With the advent of large-scale time-domain surveys such as the LSST, there is a strong desire for the 4-m SOAR Telescope to be able to respond efficiently and effectively to transient alerts. Enabling the required capabilities at SOAR will also support a greater variety of science programs than conventional telescope scheduling. These capabilities are best deployed with SOAR acting as one of several telescopes responding to alerts and supporting time domain programs. We outline how this might be done if SOAR is included as a node in the Las Cumbres Observatory network, at least part-time. This allows SOAR to make use of extensive existing software infrastructure, while adding a larger aperture to the existing network. Participation of SOAR also serves as a pathfinder for participation of other large telescopes in an evolved LCO network. The overall workflow is outlined. Required interfaces are described. Finally, the initial development efforts with this goal in mind are outlined.
The Southern Astrophysical Research (SOAR) Telescope is a 4.1 meter aperture telescope situated in Cerro Pachon, IV Region, Chile. The telescope works from the atmospheric cut-off in the blue (320 nm) to the near infrared and has been designed to deliver the highest possible angular resolution at optical wavelengths. The telescope has an altazimuth mount which is controlled by the Mount Control Unit (MCU) system.
The SOAR Mount Control Unit Upgrade Project seeks to replace the current MCU in the SOAR telescope. The new control unit will be based on the National Instruments cRIO-9039 controller, which will allow to improve the telemetry, improve fault detection and use new digital control techniques.
This will allow a more compact and robust MCU. This paper introduces the project, shows the control architecture and the current status of the new MCU implementation.
The response of the SOAR telescope to the September 2015 Illapel earthquake is documented and placed in the context of other recent, nearby seismic events. Accelerometer data collected on the telescope during these events suggest that observed intensities due to events occurring to the south of the SOAR telescope site are higher than predicted by simple models. Amplification of accelerations occurs at several places within the telescope system, most notably the telescope top end and secondary mirror assembly, and the azimuth encoder system. Damage in these areas is described, and an overview of the earthquake recovery effort is presented.
We describe design modifications to the SOAR telescope intended to reduce the impact of future major earthquakes, based on the facility’s experience during recent events, most notably the September 2015 Illapel earthquake. Specific modifications include a redesign of the encoder systems for both azimuth and elevation, seismic trigger for the emergency stop system, and additional protections for the telescope secondary mirror system. The secondary mirror protection may combine measures to reduce amplification of seismic vibration and “fail-safe” components within the assembly. The status of these upgrades is presented.
The SOAR telescope will be well situated, both in terms of location and aperture, to follow up on the stream of brighter transient events generated by the Large Synoptic Survey Telescope (LSST). A critical aspect is that the operation is less likely to be responding to occasional targets of opportunity, and more likely to be responding to a continuing flow of events that must be efficiently prioritized and observed. We discuss the implications for observatory operations, including potential modifications to the telescope itself or to the instrument suite. Representative “use cases” are described to assist in putting potential operational modes into context.
In an inauspicious start to the ultimately very successful installation of the Dark Energy Camera on the V. M. Blanco 4- m telescope at CTIO, the light-weighted Cer-Vit 1.3-m-diameter secondary mirror suffered an accident in which it fell onto its apex. This punched out a central plug of glass and destroyed the focus and tip/tilt mechanism. However, the mirror proved fully recoverable, without degraded performance. This paper describes the efforts through which the mirror was repaired and the tip/tilt mechanism rebuilt and upgraded. The telescope re-entered full service as a Ritchey- Chrétien platform in October of 2013.
The KPNO Nicholas U. Mayall 4-meter telescope is to be the host facility for the Dark Energy Spectroscopic Instrument (DESI). DESI will record broadband spectra simultaneously for 5000 objects distributed over a 3-degree diameter field of view; it will record the spectra of approximately 20 million galaxies and quasi-stellar objects during a five-year survey. This survey will improve the combined precision of measurement on the dark energy equation of state today (w0) and its evolution with redshift (wa) by approximately a factor of ten over existing spectroscopy baryon acoustic oscillation surveys (e.g., BOSS1) in both co-moving volume surveyed and number of galaxies mapped. Installation of DESI on the telescope is a complex procedure, involving a complete replacement of the telescope top end, routing of massive fiber cables, and installation of banks of spectrographs in an environmentally-controlled lab area within the dome. Furthermore, assembly of the instrument and major subsystems must be carried out on-site given their size and complexity. A detailed installation plan is being developed early in the project in order to ensure that DESI and its subsystems are designed so they can be safely and efficiently installed, and to ensure that all telescope and facility modifications required to enable installation are identified and completed in time.
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 Thirty Meter Telescope (TMT) project is a partnership between ACURA, AURA, Caltech, and the University of California. The design calls for a 3.6 m diameter secondary mirror and an elliptical tertiary mirror measuring more than 4 m along its major axis. Each mirror will weigh more than two metric tons and must be articulated to compensate for deformation of the telescope structure. The support and control of these "smaller optics" pose significant challenges for
the designers. We present conceptual designs for active and passive figure control and articulation of these optics.
A feasibility design study was undertaken to assess the requirements of a mid-infrared echelle spectrograph (MIRES)
with a resolving power of 120,000 and its associated mid-infrared adaptive optics (MIRAO) system on the Thirty-Meter
Telescope. Our baseline design incorporates a 2K×2K Si:As array or array mosaic for the spectrograph and a 1K×1K
Si:As array for the slit viewer. Various tradeoffs were studied to minimize risk and to optimize the sensitivity of the
instrument. Major challenges are to integrate the spectrograph to the MIRAO system and, later, to an adaptive
secondary, the procurement of a suitable window and large KRS-5 lenses, and the acquisition of large format mid-IR
detector arrays suitable for the range of background conditions. We conclude that the overall risk is relatively low and
there is no technical reason that should prevent this instrument from being ready for use at first light on the Thirty-
The Gemini Near-Infrared Spectrograph (GNIRS) supports a variety of observing modes over the 1-5 μm wavelength
region, matched to the infrared-optimized performance of the Gemini 8-m telescopes. We describe the optical,
mechanical, and thermal design of the instrument, with an emphasis on challenging design requirements and how they
were met. We also discuss the integration and test procedures used.
We present a discussion of the science drivers and design approach for a high-resolution, mid-infrared spectrograph for
the Thirty-Meter Telescope. The instrument will be integrated with an adaptive optics system optimized for the midinfrared;
as a consequence it is not significantly larger or more complex than similar instruments designed for use on
smaller telescopes. The high spatial and spectral resolution possible with such a design provides a unique scientific
capability. The design provides spectral resolution of up to 120,000 for the 4.5-25 μm region in a cross-dispersed format
that provides continuous spectral coverage of up to 2% to 14 μm. The basic concept is derived from the successful
TEXES mid-infrared spectrograph. To facilitate operation, there are separate imaging channels for the near-infrared and
the mid-infrared; both can be used for acquisition and the mid-infrared imaging mode can be used for science imaging
and for guiding. Because the spectrograph is matched to the diffraction limit of a 30-m telescope, gains in sensitivity are
roughly proportional to the square of the telescope diameter, opening up a volume within the Galaxy a thousand times
greater than existing instruments.
We present a preliminary optical design for a mid-infrared, high-resolution spectrograph (MIRES), together with an
integrated adaptive optics system optimized for the mid-infrared, intended for use on a 30-meter telescope. The design
includes laser guide star wavefront sensors, a near-infrared natural guide star wavefront sensor with a patrol field of 60
arcseconds, and near-infrared and mid-infrared imaging channels, in addition to the cross-dispersed spectrograph itself.
The spectrograph provides resolution of up to 120,000 and continuous spectral coverage over multiple cross-dispersed
orders, with high efficiency between 4.5 and 25 microns.
The Gemini Near-Infrared Spectrograph (GNIRS) has been in successful use on the Gemini South 8-m telescope for over two years. We describe the performance of the instrument and discuss how it matches the expectations from the design. We also examine the lessons to be learned regarding the design and operation of similar large cryogenic facility instruments.
In this paper, we provide an overview of the adaptive optics (AO) program for the Thirty Meter Telescope (TMT) project, including an update on requirements; the philosophical approach to developing an overall AO system architecture; the recently completed conceptual designs for facility and instrument AO systems; anticipated first light capabilities and upgrade options; and the hardware, software, and controls interfaces with the remainder of the observatory. Supporting work in AO component development, lab and field tests, and simulation and analysis is also discussed. Further detail on all of these subjects may be found in additional papers in this conference.
We present a design of a thermal-infrared optimized adaptive optics system for the TMT 30-meter telescope. The
approach makes use of an adaptive secondary but during an initial implementation contains a more conventional
ambient-temperature optical relay and deformable mirror. The conventional optical relay is used without sacrificing the
thermal background by using multiple off-axis laser guide stars to avoid a warm dichroic in the common path. Three
laser guide stars, equally spaced 75" off axis, and a "conventional" 30×30 deformable mirror provide a Strehl > 0.9 at
wavelengths longer than 10 microns and the LGS beams can be passed to the LGS wavefront sensors with pickoff
mirrors while a one-arcminute field is passed unvignetted to the science instrument and NGS WFSs. The overall design
is relatively simple with a wavefront correction similar to existing high-order systems (e.g. 30×30) but still provides
competitive performance over the higher-order TMT NIR AO design at wavelengths as short as 3 microns due to its
reduced thermal emissivity. We present our figures of merit and design considerations within the context of the science
drivers for high-spectral resolution NIR/MIR spectroscopy at 5-28 microns on a 30-meter ground-based telescope.
The Astronomical Instrumentation Group (AIG) of the University of Durham has recently completed an integral field unit (IFU) for use on the Gemini-South telescope with the Gemini Near-Infrared Spectrograph (GNIRS) built by the National Optical Astronomy Observatories (NOAO, USA). When the IFU is deployed remotely inside the instrument cryostat, GNIRS is converted into an integral field spectrograph with a field of 5 × 3 arcsec2 and spatial sampling of 0.15 × 0.15 arcsec2, optimised for 1-2.5μm but operable up to 5μm. We present summaries of the design and construction and results from laboratory testing. We also show results obtained at the telescope where a throughput of 90% was measured at 2.5μm, and show that this is consistent with predictions of a simple model where surface scattering is the dominant loss mechanism. The throughput data are well fit by the roughness measured in the laboratory. Finally, we show a few examples of astrophysical data from the commissioning run in April 2004.
We present case studies on the application of passive compensation in two large astronomical instruments: the Gemini Near Infrared Spectrograph (GNIRS), including actual performance, and the NOAO Extremely Wide Field Infrared Mosaic (NEWFIRM) camera. Image motion due to gravity flexure is a problem in large astronomical instruments. We present solutions for two different cases using passive mechanical compensation of the optical train. For the Gemini Near Infrared Spectrograph (GNIRS), articulation of a single sensitive optic is used. Adjustable cantilevered weights, designed to respond to specific gravity components, are employed to drive tilt flexures connected to the collimator mirror. An additional requirement is that cryocooler vibration must not dynamically excite this mirror. Performance testing of the complete instrument shows that image motion has been satisfactorily compensated. Some image blur due to dynamic excitation by the cryocoolers was noted. A successful damping scheme has been developed experimentally. For the NOAO Extremely Wide Field Infrared Mosaic camera (NEWFIRM), the entire optical support structure is mechanically tuned to deflect and rotate precisely as a rigid body relative to the telescope focal plane. This causes the optical train to remain pointed at a fixed position in the focal plane, minimizing image motion on the science detector. This instrument is still in fabrication.
The design of a near-IR spectrometer for the Gemini 8m telescopes is described. This instrument, GNIRS, provides coverage from 0.9 to 5.5 micrometers at several spectral resolutions and two pixel scales. Capabilities include an imaging mode intended primarily for acquisition, a cross- dispersed mode covering wavelengths from 0.9 to 2.5 micrometers , and provisions for an integral field unit. The design of the GNIRS is conservative, as it must meet tight schedule and resource constraints; it nonetheless provides high throughput and operational efficiency, minimal flexure, and the flexibility needed to support queue observing. The optics are a combination of diamond-turned metal optics for the fore-optics and collimator, and refractive optics for the cameras. The mechanism include a two-axis grating turret; all mechanism are deposited by means of internal detents. The instrument achieves low flexure within its weight budget by the use of a modular structure composed of cylindrical light-weighted sections into which individual mechanisms and optics modules are mounted. Extensive analyses of mechanical and optical performance have been performed. The GNIRS has passed its critical design review, and fabrication is now underway.
We present the conceptual design for a medium-resolution (R equals 2000, 6000) spectrometer for the near IR (0.9 micrometers - 5 micrometers ) to be used on the Gemini 8 m Telescopes. The design goal is to make optimum use of the unique characteristics of the telescopes: superb image quality and low near-IR background. This leads us to propose a mostly reflective design, with cold, pupil-reimaging fore-optics. We achieve a modest slit length of 100 arcsec. In addition to the basic high-spatial-resolution configuration, the design permits a number of important upgrades: a camera for use with a wider slit, a prism cross-disperser, an integral field module to spatially sample a small 2-D region of the focal plane. The spectrometer is designed around the next generation of InSb detectors, the 1024 X 1024 Aladdin arrays currently under development.
This paper describes the Cerro Tololo Infrared Spectometer (IRS), a general purpose cooled-grating spectrometer designed for 4-m and 1.5-m telescopes, which was recently upgraded to operate with the Santa Barbara Research Center 62 x 58 InSb array. Special attention is given to the optical and the mechanical designs of the IRS, its data acquisition and instrument control systems, and the operation characteristics of the instrument and the dewar. The updated IRS provides resolutions from about 0.9 micron to 5 microns.