Bendable X-ray Optics for High Resolution Imaging

NASA Technical Reports Server (NTRS)

Gubarev, M.; Ramsey, B.; Kilaru, K.; Atkins, C.; Broadway, D.

2014-01-01

Current state-of the-art for x-ray optics fabrication calls for either the polishing of massive substrates into high-angular-resolution mirrors or the replication of thin, lower-resolution, mirrors from perfectly figured mandrels. Future X-ray Missions will require a change in this optics fabrication paradigm in order to achieve sub-arcsecond resolution in light-weight optics. One possible approach to this is to start with perfectly flat, light-weight surface, bend it into a perfect cone, form the desired mirror figure by material deposition, and insert the resulting mirror into a telescope structure. Such an approach is currently being investigated at MSFC, and a status report will be presented detailing the results of finite element analyses, bending tests and differential deposition experiments.

Balloon-borne three-meter telescope for far-infrared and submillimeter astronomy

NASA Technical Reports Server (NTRS)

Fazio, G. G.

1985-01-01

Presented are scientific objectives, engineering analysis and design, and results of technology development for a Three-Meter Balloon-Borne Far-Infrared and Submillimeter Telescope. The scientific rationale is based on two crucial instrumental capabilities: high angular resolution which approaches eight arcseconds at one hundred micron wavelength, and high resolving power spectroscopy with good sensitivity throughout the telescope's 30-micron to 1-mm wavelength range. The high angular resolution will allow us to resolve and study in detail such objects as collapsing protostellar condensations in our own galaxy, clusters of protostars in the Magellanic clouds, giant molecular clouds in nearby galaxies, and spiral arms in distant galaxies. The large aperture of the telescope will permit sensitive spectral line measurements of molecules, atoms, and ions, which can be used to probe the physical, chemical, and dynamical conditions in a wide variety of objects.

Bonding Thin Mirror Segments Without Distortion for the International X-Ray Observatory

NASA Technical Reports Server (NTRS)

Evans, Tyler C.; Chan, Kai-Wing; Saha, Timo T.

2011-01-01

The International X-Ray Observatory (IXO) uses thin glass optics to maximize large effective area and precise low angular resolution. The thin glass mirror segments must be transferred from their fabricated state to a permanent structure without imparting distortion. IXO will incorporate about fourteen thousand thin mirror segments to achieve the mission goal of 3.0 square meters of effective area at 1.25 keV with an angular resolution of five arcseconds. To preserve figure and alignment, the mirror segment must be bonded with sub-micron movement at each corner. Recent advances in technology development have produced significant x-ray test results of a bonded pair of mirrors. Three specific bonding cycles will be described highlighting the improvements in procedure, temperature control, and precision bonding. This paper will highlight the recent advances in alignment and permanent bonding as well as the results they have produced.

Process of constructing a lightweight x-ray flight mirror assembly

NASA Astrophysics Data System (ADS)

McClelland, Ryan S.; Biskach, Michael P.; Chan, Kai-Wing; Espina, Rebecca A.; Hohl, Bruce R.; Saha, Timo T.; Zhang, William W.

2014-07-01

Lightweight and high resolution optics are needed for future space-based x-ray telescopes to achieve advances in highenergy astrophysics. NASA's Next Generation X-ray Optics (NGXO) project has made significant progress towards building such optics, both in terms of maturing the technology for spaceflight readiness and improving the angular resolution. Technology Development Modules (TDMs) holding three pairs of mirrors have been regularly and repeatedly integrated and tested both for optical performance and mechanical strength. X-ray test results have been improved over the past year from 10.3 arc-seconds Half Power Diameter (HPD) to 8.3 arc-seconds HPD. A vibration test has been completed to NASA standard verification levels showing the optics can survive launch and pointing towards improvements in strengthening the modules through redundant bonds. A Finite Element Analysis (FEA) study was completed which shows the mirror distortion caused by bonding is insensitive to the number of bonds. Next generation TDMs, which will demonstrate a lightweight structure and mount additional pairs of mirrors, have been designed and fabricated. The light weight of the module structure is achieved through the use of E-60 Beryllium Oxide metal matrix composite material. As the angular resolution of the development modules has improved, gravity distortion during horizontal x-ray testing has become a limiting factor. To address this issue, a facility capable of testing in the vertical orientation has been designed and planned. Test boring at the construction site suggest standard caisson construction methods can be utilized to install a subterranean vertical vacuum pipe. This facility will also allow for the testing of kinematically mounted mirror segments, which greatly reduces the effect of bonding displacements. A development platform demonstrating the feasibility of kinematically mounting mirror segments has been designed, fabricated, and successfully tested.

A complete solution for GP-B's gyroscopic precession by retarded gravitational theory

NASA Astrophysics Data System (ADS)

Tang, Keyun

Mainstream physicists generally believe that Mercury’s Perihelion precession and GP-B’ gyroscopic precession are two of the strongest evidences supporting Einstein’ curved spacetime and general relativity. However, most classical literatures and textbooks (e.g. Ohanain: Gravitation and Spacetime) paint an incorrect picture of Mercury’s orbit anomaly, namely Mercury’s perihelion precessed 43 arc-seconds per century; a correct picture should be that Mercury rotated 43 arc-seconds per century more than along Newtonian theoretical orbit. The essence of Le Verrier’s and Newcomb’s observation and analysis is that the angular speed of Mercury is slightly faster than the Newtonian theoretical value. The complete explanation to Mercury’s orbit anomaly should include two factors, perihelion precession is one of two factors, in addition, the change of orbital radius will also cause a change of angular speed, which is another component of Mercury's orbital anomaly. If Schwarzschild metric is correct, then the solution of the Schwarzschild orbit equation must contain three non-ignorable items. The first corresponds to Newtonian ellipse; the second is a nonlinear perturbation with increasing amplitude, which causes the precession of orbit perihelion; this is just one part of the angular speed anomaly of Mercury; the third part is a linear perturbation, corresponding to a similar figure of the Newton's ellipse, but with a minimal radius; this makes no contribution to the perihelion precession of the Schwarzschild orbit, but makes the Schwarzschild orbital radius slightly smaller, leading to a slight increase in Mercury’s angular speed. All classical literatures of general relativity ignored this last factor, which is a gross oversight. If you correctly take all three factors into consideration, the final result is that the difference between the angles rotated along Schwarzschild’s orbit and the angle rotated along Newton’s orbit for one hundred years should be more than 130.5 arc-seconds; this means that Le Verrier’s observation on Mercury’s orbital anomaly can not be explained correctly by the Schwarzschild metric. In contrast, Mercury’s angular speed anomaly can be explained satisfactorily by the radial induction component and angular component of retarded gravitation. From the perspective of energy, the additional radial component of retarded gravitation makes the radius of Mercury’s orbit slightly smaller, i.e. some potential energy is lost. And the angular component of retarded gravitation changes the Mercury's angular momentum; this proves that the changes of Mercury’s orbit and angular speed are the results of gravitational radiation. I have found that there are similar errors in the explanation on the gyroscopic precession of GP-B, i.e. physicists only consider the contribution of the nonlinear perturbation terms and never consider the contribution of linear perturbation terms. For the precession of GP-B, the complete Schwarzschild’s solution should be about 19.8 arc-seconds per year; it is far more than the experimental results of 6.602 arc-seconds per year. I have calculated the gyroscopic precession of GP-B due to retarded gravitation, the result is 6.607 arc-seconds per year; this matches well with the experimental results. These successful explanations for both anomalies of Mercury’s orbit and the gyroscopic precession of GP -B shows that Retarded Gravitation is indeed a sound gravitational theory, and that spacetime is in fact flat, and gravity travels at the speed of light. Both Mercury’s angular speed anomaly and GP - B gyro precession were the result of the gravitational radiation!

Evaluation of the cosmic-ray induced background in coded aperture high energy gamma-ray telescopes

NASA Technical Reports Server (NTRS)

Owens, Alan; Barbier, Loius M.; Frye, Glenn M.; Jenkins, Thomas L.

1991-01-01

While the application of coded-aperture techniques to high-energy gamma-ray astronomy offers potential arc-second angular resolution, concerns were raised about the level of secondary radiation produced in a thick high-z mask. A series of Monte-Carlo calculations are conducted to evaluate and quantify the cosmic-ray induced neutral particle background produced in a coded-aperture mask. It is shown that this component may be neglected, being at least a factor of 50 lower in intensity than the cosmic diffuse gamma-rays.

The relationship between Class I and Class II methanol masers at high angular resolution

NASA Astrophysics Data System (ADS)

McCarthy, T. P.; Ellingsen, S. P.; Voronkov, M. A.; Cimò, G.

2018-06-01

We have used the Australia Telescope Compact Array (ATCA) to make the first high-resolution observations of a large sample of class I methanol masers in the 95-GHz (80-71A+) transition. The target sources consist of a statistically complete sample of 6.7-GHz class II methanol masers with an associated 95-GHz class I methanol maser, enabling a detailed study of the relationship between the two methanol maser classes at arcsecond angular resolution. These sources have been previously observed at high resolution in the 36- and 44-GHz transitions, allowing comparison between all three class I maser transitions. In total, 172 95-GHz maser components were detected across the 32 target sources. We find that at high resolution, when considering matched maser components, a 3:1 flux density ratio is observed between the 95- and 44-GHz components, consistent with a number of previous lower angular resolution studies. The 95-GHz maser components appear to be preferentially located closer to the driving sources and this may indicate that this transition is more strongly inverted nearby to background continuum sources. We do not observe an elevated association rate between 95-GHz maser emission and more evolved sources, as indicated by the presence of 12.2-GHz class II masers. We find that in the majority of cases where both class I and class II methanol emission is observed, some component of the class I emission is associated with a likely outflow candidate.

X-Ray Optics at NASA Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

O'Dell, Stephen L.; Atkins, Carolyn; Broadway, David M.; Elsner, Ronald F.; Gaskin, Jessica A.; Gubarev, Mikhail V.; Kilaru, Kiranmayee; Kolodziejczak, Jeffery J.; Ramsey, Brian D.; Roche, Jacqueline M.;

Infrared photometry of the black hole candidate Sagittarius A*

NASA Technical Reports Server (NTRS)

Close, Laird M.; Mccarthy, Donald W. JR.; Melia, Fulvio

1995-01-01

An infrared source has been imaged within 0.2 +/- 0.3 arcseconds of the unique Galactic center radio source Sgr A* High angular resolution (averaged value of the Full Width at Half Maximum (FWHM) approximately 0.55 arcseconds) was achieved by rapid (approximately 50 Hz) real-time images motion compensation. The source's near-infrared magnitudes (K = 12.1 +/- 0.3, H = 13.7 +/- 0.3, and J = 16.6 +/- 0.4) are consistent with a hot object reddened by the local extinction A(sub v) approximately 27). At the 3 sigma level of confidence, a time series of 80 images limits the source variability to less than 50% on timescales from 3 to 30 minutes. The photometry is consistent with the emission from a simple accretion disk model for a approximately 1 x 10(exp 6) solar mass black hole. However, the fluxes are also consistent with a hot luminous (L approximately 10(exp 3.5) to 10(exp 4-6) solar luminosity) central cluster star positionally coincident with Sgr A*.

Role of the Chandra X-Ray Observatory Observations for the Study of Ionized Plasmas

NASA Technical Reports Server (NTRS)

Weisskopf, Martin C.

2010-01-01

The Chandra X-Ray Observatory, launched in 1999, is now beginning its 12-th year of operation. Chandra, the X-ray component of NASA s Great Observatory program, continues to operate efficiently, somewhat remarkable considering that the Observatory was designed for three years of operation with a goal of five. The Observatory features X-ray optics with sub-arcsecond angular resolution and a small suite of instruments, including transmission gratings, which allow for high-resolution spectroscopy of point sources. We will detail the capabilities of the Observatory for making such spectroscopic measurements and discuss a number of examples of what has been learned about the astrophysical plasmas capable of producing bright X-ray emission.

Full-sky, High-resolution Maps of Interstellar Dust

NASA Astrophysics Data System (ADS)

Meisner, Aaron Michael

We present full-sky, high-resolution maps of interstellar dust based on data from the Wide-field Infrared Survey Explorer (WISE) and Planck missions. We describe our custom processing of the entire WISE 12 micron All-Sky imaging data set, and present the resulting 15 arcsecond resolution, full-sky map of diffuse Galactic dust emission, free of compact sources and other contaminating artifacts. Our derived 12 micron dust map offers angular resolution far superior to that of all other existing full-sky, infrared dust emission maps, revealing a wealth of small-scale filamentary structure. We also apply the Finkbeiner et al. (1999) two-component thermal dust emission model to the Planck HFI maps. We derive full-sky 6.1 arcminute resolution maps of dust optical depth and temperature by fitting this two-component model to Planck 217-857 GHz along with DIRBE/IRAS 100 micron data. In doing so, we obtain the first ever full-sky 100-3000 GHz Planck-based thermal dust emission model, as well as a dust temperature correction with ~10 times enhanced angular resolution relative to DIRBE-based temperature maps. Analyzing the joint Planck/DIRBE dust spectrum, we show that two-component models provide a better fit to the 100-3000 GHz emission than do single-MBB models, though by a lesser margin than found by Finkbeiner et al. (1999) based on FIRAS and DIRBE. We find that, in diffuse sky regions, our two-component 100-217 GHz predictions are on average accurate to within 2.2%, while extrapolating the Planck Collaboration (2013) single-MBB model systematically underpredicts emission by 18.8% at 100 GHz, 12.6% at 143 GHz and 7.9% at 217 GHz. We calibrate our two-component optical depth to reddening, and compare with reddening estimates based on stellar spectra. We find the dominant systematic problems in our temperature/reddening maps to be zodiacal light on large angular scales and the cosmic infrared background anisotropy on small angular scales. Future work will focus on combining our WISE 12 micron dust map and Planck dust model to create a next-generation, full-sky dust extinction map with angular resolution several times better than Schlegel et al. (1998).

Deconvolving the Nucleus of Centaurus A Using Chandra PSF Library

NASA Technical Reports Server (NTRS)

Karovska, Margarita

2000-01-01

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.

What We Have Learned About Clusters From a Decade of Arcsecond Resolution X-ray Observations

NASA Technical Reports Server (NTRS)

Markevitch, Maxim

2012-01-01

This talk will briefly review the main findings from Chandra high angular resolution observations of galaxy clusters, emphasizing results on cluster astrophysics. Chandra has discovered shock fronts in merging systems, providing information on the shock Mach number and velocity, and for best-observed shocks, constraining the microphysical properties of the intracluster medium (ICM). Cold fronts, a Chandra discovery, are ubiquitous both in merging clusters and in the cool ccres of relaxed systems. They reveal the structure and strength of the intracluster magnetic fields and constrain the ICM viscosity a combined with radio data, these observations also shed light on the production of ultra-relativistic particles that are known to coexist with thermal plasma. Finally, in nearly all cool cores, Chandra observes cavities in the ICM that are produced by the central AGN. All these phenomena will be extremely interesting for high-resolution SZ studies.

The Chandra X-Ray Observatory and its Role for the Study of Ionized Plasmas

NASA Technical Reports Server (NTRS)

Weisskopf, Martin C.

2010-01-01

NASA's Chandra X-Ray Observatory was launched in July of 1999. Featuring a 1000cm2-class X-ray telescope with sub-arcsecond angular resolution, the Observatory has observed targets from the solar system including the earth s moon, comets, and planets to the most distant galaxy clusters and active galactic nuclei. Capable of performing moderate energy resolution image-resolved spectroscopy using its CCD detectors, and high-resolution grating spectroscopy, the Observatory has produced, and continues to produce, valuable data and insights into the emission mechanisms of the ionized plasmas in which the X-rays originate. We present a brief overview of the Observatory to provide insight as to how to use it for your investigations. We also present an, admittedly brief and biased, overview of some of the results of investigations performed with Chandra that may be of interest to this audience.

Flight programs and X-ray optics development at MSFC

NASA Astrophysics Data System (ADS)

Gubarev, M.; Ramsey, B.; O'Dell, S.; Elsner, R.; Kilaru, K.; Atkins, C.; Swartz, D.; Gaskin, J.; Weisskopf, M.

The X-ray astronomy group at the Marshall Space Flight Center (MSFC) is developing electroformed nickel/cobalt x-ray optics for suborbital and orbital experiments. Suborbital instruments include the Focusing X-ray Solar Imager (FOXSI) and Micro-X sounding rocket experiments and the HEROES balloon payload. Our current orbital program is the fabrication of mirror modules for the Astronomical Roentgen Telescope (ART) to be launched on board the Russian-German Spectrum Roentgen Gamma Mission (SRG). A second component of our work is the development of fabrication techniques and optical metrology to improve the angular resolution of thin-shell optics to the arcsecond-level.

ART-XC/SRG: Status of the X-ray Optics Development

NASA Technical Reports Server (NTRS)

Gubarev, M.; Ramsey, B.; Zavlin, V.; Swartz, D.; Elsner, R. F.; ODell, S.; Kilaru, K.; Atkins, C.; McCracken, J.; Pavlinsky, M.;

ART-XC/SRG: Status of the X-ray Optics Development

NASA Technical Reports Server (NTRS)

Gubarev, M.; Ramsey, B.; Elsner, R.; O'Dell, S.; Kolodziejczak, J.; McCracken, J.; Zavlin, V.; Swartz, D.; Kilaru, K.; Atkins, C.;

ART-XC/SRG: Status of the X-ray Optics Development

NASA Technical Reports Server (NTRS)

Gubarev, M.; Ramsey, B.; Elsner, R.; O'Dell, S.; Kolodziejczak, J.; McCracken, J.; Zavlin, V.; Swartz, D.; Kilaru, K.; Atkins, C.;

Alignment and Integration of Lightweight Mirror Segments

NASA Technical Reports Server (NTRS)

Evans, Tyler; Biskach, Michael; Mazzarella, Jim; McClelland, Ryan; Saha, Timo; Zhang, Will; Chan, Kai-Wing

2011-01-01

The optics for the International X-Ray Observatory (IXO) require alignment and integration of about fourteen thousand thin mirror segments to achieve the mission goal of 3.0 square meters of effective area at 1.25 keV with an angular resolution of five arc-seconds. These mirror segments are 0.4 mm thick, and 200 to 400 mm in size, which makes it difficult not to impart distortion at the sub-arc-second level. This paper outlines the precise alignment, permanent bonding, and verification testing techniques developed at NASA's Goddard Space Flight Center (GSFC). Improvements in alignment include new hardware and automation software. Improvements in bonding include two module new simulators to bond mirrors into, a glass housing for proving single pair bonding, and a Kovar module for bonding multiple pairs of mirrors. Three separate bonding trials were x-ray tested producing results meeting the requirement of sub ten arc-second alignment. This paper will highlight these recent advances in alignment, testing, and bonding techniques and the exciting developments in thin x-ray optic technology development.

Prospects for the design of an ultraviolet imaging Fourier transform spectrometer

NASA Astrophysics Data System (ADS)

Lemaire, Philippe

2017-11-01

Recent results from solar observations in the far and extremeultraviolet (FUV/EUV) obtained from SOHO (SOlar and Heliospheric Observatory) and TRACE (Transition Region Camera) show the extreme variability of the solar atmosphere. Within the limited resolution of the instruments (1-2 arcseconds) horizontal and vertical velocities up-to 100 to 400 km s-1 have been measured. With an horizontal velocity of 100 km s-1 an one arsecond structure crosses the one arcsecond slit width of a classical slit spectrometer in less than 10 seconds. In the future, with higher angular resolution (e.g. 0.1 arcsecond), the capability to study small structures will be greatly reduced by a classical slit spectrometer. To be able to characterize the small scale solar atmospheric structures formed in the 104 K to 106 K temperature range (which emit in the 30 to 180 nm wavelength range) a spectrometer without slit (or with wide slit) is required. At the same time to obtain an accurate measurement of the doppler velocity an high spectral resolution is needed. The two requirements, high spectral resolution and large slit, are difficult to be simultaneously fulfilled with a classical slit spectrometer within the limited volume of a space instrumentation. Also, we propose to use an Imaging Fourier Transform Spectrometer (IFTS) to provide simultaneously a bidimensionnal field and an accurate determination of line profiles and positions. The development of Fourier Transform Spectrometers (FTS), although popular in the infrared, has been very limited in the UV/FUV by the lack of very high quality beam splitter. Since 10 years, the use of diffraction gratings as beam splitters has been suggested and few intruments have been built ([Chak 94]; [Clea 92]; [File 00]). These instruments illustrate some applications in the new wavelength domain opened by using a beam splitter grating, but do not yet provide the full capabilities of an FTS. In this paper we present several optical schemes which can provide the full capabilities of a complete IFTS in the FUV/EUV spectral range.

Technology Requirements for a Square Meter, Arcsecond Resolution Telescope for X-Rays: The SMART-X Mission

NASA Technical Reports Server (NTRS)

Schwartz, Daniel A.; Allured, Ryan; Bookbinder, Jay A.; Cotroneo, Vincenzo; Forman, William R.; Freeman, Mark D.; McMuldroch, Stuart; Reid, Paul B.; Tananbaum, Harvey; Vikhlinin, Alexey A.;

Absolute Effective Area of the Chandra High-Resolution Mirror Assembly

NASA Technical Reports Server (NTRS)

Schwartz, D. A.; David, L. P.; Donnelly, R. H.; Edgar, R. J.; Gaetz, T. J.; Jerius, D.; Juda, M.; Kellogg, E. M.; McNamara, B. R.; Dewey, D.

2000-01-01

The Chandra X-ray Observatory was launched in July 1999, and is returning exquisite sub-arcsecond x-ray images of star groups, supernova remnants, galaxies, quasars, and clusters of galaxies. In addition to being the premier X-ray observatory in terms of angular and spectral resolution, Chandra is the best calibrated X-ray facility ever flown. We discuss here the calibration of the effective area of the High Resolution Mirror Assembly. Because we do not know the absolute X-ray flux density of any celestial source, this must be based primarily on ground measurements and on modeling. In particular, we must remove the calibrated modeled responses of the detectors and gratings to obtain the mirror area. For celestial sources which may be assumed to have smoothly varying spectra, such as the Crab Nebula, we may verify the continuity of the area calibration as a function of energy. This is of significance in energy regions such as the Ir M-edges, or near the critical grazing angle cutoff of the various mirror shells.

Synchrotron Radiation from Outer Space and the Chandra X-Ray Observatory

NASA Technical Reports Server (NTRS)

Weisskopf, M. C.

2006-01-01

The universe provides numerous extremely interesting astrophysical sources of synchrotron X radiation. The Chandra X-ray Observatory and other X-ray missions provide powerful probes of these and other cosmic X-ray sources. Chandra is the X-ray component of NASA's Great Observatory Program which also includes the Hubble Space telescope, the Spitzer Infrared Telescope Facility, and the now defunct Compton Gamma-Ray Observatory. The Chandra X-Ray Observatory provides the best angular resolution (sub-arcsecond) of any previous, current, or planned (for the foreseeable near future) space-based X-ray instrumentation. We present here a brief overview of the technical capability of this X-Ray observatory and some of the remarkable discoveries involving cosmic synchrotron sources.

Toward Large-Area Sub-Arcsecond X-Ray Telescopes

NASA Technical Reports Server (NTRS)

ODell, Stephen L.; Aldcroft, Thomas L.; Allured, Ryan; Atkins, Carolyn; Burrows, David N.; Cao, Jian; Chalifoux, Brandon D.; Chan, Kai-Wing; Cotroneo, Vincenzo; Elsner, Ronald F.;

The X-Ray Surveyor Mission: A Concept Study

NASA Technical Reports Server (NTRS)

Gaskin, Jessica A.; Weisskopf, Martin C.; Vikhlinin, Alexey; Tananbaum, Harvey D.; Bandler, Simon R.; Bautz, Marshall W.; Burrows, David N.; Falcone, Abraham D.; Harrison, Fiona A.; Heilmann, Ralf K.;

Direct Evidence for Maser Emission from the 36.2 GHz Class I Transition of Methanol in NGC253

NASA Astrophysics Data System (ADS)

Chen, Xi; Ellingsen, Simon P.; Shen, Zhi-Qiang; McCarthy, Tiege P.; Zhong, Wei-Ye; Deng, Hui

2018-04-01

Observations made with the Jansky Very large Array (JVLA) at an angular resolution of ∼0.″1 have detected class I methanol maser emission from the 36.2 GHz transition toward the starburst galaxy NGC 253. The methanol emission is detected toward four sites which lie within the regions of extended methanol emission detected in previous lower angular resolution (a few arcseconds) observations. The peak flux densities of the detected compact components are in the range 3–9 mJy beam‑1. Combining the JVLA data with single-dish observations from the Shanghai Tianma Radio Telescope (TMRT) and previous interferometric observations with the Australia Telescope Compact Array (ATCA), we show that the 36.2 GHz class I methanol emission consists of both extended and compact structures, with typical scales of ∼6″ (0.1 kpc) and ∼0.″05 (1 pc), respectively. The strongest components have a brightness temperature of >103 K, much higher than the maximum kinetic temperature (∼100 K) of the thermal methanol emission from NGC 253. Therefore, these observations conclusively demonstrate for the first time the presence of maser emission from a class I methanol transition in an external galaxy.

Linking Deep Astrometric Standards to the ICRF

NASA Astrophysics Data System (ADS)

Frey, S.; Platais, I.; Fey, A. L.

2007-07-01

The next-generation large aperature and large field-of-view telescopes will address fundamantal questions of astrophysica and cosmology such as the nature of dark matter and dark energy. For a variety of applications, the CCD mosaic detectors in the focal plane arrays require astronomic calibrationat the milli-arcsecond (mas) level. The existing optical reference frames are insufficient to support such calibrations. To address this problem, deep optical astronomic fields are being established near the Galactic plane. In order to achiev a 5-10-mas or better positional accuracyfor the Deepp Astrometric Standards (DAS), and to obtain bsolute stellar proper motions for the study of Galactic structure, it is crucial to link these fields to the International Celestial Reference Frame (ICRF). To this end, we selected 15 candidate compact extragalactic radio sources in the Gemini-Orion-Taurus (GOT) field. These sources were observed with the European VLBI Network (EVN) at 5 GHz in phase-reference mode. The bright compact calibrator source J0603+2159 and seven other sources were detected and imaged at the angular resolution of -1.5-8 mas. Relative astrometric positions were derived for these sources at a milli-arcsecond accuracy level. The detection of the optical counterparts of these extragalactic radio sources will allow us to establish a direct link to the ICRF locally in the GOT field.

PE-46 The Design of the Lynx X-Ray Microcalorimeter

NASA Technical Reports Server (NTRS)

Bandler, Simon; Dipirro, Michael; Eckart, Megan; Sakai, Kazuhiro; Smith, Stephen; Yoon, Wonsik; Bennett, Douglas; Kotsubo, Vincent; Mates, Benjamin; Swetz, Daneil;

Digital Signal Processing for the Event Horizon Telescope

NASA Astrophysics Data System (ADS)

Weintroub, Jonathan

2015-08-01

A broad international collaboration is building the Event Horizon Telescope (EHT). The aim is to test Einstein’s theory of General Relativity in one of the very few places it could break down: the strong gravity regime right at the edge of a black hole. The EHT is an earth-size VLBI array operating at the shortest radio wavelengths, that has achieved unprecedented angular resolution of a few tens of μarcseconds. For nearby super massive black holes (SMBH) this size scale is comparable to the Schwarzschild Radius, and emission in the immediate neighborhood of the event horizon can be directly observed. We give an introduction to the science behind the CASPER-enabled EHT, and outline technical developments, with emphasis on the secret sauce of high speed signal processing.

NIKA2, a dual-band millimetre camera on the IRAM 30 m telescope to map the cold universe

NASA Astrophysics Data System (ADS)

Désert, F.-X.; Adam, R.; Ade, P.; André, P.; Aussel, H.; Beelen, A.; Benoît, A.; Bideaud, A.; Billot, N.; Bourrion, O.; Calvo, M.; Catalano, A.; Coiffard, G.; Comis, B.; Doyle, S.; Goupy, J.; Kramer, C.; Lagache, G.; Leclercq, S.; Lestrade, J.-F.; Macías-Pérez, J. F.; Maury, A.; Mauskopf, P.; Mayet, F.; Monfardini, A.; Pajot, F.; Pascale, E.; Perotto, L.; Pisano, G.; Ponthieu, N.; Revéret, V.; Ritacco, A.; Rodriguez, L.; Romero, C.; Roussel, H.; Ruppin, F.; Soler, J.; Schuster, K.; Sievers, A.; Triqueneaux, S.; Tucker, C.; Zylka, R.

2016-12-01

A consortium led by Institut Néel (Grenoble) has just finished installing a new powerful millimetre camera NIKA2 on the IRAM 30 m telescope. It has an instantaneous field-of-view of 6.5 arcminutes at both 1.2 and 2.0 mm with polarimetric capabilities at 1.2 mm. NIKA2 provides a near diffraction-limited angular resolution (resp. 12 and 18 arcseconds). The 3 detector arrays are made of more than 1000 KIDs each. KIDs are new superconducting devices emerging as an alternative to bolometers. The commissionning is ongoing in 2016 with a likely opening to the IRAM community in early 2017. NIKA2 is a very promising multi-purpose instrument which will enable many scientific discoveries in the coming decade.

Flight Programs and X-ray Optics Development at MSFC

NASA Technical Reports Server (NTRS)

Gubarev, M.; Ramsey, B.; O'Dell, S. L.; Elsner, R.; Kilaru, K.; Atkins, C.; Swartz, D.; Gaskin, J.; Weisskopf, Martin

2012-01-01

The X-ray astronomy group at the Marshall Space Flight Center is developing electroformed nickel/cobalt x-ray optics for suborbital and orbital experiments. Suborbital instruments include the Focusing X-ray Solar Imager (FOXSI) and Micro-X sounding rocket experiments and the HERO balloon payload. Our current orbital program is the fabrication of a series of mirror modules for the Astronomical Roentgen Telescope (ART) to be launched on board the Russian-German Spectrum Roentgen Gamma Mission (SRG.) The details and status of these various programs are presented. A second component of our work is the development of fabrication techniques and optical metrology to improve the angular resolution of thin shell optics to the arcsecond-level. The status of these x-ray optics technology developments is also presented.

FIR/THz Space Interferometry: Science Opportunities, Mission Concepts, and Technical Challenges

NASA Technical Reports Server (NTRS)

Leisawitz, David

2007-01-01

Sensitive far-IR imaging and spectroscopic measurements of astronomical objects on sub-arcsecond angular scales are essential to our understanding of star and planet formation, the formation and evolution of galaxies, and to the detection and characterization of extrasolar planets. Cold single-aperture telescopes in space, such as the Spitzer Space Telescope and the Herschel Space Observatory, are very sensitive, but they lack the necessary angular resolution by two or more orders of magnitude. Far-IR space interferometers will address this need in the coming decades. Several mission concepts have already been studied, including in the US the Space Infrared Interferometric Telescope (SPIRIT) and the more ambitious Submillimeter Probe of the Evolution of Cosmic Structure (SPECS). This talk will describe science goals and summarize alternative concepts for future FIR/THz space interferometry missions. Small arrays of sensitive, fast, direct detectors are a key enabling technology for SPIRIT and SPECS. I will describe the technology requirements for far-IR interferometry, including the detector requirements, and their derivation from the mission science goals and instrument concepts.

SuperHERO: Design of a New Hard X-Ray Focusing Telescope

NASA Technical Reports Server (NTRS)

Gaskin, Jessica; Elsner, Ronald; Ramsey, Brian; Wilson-Hodge, Colleen; Tennant, Allyn; Christe, Steven; Shih, Albert; Kiranmayee, Kilaru; Swartz, Douglas; Seller, Paul;

High Spatial Resolution Forecasting of Long-Term Monthly Precipitation and Mean Temperature Trends in Data Scarce Regions

NASA Astrophysics Data System (ADS)

Mosier, T. M.; Hill, D. F.; Sharp, K. V.

2013-12-01

High spatial resolution time-series data are critical for many hydrological and earth science studies. Multiple groups have developed historical and forecast datasets of high-resolution monthly time-series for regions of the world such as the United States (e.g. PRISM for hindcast data and MACA for long-term forecasts); however, analogous datasets have not been available for most data scarce regions. The current work fills this data need by producing and freely distributing hindcast and forecast time-series datasets of monthly precipitation and mean temperature for all global land surfaces, gridded at a 30 arc-second resolution. The hindcast data are constructed through a Delta downscaling method, using as inputs 0.5 degree monthly time-series and 30 arc-second climatology global weather datasets developed by Willmott & Matsuura and WorldClim, respectively. The forecast data are formulated using a similar downscaling method, but with an additional step to remove bias from the climate variable's probability distribution over each region of interest. The downscaling package is designed to be compatible with a number of general circulation models (GCM) (e.g. with GCMs developed for the IPCC AR4 report and CMIP5), and is presently implemented using time-series data from the NCAR CESM1 model in conjunction with 30 arc-second future decadal climatologies distributed by the Consultative Group on International Agricultural Research. The resulting downscaled datasets are 30 arc-second time-series forecasts of monthly precipitation and mean temperature available for all global land areas. As an example of these data, historical and forecast 30 arc-second monthly time-series from 1950 through 2070 are created and analyzed for the region encompassing Pakistan. For this case study, forecast datasets corresponding to the future representative concentration pathways 45 and 85 scenarios developed by the IPCC are presented and compared. This exercise highlights a range of potential meteorological trends for the Pakistan region and more broadly serves to demonstrate the utility of the presented 30 arc-second monthly precipitation and mean temperature datasets for use in data scarce regions.

Hydrologic Derivatives for Modeling and Analysis—A new global high-resolution database

USGS Publications Warehouse

Verdin, Kristine L.

2017-07-17

The U.S. Geological Survey has developed a new global high-resolution hydrologic derivative database. Loosely modeled on the HYDRO1k database, this new database, entitled Hydrologic Derivatives for Modeling and Analysis, provides comprehensive and consistent global coverage of topographically derived raster layers (digital elevation model data, flow direction, flow accumulation, slope, and compound topographic index) and vector layers (streams and catchment boundaries). The coverage of the data is global, and the underlying digital elevation model is a hybrid of three datasets: HydroSHEDS (Hydrological data and maps based on SHuttle Elevation Derivatives at multiple Scales), GMTED2010 (Global Multi-resolution Terrain Elevation Data 2010), and the SRTM (Shuttle Radar Topography Mission). For most of the globe south of 60°N., the raster resolution of the data is 3 arc-seconds, corresponding to the resolution of the SRTM. For the areas north of 60°N., the resolution is 7.5 arc-seconds (the highest resolution of the GMTED2010 dataset) except for Greenland, where the resolution is 30 arc-seconds. The streams and catchments are attributed with Pfafstetter codes, based on a hierarchical numbering system, that carry important topological information. This database is appropriate for use in continental-scale modeling efforts. The work described in this report was conducted by the U.S. Geological Survey in cooperation with the National Aeronautics and Space Administration Goddard Space Flight Center.

Fabricating High-Resolution X-Ray Collimators

NASA Technical Reports Server (NTRS)

Appleby, Michael; Atkinson, James E.; Fraser, Iain; Klinger, Jill

2008-01-01

A process and method for fabricating multi-grid, high-resolution rotating modulation collimators for arcsecond and sub-arcsecond x-ray and gamma-ray imaging involves photochemical machining and precision stack lamination. The special fixturing and etching techniques that have been developed are used for the fabrication of multiple high-resolution grids on a single array substrate. This technology has application in solar and astrophysics and in a number of medical imaging applications including mammography, computed tomography (CT), single photon emission computed tomography (SPECT), and gamma cameras used in nuclear medicine. This collimator improvement can also be used in non-destructive testing, hydrodynamic weapons testing, and microbeam radiation therapy.

Adaptive grazing incidence optics for the next generation of x-ray observatories

NASA Astrophysics Data System (ADS)

Lillie, C.; Pearson, D.; Plinta, A.; Metro, B.; Lintz, E.; Shropshire, D.; Danner, R.

2010-09-01

Advances in X-ray astronomy require high spatial resolution and large collecting area. Unfortunately, X-ray telescopes with grazing incidence mirrors require hundreds of concentric mirror pairs to obtain the necessary collecting area, and these mirrors must be thin shells packed tightly together... They must also be light enough to be placed in orbit with existing launch vehicles, and able to be fabricated by the thousands for an affordable cost. The current state of the art in X-ray observatories is represented by NASA's Chandra X-ray observatory with 0.5 arc-second resolution, but only 400 cm2 of collecting area, and by ESA's XMM-Newton observatory with 4,300 cm2 of collecting area but only 15 arc-second resolution. The joint NASA/ESA/JAXA International X-ray Observatory (IXO), with {15,000 cm2 of collecting area and 5 arc-second resolution which is currently in the early study phase, is pushing the limits of passive mirror technology. The Generation-X mission is one of the Advanced Strategic Mission Concepts that NASA is considering for development in the post-2020 period. As currently conceived, Gen-X would be a follow-on to IXO with a collecting area >= 50 m2, a 60-m focal length and 0.1 arc-second spatial resolution. Gen-X would be launched in {2030 with a heavy lift Launch Vehicle to an L2 orbit. Active figure control will be necessary to meet the challenging requirements of the Gen-X optics. In this paper we present our adaptive grazing incidence mirror design and the results from laboratory tests of a prototype mirror.

The National Map seamless digital elevation model specifications

USGS Publications Warehouse

Archuleta, Christy-Ann M.; Constance, Eric W.; Arundel, Samantha T.; Lowe, Amanda J.; Mantey, Kimberly S.; Phillips, Lori A.

2017-08-02

This specification documents the requirements and standards used to produce the seamless elevation layers for The National Map of the United States. Seamless elevation data are available for the conterminous United States, Hawaii, Alaska, and the U.S. territories, in three different resolutions—1/3-arc-second, 1-arc-second, and 2-arc-second. These specifications include requirements and standards information about source data requirements, spatial reference system, distribution tiling schemes, horizontal resolution, vertical accuracy, digital elevation model surface treatment, georeferencing, data source and tile dates, distribution and supporting file formats, void areas, metadata, spatial metadata, and quality assurance and control.

High Resolution Adjustable Mirror Control for X-ray Astronomy

NASA Astrophysics Data System (ADS)

Trolier-McKinstry, Susan

We propose to build and test thin film transistor control circuitry for a new highresolution adjustable X-ray mirror technology. This control circuitry will greatly simplify the wiring scheme to address individual actuator cells. The result will be a transformative improvement for the X-ray Surveyor mission concept: mathematical models, which fit the experimental data quite well, indicate that 0.5 arcsecond imaging is feasible through this technique utilizing thin slumped glass substrates with uncorrected angular resolution of order 5-10 arcseconds. In order to correct for figures errors in a telescope with several square meters of collecting area, millions of actuator cells must be set and held at specific voltages. It is clearly not feasible to do this via millions of wires, each one connected to an actuator. Instead, we propose to develop and test thin-film technology that operates on the same principle as megapixel computer screens. We will develop the technologies needed to build thin film piezoelectric actuators, controlled by thin film ZnO transistors, on flexible polyimide films, and to connect those films to the back surfaces of X-ray mirrors on thin glass substrates without deforming the surface. These technologies represent a promising avenue of the development of mirrors for the X-Ray Surveyor mission concept. Such a telescope will make possible detailed studies of a wide variety of astrophysical sources. One example is the Warm-Hot Intergalactic Medium (WHIM), which is thought to account for a large fraction of the normal matter in the universe but which has not been detected unambiguously to date. Another is the growth of supermassive black holes in the early universe. This proposal supports NASA's goals of technical advancement of technologies suitable for future missions, and training of graduate students.

The VLA Sky Survey (VLASS): Description and Science Goals

NASA Astrophysics Data System (ADS)

Lacy, Mark; Baum, Stefi Alison; Chandler, Claire J.; Chatterjee, Shami; Murphy, Eric J.; Myers, Steven T.; VLASS Survey Science Group

2016-01-01

The VLA Sky Survey (VLASS) will cover 80% of the sky to a target depth of 70muJy in the 2-4GHz S-band of the Karl G. Jansky Very Large Array. With a resolution of 2.5 arcseconds, it will deliver the highest angular resolution of any wide area radio survey. Each area of the survey will be observed in three epochs spaced by 32 months in order to investigate the transient radio source population over an unprecedented combination of depth and area, resulting in a uniquely powerful search for hidden explosions in the Universe. The survey will be carried out in full polarization, allowing the characterization of the magneto-ionic medium in AGN and intervening galaxies over a wide range of redshifts, and the study of Faraday rotating foregrounds such as ionized bubbles in the Milky Way. The high angular resolution will allow us to make unambiguous identifications of nearly 10 million radio sources, comprised of both extragalactic objects and more nearby radio sources in the Milky Way, through matching to wide area optical/IR surveys such as SDSS, PanSTARRS, DES, LSST, EUCLID, WFIRST and WISE. Integral to the VLASS plan is an Education and Public Outreach component that will seek to inform and educate both the scientific community and the general public about radio astronomy through the use of social media, citizen science and educational activities. We will discuss opportunities for community involvement in VLASS, including the development of Enhanced Data Products and Services that will greatly increase the scientific utility of the survey.

Toward Large-Area Sub-Arcsecond X-Ray Telescopes II

NASA Technical Reports Server (NTRS)

O'Dell, Stephen L.; Allured, Ryan; Ames, Andrew O.; Biskach, Michael P.; Broadway David M.; Bruni, Ricardo J.; Burrows, David; Cao, Jian; Chalifoux, Brandon D.; Chan, Kai-Wing;

The National Map - Elevation

USGS Publications Warehouse

Gesch, Dean; Evans, Gayla; Mauck, James; Hutchinson, John; Carswell, William J.

2009-01-01

The National Elevation Dataset (NED) is the primary elevation data product produced and distributed by the USGS. The NED provides seamless raster elevation data of the conterminous United States, Alaska, Hawaii, and the island territories. The NED is derived from diverse source data sets that are processed to a specification with a consistent resolution, coordinate system, elevation units, and horizontal and vertical datums. The NED is the logical result of the maturation of the long-standing USGS elevation program, which for many years concentrated on production of topographic map quadrangle-based digital elevation models. The NED serves as the elevation layer of The National Map, and provides basic elevation information for earth science studies and mapping applications in the United States. The NED is a multi-resolution dataset that is updated bimonthly to integrate newly available, improved elevation source data. NED data are available nationally at grid spacings of 1 arc-second (approximately 30 meters) for the conterminous United States, and at 1/3 and 1/9 arc-seconds (approximately 10 and 3 meters, respectively) for parts of the United States. Most of the NED for Alaska is available at 2-arc-second (about 60 meters) grid spacing, where only lower resolution source data exist. Part of Alaska is available at the 1/3-arc-second resolution, and plans are in development for a significant upgrade in elevation data coverage of the State over the next 5 years. Specifications for the NED include the following: *Coordinate system: Geographic (decimal degrees of latitude and longitude), *Horizontal datum: North American Datum of 1983 (NAD 83), *Vertical datum: North American Vertical Datum of 1988 (NAVD 88) over the conterminous United States and varies in other areas, and *Elevation units: Decimal meters.

The Generation-X X-ray Observatory Vision Mission and Technology Study

NASA Technical Reports Server (NTRS)

Figueroa-Feliciano, Enectali

2004-01-01

The new frontier in astrophysics is the study of the birth and evolution of the first stars, galaxies and black holes in the early Universe. X-ray astronomy opens a window into these objects by studying the emission from black holes, supernova explosions and the gamma-ray burst afterglows of massive stars. However, such objects are beyond the grasp of current or near-future observatories. X-ray imaging and spectroscopy of such distant objects will require an X-ray telescope with large collecting area and high angular resolution. Our team has conceived the Generation-X Vision Mission based on an X-ray observatory with 100 sq m collecting area at 1 keV (1000 times larger than Chandra) and 0.1 arcsecond angular resolution (several times better than Chandra and 50 times better than the Constellation-X resolution goal). Such an observatory would be capable of detecting the earliest black holes and galaxies in the Universe, and will also study extremes of density, gravity, magnetic fields, and kinetic energy which cannot be created in laboratories. NASA has selected the Generation-X mission for study under its Vision Mission Program. We describe the studies being performed to develop the mission concept and define candidate technologies and performance requirements for Generation-X. The baseline Generation-X mission involves four 8m diameter X-ray telescopes operating at Sun-Earth L2. We trade against an alternate concept of a single 26m diameter telescope with focal plane instruments on a separate spacecraft. A telescope of this size will require either robotic or human-assisted in-flight assembly. The required effective area implies that extremely lightweight grazing incidence X-ray optics must be developed. To achieve the required aerial density of at least 100 times lower than in Chandra, we will study 0.1mm thick mirrors which have active on-orbit figure control. We discuss the suite of required detectors, including a large FOV high angular resolution imager, a cryogenic imaging spectrometer and a grating spectrometer. We outline the development roadmap to confront the many technological challenges far implementing the Generation-X mission.

Sub-arcsecond imaging of Arp 299-A at 150 MHz with LOFAR: Evidence for a starburst-driven outflow

NASA Astrophysics Data System (ADS)

Ramírez-Olivencia, N.; Varenius, E.; Pérez-Torres, M.; Alberdi, A.; Pérez, E.; Alonso-Herrero, A.; Deller, A.; Herrero-Illana, R.; Moldón, J.; Barcos-Muñoz, L.; Martí-Vidal, I.

2018-03-01

We report on the first sub-arcsecond (0.44 × 0.41 arcsec2) angular resolution image at 150 MHz of the A-nucleus in the luminous infrared galaxy Arp 299, from International Low Frequency Array (LOFAR) Telescope observations. The most remarkable finding is that of an intriguing two-sided, filamentary structure emanating from the A-nucleus, which we interpret as an outflow that extends up to at least 14 arcsec from the A-nucleus in the N-S direction ( ≈5 kpc deprojected size) and accounts for almost 40% of the extended emission of the entire galaxy system. We also discuss HST/NICMOS [FeII] 1.64 μm and H2 2.12 μm images of Arp 299-A, which show similar features to those unveiled by our 150 MHz LOFAR observations, providing strong morphological support for the outflow scenario. Finally, we discuss unpublished Na I D spectra that confirm the outflow nature of this structure. From energetic arguments, we rule out the low-luminosity active galactic nucleus in Arp 299-A as a driver for the outflow. On the contrary, the powerful, compact starburst in the central regions of Arp 299-A provides plenty of mechanical energy to sustain an outflow, and we conclude that the intense supernova (SN) activity in the nuclear region of Arp 299-A is driving the observed outflow. We estimate that the starburst wind can support a mass-outflow rate in the range (11-63 M⊙ yr-1) at speeds of up to 370-890 km s-1, and is relatively young, with an estimated kinematic age of 3-7 Myr. Those results open an avenue to the use of low-frequency (150 MHz), sub-arcsecond imaging with LOFAR to detect outflows in the central regions of local luminous infrared galaxies.

Angular Momentum in Disk Wind Revealed in the Young Star MWC 349A

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Qizhou; Claus, Brian; Watson, Linda

Disk winds are thought to play a critical role in star birth. As winds extract excess angular momentum from accretion disks, matter in the disk can be transported inward to the star to fuel mass growth. However, observational evidence of wind carrying angular momentum has been very limited. We present Submillimeter Array (SMA) observations of the young star MWC 349A in the H26 α and H30 α recombination lines. The high signal-to-noise ratios made possible by the maser emission process allow us to constrain the relative astrometry of the maser spots to milli-arcsecond precision. Previous observations of the H30 αmore » line with the SMA and the Plateau de Bure interferometer (PdBI) showed that masers are distributed in the disk and wind. Our new high-resolution observations of the H26 α line reveal differences in spatial distribution from that of the H30 α line. H26 α line masers in the disk are excited in a thin annulus with a radius of about 25 au, while the H30 α line masers are formed in a slightly larger annulus with a radius of 30 au. This is consistent with expectations for maser excitation in the presence of an electron density variation of approximately R {sup −4}. In addition, the H30 α and H26 α line masers arise from different parts in the wind. This difference is also expected from maser theory. The wind component of both masers exhibits line-of-sight velocities that closely follow a Keplerian law. This result provides strong evidence that the disk wind extracts significant angular momentum, thereby facilitating mass accretion in the young star.« less

Hard-X-Ray/Soft-Gamma-Ray Imaging Sensor Assembly for Astronomy

NASA Technical Reports Server (NTRS)

Myers, Richard A.

2008-01-01

An improved sensor assembly has been developed for astronomical imaging at photon energies ranging from 1 to 100 keV. The assembly includes a thallium-doped cesium iodide scintillator divided into pixels and coupled to an array of high-gain avalanche photodiodes (APDs). Optionally, the array of APDs can be operated without the scintillator to detect photons at energies below 15 keV. The array of APDs is connected to compact electronic readout circuitry that includes, among other things, 64 independent channels for detection of photons in various energy ranges, up to a maximum energy of 100 keV, at a count rate up to 3 kHz. The readout signals are digitized and processed by imaging software that performs "on-the-fly" analysis. The sensor assembly has been integrated into an imaging spectrometer, along with a pair of coded apertures (Fresnel zone plates) that are used in conjunction with the pixel layout to implement a shadow-masking technique to obtain relatively high spatial resolution without having to use extremely small pixels. Angular resolutions of about 20 arc-seconds have been measured. Thus, for example, the imaging spectrometer can be used to (1) determine both the energy spectrum of a distant x-ray source and the angular deviation of the source from the nominal line of sight of an x-ray telescope in which the spectrometer is mounted or (2) study the spatial and temporal development of solar flares, repeating - ray bursters, and other phenomena that emit transient radiation in the hard-x-ray/soft- -ray region of the electromagnetic spectrum.

Development of double-sided silicon strip detectors for solar hard x-ray observation

NASA Astrophysics Data System (ADS)

Saito, Shinya; Ishikawa, Shin-Nosuke; Watanabe, Shin; Odaka, Hirokazu; Sugimoto, Soichiro; Fukuyama, Taro; Kokubun, Motohide; Takahashi, Tadayuki; Terada, Yukikatsu; Tajima, Hiroyasu; Tanaka, Takaaki; Krucker, Säm; Christe, Steven; McBride, Steve; Glesener, Lindsay

2010-07-01

The Focusing Optics X-ray Solar Imager (FOXSI) is a rocket experiment scheduled for January 2011 launch. FOXSI observes 5 - 15 keV hard X-ray emission from quiet-region solar flares in order to study the acceleration process of electrons and the mechanism of coronal heating. For observing faint hard X-ray emission, FOXSI uses focusing optics for the first time in solar hard X-ray observation, and attains 100 times higher sensitivity than RHESSI, which is the present solar hard X-ray observing satellite. Now our group is working on developments of both Double-sided Silicon Strip Detector (DSSD) and read-out analog ASIC "VATA451" used for FOXSI. Our DSSD has a very fine strip pitch of 75 μm, which has sufficient position resolution for FOXSI mirrors with angular resolution (FWHM) of 12 arcseconds. DSSD also has high spectral resolution and efficiency in the FOXSI's energy range of 5 - 15 keV, when it is read out by our 64-channel analog ASIC. In advance of the FOXSI launch, we have established and tested a setup of 75 μm pitch DSSD bonded with "VATA451" ASICs. We successfully read out from almost all the channels of the detector, and proved ability to make a shadow image of tungsten plate. We also confirmed that our DSSD has energy resolution (FWHM) of 0.5 keV, lower threshold of 5 keV, and position resolution less than 63 μm. These performance satisfy FOXSI's requirements.

Mission Study for Generation-X: A Large Area and High Angular Observatory to Study the Early Universe

NASA Technical Reports Server (NTRS)

Brissenden, Roger

2005-01-01

In this report we provide a summary of the technical progress achieved during the last year Generation-X Vision Mission Study. In addition, we provide a brief programmatic status. The Generation-X (Gen-X) Vision Mission Study investigates the science requirements, mission concepts and technology drivers for an X-ray telescope designed to study the new frontier of astrophysics: the birth and evolution of the first stars, galaxies and black holes in the early Universe. X-ray astronomy offers an opportunity to detect these via the activity of the black holes, and the supernova explosions and gamma-ray burst afterglows of the massive stars. However, such objects are beyond the grasp of current missions which are operating or even under development. Our team has conceived a Gen-X Vision Mission based on an X-ray observatory with 100 m2 collecting area at 1 keV (1000 times larger than Chandra) and 0.1 arcsecond angular resolution (several times better than Chandra and 50 times better than the Constellation-X resolution goal). Such a high energy observatory will be capable of detecting the earliest black holes and galaxies in the Universe, and will also study extremes of density, gravity, magnetic fields, and kinetic energy which cannot be created in laboratories. In our study we develop the mission concept and define candidate technologies and performance requirements for Gen-X. The baseline Gen-X mission involves four 8 m diameter X-ray telescopes operating at Sun-Earth L2. We trade against an alternate concept of a single 26 m diameter telescope with focal plane instruments on a separate spacecraft. A telescope of this size will require either robotic or human-assisted in-flight assembly. The required effective area implies that extremely lightweight grazing incidence X-ray optics must be developed. To achieve the required areal density of at least 100 times lower than for Chandra, we study 0.2 mm thick mirrors which have active on-orbit figure control. We also study the suite of required detectors, including a large FOV high angular resolution imager, a cryogenic imaging spectrometer and a reflection grating spectrometer.

Low-Energy Microfocus X-Ray Source for Enhanced Testing Capability in the Stray Light Facility

NASA Technical Reports Server (NTRS)

Gaskin, Jessica; O'Dell, Stephen; Kolodziejczak, Jeff

2015-01-01

Research toward high-resolution, soft x-ray optics (mirrors and gratings) necessary for the next generation large x-ray observatories requires x-ray testing using a low-energy x-ray source with fine angular size (<1 arcsecond). To accommodate this somewhat demanding requirement, NASA Marshall Space Flight Center (MSFC) has procured a custom, windowless low-energy microfocus (approximately 0.1 mm spot) x-ray source from TruFocus Corporation that mates directly to the Stray Light Facility (SLF). MSFC X-ray Astronomy team members are internationally recognized for their expertise in the development, fabrication, and testing of grazing-incidence optics for x-ray telescopes. One of the key MSFC facilities for testing novel x-ray instrumentation is the SLF. This facility is an approximately 100-m-long beam line equipped with multiple x-ray sources and detectors. This new source adds to the already robust compliment of instrumentation, allowing MSFC to support additional internal and community x-ray testing needs.

Sub-arcminute pointing from a balloonborne platform

NASA Astrophysics Data System (ADS)

Craig, William W.; McLean, Ryan; Hailey, Charles J.

1998-07-01

We describe the design and performance of the pointing and aspect reconstruction system on the Gamma-Ray Arcminute Telescope Imaging System. The payload consists of a 4m long gamma-ray telescope, capable of producing images of the gamma-ray sky at an angular resolution of 2 arcminutes. The telescope is operated at an altitude of 40km in azimuth/elevation pointing mode. Using a variety of sensor, including attitude GPS, fiber optic gyroscopes, star and sun trackers, the system is capable of pointing the gamma-ray payload to within an arc-minute from the balloon borne platform. The system is designed for long-term autonomous operation and performed to specification throughout a recent 36 hour flight from Alice Springs, Australia. A star tracker and pattern recognition software developed for the mission permit aspect reconstruction to better than 10 arcseconds. The narrow field star tracker system is capable of acquiring and identifying a star field without external input. We present flight data form all sensors and the resultant gamma-ray source localizations.

The Space Infrared Interferometric Telescope (SPIRIT): Recent Study Results and Plans

NASA Astrophysics Data System (ADS)

Leisawitz, David; SPIRIT Mission Study Team

2007-12-01

SPIRIT was recommended in the 2002 "Community Plan for Far-IR/Submillimeter Space Astronomy.” A structurally connected interferometer, SPIRIT provides sensitive sub-arcsecond angular resolution images and integral field spectroscopy in the 25 to 400 micron wavelength range. SPIRIT was designed to revolutionize our understanding of planetary system formation, reveal otherwise-undetectable planets through the disk perturbations they induce, spectroscopically probe the atmospheres of extrasolar giant planets in orbits typical of most of the planets in our solar system, and yield significant new insight into the processes associated with galaxy formation and development. This paper updates previously presented study results and describes future study plans. Our SPIRIT mission concept study proposal was peer reviewed and selected by NASA for support under the Origins Probe Mission Concept Study program. NASA's Goddard Space Flight Center and four industry partners - Ball Aerospace, Boeing, Lockheed-Martin, and Northrop-Grumman - contributed generously the study. The Origins Probe study results were reviewed by an Advisory Review Panel.

The SWIFT Gamma-Ray Burst X-Ray Telescope

NASA Technical Reports Server (NTRS)

Hill, J. E.; Burrows, D. N.; Nousek, J. A.; Wells, A.; Chincarini, G.; Abbey, A. F.; Angelini, L.; Beardmore, A.; Brauninger, H. W.; Chang, W.

2006-01-01

The Swift Gamma-Ray Burst Explorer is designed to make prompt multi-wavelength observations of Gamma-Ray Bursts and GRB afterglows. The X-ray Telescope enables Swift to determine GRB positions with a few arcseconds accuracy within 100 seconds of the burst onset. The XRT utilizes a mirror set built for JET-X and an XMM-Newton/ EPIC MOS CCD detector to provide a sensitive broad-band (0.2-10 keV) X-ray imager with an effective area of more than 120 sq cm at 1.5 keV, a field of view of 23.6 x 23.6 arcminutes, and an angular resolution of 18 arcseconds (HPD). The detection sensitivity is 2x10(exp 14) erg/sq cm/s in 10(exp 4) seconds. The instrument provides automated source detection and position reporting within 5 seconds of target acquisition. It can also measure the redshifts of GRBs with Iron line emission or other spectral features. The XRT operates in an auto-exposure mode, adjusting the CCD readout mode automatically to optimize the science return as the source intensity fades. The XRT measures spectra and lightcurves of the GRB afterglow beginning about a minute after the burst and follows each burst for days or weeks. We provide an overview of the X-ray Telescope scientific background from which the systems engineering requirements were derived, with specific emphasis on the design and qualification aspects from conception through to launch. We describe the impact on cleanliness and vacuum requirements for the instrument low energy response and to maintain the high sensitivity to the fading signal of the Gamma-ray Bursts.

Is the Young UY Auriga System a Triple?

NASA Astrophysics Data System (ADS)

Wittal, Matthew; Prato, Lisa A.; Schaefer, Gail; Ciardi, David R.; Thomas, Allen; Biddle, Lauren; Avilez, Ian; Muzzio, Ryan; Patience, Jennifer; Beichman, Charles

2017-01-01

In an effort to understand the nature of the young binary, UY Aur, we examined the variable behavior of the entire, unresolved 0.9 arcsecond system, as well as the behavior of the angularly resolved, individual A and B components. UY Aur is an approximately 2 Myr old, classical T Tauri in the Taurus-Auriga star forming region and is one of a handful of young systems to host a primordial circumbinary disk, as well as individual circumstellar disks. Using the the facility infrared, high-resolution NIRSPEC spectrograph behind the adaptive optics system at the 10-meter Keck II telescope, we observed a dramatic change in the spectra of UY Aur B between 2003 and 2010. We also identified flux variability in the individual components of 1—2 magnitudes, particularly in the secondary star, on the basis of historical photometry. Thermal dust and line emission observed with millimeter interferometry indicates complex dynamical behavior of the circumbinary and circumstellar dust and led Tang et al. (2014) to speculate that UY Aur B may itself be a binary. Our adaptive optics imaging with the Keck II telescope showed no evidence for a close companion to the B component, although the marked change in our spectra of this star suggest that it could be a spectroscopic binary. We are currently limited by the paucity of angularly resolved observations, both photometric and spectroscopic, hampering the interpretation of the data. High-cadence, angularly resolved spectroscopy and photometry will be required to confirm the potential higher-order multiplicity of this system. This research was supported in part by NSF grants AST-1461200 and AST-1313399.

Cosmic Infrared Background Fluctuations and Zodiacal Light

NASA Technical Reports Server (NTRS)

Arendt, Richard G.; Kashlinsky, A.; Moseley, S. H.; Mather, J.

2017-01-01

We performed a specific observational test to measure the effect that the zodiacal light can have on measurements of the spatial fluctuations of the near-IR (near-infrared)background. Previous estimates of possible fluctuations caused by zodiacal light have often been extrapolated from observations of the thermal emission at longer wavelengths and low angular resolution or from IRAC (Infrared Array Camera) observations of high-latitude fields where zodiacal light is faint and not strongly varying with time. The new observations analyzed here target the COSMOS (Cosmic Evolution Survey) field at low ecliptic latitude where the zodiacal light intensity varies by factors of approximately 2 over the range of solar elongations at which the field can be observed. We find that the white-noise component of the spatial power spectrum of the background is correlated with the modeled zodiacal light intensity. Roughly half of the measured white noise is correlated with the zodiacal light, but a more detailed interpretation of the white noise is hampered by systematic uncertainties that are evident in the zodiacal light model. At large angular scales (greater than or approximately equal to 100 arcseconds) where excess power above the white noise is observed, we find no correlation of the power with the modeled intensity of the zodiacal light. This test clearly indicates that the large-scale power in the infrared background is not being caused by the zodiacal light.

High Spectral Resolution, High Cadence, Imaging X-Ray Microcalorimeters for Solar Physics

NASA Technical Reports Server (NTRS)

Bandler, Simon R.; Bailey, Catherine N.; Bookbinder, Jay A.; DeLuca, Edward E.; Chervenak, Jay A.; Eckart, Megan E.; Finkbeiner, Fred M.; Kelley, Daniel P.; Kelley, Richard L.; Kilbourne, Caroline A.;

Arcsecond Resolution Mapping of Sulfur Dioxide Emission in the Circumstellar Envelope of VY Canis Majoris

NASA Astrophysics Data System (ADS)

Fu, Roger R.; Moullet, Arielle; Patel, Nimesh A.; Biersteker, John; Derose, Kimberly L.; Young, Kenneth H.

2012-02-01

We report Submillimeter Array observations of SO2 emission in the circumstellar envelope (CSE) of the red supergiant VY Canis Majoris, with an angular resolution of ≈1''. SO2 emission appears in three distinct outflow regions surrounding the central continuum peak emission that is spatially unresolved. No bipolar structure is noted in the sources. A fourth source of SO2 is identified as a spherical wind centered at the systemic velocity. We estimate the SO2 column density and rotational temperature assuming local thermal equilibrium (LTE) as well as perform non-LTE radiative transfer analysis using RADEX. Column densities of SO2 are found to be ~1016 cm-2 in the outflows and in the spherical wind. Comparison with existing maps of the two parent species OH and SO shows the SO2 distribution to be consistent with that of OH. The abundance ratio f_{SO_{2}}/f_{SO} is greater than unity for all radii larger than 3 × 1016 cm. SO2 is distributed in fragmented clumps compared to SO, PN, and SiS molecules. These observations lend support to specific models of circumstellar chemistry that predict f_{SO_{2}}/f_{SO}>1 and may suggest the role of localized effects such as shocks in the production of SO2 in the CSE.

VizieR Online Data Catalog: The PAWS catalogs of GMCs and islands in M51 (Colombo+, 2014)

NASA Astrophysics Data System (ADS)

Colombo, D.; Hughes, A.; Schinnerer, E.; Meidt, S. E.; Leroy, A. K.; Pety, J.; Dobbs, C. L.; Garcia-Burillo, S.; Dumas, G.; Thompson, T. A.; Schuster, K. F.; Kramer, C.

2016-08-01

The Plateau de Bure Interferometer (PdBI) Arcsecond Whirlpool Survey (PAWS; Schinnerer et al., 2013ApJ...779...42S) is a large IRAM program involving 210hr of observations with the Plateau de Bure Interferometer (PdBI) and IRAM 30m telescope to conduct a sensitive, high angular resolution (1.16''*0.97''), 12CO(1-0) survey of the inner disk of M51a (field-of-view, FoV ~270''*170''). The spatial resolution at our assumed distance to M51 of 7.6Mpc (Ciardullo et al. 2002, cat. J/ApJ/577/31) is ~40pc. The inclusion of the 30m single dish data during joint deconvolution ensures that flux information on all spatial scales is conserved. The rms of the noise fluctuations in the cube is ~0.4K per 5km/s channel. This sensitivity is sufficient to detect an object with a gas mass of 1.2*105M{Sun} at the 5σrms level. The PAWS data cube covers the LSR velocity range between 173 and 769km/s. A detailed description of the observing strategy, calibration and data reduction is presented by Pety et al. (2013ApJ...779...43P). (2 data files).

Active x-ray optics for high resolution space telescopes

NASA Astrophysics Data System (ADS)

Doel, Peter; Atkins, Carolyn; Brooks, D.; Feldman, Charlotte; Willingale, Richard; Button, Tim; Rodriguez Sanmartin, Daniel; Meggs, Carl; James, Ady; Willis, Graham; Smith, Andy

2017-11-01

The Smart X-ray Optics (SXO) Basic Technology project started in April 2006 and will end in October 2010. The aim is to develop new technologies in the field of X-ray focusing, in particular the application of active and adaptive optics. While very major advances have been made in active/adaptive astronomical optics for visible light, little was previously achieved for X-ray optics where the technological challenges differ because of the much shorter wavelengths involved. The field of X-ray astronomy has been characterized by the development and launch of ever larger observatories with the culmination in the European Space Agency's XMM-Newton and NASA's Chandra missions which are currently operational. XMM-Newton uses a multi-nested structure to provide modest angular resolution ( 10 arcsec) but large effective area, while Chandra sacrifices effective area to achieve the optical stability necessary to provide sub-arc second resolution. Currently the European Space Agency (ESA) is engaged in studies of the next generation of X-ray space observatories, with the aim of producing telescopes with increased sensitivity and resolution. To achieve these aims several telescopes have been proposed, for example ESA and NASA's combined International X-ray Observatory (IXO), aimed at spectroscopy, and NASA's Generation-X. In the field of X-ray astronomy sub 0.2 arcsecond resolution with high efficiency would be very exciting. Such resolution is unlikely to be achieved by anything other than an active system. The benefits of a such a high resolution would be important for a range of astrophysics subjects, for example the potential angular resolution offered by active X-ray optics could provide unprecedented structural imaging detail of the Solar Wind bowshock interaction of comets, planets and similar objects and auroral phenomena throughout the Solar system using an observing platform in low Earth orbit. A major aim of the SXO project was to investigate the production of thin actively controlled grazing incident optics for the next generation of X-ray space telescopes. Currently telescope systems are limited in the resolution and sensitivity by the optical quality of the thin shell optics used. As part of its research programme an actively controlled prototype X-ray thin shell telescope optic of dimensions 30x10cm has been developed to bench test the technology. The design is based on thin nickel shells bonded to shaped piezo-electric unimorph actuators made from lead zirconate titanate (PZT).

H II REGIONS, EMBEDDED PROTOSTARS, AND STARLESS CORES IN SHARPLESS 2-157

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Chian-Chou; Williams, Jonathan P.; Pandian, Jagadheep D., E-mail: ccchen@ifa.hawaii.edu, E-mail: jpw@ifa.hawaii.edu, E-mail: jagadheep@iist.ac.in

2012-06-20

We present arcsecond resolution 1.4 mm observations of the high-mass star-forming region, Sharpless 2-157, that reveal the cool dust associated with the first stages of star formation. These data are compared with archival images at optical, infrared, and radio wavelengths, and complemented with new arcsecond resolution mid-infrared data. We identify a dusty young H II region, numerous infrared sources within the cluster envelope, and four starless condensations. Three of the cores lie in a line to the south of the cluster peak, but the most massive one is right at the center and associated with a jumble of bright radiomore » and infrared sources. This presents an interesting juxtaposition of high- and low-mass star formation within the same cluster which we compare with similar observations of other high-mass star-forming regions and discuss in the context of cluster formation theory.« less

SHARPI: Solar High Angular Resolution Photometric Imager

NASA Technical Reports Server (NTRS)

Rabin, D.; Davila, J.; Content, D.; Keski-Kuha, R.; Oegerle, William (Technical Monitor)

2002-01-01

Observing the lower solar atmosphere with enough linear resolution (< 100 km) to study individual magnetic flux tubes and other features on scales comparable to the photon mean free path has proven to be a challenging and elusive goal. Space-borne instruments based on conventional heavy optics turned out to be too expensive, and adaptive optics on the ground made slow progress for many years. Nevertheless, the scientific case for high-resolution imaging and magnetography has only become more compelling over the last ten years. Today, ground-based adaptive optics is a promising approach for small fields of view at visible wavelengths. Space experiments will need to employ lightweight optics and low cost platforms. The Sunrise balloon experiment is one example. We describe a concept for a sounding rocket experiment that will achieve 0.1-arcsecond imaging using a lightweight, ultraprecise 55-cm mirror in the far ultraviolet (160 nm continuum, Lyman alpha, and possibly C IV 155 nm). The f/1.2 parabolic primary mirror is entering the final stages of production. The mirror is a ULE honeycomb design with front and back face sheets. The front sheet will be figured to 6.3 nm rms with microroughness 1 nm or better. For the initial proof of concept, we describe a no-frills, high-cadence imager aboard a Black Brant sounding rocket. Development of lightweight UV/EUV optics at Goddard Space Flight Center has been supported by the Internal Research and Development program.

A challenge for probing the statistics of interstellar magnetic fields: beyond the Planck resolution with Herschel

NASA Astrophysics Data System (ADS)

Bracco, Andrea; André, Philippe; Boulanger, Francois

2015-08-01

The recent Planck results in polarization at sub-mm wavelengths allow us to gain insight into the Galactic magnetic field topology, revealing its statistical correlation with matter, from the diffuse interstellar medium (ISM), to molecular clouds (MCs) (Planck intermediate results. XXXII, XXXIII, XXXV). This correlation has a lot to tell us about the dynamics of the turbulent ISM, stressing the importance of considering magnetic fields in the formation of structures, some of which eventually undergo gravitational collapse producing new star-forming cores.Investigating the early phases of star formation has been a fundamental scope of the Herschel Gould Belt survey collaboration (http://gouldbelt-herschel.cea.fr), which, in the last years, has thoroughly characterized, at a resolution of few tens of arcseconds, the statistics of MCs, such as their filamentary structure, kinematics and column density.Although at lower angular resolution, the Planck maps of dust emission at 353GHz, in intensity and polarization, show that all MCs are complex environments, where we observe a non-trivial correlation between the magnetic field and their density structure. This result opens new perspectives on their formation and evolution, which we have started to explore.In this talk, I will present first results of a comparative analysis of the Herschel-Planck data, where we combine the high resolution Herschel maps of some MCs of the Gould Belt with the Planck polarization data, which sample the structure of the field weighted by the density.In particular, I will discuss the large-scale envelopes of the selected MCs, and, given the correlation between magnetic field and matter, I will show how to make use of the high resolution information of the density structure provided by Herschel to investigate the statistics of interstellar magnetic fields in the Planck data.

Development of a global slope dataset for estimation of landslide occurrence resulting from earthquakes

USGS Publications Warehouse

Verdin, Kristine L.; Godt, Jonathan W.; Funk, Christopher C.; Pedreros, Diego; Worstell, Bruce; Verdin, James

2007-01-01

Landslides resulting from earthquakes can cause widespread loss of life and damage to critical infrastructure. The U.S. Geological Survey (USGS) has developed an alarm system, PAGER (Prompt Assessment of Global Earthquakes for Response), that aims to provide timely information to emergency relief organizations on the impact of earthquakes. Landslides are responsible for many of the damaging effects following large earthquakes in mountainous regions, and thus data defining the topographic relief and slope are critical to the PAGER system. A new global topographic dataset was developed to aid in rapidly estimating landslide potential following large earthquakes. We used the remotely-sensed elevation data collected as part of the Shuttle Radar Topography Mission (SRTM) to generate a slope dataset with nearly global coverage. Slopes from the SRTM data, computed at 3-arc-second resolution, were summarized at 30-arc-second resolution, along with statistics developed to describe the distribution of slope within each 30-arc-second pixel. Because there are many small areas lacking SRTM data and the northern limit of the SRTM mission was lat 60?N., statistical methods referencing other elevation data were used to fill the voids within the dataset and to extrapolate the data north of 60?. The dataset will be used in the PAGER system to rapidly assess the susceptibility of areas to landsliding following large earthquakes.

Formation Control for the Maxim Mission.

NASA Technical Reports Server (NTRS)

Luquette, Richard J.; Leitner, Jesse; Gendreau, Keith; Sanner, Robert M.

2004-01-01

Over the next twenty years, a wave of change is occurring in the spacebased scientific remote sensing community. While the fundamental limits in the spatial and angular resolution achievable in spacecraft have been reached, based on today's technology, an expansive new technology base has appeared over the past decade in the area of Distributed Space Systems (DSS). A key subset of the DSS technology area is that which covers precision formation flying of space vehicles. Through precision formation flying, the baselines, previously defined by the largest monolithic structure which could fit in the largest launch vehicle fairing, are now virtually unlimited. Several missions including the Micro-Arcsecond X-ray Imaging Mission (MAXIM), and the Stellar Imager will drive the formation flying challenges to achieve unprecedented baselines for high resolution, extended-scene, interferometry in the ultraviolet and X-ray regimes. This paper focuses on establishing the feasibility for the formation control of the MAXIM mission. The Stellar Imager mission requirements are on the same order of those for MAXIM. This paper specifically addresses: (1) high-level science requirements for these missions and how they evolve into engineering requirements; (2) the formation control architecture devised for such missions; (3) the design of the formation control laws to maintain very high precision relative positions; and (4) the levels of fuel usage required in the duration of these missions. Specific preliminary results are presented for two spacecraft within the MAXIM mission.

Formation Control for the MAXIM Mission

NASA Technical Reports Server (NTRS)

Luquette, Richard J.; Leitner, Jesse; Gendreau, Keith; Sanner, Robert M.

2004-01-01

Over the next twenty years, a wave of change is occurring in the space-based scientific remote sensing community. While the fundamental limits in the spatial and angular resolution achievable in spacecraft have been reached, based on today s technology, an expansive new technology base has appeared over the past decade in the area of Distributed Space Systems (DSS). A key subset of the DSS technology area is that which covers precision formation flying of space vehicles. Through precision formation flying, the baselines, previously defined by the largest monolithic structure which could fit in the largest launch vehicle fairing, are now virtually unlimited. Several missions including the Micro-Arcsecond X-ray Imaging Mission (MAXIM), and the Stellar Imager will drive the formation flying challenges to achieve unprecedented baselines for high resolution, extended-scene, interferometry in the ultraviolet and X-ray regimes. This paper focuses on establishing the feasibility for the formation control of the MAXIM mission. MAXIM formation flying requirements are on the order of microns, while Stellar Imager mission requirements are on the order of nanometers. This paper specifically addresses: (1) high-level science requirements for these missions and how they evolve into engineering requirements; and (2) the development of linearized equations of relative motion for a formation operating in an n-body gravitational field. Linearized equations of motion provide the ground work for linear formation control designs.

Medium and Small Aperture Speckle Interferometry for Geostationary On-Orbit-Servicing Space Surveillance

NASA Astrophysics Data System (ADS)

Scott, R.

On-Orbit-Servicing (OOS) in Geostationary Equatorial Orbit (GEO) is likely to become a space mission reality provoking new problems for the optical space surveillance community. OOS’ close-proximity flight of servicer and client satellites with separations less than 1 kilometer in GEO challenge the metric measurement capabilities of medium and small aperture space surveillance instruments. This paper describes an OOS monitoring technique based on Cross-Spectrum speckle interferometry to compensate for atmospheric turbulence and measure the OOS satellites’ differential relative position. Cross-Spectrum speckle interferometry, an astronomical technique developed to measure the astrometric positions of binary stars, was adapted to the geostationary OOS problem and was tested using Sloan i’ observations of co-located geostationary satellites. Medium (1.6m) and small (0.35m) aperture telescopes were used to observe these satellites undergoing optical conjunctions where their apparent line-of-sight separation narrowed within 5 arcseconds. During the initial development of the Cross-Spectrum approach some weaknesses were identified where particle strikes, faint background stars, anomalous fringe orientation angles and high relative angular rates corrupt the relative position measurement process. In this paper, newly adjusted compensation techniques to remedy these issues are described and the data is reprocessed. The Cross-Spectrum’s performance is shown to work well on closely-spaced GEO satellites with separations less than 3 arcseconds and evidence is shown suggesting the technique can measure satellite separations within 1.8 arcseconds.

Accurate free and forced rotational motions of rigid Venus

NASA Astrophysics Data System (ADS)

Cottereau, L.; Souchay, J.; Aljbaae, S.

2010-06-01

Context. The precise and accurate modelling of a terrestrial planet like Venus is an exciting and challenging topic, all the more interesting because it can be compared with that of Earth for which such a modelling has already been achieved at the milli-arcsecond level. Aims: We aim to complete a previous study, by determining the polhody at the milli-arcsecond level, i.e. the torque-free motion of the angular momentum axis of a rigid Venus in a body-fixed frame, as well as the nutation of its third axis of figure in space, which is fundamental from an observational point of view. Methods: We use the same theoretical framework as Kinoshita (1977, Celest. Mech., 15, 277) did to determine the precession-nutation motion of a rigid Earth. It is based on a representation of the rotation of a rigid Venus, with the help of Andoyer variables and a set of canonical equations in Hamiltonian formalism. Results: In a first part we computed the polhody, we showed that this motion is highly elliptical, with a very long period of 525 cy compared with 430 d for the Earth. This is due to the very small dynamical flattening of Venus in comparison with our planet. In a second part we precisely computed the Oppolzer terms, which allow us to represent the motion in space of the third Venus figure axis with respect to the Venus angular momentum axis under the influence of the solar gravitational torque. We determined the corresponding tables of the nutation coefficients of the third figure axis both in longitude and in obliquity due to the Sun, which are of the same order of amplitude as for the Earth. We showed that the nutation coefficients for the third figure axis are significantly different from those of the angular momentum axis on the contrary of the Earth. Our analytical results have been validated by a numerical integration, which revealed the indirect planetary effects.

Supernova Remnant Observations with Micro-X

NASA Astrophysics Data System (ADS)

Figueroa, Enectali

Micro-X is a sounding rocket payload that combines an X-ray microcalorimeter with an imaging mirror to offer breakthrough science from high spectral resolution observations of extended X-ray sources. This payload has been in design and development for the last five years and is now completely built and undergoing integration; its first flight will be in November, 2012, as part of our current NASA award. This four-year follow-on proposal seeks funding for: (1) analysis of the first flight data, (2) the second flight and its data analysis, (3) development of payload upgrades and launch of the third flight, and (4) third flight data analysis. The scientific payload consists of a Transition Edge Sensor (TES) microcalorimeter array at the focus of a flight-proven conical imaging mirror. Micro-X capitalizes on three decades of NASA investment in the development of microcalorimeters and X-ray imaging optics. Micro-X offers a unique combination of bandpass, collecting area, and spectral and angular resolution. The spectral resolution goal across the 0.2 - 3.0 keV band is 2 - 4 eV Full-Width at Half Maximum (FWHM). The measured angular resolution of the mirror is 2.4 arcminute Half-Power Diameter (HPD). The effective area of the mirror, 300 square centimeters at 1 keV, is sufficient to provide observations of unprecedented quality of several astrophysical X-ray sources, even in a brief sounding rocket exposure of 300 sec. Our scientific program for this proposal will focus on supernova remnants (SNRs), whose spatial extent has made high-energy resolution observations with grating instruments extremely challenging. X-ray observations of SNRs with microcalorimeters will enable the study of the detailed atomic physics of the plasma; the determination of temperature, turbulence, and elemental abundances; and in conjunction with historical data, full three dimensional mapping of the kinematics of the remnant. These capabilities will open new avenues towards understanding the explosion mechanisms of supernovae and their roles in energy and heavy-element injection into galaxies, their evolution into SNRs, their interactions with their environments, and finally their roles as particle accelerators. For the first flight, we will observe an ejecta region in the Puppis A SNR. The Puppis A bright eastern knot (BEK), is the target of second flight in 2014. The third flight, in late 2015 or early 2016, will make an observation of the Cas A SNR. We will continue to advance the technology readiness of TES microcalorimeters while enhancing the science capability of the payload by implementing a series of improvements for the third flight. For the observation of Cas A in the third flight, we will upgrade from the 128-pixel array with 1 arcminute pixels used in the first two flights to a higher-energy resolution (1 eV FWHM) 256-pixel array with 20 arcsecond pixels and a new 30 arcsecond HPD mirror to enable improved imaging spectroscopy with our payload. The Micro-X team includes leaders in the development of microcalorimeters, SQUID readout systems, and segmented and full-shell grazing incidence X-ray optics, as well as highly experienced sounding rocket instrument developers, and scientific experts on supernova remnants. These investigators are located at institutions with strong space instrumentation traditions with the infrastructure to ensure a successful flight program. With Micro-X, we have designed a versatile payload capable of providing high-resolution science and a testbed for new technology. The first flight this year will make significant scientific contributions well ahead of the Astro-H mission. The program will also aid in the understanding and development of future flight-qualified microcalorimeter systems for larger orbiting missions. Finally, it will continue to attract talented young scientists to X-ray astrophysics and thus serve as a direct pipeline of future leaders of NASA missions.

Construction of a 3-arcsecond digital elevation model for the Gulf of Maine

USGS Publications Warehouse

Twomey, Erin R.; Signell, Richard P.

2013-01-01

A system-wide description of the seafloor topography is a basic requirement for most coastal oceanographic studies. The necessary detail of the topography obviously varies with application, but for many uses, a nominal resolution of roughly 100 m is sufficient. Creating a digital bathymetric grid with this level of resolution can be a complex procedure due to a multiplicity of data sources, data coverages, datums and interpolation procedures. This report documents the procedures used to construct a 3-arcsecond (approximately 90-meter grid cell size) digital elevation model for the Gulf of Maine (71°30' to 63° W, 39°30' to 46° N). We obtained elevation and bathymetric data from a variety of American and Canadian sources, converted all data to the North American Datum of 1983 for horizontal coordinates and the North American Vertical Datum of 1988 for vertical coordinates, used a combination of automatic and manual techniques for quality control, and interpolated gaps using a surface-fitting routine.

MULTI-WAVELENGTH POLARIMETRY AND SPECTRAL STUDY OF THE M87 JET DURING 2002–2008

DOE Office of Scientific and Technical Information (OSTI.GOV)

Avachat, Sayali S.; Perlman, Eric S.; Adams, Steven C.

We present a multi-wavelength polarimetric and spectral study of the M87 jet obtained at sub-arcsecond resolution between 2002 and 2008. The observations include multi-band archival VLA polarimetry data sets along with Hubble Space Telescope ( HST ) imaging polarimetry. These observations have better angular resolution than previous work by factors of 2–3 and in addition, allow us to explore the time domain. These observations envelop the huge flare in HST-1 located 0.″86 from the nucleus. The increased resolution enables us to view more structure in each knot, showing several resolved sub-components. We also see apparent helical structure in the polarizationmore » vectors in several knots, with polarization vectors turning either clockwise or counterclockwise near the flux maxima in various places as well as showing filamentary undulations. Some of these characteristics are correlated with flux and polarization maxima while others are not. We also examine the total flux and fractional polarization and look for changes in both radio and optical since the observations of Perlman et al. (1999) and test them against various models based on shocks and instabilities in the jet. Our results are broadly consistent with previous spine-sheath models and recollimation shock models; however, they require additional combinations of features to explain the observed complexity, e.g., shearing of magnetic field lines near the jet surface and compression of the toroidal component near shocks. In particular, in many regions we find apparently helical features both in total flux and polarization. We discuss the physical interpretation of these features.« less

Kuiper Airborne Observatory's Telescope Stabilization System: Disturbance Sensitivity Reduction Via Velocity Loop Feedback

NASA Technical Reports Server (NTRS)

Lawrence, David P.; Tsui, K. C.; Tucker, John; Mancini, Ronald E. (Technical Monitor)

1995-01-01

In July of 1994 the Kuiper Airborne Observatory's (KAO) Telescope Stabilization System (TSS) was upgraded to meet performance goals necessary to view the Shoemaker-Levy 9 comet collision with Jupiter. The KAO is a modified C-141 Aircraft supporting a 36 inch Infrared telescope used to gather and analyze astronomical data. Before the upgrade, the TSS exhibited approximately a 10 arc-second resolution pointing accuracy. The majority of the inaccuracy was attributable to aircraft vibration and wind buffeting entering through the aircraft's telescope door opening; in other words, the TSS was overly sensitive to external disturbances. Because of power limitations and noise requirements, improving the pointing accuracy of the telescope required more sophistication than simply raising the bandwidth as some classical control strategies might suggest. Instead, relationships were developed between the disturbance sensitivity and closed loop transfer functions. These relationships suggested that employing velocity feedback along with an increase in current loop gain would dramatically improve the pointing resolution of the TSS by decreasing the control system's sensitivity to external disturbances. With the implementation of some classical control techniques and the above philosophy, the KAO's TSS's resolution was improved to approximately 2-3 arc-seconds.

The Stellar Imager (SI) project: a deep space UV/Optical Interferometer (UVOI) to observe the Universe at 0.1 milli-arcsec angular resolution

NASA Astrophysics Data System (ADS)

Carpenter, Kenneth G.; Schrijver, Carolus J.; Karovska, Margarita

2009-04-01

The Stellar Imager (SI) is a space-based, UV/Optical Interferometer (UVOI) designed to enable 0.1 milli-arcsecond (mas) spectral imaging of stellar surfaces and of the Universe in general. It will also probe via asteroseismology flows and structures in stellar interiors. SI’s science focuses on the role of magnetism in the Universe and will revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magneto-hydrodynamically controlled processes, such as accretion, in the Universe. The ultra-sharp images of SI will revolutionize our view of many dynamic astrophysical processes by transforming point sources into extended sources, and snapshots into evolving views. SI is a “Flagship and Landmark Discovery Mission” in the 2005 Heliophysics Roadmap and a potential implementation of the UVOI in the 2006 Science Program for NASA’s Astronomy and Physics Division. We present here the science goals of the SI Mission, a mission architecture that could meet those goals, and the technology development needed to enable this mission. Additional information on SI can be found at: http://hires.gsfc.nasa.gov/si/

The COSPIX Mission: Focusing on the Energetic and Obscured Universe

NASA Technical Reports Server (NTRS)

Ferrando, P.; Goldwurm, A.; Laurent, P.; Limousin, O.; Beckmann, V; Arnaud, M.; Barcons, X.; Bomans, D.; Caballero, I.; Carrera, F.;

Ultraviolet Imaging Telescope (UIT) observations of galaxies

NASA Technical Reports Server (NTRS)

Neff, S. G.

1993-01-01

Ultraviolet images of several galaxies were obtained during the ASTRO-1 shuttle mission in December, 1990. The images have a FWHM angular resolution of approximately 3 arcsecond and are of circular fields approximately 40 arcminutes in diameter. Most galaxies were observed in at least two and sometimes as many as four broad bands. A very few fields were observed with narrower band filters. The most basic result of these observations is that most systems look dramatically different in the UV from their well-known optical appearances. Preliminary results of these studies will be presented. Information will be available on fields observed by the UTI during the ASTRO 1 mission; when that data becomes public it can be obtained from the NSSDC. The ASTRO observatory is expected to fly again in 1994 with approximately half of the observing time from that mission devoted to guest observers. The Ultraviolet Imaging telescope is extremely well suited for galaxy studies, and the UIT term is interested in encouraging a wide range of scientific studies by guest observers. Ultraviolet Imaging telescope is extremely well suited for galaxy studies, and the UIT team is interested in encouraging a wide range of scientific studies by guest observers.

PROSPECTS FOR MEASURING THE MASS OF BLACK HOLES AT HIGH REDSHIFTS WITH RESOLVED KINEMATICS USING GRAVITATIONAL LENSING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hezaveh, Yashar D.

2014-08-20

Application of the most robust method of measuring black hole masses, spatially resolved kinematics of gas and stars, is presently limited to nearby galaxies. The Atacama Large Millimeter/sub-millimeter Array (ALMA) and 30m class telescopes (the Thirty Meter Telescope, the Giant Magellan Telescope, and the European Extremely Large Telescope) with milli-arcsecond resolution are expected to extend such measurements to larger distances. Here, we study the possibility of exploiting the angular magnification provided by strong gravitational lensing to measure black hole masses at high redshifts (z ∼ 1-6), using resolved gas kinematics with these instruments. We show that in ∼15% and ∼20%more » of strongly lensed galaxies, the inner 25 and 50 pc could be resolved, allowing the mass of ≳ 10{sup 8} M {sub ☉} black holes to be dynamically measured with ALMA, if moderately bright molecular gas is present at these small radii. Given the large number of strong lenses discovered in current millimeter surveys and future optical surveys, this fraction could constitute a statistically significant population for studying the evolution of the M-σ relation at high redshifts.« less

Hubble Space Telescope: Faint object camera instrument handbook. Version 2.0

NASA Technical Reports Server (NTRS)

Paresce, Francesco (Editor)

1990-01-01

The Faint Object Camera (FOC) is a long focal ratio, photon counting device designed to take high resolution two dimensional images of areas of the sky up to 44 by 44 arcseconds squared in size, with pixel dimensions as small as 0.0007 by 0.0007 arcseconds squared in the 1150 to 6500 A wavelength range. The basic aim of the handbook is to make relevant information about the FOC available to a wide range of astronomers, many of whom may wish to apply for HST observing time. The FOC, as presently configured, is briefly described, and some basic performance parameters are summarized. Also included are detailed performance parameters and instructions on how to derive approximate FOC exposure times for the proposed targets.

Stellar Imager

NASA Technical Reports Server (NTRS)

Carpenter, Kenneth

2007-01-01

The Stellar Imager (SI) is one of NASA's "Vision Missions" - concepts for future, space-based, strategic missions that could enormously increase our capabilities for observing the Cosmos. SI is designed as a UV/Optical Interferometer which will enable 0.1 milli-arcsecond (mas) spectral imaging of stellar surfaces and, via asteroseismology, stellar interiors and of the Universe in general. The ultra-sharp images of the Stellar Imager will revolutionize our view of many dynamic astrophysical processes by transforming point sources into extended sources, and snapshots into evolving views. SI, with a characteristic angular resolution of 0.1 milli-arcseconds at 2000 Angstroms, represents an advance in image detail of several hundred times over that provided by the Hubble Space Telescope. The Stellar Imager will zoom in on what today-with few exceptions - we only know as point sources, revealing processes never before seen, thus providing a tool as fundamental to astrophysics as the microscope is to the study of life on Earth. SI's science focuses on the role of magnetism in the Universe, particularly on magnetic activity on the surfaces of stars like the Sun. It's prime goal is to enable long-term forecasting of solar activity and the space weather that it drives, in support of the Living With a Star program in the Exploration Era. SI will also revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magneto-hydrodynamically controlled processes in the Universe. Stellar Imager is included as a "Flagship and Landmark Discovery Mission" in the 2005 Sun Solar System Connection (SSSC) Roadmap and as a candidate for a "Pathways to Life Observatory" in the Exploration of the Universe Division (EUD) Roadmap (May, 2005) and as such is a candidate mission for the 2025-2030 timeframe. An artist's drawing of the current "baseline" concept for SI is presented.

Perspective View with Landsat Overlay, San Francisco Bay Area, Calif.

NASA Technical Reports Server (NTRS)

2002-01-01

The defining landmarks of San Francisco, its bay and the San Andreas Fault are clearly seen in this computer-generated perspective viewed from the south. Running from the bottom of the scene diagonally up to the left, the trough of the San Andreas Fault is occupied by Crystal Springs Reservoir and San Andreas Lake. Interstate 280 winds along the side of the fault. San Francisco International Airport is the angular feature projecting into the bay just below San Bruno Mountain, the elongated ridge cutting across the peninsula. The hills of San Francisco can be seen beyond San Bruno Mountain and beyond the city, the Golden Gate.

This 3-D perspective view was generated using topographic data from the Shuttle Radar Topography Mission (SRTM) and an enhanced color Landsat 5satellite image. Topographic expression is exaggerated two times.

Landsat has been providing visible and infrared views of the Earth since 1972. SRTM elevation data matches the 30-meter (98-foot) resolution of most Landsat images and will substantially help in analyzing the large and growing Landsat image archive.

Elevation data used in this image was acquired by the Shuttle Radar Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched on Feb. 11,2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect 3-D measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter (approximately 200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between NASA, the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Earth Science Enterprise, Washington, D.C.

Size: scale varies in this perspective image Location: 37.5 deg. North lat., 122.3 deg. West lon. Orientation: looking north Image Data: Landsat Bands 3,2,1 as red, green, blue, respectively Original Data Resolution: SRTM 1 arcsecond (30 meters or 98 feet), Thematic Mapper 1 arcsecond (30 meters or 98 feet) Date Acquired: February 2000 (SRTM)

Global DEM Errors Underpredict Coastal Vulnerability to Sea Level Rise and Flooding

NASA Astrophysics Data System (ADS)

Kulp, Scott; Strauss, Benjamin

2016-04-01

Elevation data based on NASA's Shuttle Radar Topography Mission (SRTM) have been widely used to evaluate threats from global sea level rise, storm surge, and coastal floods. However, SRTM data are known to include large vertical errors in densely urban or densely vegetated areas. The errors may propagate to derived land and population exposure assessments. We compare assessments based on SRTM data against references employing high-accuracy bare-earth elevation data generated from lidar data available for coastal areas of the United States. We find that both 1-arcsecond and 3-arcsecond horizontal resolution SRTM data systemically underestimate exposure across all assessed spatial scales and up to at least 10m above the high tide line. At 3m, 1-arcsecond SRTM underestimates U.S. population exposure by more than 60%, and under-predicts population exposure in 90% of coastal states, 87% of counties, and 83% of municipalities. These fractions increase with elevation, but error medians and variability fall to lower levels, with national exposure underestimated by just 24% at 10m. Results using 3-arcsecond SRTM are extremely similar. Coastal analyses based on SRTM data thus appear to greatly underestimate sea level and flood threats, especially at lower elevations. However, SRTM-based estimates may usefully be regarded as providing lower bounds to actual threats. We additionally assess the performance of NOAA's Global Land One-km Base Elevation Project (GLOBE), another publicly-available global DEM, but do not reach any definitive conclusion because of the spatial heterogeneity in its quality.

Detecting Multi-scale Structures in Chandra Images of Centaurus A

NASA Astrophysics Data System (ADS)

Karovska, M.; Fabbiano, G.; Elvis, M. S.; Evans, I. N.; Kim, D. W.; Prestwich, A. H.; Schwartz, D. A.; Murray, S. S.; Forman, W.; Jones, C.; Kraft, R. P.; Isobe, T.; Cui, W.; Schreier, E. J.

1999-12-01

Centaurus A (NGC 5128) is a giant early-type galaxy with a merger history, containing the nearest radio-bright AGN. Recent Chandra High Resolution Camera (HRC) observations of Cen A reveal X-ray multi-scale structures in this object with unprecedented detail and clarity. We show the results of an analysis of the Chandra data with smoothing and edge enhancement techniques that allow us to enhance and quantify the multi-scale structures present in the HRC images. These techniques include an adaptive smoothing algorithm (Ebeling et al 1999), and a multi-directional gradient detection algorithm (Karovska et al 1994). The Ebeling et al adaptive smoothing algorithm, which is incorporated in the CXC analysis s/w package, is a powerful tool for smoothing images containing complex structures at various spatial scales. The adaptively smoothed images of Centaurus A show simultaneously the high-angular resolution bright structures at scales as small as an arcsecond and the extended faint structures as large as several arc minutes. The large scale structures suggest complex symmetry, including a component possibly associated with the inner radio lobes (as suggested by the ROSAT HRI data, Dobereiner et al 1996), and a separate component with an orthogonal symmetry that may be associated with the galaxy as a whole. The dust lane and the x-ray ridges are very clearly visible. The adaptively smoothed images and the edge-enhanced images also suggest several filamentary features including a large filament-like structure extending as far as about 5 arcminutes to North-West.

Precise Alignment and Permanent Mounting of Thin and Lightweight X-ray Segments

NASA Technical Reports Server (NTRS)

Biskach, Michael P.; Chan, Kai-Wing; Hong, Melinda N.; Mazzarella, James R.; McClelland, Ryan S.; Norman, Michael J.; Saha, Timo T.; Zhang, William W.

2012-01-01

To provide observations to support current research efforts in high energy astrophysics. future X-ray telescope designs must provide matching or better angular resolution while significantly increasing the total collecting area. In such a design the permanent mounting of thin and lightweight segments is critical to the overall performance of the complete X-ray optic assembly. The thin and lightweight segments used in the assemhly of the modules are desigued to maintain and/or exceed the resolution of existing X-ray telescopes while providing a substantial increase in collecting area. Such thin and delicate X-ray segments are easily distorted and yet must be aligned to the arcsecond level and retain accurate alignment for many years. The Next Generation X-ray Optic (NGXO) group at NASA Goddard Space Flight Center has designed, assembled. and implemented new hardware and procedures mth the short term goal of aligning three pairs of X-ray segments in a technology demonstration module while maintaining 10 arcsec alignment through environmental testing as part of the eventual design and construction of a full sized module capable of housing hundreds of X-ray segments. The recent attempts at multiple segment pair alignment and permanent mounting is described along with an overview of the procedure used. A look into what the next year mll bring for the alignment and permanent segment mounting effort illustrates some of the challenges left to overcome before an attempt to populate a full sized module can begin.

Characterization of ASTER GDEM Elevation Data over Vegetated Area Compared with Lidar Data

NASA Technical Reports Server (NTRS)

Ni, Wenjian; Sun, Guoqing; Ranson, Kenneth J.

2013-01-01

Current researches based on areal or spaceborne stereo images with very high resolutions (less than 1 meter) have demonstrated that it is possible to derive vegetation height from stereo images. The second version of the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTER GDEM) is a state-of-the-art global elevation data-set developed by stereo images. However, the resolution of ASTER stereo images (15 meters) is much coarser than areal stereo images, and the ASTER GDEM is compiled products from stereo images acquired over 10 years. The forest disturbances as well as forest growth are inevitable in 10 years time span. In this study, the features of ASTER GDEM over vegetated areas under both flat and mountainous conditions were investigated by comparisons with lidar data. The factors possibly affecting the extraction of vegetation canopy height considered include (1) co-registration of DEMs; (2) spatial resolution of digital elevation models (DEMs); (3) spatial vegetation structure; and (4) terrain slope. The results show that accurate co-registration between ASTER GDEM and the National Elevation Dataset (NED) is necessary over mountainous areas. The correlation between ASTER GDEM minus NED and vegetation canopy height is improved from 0.328 to 0.43 by degrading resolutions from 1 arc-second to 5 arc-seconds and further improved to 0.6 if only homogenous vegetated areas were considered.

Development Status of Adjustable X-Ray Optics with 0.5 Arcsecond Resolution

NASA Technical Reports Server (NTRS)

Reid, P. B.; ODell, Stephen; Elsner, Ron; Ramsey, Brian; Gubarev, Misha; Aldcroft, T.; Allured, R.; Cotroneo, V.; Johnson-Wilke, R. L.; McMuldroch, S.;

Antenna Electronics Concept for the Next-Generation Very Large Array

NASA Astrophysics Data System (ADS)

Beasley, Anthony J.; Jackson, Jim; Selina, Robert

2017-01-01

The National Radio Astronomy Observatory (NRAO), in collaboration with its international partners, completed two major projects over the past decade: the sensitivity upgrade for the Karl Jansky Very Large Array (VLA) and the construction of the Atacama Large Millimeter/Sub-Millimeter Array (ALMA). The NRAO is now considering the scientific potential and technical feasibility of a next-generation VLA (ngVLA) with an emphasis on thermal imaging at milli-arcsecond resolution. The preliminary goals for the ngVLA are to increase both the system sensitivity and angular resolution of the VLA tenfold and to cover a frequency range of 1.2-116 GHz.A number of key technical challenges have been identified for the project. These include cost-effective antenna manufacturing (in the hundreds), suitable wide-band feed and receiver designs, broad-band data transmission, and large-N correlators. Minimizing the overall operations cost is also a fundamental design requirement.The designs of the antenna electronics, reference distribution system, and data transmission system are anticipated to be major construction and operations cost drivers for the facility. The electronics must achieve a high level of performance, while maintaining low operation and maintenance costs and a high level of reliability. Additionally, due to the uncertainty in the feasibility of wideband receivers, advancements in digitizer technology, and budget constraints, the hardware system architecture should be scalable to the number of receiver bands and the speed and resolution of available digitizers.Here, we present the projected performance requirements of the ngVLA, a proposed block diagram for the instrument’s electronics systems, parameter tradeoffs within the system specifications, and areas of technical risk where technical advances may be required for successful production and installation.

High precision active nutation control for a flexible momentum biased spacecraft

NASA Technical Reports Server (NTRS)

Laskin, R. A.; Kopf, E. H.

1984-01-01

The controller design for the Solar Dynamics Observatory (SDO) is presented. SDO is a momentum biased spacecraft with three flexible appendages. Its primary scientific instrument, the solar oscillations imager (SOI), is rigidly attached to the spacecraft bus and has arc-second pointing requirements. Meeting these requirements necessitates the use of an active nutation controller (ANC) which is here mechanized with a small reaction wheel oriented along a bus transverse axis. The ANC does its job by orchestrating the transfer of angular momentum out of the bus transverse axes and into the momentum wheel. A simulation study verifies that the controller provides quick, stable, and accurate response.

A laboratory demonstration of the capability to image an Earth-like extrasolar planet.

PubMed

Trauger, John T; Traub, Wesley A

2007-04-12

The detection and characterization of an Earth-like planet orbiting a nearby star requires a telescope with an extraordinarily large contrast at small angular separations. At visible wavelengths, an Earth-like planet would be 1 x 10(-10) times fainter than the star at angular separations of typically 0.1 arcsecond or less. There are several proposed space telescope systems that could, in principle, achieve this. Here we report a laboratory experiment that reaches these limits. We have suppressed the diffracted and scattered light near a star-like source to a level of 6 x 10(-10) times the peak intensity in individual coronagraph images. In a series of such images, together with simple image processing, we have effectively reduced this to a residual noise level of about 0.1 x 10(-10). This demonstrates that a coronagraphic telescope in space could detect and spectroscopically characterize nearby exoplanetary systems, with the sensitivity to image an 'Earth-twin' orbiting a nearby star.

AKARI OBSERVATION OF THE SUB-DEGREE SCALE FLUCTUATION OF THE NEAR-INFRARED BACKGROUND

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seo, H. J.; Lee, Hyung Mok; Lee, Myung Gyoon

2015-07-10

We report spatial fluctuation analysis of the sky brightness in the near-infrared from observations toward the north ecliptic pole (NEP) by the AKARI at 2.4 and 3.2 μm. As a follow-up study of our previous work on the Monitor field of AKARI, we used NEP deep survey data, which covered a circular area of about 0.4 square degrees, in order to extend fluctuation analysis at angular scales up to 1000″. We found residual fluctuation over the estimated shot noise at larger angles than the angular scale of the Monitor field. The excess fluctuation of the NEP deep field smoothly connectsmore » with that of the Monitor field at angular scales of a few hundred arcseconds and extends without any significant variation to larger angular scales up to 1000″. By comparing excess fluctuations at two wavelengths, we confirm a blue spectral feature similar to the result of the Monitor field. We find that the result of this study is consistent with Spitzer Space Telescope observations at 3.6 μm. The origin of the excess fluctuation in the near-infrared background remains to be determined, but we could exclude zodiacal light, diffuse Galactic light, and unresolved faint galaxies at low redshift based on the comparison with mid- and far-infrared brightness, ground-based near-infrared images.« less

X-Ray Diffraction and Imaging Study of Imperfections of Crystallized Lysozyme with Coherent X-Rays

NASA Technical Reports Server (NTRS)

Hu, Zheng-Wei; Chu, Y. S.; Lai, B.; Cai, Z.; Thomas, B. R.; Chernov, A. A.

2003-01-01

Phase-sensitive x-ray diffraction imaging and high angular-resolution diffraction combined with phase contrast radiographic imaging are employed to characterize defects and perfection of a uniformly grown tetragonal lysozyme crystal in symmetric Laue case. The fill width at half-maximum (FWHM) of a 4 4 0 rocking curve measured from the original crystal is approximately 16.7 arcseconds, and defects, which include point defects, line defects, and microscopic domains, have been clearly observed in the diffraction images of the crystal. The observed line defects carry distinct dislocation features running approximately along the <110> growth front, and they have been found to originate mostly at a central growth area and occasionally at outer growth regions. Individual point defects trapped at a crystal nucleus are resolved in the images of high sensitivity to defects. Slow dehydration has led to the broadening of the 4 4 0 rocking curve by a factor of approximately 2.4. A significant change of the defect structure and configuration with drying has been revealed, which suggests the dehydration induced migration and evolution of dislocations and lattice rearrangements to reduce overall strain energy. The sufficient details of the observed defects shed light upon perfection, nucleation and growth, and properties of protein crystals.

Multiframe super resolution reconstruction method based on light field angular images

NASA Astrophysics Data System (ADS)

Zhou, Shubo; Yuan, Yan; Su, Lijuan; Ding, Xiaomin; Wang, Jichao

2017-12-01

The plenoptic camera can directly obtain 4-dimensional light field information from a 2-dimensional sensor. However, based on the sampling theorem, the spatial resolution is greatly limited by the microlenses. In this paper, we present a method of reconstructing high-resolution images from the angular images. First, the ray tracing method is used to model the telecentric-based light field imaging process. Then, we analyze the subpixel shifts between the angular images extracted from the defocused light field data and the blur in the angular images. According to the analysis above, we construct the observation model from the ideal high-resolution image to the angular images. Applying the regularized super resolution method, we can obtain the super resolution result with a magnification ratio of 8. The results demonstrate the effectiveness of the proposed observation model.

Transition-Edge Sensor Pixel Parameter Design of the Microcalorimeter Array for the X-Ray Integral Field Unit on Athena

NASA Technical Reports Server (NTRS)

Smith, S. J.; Adams, J. S.; Bandler, S. R.; Betancourt-Martinez, G. L.; Chervenak, J. A.; Chiao, M. P.; Eckart, M. E.; Finkbeiner, F. M.; Kelley, R. L.; Kilbourne, C. A.;

Compression and ablation of the photo-irradiated molecular cloud the Orion Bar.

PubMed

Goicoechea, Javier R; Pety, Jérôme; Cuadrado, Sara; Cernicharo, José; Chapillon, Edwige; Fuente, Asunción; Gerin, Maryvonne; Joblin, Christine; Marcelino, Nuria; Pilleri, Paolo

2016-09-08

The Orion Bar is the archetypal edge-on molecular cloud surface illuminated by strong ultraviolet radiation from nearby massive stars. Our relative closeness to the Orion nebula (about 1,350 light years away from Earth) means that we can study the effects of stellar feedback on the parental cloud in detail. Visible-light observations of the Orion Bar show that the transition between the hot ionized gas and the warm neutral atomic gas (the ionization front) is spatially well separated from the transition between atomic and molecular gas (the dissociation front), by about 15 arcseconds or 6,200 astronomical units (one astronomical unit is the Earth-Sun distance). Static equilibrium models used to interpret previous far-infrared and radio observations of the neutral gas in the Orion Bar (typically at 10-20 arcsecond resolution) predict an inhomogeneous cloud structure comprised of dense clumps embedded in a lower-density extended gas component. Here we report one-arcsecond-resolution millimetre-wave images that allow us to resolve the molecular cloud surface. In contrast to stationary model predictions, there is no appreciable offset between the peak of the H 2 vibrational emission (delineating the H/H 2 transition) and the edge of the observed CO and HCO + emission. This implies that the H/H 2 and C + /C/CO transition zones are very close. We find a fragmented ridge of high-density substructures, photoablative gas flows and instabilities at the molecular cloud surface. The results suggest that the cloud edge has been compressed by a high-pressure wave that is moving into the molecular cloud, demonstrating that dynamical and non-equilibrium effects are important for the cloud evolution.

Absolute wind measurements in the lower thermosphere of Venus using infrared heterodyne spectroscopy

NASA Technical Reports Server (NTRS)

Goldstein, Jeffrey J.

1990-01-01

The first absolute wind velocities above the Venusian cloud-tops were obtained using NASA/Goddard infrared heterodyne spectrometers at the NASA Infrared Telescope Facility (IRTF) and the McMath Solar Telescope. Beam-integrated Doppler displacements in the non-thermal emission core of (12)C(16)O2 10.33 micron R(8) sampled the line of sight projection of the lower thermospheric wind field (100 to 120 km). A field-usable Lamb-dip laser stabilization system, developed for spectrometer absolute frequency calibration to less than + or - 0.1 MHz, allowed S/N-limited line of sight velocity resolution at the 1 m/s level. The spectrometer's diffraction-limited beam (1.7 arc-second HPBW at McMath, 0.9 arc-second HPBW at IRTF), and 1 to 2 arc-second seeing, provided the spatial resolution necessary for circulation model discrimination. Qualitative analysis of beam-integrated winds provided definitive evidence of a dominant subsolar-antisolar circulation in the lower thermosphere. Beam-integrated winds were modelled with a 100x100 grid over the beam, incorporating beam spatial rolloff and across-the-beam gradients in non-thermal emission intensity, line of sight projection geometry, and horizontal wind velocity. Horizontal wind velocity was derived from a 2-parameter model wind field comprised of subsolar-antisolar and zonal components. Best-fit models indicated a dominant subsolar-antisolar flow with 120 m/s cross-terminator winds and a retrograde zonal component with a 25 m/s equatorial velocity. A review of all dynamical indicators above the cloud-tops allowed development of an integrated and self-consistent picture of circulation in the 70 to 200 km range.

Compression and ablation of the photo-irradiated molecular cloud the Orion Bar

NASA Astrophysics Data System (ADS)

Goicoechea, Javier R.; Pety, Jérôme; Cuadrado, Sara; Cernicharo, José; Chapillon, Edwige; Fuente, Asunción; Gerin, Maryvonne; Joblin, Christine; Marcelino, Nuria; Pilleri, Paolo

2016-09-01

The Orion Bar is the archetypal edge-on molecular cloud surface illuminated by strong ultraviolet radiation from nearby massive stars. Our relative closeness to the Orion nebula (about 1,350 light years away from Earth) means that we can study the effects of stellar feedback on the parental cloud in detail. Visible-light observations of the Orion Bar show that the transition between the hot ionized gas and the warm neutral atomic gas (the ionization front) is spatially well separated from the transition between atomic and molecular gas (the dissociation front), by about 15 arcseconds or 6,200 astronomical units (one astronomical unit is the Earth-Sun distance). Static equilibrium models used to interpret previous far-infrared and radio observations of the neutral gas in the Orion Bar (typically at 10-20 arcsecond resolution) predict an inhomogeneous cloud structure comprised of dense clumps embedded in a lower-density extended gas component. Here we report one-arcsecond-resolution millimetre-wave images that allow us to resolve the molecular cloud surface. In contrast to stationary model predictions, there is no appreciable offset between the peak of the H2 vibrational emission (delineating the H/H2 transition) and the edge of the observed CO and HCO+ emission. This implies that the H/H2 and C+/C/CO transition zones are very close. We find a fragmented ridge of high-density substructures, photoablative gas flows and instabilities at the molecular cloud surface. The results suggest that the cloud edge has been compressed by a high-pressure wave that is moving into the molecular cloud, demonstrating that dynamical and non-equilibrium effects are important for the cloud evolution.

Late-time high-resolution images of the black hole candidate microlensing events, MACHO-96-BLG-5 and MACHO-98-BLG-6

NASA Astrophysics Data System (ADS)

Forest Stephens, Haynes; Lu, Jessica

2018-01-01

Stellar-mass black holes (BHs) are predicted to be abundant in the Milky Way (N=10^8 - 10^9) but only a few dozen have been detected observationally, all of which are in binary systems and actively accreting. Isolated BHs have yet to be detected. One method for attempting to detect isolated BHs is via gravitational microlensing; when a BH passes in front of a star and briefly magnifies the star's observed brightness. However, during a microlensing event, there is no certain method for determining whether the lens is a BH or another star. We present follow-up observations of two microlensing events, MACHO-1996-BLG-5 and MACHO-1998-BLG-6, which were observed in 1996 and 1998, respectively, and are both long-duration events with a high probability that the lens is a black hole. The closest projected approach between the source and lens was over 20 years ago. If the lens is an isolated BH, then the source and lens should have moved apart enough to be resolved with high-resolution imaging. Using adaptive optics images from the W. M. Keck Observatory, we observed the two candidates in 2016 July. No new sources were found within 0.3 arcseconds of the lensed source, a reasonable angular distance considering the maximum possible relative proper motion of the lens and source. We will present constraints on the lens mass, distance, and proper motion for both microlensing candidates, and explore the likelihood that the lenses are isolated BHs.

Design, Construction, and Testing of Lightweight X-ray Mirror Modules

NASA Technical Reports Server (NTRS)

McClelland, Ryan S.; Biskach, Michael P.; Chan, Kai-Wing; Espina, Rebecca A.; Hohl, Bruce R.; Matson, Elizabeth A.; Saha, Timo C.; Zhang, William W.

2013-01-01

Lightweight and high resolution optics are needed for future space-based X-ray telescopes to achieve advances in high-energy astrophysics. The Next Generation X-ray Optics (NGXO) team at NASA GSFC is nearing mission readiness for a 10 arc-second Half Power Diameter (HPD) slumped glass mirror technology while laying the groundwork for a future 1-2 arc-second technology based on polished silicon mirrors. Technology Development Modules (TDMs) have been designed, fabricated, integrated with mirrors segments, and extensively tested to demonstrate technology readiness. Tests include X-ray performance, thermal vacuum, acoustic load, and random vibration. The thermal vacuum and acoustic load environments have proven relatively benign, while the random vibration environment has proven challenging due to large input amplification at frequencies above 500 Hz. Epoxy selection, surface preparation, and larger bond area have increased bond strength while vibration isolation has decreased vibration amplification allowing for space launch requirements to be met in the near term. The next generation of TDMs, which demonstrates a lightweight structure supporting more mirror segments, is currently being fabricated. Analysis predicts superior performance characteristics due to the use of E-60 Beryllium-Oxide Metal Matrix Composite material, with only a modest cost increase. These TDMs will be larger, lighter, stiffer, and stronger than the current generation. Preliminary steps are being taken to enable mounting and testing of 1-2 arc-second mirror segments expected to be available in the future. A Vertical X-ray Test Facility (VXTF) will minimize module gravity distortion and allow for less constrained mirror mounts, such as fully kinematic mounts. Permanent kinematic mounting into a modified TDM has been demonstrated to achieve 2 arc-second level distortion free alignment.

Mirrors for High Resolution X-Ray Optics---Figure Preserving IR/PT Coating

NASA Technical Reports Server (NTRS)

Chan, Kai-Wing; Olsen, Lawrence; Sharpe, Marton; Numata, Ai; McClelland, Ryan; Saha, Timo; Zhang, Will

2016-01-01

Coating stress of 10 - 20 nm of Ir is sufficiently high to distort the figure of arc-second thin lightweight mirrors. For iridium: --Stress sigma 4 GPa for 15 nm film implies 60 Nm integrated stress-- Need less than 3 N/m (or stress less than 200 MPa) for sub-arcsecond optics. Basic Approaches for Mitigation. A. Annealing the film-- Glass can be heat up to 400 C without distortion. Silicon is even more resistant.-- It was found that recovery is limited by residual thermal stress from taking the mirror down from high T. B. Coating bi-layer films with compressive stress with tensile stress. C. Front-and-back coating with magnetron sputtering or atomic layer deposition-- Sputtering involve spanning of substrates. Geometric difference in setup (convexness/concaveness of curved mirrors) does not permit precise front-and-back matching-- Atomic layer deposition can provide a uniform deposition front and back simultaneously.

Technology Requirements For a Square-Meter, Arcsecond-Resolution Telescope for X-Rays: The SMART-X Mission

NASA Technical Reports Server (NTRS)

Schwartz, Daniel A.; Allured, Ryan; Bookbinder, Jay; Cotroneo, Vincenzo; Forman, William; Freeman, Mark; McMuldroch, Stuart; Reid, Paul; Tananbaum, Harvey; Vikhlinin, Alexey;

High angular resolution at LBT

NASA Astrophysics Data System (ADS)

Conrad, A.; Arcidiacono, C.; Bertero, M.; Boccacci, P.; Davies, A. G.; Defrere, D.; de Kleer, K.; De Pater, I.; Hinz, P.; Hofmann, K. H.; La Camera, A.; Leisenring, J.; Kürster, M.; Rathbun, J. A.; Schertl, D.; Skemer, A.; Skrutskie, M.; Spencer, J. R.; Veillet, C.; Weigelt, G.; Woodward, C. E.

2015-12-01

High angular resolution from ground-based observatories stands as a key technology for advancing planetary science. In the window between the angular resolution achievable with 8-10 meter class telescopes, and the 23-to-40 meter giants of the future, LBT provides a glimpse of what the next generation of instruments providing higher angular resolution will provide. We present first ever resolved images of an Io eruption site taken from the ground, images of Io's Loki Patera taken with Fizeau imaging at the 22.8 meter LBT [Conrad, et al., AJ, 2015]. We will also present preliminary analysis of two data sets acquired during the 2015 opposition: L-band fringes at Kurdalagon and an occultation of Loki and Pele by Europa (see figure). The light curves from this occultation will yield an order of magnitude improvement in spatial resolution along the path of ingress and egress. We will conclude by providing an overview of the overall benefit of recent and future advances in angular resolution for planetary science.

Bayesian Deconvolution for Angular Super-Resolution in Forward-Looking Scanning Radar

PubMed Central

Zha, Yuebo; Huang, Yulin; Sun, Zhichao; Wang, Yue; Yang, Jianyu

2015-01-01

Scanning radar is of notable importance for ground surveillance, terrain mapping and disaster rescue. However, the angular resolution of a scanning radar image is poor compared to the achievable range resolution. This paper presents a deconvolution algorithm for angular super-resolution in scanning radar based on Bayesian theory, which states that the angular super-resolution can be realized by solving the corresponding deconvolution problem with the maximum a posteriori (MAP) criterion. The algorithm considers that the noise is composed of two mutually independent parts, i.e., a Gaussian signal-independent component and a Poisson signal-dependent component. In addition, the Laplace distribution is used to represent the prior information about the targets under the assumption that the radar image of interest can be represented by the dominant scatters in the scene. Experimental results demonstrate that the proposed deconvolution algorithm has higher precision for angular super-resolution compared with the conventional algorithms, such as the Tikhonov regularization algorithm, the Wiener filter and the Richardson–Lucy algorithm. PMID:25806871

GLOBATO: An enhanced global relief model at 30 arc-seconds resolution

NASA Astrophysics Data System (ADS)

O'Leary, V.; Amante, C.

2017-12-01

The National Centers for Environmental Information (NCEI), an office of the National Oceanic and Atmospheric Administration (NOAA), first developed a digital bathymetric and elevation model, ETOPO5, from publicly available data in 1993. For nearly 25 years, NCEI's ETOPO family of global relief models have supported research at a planetary scale, including tsunami forecasting, ocean circulation modeling, visualization of the seafloor, understanding geological phenomena, and aiding the development of other global and regional elevation models. GLOBATO (GLObal BAThymetry and TOpography) is now the most detailed version released by NCEI with a horizontal resolution of 30 arc-seconds and succeeds ETOPO1 with the inclusion of several new or updated data-sets for the seafloor as well as land areas. GLOBATO is a compilation of data derived from models of satellite measurements, ship depth soundings, and multibeam surveys, as well as regional models developed for Greenland and Antarctica. These data were converted from different formats, resolutions, spatial distributions, and projections into a single global model using GDAL v2.2 and MB-System v5.5. As with previous NCEI models, GLOBATO is available in two formats, "bedrock elevation" (measured as the base of major ice sheets) and "ice surface elevation" (measured as the surface of major ice sheets) which provides comprehensive topographic and bathymetric coverage between +- 90 degrees latitude and +- 180 degrees longitude. Adhering to best practices, GLOBATO, all related digital products, and any supporting documentation are available online through the NCEI data portal. These new, high resolution models will better support the variety of research ETOPO1 has made possible.

MAX '91: An advanced payload for the exploration of high energy processes on the active sun

NASA Technical Reports Server (NTRS)

1986-01-01

The results of a NASA science working group established to study a follow-on to the Solar Maximum Mission are given. A complement of instruments is suggested, with the primary objective of studying the physics of energetic processes in cosmic plasmas by observing high-energy phenomena in solar flares. High-quality flare observations will be possible with these instruments during the next peak in solar activity expected to last from 1990 through at least 1995. The primary objective of MAX '91 is to study energetic processes in cosmic plasmas by observing high-energy phenomena in solar flares. These processes, which are of general astrophysical importance, include energy release, particle acceleration, and energy transport. Results from comprehensive observing programs conducted during the last solar cycle have demonstrated the great scientific potential of high-energy emissions for addressing these central physical processes. Consequently, a payload optimized for observations of high-energy solar flare phenomena is suggested for MAX '91. It consists of the following four specific instruments: (1) a Fourier-transform X-ray and gamma-ray imager covering the energy range from a few keV to 1 MeV with arcsecond spatial resolution; (2) a cooled germanium X-ray and gamma-ray spectrometer with keV spectral resolution covering the energy range from 10 keV to 50 MeV; (3) Bragg spectrometers with high spectral resolution at wavelengths between 1 and 9 angstrons; and (4) a soft X-ray, EUV, or UV imaging instrument with arcsecond spatial resolution.

A Bayesian Analysis of Scale-Invariant Processes

DTIC Science & Technology

2012-01-01

Earth Grid (EASE- Grid). The NED raster elevation data of one arc-second resolution (30 m) over the continental US are derived from multiple satellites ...instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send...empirical and ME distributions, yet ensuring computational efficiency. Instead of com- puting empirical histograms from large amount of data , only some

Goal-based angular adaptivity applied to a wavelet-based discretisation of the neutral particle transport equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goffin, Mark A., E-mail: mark.a.goffin@gmail.com; Buchan, Andrew G.; Dargaville, Steven

2015-01-15

A method for applying goal-based adaptive methods to the angular resolution of the neutral particle transport equation is presented. The methods are applied to an octahedral wavelet discretisation of the spherical angular domain which allows for anisotropic resolution. The angular resolution is adapted across both the spatial and energy dimensions. The spatial domain is discretised using an inner-element sub-grid scale finite element method. The goal-based adaptive methods optimise the angular discretisation to minimise the error in a specific functional of the solution. The goal-based error estimators require the solution of an adjoint system to determine the importance to the specifiedmore » functional. The error estimators and the novel methods to calculate them are described. Several examples are presented to demonstrate the effectiveness of the methods. It is shown that the methods can significantly reduce the number of unknowns and computational time required to obtain a given error. The novelty of the work is the use of goal-based adaptive methods to obtain anisotropic resolution in the angular domain for solving the transport equation. -- Highlights: •Wavelet angular discretisation used to solve transport equation. •Adaptive method developed for the wavelet discretisation. •Anisotropic angular resolution demonstrated through the adaptive method. •Adaptive method provides improvements in computational efficiency.« less

Spatial and Angular Resolution Enhancement of Light Fields Using Convolutional Neural Networks

NASA Astrophysics Data System (ADS)

Gul, M. Shahzeb Khan; Gunturk, Bahadir K.

2018-05-01

Light field imaging extends the traditional photography by capturing both spatial and angular distribution of light, which enables new capabilities, including post-capture refocusing, post-capture aperture control, and depth estimation from a single shot. Micro-lens array (MLA) based light field cameras offer a cost-effective approach to capture light field. A major drawback of MLA based light field cameras is low spatial resolution, which is due to the fact that a single image sensor is shared to capture both spatial and angular information. In this paper, we present a learning based light field enhancement approach. Both spatial and angular resolution of captured light field is enhanced using convolutional neural networks. The proposed method is tested with real light field data captured with a Lytro light field camera, clearly demonstrating spatial and angular resolution improvement.

Spatial and Angular Resolution Enhancement of Light Fields Using Convolutional Neural Networks.

PubMed

Gul, M Shahzeb Khan; Gunturk, Bahadir K

2018-05-01

Light field imaging extends the traditional photography by capturing both spatial and angular distribution of light, which enables new capabilities, including post-capture refocusing, post-capture aperture control, and depth estimation from a single shot. Micro-lens array (MLA) based light field cameras offer a cost-effective approach to capture light field. A major drawback of MLA based light field cameras is low spatial resolution, which is due to the fact that a single image sensor is shared to capture both spatial and angular information. In this paper, we present a learning based light field enhancement approach. Both spatial and angular resolution of captured light field is enhanced using convolutional neural networks. The proposed method is tested with real light field data captured with a Lytro light field camera, clearly demonstrating spatial and angular resolution improvement.

Interstellar Broadening of Images in the Gravitational Lens Pks 1830-211

NASA Technical Reports Server (NTRS)

Jones, D. L.; Preston, R. A.; Murphy, D. W.; Jauncey, D. L.; Reynolds, J. E.; Tzioumis, A. K.; King, E. A.; McCulloch, P. M.; Lovell, J. E. J.; Costa, M. E.

1996-01-01

The remarkably strong radio gravitational lens PKS 1830-211 consists of a one arcsecond diameter Einstein ring with two bright compact (milliarcsecond) components located on opposite sides of the ring. We have obtained 22 GHz VLBA data on this source to determine the intrinsic angular sizes of the compact components. Previous VLBI observations at lower frequencies indicate that the brightness temperatures of these components are significantly lower than 10(exp 10) K (Jauncey, et al. 1991), less than is typical for compact synchrotron radio sources and less than is implied by the short timescales of flux density variations. A possible explanation is that interstellar scattering is broadening the apparent angular size of the source and thereby reducing the observed brightness temperature. Our VLBA data support this hypothesis. At 22 GHz the measured brightness temperature is at least 10(exp 11) K, and the deconvolved 2 size of the core in the southwest compact component is proportional to upsilon(sup -2) between 1.7 and 22 GHz. VLBI observations at still higher frequencies should be unaffected by interstellar scattering.

High-resolution digital movies of emerging flux and horizontal flows in active regions on the sun

NASA Astrophysics Data System (ADS)

Topka, K.; Ferguson, S.; Frank, Z.; Tarbell, T.; Title, A.

1988-11-01

High-resolution observations of active regions in many wavelength bands obtained at the Vacuum Tower Telescope of NSO/Sunspot (Sacramento Peak) are presented. The SOUP tunable filter, HRSO 1024 x 1024 CCD camera, and a sunspot tracker for image stabilization were used. Subarrays of 512 x 512 pixels were processed digitally and recorded on videodisk in movie format. The movies with 0.5 to 1 arcsecond resolution of the following simultaneous observations were shown: green continuum, longitudinal magnetogram, Doppler velocity, Fe I 5576 A line center, H alpha wings, and H alpha line center. The best set of movies show a 90 x 90 arcsecond field-of-view of an active region at S29, W11. When viewed at speeds of a few thousand times real-time, the photospheric movies clearly show the active region fields being distorted by a remarkable combination of systematic flows and small eruptions of new flux. Flux emergence is most easily discovered in line center movies: an elongated dark feature appears first, followed soon after by bright points at one or both ends. A brief, strong upflow is seen when the dark feature first appears; downflow in the bright points persists much longer. The magnetic flux appears to increase gradually over this extended period. Some of the flux emergence events were studied in detail, with measurements of horizontal and vertical velocities and magnetic flux versus time within one footpoint of the loop.

High-resolution digital movies of emerging flux and horizontal flows in active regions on the sun

NASA Technical Reports Server (NTRS)

Topka, K.; Ferguson, S.; Frank, Z.; Tarbell, T.; Title, A.

1988-01-01

High-resolution observations of active regions in many wavelength bands obtained at the Vacuum Tower Telescope of NSO/Sunspot (Sacramento Peak) are presented. The SOUP tunable filter, HRSO 1024 x 1024 CCD camera, and a sunspot tracker for image stabilization were used. Subarrays of 512 x 512 pixels were processed digitally and recorded on videodisk in movie format. The movies with 0.5 to 1 arcsecond resolution of the following simultaneous observations were shown: green continuum, longitudinal magnetogram, Doppler velocity, Fe I 5576 A line center, H alpha wings, and H alpha line center. The best set of movies show a 90 x 90 arcsecond field-of-view of an active region at S29, W11. When viewed at speeds of a few thousand times real-time, the photospheric movies clearly show the active region fields being distorted by a remarkable combination of systematic flows and small eruptions of new flux. Flux emergence is most easily discovered in line center movies: an elongated dark feature appears first, followed soon after by bright points at one or both ends. A brief, strong upflow is seen when the dark feature first appears; downflow in the bright points persists much longer. The magnetic flux appears to increase gradually over this extended period. Some of the flux emergence events were studied in detail, with measurements of horizontal and vertical velocities and magnetic flux versus time within one footpoint of the loop.

Design of Multishell Sampling Schemes with Uniform Coverage in Diffusion MRI

PubMed Central

Caruyer, Emmanuel; Lenglet, Christophe; Sapiro, Guillermo; Deriche, Rachid

2017-01-01

Purpose In diffusion MRI, a technique known as diffusion spectrum imaging reconstructs the propagator with a discrete Fourier transform, from a Cartesian sampling of the diffusion signal. Alternatively, it is possible to directly reconstruct the orientation distribution function in q-ball imaging, providing so-called high angular resolution diffusion imaging. In between these two techniques, acquisitions on several spheres in q-space offer an interesting trade-off between the angular resolution and the radial information gathered in diffusion MRI. A careful design is central in the success of multishell acquisition and reconstruction techniques. Methods The design of acquisition in multishell is still an open and active field of research, however. In this work, we provide a general method to design multishell acquisition with uniform angular coverage. This method is based on a generalization of electrostatic repulsion to multishell. Results We evaluate the impact of our method using simulations, on the angular resolution in one and two bundles of fiber configurations. Compared to more commonly used radial sampling, we show that our method improves the angular resolution, as well as fiber crossing discrimination. Discussion We propose a novel method to design sampling schemes with optimal angular coverage and show the positive impact on angular resolution in diffusion MRI. PMID:23625329

Development of a Grazing Incidence X-Ray Interferometer

NASA Technical Reports Server (NTRS)

Shipley, Ann; Cash, Webster; Osterman, Steve; Joy, Marshall; Carter, James

1999-01-01

A grazing incidence x-ray interferometer design capable of micro-arcsecond level resolution is discussed. This practical design employs a Michelson Stellar interferometer approach to create x-ray interference fringes without the use of Wolter style optics or diffraction crystals. Design solutions accommodating alignment, vibration, and thermal constraints are reviewed. We present the development and demonstration of a working experiment along with tolerance studies, data analysis, and results.

Spectral Topography Generation for Arbitrary Grids

NASA Astrophysics Data System (ADS)

Oh, T. J.

2015-12-01

A new topography generation tool utilizing spectral transformation technique for both structured and unstructured grids is presented. For the source global digital elevation data, the NASA Shuttle Radar Topography Mission (SRTM) 15 arc-second dataset (gap-filling by Jonathan de Ferranti) is used and for land/water mask source, the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) 30 arc-second land water mask dataset v5 is used. The original source data is coarsened to a intermediate global 2 minute lat-lon mesh. Then, spectral transformation to the wave space and inverse transformation with wavenumber truncation is performed for isotropic topography smoothness control. Target grid topography mapping is done by bivariate cubic spline interpolation from the truncated 2 minute lat-lon topography. Gibbs phenomenon in the water region can be removed by overwriting ocean masked target coordinate grids with interpolated values from the intermediate 2 minute grid. Finally, a weak smoothing operator is applied on the target grid to minimize the land/water surface height discontinuity that might have been introduced by the Gibbs oscillation removal procedure. Overall, the new topography generation approach provides spectrally-derived, smooth topography with isotropic resolution and minimum damping, enabling realistic topography forcing in the numerical model. Topography is generated for the cubed-sphere grid and tested on the KIAPS Integrated Model (KIM).

First light of the Gemini Planet Imager

PubMed Central

Macintosh, Bruce; Graham, James R.; Ingraham, Patrick; Konopacky, Quinn; Marois, Christian; Perrin, Marshall; Poyneer, Lisa; Bauman, Brian; Barman, Travis; Burrows, Adam S.; Cardwell, Andrew; Chilcote, Jeffrey; De Rosa, Robert J.; Dillon, Daren; Doyon, Rene; Dunn, Jennifer; Erikson, Darren; Fitzgerald, Michael P.; Gavel, Donald; Goodsell, Stephen; Hartung, Markus; Hibon, Pascale; Kalas, Paul; Larkin, James; Maire, Jerome; Marchis, Franck; Marley, Mark S.; McBride, James; Millar-Blanchaer, Max; Morzinski, Katie; Norton, Andrew; Oppenheimer, B. R.; Palmer, David; Patience, Jennifer; Pueyo, Laurent; Rantakyro, Fredrik; Sadakuni, Naru; Saddlemyer, Leslie; Savransky, Dmitry; Serio, Andrew; Soummer, Remi; Sivaramakrishnan, Anand; Song, Inseok; Thomas, Sandrine; Wallace, J. Kent; Wiktorowicz, Sloane; Wolff, Schuyler

2014-01-01

The Gemini Planet Imager is a dedicated facility for directly imaging and spectroscopically characterizing extrasolar planets. It combines a very high-order adaptive optics system, a diffraction-suppressing coronagraph, and an integral field spectrograph with low spectral resolution but high spatial resolution. Every aspect of the Gemini Planet Imager has been tuned for maximum sensitivity to faint planets near bright stars. During first-light observations, we achieved an estimated H band Strehl ratio of 0.89 and a 5-σ contrast of 106 at 0.75 arcseconds and 105 at 0.35 arcseconds. Observations of Beta Pictoris clearly detect the planet, Beta Pictoris b, in a single 60-s exposure with minimal postprocessing. Beta Pictoris b is observed at a separation of 434 ± 6 milliarcseconds (mas) and position angle 211.8 ± 0.5°. Fitting the Keplerian orbit of Beta Pic b using the new position together with previous astrometry gives a factor of 3 improvement in most parameters over previous solutions. The planet orbits at a semimajor axis of 9.0−0.4+0.8 AU near the 3:2 resonance with the previously known 6-AU asteroidal belt and is aligned with the inner warped disk. The observations give a 4% probability of a transit of the planet in late 2017. PMID:24821792

First light of the Gemini Planet imager.

PubMed

Macintosh, Bruce; Graham, James R; Ingraham, Patrick; Konopacky, Quinn; Marois, Christian; Perrin, Marshall; Poyneer, Lisa; Bauman, Brian; Barman, Travis; Burrows, Adam S; Cardwell, Andrew; Chilcote, Jeffrey; De Rosa, Robert J; Dillon, Daren; Doyon, Rene; Dunn, Jennifer; Erikson, Darren; Fitzgerald, Michael P; Gavel, Donald; Goodsell, Stephen; Hartung, Markus; Hibon, Pascale; Kalas, Paul; Larkin, James; Maire, Jerome; Marchis, Franck; Marley, Mark S; McBride, James; Millar-Blanchaer, Max; Morzinski, Katie; Norton, Andrew; Oppenheimer, B R; Palmer, David; Patience, Jennifer; Pueyo, Laurent; Rantakyro, Fredrik; Sadakuni, Naru; Saddlemyer, Leslie; Savransky, Dmitry; Serio, Andrew; Soummer, Remi; Sivaramakrishnan, Anand; Song, Inseok; Thomas, Sandrine; Wallace, J Kent; Wiktorowicz, Sloane; Wolff, Schuyler

2014-09-02

The Gemini Planet Imager is a dedicated facility for directly imaging and spectroscopically characterizing extrasolar planets. It combines a very high-order adaptive optics system, a diffraction-suppressing coronagraph, and an integral field spectrograph with low spectral resolution but high spatial resolution. Every aspect of the Gemini Planet Imager has been tuned for maximum sensitivity to faint planets near bright stars. During first-light observations, we achieved an estimated H band Strehl ratio of 0.89 and a 5-σ contrast of 10(6) at 0.75 arcseconds and 10(5) at 0.35 arcseconds. Observations of Beta Pictoris clearly detect the planet, Beta Pictoris b, in a single 60-s exposure with minimal postprocessing. Beta Pictoris b is observed at a separation of 434 ± 6 milliarcseconds (mas) and position angle 211.8 ± 0.5°. Fitting the Keplerian orbit of Beta Pic b using the new position together with previous astrometry gives a factor of 3 improvement in most parameters over previous solutions. The planet orbits at a semimajor axis of [Formula: see text] near the 3:2 resonance with the previously known 6-AU asteroidal belt and is aligned with the inner warped disk. The observations give a 4% probability of a transit of the planet in late 2017.

Imaging a black hole: MAXIM

NASA Astrophysics Data System (ADS)

Cash, W.

With the general acceptance of black holes as real entities the astrophysics community has turned its attention to studying their behavior and properties. Because of the great distance and compact size of the central engine, astronomers are limited to spectroscopic analysis. But to take a picture, or better yet a movie, of the black hole in silhouette against its accretion disk would be a triumph of exploration and scientific inquiry. Probing to the event horizon is best accomplished in the X-ray band, where material primarily radiates in the last orbits before its final plunge. Not only will the signal be bright and minimally confused in the X-ray, but the size of the required interferometer drops dramatically. We describe MAXIM, the Micro-Arcsecond X-ray Imaging Mission, which is now being studied and developed by NASA. We will explain the preliminary mission concept which will use currently existing technology to achieve spatial resolution one million times higher than that of the Hubble Space Telescope and capture the image of an event horizon in a nearby Active Galactic Nucleus. We will also describe the MAXIM Pathfinder. Designed as a stepping stone at resolution of 100 micro-arcseconds, it will demonstrate the techniques of X-ray interferometry and perform groundbreaking science like resolving the coronae of the nearby stars.

INDICATION OF THE BLACK HOLE POWERED JET IN M87 BY VSOP OBSERVATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Asada, Keiichi; Nakamura, Masanori; Pu, Hung-Yi, E-mail: asada@asiaa.sinica.edu.tw, E-mail: nakamura@asiaa.sinica.edu.tw, E-mail: hypu@asiaa.sinica.edu.tw

2016-12-10

In order to study the collimation and acceleration mechanism of relativistic jets, the jet streamline of M87 at milliarcsecond scale is extensively investigated with images from VSOP observations at 1.6 and 5 GHz. Thanks to the higher angular resolution of VSOP, especially in the direction transverse to the jet, we resolved the jet streamline into three ridgelines at the scale of milli arcseconds. While the properties of the outer two ridgelines are in good agreement with those measured in previous observations and can be expressed by one power-law line with a power law index of 1.7, an inner ridgeline ismore » clearly observed for the first time. We compared the measured size with the outermost streamline expected by Blandford and Znajek's parabolic solutions, which are anchored at the event horizon, with different black hole spin parameters. We revealed that the observed inner ridgeline is narrower than the prediction, suggesting the origin of the inner ridgeline to be part of a spine originating from the spinning black hole. The inner ridgeline becomes very dim at large distances from the central engine at 5 GHz. We considered two possible cases for this; Doppler beaming and/or radiative cooling. Either case seems to be reasonable for its explanation, and future multi-frequency observations will discriminate those two possibilities.« less

Super-resolution and ultra-sensitivity of angular rotation measurement based on SU(1,1) interferometers using homodyne detection

NASA Astrophysics Data System (ADS)

Liu, Jun; Li, Shitao; Wei, Dong; Gao, Hong; Li, Fuli

2018-02-01

We theoretically explore the angular rotation measurement sensitivity of SU(1,1) interferometers with a coherent beam and a vacuum beam input by using orbital angular momentum (OAM). Compared with the OAM in an SU(2) interferometer, the SU(1,1) interferometer employing homodyne detection can further surpass the angular rotation shot noise limit \\tfrac{1}{2l\\sqrt{N}} and improve the resolution and sensitivity of angular rotation measurement. Two models are considered, one is that OAM is carried by a probe beam and the other one is a pump beam with the OAM. The sensitivity can be improved by higher OAM and nonlinear process with a large gain. The resolution can be enhanced in the case that the pump beam has OAM. Moreover, we present a brief discussion on the variation of resolution and sensitivity in the presence of photon loss.

Design of the STAR-X Telescope

NASA Technical Reports Server (NTRS)

Saha, Timo T.; Zhang, William W.; McClelland, Ryan S.

2017-01-01

Top-level science goals of the Survey and Time-domain Astrophysical Research eXplorer (STAR-X) include: investigations of most violent explosions in the universe, study of growth of black holes across cosmic time and mass scale, and measure how structure formation heats majority of baryons in the universe. To meet these goals, the field-of-view of the telescope should be about 1 square-degree, the angular resolution should be 5 arc-seconds or below across large part of the field-of-view. The on-axis effective area at 1 KeV should be about 2,000 sq cm. Payload cost and launch considerations limit the outer diameter, focal length, and mass to 1.3 meters, 5 meters, and 250 kilograms, respectively. Telescope design is based on a segmented meta-shell approach we have developed at Goddard Space Flight Center for the STAR-X telescope. The telescope shells are divided into 30-degree segments. Individual telescopes and meta-shells are nested inside each other to meet the effective area requirements in 0.5 - 6.0 KeV range. We consider Wolter-Schwarzschild, and Modified-Wolter-Schwarzschild telescope designs as basic building blocks of the nested STAR-X telescope. These designs offer an excellent resolution over a large field of views. Nested telescopes are vulnerable to stray light problems. We have designed a multi-component baffle system to eliminate direct and single-reflection light paths inside the telescopes. Large number of internal and external baffle vane structures are required to prevent stray rays from reaching the focal plane. We have developed a simple ray-trace based tool to determine the dimensions and locations of the baffles. In this paper, we present the results of our trade studies, baffle design studies, and optical performance analyses of the STAR-X telescope.

Optical Design of the STAR-X Telescope

NASA Technical Reports Server (NTRS)

Saha, Timo T.; Zhang, William W.; McClelland, Ryan S.

2017-01-01

Top-level science goals of the Survey and Time-domain Astrophysical Research eXplorer (STAR-X) include: investigations of most violent explosions in the universe, study of growth of black holes across cosmic time and mass scale, and measure how structure formation heats majority of baryons in the universe. To meet these goals, the field-of-view of the telescope should be about 1 square-degree, the angular resolution should be 5 arc-seconds or below across large part of the field-of-view. The on-axis effective area at 1 KeV should be about 2,000 sq cm. Payload cost and launch considerations limit the outer diameter, focal length, and mass to 1.3 meters, 5 meters, and 250 kilograms, respectively. Telescope design is based on a segmented meta-shell approach we have developed at Goddard Space Flight Center for the STAR-X telescope. The telescope shells are divided into 30-degree segments. Individual telescopes and meta-shells are nested inside each other to meet the effective area requirements in 0.5 - 6.0 KeV range. We consider Wolter-Schwarzschild, and Modified-Wolter-Schwarzschild telescope designs as basic building blocks of the nested STAR-X telescope. These designs offer an excellent resolution over a large field of views. Nested telescopes are vulnerable to stray light problems. We have designed a multi-component baffle system to eliminate direct and single-reflection light paths inside the telescopes. Large number of internal and external baffle vane structures are required to prevent stray rays from reaching the focal plane. We have developed a simple ray-trace based tool to determine the dimensions and locations of the baffles. In this paper, we present the results of our trade studies, baffle design studies, and optical performance analyses of the STAR-X telescope.

Science Priorities of the RadioAstron Space VLBI Mission

NASA Astrophysics Data System (ADS)

Langston, Glen; Kardashev, N.; International Space VLBI Collaboration

2006-12-01

The main scientific goal of the RadioAstron Space VLBI mission is study of Active Galactic Nuclei (AGN), Masers and other astronomical objects with unprecedented angular resolution, up to few millionths of an arc-second. The resolution achieved with RadioAstron will allow study the following phenomena and problems: * Central engine of AGN and physical processes near super massive black holes providing an acceleration of cosmic rays size, velocity and shape of emitting region in the core, spectrum, polarization and variability of emitting components; * Cosmological models, dark matter and dark energy by studying dependence of above mentioned AGN's parameters with redshift, and by observing gravitational lensing; * Structure and dynamics of star and planets forming regions in our Galaxy and in AGN by studying maser and Mega maser radio emission; * Neutron (quark?) stars and black holes in our Galaxy, their structure and dynamics by VLBI and measurements of visibility scintillations, proper motions and parallaxes; * Structure and distribution of interstellar and interplanetary plasma by fringe visibility scintillations of pulsars; The RadioAstron mission uses the satellite SPECTR (astrophysical module), developed by Lavochkin Association of Russian Aviation and Space Agency (RASA). This module will be used in several other scientific missions. The total mass of the scientific payload is about 2500 kg, of which the unfolding parabolic 10-m radio astronomy antenna's mass is about 1500 kg, and scientific package holding the receivers, power supply, synthesizers, control units, frequency standards and data transmission radio system. The mass of the whole system (satellite and scientific payload) to be carried into orbit by the powerful "Zenit-2SB"-"Fregat-2CB" launcher is about 5000 kg. The RadioAstron project is an international collaboration between RASA and ground radio telescope facilities around the world.

The role of Fizeau interferometry in planetary science

NASA Astrophysics Data System (ADS)

Conrad, Albert R.

2016-08-01

Historically, two types of interferometer have been used to the study of solar system objects: coaxial and Fizeau. While coaxial interferometers are well-suited to a wide range of galactic and extra-galactic science cases, solar system science cases are, in most cases, better carried out with Fizeau imagers. Targets of interest in our solar system are often bright and compact, and the science cases for these objects often call for a complete, or nearly complete, image at high angular resolution. For both methods, multiple images must be taken at varying baselines to reconstruct an image. However, with the Fizeau technique that number is far fewer than it is for the aperture synthesis method employed by co-axial interferometers. In our solar system, bodies rotate and their surfaces are sometimes changing over yearly, or even weekly, time scales. Thus, the need to be able to exploit the high angular resolution of an interferometer with only a handful of observations taken on a single night, as is the case for Fizeau interferometers, gives a key advantage to this technique. The aperture of the Large Binocular Telescope (LBT), two 8.4 circular mirrors separated center-to-center by 14.4 meters, is optimal for supporting Fizeau interferometry. The first of two Fizeau imagers planned for LBT, the LBT Interferometer (LBTI),1 saw first fringes in 2010 and has proven to be a valuable tool for solar system studies. Recent studies of Jupiters volcanic moon Io have yielded results that rely on the angular resolution provided by the full 23-meter baseline of LBT Future studies of the aurora at Jupiters poles and the shape and binarity of asteroids are planned. While many solar system studies can be carried out on-axis (i.e., using the target of interest as the beacon for both adaptive optics correction and fringe tracking), studies such as Io-in-eclipse, full disk of Jupiter and Mars, and binarity of Kuiper belt objects, require off-axis observations (i.e., using one or more nearby guide-moons or stars for adaptive optics correction and fringe tracking). These studies can be plagued by anisoplanatism, or cone effect. LINC-NIRVANA (LN),2 the first multi-conjugate adaptive optics system (MCAO) on an 8-meter class telescope in the northern hemisphere, provides a solution to the ill-effects of anisoplanatism. One of the LN ground layer wave front sensors was tested on LBT during 2014.3-5 Longer term, an upgrade planned for LN will establish its original role as the second LBT Fizeau imager. The full-disk study of several solar system bodies, most notably large and/or nearby bodies such as Jupiter and Mars which span tens of arcseconds, would be best studied with LN. We will review the past accomplishments of Fizeau interferometry with LBTI, present plans for using that instrument for future solar system studies, and, lastly, explore the unique solar system studies that require the LN MCAO system combined with Fizeau interferometry.

Calibration and Performance of the Michelson Doppler Imager on SOHO.

NASA Astrophysics Data System (ADS)

Zayer, I.; Morrison, M.; Tarbell, T. D.; Title, A.; Wolfson, C. J.; MDI Engineering Team; Bogart, R. S.; Bush, R. I.; Hoeksema, J. T.; Duvall, T.; Sa, L. A. D.; Scherrer, P. H.; Schou, J.

1996-05-01

The Michelson Doppler Imager (MDI) instrument probes the interior of the Sun by measuring the photospheric manifestations of solar oscillations. MDI was launched in December, 1995, on the Solar and Heliospheric Observatory (SOHO) and has been successfully observing the Sun since then. The instrument images the Sun on a 1024 x 1024 pixel CCD camera through a series of increasingly narrow spectral filters. The final elements, a pair of tunable Michelson interferometers, enable MDI to record filtergrams with FWHM bandwidth of 94 m Angstroms with a resolution of 4 arcseconds over the whole disk. Images can also be collected in MDI's higher resolution (1.25 arcsecond) field centered about 160 arcseconds north of the equator. An extensive calibration program has verified the end-to-end performance of the instrument in flight. MDI is working very well; we present the most important calibration results and a sample of early science observations. The Image Stabilization System (ISS) maintains overall pointing to better than ca. 0.01 arcsec, while the ISS' diagnostic mode allows us to measure spectrally narrow pointing jitter down to less than 1 mili-arcsec. We have confirmed the linearity of each CCD pixel to lie within 0.5%\\ (the FWHM of the distribution is 0.2% ), and have to date not detected any contamination on the detector, which is cooled to -72 C. The noise in a single Dopplergram is of the order of 20 m/s, and initial measurements of transverse velocities are reliable to 100 m/s. The sensitivity of magnetograms reach 5G in a 10 minute average (15G in a single magnetogram). MDI's primary observable, the p-modes from full-disk medium-l data, are of very high quality out to l=300 as seen in the initial l-nu diagram. The SOI-MDI program is supported by NASA contract NAG5-3077.

Morphological Differences Between Seyfert Hosts and Normal Galaxies

NASA Astrophysics Data System (ADS)

Shlosman, Isaac

Using new sub-arcsecond resolution imaging we compare large-scale stellar bar fraction in CfA sample of Seyferts and a closely matched control sample of normal galaxies. We find a difference between the samples on the 2.5σ level. We further compare the axial ratios of bars in all available samples quoted in the literature and find a deficiency of small axial ratio bars in Seyferts compared to normal galaxies.

Sounding Rocket Instrument Development at UAHuntsville/NASA MSFC

NASA Technical Reports Server (NTRS)

Kobayashi, Ken; Cirtain, Jonathan; Winebarger, Amy; Savage, Sabrina; Golub, Leon; Korreck, Kelly; Kuzin, Sergei; Walsh, Robert; DeForest, Craig; DePontieu, Bart;

HydroSHEDS: A global comprehensive hydrographic dataset

NASA Astrophysics Data System (ADS)

Wickel, B. A.; Lehner, B.; Sindorf, N.

2007-12-01

The Hydrological data and maps based on SHuttle Elevation Derivatives at multiple Scales (HydroSHEDS) is an innovative product that, for the first time, provides hydrographic information in a consistent and comprehensive format for regional and global-scale applications. HydroSHEDS offers a suite of geo-referenced data sets, including stream networks, watershed boundaries, drainage directions, and ancillary data layers such as flow accumulations, distances, and river topology information. The goal of developing HydroSHEDS was to generate key data layers to support regional and global watershed analyses, hydrological modeling, and freshwater conservation planning at a quality, resolution and extent that had previously been unachievable. Available resolutions range from 3 arc-second (approx. 90 meters at the equator) to 5 minute (approx. 10 km at the equator) with seamless near-global extent. HydroSHEDS is derived from elevation data of the Shuttle Radar Topography Mission (SRTM) at 3 arc-second resolution. The original SRTM data have been hydrologically conditioned using a sequence of automated procedures. Existing methods of data improvement and newly developed algorithms have been applied, including void filling, filtering, stream burning, and upscaling techniques. Manual corrections were made where necessary. Preliminary quality assessments indicate that the accuracy of HydroSHEDS significantly exceeds that of existing global watershed and river maps. HydroSHEDS was developed by the Conservation Science Program of the World Wildlife Fund (WWF) in partnership with the U.S. Geological Survey (USGS), the International Centre for Tropical Agriculture (CIAT), The Nature Conservancy (TNC), and the Center for Environmental Systems Research (CESR) of the University of Kassel, Germany.

New Maximum Tsunami Inundation Maps for Use by Local Emergency Planners in the State of California, USA

NASA Astrophysics Data System (ADS)

Wilson, R. I.; Barberopoulou, A.; Miller, K. M.; Goltz, J. D.; Synolakis, C. E.

2008-12-01

A consortium of tsunami hydrodynamic modelers, geologic hazard mapping specialists, and emergency planning managers is producing maximum tsunami inundation maps for California, covering most residential and transient populated areas along the state's coastline. The new tsunami inundation maps will be an upgrade from the existing maps for the state, improving on the resolution, accuracy, and coverage of the maximum anticipated tsunami inundation line. Thirty-five separate map areas covering nearly one-half of California's coastline were selected for tsunami modeling using the MOST (Method of Splitting Tsunami) model. From preliminary evaluations of nearly fifty local and distant tsunami source scenarios, those with the maximum expected hazard for a particular area were input to MOST. The MOST model was run with a near-shore bathymetric grid resolution varying from three arc-seconds (90m) to one arc-second (30m), depending on availability. Maximum tsunami "flow depth" and inundation layers were created by combining all modeled scenarios for each area. A method was developed to better define the location of the maximum inland penetration line using higher resolution digital onshore topographic data from interferometric radar sources. The final inundation line for each map area was validated using a combination of digital stereo photography and fieldwork. Further verification of the final inundation line will include ongoing evaluation of tsunami sources (seismic and submarine landslide) as well as comparison to the location of recorded paleotsunami deposits. Local governmental agencies can use these new maximum tsunami inundation lines to assist in the development of their evacuation routes and emergency response plans.

The NGC 1614 interacting galaxy. Molecular gas feeding a "ring of fire"

NASA Astrophysics Data System (ADS)

König, S.; Aalto, S.; Muller, S.; Beswick, R. J.; Gallagher, J. S.

2013-05-01

Minor mergers frequently occur between giant and gas-rich low-mass galaxies and can provide significant amounts of interstellar matter to refuel star formation and power active galactic nuclei (AGN) in the giant systems. Major starbursts and/or AGN result when fresh gas is transported and compressed in the central regions of the giant galaxy. This is the situation in the starburst minor merger NGC 1614, whose molecular medium we explore at half-arcsecond angular resolution through our observations of 12CO (2-1) emission using the Submillimeter Array (SMA). We compare our 12CO (2-1) maps with optical and Paα, Hubble Space Telescope and high angular resolution radio continuum images to study the relationships between dense molecular gas and the NGC 1614 starburst region. The most intense 12CO emission occurs in a partial ring with ~230 pc radius around the center of NGC 1614, with an extension to the northwest into the dust lane that contains diffuse molecular gas. We resolve ten giant molecular associations (GMAs) in the ring, which has an integrated molecular mass of ~8 × 108 M⊙. Our interferometric observations filter out a large part of the 12CO (1-0) emission mapped at shorter spacings, indicating that most of the molecular gas is diffuse and that GMAs only exist near and within the circumnuclear ring. The molecular ring is uneven with most of the mass on the western side, which also contains GMAs extending into a pronounced tidal dust lane. The spatial and kinematic patterns in our data suggest that the northwest extension of the ring is a cosmic umbilical cord that is feeding molecular gas associated with the dust lane and tidal debris into the nuclear ring, which contains the bulk of the starburst activity. The astrophysical process for producing a ring structure for the final resting place of accreted gas in NGC 1614 is not fully understood, but the presence of numerous GMAs suggests an orbit-crowding or resonance phenomenon. There is some evidence that star formation is progressing radially outward within the ring, indicating that a self-triggering mechanism may also affect star formation processes. The net result of this merger therefore very likely increases the central concentration of stellar mass in the NGC 1614 remnant giant system.

New General Relativistic Contribution to Mercury's Perihelion Advance

NASA Astrophysics Data System (ADS)

Will, Clifford M.

2018-05-01

We point out the existence of a new general relativistic contribution to the perihelion advance of Mercury that, while smaller than the contributions arising from the solar quadrupole moment and angular momentum, is 100 times larger than the second-post-Newtonian contribution. It arises in part from relativistic "crossterms" in the post-Newtonian equations of motion between Mercury's interaction with the Sun and with the other planets, and in part from an interaction between Mercury's motion and the gravitomagnetic field of the moving planets. At a few parts in 1 06 of the leading general relativistic precession of 42.98 arcseconds per century, these effects are likely to be detectable by the BepiColombo mission to place and track two orbiters around Mercury, scheduled for launch around 2018.

New General Relativistic Contribution to Mercury's Perihelion Advance.

PubMed

Will, Clifford M

2018-05-11

We point out the existence of a new general relativistic contribution to the perihelion advance of Mercury that, while smaller than the contributions arising from the solar quadrupole moment and angular momentum, is 100 times larger than the second-post-Newtonian contribution. It arises in part from relativistic "crossterms" in the post-Newtonian equations of motion between Mercury's interaction with the Sun and with the other planets, and in part from an interaction between Mercury's motion and the gravitomagnetic field of the moving planets. At a few parts in 10^{6} of the leading general relativistic precession of 42.98 arcseconds per century, these effects are likely to be detectable by the BepiColombo mission to place and track two orbiters around Mercury, scheduled for launch around 2018.

SPECS: The Kilometer-baseline Far-IR Interferometer in NASA’s Space Science Roadmap

DTIC Science & Technology

2004-01-01

planetary debris disks – are detectable with cryogenically cooled telescopes having total light collecting areas in the tens of square meters. If this...of the Hubble Space Telescope. At such resolution galaxies at high redshift, protostars, and nascent planetary systems will be resolved, and...protogalaxies, the nearest star forming regions, and all but a small handful of debris disks subtend sub- arcsecond angles in the sky. To build a single

First light of the Gemini Planet Imager

DOE PAGES

Macintosh, Bruce; Graham, James R.; Ingraham, Patrick; ...

2014-05-12

The Gemini Planet Imager is a dedicated facility for directly imaging and spectroscopically characterizing extrasolar planets. It combines a very high-order adaptive optics system, a diffraction-suppressing coronagraph, and an integral field spectrograph with low spectral resolution but high spatial resolution. Every aspect of the Gemini Planet Imager has been tuned for maximum sensitivity to faint planets near bright stars. During first-light observations, we achieved an estimated H band Strehl ratio of 0.89 and a 5-σ contrast of 10 6 at 0.75 arcseconds and 10 5 at 0.35 arcseconds. Observations of Beta Pictoris clearly detect the planet, Beta Pictoris b, inmore » a single 60-s exposure with minimal postprocessing. Beta Pictoris b is observed at a separation of 434 ± 6 milliarcseconds (mas) and position angle 211.8 ± 0.5°. Fitting the Keplerian orbit of Beta Pic b using the new position together with previous astrometry gives a factor of 3 improvement in most parameters over previous solutions. The planet orbits at a semimajor axis of 9.0 +0.8 –0.4 AU near the 3:2 resonance with the previously known 6-AU asteroidal belt and is aligned with the inner warped disk. In conclusion, the observations give a 4% probability of a transit of the planet in late 2017.« less

γ-ray telescopes using conversions to e+e- pairs: event generators, angular resolution and polarimetry

NASA Astrophysics Data System (ADS)

Gros, P.; Bernard, D.

2017-02-01

We benchmark various available event generators in Geant4 and EGS5 in the light of ongoing projects for high angular-resolution pair-conversion telescopes at low energy. We compare the distributions of key kinematic variables extracted from the geometry of the three final state particles. We validate and use as reference an exact generator using the full 5D differential cross-section of the conversion process. We focus in particular on the effect of the unmeasured recoiling nucleus on the angular resolution. We show that for high resolution trackers, the choice of the generator affects the estimated resolution of the telescope. We also show that the current available generator are unable to describe accurately a linearly polarised photon source.

Studying AGN Jets At Extreme Angular Resolution

NASA Astrophysics Data System (ADS)

Bruni, Gabriele

2016-10-01

RadioAstron is a 10m antenna orbiting on the Russian Speckt-R spacecraft, launched in 2011. Performing radio interferometry with a global array of ground telescopes, it is providing record angular resolution. The Key Science Project on AGN polarization is exploiting it to study in great detail the configuration of magnetic fields in AGN jets, and understand their formation and collimation. To date, the project has already achieved the highest angular resolution image ever obtained in Astronomy, and detected brightness temperatures exceeding the ones predicted by theory of AGN.

Micro-Slit Collimators for X-Ray/Gamma-Ray Imaging

NASA Technical Reports Server (NTRS)

Appleby, Michael; Fraser, Iain; Klinger, Jill

2011-01-01

A hybrid photochemical-machining process is coupled with precision stack lamination to allow for the fabrication of multiple ultra-high-resolution grids on a single array substrate. In addition, special fixturing and etching techniques have been developed that allow higher-resolution multi-grid collimators to be fabricated. Building on past work of developing a manufacturing technique for fabricating multi-grid, high-resolution coating modulation collimators for arcsecond and subarcsecond x-ray and gamma-ray imaging, the current work reduces the grid pitch by almost a factor of two, down to 22 microns. Additionally, a process was developed for reducing thin, high-Z (tungsten or molybdenum) from the thinnest commercially available foil (25 microns thick) down to approximately equal to 10 microns thick using precisely controlled chemical etching

The rotation of Io

NASA Astrophysics Data System (ADS)

Henrard, Jacques

2005-11-01

The paper develops, in the framework of Hamiltonian mechanics, a theory of the rotation of Io, considered as a rigid body. The theory includes the perturbation due to Jupiter (considered as an oblate body) and the indirect perturbations due to the other Galilean satellites. In order to describe the orbit of Io around Jupiter, we use the synthetic theory of Lainey [2002, PhD dissertation, Observatoire de Paris], the result of a frequency analysis of a numerically integrated jovian system. The direct effects of the other Galilean satellites are found to be negligible, but their indirect effects are important. Our theory is consistent with the rigid body model and with Lainey's description of the orbit of Io, at least down to 10 rad (0.2 arc-second). Of course the effects of the nonrigidity of Io and of a probable liquid core should be considered. We find a mean obliquity of 7.619×10 rad (157 arc-second) and the period of the three free librations to be 13.25 days (free libration in longitude), 159.39 days (free libration in latitude), and 229.85 days (free wobble). Fourier series are produced describing, in the body frame, the motion of the polar axis of Jupiter, the motion of the unit vector pointing toward Jupiter, and the "motion of the pole" (the motion of the angular momentum with respect to the axis of largest inertia). Free librations (depending on three arbitrary parameters) are also computed.

The Stability of Chandra Telescope Pointing and Spacial Resolution

NASA Astrophysics Data System (ADS)

Zhao, Ping

2018-01-01

Chandra X-ray Observatory revolutionized the X-ray astronomy as being the first, and so far the only, X-ray telescope achieving sub-arcsecond spacial resolution. Chandra is comprised of three principal elements: the High Resolution Mirror Assembly (HRMA), Pointing Control and Aspect Determination (PCAD) system, and the Science Instrument Module (SIM), which is where the X-ray detectors mounted and is connected to the HRMA by a 10-meter long Optical Bench Assembly. To achieve and retain the unprecedented imaging quality, it is critical that these three principal elements to stay rigid and stable for the entire life time of the Chandra operation. I will review the issues of telescope pointing stability, optical Axis, aimpoint and their impacts to the Chandra operation, and evaluate the integrity and stability of the telescope. I will show images taken from all four detectors since launch to demonstrate the quality and stability of the Chandra spacial resolution.

The Quality and Stability of Chandra Telescope Spacial Resolution

NASA Astrophysics Data System (ADS)

Zhao, Ping

2017-08-01

Chandra X-ray Observatory revolutionized the X-ray astronomy as being the first, and so far the only, X-ray telescope achieving sub-arcsecond spacial resolution. Chandra is comprised of three principal elements: the High Resolution Mirror Assembly (HRMA), Pointing Control and Aspect Determination (PCAD) system, and the Science Instrument Module (SIM), which is where the X-ray detectors mounted and is connected to the HRMA by a 10-meter long Optical Bench Assembly. To achieve and retain the unprecedented imaging quality, it is critical that these three principal elements to stay rigid and stable for the entire life time of the Chandra operation. I will review the issues of telescope pointing stability, optical Axis, aimpoint and their impacts to the Chandra operation, and evaluate the integrity and stability of the telescope. I will show images taken from all four detectors since launch to demonstrate the quality and stability of the Chandra spacial resolution.

CHEMICAL DIAGNOSTICS OF THE MASSIVE STAR CLUSTER-FORMING CLOUD G33.92+0.11. I. {sup 13}CS, CH{sub 3}OH, CH{sub 3}N, OCS, H{sub 2}S, SO{sub 2}, and SiO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Minh, Young Chol; Liu, Hauyu Baobab; Galvań-Madrid, Roberto

2016-06-20

Large chemical diversity was found in the gas clumps associated with the massive star cluster-forming G33.92+0.11 region with sub-arcsecond angular resolution (0.″6–0.″8) observations with ALMA. The most prominent gas clumps are associated with the dust emission peaks A1, A2, and A5. The close correlation between CH{sub 3}OH and OCS in the emission distributions strongly suggests that these species share a common origin of hot core grain mantle evaporation. The latest generation of star clusters are forming in the A5 clump, as indicated by multiple SiO outflows and its rich hot core chemistry. We also found a narrow SiO emission associatedmore » with the outflows, which may trace a cooled component of the outflows. Part of the chemical complexity may have resulted from the accreting gas from the ambient clouds, especially in the northern part of A1 and the southern part of A2. The chemical diversity found in this region is believed to mainly result from the different chemical evolutionary timescales of massive star formation. In particular, the abundance ratio between CH{sub 3}OH and CH{sub 3}CN may be a good chemical clock for the early phase of star formation.« less

Kinematic Alignment and Bonding of Silicon Mirrors for High-Resolution Astronomical X-Ray Optics

NASA Technical Reports Server (NTRS)

Chan, Kai-Wing; Mazzarella, James R.; Saha, Timo T.; Zhang, William W.; Mcclelland, Ryan S.; Biskack, Michael P.; Riveros, Raul E.; Allgood, Kim D.; Kearney, John D.; Sharpe, Marton V.;

SpIOMM and SITELLE: Wide-field Imaging FTS for the Study of Galaxy Evolution

NASA Astrophysics Data System (ADS)

Drissen, Laurent; Bernier, Anne-Pier; Robert, Carmelle; Robert

2011-12-01

SpIOMM, a wide-field Imaging Fourier Transform Spectrometer attached to the Mont Mégantic 1.6-m telescope, is capable of obtaining the visible spectrum of every source of light in a 12 arcminute field of view, with a spectral resolution ranging from R = 1 (wide-band image) to R = 25 000, resulting in 1.7 million spectra with a spatial resolution of one arcsecond. SITELLE will be a similar instrument attached to the Canada-France-Hawaii telescope, and will be in operation in early 2013. We present a short description of these instruments and illustrate their capabilities to study nearby galaxies with the results of a data cube of M51.

Identification on HST Images of Microlensed Stars from the MACHO Project

NASA Astrophysics Data System (ADS)

King, L. J.; Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Drake, A. J.; Freeman, K. C.; Griest, K.; Lehner, M. J.; Marshall, S. L.; Minniti, D.; Peterson, B. A.; Popowski, P.; Pratt, M. R.; Quinn, P. J.; Rodgers, A. W.; Stubbs, C. W.; Sutherland, W.; Tomaney, A.; Vandehei, T.; Welch, D. L.; MACHO Collaboration

1998-12-01

The MACHO collaboration has been searching for microlensing events toward the Galactic Bulge and the Magellanic Clouds. We have used the WFPC2/HST to obtain high resolution images of a number of fields centred on stars that have undergone microlensing events. Ground based optical images typically have a resolution in excess of one arcsecond, so that the microlensed star may be blended with other stars. On HST images the star is unblended. We show that microlensed stars can be identified by comparing the HST images with image subtracted ground based images. The unblended intrinsic magnitudes, lensed magnitudes and magnifications of the stars can be determined, providing invaluable constraints on lens models.

Angular resolution of the gaseous micro-pixel detector Gossip

NASA Astrophysics Data System (ADS)

Bilevych, Y.; Blanco Carballo, V.; van Dijk, M.; Fransen, M.; van der Graaf, H.; Hartjes, F.; Hessey, N.; Koppert, W.; Nauta, S.; Rogers, M.; Romaniouk, A.; Veenhof, R.

2011-06-01

Gossip is a gaseous micro-pixel detector with a very thin drift gap intended for a high rate environment like at the pixel layers of ATLAS at the sLHC. The detector outputs not only the crossing point of a traversing MIP, but also the angle of the track, thus greatly simplifying track reconstruction. In this paper we describe a testbeam experiment to examine the angular resolution of the reconstructed track segments in Gossip. We used here the low diffusion gas mixture DME/CO 2 50/50. An angular resolution of 20 mrad for perpendicular tracks could be obtained from a 1.5 mm thin drift volume. However, for the prototype detector used at the testbeam experiment, the resolution of slanting tracks was worsened by poor time resolution of the pixel chip used.

Replicated Wolter-I X-ray Optics for Lightweight, High Angular Resolution, Large Collecting Area X-Ray Telescopes

NASA Technical Reports Server (NTRS)

Joy, M.; Bilbro, J.; Elsner, R.; Jones, W.; Kolodziejczak, J.; Petruzzo, J.; ODell, S.; Weisskopf, M.

1997-01-01

The next generation of orbiting x-ray observatories will require high angular resolution telescopes that have an order of magnitude greater collecting area in the 0.1-10 keV spectral region than those currently under construction, but with a much lower weight and cost per unit area. Replicated Wolter-I x-ray optics have the potential to meet this requirement. The currently demonstrated capabilities of replicated Wolter-I optics will be described, and a development plan for creating lightweight, high angular resolution, large effective area x-ray telescopes will be presented.

World Globes, Shaded Relief and Colored Height

NASA Image and Video Library

2003-08-21

These images of the world were generated with data from the Shuttle Radar Topography Mission (SRTM). The SRTM Project has recently released a new global data set called SRTM30, where the original one arcsecond of latitude and longitude resolution (about 30 meters, or 98 feet, at the equator) was reduced to 30 arcseconds (about 928 meters, or 1496 feet.) These images were created from that data set and show the Earth as it would be viewed from a point in space centered over the Americas, Africa and the western Pacific. Two visualization methods were combined to produce the image: shading and color coding of topographic height. The shade image was derived by computing topographic slope in the northwest-southeast direction, so that northwest slopes appear bright and southeast slopes appear dark. Color coding is directly related to topographic height, with green at the lower elevations, rising through yellow and tan, to white at the highest elevations. Elevation data used in this image were acquired by the Shuttle Radar Topography Mission aboard the Space Shuttle Endeavour, launched on Feb. 11, 2000. http://photojournal.jpl.nasa.gov/catalog/PIA03394

Astronomical Optical Interferometry. I. Methods and Instrumentation

NASA Astrophysics Data System (ADS)

Jankov, S.

2010-12-01

Previous decade has seen an achievement of large interferometric projects including 8-10m telescopes and 100m class baselines. Modern computer and control technology has enabled the interferometric combination of light from separate telescopes also in the visible and infrared regimes. Imaging with milli-arcsecond (mas) resolution and astrometry with micro-arcsecond (muas) precision have thus become reality. Here, I review the methods and instrumentation corresponding to the current state in the field of astronomical optical interferometry. First, this review summarizes the development from the pioneering works of Fizeau and Michelson. Next, the fundamental observables are described, followed by the discussion of the basic design principles of modern interferometers. The basic interferometric techniques such as speckle and aperture masking interferometry, aperture synthesis and nulling interferometry are disscused as well. Using the experience of past and existing facilities to illustrate important points, I consider particularly the new generation of large interferometers that has been recently commissioned (most notably, the CHARA, Keck, VLT and LBT Interferometers). Finally, I discuss the longer-term future of optical interferometry, including the possibilities of new large-scale ground-based projects and prospects for space interferometry.

Adaptive Optics Imaging of Solar System Objects

NASA Technical Reports Server (NTRS)

Roddier, Francois; Owen, Toby

1999-01-01

Most solar system objects have never been observed at wavelengths longer than the R band with an angular resolution better than 1". The Hubble Space Telescope itself has only recently been equipped to observe in the infrared. However, because of its small diameter, the angular resolution is lower than that one can now achieved from the ground with adaptive optics, and time allocated to planetary science is limited. We have successfully used adaptive optics on a 4-m class telescope to obtain 0.1" resolution images of solar system objects in the far red and near infrared (0.7-2.5 microns), aE wavelengths which best discl"lmlnate their spectral signatures. Our efforts have been put into areas of research for which high angular resolution is essential.

The nature of the dense obscuring material in the nucleus of NGC 1068

NASA Technical Reports Server (NTRS)

Tacconi, L. J.; Genzel, R.; Blietz, M.; Cameron, M.; Harris, A. I.; Madden, S.

1994-01-01

High spatial and spectral resolution observations of the distribution, physical parameters, and kinematics of the molecular interstellar medium toward the nucleus of the Seyfert 2 galaxy NGC 1068 are reported. The data consist of 2.4 by 3.4 arcseconds resolution interferometry of the 88.6 GHz HCN J = 1 towards 0 line at 17 km/s spectral resolution, single dish observations of several mm/submm isotopic lines of CO and HCN, and 0.85 arcseconds imaging spectroscopy of the 2.12 micron H2 S(1) line at a velocity resolution of 110 km/s. The central few hundred parsecs of NGC 1068 contain a system of dense (N(H2) approximately 10(exp 5) cm(exp -3)), warm (T greater than or equal to 70 K) molecular cloud cores. The low density molecular envelopes have probably been stripped by the nuclear wind and radiation. The molecular gas layer is located in the plane of NGC 1068's large scale disk (inclination approximately 35 deg) and orbits in elliptical streamlines in response to the central stellar bar. The spatial distribution of the 2 micron H2 emission suggests that gas is shocked at the leading edge of the bar, probably resulting in gas influx into the central 100 pc at a rate of a few solar mass per year. In addition to large scale streaming (with a solid body rotation curve), the HCN velocity field requires the presence of random motions of order 100 km/s. We interpret these large random motions as implying the nuclear gas disk to be very thick (scale height/radius approximately 1), probably as the result of the impact of nuclear radiation and wind on orbiting molecular clouds. Geometry and column density of the molecular cloud layer between approximately 30 pc to 300 pc from the nucleus can plausibly account for the nuclear obscuration and anisotropy of the radiation field in the visible and UV.

EUV Solar Instrument Development at the Marshall Space Flight Center

NASA Astrophysics Data System (ADS)

Kobayashi, K.; Cirtain, J. W.; Davis, J. M.; West, E.; Golub, L.; Korreck, K. E.; Tsuneta, S.; Bando, T.

2009-12-01

The three sounding rocket instrument programs currently underway at the NASA Marshall Space Flight Center represent major advances in solar observations, made possible by improvements in EUV optics and detector technology. The Solar Ultraviolet Magnetograph Instrument (SUMI) is an EUV spectropolarimeter designed to measure the Zeeman splitting of two chromospheric EUV lines, the 280 nm MgII and 155 nm CIV lines. SUMI directly observes the magnetic field in the low-beta region where most energetic phenomena are though to originate. In conjunction with visible-light magnetographs, this observation allows us to track the evolution of the magnetic field as it evolves from the photosphere to the upper chromosphere. SUMI incorporates a normal incidence Cassegrain telescope, a MgF2 double-Wollaston polarizing beam splitter and two TVLS (toroidal varied line space) gratings, and is capable of observing two orthogonal polarizations in two wavelength bands simultaneously. SUMI has been fully assembled and tested, and currently scheduled for launch in summer of 2010. The High-resolution Coronal Imager is a normal-incidence EUV imaging telescope designed to achieve 0.2 arcsecond resolution, with a pixel size of 0.1 arcsecond. This is a factor of 25 improvement in aerial resolution over the Transition Region And Coronal Explorer (TRACE). Images obtained by TRACE indicate presence of unresolved structures; higher resolution images will reveal the scale and topology of structures that make up the corona. The telescope mirrors are currently being fabricated, and the instrument has been funded for flight. In addition, a Lyman alpha spectropolarimeter is under development in collaboration with the National Astronomical Observatory of Japan. This aims to detect the linear polarization in the chromosphere caused by the Hanle effect. Horizontal magnetic fields in the chromosphere are expected to be detectable as polarization near disk center, and off-limb observations will reveal the magnetic field structure of filaments and prominences. Laboratory tests of candidate optical components are currently underway.

A comparison of U.S. geological survey seamless elevation models with shuttle radar topography mission data

USGS Publications Warehouse

Gesch, D.; Williams, J.; Miller, W.

2001-01-01

Elevation models produced from Shuttle Radar Topography Mission (SRTM) data will be the most comprehensive, consistently processed, highest resolution topographic dataset ever produced for the Earth's land surface. Many applications that currently use elevation data will benefit from the increased availability of data with higher accuracy, quality, and resolution, especially in poorly mapped areas of the globe. SRTM data will be produced as seamless data, thereby avoiding many of the problems inherent in existing multi-source topographic databases. Serving as precursors to SRTM datasets, the U.S. Geological Survey (USGS) has produced and is distributing seamless elevation datasets that facilitate scientific use of elevation data over large areas. GTOPO30 is a global elevation model with a 30 arc-second resolution (approximately 1-kilometer). The National Elevation Dataset (NED) covers the United States at a resolution of 1 arc-second (approximately 30-meters). Due to their seamless format and broad area coverage, both GTOPO30 and NED represent an advance in the usability of elevation data, but each still includes artifacts from the highly variable source data used to produce them. The consistent source data and processing approach for SRTM data will result in elevation products that will be a significant addition to the current availability of seamless datasets, specifically for many areas outside the U.S. One application that demonstrates some advantages that may be realized with SRTM data is delineation of land surface drainage features (watersheds and stream channels). Seamless distribution of elevation data in which a user interactively specifies the area of interest and order parameters via a map server is already being successfully demonstrated with existing USGS datasets. Such an approach for distributing SRTM data is ideal for a dataset that undoubtedly will be of very high interest to the spatial data user community.

Correction of eddy current distortions in high angular resolution diffusion imaging.

PubMed

Zhuang, Jiancheng; Lu, Zhong-Lin; Vidal, Christine Bouteiller; Damasio, Hanna

2013-06-01

To correct distortions caused by eddy currents induced by large diffusion gradients during high angular resolution diffusion imaging without any auxiliary reference scans. Image distortion parameters were obtained by image coregistration, performed only between diffusion-weighted images with close diffusion gradient orientations. A linear model that describes distortion parameters (translation, scale, and shear) as a function of diffusion gradient directions was numerically computed to allow individualized distortion correction for every diffusion-weighted image. The assumptions of the algorithm were successfully verified in a series of experiments on phantom and human scans. Application of the proposed algorithm in high angular resolution diffusion images markedly reduced eddy current distortions when compared to results obtained with previously published methods. The method can correct eddy current artifacts in the high angular resolution diffusion images, and it avoids the problematic procedure of cross-correlating images with significantly different contrasts resulting from very different gradient orientations or strengths. Copyright © 2012 Wiley Periodicals, Inc.

Chiral resolution of spin angular momentum in linearly polarized and unpolarized light

PubMed Central

Hernández, R. J.; Mazzulla, A.; Provenzano, C.; Pagliusi, P.; Cipparrone, G.

2015-01-01

Linearly polarized (LP) and unpolarized (UP) light are racemic entities since they can be described as superposition of opposite circularly polarized (CP) components of equal amplitude. As a consequence they do not carry spin angular momentum. Chiral resolution of a racemate, i.e. separation of their chiral components, is usually performed via asymmetric interaction with a chiral entity. In this paper we provide an experimental evidence of the chiral resolution of linearly polarized and unpolarized Gaussian beams through the transfer of spin angular momentum to chiral microparticles. Due to the interplay between linear and angular momentum exchange, basic manipulation tasks, as trapping, spinning or orbiting of micro-objects, can be performed by light with zero helicity. The results might broaden the perspectives for development of miniaturized and cost-effective devices. PMID:26585284

Simulated cosmic microwave background maps at 0.5 deg resolution: Basic results

NASA Technical Reports Server (NTRS)

Hinshaw, G.; Bennett, C. L.; Kogut, A.

1995-01-01

We have simulated full-sky maps of the cosmic microwave background (CMB) anisotropy expected from cold dark matter (CDM) models at 0.5 deg and 1.0 deg angular resolution. Statistical properties of the maps are presented as a function of sky coverage, angular resolution, and instrument noise, and the implications of these results for observability of the Doppler peak are discussed. The rms fluctuations in a map are not a particularly robust probe of the existence of a Doppler peak; however, a full correlation analysis can provide reasonable sensitivity. We find that sensitivity to the Doppler peak depends primarily on the fraction of sky covered, and only secondarily on the angular resolution and noise level. Color plates of the simulated maps are presented to illustrate the anisotropies.

NIR Imaging Spectroscopy of the Inner Few Arcseconds of NGC 4151 with OSIRIS at Keck

NASA Technical Reports Server (NTRS)

Iserlohe, Christof; Krabbe, Alfred; Larkin, James E.; Barczys, Matthew; McElwain, Michael W.; Quirrenbach, Andreas; Weiss, Jason; Wright, Shelley A.

2013-01-01

We present H- and K-band data from the inner arcsecond of the Seyfert 1.5 galaxy NGC 4151 obtained with the adaptive optics assisted near-infrared imaging field spectrograph OSIRIS at the Keck Observatory. The angular resolution is about a few parsecs on-site and thus competes easily with optical images taken previously with the Hubble Space Telescope. We present the morphology and dynamics of most species detected but focus on the morphology and dynamics of the narrow line region (as traced by emission of [FeII]?1.644 µm), the interplay between plasma ejected from the nucleus (as traced by 21 cm continuum radio data) and hot H2 gas and characterize the detected nuclear HeI?2.058 µm absorption feature as a narrow absorption line (NAL) phenomenon. Emission from the narrow line region (NLR) as traced by [FeII] reveals a biconical morphology and we compare the measured dynamics in the [FeII] emission line with models proposing acceleration of gas in the NLR and simple ejection of gas into the NLR. In the inner 2.5 arcseconds the acceleration model reveals a better fit to our data than the ejection model.We also see evidence that the jet very locally enhances emission in [FeII] at certain positions in our field-of-view such that we were able to distinct the kinematics of these clouds from clouds generally accelerated in the NLR. Further, the radio jet is aligned with the bicone surface rather than the bicone axis such that we assume that the jet is not the dominant mechanism responsible for driving the kinematics of clouds in the NLR. The hot H2 gas is thermal with a temperature of about 1700 K. We observe a remarkable correlation between individual H2 clouds at systemic velocity with the 21 cm continuum radio jet. We propose that the radio jet is at least partially embedded in the galactic disk of NGC 4151 such that deviations from a linear radio structure are invoked by interactions of jet plasma with H2 clouds that are moving into the path of the jet because of rotation of the galactic disk of NGC 4151. Additionally, we observe a correlation of the jet as traced by the radio data, with gas as traced in Br? and H2, at velocities between systemic and +/- 200 km/s at several locations along the path of the jet. The HeI?2.058 µm line in NGC 4151 appears in emission with a blueshifted absorption component from an outflow. The emission (absorption) component has a velocity offset of 10 km/s (-280 km/s) with a Gaussian (Lorentzian) full-width (half-width) at half maximum of 160 km/s (440 km/s). The absorption component remains spatially unresolved and its kinematic measures differ from that of UV resonance absorption lines. From the amount of absorption we derive a lower limit of the HeI 2S column density of 1 × 10(exp 14) cm-2 with a covering factor along the line-of-sight of C(sub los) approximately equal to 0.1.

Hyperspectral Imagers for the Study of Massive Star Nebulae

NASA Astrophysics Data System (ADS)

Drissen, L.; Alarie, A.; Martin, T.; Spiomm/Sitelle Team

2012-12-01

We present two wide-field imaging Fourier transform spectrometers built by our team to study the interstellar medium around massive stars in the Milky Way and nearby galaxies. SpIOMM, attached to the Mont Mégantic 1.6-m telescope, is capable of obtaining the visible spectrum of every source of light in a 12 arcminute field of view, with a spectral resolution ranging from R = 1 (wide-band image) to R = 25 000, resulting in about a million spectra with a spatial resolution of one arcsecond. SITELLE will be a similar instrument attached to the Canada-France-Hawaii telescope, and will be in operation in early 2013. We illustrate SpIOMM's capabilities to study the interactions between massive stars and their environment.

Primeval galaxies in the sub-mm and mm

NASA Technical Reports Server (NTRS)

Bond, J. Richard; Myers, Steven T.

1993-01-01

Although the results of COBE's FIRAS experiment 1 constrain the deviation in energy from the CMB blackbody in the 500-5000 micron range to be delta E/E, sub cmb less than 0.005, primeval galaxies can still lead to a brilliant sub-mm sky of non-Gaussian sources that are detectable at 10 inch resolution from planned arrays such as SCUBA on the James Clerk Maxwell Telescope and, quite plausibly, at sub-arcsecond resolution in planned mm and sub-mm interferometers. Here, we apply our hierarchical peaks method to a CDM model to construct sub-mm and mm maps of bursting PG's appropriate for these instruments with minimum contours chosen to correspond to realistic observational parameters for them and which pass the FIRAS limits.

Taking the Measure of Massive Stars and their Environments with the CHARA Array Long-baseline Interferometer

NASA Astrophysics Data System (ADS)

Gies, Douglas R.

2017-11-01

Most massive stars are so distant that their angular diameters are too small for direct resolution. However, the observational situation is now much more favorable, thanks to new opportunities available with optical/IR long-baseline interferometry. The Georgia State University Center for High Angular Resolution Astronomy Array at Mount Wilson Observatory is a six-telescope instrument with a maximum baseline of 330 meters, which is capable of resolving stellar disks with diameters as small as 0.2 milliarcsec. The distant stars are no longer out of range, and many kinds of investigations are possible. Here we summarize a number of studies involving angular diameter measurements and effective temperature estimates for OB stars, binary and multiple stars (including the σ Orionis system), and outflows in Luminous Blue Variables. An enlarged visitors program will begin in 2017 that will open many opportunities for new programs in high angular resolution astronomy.

Measurement method for roll angular displacement with a high resolution by using diffraction gratings and a heterodyne interferometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Shanzhi, E-mail: shanzhit@gmail.com; School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049; Wang, Zhao

The roll angle measurement is difficult to be achieved directly using a typical commercial interferometer due to its low sensitivity in axial direction, where the axial direction is orthogonal to the plane of the roll angular displacement. A roll angle measurement method combined diffraction gratings with a laser heterodyne interferometer is discussed in this paper. The diffraction grating placed in the plane of a roll angular displacement and the interferometer arranged in the plane's orthogonal direction, constitute the measurement pattern for the roll angle with high resolution. The roll angular displacement, considered as the linear, can be tested precisely whenmore » the corresponding angle is very small. Using the proposed method, the angle roll measurement obtains the high resolution of 0.002{sup ″}. Experiment has proved its feasibility and practicability.« less

Location of γ -ray emission and magnetic field strengths in OJ 287

DOE PAGES

Hodgson, J. A.; Krichbaum, T. P.; Marscher, A. P.; ...

2017-01-06

We report the γ-ray BL Lac object OJ 287 is known to exhibit inner-parsec “jet-wobbling”, high degrees of variability at all wavelengths and quasi-stationary features, including an apparent (≈100°) position-angle change in projection on the sky plane. Sub-50 micro-arcsecond resolution 86 GHz observations with the global mm-VLBI array (GMVA) supplement ongoing multi-frequency VLBI blazar monitoring at lower frequencies. Using these maps, together with cm/mm total intensity and γ-ray observations from Fermi-LAT from 2008-2014, we aim to Observations with the GMVA offer approximately double the angular resolution compared with 43 GHz VLBA observations and enable us to observe above the synchrotronmore » self-absorption peak frequency. Fermi-LAT γ-ray data were reduced and analysed. The jet was spectrally decomposed at multiple locations along the jet. From this, we could derive estimates of the magnetic field using equipartition and synchrotron self-absorption arguments. How the field decreases down the jet provided an estimate of the distance to the jet apex and an estimate of the magnetic field strength at the jet apex and in the broad line region. Combined with accurate kinematics, we attempt to locate the site of γ-ray activity, radio flares, and spectral changes. Strong γ-ray flares appeared to originate from either the so-called core region, a downstream stationary feature, or both, with γ-ray activity significantly correlated with radio flaring in the downstream quasi-stationary feature. Magnetic field estimates were determined at multiple locations along the jet, with the magnetic field found to be ≥1.6 G in the core and ≤0.4 G in the downstream quasi-stationary feature. Finally, we therefore found upper limits on the location of the VLBI core as ≲6.0 pc from the jet apex and determined an upper limit on the magnetic field near the jet base of the order of thousands of Gauss.« less

Location of γ -ray emission and magnetic field strengths in OJ 287

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hodgson, J. A.; Krichbaum, T. P.; Marscher, A. P.

We report the γ-ray BL Lac object OJ 287 is known to exhibit inner-parsec “jet-wobbling”, high degrees of variability at all wavelengths and quasi-stationary features, including an apparent (≈100°) position-angle change in projection on the sky plane. Sub-50 micro-arcsecond resolution 86 GHz observations with the global mm-VLBI array (GMVA) supplement ongoing multi-frequency VLBI blazar monitoring at lower frequencies. Using these maps, together with cm/mm total intensity and γ-ray observations from Fermi-LAT from 2008-2014, we aim to Observations with the GMVA offer approximately double the angular resolution compared with 43 GHz VLBA observations and enable us to observe above the synchrotronmore » self-absorption peak frequency. Fermi-LAT γ-ray data were reduced and analysed. The jet was spectrally decomposed at multiple locations along the jet. From this, we could derive estimates of the magnetic field using equipartition and synchrotron self-absorption arguments. How the field decreases down the jet provided an estimate of the distance to the jet apex and an estimate of the magnetic field strength at the jet apex and in the broad line region. Combined with accurate kinematics, we attempt to locate the site of γ-ray activity, radio flares, and spectral changes. Strong γ-ray flares appeared to originate from either the so-called core region, a downstream stationary feature, or both, with γ-ray activity significantly correlated with radio flaring in the downstream quasi-stationary feature. Magnetic field estimates were determined at multiple locations along the jet, with the magnetic field found to be ≥1.6 G in the core and ≤0.4 G in the downstream quasi-stationary feature. Finally, we therefore found upper limits on the location of the VLBI core as ≲6.0 pc from the jet apex and determined an upper limit on the magnetic field near the jet base of the order of thousands of Gauss.« less

Direct Polishing of Full-Shell, High-Resolution X-Ray Optics

NASA Technical Reports Server (NTRS)

Roche, Jacqueline M.; Gubarev, Mikhail V.; Smith, W. Scott; O'Dell, Stephen L.; Kolodziejczak, Jeffrey J.; Weisskopf, Martin C.; Ramsey, Brian D.; Elsner, Ronald F.

2014-01-01

Future x-ray telescopes will likely require lightweight mirrors to attain the large collecting areas needed to accomplish the science objectives. Understanding and demonstrating processes now is critical to achieving sub-arcsecond performance in the future. Consequently, designs not only of the mirrors but of fixtures for supporting them during fabrication, metrology, handling, assembly, and testing must be adequately modeled and verified. To this end, MSFC is using finite-element modeling to study the effects of mounting on thin, full-shell grazing-incidence mirrors, during all processes leading to a flight.

Sub-arcsecond observations of the solar X-ray corona

NASA Technical Reports Server (NTRS)

Golub, L.; Nystrom, G.; Herant, M.; Kalata, K.; Lovas, I.

1990-01-01

Results from a high-resolution multi-layer-coated X-ray imaging telescope, part of the Normal Incidence X-ray Telescope sounding rocket payload are presented. Images of the peak of a two-ribbon flare showed detailed structure within each ribbon, as well as the expected bright arches of emission connecting the ribbons. The number of X-ray bright points is small, consistent with predictions based on the previous solar cycle. Topology of the magnetic structure is complex and highly tangled, implying that the magnetic complexity of the photosphere is paralleled in the corona.

Effects of inlet boundary conditions, on the computed flow in the Turbine-99 draft tube, using OpenFOAM and CFX

NASA Astrophysics Data System (ADS)

Nilsson, H.; Cervantes, M. J.

2012-11-01

The flow in the Turbine-99 Kaplan draft tube was thoroughly investigated at three workshops (1999, 2001, 2005), which aimed at determining the state of the art of draft tube simulations. The flow is challenging due to the different flow phenomena appearing simultaneously such as unsteadiness, separation, swirl, turbulence, and a strong adverse pressure gradient. The geometry and the experimentally determined inlet boundary conditions were provided to the Turbine-99 workshop participants. At the final workshop, angular resolved inlet velocity boundary conditions were provided. The rotating non-axi-symmetry of the inlet flow due to the runner blades was thus included. The effect of the rotating angular resolution was however not fully investigated at that workshop. The first purpose of this work is to further investigate this effect. Several different inlet boundary conditions are applied - the angular resolved experimental data distributed at the Turbine-99 workshop, the angular resolved results of a runner simulation with interpolated values using different resolution in the tangential and radial directions, and an axi-symmetric variant of the same numerical data. The second purpose of this work is to compare the results from the OpenFOAM and CFX CFD codes, using as similar settings as possible. The present results suggest that the experimental angular inlet boundary conditions proposed to the workshop are not adequate to simulate accurately the flow in the T-99 draft tube. The reason for this is that the experimental phase-averaged data has some important differences compared to the previously measured time-averaged data. Using the interpolated data from the runner simulation as inlet boundary condition however gives good results as long as the resolution of that data is sufficient. It is shown that the difference between the results using the angular-resolved and the corresponding symmetric inlet data is very small, suggesting that the importance of the angular resolution is small. The results from OpenFOAM and CFX are very similar as long as the inlet data resolution is fine enough. CFX seems to be more sensitive to that resolution.

Observations of Anomalous Refraction with Co-housed Telescopes

NASA Astrophysics Data System (ADS)

Taylor, Malinda S.; McGraw, J. T.; Zimmer, P. C.

2013-01-01

Anomalous refraction is described as a low frequency, large angular scale motion of the entire image plane with respect to the celestial coordinate system as observed and defined by previous astrometric catalogs. These motions of typically several tenths of an arcsecond with timescales on the order of ten minutes are ubiquitous to drift-scan ground-based astrometric measurements regardless of location or telescopes used and have been attributed to meter scale slowly evolving coherent dynamical structures in the boundary-layer below 60 meters. The localized nature of the effect and general inconsistency of the motions seen by even closely spaced telescopes in individual domes has led to the hypothesis that the dome or other type of telescope housing may be responsible. This hypothesis is tested by observing anomalous refraction using two telescopes housed in a single roll-off roof observatory building with the expected outcome that the two telescopes will see correlated anomalous refraction induced motions.

On-orbit figure sensing and figure correction control for 0.5 arc-second adjustable X-ray optics

NASA Astrophysics Data System (ADS)

Reid, Paul

This investigation seeks to develop the technology to directly monitor on-orbit changes to imaging performance of adjustable X-ray optics so as to be able to efficiently correct adverse changes at a level consistent with 0.5 arc-second X-ray telescope imaging. Adjustable X-ray optics employ thin film piezoelectric material deposited on the back of a thin glass Wolter mirror segment to introduce localized stresses in the mirror. These stresses are used in a deterministic way to improve mirror figure from 10 arc-sec, half power diameter (HPD), to 0.5 arc-sec, HPD, without the need for a heavy reaction structure. This is a realizable technology for potential future X-ray telescope missions with 0.5 arc-second resolution and several square meters effective area, such as SMART-X. We are pursuing such mirror development under an existing APRA grant. Here we propose a new investigation to accomplish the monitoring and control of the mirrors by monitoring the health of the piezoelectric actuators of the adjustable optics to a level consistent with 0.5 arcsec imaging. Such measurements are beyond the capability of conventional, thin metal film strain gauges using DC measurements. Instead, we propose to develop the technology to deposit different types of strain gauges (metal film, semiconductor) directly on the piezoelectric cells; to investigate the use of additional thin layers of piezoelectric materials such as lead zirconate titanate or zinc oxide as strain and temperature gauges; and to use AC measurement of strain gauges for precise measurement of piezoelectric adjuster performance. The intent is to use this information to correct changes in mirror shape by adjusting the voltages on the piezoelectric adjustors. Adjustable X-ray optics are designed to meet the challenge of large collecting area and high angular resolution. The mirrors are called adjustable rather than active as mirror figure error is corrected (adjusted) once or infrequently, as opposed to being changed constantly at several cycles/sec (active). In our approach, the mirror figure is corrected based on ground measurements, accounting for figure errors due to mirror manufacturing, mounting induced deformations, modeled gravity release, and modeled on-orbit thermal effects. The piezoelectric strain monitoring we seek to develop in this program extends adjustable mirror technology development, as it enables efficient adjustment and correction of mirror figure on-orbit, as required. This unprecedented level of system robustness will make telescopes less expensive to build because requirements for the non-optical systems can be looser, and it will also make the system more resistant to degradation, promoting mission success. The largest drivers for changes from ground calibration to on-orbit performance are piezoelectric material aging and an unexpected thermal environment (i.e., larger gradients than modeled or other thermal control system problem). Developing the capability to accurately monitor the health of each piezoelectric cell and the local mirror surface temperature will enable the real time sensing of any of these potential issues, help determine the cause, and enable corrections via updating models of on-orbit conditions and re-optimizing the required piezoelectric cell voltages for mirror figure correction. Our 3 year research program includes the development of the strain monitoring technology, its deposition on the adjustable optics, modeling and performance simulation, accelerated lifetime testing, and optical and electrical metrology of sample adjustable optics that incorporate monitoring sensors. Development of the capability to remotely monitor piezo performance and temperature to necessary precision will vastly improve reliability of the SMART-X mission concept, or the sub-arc-second X-ray Surveyor mission described in the 2013 NASA Astrophysics Roadmap, Enduring Quests Daring Visions.

Figure and Dimension Metrology of Extremely Lightweight X-Ray Mirrors for Space Astronomy Applications

NASA Technical Reports Server (NTRS)

Zhang, William W.

2010-01-01

The International X-ray Observatory (IXO) is the next major space X-ray observatory, performing both imaging and spectroscopic studies of all kinds of objects in the Universe. It is a collaborative mission of the National Aeronautics and Space Administration of the United States, the European Space Agency, and Japan Aerospace Exploration Agency. It is to be launched into a Sun-Earth L2 orbit in 2021. One of the most challenging aspects of the mission is the construction of a flight mirror assembly capable focusing X-rays in the band of 0.1 to 40 keY with an angular resolution of better than 5 arc-seconds and with an effective collection area of more than 3 sq m. The mirror assembly will consist of approximately 15,000 parabolic and hyperbolic mirror segments, each of which is approximately 200mm by 300mm with a thickness of 0.4mm. The manufacture and qualification of these mirror segments and their integration into the giant mirror assembly have been the objectives of a vigorous technology development program at NASA's Goddard Space Flight Center. Each of these mirror segments needs to be measured and qualified for both optical figure and mechanical dimensions. In this talk, I will describe the technology program with a particular emphasis on a measurement system we are developing to meet those requirements, including the use of coordinate measuring machines, Fizeau interferometers, and custom-designed, and -built null lens. This system is capable of measuring highly off-axis aspherical or cylindrical mirrors with repeatability, accuracy, and speed.

Spectroscopic CZT detectors development for x- and gamma-ray imaging instruments

NASA Astrophysics Data System (ADS)

Quadrini, Egidio M.; Uslenghi, Michela; Alderighi, Monica; Casini, Fabio; D'Angelo, Sergio; Fiorini, Mauro; La Palombara, Nicola; Mancini, Marcello; Monti, Serena; Bazzano, Angela; Di Cosimo, Sergio; Frutti, Massimo; Natalucci, Lorenzo; Ubertini, Pietro; Guadalupi, Giuseppe M.; Sassi, Matteo; Negri, Barbara

2007-09-01

In the context of R&D studies financed by the Italian Space Agency (ASI), a feasibility study to evaluate the Italian Industry interest in medium-large scale production of enhanced CZT detectors has been performed by an Italian Consortium. The R&D investment aims at providing in-house source of high quality solid state spectrometers for Space Astrophysics applications. As a possible spin-off industrial applications to Gamma-ray devices for non-destructive inspections in medical, commercial and security fields have been considered by ASI. The short term programme mainly consists of developing proprietary procedures for 2-3" CZT crystals growth, including bonding and contact philosophy, and a newly designed low-power electronics readout chain. The prototype design and breadboarding is based on a fast signal AD conversion with the target in order to perform a new run for an already existing low-power (<0.7 mW/pixel) ASIC. The prototype also provides digital photon energy reconstruction with particular care for multiple events and polarimetry evaluations. Scientific requirement evaluations for Space Astrophysics Satellite applications have been carried out in parallel, targeted to contribute to the ESA Cosmic Vision 2015-2025 Announcement of Opportunity. Detailed accommodation studies are undergoing, as part of this programme, to size a "Large area arcsecond angular resolution Imager" for the Gamma Ray Imager satellite (Knödlseder et al., this conference).and a new Gamma-ray Wide Field Camera for the "EDGE" proposal (Piro et al., this conference). Finally, an extended market study for cost analysis evaluation in view of the foreseen massive detector production has been performed.

WEAK AND COMPACT RADIO EMISSION IN EARLY HIGH-MASS STAR-FORMING REGIONS. I. VLA OBSERVATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rosero, V.; Hofner, P.; Claussen, M.

2016-12-01

We present a high-sensitivity radio continuum survey at 6 and 1.3 cm using the Karl G. Jansky Very Large Array toward a sample of 58 high-mass star-forming regions. Our sample was chosen from dust clumps within infrared dark clouds with and without IR sources (CMC–IRs and CMCs, respectively), and hot molecular cores (HMCs), with no previous, or relatively weak radio continuum detection at the 1 mJy level. Due to the improvement in the continuum sensitivity of the Very Large Array, this survey achieved map rms levels of ∼3–10  μ Jy beam{sup −1} at sub-arcsecond angular resolution. We extracted 70 continuum sourcesmore » associated with 1.2 mm dust clumps. Most sources are weak, compact, and prime candidates for high-mass protostars. Detection rates of radio sources associated with the millimeter dust clumps for CMCs, CMC–IRs, and HMCs are 6%, 53%, and 100%, respectively. This result is consistent with increasing high-mass star formation activity from CMCs to HMCs. The radio sources located within HMCs and CMC–IRs occur close to the dust clump centers, with a median offset from it of 12,000 au and 4000 au, respectively. We calculated 5–25 GHz spectral indices using power-law fits and obtained a median value of 0.5 (i.e., flux increasing with frequency), suggestive of thermal emission from ionized jets. In this paper we describe the sample, observations, and detections. The analysis and discussion will be presented in Paper II.« less

Report on the ESO Workshop ''Astronomy at High Angular Resolution''

NASA Astrophysics Data System (ADS)

Boffin, H.; Schmidtobreick, L.; Hussain, G.; Berger, J.-Ph.

2015-03-01

A workshop took place in Brussels in 2000 on astrotomography, a generic term for indirect mapping techniques that can be applied to a huge variety of astrophysical systems, ranging from planets, single stars and binaries to active galactic nuclei. It appeared to be timely to revisit the topic given the many past, recent and forthcoming improvements in telescopes and instrumentation. We therefore decided to repeat the astrotomography workshop, but to put it into the much broader context of high angular resolution astronomy. Many techniques, from lucky and speckle imaging, adaptive optics to interferometry, are now widely employed to achieve high angular resolution and they have led to an amazing number of new discoveries. A summary of the workshop themes is presented.

Lunar Occultations as a Simple Tool for High Angular Resolution Astronomy

NASA Astrophysics Data System (ADS)

Richichi, Andrea

1999-08-01

At the turn of the millennium, modern astronomy is seeing the creation of several new impressive facilities. Among them, large telescopes and long baseline interferometers are beginning to break the limitations imposed by seeing and to push our angular resolution limits at the level of the millisecond of arc. In this race for the state-of-the-art in angular resolution, one should not forget the considerable aid which has been provided for some decades by the more humble technique of lunar occultations. Although burdened with obvious limitations in the choice of the sources, this latter method has two main features that can make it attractive for the modern amateur astronomer: it is simple, and can be implemented also at realtively small telescopes.

k-space and q-space: combining ultra-high spatial and angular resolution in diffusion imaging using ZOOPPA at 7 T.

PubMed

Heidemann, Robin M; Anwander, Alfred; Feiweier, Thorsten; Knösche, Thomas R; Turner, Robert

2012-04-02

There is ongoing debate whether using a higher spatial resolution (sampling k-space) or a higher angular resolution (sampling q-space angles) is the better way to improve diffusion MRI (dMRI) based tractography results in living humans. In both cases, the limiting factor is the signal-to-noise ratio (SNR), due to the restricted acquisition time. One possible way to increase the spatial resolution without sacrificing either SNR or angular resolution is to move to a higher magnetic field strength. Nevertheless, dMRI has not been the preferred application for ultra-high field strength (7 T). This is because single-shot echo-planar imaging (EPI) has been the method of choice for human in vivo dMRI. EPI faces several challenges related to the use of a high resolution at high field strength, for example, distortions and image blurring. These problems can easily compromise the expected SNR gain with field strength. In the current study, we introduce an adapted EPI sequence in conjunction with a combination of ZOOmed imaging and Partially Parallel Acquisition (ZOOPPA). We demonstrate that the method can produce high quality diffusion-weighted images with high spatial and angular resolution at 7 T. We provide examples of in vivo human dMRI with isotropic resolutions of 1 mm and 800 μm. These data sets are particularly suitable for resolving complex and subtle fiber architectures, including fiber crossings in the white matter, anisotropy in the cortex and fibers entering the cortex. Copyright © 2011 Elsevier Inc. All rights reserved.

National Elevation Dataset

USGS Publications Warehouse

,

2002-01-01

The National Elevation Dataset (NED) is a new raster product assembled by the U.S. Geological Survey. NED is designed to provide National elevation data in a seamless form with a consistent datum, elevation unit, and projection. Data corrections were made in the NED assembly process to minimize artifacts, perform edge matching, and fill sliver areas of missing data. NED has a resolution of one arc-second (approximately 30 meters) for the conterminous United States, Hawaii, Puerto Rico and the island territories and a resolution of two arc-seconds for Alaska. NED data sources have a variety of elevation units, horizontal datums, and map projections. In the NED assembly process the elevation values are converted to decimal meters as a consistent unit of measure, NAD83 is consistently used as horizontal datum, and all the data are recast in a geographic projection. Older DEM's produced by methods that are now obsolete have been filtered during the NED assembly process to minimize artifacts that are commonly found in data produced by these methods. Artifact removal greatly improves the quality of the slope, shaded-relief, and synthetic drainage information that can be derived from the elevation data. Figure 2 illustrates the results of this artifact removal filtering. NED processing also includes steps to adjust values where adjacent DEM's do not match well, and to fill sliver areas of missing data between DEM's. These processing steps ensure that NED has no void areas and artificial discontinuities have been minimized. The artifact removal filtering process does not eliminate all of the artifacts. In areas where the only available DEM is produced by older methods, then "striping" may still occur.

A measurement of the cosmic microwave background from the high Chilean Andes

NASA Astrophysics Data System (ADS)

Miller, Amber Dawn

A measurement of the angular spectrum of the Cosmic Microwave Background (CMB) between l = 50 and l = 400 is described. Data were obtained using HEMT radiometers at 30 and 40 GHz with angular resolutions of ≈1 deg and ≈0.7 deg respectively and with SIS based receivers at 144 GHz with angular resolution of ≈0.2 deg. Observations were made from Cerro Toco in the Chilean altiplano at an altitude of 17,000 feet in the Northern Chilean Andes. We find that the angular spectrum rises from l = 50 to a peak at l ≈ 200 and falls off at higher angular scales. A peak in the angular spectrum with amplitude, deltaTl ≈ 85muK is thus located for the first time with a single instrument at l ≈ 200. In addition, we find that the detected anisotropy has the spectrum of the CMB. Cosmological implications of this result are discussed.

High Resolution X-ray Imaging

NASA Technical Reports Server (NTRS)

Cash, Webster

2002-01-01

NAG5-5020 covered a period of 7.5 years during which a great deal of progress was made in x-ray optical techniques under this grant. We survived peer review numerous times during the effort to keep the grant going. In 1994, when the grant started we were actively pursuing the application of spherical mirrors to improving x-ray telescopes. We had found that x-ray detectors were becoming rapidly more sophisticated and affordable, but that x-ray telescopes were only being improved through the intense application of money within the AXAF program. Clearly new techniques for the future were needed. We were successful in developing and testing at the HELSTF facility in New Mexico a four reflection coma-corrected telescope made from spheres. We were able to demonstrate 0.3 arcsecond resolution, almost to the diffraction limit of the system. The community as a whole was, at that time, not particularly interested in looking past AXAF (Chandra) and the effort needed to evolve. Since we had reached the diffraction limit using non-Wolter optics we then decided to see if we could build an x-ray interferometer in the laboratory. In the lab the potential for improved resolution was substantial. If synthetic aperture telescopes could be built in space, then orders of magnitude improvement would become feasible. In 1998 NASA, under the direction of Dr Nick White of Goddard, started a study to assess the potential and feasibility of x-ray interferometry in space. My work became of central interest to the committee because it indicated that such was possible. In early 1999 we had the breakthrough that allowed us build a practical interferometer. By using flats and hooking up with the Marshall Space Flight Center facilities we were able to demonstrate fringes at 1.25keV on a one millimeter baseline. This actual laboratory demonstration provided the solid proof of concept that NASA needed. As the year progressed the future of x-ray astronomy jelled around the Maxim program. Maxim is a set of two major x-ray astronomy missions based on the concepts I developed and demonstrated under this SR&T grant. The first Maxim is to image the sky at 100 micro-arcsecond resolution. That is one thousand times higher resolution than Hubble. The full Maxim has the ultimate goal of imaging the event horizon of a black hole in an active galactic nucleus (ALAN). This will require 0.1 micro-arcsecond resolution - one million times higher than Hubble! Nonetheless, using the techniques developed under this grant, it has become possible. Maxim Pathfinder is now in the NASA planning for a new start in approximately 20 10. The full Maxim is carried as a vision mission for the post 2015 timeframe. Finally, this grant is the evolved version of the SR&T grant we carried during the 1980s and up to 1994. At that point in time this grant was also working on x-ray optics, but concentrating on x-ray spectroscopy. The techniques developed by 1990 were not chosen for use on Chandra or XMM-Newton because they were too new. During the last year, however, the Constellation-X mission recognized the need for better spectroscopy techniques and tapped our expertise. We were able to support the initial work on Con-X through this program. It now appears that the off-plane mount will be used in Con-X, increasing performance and decreasing cost and risk.

A goal-based angular adaptivity method for thermal radiation modelling in non grey media

NASA Astrophysics Data System (ADS)

Soucasse, Laurent; Dargaville, Steven; Buchan, Andrew G.; Pain, Christopher C.

2017-10-01

This paper investigates for the first time a goal-based angular adaptivity method for thermal radiation transport, suitable for non grey media when the radiation field is coupled with an unsteady flow field through an energy balance. Anisotropic angular adaptivity is achieved by using a Haar wavelet finite element expansion that forms a hierarchical angular basis with compact support and does not require any angular interpolation in space. The novelty of this work lies in (1) the definition of a target functional to compute the goal-based error measure equal to the radiative source term of the energy balance, which is the quantity of interest in the context of coupled flow-radiation calculations; (2) the use of different optimal angular resolutions for each absorption coefficient class, built from a global model of the radiative properties of the medium. The accuracy and efficiency of the goal-based angular adaptivity method is assessed in a coupled flow-radiation problem relevant for air pollution modelling in street canyons. Compared to a uniform Haar wavelet expansion, the adapted resolution uses 5 times fewer angular basis functions and is 6.5 times quicker, given the same accuracy in the radiative source term.

Sub-arcsecond, differential deflectometry to measure thermally induced distortions of the Swift optical bench

NASA Astrophysics Data System (ADS)

Leviton, Douglas B.; Frey, Brad J.; Madison, Larry E.; Parker, James A.; Sheinman, Oren E.

2003-03-01

The Swift optical bench is a roughly 2.7 m diameter, 0.1 m thick composite structure carrying the Burst Alert Telescope (BAT), X-ray Telescope (XRT), and the Ultraviolet Optical Telescope (UVOT) as well as various attitude control instrumentation for the spacecraft. A high precision test of the optical bench using multi-aperture optical deflectometry was developed to verify that the relative boresights of the XRT and UVOT instruments would not change by more than several arcseconds when a worst case on-orbit temperature gradient is imposed through the thickness of the bench. Results of validation tests in a laminar flow cleanroom environment without vibration isolation demonstrated a differential measurement capability with 0.2 arcsecond sensitivity and 0.5 arcsecond accuracy per day. The technique is easily adaptable to similar deflection monitoring requirements for other large spacecraft structures.

Restoring the spatial resolution of refocus images on 4D light field

NASA Astrophysics Data System (ADS)

Lim, JaeGuyn; Park, ByungKwan; Kang, JooYoung; Lee, SeongDeok

2010-01-01

This paper presents the method for generating a refocus image with restored spatial resolution on a plenoptic camera, which functions controlling the depth of field after capturing one image unlike a traditional camera. It is generally known that the camera captures 4D light field (angular and spatial information of light) within a limited 2D sensor and results in reducing 2D spatial resolution due to inevitable 2D angular data. That's the reason why a refocus image is composed of a low spatial resolution compared with 2D sensor. However, it has recently been known that angular data contain sub-pixel spatial information such that the spatial resolution of 4D light field can be increased. We exploit the fact for improving the spatial resolution of a refocus image. We have experimentally scrutinized that the spatial information is different according to the depth of objects from a camera. So, from the selection of refocused regions (corresponding depth), we use corresponding pre-estimated sub-pixel spatial information for reconstructing spatial resolution of the regions. Meanwhile other regions maintain out-of-focus. Our experimental results show the effect of this proposed method compared to existing method.

Rapidly-Indexing Incremental-Angle Encoder

NASA Technical Reports Server (NTRS)

Christon, Philip R.; Meyer, Wallace W.

1989-01-01

Optoelectronic system measures relative angular position of shaft or other device to be turned, also measures absolute angular position after device turned through small angle. Relative angular position measured with fine resolution by optoelectronically counting finely- and uniformly-spaced light and dark areas on encoder disk as disk turns past position-sensing device. Also includes track containing coarsely- and nonuniformly-spaced light and dark areas, angular widths varying in proportion to absolute angular position. This second track provides gating and indexing signal.

CHARRON: Code for High Angular Resolution of Rotating Objects in Nature

NASA Astrophysics Data System (ADS)

Domiciano de Souza, A.; Zorec, J.; Vakili, F.

2012-12-01

Rotation is one of the fundamental physical parameters governing stellar physics and evolution. At the same time, spectrally resolved optical/IR long-baseline interferometry has proven to be an important observing tool to measure many physical effects linked to rotation, in particular, stellar flattening, gravity darkening, differential rotation. In order to interpret the high angular resolution observations from modern spectro-interferometers, such as VLTI/AMBER and VEGA/CHARA, we have developed an interferometry-oriented numerical model: CHARRON (Code for High Angular Resolution of Rotating Objects in Nature). We present here the characteristics of CHARRON, which is faster (≃q10-30 s per model) and thus more adapted to model-fitting than the first version of the code presented by Domiciano de Souza et al. (2002).

Angular difference feature extraction for urban scene classification using ZY-3 multi-angle high-resolution satellite imagery

NASA Astrophysics Data System (ADS)

Huang, Xin; Chen, Huijun; Gong, Jianya

2018-01-01

Spaceborne multi-angle images with a high-resolution are capable of simultaneously providing spatial details and three-dimensional (3D) information to support detailed and accurate classification of complex urban scenes. In recent years, satellite-derived digital surface models (DSMs) have been increasingly utilized to provide height information to complement spectral properties for urban classification. However, in such a way, the multi-angle information is not effectively exploited, which is mainly due to the errors and difficulties of the multi-view image matching and the inaccuracy of the generated DSM over complex and dense urban scenes. Therefore, it is still a challenging task to effectively exploit the available angular information from high-resolution multi-angle images. In this paper, we investigate the potential for classifying urban scenes based on local angular properties characterized from high-resolution ZY-3 multi-view images. Specifically, three categories of angular difference features (ADFs) are proposed to describe the angular information at three levels (i.e., pixel, feature, and label levels): (1) ADF-pixel: the angular information is directly extrapolated by pixel comparison between the multi-angle images; (2) ADF-feature: the angular differences are described in the feature domains by comparing the differences between the multi-angle spatial features (e.g., morphological attribute profiles (APs)). (3) ADF-label: label-level angular features are proposed based on a group of urban primitives (e.g., buildings and shadows), in order to describe the specific angular information related to the types of primitive classes. In addition, we utilize spatial-contextual information to refine the multi-level ADF features using superpixel segmentation, for the purpose of alleviating the effects of salt-and-pepper noise and representing the main angular characteristics within a local area. The experiments on ZY-3 multi-angle images confirm that the proposed ADF features can effectively improve the accuracy of urban scene classification, with a significant increase in overall accuracy (3.8-11.7%) compared to using the spectral bands alone. Furthermore, the results indicated the superiority of the proposed ADFs in distinguishing between the spectrally similar and complex man-made classes, including roads and various types of buildings (e.g., high buildings, urban villages, and residential apartments).

Back to the Future: Have Remotely Sensed Digital Elevation Models Improved Hydrological Parameter Extraction?

NASA Astrophysics Data System (ADS)

Jarihani, B.

2015-12-01

Digital Elevation Models (DEMs) that accurately replicate both landscape form and processes are critical to support modeling of environmental processes. Pre-processing analysis of DEMs and extracting characteristics of the watershed (e.g., stream networks, catchment delineation, surface and subsurface flow paths) is essential for hydrological and geomorphic analysis and sediment transport. This study investigates the status of the current remotely-sensed DEMs in providing advanced morphometric information of drainage basins particularly in data sparse regions. Here we assess the accuracy of three available DEMs: (i) hydrologically corrected "H-DEM" of Geoscience Australia derived from the Shuttle Radar Topography Mission (SRTM) data; (ii) the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTER GDEM) version2 1-arc-second (~30 m) data; and (iii) the 9-arc-second national GEODATA DEM-9S ver3 from Geoscience Australia and the Australian National University. We used ESRI's geospatial data model, Arc Hydro and HEC-GeoHMS, designed for building hydrologic information systems to synthesize geospatial and temporal water resources data that support hydrologic modeling and analysis. A coastal catchment in northeast Australia was selected as the study site where very high resolution LiDAR data are available for parts of the area as reference data to assess the accuracy of other lower resolution datasets. This study provides morphometric information for drainage basins as part of the broad research on sediment flux from coastal basins to Great Barrier Reef, Australia. After applying geo-referencing and elevation corrections, stream and sub basins were delineated for each DEM. Then physical characteristics for streams (i.e., length, upstream and downstream elevation, and slope) and sub-basins (i.e., longest flow lengths, area, relief and slopes) were extracted and compared with reference datasets from LiDAR. Results showed that, in the absence of high-precision and high resolution DEM data, ASTER GDEM or SRTM DEM can be used to extract common morphometric relationship which are widely used for hydrological and geomorphological modelling.

Analysis of Inter-Moss Loops in the Solar Region with IRIS and SDO AIA: Automatic Event Detection and Characterization

NASA Technical Reports Server (NTRS)

Fayock, Brian; Winebarger, Amy; De Pontieu, Bart; Alexander, Caroline

2016-01-01

The Interface Region Imaging Spectrograph (IRIS), launched in the summer of 2013, is designed specifically to observe and investigate the transition region and adjacent layers of the solar atmosphere, obtaining images in high spatial, temporal, and spectral resolution. Our particular work is focused on the evolution of inter-moss loops, which have been detected in the lower corona by the Atmospheric Imaging Assembly (AIA) and the High-Resolution Coronal Imager (Hi- C), but are known to have foot points below the transition region. With the high-resolution capabilities of IRIS and its Si IV pass band, which measures activity in the upper chromosphere, we can study these magnetic loops in detail and compare their characteristic length and time scales to those obtained from several AIA image sets, particularly the 171, 193, and 211 pass bands. By comparing the results between these four data sets, one can potentially establish a measure of the ionization equilibrium for the location in question. To explore this idea, we found a large, sit-and-stare observation within the IRIS database that fit our specifications. This data set contained a number of well-defined inter-moss loops (by visual inspection) with a cadence less than or equal to that of AIA (approximately 12 seconds). This particular data set was recorded on October 23, 2013 at 07:09:30, lasting for 3219 seconds with a field of view of 120.6 by 128.1 arcseconds, centered on -53.9 by 59.1 arcseconds from disk center. For ease of comparison, the AIA data has been interpolated to match the IRIS cadence and resolution. In the main portion of the poster, we demonstrate the detection of events, the information collected, and the immediate results to the right, showing the progress of an event with green as the start, blue as the peak, and red as the end. Below here, we demonstrate how pixels are combined to form groups. The 3D results are shown to the right

Analysis of Inter-Moss Loops in the Solar Region with IRIS and SDO AIA: Automatic Event Detection and Characterization

NASA Technical Reports Server (NTRS)

Fayock, Brian; Winebarger, Amy; De Pontieu, Bart

2014-01-01

The Interface Region Imaging Spectrograph (IRIS), launched in the summer of 2013, is designed specifically to observe and investigate the transition region and adjacent layers of the solar atmosphere, obtaining images in high spatial, temporal, and spectral resolution. Our particular work is focused on the evolution of inter-moss loops, which have been detected in the lower corona by the Atmospheric Imaging Assembly (AIA) and the High-Resolution Coronal Imager (Hi- C), but are known to have foot points below the transition region. With the high-resolution capabilities of IRIS and its Si IV pass band, which measures activity in the upper chromosphere, we can study these magnetic loops in detail and compare their characteristic length and time scales to those obtained from several AIA image sets, particularly the 171, 193, and 211 pass bands. By comparing the results between these four data sets, one can potentially establish a measure of the ionization equilibrium for the location in question. To explore this idea, we found a large, sit-and-stare observation within the IRIS database that fit our specifications. This data set contained a number of well-defined inter-moss loops (by visual inspection) with a cadence less than or equal to that of AIA (approximately 12 seconds). This particular data set was recorded on October 23, 2013 at 07:09:30, lasting for 3219 seconds with a field of view of 120.6 by 128.1 arcseconds, centered on -53.9 by 59.1 arcseconds from disk center. For ease of comparison, the AIA data has been interpolated to match the IRIS cadence and resolution. In the main portion of the poster, we demonstrate the detection of events, the information collected, and the immediate results to the right, showing the progress of an event with green as the start, blue as the peak, and red as the end. Below here, we demonstrate how pixels are combined to form groups. The 3D results are shown to the right.

Aerosol Retrieval from Multiangle Multispectral Photopolarimetric Measurements: Importance of Spectral Range and Angular Resolution

NASA Technical Reports Server (NTRS)

Wu, L.; Hasekamp, O.; Van Diedenhoven, B.; Cairns, B.

2015-01-01

We investigated the importance of spectral range and angular resolution for aerosol retrieval from multiangle photopolarimetric measurements over land. For this purpose, we use an extensive set of simulated measurements for different spectral ranges and angular resolutions and subsets of real measurements of the airborne Research Scanning Polarimeter (RSP) carried out during the PODEX and SEAC4RS campaigns over the continental USA. Aerosol retrievals performed from RSP measurements show good agreement with ground-based AERONET measurements for aerosol optical depth (AOD), single scattering albedo (SSA) and refractive index. Furthermore, we found that inclusion of shortwave infrared bands (1590 and/or 2250 nm) significantly improves the retrieval of AOD, SSA and coarse mode microphysical properties. However, accuracies of the retrieved aerosol properties do not improve significantly when more than five viewing angles are used in the retrieval.

Materials characterisation by angle-resolved scanning transmission electron microscopy.

PubMed

Müller-Caspary, Knut; Oppermann, Oliver; Grieb, Tim; Krause, Florian F; Rosenauer, Andreas; Schowalter, Marco; Mehrtens, Thorsten; Beyer, Andreas; Volz, Kerstin; Potapov, Pavel

2016-11-16

Solid-state properties such as strain or chemical composition often leave characteristic fingerprints in the angular dependence of electron scattering. Scanning transmission electron microscopy (STEM) is dedicated to probe scattered intensity with atomic resolution, but it drastically lacks angular resolution. Here we report both a setup to exploit the explicit angular dependence of scattered intensity and applications of angle-resolved STEM to semiconductor nanostructures. Our method is applied to measure nitrogen content and specimen thickness in a GaN x As 1-x layer independently at atomic resolution by evaluating two dedicated angular intervals. We demonstrate contrast formation due to strain and composition in a Si- based metal-oxide semiconductor field effect transistor (MOSFET) with Ge x Si 1-x stressors as a function of the angles used for imaging. To shed light on the validity of current theoretical approaches this data is compared with theory, namely the Rutherford approach and contemporary multislice simulations. Inconsistency is found for the Rutherford model in the whole angular range of 16-255 mrad. Contrary, the multislice simulations are applicable for angles larger than 35 mrad whereas a significant mismatch is observed at lower angles. This limitation of established simulations is discussed particularly on the basis of inelastic scattering.

Method for improving the angular resolution of a neutron scatter camera

DOEpatents

Mascarenhas, Nicholas; Marleau, Peter; Gerling, Mark; Cooper, Robert Lee; Mrowka, Stanley; Brennan, James S.

2012-12-25

An instrument that will directly image the fast fission neutrons from a special nuclear material source wherein the neutron detection efficiency is increased has been described. Instead of the previous technique that uses a time-of-flight (TOF) between 2 widely spaced fixed planes of neutron detectors to measure scatter neutron kinetic energy, we now use the recoil proton energy deposited in the second of the 2 scatter planes which can now be repositioned either much closer together or further apart. However, by doubling the separation distance between the 2 planes from 20 cm to a distance of 40 cm we improved the angular resolution of the detector from about 12.degree. to about 10.degree.. A further doubling of the separation distance to 80 cm provided an addition improvement in angular resolution of the detector to about 6.degree. without adding additional detectors or ancillary electronics. The distance between planes also may be dynamically changed using a suitable common technique such as a gear- or motor-drive to toggle between the various positions. The angular resolution of this new configuration, therefore, is increased at the expanse of detection sensitivity. However, the diminished sensitivity may be acceptable for those applications where the detector is able to interrogate a particular site for an extended period.

High Resolution Near-IR Imaging of VY Canis Majoris with LBT / LMIRCam (2 - 5 μm)

NASA Astrophysics Data System (ADS)

Shenoy, Dinesh; Jones, T. J.; Humphreys, R. M.; LMIRCam Instrument Team

2013-06-01

HST imaging of the famous red hypergiant VY Canis Majoris shows a complex circumstellar reflection nebula indicative of multiple asymmetric ejection episodes. Constructing a more complete picture of the mass loss mechanism compels extending high resolution imaging of massive stars such as VY CMa into the near-infrared, where the mechanism for emission from circumstellar ejecta transitions from scattering to thermal. We present LBT/LMIRCam observations of VY CMa at Ks (2.2 μm), L' (3.8 μm) and M (4.9 μm) at sub-arcsecond resolution, comparable to the HST in the optical. The peculiar Southwest (SW) Clump, first identified as a highly reddened feature seen only at the longest wavelength (1 μm) in the HST images, appears bright in the three LMIRCam filters. The SW Clump is found to be optically thick at all three wavelengths. A silicate grain model yields a lower limit mass on the order of 7E-4 M⊙

Angular width of the Cherenkov radiation with inclusion of multiple scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Jian, E-mail: jzheng@ustc.edu.cn

2016-06-15

Visible Cherenkov radiation can offer a method of the measurement of the velocity of charged particles. The angular width of the radiation is important since it determines the resolution of the velocity measurement. In this article, the angular width of Cherenkov radiation with inclusion of multiple scattering is calculated through the path-integral method, and the analytical expressions are presented. The condition that multiple scattering processes dominate the angular distribution is obtained.

High Resolution Spectrograph for the Hobby-Eberly Telescope

NASA Astrophysics Data System (ADS)

Tull, R. G.; MacQueen, P. J.; Good, J.; Epps, H. W.; HET HRS Team

1998-12-01

A fiber fed high-resolution spectrograph (HRS) is under construction for the Hobby-Eberly Telescope (HET). The primary resolving power originally specified, from astrophysical considerations, was R = 60,000 with a fiber of diameter at least 1 arc-second, with full spectral coverage limited only by the combined band-pass of the HET, the optical fiber, and the image detector. This was achieved in the final design with a high blaze angle R-4 echelle mosaic, white pupil design, image slicing, and a large area CCD mosaic illuminated by an eight element refractive camera. Two back-to-back, user selectable first-order diffraction gratings are employed for cross dispersion, to separate echelle spectral orders; the entire spectral range (420 - 1,000 nm) can be covered in as few as two exposures. Critical issues addressed in the design are cross dispersion and order spacing, sky subtraction, echelle and CCD selection, fiber optic feed and scrambling, and image or pupil slicing. In the final design meeting the requirements we exploited the large-area 4096 square CCD, image slicing, and the optical performance of the white-pupil design to acquire a range of 30,000 < R < 120,000 with fibers of diameter 2 and 3 arc-seconds, without sacrificing full spectral coverage. Design details will be presented. Limiting magnitude is projected to be about V = 19 (for S/N = 10) at the nominal R = 60,000 resolving power. The poster display will outline performance characteristics expected in relation to projected astrophysical research capabilities outlined by Sneden et al., in this conference. HRS is supported by generous grants from NSF, NASA, the State of Texas, and private philanthropy, with matching funds granted by the University of Texas and by McDonald Observatory.

a Near-Global Bare-Earth dem from Srtm

NASA Astrophysics Data System (ADS)

Gallant, J. C.; Read, A. M.

2016-06-01

The near-global elevation product from NASA's Shuttle Radar Topographic Mission (SRTM) has been widely used since its release in 2005 at 3 arcsecond resolution and the release of the 1 arcsecond version in late 2014 means that the full potential of the SRTM DEM can now be realised. However the routine use of SRTM for analytical purposes such as catchment hydrology, flood inundation, habitat mapping and soil mapping is still seriously impeded by the presence of artefacts in the data, primarily the offsets due to tree cover and the random noise. This paper describes the algorithms being developed to remove those offsets, based on the methods developed to produce the Australian national elevation model from SRTM data. The offsets due to trees are estimated using the GlobeLand30 (National Geomatics Center of China) and Global Forest Change (University of Maryland) products derived from Landsat, along with the ALOS PALSAR radar image data (JAXA) and the global forest canopy height map (NASA). The offsets are estimated using several processes and combined to produce a single continuous tree offset layer that is subtracted from the SRTM data. The DEM products will be made freely available on completion of the first draft product, and the assessment of that product is expected to drive further improvements to the methods.

Chemical and Physical Picture of IRAS 16293–2422 Source B at a Sub-arcsecond Scale Studied with ALMA

NASA Astrophysics Data System (ADS)

Oya, Yoko; Moriwaki, Kana; Onishi, Shusuke; Sakai, Nami; López–Sepulcre, Ana; Favre, Cécile; Watanabe, Yoshimasa; Ceccarelli, Cecilia; Lefloch, Bertrand; Yamamoto, Satoshi

2018-02-01

We have analyzed the OCS, H2CS, CH3OH, and HCOOCH3 data observed toward the low-mass protostar IRAS 16293–2422 Source B at a sub-arcsecond resolution with ALMA. A clear chemical differentiation is seen in their distributions; OCS and H2CS are extended with a slight rotation signature, while CH3OH and HCOOCH3 are concentrated near the protostar. Such a chemical change in the vicinity of the protostar is similar to the companion (Source A) case. The extended component is interpreted by the infalling-rotating envelope model with a nearly face-on configuration. The radius of the centrifugal barrier of the infalling-rotating envelope is roughly evaluated to be (30–50) au. The observed lines show the inverse P-Cygni profile, indicating the infall motion within a few 10 au from the protostar. The nearly pole-on geometry of the outflow lobes is inferred from the SiO distribution, and thus, the infalling and outflowing motions should coexist along the line of sight to the protostar. This implies that the infalling gas is localized near the protostar and the current launching points of the outflow have an offset from the protostar. A possible mechanism for this configuration is discussed.

Monitoring of Mira (omi Cet) in support of HST Observations

NASA Astrophysics Data System (ADS)

Karovska, Margarita; Templeton, Matthew R.

2007-09-01

Dr. Margarita Karovska (Harvard-Smithsonian Center for Astrophysics) and collaborators are performing a comprehensive study of the Mira AB interacting system, using the HST WFPC2 camera. Mira AB is composed of the prototype Mira variable omi Cet and its companion VZ Cet, separated by about 0.5 arcsecond. As part of this project they plan to obtain a large number of high-angular resolution images at wavelengths ranging from UV to optical. The main objectives of the HST/WFPC2 observations are 1) to determine the properties of the material ejected in December 2004 as it flows throughout the binary and interacts with the Mira A (omi Cet, Mira) circumstellar material and wind; 2) to determine the physical characteristics of mass transfer in this system and especially the role of the accretion stream between Mira A and its accreting companion Mira B (VZ Cet); 3) to determine the response of the system to the increased accretion rate onto Mira B following the outburst. The HST observations are scheduled for September 23, 1900-2300 UT. Both visual and instrumental observers are requested to observe this object, currently at minimum around visual magnitude 9-9.5. Observations should be made approximately two weeks on either side of the September 23 observation date. Visual observer should observe as usual, making not more than 3 observations spaced about 10 days apart. PEP and CCD observers should use the bluest-wavelength filters they have, and should make nightly observations, with intensive observations during the HST observations themselves. UBV and RIJH observations would be very valuable. Please make sure to use an aperture that covers both omi Cet and VZ Cet when evaluating CCD images. Observations should be submitted to the AAVSO International Database as OMI CET.

Optical design of the STAR-X telescope

NASA Astrophysics Data System (ADS)

Saha, Timo T.; Zhang, William W.; McClelland, Ryan S.

2017-08-01

Top-level science objectives of the Survey and Time-domain Astrophysical Research eXplorer (STAR-X) include: investigations of most violent explosions in the universe, study of growth of black holes across cosmic time and mass scale, and measure how structure formation heats majority of baryons in the universe. To meet these objectives, the STAR-X telescope requires a field of view of about 1 square-degree, an angular resolution of 5 arc-seconds or better across large part of the field of view. The on-axis effective area at 1 keV should be about 2,000 cm2 . Payload cost and launch considerations limit the outer diameter, focal length, and mass to 1.3 meters, 5 meters, and 250 kilograms, respectively. Telescope design is based on a segmented meta-shell approach we have developed at Goddard Space Flight Center. The telescope mirror shells are divided into segments. Individual shells are nested inside each other to meet the effective area requirements in 0.5 - 6.0 keV range. We consider Wolter-Schwarzschild, and Modified-WolterSchwarzschild telescopes. These designs offer an excellent PSF over a large field of view. Nested shells are vulnerable to stray light problems. We have designed a multi-component baffle system to eliminate direct and single-reflection light paths inside the mirror assembly. Large numbers of internal and external baffles are required to prevent stray rays from reaching the focal plane. We have developed a simple ray-trace tool to determine the dimensions and locations of the baffles. In this paper, we present the results of our trade studies, baffle design studies, and optical performance analyses of the STAR-X telescope.

Towards a coherent view at infrared wavelengths of mass loss in Betelgeuse

NASA Astrophysics Data System (ADS)

Kervella, P.; Perrin, G.; Montargès, M.; Haubois, X.

2013-05-01

The violent convective motions, low surface gravity, and high brightness of red supergiants combine to trigger an intense stellar wind. As the distance from the star increases, the standard scenario is that the ejected material forms molecules, then dust particles. But this general picture is still fragmentary. Our goal is to assemble a better understanding of mass loss in Betelgeuse, considered as a prototype for its class, from its photosphere to the interface of its wind with the interstellar medium. Thanks to its proximity ( ≈ 197 pc), it is ideally suited for such a detailed study. Over the past few years, our team obtained an extensive set of observations of Betelgeuse from high angular resolution instruments, probing a broad range of spatial scales: 1) interferometric imaging of its photosphere and close envelope in the near- and thermal-IR domains (IOTA/IONIC), 2) adaptive optics "lucky imaging" of its compact molecular envelope (VLT/NACO, 1.0-2.2 μm), and 3) diffraction-limited imaging of its dusty envelope (VLT/VISIR, 8-20 μm). From our interferometric data, we detect the presence of spots at the surface of the star, as well as CO and H2O molecules, and dust particles close to the star. Within 6 R⋆, the flux distribution of the envelope is compatible with the presence of the CN molecule. At a few arcseconds from the central star, we observe a complex dusty envelope probably containing O-rich dust (e.g. silicates, alumina). We present an overview of these recent observational results and ongoing work. They provide new hints on the physical and chemical mechanisms through which Betelgeuse interacts with its environment.

Technology development for the Advanced Technology Large Aperture Space Telescope (ATLAST) as a candidate large UV-Optical-Infrared (LUVOIR) surveyor

NASA Astrophysics Data System (ADS)

Bolcar, Matthew R.; Balasubramanian, Kunjithapatham; Clampin, Mark; Crooke, Julie; Feinberg, Lee; Postman, Marc; Quijada, Manuel; Rauscher, Bernard; Redding, David; Rioux, Norman; Shaklan, Stuart; Stahl, H. Philip; Stahle, Carl; Thronson, Harley

2015-09-01

The Advanced Technology Large Aperture Space Telescope (ATLAST) team has identified five key technologies to enable candidate architectures for the future large-aperture ultraviolet/optical/infrared (LUVOIR) space observatory envisioned by the NASA Astrophysics 30-year roadmap, Enduring Quests, Daring Visions. The science goals of ATLAST address a broad range of astrophysical questions from early galaxy and star formation to the processes that contributed to the formation of life on Earth, combining general astrophysics with direct-imaging and spectroscopy of habitable exoplanets. The key technologies are: internal coronagraphs, starshades (or external occulters), ultra-stable large-aperture telescopes, detectors, and mirror coatings. Selected technology performance goals include: 1x10-10 raw contrast at an inner working angle of 35 milli-arcseconds, wavefront error stability on the order of 10 pm RMS per wavefront control step, autonomous on-board sensing and control, and zero-read-noise single-photon detectors spanning the exoplanet science bandpass between 400 nm and 1.8 μm. Development of these technologies will provide significant advances over current and planned observatories in terms of sensitivity, angular resolution, stability, and high-contrast imaging. The science goals of ATLAST are presented and flowed down to top-level telescope and instrument performance requirements in the context of a reference architecture: a 10-meter-class, segmented aperture telescope operating at room temperature (~290 K) at the sun-Earth Lagrange-2 point. For each technology area, we define best estimates of required capabilities, current state-of-the-art performance, and current Technology Readiness Level (TRL) - thus identifying the current technology gap. We report on current, planned, or recommended efforts to develop each technology to TRL 5.

Technology Development for the Advanced Technology Large Aperture Space Telescope (ATLAST) as a Candidate Large UV-Optical-Infrared (LUVOIR) Surveyor

NASA Technical Reports Server (NTRS)

Bolcar, Matthew R.; Balasubramanian, Kunjithapatha; Clampin, Mark; Crooke, Julie; Feinberg, Lee; Postman, Marc; Quijada, Manuel; Rauscher, Bernard; Redding, David; Rioux, Norman;

X-ray optics for the LAMAR facility, an overview. [Large Area Modular Array of Reflectors

NASA Technical Reports Server (NTRS)

Gorenstein, P.

1979-01-01

The paper surveys the Large Area Modular Array of Reflectors (LAMAR), the concept of which is based on meeting two major requirements in X-ray astronomy, large collecting area and moderately good or better angular resolution for avoiding source confusion and imaging source fields. It is shown that the LAMAR provides the same sensitivity and signal to noise in imaging as a single large telescope having the same area and angular resolution but is a great deal less costly to develop, construct, and integrate into a space mission. Attention is also given to the LAMAR modular nature which will allow for an evolutionary development from a modest size array on Spacelab to a Shuttle launched free flyer. Finally, consideration is given to manufacturing methods which show promise of making LAMAR meet the criteria of good angular resolution, relatively low cost, and capability for fast volume production.

Understanding deformation with high angular resolution electron backscatter diffraction (HR-EBSD)

NASA Astrophysics Data System (ADS)

Britton, T. B.; Hickey, J. L. R.

2018-01-01

High angular resolution electron backscatter diffraction (HR-EBSD) affords an increase in angular resolution, as compared to ‘conventional’ Hough transform based EBSD, of two orders of magnitude, enabling measurements of relative misorientations of 1 x 10-4 rads (~ 0.006°) and changes in (deviatoric) lattice strain with a precision of 1 x 10-4. This is achieved through direct comparison of two or more diffraction patterns using sophisticated cross-correlation based image analysis routines. Image shifts between zone axes in the two-correlated diffraction pattern are measured with sub-pixel precision and this realises the ability to measure changes in interplanar angles and lattice orientation with a high degree of sensitivity. These shifts are linked to strains and lattice rotations through simple geometry. In this manuscript, we outline the basis of the technique and two case studies that highlight its potential to tackle real materials science challenges, such as deformation patterning in polycrystalline alloys.

Scientific Benefit of Enlarging Gravitational Wave Detector Networks

NASA Astrophysics Data System (ADS)

Chu, Qi; Wen, Linqing; Blair, David

2012-06-01

Localising the sources of gravitational waves (GWs) in the sky is crucial to observing the electromagnetic counterparts of GW sources. The localisation capability is poor by a single GW detector yet can be improved by adding more detectors to the detector network. In this paper we review recent studies on scientific benefits of global detector networks and focus on their localisation capability. We employ Wen-Chen's formula to compare this merit of current and future detector networks for localising gravitational wave bursts. We find that the addition of a new detector located in Japan, or India, or Australia will increase angular resolution 3~5 fold with respect to current LIGO-Virgo network, and that the angular resolution improvement by adding a single detector in Australia is comparable to that achieved by adding detectors in both India and Japan. A six-site network achieves a 11-fold improvement in angular resolution compared with the existing three-site network.

Development of a High Angular Resolution Diffusion Imaging Human Brain Template

PubMed Central

Varentsova, Anna; Zhang, Shengwei; Arfanakis, Konstantinos

2014-01-01

Brain diffusion templates contain rich information about the microstructure of the brain, and are used as references in spatial normalization or in the development of brain atlases. The accuracy of diffusion templates constructed based on the diffusion tensor (DT) model is limited in regions with complex neuronal micro-architecture. High angular resolution diffusion imaging (HARDI) overcomes limitations of the DT model and is capable of resolving intravoxel heterogeneity. However, when HARDI is combined with multiple-shot sequences to minimize image artifacts, the scan time becomes inappropriate for human brain imaging. In this work, an artifact-free HARDI template of the human brain was developed from low angular resolution multiple-shot diffusion data. The resulting HARDI template was produced in ICBM-152 space based on Turboprop diffusion data, was shown to resolve complex neuronal micro-architecture in regions with intravoxel heterogeneity, and contained fiber orientation information consistent with known human brain anatomy. PMID:24440528

High resolution tip-tilt positioning system for a next generation MLL-based x-ray microscope

DOE PAGES

Xu, Weihe; Schlossberger, Noah; Xu, Wei; ...

2017-11-15

Multilayer Laue lenses (MLLs) are x-ray focusing optics with the potential to focus hard x-rays down to a single nanometer level. In order to achieve point focus, an MLL microscope needs to have the capability to perform tip-tilt motion of MLL optics and to hold the angular position for an extended period of time. Here, we present a 2D tip-tilt system that can achieve an angular resolution of over 100 microdegree with a working range of 4°, by utilizing a combination of laser interferometer and mini retroreflector. The linear dimensions of the developed system are about 30 mm in allmore » directions, and the thermal dissipation of the system during operation is negligible. Compact design and high angular resolution make the developed system suitable for MLL optics alignment in the next generation of MLL-based x-ray microscopes.« less

High resolution tip-tilt positioning system for a next generation MLL-based x-ray microscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Weihe; Schlossberger, Noah; Xu, Wei

Multilayer Laue lenses (MLLs) are x-ray focusing optics with the potential to focus hard x-rays down to a single nanometer level. In order to achieve point focus, an MLL microscope needs to have the capability to perform tip-tilt motion of MLL optics and to hold the angular position for an extended period of time. Here, we present a 2D tip-tilt system that can achieve an angular resolution of over 100 microdegree with a working range of 4°, by utilizing a combination of laser interferometer and mini retroreflector. The linear dimensions of the developed system are about 30 mm in allmore » directions, and the thermal dissipation of the system during operation is negligible. Compact design and high angular resolution make the developed system suitable for MLL optics alignment in the next generation of MLL-based x-ray microscopes.« less

ALMA data suggest the presence of spiral structure in the inner wind of CW Leonis

NASA Astrophysics Data System (ADS)

Decin, L.; Richards, A. M. S.; Neufeld, D.; Steffen, W.; Melnick, G.; Lombaert, R.

2015-02-01

Context. Evolved low-mass stars lose a significant fraction of their mass through stellar winds. While the overall morphology of the stellar wind structure during the asymptotic giant branch (AGB) phase is thought to be roughly spherically symmetric, the morphology changes dramatically during the post-AGB and planetary nebula phase, during which bipolar and multi-polar structures are often observed. Aims: We aim to study the inner wind structure of the closest well-known AGB star CW Leo. Different diagnostics probing different geometrical scales have implied a non-homogeneous mass-loss process for this star: dust clumps are observed at milli-arcsec scale, a bipolar structure is seen at arcsecond-scale, and multi-concentric shells are detected beyond 1''. Methods: We present the first ALMA Cycle 0 band 9 data around 650 GHz (450 μm) tracing the inner wind of CW Leo. The full-resolution data have a spatial resolution of 0.̋42 × 0.̋24, allowing us to study the morpho-kinematical structure of CW Leo within ~6''. Results: We have detected 25 molecular emission lines in four spectral windows. The emission of all but one line is spatially resolved. The dust and molecular lines are centered around the continuum peak position, which is assumed to be dominated by stellar emission. The dust emission has an asymmetric distribution with a central peak flux density of ~2 Jy. The molecular emission lines trace different regions in the wind acceleration region and imply that the wind velocity increases rapidly from about 5 R⋆, almost reaching the terminal velocity at ~11 R⋆. The images prove that vibrational lines are excited close to the stellar surface and that SiO is a parent molecule. The channel maps for the brighter lines show a complex structure; specifically, for the 13CO J = 6-5 line, different arcs are detected within the first few arcseconds. The curved structure in the position-velocity (PV) map of the 13CO J = 6-5 line can be explained by a spiral structure in the inner wind of CW Leo, probably induced by a binary companion. From modelling the ALMA data, we deduce that the potential orbital axis for the binary system lies at a position angle of ~10-20° to the north-east and that the spiral structure is seen almost edge-on. We infer an orbital period of 55 yr and a binary separation of 25 au (or ~8.2 R⋆). We tentatively estimate that the companion is an unevolved low-mass main-sequence star. Conclusions: A scenario of a binary-induced spiral shell can explain the correlated structure seen in the ALMA PV images of CW Leo. Moreover, this scenario can also explain many other observational signatures seen at different spatial scales and in different wavelength regions, such as the bipolar structure and the almost concentric shells. ALMA data hence for the first time provide the crucial kinematical link between the dust clumps seen at milli-arcsecond scale and the almost concentric arcs seen at arcsecond scale. Appendix A is available in electronic form at http://www.aanda.org

Quadratic Finite Element Method for 1D Deterministic Transport

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tolar, Jr., D R; Ferguson, J M

2004-01-06

In the discrete ordinates, or SN, numerical solution of the transport equation, both the spatial ({und r}) and angular ({und {Omega}}) dependences on the angular flux {psi}{und r},{und {Omega}}are modeled discretely. While significant effort has been devoted toward improving the spatial discretization of the angular flux, we focus on improving the angular discretization of {psi}{und r},{und {Omega}}. Specifically, we employ a Petrov-Galerkin quadratic finite element approximation for the differencing of the angular variable ({mu}) in developing the one-dimensional (1D) spherical geometry S{sub N} equations. We develop an algorithm that shows faster convergence with angular resolution than conventional S{sub N} algorithms.

Astrophysical targets of the Fresnel diffractive imager

NASA Astrophysics Data System (ADS)

Koechlin, L.; Deba, P.; Raksasataya, T.

2017-11-01

The Fresnel Diffractive imager is an innovative concept of distributed space telescope, for high resolution (milli arc-seconds) spectro-imaging in the IR, visible and UV domains. This paper presents its optical principle and the science that can be done on potential astrophysical targets. The novelty lies in the primary optics: a binary Fresnel array, akin to a binary Fresnel zone plate. The main interest of this approach is the relaxed manufacturing and positioning constraints. While having the resolution and imaging capabilities of lens or mirrors of equivalent size, no optical material is involved in the focusing process: just vacuum. A Fresnel array consists of millions void subapertures punched into a large and thin opaque membrane, that focus light by diffraction into a compact and highly contrasted image. The positioning law of the aperture edges drives the image quality and contrast. This optical concept allows larger and lighter apertures than solid state optics, aiming to high angular resolution and high dynamic range imaging, in particular for UV applications. Diffraction focusing implies very long focal distances, up to dozens of kilometers, which requires at least a two-vessel formation flying in space. The first spacecraft, "the Fresnel Array spacecraft", holds the large punched foil: the Fresnel Array. The second, the "Receiver spacecraft" holds the field optics and focal instrumentation. A chromatism correction feature enables moderately large (20%) relative wavebands, and fields of a few to a dozen arc seconds. This Fresnel imager is adapted to high contrast stellar environments: dust disks, close companions and (we hope) exoplanets. Specific to the particular grid-like pattern of the primary focusing zone plate, is the very high dynamic range achieved in the images, in the case of compact objects. Large stellar photospheres may also be mapped with Fresnel arrays of a few meters opertaing in the UV. Larger and more complex fields can be imaged with a lesser dynamic range: galactic or extragalactic, or at the opposite distance scale: small solar system bodies. This paper will briefly address the optical principle, and in more detail the astrophysical missions and targets proposed for a 4-meter class demonstrator: - Exoplanet imaging, Exoplanet spectroscopic analysis in the visible and UV, - Stellar environments, young stellar systems, disks, - Galactic clouds, astrochemistry, - IR observation of the galactic center, - Small objects of our solar system.

DEATH-STAR: Silicon and photovoltaic fission fragment detector arrays for light-ion induced fission correlation studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koglin, J. D.; Burke, J. T.; Fisher, S. E.

Here, the Direct Excitation Angular Tracking pHotovoltaic-Silicon Telescope ARray (DEATH-STAR) combines a series of 12 silicon detectors in a ΔE–E configuration for charged particle identification with a large-area array of 56 photovoltaic (solar) cells for detection of fission fragments. The combination of many scattering angles and fission fragment detectors allows for an angular-resolved tool to study reaction cross sections using the surrogate method, anisotropic fission distributions, and angular momentum transfers through stripping, transfer, inelastic scattering, and other direct nuclear reactions. The unique photovoltaic detectors efficiently detect fission fragments while being insensitive to light ions and have a timing resolution ofmore » 15.63±0.37 ns. Alpha particles are detected with a resolution of 35.5 keV 1σ at 7.9 MeV. Measured fission fragment angular distributions are also presented.« less

DEATH-STAR: Silicon and Photovoltaic Fission Fragment Detector Arrays for Light-Ion Induced Fission Correlation Studies

NASA Astrophysics Data System (ADS)

Koglin, J. D.; Burke, J. T.; Fisher, S. E.; Jovanovic, I.

2017-05-01

The Direct Excitation Angular Tracking pHotovoltaic-Silicon Telescope ARray (DEATH-STAR) combines a series of 12 silicon detectors in a ΔE - E configuration for charged particle identification with a large-area array of 56 photovoltaic (solar) cells for detection of fission fragments. The combination of many scattering angles and fission fragment detectors allows for an angular-resolved tool to study reaction cross sections using the surrogate method, anisotropic fission distributions, and angular momentum transfers through stripping, transfer, inelastic scattering, and other direct nuclear reactions. The unique photovoltaic detectors efficiently detect fission fragments while being insensitive to light ions and have a timing resolution of 15.63±0.37 ns. Alpha particles are detected with a resolution of 35.5 keV 1σ at 7.9 MeV. Measured fission fragment angular distributions are also presented.

DEATH-STAR: Silicon and photovoltaic fission fragment detector arrays for light-ion induced fission correlation studies

DOE PAGES

Koglin, J. D.; Burke, J. T.; Fisher, S. E.; ...

2017-02-20

Here, the Direct Excitation Angular Tracking pHotovoltaic-Silicon Telescope ARray (DEATH-STAR) combines a series of 12 silicon detectors in a ΔE–E configuration for charged particle identification with a large-area array of 56 photovoltaic (solar) cells for detection of fission fragments. The combination of many scattering angles and fission fragment detectors allows for an angular-resolved tool to study reaction cross sections using the surrogate method, anisotropic fission distributions, and angular momentum transfers through stripping, transfer, inelastic scattering, and other direct nuclear reactions. The unique photovoltaic detectors efficiently detect fission fragments while being insensitive to light ions and have a timing resolution ofmore » 15.63±0.37 ns. Alpha particles are detected with a resolution of 35.5 keV 1σ at 7.9 MeV. Measured fission fragment angular distributions are also presented.« less

The High Redshift Universe Seen Through the Eyes of ALMA

NASA Astrophysics Data System (ADS)

Wiklind, Tommy

2012-07-01

The Atacama Large Millimeter/submm Array (ALMA) is an interferometric telescope currently under construction on the Chajnantor Plateau in northern Chile. It is situated at an altitude of 5000m, in one of the driest places in the world. The combination of the meteorological conditions, increased total collecting area and the use of state-of-the-art receivers means that the fully operational ALMA is a factor 10-1000 more sensitive than existing facilities, depending on the wavelength. When completed in 2013, ALMA will consists of 66 antennas, with maximum baselines of up to 15 km and it will be able to observe at wavelengths from 10 millimeter to ~350micron. ALMA will be able to provide an angular resolution of ~0.05 arcseconds. ALMA is still under construction, but has started producing science in an 'Early Science' phase. The goal with ALMA has from the beginning been to provide very high sensitivity as well as an angular resolution matching that of space based optical observatories such as the HST. One of three main drivers when designing ALMA has been the ability to study the high redshift universe. The main reason behind this is that almost half of the integrated background radiation comes from the far-infrared wavelength regime. This emission is interpreted as originating from dust re-radiated stellar emission in high redshift galaxies. Interstellar dust is almost invariably associated with molecular gas, that can be studied using molecular rotational transitions. The shape of the dust spectral energy distribution ensures that the observed flux at a fixed wavelength long-ward of the far-infrared peak (about 100micron) remains more or less constant over a redshift range z=1-10. This aspect makes dust continuum emission extraordinarily important for studying galaxies and Active Galactic Nuclei at high redshift. Through observations of line emission from molecular transitions it is possible to study the associated molecular gas distribution and its kinematics. The large spectral coverage of ALMA makes it possible to observe the most common molecules, such as CO, at any redshift. The neutral and ionized gas components can be studied through several atomic fine-structure lines. For instance, the CII fine-structure line at a rest-wavelength of 158micron is one of the most important cooling agents for ionized gas. It can be targeted with ALMA over a large fraction of cosmic history. Other atomic fine-structure lines can provide important data for studying the emergence of super-massive black holes at high redshift. In this presentation I will discuss the potential of ALMA for studying the early universe, the potential synergies with current and planned space mission (e.g. HST and JWST) and, hopefully, some results from the Early Science observations.

High Resolution Optical Imaging through the Atmosphere

DTIC Science & Technology

1989-12-28

34Iterative Blind Deconvolution Method and its Applications’, Opt. Lett., 13, p.54 7 . Fienup, J.R. 1978, Opt. Lett., 3, 27. Karovska , M., Nisenson, P., and...Noyes, R. (1987), ’High Angular Resolution Speckle Imaging of Alpha Ori", BAAS, Vol.19, No. 2. Karovska , M., Koechlin, L., Nisenson, P., Papaliolios...Publishers. Karovska , M., Nisenson, P., Papaliolios, C., Stendley, C. (1989), "High Angular Speckle Observations of SN1987A. Days 40-580.", BAAS, Vol

Grazing Incidence Nickel Replicated Optics for Hard X-ray Telescopes

NASA Technical Reports Server (NTRS)

Peturzzo, J. J., III; Elsner, R. F.; Joy, M. K.; ODell, S. L.; Weisskopf, M. C.

1997-01-01

The requirements for future hard x-ray (up to 50 keV) telescopes are lightweight, high angular resolution optics with large collecting areas. Grazing incidence replicated optics are an excellent candidate for this, type of mission, providing better angular resolution, comparable area/unit mass, and simpler fabrication than multilayer-coated foils. Most importantly, the technology to fabricate the required optics currently exists. A comparison of several hard x-ray telescope designs will be presented.

High Angular Resolution and Lightweight X-Ray Optics for Astronomical Missions

NASA Technical Reports Server (NTRS)

Zhang, W. W.; Biskach, M. P.; Blake, P. N.; Chan, K. W.; Evans, T. C.; Hong, M.; Jones, W. D.; Jones, W. D.; Kolos, L. D.; Mazzarella, J. M.;

The Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII): High Angular Resolution Astronomy at Far-Infrared Wavelengths

NASA Technical Reports Server (NTRS)

Rinehart, Stephen A.

2008-01-01

Astronomical studies at infrared wavelengths have dramatically improved our understanding of the universe, and observations with Spitzer, the upcoming Herschel mission. and SOFIA will continue to provide exciting new discoveries. The comparatively low spatial resolution of these missions, however. is insufficient to resolve the physical scales on which mid- to far-infrared emission arises, resulting in source and structure ambiguities that limit our ability to answer key science questions. Interferometry enables high angular resolution at these wavelengths. We have proposed a new high altitude balloon experiment, the Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII). High altitude operation makes far-infrared (30- 300micron) observations possible, and BETTII's 8-meter baseline provides unprecedented angular resolution (-0.5 arcsec) in this band. BETTII will use a double- Fourier instrument to simultaneously obtain both spatial and spectral informatioT. he spatially resolved spectroscopy provided by BETTII will address key questions about the nature of disks in young cluster stars and active galactic nuclei and the envelopes of evolved stars. BETTII will also lay the groundwork for future space interferometers.

A solar activity monitoring platform for SCADM

NASA Technical Reports Server (NTRS)

Kissell, K. E.; Ratcliff, D. D.

1980-01-01

The adaptation of proven space probe technology is proposed as a means of providing a solar activity monitoring platform which could be injected behind the Earth's orbital position to give 3 to 6 days advanced coverage of the solar phenomenon on the backside hemisphere before it rotates into view and affects terrestrial activities. The probe would provide some three dimensional discrimination within the ecliptic latitude. This relatively simple off-Earth probe could provide very high quality data to support the SCADM program, by transmitting both high resolution video data of the solar surface and such measurements of solar activity as particle, X-ray, ultraviolet, and radio emission fluxes. Topics covered include the orbit; constraints on the spacecraft; subsystems and their embodiments; optical imaging sensors and their operation; and the radiation-pressure attitude control system are described. The platform would be capable of mapping active regions on an hourly basis with one arc-second resolution.

Alignment and Distortion-Free Integration of Lightweight Mirrors into Meta-Shells for High-Resolution Astronomical X-Ray Optics

NASA Technical Reports Server (NTRS)

Chan, Kai-Wing; Zhang, William W.; Schofield, Mark J.; Numata, Ai; Mazzarella, James R.; Saha, Timo T.; Biskach, Michael P.; McCelland, Ryan S.; Niemeyer, Jason; Sharpe, Marton V.;

On the Relation Between Facular Bright Points and the Magnetic Field

NASA Astrophysics Data System (ADS)

Berger, Thomas; Shine, Richard; Tarbell, Theodore; Title, Alan; Scharmer, Goran

1994-12-01

Multi-spectral images of magnetic structures in the solar photosphere are presented. The images were obtained in the summers of 1993 and 1994 at the Swedish Solar Telescope on La Palma using the tunable birefringent Solar Optical Universal Polarimeter (SOUP filter), a 10 Angstroms wide interference filter tuned to 4304 Angstroms in the band head of the CH radical (the Fraunhofer G-band), and a 3 Angstroms wide interference filter centered on the Ca II--K absorption line. Three large format CCD cameras with shuttered exposures on the order of 10 msec and frame rates of up to 7 frames per second were used to create time series of both quiet and active region evolution. The full field--of--view is 60times 80 arcseconds (44times 58 Mm). With the best seeing, structures as small as 0.22 arcseconds (160 km) in diameter are clearly resolved. Post--processing of the images results in rigid coalignment of the image sets to an accuracy comparable to the spatial resolution. Facular bright points with mean diameters of 0.35 arcseconds (250 km) and elongated filaments with lengths on the order of arcseconds (10(3) km) are imaged with contrast values of up to 60 % by the G--band filter. Overlay of these images on contemporal Fe I 6302 Angstroms magnetograms and Ca II K images reveals that the bright points occur, without exception, on sites of magnetic flux through the photosphere. However, instances of concentrated and diffuse magnetic flux and Ca II K emission without associated bright points are common, leading to the conclusion that the presence of magnetic flux is a necessary but not sufficient condition for the occurence of resolvable facular bright points. Comparison of the G--band and continuum images shows a complex relation between structures in the two bandwidths: bright points exceeding 350 km in extent correspond to distinct bright structures in the continuum; smaller bright points show no clear relation to continuum structures. Size and contrast statistical cross--comparisons compiled from measurements of over two-thousand bright point structures are presented. Preliminary analysis of the time evolution of bright points in the G--band reveals that the dominant mode of bright point evolution is fission of larger structures into smaller ones and fusion of small structures into conglomerate structures. The characteristic time scale for the fission/fusion process is on the order of minutes.

The Space Infrared Interferometric Telescope (SPIRIT)

NASA Technical Reports Server (NTRS)

Rinehart, Stephen

2007-01-01

The Space Infrared Interferometric Telescope (SPIRIT) is a candidate NASA Origins Probe Mission. SPIRIT is a two-telescope Michelson interferometer covering wavelengths from 25-400 microns, providing simultaneously high spectral resolution and high angular resolution. With comparable sensitivity to Spitzer, but two orders of magnitude improvement in angular resolution, SPIRIT will enable us to address a wide array of compelling scientific questions, including how planetary systems form in disks and how new planets interact with the disk. Further, SPIRIT will lay the technological groundwork for an array of future interferometry missions with ambitious scientific goals, including the Terrestrial Planet Finder Interferometer / Darwin, and the Submillimeter Probe of the Evolution of Cosmic Structure.

The Space Infrared Interferometric Telescope (SPIRIT)

NASA Technical Reports Server (NTRS)

Rinehart, Stephen

2007-01-01

The Space Infrared Interferometric Telescope (SPIRIT) is a candidate NASA Origins Probe Mission. SPIRIT is a two-telescope Michelson interferometer covering wavelengths from 25-400 microns, providing simultaneously high spectral resolution and high angular resolution. With comparable sensitivity to Spitzer, but two orders of magnitude improvement in angular resolution, SPIRIT will enable us to address a wide array of compelling scientific questions, including how planetary systems form in disks and how new planets interact with the disk. Further, SPIRIT will lay the technological groundwork for an array of future interferometry missions with ambitious scientific goals, including the Terrestrial Planet Finder Interferometer/Darwin, and the Submillimeter Probe of the Evolution of Cosmic Structure.

First Surface-resolved Results with the Infrared Optical Telescope Array Imaging Interferometer: Detection of Asymmetries in Asymptotic Giant Branch Stars

NASA Astrophysics Data System (ADS)

Ragland, S.; Traub, W. A.; Berger, J.-P.; Danchi, W. C.; Monnier, J. D.; Willson, L. A.; Carleton, N. P.; Lacasse, M. G.; Millan-Gabet, R.; Pedretti, E.; Schloerb, F. P.; Cotton, W. D.; Townes, C. H.; Brewer, M.; Haguenauer, P.; Kern, P.; Labeye, P.; Malbet, F.; Malin, D.; Pearlman, M.; Perraut, K.; Souccar, K.; Wallace, G.

2006-11-01

We have measured nonzero closure phases for about 29% of our sample of 56 nearby asymptotic giant branch (AGB) stars, using the three-telescope Infrared Optical Telescope Array (IOTA) interferometer at near-infrared wavelengths (H band) and with angular resolutions in the range 5-10 mas. These nonzero closure phases can only be generated by asymmetric brightness distributions of the target stars or their surroundings. We discuss how these results were obtained and how they might be interpreted in terms of structures on or near the target stars. We also report measured angular sizes and hypothesize that most Mira stars would show detectable asymmetry if observed with adequate angular resolution.

A High Angular Resolution Survey of Massive Stars in Cygnus OB2: Results from the Hubble Space Telescope Fine Guidance Sensors

DTIC Science & Technology

2014-02-01

F. J. Moffat9, and N. R. Walborn2 1 Center for High Angular Resolution Astronomy, Department of Physics and Astronomy, Georgia State University, P.O...Martin Drive, Baltimore, MD 21218, USA; nelan@stsci.edu, walborn@stsci.edu 3 Department of Natural Sciences, University of South Carolina Beaufort, 1 ...Online-only material: figure set 1 . INTRODUCTION Massive stars (10M) play a fundamental role in the evo- lution of the universe, from influencing

Angular resolution of stacked resistive plate chambers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Samuel, Deepak; Onikeri, Pratibha B.; Murgod, Lakshmi P., E-mail: deepaksamuel@cuk.ac.in, E-mail: pratibhaonikeri@gmail.com, E-mail: lakshmipmurgod@gmail.com

We present here detailed derivations of mathematical expressions for the accuracy in the arrival direction of particles estimated using a set of stacked resistive plate chambers (RPCs). The expressions are validated against experimental results using data collected from the prototype detectors (without magnet) of the upcoming India-based Neutrino Observatory (INO). We also present a theoretical estimate of angular resolution of such a setup. In principle, these expressions can be used for any other detector with an architecture similar to that of RPCs.

High-precision infra-red stellar interferometry

NASA Astrophysics Data System (ADS)

Lane, Benjamin F.

2003-08-01

This dissertation describes work performed at the Palomar Testbed Interferometer (PTI) during 1998 2002. Using PTI, we developed a method to measure stellar angular diameters in the 1 3 milli-arcsecond range with a precision of better than 5%. Such diameter measurements were used to measure the mass-radius relations of several lower main sequence stars and hence verify model predictions for these stars. In addition, by measuring the changes in Cepheid angular diameters during the pulsational cycle and applying a Baade-Wesselink analysis we are able to derive the distances to two galactic Cepheids (η Aql & ζ Gem) with a precision of ˜10%; such distance determinations provide an independent calibration of the Cepheid period- luminosity relations that underpin current estimates of cosmic distance scales. Second, we used PTI and the adaptive optics facility at the Keck Telescope on Mauna Kea to resolve the low mass binary systems BY Dra and GJ 569B, resulting in dynamical mass determinations for these systems. GJ 569B most likely contains at least one sub-stellar component, and as such represents the first dynamical mass determination of a brown dwarf. Finally, a new observing technique, dual star phase referencing, was developed and demonstrated at PTI. Phase referencing allows interferometric observations of stars previously too faint to observe, and is a prerequisite for large-scale interferometric astrometry programs such as the one planned for the Keck Interferometer; interferometric astrometry is a promising technique for the study of extra-solar planetary systems, particularly ones with long-period planets.

The STIS CCD Spectroscopic Line Spread Functions

NASA Technical Reports Server (NTRS)

Gull, T.; Lindler, D.; Tennant, D.; Bowers, C.; Grady, C.; Hill, R. S.; Malumuth, E.

2002-01-01

We characterize the spectroscopic line spread functions of the spectroscopic CCD modes for high contrast objects. Our long range goal is to develop tools that accurately extract spectroscopic information of faint, point or extended sources in the vicinity of bright, point sources at separations approaching the realizable angular limits of HST with STIS. Diffracted and scattered light due to the HST optics, and scattered light effects within the STIS are addressed. Filter fringing, CCD fringing, window reflections, and scattering within the detector and other effects are noted. We have obtained spectra of several reference stars, used for flux calibration or for coronagraphic standards, that have spectral distributions ranging from very red to very blue. Spectra of each star were recorded with the star in the aperture and with the star blocked by either the F1 or F2 fiducial. Plots of the detected starlight along the spatial axis of the aperture are provided for four stars. With the star in the aperture, the line spread function is quite noticeable. Placing the star behind one of the fiducials cuts the scattered light and the diffracted light, is detectable even out to 1OOOOA. When the star is placed behind either fiducial, the scattered and diffracted light components, at three arcseconds displacement from the star, are below lop6 the peak of the star at wavelengths below 6000A; at the same angular distance, scattered light does contaminate the background longward of 6000A up to a level of 10(exp -5).

Review and latest news from the VEGA/CHARA facility

NASA Astrophysics Data System (ADS)

Nardetto, N.; Mourard, D.; Perraut, K.; Tallon-Bosc, I.; Meilland, A.; Stee, P.; Ligi, R.; Challouf, M.; Clausse, J.-M.; Berio, P.; Spang, A.

2014-12-01

The VEGA instrument located at the focus of the Center for High Angular Resolution Astronomy (CHARA) array in California is a collaborating project between the Lagrange laboratory in Nice, where it has been developed (Mourard et al. 2009, 2011), the IPAG (Grenoble) and CRAL (Lyon) laboratories, and the CHARA group at Mount Wilson Observatory. The outcome from this international collaboration is to provide to the community a visible spectro-interferometer with an unprecedented angular resolution of 0.3 milli-second of arc (mas) together with a spectral resolution of 5000 or 30000. With such an instrument it becomes possible to determine simultaneously the size and the kinematic of the photosphere and/or of the circumstellar environment of the star as a function of the wavelength, which basically means for each spectral channel in the continuum and/or within spectral lines (in Hα for instance). The only limitation is to get enough signal to noise ratio in each spectral channel. We can currently reach a limiting magnitude of 8 in visible in medium spectral resolution (5000) and 4.5 in high resolution (30000). In this proceeding, we illustrate the two main subjects studied with the VEGA instrument, namely (1) how angular diameters are useful to accurately derive the fundamental parameters of stars, (2) how the spectral resolution can allow to study the kinematical structure of stars or even to derive chromatic images of stellar objects.

Development of a high angular resolution diffusion imaging human brain template.

PubMed

Varentsova, Anna; Zhang, Shengwei; Arfanakis, Konstantinos

2014-05-01

Brain diffusion templates contain rich information about the microstructure of the brain, and are used as references in spatial normalization or in the development of brain atlases. The accuracy of diffusion templates constructed based on the diffusion tensor (DT) model is limited in regions with complex neuronal micro-architecture. High angular resolution diffusion imaging (HARDI) overcomes limitations of the DT model and is capable of resolving intravoxel heterogeneity. However, when HARDI is combined with multiple-shot sequences to minimize image artifacts, the scan time becomes inappropriate for human brain imaging. In this work, an artifact-free HARDI template of the human brain was developed from low angular resolution multiple-shot diffusion data. The resulting HARDI template was produced in ICBM-152 space based on Turboprop diffusion data, was shown to resolve complex neuronal micro-architecture in regions with intravoxel heterogeneity, and contained fiber orientation information consistent with known human brain anatomy. Copyright © 2014 Elsevier Inc. All rights reserved.

Spatial Distribution and Kinematics of the Molecular Material Associated with eta Carinae

NASA Astrophysics Data System (ADS)

Loinard, Laurent; Kamiński, Tomasz; Serra, Paolo; Menten, Karl M.; Zapata, Luis A.; Rodríguez, Luis F.

2016-12-01

Single-dish submillimeter observations have recently revealed the existence of a substantial, chemically peculiar molecular gas component located in the innermost circumstellar environment of the very massive luminous blue variable star, η Carinae. Here, we present 5″-resolution interferometric observations of the 1\\to 0 rotational transition of hydrogen cyanide (HCN) toward this star obtained with the Australia Telescope Compact Array. The emission is concentrated in the central few arcseconds around η Carinae and shows a clear 150 km s-1 velocity gradient running from west-north-west (blue) to east-south-east (red). Given the extent, location, and kinematics of this molecular material, we associate it with the complex of dusty arcs and knots seen in mid-infrared emission near the center of the Homunculus nebula. Indeed, the shielding provided by this dust could help explain how molecules survive in the presence of the intense UV radiation field produced by η Carinae. The dust located in the central few arcseconds around η Carinae and the molecular component described here most likely formed in situ and out of material expelled by the massive interacting binary system. Thus, η Carinae offers us a rare glimpse of the processes that lead to the formation of dust and molecules around massive stars, which are relevant to the interpretation of dust and molecule detections at high redshifts.

Quantifying the Uncertainty in Streamflow Predictions Using Swat for Brazos-Colorado Coastal Watershed, Texas

NASA Astrophysics Data System (ADS)

Mandal, D.; Bhatia, N.; Srivastav, R. K.

2016-12-01

Soil Water Assessment Tool (SWAT) is one of the most comprehensive hydrologic models to simulate streamflow for a watershed. The two major inputs for a SWAT model are: (i) Digital Elevation Models (DEM), and (ii) Land Use and Land Cover Maps (LULC). This study aims to quantify the uncertainty in streamflow predictions using SWAT for San Bernard River in Brazos-Colorado coastal watershed, Texas, by incorporating the respective datasets from different sources: (i) DEM data will be obtained from ASTER GDEM V2, GMTED2010, NHD DEM, and SRTM DEM datasets with ranging resolution from 1/3 arc-second to 30 arc-second, and (ii) LULC data will be obtained from GLCC V2, MRLC NLCD2011, NOAA's C-CAP, USGS GAP, and TCEQ databases. Weather variables (Precipitation and Max-Min Temperature at daily scale) will be obtained from National Climatic Data Centre (NCDC) and SWAT in-built STASGO tool will be used to obtain the soil maps. The SWAT model will be calibrated using SWAT-CUP SUFI-2 approach and its performance will be evaluated using the statistical indices of Nash-Sutcliffe efficiency (NSE), ratio of Root-Mean-Square-Error to standard deviation of observed streamflow (RSR), and Percent-Bias Error (PBIAS). The study will help understand the performance of SWAT model with varying data sources and eventually aid the regional state water boards in planning, designing, and managing hydrologic systems.

Sub-arcsecond imaging of the water emission in Arp 220.

PubMed

König, S; Martín, S; Muller, S; Cernicharo, J; Sakamoto, K; Zschaechner, L K; Humphreys, E M L; Mroczkowski, T; Krips, M; Galametz, M; Aalto, S; Vlemmings, W H T; Ott, J; Meier, D S; Fuente, A; García-Burillo, S; Neri, R

2017-06-01

Extragalactic observations of water emission can provide valuable insights into the excitation of the interstellar medium. In particular they allow us to investigate the excitation mechanisms in obscured nuclei, i.e. whether an active galactic nucleus or a starburst dominate. We use sub-arcsecond resolution observations to tackle the nature of the water emission in Arp 220. ALMA Band 5 science verification observations of the 183 GHz H 2 O 3 13 -2 20 line, in conjunction with new ALMA Band 7 H 2 O 5 15 -4 22 data at 325 GHz, and supplementary 22 GHz H 2 O 6 16 - 5 23 VLA observations, are used to better constrain the parameter space in the excitation modelling of the water lines. We detect 183 GHz H 2 O and 325 GHz water emission towards the two compact nuclei at the center of Arp 220, being brighter in Arp 220 West. The emission at these two frequencies is compared to previous single-dish data and does not show evidence of variability. The 183 and 325 GHz lines show similar spectra and kinematics, but the 22 GHz profile is significantly different in both nuclei due to a blend with an NH 3 absorption line. Our findings suggest that the most likely scenario to cause the observed water emission in Arp 220 is a large number of independent masers originating from numerous star-forming regions.

Adaptive optics and interferometry

NASA Technical Reports Server (NTRS)

Beichman, Charles A.; Ridgway, Stephen

1991-01-01

Adaptive optics and interferometry, two techniques that will improve the limiting resolution of optical and infrared observations by factors of tens or even thousands, are discussed. The real-time adjustment of optical surfaces to compensate for wavefront distortions will improve image quality and increase sensitivity. The phased operation of multiple telescopes separated by large distances will make it possible to achieve very high angular resolution and precise positional measurements. Infrared and optical interferometers that will manipulate light beams and measure interference directly are considered. Angular resolutions of single telescopes will be limited to around 10 milliarcseconds even using the adaptive optics techniques. Interferometry would surpass this limit by a factor of 100 or more. Future telescope arrays with 100-m baselines (resolution of 2.5 milliarcseconds at a 1-micron wavelength) are also discussed.

Undergraduate Observations of Separation and Position Angle of Double Stars WDS J05460+2119AB (ARY 6AD and ARY 6 AE) at Manzanita Observatory (Abstract)

NASA Astrophysics Data System (ADS)

HOffert, M. J.; Weise, E.; Clow, J.; Hirzel, J.; Leeder, B.; Molyneux, S.; Scutti, N.; Spartalis, S.; Takuhara, C.

2014-12-01

(Abstract only) Six beginning astronomy students, part of an undergraduate stellar astronomy course, one advanced undergraduate student assistant, and a professor measured the position angles and separations of Washington Double Stars (WDS) J05460+2119 (= WDS J05460+2119AB; also known as ARY 6 AD and ARY 6 AE). The measurements were made at the Manzanita Observatory (116º 20' 42" W, 32º 44' 5" N) of the Tierra Astronomical Institute on 10 Blackwood Road in Boulevard, California (www.youtube.com/watch?v=BHVdeMGBGDU), at an elevation of 4,500 ft. A Celestron 11-inch HD Edge telescope was used to measure the position angles and separations of ARY 6 AD and ARY 6 AE. The averages of our measurements are as follows: separation AD: trial 1 124.1 arcseconds and trial 2 124.5 arcseconds; separation AE: trial 1 73.3 arcseconds and trial 2 73.8 arcseconds. The averages of positon angle for AD: trial 1 159.9 degrees and trial 2 161.3 degrees, for AE: trial 1 232.6 degrees and trial 2 233.7 degrees.

Undergraduate Observations of Separation and Position Angle of Double Stars ARY 6 AD and ARY 6 AE at Manzanita Observatory

NASA Astrophysics Data System (ADS)

Hoffert, Michael J.; Weise, Eric; Clow, Jenna; Hirzel, Jacquelyn; Leeder, Brett; Molyneux, Scott; Scutti, Nicholas; Spartalis, Sarah; Tokuhara, Corey

2014-05-01

Six beginning astronomy students, part of an undergraduate stellar astronomy course, one advanced undergraduate student assistant, and a professor measured the position angles and separations of Washington Double Stars (WDS) 05460 + 2119 (also known as ARY 6 AD and ARY 6 AE). The measurements were made at the Manzanita Observatory (116° 20'42" W, 32° 44' 5" N) of the Tierra Astronomical Institute on 10 Blackwood Rd. in Boulevard, California (www.youtube.com/watch?v=BHVdcMGBGDU), at an elevation of 4,500 ft. A Celestron 11" HD Edge telescope was used to measure the position angles and separations of ARY 6 AD and ARY 6 AE. The averages of our measurements are as follows: separation AD: trial 1 124.1 arcseconds and trial 2 124.5 arcseconds. The average of separation for AE: trial 1 73.3 arcseconds and trial 2 73.8 arcseconds. The averages of position angle for AD: trial 1 159.9 degrees and trial 2 161.3 degrees. The averages of position angle for AE: trial 1 232.6 degrees and trial 2 233.7 degrees.

Hard X-Ray Footprint Source Sized

NASA Technical Reports Server (NTRS)

Dennis, Brian R.; Kontar, E. P.

2010-01-01

RHESSI has detected compact hard (25 - 100 keV) X-ray sources that are <4 arcseconds (FWHM) in extent for certain flares (Dennis and Pernak (2009). These sources are believed to be at magnetic loop footpoints that are known from observations at other wavelengths to be very small. Flare ribbons seen in the W with TRACE, for example, are approx. 1 arcsecond in width, and white light flares show structure at the approx. 1 arcsecond level. However, Kontar and Jeffrey (2010) have shown that the measured extent should be >6 arcseconds, even if the X-ray emitting thick-target source is point-like. This is because of the strong albedo contribution in the measured energy range for a source located at the expected altitude of 1 Mm near the top of the chromosphere. This discrepancy between observations and model predictions may indicate that the source altitude is significantly lower than assumed or that the RHESSI image reconstruction procedures are not sensitive to the more diffuse albedo patch in the presence of a strong compact source. Results will be presented exploring the latter possibility using the Pixon image reconstruction procedure and other methods based on visibilities.

A Chandra High-Resolution X-ray Image of Centaurus A.

PubMed

Kraft; Forman; Jones; Kenter; Murray; Aldcroft; Elvis; Evans; Fabbiano; Isobe; Jerius; Karovska; Kim; Prestwich; Primini; Schwartz; Schreier; Vikhlinin

2000-03-01

We present first results from a Chandra X-Ray Observatory observation of the radio galaxy Centaurus A with the High-Resolution Camera. All previously reported major sources of X-ray emission including the bright nucleus, the jet, individual point sources, and diffuse emission are resolved or detected. The spatial resolution of this observation is better than 1&arcsec; in the center of the field of view and allows us to resolve X-ray features of this galaxy not previously seen. In particular, we resolve individual knots of emission in the inner jet and diffuse emission between the knots. All of the knots are diffuse at the 1&arcsec; level, and several exhibit complex spatial structure. We find the nucleus to be extended by a few tenths of an arcsecond. Our image also suggests the presence of an X-ray counterjet. Weak X-ray emission from the southwest radio lobe is also seen, and we detect 63 pointlike galactic sources (probably X-ray binaries and supernova remnants) above a luminosity limit of approximately 1.7x1037 ergs s-1.

High Resolution Active Optics Observations from the Kepler Follow-up Observation Program

NASA Astrophysics Data System (ADS)

Gautier, Thomas N.; Ciardi, D. R.; Marcy, G. W.; Hirsch, L.

2014-01-01

The ground based follow-up observation program for candidate exoplanets discovered with the Kepler observatory has supported a major effort for high resolution imaging of candidate host stars using adaptive optics wave-front correction (AO), speckle imaging and lucky imaging. These images allow examination of the sky as close as a few tenths of an arcsecond from the host stars to detect background objects that might be the source of the Kepler transit signal instead of the host star. This poster reports on the imaging done with AO cameras on the Keck, Palomar 5m and Shane 3m (Lick Observatory) which have been used to obtain high resolution images of over 500 Kepler Object of Interest (KOI) exoplanet candidate host stars. All observations were made at near infrared wavelengths in the J, H and K bands, mostly using the host target star as the AO guide star. Details of the sensitivity to background objects actually attained by these observations and the number of background objects discovered are presented. Implications to the false positive rate of the Kepler candidates are discussed.

The X-Ray Optics for the High Angular Resolution Imager (HARI)

NASA Technical Reports Server (NTRS)

Weisskopf, M. C.

2010-01-01

This slide presentation shows the basic parameters of the x-ray optics, the housing,a graph of the effective area vs energy, another graph showing the angular off-set vs HEW, and a series of graphs showing the detector offsets and tilts,

Deformable complex network for refining low-resolution X-ray structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Chong; Wang, Qinghua; Ma, Jianpeng, E-mail: jpma@bcm.edu

2015-10-27

A new refinement algorithm called the deformable complex network that combines a novel angular network-based restraint with a deformable elastic network model in the target function has been developed to aid in structural refinement in macromolecular X-ray crystallography. In macromolecular X-ray crystallography, building more accurate atomic models based on lower resolution experimental diffraction data remains a great challenge. Previous studies have used a deformable elastic network (DEN) model to aid in low-resolution structural refinement. In this study, the development of a new refinement algorithm called the deformable complex network (DCN) is reported that combines a novel angular network-based restraint withmore » the DEN model in the target function. Testing of DCN on a wide range of low-resolution structures demonstrated that it constantly leads to significantly improved structural models as judged by multiple refinement criteria, thus representing a new effective refinement tool for low-resolution structural determination.« less

Design of discrete and continuous super-resolving Toraldo pupils in the microwave range.

PubMed

Olmi, Luca; Bolli, Pietro; Mugnai, Daniela

2018-03-20

The concept of super-resolution refers to various methods for improving the angular resolution of an optical imaging system beyond the classical diffraction limit. In optical microscopy, several techniques have been successfully developed with the aim of narrowing the central lobe of the illumination point spread function. In astronomy, however, no similar techniques can be used. A feasible method to design antennas and telescopes with angular resolution better than the diffraction limit consists of using variable transmittance pupils. In particular, discrete binary phase masks (0 or π ) with finite phase-jump positions, known as Toraldo pupils (TPs), have the advantage of being easy to fabricate but offer relatively little flexibility in terms of achieving specific trade-offs between design parameters, such as the angular width of the main lobe and the intensity of sidelobes. In this paper, we show that a complex transmittance filter (equivalent to a continuous TP, i.e., consisting of infinitely narrow concentric rings) can achieve more easily the desired trade-off between design parameters. We also show how the super-resolution effect can be generated with both amplitude- and phase-only masks and confirm the expected performance with electromagnetic numerical simulations in the microwave range.

Wide-angle display-type retarding field analyzer with high energy and angular resolutions

NASA Astrophysics Data System (ADS)

Muro, Takayuki; Ohkochi, Takuo; Kato, Yukako; Izumi, Yudai; Fukami, Shun; Fujiwara, Hidenori; Matsushita, Tomohiro

2017-12-01

Deployments of spherical grids to obtain high energy and angular resolutions for retarding field analyzers (RFAs) having acceptance angles as large as or larger than ±45° were explored under the condition of using commercially available microchannel plates with effective diameters of approximately 100 mm. As a result of electron trajectory simulations, a deployment of three spherical grids with significantly different grid separations instead of conventional equidistant separations showed an energy resolving power (E/ΔE) of 3200 and an angular resolution of 0.6°. The mesh number of the wire mesh retarding grid used for the simulation was 250. An RFA constructed with the simulated design experimentally showed an E/ΔE of 1100 and an angular resolution of 1°. Using the RFA and synchrotron radiation of 900 eV, photoelectron diffraction (PED) measurements were performed for single-crystal graphite. A clear C 1s PED pattern was observed even when the differential energy of the RFA was set at 0.5 eV. Further improvement of the energy resolution was theoretically examined under the assumption of utilizing a retarding grid fabricated by making a large number of radially directed cylindrical holes through a partial spherical shell instead of using a wire mesh retarding grid. An E/ΔE of 14 500 was predicted for a hole design with a diameter of 60 μm and a depth of 100 μm. A retarding grid with this hole design and a holed area corresponding to an acceptance angle of ±7° was fabricated. An RFA constructed with this retarding grid experimentally showed an E/ΔE of 1800. Possible reasons for the experimental E/ΔE lower than the theoretical values are discussed.

RadioAstron Science Program Five Years after Launch: Main Science Results

NASA Astrophysics Data System (ADS)

Kardashev, N. S.; Alakoz, A. V.; Andrianov, A. S.; Artyukhov, M. I.; Baan, W.; Babyshkin, V. E.; Bartel, N.; Bayandina, O. S.; Val'tts, I. E.; Voitsik, P. A.; Vorobyov, A. Z.; Gwinn, C.; Gomez, J. L.; Giovannini, G.; Jauncey, D.; Johnson, M.; Imai, H.; Kovalev, Y. Y.; Kurtz, S. E.; Lisakov, M. M.; Lobanov, A. P.; Molodtsov, V. A.; Novikov, B. S.; Pogodin, A. V.; Popov, M. V.; Privesenzev, A. S.; Rudnitski, A. G.; Rudnitski, G. M.; Savolainen, T.; Smirnova, T. V.; Sobolev, A. M.; Soglasnov, V. A.; Sokolovsky, K. V.; Filippova, E. N.; Khartov, V. V.; Churikova, M. E.; Shirshakov, A. E.; Shishov, V. I.; Edwards, P.

2017-12-01

The RadioAstron ground-space interferometer provides the highest angular resolution achieved now in astronomy. The detection of interferometric fringes from quasars with this angular resolution on baselines of 100-200 thousand km suggests the brightness temperatures which exceed the Compton limit by two orders of magnitude. Polarimetric measurements on ground-space baselines have revealed fine structure testifying to recollimation shocks on scales of 100-250 μas and a helical magnetic field near the base of radio emission in BL Lacertae. Substructure within a the scattering disk of pulsar emission on interferometer baselines (from 60000 to 250000 km) was discovered. This substructure is produced by action of the interstellar interferometer with an effective baseline of about 1 AU and the effective angular resolution of better than 1 μas. Diameters of scattering disks were measured for several pulsars, and distances to diffusing screens were evaluated. The ground-space observations of sources of the maser radiation in lines of water and hydroxyl have shown that the maser sources in star-forming regions remain unresolved on baselines, which considerably exceed the Earth diameter. These very compact and bright features with angular sizes of about 20-60 μas correspond to linear sizes of about 5-10 million km (several solar diameters).

Focusing X-Ray Telescopes

NASA Technical Reports Server (NTRS)

O'Dell, Stephen; Brissenden, Roger; Davis, William; Elsner, Ronald; Elvis, Martin; Freeman, Mark; Gaetz, Terrance; Gorenstein, Paul; Gubarev, Mikhall; Jerlus, Diab;

Adjustable Grazing-Incidence X-Ray Optics

NASA Technical Reports Server (NTRS)

O'Dell, Stephen L.; Reid, Paul B.

2015-01-01

With its unique subarcsecond imaging performance, NASA's Chandra X-ray Observatory illustrates the importance of fine angular resolution for x-ray astronomy. Indeed, the future of x-ray astronomy relies upon x-ray telescopes with comparable angular resolution but larger aperture areas. Combined with the special requirements of nested grazing-incidence optics, mass, and envelope constraints of space-borne telescopes render such advances technologically and programmatically challenging. The goal of this technology research is to enable the cost-effective fabrication of large-area, lightweight grazing-incidence x-ray optics with subarcsecond resolution. Toward this end, the project is developing active x-ray optics using slumped-glass mirrors with thin-film piezoelectric arrays for correction of intrinsic or mount-induced distortions.

Resolving Planet Formation in the Era of ALMA and Extreme AO Report on the joint ESO/NRAO Conference

NASA Astrophysics Data System (ADS)

Dent, W. R. F.; Hales, A.; Milli, J.

2016-12-01

ALMA in its long-baseline configuration, as well as new optical/near-infrared adaptive optics instruments such as SPHERE and GPI, are now able to achieve spatial resolutions considerably better than 0.1 arcseconds. These facilities are enabling us to observe for the first time the regions around young stars where planets form. Already, complex structures including holes, spiral waves and extreme asymmetries are being found in these protoplanetary discs. To discuss these newly-imaged phenomena, and to enable cross-fertilisation of ideas between the two wavelength ranges, a joint ESO/NRAO workshop was held in Santiago. We present here a summary and some highlights of the meeting.

The Frequency of Circumnuclear Starbursts in Seyfert Galaxies --- Testing the Starburst-AGN Connection

NASA Astrophysics Data System (ADS)

Schinnerer, E.; Colbert, E.; Armus, L.; Scoville, N. Z.; Heckman, T. M.

We obtained sub-arcsecond medium resolution near-infrared spectra of a sample of nearby bright Seyfert galaxies (8 Seyfert 1s, 11 Seyfert 2s) using the KeckII telescope. The stellar absorption lines present in the spectra were used in conjunction with population synthesis models to determine the age of the circumnuclear stellar population. Initial analysis of a sub-sample of the Seyfert galaxies has provided no evidence for a connection between the age of the circumnuclear stellar population and the Seyfert type. The derived ages for the circumnuclear stellar population are in the range of 10 Myr to < 0.5 Gyr assuming an instantaneous starburst (using the STARBURST99 models).

Polarimetry and spectroscopy of a simple sunspot. I - On the magnetic field of a sunspot penumbra

NASA Technical Reports Server (NTRS)

Schmidt, W.; Hofmann, A.; Balthasar, H.; Tarbell, T. D.; Frank, Z. A.

1992-01-01

We investigate the magnetic field structure of a medium sized sunspot using high resolution magnetograms and spectrograms and derive a relationship between the brightness of penumbral structures and the inclination of the magnetic field. The field inclination to the spot normal is larger in the dark structures than in the bright ones. We show that the field strength does not vary between dark and bright structures. At the inner penumbral boundary the field strength is 2000 Gauss and about 1000 Gauss at the outer penumbral edge. The line-of sight component of the material flow decreases rapidly within one arcsecond at the photospheric boundary of the spot.

Shower disc sampling and the angular resolution of gamma-ray shower detectors

NASA Technical Reports Server (NTRS)

Lambert, A.; Lloyd-Evans, J.

1985-01-01

As part of the design study for the new UHE gamma ray detector being constsructed at Haverah Park, a series of experiments using scintillators operated side-by-side in 10 to the 15th power eV air showers are undertaken. Investigation of the rms sampling fluctuations in the shower disc arrival time yields an upper limit to the intrinsic sampling uncertainty, sigma sub rms = (1.1 + or - 0.1)ns, implying an angular resolution capability 1 deg for an inter-detector spacing of approximately 25 m.

A new model-independent approach for finding the arrival direction of an extensive air shower

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hedayati, H. Kh., E-mail: hedayati@kntu.ac.ir

2016-11-01

A new accurate method for reconstructing the arrival direction of an extensive air shower (EAS) is described. Compared to existing methods, it is not subject to minimization of a function and, therefore, is fast and stable. This method also does not need to know detailed curvature or thickness structure of an EAS. It can have angular resolution of about 1 degree for a typical surface array in central regions. Also, it has better angular resolution than other methods in the marginal area of arrays.

The Future of X-Ray Optics

NASA Technical Reports Server (NTRS)

Weisskopf, Martin C.

2013-01-01

The most important next step is the development of X-ray optics comparable to (or better than) Chandra in angular resolution that far exceed Chandra s effective area. Use the long delay to establish an adequately funded, competitive technology program along the lines I have recommended. Don't be diverted from this objective, except for Explorer-class missions. Progress in X-ray optics, with emphasis on the angular resolution, is central to the paradigm-shifting discoveries and the contributions of X-ray astronomy to multiwavelength astrophysics over the past 51 years.

MIPS - The Multiband Imaging Photometer for SIRTF. [Multiband Imaging Photometer for SIRTF

NASA Technical Reports Server (NTRS)

Rieke, G. H.; Lada, C.; Lebofsky, M.; Low, F.; Strittmatter, P.; Young, E.; Arens, J.; Beichman, C.; Gautier, T. N.; Werner, M.

1986-01-01

The Multiband Imaging Photometer for SIRTF (MIPS) is to be designed to reach as closely as possible the fundamental sensitivity and angular resolution limits for SIRTF over the 3 to 700 micron spectral region. It will use high performance photoconductive detectors from 3 to 200 micron with integrating JFET amplifiers. From 200 to 700 microns, the MIPS will use a bolometer cooled by an adiabatic demagnetization refrigerator. Over much of its operating range, the MIPS will make possible observations at and beyond the conventional Rayleigh diffraction limit of angular resolution.

MIPS - The Multiband Imaging Photometer for SIRTF

NASA Technical Reports Server (NTRS)

Rieke, G. H.; Lada, C.; Lebofsky, M.; Low, F.; Strittmatter, P.; Young, E.; Beichman, C.; Gautier, T. N.; Mould, J.; Werner, M.

1986-01-01

The Multiband Imaging Photometer System (MIPS) for SIRTF is to be designed to reach as closely as possible the fundamental sensitivity and angular resolution limits for SIRTF over the 3 to 700 microns spectral region. It will use high performance photoconductive detectors from 3 to 200 microns with integrating JFET amplifiers. From 200 to 700 microns, the MIPS will use a bolometer cooled by an adiabatic demagnetization refrigerator. Over much of its operating range, the MIPS will make possible observations at and beyond the conventional Rayleigh diffraction limit of angular resolution.

Global multi-resolution terrain elevation data 2010 (GMTED2010)

USGS Publications Warehouse

Danielson, Jeffrey J.; Gesch, Dean B.

2011-01-01

In 1996, the U.S. Geological Survey (USGS) developed a global topographic elevation model designated as GTOPO30 at a horizontal resolution of 30 arc-seconds for the entire Earth. Because no single source of topographic information covered the entire land surface, GTOPO30 was derived from eight raster and vector sources that included a substantial amount of U.S. Defense Mapping Agency data. The quality of the elevation data in GTOPO30 varies widely; there are no spatially-referenced metadata, and the major topographic features such as ridgelines and valleys are not well represented. Despite its coarse resolution and limited attributes, GTOPO30 has been widely used for a variety of hydrological, climatological, and geomorphological applications as well as military applications, where a regional, continental, or global scale topographic model is required. These applications have ranged from delineating drainage networks and watersheds to using digital elevation data for the extraction of topographic structure and three-dimensional (3D) visualization exercises (Jenson and Domingue, 1988; Verdin and Greenlee, 1996; Lehner and others, 2008). Many of the fundamental geophysical processes active at the Earth's surface are controlled or strongly influenced by topography, thus the critical need for high-quality terrain data (Gesch, 1994). U.S. Department of Defense requirements for mission planning, geographic registration of remotely sensed imagery, terrain visualization, and map production are similarly dependent on global topographic data. Since the time GTOPO30 was completed, the availability of higher-quality elevation data over large geographic areas has improved markedly. New data sources include global Digital Terrain Elevation Data (DTEDRegistered) from the Shuttle Radar Topography Mission (SRTM), Canadian elevation data, and data from the Ice, Cloud, and land Elevation Satellite (ICESat). Given the widespread use of GTOPO30 and the equivalent 30-arc-second DTEDRegistered level 0, the USGS and the National Geospatial-Intelligence Agency (NGA) have collaborated to produce an enhanced replacement for GTOPO30, the Global Land One-km Base Elevation (GLOBE) model and other comparable 30-arc-second-resolution global models, using the best available data. The new model is called the Global Multi-resolution Terrain Elevation Data 2010, or GMTED2010 for short. This suite of products at three different resolutions (approximately 1,000, 500, and 250 meters) is designed to support many applications directly by providing users with generic products (for example, maximum, minimum, and median elevations) that have been derived directly from the raw input data that would not be available to the general user or would be very costly and time-consuming to produce for individual applications. The source of all the elevation data is captured in metadata for reference purposes. It is also hoped that as better data become available in the future, the GMTED2010 model will be updated.

Second generation stationary digital breast tomosynthesis system with faster scan time and wider angular span.

PubMed

Calliste, Jabari; Wu, Gongting; Laganis, Philip E; Spronk, Derrek; Jafari, Houman; Olson, Kyle; Gao, Bo; Lee, Yueh Z; Zhou, Otto; Lu, Jianping

2017-09-01

The aim of this study was to characterize a new generation stationary digital breast tomosynthesis system with higher tube flux and increased angular span over a first generation system. The linear CNT x-ray source was designed, built, and evaluated to determine its performance parameters. The second generation system was then constructed using the CNT x-ray source and a Hologic gantry. Upon construction, test objects and phantoms were used to characterize system resolution as measured by the modulation transfer function (MTF), and artifact spread function (ASF). The results indicated that the linear CNT x-ray source was capable of stable operation at a tube potential of 49 kVp, and measured focal spot sizes showed source-to-source consistency with a nominal focal spot size of 1.1 mm. After construction, the second generation (Gen 2) system exhibited entrance surface air kerma rates two times greater the previous s-DBT system. System in-plane resolution as measured by the MTF is 7.7 cycles/mm, compared to 6.7 cycles/mm for the Gen 1 system. As expected, an increase in the z-axis depth resolution was observed, with a decrease in the ASF from 4.30 mm to 2.35 mm moving from the Gen 1 system to the Gen 2 system as result of an increased angular span. The results indicate that the Gen 2 stationary digital breast tomosynthesis system, which has a larger angular span, increased entrance surface air kerma, and faster image acquisition time over the Gen 1 s-DBT system, results in higher resolution images. With the detector operating at full resolution, the Gen 2 s-DBT system can achieve an in-plane resolution of 7.7 cycles per mm, which is better than the current commercial DBT systems today, and may potentially result in better patient diagnosis. © 2017 American Association of Physicists in Medicine.

SU-E-T-510: Calculation of High Resolution and Material-Specific Photon Energy Deposition Kernels.

PubMed

Huang, J; Childress, N; Kry, S

2012-06-01

To calculate photon energy deposition kernels (EDKs) used for convolution/superposition dose calculation at a higher resolution than the original Mackie et al. 1988 kernels and to calculate material-specific kernels that describe how energy is transported and deposited by secondary particles when the incident photon interacts in a material other than water. The high resolution EDKs for various incident photon energies were generated using the EGSnrc user-code EDKnrc, which forces incident photons to interact at the center of a 60 cm radius sphere of water. The simulation geometry is essentially the same as the original Mackie calculation but with a greater number of scoring voxels (48 radial, 144 angular bins). For the material-specific EDKs, incident photons were forced to interact at the center of a 1 mm radius sphere of material (lung, cortical bone, silver, or titanium) surrounded by a 60 cm radius water sphere, using the original scoring voxel geometry implemented by Mackie et al. 1988 (24 radial, 48 angular bins). Our Monte Carlo-calculated high resolution EDKs showed excellent agreement with the Mackie kernels, with our kernels providing more information about energy deposition close to the interaction site. Furthermore, our EDKs resulted in smoother dose deposition functions due to the finer resolution and greater number of simulation histories. The material-specific EDK results show that the angular distribution of energy deposition is different for incident photons interacting in different materials. Calculated from the angular dose distribution for 300 keV incident photons, the expected polar angle for dose deposition () is 28.6° for water, 33.3° for lung, 36.0° for cortical bone, 44.6° for titanium, and 58.1° for silver, showing a dependence on the material in which the primary photon interacts. These high resolution and material-specific EDKs have implications for convolution/superposition dose calculations in heterogeneous patient geometries, especially at material interfaces. © 2012 American Association of Physicists in Medicine.

Angular-domain scattering interferometry.

PubMed

Shipp, Dustin W; Qian, Ruobing; Berger, Andrew J

2013-11-15

We present an angular-scattering optical method that is capable of measuring the mean size of scatterers in static ensembles within a field of view less than 20 μm in diameter. Using interferometry, the method overcomes the inability of intensity-based models to tolerate the large speckle grains associated with such small illumination areas. By first estimating each scatterer's location, the method can model between-scatterer interference as well as traditional single-particle Mie scattering. Direct angular-domain measurements provide finer angular resolution than digitally transformed image-plane recordings. This increases sensitivity to size-dependent scattering features, enabling more robust size estimates. The sensitivity of these angular-scattering measurements to various sizes of polystyrene beads is demonstrated. Interferometry also allows recovery of the full complex scattered field, including a size-dependent phase profile in the angular-scattering pattern.

VizieR Online Data Catalog: Radio continuum survey of Kepler K2 mission Field 1 (Tingay+, 2016)

NASA Astrophysics Data System (ADS)

Tingay, S. J.; Hancock, P. J.; Wayth, R. B.; Intema, H.; Jagannathan, P.; Mooley, K.

2016-10-01

We describe contemporaneous observations of K2 Field 1 with the Murchison Widefield Array (MWA) and historical (from 2010-2012) observations from the Tata Institute of Fundamental Research (TIFR) Giant Metrewave Radio Telescope (GMRT) Sky Survey (TGSS; http://tgss.ncra.tifr.res.in/), via the TGSS Alternative Data Release 1 (ADR1; Intema et al. 2016, in prep.). The MWA and GMRT are radio telescopes operating at low radio frequencies (approximately 140-200MHz for the work described here). K2 mission Campaign 1 was conducted on Field 1 (center at R.A.=11:35:45.51; decl.=+01:25:02.28; J2000), covering the North Galactic Cap, between 2014 May 30 and August 21. The parameters of MWA observations are described in Table1, showing the 15 observations conducted over a period of approximately one month in 2014 June and July. All observations were made in a standard MWA imaging mode with a 30.72MHz bandwidth consisting of 24 contiguous 1.28MHz "coarse channels", each divided into 32 "fine channels" each of 40kHz bandwidth (total of 768 fine channels across 30.72MHz). The temporal resolution of the MWA correlator output was set to 0.5s. All observations were made in full polarimetric mode, with all Stokes parameters formed from the orthogonal linearly polarized feeds. Observations were made at two center frequencies, 154.88 and 185.60MHz, with two 296s observations of the K2 field at each frequency on each night of observation, accompanied by observations of one of three calibrators (Centaurus A, Virgo A, or Hydra A) at each frequency, with 112s observations. The observed fields were tracked, and thus, due to the fixed delay settings available to point the MWA primary beam, the tracked R.A. and decl. changes slightly between different observations (always a very small change compared to the MWA field of view). The total volume of MWA visibility data processed was approximately 2.2TB. A full survey of the radio sky at 150MHz as visible from the Giant Metrewave Radio (GMRT) was performed within the scope of the PI-driven TGSS project between 2010 and early 2012, covering the declination range -55° to +90°. Summarizing the observational parameters as given on the TGSS project website (http://tgss.ncra.tifr.res.in/150MHz/obsstrategy.html), the survey consists of more than 5000 pointings on an approximate hexagonal grid. Data were recorded in full polarization (RR, LL, RL, LR) every 2s, in 256 frequency channels across 16MHz of bandwidth (140-156MHz). Each pointing was observed for about 15 minutes, split over three or more scans spaced in time to improve UV-coverage. Typically, 20-40 pointings were grouped together into single night-time observing sessions, bracketed and interleaved by primary (flux density and bandpass) calibrator scans on 3C48, 3C147, and/or 3C286. Interleaving secondary (phase) calibrator scans on a variety of standard phase calibrators were also included, but were typically too faint to be of significant benefit at these frequencies. A source catalog was produced from each of the two frequencies of MWA data (see table2) and the single TGSS image (see table3). The final set of MWA images after source finding yields a total of 1085 radio sources at 154MHz, and 1468 at 185MHz over 314 square degrees, at angular resolutions of ~4'. The GMRT images, after source finding, yields a total of 7445 radio sources over the same field, at an angular resolution of ~0.3'. Thus, the overall survey covers multiple epochs of observation, spans approximately 140-200MHz, is sensitive to structures on angular scales from arcseconds to degrees, and is contemporaneous with the K2 observations of the field over a period of approximately one month. (4 data files).

Multi-resolution anisotropy studies of ultrahigh-energy cosmic rays detected at the Pierre Auger Observatory

NASA Astrophysics Data System (ADS)

Aab, A.; Abreu, P.; Aglietta, M.; Samarai, I. Al; Albuquerque, I. F. M.; Allekotte, I.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Anastasi, G. A.; Anchordoqui, L.; Andrada, B.; Andringa, S.; Aramo, C.; Arqueros, F.; Arsene, N.; Asorey, H.; Assis, P.; Aublin, J.; Avila, G.; Badescu, A. M.; Balaceanu, A.; Barreira Luz, R. J.; Baus, C.; Beatty, J. J.; Becker, K. H.; Bellido, J. A.; Berat, C.; Bertaina, M. E.; Bertou, X.; Biermann, P. L.; Billoir, P.; Biteau, J.; Blaess, S. G.; Blanco, A.; Blazek, J.; Bleve, C.; Boháčová, M.; Boncioli, D.; Bonifazi, C.; Borodai, N.; Botti, A. M.; Brack, J.; Brancus, I.; Bretz, T.; Bridgeman, A.; Briechle, F. L.; Buchholz, P.; Bueno, A.; Buitink, S.; Buscemi, M.; Caballero-Mora, K. S.; Caccianiga, L.; Cancio, A.; Canfora, F.; Caramete, L.; Caruso, R.; Castellina, A.; Cataldi, G.; Cazon, L.; Chavez, A. G.; Chinellato, J. A.; Chudoba, J.; Clay, R. W.; Colalillo, R.; Coleman, A.; Collica, L.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cooper, M. J.; Coutu, S.; Covault, C. E.; Cronin, J.; D'Amico, S.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; de Jong, S. J.; De Mauro, G.; de Mello Neto, J. R. T.; De Mitri, I.; de Oliveira, J.; de Souza, V.; Debatin, J.; Deligny, O.; Di Giulio, C.; Di Matteo, A.; Díaz Castro, M. L.; Diogo, F.; Dobrigkeit, C.; D'Olivo, J. C.; dos Anjos, R. C.; Dova, M. T.; Dundovic, A.; Ebr, J.; Engel, R.; Erdmann, M.; Erfani, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Falcke, H.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Fick, B.; Figueira, J. M.; Filipčič, A.; Fratu, O.; Freire, M. M.; Fujii, T.; Fuster, A.; Gaior, R.; García, B.; Garcia-Pinto, D.; Gaté, F.; Gemmeke, H.; Gherghel-Lascu, A.; Ghia, P. L.; Giaccari, U.; Giammarchi, M.; Giller, M.; Głas, D.; Glaser, C.; Golup, G.; Gómez Berisso, M.; Gómez Vitale, P. F.; González, N.; Gorgi, A.; Gorham, P.; Gouffon, P.; Grillo, A. F.; Grubb, T. D.; Guarino, F.; Guedes, G. P.; Hampel, M. R.; Hansen, P.; Harari, D.; Harrison, T. A.; Harton, J. L.; Hasankiadeh, Q.; Haungs, A.; Hebbeker, T.; Heck, D.; Heimann, P.; Herve, A. E.; Hill, G. C.; Hojvat, C.; Holt, E.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huege, T.; Hulsman, J.; Insolia, A.; Isar, P. G.; Jandt, I.; Jansen, S.; Johnsen, J. A.; Josebachuili, M.; Kääpä, A.; Kambeitz, O.; Kampert, K. H.; Katkov, I.; Keilhauer, B.; Kemp, E.; Kemp, J.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Krause, R.; Krohm, N.; Kuempel, D.; Kukec Mezek, G.; Kunka, N.; Kuotb Awad, A.; LaHurd, D.; Lauscher, M.; Legumina, R.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; Lopes, L.; López, R.; López Casado, A.; Luce, Q.; Lucero, A.; Malacari, M.; Mallamaci, M.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Mariş, I. C.; Marsella, G.; Martello, D.; Martinez, H.; Martínez Bravo, O.; Masías Meza, J. J.; Mathes, H. J.; Mathys, S.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Mayotte, E.; Mazur, P. O.; Medina, C.; Medina-Tanco, G.; Melo, D.; Menshikov, A.; Messina, S.; Micheletti, M. I.; Middendorf, L.; Minaya, I. A.; Miramonti, L.; Mitrica, B.; Mockler, D.; Mollerach, S.; Montanet, F.; Morello, C.; Mostafá, M.; Müller, A. L.; Müller, G.; Muller, M. A.; Müller, S.; Mussa, R.; Naranjo, I.; Nellen, L.; Nguyen, P. H.; Niculescu-Oglinzanu, M.; Niechciol, M.; Niemietz, L.; Niggemann, T.; Nitz, D.; Nosek, D.; Novotny, V.; Nožka, H.; Núñez, L. A.; Ochilo, L.; Oikonomou, F.; Olinto, A.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Papenbreer, P.; Parente, G.; Parra, A.; Paul, T.; Pech, M.; Pedreira, F.; Pȩkala, J.; Pelayo, R.; Peña-Rodriguez, J.; Pereira, L. A. S.; Perlín, M.; Perrone, L.; Peters, C.; Petrera, S.; Phuntsok, J.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Porowski, C.; Prado, R. R.; Privitera, P.; Prouza, M.; Quel, E. J.; Querchfeld, S.; Quinn, S.; Ramos-Pollan, R.; Rautenberg, J.; Ravignani, D.; Revenu, B.; Ridky, J.; Risse, M.; Ristori, P.; Rizi, V.; Rodrigues de Carvalho, W.; Rodriguez Fernandez, G.; Rodriguez Rojo, J.; Rogozin, D.; Roncoroni, M. J.; Roth, M.; Roulet, E.; Rovero, A. C.; Ruehl, P.; Saffi, S. J.; Saftoiu, A.; Salazar, H.; Saleh, A.; Salesa Greus, F.; Salina, G.; Sánchez, F.; Sanchez-Lucas, P.; Santos, E. M.; Santos, E.; Sarazin, F.; Sarmento, R.; Sarmiento, C. A.; Sato, R.; Schauer, M.; Scherini, V.; Schieler, H.; Schimp, M.; Schmidt, D.; Scholten, O.; Schovánek, P.; Schröder, F. G.; Schulz, A.; Schulz, J.; Schumacher, J.; Sciutto, S. J.; Segreto, A.; Settimo, M.; Shadkam, A.; Shellard, R. C.; Sigl, G.; Silli, G.; Sima, O.; Śmiałkowski, A.; Šmída, R.; Snow, G. R.; Sommers, P.; Sonntag, S.; Sorokin, J.; Squartini, R.; Stanca, D.; Stanič, S.; Stasielak, J.; Stassi, P.; Strafella, F.; Suarez, F.; Suarez Durán, M.; Sudholz, T.; Suomijärvi, T.; Supanitsky, A. D.; Swain, J.; Szadkowski, Z.; Taboada, A.; Taborda, O. A.; Tapia, A.; Theodoro, V. M.; Timmermans, C.; Todero Peixoto, C. J.; Tomankova, L.; Tomé, B.; Torralba Elipe, G.; Torri, M.; Travnicek, P.; Trini, M.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van Aar, G.; van Bodegom, P.; van den Berg, A. M.; van Vliet, A.; Varela, E.; Vargas Cárdenas, B.; Varner, G.; Vázquez, J. R.; Vázquez, R. A.; Veberič, D.; Vergara Quispe, I. D.; Verzi, V.; Vicha, J.; Villaseñor, L.; Vorobiov, S.; Wahlberg, H.; Wainberg, O.; Walz, D.; Watson, A. A.; Weber, M.; Weindl, A.; Wiencke, L.; Wilczyński, H.; Winchen, T.; Wittkowski, D.; Wundheiler, B.; Yang, L.; Yelos, D.; Yushkov, A.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zepeda, A.; Zimmermann, B.; Ziolkowski, M.; Zong, Z.; Zuccarello, F.

2017-06-01

We report a multi-resolution search for anisotropies in the arrival directions of cosmic rays detected at the Pierre Auger Observatory with local zenith angles up to 80o and energies in excess of 4 EeV (4 × 1018 eV). This search is conducted by measuring the angular power spectrum and performing a needlet wavelet analysis in two independent energy ranges. Both analyses are complementary since the angular power spectrum achieves a better performance in identifying large-scale patterns while the needlet wavelet analysis, considering the parameters used in this work, presents a higher efficiency in detecting smaller-scale anisotropies, potentially providing directional information on any observed anisotropies. No deviation from isotropy is observed on any angular scale in the energy range between 4 and 8 EeV. Above 8 EeV, an indication for a dipole moment is captured; while no other deviation from isotropy is observed for moments beyond the dipole one. The corresponding p-values obtained after accounting for searches blindly performed at several angular scales, are 1.3 × 10-5 in the case of the angular power spectrum, and 2.5 × 10-3 in the case of the needlet analysis. While these results are consistent with previous reports making use of the same data set, they provide extensions of the previous works through the thorough scans of the angular scales.

A Multi-instrument and Multi-wavelength High Angular Resolution Study of MWC 614: Quantum Heated Particles Inside the Disk Cavity

NASA Astrophysics Data System (ADS)

Kluska, Jacques; Kraus, Stefan; Davies, Claire L.; Harries, Tim; Willson, Matthew; Monnier, John D.; Aarnio, Alicia; Baron, Fabien; Millan-Gabet, Rafael; Ten Brummelaar, Theo; Che, Xiao; Hinkley, Sasha; Preibisch, Thomas; Sturmann, Judit; Sturmann, Laszlo; Touhami, Yamina

2018-03-01

High angular resolution observations of young stellar objects are required to study the inner astronomical units of protoplanetary disks in which the majority of planets form. As they evolve, gaps open up in the inner disk regions and the disks are fully dispersed within ∼10 Myr. MWC 614 is a pretransitional object with a ∼10 au radius gap. We present a set of high angular resolution observations of this object including SPHERE/ZIMPOL polarimetric and coronagraphic images in the visible, Keck/NIRC2 near-infrared (NIR) aperture masking observations, and Very Large Telescope Interferometer (AMBER, MIDI, and PIONIER) and Center for High Angular Resolution Astronomy (CLASSIC and CLIMB) long-baseline interferometry at infrared wavelengths. We find that all the observations are compatible with an inclined disk (i ∼ 55° at a position angle of ∼20°–30°). The mid-infrared data set confirms that the disk inner rim is at 12.3 ± 0.4 au from the central star. We determined an upper mass limit of 0.34 M ⊙ for a companion inside the cavity. Within the cavity, the NIR emission, usually associated with the dust sublimation region, is unusually extended (∼10 au, 30 times larger than the theoretical sublimation radius) and indicates a high dust temperature (T ∼ 1800 K). As a possible result of companion-induced dust segregation, quantum heated dust grains could explain the extended NIR emission with this high temperature. Our observations confirm the peculiar state of this object where the inner disk has already been accreted onto the star, exposing small particles inside the cavity to direct stellar radiation. Based on observations made with the Keck observatory (NASA program ID N104N2) and with ESO telescopes at the Paranal Observatory (ESO program IDs 073.C-0720, 077.C-0226, 077.C-0521, 083.C-0984, 087.C-0498(A), 190.C-0963, 095.C-0883) and with the Center for High Angular Resolution Astronomy observatory.

A Broadband X-Ray Imaging Spectroscopy with High-Angular Resolution: the FORCE Mission

NASA Technical Reports Server (NTRS)

Mori, Koji; Tsuru, Takeshi Go; Nakazawac, Kazuhiro; Ueda, Yoshihiro; Okajima, Takashi; Murakami, Hiroshi; Awaki, Hisamitsu; Matsumoto, Hironori; Fukazawai, Yasushi; Tsunemi, Hiroshi;

A broadband x-ray imaging spectroscopy with high-angular resolution: the FORCE mission

NASA Astrophysics Data System (ADS)

Mori, Koji; Tsuru, Takeshi Go; Nakazawa, Kazuhiro; Ueda, Yoshihiro; Okajima, Takashi; Murakami, Hiroshi; Awaki, Hisamitsu; Matsumoto, Hironori; Fukazawa, Yasushi; Tsunemi, Hiroshi; Takahashi, Tadayuki; Zhang, William W.

2016-07-01

We are proposing FORCE (Focusing On Relativistic universe and Cosmic Evolution) as a future Japan-lead Xray observatory to be launched in the mid 2020s. Hitomi (ASTRO-H) possesses a suite of sensitive instruments enabling the highest energy-resolution spectroscopy in soft X-ray band, a broadband X-ray imaging spectroscopy in soft and hard X-ray bands, and further high energy coverage up to soft gamma-ray band. FORCE is the direct successor to the broadband X-ray imaging spectroscopy aspect of Hitomi (ASTRO-H) with significantly higher angular resolution. The current design of FORCE defines energy band pass of 1-80 keV with angular resolution of < 15 in half-power diameter, achieving a 10 times higher sensitivity above 10 keV compared to any previous missions with simultaneous soft X-ray coverage. Our primary scientific objective is to trace the cosmic formation history by searching for "missing black holes" in various mass-scales: "buried supermassive black holes (SMBHs)" (> 104 M⊙) residing in the center of galaxies in a cosmological distance, "intermediate-mass black holes" (102-104 M⊙) acting as the possible seeds from which SMBHs grow, and "orphan stellar-mass black holes" (< 102 M⊙) without companion in our Galaxy. In addition to these missing BHs, hunting for the nature of relativistic particles at various astrophysical shocks is also in our scope, utilizing the broadband X-ray coverage with high angular-resolution. FORCE are going to open a new era in these fields. The satellite is proposed to be launched with the Epsilon vehicle that is a Japanese current solid-fuel rocket. FORCE carries three identical pairs of Super-mirror and wide-band X-ray detector. The focal length is currently planned to be 10 m. The silicon mirror with multi-layer coating is our primary choice to achieve lightweight, good angular optics. The detector is a descendant of hard X-ray imager onboard Hitomi (ASTRO-H) replacing its silicon strip detector with SOI-CMOS silicon pixel detector, allowing an extension of the low energy threshold down to 1 keV or even less.

Empirical single sample quantification of bias and variance in Q-ball imaging.

PubMed

Hainline, Allison E; Nath, Vishwesh; Parvathaneni, Prasanna; Blaber, Justin A; Schilling, Kurt G; Anderson, Adam W; Kang, Hakmook; Landman, Bennett A

2018-02-06

The bias and variance of high angular resolution diffusion imaging methods have not been thoroughly explored in the literature and may benefit from the simulation extrapolation (SIMEX) and bootstrap techniques to estimate bias and variance of high angular resolution diffusion imaging metrics. The SIMEX approach is well established in the statistics literature and uses simulation of increasingly noisy data to extrapolate back to a hypothetical case with no noise. The bias of calculated metrics can then be computed by subtracting the SIMEX estimate from the original pointwise measurement. The SIMEX technique has been studied in the context of diffusion imaging to accurately capture the bias in fractional anisotropy measurements in DTI. Herein, we extend the application of SIMEX and bootstrap approaches to characterize bias and variance in metrics obtained from a Q-ball imaging reconstruction of high angular resolution diffusion imaging data. The results demonstrate that SIMEX and bootstrap approaches provide consistent estimates of the bias and variance of generalized fractional anisotropy, respectively. The RMSE for the generalized fractional anisotropy estimates shows a 7% decrease in white matter and an 8% decrease in gray matter when compared with the observed generalized fractional anisotropy estimates. On average, the bootstrap technique results in SD estimates that are approximately 97% of the true variation in white matter, and 86% in gray matter. Both SIMEX and bootstrap methods are flexible, estimate population characteristics based on single scans, and may be extended for bias and variance estimation on a variety of high angular resolution diffusion imaging metrics. © 2018 International Society for Magnetic Resonance in Medicine.

Perspective View with Landsat Overlay, Sacramento, Calif.

NASA Technical Reports Server (NTRS)

2002-01-01

California's state capitol, Sacramento, can be seen clustered along the American and Sacramento Rivers in this computer-generated perspective viewed from the west. Folsom Lake is in the center and the Sierra Nevada is above, with the edge of Lake Tahoe just visible at top center.

This 3-D perspective view was generated using topographic data from the Shuttle Radar Topography Mission (SRTM) and an enhanced color Landsat 5satellite image. Topographic expression is exaggerated two times.

Landsat has been providing visible and infrared views of the Earth since 1972. SRTM elevation data matches the 30-meter (98-foot) resolution of most Landsat images and will substantially help in analyzing the large and growing Landsat image archive.

Elevation data used in this image was acquired by the Shuttle Radar Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched on Feb. 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR)that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect 3-D measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter (approximately 200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between NASA, the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Earth Science Enterprise, Washington, D.C.

Size: scale varies in this perspective image Location: 38.6 deg. North lat., 121.3 deg. West lon. Orientation: looking east Image Data: Landsat Bands 3, 2, 1 as red, green, blue, respectively Original Data Resolution: SRTM 1 arcsecond (30 meters or 98 feet), Thematic Mapper 1 arcsecond (30 meters or 98 feet) Date Acquired: February 2000 (SRTM)

Perspective View with Landsat Overlay, Mount Shasta, Calif.

NASA Technical Reports Server (NTRS)

2002-01-01

At more than 4,300 meters (14,000 feet ), Mount Shasta is California's tallest volcano and part of the Cascade chain of volcanoes extending south from Washington. This computer-generated perspective viewed from the west also includes Shastina, a slightly smaller volcanic cone left of Shasta's summit and Black Butte, another volcano in the right foreground.

This 3-D perspective view was generated using topographic data from the Shuttle Radar Topography Mission (SRTM) and an enhanced color Landsat 5satellite image. Topographic expression is exaggerated two times.

Landsat has been providing visible and infrared views of the Earth since 1972. SRTM elevation data matches the 30-meter (98-foot) resolution of most Landsat images and will substantially help in analyzing the large and growing Landsat image archive.

Elevation data used in this image was acquired by the Shuttle Radar Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched on Feb. 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR)that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect 3-D measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter (approximately 200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between NASA, the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Earth Science Enterprise,Washington, D.C.

Size: scale varies in this perspective image Location: 41.4 deg. North lat., 122.3 deg. West lon. Orientation: looking east Image Data: Landsat Bands 3,2,1 as red, green, blue, respectively Original Data Resolution: SRTM 1 arcsecond (30 meters or 98 feet), Thematic Mapper 1 arcsecond (30 meters or 98 feet) Date Acquired: February 2000 (SRTM)

A Spatially Resolved Study of Cold Dust, Molecular Gas, H II Regions, and Stars in the z = 2.12 Submillimeter Galaxy ALESS67.1

NASA Astrophysics Data System (ADS)

Chen, Chian-Chou; Hodge, J. A.; Smail, Ian; Swinbank, A. M.; Walter, Fabian; Simpson, J. M.; Calistro Rivera, Gabriela; Bertoldi, F.; Brandt, W. N.; Chapman, S. C.; da Cunha, Elisabete; Dannerbauer, H.; De Breuck, C.; Harrison, C. M.; Ivison, R. J.; Karim, A.; Knudsen, K. K.; Wardlow, J. L.; Weiß, A.; van der Werf, P. P.

2017-09-01

We present detailed studies of a z = 2.12 submillimeter galaxy, ALESS67.1, using sub-arcsecond resolution ALMA, adaptive optics-aided VLT/SINFONI, and Hubble Space Telescope (HST)/CANDELS data to investigate the kinematics and spatial distributions of dust emission (870 μm continuum), 12CO(J = 3–2), strong optical emission lines, and visible stars. Dynamical modeling of the optical emission lines suggests that ALESS67.1 is not a pure rotating disk but a merger, consistent with the apparent tidal features revealed in the HST imaging. Our sub-arcsecond resolution data set allows us to measure half-light radii for all the tracers, and we find a factor of 4–6 smaller sizes in dust continuum compared to all the other tracers, including 12CO; also, ultraviolet (UV) and Hα emission are significantly offset from the dust continuum. The spatial mismatch between the UV continuum and the cold dust and gas reservoir supports the explanation that geometrical effects are responsible for the offset of the dusty galaxy on the IRX–β diagram. Using a dynamical method we derive an {α }CO}=1.8+/- 1.0, consistent with other submillimeter galaxies (SMGs) that also have resolved CO and dust measurements. Assuming a single {α }CO} value we also derive resolved gas and star formation rate surface densities, and find that the core region of the galaxy (≲ 5 kpc) follows the trend of mergers on the Schmidt–Kennicutt relationship, whereas the outskirts (≳ 5 kpc) lie on the locus of normal star-forming galaxies, suggesting different star formation efficiencies within one galaxy. Our results caution against using single size or morphology for different tracers of the star formation activity and gas content of galaxies, and therefore argue the need to use spatially resolved, multi-wavelength observations to interpret the properties of SMGs, and perhaps even for z> 1 galaxies in general.

Summary of the Validation of the Second Version of the Aster Gdem

NASA Astrophysics Data System (ADS)

Meyer, D. J.; Tachikawa, T.; Abrams, M.; Crippen, R.; Krieger, T.; Gesch, D.; Carabajal, C.

2012-07-01

On October 17, 2011, NASA and the Ministry of Economy, Trade and Industry (METI) of Japan released the second version of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM) to users worldwide at no charge as a contribution to the Global Earth Observing System of Systems (GEOSS). The first version of the ASTER GDEM, released on June 29, 2009, was compiled from over 1.2 million scene-based DEMs covering land surfaces between 83°N and 83°S latitudes. The second version (GDEM2) incorporates 260,000 additional scenes to improve coverage, a smaller correlation kernel to yield higher spatial resolution, and improved water masking. As with GDEM1, US and Japanese partners collaborated to validate GDEM2. Its absolute accuracy was within -0.20 meters on average when compared against 18,000 geodetic control points over the conterminous US (CONUS), with an accuracy of 17 meters at the 95% confidence level. The Japan study noted the GDEM2 differed from the 10-meter national elevation grid by -0.7 meters over bare areas, and by 7.4 meters over forested areas. The CONUS study noted a similar result, with the GDEM2 determined to be about 8 meters above the 1 arc-second US National Elevation Database (NED) over most forested areas, and more than a meter below NED over bare areas. A global ICESat study found the GDEM2 to be on average within 3 meters of altimeter-derived control. The Japan study noted a horizontal displacement of 0.23 pixels in GDEM2. A study from the US National Geospatial Intelligence Agency also determined horizontal displacement and vertical accuracy as compared to the 1 arc-second Shuttle Radar Topography Mission DEM. US and Japanese studies estimated the horizontal resolution of the GDEM2 to be between 71 and 82 meters. Finally, the number of voids and artifacts noted in GDEM1 were substantially reduced in GDEM2.

Revealing the subfemtosecond dynamics of orbital angular momentum in nanoplasmonic vortices

NASA Astrophysics Data System (ADS)

Spektor, G.; Kilbane, D.; Mahro, A. K.; Frank, B.; Ristok, S.; Gal, L.; Kahl, P.; Podbiel, D.; Mathias, S.; Giessen, H.; Meyer zu Heringdorf, F.-J.; Orenstein, M.; Aeschlimann, M.

2017-03-01

The ability of light to carry and deliver orbital angular momentum (OAM) in the form of optical vortices has attracted much interest. The physical properties of light with a helical wavefront can be confined onto two-dimensional surfaces with subwavelength dimensions in the form of plasmonic vortices, opening avenues for thus far unknown light-matter interactions. Because of their extreme rotational velocity, the ultrafast dynamics of such vortices remained unexplored. Here we show the detailed spatiotemporal evolution of nanovortices using time-resolved two-photon photoemission electron microscopy. We observe both long- and short-range plasmonic vortices confined to deep subwavelength dimensions on the scale of 100 nanometers with nanometer spatial resolution and subfemtosecond time-step resolution. Finally, by measuring the angular velocity of the vortex, we directly extract the OAM magnitude of light.

Characterisation and comparison of event generators for pair conversion: A crucial step for future low energy gamma telescope

NASA Astrophysics Data System (ADS)

Gros, P.; Bernard, D.

2017-05-01

Gamma ray astronomy suffers from a sensitivity gap between 0.1 and 100Mev. With high angular resolution for the electrons, it will also be possible to probe the linear polarisation of the photons. An accurate simulation is necessary to correctly design and compare these detectors. We establish baseline distributions of key kinematic variables as simulated by a 5D, exact down to threshold, and polarised event generator. We compare them to simulations with the low energy electromagnetic models available in Geant4 and in EGS5. We show that different generators give a different picture of the optimal angular resolution of pair telescopes. We also show that, of all the simulations we used, only the full 5D generator describes accurately the angular asymmetry in the case of polarised photons.

Spiral Transformation for High-Resolution and Efficient Sorting of Optical Vortex Modes.

PubMed

Wen, Yuanhui; Chremmos, Ioannis; Chen, Yujie; Zhu, Jiangbo; Zhang, Yanfeng; Yu, Siyuan

2018-05-11

Mode sorting is an essential function for optical multiplexing systems that exploit the orthogonality of the orbital angular momentum mode space. The familiar log-polar optical transformation provides a simple yet efficient approach whose resolution is, however, restricted by a considerable overlap between adjacent modes resulting from the limited excursion of the phase along a complete circle around the optical vortex axis. We propose and experimentally verify a new optical transformation that maps spirals (instead of concentric circles) to parallel lines. As the phase excursion along a spiral in the wave front of an optical vortex is theoretically unlimited, this new optical transformation can separate orbital angular momentum modes with superior resolution while maintaining unity efficiency.

Spiral Transformation for High-Resolution and Efficient Sorting of Optical Vortex Modes

NASA Astrophysics Data System (ADS)

Wen, Yuanhui; Chremmos, Ioannis; Chen, Yujie; Zhu, Jiangbo; Zhang, Yanfeng; Yu, Siyuan

2018-05-01

Mode sorting is an essential function for optical multiplexing systems that exploit the orthogonality of the orbital angular momentum mode space. The familiar log-polar optical transformation provides a simple yet efficient approach whose resolution is, however, restricted by a considerable overlap between adjacent modes resulting from the limited excursion of the phase along a complete circle around the optical vortex axis. We propose and experimentally verify a new optical transformation that maps spirals (instead of concentric circles) to parallel lines. As the phase excursion along a spiral in the wave front of an optical vortex is theoretically unlimited, this new optical transformation can separate orbital angular momentum modes with superior resolution while maintaining unity efficiency.

A New Determination of Planetary Precession

NASA Astrophysics Data System (ADS)

Harada, Wataru; Fukushima, Toshio

2004-01-01

By using a nonlinear method of harmonic analysis, we have analyzed the motion of two angles, Ω and ɛ, specifying the direction of the Newtonian heliocentric orbital angular momentum of the Earth-Moon barycenter in the latest lunar and planetary ephemeris, DE405, from 1629 to 2169. Here Ω is the longitude of the node of the ecliptic of date with respect to the International Celestial Reference Frame (ICRF) equator, measured from the ICRF x-axis, while ɛ is the obliquity of the ecliptic of date referred to the ICRF equator. After dropping 86 Fourier terms and four mixed secular terms that were detected, we determined their secular variation in the form of quadratic polynomials as ΩDE405=-0.02109+10.54227t+0.48609t2 and ɛDE405=84,381.40578-46.81972t+0.04817t2 , where the units are arcseconds and t is the time since J2000.0 measured in Julian centuries. This is the latest determination of the planetary precession in the inertial sense and referred to the ICRF.

TeraHertz Space Telescope (TST)

NASA Astrophysics Data System (ADS)

Dunn, Marina Madeline; Lesser, David; O'Dougherty, Stephan; Swift, Brandon; Pat, Terrance; Cortez, German; Smith, Steve; Goldsmith, Paul; Walker, Christopher K.

2017-01-01

The Terahertz Space Telescope (TST) utilizes breakthrough inflatable technology to create a ~25 m far-infrared observing system at a fraction of the cost of previous space telescopes. As a follow-on to JWST and Herschel, TST will probe the FIR/THz regime with unprecedented sensitivity and angular resolution, answering fundamental questions concerning the origin and destiny of the cosmos. Prior and planned space telescopes have barely scratched the surface of what can be learned in this wavelength region. TST will pick up where JWST and Herschel leave off. At ~30µm TST will have ~10x the sensitivity and ~3x the angular resolution of JWST. At longer wavelengths it will have ~1000x the sensitivity of Herschel and ~7 times the angular resolution. TST can achieve this at low cost through the innovative use of inflatable technology. A recently-completed NIAC Phase II study (Large Balloon Reflector) validated, both analytically and experimentally, the concept of a large inflatable spherical reflector and demonstrated critical telescope functions. In our poster we will introduce the TST concept and compare its performance to past, present, and proposed far-infrared observatories.

Photoelectron angular distributions from rotationally resolved autoionizing states of N 2

DOE PAGES

Chartrand, A. M.; McCormack, E. F.; Jacovella, U.; ...

2017-12-08

The single-photon, photoelectron-photoion coincidence spectrum of N 2 has been recorded at high (~1.5 cm -1) resolution in the region between the N 2 + X 2Σ g +, v + = 0 and 1 ionization thresholds by using a double imaging spectrometer and intense vacuum-ultraviolet light from the Synchrotron SOLEIL. This approach provides the relative photoionization cross section, the photoelectron energy distribution, and the photoelectron angular distribution as a function of photon energy. The region of interest contains autoionizing valence states, vibrationally autoionizing Rydberg states converging to vibrationally excited levels of the N 2 + X 2Σ g +more » ground state, and electronically autoionizing states converging to the N 2 + A 2Π and B 2Σ u + states. The wavelength resolution is sufficient to resolve rotational structure in the autoionizing states, but the electron energy resolution is insufficient to resolve rotational structure in the photoion spectrum. Here, a simplified approach based on multichannel quantum defect theory is used to predict the photoelectron angular distribution parameters, β, and the results are in reasonably good agreement with experiment.« less

Slumped glass optics with interfacing ribs for high angular resolution x-ray astronomy: a progress report

NASA Astrophysics Data System (ADS)

Civitani, M.; Basso, S.; Brizzolari, C.; Ghigo, M.; Pareschi, G.; Salmaso, B.; Spiga, D.; Vecchi, G.; Breunig, E.; Burwitz, V.; Hartner, G. D.; Menz, B.

2015-09-01

The Slumped Glass Optics technology, developed at INAF/OAB since a few years, is becoming a competitive solution for the realization of the future X-ray telescopes with a very large collecting area, as e.g. the proposed Athena, with more than 2 m2 effective area at 1 keV and with a high angular resolution (5'' HEW). The developed technique is based on modular elements, named X-ray Optical Units (XOUs), made of several layers of thin foils of glass, previously formed by direct hot slumping in cylindrical configuration, and then stacked in a Wolter-I configuration, through interfacing ribs. The achievable global angular resolution of the optics relies on the surface shape accuracy of the slumped foils, on the smoothness of the mirror surfaces and on the correct integration and co-alignment of the mirror segments achieved with a dedicated Integration Machine (IMA). In this paper we provide an update of the project development, reporting on the last results achieved. In particular, we will present the results obtained with full illumination X-ray tests for the last developed prototypes.

Silicon pore optics for the international x-ray observatory

NASA Astrophysics Data System (ADS)

Wille, E.; Wallace, K.; Bavdaz, M.; Collon, M. J.; Günther, R.; Ackermann, M.; Beijersbergen, M. W.; Riekerink, M. O.; Blom, M.; Lansdorp, B.; de Vreede, L.

2017-11-01

Lightweight X-ray Wolter optics with a high angular resolution will enable the next generation of X-ray telescopes in space. The International X-ray Observatory (IXO) requires a mirror assembly of 3 m2 effective area (at 1.5 keV) and an angular resolution of 5 arcsec. These specifications can only be achieved with a novel technology like Silicon Pore Optics, which is developed by ESA together with a consortium of European industry. Silicon Pore Optics are made of commercial Si wafers using process technology adapted from the semiconductor industry. We present the manufacturing process ranging from single mirror plates towards complete focusing mirror modules mounted in flight configuration. The performance of the mirror modules is tested using X-ray pencil beams or full X-ray illumination. In 2009, an angular resolution of 9 arcsec was achieved, demonstrating the improvement of the technology compared to 17 arcsec in 2007. Further development activities of Silicon Pore Optics concentrate on ruggedizing the mounting system and performing environmental tests, integrating baffles into the mirror modules and assessing the mass production.

Production of thin glass mirrors by hot slumping for x-ray telescopes: present process and ongoing development

NASA Astrophysics Data System (ADS)

Salmaso, B.; Basso, S.; Brizzolari, C.; Civitani, M.; Ghigo, M.; Pareschi, G.; Spiga, D.; Tagliaferri, G.; Vecchi, G.

2014-07-01

Thin glass foils are considered good candidates to build a segmented X-ray telescope with effective area as large as 2 m2 and angular resolution better than 5 arcsec. In order to produce thin glass mirror segments, we developed a direct hot slumping technique assisted by pressure, in which the shape of a mould is replicated onto the optical surface of the glass. In this paper we present the result obtained with AF32 (by Schott) and EAGLE XG (by Corning) glass types. The selected mould material is Zerodur K20, as it does not require any anti-sticking layer and has a good matching, in terms of Coefficient of Thermal Expansion, with both glass types. Our group already produced a few prototypes, reaching angular resolution near 20 arcsec. In this work, relevant steps forward aimed at attaining a 5 arcsec angular resolution are described, along with the tuning of few key parameters in the slumping process. The results obtained on a newly procured cylindrical Zerodur K20 mould are presented.

SPICA, Stellar Parameters and Images with a Cophased Array: a 6T visible combiner for the CHARA array.

PubMed

Mourard, Denis; Bério, Philippe; Perraut, Karine; Clausse, Jean-Michel; Creevey, Orlagh; Martinod, Marc-Antoine; Meilland, Anthony; Millour, Florentin; Nardetto, Nicolas

2017-05-01

High angular resolution studies of stars in the optical domain have highly progressed in recent years. After the results obtained with the visible instrument Visible spEctroGraph and polArimeter (VEGA) on the Center for High Angular Resolution Astronomy (CHARA) array and the recent developments on adaptive optics and fibered interferometry, we have started the design and study of a new six-telescope visible combiner with single-mode fibers. It is designed as a low spectral resolution instrument for the measurement of the angular diameter of stars to make a major step forward in terms of magnitude and precision with respect to the present situation. For a large sample of bright stars, a medium spectral resolution mode will allow unprecedented spectral imaging of stellar surfaces and environments for higher accuracy on stellar/planetary parameters. To reach the ultimate performance of the instrument in terms of limiting magnitude (Rmag≃8 for diameter measurements and Rmag≃4 to 5 for imaging), Stellar Parameters and Images with a Cophased Array (SPICA) includes the development of a dedicated fringe tracking system in the H band to reach "long" (200 ms to 30 s) exposures of the fringe signal in the visible.

The Marshall Grazing Incidence X-ray Spectrometer

NASA Astrophysics Data System (ADS)

Kobayashi, Ken; Winebarger, Amy R.; Savage, Sabrina; Champey, Patrick; Cheimets, Peter N.; Hertz, Edward; Bruccoleri, Alexander R.; Golub, Leon; Ramsey, Brian; Ranganathan, Jaganathan; Marquez, Vanessa; Allured, Ryan; Parker, Theodore; Heilmann, Ralf K.; Schattenburg, Mark L.

2017-08-01

The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a NASA sounding rocket instrument designed to obtain spatially resolved soft X-ray spectra of the solar atmosphere in the 6-24 Å (0.5-2.0 keV) range. The instrument consists of a single shell Wolter Type-I telescope, a slit, and a spectrometer comprising a matched pair of grazing incidence parabolic mirrors and a planar varied-line space diffraction grating. The instrument is designed to achieve a 50 mÅ spectral resolution and 5 arcsecond spatial resolution along a +/-4-arcminute long slit, and launch is planned for 2019. We report on the status and our approaches for fabrication and alignment for this novel optical system. The telescope and spectrometer mirrors are replicated nickel shells, and are currently being fabricated at the NASA Marshall Space Flight Center. The diffraction grating is currently under development by the Massachusetts Institute of Technology (MIT); because of the strong line spacing variation across the grating, it will be fabricated through e-beam lithography.

The Space Infrared Interferometric Telescope (SPIRIT) and its Complementarity to ALMA

NASA Technical Reports Server (NTRS)

Leisawitz, Dave

2007-01-01

We report results of a pre-Formulation Phase study of SPIRIT, a candidate NASA Origins Probe mission. SPIRIT is a spatial and spectral interferometer with an operating wavelength range 25 - 400 microns. SPIRIT will provide sub-arcsecond resolution images and spectra with resolution R = 3000 in a 1 arcmin field of view to accomplish three primary scientific objectives: (1) Learn how planetary systems form from protostellar disks, and how they acquire their chemical organization; (2) Characterize the family of extrasolar planetary systems by imaging the structure in debris disks to understand how and where planets of different types form; and (3) Learn how high-redshift galaxies formed and merged to form the present-day population of galaxies. In each of these science domains, SPIRIT will yield information complementary to that obtainable with the James Webb Space Telescope (JWST)and the Atacama Large Millimeter Array (ALMA), and all three observatories could operate contemporaneously. Here we shall emphasize the SPIRIT science goals (1) and (2) and the mission's complementarity with ALMA.

Does TRACE Resolve Isothermal Coronal Loops?

NASA Astrophysics Data System (ADS)

Weber, Mark A.; Schmelz, J.; Kashyap, V.; Roames, J.

2006-06-01

Historically, increasing resolution of solar data has revealed ever smaller length scales for both the thermodynamics and the magnetic structure of the corona. Furthermore, the dynamics there are governed by magnetohydrodynamic processes which are difficult to observe or model. Recent results in the literature suggest that some coronal loops with cross-sections near the resolution limits of the Transition Region and Coronal Explorer (pixel size = 0.5 arc-seconds, or approx. 360 km) are, in fact, isothermally homogeneous and thus may be identified as elementary loop strands. This poster presents some ongoing work that applies state-of-the-art estimation of differential emission measures in order to evaluate these claims for a sample of loops. We find that the data give no evidence to prefer the "isothermal" hypothesis over the "multithermal" hypothesis. The authors are supported by the following funds: contract SP02H820IR to the Lockheed-Martin Corp.; NSF grant ATM-0402729; NASA grant NNG05GE68G; and NASA contracts NAS8-39073 and NAS8-03060.

High resolution global gridded data for use in population studies

NASA Astrophysics Data System (ADS)

Lloyd, Christopher T.; Sorichetta, Alessandro; Tatem, Andrew J.

2017-01-01

Recent years have seen substantial growth in openly available satellite and other geospatial data layers, which represent a range of metrics relevant to global human population mapping at fine spatial scales. The specifications of such data differ widely and therefore the harmonisation of data layers is a prerequisite to constructing detailed and contemporary spatial datasets which accurately describe population distributions. Such datasets are vital to measure impacts of population growth, monitor change, and plan interventions. To this end the WorldPop Project has produced an open access archive of 3 and 30 arc-second resolution gridded data. Four tiled raster datasets form the basis of the archive: (i) Viewfinder Panoramas topography clipped to Global ADMinistrative area (GADM) coastlines; (ii) a matching ISO 3166 country identification grid; (iii) country area; (iv) and slope layer. Further layers include transport networks, landcover, nightlights, precipitation, travel time to major cities, and waterways. Datasets and production methodology are here described. The archive can be downloaded both from the WorldPop Dataverse Repository and the WorldPop Project website.

High resolution global gridded data for use in population studies.

PubMed

Lloyd, Christopher T; Sorichetta, Alessandro; Tatem, Andrew J

2017-01-31

Recent years have seen substantial growth in openly available satellite and other geospatial data layers, which represent a range of metrics relevant to global human population mapping at fine spatial scales. The specifications of such data differ widely and therefore the harmonisation of data layers is a prerequisite to constructing detailed and contemporary spatial datasets which accurately describe population distributions. Such datasets are vital to measure impacts of population growth, monitor change, and plan interventions. To this end the WorldPop Project has produced an open access archive of 3 and 30 arc-second resolution gridded data. Four tiled raster datasets form the basis of the archive: (i) Viewfinder Panoramas topography clipped to Global ADMinistrative area (GADM) coastlines; (ii) a matching ISO 3166 country identification grid; (iii) country area; (iv) and slope layer. Further layers include transport networks, landcover, nightlights, precipitation, travel time to major cities, and waterways. Datasets and production methodology are here described. The archive can be downloaded both from the WorldPop Dataverse Repository and the WorldPop Project website.

Development Status of Adjustable Grazing Incidence Optics for 0.5 Arcsecond X-Ray Imaging

NASA Technical Reports Server (NTRS)

Reid, Paul B.; Aldcroft, Thomas L.; Allured, Ryan; Cotroneo, Vincenzo; Johnson-Wilke, Raegan L.; Marquez, Vanessa; McMuldroch, Stuart; O'Dell, Stephen L.; Ramsey, Brian D.; Schwartz, Daniel A.;

Evaluation of beam tracking strategies for the THOR-CSW solar wind instrument

NASA Astrophysics Data System (ADS)

De Keyser, Johan; Lavraud, Benoit; Prech, Lubomir; Neefs, Eddy; Berkenbosch, Sophie; Beeckman, Bram; Maggiolo, Romain; Fedorov, Andrei; Baruah, Rituparna; Wong, King-Wah; Amoros, Carine; Mathon, Romain; Génot, Vincent

2017-04-01

We compare different beam tracking strategies for the Cold Solar Wind (CSW) plasma spectrometer on the ESA M4 THOR mission candidate. The goal is to intelligently select the energy and angular windows the instrument is sampling and to adapt these windows as the solar wind properties evolve, with the aim to maximize the velocity distribution acquisition rate while maintaining excellent energy and angular resolution. Using synthetic data constructed using high-cadence measurements by the Faraday cup instrument on the Spektr-R mission (30 ms resolution), we test the performance of energy beam tracking with or without angular beam tracking. The algorithm can be fed both by data acquired by the plasma spectrometer during the previous measurement cycle, or by data from another instrument, in casu the Faraday Cup (FAR) instrument foreseen on THOR. We verify how these beam tracking algorithms behave for different sizes of the energy and angular windows, and for different data integration times, in order to assess the limitations of the algorithm and to avoid situations in which the algorithm loses track of the beam.

Observation of the shadowing of cosmic rays by the Moon using a deep underground detector

NASA Astrophysics Data System (ADS)

Ambrosio, M.; Antolini, R.; Aramo, C.; Auriemma, G.; Baldini, A.; Barbarino, G. C.; Barish, B. C.; Battistoni, G.; Bellotti, R.; Bemporad, C.; Bernardini, P.; Bilokon, H.; Bisi, V.; Bloise, C.; Bower, C.; Bussino, S.; Cafagna, F.; Calicchio, M.; Campana, D.; Carboni, M.; Castellano, M.; Cecchini, S.; Cei, F.; Chiarella, V.; Choudhary, B. C.; Coutu, S.; de Benedictis, L.; de Cataldo, G.; Dekhissi, H.; de Marzo, C.; de Mitri, I.; Derkaoui, J.; de Vincenzi, M.; di Credico, A.; Erriquez, O.; Favuzzi, C.; Forti, C.; Fusco, P.; Giacomelli, G.; Giannini, G.; Giglietto, N.; Giorgini, M.; Grassi, M.; Gray, L.; Grillo, A.; Guarino, F.; Guarnaccia, P.; Gustavino, C.; Habig, A.; Hanson, K.; Heinz, R.; Huang, Y.; Iarocci, E.; Katsavounidis, E.; Kearns, E.; Kim, H.; Kyriazopoulou, S.; Lamanna, E.; Lane, C.; Levin, D. S.; Lipari, P.; Longley, N. P.; Longo, M. J.; Maaroufi, F.; Mancarella, G.; Mandrioli, G.; Manzoor, S.; Neri, A. Margiotta; Marini, A.; Martello, D.; Marzari-Chiesa, A.; Mazziotta, M. N.; Mazzotta, C.; Michael, D. G.; Mikheyev, S.; Miller, L.; Monacelli, P.; Montaruli, T.; Monteno, M.; Mufson, S.; Musser, J.; Nicoló, D.; Orth, C.; Osteria, G.; Ouchrif, M.; Palamara, O.; Patera, V.; Patrizii, L.; Pazzi, R.; Peck, C. W.; Petrera, S.; Pistilli, P.; Popa, V.; Pugliese, V.; Rainò, A.; Reynoldson, J.; Ronga, F.; Rubizzo, U.; Satriano, C.; Satta, L.; Scapparone, E.; Scholberg, K.; Sciubba, A.; Serra-Lugaresi, P.; Severi, M.; Sioli, M.; Sitta, M.; Spinelli, P.; Spinetti, M.; Spurio, M.; Steinberg, R.; Stone, J. L.; Sulak, L. R.; Surdo, A.; Tarlè, G.; Togo, V.; Ugolotti, D.; Vakili, M.; Walter, C. W.; Webb, R.

1999-01-01

Using data collected by the MACRO experiment during the years 1989-1996, we show evidence for the shadow of the Moon in the underground cosmic ray flux with a significance of 3.6σ. This detection of the shadowing effect is the first by an underground detector. A maximum-likelihood analysis is used to determine that the angular resolution of the apparatus is 0.9°+/-0.3°. These results demonstrate MACRO's capabilities as a muon telescope by confirming its absolute pointing ability and quantifying its angular resolution.

The Space High Angular Resolution Probe for the Infrared (SHARP-IR)

NASA Technical Reports Server (NTRS)

Rinehart, S. A.; Rizzo, M. J.; Leisawitz, D. T.; Staguhn, J. G.; Dipirro, M.; Mentzell, J. E.; Juanola-Parramon, R.; Dhabal, A.; Mundy, L. G.; Moseley, S. H.;

Determining neutrino mass from the cosmic microwave background alone.

PubMed

Kaplinghat, Manoj; Knox, Lloyd; Song, Yong-Seon

2003-12-12

Distortions of cosmic microwave background temperature and polarization maps caused by gravitational lensing, observable with high angular resolution and high sensitivity, can be used to measure the neutrino mass. Assuming two massless species and one with mass m(nu), we forecast sigma(m(nu))=0.15 eV from the Planck satellite and sigma(m(nu))=0.04 eV from observations with twice the angular resolution and approximately 20 times the sensitivity. A detection is likely at this higher sensitivity since the observation of atmospheric neutrino oscillations requires Deltam(2)(nu) greater, similar (0.04 eV)(2).

New Ultra-High Sensitivity, Absolute, Linear, and Rotary Encoders

NASA Technical Reports Server (NTRS)

Leviton, Douglas B.

1998-01-01

Several new types of absolute optical encoders of both rotary and linear function are discussed. The means for encoding are complete departures from conventional optical encoders and offer advantages of compact form, immunity to damage-induced dropouts of position information, and about an order of magnitude higher sensitivity over what is commercially available. Rotary versions have sensitivity from 0.02 arcseconds down to 0.003 arcsecond while linear models have sensitivity of 10 nm.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Donguk; Chae, Jongchul; Yang, Heesu

It is well-known that light bridges (LBs) inside a sunspot produce small-scale plasma ejections and transient brightenings in the chromosphere, but the nature and origin of such phenomena are still unclear. Utilizing the high-spatial and high-temporal resolution spectral data taken with the Fast Imaging Solar Spectrograph and the TiO 7057 Å broadband filter images installed at the 1.6 m New Solar Telescope of Big Bear Solar Observatory, we report arcsecond-scale chromospheric plasma ejections (1.″7) inside a LB. Interestingly, the ejections are found to be a manifestation of upwardly propagating shock waves as evidenced by the sawtooth patterns seen in themore » temporal-spectral plots of the Ca ii 8542 Å and H α intensities. We also found a fine-scale photospheric pattern (1″) diverging with a speed of about 2 km s{sup −1} two minutes before the plasma ejections, which seems to be a manifestation of magnetic flux emergence. As a response to the plasma ejections, the corona displayed small-scale transient brightenings. Based on our findings, we suggest that the shock waves can be excited by the local disturbance caused by magnetic reconnection between the emerging flux inside the LB and the adjacent umbral magnetic field. The disturbance generates slow-mode waves, which soon develop into shock waves, and manifest themselves as the arcsecond-scale plasma ejections. It also appears that the dissipation of mechanical energy in the shock waves can heat the local corona.« less

Chromospheric Plasma Ejections in a Light Bridge of a Sunspot

NASA Astrophysics Data System (ADS)

Song, Donguk; Chae, Jongchul; Yurchyshyn, Vasyl; Lim, Eun-Kyung; Cho, Kyung-Suk; Yang, Heesu; Cho, Kyuhyoun; Kwak, Hannah

2017-02-01

It is well-known that light bridges (LBs) inside a sunspot produce small-scale plasma ejections and transient brightenings in the chromosphere, but the nature and origin of such phenomena are still unclear. Utilizing the high-spatial and high-temporal resolution spectral data taken with the Fast Imaging Solar Spectrograph and the TiO 7057 Å broadband filter images installed at the 1.6 m New Solar Telescope of Big Bear Solar Observatory, we report arcsecond-scale chromospheric plasma ejections (1.″7) inside a LB. Interestingly, the ejections are found to be a manifestation of upwardly propagating shock waves as evidenced by the sawtooth patterns seen in the temporal-spectral plots of the Ca II 8542 Å and Hα intensities. We also found a fine-scale photospheric pattern (1″) diverging with a speed of about 2 km s-1 two minutes before the plasma ejections, which seems to be a manifestation of magnetic flux emergence. As a response to the plasma ejections, the corona displayed small-scale transient brightenings. Based on our findings, we suggest that the shock waves can be excited by the local disturbance caused by magnetic reconnection between the emerging flux inside the LB and the adjacent umbral magnetic field. The disturbance generates slow-mode waves, which soon develop into shock waves, and manifest themselves as the arcsecond-scale plasma ejections. It also appears that the dissipation of mechanical energy in the shock waves can heat the local corona.

Sub-arcsecond imaging of the water emission in Arp 220⋆ ⋆⋆

PubMed Central

König, S.; Martín, S.; Muller, S.; Cernicharo, J.; Sakamoto, K.; Zschaechner, L. K.; Humphreys, E. M. L.; Mroczkowski, T.; Krips, M.; Galametz, M.; Aalto, S.; Vlemmings, W. H. T.; Ott, J.; Meier, D. S.; Fuente, A.; García-Burillo, S.; Neri, R.

2017-01-01

Aims Extragalactic observations of water emission can provide valuable insights into the excitation of the interstellar medium. In particular they allow us to investigate the excitation mechanisms in obscured nuclei, i.e. whether an active galactic nucleus or a starburst dominate. Methods We use sub-arcsecond resolution observations to tackle the nature of the water emission in Arp 220. ALMA Band 5 science verification observations of the 183 GHz H2O 313−220 line, in conjunction with new ALMA Band 7 H2O 515−422 data at 325 GHz, and supplementary 22 GHz H2O 616 − 523 VLA observations, are used to better constrain the parameter space in the excitation modelling of the water lines. Results We detect 183 GHz H2O and 325 GHz water emission towards the two compact nuclei at the center of Arp 220, being brighter in Arp 220 West. The emission at these two frequencies is compared to previous single-dish data and does not show evidence of variability. The 183 and 325 GHz lines show similar spectra and kinematics, but the 22 GHz profile is significantly different in both nuclei due to a blend with an NH3 absorption line. Conclusions Our findings suggest that the most likely scenario to cause the observed water emission in Arp 220 is a large number of independent masers originating from numerous star-forming regions. PMID:29151605

A high spatial resolution X-ray and Hα study of hot gas in the halos of star-forming disk galaxies -- testing feedback models

NASA Astrophysics Data System (ADS)

Strickland, D. K.; Heckman, T. M.; Colbert, E. J. M.; Hoopes, C. G.; Weaver, K. A.

2002-12-01

We present arcsecond resolution Chandra X-ray and ground-based optical Hα imaging of a sample of ten edge-on star-forming disk galaxies (seven starburst and three ``normal'' spiral galaxies), a sample which covers the full range of star-formation intensity found in disk galaxies. The X-ray observations make use of the unprecented spatial resolution of the Chandra X-ray observatory to robustly remove X-ray emission from point sources, and hence obtain the X-ray properties of the diffuse thermal emission alone. This data has been combined with existing, comparable-resolution, ground-based Hα imaging. We compare these empirically-derived diffuse X-ray properties with various models for the generation of hot gas in the halos of star-forming galaxies: supernova feedback-based models (starburst-driven winds, galactic fountains), cosmologically-motivated accretion of the IGM and AGN-driven winds. SN feedback models best explain the observed diffuse X-ray emission. We then use the data to test basic, but fundamental, aspects of wind and fountain theories, e.g. the critical energy required for disk "break-out." DKS is supported by NASA through Chandra Postdoctoral Fellowship Award Number PF0-10012.

Constraining the Abundances of Complex Organics in the Inner Regions of Solar-Type Protostars

NASA Astrophysics Data System (ADS)

López-Sepulcre, A.; Taquet, V.; Ceccarelli, C.; Neri, R.; Kahane, C.; Charnley, S. B.

2015-12-01

We present arcsecond-resolution observations, obtained with the IRAM Plateau de Bure interferometer, of multiple complex organic molecules in two hot corino protostars: IRAS 2A and IRAS 4A, in the NGC 1333 star-forming region. The distribution of the line emission is very compact, indicating the presence of COMs is mostly concentrated in the inner hot corino regions. A comparison of the COMs abundances with astrochemical models favours a gas-phase formation route for CH3OCH3, and a grain formation of C2H5OH, C2H5CN, and HCOCH2OH. The high abundances of methyl formate (HCOOCH3) remain underpredicted by an order of magnitude.

Discovery of Super-Thin Disks in Nearby Edge-on Spiral Galaxies

NASA Astrophysics Data System (ADS)

Schechtman-Rook, A.; Bershady, M. A.

2014-03-01

We report the identification of a super-thin disk (hz˜ 60 pc) in the edge-on spiral galaxy NGC 891. This component is only apparent after we perform a physically motivated attenuation correction, based on detailed radiation transfer models, to our sub-arcsecond resolution near-infrared imaging. In addition to the super-thin disk, we also find several structural features near the center of NGC 891, including an inner disk truncation at ˜3 kpc. Inner disk truncations may be commonplace among massive spiral galaxies, possibly due to the effects of instabilities, such as bars. Having successfully demonstrated our methods, we are poised to apply them to a small sample of nearby edge-on galaxies, consisting both of massive and low-mass spirals.

Resolving the Shell of the Superbubble 30 Doradus C with Chandra

NASA Astrophysics Data System (ADS)

Lopez, Laura

2017-09-01

We propose to observe the superbubble (SB) 30 Doradus C (30 Dor C) with ACIS-S for 100 ks to resolve and characterize the non-thermal shell, point sources, and the young supernova remnant (SNR) J0536 6913 at sub-arcsecond scales. 30 Dor C has been imaged off axis repeatedly by Chandra due to its proximity to SN 1987A, but the majority of the shell has only been observed <20 ks at off-axis distances of >10 arcminutes. The on-axis spatial resolution, sensitivity, and low background of ACIS-S are necessary to disentangle point sources from diffuse emission, to localize synchrotron filaments associated with accelerated electrons, and to investigate the SNR J0536 6913.

Spatial Angular Compounding Technique for H-Scan Ultrasound Imaging.

PubMed

Khairalseed, Mawia; Xiong, Fangyuan; Kim, Jung-Whan; Mattrey, Robert F; Parker, Kevin J; Hoyt, Kenneth

2018-01-01

H-Scan is a new ultrasound imaging technique that relies on matching a model of pulse-echo formation to the mathematics of a class of Gaussian-weighted Hermite polynomials. This technique may be beneficial in the measurement of relative scatterer sizes and in cancer therapy, particularly for early response to drug treatment. Because current H-scan techniques use focused ultrasound data acquisitions, spatial resolution degrades away from the focal region and inherently affects relative scatterer size estimation. Although the resolution of ultrasound plane wave imaging can be inferior to that of traditional focused ultrasound approaches, the former exhibits a homogeneous spatial resolution throughout the image plane. The purpose of this study was to implement H-scan using plane wave imaging and investigate the impact of spatial angular compounding on H-scan image quality. Parallel convolution filters using two different Gaussian-weighted Hermite polynomials that describe ultrasound scattering events are applied to the radiofrequency data. The H-scan processing is done on each radiofrequency image plane before averaging to get the angular compounded image. The relative strength from each convolution is color-coded to represent relative scatterer size. Given results from a series of phantom materials, H-scan imaging with spatial angular compounding more accurately reflects the true scatterer size caused by reductions in the system point spread function and improved signal-to-noise ratio. Preliminary in vivo H-scan imaging of tumor-bearing animals suggests this modality may be useful for monitoring early response to chemotherapeutic treatment. Overall, H-scan imaging using ultrasound plane waves and spatial angular compounding is a promising approach for visualizing the relative size and distribution of acoustic scattering sources. Copyright © 2018 World Federation for Ultrasound in Medicine and Biology. Published by Elsevier Inc. All rights reserved.

Multi-resolution anisotropy studies of ultrahigh-energy cosmic rays detected at the Pierre Auger Observatory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aab, A.; Abreu, P.; Andringa, S.

2017-06-01

We report a multi-resolution search for anisotropies in the arrival directions of cosmic rays detected at the Pierre Auger Observatory with local zenith angles up to 80{sup o} and energies in excess of 4 EeV (4 × 10{sup 18} eV). This search is conducted by measuring the angular power spectrum and performing a needlet wavelet analysis in two independent energy ranges. Both analyses are complementary since the angular power spectrum achieves a better performance in identifying large-scale patterns while the needlet wavelet analysis, considering the parameters used in this work, presents a higher efficiency in detecting smaller-scale anisotropies, potentially providingmore » directional information on any observed anisotropies. No deviation from isotropy is observed on any angular scale in the energy range between 4 and 8 EeV. Above 8 EeV, an indication for a dipole moment is captured; while no other deviation from isotropy is observed for moments beyond the dipole one. The corresponding p -values obtained after accounting for searches blindly performed at several angular scales, are 1.3 × 10{sup −5} in the case of the angular power spectrum, and 2.5 × 10{sup −3} in the case of the needlet analysis. While these results are consistent with previous reports making use of the same data set, they provide extensions of the previous works through the thorough scans of the angular scales.« less

Multi-resolution anisotropy studies of ultrahigh-energy cosmic rays detected at the Pierre Auger Observatory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aab, A.; Abreu, P.; Aglietta, M.

We report a multi-resolution search for anisotropies in the arrival directions of cosmic rays detected at the Pierre Auger Observatory with local zenith angles up to 80(o) and energies in excess of 4 EeV (4 × 10 18 eV). This search is conducted by measuring the angular power spectrum and performing a needlet wavelet analysis in two independent energy ranges. Both analyses are complementary since the angular power spectrum achieves a better performance in identifying large-scale patterns while the needlet wavelet analysis, considering the parameters used in this work, presents a higher efficiency in detecting smaller-scale anisotropies, potentially providing directional information onmore » any observed anisotropies. No deviation from isotropy is observed on any angular scale in the energy range between 4 and 8 EeV. Above 8 EeV, an indication for a dipole moment is captured, while no other deviation from isotropy is observed for moments beyond the dipole one. The corresponding p-values obtained after accounting for searches blindly performed at several angular scales, are 1.3 × 10 -5 in the case of the angular power spectrum, and 2.5 × 10 -3 in the case of the needlet analysis. While these results are consistent with previous reports making use of the same data set, they provide extensions of the previous works through the thorough scans of the angular scales.« less

Small FDIRC designs

DOE PAGES

Dey, B.; Ratcliff, B.; Va’vra, J.

2017-02-16

In this article, we explore the angular resolution limits attainable in small FDIRC designs taking advantage of the new highly pixelated detectors that are now available. Since the basic FDIRC design concept attains its particle separation performance mostly in the angular domain as measured by two-dimensional pixels, this paper relies primarily on a pixel-based analysis, with additional chromatic corrections using the time domain, requiring single photon timing resolution at a level of 100–200 ps only. This approach differs from other modern DIRC design concepts such as TOP or TORCH detectors, whose separation performances rely more strongly on time-dependent analyses. Inmore » conclusion, we find excellent single photon resolution with a geometry where individual bars are coupled to a single plate, which is coupled in turn to a cylindrical lens focusing camera.« less

Small FDIRC designs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dey, B.; Ratcliff, B.; Va’vra, J.

In this article, we explore the angular resolution limits attainable in small FDIRC designs taking advantage of the new highly pixelated detectors that are now available. Since the basic FDIRC design concept attains its particle separation performance mostly in the angular domain as measured by two-dimensional pixels, this paper relies primarily on a pixel-based analysis, with additional chromatic corrections using the time domain, requiring single photon timing resolution at a level of 100–200 ps only. This approach differs from other modern DIRC design concepts such as TOP or TORCH detectors, whose separation performances rely more strongly on time-dependent analyses. Inmore » conclusion, we find excellent single photon resolution with a geometry where individual bars are coupled to a single plate, which is coupled in turn to a cylindrical lens focusing camera.« less

An angle encoder for super-high resolution and super-high accuracy using SelfA

NASA Astrophysics Data System (ADS)

Watanabe, Tsukasa; Kon, Masahito; Nabeshima, Nobuo; Taniguchi, Kayoko

2014-06-01

Angular measurement technology at high resolution for applications such as in hard disk drive manufacturing machines, precision measurement equipment and aspherical process machines requires a rotary encoder with high accuracy, high resolution and high response speed. However, a rotary encoder has angular deviation factors during operation due to scale error or installation error. It has been assumed to be impossible to achieve accuracy below 0.1″ in angular measurement or control after the installation onto the rotating axis. Self-calibration (Lu and Trumper 2007 CIRP Ann. 56 499; Kim et al 2011 Proc. MacroScale; Probst 2008 Meas. Sci. Technol. 19 015101; Probst et al Meas. Sci. Technol. 9 1059; Tadashi and Makoto 1993 J. Robot. Mechatronics 5 448; Ralf et al 2006 Meas. Sci. Technol. 17 2811) and cross-calibration (Probst et al 1998 Meas. Sci. Technol. 9 1059; Just et al 2009 Precis. Eng. 33 530; Burnashev 2013 Quantum Electron. 43 130) technologies for a rotary encoder have been actively discussed on the basis of the principle of circular closure. This discussion prompted the development of rotary tables which achieve reliable and high accuracy angular verification. We apply these technologies for the development of a rotary encoder not only to meet the requirement of super-high accuracy but also to meet that of super-high resolution. This paper presents the development of an encoder with 221 = 2097 152 resolutions per rotation (360°), that is, corresponding to a 0.62″ signal period, achieved by the combination of a laser rotary encoder supplied by Magnescale Co., Ltd and a self-calibratable encoder (SelfA) supplied by The National Institute of Advanced Industrial Science & Technology (AIST). In addition, this paper introduces the development of a rotary encoder to guarantee ±0.03″ accuracy at any point of the interpolated signal, with respect to the encoder at the minimum resolution of 233, that is, corresponding to a 0.0015″ signal period after interpolation of 212 (= 4096) divisions through the interpolator.

V342 Andromedae B is an eccentric-orbit eclipsing binary

NASA Astrophysics Data System (ADS)

Dimitrov, W.; Kamiński, K.; Lehmann, H.; Ligęza, P.; Fagas, M.; Bagińska, P.; Kwiatkowski, T.; Bąkowska, K.; Kowalczyk, A.; Polińska, M.; Bartczak, P.; Przybyszewska, A.; Kruszewski, A.; Kurzawa, K.; Schwarzenberg-Czerny, A.

2015-03-01

We present a photometric and spectroscopic study of the visual binary V342 Andromedae. Visual components of the system have angular separations of 3 arcseconds. We obtained two spectroscopic data sets. An examination of both the A and B component spectra reveals that the B component is a spectroscopic binary with an eccentric orbit. The orbital period, taken from the Hipparcos Catalog, agrees with the orbital period of the B component measured spectroscopically. We also collected a new set of photometric measurements. The argument of periastron is close to 270° and the orbit eccentricity is not seen in our photometric data. About five years after the first spectroscopic observations, a new set of spectroscopic data was obtained. We analysed the apsidal motion, but we did not find any significant changes in the orbital orientation. A Wilson-Devinney model was calculated based on the photometric and the radial velocity curves. The result shows two very similar stars with masses M1 = 1.27 ± 0.01 M⊙, M2 = 1.28 ± 0.01 M⊙, respectively. The radii are R1 = 1.21 ± 0.01 R⊙, R2 = 1.25 ± 0.01 R⊙, respectively. Radial velocity measurements of component A, the most luminous star in the system, reveal no significant periodic variations. We calculated the time of the eclipsing binary orbit's circularization, which is about two orders of magnitude shorter than the estimated age of the system. The discrepancies in the age estimation can be explained by the Kozai effect induced by the visual component A. The atmospheric parameters and the chemical abundances for the eclipsing pair, as well as the LSD profiles for both visual components, were calculated from two high-resolution, well-exposed spectra obtained on the 2-m class telescope. Based on spectroscopy obtained at the David Dunlap Observatory, University of Toronto, Canada, Poznań Spectroscopic Telescope 1, Poland and Thüringer Landessternwarte, Tautenburg, Germany.

Star formation and gas flows in the centre of the NUGA galaxy NGC 1808 observed with SINFONI

NASA Astrophysics Data System (ADS)

Busch, Gerold; Eckart, Andreas; Valencia-S., Mónica; Fazeli, Nastaran; Scharwächter, Julia; Combes, Françoise; García-Burillo, Santiago

2017-02-01

NGC 1808 is a nearby barred spiral galaxy which hosts young stellar clusters in a patchy circumnuclear ring with a radius of 240 pc. In order to study the gaseous and stellar kinematics and the star formation properties of the clusters, we perform seeing-limited H + K-band near-infrared integral-field spectroscopy with SINFONI of the inner 600 pc. From the MBH-σ∗ relation, we find a black hole mass of a few 107M⊙. We estimate the age of the young stellar clusters in the circumnuclear ring to be ≲10 Myr. No age gradient along the ring is visible. However, the starburst age is comparable to the travel time along the ring, indicating that the clusters almost completed a full orbit along the ring during their lifetime. In the central 600 pc, we find a hot molecular gas mass of 730 M⊙ which, with standard conversion factors, corresponds to a large cold molecular gas reservoir of several 108M⊙, in agreement with CO measurements from the literature. The gaseous and stellar kinematics show several deviations from pure disc motion, including a circumnuclear disc and signs of a nuclear bar potential. In addition, we confirm streaming motions on the 200 pc scale that have recently been detected in CO(1-0) emission. Thanks to the enhanced angular resolution of <1″, we find further streaming motion within the inner arcsecond that had not been detected until now. Despite the flow of gas towards the centre, no signs of significant AGN activity are found. This raises the question: will the infalling gas fuel an AGN or star formation? Based on observations with ESO-VLT, STS-Cologne GTO proposal ID 094.B-0009(A) and ESO archival data, proposal nos 074.A-9011(A) and 075.B-0648(A).

The Early Development of Indian Radio Astronomy: A Personal Perspective

NASA Astrophysics Data System (ADS)

Swarup, Govind

In this chapter I recall my initiation into the field of radio astronomy during 1953-1955 at CSIRO, Australia; the transfer of thirty-two 6-feet (1.8-m) diameter parabolic dishes from Potts Hill, Sydney, to India in 1958; and their erection at Kalyan, near Bombay (Mumbai), in 1963-1965. The Kalyan Radio Telescope was the first modern radio telescope built in India. This led to the establishment of a very active radio astronomy group at the Tata Institute of Fundamental Research, which subsequently built two world-class radio telescopes during the last 50 years and also contributed to the development of an indigenous microwave antenna industry in India. The Ooty Radio Telescope, built during 1965-1970, has an ingenious design which takes advantage of India's location near the Earth's Equator. The long axis of this 530-m × 30-m parabolic cylinder was made parallel to the Equator, by placing it on a hill with the same slope as the geographic latitude ( 11°), thus allowing it to track celestial sources continuously for 9.5 h every day. By utilizing lunar occultations, the telescope was able to measure the angular sizes of a large number of faint radio galaxies and quasars with arc-second resolution for the first time. Subsequently, during the 1990s, the group set up the Giant Metrewave Radio Telescope (GMRT) near Pune in western India, in order to investigate certain astrophysical phenomena which are best studied at decimetre and metre wavelengths. The GMRT is an array of 30 fully steerable 45-m diameter parabolic dishes, which operates at several frequencies below 1.43 GHz. These efforts have also contributed to the international proposal to construct the Square Kilometre Array (SKA). This chapter is a revised version of Swarup (Journal of Astronomical History and Heritage, 9: 21-33, 2006).

Time-resolved orbital angular momentum spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Noyan, Mehmet A.; Kikkawa, James M.

We introduce pump-probe magneto-orbital spectroscopy, wherein Laguerre-Gauss optical pump pulses impart orbital angular momentum to the electronic states of a material and subsequent dynamics are studied with 100 fs time resolution. The excitation uses vortex modes that distribute angular momentum over a macroscopic area determined by the spot size, and the optical probe studies the chiral imbalance of vortex modes reflected off the sample. First observations in bulk GaAs yield transients that evolve on time scales distinctly different from population and spin relaxation, as expected, but with surprisingly large lifetimes.

Shadow image on the retina of a defocused eye

NASA Astrophysics Data System (ADS)

Lenskii, A. V.

1994-04-01

Some visual conditions for transparent objects positioned within and beyond the accommodation limits on the path of the light traveling from a remote source of a small angular size are theoretically considered for the naked eye with a strong ametropia. The resolving power and admissible angular size of the light source are evaluated. The predicted possibility of seeing sufficiently extended transparent gratings at such distances has found that the density of ruling of the grating-object is higher than the ultimate angular resolution of the normal eye.

Improving angular resolution with Scan-MUSIC algorithm for real complex targets using 35-GHz millimeter-wave radar

NASA Astrophysics Data System (ADS)

Ly, Canh

2004-08-01

Scan-MUSIC algorithm, developed by the U.S. Army Research Laboratory (ARL), improves angular resolution for target detection with the use of a single rotatable radar scanning the angular region of interest. This algorithm has been adapted and extended from the MUSIC algorithm that has been used for a linear sensor array. Previously, it was shown that the SMUSIC algorithm and a Millimeter Wave radar can be used to resolve two closely spaced point targets that exhibited constructive interference, but not for the targets that exhibited destructive interference. Therefore, there were some limitations of the algorithm for the point targets. In this paper, the SMUSIC algorithm is applied to a problem of resolving real complex scatterer-type targets, which is more useful and of greater practical interest, particular for the future Army radar system. The paper presents results of the angular resolution of the targets, an M60 tank and an M113 Armored Personnel Carrier (APC), that are within the mainlobe of a Κα-band radar antenna. In particular, we applied the algorithm to resolve centroids of the targets that were placed within the beamwidth of the antenna. The collected coherent data using the stepped-frequency radar were compute magnitudely for the SMUSIC calculation. Even though there were significantly different signal returns for different orientations and offsets of the two targets, we resolved those two target centroids when they were as close as about 1/3 of the antenna beamwidth.

Science requirements and optimization of the silicon pore optics design for the Athena mirror

NASA Astrophysics Data System (ADS)

Willingale, R.; Pareschi, G.; Christensen, F.; den Herder, J.-W.; Ferreira, D.; Jakobsen, A.; Ackermann, M.; Collon, M.; Bavdaz, M.

2014-07-01

The science requirements for the Athena X-ray mirror are to provide a collecting area of 2 m2 at 1 keV, an angular resolution of ~5 arc seconds half energy eidth (HEW) and a field of view of diameter 40-50 arc minutes. This combination of area and angular resolution over a wide field are possible because of unique features of the Silicon pore optics (SPO) technology used. Here we describe the optimization and modifications of the SPO technology required to achieve the Athena mirror specification and demonstrate how the optical design of the mirror system impacts on the scientific performance of Athena.

REVIEWS OF TOPICAL PROBLEMS: Global phase-stable radiointerferometric systems

NASA Astrophysics Data System (ADS)

Dravskikh, A. F.; Korol'kov, Dimitrii V.; Pariĭskiĭ, Yu N.; Stotskiĭ, A. A.; Finkel'steĭn, A. M.; Fridman, P. A.

1981-12-01

We discuss from a unitary standpoint the possibility of building a phase-stable interferometric system with very long baselines that operate around the clock with real-time data processing. The various problems involved in the realization of this idea are discussed: the methods of suppression of instrumental and tropospheric phase fluctuations, the methods for constructing two-dimensional images and determining the coordinates of radio sources with high angular resolution, and the problem of the optimal structure of the interferometric system. We review in detail the scientific problems from the various branches of natural science (astrophysics, cosmology, geophysics, geodynamics, astrometry, etc.) whose solution requires superhigh angular resolution.

The usability of the optical parametric amplification of light for high-angular-resolution imaging and fast astrometry

NASA Astrophysics Data System (ADS)

Kurek, A. R.; Stachowski, A.; Banaszek, K.; Pollo, A.

2018-05-01

High-angular-resolution imaging is crucial for many applications in modern astronomy and astrophysics. The fundamental diffraction limit constrains the resolving power of both ground-based and spaceborne telescopes. The recent idea of a quantum telescope based on the optical parametric amplification (OPA) of light aims to bypass this limit for the imaging of extended sources by an order of magnitude or more. We present an updated scheme of an OPA-based device and a more accurate model of the signal amplification by such a device. The semiclassical model that we present predicts that the noise in such a system will form so-called light speckles as a result of light interference in the optical path. Based on this model, we analysed the efficiency of OPA in increasing the angular resolution of the imaging of extended targets and the precise localization of a distant point source. According to our new model, OPA offers a gain in resolved imaging in comparison to classical optics. For a given time-span, we found that OPA can be more efficient in localizing a single distant point source than classical telescopes.

X-ray Interferometry with Transmissive Beam Combiners for Ultra-High Angular Resolution Astronomy

NASA Technical Reports Server (NTRS)

Skinner, G. K.; Krismanic, John F.

2009-01-01

Abstract Interferometry provides one of the possible routes to ultra-high angular resolution for X-ray and gamma-ray astronomy. Sub-micro-arc-second angular resolution, necessary to achieve objectives such as imaging the regions around the event horizon of a super-massive black hole at the center of an active galaxy, can be achieved if beams from parts of the incoming wavefront separated by 100s of meters can be stably and accurately brought together at small angles. One way of achieving this is by using grazing incidence mirrors. We here investigate an alternative approach in which the beams are recombined by optical elements working in transmission. It is shown that the use of diffractive elements is a particularly attractive option. We report experimental results from a simple 2-beam interferometer using a low-cost commercially available profiled film as the diffractive elements. A rotationally symmetric filled (or mostly filled) aperture variant of such an interferometer, equivalent to an X-ray axicon, is shown to offer a much wider bandpass than either a Phase Fresnel Lens (PFL) or a PFL with a refractive lens in an achromatic pair. Simulations of an example system are presented.

VECC array for Nuclear fast Timing and angUlar corRElation studies (VENTURE)

NASA Astrophysics Data System (ADS)

Alam, S. S.; Bhattacharjee, T.; Banerjee, D.; Saha, A.; Pandit, Deepak; Mondal, D.; Mukhopadhyay, S.; Pal, Surajit; Bhaskar, P.; Das, S. K.; Banerjee, S. R.

2017-12-01

The VECC array for Nuclear fast Timing and angUlar corRElation studies (VENTURE) has been developed using several fast Cerium-Bromide (CeBr3) scintillators coupled to Hamamatsu R9779 Photomultiplier tubes. The CeBr3 detector has been characterised for the spectroscopic properties like energy response, energy resolution, timing resolution and detection efficiency. The response and efficiency of the detector have been compared with the results obtained from a Monte Carlo simulation with GEANT3 package. A time resolution of 144(1) ps and 109(1) ps was obtained for a single detector using 622-512 keV and 1173-1332 keV cascades respectively. The Generalised Centroid Difference (GCD) method has been employed with CeBr3 detectors by measuring the level lifetimes for the 511.9 keV level of 106Pd and the 160.6 and 383.8 keV levels of 133Cs. The angular correlation measurement was performed for the 1173-1332 keV cascade in 60Ni and the 228-49 keV cascade of 132I nucleus, populated from the decay of 132Te produced via 238U(α, f) reaction.

Light propagation in the Solar System for astrometry on sub-micro-arcsecond level

NASA Astrophysics Data System (ADS)

Zschocke, Sven

2018-04-01

We report on recent advancement in the theory of light propagation in the Solar System aiming at sub-micro-arcsecond level of accuracy: (1) A solution for the light ray in 1.5PN approximation has been obtained in the field of N arbitrarily moving bodies of arbitrary shape, inner structure, oscillations, and rotational motion. (2) A solution for the light ray in 2PN approximation has been obtained in the field of one arbitrarily moving pointlike body.

Motivation and Prospects for Spatio-spectral Interferometry in the Far-infrared

NASA Technical Reports Server (NTRS)

Leisawitz, David

2013-01-01

Consensus developed through a series of workshops, starting in 1998. Compelling science case for high angular resolution imaging and spectroscopy, and mission concepts. A robust plan - it has evolved over the years, but has consistently called for high resolution.

Location of γ-ray emission and magnetic field strengths in OJ 287

NASA Astrophysics Data System (ADS)

Hodgson, J. A.; Krichbaum, T. P.; Marscher, A. P.; Jorstad, S. G.; Rani, B.; Marti-Vidal, I.; Bach, U.; Sanchez, S.; Bremer, M.; Lindqvist, M.; Uunila, M.; Kallunki, J.; Vicente, P.; Fuhrmann, L.; Angelakis, E.; Karamanavis, V.; Myserlis, I.; Nestoras, I.; Chidiac, C.; Sievers, A.; Gurwell, M.; Zensus, J. A.

2017-01-01

Context. The γ-ray BL Lac object OJ 287 is known to exhibit inner-parsec "jet-wobbling", high degrees of variability at all wavelengths and quasi-stationary features, including an apparent (≈100°) position-angle change in projection on the sky plane. Aims: Sub-50 micro-arcsecond resolution 86 GHz observations with the global mm-VLBI array (GMVA) supplement ongoing multi-frequency VLBI blazar monitoring at lower frequencies. Using these maps, together with cm/mm total intensity and γ-ray observations from Fermi-LAT from 2008-2014, we aim to determine the location of γ-ray emission and to explain the inner-mas structural changes. Methods: Observations with the GMVA offer approximately double the angular resolution compared with 43 GHz VLBA observations and enable us to observe above the synchrotron self-absorption peak frequency. Fermi-LAT γ-ray data were reduced and analysed. The jet was spectrally decomposed at multiple locations along the jet. From this, we could derive estimates of the magnetic field using equipartition and synchrotron self-absorption arguments. How the field decreases down the jet provided an estimate of the distance to the jet apex and an estimate of the magnetic field strength at the jet apex and in the broad line region. Combined with accurate kinematics, we attempt to locate the site of γ-ray activity, radio flares, and spectral changes. Results: Strong γ-ray flares appeared to originate from either the so-called core region, a downstream stationary feature, or both, with γ-ray activity significantly correlated with radio flaring in the downstream quasi-stationary feature. Magnetic field estimates were determined at multiple locations along the jet, with the magnetic field found to be ≥1.6 G in the core and ≤0.4 G in the downstream quasi-stationary feature. We therefore found upper limits on the location of the VLBI core as ≲6.0 pc from the jet apex and determined an upper limit on the magnetic field near the jet base of the order of thousands of Gauss. The 3 mm GMVA data are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/597/A80

The large area high resolution gamma ray astrophysics facility - HR-GRAF

NASA Astrophysics Data System (ADS)

Fenyves, E. J.; Chaney, R. C.; Hoffman, J. H.; Cline, D. B.; Atac, M.; Park, J.; White, S. R.; Zych, A. D.; Tumer, Q. T.; Hughes, E. B.

1990-03-01

The long-term program is described in terms of its equipment, scientific objectives, and long-range scientific studies. A prototype of a space-based large-area high-resolution gamma-ray facility (HR-GRAF) is being developed to examine pointlike and diffuse gamma-ray sources in the range 1 MeV-100 GeV. The instrument for the facility is proposed to have high angular and energy resolution and very high sensitivity to permit the study of the proposed objects. The primary research targets include the mapping of galactic gamma radiation, observing the angular variations of diffuse gamma rays, and studying the Galactic center with particular emphasis on the hypothetical black hole. Also included in the research plans are obtaining data on gamma-ray bursters, investigating the transmission of gamma rays from cold dark matter, and studying nuclear gamma-ray lines.

Localization accuracy of compact binary coalescences detected by the third-generation gravitational-wave detectors and implication for cosmology

NASA Astrophysics Data System (ADS)

Zhao, Wen; Wen, Linqing

2018-03-01

We use the Fisher information matrix to investigate the angular resolution and luminosity distance uncertainty for coalescing binary neutron stars (BNSs) and neutron star-black hole binaries (NSBHs) detected by the third-generation (3G) gravitational-wave (GW) detectors. Our study focuses on an individual 3G detector and a network of up to four 3G detectors at different locations including the United States, Europe, China, and Australia for the proposed Einstein Telescope (ET) and Cosmic Explorer (CE) detectors. In particular, we examine the effect of the Earth's rotation, as GW signals from BNS and low-mass NSBH systems could be hours long for 3G detectors. In this case, an individual detector can be effectively treated as a detector network with long baselines formed by the trajectory of the detector as it rotates with the Earth. Therefore, a single detector or two-detector networks could also be used to localize the GW sources effectively. We find that a time-dependent antenna beam-pattern function can help better localize BNS and NSBH sources, especially edge-on ones. The medium angular resolution for one ET-D detector is around 150 deg2 for BNSs at a redshift of z =0.1 , which improves rapidly with a decreasing low-frequency cutoff flow in sensitivity. The medium angular resolution for a network of two CE detectors in the United States and Europe, respectively, is around 20 deg2 at z =0.2 for the simulated BNS and NSBH samples. While for a network of two ET-D detectors, the similar angular resolution can be achieved at a much higher redshift of z =0.5 . The angular resolution of a network of three detectors is mainly determined by the baselines between detectors regardless of the CE or ET detector type. The medium angular resolution of BNS for a network of three detectors of the ET-D or CE type in the United States, Europe, and Australia is around 10 deg2 at z =2 . We discuss the implications of our results for multimessenger astronomy and, in particular, for using GW sources as independent tools to constrain the Hubble constant H0, the deceleration parameter q0, and the equation-of-state (EoS) of dark energy. We find that, in general, if 10 BNSs or NSBHs at z =0.1 with known redshifts are detected by 3G networks consisting of two ET-like detectors, H0 can be measured with an accuracy of 0.9%. If 1000 face-on BNSs at z <2 are detected with known redshifts, we are able to achieve Δ q0=0.002 for the deceleration parameter, or Δ w0=0.03 and Δ wa=0.2 for EoS of dark energy, respectively.

The impact of clustering and angular resolution on far-infrared and millimeter continuum observations

NASA Astrophysics Data System (ADS)

Béthermin, Matthieu; Wu, Hao-Yi; Lagache, Guilaine; Davidzon, Iary; Ponthieu, Nicolas; Cousin, Morgane; Wang, Lingyu; Doré, Olivier; Daddi, Emanuele; Lapi, Andrea

2017-11-01

Follow-up observations at high-angular resolution of bright submillimeter galaxies selected from deep extragalactic surveys have shown that the single-dish sources are comprised of a blend of several galaxies. Consequently, number counts derived from low- and high-angular-resolution observations are in tension. This demonstrates the importance of resolution effects at these wavelengths and the need for realistic simulations to explore them. We built a new 2 deg2 simulation of the extragalactic sky from the far-infrared to the submillimeter. It is based on an updated version of the 2SFM (two star-formation modes) galaxy evolution model. Using global galaxy properties generated by this model, we used an abundance-matching technique to populate a dark-matter lightcone and thus simulate the clustering. We produced maps from this simulation and extracted the sources, and we show that the limited angular resolution of single-dish instruments has a strong impact on (sub)millimeter continuum observations. Taking into account these resolution effects, we are reproducing a large set of observables, as number counts and their evolution with redshift and cosmic infrared background power spectra. Our simulation consistently describes the number counts from single-dish telescopes and interferometers. In particular, at 350 and 500 μm, we find that the number counts measured by Herschel between 5 and 50 mJy are biased towards high values by a factor 2, and that the redshift distributions are biased towards low redshifts. We also show that the clustering has an important impact on the Herschel pixel histogram used to derive number counts from P(D) analysis. We find that the brightest galaxy in the beam of a 500 μm Herschel source contributes on average to only 60% of the Herschel flux density, but that this number will rise to 95% for future millimeter surveys on 30 m-class telescopes (e.g., NIKA2 at IRAM). Finally, we show that the large number density of red Herschel sources found in observations but not in models might be an observational artifact caused by the combination of noise, resolution effects, and the steepness of color- and flux density distributions. Our simulation, called Simulated Infrared Dusty Extragalactic Sky (SIDES), is publicly available. Our simulation Simulated Infrared Dusty Extragalactic Sky (SIDES) is available at http://cesam.lam.fr/sides.

Investigation of the Chromosphere-Corona Interface with the Upgraded Very High Angular Resolution Ultraviolet Telescope (VAULT2.0)

NASA Astrophysics Data System (ADS)

Vourlidas, Angelos; Beltran, Samuel Tun; Chintzoglou, Georgios; Eisenhower, Kevin; Korendyke, Clarence; Feldman, Ronen; Moser, John; Shea, John; Johnson-Rambert, Mary; McMullin, Don; Stenborg, Guillermo; Shepler, Ed; Roberts, David

2016-03-01

Very high angular resolution ultraviolet telescope (VAULT2.0) is a Lyman-alpha (Lyα; 1216Å) spectroheliograph designed to observe the upper chromospheric region of the solar atmosphere with high spatial (<0.5‧‧) and temporal (8s) resolution. Besides being the brightest line in the solar spectrum, Lyα emission arises at the temperature interface between coronal and chromospheric plasmas and may, hence, hold important clues about the transfer of mass and energy to the solar corona. VAULT2.0 is an upgrade of the previously flown VAULT rocket and was launched successfully on September 30, 2014 from White Sands Missile Range (WSMR). The target was AR12172 midway toward the southwestern limb. We obtained 33 images at 8s cadence at arc second resolution due to hardware problems. The science campaign was a resounding success, with all space and ground-based instruments obtaining high-resolution data at the same location within the AR. We discuss the science rationale, instrument upgrades, and performance during the first flight and present some preliminary science results.

Identifying the Location in the Host Galaxy of Short GRB 1111l7A with the Chandra Sub- Arcsecond Position

NASA Technical Reports Server (NTRS)

Sakamoto, Takanori; Troja, E.; Aoki, K.; Guiriec, S.; Im, M.; Leloudas, G.; Malesani, D.; Melandri, A.; deUgartePostigo, A.; Urata, Y.;

Fine pointing of the Solar Optical Telescope in the Space Shuttle environment

NASA Astrophysics Data System (ADS)

Gowrinathan, S.

Instruments requiring fine (i.e., sub-arcsecond) pointing, such as the Solar Optical Telescope (SOT), must be equipped with two-stage pointing devices, coarse and fine. Coarse pointing will be performed by a gimbal system, such as the Instrument Pointing System, while the image motion compensation (IMC) will provide fine pointing. This paper describes work performed on the SOT concept design that illustrates IMC as applied to SOT. The SOT control system was modeled in the frequency domain to evaluate performance, stability, and bandwidth requirements. The two requirements of the pointing control, i.e., the 2 arcsecond reproducibility and 0.03 arcsecond rms pointing jitter, can be satisfied by use of IMC at about 20 Hz bandwidth. The need for this high bandwidth is related to Shuttle-induced disturbances that arise primarily from man push-offs and vernier thruster firings. A block diagram of SOT model/stability analysis, schematic illustrations of the SOT pointing system, and a structural model summary are included.

High-resolution imaging gamma-ray spectroscopy with externally segmented germanium detectors

NASA Technical Reports Server (NTRS)

Callas, J. L.; Mahoney, W. A.; Varnell, L. S.; Wheaton, W. A.

1993-01-01

Externally segmented germanium detectors promise a breakthrough in gamma-ray imaging capabilities while retaining the superb energy resolution of germanium spectrometers. An angular resolution of 0.2 deg becomes practical by combining position-sensitive germanium detectors having a segment thickness of a few millimeters with a one-dimensional coded aperture located about a meter from the detectors. Correspondingly higher angular resolutions are possible with larger separations between the detectors and the coded aperture. Two-dimensional images can be obtained by rotating the instrument. Although the basic concept is similar to optical or X-ray coded-aperture imaging techniques, several complicating effects arise because of the penetrating nature of gamma rays. The complications include partial transmission through the coded aperture elements, Compton scattering in the germanium detectors, and high background count rates. Extensive electron-photon Monte Carlo modeling of a realistic detector/coded-aperture/collimator system has been performed. Results show that these complicating effects can be characterized and accounted for with no significant loss in instrument sensitivity.

Compressive light field imaging

NASA Astrophysics Data System (ADS)

Ashok, Amit; Neifeld, Mark A.

2010-04-01

Light field imagers such as the plenoptic and the integral imagers inherently measure projections of the four dimensional (4D) light field scalar function onto a two dimensional sensor and therefore, suffer from a spatial vs. angular resolution trade-off. Programmable light field imagers, proposed recently, overcome this spatioangular resolution trade-off and allow high-resolution capture of the (4D) light field function with multiple measurements at the cost of a longer exposure time. However, these light field imagers do not exploit the spatio-angular correlations inherent in the light fields of natural scenes and thus result in photon-inefficient measurements. Here, we describe two architectures for compressive light field imaging that require relatively few photon-efficient measurements to obtain a high-resolution estimate of the light field while reducing the overall exposure time. Our simulation study shows that, compressive light field imagers using the principal component (PC) measurement basis require four times fewer measurements and three times shorter exposure time compared to a conventional light field imager in order to achieve an equivalent light field reconstruction quality.

High-resolution bottom-loss estimation using the ambient-noise vertical coherence function.

PubMed

Muzi, Lanfranco; Siderius, Martin; Quijano, Jorge E; Dosso, Stan E

2015-01-01

The seabed reflection loss (shortly "bottom loss") is an important quantity for predicting transmission loss in the ocean. A recent passive technique for estimating the bottom loss as a function of frequency and grazing angle exploits marine ambient noise (originating at the surface from breaking waves, wind, and rain) as an acoustic source. Conventional beamforming of the noise field at a vertical line array of hydrophones is a fundamental step in this technique, and the beamformer resolution in grazing angle affects the quality of the estimated bottom loss. Implementation of this technique with short arrays can be hindered by their inherently poor angular resolution. This paper presents a derivation of the bottom reflection coefficient from the ambient-noise spatial coherence function, and a technique based on this derivation for obtaining higher angular resolution bottom-loss estimates. The technique, which exploits the (approximate) spatial stationarity of the ambient-noise spatial coherence function, is demonstrated on both simulated and experimental data.

The Large Deployable Reflector (LDR) report of the Science Coordination Group

NASA Technical Reports Server (NTRS)

1986-01-01

The Large Deployable Reflector (LDR) is a telescope designed to carry out high-angular resolution, high-sensitivity observations at far-infrared and submillimeter wavelengths. The scientific rationale for the LDR is discussed in light of the recent Infrared Astronomical Satellite (IRAS) and Kuiper Airborne Observatory (KAO) results and the several new ground-based observatories planned for the late 1980s. The importance of high sensitivity and high angular resolution observations from space in the submillimeter region is stressed. The scientific and technical problems of using the LDR in a light bucket mode at approx. less than 5 microns and in designing the LDR as an unfilled aperture with subarcsecond resolution are also discussed. The need for an aperture as large as 20 m is established, along with the requirements of beam-shape stability, spatial chopping, thermal control, and surface figure stability. The instrument complement required to cover the wavelength-spectral resolution region of interest to the LDR is defined.

Aligning, Bonding, and Testing Mirrors for Lightweight X-ray Telescopes

NASA Technical Reports Server (NTRS)

Chan, Kai-Wing; Zhang, William W.; Saha, Timo T.; McClelland, Ryan S.; Biskach, Michael P.; Niemeyer, Jason; Schofield, Mark J.; Mazzarella, James R.; Kolos, Linette D.; Hong, Melinda M.;

Keck Observations of the Gas Dynamics at the Galactic Center

NASA Astrophysics Data System (ADS)

Campbell, Randall; Ciurlo, Anna; Morris, Mark; Sitarski, Breann N.; Ghez, Andrea M.; Do, Tuan

2018-06-01

In the central parsec of the Milky Way Galaxy the environment of the super-massive black hole (SMBH) presents a complicated mixture of stars, gas, and dust. These inner few tens of arcseconds of the GC have been observed at high resolution with Keck for 20 years with the primary goal of monitoring stars orbiting the SMBH. However, the gas features and their dynamics can also be closely examined using this unique baseline of data. In particular, observations with the Keck OSIRIS integral field spectrometer allow us to examine of the dynamical properties of the gas and to possibly identify new “G-type” objects, or dusty stellar objects. We present a study of morphology and orbital dynamics of sub-parsec scale gas features in the central region.

The VLA Sky Survey

NASA Astrophysics Data System (ADS)

Lacy, Mark; VLASS Survey Team, VLASS Survey Science Group

2018-01-01

The VLA Sky Survey (VLASS), which began in September 2017, is a seven year project to image the entire sky north of Declination -40 degrees in three epochs. The survey is being carried out in I,Q and U polarization at a frequency of 2-4GHz, and a resolution of 2.5 arcseconds, with each epoch being separated by 32 months. Raw data from the survey, along with basic "quicklook" images are made freely available shortly after observation. Within a few months, NRAO will begin making available further basic data products, including refined images and source lists. In this talk I shall describe the science goals and methodology of the survey, the current survey status, and some early results, along with plans for collaborations with external groups to produce enhanced, high level data products.

Forming Disc Galaxies In Major Mergers: Radial Density Profiles And Angular Momentum

NASA Astrophysics Data System (ADS)

Peschken, Nicolas; Athanassoula, E.; Rodionov, S. A.; Lambert, J. C.

2017-06-01

In Athanassoula et al. (2016), we used high resolution N-body hydrodynamical simulations to model the major merger between two disc galaxies with a hot gaseous halo each, and showed that the remnant is a spiral galaxy. The two discs are destroyed by the collision, but after the merger, accretion from the surrounding gaseous halo allows the building of a new disc in the remnant galaxy. In Peschken et al. (2017), we used these simulations to study the radial surface density profiles of the remnant galaxies with downbending profiles (type II), i.e. composed of an inner and an outer exponential disc separated by a break. We analyzed the effect of angular momentum on these profiles, and found that the inner and outer disc scalelengths, as well as the break radius, all increase linearly with the total angular momentum of the initial merging system. Following the angular momentum redistribution in our simulations, we find that the disc angular momentum is acquired via accretion from the gaseous halo. Furthermore, high angular momentum systems give more angular momentum to their discs, which affects directly their radial density profile.

Unraveling the Origin of Short Gamma-ray Bursts

NASA Technical Reports Server (NTRS)

Barthelmy, S. D.; Chincarini, G.; Burrows, D. N.; Gehrels, N.; Covino, S.; Moretti, A.; Romano, P.; OBrien, P. T.; Sarazin, C. L.; Kouveliotou, C.

2005-01-01

The origin of the short (<2 s) class of gamma-ray bursts (GRBs) is finally becoming clear after decades of search. The first one localized to a few arcseconds accuracy, GRB 050509B, was found to have a highly probable association with a nearby (z = 0.225) elliptical galaxy. A second one with arcsecond localization, GRB 050709, was also associated with a low redshift (z = 0.16) galaxy. We report here the detection of short GRB 050724 with remarkable properties; in particular, it has low energy gamma-ray emission that lasts for 100 s after the main short pulse, strong early X-ray afterglow, and an unusual lightcurve that rebrightens at 3x10(exp 4) s. A position on the sky accurate to 9 arcsec was determined and provided as a GCN alert to ground-based telescopes within 80 s. A subsequent high-resolution X-ray image provided a sub-arcsec position coincident with ground-based optical and radio observations of the afterglow. Like GRB 050509B, this burst is located off-center in an elliptical galaxy. The energy output of the GRB at the host distance of z = 0.258 is 2-3 orders of magnitude less than for long bursts. The low level of star formation in such galaxies is strong evidence against a collapsar or hypernova origin like that associated with long GRBs. Based on these new data, it is highly probable that short GRBs are produced by the coalescence of orbiting neutron stars (NSs) or black holes (BHs), with some evidence for a NS-BH merger in this burst.

Observations of photospheric magnetic fields and shear flows in flaring active regions

NASA Astrophysics Data System (ADS)

Tarbell, T.; Ferguson, S.; Frank, Z.; Title, A.; Topka, K.

1988-11-01

Horizontal flows in the photosphere and subsurface convection zone move the footpoints of coronal magnetic field lines. Magnetic energy to power flares can be stored in the corona if the flows drive the fields far from the potential configuration. Videodisk movies were shown with 0.5 to 1 arcsecond resolution of the following simultaneous observations: green continuum, longitudinal magnetogram, Fe I 5576 A line center (mid-photosphere), H alpha wings, and H alpha line center. The movies show a 90 x 90 arcsecond field of view of an active region at S29, W11. When viewed at speeds of a few thousand times real-time, the photospheric movies clearly show the active region fields being distorted by a remarkable combination of systematic flows and small eruptions of new flux. Magnetic bipoles are emerging over a large area, and the polarities are systematically flowing apart. The horizontal flows were mapped in detail from the continuum movies, and these may be used to predict the future evolution of the region. The horizontal flows are not discernable in H alpha. The H alpha movies strongly suggest reconnection processes in the fibrils joining opposite polarities. When viewed in combination with the magnetic movies, the cause for this evolution is apparent: opposite polarity fields collide and partially cancel, and the fibrils reconnect above the surface. This type of reconnection, driven by subphotospheric flows, complicates the chromospheric and coronal fields, causing visible braiding and twisting of the fibrils. Some of the transient emission events in the fibrils and adjacent plage may also be related.

Tectonic geomorphology of the New Madrid seismic zone based on imaging of digital topographic data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mayer, L.

1993-03-01

Topographic analysis using digital elevation data of the New Madrid region focuses on topographic features that occur at several spatial scales and can be used to delineate distinct anomalies. In this region, topographic anomalies occur as domal or elongate uplifts and bowl-shaped depressions approximately 1--10 km in size, topographic lineaments, and differences in topographic blocking across 50 km long boundaries. In order to fully explain these topographic anomalies, tectonic processes may be required. Imaging is based on digital topographic data from USGS 30 arc-second, 3 arc-second, and 30 m resolutions. Imaging of these data uses standard imaging processing techniques tomore » examine topography within the contexts of geomorphological hypothesis testing. A good example is the use of thresholding to highlight areas of unusually high elevation given the hypothesis of fluvial landscape architecture. Thresholding delineates topographic features such as the Tiptonville dome which is strongly believed to be tectonic in origin. To determine the pattern of topographic blocking, defined as a pattern that topography assumes when constrained by active forces other than erosion alone, low frequency passing spatial convolutions are used as filters and the resulting data are sliced into blocks according to pseudoelevations that produce a stable block pattern. The resultant blocks are analyzed according to its structural pattern of block size and block orientation. This analysis suggests that a topographic boundary cuts across the Mississippi embayment from near the Newport pluton on the west, to the area south of Memphis on east.« less

The focusing optics x-ray solar imager (FOXSI): instrument and first flight

NASA Astrophysics Data System (ADS)

Krucker, Säm.; Christe, Steven; Glesener, Lindsay; Ishikawa, Shinnosuke; Ramsey, Brian; Gubarev, Mikhail; Saito, Shinya; Takahashi, Tadayuki; Watanabe, Shin; Tajima, Hiroyasu; Tanaka, Takaaki; Turin, Paul; Glaser, David; Fermin, Jose; Lin, Robert P.

2013-09-01

Solar flares accelerate particles up to high energies (MeV and GeV scales for electrons and ions, respectively) through efficient acceleration processes that are not currently understood. Hard X-rays (HXRs) are the most direct diagnostic of flare-accelerated electrons. However, past and current solar HXR observers lack the necessary sensitivity and imaging dynamic range to make detailed studies of faint HXR sources in the solar corona (where particle acceleration is thought to occur); these limitations are mainly due to the indirect Fourier imaging techniques used by these observers. With greater sensitivity and dynamic range, electron acceleration sites could be systematically studied in detail. Both these capabilities can be advanced by the use of direct focusing optics. The recently own Focusing Optics X-ray Solar Imager (FOXSI) sounding rocket payload demonstrates the unique diagnostic power of focusing optics for observations of solar HXRs. FOXSI features grazing-incidence replicated nickel optics with 5 arcsecond resolution and fine-pitch silicon strip detectors with a 7.7 arcsecond strip pitch. FOXSI flew successfully on 2012 November 2, producing images and spectra of a microflare and performing a search for non-thermal emission (4{15 keV) from nanoflares occurring outside active regions in the quiet Sun. A future spacecraft version of FOXSI, featuring similar optics and detectors, could make detailed observations of HXRs from flare-accelerated electrons, identifying and characterizing particle acceleration sites and mapping out paths of energetic electrons as they leave these sites and propagate throughout the solar corona. This paper will describe the FOXSI instrument and present images from the first flight.

CANYVAL-X: Enabling a new class of scientific instruments

NASA Astrophysics Data System (ADS)

Shah, Neerav; Calhoun, Philip C.; Park, Sang-young; Keidar, Michael

2016-05-01

Significant new discoveries in space science can be realized by replacing the traditional large monolithic space telescopes with precision formation flying spacecraft to form a “virtual telescope.” Such virtual telescopes will revolutionize occulting imaging systems, provide images of the Sun, accretion disks, and other astronomical objects with unprecedented milli-arcsecond resolution (several orders of magnitude beyond current capability).Since the days of Apollo, NASA and other organizations have been conducting formation flying in space, but not with the precision required for virtual telescopes. These efforts have focused on rendezvous and docking (e.g., crew docking, satellite servicing, etc.) and/or ground-controlled coordinated flight (e.g., EO-1, GRAIL, MMS, etc.). While the TRL of the component level technology for formation flying is high, the capability for the system-level guidance, navigation, and control (GN&C) technology required to align a virtual telescope to an inertial astronomical target with sub-arcsecond precision is not fully developed.The CANYVAL-X (CubeSat Astronomy by NASA and Yonsei using Virtual Telescope Alignment eXperiment) mission is an engineering proof of concept featuring a pair of CubeSats flying as a tandem telescope with a goal of demonstrating the system-level GN&C needed to form a virtual telescope. NASA partnered with the George Washington University and the Yonsei University to design and develop CANYVAL-X. CANYVAL-X will demonstrate key technologies for using virtual telescopes in space, including micro-propulsion using millinewton thrusters, relative position sensing, and communications control between the two spacecraft. CANYVAL-X is scheduled to launch on a Flacon-9 in summer of 2016.

The Atacama Cosmology Telescope: The Polarization-Sensitive ACTPol Instrument

NASA Technical Reports Server (NTRS)

Thornton, R. J.; Ade, P. A. R.; Aiola, S.; Angile, F. E.; Amiri, M.; Beall, J. A.; Becker, D. T.; Cho, H.-M.; Choi, S. K.; Corlies, P.;

The Atacama Cosmology Telescope: The Polarization-sensitive ACTPol Instrument

NASA Astrophysics Data System (ADS)

Thornton, R. J.; Ade, P. A. R.; Aiola, S.; Angilè, F. E.; Amiri, M.; Beall, J. A.; Becker, D. T.; Cho, H.-M.; Choi, S. K.; Corlies, P.; Coughlin, K. P.; Datta, R.; Devlin, M. J.; Dicker, S. R.; Dünner, R.; Fowler, J. W.; Fox, A. E.; Gallardo, P. A.; Gao, J.; Grace, E.; Halpern, M.; Hasselfield, M.; Henderson, S. W.; Hilton, G. C.; Hincks, A. D.; Ho, S. P.; Hubmayr, J.; Irwin, K. D.; Klein, J.; Koopman, B.; Li, Dale; Louis, T.; Lungu, M.; Maurin, L.; McMahon, J.; Munson, C. D.; Naess, S.; Nati, F.; Newburgh, L.; Nibarger, J.; Niemack, M. D.; Niraula, P.; Nolta, M. R.; Page, L. A.; Pappas, C. G.; Schillaci, A.; Schmitt, B. L.; Sehgal, N.; Sievers, J. L.; Simon, S. M.; Staggs, S. T.; Tucker, C.; Uehara, M.; van Lanen, J.; Ward, J. T.; Wollack, E. J.

2016-12-01

The Atacama Cosmology Telescope (ACT) makes high angular resolution measurements of anisotropies in the Cosmic Microwave Background (CMB) at millimeter wavelengths. We describe ACTPol, an upgraded receiver for ACT, which uses feedhorn-coupled, polarization-sensitive detector arrays, a 3° field of view, 100 mK cryogenics with continuous cooling, and meta material antireflection coatings. ACTPol comprises three arrays with separate cryogenic optics: two arrays at a central frequency of 148 GHz and one array operating simultaneously at both 97 GHz and 148 GHz. The combined instrument sensitivity, angular resolution, and sky coverage are optimized for measuring angular power spectra, clusters via the thermal Sunyaev–Zel’dovich (SZ) and kinetic SZ signals, and CMB lensing due to large-scale structure. The receiver was commissioned with its first 148 GHz array in 2013, observed with both 148 GHz arrays in 2014, and has recently completed its first full season of operations with the full suite of three arrays. This paper provides an overview of the design and initial performance of the receiver and related systems.

A new multidimensional diagnostic method for measuring the properties of intense ion beams

NASA Astrophysics Data System (ADS)

Yasuike, Kazuhito; Miyamoto, Shuji; Nakai, Sadao

1996-02-01

A new arrayed pinhole camera (APC) diagnostic method for intense ion beams has been developed. The APC diagnostic technique permits the acquisition of the angular divergences and the ion fluxes of high intensity ion beams, in one shot, with a spatial resolution on the source of better than 1 mm and an effective angular divergence resolution of better than 10 mrad. A prototype time integrated APC has been designed and evaluated. The demonstration experiments have been performed on a Reiden-IV, 1 MV and 1 Ω pulsed power machine [1 T W (tera-watt or trillion watts)]. Proton beams of 0.7 MeV, with a pulse duration of ˜50 ns and an ion current density of about 100 A/cm2, were generated in an applied-Br type ion diode source using paraffin-filled grooves. These experimental results show that the APC can measure nonuniformities in the ion beam intensity generated from the ion source and the dependence of beam angular divergence on ion beam intensity.

High-resolution mapping reveals linkage between genes in common bean cultivar Ouro Negro conferring resistance to the rust, anthracnose, and angular leaf spot diseases

USDA-ARS?s Scientific Manuscript database

Rust, Anthracnose, and angular leaf spot are major diseases of common bean in the world and most particularly in the Americas and Africa, which are the largest common bean production regions of the world. The Mesoamerican black-seeded cultivar Ouro Negro is unusual in that it has resistance to all t...

High Frequency Variations of Earth Rotation Parameters from GPS and GLONASS Observations

PubMed Central

Wei, Erhu; Jin, Shuanggen; Wan, Lihua; Liu, Wenjie; Yang, Yali; Hu, Zhenghong

2015-01-01

The Earth's rotation undergoes changes with the influence of geophysical factors, such as Earth's surface fluid mass redistribution of the atmosphere, ocean and hydrology. However, variations of Earth Rotation Parameters (ERP) are still not well understood, particularly the short-period variations (e.g., diurnal and semi-diurnal variations) and their causes. In this paper, the hourly time series of Earth Rotation Parameters are estimated using Global Positioning System (GPS), Global Navigation Satellite System (GLONASS), and combining GPS and GLONASS data collected from nearly 80 sites from 1 November 2012 to 10 April 2014. These new observations with combining different satellite systems can help to decorrelate orbit biases and ERP, which improve estimation of ERP. The high frequency variations of ERP are analyzed using a de-trending method. The maximum of total diurnal and semidiurnal variations are within one milli-arcseconds (mas) in Polar Motion (PM) and 0.5 milli-seconds (ms) in UT1-UTC. The semidiurnal and diurnal variations are mainly related to the ocean tides. Furthermore, the impacts of satellite orbit and time interval used to determinate ERP on the amplitudes of tidal terms are analyzed. We obtain some small terms that are not described in the ocean tide model of the IERS Conventions 2010, which may be caused by the strategies and models we used or the signal noises as well as artifacts. In addition, there are also small differences on the amplitudes between our results and IERS convention. This might be a result of other geophysical excitations, such as the high-frequency variations in atmospheric angular momentum (AAM) and hydrological angular momentum (HAM), which needs more detailed analysis with more geophysical data in the future. PMID:25635416

On-Sky Tests of a High-Power Pulsed Laser for Sodium Laser Guide Star Adaptive Optics

NASA Astrophysics Data System (ADS)

Otarola, Angel; Hickson, Paul; Gagné, Ronald; Bo, Yong; Zuo, Junwei; Xie, Shiyong; Feng, Lu; Rochester, Simon; Budker, Dmitry; Shen, Shixia; Xue, Suijian; Min, Li; Wei, Kai; Boyer, Corinne; Ellerbroek, Brent; Hu, Jingyao; Peng, Qinjun; Xu, Zuyan

2016-03-01

We present results of on-sky tests performed in the summer of 2013 to characterize the performance of a prototype high-power pulsed laser for adaptive optics. The laser operates at a pulse repetition rate (PRR) of 600-800Hz, with a 6% duty cycle. Its coupling efficiency was found to be, in the best test case (using 18W of transmitted power), 231±14 photons s-1 sr-1 atom-1 W-1 m2 when circular polarization was employed and 167±17 photons s-1 sr-1 atom-1 W-1 m2 with linear polarization. No improvement was seen when D2b repumping was used, but this is likely due to the relatively large laser guide star (LGS) diameter, typically 10 arcsec or more, which resulted in low irradiance levels. Strong relaxation oscillations were present in the laser output, which have the effect of reducing the coupling efficiency. To better understand the results, a physical modeling was performed using the measured pulse profiles and parameters specific to these tests. The model results, for a 10 arcsec angular size LGS spot, agree well with the observations. When extrapolating the physical model for a sub-arcsecond angular size LGS (typical of what is needed for a successful astronomical guide star), the model predicts that this laser would have a coupling efficiency of 130 photons s-1 sr-1 atom-1 W-1 m2, using circular polarization and D2b repumping, for a LGS diameter of 0.6 arcsec Full Width at Half Maximum (FWHM), and free of relaxation oscillations in the 589 nm laser light.

Lucky Imaging in Astronomy

NASA Astrophysics Data System (ADS)

Brandner, Wolfgang; Hormuth, Felix

Lucky Imaging improves the angular resolution of astronomical observations hampered by atmospheric turbulence ("seeing"). Unlike adaptive optics, Lucky Imaging is a passive observing technique with individual integration times comparable to the atmospheric coherence time. Thanks to the advent of essentially noise free "Electron multiplying CCD" detectors, Lucky Imaging saw a renewed interest in the past decade. It is now routinely used at a number of 2-5-m class telescopes, such as ESO's NTT. We review the history of Lucky Imaging, present the technical implementation, describe the data analysis philosophy, and show some recent results obtained with this technique. We also discuss the advantages and limitations of Lucky Imaging compared to other passive and active high angular resolution observing techniques.

Note: A versatile mass spectrometer chamber for molecular beam and temperature programmed desorption experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tonks, James P., E-mail: james.tonks@awe.co.uk; AWE Plc, Aldermaston, Reading, Berkshire RG7 4PR; Galloway, Ewan C., E-mail: ewan.galloway@awe.co.uk

2016-08-15

A dual purpose mass spectrometer chamber capable of performing molecular beam scattering (MBS) and temperature programmed desorption (TPD) is detailed. Two simple features of this design allow it to perform these techniques. First, the diameter of entrance aperture to the mass spectrometer can be varied to maximize signal for TPD or to maximize angular resolution for MBS. Second, the mass spectrometer chamber can be radially translated so that it can be positioned close to the sample to maximize signal or far from the sample to maximize angular resolution. The performance of this system is described and compares well with systemsmore » designed for only one of these techniques.« less

K-KIDS: Companioins to K Dwarfs Within 50 Parsecs

NASA Astrophysics Data System (ADS)

Nusdeo, Daniel Anthony; Winters, Jennifer; Paredes-Alvarez, Leonardo; Horch, Elliott; Jao, Wei-Chun; Henry, Todd J.; RECONS Institute

2017-01-01

How many K dwarfs have “kids?” Stellar multiplicity fractions have been obtained for most spectral types, most recently by Raghavan et al. (2010) and Winters et al. (2015), finding rates of 50% for solar-type stars and 27% for M dwarfs, respectively. These findings will be crucial to improving our understanding of solar-system formation, but there has not yet been a statistically significant survey for K dwarfs to bridge the gap between G and M stars. To create a sample for a robust multiplicity survey, an initial set of 1048 K dwarfs was built using the Hipparcos and 2MASS catalogs, the companions of which are called “K-KIDS.” Future releases from Gaia will help us to expand K-KIDS into a volume-complete sample out to 50-pc, and we project that the final sample will contain over 3000 stars, making this the largest volume-complete multiplicity survey ever undertaken. For observational purposes, the targeted K dwarfs are confined equatorially to -30 < DEC < +30 to ensure all stars are observable from either hemisphere. The survey for K-KIDS is split into three companion-separation regimes: small (0.02 - 2.00 arcseconds), medium (2.00 - 10.00 arcseconds), and distant (10.00+ arcseconds). Small separation companions are resolved using the Differential Speckle Survey Instrument, with which we have observed 964 out of 1048 systems to date, already finding 135 new K-KIDS. Medium separation companions are observed via a series of three observations per star at the CTIO 0.9-m telescope, integrating for 3, 30, and 300 seconds to reveal companions of various brightnesses. Finally, a common proper-motion search is used to find companions at distant separations via blinking of digitialized images in the SuperCOSMOS archive, in addition to a large-scale literature survey for previously-discovered multiples. The small and distant surveys are nearing completion, and continued progress on the medium survey ensures that a statistically significant multiplicity rate for K dwarfs will soon be in achieved. Furthermore, a new RV survey is planned using the CHIRON high-resolution spectrograph to find companions that cannot be directly imaged. This effort has been supported by the NSF through grants AST-1412026 and AST-1517413.

Extreme Ultraviolet Fractional Orbital Angular Momentum Beams from High Harmonic Generation

PubMed Central

Turpin, Alex; Rego, Laura; Picón, Antonio; San Román, Julio; Hernández-García, Carlos

2017-01-01

We investigate theoretically the generation of extreme-ultraviolet (EUV) beams carrying fractional orbital angular momentum. To this end, we drive high-order harmonic generation with infrared conical refraction (CR) beams. We show that the high-order harmonic beams emitted in the EUV/soft x-ray regime preserve the characteristic signatures of the driving beam, namely ringlike transverse intensity profile and CR-like polarization distribution. As a result, through orbital and spin angular momentum conservation, harmonic beams are emitted with fractional orbital angular momentum, and they can be synthesized into structured attosecond helical beams –or “structured attosecond light springs”– with rotating linear polarization along the azimuth. Our proposal overcomes the state of the art limitations for the generation of light beams far from the visible domain carrying non-integer orbital angular momentum and could be applied in fields such as diffraction imaging, EUV lithography, particle trapping, and super-resolution imaging. PMID:28281655

Anisotropy of the Cosmic Microwave Background Radiation on Large and Medium Angular Scales

NASA Technical Reports Server (NTRS)

Houghton, Anthony; Timbie, Peter

1998-01-01

This grant has supported work at Brown University on measurements of the 2.7 K Cosmic Microwave Background Radiation (CMB). The goal has been to characterize the spatial variations in the temperature of the CMB in order to understand the formation of large-scale structure in the universe. We have concurrently pursued two measurements using millimeter-wave telescopes carried aloft by scientific balloons. Both systems operate over a range of wavelengths, chosen to allow spectral removal of foreground sources such as the atmosphere, Galaxy, etc. The angular resolution of approx. 25 arcminutes is near the angular scale at which the most structure is predicted by current models to be visible in the CMB angular power spectrum. The main goal is to determine the angular scale of this structure; in turn we can infer the density parameter, Omega, for the universe as well as other cosmological parameters, such as the Hubble constant.

Arcsecond positions for milliarcsecond VLBI nuclei of extragalactic radio sources. IV - Seventeen sources

NASA Technical Reports Server (NTRS)

Morabito, D. D.; Preston, R. A.; Linfield, R. P.; Slade, M. A.; Jauncey, D. L.

1986-01-01

VLBI measurements of time delay and delay rate at 2.29 and 8.42 GHz on baselines of 10,000 km have been used to determine the positions of the milliarcsecond nuclei in 17 extragalactic radio sources with estimated accuracies of 0.1 to 0.3 arcsec. The observed sources are part of an all-sky VLBI catalog of milliarcsecond radio sources. In addition, slightly improved positions are presented for 101 sources originally reported by Morabito et al. (1983). Arcsecond positions have now been determined for 836 sources.

Improving X-ray Optics Through Differential Deposition

NASA Technical Reports Server (NTRS)

Ramsey, Brian; Kilaru, Kiranmayee; Atkins, Carolyn; Gubarev, Mikhail V.; Gaskin, Jessica A.; O'Dell, Steve; Weisskopf, Martin; Zhang, William; Romaine, Suzanne

2012-01-01

The differential deposition technique can in theory correct shell figures to approximate arcsecond value. We have received APRA funding and are building two custom system to demonstrate the technique on full shell and segmented optics. We hope to be able to demonstrate < 5 arcsec performance in < 2 years. To go beyond this, (arcsecond level) is very difficult to judge as we have not yet discovered the problems. May necessitate in-situ metrology, stress reduction investigations, correcting for gravity effects, correcting for temperature effects. Some of this will become obvious in early parts of the investigation.

Student Measurements of the Double Star Eta Cassiopeiae

NASA Astrophysics Data System (ADS)

Brewer, Mark; Cacace, Gabriel; Do, Vivian; Griffith, Nicholas; Malan, Alexandria; Paredes, Hanna; Peticolas, Brian; Stasiak, Kathryne

2016-10-01

The double star Eta Cassiopeiae was measured at Vanguard Preparatory School. Digital measurements were made with a 14-inch telescope equipped with a CCD camera. The plate scale was determined to be 0.50 arcseconds per pixel. The separations and position angles were determined to be 13.3 arcseconds and 340.4 degrees, by the use of astronomy software. Previous observations reported in the Washington Double Star Catalog were used as a comparison. The camera angle was found to be the ultimate issue in the skewed data gathered for the double star.

A balloon-borne payload for imaging hard X-rays and gamma rays from solar flares

NASA Technical Reports Server (NTRS)

Crannell, Carol J.; Dennis, Brian R.; Orwig, Larry E.; Schmahl, Edward J.; Lang, Frederic L.; Starr, Richard; Norris, Jay P.; Greene, Michael E.; Hurford, Gordon J.; Johnson, W. N.

1991-01-01

Hard X-rays and gamma rays provide direct evidence of the roles of accelerated particles in solar flares. An approach that employs a spatial Fourier-transform technique for imaging the sources of these emissions is described, and the development of a balloon-borne imaging device based on this instrumental technique is presented. The detectors, together with the imaging optics, are sensitive to hard X-ray and gamma-ray emission in the energy-range from 20 to 700 keV. This payload, scheduled for its first flight in June 1992, will provide 11-arc second angular resolution and millisecond time resolution with a whole-sun field of view. For subsequent flights, the effective detector area can be increased by as much as a factor of four, and imaging optics with angular resolution as fine as 2 arcsec can be added to the existing gondola and metering structures.

Two-Dimensional Micro-/Nanoradian Angle Generator with High Resolution and Repeatability Based on Piezo-Driven Double-Axis Flexure Hinge and Three Capacitive Sensors.

PubMed

Tan, Xinran; Zhu, Fan; Wang, Chao; Yu, Yang; Shi, Jian; Qi, Xue; Yuan, Feng; Tan, Jiubin

2017-11-19

This study presents a two-dimensional micro-/nanoradian angle generator (2D-MNAG) that achieves high angular displacement resolution and repeatability using a piezo-driven flexure hinge for two-dimensional deflections and three capacitive sensors for output angle monitoring and feedback control. The principal error of the capacitive sensor for precision microangle measurement is analyzed and compensated for; so as to achieve a high angle output resolution of 10 nrad (0.002 arcsec) and positioning repeatability of 120 nrad (0.024 arcsec) over a large angular range of ±4363 μrad (±900 arcsec) for the 2D-MNAG. The impact of each error component, together with the synthetic error of the 2D-MNAG after principal error compensation are determined using Monte Carlo simulation for further improvement of the 2D-MNAG.

Two-Dimensional Micro-/Nanoradian Angle Generator with High Resolution and Repeatability Based on Piezo-Driven Double-Axis Flexure Hinge and Three Capacitive Sensors

PubMed Central

Tan, Xinran; Zhu, Fan; Wang, Chao; Yu, Yang; Shi, Jian; Qi, Xue; Yuan, Feng; Tan, Jiubin

2017-01-01

This study presents a two-dimensional micro-/nanoradian angle generator (2D-MNAG) that achieves high angular displacement resolution and repeatability using a piezo-driven flexure hinge for two-dimensional deflections and three capacitive sensors for output angle monitoring and feedback control. The principal error of the capacitive sensor for precision microangle measurement is analyzed and compensated for; so as to achieve a high angle output resolution of 10 nrad (0.002 arcsec) and positioning repeatability of 120 nrad (0.024 arcsec) over a large angular range of ±4363 μrad (±900 arcsec) for the 2D-MNAG. The impact of each error component, together with the synthetic error of the 2D-MNAG after principal error compensation are determined using Monte Carlo simulation for further improvement of the 2D-MNAG. PMID:29156595

CCD scanning for asteroids and comets

NASA Technical Reports Server (NTRS)

Gehrels, T.; Mcmillan, R. S.

1986-01-01

A change coupled device (CCD) is used in a scanning mode to find new asteroids and recover known asteroids and comet nuclei. Current scientific programs include recovery of asteroids and comet nuclei requested by the Minor Planet Center (MPC), discovery of new asteroids in the main belt and of unusual orbital types, and follow-up astrometry of selected new asteroids discovered. The routine six sigma limiting visual magnitude is 19.6 and slightly more than a square degree is scanned three times every 90 minutes of observing time during the fortnight centered on New Moon. Semiautomatic software for detection of moving objects is in routine use; angular speeds as low as 11.0 arcseconds per hour were distinguished from the effects of the Earth's atmosphere on the field of view. A typical set of three 29-minute scans near the opposition point along the ecliptic typically nets at least 5 new main-belt asteroids down to magnitude 19.6. In 18 observing runs (months) 43 asteroids were recovered, astrometric and photometric data on 59 new asteroids were reported, 10 new asteroids with orbital elements were consolidated, and photometry and positions of 22 comets were reported.

High-Resolution X-Ray Telescopes

NASA Technical Reports Server (NTRS)

ODell, Stephen L.; Brissenden, Roger J.; Davis, William; Elsner, Ronald F.; Elvis, Martin; Freeman, Mark; Gaetz, Terry; Gorenstein, Paul; Gubarev, Mikhail V.

2010-01-01

Fundamental needs for future x-ray telescopes: a) Sharp images => excellent angular resolution. b) High throughput => large aperture areas. Generation-X optics technical challenges: a) High resolution => precision mirrors & alignment. b) Large apertures => lots of lightweight mirrors. Innovation needed for technical readiness: a) 4 top-level error terms contribute to image size. b) There are approaches to controlling those errors. Innovation needed for manufacturing readiness. Programmatic issues are comparably challenging.

Prospects for Studying Interstellar Magnetic Fields with a Far-Infrared Polarimeter for SAFIR

NASA Technical Reports Server (NTRS)

Dowell, C. Darren; Chuss, D. T.; Dotson, J. L.

2008-01-01

Polarimetry at mid-infrared through millimeter wavelengths using airborne and ground-based telescopes has revealed magnetic structures in dense molecular clouds in the interstellar medium, primarily in regions of star formation. Furthermore, spectropolarimetry has offered clues about the composition of the dust grains and the mechanism by which they are aligned with respect to the local magnetic field. The sensitivity of the observations to date has been limited by the emission from the atmosphere and warm telescopes. A factor of 1000 in sensitivity can be gained by using instead a cold space telescope. With 5 arcminute resolution, Planck will make the first submillimeter polarization survey of the full Galaxy early in the next decade. We discuss the science case for and basic design of a far-infrared polarimeter on the SAFIR space telescope, which offers resolution in the few arcsecond range and wavelength selection of cold and warm dust components. Key science themes include the formation and evolution of molecular clouds in nearby spiral galaxies, the magnetic structure of the Galactic center, and interstellar turbulence.

Spatial distribution of arable and abandoned land across former Soviet Union countries

NASA Astrophysics Data System (ADS)

Lesiv, Myroslava; Schepaschenko, Dmitry; Moltchanova, Elena; Bun, Rostyslav; Dürauer, Martina; Prishchepov, Alexander V.; Schierhorn, Florian; Estel, Stephan; Kuemmerle, Tobias; Alcántara, Camilo; Kussul, Natalia; Shchepashchenko, Maria; Kutovaya, Olga; Martynenko, Olga; Karminov, Viktor; Shvidenko, Anatoly; Havlik, Petr; Kraxner, Florian; See, Linda; Fritz, Steffen

2018-04-01

Knowledge of the spatial distribution of agricultural abandonment following the collapse of the Soviet Union is highly uncertain. To help improve this situation, we have developed a new map of arable and abandoned land for 2010 at a 10 arc-second resolution. We have fused together existing land cover and land use maps at different temporal and spatial scales for the former Soviet Union (fSU) using a training data set collected from visual interpretation of very high resolution (VHR) imagery. We have also collected an independent validation data set to assess the map accuracy. The overall accuracies of the map by region and country, i.e. Caucasus, Belarus, Kazakhstan, Republic of Moldova, Russian Federation and Ukraine, are 90±2%, 84±2%, 92±1%, 78±3%, 95±1%, 83±2%, respectively. This new product can be used for numerous applications including the modelling of biogeochemical cycles, land-use modelling, the assessment of trade-offs between ecosystem services and land-use potentials (e.g., agricultural production), among others.

High resolution global gridded data for use in population studies

PubMed Central

Lloyd, Christopher T.; Sorichetta, Alessandro; Tatem, Andrew J.

2017-01-01

Recent years have seen substantial growth in openly available satellite and other geospatial data layers, which represent a range of metrics relevant to global human population mapping at fine spatial scales. The specifications of such data differ widely and therefore the harmonisation of data layers is a prerequisite to constructing detailed and contemporary spatial datasets which accurately describe population distributions. Such datasets are vital to measure impacts of population growth, monitor change, and plan interventions. To this end the WorldPop Project has produced an open access archive of 3 and 30 arc-second resolution gridded data. Four tiled raster datasets form the basis of the archive: (i) Viewfinder Panoramas topography clipped to Global ADMinistrative area (GADM) coastlines; (ii) a matching ISO 3166 country identification grid; (iii) country area; (iv) and slope layer. Further layers include transport networks, landcover, nightlights, precipitation, travel time to major cities, and waterways. Datasets and production methodology are here described. The archive can be downloaded both from the WorldPop Dataverse Repository and the WorldPop Project website. PMID:28140386

Spatial distribution of arable and abandoned land across former Soviet Union countries.

PubMed

Lesiv, Myroslava; Schepaschenko, Dmitry; Moltchanova, Elena; Bun, Rostyslav; Dürauer, Martina; Prishchepov, Alexander V; Schierhorn, Florian; Estel, Stephan; Kuemmerle, Tobias; Alcántara, Camilo; Kussul, Natalia; Shchepashchenko, Maria; Kutovaya, Olga; Martynenko, Olga; Karminov, Viktor; Shvidenko, Anatoly; Havlik, Petr; Kraxner, Florian; See, Linda; Fritz, Steffen

2018-04-03

Knowledge of the spatial distribution of agricultural abandonment following the collapse of the Soviet Union is highly uncertain. To help improve this situation, we have developed a new map of arable and abandoned land for 2010 at a 10 arc-second resolution. We have fused together existing land cover and land use maps at different temporal and spatial scales for the former Soviet Union (fSU) using a training data set collected from visual interpretation of very high resolution (VHR) imagery. We have also collected an independent validation data set to assess the map accuracy. The overall accuracies of the map by region and country, i.e. Caucasus, Belarus, Kazakhstan, Republic of Moldova, Russian Federation and Ukraine, are 90±2%, 84±2%, 92±1%, 78±3%, 95±1%, 83±2%, respectively. This new product can be used for numerous applications including the modelling of biogeochemical cycles, land-use modelling, the assessment of trade-offs between ecosystem services and land-use potentials (e.g., agricultural production), among others.

Spatial distribution of arable and abandoned land across former Soviet Union countries

PubMed Central

Lesiv, Myroslava; Schepaschenko, Dmitry; Moltchanova, Elena; Bun, Rostyslav; Dürauer, Martina; Prishchepov, Alexander V.; Schierhorn, Florian; Estel, Stephan; Kuemmerle, Tobias; Alcántara, Camilo; Kussul, Natalia; Shchepashchenko, Maria; Kutovaya, Olga; Martynenko, Olga; Karminov, Viktor; Shvidenko, Anatoly; Havlik, Petr; Kraxner, Florian; See, Linda; Fritz, Steffen

2018-01-01

Knowledge of the spatial distribution of agricultural abandonment following the collapse of the Soviet Union is highly uncertain. To help improve this situation, we have developed a new map of arable and abandoned land for 2010 at a 10 arc-second resolution. We have fused together existing land cover and land use maps at different temporal and spatial scales for the former Soviet Union (fSU) using a training data set collected from visual interpretation of very high resolution (VHR) imagery. We have also collected an independent validation data set to assess the map accuracy. The overall accuracies of the map by region and country, i.e. Caucasus, Belarus, Kazakhstan, Republic of Moldova, Russian Federation and Ukraine, are 90±2%, 84±2%, 92±1%, 78±3%, 95±1%, 83±2%, respectively. This new product can be used for numerous applications including the modelling of biogeochemical cycles, land-use modelling, the assessment of trade-offs between ecosystem services and land-use potentials (e.g., agricultural production), among others. PMID:29611843

Protostellar Outflows Mapped with ALMA and Techniques to Include Short Spacings

NASA Astrophysics Data System (ADS)

Plunkett, Adele

2018-01-01

Protostellar outflows are early signs of star formation, yet in cluster environments - common sites of star formation - their role and interaction with surrounding gas are complicated. Protostellar outflows are interesting and complex because they connect protostars (scales 10s au) to the surrounding gas environment (few pc), and their morphology constrains launching and/or accretion modes. A complete outflow study must use observing methods that recover several orders of magnitude of spatial scales, ideally with sub-arcsecond resolution and mapping over a few parsecs. ALMA provides high-resolution observations of outflows, and in some cases outflows have been mapped in clusters. Combining with observations using the Total Power array is possible, but challenging, and a large single dish telescope providing more overlap in uv space is advantageous. In this presentation I show protostellar outflows observed with ALMA using 12m, 7m, and To tal Power arrays. With a new CASA tool TP2VIS we create total power ``visibility'' data and perform joint imaging and deconvolution of interferometry and single dish data. TP2VIS will ultimately provide synergy between ALMA and AtLAST data.

The Normalization of Surface Anisotropy Effects Present in SEVIRI Reflectances by Using the MODIS BRDF Method

NASA Technical Reports Server (NTRS)

Proud, Simon Richard; Zhang, Qingling; Schaaf, Crystal; Fensholt, Rasmus; Rasmussen, Mads Olander; Shisanya, Chris; Mutero, Wycliffe; Mbow, Cheikh; Anyamba, Assaf; Pak, Ed;

Dislocation Content Measured Via 3D HR-EBSD Near a Grain Boundary in an AlCu Oligocrystal

NASA Technical Reports Server (NTRS)

Ruggles, Timothy; Hochhalter, Jacob; Homer, Eric

2016-01-01

Interactions between dislocations and grain boundaries are poorly understood and crucial to mesoscale plasticity modeling. Much of our understanding of dislocation-grain boundary interaction comes from atomistic simulations and TEM studies, both of which are extremely limited in scale. High angular resolution EBSD-based continuum dislocation microscopy provides a way of measuring dislocation activity at length scales and accuracies relevant to crystal plasticity, but it is limited as a two-dimensional technique, meaning the character of the grain boundary and the complete dislocation activity is difficult to recover. However, the commercialization of plasma FIB dual-beam microscopes have made 3D EBSD studies all the more feasible. The objective of this work is to apply high angular resolution cross correlation EBSD to a 3D EBSD data set collected by serial sectioning in a FIB to characterize dislocation interaction with a grain boundary. Three dimensional high angular resolution cross correlation EBSD analysis was applied to an AlCu oligocrystal to measure dislocation densities around a grain boundary. Distortion derivatives associated with the plasma FIB serial sectioning were higher than expected, possibly due to geometric uncertainty between layers. Future work will focus on mitigating the geometric uncertainty and examining more regions of interest along the grain boundary to glean information on dislocation-grain boundary interaction.

A lower limit to the accretion disc radius in the low-luminosity AGNNGC 1052 derived from high-angular resolution data

NASA Astrophysics Data System (ADS)

Reb, Lennart; Fernández-Ontiveros, Juan A.; Prieto, M. Almudena; Dolag, Klaus

2018-07-01

We investigate the central sub-arcsec region of the low-luminosity active galactic nucleusNGC 1052, using a high-angular resolution data set that covers 10 orders of magnitude in frequency. This allows us to infer the continuum emission within the innermost ˜17 pc around the black hole to be of non-thermal, synchrotron origin and to set a limit to the maximum contribution of a standard accretion disc. Assuming the canonical 10 per cent mass-light conversion efficiency for the standard accretion disc, its inferred accretion power would be too low by one order of magnitude to account for the observed continuum luminosity. We thus introduce a truncated accretion disc and derive a truncation radius to mass-light conversion efficiency relation, which we use to reconcile the inferred accretion power with the continuum luminosity. As a result we find that a disc providing the necessary accretion power must be truncated at rtr ≳ 26 rg, consistent with the inner radius derived from the observations of the Fe Kα line in the X-ray spectrum of this nucleus. This is the first time to derive a limit on the truncation radius of the accretion disc from high-angular resolution data only.

A lower limit to the accretion disc radius in the low-luminosity AGN NGC 1052 derived from high-angular resolution data

NASA Astrophysics Data System (ADS)

Reb, Lennart; Fernández-Ontiveros, Juan A.; Prieto, M. Almudena; Dolag, Klaus

2018-05-01

We investigate the central sub-arcsec region of the low-luminosity active galactic nucleus NGC 1052, using a high-angular resolution dataset that covers 10 orders of magnitude in frequency. This allows us to infer the continuum emission within the innermost ˜17 pc around the black hole to be of non-thermal, synchrotron origin and to set a limit to the maximum contribution of a standard accretion disc. Assuming the canonical 10 per cent mass-light conversion efficiency for the standard accretion disc, its inferred accretion power would be too low by one order of magnitude to account for the observed continuum luminosity. We thus introduce a truncated accretion disc and derive a truncation radius to mass-light conversion efficiency relation, which we use to reconcile the inferred accretion power with the continuum luminosity. As a result we find that a truncated disc providing the necessary accretion power must be truncated at rtr ≳ 26 rg, consistent with the inner radius derived from the observations of the Fe Kα line in the X-ray spectrum of this nucleus. This is the first time to derive a limit on the truncation radius of the accretion disc from high-angular resolution data only.

DUAL-FREQUENCY OBSERVATIONS OF 140 COMPACT, FLAT-SPECTRUM ACTIVE GALACTIC NUCLEI FOR SCINTILLATION-INDUCED VARIABILITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koay, J. Y.; Macquart, J.-P.; Bignall, H. E.

2011-10-15

The 4.9 GHz Micro-Arcsecond Scintillation-Induced Variability (MASIV) Survey detected a drop in interstellar scintillation (ISS) for sources at redshifts z {approx}> 2, indicating an apparent increase in angular diameter or a decrease in flux density of the most compact components of these sources relative to their extended emission. This can result from intrinsic source size effects or scatter broadening in the intergalactic medium (IGM) in excess of the expected (1 + z){sup 1/2} angular diameter scaling of brightness temperature limited sources resulting from cosmological expansion. We report here 4.9 GHz and 8.4 GHz observations and data analysis for a samplemore » of 140 compact, flat-spectrum sources which may allow us to determine the origin of this angular diameter-redshift relation by exploiting their different wavelength dependences. In addition to using ISS as a cosmological probe, the observations provide additional insight into source morphologies and the characteristics of ISS. As in the MASIV Survey, the variability of the sources is found to be significantly correlated with line-of-sight H{alpha} intensities, confirming its link with ISS. For 25 sources, time delays of about 0.15-3 days are observed between the scintillation patterns at both frequencies, interpreted as being caused by a shift in core positions when probed at different optical depths. Significant correlation is found between ISS amplitudes and source spectral index; in particular, a large drop in ISS amplitudes is observed at {alpha} < -0.4 confirming that steep spectrum sources scintillate less. We detect a weakened redshift dependence of ISS at 8.4 GHz over that at 4.9 GHz, with the mean variance at four-day timescales reduced by a factor of 1.8 in the z > 2 sources relative to the z < 2 sources, as opposed to the factor of three decrease observed at 4.9 GHz. This suggests scatter broadening in the IGM, but the interpretation is complicated by subtle selection effects that will be explored further in a follow-up paper.« less

Dual-Frequency Observations of 140 Compact, Flat-Spectrum Active Galactic Nuclei for Scintillation-Induced Variability

NASA Technical Reports Server (NTRS)

Koay, J. Y.; Macquart, J.- P.; Rickett, B. J.; Bignall, H. E.; Lovell, J. E. J.; Reynolds, C.; Jauncey, D. L.; Pursimo, T.; Kedziora-Chudczer, L.; Ojha, R.

2012-01-01

The 4.9 GHz Micro-Arcsecond Scintillation-Induced Variability (MASIV) Survey detected a drop in Interstellar Scintillation (ISS) for sources at red shifts z > or approx. 2, indicating an apparent increase in angular diameter or a decrease in flux density of the most compact components of these sources, relative to their extended emission. This can result from intrinsic source size effects or scatter broadening in the Intergalactic Medium (IGM) , in excess of the expected (1+z)1/2 angular diameter scaling of brightness temperature limited sources resulting from cosmological expansion. We report here 4.9 GHz and 8.4 GHz observations and data analysis for a sample of 140 compact, fiat-spectrum sources which may allow us to determine the origin of this angular diameter-redshift relation by exploiting their different wavelength dependences. In addition to using ISS as a cosmological probe, the observations provide additional insight into source morphologies and the characteristics of ISS. As in the MASIV Survey, the variability of the sources is found to be significantly correlated with line-of-sight H(alpha) intensities, confirming its link with ISS. For 25 sources, time delays of about 0.15 to 3 days are observed between the scintillation patterns at both frequencies, interpreted as being caused by a shift in core positions when probed at different optical depths. Significant correlation is found between ISS amplitudes and source spectral index; in particular, a large drop in ISS amplitudes is observed at alpha < -0.4 confirming that steep spectrum sources scintillate less. We detect a weakened redshift dependence of ISS at 8.4 GHz over that at 4.9 GHz, with the mean variance at 4-day timescales reduced by a factor of 1.8 in the z > 2 sources relative to the z < 2 sources, as opposed to the factor of 3 decrease observed at 4.9 GHz. This suggests scatter broadening in the IGM, but the interpretation is complicated by subtle selection effects that will be explored further in a follow-up paper.

Earth-orbiting extreme ultraviolet spectroscopic mission: SPRINT-A/EXCEED

NASA Astrophysics Data System (ADS)

Yoshikawa, I.; Tsuchiya, F.; Yamazaki, A.; Yoshioka, K.; Uemizu, K.; Murakami, G.; Kimura, T.; Kagitani, M.; Terada, N.; Kasaba, Y.; Sakanoi, T.; Ishii, H.; Uji, K.

2012-09-01

The EXCEED (Extreme Ultraviolet Spectroscope for Exospheric Dynamics) mission is an Earth-orbiting extreme ultraviolet (EUV) spectroscopic mission and the first in the SPRINT series being developed by ISAS/JAXA. It will be launched in the summer of 2013. EUV spectroscopy is suitable for observing tenuous gases and plasmas around planets in the solar system (e.g., Mercury, Venus, Mars, Jupiter, and Saturn). Advantage of remote sensing observation is to take a direct picture of the plasma dynamics and distinguish between spatial and temporal variability explicitly. One of the primary observation targets is an inner magnetosphere of Jupiter, whose plasma dynamics is dominated by planetary rotation. Previous observations have shown a few percents of the hot electron population in the inner magnetosphere whose temperature is 100 times higher than the background thermal electrons. Though the hot electrons have a significant impact on the energy balance in the inner magnetosphere, their generation process has not yet been elucidated. In the EUV range, a number of emission lines originate from plasmas distributed in Jupiter's inner magnetosphere. The EXCEED spectrograph is designed to have a wavelength range of 55-145 nm with minimum spectral resolution of 0.4 nm, enabling the electron temperature and ion composition in the inner magnetosphere to be determined. Another primary objective is to investigate an unresolved problem concerning the escape of the atmosphere to space. Although there have been some in-situ observations by orbiters, our knowledge is still limited. The EXCEED mission plans to make imaging observations of plasmas around Venus and Mars to determine the amounts of escaping atmosphere. The instrument's field of view (FOV) is so wide that we can get an image from the interaction region between the solar wind and planetary plasmas down to the tail region at one time. This will provide us with information about outward-flowing plasmas, e.g., their composition, rate, and dependence on solar activity. EXCEED has two mission instruments: the EUV spectrograph and a target guide camera that is sensitive to visible light. The EUV spectrograph is designed to have a wavelength range of 55-145 nm with a spectral resolution of 0.4-1.0 nm. The spectrograph slits have a FOV of 400 x 140 arcseconds (maximum). The optics of the instrument consists of a primary mirror with a diameter of 20cm, a laminar type grating, and a 5-stage micro-channel plate assembly with a resistive anode encoder. To achieve high efficiencies, the surfaces of the primary mirror and the grating are coated with CVD-SiC. Because of the large primary mirror and high efficiencies, good temporal resolution and complete spatial coverage for Io plasma torus observation is expected. Based on a feasibility study using the spectral diagnosis method, it is shown that EXCEED can determine the Io plasma torus parameters, such as the electron density, temperatures, hot electron fraction and so on, using an exposure time of 50 minutes. The target guide camera will be used to capture the target and guide the observation area of interest to the slit. Emissions from outside the slit's FOV will be reflected by the front of the slit and guided to the target guide camera. The guide camera's FOV is 240" x 240". The camera will take an image every 3 seconds and the image is sent to a mission data processor (MDP), which calculates the centroid of the image. During an observation, the bus system controls the attitude to keep the centroid position of the target in the guide camera with an accuracy of ±5 arc-seconds. With the help of the target guide camera, we will take spectral images with a long exposure time of 50 minutes and good spatial resolution of 20 arc-seconds.

Perspective View with Landsat Overlay, Palm Springs, Calif.

NASA Technical Reports Server (NTRS)

2002-01-01

The city of Palm Springs nestles at the base of Mount San Jacinto in this computer-generated perspective viewed from the east. The many golf courses in the area show up as irregular green areas while the two prominent lines passing through the middle of the image are Interstate 10 and the adjacent railroad tracks. The San Andreas Fault passes through the middle of the sandy Indio Hills in the foreground.

This 3-D perspective view was generated using topographic data from the Shuttle Radar Topography Mission (SRTM) and an enhanced color Landsat 5satellite image. Topographic expression is exaggerated two times.

Landsat has been providing visible and infrared views of the Earth since 1972. SRTM elevation data matches the 30-meter (98-foot) resolution of most Landsat images and will substantially help in analyzing the large and growing Landsat image archive.

Elevation data used in this image was acquired by the Shuttle Radar Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched on Feb. 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR)that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect 3-D measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter (approximately 200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between NASA, the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Earth Science Enterprise,Washington, D.C.

Size: scale varies in this perspective image Location: 33.8 deg. North lat., 116.3 deg. West lon. Orientation: looking west Image Data: Landsat Bands 3, 2, 1 as red, green, blue, respectively Original Data Resolution: SRTM 1 arcsecond (30 meters or 98 feet), Thematic Mapper 1 arcsecond (30 meters or 98 feet) Date Acquired: February 2000 (SRTM)

Perspective View with Landsat Overlay, San Diego, Calif.

NASA Technical Reports Server (NTRS)

2002-01-01

The influence of topography on the growth of the city of San Diego is seen clearly in this computer-generated perspective viewed from the south. The Peninsular Ranges to the east of the city have channeled development of the cities of La Mesa and El Cajon, above the center. San Diego itself clusters around the bay enclosed by Point Loma and Coronado Island. In the mountains to the right, Lower Otay Lake and Sweetwater Reservoir are the dark patches.

This 3-D perspective view was generated using topographic data from the Shuttle Radar Topography Mission (SRTM) and an enhanced color Landsat 5satellite image. Topographic expression is exaggerated two times.

Landsat has been providing visible and infrared views of the Earth since 1972. SRTM elevation data matches the 30-meter (98-foot) resolution of most Landsat images and will substantially help in analyzing the large and growing Landsat image archive.

Elevation data used in this image was acquired by the Shuttle Radar Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched on Feb. 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR)that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect 3-D measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter (approximately 200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between NASA, the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Earth Science Enterprise, Washington, D.C.

Size: scale varies in this perspective image Location: 32.6 deg. North lat., 117.1 deg. West lon. Orientation: looking north Image Data: Landsat Bands 3, 2, 1 as red, green, blue, respectively Original Data Resolution: SRTM 1 arcsecond (30 meters or 98 feet), Thematic Mapper 1 arcsecond (30 meters or 98 feet) Date Acquired: February 2000 (SRTM)

X-Ray Spectroscopy of Optically Bright Planets using the Chandra Observatory

NASA Technical Reports Server (NTRS)

Ford, P. G.; Elsner, R. F.

2005-01-01

Since its launch in July 1999, Chandra's Advanced CCD Imaging Spectrometer (ACIS) has observed several planets (Venus, Mars, Jupiter and Saturn) and 6 comets. At 0.5 arc-second spatial resolution, ACIS detects individual x-ray photons with good quantum efficiency (25% at 0.6 KeV) and energy resolution (20% FWHM at 0.6 KeV). However, the ACIS CCDs are also sensitive to optical and near-infrared light, which is absorbed by optical blocking filters (OBFs) that eliminate optical contamination from all but the brightest extended sources, e.g., planets. .Jupiter at opposition subseconds approx.45 arc-seconds (90 CCD pixels.) Since Chandra is incapable of tracking a moving target, the planet takes 10 - 20 kiloseconds to move across the most sensitive ACIS CCD, after which the observatory must be re-pointed. Meanwhile, the OBF covering that CCD adds an opt,ical signal equivalent to approx.110 eV to each pixel that lies within thc outline of the Jovian disk. This has three consequences: (1) the observatory must be pointed away from Jupiter while CCD bias maps are constructed; (2) most x-rays from within the optical image will be misidentified as charged-particle background and ignored; and (3) those x-rays that are reported will bc assigned anomalously high energies. The same also applies to thc other planets, but is less serious since they are either dimmer at optical wavelengths, or they show less apparent motion across the sky, permitting reduced CCD exposure times: the optical contamination from Saturn acids approx.15 eV per pixel, and from Mars and Venus approx.31 eV. After analyzing a series of short .Jupiter observations in December 2000, ACIS parameters were optimized for the February 2003 opposition. CCD bias maps were constructed while Chandra pointed away from Jupiter, and the subsequent observations employed on-board software to ignore any pixel that contained less charge than that expected from optical leakage. In addition, ACIS was commanded to report 5 x 5 arrays of pixel values surrounding each x-ray event, and the outlying values were employed during ground processing to correct for the optical contamination.

Optical simulations for design, alignment, and performance prediction of silicon pore optics for the ATHENA x-ray telescope (Conference Presentation)

NASA Astrophysics Data System (ADS)

Spiga, D.; Della Monica Ferreira, D.; Shortt, B.; Bavdaz, M.; Bergback Knudsen, E.; Bianucci, G.; Christensen, F.; Civitani, M.; Collon, M.; Conconi, P.; Fransen, S.; Marioni, F.; Massahi, S.; Pareschi, G.; Salmaso, B.; Jegers, A. S.; Tayabaly, K.; Valsecchi, G.; Westergaard, N.; Wille, E.

2017-09-01

The ATHENA X-ray observatory is a large-class ESA approved mission, with launch scheduled in 2028. The technology of silicon pore optics (SPO) was selected as baseline to assemble ATHENA's optic with hundreds of mirror modules, obtained by stacking wedged and ribbed silicon wafer plates onto silicon mandrels to form the Wolter-I configuration. In the current configuration, the optical assembly has a 3 m diameter and a 2 m2 effective area at 1 keV, with a required angular resolution of 5 arcsec. The angular resolution that can be achieved is chiefly the combination of 1) the focal spot size determined by the pore diffraction, 2) the focus degradation caused by surface and profile errors, 3) the aberrations introduced by the misalignments between primary and secondary segments, 4) imperfections in the co-focality of the mirror modules in the optical assembly. A detailed simulation of these aspects is required in order to assess the fabrication and alignment tolerances; moreover, the achievable effective area and angular resolution depend on the mirror module design. Therefore, guaranteeing these optical performances requires: a fast design tool to find the most performing solution in terms of mirror module geometry and population, and an accurate point spread function simulation from local metrology and positioning information. In this paper, we present the results of simulations in the framework of ESA-financed projects (SIMPOSiuM, ASPHEA, SPIRIT), in preparation of the ATHENA X-ray telescope, analyzing the mentioned points: 1) we deal with a detailed description of diffractive effects in an SPO mirror module, 2) we show ray-tracing results including surface and profile defects of the reflective surfaces, 3) we assess the effective area and angular resolution degradation caused by alignment errors between SPO mirror module's segments, and 4) we simulate the effects of co-focality errors in X-rays and in the UV optical bench used to study the mirror module alignment and integration.

A comparison of multi-spectral, multi-angular, and multi-temporal remote sensing datasets for fractional shrub canopy mapping in Arctic Alaska

USGS Publications Warehouse

Selkowitz, D.J.

2010-01-01

Shrub cover appears to be increasing across many areas of the Arctic tundra biome, and increasing shrub cover in the Arctic has the potential to significantly impact global carbon budgets and the global climate system. For most of the Arctic, however, there is no existing baseline inventory of shrub canopy cover, as existing maps of Arctic vegetation provide little information about the density of shrub cover at a moderate spatial resolution across the region. Remotely-sensed fractional shrub canopy maps can provide this necessary baseline inventory of shrub cover. In this study, we compare the accuracy of fractional shrub canopy (> 0.5 m tall) maps derived from multi-spectral, multi-angular, and multi-temporal datasets from Landsat imagery at 30 m spatial resolution, Moderate Resolution Imaging SpectroRadiometer (MODIS) imagery at 250 m and 500 m spatial resolution, and MultiAngle Imaging Spectroradiometer (MISR) imagery at 275 m spatial resolution for a 1067 km2 study area in Arctic Alaska. The study area is centered at 69 ??N, ranges in elevation from 130 to 770 m, is composed primarily of rolling topography with gentle slopes less than 10??, and is free of glaciers and perennial snow cover. Shrubs > 0.5 m in height cover 2.9% of the study area and are primarily confined to patches associated with specific landscape features. Reference fractional shrub canopy is determined from in situ shrub canopy measurements and a high spatial resolution IKONOS image swath. Regression tree models are constructed to estimate fractional canopy cover at 250 m using different combinations of input data from Landsat, MODIS, and MISR. Results indicate that multi-spectral data provide substantially more accurate estimates of fractional shrub canopy cover than multi-angular or multi-temporal data. Higher spatial resolution datasets also provide more accurate estimates of fractional shrub canopy cover (aggregated to moderate spatial resolutions) than lower spatial resolution datasets, an expected result for a study area where most shrub cover is concentrated in narrow patches associated with rivers, drainages, and slopes. Including the middle infrared bands available from Landsat and MODIS in the regression tree models (in addition to the four standard visible and near-infrared spectral bands) typically results in a slight boost in accuracy. Including the multi-angular red band data available from MISR in the regression tree models, however, typically boosts accuracy more substantially, resulting in moderate resolution fractional shrub canopy estimates approaching the accuracy of estimates derived from the much higher spatial resolution Landsat sensor. Given the poor availability of snow and cloud-free Landsat scenes in many areas of the Arctic and the promising results demonstrated here by the MISR sensor, MISR may be the best choice for large area fractional shrub canopy mapping in the Alaskan Arctic for the period 2000-2009.

Orbital angular momentum light in microscopy

PubMed Central

2017-01-01

Light with a helical phase has had an impact on optical imaging, pushing the limits of resolution or sensitivity. Here, special emphasis will be given to classical light microscopy of phase samples and to Fourier filtering techniques with a helical phase profile, such as the spiral phase contrast technique in its many variants and areas of application. This article is part of the themed issue ‘Optical orbital angular momentum’. PMID:28069768

Rotation of the asymptotic giant branch star R Doradus

NASA Astrophysics Data System (ADS)

Vlemmings, W. H. T.; Khouri, T.; Beck, E. De; Olofsson, H.; García-Segura, G.; Villaver, E.; Baudry, A.; Humphreys, E. M. L.; Maercker, M.; Ramstedt, S.

2018-05-01

High-resolution observations of the extended atmospheres of asymptotic giant branch (AGB) stars can now directly be compared to the theories that describe stellar mass loss. Using Atacama Large Millimeter/submillimeter Array (ALMA) high angular resolution (30 × 42 mas) observations, we have for the first time resolved stellar rotation of an AGB star, R Dor. We measure an angular rotation velocity of ωR sin i = (3.5 ± 0.3) × 10-9 rad s-1, which indicates a rotational velocity of |υrot sin i| = 1.0 ± 0.1 km s-1 at the stellar surface (R* = 31.2 mas at 214 GHz). The rotation axis projected on the plane of the sky has a position angle Φ = 7 ± 6°. We find that the rotation of R Dor is two orders of magnitude faster than expected for a solitary AGB star that will have lost most of its angular momentum. Its rotational velocity is consistent with angular momentum transfer from a close companion. As a companion has not been directly detected, we suggest R Dor has a low-mass, close-in companion. The rotational velocity approaches the critical velocity, set by the local sound speed in the extended envelope, and is thus expected to affect the mass-loss characteristics of R Dor.

Bringing the Visible Universe into Focus with Robo-AO

PubMed Central

Baranec, Christoph; Riddle, Reed; Law, Nicholas M.; Ramaprakash, A.N.; Tendulkar, Shriharsh P.; Bui, Khanh; Burse, Mahesh P.; Chordia, Pravin; Das, Hillol K.; Davis, Jack T.C.; Dekany, Richard G.; Kasliwal, Mansi M.; Kulkarni, Shrinivas R.; Morton, Timothy D.; Ofek, Eran O.; Punnadi, Sujit

2013-01-01

The angular resolution of ground-based optical telescopes is limited by the degrading effects of the turbulent atmosphere. In the absence of an atmosphere, the angular resolution of a typical telescope is limited only by diffraction, i.e., the wavelength of interest, λ, divided by the size of its primary mirror's aperture, D. For example, the Hubble Space Telescope (HST), with a 2.4-m primary mirror, has an angular resolution at visible wavelengths of ~0.04 arc seconds. The atmosphere is composed of air at slightly different temperatures, and therefore different indices of refraction, constantly mixing. Light waves are bent as they pass through the inhomogeneous atmosphere. When a telescope on the ground focuses these light waves, instantaneous images appear fragmented, changing as a function of time. As a result, long-exposure images acquired using ground-based telescopes - even telescopes with four times the diameter of HST - appear blurry and have an angular resolution of roughly 0.5 to 1.5 arc seconds at best. Astronomical adaptive-optics systems compensate for the effects of atmospheric turbulence. First, the shape of the incoming non-planar wave is determined using measurements of a nearby bright star by a wavefront sensor. Next, an element in the optical system, such as a deformable mirror, is commanded to correct the shape of the incoming light wave. Additional corrections are made at a rate sufficient to keep up with the dynamically changing atmosphere through which the telescope looks, ultimately producing diffraction-limited images. The fidelity of the wavefront sensor measurement is based upon how well the incoming light is spatially and temporally sampled1. Finer sampling requires brighter reference objects. While the brightest stars can serve as reference objects for imaging targets from several to tens of arc seconds away in the best conditions, most interesting astronomical targets do not have sufficiently bright stars nearby. One solution is to focus a high-power laser beam in the direction of the astronomical target to create an artificial reference of known shape, also known as a 'laser guide star'. The Robo-AO laser adaptive optics system2,3 employs a 10-W ultraviolet laser focused at a distance of 10 km to generate a laser guide star. Wavefront sensor measurements of the laser guide star drive the adaptive optics correction resulting in diffraction-limited images that have an angular resolution of ~0.1 arc seconds on a 1.5-m telescope. PMID:23426078

Bringing the visible universe into focus with Robo-AO.

PubMed

Baranec, Christoph; Riddle, Reed; Law, Nicholas M; Ramaprakash, A N; Tendulkar, Shriharsh P; Bui, Khanh; Burse, Mahesh P; Chordia, Pravin; Das, Hillol K; Davis, Jack T C; Dekany, Richard G; Kasliwal, Mansi M; Kulkarni, Shrinivas R; Morton, Timothy D; Ofek, Eran O; Punnadi, Sujit

2013-02-12

The angular resolution of ground-based optical telescopes is limited by the degrading effects of the turbulent atmosphere. In the absence of an atmosphere, the angular resolution of a typical telescope is limited only by diffraction, i.e., the wavelength of interest, λ, divided by the size of its primary mirror's aperture, D. For example, the Hubble Space Telescope (HST), with a 2.4-m primary mirror, has an angular resolution at visible wavelengths of ~0.04 arc seconds. The atmosphere is composed of air at slightly different temperatures, and therefore different indices of refraction, constantly mixing. Light waves are bent as they pass through the inhomogeneous atmosphere. When a telescope on the ground focuses these light waves, instantaneous images appear fragmented, changing as a function of time. As a result, long-exposure images acquired using ground-based telescopes--even telescopes with four times the diameter of HST--appear blurry and have an angular resolution of roughly 0.5 to 1.5 arc seconds at best. Astronomical adaptive-optics systems compensate for the effects of atmospheric turbulence. First, the shape of the incoming non-planar wave is determined using measurements of a nearby bright star by a wavefront sensor. Next, an element in the optical system, such as a deformable mirror, is commanded to correct the shape of the incoming light wave. Additional corrections are made at a rate sufficient to keep up with the dynamically changing atmosphere through which the telescope looks, ultimately producing diffraction-limited images. The fidelity of the wavefront sensor measurement is based upon how well the incoming light is spatially and temporally sampled. Finer sampling requires brighter reference objects. While the brightest stars can serve as reference objects for imaging targets from several to tens of arc seconds away in the best conditions, most interesting astronomical targets do not have sufficiently bright stars nearby. One solution is to focus a high-power laser beam in the direction of the astronomical target to create an artificial reference of known shape, also known as a 'laser guide star'. The Robo-AO laser adaptive optics system, employs a 10-W ultraviolet laser focused at a distance of 10 km to generate a laser guide star. Wavefront sensor measurements of the laser guide star drive the adaptive optics correction resulting in diffraction-limited images that have an angular resolution of ~0.1 arc seconds on a 1.5-m telescope.

A combined Compton and coded-aperture telescope for medium-energy gamma-ray astrophysics

NASA Astrophysics Data System (ADS)

Galloway, Michelle; Zoglauer, Andreas; Boggs, Steven E.; Amman, Mark

2018-06-01

A future mission in medium-energy gamma-ray astrophysics would allow for many scientific advancements, such as a possible explanation for the excess positron emission from the Galactic center, a better understanding of nucleosynthesis and explosion mechanisms in Type Ia supernovae, and a look at the physical forces at play in compact objects such as black holes and neutron stars. Additionally, further observation in this energy regime would significantly extend the search parameter space for low-mass dark matter. In order to achieve these objectives, an instrument with good energy resolution, good angular resolution, and high sensitivity is required. In this paper we present the design and simulation of a Compton telescope consisting of cubic-centimeter cadmium zinc telluride detectors as absorbers behind a silicon tracker with the addition of a passive coded mask. The goal of the design was to create a very sensitive instrument that is capable of high angular resolution. The simulated telescope achieved energy resolutions of 1.68% FWHM at 511 keV and 1.11% at 1809 keV, on-axis angular resolutions in Compton mode of 2.63° FWHM at 511 keV and 1.30° FWHM at 1809 keV, and is capable of resolving sources to at least 0.2° at lower energies with the use of the coded mask. An initial assessment of the instrument in Compton-imaging mode yields an effective area of 183 cm2 at 511 keV and an anticipated all-sky sensitivity of 3.6 × 10-6 photons cm-2 s-1 for a broadened 511 keV source over a two-year observation time. Additionally, combining a coded mask with a Compton imager to improve point-source localization for positron detection has been demonstrated.

The Space Infrared Interferometric Telescope (SPIRIT): High-resolution Imaging and Spectroscopy in the Far-infrared

NASA Technical Reports Server (NTRS)

Leisawitz, D,; Baker, G.; Barger, A.; Benford, D.; Blain, A; Boyle, R.; Broderick, R.; Budinoff, J.; Carpenter, J.; Caverly, R.;

Development of Global 30m Resolution Water Body Map with Permanent/Temporal Water Body Separation Using Satellite Acquired Images of Landsat GLS Datasets

NASA Astrophysics Data System (ADS)

Ikeshima, D.; Yamazaki, D.; Yoshikawa, S.; Kanae, S.

2015-12-01

The specification of worldwide water body distribution is important for discovering hydrological cycle. Global 3-second Water Body Map (G3WBM) is a global scale map, which indicates the distribution of water body in 90m resolutions (http://hydro.iis.u-tokyo.ac.jp/~yamadai/G3WBM/index.html). This dataset was mainly built to identify the width of river channels, which is one of major uncertainties of continental-scale river hydrodynamics models. To survey the true width of the river channel, this water body map distinguish Permanent Water Body from Temporary Water Body, which means separating river channel and flood plain. However, rivers with narrower width, which is a major case in usual river, could not be observed in this map. To overcome this problem, updating the algorithm of G3WBM and enhancing the resolutions to 30m is the goal of this research. Although this 30m-resolution water body map uses similar algorithm as G3WBM, there are many technical issues attributed to relatively high resolutions. Those are such as lack of same high-resolution digital elevation map, or contamination problem of sub-pixel scale object on satellite acquired image, or invisibility of well-vegetated water body such as swamp. To manage those issues, this research used more than 30,000 satellite images of Landsat Global Land Survey (GLS), and lately distributed topography data of Shuttle Rader Topography Mission (SRTM) 1 arc-second (30m) digital elevation map. Also the effect of aerosol, which would scatter the sun reflectance and disturb the acquired result image, was considered. Due to these revises, the global water body distribution was established in more precise resolution.

The Advanced Pair Telescope (APT) Mission Concept

NASA Technical Reports Server (NTRS)

Hunter, Stanley; Buckley, James H.

2008-01-01

We present a mission concept for the Advanced Pair Telescope (APT), a high-energy gamma-ray instrument with an order of magnitude improvement in sensitivity, 6 sr field of view, and angular resolution a factor of 3-10 times that of GLAST. With its very wide instantaneous field-of-view and large effective area, this instrument would be capable of detecting GRBs at very large redshifts, would enable a very high resolution study of SNRs and PWN, and could provide hour-scale temporal resolution of transients from many AGN and galactic sources. The APT instrument will consist of a Xe time-projection-chamber tracker that bridges the energy regime between Compton scattering and pair production and will provide an unprecedented improvement in angular resolution; a thick scintillating-fiber trackerlcalorimeter that will provide sensitivity and energy resolution to higher energies and will possess a factor of 10 improvement in geometric factor over GLAST; and an anticoincidence detector using scintillator-tiles to reject charged particles. After the anticipated 10-years of GLAST operation , the APT instrument would provide continued coverage of the critial high-energy gamma-ray band (between 30 MeV to 100 GeV), providing an essential component of broad-band multiwavelength studies of the high-energy universe.

Combining and Comparing Astrometric Data from Different Epochs: A Case Study with Hipparcos and Nano-JASMINE

NASA Astrophysics Data System (ADS)

Michalik, D.; Lindegren, L.; Hobbs, D.; Lammers, U.; Yamada, Y.

2012-09-01

The Hipparcos mission (1989-1993) resulted in the first space-based stellar catalogue including measurements of positions, parallaxes and annual proper motions accurate to about one milli-arcsecond. More space astrometry missions will follow in the near future. The ultra-small Japanese mission Nano-JASMINE (launch in late 2013) will determine positions and annual proper motions with some milli-arcsecond accuracy. In mid 2013 the next-generation ESA mission Gaia will deliver some tens of micro-arcsecond accurate astrometric parameters. Until the final Gaia catalogue is published in early 2020 the best way of improving proper motion values is the combination of positions from different missions separated by long time intervals. Rather than comparing positions from separately reduced catalogues, we propose an optimal method to combine the information from the different data sets by making a joint astrometric solution. This allows to obtain good results even when each data set alone is insufficient for an accurate reduction. We demonstrate our method by combining Hipparcos and simulated Nano-JASMINE data in a joint solution. We show a significant improvement over the conventional catalogue combination.

Angular Resolution of an EAS Array for Gamma Ray Astronomy at Energies Greater Than 5 x 10 (13) Ev

NASA Technical Reports Server (NTRS)

Apte, A. R.; Gopalakrishnan, N. V.; Tonwar, S. C.; Uma, V.

1985-01-01

A 24 detector extensive air shower array is being operated at Ootacamund (2300 m altitude, 11.4 deg N latitude) in southern India for a study of arrival directions of showers of energies greater than 5 x 10 to the 13th power eV. Various configurations of the array of detectors have been used to estimate the accuracy in determination of arrival angle of showers with such an array. These studies show that it is possible to achieve an angular resolution of better than 2 deg with the Ooty array for search for point sources of Cosmic gamma rays at energies above 5 x 10 to the 13th power eV.

Curved position-sensitive detector for X-ray crystallography

NASA Astrophysics Data System (ADS)

Izumi, T.

1980-11-01

A new curved position-sensitive proportional detector has been constructed for X-ray crystallography. A very hard steel wire 0.2 mm in diameter was used as a single anode wire. It was bent to a radius of 6.5 cm and was suspended elastically in a wide 160° 2θ angular aperture. An amplifier and ADC-per-cathode strip system was made in order to encode the position. The spatial resolution is better than 0.37 mm (fwhm) along the curved anode wire, and this value corresponds to an angular resolution of 0.28° in 2θ. It is shown that a thick hard anode wire is quite suitable for use as a curved position-sensitive detector.

The Advanced Gamma-ray Imaging System (AGIS): Extragalactic Science

NASA Astrophysics Data System (ADS)

Coppi, Paolo S.; Extragalactic Science Working Group; AGIS Collaboration

2010-03-01

The Advanced Gamma-ray Imaging System (AGIS), a proposed next-generation array of Cherenkov telescopes, will provide an unprecedented view of the high energy universe. We discuss how AGIS, with its larger effective area, improved angular resolution, lower threshold, and an order of magnitude increase in sensitivity, impacts the extragalactic science possible in the very high energy domain. Likely source classes detectable by AGIS include AGN, GRBs, clusters, star-forming galaxies, and possibly the cascade radiation surrounding powerful cosmic accelerators. AGIS should see many of the sources discovered by Fermi. With its better sensitivity and angular resolution, AGIS then becomes a key instrument for identifying and characterizing Fermi survey sources, the majority of which will have limited Fermi photon statistics and localizations.

Focal Plane Detectors for the Advanced Gamma-Ray Imaging System (AGIS)

NASA Astrophysics Data System (ADS)

Wagner, R. G.; Byrum, K.; Drake, G.; Funk, S.; Otte, N.; Smith, A.; Tajima, H.; Williams, D.

2009-05-01

The Advanced Gamma-Ray Imaging System (AGIS) is a concept for the next generation observatory in ground-based very high energy gamma-ray astronomy. It is being designed to achieve a significant improvement in sensitivity compared to current Imaging Air Cherenkov Telescope (IACT) Arrays. One of the main requirements in order that AGIS fulfills this goal will be to achieve higher angular resolution than current IACTs. Simulations show that a substantial improvement in angular resolution may be achieved if the pixel size is reduced to 0.05 deg, i.e. two to three times smaller than for current IACT cameras. Here we present results from testing of alternatives being considered for AGIS, including both silicon photomultipliers (SiPMs) and multi-anode photomultipliers (MAPMTs).

High resolution energy-angle correlation measurement of hard x rays from laser-Thomson backscattering.

PubMed

Jochmann, A; Irman, A; Bussmann, M; Couperus, J P; Cowan, T E; Debus, A D; Kuntzsch, M; Ledingham, K W D; Lehnert, U; Sauerbrey, R; Schlenvoigt, H P; Seipt, D; Stöhlker, Th; Thorn, D B; Trotsenko, S; Wagner, A; Schramm, U

2013-09-13

Thomson backscattering of intense laser pulses from relativistic electrons not only allows for the generation of bright x-ray pulses but also for the investigation of the complex particle dynamics at the interaction point. For this purpose a complete spectral characterization of a Thomson source powered by a compact linear electron accelerator is performed with unprecedented angular and energy resolution. A rigorous statistical analysis comparing experimental data to 3D simulations enables, e.g., the extraction of the angular distribution of electrons with 1.5% accuracy and, in total, provides predictive capability for the future high brightness hard x-ray source PHOENIX (photon electron collider for narrow bandwidth intense x rays) and potential gamma-ray sources.

The Circumstellar Environment of Low Mass Star Forming Regions

NASA Technical Reports Server (NTRS)

Butner, Harold M.

1997-01-01

We have obtained the complete SED from 10 microns out to 1.3 mm for all of our sources. We have the FIR imaging data, processed to reveal the maximum angular resolution possible, which allows us to model the disk. To model the disk, we have high resolution millimeter interferometry data.

VizieR Online Data Catalog: APEX CO and HI observations of Lupus I (Gaczkowski+, 2017)

NASA Astrophysics Data System (ADS)

Gaczkowski, B.; Roccatagliata, V.; Flaischlen, S.; Kroell, D.; Krause, M. G. H. Burkert A.; Diehl, R.; Fierlinger, K.; Ngoumou, J.; Preibisch, T.

2017-11-01

The FITS files contain the data cubes corresponding to the 13C and C18O(3-2) lines. They were taken using the Atacama Pathfinder EXperiment (APEX) telescope, with an angular resolution of 30" and a velocity resolution of 0.1km/s. (2 data files).

The ALMA Phasing System: A Beamforming Capability for Ultra-high-resolution Science at (Sub)Millimeter Wavelengths

NASA Astrophysics Data System (ADS)

Matthews, L. D.; Crew, G. B.; Doeleman, S. S.; Lacasse, R.; Saez, A. F.; Alef, W.; Akiyama, K.; Amestica, R.; Anderson, J. M.; Barkats, D. A.; Baudry, A.; Broguière, D.; Escoffier, R.; Fish, V. L.; Greenberg, J.; Hecht, M. H.; Hiriart, R.; Hirota, A.; Honma, M.; Ho, P. T. P.; Impellizzeri, C. M. V.; Inoue, M.; Kohno, Y.; Lopez, B.; Martí-Vidal, I.; Messias, H.; Meyer-Zhao, Z.; Mora-Klein, M.; Nagar, N. M.; Nishioka, H.; Oyama, T.; Pankratius, V.; Perez, J.; Phillips, N.; Pradel, N.; Rottmann, H.; Roy, A. L.; Ruszczyk, C. A.; Shillue, B.; Suzuki, S.; Treacy, R.

2018-01-01

The Atacama Millimeter/submillimeter Array (ALMA) Phasing Project (APP) has developed and deployed the hardware and software necessary to coherently sum the signals of individual ALMA antennas and record the aggregate sum in Very Long Baseline Interferometry (VLBI) Data Exchange Format. These beamforming capabilities allow the ALMA array to collectively function as the equivalent of a single large aperture and participate in global VLBI arrays. The inclusion of phased ALMA in current VLBI networks operating at (sub)millimeter wavelengths provides an order of magnitude improvement in sensitivity, as well as enhancements in u–v coverage and north–south angular resolution. The availability of a phased ALMA enables a wide range of new ultra-high angular resolution science applications, including the resolution of supermassive black holes on event horizon scales and studies of the launch and collimation of astrophysical jets. It also provides a high-sensitivity aperture that may be used for investigations such as pulsar searches at high frequencies. This paper provides an overview of the ALMA Phasing System design, implementation, and performance characteristics.

VLBA Observations of Low Luminosity Flat Spectrum Radio Galaxies and BL Lac Objects: Polarisation Properties

NASA Astrophysics Data System (ADS)

Bondi, M.; Dallacasa, D.; Stanghellini, C.; Marchã, M. J. M.

We obtained two-epoch VLBA observations at 5 GHz of a list of radio galaxies drawn from the 200 mJy sample (Marcha et al. 1996). The objects selected for milli-arcsecond scale observations are classified, on the basis of their optical spectroscopic and polarimetric properties, as BL Lac objects, normal weak line radio galaxies, broad line radio galaxies, and transition objects (those with intermediate properties). We present preliminary results on the radio polarization properties, on the milli-arcsecond scale, of objects with different optical properties and discuss structural variations detected from the two epochs.

Carma 1 CM Line Survey of Orion-Kl

NASA Astrophysics Data System (ADS)

Friedel, Douglas; Looney, Leslie; Corby, Joanna F.; Remijan, Anthony

2015-06-01

We have conducted the first 1 cm (27-35 GHz) line survey of the Orion-KL region by an array. With a primary beam of ˜4.5 arcminutes, the survey looks at a region ˜166,000 AU (0.56 pc) across. The data have a resolution of ˜6 arcseconds on the sky and 97.6 kHz(1.07-0.84 km/s) in frequency. This region of frequency space is much less crowded than at 3mm or 1mm frequencies and contains the fundamental transitions of several complex molecular species, allowing us to probe the largest extent of the molecular emission. We present the initial results, and comparison to 3mm results, from several species including, dimethyl ether [(CH_3)_2O], ethyl cyanide [C_2H_5CN], acetone [(CH_3)_2CO], SO, and SO_2.

Thermal Evolution and Composition of the July 2009 Jupiter Impact Site from 7-25 Micron Imaging and Spectroscopy

NASA Astrophysics Data System (ADS)

Fletcher, L. N.; Orton, G. S.; Mousis, O.; de Pater, I.; Hammel, H. B.; Golisch, W.; Edwards, M.; Yanamandra-Fisher, P. A.; Fisher, B.; Greene, Z.; Lai, S.; Otto, E.; Reshetnikov, N.; Sanchez-Lavega, A.; Simon-Miller, A. A.; Hueso, R.; Perez-Hoyos, S.

2009-12-01

We present analysis of thermal-infrared imaging and spectroscopy of the impact site near the south polar region of Jupiter (see Orton et al., AGU 2009). Enhanced thermal emission was first detected on July 20 2009 in 7-25 micron imaging from the MIRSI instrument on NASA’s IRTF. These observations, just two rotations after the impact, indicated the localised, high-temperature thermal signature of the ejecta field, coincident with the location of high-altitude particulate debris observed in the near-IR and visible. The impact feature was most visible in the 9-11 micron range, suggestive of enhanced emission from hydrocarbons and ammonia gas in the lower stratosphere. Subsequent thermal imaging of the impact region reveals the radiative cooling of the impact site and the changing morphology due to the redistribution of material by Jupiter’s zonal and meridional wind field. We acquired Gemini-N/Michelle imaging on July 22, Gemini-S/TReCS imaging on July 24 and August 5 and 9, and an extensive campaign of VLT/VISIR imaging on July 24, 26 and August 5, 10, 15, 16, at which point (4 weeks after the impact) the thermal signature could no longer be reliably distinguished, even with sub-arcsecond diffraction-limited angular resolution. Tropospheric and stratospheric temperatures and aerosol opacity are derived via optimal estimation retrievals (Fletcher et al. 2009, Icarus, 200, p154). Enhancement of hydrocarbons and gaseous ammonia are determined via iterative forward modelling, aided by spectral observations obtained with the slit aligned east-west through the impact feature from Gemini-S/TReCS (July 24) and VLT/VISIR (July 26, August 12-13). Low-resolution N-band (8-13 microns) Gemini-S/TReCS spectra confirm the enhanced emission over a broad range of wavelengths; Q-band (17-25 micron) spectra are used to study upper tropospheric temperatures in the aftermath of the collision and the rate of radiative cooling. VLT/VISIR spectra provide higher spectral resolutions in narrow wavelength ranges near 8.02, 10.49, 11.31, 11.60, 12.24 and 13.36 microns, sensitive to NH3, CH4 and hydrocarbon emission features. Iterative forward modelling of these spectra will be used to deduce the unique chemical composition and the three-dimensional thermal structure of the impact site, compared with the ‘unperturbed’ atmosphere at the same latitude. * Fletcher is supported by an appointment to the NASA Postdoctoral Program at the Jet Propulsion Laboratory/California Institute of Technology, administered by Oak Ridge Associated Universities through a contract with NASA. We wish to acknowledge the invaluable contributions of the support staff at IRTF, VLT and Gemini.

Space Mirror Alignment System

NASA Technical Reports Server (NTRS)

Jau, Bruno M.; McKinney, Colin; Smythe, Robert F.; Palmer, Dean L.

2011-01-01

An optical alignment mirror mechanism (AMM) has been developed with angular positioning accuracy of +/-0.2 arcsec. This requires the mirror s linear positioning actuators to have positioning resolutions of +/-112 nm to enable the mirror to meet the angular tip/tilt accuracy requirement. Demonstrated capabilities are 0.1 arc-sec angular mirror positioning accuracy, which translates into linear positioning resolutions at the actuator of 50 nm. The mechanism consists of a structure with sets of cross-directional flexures that enable the mirror s tip and tilt motion, a mirror with its kinematic mount, and two linear actuators. An actuator comprises a brushless DC motor, a linear ball screw, and a piezoelectric brake that holds the mirror s position while the unit is unpowered. An interferometric linear position sensor senses the actuator s position. The AMMs were developed for an Astrometric Beam Combiner (ABC) optical bench, which is part of an interferometer development. Custom electronics were also developed to accommodate the presence of multiple AMMs within the ABC and provide a compact, all-in-one solution to power and control the AMMs.

High resolution gamma-ray spectroscopy and the fascinating angular momentum realm of the atomic nucleus

NASA Astrophysics Data System (ADS)

Riley, M. A.; Simpson, J.; Paul, E. S.

2016-12-01

In 1974 Aage Bohr and Ben Mottelson predicted the different ‘phases’ that may be expected in deformed nuclei as a function of increasing angular momentum and excitation energy all the way up to the fission limit. While admitting their picture was highly conjectural they confidently stated ‘...with the ingenious experimental approaches that are being developed, we may look forward with excitement to the detailed spectroscopic studies that will illuminate the behaviour of the spinning quantised nucleus’. High resolution gamma-ray spectroscopy has indeed been a major tool in studying the structure of atomic nuclei and has witnessed numerous significant advances over the last four decades. This article will select highlights from investigations at the Niels Bohr Institute, Denmark, and Daresbury Laboratory, UK, in the late 1970s and early 1980s, some of which have continued at other national laboratories in Europe and the USA to the present day. These studies illustrate the remarkable diversity of phenomena and symmetries exhibited by nuclei in the angular momentum-excitation energy plane that continue to surprise and fascinate scientists.

The Atacama Cosmology Telescope: The Polarization-Sensitive ACTPol Instrument

DOE PAGES

Thornton, R. J.; Ade, P. A. R.; Aiola, S.; ...

2016-12-09

The Atacama Cosmology Telescope (ACT) makes high angular resolution measurements of anisotropies in the Cosmic Microwave Background (CMB) at millimeter wavelengths. We describe ACTPol, an upgraded receiver for ACT, which uses feedhorn-coupled, polarization-sensitive detector arrays, a 3° field of view, 100 mK cryogenics with continuous cooling, and meta material antireflection coatings. ACTPol comprises three arrays with separate cryogenic optics: two arrays at a central frequency of 148 GHz and one array operating simultaneously at both 97 GHz and 148 GHz. The combined instrument sensitivity, angular resolution, and sky coverage are optimized for measuring angular power spectra, clusters via the thermalmore » Sunyaev–Zel'dovich (SZ) and kinetic SZ signals, and CMB lensing due to large-scale structure. The receiver was commissioned with its first 148 GHz array in 2013, observed with both 148 GHz arrays in 2014, and has recently completed its first full season of operations with the full suite of three arrays. This paper provides an overview of the design and initial performance of the receiver and related systems.« less

THE ATACAMA COSMOLOGY TELESCOPE: THE POLARIZATION-SENSITIVE ACTPol INSTRUMENT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thornton, R. J.; Ade, P. A. R.; Aiola, S.

The Atacama Cosmology Telescope (ACT) makes high angular resolution measurements of anisotropies in the Cosmic Microwave Background (CMB) at millimeter wavelengths. We describe ACTPol, an upgraded receiver for ACT, which uses feedhorn-coupled, polarization-sensitive detector arrays, a 3° field of view, 100 mK cryogenics with continuous cooling, and meta material antireflection coatings. ACTPol comprises three arrays with separate cryogenic optics: two arrays at a central frequency of 148 GHz and one array operating simultaneously at both 97 GHz and 148 GHz. The combined instrument sensitivity, angular resolution, and sky coverage are optimized for measuring angular power spectra, clusters via the thermalmore » Sunyaev–Zel’dovich (SZ) and kinetic SZ signals, and CMB lensing due to large-scale structure. The receiver was commissioned with its first 148 GHz array in 2013, observed with both 148 GHz arrays in 2014, and has recently completed its first full season of operations with the full suite of three arrays. This paper provides an overview of the design and initial performance of the receiver and related systems.« less

The Atacama Cosmology Telescope: The Polarization-Sensitive ACTPol Instrument

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thornton, R. J.; Ade, P. A. R.; Aiola, S.

The Atacama Cosmology Telescope (ACT) makes high angular resolution measurements of anisotropies in the Cosmic Microwave Background (CMB) at millimeter wavelengths. We describe ACTPol, an upgraded receiver for ACT, which uses feedhorn-coupled, polarization-sensitive detector arrays, a 3° field of view, 100 mK cryogenics with continuous cooling, and meta material antireflection coatings. ACTPol comprises three arrays with separate cryogenic optics: two arrays at a central frequency of 148 GHz and one array operating simultaneously at both 97 GHz and 148 GHz. The combined instrument sensitivity, angular resolution, and sky coverage are optimized for measuring angular power spectra, clusters via the thermalmore » Sunyaev–Zel'dovich (SZ) and kinetic SZ signals, and CMB lensing due to large-scale structure. The receiver was commissioned with its first 148 GHz array in 2013, observed with both 148 GHz arrays in 2014, and has recently completed its first full season of operations with the full suite of three arrays. This paper provides an overview of the design and initial performance of the receiver and related systems.« less

A Detailed Comparison of Multidimensional Boltzmann Neutrino Transport Methods in Core-collapse Supernovae

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richers, Sherwood; Nagakura, Hiroki; Ott, Christian D.

The mechanism driving core-collapse supernovae is sensitive to the interplay between matter and neutrino radiation. However, neutrino radiation transport is very difficult to simulate, and several radiation transport methods of varying levels of approximation are available. We carefully compare for the first time in multiple spatial dimensions the discrete ordinates (DO) code of Nagakura, Yamada, and Sumiyoshi and the Monte Carlo (MC) code Sedonu, under the assumptions of a static fluid background, flat spacetime, elastic scattering, and full special relativity. We find remarkably good agreement in all spectral, angular, and fluid interaction quantities, lending confidence to both methods. The DOmore » method excels in determining the heating and cooling rates in the optically thick region. The MC method predicts sharper angular features due to the effectively infinite angular resolution, but struggles to drive down noise in quantities where subtractive cancellation is prevalent, such as the net gain in the protoneutron star and off-diagonal components of the Eddington tensor. We also find that errors in the angular moments of the distribution functions induced by neglecting velocity dependence are subdominant to those from limited momentum-space resolution. We briefly compare directly computed second angular moments to those predicted by popular algebraic two-moment closures, and we find that the errors from the approximate closures are comparable to the difference between the DO and MC methods. Included in this work is an improved Sedonu code, which now implements a fully special relativistic, time-independent version of the grid-agnostic MC random walk approximation.« less

A Detailed Comparison of Multidimensional Boltzmann Neutrino Transport Methods in Core-collapse Supernovae

DOE PAGES

Richers, Sherwood; Nagakura, Hiroki; Ott, Christian D.; ...

2017-10-03

The mechanism driving core-collapse supernovae is sensitive to the interplay between matter and neutrino radiation. However, neutrino radiation transport is very difficult to simulate, and several radiation transport methods of varying levels of approximation are available. In this paper, we carefully compare for the first time in multiple spatial dimensions the discrete ordinates (DO) code of Nagakura, Yamada, and Sumiyoshi and the Monte Carlo (MC) code Sedonu, under the assumptions of a static fluid background, flat spacetime, elastic scattering, and full special relativity. We find remarkably good agreement in all spectral, angular, and fluid interaction quantities, lending confidence to bothmore » methods. The DO method excels in determining the heating and cooling rates in the optically thick region. The MC method predicts sharper angular features due to the effectively infinite angular resolution, but struggles to drive down noise in quantities where subtractive cancellation is prevalent, such as the net gain in the protoneutron star and off-diagonal components of the Eddington tensor. We also find that errors in the angular moments of the distribution functions induced by neglecting velocity dependence are subdominant to those from limited momentum-space resolution. We briefly compare directly computed second angular moments to those predicted by popular algebraic two-moment closures, and we find that the errors from the approximate closures are comparable to the difference between the DO and MC methods. Finally, included in this work is an improved Sedonu code, which now implements a fully special relativistic, time-independent version of the grid-agnostic MC random walk approximation.« less

A Detailed Comparison of Multidimensional Boltzmann Neutrino Transport Methods in Core-collapse Supernovae

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richers, Sherwood; Nagakura, Hiroki; Ott, Christian D.

The mechanism driving core-collapse supernovae is sensitive to the interplay between matter and neutrino radiation. However, neutrino radiation transport is very difficult to simulate, and several radiation transport methods of varying levels of approximation are available. In this paper, we carefully compare for the first time in multiple spatial dimensions the discrete ordinates (DO) code of Nagakura, Yamada, and Sumiyoshi and the Monte Carlo (MC) code Sedonu, under the assumptions of a static fluid background, flat spacetime, elastic scattering, and full special relativity. We find remarkably good agreement in all spectral, angular, and fluid interaction quantities, lending confidence to bothmore » methods. The DO method excels in determining the heating and cooling rates in the optically thick region. The MC method predicts sharper angular features due to the effectively infinite angular resolution, but struggles to drive down noise in quantities where subtractive cancellation is prevalent, such as the net gain in the protoneutron star and off-diagonal components of the Eddington tensor. We also find that errors in the angular moments of the distribution functions induced by neglecting velocity dependence are subdominant to those from limited momentum-space resolution. We briefly compare directly computed second angular moments to those predicted by popular algebraic two-moment closures, and we find that the errors from the approximate closures are comparable to the difference between the DO and MC methods. Finally, included in this work is an improved Sedonu code, which now implements a fully special relativistic, time-independent version of the grid-agnostic MC random walk approximation.« less

A POD reduced order model for resolving angular direction in neutron/photon transport problems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buchan, A.G., E-mail: andrew.buchan@imperial.ac.uk; Calloo, A.A.; Goffin, M.G.

2015-09-01

This article presents the first Reduced Order Model (ROM) that efficiently resolves the angular dimension of the time independent, mono-energetic Boltzmann Transport Equation (BTE). It is based on Proper Orthogonal Decomposition (POD) and uses the method of snapshots to form optimal basis functions for resolving the direction of particle travel in neutron/photon transport problems. A unique element of this work is that the snapshots are formed from the vector of angular coefficients relating to a high resolution expansion of the BTE's angular dimension. In addition, the individual snapshots are not recorded through time, as in standard POD, but instead theymore » are recorded through space. In essence this work swaps the roles of the dimensions space and time in standard POD methods, with angle and space respectively. It is shown here how the POD model can be formed from the POD basis functions in a highly efficient manner. The model is then applied to two radiation problems; one involving the transport of radiation through a shield and the other through an infinite array of pins. Both problems are selected for their complex angular flux solutions in order to provide an appropriate demonstration of the model's capabilities. It is shown that the POD model can resolve these fluxes efficiently and accurately. In comparison to high resolution models this POD model can reduce the size of a problem by up to two orders of magnitude without compromising accuracy. Solving times are also reduced by similar factors.« less

A Detailed Comparison of Multidimensional Boltzmann Neutrino Transport Methods in Core-collapse Supernovae

NASA Astrophysics Data System (ADS)

Richers, Sherwood; Nagakura, Hiroki; Ott, Christian D.; Dolence, Joshua; Sumiyoshi, Kohsuke; Yamada, Shoichi

2017-10-01

The mechanism driving core-collapse supernovae is sensitive to the interplay between matter and neutrino radiation. However, neutrino radiation transport is very difficult to simulate, and several radiation transport methods of varying levels of approximation are available. We carefully compare for the first time in multiple spatial dimensions the discrete ordinates (DO) code of Nagakura, Yamada, and Sumiyoshi and the Monte Carlo (MC) code Sedonu, under the assumptions of a static fluid background, flat spacetime, elastic scattering, and full special relativity. We find remarkably good agreement in all spectral, angular, and fluid interaction quantities, lending confidence to both methods. The DO method excels in determining the heating and cooling rates in the optically thick region. The MC method predicts sharper angular features due to the effectively infinite angular resolution, but struggles to drive down noise in quantities where subtractive cancellation is prevalent, such as the net gain in the protoneutron star and off-diagonal components of the Eddington tensor. We also find that errors in the angular moments of the distribution functions induced by neglecting velocity dependence are subdominant to those from limited momentum-space resolution. We briefly compare directly computed second angular moments to those predicted by popular algebraic two-moment closures, and we find that the errors from the approximate closures are comparable to the difference between the DO and MC methods. Included in this work is an improved Sedonu code, which now implements a fully special relativistic, time-independent version of the grid-agnostic MC random walk approximation.

Control of Rotational Energy and Angular Momentum Orientation with an Optical Centrifuge

NASA Astrophysics Data System (ADS)

Ogden, Hannah M.; Murray, Matthew J.; Mullin, Amy S.

2017-04-01

We use an optical centrifuge to trap and spin molecules to an angular frequency of 30 THz with oriented angular momenta and extremely high rotational energy and then investigate their subsequent collision dynamics with transient high resolution IR spectroscopy. The optical centrifuge is formed by combining oppositely-chirped pulses of 800 nm light, and overlapping them spatially and temporally. Polarization-sensitive Doppler-broadened line profiles characterize the anisotropic kinetic energy release of the super rotor molecules, showing that they behave like molecular gyroscopes. Studies are reported for collisions of CO2 super rotors with CO2, He and Ar. These studies reveal how mass, velocity and rotational adiabaticity impact the angular momentum relaxation and reorientation. Quantum scattering calculations provide insight into the J-specific collision cross sections that control the relaxation. NSF-CHE 105 8721.

Resolving the Inner Arcsecond of the RY Tau Jet with HST

NASA Astrophysics Data System (ADS)

Skinner, Stephen L.; Schneider, P. Christian; Audard, Marc; Güdel, Manuel

2018-03-01

Faint X-ray emission from hot plasma (T x > 106 K) has been detected extending outward a few arcseconds along the optically delineated jets of some classical T Tauri stars including RY Tau. The mechanism and location where the jets are heated to X-ray temperatures are unknown. We present high spatial resolution Hubble Space Telescope (HST) far-ultraviolet long-slit observations of RY Tau with the slit aligned along the jet. The primary objective was to search for C IV emission from warm plasma at T C IV ∼ 105 K within the inner jet (<1″) that cannot be fully resolved by X-ray telescopes. Spatially resolved C IV emission is detected in the blueshifted jet extending outward from the star to 1″ and in the redshifted jet out to 0.″5. C IV line centroid shifts give a radial velocity in the blueshifted jet of ‑136 ± 10 km s‑1 at an offset of 0.″29 (39 au) and deceleration outward is detected. The deprojected jet speed is subject to uncertainties in the jet inclination, but values ≳200 km s‑1 are likely. The mass-loss rate in the blueshifted jet is at least {\\dot{M}}jet,{blue}}=2.3× {10}-9 M ⊙ yr‑1, consistent with optical determinations. We use the HST data along with optically determined jet morphology to place meaningful constraints on candidate jet-heating models including a hot-launch model in which the jet is heated near the base to X-ray temperatures by an unspecified (but probably magnetic) process, and downstream heating from shocks or a putative jet magnetic field.

Digging deep into the ULIRG phenomenon: When radio beats dust

NASA Astrophysics Data System (ADS)

Pérez-Torres, M. A.

2013-05-01

Luminous and Ultra-Luminous Infrared Galaxies (U/LIRGs) do also radiate copious amounts of radio emission, both thermal (free-free) and non-thermal (mainly synchrotron). This is very handy since, unlike optical and infra-red observations, radio is not obscured by the ubiquitous dust present in U/LIRGs, which allows a direct view of the ongoing activity in the hearts of those prolific star-forming galaxies. Here, I first justify the need for this high-angular resolution radio studies of local U/LIRGs, discuss the energy budget and the magnetic field, as well as IC and synchrotron losses in U/LIRGs, and present some selected results obtained by our team on high-angular resolution radio continuum studies of U/LIRGs. Among other results, I show the impressive discovery of an extremely prolific supernova factory in the central ˜150 pc of the galaxy Arp 299-A (D = 45 Mpc) and the monitoring of a large number of very compact radio sources in it, the detection and precise location of the long-sought AGN in Arp 299-A. A movie summarizing those results can be found in http://www.iaa.es/ torres/research/arp299a.html. All those results demonstrate that very-high angular resolution studies of nearby U/LIRGs are of high relevance for the comprehension of both local and high-z starbursting galaxies.

The Advanced Energetic Pair Telescope (AdEPT}: A Future Medium-Energy Gamma-Ray Balloon (and Explorer?) Mission

NASA Technical Reports Server (NTRS)

Hunter, Stanley D.

2011-01-01

Gamma-ray astrophysics probes the highest energy, exotic phenomena in astrophysics. In the medium-energy regime, 0.1-200 MeV, many astrophysical objects exhibit unique and transitory behavior such as the transition from electron dominated to hadron dominated processes, spectral breaks, bursts, and flares. Medium-energy gamma-ray imaging however, continues to be a major challenge particularly because of high background, low effective area, and low source intensities. The sensitivity and angular resolution required to address these challenges requires a leap in technology. The Advance Energetic Pair Telescope (AdEPT) being developed at GSFC is designed to image gamma rays above 5 MeV via pair production with angular resolution of 1-10 deg. In addition AdEPT will, for the first time, provide high polarization sensitivity in this energy range. This performance is achieved by reducing the effective area in favor of enhanced angular resolution through the use of a low-density gaseous conversion medium. AdEPT is based on the Three-Dimensional Track Imager (3-DTI) technology that combines a large volume Negative Ion Time Projection Chamber (NITPC) with 2-D Micro-Well Detector (MWD) readout. I will review the major science topics addressable with medium-energy gamma-rays and discuss the current status of the AdEPT technology, a proposed balloon instrument, and the design of a future satellite mission.

Linear Transforms for Fourier Data on the Sphere: Application to High Angular Resolution Diffusion MRI of the Brain

PubMed Central

Haldar, Justin P.; Leahy, Richard M.

2013-01-01

This paper presents a novel family of linear transforms that can be applied to data collected from the surface of a 2-sphere in three-dimensional Fourier space. This family of transforms generalizes the previously-proposed Funk-Radon Transform (FRT), which was originally developed for estimating the orientations of white matter fibers in the central nervous system from diffusion magnetic resonance imaging data. The new family of transforms is characterized theoretically, and efficient numerical implementations of the transforms are presented for the case when the measured data is represented in a basis of spherical harmonics. After these general discussions, attention is focused on a particular new transform from this family that we name the Funk-Radon and Cosine Transform (FRACT). Based on theoretical arguments, it is expected that FRACT-based analysis should yield significantly better orientation information (e.g., improved accuracy and higher angular resolution) than FRT-based analysis, while maintaining the strong characterizability and computational efficiency of the FRT. Simulations are used to confirm these theoretical characteristics, and the practical significance of the proposed approach is illustrated with real diffusion weighted MRI brain data. These experiments demonstrate that, in addition to having strong theoretical characteristics, the proposed approach can outperform existing state-of-the-art orientation estimation methods with respect to measures such as angular resolution and robustness to noise and modeling errors. PMID:23353603

Development of the Advanced Energetic Pair Telescope (AdEPT) for Medium-Energy Gamma-Ray Astronomy

NASA Technical Reports Server (NTRS)

Hunter, Stanley D.; Bloser, Peter F.; Dion, Michael P.; McConnell, Mark L.; deNolfo, Georgia A.; Son, Seunghee; Ryan, James M.; Stecker, Floyd W.

2011-01-01

Progress in high-energy gamma-ray science has been dramatic since the launch of INTEGRAL, AGILE and FERMI. These instruments, however, are not optimized for observations in the medium-energy (approx.0.3< E(sub gamma)< approx.200 MeV) regime where many astrophysical objects exhibit unique, transitory behavior, such as spectral breaks, bursts, and flares. We outline some of the major science goals of a medium-energy mission. These science goals are best achieved with a combination of two telescopes, a Compton telescope and a pair telescope, optimized to provide significant improvements in angular resolution and sensitivity. In this paper we describe the design of the Advanced Energetic Pair Telescope (AdEPT) based on the Three-Dimensional Track Imager (3-DTI) detector. This technology achieves excellent, medium-energy sensitivity, angular resolution near the kinematic limit, and gamma-ray polarization sensitivity, by high resolution 3-D electron tracking. We describe the performance of a 30x30x30 cm3 prototype of the AdEPT instrument.

"Phoswich Wall": A charged-particle detector array for inverse-kinematic reactions with the Gretina/GRETA γ-ray arrays

NASA Astrophysics Data System (ADS)

Sarantites, D. G.; Reviol, W.; Elson, J. M.; Kinnison, J. E.; Izzo, C. J.; Manfredi, J.; Liu, J.; Jung, H. S.; Goerres, J.

2015-08-01

A high-efficiency, forward-hemisphere detector system for light charged particles and low-Z heavy ions, as obtained in an accelerator experiment, is described. It consists of four 8×8 pixel multianode photomultiplier tubes with 2.2-mm thick CsI(Tl) and 12 -μm thick fast-plastic scintillation detectors. Its phoswich structure allows individual Z resolution for 1H, 4He, 7Li, 4He+4He, 9Be, 11B, 12C, and 14N ions, which are target-like fragments detected in strongly inverse kinematics. The device design has been optimized for use with a 4π γ-ray array, and the main applications are transfer reactions and Coulomb excitation. A high-angular resolution for the detection of the target-like fragments is achieved which permits angular distributions to be measured in the rest frame of the projectile-like fragment with a resolution of ~ 2 °.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Aiwu; Hohlmann, Marcus; Azmoun, Babak

Here, we study the position sensitivity of radial zigzag strips intended to read out large GEM detectors for tracking at future experiments. Zigzag strips can cover a readout area with fewer strips than regular straight strips while maintaining good spatial resolution. Consequently, they can reduce the number of required electronic channels and related cost for large-area GEM detector systems. A non-linear relation between incident particle position and hit position measured from charge sharing among zigzag strips was observed in a previous study. We significantly reduce this non-linearity by improving the interleaving of adjacent physical zigzag strips. Zigzag readout structures aremore » implemented on PCBs and on a flexible foil and are tested using a 10 cm × 10 cm triple-GEM detector scanned with a strongly collimated X-ray gun on a 2D motorized stage. Lastly, angular resolutions of 60–84 μrad are achieved with a 1.37 mrad angular strip pitch at a radius of 784 mm. On a linear scale this corresponds to resolutions below 100 μm.« less

Coherence Volume of an Optical Wave Field with Broad Frequency and Angular Spectra

NASA Astrophysics Data System (ADS)

Lyakin, D. V.; Mysina, N. Yu.; Ryabukho, V. P.

2018-03-01

We consider the sizes of a region in a three-dimensional space in which an optical wave field excites mutually coherent perturbations. We discuss the conditions under which the length of this region along the direction of propagation of the wave field and, correspondingly, its volume are determined either by the width of the frequency spectrum of the field or by the width of its angular spectrum, or by the parameters of these spectra simultaneously. We obtain expressions for estimating extremely small values of the coherence volume of the fields with a broad frequency spectrum and an extremely broad angular spectrum. Using the notion of instantaneous speckle-modulation of the wave field, we give a physical interpretation to the occurrence of a limited coherence volume of the field. The length of the spatiotemporal coherence region in which mutually coherent perturbations occur at different times is determined. The coherence volume of a wave field that illuminates an object in high-resolution microscopy with frequency broadband light is considered. The conditions for the dominant influence of the angular or frequency spectra on the longitudinal length of the coherence region are given, and the conditions for the influence of the frequency spectrum width on the transverse coherence of the wave field are examined. We show that, when using fields with broad and ultrabroad spectra in high-resolution microscopy, this influence should be taken into account.

Magnetic effects in the paraxial regime of elastic electron scattering

NASA Astrophysics Data System (ADS)

Edström, Alexander; Lubk, Axel; Rusz, Ján

2016-11-01

Motivated by a recent claim [Phys. Rev. Lett. 116, 127203 (2016), 10.1103/PhysRevLett.116.127203] that electron vortex beams can be used to image magnetism at the nanoscale in elastic scattering experiments, using transmission electron microscopy, a comprehensive computational study is performed to study magnetic effects in the paraxial regime of elastic electron scattering in magnetic solids. Magnetic interactions from electron vortex beams, spin polarized electron beams, and beams with phase aberrations are considered, as they pass through ferromagnetic FePt or antiferromagnetic LaMnAsO. The magnetic signals are obtained by comparing the intensity over a disk in the diffraction plane for beams with opposite angular momentum or aberrations. The strongest magnetic signals are obtained from vortex beams with large orbital angular momentum, where relative magnetic signals above 10-3 are indicated for 10 ℏ orbital angular momentum, meaning that relative signals of one percent could be expected with the even larger orbital angular momenta, which have been produced in experimental setups. All results indicate that beams with low acceleration voltage and small convergence angles yield stronger magnetic signals, which is unfortunately problematic for the possibility of high spatial resolution imaging. Nevertheless, under atomic resolution conditions, relative magnetic signals in the order of 10-4 are demonstrated, corresponding to an increase with one order of magnitude compared to previous work.

Far Infrared All-Sky Survey

NASA Technical Reports Server (NTRS)

Richards, Paul L.

1998-01-01

Precise measurements of the angular power spectrum of the Cosmic Microwave Background (CMB) anisotropy will revolutionize cosmology. These measurements will discriminate between competing cosmological models and, if the standard inflationary scenario is correct, will determine each of the fundamental cosmological parameters with high precision. The astrophysics community has recognized this potential: the orbital experiments MAP and PLANCK, have been approved to measure CMB anisotropy. Balloon-borne experiments can realize much of this potential before these missions are launched. Additionally, properly designed balloon-borne experiments can complement MAP in frequency and angular resolution and can give the first realistic test of the instrumentation proposed for the high frequency instrument on PLANCK. The MAXIMA experiment is part of the MAXIMA/BOOMERANG collaboration which is doing balloon observations of the angular power spectrum of the Cosmic Microwave Background from l = 10 to l = 800. These experiments are designed to use the benefits of both North American and Antarctic long-duration ballooning to full advantage. We have developed several new technologies that together allow the power spectrum to be measured with unprecedented combination of angular resolution, beam throw, sensitivity, sky coverage and control of systematic effects. These technologies are the basis for the high frequency instrument for the PLANCK mission. Our measurements will strongly discriminate between models of the origin and evolution of structure in the universe and, for many models, will determine the value of the basic cosmological parameters to high precision.

Marine algae are `taught' the basics of angular momentum

NASA Astrophysics Data System (ADS)

Allen, John Taylor

2017-11-01

Advanced modelling studies and high-resolution observations have shown that flows related to instability of the mesoscale ( 1-10 km scale) may provide both the fertilisation mechanism for nutrient-depleted (oligotrophic) surface waters and a subduction mechanism for the rapid export of phytoplankton biomass to the deep ocean. Here, a detailed multidisciplinary analysis of the data from an example high-resolution observational campaign is presented. The data provide direct observations of the transport of phytoplankton through baroclinic instability. Furthermore, the data confirm that this transport is constrained by the requirement to conserve angular momentum, expressed in a stratified water column as the conservation of potential vorticity. This constraint is clearly seen to produce long thin filaments of phytoplankton populations strained out along isopycnal vorticity annuli associated with mesoscale frontal instabilities.

Internal reflection sensors with high angular resolution

NASA Astrophysics Data System (ADS)

Shavirin, I.; Strelkov, O.; Vetskous, A.; Norton-Wayne, L.; Harwood, R.

1996-07-01

We discuss the use of total internal reflection for the production of sensors with high angular resolution. These sensors are intended for measurement of the angle between a sensor's axis and the direction to a source of radiation or reflecting object. Sensors of this type are used in controlling the position of machine parts in robotics and industry, orienting space vehicles and astronomic devices in relation to the Sun, and as autocollimators for checking angles of deviation. This kind of sensor was used in the Apollo space vehicle some 20 years ago. Using photodetectors with linear and area CCD arrays has opened up new application possibilities for appropriately designed sensors. A generalized methodology is presented applicable to a wide range of tasks. Some modifications that can improve the performance of the basic design are described.

Olivier Chesneau's Work on Low Mass Stars

NASA Astrophysics Data System (ADS)

Lagadec, E.

2015-12-01

During his too short career, Olivier Chesneau pioneered the study of the circumstellar environments of low mass evolved stars using very high angular resolution techniques. He applied state of the art high angular resolution techniques, such as optical interferometry and adaptive optics imaging, to the the study of a variety of objects, from AGB stars to Planetary Nebulae, via e.g. Born Again stars, RCB stars and Novae. I present here an overview of this work and most important results by focusing on the paths he followed and key encounters he made to reach these results. Olivier liked to work in teams and was very strong at linking people with complementary expertises to whom he would communicate his enthusiasm and sharp ideas. His legacy will live on through the many people he inspired.

Poster 8: ALMA observations of Titan : Vertical and spatial distributions of nitriles

NASA Astrophysics Data System (ADS)

Moreno, Raphael; Lellouch, Emmanuel; Vinatier, Sandrine; Gurwell, Mark; Moullet, Arielle; Lara, Luisa; Hidayat, Taufiq

2016-06-01

We report submm observations of Titan performed with the ALMA interferometer centered at the rotational frequencies of HCN(4-3) and HNC(4-3), i.e. 354 and 362 GHz. These measurements yielded disk-resolved emission spectra of Titan with an angular resolution of ˜0.47". Titan's angular surface diameter was 0.77". Data were acquired in summer 2012 near the greatest eastern and western elongations of Titan at a spectral resolution of 122 kHz (λ/dλ = 3106). We will present radiative transfer analysis of the acquired spectra. With the combination of all the detected rotational lines, we will constrain the atmospheric temperature, the spatial and vertical distribution HCN, HC3N, CH3CN, HNC, C2H5CN, as well as isotopic ratios.

Performance Evaluation of 98 CZT Sensors for Their Use in Gamma-Ray Imaging

NASA Astrophysics Data System (ADS)

Dedek, Nicolas; Speller, Robert D.; Spendley, Paul; Horrocks, Julie A.

2008-10-01

98 SPEAR sensors from eV Products have been evaluated for their use in a portable Compton camera. The sensors have a 5 mm times 5 mm times 5 mm CdZnTe crystal and are provided together with a preamplifier. The energy resolution was studied in detail for all sensors and was found to be 6% on average at 59.5 keV and 3% on average at 662 keV. The standard deviations of the corresponding energy resolution distributions are remarkably small (0.6% at 59.5 keV, 0.7% at 662 keV) and reflect the uniformity of the sensor characteristics. For a possible outside use the temperature dependence of the sensor performances was investigated for temperatures between 15 and 45 deg Celsius. A linear shift in calibration with temperature was observed. The energy resolution at low energies (81 keV) was found to deteriorate exponentially with temperature, while it stayed constant at higher energies (356 keV). A Compton camera built of these sensors was simulated. To obtain realistic energy spectra a suitable detector response function was implemented. To investigate the angular resolution of the camera a 137Cs point source was simulated. Reconstructed images of the point source were compared for perfect and realistic energy and position resolutions. The angular resolution of the camera was found to be better than 10 deg.

MEMS SoC: observer-based coplanar gyro-free inertial measurement unit

NASA Astrophysics Data System (ADS)

Chen, Tsung-Lin; Park, Sungsu

2005-09-01

This paper presents a novel design of a coplanar gyro-free inertial measurement unit (IMU) that consists of seven to nine single-axis linear accelerometers, and it can be utilized to perform the six DOF measurements for an object in motion. Unlike other gyro-fee IMUs, this design uses redundant accelerometers and state estimation techniques to facilitate the in situ and mass fabrication for the employed accelerometers. The alignment error from positioning accelerometers onto a measurement unit and the fabrication cost of an IMU can greatly be reduced. The outputs of the proposed design are three linear accelerations and three angular velocities. As compared to other gyro-free IMUs, the proposed design uses less integral operation and thus improves its sensing resolution and drifting problem. The sensing resolution of a gyro-free IMU depends on the sensing resolution of the employed accelerometers as well as the size of the measurement unit. Simulation results indicate that the sensing resolution of the proposed design is 2° s-1 for the angular velocity and 10 μg for the linear acceleration when nine single-axis accelerometers, each with 10 μg sensing resolution, are deployed on a 4 inch diameter disc. Also, thanks to the iterative EKF algorithm, the angle estimation error is within 10-3 deg at 2 s.

Student Observations of Double Star Delta Orionis (STFA 14 AC)

NASA Astrophysics Data System (ADS)

Estrada, Reed; Aguilera, Sophia; Bowden, Sam; Gillette, Travis; Givens, Jalynn; Reder, Gabriel; Rhoades, Breauna; Sharpe, Scott; Shattles, Jenna; Cha, Brendon; Do, Vicky; Ewing, Malachi; Kiamco, Alex Junior; Nelms, Brenda; Peña, Emilie; Maricarmen, Richard; Thielen, Austin

2018-01-01

A group of eight eighth graders and eight high schoolers studied the double star STFA 14 AC. They used the procedure from Argyle's book to get the separation and position angle for the double star. The students used a Celestron C8 Schmidt-Cassegrain telescope with a Baader Planetarium microguide eyepiece with similar markings to a Celestron Eyepiece. The students determined the separation to be 56 arcseconds and the position angle to be 4.19°. They compared their results to the Washington Double Star Catalog and found that they had a 2.88 arcseconds difference in separation and a 2.19° in position angle.

Infrared Space Astrometry Missions ˜ JASMINE Missions ˜

NASA Astrophysics Data System (ADS)

Gouda, N.

2012-08-01

"JASMINE" is an abbreviation of Japan Astrometry Satellite Mission for Infrared Exploration. Three satellites are planned as a series of JASMINE missions, as a step-by-step approach, to overcome technical issues and promote scientific results. These are Nano-JASMINE, Small-JASMINE and (medium-sized) JASMINE. JASMINE missions provide the positions and proper motions of celestial objects. Nano-JASMINE uses a very small nano-satellite and is scheduled to be launched in 2013. Nano-JASMINE will operate in zw-band (˜ 0.8μm) to perform an all sky survey with an accuracy of 3 milli-arcseconds for position and parallaxes. Small-JASMINE will observe towards a region around the Galactic center and other small regions, which include interesting scientific targets, with accuracies of 10 to 50 μ-arcseconds in an infrared Hw-band (˜ 1.7 μm). The target launch date is around 2017. (Medium-sized) JASMINE is an extended mission of Small-JASMINE, which will observe towards almost the whole region of the Galactic bulge with accuracies of ˜ 10 μ arcseconds in Kw-band (˜ 2.0μ m). The target launch date is the first half of the 2020s.

Center for Adaptive Optics | Jobs

Science.gov Websites

, 2015 University of Geneva Adaptive Optics Scientist or Engineer March 16, 2015 NRC-Herzberg Astronomy Max Planck Institute for Astronomy (MPIA) Post-doctoral Fellowships in High-angular Resolution

Appalachian Mountains

Atmospheric Science Data Center

2014-05-15

... Radiance Ellipsoid Product. MISR uses this enhanced sensitivity along with the angular variation in signal to monitor particulate ... of MISR's unique capability of providing moderately high spatial resolution, calibrated imagery at very oblique angles. Gradations ...

CONNECTING ANGULAR MOMENTUM AND GALACTIC DYNAMICS: THE COMPLEX INTERPLAY BETWEEN SPIN, MASS, AND MORPHOLOGY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teklu, Adelheid F.; Remus, Rhea-Silvia; Dolag, Klaus

The evolution and distribution of the angular momentum of dark matter (DM) halos have been discussed in several studies over the past decades. In particular, the idea arose that angular momentum conservation should allow us to infer the total angular momentum of the entire DM halo from measuring the angular momentum of the baryonic component, which is populating the center of the halo, especially for disk galaxies. To test this idea and to understand the connection between the angular momentum of the DM halo and its galaxy, we use a state-of-the-art, hydrodynamical cosmological simulation taken from the set of Magneticummore » Pathfinder simulations. Thanks to the inclusion of the relevant physical processes, the improved underlying numerical methods, and high spatial resolution, we successfully produce populations of spheroidal and disk galaxies self-consistently. Thus, we are able to study the dependence of galactic properties on their morphology. We find that (1) the specific angular momentum of stars in disk and spheroidal galaxies as a function of their stellar mass compares well with observational results; (2) the specific angular momentum of the stars in disk galaxies is slightly smaller compared to the specific angular momentum of the cold gas, in good agreement with observations; (3) simulations including the baryonic component show a dichotomy in the specific stellar angular momentum distribution when splitting the galaxies according to their morphological type (this dichotomy can also be seen in the spin parameter, where disk galaxies populate halos with slightly larger spin compared to spheroidal galaxies); (4) disk galaxies preferentially populate halos in which the angular momentum vector of the DM component in the central part shows a better alignment to the angular momentum vector of the entire halo; and (5) the specific angular momentum of the cold gas in disk galaxies is approximately 40% smaller than the specific angular momentum of the total DM halo and shows a significant scatter.« less

Anisotropic kinetic energy release and gyroscopic behavior of CO2 super rotors from an optical centrifuge.

PubMed

Murray, Matthew J; Ogden, Hannah M; Mullin, Amy S

2017-10-21

An optical centrifuge is used to generate an ensemble of CO 2 super rotors with oriented angular momentum. The collision dynamics and energy transfer behavior of the super rotor molecules are investigated using high-resolution transient IR absorption spectroscopy. New multipass IR detection provides improved sensitivity to perform polarization-dependent transient studies for rotational states with 76 ≤ J ≤ 100. Polarization-dependent measurements show that the collision-induced kinetic energy release is spatially anisotropic and results from both near-resonant energy transfer between super rotor molecules and non-resonant energy transfer between super rotors and thermal molecules. J-dependent studies show that the extent and duration of the orientational anisotropy increase with rotational angular momentum. The super rotors exhibit behavior akin to molecular gyroscopes, wherein molecules with larger amounts of angular momentum are less likely to change their angular momentum orientation through collisions.

Anisotropic kinetic energy release and gyroscopic behavior of CO2 super rotors from an optical centrifuge

NASA Astrophysics Data System (ADS)

Murray, Matthew J.; Ogden, Hannah M.; Mullin, Amy S.

2017-10-01

An optical centrifuge is used to generate an ensemble of CO2 super rotors with oriented angular momentum. The collision dynamics and energy transfer behavior of the super rotor molecules are investigated using high-resolution transient IR absorption spectroscopy. New multipass IR detection provides improved sensitivity to perform polarization-dependent transient studies for rotational states with 76 ≤ J ≤ 100. Polarization-dependent measurements show that the collision-induced kinetic energy release is spatially anisotropic and results from both near-resonant energy transfer between super rotor molecules and non-resonant energy transfer between super rotors and thermal molecules. J-dependent studies show that the extent and duration of the orientational anisotropy increase with rotational angular momentum. The super rotors exhibit behavior akin to molecular gyroscopes, wherein molecules with larger amounts of angular momentum are less likely to change their angular momentum orientation through collisions.

Semiclassical analysis of angular differential cross sections for single-electron capture in 250-eV H++H collisions

NASA Astrophysics Data System (ADS)

Frémont, F.

2015-05-01

A classical model based on the resolution of Hamilton equations of motion is used to determine the angular distribution of H projectiles following single-electron capture in H++H collisions at an incident projectile energy of 250 eV. At such low energies, the experimental charge-exchange probability and angular differential cross sections exhibit oscillatory structures that are classically related to the number of swaps the electron experiences between the target and the projectile during the collision. These oscillations are well reproduced by models based on quantum mechanics. In the present paper, the angular distribution of H projectiles is determined classically, at angles varying from 0.1° up to 7°. The variation in intensity due to interferences caused by the indiscernibility between different trajectories is calculated, and the role of these interferences is discussed.

The CHARA optical array

NASA Astrophysics Data System (ADS)

McAlister, Harold A.

1992-11-01

The Center for High Angular Resolution Astronomy (CHARA) was established in the College of Arts and Sciences at Georgia State University in 1984 with the goals of designing, constructing, and then operating a facility for very high spatial resolution astronomy. The interest in such a facility grew out of the participants' decade of activity in speckle interferometry. Although speckle interferometry continues to provide important astrophysical measurements of a variety of objects, many pressing problems require resolution far beyond that which can be expected from single aperture telescopes. In early 1986, CHARA received a grant from the National Science Foundation which has permitted a detailed exploration of the feasibility of constructing a facility which will provide a hundred-fold increase in angular resolution over what is possible by speckle interferometry at the largest existing telescopes. The design concept for the CHARA Array was developed initially with the contractural collaboration of United Technologies Optical Systems, Inc., in West Palm Beach, Florida, an arrangement that expired in August 1987. In late November 1987, the Georgia Tech Research Institute joined with CHARA to continue and complete the design concept study. Very high-resolution imaging at optical wavelengths is clearly coming of age in astronomy. The CHARA Array and other related projects will be important and necessary milestones along the way toward the development of a major national facility for high-resolution imaging--a true optical counterpart to the Very Large Array. Ground-based arrays and their scientific output will lead to high resolution facilities in space and, ultimately, on the Moon.

Thin fused silica optics for a high angular resolution and large collecting area X Ray telescope after Chandra

NASA Astrophysics Data System (ADS)

Pareschi, Giovanni; Citterio, Oberto; Civitani, Marta M; Basso, Stefano; Campana, Sergio; Conconi, Paolo; Ghigo, Mauro; Mattaini, Enrico; Moretti, Alberto; Parodi, Giancarlo; Tagliaferri, Gianpiero

2014-08-01

The implementation of an X-ray mission with high imaging capabilities, similar to those achieved with Chandra (<1 arcsec Half Energy Width, HEW), but with a much larger throughput is very attractive, even if challenging. For such a mission the scientific opportunities, in particular for the study of the early Universe, would remain at the state of the art for the next decades. Initially the ESA-led XEUS mission was proposed, with an effective area of several m2 and an angular resolution better than 2 arcsec HEW. Unfortunately, this mission was not implemented, mainly due to the costs and the low level of technology readiness. Currently the most advanced proposal for such a mission is the SMART-X project, led by CfA together with other US institutes. This project is based on adjustable segments of thin foil mirrors with piezo-electric actuators, aiming to achieve an effective area >2 m2 at 1 keV and an angular resolution better than 1 arcsec HEW. Another attractive technology to realize an X-ray telescope with similar characteristics is being developed at NASA/Goddard. In this case the mirrors are based on Si substrates that are super-polished and figured starting from a bulky Si ingot, from which they are properly cut. Here we propose an alternative method based on precise direct grinding, figuring and polishing of thin (a few mm) glass shells with innovative deterministic polishing methods. This is followed by a final correction via ion figuring to obtain the desired accuracy. For this purpose, a temporary stiffening structure is used to support the shell from the polishing operations up to its integration in the telescope supporting structure. This paper deals with the technological process under development, the results achieved so far and some mission scenarios based on this kind of optics, aiming to achieve an effective area more than 10 times larger than Chandra and an angular resolution of 1 arcsec HEW on axis and of a few arcsec off-axis across a large field of view (1o in diameter).

On-ground calibration of the Hitomi Hard X-ray Telescopes

NASA Astrophysics Data System (ADS)

Mori, Hideyuki; Miyazawa, Takuya; Awaki, Hisamitsu; Matsumoto, Hironori; Babazaki, Yasunori; Bandai, Ayako; Demoto, Tadatsugu; Furuzawa, Akihiro; Haba, Yoshito; Hayashi, Takayuki; Iizuka, Ryo; Ishibashi, Kazunori; Ishida, Manabu; Ishida, Naoki; Itoh, Masayuki; Iwase, Toshihiro; Kato, Hiroyoshi; Kobayashi, Hiroaki; Kosaka, Tatsuro; Kunieda, Hideyo; Kurashima, Shou; Kurihara, Daichi; Kuroda, Yuuji; Maeda, Yoshitomo; Meshino, Yoshifumi; Mitsuishi, Ikuyuki; Miyata, Yuusuke; Nagano, Housei; Namba, Yoshiharu; Ogasaka, Yasushi; Ogi, Keiji; Okajima, Takashi; Saji, Shigetaka; Shimasaki, Fumiya; Sato, Takuro; Sato, Toshiki; Shima, Naotsugu; Sugita, Satoshi; Suzuki, Yoshio; Tachibana, Kenji; Tachibana, Sasagu; Takizawa, Shun'ya; Tamura, Keisuke; Tawara, Yuzuru; Tomikawa, Kazuki; Torii, Tatsuharu; Uesugi, Kentaro; Yamashita, Koujun; Yamauchi, Shigeo

2018-01-01

We present x-ray characteristics of the Hard X-ray Telescopes (HXTs) on board the Hitomi (ASTRO-H) satellite. Measurements were conducted at the SPring-8 BL20B2 beamline and the ISAS/JAXA 27-m beamline. The angular resolution defined by a half-power diameter was 1.9‧ (HXT-1) and 2.1‧ (HXT-2) at 8 keV, 1.9‧ at 30 keV, and 1.8‧ at 50 keV. The effective area was found to be 620 cm2 at 8 keV, 178 cm2 at 30 keV, and 82 cm2 at 50 keV per mirror module. Although the angular resolutions were slightly worse than the requirement (1.7‧), the effective areas sufficiently exceeded the requirements of 150 cm2 at 30 keV and 55 cm2 at 50 keV. The off-axis measurements of the effective areas resulted in the field of view being 6.1‧ at 50 keV, 7.7‧ at 30 keV, and 9.7‧ at 8 keV in diameter. We confirmed that the main component of the stray x-ray light was significantly reduced by mounting the precollimator as designed. Detailed analysis of the data revealed that the angular resolution was degraded mainly by figure errors of mirror foils, and the angular resolution is completely explained by the figure errors, positioning errors of the foils, and conical approximation of the foil shape. We found that the effective areas were ˜80% of the designed values below 40 keV, whereas they steeply decline above 40 keV and become only ˜50%. We investigated this abrupt decline and found that neither the error of the multilayer design nor the errors of the incident angles induced by the positioning errors of the foils can be the cause. The reflection profile of each foil pair from the defocused image strongly suggests that the figure errors of the foils probably bring about the reduction in the effective areas at higher energies.

Future Prospects for Very High Angular Resolution Imaging in the UV/Optical

NASA Astrophysics Data System (ADS)

Allen, R. J.

2004-05-01

Achieving the most demanding science goals outlined by the previous speakers will ultimately require the development of coherent space-based arrays of UV/Optical light collectors spread over distances of hundreds of meters. It is possible to envisage ``in situ" assembly of large segmented filled-aperture telescopes in space using components ferried up with conventional launchers. However, the cost will grow roughly as the mass of material required, and this will ultimately limit the sizes of the apertures we can afford. Furthermore, since the collecting area and the angular resolution are coupled for diffraction-limited filled apertures, the sensitivity may be much higher than is actually required to do the science. Constellations of collectors deployed over large areas as interferometer arrays or sparse apertures offer the possibility of independently tailoring the angular resolution and the sensitivity in order to optimally match the science requirements. Several concept designs have been proposed to provide imaging data for different classes of targets such as protoplanetary disks, the nuclear regions of the nearest active galaxies, and the surfaces of stars of different types. Constellations of identical collectors may be built and launched at lower cost through mass production, but new challenges arise when they have to be deployed. The ``aperture" synthesized is only as good as the accuracy with which the individual collectors can be placed and held to the required figure. This ``station-keeping" problem is one of the most important engineering problems to be solved before the promise of virtually unlimited angular resolution in the UV/Optical can be realized. Among the attractive features of an array of free-flying collectors configured for imaging is the fact that the figure errors of the ``aperture" so produced may be much more random than is the case for monolithic or segmented telescopes. This can result in a significant improvement in the dynamic range and permit imaging of faint objects near much brighter extraneous nearby sources, a task presently reserved for specially-designed coronagraphs on filled apertures.

Tagged Neutron Source for API Inspection Systems with Greatly Enhanced Spatial Resolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

2012-06-04

We recently developed induced fission and transmission imaging methods with time- and directionally-tagged neutrons offer new capabilities for characterization of fissile material configurations and enhanced detection of special nuclear materials (SNM). An Advanced Associated Particle Imaging (API) generator with higher angular resolution and neutron yield than existing systems is needed to fully exploit these methods.

An alternative resolution to the Mansuripur paradox

NASA Astrophysics Data System (ADS)

Redfern, Francis

2016-04-01

In 2013 an article published online by the journal Science declared that the paradox proposed by Masud Mansuripur was resolved. This paradox concerns a point charge-Amperian magnetic dipole system as seen in a frame of reference where they are at rest and one in which they are moving. In the latter frame an electric dipole appears on the magnetic dipole. A torque is then exerted upon the electric dipole by the point charge, a torque that is not observed in the at-rest frame. Mansuripur points out this violates the relativity principle and suggests the Lorentz force responsible for the torque be replaced by the Einstein-Laub force. The resolution of the paradox reported by Science, based on numerous papers in the physics literature, preserves the Lorentz force but depends on the concept of hidden momentum. Here I propose a different resolution based on the overlooked fact that the charge-magnetic dipole system contains linear and angular electromagnetic field momentum. The time rate of change of the field angular-momentum in the frame through which the system is moving cancels that due to the charge-electric dipole interaction. From this point of view hidden momentum is not needed in the resolution of the paradox.

Landsat and Sentinel-2A Surface Albedo Estimation and Evaluation Against In Situ Measurements Across the US SURFRAD Network

NASA Astrophysics Data System (ADS)

Franch, B.; Skakun, S.; Vermote, E.; Roger, J. C.

2017-12-01

Surface albedo is an essential parameter not only for developing climate models, but also for most energy balance studies. While climate models are usually applied at coarse resolution, the energy balance studies, which are mainly focused on agricultural applications, require a high spatial resolution. The albedo, estimated through the angular integration of the BRDF, requires an appropriate angular sampling of the surface. However, Sentinel-2A sampling characteristics, with nearly constant observation geometry and low illumination variation, prevent from deriving a surface albedo product. In this work, we apply an algorithm developed to derive a Landsat surface albedo to Sentinel-2A. It is based on the BRDF parameters estimated from the MODerate Resolution Imaging Spectroradiometer (MODIS) CMG surface reflectance product (M{O,Y}D09) using the VJB method (Vermote et al., 2009). Sentinel-2A unsupervised classification images are used to disaggregate the BRDF parameters to the Sentinel-2 spatial resolution. We test the results over five different sites of the US SURFRAD network and plot the results versus albedo field measurements. Additionally, we also test this methodology using Landsat-8 images.

Online Mapping and Perception Algorithms for Multi-robot Teams Operating in Urban Environments

DTIC Science & Technology

2015-01-01

each method on a 2.53 GHz Intel i5 laptop. All our algorithms are hand-optimized, implemented in Java and single threaded. To determine which algorithm...approach would be to label all the pixels in the image with an x, y, z point. However, the angular resolution of the camera is finer than that of the...edge criterion. That is, each edge is either present or absent. In [42], edge existence is further screened by a fixed threshold for angular

Angularly resolved characterization of ion beams from laser-ultrathin foil interactions

NASA Astrophysics Data System (ADS)

Scullion, C.; Doria, D.; Romagnani, L.; Ahmed, H.; Alejo, A.; Ettlinger, O. C.; Gray, R. J.; Green, J.; Hicks, G. S.; Jung, D.; Naughton, K.; Padda, H.; Poder, K.; Scott, G. G.; Symes, D. R.; Kar, S.; McKenna, P.; Najmudin, Z.; Neely, D.; Zepf, M.; Borghesi, M.

2016-09-01

Methods and techniques used to capture and analyze beam profiles produced from the interaction of intense, ultrashort laser pulses and ultrathin foil targets using stacks of Radiochromic Film (RCF) and Columbia Resin #39 (CR-39) are presented. The identification of structure in the beam is particularly important in this regime, as it may be indicative of the dominance of specific acceleration mechanisms. Additionally, RCF can be used to deconvolve proton spectra with coarse energy resolution while mantaining angular information across the whole beam.

Developing Soft-Kill Capability for Light Armoured Vehicles through Battlefield Simulations

DTIC Science & Technology

2007-02-01

scripted so they can move, fire, sense, communicate and react without operator intervention. The entities, can interact with each other as well as manned...trace of the laser illuminator. The horizontal scan is 135◦ followed by a vertical angular displacement of 15◦ and retracement. The 15◦ vertical scan...properties based on combined characteristics. An example of a new detector is the laser detecting HARLID. With an angular resolution of ±1◦, it is a

Scalar and tensor spherical harmonics expansion of the velocity correlation in homogeneous anisotropic turbulence

DOE PAGES

Rubinstein, Robert; Kurien, Susan; Cambon, Claude

2015-06-22

The representation theory of the rotation group is applied to construct a series expansion of the correlation tensor in homogeneous anisotropic turbulence. The resolution of angular dependence is the main analytical difficulty posed by anisotropic turbulence; representation theory parametrises this dependence by a tensor analogue of the standard spherical harmonics expansion of a scalar. As a result, the series expansion is formulated in terms of explicitly constructed tensor bases with scalar coefficients determined by angular moments of the correlation tensor.

Development of the fibres of MOONS

NASA Astrophysics Data System (ADS)

Guinouard, Isabelle; Lee, David; Schnetler, Hermine; Taylor, William; Amans, Jean-Philippe; Montgomery, David; Oliva, Ernesto

2014-07-01

MOONS will exploit the full 500 square arcmin field of view offered by the Nasmyth focus of the Very Large Telescope and will be equipped with two identical triple arm cryogenic spectrographs covering the wavelength range 0.8 - 1.8 μm, with a multiplex capability of approximately 1000 fibres. Each triple arm spectrograph will produce spectra for half of the targets simultaneously. The system will have both a medium resolution (R~4000-6000) mode and a high resolution (R~20000) mode. The fibres are used to pick off each sub field of 1.05 arcseconds and are used to transport the light from the instrument focal plane to the two spectrographs. Each fibre has a microlens to focus the beam into the fibre at a relative fast focal ratio of F/3.65 to reduce the Focal Ratio Degradation (FRD). This paper presents the overall design of the fibre system and describes the specific developments required to optimise its performance. The design of the fibre input optics, the choice of the fibre connector, and the layout of the slit end are described. The results of preliminary tests to measure the effect of twisting on the FRD performance of prototype fibres are also discussed.

Star formation in AGNs at the hundred parsec scale using MIR high-resolution images

NASA Astrophysics Data System (ADS)

Ruschel-Dutra, Daniel; Rodríguez Espinosa, José Miguel; González Martín, Omaira; Pastoriza, Miriani; Riffel, Rogério

2017-04-01

It has been well established in the past decades that the central black hole masses of galaxies correlate with dynamical properties of their harbouring bulges. This notion begs the question of whether there are causal connections between the active galactic nucleus (AGN) and its immediate vicinity in the host galaxy. In this paper, we analyse the presence of circumnuclear star formation in a sample of 15 AGN using mid-infrared observations. The data consist of a set of 11.3 μm polycyclic aromatic hydrocarbon emission and reference continuum images, taken with ground-based telescopes, with sub-arcsecond resolution. By comparing our star formation estimates with AGN accretion rates, derived from X-ray luminosities, we investigate the validity of theoretical predictions for the AGN-starburst connection. Our main results are: (I) circumnuclear star formation is found, at distances as low as tens of parsecs from the nucleus, in nearly half of our sample (7/15); (II) star formation luminosities are correlated with the bolometric luminosity of the AGN (LAGN) only for objects with LAGN ≥ 1042 erg s-1; (III) low-luminosity AGNs (LAGN < 1042 erg s-1) seem to have starburst luminosities far greater than their bolometric luminosities.

The Focusing Optics X-ray Solar Imager (FOXSI)

NASA Astrophysics Data System (ADS)

Krucker, S.

2011-12-01

The Focusing Optics X-ray Solar Imager (FOXSI) is a NASA Low Cost Access to Space sounding rocket payload that will launch in early 2012. A larger sensitivity and dynamic range than currently available are needed in order to image faint X-rays from electron beams in the tenuous corona, particularly those near the coronal acceleration region and those that escape into interplanetary space. FOXSI combines nested, grazing-incidence replicated optics with double-sided silicon strip detectors to achieve a dynamic range of >100 and a sensitivity 100 times that of RHESSI. Advances in the fabrication and assembly of the optics at the NASA Marshall Space Flight Center provide a spatial resolution of 8 arcseconds (FWHM), while the silicon detectors, developed by the Astro-H team at ISAS/JAXA, offer an energy resolution of 0.4 keV. FOXSI's first flight will conduct a search for nonthermal electrons in the quiet Sun, possibly related to nanoflares. FOXSI will serve as a pathfinder for future space-based solar hard X-ray spectroscopic imagers, which will be able to image nonthermal electrons in flare acceleration sites and provide quantitative measurements such as energy spectra, densities, and energy content in accelerated electrons.

The Focusing Optics X-ray Solar Imager

NASA Astrophysics Data System (ADS)

Glesener, Lindsay; Krucker, S.; Christe, S.; Ramsey, B.; Ishikawa, S.; Takahashi, T.; Saito, S.

2011-05-01

The Focusing Optics X-ray Solar Imager (FOXSI) is a NASA Low Cost Access to Space sounding rocket payload that will launch in late 2011. A larger sensitivity and dynamic range than currently available are needed in order to image faint X-rays from electron beams in the tenuous corona, particularly those near any coronal acceleration region and those that escape into interplanetary space. FOXSI combines fast-replication, nested, grazing-incidence optics with double-sided silicon strip detectors to achieve a dynamic range of >100 and a sensitivity 100 times that of RHESSI. Advances in the fabrication and assembly of the optics at the NASA Marshall Space Flight Center provide a spatial resolution of 8 arcseconds, while the silicon detectors, developed by the Astro-H team at ISAS/JAXA, offer an energy resolution of 0.5 keV. FOXSI's first flight will be used to conduct a search for X-ray emission from nonthermal electron beams in quiet Sun nanoflares. In addition, FOXSI will serve as a pathfinder for future space-based solar hard X-ray spectroscopic imagers, which will be able to image nonthermal electrons in flare acceleration sites and provide quantitative measurements such as energy spectra, densities, and energy content in accelerated electrons.

RIMAS - Optical Design Development of the Imager/Spectrometer for the Discovery Channel Telescope

NASA Technical Reports Server (NTRS)

Capone, John

2012-01-01

The Rapid IMAger - Spectrometer (RIMAS) is a collaborative effort between the University of Maryland at College Park, NASA-GSFC and Lowell Observatory designed for use on the 4.3 meter Discovery Channel Telescope at Lowell. The primary science goal of the instrument is the study of gamma-ray burst (ORB) afterglow appearing in the near-infrared. Continuous operation will allow measurements beginning minutes after the prompt emission. We present the results of the RIMAS optical design development. The instrument consists of two arms separated by a dichroic: the first for the Y and J bands (0.9 - 1.35 microns) and the second for the Hand K-bands (1.5 - 1.8 and 2.0 - 2.4 microns). Each arm will be equipped with two broad band filters for imaging, as well as low resolution and echelle grisms. The imaging modes are designed to be diffraction limited, with one pixel corresponding to approx.0.35 arcseconds, while the diffractive modes have resolving powers of approximately 20 and 4,000. With photometric and spectroscopic capabilities, RIMAS will be well positioned to quickly determine redshifts, followed by high resolution spectroscopic studies of ORB afterglow.

Southern Alaska Coastal Relief Model

NASA Astrophysics Data System (ADS)

Lim, E.; Eakins, B.; Wigley, R.

2009-12-01

The National Geophysical Data Center (NGDC), an office of the National Oceanic and Atmospheric Administration (NOAA), in conjunction with the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado at Boulder, has developed a 24 arc-second integrated bathymetric-topographic digital elevation model of Southern Alaska. This Coastal Relief Model (CRM) was generated from diverse digital datasets that were obtained from NGDC, the United States Geological Survey, and other U.S. and international agencies. The CRM spans 170° to 230° E and 48.5° to 66.5° N, including the Gulf of Alaska, Bering Sea, Aleutian Islands, and Alaska’s largest communities: Anchorage, Fairbanks, and Juneau. The CRM provides a framework for enabling scientists to refine tsunami propagation and ocean circulation modeling through increased resolution of geomorphologic features. It may also be useful for benthic habitat research, weather forecasting, and environmental stewardship. Shaded-relief image of the Southern Alaska Coastal Relief Model.

Optical Reflection Spectroscopy of GEO Objects

NASA Technical Reports Server (NTRS)

Seitzer, Patrick; Cardona, Tammaso; Lederer, Susan M.; Cowardin, Heather; Abercromby, Kira J.; Barker, Edwin S.; Bedard, Donald

2013-01-01

We report on optical reflection spectroscopy of geosynchronous (GEO) objects in the US Space Surveillance Network (SSN) catalog. These observations were obtained using imaging spectrographs on the 6.5-m Magellan telescopes at the Las Campanas Observatory in Chile. Our goal is to determine the composition of these objects by comparing these spectral observations with ground-based laboratory measurements of spacecraft materials. The observations are all low resolution (1 nm after smoothing) obtained through a 5 arcsecond wide slit and using a grism as the dispersing element. The spectral range covered was from 450 nm to 800 nm. All spectra were flux calibrated using observations of standard stars with the exact same instrumental setup. An effort was made to obtain all observations within a limited range of topocentric phase angle, although the solar incident angle is unknown due to the lack of any knowledge of the attitude of the observed surface at the time of observation.

Nova Mus 2008 = QY Mus

NASA Astrophysics Data System (ADS)

Templeton, Matthew R.

2008-10-01

Nova Mus 2008 = QY Mus was discovered by William Liller, Vina del Mar, Chile, on 2008 September 28.998 UT at magnitude 8.6 (Tech Pan film + orange filter). The position is RA = 13h 16m 36.44s , Dec = -67d 36m 47.8s (from P. Nelson). This object was announced as a nova in IAU Circular 8990 (Daniel W.E. Green, editor). The nova classification was determined using low-resolution spectra by W. Liller indicating the presence of broad H-alpha lines at least 2300 angstroms wide. Several observers confirmed the nova and provided photometry. The position above was provided by Peter Nelson (Ellinbank, Vic., Aus.), and is averaged from four separate exposures (rms error approx. 0.4 arcseconds). The GCVS team have formally designated Nova Mus 2008 as QY MUS. Observations should be reported to the AAVSO International Database as QY MUS.

A Daytime Aspect Camera for Balloon Altitudes

NASA Technical Reports Server (NTRS)

Dietz, Kurt L.; Ramsey, Brian D.; Alexander, Cheryl D.; Apple, Jeff A.; Ghosh, Kajal K.; Swift, Wesley R.; Six, N. Frank (Technical Monitor)

2001-01-01

We have designed, built, and flight-tested a new star camera for daytime guiding of pointed balloon-borne experiments at altitudes around 40km. The camera and lens are commercially available, off-the-shelf components, but require a custom-built baffle to reduce stray light, especially near the sunlit limb of the balloon. This new camera, which operates in the 600-1000 nm region of the spectrum, successfully provided daytime aspect information of approximately 10 arcsecond resolution for two distinct star fields near the galactic plane. The detected scattered-light backgrounds show good agreement with the Air Force MODTRAN models, but the daytime stellar magnitude limit was lower than expected due to dispersion of red light by the lens. Replacing the commercial lens with a custom-built lens should allow the system to track stars in any arbitrary area of the sky during the daytime.

Chandra/ACIS Observations of the 30 Doradus Star-Forming Complex

NASA Astrophysics Data System (ADS)

Townsley, Leisa; Broos, Patrick; Feigelson, Eric; Burrows, David; Chu, You-Hua; Garmire, Gordon; Griffiths, Richard; Maeda, Yoshitomo; Pavlov, George; Tsuboi, Yohko

2002-04-01

30 Doradus is the archetype giant extragalactic H II region, a massive star-forming complex in the Large Magellanic Cloud. We examine high-spatial-resolution X-ray images and spectra of the essential parts of 30 Doradus, obtained with the Advanced CCD Imaging Spectrometer (ACIS) aboard the Chandra X-ray Observatory. The central cluster of young high-mass stars, R136, is resolved at the arcsecond level, allowing spectral analysis of bright constituents; other OB/Wolf-Rayet binaries and multiple systems (e.g. R139, R140) are also detected. Spatially-resolved spectra are presented for N157B, the composite SNR containing a 16-msec pulsar. The spectrally soft superbubble structures seen by ROSAT are dramatically imaged by Chandra; we explore the spectral differences they exhibit. Taken together, the components of 30 Doradus give us an excellent microscopic view of high-energy phenomena seen on larger scales in more distant galaxies as starbursts and galactic winds.

Chandra/ACIS Observations of Rosette: Diffuse X-rays Discovered in a Galactic H II Region

NASA Astrophysics Data System (ADS)

Townsley, L. K.; Feigelson, E. D.; Broos, P. S.; Chu, Y.-H.; Montmerle, T.

2001-12-01

We present the first high-spatial-resolution X-ray images of the Rosette Nebula and Rosette Molecular Cloud (RMC), obtained in a series of 4 20-ksec snapshots with the Advanced CCD Imaging Spectrometer aboard the Chandra X-ray Observatory in January 2001. These images form a striking 1-degree X-ray panorama of a rich high-mass star formation region. The OB association is resolved at the arcsecond level into >300 sources. The other 3 pointings step across the RMC, with >100 X-ray sources in each. Soft diffuse emission is seen at the center of the H II region and is resolved from the point source population. This extended emission is most likely from the fast O-star winds, which thermalize and shock the surrounding media. Support for this effort was provided by the Chandra X-ray Observatory GO2 grant G01-2008X.

New Views of the Solar Corona from STEREO and SDO

NASA Astrophysics Data System (ADS)

Vourlidas, A.

2012-01-01

In the last few years, we have been treated to an unusual visual feast of solar observations of the corona in EUV wavelengths. The observations from the two vantage points of STEREO/SECCHI are now capturing the entire solar atmosphere simultaneously in four wavelengths. The SDO/AIA images provide us with arcsecond resolution images of the full visible disk in ten wavelengths. All these data are captured with cadences of a few seconds to a few minutes. In this talk, I review some intriguing results from our first attempts to deal with these observations which touch upon the problems of coronal mass ejection initiation and solar wind generation. I will also discuss data processing techniques that may help us recover even more information from the images. The talk will contain a generous portion of beautiful EUV images and movies of the solar corona.

SuperHERO: the next generation hard x-ray HEROES telescope

NASA Astrophysics Data System (ADS)

Gaskin, Jessica A.; Christe, Steven D.; Elsner, Ronald F.; Kilaru, Kiranmayee; Ramsey, Brian D.; Seller, Paul; Shih, Albert Y.; Stuchlik, David W.; Swartz, Douglas A.; Tennant, Allyn F.; Weddendorf, Bruce; Wilson, Matthew D.; Wilson-Hodge, Colleen A.

2014-07-01

SuperHERO is a new high-resolution, Long Duration Balloon-capable, hard-x-ray (20-75 keV) focusing telescope for making novel astrophysics and heliophysics observations. The SuperHERO payload, currently in its proposal phase, is being developed jointly by the Astrophysics Office at NASA Marshall Space Flight Center and the Solar Physics Laboratory and the Wallops Flight Facility at NASA Goddard Space Flight Center. SuperHERO is a follow-on payload to the High Energy Replicated Optics to Explore the Sun (HEROES) balloon-borne telescope that recently flew from Fort Sumner, NM in September of 2013, and will utilize many of the same features. Significant enhancements to the HEROES payload will be made, including the addition of optics, novel solid-state multi-pixel CdTe detectors, integration of the Wallops Arc-Second Pointer and a significantly lighter gondola suitable for Long Duration Flights.

ATLAS Beam Steering Mechanism (BSM) Lessons Learned

NASA Technical Reports Server (NTRS)

Blumenstock, Kenneth A.; Cramer, Alexander K.; Gosten, Alan B.; Hakun, Claef F.; Haney, Paul G.; Hinkle, Matthew R.; Lee, Kenneth Y.; Lugo, Carlos F.; Matuszeski, Adam J.; Morell, Armando;

ATLAS Beam Steering Mechanism Lessons Learned

NASA Technical Reports Server (NTRS)

Blumenstock, Kenneth A.; Cramer, Alexander K.; Gostin, Alan B.; Hakun, Claef F.; Haney, Paul G.; Hinkle, Matthew R.; Lee, Kenneth Y.; Lugo, Carlos F.; Matuszeski, Adam J.; Morrell, Armando;

Localized sources of propagating acoustic waves in the solar photosphere

NASA Technical Reports Server (NTRS)

Brown, Timothy M.; Bogdan, Thomas J.; Lites, Bruce W.; Thomas, John H.

1992-01-01

A time series of Doppler measurements of the solar photosphere with moderate spatial resolution is described which covers a portion of the solar disk surrounding a small sunspot group. At temporal frequencies above 5.5 mHz, the Doppler field probes the spatial and temporal distribution of regions that emit acoustic energy. In the frequency range between 5.5 and 7.5 mHz, inclusive, a small fraction of the surface area emits a disproportionate amount of acoustic energy. The regions with excess emission are characterized by a patchy structure at spatial scales of a few arcseconds and by association (but not exact co-location) with regions having substantial magnetic field strength. These observations bear on the conjecture that most of the acoustic energy driving solar p-modes is created in localized regions occupying a small fraction of the solar surface area.

Fine-scale structure in the -185 kilometers per second absorption by HCO(+) in the Galactic center

NASA Technical Reports Server (NTRS)

Marr, Jonathan M.; Rudolph, Alexander L.; Pauls, Thomas A.; Wright, Melvyn C. H.; Backer, Donald C.

1992-01-01

We present a high-resolution study of the HCO(+) (J = 1-0) absorption by the 'high-velocity gas' at velocities between -170 and -200 km/s in Sgr A West. The absorption against the continuum radiation from the ionized gas features in Sgr A West (in particular the 'bar') is stronger than it is against Sgr A which is separated from the ionized gas by a few arcseconds. The positions of peak HCO(+) opacity coincide with the positions of Ne II emission at these velocities. These observations suggest that, even though emission is detected from gas at these high velocities over several arcminutes, some of the absorbing molecular gas may be mixed in with the ionized gas close to Sgr A. Simple calculations show that sufficient shielding can exist in the ionized features to allow molecules to survive very close to the ionizing source.

X-ray long-term variations in the low-luminosity AGN NGC 835 and its circumnuclear emission

NASA Astrophysics Data System (ADS)

González-Martín, O.; Hernández-García, L.; Masegosa, J.; Márquez, I.; Rodríguez-Espinosa, J. M.; Acosta-Pulido, J. A.; Alonso-Herrero, A.; Dultzin, D.; Esparza Arredondo, D.

2016-03-01

Context. Obscured active galactic nuclei (AGNs) are thought to be very common in the Universe. Observations and surveys have shown that the number of sources increases for near galaxies and at the low-luminosity regime (the so-called LLAGNs). Furthermore, many AGNs show changes in their obscuration properties at X-rays that may suggest a configuration of clouds very close to the accretion disk. However, these variations could also be due to changes in the intrinsic continuum of the source. It is therefore important to study nearby AGN to better understand the locus and distribution of clouds in the neighbourhood of the nucleus. Aims: We aim to study the nuclear obscuration of LLAGN NGC 835 and its extended emission using mid-infrared observations. Methods: We present sub-arcsecond-resolution mid-infrared 11.5 μm imaging of the LLAGN galaxy NGC 835 obtained with the instrument CanariCam in the Gran Telescopio CANARIAS (GTC), archival Spitzer/IRS spectroscopy, and archival Chandra data observed in 2000, 2008, and 2013. Results: The GTC/CanariCam 11.5 μm image reveals faint extended emission out to ~6 arcsec. We obtained a nuclear flux of F(11.5 μm) ~ 18 mJy, whereas the extended emission accounts for 90% of the total flux within the 6 arcsec. This means that the low angular resolution (~4 arcsec) IRS spectrum is dominated by this extended emission and not by the AGN. This is clearly seen in the Spitzer/IRS spectrum, which resembles that of star-forming galaxies. Although the extended soft X-ray emission shows some resemblance with that of the mid-infrared, the knots seen at X-rays are mostly located in the inner side of this mid-infrared emission. The nuclear X-ray spectrum of the source has undergone a spectral change between 2000/2008 and 2013. We argue that this variation is most probably due to changes in the hydrogen column density from ~8 × 1023 cm-2 to ~3 × 1023 cm-2. NGC 835 therefore is one of the few LLAGN, together with NGC 1052, in which changes in the absorber can be claimed. FITS file for the 11.5 microns CanariCam/GTC image is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/587/A1

Modeling an Optical and Infrared Search for Extraterrestrial Intelligence Survey with Exoplanet Direct Imaging

NASA Astrophysics Data System (ADS)

Vides, Christina; Macintosh, Bruce; Ruffio, Jean-Baptiste; Nielsen, Eric; Povich, Matthew Samuel

2018-01-01

Gemini Planet Imager (GPI) is a direct high contrast imaging instrument coupled to the Gemini South Telescope. Its purpose is to image extrasolar planets around young (~<100Myr) and relatively close (=< 100 pc) stars in the near infrared. Using a combination of adaptive optics (AO) and image processing techniques, the signal of a planet can be differentiated from diffraction in the images. A coronagraph is vital to achieving high contrast images at small angular separations (=<0.2 arcseconds).With the emergence of OIRSETI (Optical and Infrared Search for Extraterrestrial Intelligence), we modeled GPI’s capabilities to detect an extraterrestrial continuous wave (CW) laser broadcasted within the H-band have been modeled. By using sensitivity evaluated for actual GPI observations of young target stars, we produced models of the CW laser power as a function of distance from the star that could be detected if GPI were to observe nearby (~ 3-5 pc) planet-hosting G-type stars. We took a variety of transmitters into consideration in producing these modeled values. GPI is known to be sensitive to both pulsed and CW coherent electromagnetic radiation. The results were compared to similar studies and it was found that these values are competitive to other optical and infrared observations.

In vivo High Angular Resolution Diffusion-Weighted Imaging of Mouse Brain at 16.4 Tesla

PubMed Central

Alomair, Othman I.; Brereton, Ian M.; Smith, Maree T.; Galloway, Graham J.; Kurniawan, Nyoman D.

2015-01-01

Magnetic Resonance Imaging (MRI) of the rodent brain at ultra-high magnetic fields (> 9.4 Tesla) offers a higher signal-to-noise ratio that can be exploited to reduce image acquisition time or provide higher spatial resolution. However, significant challenges are presented due to a combination of longer T 1 and shorter T 2/T2* relaxation times and increased sensitivity to magnetic susceptibility resulting in severe local-field inhomogeneity artefacts from air pockets and bone/brain interfaces. The Stejskal-Tanner spin echo diffusion-weighted imaging (DWI) sequence is often used in high-field rodent brain MRI due to its immunity to these artefacts. To accurately determine diffusion-tensor or fibre-orientation distribution, high angular resolution diffusion imaging (HARDI) with strong diffusion weighting (b >3000 s/mm2) and at least 30 diffusion-encoding directions are required. However, this results in long image acquisition times unsuitable for live animal imaging. In this study, we describe the optimization of HARDI acquisition parameters at 16.4T using a Stejskal-Tanner sequence with echo-planar imaging (EPI) readout. EPI segmentation and partial Fourier encoding acceleration were applied to reduce the echo time (TE), thereby minimizing signal decay and distortion artefacts while maintaining a reasonably short acquisition time. The final HARDI acquisition protocol was achieved with the following parameters: 4 shot EPI, b = 3000 s/mm2, 64 diffusion-encoding directions, 125×150 μm2 in-plane resolution, 0.6 mm slice thickness, and 2h acquisition time. This protocol was used to image a cohort of adult C57BL/6 male mice, whereby the quality of the acquired data was assessed and diffusion tensor imaging (DTI) derived parameters were measured. High-quality images with high spatial and angular resolution, low distortion and low variability in DTI-derived parameters were obtained, indicating that EPI-DWI is feasible at 16.4T to study animal models of white matter (WM) diseases. PMID:26110770

Transit time spreads in biased paracentric hemispherical deflection analyzers

NASA Astrophysics Data System (ADS)

Sise, Omer; Zouros, Theo J. M.

2016-02-01

The biased paracentric hemispherical deflection analyzers (HDAs) are an alternative to conventional (centric) HDAs maintaining greater dispersion, lower angular aberrations, and hence better energy resolution without the use of any additional fringing field correctors. In the present work, the transit time spread of the biased paracentric HDA is computed over a wide range of analyzer parameters. The combination of high energy resolution with good time resolution and simplicity of design makes the biased paracentric analyzers very promising for both coincidence and singles spectroscopy applications.

Development of ultrahigh-resolution inelastic x-ray scattering optics

NASA Astrophysics Data System (ADS)

Huang, Xian-Rong; Zhong, Zhong; Cai, Yong Q.; Coburn, S.

2008-08-01

One of the major goals of the National Synchrotron Light Source II project is to achieve ultrahigh energy resolution up to 0.1 meV for medium-energy inelastic X-ray scattering spectroscopy based on the angular dispersion optics employing extremely asymmetric backscattering geometry. In this papaer, we describe the complete monochromatization mechanisms underlying the new optics. We have also designed and tested a CDW-CDW prototype under ambient condition, with which we have successfully demonstrated the important angular dispersion effect, the Borrman enhanced transmission effect, and other optical principles involved in every step of the entire diffraction process, and found good agreement with the theoretical expectations. These studies indicate that the new optics are feasible in principle but face some technical challenges that need to be solved by our future systematic research and development activities before their practical applications.

Optical circular deflector with attosecond resolution for ultrashort electron beam

DOE PAGES

Zhang, Zhen; Du, Yingchao; Tang, Chuanxiang; ...

2017-05-25

A novel method using high-power laser as a circular deflector is proposed for the measurement of femtosecond (fs) and sub-fs electron beam. In the scheme, the electron beam interacts with a laser pulse operating in a radially polarized doughnut mode ( TEM 01 * ) in a helical undulator, generating angular kicks along the beam in two directions at the same time. The phase difference between the two angular kicks makes the beam form a ring after a propagation section with appropriate phase advance, which can reveal the current profile of the electron beam. Detailed theoretical analysis of the methodmore » and numerical results with reasonable parameters are both presented. Lastly, it is shown that the temporal resolution can reach up to ~ 100 attosecond, which is a significant improvement for the diagnostics of ultrashort electron beam.« less

Optical circular deflector with attosecond resolution for ultrashort electron beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Zhen; Du, Yingchao; Tang, Chuanxiang

A novel method using high-power laser as a circular deflector is proposed for the measurement of femtosecond (fs) and sub-fs electron beam. In the scheme, the electron beam interacts with a laser pulse operating in a radially polarized doughnut mode ( TEM 01 * ) in a helical undulator, generating angular kicks along the beam in two directions at the same time. The phase difference between the two angular kicks makes the beam form a ring after a propagation section with appropriate phase advance, which can reveal the current profile of the electron beam. Detailed theoretical analysis of the methodmore » and numerical results with reasonable parameters are both presented. Lastly, it is shown that the temporal resolution can reach up to ~ 100 attosecond, which is a significant improvement for the diagnostics of ultrashort electron beam.« less

Angular Distribution of light emission in ELVES events

NASA Astrophysics Data System (ADS)

Mussa, Roberto

2017-04-01

The Pierre Auger Observatory, located in Malargüe (Argentina), is the largest facility (3000 kmq ) for the study of Ultra High Energy Cosmic Rays (E>0.3 EeV). The four sites of the Fluorescence Detector (FD) are continuously observing the night sky with moon fraction below 50% (13% duty cycle) with 100 ns time resolution and a space resolution below one degree. Since 2013, the Observatory has implemented a dedicated trigger for the study of ELVES events, produced by lightning activity in Northern Argentina during summer months. A network of ancillary devices (lidars, cloud cameras, weather stations, lightning sensors, E-field mills) complements the FD data to correct for the variation of atmospheric optical properties. This paper will report about the angular distribution of the light emission around the vertical above the lightning source and compare with existing models.

The Advanced Gamma-ray Imaging System (AGIS): Focal Plane Detectors

NASA Astrophysics Data System (ADS)

Mukherjee, Reshmi; Byrum, K.; Drake, G.; Falcone, A.; Funk, S.; Horan, D.; Tajima, H.; Wagner, B.; Williams, D.

2008-04-01

Report of the Focal Plane Instrumentation Working Group, AGIS collaboration: The Advanced Gamma-ray Imaging System (AGIS) is a concept for the next generation instrument in ground-based very high energy gamma-ray astronomy. It has the goal of achieving significant improvement in sensitivity over current experiments. One of the main requirements for AGIS will be to achieve higher angular resolution than current imaging atmospheric Cherenkov telescopes (IACTs). Simulations show that a substantial improvement in angular resolution may be achieved if the pixel size is reduced to 0.05 deg, below that of current IACTs. Reducing the cost per channel and improving reliability and modularity are other important considerations. Here we present several alternatives being considered for AGIS, including both silicon photomultipliers (SiPMs) and multi-anode photomultipliers (MAPMTs) and summarize results from feasibility testing by various AGIS photodetector group members.

Differential Deposition for Surface Figure Corrections in Grazing Incidence X-Ray Optics

NASA Technical Reports Server (NTRS)

Ramsey, Brian D.; Kilaru, Kiranmayee; Atkins, Carolyn; Gubarev, Mikhail V.; Broadway, David M.

2015-01-01

Differential deposition corrects the low- and mid- spatial-frequency deviations in the axial figure of Wolter-type grazing incidence X-ray optics. Figure deviations is one of the major contributors to the achievable angular resolution. Minimizing figure errors can significantly improve the imaging quality of X-ray optics. Material of varying thickness is selectively deposited, using DC magnetron sputtering, along the length of optic to minimize figure deviations. Custom vacuum chambers are built that can incorporate full-shell and segmented Xray optics. Metrology data of preliminary corrections on a single meridian of full-shell x-ray optics show an improvement of mid-spatial frequencies from 6.7 to 1.8 arc secs HPD. Efforts are in progress to correct a full-shell and segmented optics and to verify angular-resolution improvement with X-ray testing.

Milliarcsecond Astronomy with the CHARA Array

NASA Astrophysics Data System (ADS)

Schaefer, Gail; ten Brummelaar, Theo; Gies, Douglas; Jones, Jeremy; Farrington, Christopher

2018-01-01

The Center for High Angular Resolution Astronomy offers 50 nights per year of open access time at the CHARA Array. The Array consists of six telescopes linked together as an interferometer, providing sub-milliarcsecond resolution in the optical and near-infrared. The Array enables a variety of scientific studies, including measuring stellar angular diameters, imaging stellar shapes and surface features, mapping the orbits of close binary companions, and resolving circumstellar environments. The open access time is part of an NSF/MSIP funded program to open the CHARA Array to the broader astronomical community. As part of the program, we will build a searchable database for the CHARA data archive and run a series of one-day community workshops at different locations across the country to expand the user base for stellar interferometry and encourage new scientific investigations with the CHARA Array.

C 3, A Command-line Catalog Cross-match Tool for Large Astrophysical Catalogs

NASA Astrophysics Data System (ADS)

Riccio, Giuseppe; Brescia, Massimo; Cavuoti, Stefano; Mercurio, Amata; di Giorgio, Anna Maria; Molinari, Sergio

2017-02-01

Modern Astrophysics is based on multi-wavelength data organized into large and heterogeneous catalogs. Hence, the need for efficient, reliable and scalable catalog cross-matching methods plays a crucial role in the era of the petabyte scale. Furthermore, multi-band data have often very different angular resolution, requiring the highest generality of cross-matching features, mainly in terms of region shape and resolution. In this work we present C 3 (Command-line Catalog Cross-match), a multi-platform application designed to efficiently cross-match massive catalogs. It is based on a multi-core parallel processing paradigm and conceived to be executed as a stand-alone command-line process or integrated within any generic data reduction/analysis pipeline, providing the maximum flexibility to the end-user, in terms of portability, parameter configuration, catalog formats, angular resolution, region shapes, coordinate units and cross-matching types. Using real data, extracted from public surveys, we discuss the cross-matching capabilities and computing time efficiency also through a direct comparison with some publicly available tools, chosen among the most used within the community, and representative of different interface paradigms. We verified that the C 3 tool has excellent capabilities to perform an efficient and reliable cross-matching between large data sets. Although the elliptical cross-match and the parametric handling of angular orientation and offset are known concepts in the astrophysical context, their availability in the presented command-line tool makes C 3 competitive in the context of public astronomical tools.

Longitudinal spatial coherence gated high-resolution tomography and quantitative phase microscopy of biological cells and tissues with uniform illumination

NASA Astrophysics Data System (ADS)

Mehta, Dalip Singh; Ahmad, Azeem; Dubey, Vishesh; Singh, Veena; Butola, Ankit; Mohanty, Tonmoy; Nandi, Sreyankar

2018-02-01

We report longitudinal spatial coherence (LSC) gated high-resolution tomography and quantitative phase microscopy of biological cells and tissues with uniform illumination using laser as a light source. To accomplish this a pseudo thermal light source was synthesized by passing laser beams through an optical system, which is basically a speckle reduction system with combined effect of spatial, temporal, angular and polarisation diversity. The longitudinal spatial coherence length of such light was significantly reduced by synthesizing a pseudo thermal source with the combined effect of spatial, angular and temporal diversity. This results in a low spatially coherent (i.e., broad angular frequency spectrum) light source with narrow temporal frequency spectrum. Light from such a pseudo thermal light source was passed through an interference microscope with varying magnification, such as, 10X and 50X. The interference microscope was used for full-field OCT imaging of multilayer objects and topography of industrial objects. Experimental results of optical sectioning of multilayer biological objects with high axial-resolution less than 10μm was achieved which is comparable to broadband white light source. The synthesized light source with reduced speckles having uniform illumination on the sample, which can be very useful for fluorescence microscopy as well as quantitative phase microscopy with less phase noise. The present system does not require any dispersion compensation optical system for biological samples as a highly monochromatic light source is used.

Linear transforms for Fourier data on the sphere: application to high angular resolution diffusion MRI of the brain.

PubMed

Haldar, Justin P; Leahy, Richard M

2013-05-01

This paper presents a novel family of linear transforms that can be applied to data collected from the surface of a 2-sphere in three-dimensional Fourier space. This family of transforms generalizes the previously-proposed Funk-Radon Transform (FRT), which was originally developed for estimating the orientations of white matter fibers in the central nervous system from diffusion magnetic resonance imaging data. The new family of transforms is characterized theoretically, and efficient numerical implementations of the transforms are presented for the case when the measured data is represented in a basis of spherical harmonics. After these general discussions, attention is focused on a particular new transform from this family that we name the Funk-Radon and Cosine Transform (FRACT). Based on theoretical arguments, it is expected that FRACT-based analysis should yield significantly better orientation information (e.g., improved accuracy and higher angular resolution) than FRT-based analysis, while maintaining the strong characterizability and computational efficiency of the FRT. Simulations are used to confirm these theoretical characteristics, and the practical significance of the proposed approach is illustrated with real diffusion weighted MRI brain data. These experiments demonstrate that, in addition to having strong theoretical characteristics, the proposed approach can outperform existing state-of-the-art orientation estimation methods with respect to measures such as angular resolution and robustness to noise and modeling errors. Copyright © 2013 Elsevier Inc. All rights reserved.

Exploring the particle nature of dark matter with the All-sky Medium Energy Gamma-ray Observatory (AMEGO)

NASA Astrophysics Data System (ADS)

Caputo, Regina; Meyer, Manuel; Sánchez-Conde, Miguel; AMEGO

2018-01-01

The era of precision cosmology has revealed that ~80% of the matter in the universe is dark matter. Two leading candidates, motivated by both particle and astrophysics, are Weakly Interacting Massive Particles (WIMPs) and Weakly Interacting Sub-eV Particles (WISPs) like axions and axionlike particles. Both WIMPs and WISPs have distinct gamma-ray signatures. Data from the Fermi Large Area Telescope (Fermi-LAT) continues to be an integral part of the search for these dark matter signatures spanning the 50 MeV to >300 GeV energy range in a variety of astrophysical targets. Thus far, there are no conclusive detections; however, there is an intriguing excess of gamma rays associated with Galactic center (GCE) that could be explained with WIMP annihilation. The angular resolution of the LAT at lower energies makes source selection challenging and the true nature of the detected signal remains unknown. WISP searches using, e.g. supernova explosions, spectra of blazars, or strongly magnetized environments, would also greatly benefit from increased angular and energy resolution, as well as from polarization measurements. To address these, we are developing AMEGO, the All-sky Medium Energy Gamma-ray Observatory. This instrument has a projected energy and angular resolution that will increase sensitivity by a factor of 20-50 over previous instruments. This will allow us to explore new areas of dark matter parameter space and provide unprecedented access to its particle nature.

Fault Detection and Correction for the Solar Dynamics Observatory Attitude Control System

NASA Technical Reports Server (NTRS)

Starin, Scott R.; Vess, Melissa F.; Kenney, Thomas M.; Maldonado, Manuel D.; Morgenstern, Wendy M.

2007-01-01

The Solar Dynamics Observatory is an Explorer-class mission that will launch in early 2009. The spacecraft will operate in a geosynchronous orbit, sending data 24 hours a day to a devoted ground station in White Sands, New Mexico. It will carry a suite of instruments designed to observe the Sun in multiple wavelengths at unprecedented resolution. The Atmospheric Imaging Assembly includes four telescopes with focal plane CCDs that can image the full solar disk in four different visible wavelengths. The Extreme-ultraviolet Variability Experiment will collect time-correlated data on the activity of the Sun's corona. The Helioseismic and Magnetic Imager will enable study of pressure waves moving through the body of the Sun. The attitude control system on Solar Dynamics Observatory is responsible for four main phases of activity. The physical safety of the spacecraft after separation must be guaranteed. Fine attitude determination and control must be sufficient for instrument calibration maneuvers. The mission science mode requires 2-arcsecond control according to error signals provided by guide telescopes on the Atmospheric Imaging Assembly, one of the three instruments to be carried. Lastly, accurate execution of linear and angular momentum changes to the spacecraft must be provided for momentum management and orbit maintenance. In thsp aper, single-fault tolerant fault detection and correction of the Solar Dynamics Observatory attitude control system is described. The attitude control hardware suite for the mission is catalogued, with special attention to redundancy at the hardware level. Four reaction wheels are used where any three are satisfactory. Four pairs of redundant thrusters are employed for orbit change maneuvers and momentum management. Three two-axis gyroscopes provide full redundancy for rate sensing. A digital Sun sensor and two autonomous star trackers provide two-out-of-three redundancy for fine attitude determination. The use of software to maximize chances of recovery from any hardware or software fault is detailed. A generic fault detection and correction software structure is used, allowing additions, deletions, and adjustments to fault detection and correction rules. This software structure is fed by in-line fault tests that are also able to take appropriate actions to avoid corruption of the data stream.

Mid-infrared interferometry towards the massive young stellar object CRL 2136: inside the dust rim

NASA Astrophysics Data System (ADS)

de Wit, W. J.; Hoare, M. G.; Oudmaijer, R. D.; Nürnberger, D. E. A.; Wheelwright, H. E.; Lumsden, S. L.

2011-02-01

Context. Establishing the importance of circumstellar disks and their properties is crucial to fully understand massive star formation. Aims: We aim to spatially resolve the various components that make-up the accretion environment of a massive young stellar object (⪉100 AU), and reproduce the emission from near-infrared to millimeter wavelengths using radiative transfer codes. Methods: We apply mid-infrared spectro-interferometry to the massive young stellar object CRL 2136. The observations were performed with the Very Large Telescope Interferometer and the MIDI instrument at a 42 m baseline probing angular scales of 50 milli-arcseconds. We model the observed visibilities in parallel with diffraction-limited images at both 24.5 μm and in the N-band (with resolutions of 0.6´´and 0.3´´, respectively), as well as the spectral energy distribution. Results: The arcsec-scale spatial information reveals the well-resolved emission from the dusty envelope. By simultaneously modelling the spatial and spectral data, we find that the bulk of the dust emission occurs at several dust sublimation radii (approximately 170 AU). This reproduces the high mid-infrared fluxes and at the same time the low visibilities observed in the MIDI data for wavelengths longward of 8.5 μm. However, shortward of this wavelength the visibility data show a sharp up-turn indicative of compact emission. We discuss various potential sources of this emission. We exclude a dust disk being responsible for the observed spectral imprint on the visibilities. A cool supergiant star and an accretion disk are considered and both shown to be viable origins of the compact mid-infrared emission. Conclusions: We propose that CRL 2136 is embedded in a dusty envelope, which truncates at several times the dust sublimation radius. A dust torus is manifest in the equatorial region. We find that the spectro-interferometric N-band signal can be reproduced by either a gaseous disk or a bloated central star. If the disk extends to the stellar surface, it accretes at a rate of 3.0 × 10-3 M⊙ yr-1. Based on observations with the VLTI, proposal 381.C-0607.

Toward Measuring Galactic Dense Molecular Gas Properties and 3D Distribution with Hi-GAL

NASA Astrophysics Data System (ADS)

Zetterlund, Erika; Glenn, Jason; Maloney, Phil

2016-01-01

The Herschel Space Observatory's submillimeter dust continuum survey Hi-GAL provides a powerful new dataset for characterizing the structure of the dense interstellar medium of the Milky Way. Hi-GAL observed a 2° wide strip covering the entire 360° of the Galactic plane in broad bands centered at 70, 160, 250, 350, and 500 μm, with angular resolution ranging from 10 to 40 arcseconds. We are adapting a molecular cloud clump-finding algorithm and a distance probability density function distance-determination method developed for the Bolocam Galactic Plane Survey (BGPS) to the Hi-GAL data. Using these methods we expect to generate a database of 105 cloud clumps, derive distance information for roughly half the clumps, and derive precise distances for approximately 20% of them. With five-color photometry and distances, we will measure the cloud clump properties, such as luminosities, physical sizes, and masses, and construct a three-dimensional map of the Milky Way's dense molecular gas distribution.The cloud clump properties and the dense gas distribution will provide critical ground truths for comparison to theoretical models of molecular cloud structure formation and galaxy evolution models that seek to emulate spiral galaxies. For example, such models cannot resolve star formation and use prescriptive recipes, such as converting a fixed fraction of interstellar gas to stars at a specified interstellar medium density threshold. The models should be compared to observed dense molecular gas properties and galactic distributions.As a pilot survey to refine the clump-finding and distance measurement algorithms developed for BGPS, we have identified molecular cloud clumps in six 2° × 2° patches of the Galactic plane, including one in the inner Galaxy along the line of sight through the Molecular Ring and the termination of the Galactic bar and one toward the outer Galaxy. Distances have been derived for the inner Galaxy clumps and compared to Bolocam Galactic Plane Survey results. We present the pilot survey clump catalog, distances, clump properties, and a comparison to BGPS.

Characterization of the angular memory effect of scattered light in biological tissues.

PubMed

Schott, Sam; Bertolotti, Jacopo; Léger, Jean-Francois; Bourdieu, Laurent; Gigan, Sylvain

2015-05-18

High resolution optical microscopy is essential in neuroscience but suffers from scattering in biological tissues and therefore grants access to superficial brain layers only. Recently developed techniques use scattered photons for imaging by exploiting angular correlations in transmitted light and could potentially increase imaging depths. But those correlations ('angular memory effect') are of a very short range and should theoretically be only present behind and not inside scattering media. From measurements on neural tissues and complementary simulations, we find that strong forward scattering in biological tissues can enhance the memory effect range and thus the possible field-of-view by more than an order of magnitude compared to isotropic scattering for ∼1 mm thick tissue layers.

Quantum entanglement of high angular momenta.

PubMed

Fickler, Robert; Lapkiewicz, Radek; Plick, William N; Krenn, Mario; Schaeff, Christoph; Ramelow, Sven; Zeilinger, Anton

2012-11-02

Single photons with helical phase structures may carry a quantized amount of orbital angular momentum (OAM), and their entanglement is important for quantum information science and fundamental tests of quantum theory. Because there is no theoretical upper limit on how many quanta of OAM a single photon can carry, it is possible to create entanglement between two particles with an arbitrarily high difference in quantum number. By transferring polarization entanglement to OAM with an interferometric scheme, we generate and verify entanglement between two photons differing by 600 in quantum number. The only restrictive factors toward higher numbers are current technical limitations. We also experimentally demonstrate that the entanglement of very high OAM can improve the sensitivity of angular resolution in remote sensing.

MISR Level 2 TOA/Cloud Classifier parameters (MIL2TCCL_V3)

NASA Technical Reports Server (NTRS)

Diner, David J. (Principal Investigator)

The TOA/Cloud Classifiers contain the Angular Signature Cloud Mask (ASCM), a scene classifier calculated using support vector machine technology (SVM) both of which are on a 1.1 km grid, and cloud fractions at 17.6 km resolution that are available in different height bins (low, middle, high) and are also calculated on an angle-by-angle basis. [Temporal_Coverage: Start_Date=2000-02-24; Stop_Date=] [Spatial_Coverage: Southernmost_Latitude=-90; Northernmost_Latitude=90; Westernmost_Longitude=-180; Easternmost_Longitude=180] [Data_Resolution: Latitude_Resolution=1.1 km; Longitude_Resolution=1.1 km; Temporal_Resolution=about 15 orbits/day].

Measurements and calculations of high-angular-momentum satellite transitions in Li 1s photoionization

NASA Astrophysics Data System (ADS)

Cheng, W. T.; Kukk, E.; Cubaynes, D.; Chang, J.-C.; Snell, G.; Bozek, J. D.; Wuilleumier, F. J.; Berrah, N.

2000-12-01

Lithium 1s photoelectron spectra are reported in high electron and photon energy resolution, with resolved LS term structure of the Li+ 1snl satellite transitions up to n=6. Branching ratios and anisotropy parameters of individual lines, determined over the 85-130 eV photon energy range, are compared with R-matrix calculations and with previous works. The high-angular-momentum satellite lines (L>=2) are found to contribute significantly to the 1snl satellite cross sections for n=3 and 4, and to become the dominant terms for n>=5. The high-angular-momentum lines exhibit the same photon-energy-dependence as the P-lines, providing experimental evidence that the continuum-continuum state coupling (equivalent to virtual electron collision processes) is responsible for the L>=1 terms in the satellite spectrum, in contrast to the electron relaxation (shake-up) mechanism responsible for the S-terms. The angular distribution of the lines in the Li+ 1snl, n=2-6 groups, determined at 110 eV photon energy, is in good agreement with calculations, showing more isotropic distributions for high-angular-momentum lines.

Radial q-space sampling for DSI

PubMed Central

Baete, Steven H.; Yutzy, Stephen; Boada, Fernando, E.

2015-01-01

Purpose Diffusion Spectrum Imaging (DSI) has been shown to be an effective tool for non-invasively depicting the anatomical details of brain microstructure. Existing implementations of DSI sample the diffusion encoding space using a rectangular grid. Here we present a different implementation of DSI whereby a radially symmetric q-space sampling scheme for DSI (RDSI) is used to improve the angular resolution and accuracy of the reconstructed Orientation Distribution Functions (ODF). Methods Q-space is sampled by acquiring several q-space samples along a number of radial lines. Each of these radial lines in q-space is analytically connected to a value of the ODF at the same angular location by the Fourier slice theorem. Results Computer simulations and in vivo brain results demonstrate that RDSI correctly estimates the ODF when moderately high b-values (4000 s/mm2) and number of q-space samples (236) are used. Conclusion The nominal angular resolution of RDSI depends on the number of radial lines used in the sampling scheme, and only weakly on the maximum b-value. In addition, the radial analytical reconstruction reduces truncation artifacts which affect Cartesian reconstructions. Hence, a radial acquisition of q-space can be favorable for DSI. PMID:26363002

Absolute angular encoder based on optical diffraction

NASA Astrophysics Data System (ADS)

Wu, Jian; Zhou, Tingting; Yuan, Bo; Wang, Liqiang

2015-08-01

A new encoding method for absolute angular encoder based on optical diffraction was proposed in the present study. In this method, an encoder disc is specially designed that a series of elements are uniformly spaced in one circle and each element is consisted of four diffraction gratings, which are tilted in the directions of 30°, 60°, -60° and -30°, respectively. The disc is illuminated by a coherent light and the diffractive signals are received. The positions of diffractive spots are used for absolute encoding and their intensities are for subdivision, which is different from the traditional optical encoder based on transparent/opaque binary principle. Since the track's width in the disc is not limited in the diffraction pattern, it provides a new way to solve the contradiction between the size and resolution, which is good for minimization of encoder. According to the proposed principle, the diffraction pattern disc with a diameter of 40 mm was made by lithography in the glass substrate. A prototype of absolute angular encoder with a resolution of 20" was built up. Its maximum error was tested as 78" by comparing with a small angle measuring system based on laser beam deflection.

Forming disc galaxies in major mergers - III. The effect of angular momentum on the radial density profiles of disc galaxies

NASA Astrophysics Data System (ADS)

Peschken, N.; Athanassoula, E.; Rodionov, S. A.

2017-06-01

We study the effect of angular momentum on the surface density profiles of disc galaxies, using high-resolution simulations of major mergers whose remnants have downbending radial density profiles (type II). As described in the previous papers of this series, in this scenario, most of the disc mass is acquired after the collision via accretion from a hot gaseous halo. We find that the inner and outer disc scalelengths, as well as the break radius, correlate with the total angular momentum of the initial merging system, and are larger for high-angular momentum systems. We follow the angular momentum redistribution in our simulated galaxies, and find that like the mass, the disc angular momentum is acquired via accretion, I.e. to the detriment of the gaseous halo. Furthermore, high-angular momentum systems give more angular momentum to their discs, which directly affects their radial density profile. Adding simulations of isolated galaxies to our sample, we find that the correlations are valid also for disc galaxies evolved in isolation. We show that the outer part of the disc at the end of the simulation is populated mainly by inside-out stellar migration, and that in galaxies with higher angular momentum, stars travel radially further out. This, however, does not mean that outer disc stars (in type II discs) were mostly born in the inner disc. Indeed, generally the break radius increases over time, and not taking this into account leads to overestimating the number of stars born in the inner disc.

MISR Level 2 TOA/Cloud Classifier parameters (MIL2TCCL_V2)

NASA Technical Reports Server (NTRS)

Diner, David J. (Principal Investigator)

The TOA/Cloud Classifiers contain the Angular Signature Cloud Mask (ASCM), a scene classifier calculated using support vector machine technology (SVM) both of which are on a 1.1 km grid, and cloud fractions at 17.6 km resolution that are available in different height bins (low, middle, high) and are also calculated on an angle-by-angle basis. [Location=GLOBAL] [Temporal_Coverage: Start_Date=2000-02-24; Stop_Date=] [Spatial_Coverage: Southernmost_Latitude=-90; Northernmost_Latitude=90; Westernmost_Longitude=-180; Easternmost_Longitude=180] [Data_Resolution: Latitude_Resolution=17.6 km; Longitude_Resolution=17.6 km; Horizontal_Resolution_Range=10 km - < 50 km or approximately .09 degree - < .5 degree; Temporal_Resolution=about 15 orbits/day; Temporal_Resolution_Range=Daily - < Weekly, Daily - < Weekly].

Global astrometry with OSI

NASA Astrophysics Data System (ADS)

Loiseau, Sacha; Malbet, Fabien; Yu, Jeffrey W.

1995-06-01

We present a method for performing global astrometry with the proposed Orbiting Stellar Interferometer. Because it is dedicated to wide-angle astrometry, OSI has the intrinsic capabilities to achieve global astrometry, even though it doesn't measure directly relative angles between pairs of stars, such as HIPPARCOS. In this paper, a time-independent model is shown, leading to a coherent solution for the positions of reference stars on the whole sky. With an initial measurement accuracy of 10 micro-arcseconds, corresponding to an accuracy of 340 picometers in the knowledge of the delay-line position of the observing interferometer, the consistent least-squares solution gives an accuracy by which the astrometric parameters can be obtained around 2 - 3 micro-arcseconds.

Modeling Protostar Envelopes and Disks Seen With ALMA: A Focus on L1527 Kinematics

NASA Astrophysics Data System (ADS)

Terebey, Susan; Flores Rivera, Lizxandra; Willacy, Karen

2018-06-01

ALMA probes continuum and spectral line emission from protostars that comes from both the envelope and circumstellar disk. The dust and gas emit on a variety of spatial scales, ranging from sub-arcseconds for disks to roughly 10 arcseconds for envelopes for nearby protostars. We present models of what ALMA should detect that incorporate a self-consistent collapse solution, radiative transfer, and realistic dust properties. Molecular abundances are also calculated; we present results for CO and isotopologues for the Class 0 source L1527. Results for the outer disk show that there can be significant differences from standard assumptions due to the effect of CO freeze out and non-Keplerian dynamics.

A Universal Angular Momentum Profile for Dark Matter Halos

NASA Astrophysics Data System (ADS)

Liao, Shihong; Chen, Jianxiong; Chu, M.-C.

2017-07-01

The angular momentum distribution in dark matter halos and galaxies is a key ingredient in understanding their formation. Specifically, the internal distribution of angular momenta is closely related to the formation of disk galaxies. In this article, we use halos identified from a high-resolution simulation, the Bolshoi simulation, to study the spatial distribution of specific angular momenta, j(r,θ ). We show that by stacking halos with similar masses to increase the signal-to-noise ratio, the profile can be fitted as a simple function, j{(r,θ )={j}s{\\sin }2{(θ /{θ }s)(r/{r}s)}2/(1+r/{r}s)}4, with three free parameters, {j}s,{r}s, and {θ }s. Specifically, j s correlates with the halo mass M vir as {j}s\\propto {M}{vir}2/3, r s has a weak dependence on the halo mass as {r}s\\propto {M}{vir}0.040, and {θ }s is independent of M vir. This profile agrees with that from a rigid shell model, though its origin is unclear. Our universal specific angular momentum profile j(r,θ ) is useful in modeling the angular momenta of halos. Furthermore, by using an empirical stellar mass-halo mass relation, we can infer the average angular momentum distribution of a dark matter halo. The specific angular momentum-stellar mass relation within a halo computed from our profile is shown to share a similar shape as that from the observed disk galaxies.

First results from stellar occultations in the "GAIA era"

NASA Astrophysics Data System (ADS)

Benedetti-Rossi, G.; Vieira-Martins, R.; Sicardy, B.

2017-09-01

Stellar occultation is a powerful technique to study distant solar system bodies. It allows high angular resolution of the occulting body from the analysis of a light curve acquired with high temporal resolution with uncertainties comparable as probes. In the "GAIA era", stellar occultations is now able to obtain even more impressive results such as the presence of atmosphere, rings and topographic features.

Prototype Test Results for the Single Photon Detection SLR2000 Satellite Laser Ranging System

NASA Technical Reports Server (NTRS)

Zagwodzki, Thomas W.; McGarry, Jan F.; Degnan, John J.; Cheek, Jack W.; Dunn, Peter J.; Patterson, Don; Donovan, Howard

2004-01-01

NASA's aging Satellite Laser Ranging (SLR) network is scheduled to be replaced over the next few years with a fully automated single photon detection system. A prototype of this new system, called SLR2000, is currently undergoing field trials at the Goddard Space Flight Center in Greenbelt, Maryland to evaluate photon counting techniques and determine system hardware, software, and control algorithm performance levels and limitations. Newly developed diode pumped microchip lasers and quadrant microchannel plate-based photomultiplier tubes have enabled the development of this high repetition rate single photon detection SLR system. The SLR2000 receiver threshold is set at the single photoelectron (pe) level but tracks satellites with an average signal level typically much less than 1 pe. The 2 kHz laser fire rate aids in satellite acquisition and tracking and will enable closed loop tracking by accumulating single photon count statistics in a quadrant detector and using this information to correct for pointing errors. Laser transmitter beamwidths of 10 arcseconds (FWHM) or less are currently being used to maintain an adequate signal level for tracking while the receiver field of view (FOV) has been opened to 40 arcseconds to accommodate point ahead/look behind angular offsets. In the near future, the laser transmitter point ahead will be controlled by a pair of Risley prisms. This will allow the telescope to point behind and enable closure of the receiver FOV to roughly match the transmitter beam divergence. Bandpass filters (BPF) are removed for night tracking operations while 0.2 nm or 1 nm filters are used during daylight operation. Both day and night laser tracking of Low Earth Orbit (LEO) satellites has been achieved with a laser transmitter energy of only 65 microjoules per pulse. Satellite tracking is presently limited to LEO satellites until the brassboard laser transmitter can be upgraded or replaced. Simultaneous tracks have also been observed with NASA s SLR standard, MOBLAS 7, for the purposes of data comparison and identification of biases. Work continues to optimize the receive optics; upgrade or replace the laser transmitter; calibrate the quadrant detector, the point ahead Risley prisms, and event timer verniers; and test normal point generation with SLR2000 data. This paper will report on the satellite tracking results to date, issues yet to be resolved, and future plans for the SLR2000 system.

A GEM readout with radial zigzag strips and linear charge-sharing response

DOE PAGES

Zhang, Aiwu; Hohlmann, Marcus; Azmoun, Babak; ...

2018-01-10

Here, we study the position sensitivity of radial zigzag strips intended to read out large GEM detectors for tracking at future experiments. Zigzag strips can cover a readout area with fewer strips than regular straight strips while maintaining good spatial resolution. Consequently, they can reduce the number of required electronic channels and related cost for large-area GEM detector systems. A non-linear relation between incident particle position and hit position measured from charge sharing among zigzag strips was observed in a previous study. We significantly reduce this non-linearity by improving the interleaving of adjacent physical zigzag strips. Zigzag readout structures aremore » implemented on PCBs and on a flexible foil and are tested using a 10 cm × 10 cm triple-GEM detector scanned with a strongly collimated X-ray gun on a 2D motorized stage. Lastly, angular resolutions of 60–84 μrad are achieved with a 1.37 mrad angular strip pitch at a radius of 784 mm. On a linear scale this corresponds to resolutions below 100 μm.« less