59 research outputs found
The InfraRed Imaging Spectrograph (IRIS) for TMT: photometric precision and ghost analysis
The InfraRed Imaging Spectrograph (IRIS) is a first-light instrument for the
Thirty Meter Telescope (TMT) that will be used to sample the corrected adaptive
optics field by NFIRAOS with a near-infrared (0.8 - 2.4 m) imaging camera
and Integral Field Spectrograph (IFS). In order to understand the science case
specifications of the IRIS instrument, we use the IRIS data simulator to
characterize photometric precision and accuracy of the IRIS imager. We present
the results of investigation into the effects of potential ghosting in the IRIS
optical design. Each source in the IRIS imager field of view results in ghost
images on the detector from IRIS's wedge filters, entrance window, and
Atmospheric Dispersion Corrector (ADC) prism. We incorporated each of these
ghosts into the IRIS simulator by simulating an appropriate magnitude point
source at a specified pixel distance, and for the case of the extended ghosts
redistributing flux evenly over the area specified by IRIS's optical design. We
simulate the ghosting impact on the photometric capabilities, and found that
ghosts generally contribute negligible effects on the flux counts for point
sources except for extreme cases where ghosts coalign with a star of
m2 fainter than the ghost source. Lastly, we explore the photometric
precision and accuracy for single sources and crowded field photometry on the
IRIS imager.Comment: SPIE 2018, 14 pages, 14 figures, 4 tables, Proceedings of SPIE
10702-373, Ground-based and Airborne Instrumentation for Astronomy VII,
10702A7 (16 July 2018
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
The Infrared Imaging Spectrograph (IRIS) for TMT: motion planning with collision avoidance for the on-instrument wavefront sensors
The InfraRed Imaging Spectrograph (IRIS) will be a first-light client instrument for the Narrow Field Infrared Adaptive Optics System (NFIRAOS) on the Thirty Meter Telescope. IRIS includes three configurable tip/tilt (TT) or tip/tilt/focus (TTF) On-Instrument Wavefront Sensors (OIWFS). These sensors are positioned over natural guide star (NGS) asterisms using movable polar-coordinate pick-ofi arms (POA) that patrol an approximately 2-arcminute circular field-of-view (FOV). The POAs are capable of colliding with one another, so an algorithm for coordinated motion that avoids contact is required. We have adopted an approach in which arm motion is evaluated using the gradient descent of a scalar potential field that includes an attractive component towards the goal configuration (locations of target stars), and repulsive components to avoid obstacles (proximity to adjacent arms). The resulting vector field is further modified by adding a component transverse to the repulsive gradient to avoid problematic local minima in the potential. We present path planning simulations using this computationally inexpensive technique, which exhibit smooth and efficient trajectories
Safety and optimal neuroprotection of neu2000 in acute ischemic stroke with reCanalization: study protocol for a randomized, double-blinded, placebo-controlled, phase-II trial
BACKGROUND: The potential of neuroprotective agents should be revisited in the era of endovascular thrombectomy (EVT) for acute large-artery occlusion because their preclinical effects have been optimized for ischemia and reperfusion injury. Neu2000, a derivative of sulfasalazine, is a multi-target neuroprotectant. It selectively blocks N-methyl-D-aspartate receptors and scavenges for free radicals. This trial aimed to determine whether neuroprotectant administration before EVT is safe and leads to a more favorable outcome. METHODS: This trial is a phase-II, multicenter, three-arm, randomized, double-blinded, placebo-controlled, blinded-endpoint drug trial that enrolled participants aged ≥ 19 years undergoing an EVT attempt less than 8 h from symptom onset, with baseline National Institutes of Health Stroke Scale (NIHSS) score ≥ 8, Alberta Stroke Program Early CT score ≥ 6, evidence of large-artery occlusion, and at least moderate collaterals on computed tomography angiography. EVT-attempted patients are randomized into control, low-dose (2.75 g), and high-dose (5.25 g) Neu2000KWL over 5 days. Seventy participants per group are enrolled for 90% power, assuming that the treatment group has a 28.4% higher proportion of participants with functional independence than the placebo group. The primary outcome, based on intention-to-treat criteria is the improvement of modified Rankin Scale (mRS) scores at 3 months using a dichotomized model. Safety outcomes include symptomatic intracranial hemorrhage within 5 days. Secondary outcomes are distributional change of mRS, mean differences in NIHSS score, proportion of NIHSS score 0-2, and Barthel Index > 90 at 1 and 4 weeks, and 3 months. DISCUSSION: The trial results may provide information on new therapeutic options as multi-target neuroprotection might mitigate reperfusion injury in patients with acute ischemic stroke before EVT
An overview of the NIRSPEC upgrade for the Keck II telescope
NIRSPEC is a 1-5 micron echelle spectrograph in use on the Keck II Telescope
since 1999. The spectrograph is capable of both moderate (R~2,000) and high
(R~25,000) resolution observations and has been a workhorse instrument across
many astronomical fields, from planetary science to extragalactic observations.
In the latter half of 2018, we will upgrade NIRSPEC to improve the sensitivity
and stability of the instrument and increase its lifetime. The major components
of the upgrade include replacing the spectrometer and slit-viewing camera
detectors with Teledyne H2RG arrays and replacing all transputer-based
electronics. We present detailed design, testing, and analysis of the upgraded
instrument, including the finalized optomechanical design of the new 1-5 micron
slit-viewing camera, final alignment and assembly of the science array,
electronics systems, and updated software design.Comment: Proceedings of the 2018 SPIE Astronomical Telescopes &
Instrumentatio
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: photometric characterization of anisoplanatic PSFs and testing of PSF-Reconstruction via AIROPA
The InfraRed Imaging Spectrograph (IRIS) is a first-light instrument for the Thirty Meter Telescope (TMT) that will be used to sample the corrected adaptive optics field by the Narrow-Field Infrared Adaptive Optics System (NFIRAOS) with a near-infrared (0.8 - 2.4 µm) imaging camera and integral field spectrograph. To better understand IRIS science specifications we use the IRIS data simulator to characterize relative photometric precision and accuracy across the IRIS imaging camera 34”x34” field of view. Because the Point Spread Function (PSF) varies due to the effects of anisoplanatism, we use the Anisoplanatic and Instrumental Reconstruction of Off-axis PSFs for AO (AIROPA) software package to conduct photometric measurements on simulated frames using PSF-fitting as the PSF varies in single-source, binary, and crowded field use cases. We report photometric performance of the imaging camera as a function of the instrumental noise properties including dark current and read noise. Using the same methods, we conduct comparisons of photometric performance with reconstructed PSFs, in order to test the veracity of the current PSF-Reconstruction algorithms for IRIS/TMT
The InfraRed Imaging Spectrograph (IRIS) for TMT: photometric characterization of anisoplanatic PSFs and testing of PSF-Reconstruction via AIROPA
The InfraRed Imaging Spectrograph (IRIS) is a first-light instrument for the Thirty Meter Telescope (TMT) that will be used to sample the corrected adaptive optics field by the Narrow-Field Infrared Adaptive Optics System (NFIRAOS) with a near-infrared (0.8 - 2.4 µm) imaging camera and integral field spectrograph. To better understand IRIS science specifications we use the IRIS data simulator to characterize relative photometric precision and accuracy across the IRIS imaging camera 34”x34” field of view. Because the Point Spread Function (PSF) varies due to the effects of anisoplanatism, we use the Anisoplanatic and Instrumental Reconstruction of Off-axis PSFs for AO (AIROPA) software package to conduct photometric measurements on simulated frames using PSF-fitting as the PSF varies in single-source, binary, and crowded field use cases. We report photometric performance of the imaging camera as a function of the instrumental noise properties including dark current and read noise. Using the same methods, we conduct comparisons of photometric performance with reconstructed PSFs, in order to test the veracity of the current PSF-Reconstruction algorithms for IRIS/TMT
The Infrared Imaging Spectrograph (IRIS) for TMT: advancing the data reduction system
Infrared Imaging Spectrograph (IRIS) is the first light instrument for the
Thirty Meter Telescope (TMT) that consists of a near-infrared (0.84 to 2.4
micron) imager and integral field spectrograph (IFS) which operates at the
diffraction-limit utilizing the Narrow-Field Infrared Adaptive Optics System
(NFIRAOS). The imager will have a 34 arcsec x 34 arcsec field of view with 4
milliarcsecond (mas) pixels. The IFS consists of a lenslet array and slicer,
enabling four plate scales from 4 mas to 50 mas, multiple gratings and filters,
which in turn will operate hundreds of individual modes. IRIS, operating in
concert with NFIRAOS will pose many challenges for the data reduction system
(DRS). Here we present the updated design of the real-time and post-processing
DRS. The DRS will support two modes of operation of IRIS: (1) writing the raw
readouts sent from the detectors and performing the sampling on all of the
readouts for a given exposure to create a raw science frame; and (2) reduction
of data from the imager, lenslet array and slicer IFS. IRIS is planning to save
the raw readouts for a given exposure to enable sophisticated processing
capabilities to the end users, such as the ability to remove individual poor
seeing readouts to improve signal-to-noise, or from advanced knowledge of the
point spread function (PSF). The readout processor (ROP) is a key part of the
IRIS DRS design for writing and sampling of the raw readouts into a raw science
frame, which will be passed to the TMT data archive. We discuss the use of
sub-arrays on the imager detectors for saturation/persistence mitigation,
on-detector guide windows, and fast readout science cases (< 1 second).Comment: 14 pages, 5 figures, 6 tables, Proceeding 10707-112 of the SPIE
Astronomical Telescopes + Instrumentation 201
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