A novel image reconstruction method applied to deep Hubble Space Telescope Images

We have developed a method for the linear reconstruction of an image from undersampled, dithered data, which has been used to create the distributed, combined Hubble Deep Field images -- the deepest optical images yet taken of the universe. The algorithm, known as Variable-Pixel Linear Reconstruction (or informally as "drizzling"), preserves photometry and resolution, can weight input images according to the statistical significance of each pixel, and removes the effects of geometric distortion both on image shape and photometry. In this paper, the algorithm and its implementation are described, and measurements of the photometric accuracy and image fidelity are presented. In addition, we describe the use of drizzling to combine dithered images in the presence of cosmic rays.Comment: Invited paper, to appear in Applications of Digital Image Processing XX, ed. A. Tescher, Proc. S.P.I.E. vol. 3164, in press; 6 pages, 4 included figures, SPIE LaTex style file include

CEG 2350: OS Concepts and Usage

Provides introduction to Linux and Windows operating systems and system administration. Covers files and directories, ownership and sharing, programs and processes, system calls, libraries, dynamic linking, command line shells, scripting, regular expressions and secure network protocols

The WFPC2 Archival Parallels Project

We describe the methods and procedures developed to obtain a near-automatic combination of WFPC2 images obtained as part of the WFPC2 Archival Pure Parallels program. Several techniques have been developed or refined to ensure proper alignment, registration, and combination of overlapping images that can be obtained at different times and with different orientations. We quantify the success rate and the accuracy of the registration of images of different types, and we develop techniques suitable to equalize the sky background without unduly affecting extended emission. About 600 combined images of the 1,500 eventually planned have already been publicly released through the STScI Archive. The images released to date are especially suited to study star formation in the Magellanic Clouds, the stellar population in the halo of nearby galaxies, and the properties of star-forming galaxies at $z \sim 3$.Comment: 12 pages, 7 figures, to appear in the PAS

Patch-based gaussian mixture model for scene motion detection in the presence of atmospheric optical turbulence

In long-range imaging regimes, atmospheric turbulence degrades image quality. In addition to blurring, the turbulence causes geometric distortion effects that introduce apparent motion in acquired video. This is problematic for image processing tasks, including image enhancement and restoration (e.g., superresolution) and aided target recognition (e.g., vehicle trackers). To mitigate these warping effects from turbulence, it is necessary to distinguish between actual in-scene motion and apparent motion caused by atmospheric turbulence. Previously, the current authors generated a synthetic video by injecting moving objects into a static scene and then applying a well-validated anisoplanatic atmospheric optical turbulence simulator. With known per-pixel truth of all moving objects, a per-pixel Gaussian mixture model (GMM) was developed as a baseline technique. In this paper, the baseline technique has been modified to improve performance while decreasing computational complexity. Additionally, the technique is extended to patches such that spatial correlations are captured, which results in further performance improvement

The volcanic stratigraphy of the Mickey Hot Springs area, Harney County, Oregon

Steens Mountain is a major horst block near the northern terminus of the Basin and Range geomorphic province of southeastern Oregon. A section of Miocene volcanic rocks totaling 5000 feet in thickness are exposed in a fault escarpment on the eastern side of Steens Nountain. These include: the Pike Creek Formation, consisting of rhyolite and dacite flows and tuffs about 1000 feet in thickness, including one rhyolite ignimbrite locally 900 feet thick; the Andesite Series (also known as Steens Mountain Volcanics), a sequence of andesite and basaltic andesite flows totaling about 1500 feet in thickness; Steens Basalt, a series of 15 million year old high-alumina olivine basalt flows totaling about 3000 feet in thickness, which crop out extensively in southeastern Oregon. Steens Basalt also crops out in the Mickey Hot Springs area, 16 miles east of Steens Mountain, where it is overlain by a thin, continuous ignimbrite and a younger basalt, here informally named Mickey basalt. The basalts of Steens Mountain were compared to those o the Mickey Rot Springs area. Correlation is established on the basis of a paleomagnetic reversal observed in the two areas, and supported by petrologic observations and chemical analysis. A large circular fault basin north of Mickey Hot Springs is suggestive of a collapsed caldera structure. The great thickness of a rhyolite ignimbrite in the Pike Creek formation may have been deposited in a rhyolite-flood eruption associated with a caldera collapse, creating a structure such as the one north of Mickey Hot Springs

Briquetting of waste glass cullet fine particles for energy-saving glass manufacture

Fine particles of glass cullet (fines) arising during glass recycling cannot presently be recycled into glass manufacture due to the potential for bubble formation and foaming. Consolidation of glass fines into briquettes could enable their re-introduction into furnaces, reducing waste and glass melting energies. Properties of briquetted cullet fines and briquette melting behaviour in soda-lime-silica glass batches are presented. Morphology and density of glass fines and briquettes; and briquette mass and mechanical properties as functions of time after formation were analyzed. Compressive strength increases linearly with time after briquette formation. With slight batch modifications to maintain the same final glass composition, up to 15 wt % briquettes were successfully added to a representative container glass batch and melted. Results confirm that briquette batch additions can provide equivalent final glass composition, optical absorption characteristics and redox to briquette-free batches, supporting their industrial uptake

Application of tilt correlation statistics to anisoplanatic optical turbulence modeling and mitigation

Atmospheric optical turbulence can be a significant source of image degradation, particularly in long range imaging applications. Many turbulence mitigation algorithms rely on an optical transfer function (OTF) model that includes the Fried parameter. We present anisoplanatic tilt statistics for spherical wave propagation. We transform these into 2D autocorrelation functions that can inform turbulence modeling and mitigation algorithms. Using these, we construct an OTF model that accounts for image registration. We also propose a spectral ratio Fried parameter estimation algorithm that is robust to camera motion and requires no specialized scene content or sources. We employ the Fried parameter estimation and OTF model for turbulence mitigation. A numerical wave-propagation turbulence simulator is used to generate data to quantitatively validate the proposed methods. Results with real camera data are also presented

Discovery of a possibly old galaxy at z=6.027z=6.027, multiply imaged by the massive cluster Abell 383

We report the discovery of a unique $z=6.027$ galaxy, multiply imaged by the cluster Abell 383 and detected in new Hubble Space Telescope ACS and WFC3 imaging, as well as in Warm Spitzer observations. This galaxy was selected as a pair of i-dropouts; its suspected high redshift was confirmed by the measurement of a strong Lyman-alpha line in both images using Keck/DEIMOS. Combining Hubble and Spitzer photometry after correcting for contamination by line emission (estimated to be a small effect), we identify a strong Balmer break of 1.5 magnitudes. Taking into account the magnification factor of 11.4+/-1.9 (2.65+/-0.17 mag) for the brightest image, the unlensed AB magnitude for the source is 27.2+/-0.05 in the H band, corresponding to a 0.4 L* galaxy, and 25.7+/-0.08 at 3.6 um. The UV slope is consistent with beta~2.0, and from the rest-frame UV continuum we measure a current star formation rate of 2.4+/-1.1 Msol/yr. The unlensed half-light radius is measured to be 300 pc, from which we deduce a star-forming surface density of ~10 Msol/yr/kpc2. The Lyman-alpha emission is found to be extended over ~3" along the slit, corresponding to ~5 kpc in the source plane. This can be explained by the presence of a much larger envelope of neutral hydrogen around the star-forming region. Finally, fitting the spectral energy distribution using 7 photometric data points with simple SED models, we derive the following properties: very little reddening, an inferred stellar mass of M*=6e9 Msol, and an inferred age of ~800 Myrs (corresponding to a redshift of formation of ~18). The star-formation rate of this object was likely much stronger in the past than at the time of observation, suggesting that we may be missing a fraction of galaxies at z~6 which have already faded in rest-frame UV wavelengths.Comment: 6 pages, 3 figures, MNRAS in press, replaced with accepted version including minor comment