Showing papers by "Edward L. Wright published in 2004"
TL;DR: The Infrared Array Camera (IRAC) is one of three focal plane instruments on the Spitzer Space Telescope as mentioned in this paper, which is a four-channel camera that obtains simultaneous broadband images at 3.6, 4.5, 5.8, and 8.0 m.
Abstract: The Infrared Array Camera (IRAC) is one of three focal plane instruments on the Spitzer Space Telescope. IRAC is a four-channel camera that obtains simultaneous broadband images at 3.6, 4.5, 5.8, and 8.0 � m. Two nearly adjacent 5A2 ; 5A2 fields of view in the focal plane are viewed by the four channels in pairs (3.6 and 5.8 � m; 4.5 and 8 � m). All four detector arrays in the camera are 256 ; 256 pixels in size, with the two shorter wavelength channels using InSb and the two longer wavelength channels using Si:As IBC detectors. IRAC is a powerful survey instrument because of its high sensitivity, large field of view, and four-color imaging. This paper summarizes the in-flight scientific, technical, and operational performance of IRAC.
3,567 citations
TL;DR: The Spitzer Space Telescope, NASA's great Observatory for infrared astronomy, was launched 2003 August 25 and is returning excellent scientific data from its Earth-trailing solar orbit as mentioned in this paper.
Abstract: The Spitzer Space Telescope, NASA's Great Observatory for infrared astronomy, was launched 2003 August 25 and is returning excellent scientific data from its Earth-trailing solar orbit. Spitzer combines the intrinsic sensitivity achievable with a cryogenic telescope in space with the great imaging and spectroscopic power of modern detector arrays to provide the user community with huge gains in capability for exploration of the cosmos in the infrared. The observatory systems are largely performing as expected, and the projected cryogenic lifetime is in excess of 5 years. This paper summarizes the on-orbit scientific, technical, and operational performance of Spitzer. Subsequent papers in this special issue describe the Spitzer instruments in detail and highlight many of the exciting scientific results obtained during the first 6 months of the Spitzer mission.
3,177 citations
TL;DR: In this paper, galaxy counts at 3.6 and 4.5μm were shown to follow the expectations of a Euclidean world model down to ~16.5 mag.
Abstract: Infrared source counts at wavelengths 3 μm < λ < 10 μm cover more than 10 mag in source brightness, reach 4 orders of magnitude in surface density, and reach an integrated surface density of 105 sources deg-2. At m < 14 mag, most of the sources are Galactic stars, in agreement with models. After removal of Galactic stars, galaxy counts are consistent with what few measurements exist at nearby wavelengths. At 3.6 and 4.5 μm, the galaxy counts follow the expectations of a Euclidean world model down to ~16 mag and drop below the Euclidean curve for fainter magnitudes. Counts at these wavelengths begin to show decreasing completeness around 19.5 mag. At 5.8 and 8 μm, the counts relative to a Euclidean world model show a large excess at bright magnitudes. This is probably because local galaxies emit strongly in the aromatic dust (polycyclic aromatic hydrocarbon) features. The counts at 3.6 μm resolve less than 50% of the cosmic infrared background at that wavelength.
279 citations
TL;DR: In this article, galaxy counts at wavelengths 3 < lambda < 10 um cover more than 10 magnitudes in source brightness, four orders of magnitude in surface density, and reach an integrated surface density of 10^5 sources/deg^2.
Abstract: Infrared source counts at wavelengths 3 < lambda < 10 um cover more than 10 magnitudes in source brightness, four orders of magnitude in surface density, and reach an integrated surface density of 10^5 sources/deg^2. At m<14 mag, most of the sources are Galactic stars, in agreement with models. After removal of Galactic stars, galaxy counts are consistent with what few measurements exist at nearby wavelengths. At 3.6 and 4.5 um, the galaxy counts follow the expectations of a Euclidean world model down to ~16 mag and drop below the Euclidean curve for fainter magnitudes. Counts at these wavelengths begin to show decreasing completeness around magnitude 19.5. At 5.8 and 8 um, the counts relative to a Euclidean world model show a large excess at bright magnitudes. This is probably because local galaxies emit strongly in the aromatic dust (``PAH'') features. The counts at 3.6 um resolve <50% of the Cosmic Infrared Background at that wavelength.
271 citations
TL;DR: In this article, an overview of the survey design, reduction, calibration, star-galaxy separation, and initial results is provided, as well as initial results of the NOAO Deep Wide-Field Survey in Bootes with three or more 30 s exposures per position.
Abstract: The Infrared Array Camera (IRAC) shallow survey covers 8.5 deg2 in the NOAO Deep Wide-Field Survey in Bootes with three or more 30 s exposures per position. An overview of the survey design, reduction, calibration, star-galaxy separation, and initial results is provided. The survey includes ≈370,000, 280,000, 38,000, and 34,000 sources brighter than the 5 σ limits of 6.4, 8.8, 51, and 50 μJy at 3.6, 4.5, 5.8, and 8 μm, respectively, including some with unusual spectral energy distributions.
244 citations
TL;DR: In this paper, the first-year Wilkinson Microwave Anisotropy Probe (WMAP) data, in combination with any one of a number of other cosmic probes, show that we live in a flat Λ-dominated cold dark matter (CDM) universe with Ωm ≈ 0.28, h = 0.33, and no dark energy component (ΩΛ = 0) would produce an anticorrelation between the matter distribution and the CMB.
Abstract: The first-year Wilkinson Microwave Anisotropy Probe (WMAP) data, in combination with any one of a number of other cosmic probes, show that we live in a flat Λ-dominated cold dark matter (CDM) universe with Ωm ≈ 0.27 and ΩΛ ≈ 0.73. In this model the late-time action of the dark energy, through the integrated Sachs-Wolfe effect, should produce cosmic microwave background (CMB) anisotropies correlated with matter density fluctuations at z 2 (Crittenden & Turok 1996). The measurement of such a signal is an important independent check of the model. We cross-correlate the NRAO VLA Sky Survey (NVSS) radio source catalog (Condon et al. 1998) with the WMAP data in search of this signal, and see indications of the expected correlation. Assuming a flat ΛCDM cosmology, we find ΩΛ > 0 (95% CL, statistical errors only) with the peak of the likelihood at ΩΛ = 0.68, consistent with the preferred WMAP value. A closed model with Ωm = 1.28, h = 0.33, and no dark energy component (ΩΛ = 0), marginally consistent with the WMAP CMB TT angular power spectrum, would produce an anticorrelation between the matter distribution and the CMB. Our analysis of the cross-correlation of the WMAP data with the NVSS catalog rejects this cosmology at the 3 σ level.
205 citations
TL;DR: The Spitzer Space Telescope, NASA's great Observatory for infrared astronomy, was launched 2003 August 25 and is returning excellent scientific data from its Earth-trailing solar orbit as discussed by the authors.
Abstract: The Spitzer Space Telescope, NASA's Great Observatory for infrared astronomy, was launched 2003 August 25 and is returning excellent scientific data from its Earth-trailing solar orbit. Spitzer combines the intrinsic sensitivity achievable with a cryogenic telescope in space with the great imaging and spectroscopic power of modern detector arrays to provide the user community with huge gains in capability for exploration of the cosmos in the infrared. The observatory systems are largely performing as expected and the projected cryogenic lifetime is in excess of 5 years. This paper summarizes the on-orbit scientific, technical and operational performance of Spitzer. Subsequent papers in this special issue describe the Spitzer instruments in detail and highlight many of the exciting scientific results obtained during the first six months of the Spitzer mission.
174 citations
TL;DR: In this paper, the authors summarize the in-flight scientific, technical, and operational performance of IRAC in two nearly adjacent fields of view on the Spitzer Space Telescope (SST) and show that IRAC is a four-channel camera that obtains simultaneous broad-band images at 3.6, 4.5, 5.8, and 8.0 μm.
Abstract: The Infrared Array Camera (IRAC) is one of three focal plane instruments on board the Spitzer Space Telescope. IRAC is a four-channel camera that obtains simultaneous broad-band images at 3.6, 4.5, 5.8, and 8.0 μm in two nearly adjacent fields of view. We summarize here the in-flight scientific, technical, and operational performance of IRAC.
148 citations
TL;DR: The diffuse infrared background experiment (DIRBE) on the COsmic Background Explorer (COBE) measured the total infrared signal seen from space at a distance of 1 AU from the Sun as discussed by the authors.
44 citations
TL;DR: The Wide-Field Infrared Survey Explorer (WISE) is a NASA MIDEX mission that will survey the entire sky in four bands from 3.5 to 23 microns with a sensitivity 1000 times greater than the IRAS survey.
Abstract: The Wide-field Infrared Survey Explorer (WISE), a NASA MIDEX mission, will survey the entire sky in four bands from 3.5 to 23 microns with a sensitivity 1000 times greater than the IRAS survey. The WISE survey will extend the Two Micron All Sky Survey into the thermal infrared and will provide the essential catalog for the James Webb Space Telescope. Using 10242 HgCdTe and Si:As arrays at 3.5, 4.6, 12 and 23 microns, WISE will find the most luminous galaxies in the universe, the closest stars to the Sun, and it will detect most of the main belt asteroids larger than 3 km. The single WISE instrument consists of a 40 cm diamond-turned aluminum three mirror anastigmatic telescope, a two-stage solid hydrogen cryostat, a scan mirror mechanism, and reimaging optics giving 5" resolution (full-width-half-maximum). The use of dichroics and beamsplitters allows four color images of a 47'x47' field of view to be taken every 8.8 seconds, synchronized with the orbital motion to provide total sky coverage with overlap between revolutions. WISE will be placed into a Sun-synchronous polar orbit on a Taurus 2210 launch vehicle. The WISE survey approach is simple and efficient. The three-axis-stabilized spacecraft rotates at a constant rate while the scan mirror freezes the telescope line of sight during each exposure. WISE has been selected by NASA to execute an extended Phase A study which will be completed in August, 2004. WISE is scheduled to launch in mid 2008.
Goddard Space Flight Center1, Pennsylvania State University2, Space Telescope Science Institute3, California Institute of Technology4, Harvard University5, University of Texas at Austin6, United States Naval Research Laboratory7, Cornell University8, Princeton University9, Max Planck Society10, University of Maryland, College Park11, Japan Aerospace Exploration Agency12, Johns Hopkins University13, Jet Propulsion Laboratory14, National Research Council15, George Mason University16, University of California, Los Angeles17
TL;DR: The Space Infrared Interferometric Telescope (SPIRIT) and the Submillimeter Probe of the Evolution of Cosmic Structure (SPECS) were proposed in 2000 as discussed by the authors.
Abstract: Ultimately, after the Single Aperture Far-IR (SAFIR) telescope, astrophysicists will need a far-IR observatory that provides angular resolution comparable to that of the Hubble Space Telescope. At such resolution galaxies at high redshift, protostars, and nascent planetary systems will be resolved, and theoretical models for galaxy, star, and planet formation and evolution can be subjected to important observational tests. This paper updates information provided in a 2000 SPIE paper on the scientific motivation and design concepts for interferometric missions SPIRIT (the Space Infrared Interferometric Telescope) and SPECS (the Submillimeter Probe of the Evolution of Cosmic Structure). SPECS is a kilometer baseline far-IR/submillimeter imaging and spectral interferometer that depends on formation flying, and SPIRIT is a highly-capable pathfinder interferometer on a boom with a maximum baseline in the 30 - 50 m range. We describe recent community planning activities, remind readers of the scientific rationale for space-based far-infrared imaging interferometry, present updated design concepts for the SPIRIT and SPECS missions, and describe the main issues currently under study. The engineering and technology requirements for SPIRIT and SPECS, additional design details, recent technology developments, and technology roadmaps are given in a companion paper in the Proceedings of the conference on New Frontiers in Stellar Interferometry.
01 Jan 2004
TL;DR: The theoretical basis for the prediction of anisotropies in the cosmic microwave background is very well developed as discussed by the authors, and all of the primary anisotropy can be handled by linear perturbation theory, which allows a very accurate calculation of predicted anisotropic from different models of the Universe.
Abstract: The theoretical basis for the prediction of anisotropies in the cosmic microwave background is very well developed. Very low amplitude density and temperature perturbations produce small gravitational effects, leading to an anisotropy that is a combination of temperature fluctuations at the surface of last scattering and gravitational redshifts both at last scattering and along the path to the observer. All of the primary anisotropy can be handled by linear perturbation theory, which allows a very accurate calculation of the predicted anisotropy from different models of the Universe. 1.
Goddard Space Flight Center1, Space Telescope Science Institute2, Harvard University3, University of Texas at Austin4, Max Planck Society5, University of Maryland, College Park6, Japan Aerospace Exploration Agency7, Jet Propulsion Laboratory8, George Mason University9, University of California, Los Angeles10
TL;DR: The Submillimeter Probe of the Evolution of Cosmic Structure (SPECS) is a space-based imaging and spectral interferometer with kilometer maximum baseline lengths for imaging as mentioned in this paper.
Abstract: The Submillimeter Probe of the Evolution of Cosmic Structure (SPECS) is a space-based imaging and spectral ("double Fourier") interferometer with kilometer maximum baseline lengths for imaging. This NASA "vision mission" will provide spatial resolution in the far-IR and submillimeter spectral range comparable to that of the Hubble Space Telescope, enabling astrophysicists to extend the legacy of current and planned far-IR observatories. The astrophysical information uniquely available with SPECS and its pathfinder mission SPIRIT will be briefly described, but that is more the focus of a companion paper in the Proceedings of the Optical, Infrared, and Millimeter Space Telescopes conference. Here we present an updated design concept for SPECS and for the pathfinder interferometer SPIRIT (Space Infrared Interferometric Telescope) and focus on the engineering and technology requirements for far-IR double Fourier interferometry. We compare the SPECS optical system requirements with those of existing ground-based and other planned space-based interferometers, such as SIM and TPF-I/Darwin.
01 Sep 2004
TL;DR: The conclusion was that there are many exciting observing programmes waiting to be done with FLAMES and that the user community is waiting with anticipation for the data avalanche.
Abstract: some checking of the validity of the users’ co-ordinates was recommended and could save wasted observations. There was discussion about selection of filters for VST when it replaces WFI. Although Sloan bands are broader than Johnson ones they are not much used in globular cluster photometry. A few users asked if Stromgren filters could be provided for VST but generally the Johnson set was preferred. If Sloan filters are used, then good standards must be provided to allow transformation to the standard system. At the end of the two days of the Workshop, the conclusion was that there are many exciting observing programmes waiting to be done with FLAMES and that the user community is waiting with anticipation for the data avalanche. The Workshop was informal in the sense that no published proceedings are foreseen. However, many speakers contributed printed versions of their presentations and a bound copy is available on request from jwalsh@eso.org.
27 Apr 2004
TL;DR: In this article, a beamforming system for high-average-power broadband S-band multiple-beam amplifiers, developed at the Naval Research Laboratory (NRL), is described. But the design of beamforming is not discussed.
Abstract: Summary form only given. In multiple-beam amplifiers, beamlets are transported in individual beam tunnels but interact with RF fields in a common interaction region. This approach enables the designer to have the best of both worlds: individual beamlets can have low perveance which is conducive to efficient bunching and beam transport, leading to higher gain, electronic efficiencies, and average power, while the aggregate beam current can be high, facilitating high beam and RF power, and also broad bandwidth. A fundamental mode multiple-beam amplifier is described in this paper and we report on the design of a beam forming system for high-average-power broadband S-band multiple-beam amplifiers, developed at the Naval Research Laboratory (NRL). These amplifiers utilize eight individual electron beams and operates in the fundamental TM/sub 01/ mode.
01 Jan 2004
TL;DR: The past year has seen very dramatic progress in the observational study of the CMB anisotropy as discussed by the authors, including the first detection of polarization anisotropic of CMB by DASIPOL, extensive sky coverage from the ARCHEOPS balloon experiment and very high angular resolution data from CBI and ACBAR.
Abstract: The past year has seen very dramatic progress in the observational study of the CMB anisotropy. New results include the first detection of polarization anisotropy of the CMB by DASIPOL; extensive sky coverage from the ARCHEOPS balloon experiment; and very high angular resolution data from CBI and ACBAR. But the most significant new data are the first year results from the WMAP satellite, which cover 100% of the sky in 5 bands from 23 to 94 GHz with angular resolutions up to 13′.
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TL;DR: In the near infrared 1-2.2 micron range the space infrared sky is a thousand times fainter than the OH nightglow from the Earth's atmosphere as mentioned in this paper, but the foreground from interplanetary dust is very bright.
Abstract: The infrared sky from space is the sum of a cosmic signal from galaxies, quasars, and perhaps more exotic sources; and foregrounds from the Milky Way and from the Solar System. At a distance of 1 AU from the Sun, the foreground from interplanetary dust is very bright between 5 and 100 microns, but ``very bright'' is still several million times fainter than the background produced by ground-based telescopes. In the near infrared 1-2.2 micron range the space infrared sky is a thousand times fainter than the OH nightglow from the Earth's atmosphere. As a result of these advantages, wide-field imaging from space in the infrared can be an incredibly sensitive method to study the Universe.
01 Jul 2004
TL;DR: A beamforming system for high-average-power broadband S-band multiple-beam amplifiers was developed at the Naval Research Laboratory (NRL) in this paper, where eight individual electron beams and operates in the fundamental TM/sub 01/ mode.
Abstract: Summary form only given. In multiple-beam amplifiers, beamlets are transported in individual beam tunnels but interact with RF fields in a common interaction region. This approach enables the designer to have the best of both worlds: individual beamlets can have low perveance which is conducive to efficient bunching and beam transport, leading to higher gain, electronic efficiencies, and average power, while the aggregate beam current can be high, facilitating high beam and RF power, and also broad bandwidth. We will report on the design of a beam forming system for high-average-power broadband S-band multiple-beam amplifiers to be developed at the Naval Research Laboratory (NRL). These amplifiers will utilize eight individual electron beams and operates in the fundamental TM/sub 01/ mode. The singly convergent electron gun topology has fourfold symmetry with four inner and four outer emitters, interlaced 90/spl deg/ apart. The operating voltage is 45 kV with a total beam current of 32 A, evenly divided among the beamlets. Each individual beam perveance is 0.42 micro-pervs, for a total beam microperveance of 3.35. Cathode loading is kept below 10 A/cm/sup 2/ (space charge limited) for lifetime considerations. The cathode is magnetically shielded and the magnetic field in the interaction region is 1.1-1.8 kG. A key design feature is the magnetic focusing system, designed to ensure minimal beam corkscrewing, which limits the beam clearance in the beam tunnel. The primary computational tools used in this design were the 3-D gun code, MICHELLE, and the magnetic code, MAXWELL-3D. Beam optics simulations of the gun design demonstrate excellent beam transport characteristics with a final beam-to-tunnel fill factor less than 40%.