIS-X is an integral-field spectrograph specifically designed for MagAO-X, and it will cover the optical spectral range (450 - 900 nm) at high-spectral (R=15.000) and high-spatial resolution (7 mas spaxels) over a 0.525 arsecond field of view. VIS-X will be used to observe accreting protoplanets such as PDS70 b and c. End-to-end simulations show that the combination of MagAO-X with VIS-X is 100 times more sensitive to accr…
One source of error in high-precision radial velocity measurements of exoplanet host stars is chromatic change in Earth's atmospheric transmission during observations. Mitigation of this error requires that the photon-weighted barycentric correction be applied as a function of wavelength across the stellar spectrum. We have designed a system for chromatic photon-weighted barycentric corrections with the EXtreme PREcision Spectrograph (EXPRES) and present results from the first year of operations, based on radial velocity measurements of more than $10^3$ high-resolution stellar spectra. For obs…
The EXtreme PREcision Spectrograph (EXPRES) is an environmentally stabilized, fiber-fed, $R=137,500$, optical spectrograph. It was recently commissioned at the 4.3-m Lowell Discovery Telescope (LDT) near Flagstaff, Arizona. The spectrograph was designed with a target radial-velocity (RV) precision of 30$\mathrm{~cm~s^{-1}}$. In addition to instrumental innovations, the EXPRES pipeline, presented here, is the first for an on-sky, optical, fiber-fed spectrograph to employ many novel techniques---including an "extended flat" fiber used for wavelength-dependent quantum efficiency characterization …
EIFIS (Extreme Integral FIeld Spectrograph) is a modular integral field spectrograph, based on image slicers, and makes use of new, large format detectors. The concept is thought to cover the largest possible field of view while producing spectroscopy over the complete optical range (3 000 - 10 000 Å) at a medium resolving power of about 2400. In the optimal concept, each module covers a field of view of 38" x 38" with 0.3" spaxels, which is fed into a double spectrograph with common collimator optics. The blue arm covers the spectral range between 3000 and 5600 Å and the red arm between 5400 …
Extremely precise radial velocity (EPRV) measurements are critical for characterizing nearby terrestrial worlds. EPRV instrument precisions of $σ_{\mathrm{RV}} = 1-10\,\mathrm{cm/s}$ are required to study Earth-analog systems, imposing stringent, sub-mK, thermo-mechanical stability requirements on Doppler spectrograph designs. iLocater is a new, high-resolution ($R=190,500$ median) near infrared (NIR) EPRV spectrograph under construction for the dual 8.4 m diameter Large Binocular Telescope (LBT). The instrument is one of the first to operate in the diffraction-limited regime enabled by the us…
SOXS (Son Of X-Shooter) is a medium resolution (~4500) wide-band (0.35 - 2.0 μm) spectrograph which passed the Final Design Review in 2018. The instrument is planned to be installed at the NTT in La Silla and it is mainly composed by five different optomechanical subsystems (Common Path, NIR spectrograph, UV-VIS spectrograph, Camera, and Calibration) and other mechanical subsystems (Interface flange, Platform, cable corotator, and cooling). It is currently in the procurement and integration phase. In this paper we present the post-FDR modifications in the mechanical design due to the various i…
TOU is an extremely high resolution optical spectrograph (R=$100,000$, 380-900~nm), which is designed to detect low mass exoplanets using the radial velocity technique.We describe an IDL-based radial velocity (RV) data reduction pipeline for the TOU spectrograph and its performance with stable stars. This pipeline uses a least-squares fitting algorithm to match observed stellar spectra to a high signal-to-noise template created for each star. By carefully controlling all of the error contributions to RV measurements in both the hardware and data pipeline, we have achieved $\sim$0.9\ms long-ter…
Excalibur is a non-parametric, hierarchical framework for precision wavelength-calibration of spectrographs. It is designed with the needs of extreme-precision radial velocity (EPRV) in mind, which require that instruments be calibrated or stabilized to better than $10^{-4}$ pixels. Instruments vary along only a few dominant degrees of freedom, especially EPRV instruments that feature highly stabilized optical systems and detectors. Excalibur takes advantage of this property by using all calibration data to construct a low-dimensional representation of all accessible calibration states for an …
The Cosmic Origins Spectrograph: On-Orbit Instrument Performance
宇宙起源光谱仪（COS）于2009年5月安装在哈勃太空望远镜上，作为服务任务4的一部分，以提供远紫外和近紫外波长（FUV，NUV）的高灵敏度，中分辨率和低分辨率光谱。COS是迄今为止最灵敏的FUV/NUV摄谱仪，波长范围从900 nm到3200 nm，峰值有效面积接近3000 cm ^2。本文介绍了仪器设计，服务任务轨道验证（SMOV）的结果，和正在进行的性能监测计划。
PARAS is a fiber-fed stabilized high-resolution cross-dispersed echelle spectrograph, located on the 1.2 m telescope in Mt. Abu India. Designed for exoplanet detection, PARAS is capable of single-shot spectral coverage of 3800 - 9600 A, and currently achieving radial velocity (RV) precisions approaching ~1 m/s over several months using simultaneous ThAr calibration. As such, it is one of the few dedicated stabilized fiber-fed spectrographs on small (1-2 m) telescopes that are able to fill an important niche in RV follow-up and stellar characterization. The success of ground-based RV surveys is…
The Son Of X-Shooter (SOXS) is a single object spectrograph offering simultaneous spectral coverage in UV-VIS (350-850 nm) and NIR (800-2000 nm) wavelength regimes with an average of R close to 4500 for a 1 slit. SOXS also has imaging capabilities in the visible wavelength regime. It is designed and optimized to observe all kinds of transients and variable sources. The final destination of SOXS is the Nasmyth platform of the ESO NTT at La Silla, Chile. The SOXS consortium has a relatively large geographic spread, and therefore the Assembly Integration and Verification (AIV) of this medium-clas…
SOXS (SOn of X-Shooter) is a medium resolution (~4500) wide-band (0.35 - 2.0 μm) spectrograph which passed the Final Design Review in 2018. The instrument is in the final integration phase and it is planned to be installed at the NTT in La Silla by next year. It is mainly composed of five different optomechanical subsystems (Common Path, NIR spectrograph, UV-VIS spectrograph, Camera, and Calibration) and other mechanical subsystems (Interface flange, Platform, cable corotator, and cooling system). A brief overview of the optomechanical subsystems is presented here as more details can be found …
The RISTRETTO project is aiming to build an instrument that will detect the reflected light from close-by exoplanet. It is a two stage instrument: An extreme AO system in the visible, followed by a seven spaxel single mode High resolution Spectrograph. In this paper we present the design of this spectrograph: a classical echelle spectrograph fed with single mode fibers. Standard single mode fibers have been chosen and are forming a long tilted slit in order to have the right order spacing on the detector. The instrument will be under vacuum and thermally controlled in order to make it stable.
iLocater is a near-infrared, extremely precise radial velocity (EPRV) spectrograph under construction for the dual 8.4 m diameter Large Binocular Telescope (LBT). The instrument will undertake precision radial velocity studies of Earth-like planets orbiting low-mass stars. Operating in the diffraction-limited regime, iLocater uses adaptive optics to efficiently inject starlight directly into single-mode fibers that illuminate a high spectral resolution (R=190,500 median), cryogenic, diffraction-limited spectrograph. To maximize performance, the spectrograph uses a new design strategy for EPRV …
The EXtreme PREcision Spectrograph (EXPRES) is an optical fiber fed echelle instrument being designed and built at the Yale Exoplanet Laboratory to be installed on the 4.3-meter Discovery Channel Telescope operated by Lowell Observatory. The primary science driver for EXPRES is to detect Earth-like worlds around Sun-like stars. With this in mind, we are designing the spectrograph to have an instrumental precision of 15 cm/s so that the on-sky measurement precision (that includes modeling for RV noise from the star) can reach to better than 30 cm/s. This goal places challenging requirements on …
Single-mode fiber (SMF) spectrographs fed with adaptive optics (AO) offer a unique path for achieving extremely precise radial velocity (EPRV) measurements. We present a radial velocity (RV) error budget based on end-to-end numerical simulations of an instrument named iLocater that is being developed for the Large Binocular Telescope(LBT). Representing the first AO-fed, SMF spectrograph, iLocater's design is used to quantify and assess the relative advantages and drawbacks of precise Doppler time series measurements made at the diffraction limit. This framework can be applied for trade-study w…
iLocater is a near-infrared (NIR) radial velocity (RV) spectrograph that is being developed for the Large Binocular Telescope in Arizona. Unlike seeing limited designs, iLocater uses adaptive optics to inject starlight directly into a single mode fiber. This feature offers high spectral resolution while simultaneously maintaining a compact optical design. Although this approach shows promise to generate extremely precise RV measurements, it differs from conventional Doppler spectrographs, and therefore carries additional risk. To aid with the design of the instrument, we have developed a compr…
By combining IFS with ExAO we are now able to resolve objects close to the diffraction-limit of large telescopes, exploring new science cases. We introduce an IFU designed to couple light with a minimal platescale from the SCExAO facility at NIR wavelengths to a SM spectrograph. The IFU has a 3D-printed MLA on top of a custom SM MCF, to optimize the coupling of light into the fiber cores. We demonstrate the potential of the instrument via initial results from the first on-sky runs at the 8.2 m Subaru Telescope with a spectrograph using off-the-shelf optics, allowing for rapid development with …
Radial velocity instruments require high spectral resolution and extreme thermo-mecanical stability, even more difficult to achieve in near-infra red (NIR) where the spectrograph has to be cooled down. For a seeing-limited spectrograph, the price of high spectral resolution is an increased instrument volume, proportional to the diameter of the primary mirror. A way to control the size, cost, and stability of radial velocity spectrographs is to reduce the beam optical etendue thanks to an Adaptive Optics (AO) system. While AO has revolutionized the field of high angular resolution and high cont…
Optical fiber modal noise is a limiting factor for high precision spectroscopy signal-to-noise in the near-infrared and visible. Unabated, especially when using highly coherent light sources for wavelength calibration, modal noise can induce radial velocity (RV) errors that hinder the discovery of low-mass (and potentially Earth-like) planets. Previous research in this field has found sufficient modal noise mitigation through the use of an integrating sphere, but this requires extremely bright light sources, a luxury not necessarily afforded by the next generation of high-resolution optical sp…
The 39-meter European Extremely Large Telescope (E-ELT) is expected to have very low throughput in the blue part of the visible spectrum. Because of that, a blue-optimised spectrograph at the 8-meter Very Large Telescope could potentially be competitive against the E-ELT at wavelengths shorter than 400 nm. A concept study for such an instrument was concluded in 2012. This would be a high-throughput, medium resolution (R $\sim$ 20\,000) spectrograph, operating between 300 and 400 nm. It is currently expected that construction of this instrument will start in the next few years. In this contribu…
The next generation of Extremely Large Telescopes (ELT), with diameters up to 39 meters, will start opera- tion in the next decade and promises new challenges in the development of instruments. The growing field of astrophotonics (the use of photonic technologies in astronomy) can partly solve this problem by allowing mass production of fully integrated and robust instruments combining various optical functions, with the potential to reduce the size, complexity and cost of instruments. In this paper, we focus on developments in integrated micro-spectrographs and their potential for ELTs. We ta…
Investigating the differential limb coupling effect for diffraction-limited spectrographs with PARVI
California Institute of Technology（加州理工学院）；Caltech Optical Observatories, California Institute of Technology（加州理工学院光学观测台）；Jet Propulsion Laboratory, California Institute of Technology（加州理工学院喷气推进实验室）；American Museum of Natural History（美国自然历史博物馆）
As telescope apertures increase, the challenge of scaling spectrographic astronomical instruments becomes acute. The next generation of extremely large telescopes (ELTs) strain the availability of glass blanks for optics and engineering to provide sufficient mechanical stability. While breaking the relationship between telescope diameter and instrument pupil size by adaptive optics is a clear path for small fields of view, survey instruments exploiting multiplex advantages will be pressed to find cost-effective solutions. In this review we argue that exploiting the full potential of ELTs will …
Precise wavelength calibration is a critical issue for high-resolution spectroscopic observations. The ideal calibration source should be able to provide a very stable and dense grid of evenly distributed spectral lines of constant intensity. A new method which satisfies all mentioned conditions has been developed by our group. The approach is to actively measure the exact position of a single spectral line of a Fabry-Perot etalon with very high precision with a wavelength-tuneable laser and compare it to an extremely stable wavelength standard. The ideal choice of standard is the D2 absorptio…
A primary goal of direct imaging techniques is to spectrally characterize the atmospheres of planets around other stars at extremely high contrast levels. To achieve this goal, coronagraphic instruments have favored integral field spectrographs (IFS) as the science cameras to disperse the entire search area at once and obtain spectra at each location, since the planet position is not known a priori. These spectrographs are useful against confusion from speckles and background objects, and can also help in the speckle subtraction and wavefront control stages of the coronagraphic observation. We…
The next generation of Extremely Large Telescopes (ELT), with diameters up to 39 meters, is planned to begin operation in the next decade and promises new challenges in the development of instruments since the instrument size increases in proportion to the telescope diameter D, and the cost as D2 or faster. The growing field of astrophotonics (the use of photonic technologies in astronomy) could solve this problem by allowing mass production of fully integrated and robust instruments combining various optical functions, with the potential to reduce the size, complexity and cost of instruments.…
The direct measurement of the Universe's expansion history and the search for terrestrial planets in habitable zones around solar-type stars require extremely high-precision radial velocity measures over a decade. This study proposes an approach for enabling high-precision radial velocity measurements from space. The concept presents a combination of a high-dispersion densified pupil spectrograph and a novel telescope line-of-sight monitor. The precision of the radial velocity measurements is determined by combining the spectrophotometric accuracy and the quality of the absorption lines in the…
We present the Phase A Science Case for the Multi-conjugate Adaptive-optics Visible Imager-Spectrograph (MAVIS), planned for the Adaptive Optics Facility (AOF) of the Very Large Telescope (VLT). MAVIS is a general-purpose instrument for exploiting the highest possible angular resolution of any single optical telescope available in the next decade, either on Earth or in space, and with sensitivity comparable to (or better than) larger aperture facilities. MAVIS uses two deformable mirrors in addition to the deformable secondary mirror of the AOF, providing a mean V-band Strehl ratio of >10% (go…
This article reviews the two major recent developments that significantly improved cosmological measurements of fundamental constants derived from high resolution quasar spectroscopy. The first one is the deployment of astronomical Laser Frequency Combs on high resolution spectrographs and the second one is the development of spectral analysis tools based on Artificial Intelligence methods. The former all but eliminated the previously dominant source of instrumental uncertainty whereas the latter established optimal methods for measuring the fine structure constant ($α$) in quasar absorption s…
The Large Ultraviolet / Optical / Infrared Surveyor (LUVOIR) is one of four large mission concepts currently undergoing community study for consideration by the 2020 Astronomy and Astrophysics Decadal Survey. The LUVOIR Ultraviolet Multi-Object Spectrograph, LUMOS, is being designed to support all of the UV science requirements of LUVOIR, from exoplanet host star characterization to tomography of circumgalactic halos to water plumes on outer solar system satellites. LUMOS offers point source and multi-object spectroscopy across the UV bandpass, with multiple resolution modes to support differe…
Radial velocities (RV) measured from near-infrared (NIR) spectra are a potentially excellent tool to search for extrasolar planets around cool or active stars. High resolution infrared (IR) spectrographs now available are reaching the high precision of visible instruments, with a constant improvement over time. GIANO is an infrared echelle spectrograph at the Telescopio Nazionale Galileo (TNG) and it is a powerful tool to provide high resolution spectra for accurate RV measurements of exoplanets and for chemical and dynamical studies of stellar or extragalactic objects. No other high spectral …
The InfraRed Imaging Spectrograph (IRIS) is a first-light instrument for the Thirty Meter Telescope (TMT) that will be used to sample the corrected adaptive optics field by NFIRAOS with a near-infrared (0.8 - 2.4 $μ$m) imaging camera and Integral Field Spectrograph (IFS). In order to understand the science case specifications of the IRIS instrument, we use the IRIS data simulator to characterize photometric precision and accuracy of the IRIS imager. We present the results of investigation into the effects of potential ghosting in the IRIS optical design. Each source in the IRIS imager field of…
The redshift drift is a small, dynamic change in the redshift of objects following the Hubble flow. Its measurement provides a direct, real-time, model-independent mapping of the expansion rate of the Universe. It is fundamentally different from other cosmological probes: instead of mapping our (present-day) past light-cone, it directly compares different past light-cones. Being independent of any assumptions on gravity, geometry or clustering, it directly tests the pillars of the Lambda-CDM paradigm. Recent theoretical studies have uncovered unique synergies with other cosmological probes, in…
MOSAIC is the planned multi-object spectrograph for the 39m Extremely Large Telescope (ELT). Conceived as a multi-purpose instrument, it offers both high multiplex and multi-IFU capabilities at a range of intermediate to high spectral resolving powers in the visible and the near-infrared. MOSAIC will enable unique spectroscopic surveys of the faintest sources, from the oldest stars in the Galaxy and beyond to the first populations of galaxies that completed the reionisation of the Universe--while simultaneously opening up a wide discovery space. In this contribution we present the status of th…
The Calibration System of the iLocater Spectrograph
The Ohio State University（俄亥俄州立大学）；University of Notre Dame（圣母大学）；Macquarie University（麦考瑞大学）；Landessternwarte, Zentrum für Astronomie der Universität Heidelberg（海德堡大学天文台中心）；Max-Planck-Institute for Astronomy（马克斯·普朗克天文学研究所）；Un Santa Cruz（圣克鲁斯加州大学）；Universität Heidelberg（海德堡大学）；Physikalisch-Technische Bundesanstalt（德国联邦物理技术研究院）
The Wide-field Spectroscopic Telescope (WST): design trade-offs for the low-resolution multi-object spectrograph instrument
Aix-Marseille Université（艾克斯-马赛大学）；CNRS（法国国家科学研究中心）；CNES（法国国家空间研究中心）；LAM UMR7326（天体物理与行星学研究混合单位7326）；Australian Astronomical Optics（澳大利亚天文光学）；Macquarie Univ.（麦考瑞大学）；STFC UK Astronomy Technology Centre（英国科学与技术设施委员会英国天文技术中心）；Royal Observatory Edinburgh（爱丁堡皇家天文台）；Université Claude Bernard Lyon 1（里昂第一大学克洛德·贝尔纳）；Centre de Recherche Astrophysique de Lyon（里昂天体物理研究中心）；INAF（意大利国家天体物理研究所）；Osservatorio Astronomico di Brera（布雷拉天文台）；Department of Astrophysics, University of Vienna（维也纳大学天体物理学系）；Leibniz-Institut für Astrophysik Potsdam (AIP)（波茨坦莱布尼茨天体物理研究所）；CEA（法国原子能和替代能源委员会）；European Southern Observatory（欧洲南方天文台）
Direct imaging instruments have the spatial resolution to resolve exoplanets from their host star. This enables direct characterization of the exoplanets atmosphere, but most direct imaging instruments do not have spectrographs with high enough resolving power for detailed atmospheric characterization. We investigate the use of a single-mode diffraction-limited integral-field unit that is compact and easy to integrate into current and future direct imaging instruments for exoplanet characterization. This achieved by making use of recent progress in photonic manufacturing to create a single-mod…
SPHERE is the high-contrast exoplanet imager and spectrograph installed at the Unit Telescope 3 of the Very Large Telescope. After more than two years of regular operations, we analyse statistically the performance of the adaptive optics system and its dependence on the atmospheric conditions above the Paranal observatory, as measured by the suite of dedicated instruments which are part of the Astronomical Site Monitor and as estimated by the SPHERE real-time calculator. We also explain how this information can be used to schedule the observations in order to yield the best data quality and to…
The use of Immersed Gratings offers advantages for both space- and ground-based spectrographs. As diffraction takes place inside the high-index medium, the optical path difference and angular dispersion are boosted proportionally, thereby allowing a smaller grating area and a smaller spectrometer size. Short-wave infrared (SWIR) spectroscopy is used in space-based monitoring of greenhouse and pollution gases in the Earth atmosphere. On the extremely large telescopes currently under development, mid-infrared high-resolution spectrographs will, among other things, be used to characterize exo-pla…
