High-resolution Imaging Instrument Research Articles

A high-frequency study of the Sunyaev-Zel’dovich effect morphology in galaxy clusters

High-frequency, high-resolution imaging of the Sunyaev-Zel'dovich (SZ) effect is an important technique to study the complex structures of the atmospheres of merging galaxy clusters. Such observations are sensitive to the details of the electron spectrum. We show that the morphology of the SZ intensity maps in simulated galaxy clusters observed at 345 GHz, 600 GHz, and 857 GHz are significantly different because of SZ relativistic corrections. These differences can be revealed by high-resolution imaging instruments. We calculate relativistically corrected SZ intensity maps of a simulated, massive, merging galaxy cluster and of the massive, merging clusters 1E0657-558 (the Bullet Cluster) and Abell 2219. The morphologies of the SZ intensity maps are remarkably different between 345 GHz and 857 GHz for each merging cluster. We show that high-resolution imaging observations of the SZ intensity maps at these frequencies, obtainable with the LABOCA and HERSCHEL-SPIRE instruments, allow to fully exploit the astrophysical relevance of the predicted SZ morphological effect.

ORIGIN: metal creation and evolution from the cosmic dawn

ORIGIN is a proposal for the M3 mission call of ESA aimed at the study of metal creation from the epoch of cosmic dawn. Using high-spectral resolution in the soft X-ray band, ORIGIN will be able to identify the physical conditions of all abundant elements between C and Ni to red-shifts of z=10, and beyond. The mission will answer questions such as: When were the first metals created? How does the cosmic metal content evolve? Where do most of the metals reside in the Universe? What is the role of metals in structure formation and evolution? To reach out to the early Universe ORIGIN will use Gamma-Ray Bursts (GRBs) to study their local environments in their host galaxies. This requires the capability to slew the satellite in less than a minute to the GRB location. By studying the chemical composition and properties of clusters of galaxies we can extend the range of exploration to lower redshifts (z ~ 0.2). For this task we need a high-resolution spectral imaging instrument with a large field of view. Using the same instrument, we can also study the so far only partially detected baryons in the Warm-Hot Intergalactic Medium (WHIM). The less dense part of the WHIM will be studied using absorption lines at low redshift in the spectra for GRBs.

Polarization maintaining fiber based ultra-high resolution spectral domain polarization sensitive optical coherence tomography

We present a new ultra high resolution spectral domain polarization sensitive optical coherence tomography (PS-OCT) system based on polarization maintaining (PM) fibers. The method transfers the principles of our previous bulk optic PS-OCT systems to a fiberized setup. The phase shift between the orthogonal polarization states travelling in the two orthogonal modes of the PM fiber is compensated by software in post processing. Thereby, the main advantage of our bulk optics setups, i.e. the use of only a single input polarization state to simultaneously acquire reflectivity, retardation, optic axis orientation, and Stokes vector, is maintained. The use of a broadband light source of 110 nm bandwidth provides improved depth resolution and smaller speckle size. The latter is important for improved resolution of depolarization imaging. We demonstrate our instrument for high-resolution PS-OCT imaging of the healthy human retina.

Simulation of high-resolution mid-infrared (3–5 μm) images using an atmosphere radiative transfer analytic model

Future mid-infrared satellite missions exploring the Earth will feature advanced high spatial resolution and directional imaging instruments. Consistent end-to-end simulation of them is an important task, and is sometimes the only way to adapt and optimize a sensor and its observation conditions, to choose and test algorithms for data processing, to estimate errors and to evaluate the capabilities of the whole sensor system. However, contrary to other wavelength ranges, the mid-infrared is highly dependent on atmospheric scattering and emission. Therefore, simulation of atmospheric radiative transfer for remote sensing images will remain a challenging task, because few studies on this topic include a full treatment of atmospheric effects. With a given resolution and directional capabilities of the instrument, and combining with land surface temperature and emissivity data obtained from airborne imagery, TOA (top of atmosphere) radiance images have been simulated pixel by pixel, coupling the atmospheric radiative transfer analytic model extended from MODTRAN4 and the atmospheric adjacency effect model derived from point spread function (for atmospheric directional and adjacency effect). In this way, all major scattering and emission contributions of atmosphere were considered. Based on different atmospheric conditions and geometrical relations between the scene, the Sun and the sensor, simulated TOA radiance images were produced according to simulated workflows, 10-m spatial resolution and a spectral range of 3.5–3.9 μm. Analysis of results indicates that the analytic model and adjacency effect model are more suitable for mid-infrared imaging simulation than other existing models. This paper describes the principle of the two models, the applied methodology, the set-up of the actual image simulations, and then discusses the final results obtained.

Multi-Frame Energy-Selective Imaging System for Fast-Neutron Radiography

A new instrument for high resolution imaging of fast-neutrons is presented here. It is designed for energy selective radiography in nanosecond-pulsed broad-energy (1 - 10 MeV) neutron beams. The device presented here is based on hydrogenous scintillator screens and single- or multiple-gated intensified camera systems (ICCD). A key element is a newly developed optical amplifier which generates sufficient light for the high-speed intensified camera system, even from such faint light sources as fast plastic and liquid scintillators. Utilizing the Time-of-Flight (TOF) method, the detector incorporating the above components is capable of simultaneously taking up to 8 images, each at a different neutron energy.

Evaluation of pixellated, back-sided planar photodetectors for high-resolution imaging instrumentation

Future generations of solid-state high-energy gamma imaging cameras require pixellated semiconductor photodetectors with the greatest possible detection efficiency. In this paper, a new type of planar silicon PIN photodiode is presented, in which both p+ and n+ electrodes are located on the same side of the device. The design offers highly efficient optical coupling between the backside and scintillator, providing a fill factor of close to 100%. The performance of this detector is modelled using the ISE-TCAD simulator and its electrical and spectroscopic characteristics are experimentally investigated for the case of direct interaction of ionising radiation and also with an attached CsI(Tl) scintillator. The energy resolutions obtained at room temperature (21∘C) at 662keV (scintillated) and 27keV (direct) were 6.3% and 7.0% respectively, measured at full width at half maximum (FWHM). The new detector can be easily manufactured into arrays, for a variety of imaging (instrumentation) applications.

Subcellular-resolution molecular imaging within living tissue by fiber microendoscopy

Conventional histopathology involves sampling, sectioning and staining of tissue specimens prior to microscopic evaluation, and provides diagnostic information at a single location and point in time. In vivo microscopy and molecular-targeted optical labeling are two rapidly developing fields, which together have the potential to provide anatomical and functional indications of disease by staining and imaging tissue in situ. To address the need for high-resolution imaging instrumentation, we have developed a compact, robust, and inexpensive fiber-optic microendoscopy system based around wide-field LED illumination, a flexible 1 mm diameter fiber-optic bundle, and a color CCD camera. We demonstrate the sub-cellular resolution imaging capabilities of the system through a series of experiments, beginning with simultaneous imaging of three different cancer cell lines in culture, each targeted with a distinct fluorescent label. We used the narrow diameter probe to access subcutaneous tumors in an in vivo murine model, allowing direct comparison of microendoscopy images with macroscopic images and histopathology. A surgically resected tissue specimen from the human oral cavity was imaged across the clinical margin, demonstrating qualitative and quantitative distinction between normal and cancerous tissue based on sub-cellular image features. Finally, the fiber-optic microendoscope was used on topically-stained normal human oral mucosa in vivo, resolving epithelial cell nuclei and membranes in real-time fluorescence images. Our results demonstrate that this imaging system can potentially complement conventional diagnostic techniques, and support efforts to translate emerging molecular-diagnostic and therapeutic agents into clinical use.

Long-Range Reconnaissance Imager on New Horizons

The LOng-Range Reconnaissance Imager (LORRI) is the high resolution imaging instrument for the New Horizons mission to Pluto, its giant satellite Charon, its small moons Nix and Hydra, and the Kuiper Belt, which is the vast region of icy bodies extending roughly from Neptune's orbit out to 50 astronomical units (AU). New Horizons launched on January 19, 2006 as the inaugural mission in NASA's New Frontiers program. LORRI is a narrow angle (field of view=0.29 deg), high resolution (4.95 microrad pixels), Ritchey-Chretien telescope with a 20.8 cm diameter primary mirror, a focal length of 263 cm, and a three lens field-flattening assembly. A 1024 x 1024 pixel (optically active region), thinned, backside-illuminated charge-coupled device (CCD) detector is used in the focal plane unit and is operated in frame transfer mode. LORRI provides panchromatic imaging over a bandpass that extends approximately from 350 nm to 850 nm. LORRI operates in an extreme thermal environment, situated inside the warm spacecraft with a large, open aperture viewing cold space. LORRI has a silicon carbide optical system, designed to maintain focus over the operating temperature range without a focus adjustment mechanism. Moreover, the spacecraft is thruster-stabilized without reaction wheels, placing stringent limits on the available exposure time and the optical throughput needed to satisfy the measurement requirements.

Gamma Rays and the Evolving, Compact Structures of the 2003 October 28 X17 Flare

The X17 flare on 2003 October 28 was observed by high-resolution imaging or spectroscopic instruments on CORONAS, GOES, INTEGRAL, RHESSI, SOHO, and TRACE. These spacecraft observed the temporal evolution of the γ-ray positron-annihilation and nuclear de-excitation line spectra, imaged the hard X-ray bremsstrahlung and EUV and UV emission, and measured the surface magnetic field and subphotospheric pressure perturbations. In the usual pattern, the onset of the flare is dominated by particle acceleration and interaction, and by the filling of coronal magnetic structures with hot plasma. The associated positron-annihilation signatures early in the impulsive phase from 11:06 to 11:16 UT have a line-broadening temperature characteristic of a few hundred thousand kelvins. The most intense precipitation sites within the extended flare ribbons are very compact, with diameters of less than 1400 km, and a 195 A TRACE intensity that can exceed 7500 times the quiescent active-region value. These regions appear to move at speeds of up to 60 km s-1. The associated rapidly evolving, compact perturbations of the photosphere below these sites excite acoustic pulses that propagate into the solar interior. Less intense precipitation sites typically persist for several minutes behind the advancing flare ribbons. After ~1 ks, the flare enters a second phase, dominated by coronal plasma cooling and downflows and by annihilation-line radiation characteristic of a photospheric environment. We point out (1) that these detailed observations underscore that flare models need to explicitly incorporate the multitude of successively excited environments whose evolving signals differ at least in their temporal offsets and energy budgets, if not also in the exciting particle populations and penetration depths, and (2) that the spectral signatures of the positron annihilation do not fit conventional model assumptions.

Imaging with isotopes: high resolution and quantitation

nothing so small as to escape our inquiry; hence there is a new visible World discovered to the understanding.” Thus wrote Robert Hooke in his pioneering work Micrographia [1] published by the Royal Society in 1664. In this revolutionary book, Hooke described with excitement his discoveries using a simple light microscope, coining the word ‘cell’ to define the microscopic structures he saw in cork and plant samples. In this issue of Journal of Biology [2], Claude Lechene and colleagues describe a 21st century microscopy technology (Figure 1) that also reveals images we have never seen before. Hooke was fascinated by the new vision of the world and the planets afforded by the lenses of the early light microscopes and telescopes of the 17th century. Ever since these discoveries, researchers have been gazing at the microscopic world and developing better and better instruments to do so. Over the centuries, the demanding needs of biologists have fuelled countless improvements in imaging technologies. For example, electron microscopy has become a standard instrument for high-resolution imaging (in the nanometer range) in biology, and scanning probe microscopy techniques provide three-dimensional images of atomic surfaces.

Correction for the Flux Measurement Bias in X‐Ray Source Detection

With a high spatial resolution imaging instrument such as the Chandra/ACIS, one can confidently identify an X-ray source with only a few detected counts. The detection threshold of such sources, however, varies strongly across the field-of-view of the instrument. Furthermore, the low detection counting statistics, together with a typical steep source number-flux relation, causes more intrinsically faint sources to be detected at apparently higher fluxes than the other way around. We quantify this ``X-ray Eddington bias'' as well as the detection threshold variation and devise simple procedures for their corrections. To illustrate our technique, we present results from our analysis of X-ray sources detected in the fields of the large-scale hierarchical complex Abell 2125 at $z = 0.247$ and the nearby galaxy NGC 4594 (Sombrero). We show that the sources detected in the Abell 2125 field, excluding 10 known complex members, have a number-flux relation consistent with the expected from foreground or background objects. In contrast, the number-flux relation of the NGC 4594 field is dominated by X-ray sources associated with the galaxy. This galactic component of the relation is well characterized by a broken power law.

Morphological biosignatures and the search for life on Mars.

This report provides a rationale for the advances in instrumentation and understanding needed to assess claims of ancient and extraterrestrial life made on the basis of morphological biosignatures. Morphological biosignatures consist of bona fide microbial fossils as well as microbially influenced sedimentary structures. To be recognized as evidence of life, microbial fossils must contain chemical and structural attributes uniquely indicative of microbial cells or cellular or extracellular processes. When combined with various research strategies, high-resolution instruments can reveal such attributes and elucidate how morphological fossils form and become altered, thereby improving the ability to recognize them in the geological record on Earth or other planets. Also, before fossilized microbially influenced sedimentary structures can provide evidence of life, criteria to distinguish their biogenic from non-biogenic attributes must be established. This topic can be advanced by developing process-based models. A database of images and spectroscopic data that distinguish the suite of bona fide morphological biosignatures from their abiotic mimics will avoid detection of false-positives for life. The use of high-resolution imaging and spectroscopic instruments, in conjunction with an improved knowledge base of the attributes that demonstrate life, will maximize our ability to recognize and assess the biogenicity of extraterrestrial and ancient terrestrial life.

Force sensing and mapping by atomic force microscopy

Over the past 15 years, advances in the field of atomic force microscopy (AFM) have broadened its use from a high-resolution imaging instrument to a device capable of detecting and quantifying single molecular forces between surfaces in near-native conditions. This article reviews developments in the force sensing field and focuses particularly on research that has seen the AFM utilised to produce two-dimensional maps of specific molecular interaction sites on a sample surface.

The Brera Multiscale WaveletROSATHRI Source Catalog. II. Application to the HRI and First Results

The wavelet detection algorithm (WDA) described in the accompanying paper by Lazzati et al. is suited to a fast and efficient analysis of images taken with the High-Resolution Imager (HRI) instrument on board the ROSAT satellite. An extensive testing is carried out on the detection pipeline: HRI fields with different exposure times are simulated and analyzed in the same fashion as the real data. Positions are recovered with errors of a few arcseconds, whereas fluxes are within a factor of 2 from their input values in more than 90% of the cases in the deepest images. Unlike the sliding-box detection algorithms, the WDA also provides a reliable description of the source extension, allowing for a complete search of, e.g., supernova remnants or clusters of galaxies in the HRI fields. A completeness analysis on simulated fields shows that for the deepest exposures considered (~120 ks) a limiting flux of ~3 × 10-15 ergs s-1 cm-2 can be reached over the entire field of view. We test the algorithm on real HRI fields selected for their crowding and/or the presence of extended or bright sources (e.g., clusters of galaxies and stars, supernova remnants). We show that our algorithm compares favorably with other X-ray detection algorithms, such as XIMAGE and EXSAS. Analysis with the WDA of the large set of HRI data will allow us to survey ~400 deg2 down to a limiting flux of ~10-13 ergs s-1 cm-2, and ~0.3 deg2 down to ~3 × 10-15 ergs s-1 cm-2. A complete catalog will result from our analysis, consisting of the Brera Multiscale Wavelet Bright Source Catalog (BMW-BSC), with sources detected with a significance of 4.5 σ, and the Faint Source Catalog (BMW-FSC), with sources at 3.5 σ. A conservative estimate based on the extragalactic log N-log S indicates that at least 16,000 sources will be revealed in the complete analysis of the entire HRI data set.

Cathodoluminescence géosciences

Cathodoluminescence, or the emission of photons in the visible range of the electromagnetic spectrum under cathodic excitation is routinely used in mineralogy and sedimentary petrography. Currently, an improved knowledge of the physical causes of CL and the use of high-resolution SEM-CL imaging and SEM-CL spectroscopic instruments, which permit new observations of UV and infrared emission, demonstrate the limits in interpreting the CL characteristics of geomaterials. Applying these new CL instruments in combination with micro-scale trace-chemical analytical techniques bas a great potential for improving CL interpretations as shown by the few recent studies on carbonates and silicates in geosciences.

Novel instrument for high-resolution ultrasound flow imaging

In multigate systems employed in Doppler flow-imaging equipment, the velocities of targets located at different ranges along the ultrasound beam axis are simultaneously detected. Typically, to reduce the computation efforts, this processing is aimed at extracting a single parameter (e.g., the mean velocity) from each signal. In this article, a novel ultrasound multigate instrument is presented capable of providing a detailed analysis of Doppler signals originated from 64 different range cells. By means of a dedicated high-speed fast-Fourier transform processor, these signals are transformed into the frequency domain without loss of information. The implementation of the new multigate system is described here, and the pieces of information which it can provide are discussed. Significant results obtained in vitro and in vivo demonstrate that the new instrument is capable of accurately reproducing the actual velocity profiles of the interrogated flow. © 1997 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 8, 438–443, 1997

Simulated Aster data for geologic studies

The Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) is a high spatial resolution imaging instrument, scheduled to be launched on NASA's Earth Observing System AM-1 satellite platform in 1988, ASTER acquires data in 14 bands, spanning the visible, near-infrared, short-wavelength infrared, and thermal infrared spectral regions, with spatial resolution varying from 15-90 m, depending on wavelength. In order to evaluate the authors ability to use ASTER data for geological mapping, they created a simulated 14-band ASTER data set for Cuprite, Nevada. The study site has sparse vegetation and exposes a wide range of unaltered and hydrothermally altered volcanic rocks. The wide range of wavelengths covered by ASTER allowed them to distinguish iron oxide minerals, clay-bearing minerals, sulfate minerals, ammonia minerals, siliceous rocks, and carbonates. Based on interpretation of the ASTER data, and in conjunction with laboratory and field spectral measurements, they produced an alteration map showing the distribution of argillized rocks, opalized rocks with alunite, silicified rocks, and areas dominated by kaolinite and buddingtonite. The map was as accurate as published maps made by traditional field methods. ASTER should be an improvement over existing satellite systems for geologic mapping.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Photon tunnelling microscopy: new instruments from old theory

Photon tunnelling has been observed since Newton. It has only recently been developed into a practical instrument for high-resolution imaging and profilometry. Vertical resolution is less than 1 nm while lateral resolution is approximately 0.29λ, or 150 nm for green light. Imaging is done in real time.

A search for millisecond periodic and quasi-periodic pulsations in low-mass X-ray binaries

view Abstract Citations (16) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Search for Millisecond Periodic and Quasi-periodic Pulsations in Low-Mass X-Ray Binaries Mereghetti, S. ; Grindlay, J. E. Abstract The results of a Fourier analysis to detect fast periodic and quasi-periodic pulsations in the X-ray emission from the sources 4U 0614 + 091, 4U 1636 - 536, 4U 1735 - 44, 4U 1820 30, GX 5 - 1, GX 9 + 9, Ser X-1, and Cyg X-2 are presented. This search has been carried out for the first time in the soft energy band (0.2-2.0 keV), using data from the Einstein Observatory high resolution imager instrument. An approximate method of minimizing the decrease in search sensitivity produced by the Doppler shift of the pulse periods due to source orbital motion is discussed. No pulsations have been detected, and upper limits, which depend on the orbital parameters assumed for the sources, are set on the pulsed flux fraction. Publication: The Astrophysical Journal Pub Date: January 1987 DOI: 10.1086/164915 Bibcode: 1987ApJ...312..727M Keywords: Stellar Mass; Stellar Oscillations; Variable Stars; X Ray Binaries; Fourier Analysis; Heao 2; Milky Way Galaxy; Periodic Variations; Spaceborne Astronomy; Astrophysics; STARS: NEUTRON; STARS: PULSATION; X-RAYS: BINARIES full text sources ADS | data products SIMBAD (8)

High-Resolution X-ray Observations of the Orion Nebula

Observations of the Trapezium region in the Orion Nebula obtained with the high-resolution x-ray imaging instrument on board the Einstein Observatory reveal at least 58 sources of x-ray emission. All but two of the sources can be identified with visible stars. The strongest x-ray source is the star Theta(1)C, which excites the emission nebula. Its x-ray luminosity is 6 x 10(32) ergs per second. The rest of the x-ray sources may be identified with stars of all spectral types. Strong x-ray emission is not observed from members of the infrared cluster embedded within the Orion molecular cloud.