We follow the history of the US National Gemini Office from its origin when the US National New Technology Telescope was reshaped into two 8m telescopes for the International Gemini Observatory. The development of the office in the decade of the 1990s continues to shape its function to the present. The following decade, 2000–2010, marked major milestones including the dedication of the telescopes, the reshaping of the Gemini instrumentation program, and dissatisfaction of the US community as expressed in the ALTAIR report. Nationally funded facilities are under financial pressure, as new projects must be funded from a nearly fixed budget. We will discuss how the US NGO should be used to advocate for both the US community and the Gemini Observatory. This role could be an essential one in protecting open access to 8m-class facilities.
High-resolution near-infrared echelle spectrographs require coarse rulings in order to match the free spectral range to the
detector size. Standard near-IR detector arrays typically are 2 K x 2 K or 4 K x 4 K. Detectors of this size combined
with resolutions in the range 30000 to 100000 require grating groove spacings in the range 5 to 20 lines/mm.
Moderately high blaze angles are desirable to reduce instrument size. Echelle gratings with these characteristics have
potential wide application in both ambient temperature and cryogenic astronomical echelle spectrographs. We discuss
optical designs for spectrographs employing immersed and reflective echelle gratings. The optical designs set constraints
on grating characteristics. We report on market choices for obtaining these gratings and review our experiments with
custom diamond turned rulings.
We report on echelle gratings produced by diamond turning with groove spacings coarser than 20 lines per mm. Increasing the groove spacing of an echelle reduces the free spectral range allowing infrared orders to be matched to the detector size. Reflection echelle gratings designed for the near-infrared have potential wide application in both ambient temperature as well as cryogenic astronomical spectrographs. Diamond turned reflection echelle gratings are currently employed in space-based high-resolution spectrographs for 2 – 4 μm planetary spectroscopy. Using a sample diamond turned grating we investigate the suitability of a 15 line/mm R3 echelle for use in ground-based 1 – 5 μm spectroscopy. We find this grating suitable for 3 – 5 μm high signal-to-noise, high-resolution applications. Controlling wavefront errors by an additional factor of two would permit use at high-resolution in the 1.5 – 2.5 μm region.
While a premier technique for laboratory spectroscopy, Fourier transform (FT) spectroscopy has fallen into disuse in
astronomical applications. The speed of a FT spectroscopy is significantly less than that of a dispersive spectrograph
with an array detector due to multiplex disadvantage. However, there are a number of advantages of the FT technique
that can be exploited to offer spectroscopic capabilities that would otherwise not be available. For very large telescopes
these include spectral resolutions significantly in excess of 100000 and 2-D spectral spatial imaging. By using postdispersers
with array detectors the speed difference between cryogenic grating and FT spectrographs can be reduced. We
explore the possibilities of using pre-existing FT equipment upgraded with modern detectors on next generation
telescopes. For specificity, we will adopt as our model FTS at the 4-m Mayall telescope and study how it could be
adapted to an ELT, and with what resulting performance.
The combination of immersion grating and infrared array detector technologies allows the construction of highresolution
spectrographs in the near-infrared that have capabilities similar to those of optical spectrographs. It is
possible, for instance, to design multi-object spectrographs with very large wavelength coverage and high throughput.
We explored the science and functional drivers for these spectrograph designs. Several key inputs into the design are
reviewed including risk, mechanical-optical trades, and operations. We discuss a design for a fixed configuration
spectrograph with either 1.1 - 2.5 or 3 - 5 μm simultaneous wavelength coverage.
The combination of immersion grating and infrared array detector technologies now allows the construction
of high-resolution spectrographs in the near-infrared that have capabilities approaching those of optical
spectrographs. It is possible, for instance, to design multi-object spectrographs with very large wavelength
coverage and high throughput. However, infrared spectrographs must be cryogenic and the cost of
complexity can be large. We investigate lower cost design options for single-object high-resolution
spectrographs. The trade-off in these designs is between the size/number of infrared arrays and the
inclusion of moving parts. We present a design for a no moving parts spectrograph with either 1.1-2.5 or 3-
5 μm simultaneous wavelength coverage. The design was undertaken with attention to cost as well as
scientific merit. Here we review the science drivers and key functional requirements. We present a general
overview of the instrument and estimate the limiting performance. The performance is compared with that
of medium-resolution infrared spectrographs as well as other high-resolution infrared spectrographs.
The High-resolution Near-infrared Spectrograph (HRNIRS) concept for the Gemini telescopes combines a seeing-limited R ~ 70000 cross-dispersed mode and a MCAO-fed near diffraction-limited R ~ 20000 multi-object mode into a single compact instrument operating over the 0.9-5.5μm range. We describe the mechanical design, emphasizing the challenging design requirements and how they were met. The approach of developing the optical and mechanical designs in concert and utilizing proven working concepts from the Gemini Near Infra-Red Spectrograph were key elements of the design philosophy. Liang, et al. provides a detailed discussion of the optical design, Hinkle, et al. describes the science cases and requirements as well as a general overview, and Eikenberry, et al. describes the systems engineering and performance aspects of HRNIRS.
The High-Resolution Near-InfraRed Spectrograph (HRNIRS) concept for the Gemini telescopes combines a seeing limited R ~ 70000 cross-dispersed mode and an MCAO-fed near diffraction-limited R ~ 30000 multi-object mode into a single compact instrument operating over the 1 - 5 μm range. The HRNIRS concept was developed in response to proposals issued through the Aspen instrument process by Gemini. Here we review the science drivers and key functional requirements. We present a general overview of the instrument and estimate the limiting performance.
HRNIRS is an extremely versatile high-resolution infrared facility spectrograph designed for the Gemini South telescope. Operating over the 1.05 - 5.5 micron wavelength range, it has the capability to carry out a wide range of scientific programs by incorporating two separate modes of operation. The first is a conventional single slit cross-dispersed mode providing spectral resolution R ~ 70000 with a 0.4 arcsec slit over as much as an octave in wavelength, thus covering most of the JHK or LM windows in a single observation. In this mode the spectrograph accepts the Gemini seeing-limited f/16 input over a small field. A built-in modulator and polarizer allow HRNIRS to measure both linear and circular polarization. The second mode is a moderately-high resolution (R ~ 30000) spectrograph observing multiple objects simultaneously within a 2 arcmin field fed by the f/33.2 Gemini MCAO beam. In this paper, we discuss the optical design considerations, present the resulting design and show that the predicted performance meets the design requirements.
The High-resolution Near-infrared Spectrograph (HRNIRS) concept for the Gemini telescopes combines a seeing-limited R ~ 7000 cross-dispersed mode and an MCAO-fed near diffraction-limited R ~ 20000 multi-object mode into a single compact instrument operating over the 0.9 - 5.5 μm range. We describe the systems engineering and performance modeling aspects of this study, emphasizing simulations of high-precision radial verlocity measurements in the Gemini Cassegrain-focus instrument environment.
Phoenix, a high resolution near-infrared spectrograph build by NOAO, was first used on the Gemini South telescope in December 2001. Previously on the Kitt Peak 2.1 and 4 meter telescopes, Phoenix received a new detector, as well as modified refrigeration, mounting, and handling equipment, prior to being sent to Gemini South. Using a two-pixel slit the resolution is ~75,000, making Phoenix the highest resolution infrared spectrograph available on a 6-10 meter class telescope at the current time. Modifications to and performance of the instrument are discussed. Some results on Magellanic cloud stars, brown dwarf stars, premain-sequence objects, and stellar exotica are reviewed briefly.
At the 1998 SPIE meeting we described a cryogenic, high- resolution spectrograph for use in the 1-5 micrometers region. At that time Phoenix had been used at Kitt Peak for about a year. In the intervening two years we have worked extensively with the instrument and have modified a few aspects of the design to bring the operational characteristics more closely into agreement with the original specifications. Changes to the instrument since 1998 that resulted in significant improvements in performance will be discussed. We will review the current operational characteristics of the spectrograph. Phoenix is a facility instrument of the National Optical Astronomy Observatory with use planned at Gemini South and CTIO.
We describe a cryogenic, high-resolution spectrograph (Phoenix) for the 1-5 micrometers region. Phoenix is an echelle spectrograph of the near-Littrow over-under configuration without cross dispersion. The foreoptics include Lyot re- imaging, discrete and circular variable order sorting filters, a selection of slits, and optics for post-slit and Lyot imaging. The entire instrument is cooled to 50 K using two closed cycle coolers. The detector is a Hughes-Santa Barbara 512 X 1024 InSb array. Resolution of 65,000 has been obtained. Throughput without slit losses is 13 percent at 2.3 micrometers . Recent results are discussed. Phoenix is a facility instrument of the National Optical Astronomy Observatories and will be available at CTIO, KPNO, and Gemini.
Large astronomical spectrographs designed for use in the visible for use in the visible can operate efficiently well beyond the long wavelength cutoff of CCD detectors. Given the expense and complexity of constructing IR-optimized high resolution or multi-object spectrographs, it is prudent to explore the range of scientific programs possible utilizing modern near-IR arrays at the focal plane of historically visible wavelength instruments. For the past three years, we have used the NICMASS camera, a 256 by 256 HgCdTe imager developed at the University of Massachusetts, at the camera 5 focus of the Coude Feed Spectrograph on Kitt Peak for moderate and high resolution IR spectroscopy in the 1-1.8 micrometers range. This configuration has been used at a spectral resolution 7200 using a 316 1/mm grating an extremely stable platform permitting radial velocity determinations to better than 1 km-s -1. We will discuss some scientific results obtained with this novel configuration and the performance limitations imposed by the ambient temperature spectrograph beyond a wavelength of 1 micrometers . We also discuss plans to evaluate the suitability of NICMASS for multi- object near-IR spectroscopy on the Hydra Bench Spectrograph at the WIYN telescope on Kitt Peak.
The thermal conductivity, specific heat, and elastic moduli of silicon indicate that silicon is an attractive material for the substrates of large cryogenic mirrors. Elemental silicon is available in large single crystals as well as polycrystalline blanks. Silicon is already used extensively in optics for both high-index IR lenses and IR filter substrates. We report on cryogenic tests of silicon mirrors. Our samples show that on cycling from room temperature to 77 K, the dimensional stability is only slightly worse than that of fused silica, which is a known highly stable, cryogenic mirror substrate. The dimensional stability of silicon is much better than that of metal mirrors. The fabrication of silicon mirrors, including a 20 by 40 cm grating blank, for a high-resolution, IR spectrograph now under construction at NOAO is discussed.
The optical design of a high-resolution 2-5-micron IR cryogenic echelle spectrometer which is currently under construction at NOAO is described. Special attention is given to the design and the purpose of the four units into which the spectrometer's optic can be divided: the foreoptics unit, the order-separation filter and slit unit, the echelle-collimator unit, and the camera unit. Optical specifications of each of these units are summarized.