The Sloan Digital Sky Survey V (SDSS-V) is an all-sky spectroscopic survey of >6 million objects, designed to decode the history of the Milky Way, reveal the inner workings of stars, investigate the origin of solar systems, and track the growth of supermassive black holes across the Universe. The Local Volume Mapper (LVM) is a facility designed to provide a contiguous 2500 deg2 integral-field survey over a 3.5 year period from Las Campanas Observatory (LCO) in Chile. The facility comprises four small (16 cm) telescopes that deliver science, calibration, and spectro-photometric light to three bench-mounted multi-object spectrographs, designed and build by Winlight Systems. All four telescopes will be equipped with a microlens array integral-field unit (IFU) to slice the focal plane into 35–arcsec large spatial elements while maintaining near-telecentric coupling at the fiber input. The science IFU comprises 1801 fibers, additional 143 fibers are allocated for sky-background and spectro-photometric calibration, totaling 1944 fibers. Each spectrograph will be fed by 648 fibers, which are reformatted into a linear array, forming the entrance slit. In this paper, we present the opto-mechanical design of the LVM-LCO fiber cable system.
The Sloan Digital Sky Survey V (SDSS-V) is an all-sky spectroscopic survey of <6 million objects, designed to decode the history of the Milky Way, reveal the inner workings of stars, investigate the origin of solar systems, and track the growth of supermassive black holes across the Universe. The Local Volume Mapper (LVM) is one of three surveys that form SDSS-V. LVM will employ a coordinated system of four telescopes feeding three fiber spectrographs at Las Campanas Observatory in Chile. The goal is to map approximately 2500 square degrees of the Galactic plane over the wavelength range 360-980 nm with R~4000 spectral resolution. These observations will reveal for the first time how distinct gaseous environments within the Galaxy interact with each other and with the stellar population, producing the large-scale interstellar medium that we observe. Accurately mapping and calibrating a substantial portion of the sky at this spatial resolution requires a unique type of telescope system. Each of the four LVM telescopes has a diameter of 16 cm, making them considerably smaller and lighter than the instruments they feed. One telescope will host the science IFU containing ~1800 fibers arranged in a close-packed hexagon. Two additional Calibration telescopes will observe fields adjacent to the science IFU, in order to calibrate out terrestrial airglow and other geo-coronal emission. The fourth, Spectrophotometric telescope will make rapid observations of bright stars (typically 12 during a single IFU / Calibration exposure) to correct for telluric absorption lines and overall extinction. The fibers from all three types of telescope will be interspersed in the entrance slits of the spectrographs, allowing for simultaneous science and calibration exposures. Although considerably smaller than the next generation of giants, the LVM telescopes must also operate close to the limits of physical optics, and the geometry and scope of the LVM survey present unique challenges. For example, with this type of telescope at the Las Campanas site, the effects of optical aberrations, diffraction, seeing, and (uncorrected) atmospheric dispersion are all of comparable scale. This, coupled with the need for repeated and reliable measurements over years, leads to some unconventional design choices. This paper presents the preliminary design of the LVM telescope system and discusses the requirements and tradeoffs that led to the baseline choices.
The Sloan Digital Sky Survey V (SDSS-V) is an all-sky spectroscopic survey of <6 million objects, designed to decode the history of the Milky Way, reveal the inner workings of stars, investigate the origin of solar systems, and track the growth of supermassive black holes across the Universe. The Local Volume Mapper (LVM) is a facility designed to provide a contiguous 2,500 deg2 integral-field survey over a 3.5 year period from Las Campanas Observatory in Chile. In this paper we provide an overview and status update for the LVM instrument (hereafter LVM-I). Each integral-field unit’s spaxel probes linear scales that are sub-parsec (Milky Way) to ∼10 pc (Magellanic Clouds) which is accomplished with an angular diameter of 36.900. LVM’s spectral resolution is R = λ/∆λ ∼ 4, 000 which probes velocities of 33 kms−1 (1 σ) from 365 nm to 950 nm. LVM uses four 16-cm telescopes feeding three spectrographs. One telescope carries the bulk of the science load with ∼1,800 fibers coupled to the field via a pair of lenslet arrays, two telescopes are used to measure the night sky spectra in fields that flank the science field, and a fourth telescope contemporaneously monitors bright standard stars to determine atmospheric extinction. We expect LVM-I to deliver percent-level precision on important line ratios down to a few Rayleigh. The three spectrographs are being built by Winlight corporation in France based on those for the Dark Energy Spectroscopic Instrument (DESI). In this paper we present the high-level system design of LVM-I including the lenslet-coupled fiber IFUs, telescopes, guiding+acquisition system, calibration systems, enclosures, and spectrographs.
This paper describes the design, status, and test program for the Giant Magellan Telescope (GMT) Primary Mirror Subsystem (M1). It consists of the mirror cells, positioning system, support systems, and thermal control system. The seven 8.4m mirror segments are excluded from this paper because they are considered a separate subsystem of the M1 System.
The M1 Subsystem leverages heritage design of similar telescope systems; for example, the Magellan telescopes and the Large Binocular Telescope. The M1 Subsystem incorporates pneumatic force actuators, hardpoints, and a thermal control ventilation system.
Design developments have been introduced to address the challenging levels of performance and unique requirements needed by the GMT telescope. Imaging goals necessitate an increase in mirror support performance, figure control, and higher-levels of thermal control. Additionally, there are challenges associated with matching and tracking the relative position of the seven mirror segments for mirror phasing. The design of the static support system needs to protect the mirrors from loads transmitted through the structure during an earthquake. Finally, the telescope design with interchangeable off-axis mirror cells necessitate mirror cells and support components that function under any range of gravitational vector orientations
. A full-scale Test Cell prototype is being constructed including production versions of mirror cell components to test and validate the M1 subsystem design. A Mirror Simulator will be used with the Test Cell to validate the M1 Control System. Later, a primary mirror segment will be used with the Test Cell to perform optical tests at the University of Arizona.