Ground-based telescopes require useful and productive instruments to stay relevant in astronomy. The Kitt Peak Ohio State Multi-Object Spectrograph (KOSMOS), originally on the Kitt Peak National Observatory (KPNO) Mayall 4 m Telescope, is a long-slit and multi-object, low-resolution spectrograph. KOSMOS was acquired by the Astrophysical Research Consortium (ARC) for the Apache Point Observatory (APO) ARC 3.5 m telescope, implemented redesigns to the instrument, and renamed KOSMOS II. The instrument was integrated into the ARC 3.5 m’s operational environment by adding a Nasmyth port adapter, a cart with a truss for mechanical support, and telescope user interface (TUI) software. Upgrades include slit-viewing guiding, internal calibration lamps, heat exhaust, and a new cryostat. Since 2021, KOSMOS II has proven capable of the high-throughput, low-resolution spectroscopy required by the ARC 3.5 m user community. This paper describes the design updates and revisions made to the instrument along with measurements of its performance.
Ground-based telescopes require useful and productive instruments to stay relevant in astronomy. The Kitt Peak Ohio State Multi Object Spectrograph (KOSMOS), originally on the Kitt Peak National Observatory (KPNO) 4-meter Mayall Telescope, is a long-slit and multi-object, low-resolution spectrograph. KOSMOS was acquired by the Astrophysical Research Consortium (ARC) for the Apache Point Observatory (APO) ARC 3.5m telescope, implemented redesigns to the instrument, and renamed KOSMOS II. The instrument was integrated into the ARC 3.5m's operational environment by adding a Nasmyth port adapter, a cart with truss for mechanical support, and telescope user interface (TUI) software. Upgrades include slit-viewing guiding, internal calibration lamps, heat exhaust, and a new cryostat. Since 2021, KOSMOS II has proven capable of the high-throughput, low-resolution spectroscopy required by the ARC 3.5m user community. This paper describes the design updates and revisions made to the instrument along with measurements of its performance.
We present the conceptual design of a new optical echelle spectrograph for the Astrophysical Research Consortium 3.5-m Telescope at Apache Point Observatory in New Mexico. The Nasmyth-mounted slit spectrograph, intended to replace the existing echelle spectrograph that is over 20 years old, will provide continuous spectra for wavelengths spanning the range 350 nm – 1000 nm with a white pupil design featuring separate blue and red arms. A real-time slit change mechanism will allow three primary modes: 1) Resolution R ~ 32,000 for the median seeing of 1.2 arcsec FWHM, 2) R ~ 40,000 when using a smaller slit with tip-tilt image stabilization, and 3) R ~ 64,000 using a two-slice image slicer. The peak instrument throughput is ~ 38% and at 350 nm the throughput is ~ 22%. High throughput, particularly in the blue, will be enabled through the use of an atmospheric dispersion corrector, high performance coatings, tip-tilt image stabilization, and careful attention to refractive material choices. Expected instrument sensitivity for magnitude 14 stars is SNR per pixel of 50 in 3600 sec at 355 nm (u-band) and about 1800 sec for the centers of griz bands for both the R ~32,000 and R~ 40,000 modes.
We discuss the field retermination of high-fiber count MTP fiber connectors used with the APOGEE spectrograph at Apache Point Observatory (APO) in 2021. We address lessons-learned, wear-analysis of removed MTPs, and throughput of the fiber train with the newly terminated fibers in SDSS-V. For the past decade the spectrograph at APO, as part of multiple incarnations of the Sloan Digital Sky Survey (SDSS), has relied upon rapid changes of ten MTP connectors, each containing 30 terminated fibers, and all contained within a custom gang connector system. These rapid changes enable the iterative plugging of the gang connector into multiple cartridges with different plug plates to observe various survey fields throughout the night. While robotic Focal Plane Systems have been developed for SDSS-V to replace plug plates, which will minimize the fiber connector cycles, we nonetheless reterminated the most heavily used MTP connectors. The connector cycles had far exceeded manufacturer lifetimes and the overall system throughput was degrading.
SDSS-V is the fifth generation of the Sloan Digital Sky Survey and is an ambitious follow-on to a project that has been producing ground-breaking science for two decades. SDSS-V uses two dedicated 2.5m telescopes – the SDSS telescope at Apache Point Observatory in New Mexico, and the du Pont telescope at Las Campanas Observatory in Chile – feeding BOSS and APOGEE spectrographs at each site. These survey machines generate multi-object, all-sky spectroscopy in the optical and near-IR in support of primary science programs. The new wide field corrector for the SDSS 2.5m telescope is one of several major infrastructure upgrades undertaken for SDSS-V, necessitated by the replacement of the legacy fiber plug plate system with a new robotic Fiber Positioning System (FPS), which places different requirements on the focal characteristics of the telescope. The original 2-element corrector produced a focal surface which was non-telecentric and suffered from axial color, throughput, and image quality issues when used in the H-band with the APOGEE spectrograph. We have designed and built a 3-element, all fused silica corrector which addresses the optical shortcomings in relation to the FPS. In addition, the optomechanical design required very minimal changes to the telescope interfaces and also facilitates in-situ axial adjustment of one lens element to fine-tune the as-built spherical radius of the focal surface, to match the nominal design value to which the FPS was built. This paper discusses the optical and optomechanical design details of the new wide field corrector, concluding with a brief summary of recent commissioning results.
We present measurements of the adapted SDSS-V BOSS fiber slit, as well as measurements of the APOGEE fiber tributaries in order to better our understanding of throughput loss at multi-fiber termination junctions. The BOSS fiber slit was adapted from the original slit used on sky, and multi fiber termination connectors were added in order to extend the fiber length for the new SDSS-V FPS configuration. Testing on multi fiber termination junctions was conducted with APOGEE tributaries to characterize the expected throughput loss due to multi fiber terminations for the APOGEE spectrograph. Multi fiber connectors were tested with and without index matching gel to evaluate whether throughput loss could be mitigated
We present the on-sky performance of the new wide field corrector for the fifth generation of the Sloan Digital Sky Survey (SDSS-V). This new three-element corrector was designed to replace the previous two-element design, which had an aspherical focal surface and was not optimized for the infrared (H-band). The purpose of the new corrector is to improve the imaging performance required for a new robotic Fiber Positioning System (FPS). For commissioning, a Focal Surface Camera (FSC) was developed and used to determine the focal surface location relative to the telescope interface, and to verify imaging performance across the 3-degree field of view of the corrector. This paper discusses the commissioning process in detail, describes how the imaging data were processed, and presents the measured image quality across the field.
Several external hardware upgrades have been developed for the APOGEE Spectrographs as part of the Sloan Digital Sky Survey-V (SDSS-V) to improve their radial velocity (RV) precision from a floor of 100-200 m/sec to approx. 30 m/sec. The upgrades include: (1) Back Pressure Regulator (BPR) systems to stabilize the internal instrument LN2 tank boil-off pressure, lessening induced movement of the APOGEE optical bench; (2) Fabry-Perot Interferometer (FPI) calibration sources to improve wavelength calibration; and (3), the use of octagonal core fiber segments in the fiber train to improve radial scrambling. We discuss the fabrication, commissioning, and early performance of these upgrades.
We describe the on-sky performance of the robotic Focal Plane System (FPS) units that replace the fiber plug-plate systems at the Sloan and duPont telescopes for the SDSS-V survey. The first FPS was arrived at Apache Point in December 2021, and the second unit will be delivered to Las Campanas in spring 2022. Each FPS carries 500 zonal fiber positioners carrying three fibers: two science fibers for the BOSS and APOGEE spectrographs and a back-illuminated metrology fiber. The FPS enables the SDSS-V Milky Way and Black Hole Mapper surveys that will begin survey operations in 2022.
We describe the design and implementation of a fourth version of the TripleSpec near-infrared spectrograph (TSpec4). This version of the instrument was designed for and first implemented on the 4-m Blanco telescope on Cerro Tololo, and subsequently converted for use on the 4-m Southern Astrophysical Research (SOAR) Telescope on Cerro Pachon. Details of the changed opto-mechanical design and mounting arrangements are discussed. An updated data pipeline provides reduced spectra from the instrument. We describe the required modifications and the performance of both implementations of TSpec4.
The move from the Blanco to SOAR required changing from operation at a classical Cassegrain f/8 focus to operation at a Nasmyth f/16 focus. The SOAR mount also employs a rotator and required accommodation to a significantly different back-focal distance inside the instrument. These changes were implemented by modifying the instrument fore-optics which feeds light onto the slit at f/10.6. The spectrograph and slit viewer optics are unchanged. A dichroic reflects infrared light toward the instrument while passing visible light to a SOAR facility guider; this removes the shortest wavelengths from the spectra and in turn required modification of the data reduction pipeline.
As the telescopes have similar apertures, the performance of the instrument is similar on both, though on SOAR image quality is somewhat better and details of the instrument’s optical properties differ also. Flexure performance differs as well due to the different instrument locations.
The Large Binocular Telescope Interferometer (LBTI) is a strategic instrument of the LBT designed for highsensitivity, high-contrast, and high-resolution infrared (1.5-13 μm) imaging of nearby planetary systems. To carry out a wide range of high-spatial resolution observations, it can combine the two AO-corrected 8.4-m apertures of the LBT in various ways including direct (non-interferometric) imaging, coronagraphy (APP and AGPM), Fizeau imaging, non-redundant aperture masking, and nulling interferometry. It also has broadband, narrowband, and spectrally dispersed capabilities. In this paper, we review the performance of these modes in terms of exoplanet science capabilities and describe recent instrumental milestones such as first-light Fizeau images (with the angular resolution of an equivalent 22.8-m telescope) and deep interferometric nulling observations.
Integral field spectrographs are an important technology for exoplanet imaging, due to their ability to take spectra in a high-contrast environment, and improve planet detection sensitivity through spectral differential imaging. ALES is the first integral field spectrograph capable of imaging exoplanets from 3-5 μm, and will extend our ability to characterize self-luminous exoplanets into a wavelength range where they peak in brightness. ALES is installed inside LBTI/LMIRcam on the Large Binocular Telescope, taking advantage of existing AO systems, camera optics, and a HAWAII-2RG detector. The new optics that comprise ALES are a Keplerian magnifier, a silicon lenslet array with diffraction suppressing pinholes, a direct vision prism, and calibration optics. All of these components are installed in filter wheels making ALES a completely modular design. ALES saw first light at the LBT in June 2015.
TripleSpec 4 (TS4) is a near-infrared (0.8um to 2.45um) moderate resolution (R ~ 3200) cross-dispersed spectrograph
for the 4m Blanco Telescope that simultaneously measures the Y, J, H and K bands for objects reimaged
within its slit. TS4 is being built by Cornell University and NOAO with scheduled commissioning in 2015.
TS4 is a near replica of the previous TripleSpec designs for Apache Point Observatory's ARC 3.5m, Palomar
5m and Keck 10m telescopes, but includes adjustments and improvements to the slit, fore-optics, coatings and
the detector. We discuss the changes to the TripleSpec design as well as the fabrication status and expected
sensitivity of TS4.
The Large Binocular Telescope (LBT) houses two 8.4-meter mirrors separated by 14.4 meters on a common mount. Coherent combination of these two AO-corrected apertures via the LBT Interferometer (LBTI) produces Fizeau interferometric images with a spatial resolution equivalent to that of a 22.8-meter telescope and the light- gathering power of single 11.8-meter mirror. Capitalizing on these unique capabilities, we used LBTI/LMIRcam to image thermal radiation from volcanic activity on the surface of Io at M-Band (4.8 μm) over a range of parallactic angles. At the distance of Io, the M-Band resolution of the interferometric baseline corresponds to a physical distance of ~135 km, enabling high-resolution monitoring of Io volcanism such as ares and outbursts inaccessible from other ground-based telescopes operating in this wavelength regime. Two deconvolution routines are used to recover the full spatial resolution of the combined images, resolving at least sixteen known volcanic hot spots. Coupling these observations with advanced image reconstruction algorithms demonstrates the versatility of Fizeau interferometry and realizes the LBT as the first in a series of extremely large telescopes.
We present performance reports of a new near-infrared (NIR) Fiber-Fabry Perot Interferometer (FFP) as a precise Doppler radial velocity (RV) wavelength reference.
FFPs are monolithic single-mode fiber devices that create emission spectra by interfering light traversing separate delay paths. The resulting interference spectrum provides a rich distribution of narrow lines, ideal for use as a precise spectrograph reference. The FFP has the advantages that the uniform density of emission lines gives a much wider bandwidth over which RV measurements are possible, and the finesse and bandwidth can be optimized for the specific application.
John Wilson, F. Hearty, M. Skrutskie, S. Majewski, R. Schiavon, D. Eisenstein, J. Gunn, J. Holtzman, D. Nidever, B. Gillespie, D. Weinberg, B. Blank, C. Henderson, S. Smee, R. Barkhouser, A. Harding, S. Hope, G. Fitzgerald, T. Stolberg, J. Arns, M. Nelson, S. Brunner, A. Burton, E. Walker, C. Lam, P. Maseman, J. Barr, F. Leger, L. Carey, N. MacDonald, G. Ebelke, S. Beland, T. Horne, E. Young, G. Rieke, M. Rieke, T. O'Brien, J. Crane, M. Carr, C. Harrison, R. Stoll, M. Vernieri, M. Shetrone, C. Allende-Prieto, J. Johnson, P. Frinchaboy, G. Zasowski, A. Garcia Perez, D. Bizyaev, K. Cunha, V. Smith, Sz. Meszaros, B. Zhao, M. Hayden, S. D. Chojnowski, B. Andrews, C. Loomis, R. Owen, M. Klaene, J. Brinkmann, F. Stauffer, D. Long, W. Jordan, D. Holder, F. Cope, T. Naugle, B. Pfaffenberger, D. Schlegel, M. Blanton, D. Muna, B. Weaver, S. Snedden, K. Pan, H. Brewington, E. Malanushenko, V. Malanushenko, A. Simmons, D. Oravetz, S. Mahadevan, S. Halverson
The Apache Point Observatory Galactic Evolution Experiment (APOGEE) uses a dedicated 300-fiber, narrow-band
near-infrared (1.51-1.7 μm), high resolution (R~22,500) spectrograph to survey approximately 100,000 giant stars across
the Milky Way. This three-year survey, in operation since late-summer 2011 as part of the Sloan Digital Sky Survey III
(SDSS III), will revolutionize our understanding of the kinematical and chemical enrichment histories of all Galactic
stellar populations. We present the performance of the instrument from its first year in operation. The instrument is
housed in a separate building adjacent to the 2.5-m SDSS telescope and fed light via approximately 45-meter fiber runs
from the telescope. The instrument design includes numerous innovations including a gang connector that allows
simultaneous connection of all fibers with a single plug to a telescope cartridge that positions the fibers on the sky,
numerous places in the fiber train in which focal ratio degradation had to be minimized, a large mosaic-VPH (290 mm x
475 mm elliptically-shaped recorded area), an f/1.4 six-element refractive camera featuring silicon and fused silica
elements with diameters as large as 393 mm, three near-infrared detectors mounted in a 1 x 3 mosaic with sub-pixel
translation capability, and all of these components housed within a custom, LN2-cooled, stainless steel vacuum cryostat
with dimensions 1.4-m x 2.3-m x 1.3-m.
The L/M-band (3−5 μm) InfraRed Camera (LMIRcam) sits at the combined focal plane of the Large Binocular
Telescope Interferometer (LBTI), ultimately imaging the coherently combined focus of the LBT’s two 8.4-meter
mirrors. LMIRcam achieved first light at the LBT in May 2011 using a single AO-enabled 8.4-meter aperture.
With the delivery of LBT’s final adaptive secondary mirror in Fall of 2011, dual-aperture AO-corrected interferometric
fringes were realized in April 2012. We report on the performance of these configurations and characterize
the noise performance of LMIRcam’s HAWAII-2RG 5.3-μm cutoff array paired with Cornell FORCAST readout
electronics. In addition, we describe recent science highlights and discuss future improvements to the LMIRcam
hardware.
We diamond fly cut 2 sets of germanium grisms for the LMIRcam 3-5 micron Fizeau imager for the combined focus of
the Large Binocular Telescope (LBT). The grisms mount in a filter wheel near a pupil to enable moderate resolution
(R~300) spectroscopy. Both sets have a measured blaze angle of 2.9°. The first set has a groove period of 40 lines/mm
and will be used in first order with peak efficiency at 3.6 μm. The second set has 32 lines/mm. It can operate in first
order with an efficiency peak near 4.4 μm and in second order with a peak near 2.3 μm. First results from testing the
grisms in the instrument on the sky with the LBT are presented.
The Apodizing Phase Plate (APP) is a simple optic that provides coronagraphic suppression of diffraction without
the need for any focal plane occulters. We present the design of a broadband APP (the BAPP) for LMIRCam
that is optimised for the direct imaging of cool extrasolar giant planets around nearby stars at thermal infrared
wavelengths. These optics have a high throughput and require no precision alignment. We cover earlier results
using a chromatic APP, the basic principle and manufacture of the optic.
Basil Blank, Chuck Henderson, John Wilson, Fred Hearty, Michael Skrutskie, Thomas O'Brien, Steven Majewski, Ricardo Schiavon, Paul Maseman, Sophia Brunner, Adam Burton, Eric Walker
The Apache Point Observatory Galactic Evolution Experiment (APOGEE) is a survey of all Galactic stellar populations
that will employ an R=30,000 spectrograph operating in the near-infrared (1.5-1.7μm) wavelength range. The fiber-fed
spectrograph is housed in a large (1.4m x 2.3m x 1.3m) stainless steel cryostat or Dewar that is LN2-cooled and will be
located in a building near the 2.5m Sloan Digital Sky Survey (SDSS) telescope to which it will be coupled. The choice
of shell material and configuration was an optimization among optics packaging, weight, strength, external dimensions,
rigging and transportation, the available integration and testing room, and the ultimate instrument room at APO.
Internals are fabricated of more traditional 6061-T6 aluminum which is well proven in cryogenic applications. An active
thermal shield with MLI blanketing yields an extremely low thermal load of 45-50 watts for this ~3000 liter instrument.
Cryostat design details are discussed with applicable constraints and trade decisions. APOGEE is one of four
experiments that are part of Sloan Digital Sky Survey III (SDSS-III).
Development of the Apache Point Observatory Galactic Evolution Experiment (APOGEE) near-infrared spectrograph
has motivated thorough investigation into the properties and performance of optical fibers. The fiber selected for
APOGEE is a step index, multi-mode fiber, developed by PolyMicro, with a 120μm low OH, fused silica core, 25μm
cladding, and 10μm buffer. The instrument design includes a 40 meter fiber run, connecting the spectrograph to the
2.5m Sloan Digital Sky Survey (SDSS) telescope, and an additional 2.5 meter fiber segment located within the
instrument dewar, a vacuum-sealed, cryogenic environment. This light path is convoluted and includes many transitions
and connections where the beam is susceptible irrevocable loss. To optimize the spectrograph performance it is
necessary to minimize the losses incurred in the fiber system, especially those resulting in focal ratio degradation (FRD).
The focus of this research has been to identify potential sources of loss and where applicable, select material components
to minimize this effect. There is little previous documented work concerning the performance of optical fibers within
this wavelength band (1.5-1.7μm). Consequently, the following includes comprehensive explanations of the APOGEE
fiber system components, our experimental design and optical test bed set-up, beam alignment procedures, fiber
terminating and polishing techniques, and results from our examination of FRD as correlated with source wavelength,
fiber length and termination, and environmental conditions.
We report on the final design and the fabrication status of LMIRcam - a mid-infrared imager/spectrograph that will
operate behind the Large Binocular Telescope Interferometer (LBTI) primarily at wavelengths between 3 and 5um (the
astronomical L- and M-bands). Within LMIRcam a pair of diamond-turned biconic mirrors re-images a ten arcsecond
square field onto a 1024x1024 HAWAII-1RG 5.1um cutoff array. The re-imaging optics provide two pupil planes for
the placement of filters and grisms as well as an intermediate image plane. Flexible readout electronics enable operating
modes ranging from high frame rate broadband imaging at the longest wavelengths to low background R=400
spectroscopy at shorter wavelengths. The LBTI will provide LMIRcam with a diffraction limited two-mirror PSF with
first null dictated by the 14.4 meter separation of the two LBT mirror centers (22.8 meter baseline from edge to edge).
We present the integration of a low dark current extended wavelength (2.3μm cutoff) InGaAs array into the
Cornell-Massachusetts Slit Spectrograph (CorMASS) spectrograph. The InGaAs array was fabricated onto a SB-
206 512×512 readout integrated circuit (ROIC) by Goodrich/Sensors Unlimited and subsequently went through a
series of laboratory characterization tests at the University of Virginia demonstrating dark current performance
of better than 10 e-/s. The InGaAs array is adapted for use with the CorMASS to verify its performance in a
proven astronomical instrument, and for eventual deployment to a telescope to test stability and performance.
Volume phase holographic (VPH) gratings are increasingly being used as diffractive elements in astronomical
instruments due to their potential for very high peak diffraction efficiencies and the possibility of a compact instrument
design when the gratings are used in transmission. Historically, VPH grating (VPHG) sizes have been limited by the size
of manufacturer's holographic recording optics. We report on the design, specification and fabrication of a large, 290
mm × 475 mm elliptically-shaped, mosaic VPHG for the Apache Point Observatory Galactic Evolution Experiment
(APOGEE) spectrograph. This high-resolution near-infrared multi-object spectrograph is in construction for the Sloan
Digital Sky Survey III (SDSS III). The 1008.6 lines/mm VPHG was designed for optimized performance over a
wavelength range from 1.5 to 1.7 μm. A step-and-repeat exposure method was chosen to fabricate a three-segment
mosaic on a 305 mm × 508 mm monolithic fused-silica substrate. Specification considerations imposed on the VPHG to
assure the mosaic construction will satisfy the end use requirements are discussed. Production issues and test results of
the mosaic VPHG are discussed.
The Apache Point Observatory Galactic Evolution Experiment (APOGEE) will use a dedicated 300-fiber, narrow-band
(1.5-1.7 micron), high resolution (R~30,000), near-infrared spectrograph to survey approximately 100,000 giant stars
across the Milky Way. This survey, conducted as part of the Sloan Digital Sky Survey III (SDSS III), will revolutionize
our understanding of kinematical and chemical enrichment histories of all Galactic stellar populations. The instrument,
currently in fabrication, will be housed in a separate building adjacent to the 2.5 m SDSS telescope and fed light via
approximately 45-meter fiber runs from the telescope. The instrument design includes numerous technological
challenges and innovations including a gang connector that allows simultaneous connection of all fibers with a single
plug to a telescope cartridge that positions the fibers on the sky, numerous places in the fiber train in which focal ratio
degradation must be minimized, a large (290 mm x 475 mm elliptically-shaped recorded area) mosaic-VPH, an f/1.4 sixelement
refractive camera featuring silicon and fused silica elements with diameters as large as 393 mm, three near-within a custom, LN2-cooled, stainless steel vacuum cryostat with dimensions 1.4 m x 2.3 m x 1.3 m.
The L/M-band mid-InfraRed Camera (LMIRcam) will use a mid-wave (5.1 μm cut-off) Teledyne Imaging Systems
HgCdTe HAWAII 1-RG array to image the coherently combined (Fizeau) focus of the Large Binocular Telescope's
twin 8.4-meter primary mirrors generated by the University of Arizona's beam combiner - the Large Binocular
Telescope Interferometer (LBTI). The 1024x1024 array will have a pixel scale of 10.9 milliarcsec (mas) per
pixel and a field of view of 10"x10". The highest achievable angular resolution will be 26mas (34mas) for
3.6 μm (4.8 μm). LMIRcam will operate in parallel with the Nulling Infrared Camera (NIC), sharing the same
Dewar. In addition to a suite of broad and narrow-band filters, LMIRcam will contain grisms for low-resolution
spectroscopy, and serve as a test-bed for novel pupil masks to enable high-contrast imaging. The opto-mechanical
design, anticipated performance, and a sample of potential science applications are presented. LMIRcam is funded
by the National Science Foundation and the University of Virginia.
We report the performance of Triplespec from commissioning observations on the 200-inch Hale Telescope
at Palomar Observatory. Triplespec is one of a set of three near-infrared, cross-dispersed spectrographs
covering wavelengths from 1 - 2.4 microns simultaneously at a resolution of ~2700. At Palomar, Triplespec
uses a 1×30 arcsecond slit. Triplespec will be used for a variety of scientific observations, including
moderate to high redshift galaxies, star formation, and low mass stars and brown dwarfs. When used in
conjunction with an externally dispersed interferometer, Triplespec will also detect and characterize
extrasolar planets.
The most difficult aspects in manufacturing a reflective slit substrate are achieving a precisely fabricated slit
surrounded by an optically flat surface. A commonly used technique is to polish a metal substrate that has a slit cut by
electric discharge machine (EDM) methods. This process can produce 'optically flat' surfaces; however, the EDM can
produce a slit with edge roughness on the order of 10 microns and a RMS field roughness of ~1 micron. Here, we
present a departure from these traditional methods and employ the advantages inherent in integrated circuit fabrication.
By starting with a silicon wafer, we begin with a nearly atomically flat surface. In addition, the fabrication tools and
methodologies employed are traditionally used for high precision applications: this allows for the placement and
definition of the slit with high accuracy. If greater accuracy in slit definition is required, additional tools, such as a
focused ion beam, are used to define the slit edge down to tens of nanometers. The deposition of gold, after that of a
suitable bonding layer, in an ultra-high vacuum chamber creates a final surface without the need of polishing. Typical
results yield a surface RMS-roughness of approximately 2nm. Most of the techniques and tools required for this process
are commonly available at research universities and the cost to manufacture said mirrors is a small fraction of the
purchase price of the traditional ones.
A small research grant from the AAS has enabled the addition of a pair of MgF2 Wollaston prism polarization analyzers to the Fan Mountain Near Infrared Camera (FanCam). FanCam is a HAWAII-1 (1K × 1K HgCdTe) near infrared camera attached to the 0.8m Cassegrain reflector at Fan Mountain Observatory, 15 miles south of Charlottesville, Virginia. It images an 8.5 × 8.5 arcmin field of view with 0.51 arcsec pixels through a variety of broad band and narrow band filters, including JHKs, Brγ, and H2. The polarizers are mounted in one of the two camera filter wheels in the cold collimated beam near the re-imaged pupil and are oriented such that the direction of the separation of the split polarized images from one prism is rotated 45° relative to that from the other prism. The linear Stokes parameters of uncrowded point sources over a 7.5 × 7.5arcmin field of view may be measured by aperture photometry of pairs of images acquired through the two prisms. Initial obervations of polarized and unpolarized standard stars show that measurements of the degree of polarization are repeatable to within a few tenths of a percent, consistent with photon counting statistics. More standard star observations will be necessary to determine precisely the instrumental polarization and position angle offsets, but they appear to be stable and reasonably small.
We describe the optical and mechanical design of a simple hand-held near infrared spectrograph constructed
to produce observations of the spectrum of scrambled light from the Earth from aboard the International Space
Station. Observing the Earth in this manner simulates the changing perspective on an extra-solar terrestrial
planet observed as a point source by the Terrestrial Planet Finder. A Sensors Unlimited, Inc. SU320-M
InGaAs(0.86 - 1.72μm) camera detects the dispersed spectrum and outputs NTSC video to be recorded and
also permits frame grabbing. One of the three copies of the instrument is currently aboard the International
Space Station. The optical and mechanical design was conceived and executed by graduate and undergraduate
students at the University of Virginia.
Shipboard infrared search and track (IRST) systems can detect sea-skimming anti-ship missiles at long ranges. Since IRST systems cannot measure range and line-of-sight velocity, they have difficulty distinguishing missiles from slowly moving false targets and clutter. In a joint Army-Navy program, the Army Research Laboratory (ARL) is developing a chirped amplitude modulation ladar to provide range and velocity measurements for tracking of targets handed over to it by the distributed aperture system IRST (DAS-IRST) under development at the Naval Research Laboratory (NRL) under Office of Naval Research (ONR) sponsorship. By using an array receiver based on Intevac Inc.'s Electron Bombarded Active Pixel Sensor (EBAPS) operating near 1.5 μm wavelength, ARL's ladar also provides 3D imagery of potential threats in support of the force protection mission. In Phase I, ARL designed and built a breadboard ladar system for proof-of-principle static platform field tests. In Phase II, ARL is improving the ladar system to process and display 3D imagery and range-Doppler plots in near real-time, to re-register frames in near real-time to compensate for platform and target lateral motions during data acquisition, and to operate with better quality EBAPS tubes with higher quantum efficiency and better response spatial uniformity. The chirped AM ladar theory, breadboard design, performance model results, and initial breadboard preliminary test results were presented last year at this conference. This paper presents the results of tests at the Navy's Chesapeake Bay Detachment facility. The improvements to the ladar breadboard since last year are also presented.
Four institutions are collaborating to design and build three near identical R ~2700 cross-dispersed near-infrared spectrographs for use on various 5-10 meter telescopes. The instrument design addresses the common observatory need for efficient, reliable near-infrared spectrographs through such features as broad wavelength coverage across 6 simultaneous orders (0.8 - 2.4 microns) in echelle format, real-time slit viewing through separate optics and detector, and minimal moving parts. Lastly, the collaborators are saving money and increasing the likelihood of success through economies of scale and sharing intellectual capital.
The availability of both large aperture telescopes and large
format near-infrared (NIR) detectors are making wide-field NIR
imaging a reality. We describe the Wide-field Infrared Camera
(WIRC), a newly commissioned instrument that provides the Palomar
200-inch telescope with such an imaging capability. WIRC features
a field-of-view (FOV) of 4.33 arcminutes on a side with its
currently installed 1024-square Rockwell Hawaii-I NIR detector. A
2048-square Rockwell Hawaii-II NIR detector will be installed and
commissioned later this year, in collaboration with Caltech, to
give WIRC an 8.7 arcminute FOV on a side. WIRC mounts at the
telescope's f/3.3 prime focus. The instrument's seeing-limited
optical design, optimized for the JHK atmospheric bands,
includes a 4-element refractive collimator, two 7-position filter
wheels that straddle a Lyot stop, and a 5-element refractive f/3
camera. Typical seeing-limited point spread functions are slightly
oversampled with a 0.25 arcsec per pixel plate scale at the detector. The entire optical train is contained within a cryogenic dewar with a 2.5 day hold-time. Entrance hatches at the top of the dewar allow access to the detector without disruption of the optics and optical alignment. The optical, mechanical, cryogenic, and electronic design of the instrument are described, a commissioning science image and performance analyses are presented.
SCORE is a cross-dispersed echelle spectrograph, built as a prototype for the Short-High module of SIRTF's IRS instrument. It operates over the 7.5-15 micrometers N-band atmospheric window, and has ben used on Palomar's Hale telescope several times since November, 1996. Since the initial run, a number of improvements have ben undertaken or are in the process being undertaken which enhance SCORE's performance and simplify its operation. One such addition, now completed, is a second detector array which serves as a slit-viewer with 12 inch diameter field of view around the slit. This viewer allows easy acquisition and guidance for sources with dim or absent optical counterparts, and accurately registers the position of the slit on the source with the recorded spectrum. Software written in the IDL environment optimizes the extraction of spectra form SCORE's mid-IR crossed-echelle data. The echelle, while providing the advantage of increased pixel utilization, introduces several difficulties, including curved orders, order cross- talk, and differentially slanted lines. These and other instrumental artifacts must be removed to achieve the highest spectral signal-to-noise. The pixel efficiency will be further increased by the use of a grism predisperser. The grism will provide approximately even spacing between orders of the echelle, in contrast with the decreasing spacing towards shorter wavelength orders generated by the current grating. SCORE is already one of the most powerful short- slit spectrographs operating in this wavelength band, and, with the implementation of these improvements, will deliver even greater capability.
We report narrow band adaptive optics near infrared imaging of the planetary nebula IC418. Our 25."6 x 25."6 images were recorded with the SHARP 11+ camera at the ESO 3.6m telescope, using the adaptive optics system ADONIS. The high spatial resolution was combined with the high spectral resolution provided by two Fabry-Perot etalons and a circular variable filter. Here we present images in the Br? and He I emission lines at 2.1655µm and 2.0581µm, respectively and discuss their astrophysical implications. Our results show that combining adaptive optics techniques with high spectral resolution opens a wide field of astrophysical studies.
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