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Results for “Astronomy image processing”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

On determination of charge transfer efficiency of thick, fully depleted CCDs with 55 Fe x-rays

Charge transfer efficiency (CTE) is one of the most important CCD characteristics. Our paper examines ways to optimize the algorithms used to analyze 55 Fe x-ray data on the CCDs, as well as explores new types of observables for CTE determination that can be used for testing LSST CCDs. Furthermore, the observables are modeled employing simple Monte Carlo simulations to determine how the charge diffusion in thick, fully depleted silicon affects the measurement. The data is compared to the simulations for one of the observables, integral flux of the x-ray hit.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

HIGH-RESOLUTION LINEAR POLARIMETRIC IMAGING FOR THE EVENT HORIZON TELESCOPE

Images of the linear polarizations of synchrotron radiation around active galactic nuclei (AGNs) highlight their projected magnetic field lines and provide key data for understanding the physics of accretion and outflow from supermassive black holes. The highest-resolution polarimetric images of AGNs are produced with Very Long Baseline Interferometry (VLBI). Because VLBI incompletely samples the Fourier transform of the source image, any image reconstruction that fills in unmeasured spatial frequencies will not be unique and reconstruction algorithms are required. In this paper, we explore some extensions of the Maximum Entropy Method (MEM) to linear polarimetric VLBI imaging. In contrast to previous work, our polarimetric MEM algorithm combines a Stokes I imager that only uses bispectrum measurements that are immune to atmospheric phase corruption, with a joint Stokes Q and U imager that operates on robust polarimetric ratios. We demonstrate the effectiveness of our technique on 7 and 3 mm wavelength quasar observations from the VLBA and simulated 1.3 mm Event Horizon Telescope observations of Sgr A* and M87. Consistent with past studies, we find that polarimetric MEM can produce superior resolution compared to the standard CLEAN algorithm, when imaging smooth and compact source distributions. As an imaging framework, MEM is highly adaptable, allowing a range of constraints on polarization structure. Polarimetric MEM is thus an attractive choice for image reconstruction with the EHT.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

GW150914: FIRST SEARCH FOR THE ELECTROMAGNETIC COUNTERPART OF A GRAVITATIONAL-WAVE EVENT BY THE TOROS COLLABORATION

We present the results of the optical follow-up conducted by the TOROS collaboration of the first gravitational-wave event GW150914. We conducted unfiltered CCD observations (0.35–1 μ m) with the 1.5 m telescope at Bosque Alegre starting ∼2.5 days after the alarm. Given our limited field of view (∼100 arcmin{sup 2}), we targeted 14 nearby galaxies that were observable from the site and were located within the area of higher localization probability. We analyzed the observations using two independent implementations of difference-imaging algorithms, followed by a Random-Forest-based algorithm to discriminate between real and bogus transients. We did not find any bona fide transient event in the surveyed area down to a 5 σ limiting magnitude of r = 21.7 mag (AB). Our result is consistent with the LIGO detection of a binary black hole merger, for which no electromagnetic counterparts are expected, and with the expected rates of other astrophysical transients.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Performance evaluation of cosmic ray muon trajectory estimation algorithms

Muons, being elementary particles with minimal interaction with nuclear materials and abundant at sea level, have sparked interest in utilizing them for imaging various applications, such as mining [Borselli et al., Sci. Rep. 12, 22329 (2022)], volcano imaging [Nagamine et al., Nucl. Instrum. Meth. A, 356, 585(1995)], and underground tunnel detection [Guardincerri et al., Pure Appl. Geophys. 174, 2133 (2017)]. Recently, their use in nuclear nonproliferation and safeguard verification has gained attention, particularly in cargo screening for nuclear waste smuggling [Baesso et al., J. Instrum. 9, C10041 (2014)], source localization [L. J. Schultz et al., Nucl. Instrum. Meth. A 519, 687 (2004)], and locating nuclear fuel debris in reactors [Borozdin et al., Phys. Rev. Let. 109, 152501 (2012)]. However, the resolution of muon image reconstruction techniques is limited due to multiple Coulomb scattering (MCS) within the target object. To achieve robust muon tomography, it is crucial to develop efficient and flexible physics-based algorithms that can model the MCS process accurately and estimate the most probable trajectory of muons as they pass through the target object. To address this limitation, in this study, a novel algorithmic approach utilizing the Bayesian probability theory and Gaussian approximation of MCS is chosen. Different energy levels, materials, and target sizes were considered in the evaluations. The results demonstrate that the Generalized Muon Trajectory Estimation (GMTE) algorithm offers significant improvements over currently used algorithms. Across all test scenarios, the GMTE algorithm demonstrated ~50% and 38% increase in precision compared to Straight Line Path (SLP) and Point of Closest Approach (PoCA) algorithms, respectively. Furthermore, it exhibited 10%–35% and 10%–15% increases in muon flux utilization for high and medium Z materials, respectively, compared to the PoCA algorithm. In conclusion, the extensive simulations confirm the enhanced performance and efficiency of the GMTE algorithm, offering improved resolution and reduced measurement time for cosmic ray muon imaging compared to the current SLP and PoCA algorithms.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1991

Development of a high resolution liquid xenon imaging chamber for gamma-ray astronomy

The objective was to develop the technology of liquid xenon (LXe) detectors for spectroscopy and imaging of gamma rays from astrophysical sources emitting in the low to medium energy regime. In particular, the technical challenges and the physical processes relevant to the realization of the LXe detector operated as a Time Projection Chamber (TPC) were addressed and studied. Experimental results were obtained on the following topics: (1) long distance drift of free electrons in LXe (purity); (2) scintillation light yield for electrons and alphas in LXe (triggering); and (3) ionization yield for electrons and gamma rays in LXe (energy resolution). The major results from the investigations are summarized.

Aprile, Elena↗
DOE OSTI2025

Legacy Survey of Space and Time Data Preview 1: visit_image dataset type

The Legacy Survey of Space and Time Data Preview 1 (DP1) is the first release of data from the NSF-DOE Vera C. Rubin Observatory. It consists of raw and calibrated single-epoch images, co-adds, difference images, detection catalogs, and other derived data products. DP1 is based on 1792 science-grade optical/near-infrared exposures acquired over 48 distinct nights by the Rubin Commissioning Camera, LSSTComCam, on the Simonyi Survey Telescope at the Summit Facility on Cerro Pachón, Chile during the first on-sky commissioning campaign in late 2024. DP1 covers a total of approximately 15 sq. deg. over seven roughly equally-sized non-contiguous fields, each independently observed in six broad photometric bands, ugrizy, spanning a range of stellar densities and latitudes and overlapping with external reference datasets. This dataset is a subset of the full data release consisting of the visit_image dataset type. These are individual processed and calibrated sky images obtained from a single observation with a single filter. This release contains 15,972 datasets of this type.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Cataloging the visible universe through Bayesian inference in Julia at petascale

A key task in astronomy is to locate astronomical objects in images and to characterize them according to physical parameters such as brightness, color, and morphology. This task, known as cataloging, is challenging for several reasons: many astronomical objects are much dimmer than the sky background, labeled data is generally unavailable, overlapping astronomical objects must be resolved collectively, and the datasets are enormous – terabytes now, petabytes soon. In this work, we infer an astronomical catalog from 55 TB of imaging data using Celeste, a Bayesian variational inference code written entirely in the high-productivity programming language Julia. Using over 1.3 million threads on 650,000 Intel Xeon Phi cores of the Cori Phase II supercomputer, Celeste achieves a peak rate of 1.54 DP PFLOP/s. Celeste is able to jointly optimize parameters for 188 M stars and galaxies, loading and processing 178 TB across 8192 nodes in 14.6 min. To achieve this, Celeste exploits parallelism at multiple levels (cluster, node, and thread) and accelerates I/O through Cori’s burst buffer. Julia’s native performance enables Celeste to employ high-level constructs without resorting to hand-written or generated low-level code (C/C++/Fortran) while still achieving petascale performance.

Regier, Jeffrey↗
NASA NTRS1982

U.S. mission plans for Spacelab

Mission configurations, instrumentation, and objectives for Spacelab sorties on board the Shuttle beginning in Sept. 1983 are reviewed. The first two flights will serve to verify the Spacelab systems and will be followed by operational status, including the fifth flight, which will be a reimbursible venture. Scientific investigations in the fields of atmospheric physics and environmental observation, space plasma physics, astronomy and solar physics, materials processing, and life sciences will be performed using the habitable long module, instrument pallets, and/or an instrument igloo mounted in the payload bay. Instrumentation, such as the imaging spectrometric observatory, which was developed in the U.S., will originate in either the U.S. or Europe. Details of the first four Spacelab flights are presented, noting that the OSS-3 through -7 missions will feature the first time that entire NASA payloads have returned to space.

Sander, M. J.↗
NASA NTRS2011

From X-Ray Telescopes to Neutron Focusing

In the case of neutrons the refractive index is slightly less than unity for most elements and their isotopes. Consequently, thermal and cold neutrons can be reflected from smooth surfaces at grazing-incidence angles. Hence, the optical technologies developed for x-ray astronomy can be applied for neutron focusing. The focusing capabilities of grazing incidence neutron imaging optics have been successfully demonstrated using nickel mirrors. The mirrors were fabricated using an electroformed nickel replication process at Marshall Space Flight Center. Results of the neutron optics experiments will be presented. Challenges of the neutron imaging optics as well as possible applications of the optics will be discussed.

Gubarev, M. V.↗
DOE OSTI2021

Dark energy survey year 3 results: weak lensing shape catalogue

ABSTRACT We present and characterize the galaxy shape catalogue from the first 3 yr of Dark Energy Survey (DES) observations, over an effective area of 4143 deg2 of the southern sky. We describe our data analysis process and our self-calibrating shear measurement pipeline metacalibration, which builds and improves upon the pipeline used in the DES Year 1 analysis in several aspects. The DES Year 3 weak-lensing shape catalogue consists of 100 204 026 galaxies, measured in the riz bands, resulting in a weighted source number density of neff = 5.59 gal arcmin−2 and corresponding shape noise σe = 0.261. We perform a battery of internal null tests on the catalogue, including tests on systematics related to the point spread function (PSF) modelling, spurious catalogue B-mode signals, catalogue contamination, and galaxy properties.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Characterization of multilayer coated replicated Wolter optics for imaging x-ray emission from pulsed power

Here, we have developed a process for indirectly coating small diameter electroformed nickel replicated optics with multilayers to increase their response at high energy (i.e. >10 keV). The ability to fabricate small diameter multilayer-coated full-shell Wolter X-ray optics with narrow bandpass opens the door to several applications within astronomy and also provides a path for cross-fertilization to other fields. We report on the characterization and evaluation of the first two prototype X-ray Wolter optics to be delivered to the Z Pulsed Power Facility at Sandia National Laboratories. The intent is to develop and field several optics as part of an imaging system with targeted spectral ranges.

36 MATERIALS SCIENCE↗
NASA NTRS1988

Research in planetary astronomy

The objective is the continuation of a long-term research program designed to study the composition, structure and processes operating on the surfaces of solar system objects using the Mauna Kea Observatory with techniques and modern instrumentation. Reflectance spectroscopy and multispectral imaging in the spectral region, 0.3 to 5.0 micrometer are the major techniques used, although thermal (10 micrometer and 20 micrometer) radiometry are used in some aspects of the research. Some specific projects include: (1) systematic spectral imaging observations of the Moon; (2) systematic spectral imaging and spectral monitoring of the Martian surface; (3) thermal radiometry of asteroids as part of the IRAS follow-up and other target specific programs; (4) searches for asteroid satellites and dust belts using a stellar coronagraph; and (5) studies of circumstellar disks using a stellar coronagraph. Progress for each of the programs included is discussed. minerals; (2) completed observations of lunar multi-ringed basins and crater deposits in search of high-Ca spectral anomalies; (3) completed data reduction of an additional 5 asteroids observed by the coronagraphic technique in the search for asteroids satellites and debris clouds; and (4) completed the reduction and calibration of 350 asteroids observed at 10 micron and 20 micron using the NASA IRTF.

Mccord, Thomas B.↗
DOE OSTI2016

A selection of giant radio sources from NVSS

Results of the application of pattern-recognition techniques to the problem of identifying giant radio sources (GRSs) from the data in the NVSS catalog are presented, and issues affecting the process are explored. Decision-tree pattern-recognition software was applied to training-set source pairs developed from known NVSS large-angular-size radio galaxies. The full training set consisted of 51,195 source pairs, 48 of which were known GRSs for which each lobe was primarily represented by a single catalog component. The source pairs had a maximum separation of $20^{\prime} $ and a minimum component area of 1.87 square arcmin at the 1.4 mJy level. The importance of comparing the resulting probability distributions of the training and application sets for cases of unknown class ratio is demonstrated. The probability of correctly ranking a randomly selected (GRS, non-GRS) pair from the best of the tested classifiers was determined to be 97.8 ± 1.5%. The best classifiers were applied to the over 870,000 candidate pairs from the entire catalog. Images of higher-ranked sources were visually screened, and a table of over 1600 candidates, including morphological annotation, is presented. These systems include doubles and triples, wide-angle tail and narrow-angle tail, S- or Z-shaped systems, and core-jets and resolved cores. In conclusion, while some resolved-lobe systems are recovered with this technique, generally it is expected that such systems would require a different approach.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

GRADUAL MAGNETIC EVOLUTION OF SUNSPOT STRUCTURE AND FILAMENT–CORONA DYNAMICS ASSOCIATED WITH THE X1.8 FLARE IN AR11283

In this paper, we present a study of the persistent and gradual penumbral decay and the correlated decline of the photospheric transverse field component 10–20 hr before a major flare (X1.8) eruption on 2011 September 7. This long-term pre-eruption behavior is corroborated by the well-imaged pre-flare filament rising, the consistent expansion of the coronal arcades overlying the filament, and the nonlinear force-free field modeling results in the literature. We suggest that both the long-term pre-flare penumbral decay and the transverse field decline are photospheric manifestations of the gradual rise of the coronal filament–flux rope system. We also suggest that the C3 flare and the subsequent reconnection process preceding the X1.8 flare play an important role in triggering the later major eruption.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

DEEP WIDEBAND SINGLE POINTINGS AND MOSAICS IN RADIO INTERFEROMETRY: HOW ACCURATELY DO WE RECONSTRUCT INTENSITIES AND SPECTRAL INDICES OF FAINT SOURCES?

Many deep wideband wide-field radio interferometric surveys are being designed to accurately measure intensities, spectral indices, and polarization properties of faint source populations. In this paper, we compare various wideband imaging methods to evaluate the accuracy to which intensities and spectral indices of sources close to the confusion limit can be reconstructed. We simulated a wideband single-pointing (C-array, L-Band (1–2 GHz)) and 46-pointing mosaic (D-array, C-Band (4–8 GHz)) JVLA observation using a realistic brightness distribution ranging from 1 μ Jy to 100 mJy and time-, frequency-, polarization-, and direction-dependent instrumental effects. The main results from these comparisons are (a) errors in the reconstructed intensities and spectral indices are larger for weaker sources even in the absence of simulated noise, (b) errors are systematically lower for joint reconstruction methods (such as Multi-Term Multi-Frequency-Synthesis (MT-MFS)) along with A-Projection for accurate primary beam correction, and (c) use of MT-MFS for image reconstruction eliminates Clean-bias (which is present otherwise). Auxiliary tests include solutions for deficiencies of data partitioning methods (e.g., the use of masks to remove clean bias and hybrid methods to remove sidelobes from sources left un-deconvolved), the effect of sources not at pixel centers, and the consequences of various other numerical approximations within software implementations. This paper also demonstrates the level of detail at which such simulations must be done in order to reflect reality, enable one to systematically identify specific reasons for every trend that is observed, and to estimate scientifically defensible imaging performance metrics and the associated computational complexity of the algorithms/analysis procedures.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

CHANGES IN THE PHYSICAL ENVIRONMENT OF THE INNER COMA OF 67P/CHURYUMOV–GERASIMENKO WITH DECREASING HELIOCENTRIC DISTANCE

The Wide Angle Camera of the OSIRIS instrument on board the Rosetta spacecraft is equipped with several narrow-band filters that are centered on the emission lines and bands of various fragment species. These are used to determine the evolution of the production and spatial distribution of the gas in the inner coma of comet 67P with time and heliocentric distance, here between 2.6 and 1.3 au pre-perihelion. Our observations indicate that the emission observed in the OH, O i, CN, NH, and NH{sub 2} filters is mostly produced by dissociative electron impact excitation of different parent species. We conclude that CO{sub 2} rather than H{sub 2}O is a significant source of the [O i] 630 nm emission. A strong plume-like feature observed in the CN and O i filters is present throughout our observations. This plume is not present in OH emission and indicates a local enhancement of the CO{sub 2}/H{sub 2}O ratio by as much as a factor of 3. We observed a sudden decrease in intensity levels after 2015 March, which we attribute to decreased electron temperatures in the first few kilometers above the surface of the nucleus.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Cloud structure of galactic OB cluster-forming regions from combining ground- and space-based bolometric observations

We have developed an iterative procedure to systematically combine the millimeter and submillimeter images of OB cluster-forming molecular clouds, which were taken by ground-based (CSO, JCMT, APEX, and IRAM-30 m) and space telescopes (Herschel and Planck). For the seven luminous (L>10{sup 6} L {sub ⊙}) Galactic OB cluster-forming molecular clouds selected for our analyses, namely W49A, W43-Main, W43-South, W33, G10.6-0.4, G10.2-0.3, and G10.3-0.1, we have performed single-component, modified blackbody fits to each pixel of the combined (sub)millimeter images, and the Herschel PACS and SPIRE images at shorter wavelengths. The ∼10″ resolution dust column density and temperature maps of these sources revealed dramatically different morphologies, indicating very different modes of OB cluster-formation, or parent molecular cloud structures in different evolutionary stages. The molecular clouds W49A, W33, and G10.6-0.4 show centrally concentrated massive molecular clumps that are connected with approximately radially orientated molecular gas filaments. The W43-Main and W43-South molecular cloud complexes, which are located at the intersection of the Galactic near 3 kpc (or Scutum) arm and the Galactic bar, show a widely scattered distribution of dense molecular clumps/cores over the observed ∼10 pc spatial scale. The relatively evolved sources G10.2-0.3 and G10.3-0.1 appear to be affected by stellar feedback, and show a complicated cloud morphology embedded with abundant dense molecular clumps/cores. We find that with the high angular resolution we achieved, our visual classification of cloud morphology can be linked to the systematically derived statistical quantities (i.e., the enclosed mass profile, the column density probability distribution function (N-PDF), the two-point correlation function of column density, and the probability distribution function of clump/core separations). In particular, the massive molecular gas clumps located at the center of G10.6-0.4 and W49A, which contribute to a considerable fraction of their overall cloud masses, may be special OB cluster-forming environments as a direct consequence of global cloud collapse. These centralized massive molecular gas clumps also uniquely occupy much higher column densities than what is determined by the overall fit of power-law N-PDF. We have made efforts to archive the derived statistical quantities of individual target sources, to permit comparisons with theoretical frameworks, numerical simulations, and other observations in the future.

79 ASTRONOMY AND ASTROPHYSICS↗