MIRADAS (Mid-resolution InfRAreD Astronomical Spectrograph) is the facility near-infrared multi-object echelle spectrograph for the Gran Telescopio Canarias (GTC) 10.4-meter telescope. MIRADAS operates at spectral resolution R=20,000 over the 1-2.5µm bandpass), and provides multiplexing (up to N=12 targets) and spectro-polarimetry. The MIRADAS consortium includes the University of Florida, Universidad de Barcelona, Universidad Complutense de Madrid, Instituto de Astrofísica de Canarias, Institut d'Estudis Espacials de Catalunya and Universidad Nacional Autonoma de Mexico, as well as partners at A-V-S (Spain), New England Optical Systems (USA), and IUCAA (India). MIRADAS completed its Final Design Review in 2015, and in this paper, we review the current status and overall system design for the instrument, with scheduled delivery in 2018. We particularly emphasize key developments in cryogenic robotic probe arms for multiplexing, a macro-slicer mini-IFU, an advanced cryogenic spectrograph optical system, and a SIDECAR-based array control system for the 1x2 HAWAII-2RG detector mosaic.
The TOU robotic, compact very high resolution optical spectrograph (R=100,000, 0.38-0.9 microns) has been fully characterized at the 2 meter Automatic Spectroscopy Telescope (AST) at Fairborn Observatory in Arizona during its pilot survey of 12 bright FGK dwarfs in 2015. This instrument has delivered sub m/s Doppler precision for bright reference stars (e.g., 0.7 m/s for Tau Ceti over 60 days) with 5-30 min exposures and 0.7 m/s long-term instrument stability, which is the best performance among all of the known Doppler spectrographs to our knowledge. This performance was achieved by maintaining the instrument in a very high vacuum of 1 micron torr and about 0.5 mK (RMS) long-term temperature stability through an innovative close-loop instrument bench temperature control. It has discovered a 21 Earth-mass planet (P=43days) around a bright K dwarf and confirmed three super-Earth planetary systems, HD 1461, 190360 and HD 219314. This instrument will be used to conduct the Dharma Planet Survey (DPS) in 2016-2019 to monitor ~100 nearby very bright FGK dwarfs (most of them brighter than V=8) at the dedicated 50-inch Robotic Telescope on Mt. Lemmon. With very high RV precision and high cadence (~100 observations per target randomly spread over 450 days), a large number of rocky planets, including possible habitable ones, are expected to be detected. The survey also provides the largest single homogenous high precision RV sample of nearby stars for studying low mass planet populations and constraining various planet formation models. Instrument on-sky performance is summarized.
We are developing a stable and precise spectrograph for the Large Binocular Telescope (LBT) named “iLocater.” The instrument comprises three principal components: a cross-dispersed echelle spectrograph that operates in the YJ-bands (0.97-1.30 μm), a fiber-injection acquisition camera system, and a wavelength calibration unit. iLocater will deliver high spectral resolution (R~150,000-240,000) measurements that permit novel studies of stellar and substellar objects in the solar neighborhood including extrasolar planets. Unlike previous planet-finding instruments, which are seeing-limited, iLocater operates at the diffraction limit and uses single mode fibers to eliminate the effects of modal noise entirely. By receiving starlight from two 8.4m diameter telescopes that each use “extreme” adaptive optics (AO), iLocater shows promise to overcome the limitations that prevent existing instruments from generating sub-meter-per-second radial velocity (RV) precision. Although optimized for the characterization of low-mass planets using the Doppler technique, iLocater will also advance areas of research that involve crowded fields, line-blanketing, and weak absorption lines.
The Mid-resolution InfRAreD Astronomical Spectrograph (MIRADAS, a near-infrared multi-object echelle spectrograph operating at spectral resolution R=20,000 over the 1-2.5μm bandpass) was selected by the Gran Telescopio Canarias (GTC) partnership as the next-generation near-infrared spectrograph for the world's largest optical/infrared telescope, and is being developed by an international consortium. The MIRADAS consortium includes the University of Florida, Universidad de Barcelona, Universidad Complutense de Madrid, Instituto de Astrofísica de Canarias, and Institut d'Estudis Espacials de Catalunya, as well as probe arm industrial partner A-V-S (Spain), with more than 45 Science Working Group members in 10 institutions primarily in Spain, Mexico, and the USA. In this paper, we review the overall system design and project status for MIRADAS during its early fabrication phase in 2016.
Existing planet-finding spectrometers are limited by systematic errors that result from their seeing-limited design. Of particular concern is the use of multi-mode fibers (MMFs), which introduce modal noise and accept significant amounts of background radiation from the sky. We present the design of a single-mode fiber-based acquisition camera for a diffraction-limited spectrometer named “iLocater." By using the “extreme" adaptive optics (AO) system of the Large Binocular Telescope (LBT), iLocater will overcome the limitations that prevent Doppler instruments from reaching their full potential, allowing precise radial velocity (RV) measurements of terrestrial planets around nearby bright stars. The instrument presented in this paper, which we refer to as the acquisition camera “demonstration system," will measure on-sky single-mode fiber (SMF) coupling efficiency using one of the 8.4m primaries of the LBT in fall 2015.
Broad-band infrared (IR) spectroscopy, especially at high spectral resolution, is a largely unexplored area for the far IR (FIR) and submm wavelength region due to the lack of proper grating technology to produce high resolution within the very constrained volume and weight required for space mission instruments. High resolution FIR spectroscopy is an essential tool to resolve many atomic and molecular lines to measure physical and chemical conditions and processes in the environments where galaxy, star and planets form. A silicon immersion grating (SIG), due to its over three times high dispersion over a traditional reflective grating, offers a compact and low cost design of new generation IR high resolution spectrographs for space missions. A prototype SIG high resolution spectrograph, called Florida IR Silicon immersion grating spectromeTer (FIRST), has been developed at UF and was commissioned at a 2 meter robotic telescope at Fairborn Observatory in Arizona. The SIG with 54.74 degree blaze angle, 16.1 l/mm groove density, and 50x86 mm2 grating area has produced R=50,000 in FIRST. The 1.4-1.8 um wavelength region is completely covered in a single exposure with a 2kx2k H2RG IR array. The on-sky performance meets the science requirements for ground-based high resolution spectroscopy. Further studies show that this kind of SIG spectrometer with an airborne 2m class telescope such as SOFIA can offer highly sensitive spectroscopy with R~20,000-30,000 at 20 to 55 microns. Details about the on-sky measurement performance of the FIRST prototype SIG spectrometer and its predicted performance with the SOFIA 2.4m telescope are introduced.
Jian Ge, Scott Powell, Bo Zhao, Frank Varosi, Bo Ma, Sirinrat Sithajan, Jian Liu, Rui Li, Nolan Grieves, Sidney Schofield, Louis Avner, Hali Jakeman, William Yoder, Jakob Gittelmacher, Michael Singer, Matthew Muterspaugh, Michael Williamson, J. Maxwell
One of the most astonishing results from the HARPS and Kepler planet surveys is the recent
discovery of close-in super-Earths orbiting more than half of FGKM dwarfs. This new
population of exoplanets represents the most dominant class of planetary systems known to date,
is totally unpredicted by the classical core-accretion disk planet formation model. High cadence
and high precision Doppler spectroscopy is the key to characterize properties of this new
population and constrain planet formation models.
A new robotic, compact high resolution optical spectrograph, called TOU (formerly called
EXPERT-III), was commissioned at the Automatic Spectroscopic Telescope (AST) at Fairborn
Observatory in Arizona in July 2013 and has produced a spectral resolution of about 100,000 and
simultaneous wavelength coverage of 0.38-0.9 μm with a 4kx4k back-illuminated Fairchild CCD
detector. The instrument holds a very high vacuum of 1 micro torr and about 2 mK temperature
stability over a month. The early on-sky RV measurements show that this instrument is
approaching a Doppler precision of 1 m/s (rms) for bright reference stars (such as Tau Ceti) with
5 min exposures and better than 3 m/s (P-V, RMS~1 m/s) daily RV stability before calibration
exposures are applied. A pilot survey of 20 V<9 FGK dwarfs, including known super-Earth
systems and known RV stable stars, is being launched and every star will be observed ~100
times over ~300 days time window between this summer and next spring, following up with a
full survey of ~150 V< 10 FGKM dwarfs in 2015-2017.
Jian Ge, Scott Powell, Bo Zhao, Sidney Schofield, Frank Varosi, Craig Warner, Jian Liu, Sirinrat Sithajan, Louis Avner, Hali Jakeman, Jakob Gittelmacher, William Yoder, Matthew Muterspaugh, Michael Williamson, J. Maxwell
High resolution infrared spectroscopy has been a major challenging task to accomplish in astronomy due to the enormous size and cost of IR spectrographs built with traditional gratings. A silicon immersion grating, due to its over three times high dispersion over a traditional reflective grating, offers a compact and low cost design of new generation IR high resolution spectrographs. Here we report the on-sky performance of the first silicon immersion grating spectrometer, called Florida IR Silicon immersion grating spectromeTer (FIRST), commissioned at the 2-meter Automatic Spectroscopic Telescope (AST) of Fairborn Observatory in Arizona in October 2013. The measured spectral resolution is R=50,000 with a 50 mm diameter spectrograph pupil and a blaze angle of 54.7 degree. The 1.4-1.8 m wavelength region (the Red channel) is completely covered in a single exposure with a 2kx2k H2RG IR array while the 0.8-1.35 μm region is nearly completely covered by the cross-dispersed echelle mode (the Blue channel) at R=50,000 in a single exposure. The instrument is operated in a high vacuum (about 1 micro torr) and cryogenic temperatures (the bench at 189K and the detector at 87K) and with a precise temperature control. It is primarily used for high precision Doppler measurements (~3 m/s) of low mass M dwarf stars for the identification and characterization of extrasolar planets. A plan for a high cadence and high precision survey of habitable super-Earths around ~150 nearby M dwarfs and a major upgrade with integral field unit low resolution spectroscopy are also introduced.
Jian Ge, Bo Zhao, Scott Powell, Ji Wang, Adam Fletcher, Liang Chang, John Groot, Xiaoke Wan, Hali Jakeman, Derek Myers, Elliot Grafer, Jian Liu, Frank Varosi, Sidney Schofield, Alexandria Moore, Maria-Ines van Olphen, Jordan Katz, Rory Barnes
This paper is to report the design and performance of a very high Doppler precision cross-dispersed
echelle spectrograph, EXtremely high Precision ExtrasolaR planet Tracker III (EXPERT-III), as part of a
global Exoplanet Tracker (ET) network. The ET network is designed to hunt low mass planets, especially
habitable rocky planets, around GKM dwarfs. It has an extremely high spectral resolution (EHR) mode of
R=110,000 and a high resolution (HR) mode of R=56,000 and can simultaneously cover 0.38-0.9 μm
with a 4kx4k back-illuminated Fairchild CCD detector with a single exposure. EXPERT-III is optimized
for high throughput by using two-prisms cross-disperser and a large core diameter fiber (2 arcsec on sky,
or 80 μm at f/4) to collect photons from the Kitt Peak National Observatory (KPNO) 2.1m telescope. The
average overall detection efficiency is ~6% from above the atmosphere to the detector for the EHR Mode
and about 11% for the HR mode. The extremely high spectral resolution in a compact design (the
spectrograph dimension, 1.34x0.8x0.48 m) is realized by coupling the single input 80 μm telescope fiber
into four 40 μm fibers and re-arranging the four small core diameter fibers into a linear fiber slit array (a
one-to-four fiber image slicer). EXPERT-III is operated in a vacuum chamber with temperature controlled
to ~2 milli-Kelvin rms for an extended period of time. The radial velocity (RV) drift is controlled to
within 10 meters/second (m/s) over a month. EXPERT-III can reach a photon noise limited RV
measurement precision of ~0.3 m/s for a V=8 mag GKM type dwarf with small rotation (vsini =2 km/s) in
a 15 min exposure. EXPERT-III’s RV measurement uncertainties for bright stars are primarily limited by
the Thorium-Argon (ThAr) calibration source (~0.5 m/s). EXPERT-III will serve as an excellent public
accessible high resolution optical spectroscope facility at the KPNO 2.1m telescope.
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.
We report the update optical design of a versatile FIRST high resolution near IR spectrograph, which is called Florida IR Silicon immersion grating spectromeTer (FIRST). This spectrograph uses cross-dispersed echelle design with white pupils and also takes advantage of the image slicing to increase the spectra resolution, while maintaining the instrument throughput. It is an extremely high dispersion R1.4 (blazed angle of 54.74°) silicon immersion grating with a 49 mm diameter pupil is used as the main disperser at 1.4μm -1.8μm to produce R=72,000 while an R4 echelle with the same pupil diameter produces R=60,000 at 0.8μm -1.35μm. Two cryogenic Volume Phase Holographic (VPH) gratings are used as cross-dispersers to allow simultaneous wavelength coverage of 0.8μm -1.8μm. The butterfly mirrors and dichroic beamsplitters make a compact folding system to record these two wavelength bands with a 2kx2k H2RG array in a single exposure. By inserting a mirror before the grating disperser (the SIG and the echelle), this spectrograph becomes a very efficient integral field 3-D imaging spectrograph with R=2,000-4,000 at 0.8μm-1.8μm by coupling a 10x10 telescope fiber bundle with the spectrograph. Details about the optical design and performance are reported.
We report the system design and predicted performance of the Florida IR Silicon immersion grating
spectromeTer (FIRST). This new generation cryogenic IR spectrograph offers broad-band high resolution
IR spectroscopy with R=72,000 at 1.4-1.8 μm and R=60,000 at 0.8-1.35 μm in a single exposure with a
2kx2k H2RG IR array. It is enabled by a compact design using an extremely high dispersion silicon
immersion grating (SIG) and an R4 echelle with a 50 mm diameter pupil in combination with an Image
Slicer. This instrument is operated in vacuum with temperature precisely controlled to reach long term
stability for high precision radial velocity (RV) measurements of nearby stars, especially M dwarfs and
young stars. The primary technical goal is to reach better than 4 m/s long term RV precision with J<9 M
dwarfs within 30 min exposures. This instrument is scheduled to be commissioned at the Tennessee State
University (TSU) 2-m Automatic Spectroscopic Telescope (AST) at Fairborn Observatory in spring 2013.
FIRST can also be used for observing transiting planets, young stellar objects (YSOs), magnetic fields,
binaries, brown dwarfs (BDs), ISM and stars.
We plan to launch the FIRST NIR M dwarf planet survey in 2014 after FIRST is commissioned at the
AST. This NIR M dwarf survey is the first large-scale NIR high precision Doppler survey dedicated to
detecting and characterizing planets around 215 nearby M dwarfs with J< 10. Our primary science goal is
to look for habitable Super-Earths around the late M dwarfs and also to identify transiting systems for
follow-up observations with JWST to measure the planetary atmospheric compositions and study their
habitability. Our secondary science goal is to detect and characterize a large number of planets around M
dwarfs to understand the statistics of planet populations around these low mass stars and constrain planet
formation and evolution models. Our survey baseline is expected to detect ~30 exoplanets, including 10
Super Earths, within 100 day periods. About half of the Super-Earths are in their habitable zones and one
of them may be a transiting planet. The AST, with its robotic control and ease of switching between
instruments (in seconds), enables great flexibility and efficiency, and enables an optimal strategy, in terms
of schedule and cadence, for this NIR M dwarf planet survey.
We report optical design of new generation compact, high resolution, high throughput and high Doppler precision optical
spectrograph. This spectrograph uses cross-dispersed echelle design with white pupils and also takes advantage of a fiber
image slicer to slice one 2 arcsec telescope input fiber image (80 micron at f/4 at the KPNO 2.1 meter telescope) into
four 1 arcsec images (40 micron). The small sliced images coupled with slow optics play a key role in achieving high
spectral resolution within very compact instrument design to substantially reduce construction cost while increasing the
instrument stability for high Doppler precision over a long time. This optical spectrograph is called EXtremely high
Precision ExtrasolaR planet Tracker III (EXPERT-III). The coupling of the fiber sliced images with an R4 echelle with a
98mm diameter pupil produces R=110,000 in the entire optical wavelength region. It also uses a two-prism
cross-disperser to produce nearly homogeneous spectral order coverage while taking advantage of the anamorphic
magnification of the prisms to allow large wavelength coverage (380nm-900nm) in a single exposure with a 4kx4k CCD
detector. This very high resolution mode is designed to reach extremely high Doppler precision for radial velocity
measurements of bright solar type stars. The spectrograph is also directly coupled with an 80 micron telescope fiber-fed
image to obtain high throughput with R=60,000 for stellar spectroscopy. Details about the optical design and
performance are reported.
Silicon immersion gratings (SIGs) offer several advantages over the commercial echelle gratings for high
resolution infrared (IR) spectroscopy: 3.4 times the gain in dispersion or ~10 times the reduction in the
instrument volume, a multiplex gain for a large continuous wavelength coverage and low cost. We
present results from lab characterization of a large format SIG of astronomical observation quality. This
SIG, with a 54.74 degree blaze angle (R1.4), 16.1 l/mm groove density, and 50x86 mm2 grating area, was
developed for high resolution IR spectroscopy (R~70,000) in the near IR (1.1-2.5 μm). Its entrance
surface was coated with a single layer of silicon nitride antireflection (AR) coating and its grating surface
was coated with a thin layer of gold to increase its throughput at 1.1-2.5 m. The lab measurements have
shown that the SIG delivered a spectral resolution of R=114,000 at 1.55 m with a lab testing
spectrograph with a 20 mm diameter pupil. The measured peak grating efficiency is 72% at 1.55 m,
which is consistent with the measurements in the optical wavelengths from the grating surface at the air
side. This SIG is being implemented in a new generation cryogenic IR spectrograph, called the Florida IR
Silicon immersion grating spectrometer (FIRST), to offer broad-band high resolution IR spectroscopy
with R=72,000 at 1.4-1.8 um under a typical seeing condition in a single exposure with a 2kx2k H2RG IR
array at the robotically controlled Tennessee State University 2-meter Automatic Spectroscopic Telescope
(AST) at Fairborn Observatory in Arizona. FIRST is designed to provide high precision Doppler
measurements (~4 m/s) for the identification and characterization of extrasolar planets, especially rocky
planets in habitable zones, orbiting low mass M dwarf stars. It will also be used for other high resolution
IR spectroscopic observations of such as young stars, brown dwarfs, magnetic fields, star formation and
interstellar mediums. An optimally designed SIG of the similar size can be used in the Silicon Immersion
Grating Spectrometer (SIGS) to fill the need for high resolution spectroscopy at mid IR to far IR (~25-300 μm) for the NASA SOFIA airborne mission in the future.
The Habitable Zone Planet Finder (HZPF) is a proposed instrument for the 10m class Hobby Eberly telescope that will
be capable of discovering low mass planets around M dwarfs. HZPF will be fiber-fed, provide a spectral resolution R~
50,000 and cover the wavelength range 0.9-1.65μm, the Y, J and H NIR bands where most of the flux is emitted by midlate
type M stars, and where most of the radial velocity information is concentrated. Enclosed in a chilled vacuum vessel
with active temperature control, fiber scrambling and mechanical agitation, HZPF is designed to achieve a radial
velocity precision < 3m/s, with a desire to obtain <1m/s for the brightest targets. This instrument will enable a study of
the properties of low mass planets around M dwarfs; discover planets in the habitable zones around these stars, as well
serve as an essential radial velocity confirmation tool for astrometric and transit detections around late M dwarfs. Radial
velocity observation in the near-infrared (NIR) will also enable a search for close in planets around young active stars,
complementing the search space enabled by upcoming high-contrast imaging instruments like GPI, SPHERE and
PALM3K. Tests with a prototype Pathfinder instrument have already demonstrated the ability to recover radial velocities
at 7-10 m/s precision from integrated sunlight and ~15-20 m/s precision on stellar observations at the HET. These tests
have also demonstrated the ability to work in the NIR Y and J bands with an un-cooled instrument. We will also discuss
lessons learned about calibration and performance from our tests and how they impact the overall design of the HZPF.
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.
Doppler searches are extending to the near infrared to detect and characterize habitable planets around low mass stars.
We present an optical design and performance of a near-IR Doppler instrument. This instrument has two operating
modes covering 0.8-1.8 microns. One mode is called IRET, which consists of a fix-delay interferometer and a crossdispersed
echelle spectrograph to simultaneously cover 0.8-1.35 microns with a spectral resolution of R=22000 on a 2k x
2k H2RG IR array. The other mode is called FIRST, which uses a silicon immersion grating as the main disperser to
simultaneously cover 1.4-1.8 microns with a spectral resolution of R=55000 on the same detector as IRET. The triplepass
parabola white pupil design is used to restrain background scatter radiation with stable configuration for precision
radial velocity measurements. We used high index standard glasses for camera optics and VPH gratings as crossdispersers
in both modes. The FIRST mode can be switched in and out conveniently while the IRET mode is kept
without moving parts to increase its stability. This instrument is designed to deliver up to 1 m/s Doppler precision RV
measurements of nearby bright M dwarfs at the Apache Point Observatory 3.5 meter telescope. The instrument is
expected to be operational in the spring 2011.
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.
Jian Ge, Bo Zhao, John Groot, Liang Chang, Frank Varosi, Xiaoke Wan, Scott Powell, Peng Jiang, Kevin Hanna, Ji Wang, Rohan Pais, Jian Liu, Liming Dou, Sidney Schofield, Shaun McDowell, Erin Costello, Adriana Delgado-Navarro, Scott Fleming, Brian Lee, Sandeep Bollampally, Troy Bosman, Hali Jakeman, Adam Fletcher, Gabriel Marquez
We report design, performance and early results from two of the Extremely High Precision Extrasolar
Planet Tracker Instruments (EXPERT) as part of a global network for hunting for low mass planets in the
next decade. EXPERT is a combination of a thermally compensated monolithic Michelson interferometer
and a cross-dispersed echelle spectrograph for extremely high precision Doppler measurements for nearby
bright stars (e.g., 1m/s for a V=8 solar type star in 15 min exposure). It has R=18,000 with a 72 micron
slit and a simultaneous coverage of 390-694 nm. The commissioning results show that the instrument has
already produced a Doppler precision of about 1 m/s for a solar type star with S/N~100 per pixel. The
instrument has reached ~4 mK (P-V) temperature stability, ~1 mpsi pressure stability over a week and a
total instrument throughput of ~30% at 550 nm from the fiber input to the detector. EXPERT also has a
direct cross-dispersed echelle spectroscopy mode fed with 50 micron fibers. It has spectral resolution of
R=27,000 and a simultaneous wavelength coverage of 390-1000 nm.
We describe the optical design and performance of a cross-dispersed echelle spectrograph designed to deliver high
precision radial velocities. The spectrograph design enables two working modes, a Radial Velocity Mode (RVM) and a
Direct Echelle Mode (DEM). The spectra resolving power of the RVM is R=18000 over 390nm-690nm when used with
1 arcsec slit, and delivering a R=27000 over 390nm-1000nm while using 0.6 arcsec slit for DEM. The focal ratio of this
spectrograph is f/4 and the collimated beam diameter is 85mm. An R2 Echelle with 87 l/mm groove density and a 63
degree normal blaze angle will be used as the main disperse grating. A 45 degree PBM2Y prism operated in a double
pass serves as a cross-disperser to separate the dispersion orders. Two objects spectra will be recorded on the top and
bottom half of the one 4k by 4k CCD (15-micron pixel size) respectively in RVM, while one object spectra will be
recorded on the same entire CCD. The total throughput of this spectrograph, in which consists of all spherical surface
lenses is around 60%.
This paper describes an optical spectrograph design for the Multi-object APO Radial-Velocity Exoplanet Large-area
Survey (MARVELS) instrument. This MARVELS instrument is currently installed at the Sloan 2.5m telescope, and is
capable of simultaneously monitoring 60 stars at high radial velocity precision for a planet survey. The MARVELS
spectrograph consists of an entrance slit (multi-slits), collimator optics, a Volume Phase Holographic (VPH) grating,
camera optics and a 4kx4k CCD camera, which with a 160mm diameter collimated beam provides a spectral resolution
of R =10000. This spectrograph is transmissive and optimized for delivering high throughput and high image quality
over the entire operation bandwidth 500-570nm and the whole 160mmx30mm square shape FOV. The collimator and
camera optics (280 mm largest diameter) are all made of standard optical grade glasses. The f/4 input beams from the
MARVELS monolithic interferometer are converted to f/1.5 beams on the detector by this spectrograph, and form 120
stellar fringe spectra.
We report performance of a new generation multi-object Doppler instrument for the on-going
Multi-object APO Radial-velocity Exoplanet Large-area Survey (MARVELS) of the Sloan
Digital Sky Survey III (SDSS-III) program. This instrument is based on dispersed fixed-delay
interferomtry design. It consists of a multi-object fiber-feed, a thermally compensated monolithic
fixed-delay interferometer, a high throughput spectrograph and a 4kx4k CCD camera. The
spectrograph resolving power is R=11,000 and the wavelength coverage is 500-570 nm. The
instrument is capable of measuring 60 stars in a single exposure for high to moderate precision
radial velocity (3-20 m/s) measurements depending on the star magnitudes (V=7.6-12). The
instrument was commissioned at the SDSS telescope in September 2008 and used to collect
science data starting in October 2008. Observations of reference stars show that the measured
photon noise limiting errors are consistent with the prediction for most of the measurements.
We report the design of a new generation multi-object high throughput Doppler instrument and
first light results at the Sloan Digital Sky Survey (SDSS) telescope. This instrument, capable of
simultaneously monitoring 60 stars for planet detection, is called the W.M. Keck Exoplanet
Tracker (or Keck ET) thanks to the generous gift from the W.M. Keck Foundation. It is designed
for a planet survey around hundreds of thousands of stars with V =8-13 for detecting tens of
thousands of planets in 2006-2020. The Doppler precision is between 3-25 m/s depending on the
star magnitude.
We also report a new planet detected with a prototype single object version ET instrument at the
KPNO Coude Feed/2.1 m telescopes. The extrasolar planet, ET-1 (HD 102195b), has a minimum
mass of 0.49 Jupiter masses and orbits a V = 8.1 G8V star with a 4.1 day period. The planet was
identified using the Coude Feed 0.9 meter telescope in spring 2005. This is the first time an
extrasolar planet around a star fainter than V=8 magnitude has been discovered with an under 1
meter size astronomical telescope and Doppler instrument. This planet discovery is possible due
to the extremely high throughput of the instrument, 49% measured from the fiber output end to
the detector.
We report progress on development of large format silicon immersion gratings (SIG) at UF. Currently SIGs on 4 inch diameter thick silicon disks can be routinely produced with groove periods from 7 microns to 250 microns and blaze angles from 20 degrees to 76 degrees. A new capability of making SIGs from 6 inch diameter silicon disks has also been demonstrated. A new Space Astronomy Instrumentation Lab (SAIL) facility is being established at UF to have a capability of fabricating SIGs on 8 inch diameter silicon disks with up to 4 inch thickness. Our prototype SIG with an 85x50 mm2 etched grating area and a 54.7 deg blaze angle has produced a nearly diffraction-limited wavefront, less than 1% integrated scattered light and ghost intensity, a 74% peak blaze efficiency and a R = 55,000 resolving power at 1.55 μm.
This paper describes an optical spectrograph design for the W.M. Keck Exoplanet Tracker (ET) multi-object Doppler radial velocity instrument. The Keck ET is currently installed at the Sloan 2.5m telescope (Ge et al. this proceedings), and is capable of simultaneously monitoring 60 stars with high precision for a planet survey. The spectrograph consists of an entrance slit, collimator optics, a Volume Phase Holographic (VPH) grating, camera optics and a 4kx4k CCD camera, and provides a spectral resolution of R =5000, with a 180 mm diameter collimated beam. The collimator and camera optics (300 mm largest diameter) are made of two standard optical grade glasses: BK7 and F2, respectively. The spectrograph is transmissive and optimized for delivering high throughput and high image quality over the entire operation bandwidth: 500-590 nm. The f/4 input beams from the Keck ET interferometer are converted to f/1.5 beams on the detector by this spectrograph, and form 60 stellar fringe spectra.
A fiber feed system has been developed to allow a new generation multiple object Doppler instrument, called the WM Keck Exoplanet Tracker, simultaneously tracking 59 stars for high precision radial velocity measurements for planet detection, and switching among over 500 targets per night. The system includes 27 plug fiber bundles and 3 instrument fiber bundles, and each fiber bundle includes 22 fibers. Individual fibers of a plug fiber bundle are plugged to a plate to receive star lights, and then they are grouped together to form a compact 22-fiber connector. An instrument fiber bundle with a matching fiber bundle connector can connect and disconnect with the plug fiber bundle. The 45 m long instrument fiber bundles deliver the light from the telescope to an environment controlled instrument room in distance. We characterizes the light loses including the position and pointing error of plug connectors, the fiber end reflection, fiber misalignment at the mating connectors, focal ratio degradation and fiber absorption through the long fiber link. All fiber bundles are tested and average total throughput of 61% is achieved.
We report the development of the first high resolution cross-dispersed silicon immersion grating spectrometer. This instrument is called the Florida IR Silicon immersion grating specTrometer (FIRST). FIRST can produce R = 50,000 under a 0.6 arcsec seeing and
simultaneously cover 1.3-1.8 μm with a 1kx1k HgCdTe array at the Apache Point Observatory 3.5 meter telescope. FIRST has a 50 mm diameter collimated beam and the overall instrument is within a volume of 0.8x0.5x0.5 m3. The high dispersion, large wavelength coverage and small instrument volume become possible due to the use of a silicon immersion grating (54.7 deg blaze angle and 50 mm diameter entrance pupil) with extremely high dispersion power (3.4 times dispersion power of a conventional echelle) and coarse grooves (16.1 l/mm, coarser than the commercially available echelles). The silicon immersion grating used in a lab bench mounted Czeney-Turner spectrograph with an only 25 mm diameter collimated beam and a 100 um core fiber has produced R = 55,000 cross-dispersed solar spectra. This instrument is designed to precisely measure radial velocities of low mass stars, M dwarfs for detecting 5-10 Earth mass planets. The estimated Doppler precision is ~ 3 m/s for a J = 9 M5V dwarf in 15 min at the APO 3.5m telescope.
We report our progress in development of extremely coherent single mode fiber bundle arrays for high contrast imaging of extrasolar planets with TPF-C. These bundles with 32x32 fiber arrays are designed to reject scattered light while improving the image contrast by three orders of magnitude in the TPF-C visible nulling coronagraph, studied as one of the five TPF-C instrument concepts. We have developed 10x10 fiber prototype fiber bundle arrays using a combination of precision V-grooves on double side polished silicon wafers, single mode fibers and custom made lenslet arrays. The initial lab results are presented.
Interferometric imaging systems measure the complex visibility, which is the Fourier transform of the source brightness distribution, according to the van Cittert-Zernike theorem. Both the amplitude and phase of the visibility are needed to produce images of a complex object structure by Fourier inversion. In this paper, by using the generalized imaging theory of a diffraction-limited incoherent imaging system, the pinhole model and the circular aperture model of the interferometry are presented and derived. The approximate condition, which should be followed by optical aperture synthesis imaging interferometry, is obtained by comparing two models. Based on this condition, the angle of field-of-view (FOV) in the object space is analyzed and determined. At the good approximation, the FOV is about one-sixth of an Airy disk of an elementary aperture diffraction. Also the computer simulation results are presented and match the theoretical results very well. This suggests that the extremely high image resolution can be achieved in the interferometric imaging systems, but it generally has a very small field of view. Such imaging systems are suitable only for the astronomical application.
In order to research the global change and analyze the characteristics of land surface or atmosphere, an Earth Observation Station usually needs a high-definition large screen to display the satellite remote sensing image. Under the development of digital imaging technology, this application can be put into practice. In this paper, the optical engine, a key technique in the digital imaging, is introduced. Then the basic principle and technical difficulties of optical engine are discussed in detail. It is testified that the optical engine technique can make the satellite remote sensing image displayed in high-definition model.
In order to know how we can design effective NLO materials, we have studied several series of aromatic hydrocarbons used as NLO materials and found criteria as follows: (1) When the conjugated system is small then the nitro-group is an effective acceptor, and some of this kind of compound has a very high SHG response while fairly big conjugated compounds whose acceptor is nitro-group often reveal weak or no nonlinearity. (2) The compounds whose acceptor (-NO2) and donor (-NH2, -NHR or -NR2) are para-substituted on both ends of the conjugated chains always have very weak or SHG (second harmonic generation). (3) The substituted groups such as -CH3, -OCH3, -X(-Cl, -Br, -1) and biphenyl (C6H5C6H4-) are the best donors which are beneficial to SHG response and transparency. (4) The relatively big conjugated compounds often reveal fairly good second-order nonlinearity when greater than C equals O acts as their acceptor. We studied these laws theoretically and experimentally so as to give some useful guides to the research of the SHG materials.
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