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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Design and performance of 4 x 5120-element visible and 2 x 2560-element shortwave infrared multispectral focal planes

Two solid-state sensors for use in remote sensing instruments operating in the pushbroom mode are examined. The design and characteristics of the visible/near-infrared (VIS/NIR) device and the short-wavelength infrared (SWIR) device are described. The VIS/NIR is a CCD imager with four parallel sensor lines, each 1024 pixel long; the chip design and filter system of the VIS/NIR are studied. The performance of the VIS/NIR sensor with mask and its system performance are measured. The SWIR is a dual-band line imager consisting of palladium silicide Schottky-barrier detectors coupled to CCD multiplexers; the performance of the device is analyzed. The substrate materials and layout designs used to assemble the 4 x 5120-element VIS/NIR array and the 2 x 2560-element SWIR array are discussed, and the planarity of the butted arrays are verified using a profilometer. The optical and electrical characteristics, and the placement and butting accuracy of the arrays are evaluated. It is noted that the arrays met or exceed their expected performance.

Tower, J. R.↗
NASA NTRS1991

Three-Dimensional Acousto-Optical Spectrum Analyzer

Experimental acousto-optical Bragg-cell spectrum analyzer achieves subhertz frequency resolution. System represents extension to three dimensions of two-dimensional spectrum-analyzer concept described in, "Two-Dimensional Acousto-Optical Spectrum Analyzer" (NPO-18092). First and second dimensions two spatial dimensions of charge-coupled-device (CCD) imaging array. Third dimension time, as sampled at frame rate of CCD array.

Ansari, Homayoon↗
NASA NTRS1982

Progress in 800 x 800 charge-coupled device /CCD/ imager development and applications

Performance parameters of the 800 x 800 three phase and virtual phase CCD imaging sensors for the planned Project Galileo and Space Telescope Wide Field/Planetary Camera are compared, and the significance of some of the parameters for device radiation performance is discussed. The problems encountered by the three phase device that resulted in its being considered not suitable for the Galileo mission are described, and the radiation hardening performed on the virtual phase device to permit it to cope with Jupiter's radiation belts is addressed. Major research tasks in the effort to advance the technology of large area virtual phase imagers are stated.

Norris, D. D.↗
NASA NTRS1990

Narrow band images of suspected cooling flow galaxies

Narrow-band (H alpha and (NII)) charge coupled device (CCD) images of elliptical galaxies suspected of having cooling flows are discussed. Researchers find evidence of optical emission from cool gas which is most likely associated with a cooling flow. At least 4 galaxies (NGC 3998, NGC 4203, NGC 4550 and NGC 4697) show emission of (NII) and/or H alpha within the central 20 seconds, a fraction consistent with results from Phillips et al. (1987) and Caldwell (1984). In these four, (NII) lambda 6584A emission is stronger than H alpha (which is often in absorption e.g., as seen in long slit spectra of NGC4697). From long slit spectra of these galaxies, Deustua and Teske (1989) infer electron densities, N sub e, of order 1.2x10 to the 3rd power cm(-3) assuming T = 10 to the 4th power K for the optically emitting gas. NGC 2685, NGC 3489 appear to have emission in (NII); NGC 4636 may also, but, is difficult to see in the data (Demoulin-Ulrich, Butcher and Boksenberg (1984) did not see emission from this galaxy). NGC 4472, NGC 4473, NGC 4365, NGC 4638 and NGC 4649 show no emission.

Deustua, Susana↗
NASA NTRS1993

Optical imaging and long-slit spectroscopy of Markarian galaxies with multiple nuclei. I - Basic data

Optical CCD images and long-slit spectroscopic data are presented for over 100 Markarian (UV-excess) galaxies reported in early studies to possess multiple optical nuclei or extreme morphological peculiarities suggestive of galaxy collisions and mergers. Stacked broad-band images are presented with histogram equalization in order to show simultaneously the nuclei and features at very low surface-brightness levels. Morphological properties, luminosities and colors of the integral systems are given. Photometric and image properties of over 200 individual nuclei and giant H II regions have been measured with respect to the local backgrounds in the galaxies using an objective image finding algorithm. Labeled contour plots identify the measured subcomponents. Two-dimensional spectral data are presented, in addition to intensity profiles along the slit in the light of H-alpha + forbidden N II emission lines and adjacent continuum. Nuclear emission-line measurements, reddening estimates, monochromatic continuum magnitudes, and colors are given.

Mazzarella, Joseph M.↗
NASA NTRS1983

Acousto-optic/CCD real-time SAR data processor

The SAR processor which uses an acousto-optic device as the input electronic-to-optical transducer and a 2-D CCD image sensor, which is operated in the time-delay-and-integrate (TDI) mode is presented. The CCD serves as the optical detector, and it simultaneously operates as an array of optically addressed correlators. The lines of the focused SAR image form continuously (at the radar PRF) at the final row of the CCD. The principles of operation of this processor, its performance characteristics, the state-of-the-art of the devices used and experimental results are outlined. The methods by which this processor can be made flexible so that it can be dynamically adapted to changing SAR geometries is discussed.

Psaltis, D.↗
NASA NTRS1990

Optical and near-IR imaging observations of comet Austin 1989c1

Near-nucleus imaging observations of comet Austin (1989c1) were carried out by the Japanese CCD imaging team. Six telescopes were used to monitor the time variation of the near-nucleus images in C2, CN, H2O, and Na continuum in the optical region, and in J, H, and K bands in the near-IR region. A featureless, round shape of the comet was revealed in all images. Although some of the jet features are recognized by using an image enhancement technique, the azimuthal difference of the intensity distribution is about 10 percent. The images in the H2O band show complex ion structures near the nucleus.

Watanabe, J.↗
NASA NTRS1979

Charge-coupled device /CCD/ trackers for high accuracy guidance applications

Recent advances in large area charge coupled device (CCD) imaging detectors and high speed microprocessors have prompted the development of a new class of electro-optical tracking instruments at the Jet Propulsion Laboratory (JPL). These instruments are designed for standardized NASA-wide usage and are characterized by their extremely high pointing accuracy and stability and performance capabilities which are largely software defined and thus easily adapted to a variety of mission requirements. This paper presents an examination of the methods by which CCD detectors are being incorporated in star tracker instruments and the performance capabilities that can be expected from currently available devices. The multi-function sensor concept, in which a single sensor can function in a variety of guidance applications, is described. Software algorithms designed to provide efficient extraction of guidance information from both point and extended images are also presented. CCD star tracker implementations currently underway at JPL are described, and performance data obtained during laboratory testing is presented and discussed.

Salomon, P. M.↗
NASA NTRS1993

Imaging of the Wolf-Rayet galaxy He 2-10

We present B, V, and emission-line CCD images of the Wolf-Rayet galaxy He 2-10. The broad band images reveal the galaxy to consist of two starburst regions at the center of an elliptical stellar envelope about 10 times their size, with a major axis diameter of approximately 3.8 kpc. Previous imaging detected only the starburst regions, leading to the erroneous description of the object as an interacting pair. Morphologically, He 2-10 resembles the majority of blue compact dwarf galaxies (BCDGs), some of which also show Wolf-Rayet features in their spectra. The lack of nearby neighbors to He 2-10 suggests that its star formation is proceeding stochastically, rather than as the result of interaction, and its morphological similarity to other BCDGs suggests that all such galaxies may pass through a Wolf-Rayet phase. The similarity of the outer regions of He 2-10 and other BCDGs to normal dwarf ellipticals also supports models in which the former evolve into the latter.

Corbin, Michael R.↗
NASA NTRS1992

Fabry-Perot images of NGC 1275 and its puzzling high-velocity system

The Fabry-Perot imager is used to obtain a velocity sequence of calibrated narrow-band CCD images to cover 3000 km/s velocity space between the redshifted H-alpha emission lines of NGC 1275, its extended associated system of low-velocity (LV) filaments, and the high-velocity (HV) system of knots, projected on the same line of sight in the sky. The lack of intermediate-velocity emission-line gas between the two systems leads to an upper limit of 1.5 x 10 exp -16 ergs/sq cm s sq arcsec (3 sigma) on stripped ionized gas due to the dynamical interaction between NGC 1275 and its HV companion galaxy. It also confirms previous reports that the level of continuum light arising from stellar and nonstellar sources must be very low in otherwise bright, strongly concentrated emission-line knots with unresolved diameters of 425/h pc. The H-alpha luminosities of the emission-line regions of the two systems were measured and star formation rates derived in order to investigate quantitatively the physical relation between the HV galaxy, NGC 1275, and the surrounding cooling flow filaments.

Caulet, Adeline↗
NASA NTRS2000

An Ultraviolet/Optical Atlas of Bright Galaxies

We present wide-field, imagery and photometry of 43 selected nearby galaxies of all morphology types at ultraviolet and optical wavelengths. The ultraviolet images, in two broad bands at 1500 Angstroms and 2500 Angstroms, were obtained by the Ultraviolet Imaging Telescope (UIT) during the Astro-1 Spacelab mission. The UV images have approx. 3" resolution, and the comparison sets of ground-based, CCD images (in one or more of B, V, R, and H alpha ) have pixel scales and fields of view closely matching the UV frames. The atlas consists of multiband images together with plots of UV/optical radial surface brightnesses, colors and other associated photometric parameters such as half-light radii. In an appendix, we discuss the sensitivity of different wavebands to a galaxy's star formation history in the form of "history weighting functions" and the importance of UV observations as probes of evolution during the past 10-1000 Myr. We find that UV galaxy morphologies are usually significantly different from visible band morphologies as a consequence of spatially inhomogeneous stellar populations. Differences are quite pronounced for systems in the middle range of Hubble types, Sa through Sc, but less so for ellipticals or late-type disks. Normal ellipticals and large spiral bulges are fainter and more compact in the UV. They typically exhibit smooth and unresolved far-UV profiles with, however, far-UV/optical color gradients which are larger than any at optical/IR wavelengths. The far-UV light in these cases is probably produced by extreme horizontal branch stars and their descendants in the dominant, low-mass, metal-rich population.

Stecher, Theodore↗
NASA NTRS2010

Optimal Compression of Floating-Point Astronomical Images Without Significant Loss of Information

We describe a compression method for floating-point astronomical images that gives compression ratios of 6 - 10 while still preserving the scientifically important information in the image. The pixel values are first preprocessed by quantizing them into scaled integer intensity levels, which removes some of the uncompressible noise in the image. The integers are then losslessly compressed using the fast and efficient Rice algorithm and stored in a portable FITS format file. Quantizing an image more coarsely gives greater image compression, but it also increases the noise and degrades the precision of the photometric and astrometric measurements in the quantized image. Dithering the pixel values during the quantization process greatly improves the precision of measurements in the more coarsely quantized images. We perform a series of experiments on both synthetic and real astronomical CCD images to quantitatively demonstrate that the magnitudes and positions of stars in the quantized images can be measured with the predicted amount of precision. In order to encourage wider use of these image compression methods, we have made available a pair of general-purpose image compression programs, called fpack and funpack, which can be used to compress any FITS format image.

Pence, William D.↗
NASA NTRS2022

X-Ray Imaging Observations of the High-Mass γ-Ray Binary HESS J0632+057

The Chandra X-ray Observatory (CXO)imaged the high-massγ-ray binary (HMGB) HESS8J0632+057 with the Advanced CCD Imaging Spectrometer (ACIS). We analyzed the CXO data to-9gether with 967 ks of archival imaging Swift-XRT observations. On arcsecond scales we find a hint10of asymmetric extended emission. On arcminute scales, there is a region of extended emission (“the11blob”) which is located≈5.5′east of the binary. The blob is seen in both the CXO-ACIS and the12Swift-XRT images but it does not have a counterpart in the radio, NIR, IR, or optical images. The13ACIS spectrum of the blob fits either an absorbed power-law model with Γ'2.6, or a thermal plasma14model withkT'3 keV. Since the blob’s NH is significantly larger than that of the binary we conclude15that the blob and binary are not directly related. The somewhat larger very deep XRT image suggests16that the binary may be located within a shell (or cavity). The four ACIS spectra taken within the∼2017day interval near the light curve minimum suggests that the NH is varying on timescales of days, pos-18sibly due to the inhomogenous circumbinary environment. The XRT spectra extracted from the wider19orbital phase intervals support significant changes in NH near the light curve maximum/minimum,20which may be responsible for the substantial systematic residuals seen near 1 keV, and provide tenta-21tive evidence for a Fe line at 6.4 keV. We find no significant periodic signal in the ACIS data up to 0.156 Hz.

O Kargaltsev↗
NASA NTRS1987

Optical tracking using charge-coupled devices

The extraction of precise positional information from CCD images of point-source and extended optical targets is considered, and three examples of CCD optical trackers for space-based operation are described. For ideal point sources, a centerfinding accuracy of 1/100 pixel and a measuremet jitter of less than 1/250 pixel have been obtained using thinned, backside-illuminated devices. Tracker accuracy is shown to be limited by small variation in the optical image shape. Techniques for tracking, and methods for searching the entire field for the desired targets, are also discussed.

Stanton, Richard H.↗
DOE OSTI2022

SNIa Cosmology Analysis Results from Simulated LSST Images: From Difference Imaging to Constraints on Dark Energy

Abstract The Vera Rubin Observatory Legacy Survey of Space and Time (LSST) is expected to process ∼10 6 transient detections per night. For precision measurements of cosmological parameters and rates, it is critical to understand the detection efficiency, magnitude limits, artifact contamination levels, and biases in the selection and photometry. Here we rigorously test the LSST Difference Image Analysis (DIA) pipeline using simulated images from the Rubin Observatory LSST Dark Energy Science Collaboration Data Challenge (DC2) simulation for the Wide-Fast-Deep survey area. DC2 is the first large-scale (300 deg 2 ) image simulation of a transient survey that includes realistic cadence, variable observing conditions, and CCD image artifacts. We analyze ∼15 deg 2 of DC2 over a 5 yr time span in which artificial point sources from Type Ia supernova (SNIa) light curves have been overlaid onto the images. The magnitude limits per filter are u = 23.66 mag, g = 24.69 mag, r = 24.06 mag, i = 23.45 mag, z = 22.54 mag, and y = 21.62 mag. The artifact contamination levels are ∼90% of all detections, corresponding to ∼1000 artifacts deg –2 in g band, and falling to 300 deg –2 in y band. The photometry has biases <1% for magnitudes 19.5 < m < 23. Our DIA performance on simulated images is similar to that of the Dark Energy Survey difference-imaging pipeline on real images. We also characterize DC2 image properties to produce catalog-level simulations needed for distance bias corrections. We find good agreement between DC2 data and simulations for distributions of signal-to-noise ratio, redshift, and fitted light-curve properties. Applying a realistic SNIa cosmology analysis for redshifts z < 1, we recover the input cosmology parameters to within statistical uncertainties.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1985

Photon-counting image sensors for the ultraviolet

An investigation on specific performance details of photon counting, ultraviolet image sensors having 2-dimensional formats is reviewed. In one study, controlled experiments were performed which compare the quantum efficiencies, in pulse counting mode, of CsI photocathodes deposited on: (1) the front surface of a microchannel plate (MCP), (2) a solid surface in front of an MCP, and (3) an intensified CCD image sensor (ICCD) where a CCD is directly bombarded by accelerated photoelectrons. Tests indicated that the detection efficiency of the CsI-coated MCP at 1026 A is lower by a factor of 2.5 than that of the MCP with a separate, opaque CsI photocathode, and the detection efficiency ratio increases substantially at longer wavelengths (ratio is 5 at 1216 A and 20 at 1608 A).

Jenkins, E. B.↗
NASA NTRS2000

Discovery of Spatial and Spectral Structure in the X-Ray Emission from the Crab Nebula

The Chandra X-ray Observatory observed the Crab Nebula and Pulsar During orbital calibration. Zeroth-order images with the High-Energy Transmission Grating (HETG) read-out by the Advanced CCD Imaging Spectrometer spectroscopy array (ACIS-S) show a striking richness of X-ray structure, at a resolution comparable to that of the best ground-based visible-light observations. The HETG-ACIS-S images reveal, for the first time, an X-ray knots along the inner ring and (perhaps) along the inward extension of the X-ray jet. Although complicated by instrumental effects and the brightness of the Crab Nebula, the spectrometric analysis shows systematic variations of the X-ray spectrum throughout the Nebula.

Weisskopf, M.↗