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NASA NTRS2000

Deconvolving the Nucleus of Centaurus A Using Chandra PSF Library

Centaurus A (NGC 5128) is a giant early-type galaxy containing the nearest (at 3.5 Mpc) radio-bright Active Galactic Nucleus (AGN). Cen A was observed with the High Resolution Camera (HRC) on the Chandra X-ray Observatory on several occasions since the launch in July 1999. The high-angular resolution (less than 0.5 arcsecond) Chandra/HRC images reveal X ray multi-scale structures in this object with unprecedented detail and clarity, including the bright nucleus believed to be associated with a supermassive black hole. We explored the spatial extent of the Cen A nucleus using deconvolution techniques on the full resolution Chandra images. Model point spread functions (PSFs) were derived from the standard Chandra raytrace PSF library as well as unresolved point sources observed with Chandra. The deconvolved images show that the Cen A nucleus is resolved and asymmetric. We discuss several possible causes of this extended emission and of the asymmetries.

Karovska, Margarita↗

NASA NTRS2009

Amplitude Metrics for Field Retrieval with Hard-Edged and Uniformly Illuminated Apertures

In field retrieval, the amplitude and phase of the generalized pupil function for an optical system are estimated from multiple defocused measurements of the system point-spread function. A baseline field reconstruction algorithm optimizing a data consistency metric is described. Additionally, two metrics specifically designed to incorporate a priori knowledge about pupil amplitude for hard-edged and uniformly illuminated aperture systems are given. Experimental results demonstrate the benefit of using these amplitude metrics in addition to the baseline metric

Thurman, Samuel T.↗

NASA NTRS1991

A study of the thermal and optical characteristics of radiometric channels for Earth radiation budget applications

An improved dynamic electrothermal model for the Earth Radiation Budget Experiment (ERBE) total, nonscanning channels is formulated. This model is then used to accurately simulate two types of dynamic solar observation: the solar calibration and the so-called pitchover maneuver. Using a second model, the nonscanner active cavity radiometer (ACR) thermal noise is studied. This study reveals that radiative emission and scattering by the surrounding parts of the nonscanner cavity are acceptably small. The dynamic electrothermal model is also used to compute ACR instrument transfer function. Accurate in-flight measurement of this transfer function is shown to depend on the energy distribution over the frequency spectrum of the radiation input function. A new array-type field of view limiter, whose geometry controls the input function, is proposed for in-flight calibration of an ACR and other types of radiometers. The point spread function (PSF) of the ERBE and the Clouds and Earth's Radiant Energy System (CERES) scanning radiometers is computed. The PSF is useful in characterizing the channel optics. It also has potential for recovering the distribution of the radiative flux from Earth by deconvolution.

Mahan, J. R.↗

DOE OSTI2016

Towards an improved understanding of the influence of subpixel vegetation structure on pixel-level spectra: a simulation approach

The planned NASA Hyperspectral Infrared Imager (HyspIRI) mission, equipped with an imaging spectrometer that has the capability of monitoring ecosystems globally, will provide an unprecedented opportunity to address scientific challenges related to ecosystem function and change. However, uncertainty remains around the impact of subpixel vegetation structure, in combination with the point spread function, on pixel-level imaging spectroscopy data. We estimated structural parameters, e.g., leaf area index (LAI), canopy cover, and tree location, from HyspIRI spectral data, with the goal of assessing how subpixel variation in these parameters impact pixel-level imaging spectroscopy data. The fine-scale variability of real vegetation structure makes this a challenging endeavor. Therefore, we utilized a simulation-based approach to counter the time-consuming and often destructive sampling needs of vegetation structural analysis and to simultaneously generate synthetic HyspIRI data pre-launch. Three virtual scenes were constructed, corresponding to the actual vegetation structure in the National Ecological Observatory Network’s (NEON) Pacific Southwest Domain (Fresno, CA). These included an oak savanna, a dense coniferous forest, and a conifer-manzanita-mixed forest. Simulated spectroscopy data for these scenes were then generated using the Digital Imaging and Remote Sensing Image Generation (DIRSIG) model. Simulations first were used to verify the physical model, virtual scene geometrical information, and simulation parameters. This was followed by simulations of HyspIRI data, where within-pixel structural variability was introduced, e.g., by iteratively changing per-pixel canopy cover and tree placement, tree clustering, leaf area index (LAI), etc., between simulation runs for the virtual scenes. Finally, narrow-band vegetation indices (VIs) were extracted from the data in an attempt to describe the variability of the subpixel structural parameters; this was done in order to assess VI robustness to changes in structural “levels”, as well as placement of trees/canopies within the instrument’s instantaneous field-of-view (IFOV). Our ultimate goal is not only to better understand how such subpixel variability influence imaging spectroscopy outputs, but also to better estimate vegetation structural parameters using spectra. We constructed regression models for LAI (R2 = 0.92) and canopy cover (R2 = 0.97) with narrow-band VIs via this simulation approach. Our models ultimately are intended to improve the HyspIRI mission’s ability to monitor global vegetation structure.

Van Aardt, Jan↗

NASA NTRS1999

NGST/XRCF Design and Build Wavescope System Pallet

Based on the successful Wavescope demonstration at MSFC at the end of March, the decision was made by the optical testing team to purchase an upgraded Wavescope from AOA. The MSFC version would include: a higher resolution camera (1000 x 1000 pixels); a higher density lenslet array (150 x 150); updated software; and longer cables (to accommodate the remote operation of the Wavescope optical head which was resident in the Beam Guide Tube). The AOA proposal for the new instrument was received in mid-April, and delivered to MSFC in mid-July. A considerable amount of effort was expended to provide the infrastructure needed for Wavescope operation, and to incorporate it into the overall test system. This was provided by the Wavescope System Pallet (WSP) built by UAH. The WSP is illustrated. Several instruments are incorporated on this pallet. These include the: Wavescope optical head; a PDI wavefront sensor; a point spread function sensor; a Leica light-based distance measuring sensor. In addition there is a single mode fiber point source (fed from a separate source pallet) which serves both as a reference for the Wavescope and as a source point for the test mirror. There is a dual function lens which both collimates the beam from the test image point, and images the test mirror onto the lenslet array. There is a high quality Collimator which can provide a flat input wavefront directly into the Wavescope. There are also various aids such as an alignment laser, an alignment telescope, alignment sticks and apertures. The WSP was delivered to MSFC on 7/28/99. An picture shows the WSP installed in the Guide Tube at the X-Ray Calibration Facility (XRCF).

Geary, Joe↗

DOE OSTI2026

The Vera C. Rubin Observatory Data Preview 1

We present Rubin Data Preview 1 (DP1), the first data from the National Science Foundation–Department of Energy Vera C. Rubin Observatory, comprising raw and calibrated single-epoch images, coadds, difference images, detection catalogs, and ancillary data products. DP1 is based on 1792 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 in late 2024. DP1 covers ∼15 deg 2 distributed across seven roughly equal-sized noncontiguous fields, each independently observed in six broad photometric bands, ugrizy. The median FWHM of the point-spread function across all bands is approximately 1"14, with the sharpest images reaching about 0." 58. The 5σ point-source depths for coadded images in the deepest field, the Extended Chandra Deep Field South, are u = 24.55, g = 26.18, r = 25.96, i = 25.71, z = 25.07, and y = 23.1. Other fields are no more than 2.2 mag shallower in any band, where they have nonzero coverage. DP1 contains approximately 2.3 million distinct astrophysical objects, of which 1.6 million are extended in at least one band in coadds, and 431 solar system objects, of which 93 are new discoveries. DP1 is approximately 3.5 TB in size and is available to Vera C. Rubin Observatory data rights holders via the Rubin Science Platform, a cloud-based environment for the analysis of petascale astronomical data. While small compared to future LSST releases, its high quality and diversity of data support a broad range of early science investigations ahead of full operations in 2026.

Ground-based astronomy↗

NASA NTRS1991

Photographic Image Restoration

Deblurring capabilities would significantly improve the Flight Science Support Office's ability to monitor the effects of lift-off on the shuttle and landing on the orbiter. A deblurring program was written and implemented to extract information from blurred images containing a straight line or edge and to use that information to deblur the image. The program was successfully applied to an image blurred by improper focussing and two blurred by different amounts of blurring. In all cases, the reconstructed modulation transfer function not only had the same zero contours as the Fourier transform of the blurred image but the associated point spread function also had structure not easily described by simple parameterizations. The difficulties posed by the presence of noise in the blurred image necessitated special consideration. An amplitude modification technique was developed for the zero contours of the modulation transfer function at low to moderate frequencies and a smooth filter was used to suppress high frequency noise.

Hite, Gerald E.↗

DOE OSTI2020

Advanced Laser-driven Plasma Accelerator Electron-beam Diagnostics with COTR Techniques

A significant advance in laser-driven plasma accelerator (LPA) electron-beam diagnostics has recently been demonstrated based on coherent optical transition radiation (COTR) imaging. We find COTR signal strengths from a microbunched subset of beam exiting the LPA to be several orders of magnitude higher than that of incoherent optical transition radiation (OTR). The transverse sizes are only a few microns as deduced from the point-spread-function-related lobe structure. In addition, the far-field COTR interferometric images obtained on the same shot provide beam-size limits plus divergence and pointing information at the sub-mrad level when compared to a modified analytical model. The integrated image intensities can be used to estimate the microbunching fraction and relatable to the LPA process. Initial results in a collaborative LPA experiment will be reported for electron beam energies of about 215 MeV. A revised configuration is proposed to record energy and ene rgy spread via COTR on the same shot with the interferometer.

43 PARTICLE ACCELERATORS↗

NASA NTRS1990

Diffraction image formation in optical systems with polarization aberrations. I - Formulation and example

This paper is the first in a series that will examine image formation in optical systems with polarization aberrations. The present paper derives the point-spread function (PSF) and the optical transfer function for optical systems with polarization aberration and explores how image formation depends on the coherence and polarization state of the source. It is shown that the scalar PSF of Fourier optics can be generalized in the presence of polarization aberration to a 4 x 4 point-spread matrix (PSM) in Mueller matrix notation. A similar 4 x 4 optical transfer matrix (OTM) is shown to be an appropriate generalization of the optical transfer function. The PSM and the OTM are associated with the optical system and are independent of the incident polarization state but dependent on the coherence of the illumination. Since an optical system with polarization aberrations will have a different PSF and optical transfer function for different incident polarization states, the PSM and the OTM act as filters with regard to the incident polarization state. Example calculations are performed for a circularly retarding lens.

Mcguire, James P., Jr.↗

DOE OSTI2017

Inference of Unresolved Point Sources at High Galactic Latitudes Using Probabilistic Catalogs

The detection of point sources in images is a fundamental operation in astrophysics, and is crucial for constraining population models of the underlying point sources or characterizing the background emission. Standard techniques fall short in the crowded-field limit, losing sensitivity to faint sources and failing to track their covariance with close neighbors. We construct a Bayesian framework to perform inference of faint or overlapping point sources. The method involves probabilistic cataloging, where samples are taken from the posterior probability distribution of catalogs consistent with an observed photon count map. In order to validate our method, we sample random catalogs of the gamma-ray sky in the direction of the North Galactic Pole (NGP) by binning the data in energy and point-spread function classes. Using three energy bins spanning 0.3–1, 1–3, and 3–10 GeV, we identify 270{sub −10}{sup +30} point sources inside a 40{sup ∘}×40{sup ∘} region around the NGP above our point-source inclusion limit of 3×10{sup −11} cm{sup −2} s{sup −1} sr{sup −1} GeV{sup −1} at the 1–3 GeV energy bin. Modeling the flux distribution as a power law, we infer the slope to be −1.92{sub −0.05}{sup +0.07} and estimate the contribution of point sources to the total emission as 18{sub −2}{sup +2}%. These uncertainties in the flux distribution are fully marginalized over the number as well as the spatial and spectral properties of the unresolved point sources. This marginalization allows a robust test of whether the apparently isotropic emission in an image is due to unresolved point sources or of truly diffuse origin.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2022

The eROSITA Final Equatorial-Depth Survey (eFEDS)

Aims. The eROSITA Final Equatorial-Depth Survey (eFEDS), executed during the performance verification phase of the Spectrum-Roentgen-Gamma (SRG)/eROSITA telescope, was completed in November 2019. One of the science goals of this survey is to demonstrate the ability of eROSITA to detect samples of clusters and groups at the final depth of the eROSITA all-sky survey. Methods. Because of the sizeable (≈26" HEW FOV average) point-spread function of eROSITA, high-redshift clusters of galaxies or compact nearby groups hosting bright active galactic nuclei (AGN) can be misclassified as point sources by the source detection algorithms. A total of 346 galaxy clusters and groups in the redshift range of 0.1 < z < 1.3 were identified based on their red sequenc in the eFEDS point source catalog. Results. We examine the multiwavelength properties of these clusters and groups to understand the potential biases in our selection process and the completeness of the extent-selected sample. We find that the majority of the clusters and groups in the point source sample are indeed underluminous and compact compared to the extent-selected sample. Their faint X-ray emission, well below the flux limit of the extent-selected eFEDS clusters, and their compact X-ray emission are likely to be the main reason for this misclassification. In the sample, we confirm that 10% of the sources host AGN in their brightest cluster galaxies (BCGs) through optical spectroscopy and visual inspection. By studying their X-ray, optical, infrared, and radio properties, we establish a method for identifying clusters and groups that host AGN in their BCGs. We successfully test this method on the current point source catalog through the Sloan Digital Sky Survey optical spectroscopy and find eight low-mass clusters and groups with active radio-loud AGN that are particularly bright in the infrared. They include eFEDS J091437.8+024558, eFEDS J083520.1+012516, and eFEDS J092227.1+043339 at redshifts 0.3-0.4. Conclusions. This study helps us to characterize and understand our selection process and assess the completeness of the eROSITA extent-selected samples. The method we developed will be used to identify high-redshift clusters, AGN-dominated groups, and low-mass clusters that are misclassified in the future eROSITA all-sky survey point source catalogs.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2021

Mitigating the effects of undersampling in weak lensing shear estimation with metacalibration

ABSTRACT metacalibration is a state-of-the-art technique for measuring weak gravitational lensing shear from well-sampled galaxy images. We investigate the accuracy of shear measured with metacalibration from fitting elliptical Gaussians to undersampled galaxy images. In this case, metacalibration introduces aliasing effects leading to an ensemble multiplicative shear bias about 0.01 for Euclid and even larger for the Roman Space Telescope, well exceeding the missions’ requirements. We find that this aliasing bias can be mitigated by computing shapes from weighted moments with wider Gaussians as weight functions, thereby trading bias for a slight increase in variance of the measurements. We show that this approach is robust to the point-spread function in consideration and meets the stringent requirements of Euclid for galaxies with moderate to high signal-to-noise ratios. We therefore advocate metacalibration as a viable shear measurement option for weak lensing from upcoming space missions.

Kannawadi, Arun↗

DOE OSTI2022

LensingETC: A Tool to Optimize Multifilter Imaging Campaigns of Galaxy-scale Strong Lensing Systems

Imaging data is the principal observable required to use galaxy-scale strong lensing in a multitude of applications in extragalactic astrophysics and cosmology. In this paper, we develop Lensing Exposure Time Calculator (LensingETC; to optimize the efficiency of telescope-time usage when planning multifilter imaging campaigns for galaxy-scale strong lenses. This tool simulates realistic data tailored to specified instrument characteristics and then automatically models them to assess the power of the data in constraining lens model parameters. We demonstrate a use case of this tool by optimizing a two-filter observing strategy (in the IR and ultraviolet-visual (UVIS)) within the limited exposure time per system allowed by a Hubble Space Telescope (HST) Snapshot program. We find that higher resolution is more advantageous to gain constraining power on the lensing observables, when there is a trade-off between signal-to-noise ratio and resolution; for example, between the UVIS and IR filters of the HST. We also find that, whereas a point-spread function (PSF) with sub-Nyquist sampling allows the sample mean for a model parameter to be robustly recovered for both galaxy–galaxy and point-source lensing systems, a sub-Nyquist-sampled PSF introduces a larger scatter than a Nyquist-sampled one in the deviation from the ground truth for point-source lens systems.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2017

Novel Analysis of the Multiwavelength Structure of the Relativistic Jet in Quasar 3C 273

We present a detailed analysis of the best-quality multiwavelength data gathered for the large-scale jet in the core-dominated quasar 3C 273. We analyze all the archival observations of the target with the Chandra X-ray Observatory, the far-ultraviolet observations with the Hubble Space Telescope, and the 8.4 GHz map obtained with the Very Large Array. In our study, we focus on investigating the morphology of the outflow at different frequencies, and therefore we apply various techniques for the image deconvolution, paying particular attention to a precise modeling of the Chandra and Hubble point-spread functions. We find that the prominent brightness enhancements in the X-ray and far-ultraviolet jet of 3C 273—the “knots”—are not point-like, and can be resolved transversely as extended features with sizes of about ≃0.5 kpc. Also, the radio outflow is wider than the deconvolved X-ray/ultraviolet jet. We have also found circumstantial evidence that the intensity peaks of the X-ray knots are located systematically upstream of the corresponding radio intensity peaks, with the projected spatial offsets along the jet ranging from ≲0.2 kpc up to ≃1 kpc. We discuss our findings in the wider context of multi-component models for the emission and structure of large-scale quasar jets, and speculate on the physical processes enabling an efficient acceleration of the emitting ultrarelativistic electrons along the entire jet length that exceeds 100 kpc.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2017

SPITZER PHOTOMETRY OF ∼1 MILLION STARS IN M31 AND 15 OTHER GALAXIES

We present Spitzer IRAC 3.6–8 μ m and Multiband Imaging Photometer 24 μ m point-source catalogs for M31 and 15 other mostly large, star-forming galaxies at distances ∼3.5–14 Mpc, including M51, M83, M101, and NGC 6946. These catalogs contain ∼1 million sources including ∼859,000 in M31 and ∼116,000 in the other galaxies. They were created following the procedures described in Khan et al. through a combination of point-spread function (PSF) fitting and aperture photometry. These data products constitute a resource to improve our understanding of the IR-bright (3.6–24 μ m) point-source populations in crowded extragalactic stellar fields and to plan observations with the James Webb Space Telescope .

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS2010

Solar Polar Spicules Observed with Hinode

We examine solar polar region spicules using high-cadence Ca II data from the Solar Optical Telescope (SOT) on the Hinode spacecraft. We sharpened the images by convolving them with the inverse-point-spread function of the SOT Ca II filter, and we are able to see some of the spicules originating on the disk just inside the limb. Bright points are frequently at the root of the disk spicules. These "Ca II brightenings" scuttle around at approx.few x 10 km/s, live for approx.100 sec, and may be what are variously known as "H_{2V} grains," "K_{2V} grains," or "K_{2V} bright points." When viewed extending over the limb, some of the spicules appear to expand horizontally or split into two or more components, with the horizontal expansion or splitting velocities reaching approx.50 km/s. This work was funded by NASA's Science Mission Directorate through the Living With a Star Targeted Research and Technology Program, the Supporting Research and Program, the Heliospheric Guest Investigator Program, and the Hinode project.

Sterling, Alphonse C.↗

NASA NTRS2016

Impact of Spatial Sampling on Continuity of MODIS-VIIRS Land Surface Reflectance Products: A Simulation Approach

With the increasing need to construct long-term climate-quality data records to understand, monitor, and predict climate variability and change, it is vital to continue systematic satellite measurements along with the development of new technology for more quantitative and accurate observations. The Suomi National Polar-orbiting Partnership mission provides continuity in monitoring the Earths surface and its atmosphere in a similar fashion as the heritage MODIS instruments onboard the National Aeronautics and Space Administrations Terra and Aqua satellites. In this paper, we aim at quantifying the consistency of Aqua MODIS and Suomi-NPP Visible Infrared Imaging Radiometer Suite (VIIRS) Land Surface Reflectance (LSR) and NDVI products as related to their inherent spatial sampling characteristics. To avoid interferences from sources of measurement and/or processing errors other than spatial sampling, including calibration, atmospheric correction, and the effects of the bidirectional reflectance distribution function, the MODIS and VIIRSLSR products were simulated using the Landsat-8s Operational Land Imager (OLI) LSR products. The simulations were performed using the instruments point spread functions on a daily basis for various OLI scenes over a 16-day orbit cycle. It was found that the daily mean differences due to discrepancies in spatial sampling remain below 0.0015 (1) in absolute surface reflectance at subgranule scale (i.e., OLI scene size).We also found that the MODISVIIRS product intercomparisons appear to be minimally impacted when differences in the corresponding view zenith angles (VZAs) are within the range of -15deg to -35deg (VZA(sub v) - VZA(sub m)), where VIIRS and MODIS footprints resemble in size. In general, depending on the spatial heterogeneity of the OLI scene contents, per-grid-cell differences can reach up to 20.Further spatial analysis of the simulated NDVI and LSR products revealed that, depending on the user accuracy requirements for product intercomparisons, spatial aggregations may be used. It was found that if per-grid-cell differences on the order of 10(in LSR or NDVI) are tolerated, the product intercomparisons are expected to be immune from differences in spatial sampling.

VIIRS↗

DOE OSTI2025

Massively parallel and universal approximation of nonlinear functions using diffractive processors

Nonlinear computation is essential for a wide range of information processing tasks, yet implementing nonlinear functions using optical systems remains a challenge due to the weak and power-intensive nature of optical nonlinearities. Overcoming this limitation without relying on nonlinear optical materials could unlock unprecedented opportunities for ultrafast and parallel optical computing systems. Here, we demonstrate that large-scale nonlinear computation can be performed using linear optics through optimized diffractive processors composed of passive phase-only surfaces. In this framework, the input variables of nonlinear functions are encoded into the phase of an optical wavefront—e.g., via a spatial light modulator (SLM)—and transformed by an optimized diffractive structure with spatially varying point-spread functions to yield output intensities that approximate a large set of unique nonlinear functions–all in parallel. We provide proof establishing that this architecture serves as a universal function approximator for an arbitrary set of bandlimited nonlinear functions, also covering wavelength-multiplexed nonlinear functions as well as multi-variate and complex-valued functions that are all-optically cascadable. Our analysis also indicates the successful approximation of typical nonlinear activation functions commonly used in neural networks, including the sigmoid, tanh, ReLU (rectified linear unit), and softplus. We numerically demonstrate the parallel computation of one million distinct nonlinear functions, accurately executed at wavelength-scale spatial density at the output of a diffractive optical processor. Furthermore, we experimentally validated this framework using in situ optical learning and approximated 35 unique nonlinear functions in a single shot using a compact setup consisting of an SLM and an image sensor. These results establish diffractive optical processors as a scalable platform for massively parallel universal nonlinear function approximation, paving the way for new capabilities in analog optical computing based on linear materials.

Rahman, Md Sadman Sakib [University of California,↗