666 research outputs found
An Open-Source Gaussian Beamlet Decomposition Tool for Modeling Astronomical Telescopes
In the pursuit of directly imaging exoplanets, the high-contrast imaging
community has developed a multitude of tools to simulate the performance of
coronagraphs on segmented-aperture telescopes. As the scale of the telescope
increases and science cases move toward shorter wavelengths, the required
physical optics propagation to optimize high-contrast imaging instruments
becomes computationally prohibitive. Gaussian Beamlet Decomposition (GBD) is an
alternative method of physical optics propagation that decomposes an arbitrary
wavefront into paraxial rays. These rays can be propagated expeditiously using
ABCD matrices, and converted into their corresponding Gaussian beamlets to
accurately model physical optics phenomena without the need of diffraction
integrals. The GBD technique has seen recent development and implementation in
commercial software (e.g. FRED, CODE V, ASAP) but appears to lack an
open-source platform. We present a new GBD tool developed in Python to model
physical optics phenomena, with the goal of alleviating the computational
burden for modeling complex apertures, many-element systems, and introducing
the capacity to model misalignment errors. This study demonstrates the synergy
of the geometrical and physical regimes of optics utilized by the GBD
technique, and is motivated by the need for advancing open-source physical
optics propagators for segmented-aperture telescope coronagraph design and
analysis. This work illustrates GBD with Poisson's spot calculations and show
significant runtime advantage of GBD over Fresnel propagators for many-element
systems.Comment: 13 pages, 9 figures, submitted to SPIE Astronomical Telescopes &
Instrumentation 202
Hybrid propagation physics for the design and modeling of astronomical observatories: a coronagraphic example
For diffraction-limited optical systems an accurate physical optics model is
necessary to properly evaluate instrument performance. Astronomical
observatories outfitted with coronagraphs for direct exoplanet imaging require
physical optics models to simulate the effects of misalignment and diffraction.
Accurate knowledge of the observatory's PSF is integral for the design of
high-contrast imaging instruments and simulation of astrophysical observations.
The state of the art is to model the misalignment, ray aberration, and
diffraction across multiple software packages, which complicates the design
process. Gaussian Beamlet Decomposition (GBD) is a ray-based method of
diffraction calculation that has been widely implemented in commercial optical
design software. By performing the coherent calculation with data from the ray
model of the observatory, the ray aberration errors can be fed directly into
the physical optics model of the coronagraph, enabling a more integrated model
of the observatory. We develop a formal algorithm for the transfer-matrix
method of GBD, and evaluate it against analytical results and a traditional
physical optics model to assess the suitability of GBD for high-contrast
imaging simulations. Our GBD simulations of the observatory PSF, when compared
to the analytical Airy function, have a sum-normalized RMS difference of
~10^-6. These fields are then propagated through a Fraunhofer model of a
exoplanet imaging coronagraph where the mean residual numerical contrast is
4x10^-11, with a maximum near the inner working angle at 5x10^-9. These results
show considerable promise for the future development of GBD as a viable
propagation technique in high-contrast imaging. We developed this algorithm in
an open-source software package and outlined a path for its continued
development to increase the fidelity and flexibility of diffraction simulations
using GBD.Comment: 58 pages, 15 figures, preprint version for article in press. Accepted
to SPIE's Journal of Astronomical Telescopes, Instruments, and Systems on
October 23 202
How universal is the fractional-quantum-Hall edge Luttinger liquid?
This article reports on our microscopic investigations of the edge of the
fractional quantum Hall state at filling factor . We show that the
interaction dependence of the wave function is well described in an
approximation that includes mixing with higher composite-fermion Landau levels
in the lowest order. We then proceed to calculate the equal time edge Green
function, which provides evidence that the Luttinger exponent characterizing
the decay of the Green function at long distances is interaction dependent. The
relevance of this result to tunneling experiments is discussed.Comment: 5 page
Polarimetric modeling and assessment of science cases for Giant Magellan Telescope-Polarimeter (GMT-Pol)
Polarization observations through the next-generation large telescopes will
be invaluable for exploring the magnetic fields and composition of jets in AGN,
multi-messenger transients follow-up, and understanding interstellar dust and
magnetic fields. The 25m Giant Magellan Telescope (GMT) is one of the
next-generation large telescopes and is expected to have its first light in
2029. The telescope consists of a primary mirror and an adaptive secondary
mirror comprising seven circular segments. The telescope supports instruments
at both Nasmyth as well as Gregorian focus. However, none of the first or
second-generation instruments on GMT has the polarimetric capability. This
paper presents a detailed polarimetric modeling of the GMT for both Gregorian
and folded ports for astronomical B-K filter bands and a field of view of 5 arc
minutes. At 500nm, The instrumental polarization is 0.1% and 3% for the
Gregorian and folded port, respectively. The linear to circular crosstalk is
0.1% and 30% for the Gregorian and folded ports, respectively. The Gregorian
focus gives the GMT a significant competitive advantage over TMT and ELT for
sensitive polarimetry, as these telescopes support instruments only on the
Nasmyth platform. We also discuss a list of polarimetric science cases and
assess science case requirements vs. the modeling results. Finally, we discuss
the possible routes for polarimetry with GMT and show the preliminary optical
design of the GMT polarimeter.Comment: 13 pages, 5 figures,SPIE Optics + Photonics 2023 conference
proceeding, Paper no 12690-2
Agrammatic but numerate
A central question in cognitive neuroscience concerns the extent to
which language enables other higher cognitive functions. In the
case of mathematics, the resources of the language faculty, both
lexical and syntactic, have been claimed to be important for exact
calculation, and some functional brain imaging studies have shown
that calculation is associated with activation of a network of
left-hemisphere language regions, such as the angular gyrus and
the banks of the intraparietal sulcus. We investigate the integrity
of mathematical calculations in three men with large left-hemisphere
perisylvian lesions. Despite severe grammatical impairment
and some difficulty in processing phonological and orthographic
number words, all basic computational procedures were intact
across patients. All three patients solved mathematical problems
involving recursiveness and structure-dependent operations (for
example, in generating solutions to bracket equations). To our
knowledge, these results demonstrate for the first time the remarkable
independence of mathematical calculations from language
grammar in the mature cognitive system
Estimation of polarization aberrations and their effect on the coronagraphic performance for future space telescopes
A major goal of proposed future space observatories, such as the Habitable
World Observatory, is to directly image and characterize Earth-like planets
around Sun-like stars to search for habitability signatures requiring the
starlight suppression (contrast) of 1e-10. One of the significant aspects
affecting this contrast is the polarization aberrations generated from the
reflection from mirror surfaces. The polarization aberrations are the
phase-dependent amplitude and phase patterns originating from the Fresnel
reflections of the mirror surfaces. These aberrations depend on the angle of
incidence and coating parameters of the surface. This paper simulates the
polarization aberrations for an on-axis and off-axis TMA telescope of a 6.5 m
monolithic primary mirror. We analyze the polarization aberrations and their
effect on the coronagraphic performance for eight different recipes of mirror
coatings for Astronomical filter bands g-I: three single-layer metal coatings
and five recipes of protective coatings. First, the Jones pupils are estimated
for each coating and filter band using the polarization ray tracing in Zemax.
Then, we propagate these Jones pupils through a Vector Vortex Coronagraph and
Perfect Coronagraphs using hcipy, a physical optics-based simulation framework.
The analysis shows that the two main polarization aberrations generated from
the four mirrors are the retardance-defocus and retardance-tilt. The
simulations also show that the coating plays a significant role in determining
the strength of the aberrations. The bare/oxi-aluminum and Al+18nm LiF coating
outperforms all the other coatings by one order of magnitude.Comment: 13 pages, 11 figures, SPIE Optics+Photonics 2023 proceeding, Paper
no: 12680-2
Poke: An open-source ray-based physical optics platform
Integrated optical models allow for accurate prediction of the as-built
performance of an optical instrument. Optical models are typically composed of
a separate ray trace and diffraction model to capture both the geometrical and
physical regimes of light. These models are typically separated across both
open-source and commercial software that don't interface with each other
directly. To bridge the gap between ray trace models and diffraction models, we
have built an open-source optical analysis platform in Python called Poke that
uses commercial ray tracing APIs and open-source physical optics engines to
simultaneously model scalar wavefront error, diffraction, and polarization.
Poke operates by storing ray data from a commercial ray tracing engine into a
Python object, from which physical optics calculations can be made. We present
an introduction to using Poke, and highlight the capabilities of two new
propagation physics modules that add to the utility of existing scalar
diffraction models. Gaussian Beamlet Decomposition is a ray-based approach to
diffraction modeling that allows us to integrate physical optics models with
ray trace models to directly capture the influence of ray aberrations in
diffraction simulations. Polarization Ray Tracing is a ray-based method of
vector field propagation that can diagnose the polarization aberrations in
optical systems. Poke has been recently used to study the next generation of
astronomical observatories, including the ground-based Extremely Large
Telescopes and a 6 meter space telescope early concept for NASA's Habitable
Worlds Observatory.Comment: 11 Pages, 9 Figures, Published in Proceedings of SPIE Optical
Modeling and Performance Predictions XIII Paper 12664-
The space coronagraph optical bench (SCoOB): 2. wavefront sensing and control in a vacuum-compatible coronagraph testbed for spaceborne high-contrast imaging technology
The 2020 Decadal Survey on Astronomy and Astrophysics endorsed space-based
high contrast imaging for the detection and characterization of habitable
exoplanets as a key priority for the upcoming decade. To advance the maturity
of starlight suppression techniques in a space-like environment, we are
developing the Space Coronagraph Optical Bench (SCoOB) at the University of
Arizona, a new thermal vacuum (TVAC) testbed based on the Coronagraphic Debris
Exoplanet Exploring Payload (CDEEP), a SmallSat mission concept for high
contrast imaging of circumstellar disks in scattered light. When completed, the
testbed will combine a vector vortex coronagraph (VVC) with a Kilo-C
microelectromechanical systems (MEMS) deformable mirror from Boston
Micromachines Corp (BMC) and a self-coherent camera (SCC) with a goal of raw
contrast surpassing at visible wavelengths. In this proceedings, we
report on our wavefront sensing and control efforts on this testbed in air,
including the as-built performance of the optical system and the implementation
of algorithms for focal-plane wavefront control and digging dark holes (regions
of high contrast in the focal plane) using electric field conjugation (EFC) and
related algorithms.Comment: 7 pages, 5 figures, SPIE Astronomical Telescopes and Instrumentation
202
Polarization aberrations in next-generation giant segmented mirror telescopes (GSMTs) I. Effect on the coronagraphic performance
Next-generation large segmented mirror telescopes are expected to perform
direct imaging and characterization of Earth-like rocky planets, which requires
contrast limits of to at wavelengths from I to J band. One
critical aspect affecting the raw on-sky contrast are polarization aberrations
arising from the reflection from the telescope's mirror surfaces and instrument
optics. We simulate the polarization aberrations and estimate their effect on
the achievable contrast for three next-generation ground-based large segmented
mirror telescopes. We performed ray-tracing in Zemax and computed the
polarization aberrations and Jones pupil maps using the polarization
ray-tracing algorithm. The impact of these aberrations on the contrast is
estimated by propagating the Jones pupil maps through a set of idealized
coronagraphs using hcipy, a physical optics-based simulation framework. The
optical modeling of the giant segmented mirror telescopes (GSMTs) shows that
polarization aberrations create significant leakage through a coronagraphic
system. The dominant aberration is retardance defocus, which originates from
the steep angles on the primary and secondary mirrors. The retardance defocus
limits the contrast to to at 1 at visible
wavelengths, and to at infrared wavelengths. The
simulations also show that the coating plays a major role in determining the
strength of the aberrations. Polarization aberrations will need to be
considered during the design of high-contrast imaging instruments for the next
generation of extremely large telescopes. This can be achieved either through
compensation optics, robust coronagraphs, specialized coatings, calibration,
and data analysis approaches or by incorporating polarimetry with high-contrast
imaging to measure these effects.Comment: 18 pages, 12 figures, Accepted in Astronomy & Astrophysics manuscript
no. aa45651-2
Cost-benefit analysis of BIM-enabled design clash detection and resolution
Building Information Modelling (BIM) is increasingly deployed as part of the processes in Architecture, Engineering and Construction (AEC) industry projects. While the benefits of BIM have been extensively proclaimed, explicit justification in terms of direct cost savings for BIM implementation on real-life projects, particularly for clash detection BIM workstream, are not well documented. This paper proposes and demonstrates a methodology to prove how BIM-based clash detection leads to cost savings. A schema is developed based on literature review and industrial expertise to quantify cost savings achieved by the utilisation of BIM-based clash detection and resolution. This paper provides validation of the proposed schema on a major infrastructure project. The developed schema includes the categorisation of identified clashes based on stakeholder involvement and required actions. The validation used the estimated cost of clashes were those not resolved before site operations took place. This schema simplifies both the categorisation and cost estimation of clashes in design. Estimated savings yielded 20% of contract value using the schema, for the multi-million-dollar project case study, thus extending evidence of BIM savings and benefits. The schema improves the existing process and valorises clash detection, thus allowing stakeholders to conduct a cost-benefit analysis. In addition, the categorisation methodology allows prioritising on the most costly clashes, and draw lessons learnt for further projects. This schema opens the path towards a systematic methodology to appraise the benefits of different BIM uses or processes
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