11,648 research outputs found
The Infrared Imaging Spectrograph (IRIS) for TMT: multi-tiered wavefront measurements and novel mechanical design
The InfraRed Imaging Spectrograph (IRIS) will be the first light adaptive optics instrument on the Thirty Meter Telescope (TMT). IRIS is being built by a collaboration between Caltech, the University of California, NAOJ and NRC Herzberg. In this paper we present novel aspects of the Support Structure, Rotator and On-Instrument Wavefront Sensor systems being developed at NRC Herzberg. IRIS is suspended from the bottom port of the Narrow Field Infrared Adaptive Optics System (NFIRAOS), and provides its own image de-rotation to compensate for sidereal rotation of the focal plane. This arrangement is a challenge because NFIRAOS is designed to host two other science instruments, which imposes strict mass requirements on IRIS. As the mechanical design of all elements has progressed, we have been tasked with keeping the instrument mass under seven tonnes. This requirement has resulted in a mass reduction of 30 percent for the support structure and rotator compared to the most recent IRIS designs. To accomplish this goal, while still being able to withstand earthquakes, we developed a new design with composite materials. As IRIS is a client instrument of NFIRAOS, it benefits from NFIRAOS’s superior AO correction. IRIS plays an important role in providing this correction by sensing low-order aberrations with three On-Instrument Wavefront Sensors (OIWFS). The OIWFS consists of three independently positioned natural guide star wavefront sensor probe arms that patrol a 2-arcminute field of view. We expect tip-tilt measurements from faint stars within the IRIS imager focal plane will further stabilize the delivered image quality. We describe how the use of On-Detector Guide Windows (ODGWs) in the IRIS imaging detector can be incorporated into the AO correction. In this paper, we present our strategies for acquiring and tracking sources with this complex AO system, and for mitigating and measuring the various potential sources of image blur and misalignment due to properties of the mechanical structure and interfaces
The infrared imaging spectrograph (IRIS) for TMT: sensitivities and simulations
We present sensitivity estimates for point and resolved astronomical sources
for the current design of the InfraRed Imaging Spectrograph (IRIS) on the
future Thirty Meter Telescope (TMT). IRIS, with TMT's adaptive optics system,
will achieve unprecedented point source sensitivities in the near-infrared
(0.84 - 2.45 {\mu}m) when compared to systems on current 8-10m ground based
telescopes. The IRIS imager, in 5 hours of total integration, will be able to
perform a few percent photometry on 26 - 29 magnitude (AB) point sources in the
near-infrared broadband filters (Z, Y, J, H, K). The integral field
spectrograph, with a range of scales and filters, will achieve good
signal-to-noise on 22 - 26 magnitude (AB) point sources with a spectral
resolution of R=4,000 in 5 hours of total integration time. We also present
simulated 3D IRIS data of resolved high-redshift star forming galaxies (1 < z <
5), illustrating the extraordinary potential of this instrument to probe the
dynamics, assembly, and chemical abundances of galaxies in the early universe.
With its finest spatial scales, IRIS will be able to study luminous, massive,
high-redshift star forming galaxies (star formation rates ~ 10 - 100 M yr-1) at
~100 pc resolution. Utilizing the coarsest spatial scales, IRIS will be able to
observe fainter, less massive high-redshift galaxies, with integrated star
formation rates less than 1 M yr-1, yielding a factor of 3 to 10 gain in
sensitivity compared to current integral field spectrographs. The combination
of both fine and coarse spatial scales with the diffraction-limit of the TMT
will significantly advance our understanding of early galaxy formation
processes and their subsequent evolution into presentday galaxies.Comment: SPIE Astronomical Instrumentation 201
The Infrared Imaging Spectrograph (IRIS) for TMT: Multi-tiered wavefront measurements and novel mechanical design
The InfraRed Imaging Spectrograph (IRIS) will be the first light adaptive optics instrument on the Thirty Meter Telescope (TMT). IRIS is being built by a collaboration between Caltech, the University of California, NAOJ and NRC Herzberg. In this paper we present novel aspects of the Support Structure, Rotator and On-Instrument Wavefront Sensor systems being developed at NRC Herzberg. IRIS is suspended from the bottom port of the Narrow Field Infrared Adaptive Optics System (NFIRAOS), and provides its own image de-rotation to compensate for sidereal rotation of the focal plane. This arrangement is a challenge because NFIRAOS is designed to host two other science instruments, which imposes strict mass requirements on IRIS. As the mechanical design of all elements has progressed, we have been tasked with keeping the instrument mass under seven tonnes. This requirement has resulted in a mass reduction of 30 percent for the support structure and rotator compared to the most recent IRIS designs. To accomplish this goal, while still being able to withstand earthquakes, we developed a new design with composite materials. As IRIS is a client instrument of NFIRAOS, it benefits from NFIRAOS’s superior AO correction. IRIS plays an important role in providing this correction by sensing low-order aberrations with three On-Instrument Wavefront Sensors (OIWFS). The OIWFS consists of three independently positioned natural guide star wavefront sensor probe arms that patrol a 2-arcminute field of view. We expect tip-tilt measurements from faint stars within the IRIS imager focal plane will further stabilize the delivered image quality. We describe how the use of On-Detector Guide Windows (ODGWs) in the IRIS imaging detector can be incorporated into the AO correction. In this paper, we present our strategies for acquiring and tracking sources with this complex AO system, and for mitigating and measuring the various potential sources of image blur and misalignment due to properties of the mechanical structure and interface
Adaptive Optics for Extremely Large Telescopes
Adaptive Optics has become a key technology for the largest ground-based
telescopes currently under or close to begin of construction. Adaptive optics
is an indispensable component and has basically only one task, that is to
operate the telescope at its maximum angular resolution, without optical
degradations resulting from atmospheric seeing. Based on three decades of
experience using adaptive optics usually as an add-on component, all extremely
large telescopes and their instrumentation are designed for diffraction limited
observations from the very beginning. This review illuminates the various
approaches of the Extremely Large Telescope, the Giant Magellan Telescope, and
the Thirty-Meter Telescope, to fully integrate adaptive optics in their
designs. The article concludes with a brief look into the requirements that
high-contrast imaging poses on adaptive optics.Comment: 29 pages, 13 figures, published in Journal of Astronomical
Instrumentation, November 2, 201
The InfraRed Imaging Spectrograph (IRIS) for TMT: latest science cases and simulations
The Thirty Meter Telescope (TMT) first light instrument IRIS (Infrared
Imaging Spectrograph) will complete its preliminary design phase in 2016. The
IRIS instrument design includes a near-infrared (0.85 - 2.4 micron) integral
field spectrograph (IFS) and imager that are able to conduct simultaneous
diffraction-limited observations behind the advanced adaptive optics system
NFIRAOS. The IRIS science cases have continued to be developed and new science
studies have been investigated to aid in technical performance and design
requirements. In this development phase, the IRIS science team has paid
particular attention to the selection of filters, gratings, sensitivities of
the entire system, and science cases that will benefit from the parallel mode
of the IFS and imaging camera. We present new science cases for IRIS using the
latest end-to-end data simulator on the following topics: Solar System bodies,
the Galactic center, active galactic nuclei (AGN), and distant
gravitationally-lensed galaxies. We then briefly discuss the necessity of an
advanced data management system and data reduction pipeline.Comment: 15 pages, 7 figures, SPIE (2016) 9909-0
The Infrared Imaging Spectrograph (IRIS) for TMT: optical design of IRIS imager with "Co-axis double TMA"
IRIS (InfraRed Imaging Spectrograph) is one of the first-generation
instruments for the Thirty Meter Telescope (TMT). IRIS is composed of a
combination of near-infrared (0.84--2.4 m) diffraction limited imager and
integral field spectrograph. To achieve near-diffraction limited resolutions in
the near-infrared wavelength region, IRIS uses the advanced adaptive optics
system NFIRAOS (Narrow Field Infrared Adaptive Optics System) and integrated
on-instrument wavefront sensors (OIWFS). However, IRIS itself has challenging
specifications. First, the overall system wavefront error should be less than
40 nm in Y, z, J, and H-band and 42 nm in K-band over a 34.0 34.0
arcsecond field of view. Second, the throughput of the imager components should
be more than 42 percent. To achieve the extremely low wavefront error and high
throughput, all reflective design has been newly proposed. We have adopted a
new design policy called "Co-Axis double-TMA", which cancels the asymmetric
aberrations generated by "collimator/TMA" and "camera/TMA" efficiently. The
latest imager design meets all specifications, and, in particular, the
wavefront error is less than 17.3 nm and throughput is more than 50.8 percent.
However, to meet the specification of wavefront error and throughput as built
performance, the IRIS imager requires both mirrors with low surface
irregularity after high-reflection coating in cryogenic and high-level Assembly
Integration and Verification (AIV). To deal with these technical challenges, we
have done the tolerance analysis and found that total pass rate is almost 99
percent in the case of gauss distribution and more than 90 percent in the case
of parabolic distribution using four compensators. We also have made an AIV
plan and feasibility check of the optical elements. In this paper, we will
present the details of this optical system.Comment: 18 pages, 14 figures, Proceeding 9908-386 of the SPIE Astronomical
Telescopes + Instrumentation 201
The infrared imaging spectrograph (IRIS) for TMT: spectrograph design
The Infra-Red Imaging Spectrograph (IRIS) is one of the three first light
instruments for the Thirty Meter Telescope (TMT) and is the only one to
directly sample the diffraction limit. The instrument consists of a parallel
imager and off-axis Integral Field Spectrograph (IFS) for optimum use of the
near infrared (0.84um-2.4um) Adaptive Optics corrected focal surface. We
present an overview of the IRIS spectrograph that is designed to probe a range
of scientific targets from the dynamics and morphology of high-z galaxies to
studying the atmospheres and surfaces of solar system objects, the latter
requiring a narrow field and high Strehl performance. The IRIS spectrograph is
a hybrid system consisting of two state of the art IFS technologies providing
four plate scales (4mas, 9mas, 25mas, 50mas spaxel sizes). We present the
design of the unique hybrid system that combines the power of a lenslet
spectrograph and image slicer spectrograph in a configuration where major
hardware is shared. The result is a powerful yet economical solution to what
would otherwise require two separate 30m-class instruments.Comment: 15 pages, 11 figure
The infrared imaging spectrograph (IRIS) for TMT: the science case
The InfraRed Imaging Spectrograph (IRIS) is a first-light instrument being
designed for the Thirty Meter Telescope (TMT). IRIS is a combination of an
imager that will cover a 16.4" field of view at the diffraction limit of TMT (4
mas sampling), and an integral field unit spectrograph that will sample objects
at 4-50 mas scales. IRIS will open up new areas of observational parameter
space, allowing major progress in diverse fields of astronomy. We present the
science case and resulting requirements for the performance of IRIS.
Ultimately, the spectrograph will enable very well-resolved and sensitive
studies of the kinematics and internal chemical abundances of high-redshift
galaxies, shedding light on many scenarios for the evolution of galaxies at
early times. With unprecedented imaging and spectroscopy of exoplanets, IRIS
will allow detailed exploration of a range of planetary systems that are
inaccessible with current technology. By revealing details about resolved
stellar populations in nearby galaxies, it will directly probe the formation of
systems like our own Milky Way. Because it will be possible to directly
characterize the stellar initial mass function in many environments and in
galaxies outside of the the Milky Way, IRIS will enable a greater understanding
of whether stars form differently in diverse conditions. IRIS will reveal
detailed kinematics in the centers of low-mass galaxies, allowing a test of
black hole formation scenarios. Finally, it will revolutionize the
characterization of reionization and the first galaxies to form in the
universe.Comment: to appear in Proc. SPIE 773
The Infrared Imaging Spectrograph (IRIS) for TMT: Instrument Overview
We present an overview of the design of IRIS, an infrared (0.84 - 2.4 micron)
integral field spectrograph and imaging camera for the Thirty Meter Telescope
(TMT). With extremely low wavefront error (<30 nm) and on-board wavefront
sensors, IRIS will take advantage of the high angular resolution of the narrow
field infrared adaptive optics system (NFIRAOS) to dissect the sky at the
diffraction limit of the 30-meter aperture. With a primary spectral resolution
of 4000 and spatial sampling starting at 4 milliarcseconds, the instrument will
create an unparalleled ability to explore high redshift galaxies, the Galactic
center, star forming regions and virtually any astrophysical object. This paper
summarizes the entire design and basic capabilities. Among the design
innovations is the combination of lenslet and slicer integral field units, new
4Kx4k detectors, extremely precise atmospheric dispersion correction, infrared
wavefront sensors, and a very large vacuum cryogenic system.Comment: Proceedings of the SPIE, 9147-76 (2014
The Infrared Imaging Spectrograph (IRIS) for TMT: Data Reduction System
IRIS (InfraRed Imaging Spectrograph) is the diffraction-limited first light
instrument for the Thirty Meter Telescope (TMT) that consists of a
near-infrared (0.84 to 2.4 m) imager and integral field spectrograph
(IFS). The IFS makes use of a lenslet array and slicer for spatial sampling,
which will be able to operate in 100's of different modes, including a
combination of four plate scales from 4 milliarcseconds (mas) to 50 mas with a
large range of filters and gratings. The imager will have a field of view of
3434 arcsec with a plate scale of 4 mas with many selectable
filters. We present the preliminary design of the data reduction system (DRS)
for IRIS that need to address all of these observing modes. Reduction of IRIS
data will have unique challenges since it will provide real-time reduction and
analysis of the imaging and spectroscopic data during observational sequences,
as well as advanced post-processing algorithms. The DRS will support three
basic modes of operation of IRIS; reducing data from the imager, the lenslet
IFS, and slicer IFS. The DRS will be written in Python, making use of
open-source astronomical packages available. In addition to real-time data
reduction, the DRS will utilize real-time visualization tools, providing
astronomers with up-to-date evaluation of the target acquisition and data
quality. The quicklook suite will include visualization tools for 1D, 2D, and
3D raw and reduced images. We discuss the overall requirements of the DRS and
visualization tools, as well as necessary calibration data to achieve optimal
data quality in order to exploit science cases across all cosmic distance
scales.Comment: 13 pages, 2 figures, 6 tables, Proceeding 9913-165 of the SPIE
Astronomical Telescopes + Instrumentation 201
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