The Dark Energy Spectroscopic Instrument (DESI) is under construction to measure the expansion history of the Universe using the Baryon Acoustic Oscillation technique. The spectra of 40 million galaxies over 14,000 sq deg will be measured during the life of the experiment. A new prime focus corrector for the KPNO Mayall telescope will deliver light to 5,000 fiber optic positioners. The fibers in turn feed ten broad-band spectrographs. We present the design details of the instrument mechanism control systems for the spectrographs. Each spectrograph has a stand-alone mechanism control box that operates the unit's four remotely-operated mechanisms (two shutters and two Hartmannn doors), and provides a suite of temperature and humidity sensors. Each control box is highly modular, and is operated by a dedicated on-board Linux computer to provide all of the control and monitoring functions. We describe our solution for integrating a number of network-connected devices within each unit spectrograph, and describe the basic software architecture.
The Dark Energy Spectroscopic Instrument (DESI) is under construction to measure the expansion history of the Universe using the Baryon Acoustic Oscillation technique. The spectra of 40 million galaxies over 14,000 sq deg will be measured during the life of the experiment. A new prime focus corrector for the KPNO Mayall telescope will deliver light to 5000 fiber optic positioners. The fibers in turn feed ten broad-band spectrographs. We describe the unique shutter design that incorporates a fiber illumination system into the shutter blade. When activated, the fiber illumination system directs intense 430-480nm wavelength light at the instrument’s fiber slit in order to back-illuminate the telescope’s focal plane and verify the location of the robotic fiber positioners. The back-illumination is typically active during science exposure read-outs and therefore requires the shutter to attenuate light by a factor of at least 10<sup>7</sup>. This paper describes how we have integrated the fiber illumination system into the shutter blade, as well as incorporated an inflatable seal around the shutter aperture to achieve the light attenuation requirement. We also present lab results that characterize the fiber illumination and shutter attenuation. Finally, we discuss the control scheme that executes exposure and fiber illumination modes, and meets the shutter timing requirements.
We present the design and development of the DEdicatedMONitor of EXotransits and Transients (DEMONEXT), an automated and robotic 20 inch telescope jointly funded by The Ohio State University and Vanderbilt University. The telescope is a PlaneWave CDK20 f/6.8 Corrected Dall-Kirkham Astrograph telescope on a Mathis Instruments MI-750/1000 Fork Mount located atWiner Observatory in Sonoita, AZ. DEMONEXT has a Hedrick electronic focuser, Finger Lakes Instrumentation (FLI) CFW-3-10 filter wheel, and a 2048 x 2048 pixel FLI Proline CCD3041 camera with a pixel scale of 0.90 arc-seconds per pixel and a 30.7× 30.7 arc-minute field-of-view. The telescope’s automation, controls, and scheduling are implemented in Python, including a facility to add new targets in real time for rapid follow-up of time-critical targets. DEMONEXT will be used for the confirmation and detailed investigation of newly discovered planet candidates from the Kilodegree Extremely Little Telescope (KELT) survey, exploration of the atmospheres of Hot Jupiters via transmission spectroscopy and thermal emission measurements, and monitoring of select eclipsing binary star systems as benchmarks for models of stellar evolution. DEMONEXT will enable rapid confirmation imaging of supernovae, flare stars, tidal disruption events, and other transients discovered by the All Sky Automated Survey for SuperNovae (ASAS-SN). DEMONEXT will also provide follow-up observations of single-transit planets identified by the Transiting Exoplanet Survey Satellite (TESS) mission, and to validate long-period eclipsing systems discovered by Gaia.
Facility Instruments at the Large Binocular Telescope (LBT) include two spectrograph pairs, the LBT
Near-IR Spectroscopic Utility with Camera and Integral Field Unit for Extragalactic Research (LUCI), a
near-infrared imager and spectrograph pair, and the Multi-Object Double Spectrograph (MODS), a pair of
dual-beam long-slit spectrographs. Both spectrograph designs utilize focal plane masks for long-slit and
multi-slit observations. This paper describes the mask configuration and specification process for each
instrument, as well as the steps in mask fabrication, handling, and installation.
We describe the design, construction and measured performance of the Kitt Peak Ohio State Multi-Object Spectrograph
(KOSMOS) for the 4-m Mayall telescope and the Cerro Tololo Ohio State Multi-Object Spectrograph (COSMOS) for
the 4-m Blanco telescope. These nearly identical imaging spectrographs are modified versions of the OSMOS
instrument; they provide a pair of new, high-efficiency instruments to the NOAO user community. KOSMOS and
COSMOS may be used for imaging, long-slit, and multi-slit spectroscopy over a 100 square arcminute field of view with
a pixel scale of 0.29 arcseconds. Each contains two VPH grisms that provide R~2500 with a one arcsecond slit and their
wavelengths of peak diffraction efficiency are approximately 510nm and 750nm. Both may also be used with either a
thin, blue-optimized CCD from e2v or a thick, fully depleted, red-optimized CCD from LBNL. These instruments were
developed in response to the ReSTAR process. KOSMOS was commissioned in 2013B and COSMOS was
commissioned in 2014A.
The Multi-Object Double Spectrographs (MODS) are two identical high-throughput optical dichroic-split double-beam
low- to medium-dispersion CCD spectrometers being deployed at the Large Binocular Telescope (LBT). They operate in
the 3200-10500Å range at a nominal resolution of λ/δλ≈2000. MODS1 saw first-light at the LBT in September 2010,
finished primary commissioning in May 2011, and began regular partner science operations in September 2011. MODS2
is being readied for delivery and installation at the end of 2012. This paper describes the on-sky performance of MODS1
and presents highlights from the first year of science operations.
The Ohio State Multi-Object Spectrograph (OSMOS) is a new facility imager and spectrograph for the 2.4m
Hiltner telescope at the MDM Observatory. We present a detailed description of the mechanical and electronic
solutions employed in OSMOS, many of which have been developed and extensively tested in a large number
of instruments built at Ohio State over the past ten years. These solutions include robust aperture wheel and
linear stage designs, mechanism control with MicroLYNX programmable logic controllers, and WAGO fieldbus
The Multi-Object Double Spectrographs (MODS) are two identical high-throughput optical low- to medium-resolution
CCD spectrometers being deployed at the Large Binocular Telescope (LBT). Operating in the 340-1000nm range, they
use a large dichroic to split light into separately-optimized red and blue channels that feature reflective collimators and
decentered Maksutov-Schmidt cameras with monolithic 8×3K CCD detectors. A parallel infrared laser closed-loop
image motion compensation system nulls spectrograph flexure giving it high calibration stability. The two MODS
instruments may be operated together with digital data combination as a single instrument giving the LBT an effective
aperture of 11.8-meter, or separately configured to flexibly use the twin 8.4-meter apertures. This paper describes the
properties and performance of the completed MODS1 instrument. MODS1 was delivered to LBT in May 2010 and is
being prepared for first-light in September 2010.
Laser guide star adaptive optics and interferometry are currently revolutionizing ground-based near-IR astronomy, as
demonstrated at various large telescopes. The Large Binocular Telescope from the beginning included adaptive optics in
the telescope design. With the deformable secondary mirrors and a suite of instruments taking advantage of the AO
capabilities, the LBT will play an important role in addressing major scientific questions. Extending from a natural guide
star based system, towards a laser guide stars will multiply the number of targets that can be observed. In this paper we
present the laser guide star and wavefront sensor program as currently being planned for the LBT. This program will
provide a multi Rayleigh guide star constellation for wide field ground layer correction taking advantage of the multi
object spectrograph and imager LUCIFER in a first step. The already foreseen upgrade path will deliver an on axis
diffraction limited mode with LGS AO based on tomography or additional sodium guide stars to even further enhance
the scientific use of the LBT including the interferometric capabilities.
We discuss the performance of the Image Motion Compensation System (IMCS) for the Multi-Object Double Spectrograph (MODS). The system performs closed-loop image motion compensation, actively correcting for image motion in the spectrograph's focal plane caused by large scale structural bending due to gravity as well as other effects such as temperature fluctuation and mechanism flexure within the instrument. Not only does the system control instrumental flexure to within the specifications (0.1 pixels on the science CCD, or 1.5 μm), but it also has proven to be an excellent diagnostic tool for assembling and testing the spectrograph. We describe both the final performance of the system as deployed in the spectrograph as well as the instrumental tests made possible by the IMCS.
Ohio State is building two identical Multi-Object Double Spectrographs (MODS), one for each of the f/15 Gregorian foci of the Large Binocular Telescope (LBT). Each MODS is a high-throughput optical low- to medium-resolution CCD spectrometer operating in the 320-1000nm range with a 6.5-arcminute field-of-view. A dichroic distributes the science beam into separately-optimized red and blue channels that provide for direct imaging and up to 3 spectroscopic modes per channel. The identical MODS instruments may be operated together with digital data combination as a single instrument giving the LBT an effective aperture of 11.8-meter, or separately configured to flexibly use the twin 8.4-meter apertures. This paper describes progress on the integration and testing of MODS1, and plans for the deployment of MODS2 by the end of 2008 at the LBT.
We are building a Multi-Object Double Spectrograph for the Large Binocular Telescope. The instrument is designed to have high throughput from 320 to 1000 nm, spectral resolutions of 1,000-10,000, and multi-object capability over a 6 arcminute field. The design incorporates a dichroic and splits the science beam into a blue and a red channel, each of which can illuminate an 8,192 pixel long detector (with 15 micron pixels) with good image quality. The highly modular design can hold up to three gratings and an imaging flat and a selection of filters in each channel, all of which are quickly accessible; this allows for substantial observing flexibility. Progress on the construction of the instrument and future plans will be described.
We describe progress on a closed-loop image motion compensation system (IMCS) for the Multi-Object Double Spectrograph (MODS). The IMCS actively compensates for image motion in the focal plane within the instrument caused by temperature fluctuation, mechanism flexure, and large scale structural bending due to gravity. The system utilizes an infrared laser as a reference beam that shares a light path with the science beam and is detected by an infrared reference detector adjacent to the science detector. The reference detector is read out frequently and detects any image motion in the focal plane. The IMCS compensates for this motion during a science exposure by adjusting the tip and tilt angles of the collimator mirror. A working lab prototype meets specifications and is described.
We describe an instrument that is capable of taking simultaneous images at one optical (UBVRI) and one near-infrared (JHK) wavelength. The instrument uses relatively simple optics and a dichroic to image the same field on to an optical CCD and an HgCdTe array. The mechanical and thermal design is similar to previous instruments built by our group and the array controllers are based on the same architecture. The instrument has been in use for the past four years on the CTIO/Yale 1m telescope in Chile and has an excellent operational/reliability record. A number of notable science results have been obtained with the instrument; especially interesting are several photometric monitoring projects that have been possible, since the instrument is available every night on the telescope.
We describe a closed-loop image motion compensation system (IMCS) for the Multi-Object Double Spectrograph (MODS). The IMCS compensates for structural bending due to gravity and eliminates image motion from temperature fluctuation and mechanism flexure within the instrument during an observing period. The system makes use of an infrared laser source at the telescope focal plane, which produces reference spots in the science detector plane. Movement of these spots accurately tracks science image motion, since the two beams share a common optical path. Small real-time adjustments to the position of the MODS collimator mirror compensate for the image motions.
We are building a Multi-Object Double Spectrograph for the Large Binocular Telescope. The main themes of our planned research with the instrument are the formation and evolution of galaxies and their nuclei and the evolution of large- scale structure in the universe, although we expect that the spectrograph will be used for many other varieties of programs as well. The science goals for the instrument dictate that it have the highest possible throughput form 320 to 1000 nm, spectral resolutions of 10<SUP>3</SUP> to 10<SUP>4</SUP>, and multi-object capability over an approximately 6 foot field. Our design is highly modular, so future upgrades should be straightforward.
The MDM/Ohio State/ALADDIN IR Camera (MOSAIC) is a general purpose near IR imaging camera and medium-resolution long- slit spectrometer in use on the MDM 1.3-m and 2.4-m telescopes and the Kitt Peak 2.1-m and 4-m telescopes. In cooperation with NOAO and USNO, MOSAIC is one of the first general-purpose near-IR instruments available to the astronomical community that uses a first-generation 1024 X 512 ALADDIN InSb array, with the capability to use a full 1024 X 1024 array once one becomes available. MOSAIC provides tow imaging plate scales, and a variety of long- slit grism spectroscopic modes. This paper describes the general instrument design and capabilities, and presents representative scientific results.
The ISL is a successful astronomical instrumentation program that has completed three major instruments and many smaller projects since 1987. We have developed the capabilities to perform all aspects of instrument design and construction and a range of unique skills and methods. We maintain a permanent staff that currently consists of two scientists specializing in optical design and detector systems, a seniors mechanical engineer, a programmer, an electronic engineer, a mechanical designer, two machinists, and a lab assistant. Instrumentation projects also draw upon faculty and graduate student effort.
The Ohio State Instrument Control and IMage ACquisition System, ICIMACS, is the computer hardware and software used by all instruments developed by the Imaging Science Laboratory (ISL) to control the detector, pre-process data, record image data on a separate computer system for data reduction and analysis, generate real time data display, control the mechanisms within an instrument, interface with the telescope controller, connect to a user interface, and perform engineering functions such as temperature or pressure logging. ICIMACS has now been used on 12 different instruments and is herein described as applied to 'MOSAIC' the near IR imager/spectrometer in use on the Kitt Peak 2.1 and 4 meter telescopes and on the MDM 2.4 and 1.3 meter telescopes.
We present a design for a near-infrared (0.9 to 5.5 micrometers ) spectrograph for use on any large telescope. For example, the instrument meets all of the scientific and technical objectives requested by the Gemini Telescope Project for their facility infrared spectrograph. The features of the instrument include a wide range of rapidly selectable spectral and spatial resolutions, full-broad-band imaging, integral field spectroscopy, and several cross-dispersed modes. Much of the instrument is based on optical, mechanical, and electronic designs currently in use. The optical design has diffraction-limited performance and no vignetting over a 150" X 150" field of view. The mechanical design draws heavily on our extensive experience with cryogenic mechanisms and uses a cassette system for selection of the large number of possible configurations. The design is very modular and allows a staged implementation of the complete set of potential operational modes.