Science.gov

Sample records for radio polarimetry signatures

  1. Radio polarimetry of Galactic Centre pulsars

    NASA Astrophysics Data System (ADS)

    Schnitzeler, D. H. F. M.; Eatough, R. P.; Ferrière, K.; Kramer, M.; Lee, K. J.; Noutsos, A.; Shannon, R. M.

    2016-07-01

    To study the strength and structure of the magnetic field in the Galactic Centre (GC), we measured Faraday rotation of the radio emission of pulsars which are seen towards the GC. Three of these pulsars have the largest rotation measures (RMs) observed in any Galactic object with the exception of Sgr A⋆. Their large dispersion measures, RMs and the large RM variation between these pulsars and other known objects in the GC implies that the pulsars lie in the GC and are not merely seen in projection towards the GC. The large RMs of these pulsars indicate large line-of-sight magnetic field components between ˜ 16 and 33 μG; combined with recent model predictions for the strength of the magnetic field in the GC this implies that the large-scale magnetic field has a very small inclination angle with respect to the plane of the sky (˜12°). Foreground objects like the Radio Arc or possibly an ablated, ionized halo around the molecular cloud G0.11-0.11 could contribute to the large RMs of two of the pulsars. If these pulsars lie behind the Radio Arc or G0.11-0.11 then this proves that low-scattering corridors with lengths ≳100 pc must exist in the GC. This also suggests that future, sensitive observations will be able to detect additional pulsars in the GC. Finally, we show that the GC component in our most accurate electron density model oversimplifies structure in the GC.

  2. Multifrequency RATAN-600 radio polarimetry of the moon

    SciTech Connect

    Naugolnaia, M.N.; Soboleva, N.S.

    1986-04-01

    Polarization measurements of lunar radio emission at six wavelengths (1.38-31 cm) have improved the disk-averaged wavelength dependence of the dielectric constant. The shortward decrease in the dielectric constant testifies to a steep rise in density downward in the top 4-6 cm layer on the moon; at that level the radio data indicate a mean density within 10 percent of the value derived from the Apollo 12 sampling. As the surface temperature fluctuates from 90 to 360 K, the dielectric constant remains essentially unchanged. 12 references.

  3. Radio Astronomical Polarimetry and Point-Source Calibration

    NASA Astrophysics Data System (ADS)

    van Straten, W.

    2004-05-01

    A mathematical framework is presented for use in the experimental determination of the polarimetric response of observatory instrumentation. Elementary principles of linear algebra are applied to model the full matrix description of the polarization measurement equation by least-squares estimation of nonlinear, scalar parameters. The formalism is applied to calibrate the center element of the Parkes Multibeam receiver using observations of the millisecond pulsar PSR J0437-4715 and the radio galaxy 3C 218 (Hydra A).

  4. Polarimetry and Unification of Low-Redshift Radio Galaxies

    SciTech Connect

    Cohen, Marshall H.; Ogle, Patrick M.; Tran, Hien D.; Goodrich, Robert W.; Miller, Joseph S.

    1999-11-01

    We have made high-quality measurements of the polarization spectra of 13 FR II radio galaxies and taken polarization images for 11 of these with the Keck telescopes. Seven of the eight narrow-line radio galaxies (NLRGs) are polarized, and six of the seven show prominent broad Balmer lines in polarized light. The broad lines are also weakly visible in total flux. Some of the NLRGs show bipolar regions with roughly circumferential polarization vectors, revealing a large reflection nebula illuminated by a central source. Our observations powerfully support the hidden quasar hypothesis for some NLRGs. According to this hypothesis, the continuum and broad lines are blocked by a dusty molecular torus, but can be seen by reflected, hence polarized, light. Classification as a NLRG, a broad-line radio galaxy (BLRG), or a quasar therefore depends on orientation. However, not all objects fit into this unification scheme. Our sample is biased toward objects known in advance to be polarized, but the combination of our results with the 1996 findings of Hill, Goodrich, and DePoy show that at least six out of a complete, volume and flux-limited sample of nine FR II NLRGs have broad lines, seen either in polarization or P{alpha}.The BLRGs in our sample range from 3C 382, which has a quasar-like spectrum, to the highly reddened IRAS source FSC 2217+259. This reddening sequence suggests a continuous transition from unobscured quasar to reddened BLRG to NLRG. Apparently the obscuring torus does not have a distinct edge. The BLRGs have polarization images that are consistent with a point source broadened by seeing and diluted by starlight. We do not detect extended nebular or scattered emission, perhaps because it is swamped by the nuclear source. Our starlight-corrected BLRG spectra can be explained with a two-component model: a quasar viewed through dust and quasar light scattered by dust. The direct flux is more reddened than the scattered flux, causing the polarization to rise

  5. Multifrequency polarimetry of a complete sample of PACO radio sources

    NASA Astrophysics Data System (ADS)

    Galluzzi, V.; Massardi, M.; Bonaldi, A.; Casasola, V.; Gregorini, L.; Trombetti, T.; Burigana, C.; De Zotti, G.; Ricci, R.; Stevens, J.; Ekers, R. D.; Bonavera, L.; di Serego Alighieri, S.; Liuzzo, E.; López-Caniego, M.; Mignano, A.; Paladino, R.; Toffolatti, L.; Tucci, M.

    2017-03-01

    We present high-sensitivity polarimetric observations (σP ≃0.6 mJy) in six bands covering the 5.5-38 GHz range of a complete sample of 53 compact extragalactic radio sources brighter than 200 mJy at 20 GHz. The observations, carried out with the Australia Telescope Compact Array, achieved a 91 per cent detection rate (at 5σ). Within this frequency range, the spectra of about 95 per cent of sources are well fitted by double power laws, both in total intensity and in polarization, but the spectral shapes are generally different in the two cases. Most sources were classified as either steep- or peaked-spectrum but less than 50 per cent have the same classification in total and in polarized intensity. No significant trends of the polarization degree with flux density or with frequency were found. The mean variability index in total intensity of steep-spectrum sources increases with frequency for a 4-5 yr lag, while no significant trend shows up for the other sources and for the 8 yr lag. In polarization, the variability index, which could be computed only for the 8 yr lag, is substantially higher than in total intensity and has no significant frequency dependence.

  6. Unraveling the Structure in the ISM Through Radio Polarimetry

    NASA Astrophysics Data System (ADS)

    Haverkorn, M.; Katgert, P.; de Bruyn, A. G.; Heitsch, F.

    2004-02-01

    We present two models of the Galactic warm interstellar gas to study depolarization and derive properties of the interstellar medium (ISM). First, a single-cell-size model of the ISM including magnetic fields and thermal and relativistic electrons is used to derive the magnetic field strength and typical scale of structure in the ISM. The polarized radiation in the model is compared to observations of the polarized synchrotron background at 350 MHz, taken with the Westerbork Synthesis Radio Telescope (WSRT). The modeling yields a random magnetic field component Bran ≈ 1-3 μG, a regular magnetic field component Breg ≈ 2-4 μG directed almost perpendicular to the line of sight, and a typical scale of the structure d ≈ 15 pc. A three-dimensional magnetohydrodynamical model of a Faraday screen is used to estimate the effect of beam depolarization on diffuse polarization observations. It suggests that sharp gradients in RM are a common feature in the warm ISM, and that the depolarization canals in the WSRT observations are most likely caused by beam depolarization. The additional error in RM in these observations introduced by beam depolarization is estimated to be ˜ 20%.

  7. BROADBAND RADIO POLARIMETRY AND FARADAY ROTATION OF 563 EXTRAGALACTIC RADIO SOURCES

    SciTech Connect

    Anderson, C. S.; Gaensler, B. M.; Feain, I. J.; Franzen, T. M. O.

    2015-12-10

    We present a broadband spectropolarimetric survey of 563 discrete, mostly unresolved radio sources between 1.3 and 2.0 GHz using data taken with the Australia Telescope Compact Array. We have used rotation-measure synthesis to identify Faraday-complex polarized sources, those objects whose frequency-dependent polarization behavior indicates the presence of material possessing complicated magnetoionic structure along the line of sight (LOS). For sources classified as Faraday-complex, we have analyzed a number of their radio and multiwavelength properties to determine whether they differ from Faraday-simple polarized sources (sources for which LOS magnetoionic structures are comparatively simple) in these properties. We use this information to constrain the physical nature of the magnetoionic structures responsible for generating the observed complexity. We detect Faraday complexity in 12% of polarized sources at ∼1′ resolution, but we demonstrate that underlying signal-to-noise limitations mean the true percentage is likely to be significantly higher in the polarized radio source population. We find that the properties of Faraday-complex objects are diverse, but that complexity is most often associated with depolarization of extended radio sources possessing a relatively steep total intensity spectrum. We find an association between Faraday complexity and LOS structure in the Galactic interstellar medium (ISM) and claim that a significant proportion of the Faraday complexity we observe may be generated at interfaces of the ISM associated with ionization fronts near neutral hydrogen structures. Galaxy cluster environments and internally generated Faraday complexity provide possible alternative explanations in some cases.

  8. Broadband Radio Polarimetry and Faraday Rotation of 563 Extragalactic Radio Sources

    NASA Astrophysics Data System (ADS)

    Anderson, C. S.; Gaensler, B. M.; Feain, I. J.; Franzen, T. M. O.

    2015-12-01

    We present a broadband spectropolarimetric survey of 563 discrete, mostly unresolved radio sources between 1.3 and 2.0 GHz using data taken with the Australia Telescope Compact Array. We have used rotation-measure synthesis to identify Faraday-complex polarized sources, those objects whose frequency-dependent polarization behavior indicates the presence of material possessing complicated magnetoionic structure along the line of sight (LOS). For sources classified as Faraday-complex, we have analyzed a number of their radio and multiwavelength properties to determine whether they differ from Faraday-simple polarized sources (sources for which LOS magnetoionic structures are comparatively simple) in these properties. We use this information to constrain the physical nature of the magnetoionic structures responsible for generating the observed complexity. We detect Faraday complexity in 12% of polarized sources at ∼1‧ resolution, but we demonstrate that underlying signal-to-noise limitations mean the true percentage is likely to be significantly higher in the polarized radio source population. We find that the properties of Faraday-complex objects are diverse, but that complexity is most often associated with depolarization of extended radio sources possessing a relatively steep total intensity spectrum. We find an association between Faraday complexity and LOS structure in the Galactic interstellar medium (ISM) and claim that a significant proportion of the Faraday complexity we observe may be generated at interfaces of the ISM associated with ionization fronts near neutral hydrogen structures. Galaxy cluster environments and internally generated Faraday complexity provide possible alternative explanations in some cases.

  9. Possible radio-emission signatures of exoplanets

    NASA Astrophysics Data System (ADS)

    Budding, E.; Slee, O. B.; Johnston-Hollitt, M.

    2015-03-01

    A brief review of possibly detectable radio-effects from exoplanets is presented. Previous observations may show relevant effects, when appropriate theory is taken into account. Pointers to contemporary and future lines of investigation are also presented.

  10. Radio signatures of CME-streamer interaction

    NASA Astrophysics Data System (ADS)

    CHEN, Y.; Feng, S.; Kong, X.; Li, G.; Song, H.

    2011-12-01

    Recent observational finding of streamer waves using the LASCO white light data presents us interesting physical consequence of CME-streamer interactions [1, 2, 3]. CME-streamer interactions can also manifest themselves in the Type-II-related radio dynamic spectra as recorded by the ground-based or space-borne instruments. A large body of studies exists revealing the possible roles of pre-existing helmet streamers in the radio emission during a solar eruption. In this presentation, we will summary our efforts in classifying the roles of streamers affecting Type-II radio emissions. Generally speaking, there exist two groups of CME-streamer-Type-II events. In the first group, the shock as well as the Type-II radio emission seems to exist prior to the CME-streamer interaction. The interaction can be clearly discerned from the well-defined bump of the Type-II radio dynamic spectra. The spectral bump is a direct result of plasma emissions when the radio emitting region traversing the denser streamer structure. In the other group of events, the Type-II burst is excited as a result of the CME-streamer interaction. Either the shock is formed and radio-emitting electrons are accelerated inside the streamer, or a prior non-emitting shock becomes radio aloud during the interacting process. A novel triangular-streamer-shock model is proposed to interpret the associated electron acceleration inside the streamer. Observational examples of CME-streamer-radio events corresponding to both cases will be presented. [1] Chen, Y., Song, H.Q., Li, B., Xia, L.D., Wu, Z., Fu, H., Li, X., 2010, Astrophys. J. 714, 644 [2] Chen, Y., Feng, S.W., Li, B., Song, H.Q., Xia, L.D., Kong, X.L., Li, X., 2011, Astrophys. J. 728, 147 [3] Feng S. W., Chen Y., Li B., Song H. Q., Kong X. L., Xia L. D., Feng, X. S., 2011, Sol. Phys., DOI 10.1007/s11207-011-9814-6

  11. Single-Dish Radio Polarimetry in the F-GAMMA Program with the Effelsberg 100-m Radio Telescope

    NASA Astrophysics Data System (ADS)

    Beuchert, Tobias; Kadler, Matthias; Wilms, Jörn; Angelakis, Emmanouil; Fuhrmann, Lars; Myserlis, Ioannis; Nestoras, Ioannis; Kraus, Alex; Bach, Uwe; Ros, Eduardo; Grossberger, Christoph; Schulz, Robert

    2013-12-01

    Studying the variability of polarized AGN jet emission in the radio band is crucial for understanding the dynamics of moving shocks as well as the structure of the underlying magnetic field. The 100-m Effelsberg Telescope is a high-quality instrument for studying the long-term variability of both total and polarized intensity as well as the electric-vector position angle. Since 2007, the F-GAMMA program has been monitoring the linear polarized emission of roughly 60 blazars at 11 frequencies between 2.7 and 43 GHz. Here, we describe the calibration of the polarimetric data at 5 and 10 GHz and the resulting F-GAMMA full-Stokes light curves for the exemplary case of the radio galaxy 3C 111.

  12. ALMA Science Verification Data: Millimeter Continuum Polarimetry of the Bright Radio Quasar 3C 286

    NASA Astrophysics Data System (ADS)

    Nagai, H.; Nakanishi, K.; Paladino, R.; Hull, C. L. H.; Cortes, P.; Moellenbrock, G.; Fomalont, E.; Asada, K.; Hada, K.

    2016-06-01

    We present full-polarization observations of the compact, steep-spectrum radio quasar 3C 286 made with the Atacama Large Millimeter and Submillimeter Array (ALMA) at 1.3 mm. These are the first full-polarization ALMA observations, which were obtained in the framework of Science Verification. A bright core and a south-west component are detected in the total intensity image, similar to previous centimeter images. Polarized emission is also detected toward both components. The fractional polarization of the core is about 17%; this is higher than the fractional polarization at centimeter wavelengths, suggesting that the magnetic field is even more ordered in the millimeter radio core than it is further downstream in the jet. The observed polarization position angle (or electric vector position angle (EVPA)) in the core is ˜39◦, which confirms the trend that the EVPA slowly increases from centimeter to millimeter wavelengths. With the aid of multi-frequency VLBI observations, we argue that this EVPA change is associated with the frequency-dependent core position. We also report a serendipitous detection of a sub-mJy source in the field of view, which is likely to be a submillimeter galaxy.

  13. The Statistics of Radio Astronomical Polarimetry: Disjoint, Superposed, and Composite Samples

    NASA Astrophysics Data System (ADS)

    van Straten, W.; Tiburzi, C.

    2017-02-01

    A statistical framework is presented for the study of the orthogonally polarized modes of radio pulsar emission via the covariances between the Stokes parameters. To accommodate the typically heavy-tailed distributions of single-pulse radio flux density, the fourth-order joint cumulants of the electric field are used to describe the superposition of modes with arbitrary probability distributions. The framework is used to consider the distinction between superposed and disjoint modes, with particular attention to the effects of integration over finite samples. If the interval over which the polarization state is estimated is longer than the timescale for switching between two or more disjoint modes of emission, then the modes are unresolved by the instrument. The resulting composite sample mean exhibits properties that have been attributed to mode superposition, such as depolarization. Because the distinction between disjoint modes and a composite sample of unresolved disjoint modes depends on the temporal resolution of the observing instrumentation, the arguments in favor of superposed modes of pulsar emission are revisited, and observational evidence for disjoint modes is described. In principle, the four-dimensional covariance matrix that describes the distribution of sample mean Stokes parameters can be used to distinguish between disjoint modes, superposed modes, and a composite sample of unresolved disjoint modes. More comprehensive and conclusive interpretation of the covariance matrix requires more detailed consideration of various relevant phenomena, including temporally correlated subpulse modulation (e.g., jitter), statistical dependence between modes (e.g., covariant intensities and partial coherence), and multipath propagation effects (e.g., scintillation and scattering).

  14. Radio Searches for Signatures of Advanced Extraterrestrial Life

    NASA Astrophysics Data System (ADS)

    Siemion, Andrew

    Over the last several decades, observational astronomy has produced a flood of discoveries that suggest that the building blocks and circumstances that gave rise to life on Earth may be the rule rather than the exception. It has now been conclusively shown that planets are common and that some 5-15% of FGKM stars host planets existing in their host star's habitable zone. Further, terrestrial biology has demonstrated that life on our own planet can thrive in extraordinarily extreme environments, dramatically extending our notion of what constitutes habitability. The deeper question, yet unanswered, is whether or not life in any form has ever existed in an environment outside of the Earth. As humans, we are drawn to an even more profound question, that of whether or not extraterrestrial life may have evolved a curiosity about the universe similar to our own and the technology with which to explore it. Radio astronomy has long played a prominent role in searches for extraterrestrial intelligence (SETI), beginning with the first suggestions by Cocconi and Morrison (1959) that narrow-band radio signals near 1420 MHz might be effective tracers of advanced technology and early experiments along these lines by Frank Drake in 1961, continuing through to more recent investigations searching for several types of coherent radio signals indicative of technology at a wider range of frequencies. The motivations for radio searches for extraterrestrial intelligence have been throughly discussed in the literature, but the salient arguments are the following: 1. coherent radio emission is commonly produced by advanced technology (judging by Earth’s technological development), 2. electromagnetic radiation can convey information at the maximum velocity currently known to be possible, 3. radio photons are energetically cheap to produce, 4. certain types of coherent radio emissions are easily distinguished from astrophysical background sources, especially within the so

  15. [Review] Polarization and Polarimetry

    NASA Astrophysics Data System (ADS)

    Trippe, Sascha

    2014-02-01

    Polarization is a basic property of light and is fundamentally linked to the internal geometry of a source of radiation. Polarimetry complements photometric, spectroscopic, and imaging analyses of sources of radiation and has made possible multiple astrophysical discoveries. In this article I review (i) the physical basics of polarization: electromagnetic waves, photons, and parameterizations; (ii) astrophysical sources of polarization: scattering, synchrotron radiation, active media, and the Zeeman, Goldreich-Kylafis, and Hanle effects, as well as interactions between polarization and matter (like birefringence, Faraday rotation, or the Chandrasekhar-Fermi effect); (iii) observational methodology: on-sky geometry, influence of atmosphere and instrumental polarization, polarization statistics, and observational techniques for radio, optical, and X/γ wavelengths; and (iv) science cases for astronomical polarimetry: solar and stellar physics, planetary system bodies, interstellar matter, astrobiology, astronomical masers, pulsars, galactic magnetic fields, gamma-ray bursts, active galactic nuclei, and cosmic microwave background radiation.

  16. Radio emission signature of Saturn immersions in Jupiter's magnetic tail

    NASA Technical Reports Server (NTRS)

    Desch, M. D.

    1983-01-01

    During the interval from about May through August 1981, when Voyager 2 was inbound to Saturn, the Planetary Radio Astronomy instrument measured repeated, dramatic decreases in the intensity of the Saturn Kilometric Radiation (SKR). The emission dropouts averaged two orders of magnitude below mean energy levels and varied from about 1 to 10 Saturn rotations in duration. Comparison with pre-Saturn encounter Voyager 1 observations (June to November, 1980) shows that the SKR dropouts were unique to the Voyager 2 observing interval, consistent with the closer proximity of Saturn to Jupiter's distant magnetotail in 1981. Further, the dropouts occurred on the average at times when Voyager 2 is known to have been within or near Jupiter's magnetic tail.

  17. Interaction Between Two CMEs During 14 - 15 February 2011 and Their Unusual Radio Signature

    NASA Astrophysics Data System (ADS)

    Shanmugaraju, A.; Prasanna Subramanian, S.; Vrsnak, Bojan; Ibrahim, M. Syed

    2014-12-01

    We report a detailed analysis of an interaction between two coronal mass ejections (CMEs) that were observed on 14 - 15 February 2011 and the corresponding radio enhancement, which was similar to the "CME cannibalism" reported by Gopalswamy et al. ( Astrophys. J. 548, L91, 2001). A primary CME, with a mean field-of-view velocity of 669 km s-1 in the Solar and Heliospheric Observatory (SOHO)/ Large Angle Spectrometric Coronagraph (LASCO), was more than as twice as fast as the slow CME preceding it (326 km s-1), which indicates that the two CMEs interacted. A radio-enhancement signature (in the frequency range 1 MHz - 400 kHz) due to the CME interaction was analyzed and interpreted using the CME data from LASCO and from the Solar Terrestrial Relations Observatory (STEREO) HI-1, radio data from Wind/ Radio and Plasma Wave Experiment (WAVES), and employing known electron-density models and kinematic modeling. The following results are obtained: i) The CME interaction occurred around 05:00 - 10:00 UT in a height range 20 - 25 R⊙. An unusual radio signature is observed during the time of interaction in the Wind/WAVES dynamic radio spectrum. ii) The enhancement duration shows that the interaction segment might be wider than 5 R⊙. iii) The shock height estimated using density models for the radio enhancement region is 10 - 30 R⊙. iv) Using kinematic modeling and assuming a completely inelastic collision, the decrease of kinetic energy based on speeds from LASCO data is determined to be 0.77×1023 J, and 3.67×1023 J if speeds from STEREO data are considered. vi) The acceleration, momentum, and force are found to be a=-168 m s-2, I=6.1×1018 kg m s-1, and F=1.7×1015 N, respectively, using STEREO data.

  18. Kinematic signatures of AGN feedback in moderately powerful radio galaxies at z ~ 2 observed with SINFONI

    NASA Astrophysics Data System (ADS)

    Collet, C.; Nesvadba, N. P. H.; De Breuck, C.; Lehnert, M. D.; Best, P.; Bryant, J. J.; Hunstead, R.; Dicken, D.; Johnston, H.

    2016-02-01

    Most successful galaxy formation scenarios now postulate that the intense star formation in massive, high-redshift galaxies during their major growth period was truncated when powerful AGNs launched galaxy-wide outflows of gas that removed large parts of the interstellar medium. SINFONI imaging spectroscopy of the most powerful radio galaxies at z ~ 2 show clear signatures of such winds, but are too rare to be good representatives of a generic phase in the evolution of all massive galaxies at high redshift. Here we present SINFONI imaging spectroscopy of the rest-frame optical emission-line gas in 12 radio galaxies at redshifts ~2. Our sample spans a range in radio power that is intermediate between the most powerful radio galaxies with known wind signatures at these redshifts and vigorous starburst galaxies, and are about two orders of magnitude more common than the most powerful radio galaxies. Thus, if AGN feedback is a generic phase of massive galaxy evolution for reasonable values of the AGN duty cycle, these are just the sources where AGN feedback should be most important. Our sources show a diverse set of gas kinematics ranging from regular velocity gradients with amplitudes of Δv = 200-400 km s-1 consistent with rotating disks to very irregular kinematics with multiple velocity jumps of a few 100 km s-1. Line widths are generally high, typically around FWHM = 800 km s-1, more similar to the more powerful high-z radio galaxies than mass-selected samples of massive high-z galaxies without bright AGNs, and consistent with the velocity range expected from recent hydrodynamic models. A broad Hα line in one target implies a black hole mass of a few 109 M⊙. Velocity offsets of putative satellite galaxies near a few targets suggest dynamical masses of a few 1011 M⊙ for our sources, akin to the most powerful high-z radio galaxies. Ionized gas masses are 1-2 orders of magnitude lower than in the most powerful radio galaxies, and the extinction in the gas is

  19. Multi-wavelength polarimetry: a powerful tool to study the physics of active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Goosmann, R. W.

    2009-11-01

    Accreting supermassive black holes reside in a very complex environment and the inner structure and dynamics of active galactic nuclei (AGN) are not well understood yet. In this note, I point out the important role that multi-wavelength polarimetry can play in understanding AGN. In addition to spectroscopy, the measurement of the polarization percentage and position angle provides two more observables that are sensitive to the geometry and kinematics of emission and scattering regions. Furthermore, time-dependent polarimetry allows to measure spatial distances between emission regions and scattering mirrors by applying a reverberation technique. For radiation coming from the direct vicinity of the black hole, the polarization also contains information about the space-time metric. Spectropolarimetry observations of AGN are obtained in the radio, the infrared, the optical, and the ultraviolet wave bands and in the future they are going be available also in the X-ray range. To interpret these observations in a coherent way, it is necessary to study models that do not only reproduce the broad-band spectroscopy properties of AGN but also their multi-wavelength polarization signature. I present a first step towards such models for the case of radio-quiet AGN. The modeling reveals the optical/UV and X-ray polarization properties of the reprocessed radiation coming from the obscuring torus. The discussion about the implications of such models includes prospects for the up-coming technique of X-ray (spectro-)polarimetry.

  20. Large Scale Assessment of Radio Frequency Interference Signatures in L-band SAR Data

    NASA Astrophysics Data System (ADS)

    Meyer, F. J.; Nicoll, J.

    2011-12-01

    Imagery of L-band Synthetic Aperture Radar (SAR) systems such as the PALSAR sensor on board the Advanced Land Observing Satellite (ALOS) has proven to be a valuable tool for observing environmental changes around the globe. Besides offering 24/7 operability, the L-band frequency provides improved interferometric coherence, and L-band polarimetric data has shown great potential for vegetation monitoring, sea ice classification, and the observation of glaciers and ice sheets. To maximize the benefit of missions such as ALOS PALSAR for environmental monitoring, data consistency and calibration are vital. Unfortunately, radio frequency interference (RFI) signatures from ground-based radar systems regularly impair L-band SAR data quality and consistency. With this study we present a large-scale analysis of typical RFI signatures that are regularly observed in L-band SAR data over the Americas. Through a study of the vast archive of L-band SAR data in the US Government Research Consortium (USGRC) data pool at the Alaska Satellite Facility (ASF) we were able to address the following research goals: 1. Assessment of RFI Signatures in L-band SAR data and their Effects on SAR Data Quality: An analysis of time-frequency properties of RFI signatures in L-band SAR data of the USGRC data pool is presented. It is shown that RFI-filtering algorithms implemented in the operational ALOS PALSAR processor are not sufficient to remove all RFI-related artifacts. In examples, the deleterious effects of RFI on SAR image quality, polarimetric signature, SAR phase, and interferometric coherence are presented. 2. Large-Scale Assessment of Severity, Spatial Distribution, and Temporal Variation of RFI Signatures in L-band SAR data: L-band SAR data in the USGRC data pool were screened for RFI using a custom algorithm. Per SAR frame, the algorithm creates geocoded frame bounding boxes that are color-coded according to RFI intensity and converted to KML files for analysis in Google Earth. From

  1. Precision electron polarimetry

    SciTech Connect

    Chudakov, Eugene A.

    2013-11-01

    A new generation of precise Parity-Violating experiments will require a sub-percent accuracy of electron beam polarimetry. Compton polarimetry can provide such accuracy at high energies, but at a few hundred MeV the small analyzing power limits the sensitivity. M{\\o}ller polarimetry provides a high analyzing power independent on the beam energy, but is limited by the properties of the polarized targets commonly used. Options for precision polarimetry at ~300 MeV will be discussed, in particular a proposal to use ultra-cold atomic hydrogen traps to provide a 100\\%-polarized electron target for M{\\o}ller polarimetry.

  2. Precision electron polarimetry

    NASA Astrophysics Data System (ADS)

    Chudakov, E.

    2013-11-01

    A new generation of precise Parity-Violating experiments will require a sub-percent accuracy of electron beam polarimetry. Compton polarimetry can provide such accuracy at high energies, but at a few hundred MeV the small analyzing power limits the sensitivity. Mo/ller polarimetry provides a high analyzing power independent on the beam energy, but is limited by the properties of the polarized targets commonly used. Options for precision polarimetry at 300 MeV will be discussed, in particular a proposal to use ultra-cold atomic hydrogen traps to provide a 100%-polarized electron target for Mo/ller polarimetry.

  3. Precision electron polarimetry

    SciTech Connect

    Chudakov, E.

    2013-11-07

    A new generation of precise Parity-Violating experiments will require a sub-percent accuracy of electron beam polarimetry. Compton polarimetry can provide such accuracy at high energies, but at a few hundred MeV the small analyzing power limits the sensitivity. Mo/ller polarimetry provides a high analyzing power independent on the beam energy, but is limited by the properties of the polarized targets commonly used. Options for precision polarimetry at 300 MeV will be discussed, in particular a proposal to use ultra-cold atomic hydrogen traps to provide a 100%-polarized electron target for Mo/ller polarimetry.

  4. Detecting signatures of cosmological recombination and reionization in the cosmic radio background

    NASA Astrophysics Data System (ADS)

    Subrahmanyan, Ravi; Shankar Narayana Rao, Udaya; Sathyanarayana Rao, Mayuri; Singh, Saurabh

    2015-08-01

    Evolution of the baryons during the Epochs of cosmological Recombination and Reionization has left traces in the cosmic radio background in the form of spectral distortions (Sunyaev & Chluba 2008 Astron. Nachrichten, 330, 657; Pritchard & Loeb 2012 Rep Prog Phys 75(8):086901). The spectral signature depends on the evolution in the ionization state in hydrogen and helium and on the spin temperature of hydrogen. These probe the physics of energy release beyond the last scattering surface at redshifts exceeding 1090 and the nature of the first sources and gas evolution down to redshift about 6. The spectral distortions are sensitive to the nature of the first stars, ultra-dwarf galaxies, accreting compact objects, and the evolving ambient radiation field: X-rays and UV from the first sources. Detection of the all-sky or global spectral distortions in the radio background is hence a probe of cosmological recombination and reionization.We present new spectral radiometers that we have purpose designed for precision measurements of spectral distortions at radio wavelengths. New antenna elements include frequency independent and electrically small fat-dipole (Raghunathan et al. 2013 IEEE TAP, 61, 3411) and monopole designs. Receiver configurations have been devised that are self-calibratable (Patra et al. 2013 Expt Astron, 36, 319) so that switching of signal paths and of calibration noise sources provide real time calibration for systematics and receiver noise. Observing strategies (Patra et al. arXiv:1412.7762) and analysis methods (Satyanarayana Rao et al. arXiv:1501.07191) have been evolved that are capable of discriminating between the cosmological signals and the substantially brighter foregrounds. We have also demonstrated the value of system designs that exploit advantages of interferometer detection (Mahesh et al. arXiv:1406.2585) of global spectral distortions.Finally we discuss how the Square Kilometer Array stations may be outfitted with precision spectral

  5. Very low frequency radio signatures of transient luminous events above thunderstorms

    NASA Astrophysics Data System (ADS)

    Marshall, Robert Andrew

    Lightning discharges emit intense optical and acoustic energy, in the form of lightning and thunder, respectively, but a large amount of energy is emitted as radio-frequency electromagnetic pulses (EMP). These pulses can be detected thousands of kilometers away, thanks to efficient propagation in the waveguide formed by the conducting Earth and the overlying ionosphere. In addition, intense discharges interact with the overlying ionosphere at 80-100 km altitude. The EMP-ionosphere interaction is directly observed in one manifestation as the bright transient optical emissions known as "elves", but in addition, the interaction can directly modify the free electron density in the nighttime lower ionosphere. Modifications of the ionospheric electron density can be detected via subionospheric Very Low Frequency (VLF) remote sensing. In this method, coherent signals from powerful VLF transmitters, built for submarine communication and operated by the Navy, are monitored and their amplitude and phase are tracked in time. The variations of these signais are used to sense ionospheric modifications through rapid changes in the received amplitude and/or phase when the transmitted signal propagates through an ionospheric perturbation. When these perturbations are caused by lightning, they are known as "Early VLF" perturbations, due to the negligible delay between the lightning discharge and the appearance of the VLF signal change, whereas lightning-induced electron precipitation (LEP) events have a delay of 1--2 seconds. In this work, correlations between VLF signatures and optical events are used to show that these Early VLF events may be the signature of ionospheric modification by in-cloud (IC) lightning discharges. While the more impressive cloud-to-ground (CG) lightning discharges are more commonly observed and better understood, they are outnumbered in occurrence 3:1 by IC discharges, whose effects may be relatively stronger in the overlying ionosphere. We use a 3D time

  6. RADIO SIGNATURES OF CORONAL-MASS-EJECTION-STREAMER INTERACTION AND SOURCE DIAGNOSTICS OF TYPE II RADIO BURST

    SciTech Connect

    Feng, S. W.; Chen, Y.; Kong, X. L.; Li, G.; Song, H. Q.; Feng, X. S.; Liu Ying

    2012-07-01

    It has been suggested that type II radio bursts are due to energetic electrons accelerated at coronal shocks. Radio observations, however, have poor or no spatial resolutions to pinpoint the exact acceleration locations of these electrons. In this paper, we discuss a promising approach to infer the electron acceleration location by combining radio and white light observations. The key assumption is to relate specific morphological features (e.g., spectral bumps) of the dynamic spectra of type II radio bursts to imaging features (e.g., coronal mass ejection (CME) going into a streamer) along the CME (and its driven shock) propagation. In this study, we examine the CME-streamer interaction for the solar eruption dated on 2003 November 1. The presence of spectral bump in the relevant type II radio burst is identified, which is interpreted as a natural result of the shock-radio-emitting region entering the dense streamer structure. The study is useful for further determinations of the location of type II radio burst and the associated electron acceleration by CME-driven shock.

  7. Polarized foreground removal at low radio frequencies using rotation measure synthesis: uncovering the signature of hydrogen reionization

    NASA Astrophysics Data System (ADS)

    Geil, Paul M.; Gaensler, B. M.; Wyithe, J. Stuart B.

    2011-11-01

    Measurement of redshifted 21-cm emission from neutral hydrogen promises to be the most effective method for studying the reionization history of hydrogen and, indirectly, the first galaxies. These studies will be limited not by raw sensitivity to the signal, but rather, by bright foreground radiation from Galactic and extragalactic radio sources and the Galactic continuum. In addition, leakage due to gain errors and non-ideal feeds conspire to further contaminate low-frequency radio observations. This leakage leads to a portion of the complex linear polarization signal finding its way into Stokes I, and inhibits the detection of the non-polarized cosmological signal from the epoch of reionization. In this work, we show that rotation measure synthesis can be used to recover the signature of cosmic hydrogen reionization in the presence of contamination by polarized foregrounds. To achieve this, we apply the rotation measure synthesis technique to the Stokes I component of a synthetic data cube containing Galactic foreground emission, the effect of instrumental polarization leakage and redshifted 21-cm emission by neutral hydrogen from the epoch of reionization. This produces an effective Stokes I Faraday dispersion function for each line of sight, from which instrumental polarization leakage can be fitted and subtracted. Our results show that it is possible to recover the signature of reionization in its late stages (z≈ 7) by way of the 21-cm power spectrum, as well as through tomographic imaging of ionized cavities in the intergalactic medium.

  8. Radio AGN signatures in massive quiescent galaxies out to z=1.5

    NASA Astrophysics Data System (ADS)

    Järvelä, Emilia

    2016-08-01

    Detection of gamma-rays from narrow-line Seyfert 1 galaxies (NLS1) by Fermi confirmed the presence of powerful relativistic jets in them, and thus challenged our understanding of active galactic nuclei (AGN). In the current AGN paradigm powerful relativistic jets are produced in massive elliptical galaxies with supermassive black holes. NLS1s differ from them significantly; they harbour lower mass black holes accreting at higher Eddington ratios, have preferably compact radio morphology, reside mostly in spiral galaxies, and were thought to be radio-quiet.Fermi's discovery invokes questions about the AGN evolution; what triggers and maintains the AGN activity, and what are the evolutionary lines of the different populations? It is also necessary to revise the AGN unification schemes to fit in NLS1s. They convolute the whole AGN scenario, but offer us a new look on the jet phenomena and will help us construct a more comprehensive big picture of AGN.Despite their importance, NLS1s are rather poorly studied as a class. For example, some NLS1s seem to be totally radio-silent, but a considerable fraction are radio-loud and thus probably host jets. This, along with other observational evidence, implies that they do not form a homogeneous class. However, it remains unclear what is triggering the radio loudness in some of them, but, for example, the properties of the host galaxy and the large-scale environment might play a role. Also the parent population of NLS1s remains an open question.We used various statistical methods, for example, multiwavelength correlations and principal component analysis to study a large sample of NLS1 sources. We will present the results and discuss the interplay between their properties, such as emission properties, black hole masses, large-scale environments, and their effect on radio loudness. We will also introduce the Metsähovi Radio Observatory NLS1 galaxy observing programme, which is the first one dedicated to systematical observations

  9. ON THE RADIO POLARIZATION SIGNATURE OF EFFICIENT AND INEFFICIENT PARTICLE ACCELERATION IN SUPERNOVA REMNANT SN 1006

    SciTech Connect

    Reynoso, Estela M.; Hughes, John P.; Moffett, David A. E-mail: jph@physics.rutgers.edu

    2013-04-15

    Radio polarization observations provide essential information on the degree of order and orientation of magnetic fields, which themselves play a key role in the particle acceleration processes that take place in supernova remnants (SNRs). Here we present a radio polarization study of SN 1006, based on combined Very Large Array and Australia Telescope Compact Array observations at 20 cm that resulted in sensitive images with an angular resolution of 10 arcsec. The fractional polarization in the two bright radio and X-ray lobes of the SNR is measured to be 0.17, while in the southeastern sector, where the radio and non-thermal X-ray emission are much weaker, the polarization fraction reaches a value of 0.6 {+-} 0.2, close to the theoretical limit of 0.7. We interpret this result as evidence of a disordered, turbulent magnetic field in the lobes, where particle acceleration is believed to be efficient, and a highly ordered field in the southeast, where the acceleration efficiency has been shown to be very low. Utilizing the frequency coverage of our observations, an average rotation measure of {approx}12 rad m{sup -2} is determined from the combined data set, which is then used to obtain the intrinsic direction of the magnetic field vectors. While the orientation of magnetic field vectors across the SNR shell appear to be radial, a large fraction of the magnetic vectors lie parallel to the Galactic plane. Along the highly polarized southeastern rim, the field is aligned tangent to the shock, and therefore also nearly parallel to the Galactic plane. These results strongly suggest that the ambient field surrounding SN 1006 is aligned with this direction (i.e., from northeast to southwest) and that the bright lobes are due to a polar cap geometry. Our study establishes that the most efficient particle acceleration and generation of magnetic turbulence in SN 1006 is attained for shocks in which the magnetic field direction and shock normal are quasi-parallel, while

  10. The prospects of X-ray polarimetry for Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Goosmann, René W.

    2016-08-01

    Polarimetry at optical and other wavelength continues to play an important role in our struggle to develop (super-)unification schemes for active galactic nuclei (AGN). Therefore, radio-loud and radio-quiet AGN are important targets for the future small and medium-size X-ray polarimetry missions that are currently under phase A study at NASA and ESA. After briefly pointing out the detection principle of polarization imaging in the soft X-ray band, I am going to review the prospects of X-ray polarimetry for our understanding of AGN ejection (winds and blazar jets) and accretion flows (accretion disk and corona). The X-ray polarimetry signal between 2 and 8 keV is going to give us important new constraints on the geometry of the central engine as well as on the acceleration effects in AGN jets, in particular when combined with spectral and/or polarization information at other wavelengths.

  11. Multi-frequency polarimetry of the Galactic radio background around 350 MHz. I. A region in Auriga around l = 161 deg, b = 16 deg

    NASA Astrophysics Data System (ADS)

    Haverkorn, M.; Katgert, P.; de Bruyn, A. G.

    2003-06-01

    With the Westerbork Synthesis Radio Telescope (WSRT), multi-frequency polarimetric images were taken of the diffuse radio synchrotron background in a ~ 5 deg times 7 deg region centered on (l,b) = (161 deg ,16 deg ) in the constellation of Auriga. The observations were done simultaneously in 5 frequency bands, from 341 MHz to 375 MHz, and have a resolution of ~ 5.0arcminx5 .0arcmin cosec delta . The polarized intensity P and polarization angle phi show ubiquitous structure on arcminute and degree scales, with polarized brightness temperatures up to about 13 K. On the other hand, no structure at all is observed in total intensity I to an rms limit of 1.3 K, indicating that the structure in the polarized radiation must be due to Faraday rotation and depolarization mostly in the warm component of the nearby Galactic interstellar medium (ISM). Different depolarization processes create structure in polarized intensity P. Beam depolarization creates ``depolarization canals'' of one beam wide, while depth depolarization is thought to be responsible for creating most of the structure on scales larger than a beam width. Rotation measures (RM) can be reliably determined, and are in the range -17 <~ RM <~ 10 rad m-2 with a non-zero average RM0 ~ -3.4 rad m-2. The distribution of RMs on the sky shows both abrupt changes on the scales of the beam and a gradient in the direction of positive Galactic longitude of ~ 1 rad m-2 per degree. The gradient and average RM are consistent with a regular magnetic field of ~ 1 mu G which has a pitch angle of p = -14 deg. There are 13 extragalactic sources in the field for which RMs could be derived, and those have |RM| <~ 13 rad m-2, with an estimated intrinsic source contribution of ~ 3.6 rad m-2. The RMs of the extragalactic sources show a gradient that is about 3 times larger than the gradient in the RMs of the diffuse emission and that is approximately in Galactic latitude. This difference is ascribed to a vastly different effective

  12. Polarimetry in the infrared.

    NASA Astrophysics Data System (ADS)

    Deming, D.; Hewagama, T.; Jennings, D. E.; Wiedemann, G.

    1991-01-01

    Polarimetry at infrared (IR) wavelengths is advantageous because the larger Zeeman splitting of IR lines results in larger net solar polarization signal. Also, oblique reflections at telescope mirror surfaces have less effect, due to the increase in the index of refraction for Aluminum films at IR wavelengths. Recent developments in IR detector arrays, and the availability of lines formed at altitudes from the deep photosphere (e.g. 1.56 μm Fe I) to the base of the chromosphere (12 μm) represent additional motivation to pursue polarimetry in the IR. Recent measurements using a CdS quarterwave plate and Ge thin-film linear polarizer successfully obtained Stokes I.Q.U. and V profiles of the 12.32 μm Mg I line at high spectral resolution. A significant result from these measurements is the finding that the 12 μm line is essentially 100% polarized in sunspots.

  13. Stokes-polarimetry imaging of tissue

    NASA Astrophysics Data System (ADS)

    Wu, Paul J.

    A novel Stokes-polarimetry imaging system and technique was developed to quantify fully the polarization properties of light remitted from tissue. The uniqueness of the system and technique is established in the incident polarization. Here, the diffuse illumination is varied and controlled with the intention to improve the visibility of tissue structures. Since light retains some polarization even after multiple-scattering events, the polarization of remitted light depends upon the interactions within the material. Differentiation between tissue structures is accomplished by two-dimensional mapping of the imaged area using metrics such as the degree of linear polarization, degree of circular polarization, ellipticity, and Stokes parameters. While Stokes-polarimetry imaging can be applied to a variety of tissues and conditions, this thesis focuses on tissue types associated with the disease endometriosis. The current standard in diagnosing endometriosis is visual laparoscopy with tissue biopsy. The documented correlation between laparoscopy inspection and histological confirmation of suspected lesions was at best 67%. Endometrial lesions vary greatly in their appearance and depth of infiltration. Although laparoscopy permits tissue to be assessed by color and texture, to advance beyond the state-of-the-art, a new imaging modality involving polarized light was investigated; in particular, Stokes-polarimetry imaging was used to determine the polarization signature of light that interacted with tissue. Basic science studies were conducted on rat tails embedded within turbid gelatin. The purpose of these experiments was to determine how identification of sub-surface structures could be improved. Experimental results indicate image contrast among various structures such as tendon, soft tissue and intervertebral discs. Stokes-polarimetry imaging experiments were performed on various tissues associated with endometriosis to obtain a baseline characterization for each

  14. Characteristics of Gamma-Ray Loud Blazars in the VLBA Imaging and Polarimetry Survey

    NASA Technical Reports Server (NTRS)

    Linford, J. D.; Taylor, G. B.; Romani, R. W.; Healey, S. E.; Helmboldt, J. F.; Readhead, A. C.; Reeves, R.; Richards, J. L.; Cotter, G.

    2010-01-01

    The radio properties of blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have been observed as part of the VLBA Imaging and Polarimetry Survey. This large, flux-limited sample of active galactic nuclei (AGNs) provides insights into the mechanism that produces strong gamma-ray emission. At lower flux levels, radio flux density does not directly correlate with gamma-ray flux. We find that the LAT-detected BL Lac objects tend to be similar to the non-LAT BL Lac objects, but that the LAT-detected FSRQs are often significantly different from the non-LAT FSRQs. The differences between the gamma-ray loud and quiet FSRQS can be explained by Doppler boosting; these objects appear to require larger Doppler factors than those of the BL Lac objects. It is possible that the gamma-ray loud FSRQs are fundamentally different from the gamma-ray quiet FSRQs. Strong polarization at the base of the jet appears to be a signature for gamma-ray loud AGNs.

  15. Uncovering Exoplanets using Polarimetry

    NASA Astrophysics Data System (ADS)

    Stam, D. M.

    2012-12-01

    Since the first discovery of a planet around a solar-type star by Mayor & Queloz in 1995, more than 700 of these exoplanets have been detected. Most of these are giant, gaseous planets, but small, presumably solid, exoplanets, that are much harder to detect, have also been found. Among the latter are even some that orbit in their star's habitable zone, where temperatures could be just right to allow liquid water on a planet's surface. Liquid water is generally considered to be essential for the existence of life. Whether liquid water actually exists on a planet depends strongly on the atmosphere's thickness and characteristics, such as the surface pressure and composition. Famous examples in the Solar System are Venus and the Earth, with similar sizes, inner compositions and orbital radii, but wildly different surface conditions. The characterization of the atmospheres of giant, gaseous exoplanets, and of the atmospheres and/or surfaces of small, solid exoplanets will allow a comparison with Solar System planets and it will open up a treasure trove of knowledge about the formation and evolution of planetary atmospheres and surfaces, thanks to the vast range of orbital distances, planet sizes and ages that can be studied. Characterization will also allow studying conditions for life and ultimately the existence of life around other stars. Some information about the upper atmospheric properties has already been derived for a few close-in, hot, giant exoplanets, whose thermal flux can be derived from measurements of the combined flux of the star and the planet. This method has also provided traces of an atmosphere around a large solid planet orbiting red dwarf star GJ1214. Characterization of the atmosphere and/or surface of exoplanets in wide orbits, resembling the cool planets in our Solar System, and in particular of small, solid, Earth-like planets in the habitable zone of Sun-like stars, is virtually impossible with transit observations. Indeed, polarimetry

  16. Two Centuries of Solar Polarimetry

    NASA Astrophysics Data System (ADS)

    Harvey, J. W.

    2015-10-01

    In 1811, François Arago observed the disk of the Sun with his "lunette polariscopique". From the absence of detectable polarization compared with his laboratory observations of glowing solids, liquids, and flames he concluded that the Sun's visible surface is an incandescent gas. From this beginning, thanks to orders of magnitude technology improvements, a remarkable amount of what we know about the physics of the Sun has continued to flow from solar polarimetry. This short review compares some selected polarimetric discoveries with subsequent recent observations to illustrate the tremendous progress of solar polarimetry during the last two centuries.

  17. Probes of Fundamental Physics using X-ray Polarimetry

    NASA Astrophysics Data System (ADS)

    Baring, Matthew G.

    2016-04-01

    The advent of X-ray polarimetry as an astronomical discipline is on the near horizon. Prospects of Explorer class missions currently under study in the NASA SMEX program, the Xipe mission under ESA study in Europe, and beyond to initiatives under development in Asia, indicate that the worldwide high energy astrophysics community view this as a high priority. The focal goal of X-ray polarization measurements is often to discern the geometry of a source, for example an accreting black hole, pulsing neutron star or a relativistic jet; these are addressed in other talks in this HEAD special session. In this talk, I discuss a parallel agenda, to employ X-ray polarimetry to glean insights into fundamental physics that is presently difficult or impossible to test in laboratory settings. Much of this is centered around neutron stars, and I willaddress theoretically-expected signatures of vacuum birefringence and photon splitting, predictions of QED theory in the strong magnetic fields possessed by pulsars and magnetars. Of particular note is that time-dependent polarimetry coupled with spectroscopy can help disentangle purely geometrical effects and fundamental physics ones. A brief discussion of possible tests of Lorentz invariance violation, expected in some theories of quantum gravity, will also be presented. Instrument requirements to realize such science goals will also be briefly covered.

  18. Optical Polarimetry Campaign on Markarian 421 during the 2012 Large Flaring Episodes

    NASA Astrophysics Data System (ADS)

    Barres de Almeida, Ulisses; Jermak, Helen; Lindfors, Elina; Mundell, Carole; Nilsson, Kari; Steele, Iain

    2015-08-01

    In 2012, Fermi/LAT gamma-ray and radio observations registered the largest flaring episodes ever recorded from the blazar Markarian 421. The unprecedented activity state of the source has remained high and much above the normal emission state seem from the source also for the year 2013, characterising a dramatic and long-lasting, albeit puzzling, change of behaviour in the emission of this object. This unique event has been followed by observations over the entire electromagnetic spectrum, showing extreme signatures in all bands, from radio to VHE gamma-rays. Polarisation monitoring of the source has nevertheless been somewhat more scarce, and direct observation of the peak activity in 2012 was prevented by the source's proximity to the Sun at that time. As part of our continuous monitoring programme of VHE-emitting blazars in optical polarimetry at the Liverpool Telescope, which used the RINGO2 fast polarimeter and lasted from 2010 to 2013, we have observed Mkn 421 with regular coverage and a sub-weekly cadence for over two years. This continued monitoring allowed us to continually follow the polarisation behaviour of the source for a long time and up to the days preceding the dramatic flare event in 2012. In the weeks before the extreme 2012 outbursts, Mrk 421 underwent an unprecedented increase in its degree of polarisation, which rose by a factor of 5, not witnessed in decades from this object. The source also showed a large rotation of its polarisation angle, by over 180 degrees, which has never been registered before for this objetc. In this talk we will present our entire dataset on Mkn 421, concentrating in discussing the unprecedented events in optical polarisation that preceded the high-energy outburst. The main question we put ourselves is if what we have seen could be regarded as a polarimetric precursor to the high activity that followed. And if yes, what connections can we establish between them, and what remains mysterious to us about it?

  19. Scanning laser polarimetry - a review.

    PubMed

    Da Pozzo, Stefano; Marchesan, Roberta; Ravalico, Giuseppe

    2009-01-01

    Glaucoma is a leading cause of irreversible blindness worldwide. Retinal ganglion cells and their axons represent the selective target of the disease. When visual function is still intact on standard automated perimetry and optic disc appearance is suspicious, an early diagnosis may be supported by the identification of a retinal nerve fibre layer (RNFL) defect in the peripapillary area. At present days, computer-based, real-time imaging of the peripapillary RNFL is available through instruments of easy use and with high levels of accuracy and reproducibility. Scanning laser polarimetry is performed by a confocal scanning laser ophthalmoscope with an integrated polarimeter (GDx-VCC). There is a considerable amount of scientific evidence about the role of this imaging technique for glaucoma diagnosis. The aim of this review is to describe the principles of operation, the examination procedure, the clinical role, the results of main diagnostic studies and the future development of the software for the scanning laser polarimetry.

  20. Terahertz polarimetry based on metamaterial devices

    NASA Astrophysics Data System (ADS)

    Metcalfe, Grace D.; Wraback, Michael; Strikwerda, Andrew; Fan, Kebin; Zhang, Xin; Averitt, Richard

    2012-05-01

    Polarimetry is a well-developed technique in radar based applications and stand-off spectroscopic analysis at optical frequencies. Extension to terahertz (THz) frequencies could provide a breakthrough in spectroscopic methods since the THz portion of the electromagnetic spectrum provides unique spectral signatures of chemicals and biological molecules, useful for filling gaps in detection and identification. Distinct advantages to a THz polarimeter include enhanced image-contrast based on differences in scattering of horizontally and vertically polarized radiation, and measurements of the dielectric response, and thereby absorption, of materials in reflection in real-time without the need of a reference measurement. To implement a prototype THz polarimeter, we have developed low profile, high efficiency metamaterial-based polarization control components at THz frequencies. Static metamaterial-based half- and quarter-wave plates operating at 0.35 THz frequencies were modeled and fabricated, and characterized using a MHz resolution, continuous-wave spectrometer operating in the 0.09 to 1.2 THz range to verify the design parameters such as operational frequency and bandwidth, insertion loss, and phase shift. The operation frequency was chosen to be in an atmospheric window (between water absorption lines) but can be designed to function at any frequency. Additional advantages of metamaterial devices include their compact size, flexibility, and fabrication ease over large areas using standard microfabrication processing. Wave plates in both the transmission and reflection mode were modeled, tested, and compared. Data analysis using Jones matrix theory showed good agreement between experimental data and simulation.

  1. Efficient Ways to Learn Weather Radar Polarimetry

    ERIC Educational Resources Information Center

    Cao, Qing; Yeary, M. B.; Zhang, Guifu

    2012-01-01

    The U.S. weather radar network is currently being upgraded with dual-polarization capability. Weather radar polarimetry is an interdisciplinary area of engineering and meteorology. This paper presents efficient ways to learn weather radar polarimetry through several basic and practical topics. These topics include: 1) hydrometeor scattering model…

  2. Signatures support program

    NASA Astrophysics Data System (ADS)

    Hawley, Chadwick T.

    2009-05-01

    The Signatures Support Program (SSP) leverages the full spectrum of signature-related activities (collections, processing, development, storage, maintenance, and dissemination) within the Department of Defense (DOD), the intelligence community (IC), other Federal agencies, and civil institutions. The Enterprise encompasses acoustic, seismic, radio frequency, infrared, radar, nuclear radiation, and electro-optical signatures. The SSP serves the war fighter, the IC, and civil institutions by supporting military operations, intelligence operations, homeland defense, disaster relief, acquisitions, and research and development. Data centers host and maintain signature holdings, collectively forming the national signatures pool. The geographically distributed organizations are the authoritative sources and repositories for signature data; the centers are responsible for data content and quality. The SSP proactively engages DOD, IC, other Federal entities, academia, and industry to locate signatures for inclusion in the distributed national signatures pool and provides world-wide 24/7 access via the SSP application.

  3. SYNCHROTRON HEATING BY A FAST RADIO BURST IN A SELF-ABSORBED SYNCHROTRON NEBULA AND ITS OBSERVATIONAL SIGNATURE

    SciTech Connect

    Yang, Yuan-Pei; Dai, Zi-Gao; Zhang, Bing

    2016-03-01

    Fast radio bursts (FRBs) are mysterious transient sources. If extragalactic, as suggested by their relative large dispersion measures, their brightness temperatures must be extremely high. Some FRB models (e.g., young pulsar model, magnetar giant flare model, or supra-massive neutron star collapse model) suggest that they may be associated with a synchrotron nebula. Here we study a synchrotron-heating process by an FRB in a self-absorbed synchrotron nebula. If the FRB frequency is below the synchrotron self-absorption frequency of the nebula, electrons in the nebula would absorb FRB photons, leading to a harder electron spectrum and enhanced self-absorbed synchrotron emission. In the meantime, the FRB flux is absorbed by the nebula electrons. We calculate the spectra of FRB-heated synchrotron nebulae, and show that the nebula spectra would show a significant hump in several decades near the self-absorption frequency. Identifying such a spectral feature would reveal an embedded FRB in a synchrotron nebula.

  4. Imaging radar polarimetry - A review

    NASA Technical Reports Server (NTRS)

    Zebker, Howard A.; Van Zyl, Jakob J.

    1991-01-01

    The authors present a tutorial review of the broad sweep of topics relating to imaging radar polarimetry, ranging from mathematical foundations to hardware and from implementation approaches to signal processing and calibration. The authors examine current developments in sensor technology and implementation for recording polarimetric measurements, and describe techniques and areas of application for this form of remotely sensed data. Those aspects of ground signal processing and calibration peculiar to the polarimetric signals are addressed. Several of the currently operating instruments and some of the implementations planned for future use are discussed.

  5. Polarimetry for rocky exoplanet characterization

    NASA Astrophysics Data System (ADS)

    Stam, Daphne; Karalidi, Theodora

    2013-04-01

    Since the first discovery of a planet around a solar-type star by Mayor & Queloz in 1995, several hundreds of exoplanets have been detected. Indeed, it appears that practically all Sun-like stars have planets. Inevitable, Earth-sized, rocky planets that orbit in their star's habitable zone, where temperatures could be just right to allow liquid water on a planet's surface, will be found. Liquid water is generally considered to be essential for the existence of life. Whether liquid water actually exists on a planet depends strongly on the atmosphere's thickness and characteristics, such as the surface pressure and composition. Famous examples in the Solar System are Venus and the Earth, with similar sizes, inner compositions and orbital radii, but wildly different surface conditions. The characterization of the atmospheres and/or surfaces of exoplanets will allow a comparison with Solar System planets and it will open up a treasure trove of knowledge about the formation and evolution of planetary atmospheres and surfaces, thanks to the vast range of orbital distances, planet sizes and ages that can be studied. Characterization will also allow studying conditions for life and ultimately the existence of life around other stars. Information about the upper atmospheres of close-in, hot, giant exoplanets, can be derived from measurements of the combined flux of the star and the planet, in particular when the planet is transiting its star. This method has also provided traces of an atmosphere around a large solid planet orbiting red dwarf star GJ1214. Detection and characterization of the atmospheres and/or surfaces of small, solid, Earth-like exoplanets in the habitable zones of Sun-like stars, is virtually impossible with transit observations. For these exiting planets, polarimetry appears to be a strong tool. Polarimetry helps the detection of exoplanets, because direct starlight is usually unpolarized, while starlight that has been reflected by a planet is usually

  6. K-band Polarimetry of NGC 891

    NASA Astrophysics Data System (ADS)

    Montgomery, Jordan; Clemens, Dan P.

    2014-06-01

    We present the first K-band (2.2 um) polarimetry observations of the edge-on galaxy NGC 891. Near-infrared (NIR) polarimetry reveals the plane-of-sky projected magnetic (B) field orientations in dusty, star-forming interstellar media. Previous optical wavelength polarimetry of NGC 891 found predominantly disk-perpendicular polarizations (Scarrott & Draper 1996) while H-band polarimetry revealed mostly disk-parallel polarizations with an interesting 15 degree offset from the major axis position angle (Jones 1997; Montgomery & Clemens 2014). In H-band, Montgomery & Clemens also detected the first NIR polarization null-point, located about 5 kpc northeast of NGC891's center. It may be related to the polarization null-points predicted by Wood (1997) and modeled by Wood & Jones (1997). At the longer K-band wavelength, these new observations better reveal B-field orientation changes in the disk. The Wood (1997) radiative transfer polarization model predicted null-point location changes with wavelengeth. We will use the new K-band polarimetry, along with our H-band polarimetry, to test this prediction. If the null-point location does not depend on wavelength, then the null-point may instead be due to spiral arm aligned B-fields (e.g., Fletcher et al. 2011).This research was supported through NSF grant AST 09-07790.

  7. Polarimetry in astrophysics and cosmology

    NASA Astrophysics Data System (ADS)

    Zeng, Lingzhen

    Astrophysicists are mostly limited to passively observing electromagnetic radiation from a distance, which generally shows some degree of polarization. Polarization often carries a wealth of information on the physical state and geometry of the emitting object and intervening material. In the microwave part of the spectrum, polarization provides information about galactic magnetic fields and the physics of interstellar dust. The measurement of this polarized radiation is central to much modern astrophysical research. The first part of this thesis is about polarimetry in astrophysics. In Chapter 1, I review the basics of polarization and summarize the most important mechanisms that generate polarization in astrophysics. In Chapter 2, I describe the data analysis of polarization observation on M17 (a young, massive star formation region in the Galaxy) from Caltech Submillimeter Observatory (CSO) and show the physics that we learn about M17 from the polarimetry. Polarimetry also plays an important role in modern cosmology. Inflation theory predicts two types of polarization in the Cosmic Microwave Background (CMB) radiation, called E-modes and B-modes. Measurements to date of the E-mode signal are consistent with the predictions of anisotropic Thompson scattering, while the B-mode signal has yet to be detected. The B-mode power spectrum amplitude can be parameterized by the relative amplitude of the tensor to scalar modes r. For the simplest inflation models, the expected deviation from scale invariance (ns = 0.963 ± 0.012) is coupled to gravitational waves with r ≈ 0.1. These considerations establish a strong motivation to search for this remnant from when the universe was about 10-32 seconds old. The second part of this thesis is about the Cosmology Large Angular Scale Surveyor (CLASS) experiment, that is designed to have an unprecedented ability to detect the B-mode polarization to the level of r ≤ 0.01. Chapter 3 is an introduction to cosmology, including the

  8. Put X-Ray Polarimetry on the MAP!

    NASA Technical Reports Server (NTRS)

    Weisskopf, Martin C.

    2013-01-01

    difficult than narrow-line spectroscopy. X-ray polarimetry thus requires a dedicated mission that can, without programmatic pressures from other instruments/users, devote the integration time to perform meaningful measurements. The recently cancelled GEMS might have been such a mission. At least it was dedicated to polarimetry. Performing meaningful measurements is not going to be easy. In part because of the long hiatus and lack of experience, there appears to be too much pressure to "sell" polarimetry missions by the number of sources for which one might answer the simple question is, or is not, the integrated and time averaged emission from the source polarized at some confidence level? This was a fine question for the 1970 s but, I maintain, it is not today. One simply doesn't want to measure the time averaged polarization of the Crab s pulsar, but one wants to know the polarization as a function of energy and pulse phase to compare, e.g. to optical and radio measurements which divide even the primary pulse into dozens of phase bins. Such observations can distinguish amongst competing theories for the pulsed emission. The Roadmap should define what meaningful experiments are. I will pose some suggestions. Note that , because X-rays are usually believed originate in either non-thermal or highly aspherical situations we expect X-ray polarimetry to be much more important and rich in astrophysical information as opposed to the visible, where starlight often dominates the emission. One has often dreamt about an instrument that does polarimetry whilst it does other things, and I will discuss this. Even in this case, one needs to realize that the observing time will be driven by the polarimetry, otherwise no useful polarization measurements will be made. Finally, I will discuss some misconceptions that have appeared in the literature and at conferences which indicate to me that certain fundamental principles of polarimeter design and performance are not clearly understoodt is

  9. Hydrogen Lines in Mira Stars Through Interferometry and Polarimetry

    NASA Astrophysics Data System (ADS)

    Fabas, N.; Chiavassa, A.; Millour, F.; Wittkowski, M.

    2015-12-01

    Balmer lines in emission are the most prominent features in Mira stars spectra and have a strong potential as a proxy to study the lower atmosphere's dynamics. In Fabas et al. ([1]), we accumulated spectropolarimetric observations of Balmer lines in emission. As the shock is propagating outwards, linear polarization rate increases and the angle of this polarization evolves. Assuming that linear polarization arises from anisotropic scattering, it has the potential of telling us about the geometric structure of the shock as it propagates and the study of such atmospheric structures can typically be performed with interferometry. In 2012, AMBER data on the Mira star omicron Ceti were collected in which the Brackett γ line is studied. The data show signatures in the interferometric observables around this line. Olivier Chesneau was in the jury evaluating the PhD thesis of N. Fabas and he was seduced by the idea to study these shock waves with interferometry and use polarimetry as a complementary study.

  10. Polarized Sources, Targets and Polarimetry

    NASA Astrophysics Data System (ADS)

    Ciullo, Guiseppe; Contalbrigo, Marco; Lenisa, P.

    2011-01-01

    Remarks on the history of workshops on "spin tools" / E. Steffens -- Polarized proton beams in RHIC / A. Zelenski -- The COSY/Julich polarized H[symbol] and D[symbol] ion source / O. Felden -- The new source of polarized ions for the JINR accelerator complex / V. V. Fimushkin -- Resonance effects in nuclear dichroism - an inexpensive source of tensor-polarized deuterons / H. Seyfarth -- Polarized electrons and positrons at the MESA accelerator / K. Aulenbacher -- Status report of the Darmstadt polarized electron injector / Y. Poltoratska -- The Mott polarimeter at MAMI / V. Tioukine -- Proton polarimetry at the relativistic heavy ion collider / Y. Makdisi -- Polarisation and polarimetry at HERA / B. Sobloher -- Polarisation measurement at the ILC with a Compton polarimeter / C. Bartels -- Time evolution of ground motion-dependent depolarisation at linear colliders / A. Hartin -- Electron beam polarimetry at low energies and its applications / R. Barday -- Polarized solid targets: recent progress and future prospects / C. D. Keith -- HD gas distillation and analysis for HD frozen spin targets / A. D'Angelo -- Electron spin resonance study of hydrogen and alkyl free radicals trapped in solid hydrogen aimed for dynamic nuclear polarization of solid HD / T. Kumada -- Change of ultrafast nuclear-spin polarization upon photoionization by a short laser pulse / T. Nakajima -- Radiation damage and recovery in polarized [symbol]NH[symbol] ammonia targets at Jefferson lab / J. D. Maxwell.Polarized solid proton target in low magnetic field and at high temperature / T. Uesaka -- Pulse structure dependence of the proton spin polarization rate / T. Kawahara -- Proton NMR in the large COMPASS [symbol]NH[symbol] target / J. Koivuniemi -- DNP with TEMPO and trityl radicals in deuterated polystyrene / L. Wang -- The CLIC electron and positron polarized sources / L. Rinolfi -- Status of high intensity polarized electron gun at MIT-Bates / E. Tsentalovich -- Target section for spin

  11. Scanning laser polarimetry in glaucoma.

    PubMed

    Dada, Tanuj; Sharma, Reetika; Angmo, Dewang; Sinha, Gautam; Bhartiya, Shibal; Mishra, Sanjay K; Panda, Anita; Sihota, Ramanjit

    2014-11-01

    Glaucoma is an acquired progressive optic neuropathy which is characterized by changes in the optic nerve head and retinal nerve fiber layer (RNFL). White-on-white perimetry is the gold standard for the diagnosis of glaucoma. However, it can detect defects in the visual field only after the loss of as many as 40% of the ganglion cells. Hence, the measurement of RNFL thickness has come up. Optical coherence tomography and scanning laser polarimetry (SLP) are the techniques that utilize the evaluation of RNFL for the evaluation of glaucoma. SLP provides RNFL thickness measurements based upon the birefringence of the retinal ganglion cell axons. We have reviewed the published literature on the use of SLP in glaucoma. This review elucidates the technological principles, recent developments and the role of SLP in the diagnosis and monitoring of glaucomatous optic neuropathy, in the light of scientific evidence so far.

  12. Polarimetry Microlensing of Close-in Planetary Systems

    NASA Astrophysics Data System (ADS)

    Sajadian, Sedighe; Hundertmark, Markus

    2017-04-01

    A close-in giant planetary (CGP) system has a net polarization signal whose value varies depending on the orbital phase of the planet. This polarization signal is either caused by the stellar occultation or by reflected starlight from the surface of the orbiting planet. When the CGP system is located in the Galactic bulge, its polarization signal becomes too weak to be measured directly. One method for detecting and characterizing these weak polarization signatures due to distant CGP systems is gravitational microlensing. In this work, we focus on potential polarimetric observations of highly magnified microlensing events of CGP systems. When the lens is passing directly in front of the source star with its planetary companion, the polarimetric signature caused by the transiting planet is magnified. As a result, some distinct features in the polarimetry and light curves are produced. In the same way, microlensing amplifies the reflection-induced polarization signal. While the planet-induced perturbations are magnified whenever these polarimetric or photometric deviations vanish for a moment, the corresponding magnification factor of the polarization component(s) is related to the planet itself. Finding these exact times in the planet-induced perturbations helps us to characterize the planet. In order to evaluate the observability of such systems through polarimetric or photometric observations of high-magnification microlensing events, we simulate these events by considering confirmed CGP systems as their source stars and conclude that the efficiency for detecting the planet-induced signal with the state-of-the-art polarimetric instrument (FORS2/VLT) is less than 0.1%. Consequently, these planet-induced polarimetry perturbations can likely be detected under favorable conditions by the high-resolution and short-cadence polarimeters of the next generation.

  13. HST And VLA Polarimetry Of 3C 264 And 3C 66B

    NASA Astrophysics Data System (ADS)

    Padgett, C. Alexander; Perlman, E. S.; Georganopoulos, M.; O'Dea, C. P.; Baum, S. A.; Sparks, W. B.; Biretta, J. A.

    2006-09-01

    We present new VLA A- and B-array radio polarimetry at 22.5 GHz, and images at 8.4GHz of 3C 264, a low luminosity FR I in Abell 1367. We also present high resolution VLA A-array polarimetry of the jet of 3C 66B, both at 22.5 GHz and 43 GHz. This is the latest addition to an ongoing study of these objects, which includes optical polarimetry in several bands and multiband imaging with HST, and X-ray observations with Chandra. We find further evidence for the hypothesis that 3C 264 falls into the category of low luminosity BL Lac objects (Rector, Stocke & Perlman, 1999) in significant variability of the polarization position angle in the core of this object in only 4 years (Lara et al, 2003). This variability, together with our measured value of its optical spectral index of alpha = 0.77, and a previously derived viewing angle of < 50 degrees (Baum et al, 1997; Lara et al, 2003), puts a fairly strong constraint on the classification of 3C 264 as a low luminosity BL Lac. We also present matched resolution HST and VLA data for both of these objects, allowing for direct morphological comparisons to be made, as well as full resolution radio to optical spectral index maps.

  14. UNRAVELING THE NATURE OF COHERENT PULSAR RADIO EMISSION

    SciTech Connect

    Mitra, Dipanjan; Gil, Janusz; Melikidze, George I. E-mail: jag@astro.ia.uz.zgora.pl

    2009-05-10

    Forty years have passed since the discovery of pulsars, yet the physical mechanism of their coherent radio emission is a mystery. Recent observational and theoretical studies strongly suggest that the radiation coming out from the pulsar magnetosphere mainly consists of extraordinary waves polarized perpendicular to the planes of pulsar dipolar magnetic field. However, the fundamental question of whether these waves are excited by maser or coherent curvature radiation, remains open. High-quality single-pulse polarimetry is required to distinguish between these two possible mechanisms. Here we showcase such decisive, strong single pulses from 10 pulsars observed with the Giant Meterwave Radio Telescope, showing extremely high linear polarization with the position angle following locally the mean position angle traverse. These pulses, which are relatively free from depolarization, must consist exclusively of a single polarization mode. We associate this mode with the extraordinary wave excited by the coherent curvature radiation. This crucial observational signature enables us to argue, for the first time, in favor of the coherent curvature emission mechanism, excluding the maser mechanism.

  15. NEAR-INFRARED POLARIMETRY OF A NORMAL SPIRAL GALAXY VIEWED THROUGH THE TAURUS MOLECULAR CLOUD COMPLEX

    SciTech Connect

    Clemens, Dan P.; Cashman, L. R.; Pavel, M. D. E-mail: pavelmi@utexas.edu

    2013-03-15

    Few normal galaxies have been probed using near-infrared polarimetry, even though it reveals magnetic fields in the cool interstellar medium better than either optical or radio polarimetry. Deep H-band (1.6 {mu}m) linear imaging polarimetry toward Taurus serendipitously included the galaxy 2MASX J04412715+2433110 with adequate sensitivity and resolution to map polarization across nearly its full extent. The observations revealed the galaxy to be a steeply inclined ({approx}75 Degree-Sign ) disk type with a diameter, encompassing 90% of the Petrosian flux, of 4.2 kpc at a distance of 53 Mpc. Because the sight line passes through the Taurus Molecular Cloud complex, the foreground polarization needed to be measured and removed. The foreground extinction A{sub V} of 2.00 {+-} 0.10 mag and reddening E(H - K) of 0.125 {+-} 0.009 mag were also assessed and removed, based on analysis of Two Micron All Sky Survey, UKIRT Infrared Deep Sky Survey, Spitzer, and Wide-field Infrared Survey Explorer photometry using the Near-Infrared Color Excess, NICE-Revisited, and Rayleigh-Jeans Color Excess methods. Corrected for the polarized foreground, the galaxy polarization values range from 0% to 3%. The polarizations are dominated by a disk-parallel magnetic field geometry, especially to the northeast, while either a vertical field or single scattering of bulge light produces disk-normal polarizations to the southwest. The multi-kiloparsec coherence of the magnetic field revealed by the infrared polarimetry is in close agreement with short-wavelength radio synchrotron observations of edge-on galaxies, indicating that both cool and warm interstellar media of disk galaxies may be threaded by common magnetic fields.

  16. Helium 3 neutron precision polarimetry

    NASA Astrophysics Data System (ADS)

    Menard, Christopher

    2009-10-01

    Measuring neutron polarization to a high degree of precision is critical for the next generation of neutron decay correlation experiments. Polarized neutrons are also used in experiments to probe the hadronic weak interaction which contributes a small portion (˜10-7) of the force between nucleons. Using a beam of cold neutrons at Los Alamos Neutron Science Center (LANSCE), we polarized neutrons and measured their absolute polarization to ˜0.1%. Neutrons were polarized by passing them through a ^3He spin filter, relying on the maximally spin dependent 3He neutron absorption cross section. The neutron polarization can be determined by measuring the wavelength-dependent neutron transmission through the ^3He cell. An independent measurement of the neutron polarization was also obtained by passing the polarized beam through an RF spin flipper and a second polarized ^3He cell, used as an analyzer. To measure the efficiency of the spin flipper, the same measurements were made after reversing the ^3He polarization in the polarizer by using NMR techniques (adiabatic fast passage). We will show the consistency of these two measurements and the resulting precision of neutron polarimetry using these techniques.

  17. PETS - A GRB Polarimetry Mission on the International Space Station

    NASA Astrophysics Data System (ADS)

    McConnell, Mark L.; Baring, M. G.; Bloser, P. F.; Greiner, J.; Harding, A. K.; Hartmann, D.; Hill, J. E.; Kaaret, P.; Kippen, R. M.; Pearce, M.; Produit, N.; Roming, P.; Ryan, J. M.; Ryde, F.; Sakamoto, T.; Toma, K.; Zhang, B.

    2013-04-01

    Polarimetry of Energetic Transients in Space (PETS) is a gamma-ray polarimetry mission that was recently proposed as an NASA Astrophysics Mission of Opportunity. It will make the first definitive observations of the inner jets of GRBs, which cannot be probed with conventional non-polarization instruments. It will also observe, for the first time, the polarization signature from SGRs, revealing high-energy emission processes originating from the most intense magnetic field conditions known to exist. PETS will use gamma-ray polarimetry to uncover the energy release mechanism associated with the formation of stellar-mass black holes and investigate the physics of extreme magnetic fields in the vicinity of compact objects. The objectives are : 1) determine the structure and composition of GRB jets and uncover the mechanisms powering them; and 2) determine the emission geometry and mechanisms under the extreme magnetic field conditions found in SGRs. The PETS science objectives are met with two instruments. The primary instrument, the TRAnsient Polarimeter (TRAP), is a wide FOV non-imaging polarimeter that measures polarization over the energy range from 50-500 keV. Knowledge of the transient source location, required for the polarization analysis, is provided by the TRAnsient Location Experiment (TRALE). PETS will be mounted on the ISS with the two instruments pointed towards the zenith, scanning the sky as it orbits the Earth. During the two-year baseline mission, PETS will achieve its primary science objective with the polarization measurement of ~100 GRBs with a minimum detectable polarization (MDP) better than 50%, ~35 GRBs with an MDP of better than 30%, and ~5 with an MDP of better than 15%. These data will be sufficient to distinguish amongst three basic models for the inner jet at a 90% confidence level. The secondary science objective will be achieved with the measurement of 3-4 SGRs with a minimum detectable polarization of 15-50%. PETS is a self

  18. Infrared photometry and polarimetry of Cygnus X-3

    NASA Technical Reports Server (NTRS)

    Jones, Terry Jay; Gehrz, Robert D.; Kobulnicky, Henry A.; Molnar, Lawrence A.; Howard, Eric M.

    1994-01-01

    We present photometry and linear polarimetry of Cygnus X-3 at K (2.2 micrometers) obtained over a 5 yr period. Photometry and polarimetry at J, H, and K of nearby field stars is also presented. From an analysis of these data we find: (1) Using the x-ray ephemeris of Kitamoto et al. (ApJ, 384, 263 (1992), including the first and second derivatives of the period, the leading edge of the decline to minimum in the quiescent K light curve has not changed in phase since 1974. The duration of the minimum in the light curve has changed significantly between different epochs, becoming much broader in 1993 than it was previously. (2) In addition to an interstellar polarization component, it is likely Cyg X-3 has an intrinsic polarization component that is variable. The variations in the polarization do not show any diagnostic pattern with orbital phase. A crude analysis of the polarization suggests the intrinsic polarization of Cyg X-3 has a mean position angle of approximately 12 deg, nearly the same as the direction of the expanding radio lobes. This is consistent with circumstellar electrons scattering in an equatorial disk that is perpendicular to the lobe axis. (3) The mean position angle for the interstellar polarization in the direction of Cyg X-3 is 150 deg. This is nearly perpendicular to the axis of interstellar radio scattering seen in the extended (Very Long Baseline Inteferometry (VLBI) images. Since the position angle of interstellar polarization is the same as the projected magnetic field direction, this suggests the interstellar (not circumstellar) scattering must be taking place perpendicular to the interstellar magnetic field lines. (4) Cyg X-3 was observed at K during a flare on 1992 September 30 with a temporal resolution of 6 s. The flaring had rise and fall times of approximately 50 s with peak intensities up to 80 mJy. The flux between individual flare events never dropped to quiescent levels for the duration of our observations (approximately 2000 s).

  19. Tissue polarimetry: concepts, challenges, applications, and outlook

    NASA Astrophysics Data System (ADS)

    Ghosh, Nirmalya; Vitkin, I. Alex

    2011-11-01

    Polarimetry has a long and successful history in various forms of clear media. Driven by their biomedical potential, the use of the polarimetric approaches for biological tissue assessment has also recently received considerable attention. Specifically, polarization can be used as an effective tool to discriminate against multiply scattered light (acting as a gating mechanism) in order to enhance contrast and to improve tissue imaging resolution. Moreover, the intrinsic tissue polarimetry characteristics contain a wealth of morphological and functional information of potential biomedical importance. However, in a complex random medium-like tissue, numerous complexities due to multiple scattering and simultaneous occurrences of many scattering and polarization events present formidable challenges both in terms of accurate measurements and in terms of analysis of the tissue polarimetry signal. In order to realize the potential of the polarimetric approaches for tissue imaging and characterization/diagnosis, a number of researchers are thus pursuing innovative solutions to these challenges. In this review paper, we summarize these and other issues pertinent to the polarized light methodologies in tissues. Specifically, we discuss polarized light basics, Stokes-Muller formalism, methods of polarization measurements, polarized light modeling in turbid media, applications to tissue imaging, inverse analysis for polarimetric results quantification, applications to quantitative tissue assessment, etc.

  20. Radar Polarimetry: Theory, Analysis, and Applications

    NASA Astrophysics Data System (ADS)

    Hubbert, John Clark

    The fields of radar polarimetry and optical polarimetry are compared. The mathematics of optic polarimetry are formulated such that a local right handed coordinate system is always used to describe the polarization states. This is not done in radar polarimetry. Radar optimum polarization theory is redeveloped within the framework of optical polarimetry. The radar optimum polarizations and optic eigenvalues of common scatterers are compared. In addition a novel definition of an eigenpolarization state is given and the accompanying mathematics is developed. The polarization response calculated using optic, radar and novel definitions is presented for a variety of scatterers. Polarimetric transformation provides a means to characterize scatters in more than one polarization basis. Polarimetric transformation for an ensemble of scatters is obtained via two methods: (1) the covariance method and (2) the instantaneous scattering matrix (ISM) method. The covariance method is used to relate the mean radar parameters of a +/-45^circ linear polarization basis to those of a horizontal and vertical polarization basis. In contrast the ISM method transforms the individual time samples. Algorithms are developed for transforming the time series from fully polarimetric radars that switch between orthogonal states. The transformed time series are then used to calculate the mean radar parameters of interest. It is also shown that propagation effects do not need to be removed from the ISM's before transformation. The techniques are demonstrated using data collected by POLDIRAD, the German Aerospace Research Establishment's fully polarimetric C-band radar. The differential phase observed between two copolar states, Psi_{CO}, is composed of two phases: (1) differential propagation phase, phi_{DP}, and (2) differential backscatter phase, delta. The slope of phi_{DP } with range is an estimate of the specific differential phase, K_{DP}. The process of estimating K_{DP} is complicated when

  1. ADDITIONAL OBSERVATIONS OF PLANETS AND QUASI-STELLAR RADIO SOURCES AT 3 MM,

    DTIC Science & Technology

    MERCURY ( PLANET ), VENUS( PLANET ), PERIODIC VARIATIONS, RADIO ASTRONOMY, SPECTRUM SIGNATURES...EXTRATERRESTRIAL RADIO WAVES, SOURCES), GALAXIES, BLACKBODY RADIATION, BRIGHTNESS, TEMPERATURE, MARS( PLANET ), JUPITER( PLANET ), SATURN( PLANET

  2. Radio Galaxies.

    ERIC Educational Resources Information Center

    Downes, Ann

    1986-01-01

    Provides background information on radio galaxies. Topic areas addressed include: what produces the radio emission; radio telescopes; locating radio galaxies; how distances to radio galaxies are found; physics of radio galaxies; computer simulations of radio galaxies; and the evolution of radio galaxies with cosmic time. (JN)

  3. Recent Advances in Radar Polarimetry and Polarimetric SAR Interferometry

    NASA Technical Reports Server (NTRS)

    Boerner, Wolfgang-Martin

    2005-01-01

    The development of Radar Polarimetry and Radar Interferometry is advancing rapidly, and these novel radar technologies are revamping Synthetic Aperture Radar Imaging decisively. In this exposition the successive advancements are sketched; beginning with the fundamental formulations and high-lighting the salient points of these diverse remote sensing techniques. Whereas with radar polarimetry the textural fine-structure, target-orientation and shape, symmetries and material constituents can be recovered with considerable improvements above that of standard amplitude-only Polarization Radar ; with radar interferometry the spatial (in depth) structure can be explored. In Polarimetric-Interferometric Synthetic Aperture Radar (POL-IN-SAR) Imaging it is possible to recover such co-registered textural plus spatial properties simultaneously. This includes the extraction of Digital Elevation Maps (DEM) from either fully Polarimetric (scattering matrix) or Interferometric (dual antenna) SAR image data takes with the additional benefit of obtaining co-registered three-dimensional POL-IN-DEM information. Extra-Wide-Band POL-IN-SAR Imaging - when applied to Repeat-Pass Image Overlay Interferometry - provides differential background validation and measurement, stress assessment, and environmental stress-change monitoring capabilities with hitherto unattained accuracy, which are essential tools for improved global biomass estimation. More recently, by applying multiple parallel repeat-pass EWB-POL-D(RP)-IN-SAR imaging along stacked (altitudinal) or displaced (horizontal) flight-lines will result in Tomographic (Multi- Interferometric) Polarimetric SAR Stereo-Imaging , including foliage and ground penetrating capabilities. It is shown that the accelerated advancement of these modern EWB-POL-D(RP)-IN-SAR imaging techniques is of direct relevance and of paramount priority to wide-area dynamic homeland security surveillance and local-to-global environmental ground-truth measurement

  4. The FIELDS Instrument Suite for Solar Probe Plus Measuring the Coronal Plasma and Magnetic Field, Plasma Waves and Turbulence, and Radio Signatures of Solar Transients

    NASA Technical Reports Server (NTRS)

    Bale, S. D.; Goetz, K.; Harvey, P. R.; Turin, P.; Bonnell, J. W.; Dudok de Wit, T.; Ergun, R. E.; MacDowall, R. J.; Pulupa, M.; Choi, M. K.; Farrell, W. M.; Goldstein, M.; Klimchuk, J. A.; Odom, J.; Oliversen, R.; Sheppard, D. A.; Szabo, A.

    2016-01-01

    NASA's Solar Probe Plus (SPP) mission will make the first in situ measurements of the solar corona and the birthplace of the solar wind. The FIELDS instrument suite on SPP will make direct measurements of electric and magnetic fields, the properties of in situ plasma waves, electron density and temperature profiles, and interplanetary radio emissions, amongst other things. Here, we describe the scientific objectives targeted by the SPP/FIELDS instrument, the instrument design itself, and the instrument concept of operations and planned data products.

  5. The FIELDS Instrument Suite for Solar Probe Plus. Measuring the Coronal Plasma and Magnetic Field, Plasma Waves and Turbulence, and Radio Signatures of Solar Transients

    NASA Astrophysics Data System (ADS)

    Bale, S. D.; Goetz, K.; Harvey, P. R.; Turin, P.; Bonnell, J. W.; Dudok de Wit, T.; Ergun, R. E.; MacDowall, R. J.; Pulupa, M.; Andre, M.; Bolton, M.; Bougeret, J.-L.; Bowen, T. A.; Burgess, D.; Cattell, C. A.; Chandran, B. D. G.; Chaston, C. C.; Chen, C. H. K.; Choi, M. K.; Connerney, J. E.; Cranmer, S.; Diaz-Aguado, M.; Donakowski, W.; Drake, J. F.; Farrell, W. M.; Fergeau, P.; Fermin, J.; Fischer, J.; Fox, N.; Glaser, D.; Goldstein, M.; Gordon, D.; Hanson, E.; Harris, S. E.; Hayes, L. M.; Hinze, J. J.; Hollweg, J. V.; Horbury, T. S.; Howard, R. A.; Hoxie, V.; Jannet, G.; Karlsson, M.; Kasper, J. C.; Kellogg, P. J.; Kien, M.; Klimchuk, J. A.; Krasnoselskikh, V. V.; Krucker, S.; Lynch, J. J.; Maksimovic, M.; Malaspina, D. M.; Marker, S.; Martin, P.; Martinez-Oliveros, J.; McCauley, J.; McComas, D. J.; McDonald, T.; Meyer-Vernet, N.; Moncuquet, M.; Monson, S. J.; Mozer, F. S.; Murphy, S. D.; Odom, J.; Oliverson, R.; Olson, J.; Parker, E. N.; Pankow, D.; Phan, T.; Quataert, E.; Quinn, T.; Ruplin, S. W.; Salem, C.; Seitz, D.; Sheppard, D. A.; Siy, A.; Stevens, K.; Summers, D.; Szabo, A.; Timofeeva, M.; Vaivads, A.; Velli, M.; Yehle, A.; Werthimer, D.; Wygant, J. R.

    2016-12-01

    NASA's Solar Probe Plus (SPP) mission will make the first in situ measurements of the solar corona and the birthplace of the solar wind. The FIELDS instrument suite on SPP will make direct measurements of electric and magnetic fields, the properties of in situ plasma waves, electron density and temperature profiles, and interplanetary radio emissions, amongst other things. Here, we describe the scientific objectives targeted by the SPP/FIELDS instrument, the instrument design itself, and the instrument concept of operations and planned data products.

  6. Radio spectrum surveillance station

    NASA Technical Reports Server (NTRS)

    Hersey, D. R.

    1979-01-01

    The paper presents a general and functional description of a low-cost surveillance station designed as the first phase of NASA's program to develop a radio spectrum surveillance capability for deep space stations for identifying radio frequency interference sources. The station described has identified several particular interferences and is yielding spectral signature data which, after cataloging, will serve as a library for rapid identification of frequently observed interference. Findings from the use of the station are discussed.

  7. Polarimetry of uncoupled light on the NIF

    SciTech Connect

    Turnbull, D. Moody, J. D.; Michel, P.; Ralph, J. E.; Divol, L.

    2014-11-15

    Polarimetry has been added to the full aperture backscatter diagnostic on the NIF. Wollaston prisms are used to sample a small region of a beam's backscatter, effectively separating it into two linear polarizations, one of which is parallel to the incident beam. A time-averaged measurement of each polarization is obtained by imaging the separated spots off of a scatter plate. Results have improved understanding of crossed beam energy transfer, glint, and sidescatter, and motivated plans to upgrade to a time-resolved polarimeter measuring the full Stokes vector.

  8. Polarimetry of uncoupled light on the NIF.

    PubMed

    Turnbull, D; Moody, J D; Michel, P; Ralph, J E; Divol, L

    2014-11-01

    Polarimetry has been added to the full aperture backscatter diagnostic on the NIF. Wollaston prisms are used to sample a small region of a beam's backscatter, effectively separating it into two linear polarizations, one of which is parallel to the incident beam. A time-averaged measurement of each polarization is obtained by imaging the separated spots off of a scatter plate. Results have improved understanding of crossed beam energy transfer, glint, and sidescatter, and motivated plans to upgrade to a time-resolved polarimeter measuring the full Stokes vector.

  9. TSUBAME: a small satellite for GRB polarimetry

    NASA Astrophysics Data System (ADS)

    Kawai, Nobuyuki; Yatsu, Yoichi

    2012-07-01

    A GRB polarimetry mission TSUBAME is being built at Tokyo Tech, targeting a launch in late 2012. It is a small satellite with a mass of 50 kg. The unique capability of TSUBAME is the rapid attitude maneuver using CMG. When a GRB is detected, its location is quickly determined based on the X-ray count ratio in the five detectors on the five faces within a few seconds, then the satellite orient itself to the source location in 15 seconds, and start measurement using a Compton polarimeter in the energy range 30--200 keV. The current development status and the ground test results will be presented.

  10. Neutron electric form factor via recoil polarimetry

    SciTech Connect

    Madey, Richard; Semenov, Andrei; Taylor, Simon; Aghalaryan, Aram; Crouse, Erick; MacLachlan, Glen; Plaster, Bradley; Tajima, Shigeyuki; Tireman, William; Yan, Chenyu; Ahmidouch, Abdellah; Anderson, Brian; Asaturyan, Razmik; Baker, O; Baldwin, Alan; Breuer, Herbert; Carlini, Roger; Christy, Michael; Churchwell, Steve; Cole, Leon; Danagoulian, Samuel; Day, Donal; Elaasar, Mostafa; Ent, Rolf; Farkhondeh, Manouchehr; Fenker, Howard; Finn, John; Gan, Liping; Garrow, Kenneth; Gueye, Paul; Howell, Calvin; Hu, Bitao; Jones, Mark; Kelly, James; Keppel, Cynthia; Khandaker, Mahbubul; Kim, Wooyoung; Kowalski, Stanley; Lung, Allison; Mack, David; Manley, D; Markowitz, Pete; Mitchell, Joseph; Mkrtchyan, Hamlet; Opper, Allena; Perdrisat, Charles; Punjabi, Vina; Raue, Brian; Reichelt, Tilmann; Reinhold, Joerg; Roche, Julie; Sato, Yoshinori; Seo, Wonick; Simicevic, Neven; Smith, Gregory; Stepanyan, Samuel; Tadevosyan, Vardan; Tang, Liguang; Ulmer, Paul; Vulcan, William; Watson, John; Wells, Steven; Wesselmann, Frank; Wood, Stephen; Yan, Chen; Yang, Seunghoon; Yuan, Lulin; Zhang, Wei-Ming; Zhu, Hong Guo; Zhu, Xiaofeng

    2003-05-01

    The ratio of the electric to the magnetic form factor of the neutron, G_En/G_Mn, was measured via recoil polarimetry from the quasielastic d({pol-e},e'{pol-n)p reaction at three values of Q^2 [viz., 0.45, 1.15 and 1.47 (GeV/c)^2] in Hall C of the Thomas Jefferson National Accelerator Facility. Preliminary data indicate that G_En follows the Galster parameterization up to Q^2 = 1.15 (GeV/c)^2 and appears to rise above the Galster parameterization at Q^2 = 1.47 (GeV/c)^2.

  11. An Imaging X-Ray Polarimetry Mission

    NASA Technical Reports Server (NTRS)

    Weisskopf, Martin C.; Bellazini, Ronaldo; Costa, Enrico; Ramsey, Brian; O'Dell, Steve; Tennant, Allyn; Elsner, Ronald; Pavlov, George; Matt, Girogio; Kaspi, Vicky; Coppi, Paolo; Wu, Kinwah; Siegmund, Oswald

    2008-01-01

    Technical progress both in x-ray optics and in polarization-sensitive x-ray detectors, which our groups have pioneered, enables a scientifically powerful - yet inexpensive - dedicated mission for imaging x-ray polarimetry. Such a mission is sufficiently sensitive to measure x-ray (linear) polarization for a broad range of cosmic sources --- particularly those involving neutron stars, stellar black holes, and supermassive black holes (active galactic nuclei). We describe the technical elements, discuss a mission concept, and synopsiz:e the important physical and astrophysical questions such as mission would address.

  12. An Imaging X-Ray Polarimetry Mission

    NASA Technical Reports Server (NTRS)

    Weisskopf, Martin C.; Bellazini, Ronaldo; Costa, Enrico; Ramsey, Brian; O'Dell, Steve; Elsner, Ronald; Pavlov, George; Matt, Giorgio; Kaspi, Victoria; Tennant, Allyn; Coppi, Paolo; Wu, Kinwah; Siegmund, Oswald

    2008-01-01

    Technical progress both in x-ray optics and in polarization-sensitive x-ray detectors, which our groups have pioneered, enables a scientifically powerful---yet inexpensive---dedicated mission for imaging x-ray polarimetry. Such a mission is sufficiently sensitive to measure x-ray (linear) polarization for a broad range of cosmic sources --particularly those involving neutron stars, stellar black holes, and supermassive black holes (active galactic nuclei). We describe the technical elements, discuss a mission concept, and synopsize the important physical and astrophysical questions such a mission would address.

  13. Electron polarimetry at low energies in Hall C at JLab

    NASA Astrophysics Data System (ADS)

    Gaskell, D.

    2013-11-01

    Although the majority of Jefferson Lab experiments require multi-GeV electron beams, there have been a few opportunities to make electron beam polarization measurements at rather low energies. This proceedings will discuss some of the practical difficulties encountered in performing electron polarimetry via Mo/ller scattering at energies on the order of a few hundred MeV. Prospects for Compton polarimetry at very low energies will also be discussed. While Mo/ller scattering is likely the preferred method for electron polarimetry at energies below 500 MeV, there are certain aspects of the polarimeter and experiment design that must be carefully considered.

  14. Electron polarimetry at low energies in Hall C at JLab

    SciTech Connect

    Gaskell, D.

    2013-11-07

    Although the majority of Jefferson Lab experiments require multi-GeV electron beams, there have been a few opportunities to make electron beam polarization measurements at rather low energies. This proceedings will discuss some of the practical difficulties encountered in performing electron polarimetry via Mo/ller scattering at energies on the order of a few hundred MeV. Prospects for Compton polarimetry at very low energies will also be discussed. While Mo/ller scattering is likely the preferred method for electron polarimetry at energies below 500 MeV, there are certain aspects of the polarimeter and experiment design that must be carefully considered.

  15. Signatures and Characteristics of Internal Gravity Waves in the Venus' and Mars' Atmospheres as Revealed by the Radio Occultation Temperature Data Analysis

    NASA Astrophysics Data System (ADS)

    Gubenko, Vladimir; Pavelyev, Alexander; Andreev, Vitali; Salimzyanov, Rishat; Pavelyev, Alexey

    2012-07-01

    It is well known that internal gravity waves (IGWs) affect the structure and mean circulation of the Earth' middle and upper atmosphere by transporting energy and horizontal momentum upward from the lower atmosphere. The IGWs modulate the background atmospheric structure, producing a periodic pattern of spatial and temporal variations in the wind velocity, temperature and density. Similar effects are anticipated for the Venus and Mars since IGWs are a characteristic of stably stratified atmosphere. For instance, Yakovlev et al. (1991) and Gubenko et al. (2008a) used the radio occultation (RO) data from Venera 15 and 16 missions to investigate the thermal structure and layering of the Venus' middle atmosphere. They noted that a wavelike periodic structure commonly appears in retrieved vertical profiles at altitudes above 60 km in the atmosphere where the static stability is large. Through comparisons between Magellan RO observations in the Venus' atmosphere, Hinson and Jenkins (1995) have demonstrated that small scale variations in retrieved temperature profiles at altitudes from 60 to 90 km are caused by a spectrum of vertical propagating IGWs. Temperature profiles from the Mars Global Surveyor (MGS) measurements reveal vertical wavelike structures assumed to be atmospheric IGWs in the Mars' lower atmosphere (Creasey et al., 2006). The very large IGW amplitudes inferred from MGS RO data imply a very significant role for IGWs in the atmospheric dynamics of Mars as well. There is one general problem inherent to all measurements of IGWs. Observed wavelike variations may alternatively be caused by the IGWs, turbulence or persistent layers in the atmosphere, and it is necessary to have an IGW identification criterion for the correct interpretation of obtained results. In this context, we have developed an original method for the determination of internal gravity wave parameters from a single vertical temperature profile measurement in a planetary atmosphere (Gubenko et

  16. Signatures of Accretion onto the SMBH Sagittarius A* at the Center of the Milky Way

    NASA Astrophysics Data System (ADS)

    Eckart, Andreas

    Several successful, simultaneous global campaigns have revealed millimeter to X-ray flare emis-sion of the Sgr A* counterpart associated with the super-massive 4 million solar mass black hole at the Galactic Center. NIR polarimetry now shows signatures of strong gravity that are statistically significant against randomly polarized red noise allowing to derive spin and inclination information. The light curves suggest that the mm flare emission follows the NIR emission with a delay of 1.5 -2 hours. A combined synchrotron self Compton (SSC) and adia-batic expansion model with source components peaking at a few THz can fully account for the observed flare flux densities and delay times covering the spectral range from the X-ray to the mm-radio domain. The derived model parameters suggest that the adiabatic expansion takes place in source components that have a bulk motion larger than the expansion velocity or the expanding material contributes to a corona or disk, confined to the immediate surroundings of SgrA*.

  17. Factors controlling discrimination in imaging polarimetry

    NASA Astrophysics Data System (ADS)

    Duggin, Michael J.

    2004-07-01

    The discrimination of scene elements in polarimetric and in non-polarimetric images is governed by both environmental and instrumental factors. These factors consist of systematic elements, which are dealt with by means of appropriate calibration, and random errors. In the case of imaging polarimetry, the Stokes parameter images are calculated from images obtained with orthogonal orientations of the linear polarizer about the optic axis. For the stokes images to contain significant information, the orthogonal, registered image pair from which the Stokes images S1 and S2 are calculated must be significantly different. Misregistration of the orthrogonal input images also impacts the correlation of the resulting Stokes image to scene elements. The system MTF, sampling patter and geometry further impact the discrimination of features in the scene. These factors are discussed. The effects of systematic and random error sources on resolved target discriminability from clutter background is considered in depth. While the issue of spatially unresolved target detection is considered, it does not form a major component of this discussion. The intent of these considerations of the physics and phenomenology of imaging polarimetry is to progress towards the predictive modeling of target discriminability. This will aid in sensor design and mission parameter optimization.

  18. 43 and 86 GHz VLBI Polarimetry of 3C454.3

    NASA Astrophysics Data System (ADS)

    Hunacek, A.; Attridge, J. M.

    2004-12-01

    Very Long Baseline Array (VLBA) observations of the quasar 3C454.3 were made at epoch 2003.75, at 43 and 86 GHz in full polarization mode. Very Long Baseline Polarimetry (VLBP) is used to determine magnetic field structures in the jets of extragalactic radio sources at very high angular resolution - on the order of 0.3 milliarcseconds at 86 GHz. As Faraday rotation decreases with decreasing wavelength, high-frequency, high-resolution VLBP observations allow us to probe the polarization properties of Active Galactic Nuclei (AGNs) close to the super-massive black holes thought to be the central engines of these objects. New total intensity and linear polarization images of 3C454.3 at both 43 and 86 GHz are presented here, along with historical images for comparison. The new images include the first 86 GHz linear polarization images ever made of the source 3C454.3, and these results bring the number of sources for which successful 86 GHz polarimetry has been accomplished to three. As 3C454.3 is fainter at 86 GHz than its counterparts 3C273 and 3C279, the new observations are quite promising for the success of 86 GHz VLBP on weaker sources. This research was carried out as part of MIT Haystack Observatory's Research Experiences for Undergraduates program funded by the National Science Foundation.

  19. WHT, DIPOL-2 polarimetry of Nova Sgr 2015b

    NASA Astrophysics Data System (ADS)

    Harvey, Eamonn; Berdyugin, Andrei; Redman, Matt

    2015-09-01

    We report polarimetry data from three nights observing of Nova Sgr 2015b (also PNV J18365700-2855420 or V5668 Sgr) with the William Herschel Telescope in the BVR passbands using the DIPOL-2 instrument.

  20. Review of passive imaging polarimetry for remote sensing applications.

    PubMed

    Tyo, J Scott; Goldstein, Dennis L; Chenault, David B; Shaw, Joseph A

    2006-08-01

    Imaging polarimetry has emerged over the past three decades as a powerful tool to enhance the information available in a variety of remote sensing applications. We discuss the foundations of passive imaging polarimetry, the phenomenological reasons for designing a polarimetric sensor, and the primary architectures that have been exploited for developing imaging polarimeters. Considerations on imaging polarimeters such as calibration, optimization, and error performance are also discussed. We review many important sources and examples from the scientific literature.

  1. Signature control

    NASA Astrophysics Data System (ADS)

    Pyati, Vittal P.

    The reduction of vehicle radar signature is accomplished by means of vehicle shaping, the use of microwave frequencies-absorbent materials, and either passive or active cancellation techniques; such techniques are also useful in the reduction of propulsion system-associated IR emissions. In some anticipated scenarios, the objective is not signature-reduction but signature control, for deception, via decoy vehicles that mimic the signature characteristics of actual weapons systems. As the stealthiness of airframes and missiles increases, their propulsion systems' exhaust plumes assume a more important role in detection by an adversary.

  2. Random Noise Polarimetry Technique for Covert Detection of Targets Obscured by Foliage

    NASA Astrophysics Data System (ADS)

    Narayanan, Ram M.; Xu, Xiaojian; Henning, Joseph A.; Kumru, Cihan

    2002-07-01

    The University of Nebraska has been investigating a novel technique called random noise polarimetry for foliage penetration (FOPEN) imaging applications, under support from the US Air Force Office of Scientific Research (AFOSR). In this final report, we summarize the main activities and results of the research during the past three years (1999-2002). These include: (a) Development of an experimental UHF band ultra wideband (UWB) FOPEN noise radar system; (b) Development of a down range sidelobe suppression; (c) Study of the foliage transmission model and the impact of foliage obscuration; (d) Development of FOPEN SAR imaging model and image formation algorithms; (e) Study of the impact of frequency and aspect angle dependent target signatures on UWB SAR images; (f) Three-dimensional interferometric SAR and ISAR imaging techniques; (g) Development of SAR image enhancement techniques; and (h) Field tests, data acquisition and image processing using the experimental random noise radar system. Suggestions for future work are also presented.

  3. Extrapolation procedures in Mott electron polarimetry

    NASA Technical Reports Server (NTRS)

    Gay, T. J.; Khakoo, M. A.; Brand, J. A.; Furst, J. E.; Wijayaratna, W. M. K. P.; Meyer, W. V.; Dunning, F. B.

    1992-01-01

    In standard Mott electron polarimetry using thin gold film targets, extrapolation procedures must be used to reduce the experimentally measured asymmetries A to the values they would have for scattering from single atoms. These extrapolations involve the dependent of A on either the gold film thickness or the maximum detected electron energy loss in the target. A concentric cylindrical-electrode Mott polarimeter, has been used to study and compare these two types of extrapolations over the electron energy range 20-100 keV. The potential systematic errors which can result from such procedures are analyzed in detail, particularly with regard to the use of various fitting functions in thickness extrapolations, and the failure of perfect energy-loss discrimination to yield accurate polarizations when thick foils are used.

  4. Polarimetry with the Event Horizon Telescope

    NASA Astrophysics Data System (ADS)

    Johnson, Michael; Doeleman, Sheperd; Fish, Vincent L.; Plambeck, Richard L.; Marrone, Daniel P.; Kosowsky, Michael; Wardle, John F. C.; Lu, Rusen

    2014-06-01

    The Event Horizon Telescope (EHT) is an effort to develop millimeter and submillimeter VLBI to image nearby black holes at resolutions comparable to their event horizons. Past work with the EHT has measured compact emission on such scales for Sgr A* and M87, and has also measured sub-parsec structure in more distant quasars. Polarimetry with the EHT enables a powerful extension of this work, mapping magnetic field structures via the highly polarized synchrotron emission. Polarization is also an excellent probe of rapid variability, especially for Sgr A*, and can convey rich astrometric information even with incomplete imaging. We report on results from our 2013 campaign, which demonstrate a sharp increase in the linear polarization fraction and variability with increasing baseline, and we demonstrate that current EHT data can potentially achieve microarcsecond relative astrometry of flaring regions on timescales of minutes.

  5. GEO Satellite Characterization through Polarimetry using Simultaneous Observations from nearby Optical Sensors

    NASA Astrophysics Data System (ADS)

    Cegarra Polo, M.; Alenin, A.; Vaughn, I.; Lambert, A.

    2016-09-01

    Polarimetry has shown capacity for both geometry inference and material classification in recent years. By carefully selecting a polarimetric modality with higher contrast for the objects of interest, it becomes possible to discriminate those objects by leveraging the understanding of differing geometry, material characteristics, and its mapping into consequent polarisation measurements. Expansion of the measurement dimensionality increases the potential to discriminate unresolved objects, thereby widening the possible set of imaging tasks. The use of polarimetry as a technique to characterise non-resolved GEO satellites using telescopes of small aperture (less than 0.5 meters) is currently under study by the Space Research Group in UNSW Canberra. First experiments are currently being performed in order to evaluate the use of this technique to characterise GEO satellites. A comparison of both polarimetric and irradiance only acquisitions is being implemented. Two telescopes separated by 1000m are used for the experiments. One of them (USAFA funded Falcon Telescope Network) has the capability to be remote controlled and time tasks assigned, and the other can be operated on-site and is connected to a computer in a network which can control the former with known latency, both synchronised by the same GPS clock. A linear polariser is situated in a collimated beam section of the light path in one of the telescopes to capture polarised photometric measurements, while the other is acquiring the non-polarised photometric signature of the same GEO satellite under observation. The telescope detectors are to be radiometrically calibrated to one another in order to evaluate the photometric data at the same scale. We evaluate the polarised and non-polarised synchronous time photometric curves as a preliminary test to determine satellite signature and its variation over time. We report on the discrimination of unresolved satellites and the merit of including polarisation sensing

  6. OPTICAL I-BAND LINEAR POLARIMETRY OF THE MAGNETAR 4U 0142+61 WITH SUBARU

    SciTech Connect

    Wang, Zhongxiang; Tziamtzis, Anestis; Tanaka, Yasuyuki T.; Kawabata, Koji S.; Wang, Chen; Fukazawa, Yasushi; Itoh, Ryosuke

    2015-12-01

    Magnetars are known to have optical and/or infrared (IR) emission, but the origin of the emission is not well understood. In order to fully study their emission properties, we have carried out for the first time optical linear polarimetry of the magnetar 4U 0142+61, which has been determined from different observations to have a complicated broadband spectrum over optical and IR wavelengths. From our I-band imaging polarimetric observation, conducted with the 8.2-m Subaru telescope, we determine the degree of linear polarization to be P = 1.0 ± 3.4%, or P ≤ 5.6% (90% confidence level). Considering models that were suggested for optical emission from magnetars, we discuss the implications of our result. The upper limit measurement indicates that, differing from radio pulsars, magnetars probably would not have strongly polarized optical emission if the emission arises from their magnetosphere as suggested.

  7. Multi-wavelength Polarimetry and Spectral Study of the M87 Jet During 2002-2008

    NASA Astrophysics Data System (ADS)

    Avachat, Sayali S.; Perlman, Eric S.; Adams, Steven C.; Cara, Mihai; Owen, Frazer; Sparks, William B.; Georganopoulos, Markos

    2016-11-01

    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 polarization 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. Based on the observations made with the Karl G. Jansky Very Large Array (VLA), operated by the National Radio Astronomy Observatory (NRAO), and Hubble Sapce Telescope (HST), obtained at the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy, Inc.

  8. Low Frequency Radio Experiment (LORE)

    NASA Astrophysics Data System (ADS)

    Manoharan, P. K.; Naidu, Arun; Joshi, B. C.; Roy, Jayashree; Kate, G.; Pethe, Kaiwalya; Galande, Shridhar; Jamadar, Sachin; Mahajan, S. P.; Patil, R. A.

    2016-03-01

    In this paper, we present a case study of Low Frequency Radio Experiment (LORE) payload to probe the corona and the solar disturbances at solar offsets greater than 2 solar radii, i.e., at frequencies below 30 MHz. The LORE can be complimentary to the planned Indian solar mission, “Aditya-L1” and its other payloads as well as synergistic to ground-based interplanetary scintillation (IPS) observations, which are routinely carried out by the Ooty Radio Telescope. We discuss the baseline design and technical details of the proposed LORE and its particular suitability for providing measurements on the detailed time and frequency structure of fast drifting type-III and slow drifting type-II radio bursts with unprecedented time and frequency resolutions. We also brief the gonio-polarimetry, which is possible with better-designed antennas and state-of-the-art electronics, employing FPGAs and an intelligent data management system. These would enable us to make a wide range of studies, such as nonlinear plasma processes in the Sun-Earth distance, in-situ radio emission from coronal mass ejections (CMEs), interplanetary CME driven shocks, nature of ICMEs driving decelerating IP shocks and space weather effects of solar wind interaction regions.

  9. Application of radar polarimetry to forestry

    NASA Technical Reports Server (NTRS)

    Durden, S. L.; Zebker, H. A.; Vanzyl, J. J.

    1988-01-01

    In order to understand L-band multipolarization radar measurements of forested areas, a model for the forest polarization signature was developed. The model is based on backscatter from dielectric cylinders which represent branches and trunks. In the model the Stokes matrices corresponding to several different scattering mechanisms is calculated, combining the results to get the total Stokes matrix. Comparison of model predictions with radar measurements shows that the model can accurately predict the forest polarization signature.

  10. IXPE: The Imaging X-ray Polarimetry Explorer, Implementing a Dedicated Polarimetry Mission

    NASA Technical Reports Server (NTRS)

    Ramsey, Brian

    2014-01-01

    Only a few experiments have conducted x-ray polarimetry of cosmic sources since Weisskopf et al confirmed the 19% polarization of the Crab Nebula with the Orbiting Solar Observatory (OSO-8) in the 70's center dot The challenge is to measure a faint polarized component against a background of non-polarized signal (as well as the other, typical background components) center dot Typically, for a few % minimum detectable polarization, 106 photons are required. center dot So, a dedicated mission is vital with instruments that are designed specifically to measure polarization (with minimal systematic effects) Over the proposed mission life (2- 3 years), IXPE will first survey representative samples of several categories of targets: magnetars, isolated pulsars, pulsar wind nebula and supernova remnants, microquasars, active galaxies etc. The survey results will guide detailed follow-up observations. Precise calibration of IXPE is vital to ensuring sensitivity goals are met. The detectors will be characterized in Italy, and then a full calibration of the complete instrument will be performed at MSFC's stray light facility. Polarized flux at different energies Heritage: X-ray Optics at MSFC polarimetry mission.

  11. Multispectral Stokes polarimetry for dermatoscopic imaging

    NASA Astrophysics Data System (ADS)

    Castillejos, Y.; Martínez-Ponce, Geminiano; Mora-Nuñez, Azael; Castro-Sanchez, R.

    2015-12-01

    Most of skin pathologies, including melanoma and basal/squamous cell carcinoma, are related to alterations in external and internal order. Usually, physicians rely on their empirical expertise to diagnose these ills normally assisted with dermatoscopes. When there exists skin cancer suspicion, a cytology or biopsy is made, but both laboratory tests imply an invasive procedure. In this regard, a number of non-invasive optical techniques have been proposed recently to improve the diagnostic certainty and assist in the early detection of cutaneous cancer. Herein, skin optical properties are derived with a multispectral polarimetric dermatoscope using three different illumination wavelength intervals centered at 470, 530 and 635nm. The optical device consist of two polarizing elements, a quarter-wave plate and a linear polarizer, rotating at a different angular velocity and a CCD array as the photoreceiver. The modulated signal provided by a single pixel in the acquired image sequence is analyzed with the aim of computing the Stokes parameters. Changes in polarization state of selected wavelengths provide information about the presence of skin pigments such as melanin and hemoglobin species as well as collagen structure, among other components. These skin attributes determine the local physiology or pathology. From the results, it is concluded that optical polarimetry will provide additional elements to dermatologists in their diagnostic task.

  12. The potential of X-ray polarimetry

    NASA Astrophysics Data System (ADS)

    Tamborra, F.

    2014-07-01

    Up-scattering of low-energy photons by Inverse Compton processes in a hot gas of electrons (i.e. Comptonization) is a common astrophysical mechanism particularly important in accreting systems like X-ray binaries (XRBs) and Active Galactic Nuclei (AGN). Polarization signals produced by scattering strongly depend on the optical thickness and geometry of the scattering medium as well as on the observer's viewing angle. The polarization degree and angle can be used to constrain, for example, the still unknown parameters which characterize the hot corona responsible for the production of X-ray radiation in AGN or the dominant mechanism responsible for the broadening of the Iron K-alpha emission line whose origin is still a matter of debate in the case of low mass X-ray binaries with a neutron star. Conducting accurate Monte Carlo simulations we show the potential of X-ray polarimetry, a new perspective of X-ray astronomy. The spectroscopic part of our results can already be exploited today in the light of XMM-Newton and Chandra data and is even more appealing in the perspective of data from NuStar and future X-ray missions.

  13. Stokes polarimetry imaging of dog prostate tissue

    NASA Astrophysics Data System (ADS)

    Kim, Jihoon; Johnston, William K., III; Walsh, Joseph T., Jr.

    2010-02-01

    Prostate cancer is the second leading cause of death in the United States in 2009. Radical prostatectomy (complete removal of the prostate) is the most common treatment for prostate cancer, however, differentiating prostate tissue from adjacent bladder, nerves, and muscle is difficult. Improved visualization could improve oncologic outcomes and decrease damage to adjacent nerves and muscle important for preservation of potency and continence. A novel Stokes polarimetry imaging (SPI) system was developed and evaluated using a dog prostate specimen in order to examine the feasibility of the system to differentiate prostate from bladder. The degree of linear polarization (DOLP) image maps from linearly polarized light illumination at different visible wavelengths (475, 510, and 650 nm) were constructed. The SPI system used the polarization property of the prostate tissue. The DOLP images allowed advanced differentiation by distinguishing glandular tissue of prostate from the muscular-stromal tissue in the bladder. The DOLP image at 650 nm effectively differentiated prostate and bladder by strong DOLP in bladder. SPI system has the potential to improve surgical outcomes in open or robotic-assisted laparoscopic removal of the prostate. Further in vivo testing is warranted.

  14. On demand polarimetry using a movable microgrid polarizer

    NASA Astrophysics Data System (ADS)

    King, Page E.; Fest, Eric C.

    2015-09-01

    A movable pixelated filter array is proposed to provide low cost, on demand polarimetry and wavefront sensing. With this concept, an optical system can turn polarimetry on and off by using a shutter to move a microgrid polarizer array in and out of the optical path of the system. This allows an optical system to operate in two modes, a non-polarimetric mode in which sensor range is maintained, and a polarimetric mode in which it is reduced. In implementing this concept, adequate knowledge of the position of the filter in the optical path and calibration procedures become critical topics. This paper discusses simulated and hardware-tested results of this invention.

  15. The VLBA Imaging And Polarimetry Survey at 5 GHz

    SciTech Connect

    Helmboldt, J.F.; Taylor, G.B.; Tremblay, S.; Fassnacht, C.D.; Walker, R.C.; Myers, S.T.; Sjouwerman, L.O.; Pearson, T.J.; Readhead, A.C.S.; Weintraub, L.; Gehrels, N.; Romani, R.W.; Healey, S.; Michelson, P.F.; Blandford, R.D.; Cotter, G.; /New Mexico U. /UC, Davis /NRAO, Socorro /Caltech /NASA, Goddard /Stanford U., Phys. Dept. /KIPAC, Menlo Park /Oxford U.

    2006-11-20

    We present the first results of the VLBA Imaging and Polarimetry Survey (VIPS), a 5 GHz VLBI survey of 1,127 sources with flat radio spectra. Through automated data reduction and imaging routines, we have produced publicly available I, Q, and U images and have detected polarized flux density from 37% of the sources. We have also developed an algorithm to use each source's I image to automatically classify it as a point-like source, a core-jet, a compact symmetric object (CSO) candidate, or a complex source. Using data from the Sloan Digital Sky Survey (SDSS), we have found no significant trend between optical flux and 5 GHz flux density for any of the source categories. Using the velocity width of the H{beta} emission line and the monochromatic luminosity at 5100 to estimate the central black hole mass, M{sub BH}, we have found a weak trend between M{sub BH} and 5 GHz luminosity density for objects with SDSS spectra. Ongoing optical follow-up for all VIPS sources will allow for more detailed explorations of these issues. The mean ratio of the polarized to total 5 GHz flux density for VIPS sources with detected polarized flux density ranges from 1% to 20% with a median value of about 5%. This ratio is a factor of {approx}3 larger if only the jet components of core-jet systems are considered and is noticeably higher for relatively large core-jet systems than for other source types, regardless of which components (i.e., core, jet, or both) are considered. We have also found significant evidence that the directions of the jets in core-jet systems tend to be perpendicular to the electric vector position angles (EVPAs). The data is consistent with a scenario in which {approx}24% of the polarized core-jets have EVPAs that are anti-aligned with the directions of their jet components and which have a substantial amount of Faraday rotation. Follow-up observations at multiple frequencies will address this issue in more detail. In addition to these initial results, plans for

  16. Optical linear polarimetry of Solar System bodies using a Wedged Double Wollaston.

    NASA Astrophysics Data System (ADS)

    Gorosabel, J.; García Muñoz, A.; Sánchez-Lavega, A.; Hueso, R.; Pérez Hoyos, S.

    2015-05-01

    The gases and aerosols contained in a planetary atmosphere leave characteristic signatures on the reflected radiation. Hence we could use the polarization state of emergent radiation to investigate the atmospheric optical properties of the planet. We report on the first polarimetric tests of Jupiter and Saturn recently carried out with a Wedged Double Wollaston (WeDoWo) prism attached to the ALFOSC instrument mounted at NOT. A WeDoWo is composed of a suitable combination of two glass wedges and two Wollaston prisms in the parallel beam ALFOSC. The edges split the beam and feed the Wollaston prims with axes rotated by 45 deg. Thus, the relative intensities of the output light provides the angle and degree of the input photons. The four images are taken simultaneously and hence at identical planet rotation and atmospheric conditions. In order avoid overlap of the 4 images in the CCD, a 10" wide slit is placed on the telescope focal plane. Polarimetry complements the extended technique of photometry by probing different atmospheric altitudes, characterizing the particles in suspension in the atmosphere. In observations with spatial resolution of the planet disk, polarimetry may be sensitive to the phenomenon of limb polarization and to the occurrence of polar hazes (as for Jupiter). We plan to complement the observational work with modelling. For that purpose, we are using a novel Pre-conditioned Backward Monte Carlo (PBMC) algorithm that computes the full Stokes vector for multiple scattering. We are also developing a new calibration code in order to systematize the data reduction. Despite the potentialities of the technique, there has been no systematic survey of the Solar System planets in polarimetric mode. In the medium term we plan to extend the WeDoWo use to other objects of the Solar System.

  17. Probing magnetic turbulence by synchrotron polarimetry: statistics and structure of magnetic fields from Stokes correlators

    NASA Astrophysics Data System (ADS)

    Waelkens, A. H.; Schekochihin, A. A.; Enßlin, T. A.

    2009-10-01

    We describe a novel technique for probing the statistical properties of cosmic magnetic fields based on radio polarimetry data. Second-order magnetic field statistics like the power spectrum cannot always distinguish between magnetic fields with essentially different spatial structure. Synchrotron polarimetry naturally allows certain fourth-order magnetic field statistics to be inferred from observational data, which lifts this degeneracy and can thereby help us gain a better picture of the structure of the cosmic fields and test theoretical scenarios describing magnetic turbulence. In this work we show that a fourth-order correlator of specific physical interest, the tension force spectrum, can be recovered from the polarized synchrotron emission data. We develop an estimator for this quantity based on polarized emission observations in the Faraday rotation free frequency regime. We consider two cases: a statistically isotropic field distribution, and a statistically isotropic field superimposed on a weak mean field. In both cases the tension force power spectrum is measurable; in the latter case, the magnetic power spectrum may also be obtainable. The method is exact in the idealized case of a homogeneous relativistic electron distribution that has a power-law energy spectrum with a spectral index of p = 3, and assumes statistical isotropy of the turbulent field. We carry out numerical tests of our method using synthetic polarized emission data generated from numerically simulated magnetic fields. We show that the method is valid, that it is not prohibitively sensitive to the value of the electron spectral index p, and that the observed tension force spectrum allows one to distinguish between e.g. a randomly tangled magnetic field (a default assumption in many studies) and a field organized in folded flux sheets or filaments.

  18. Evaluating compact SAR polarimetry for tropical forest monitoring

    NASA Astrophysics Data System (ADS)

    Trisasongko, Bambang H.

    2015-01-01

    Fully polarimetric Synthetic Aperture Radar (SAR) or PolSAR has been proven useful for diverse applications related to environment. Nevertheless, problems are arising since satellite-borne PolSAR requires special arrangements on data acquisition and consumes higher energy for signal transmission. Complexity of data acquisition and analysis can be reduced using compact polarimetry. The technique has been demonstrated to some extent; however, tests on various environments are still required. This paper assesses compact polarimetry on a tropical forest fringe, especially to monitor expanding oil palm estate and forest disturbance, in comparison to fully polarimetric mode. PALSAR data of Manokwari, Indonesia, were collected from JAXA through RA4.1029 project. In this paper, linear 45 degrees transmission is evaluated to detect various land cover classes using Wishart supervised classifier. Tonal discrepancies between both polarimetric modes are evident, suggesting compact polarimetry has limitation to recover information contained in fully polarimetric mode. However, Wishart classification procedure indicates that compact polarimetry is still useful for mapping.

  19. Millimeter-wave interferometric SAR and polarimetry

    NASA Astrophysics Data System (ADS)

    Boehmsdorff, Stephan; Essen, Helmut; Schimpf, Hartmuf; Wahlen, Alfred

    1998-07-01

    Using synthetic aperture radars with appropriate signal processing algorithms is a recognized technique for remote sensing applications. A wide spectrum of radar frequencies is used and a high degree of sophistication implies polarimetric and further multichannel approaches. Each frequency band used, exhibits special sensitivities to features of the earth's surface or man-made targets. This is mostly due to the coupling of the electromagnetic waves to backscattering geometries which are related to the radarwavelength. A part of the spectrum which has been covered not very intensely is the millimeterwave region. This may be mostly due to the relatively high atmospheric absorption at millimeterwaves which obstructs the use of such sensors for long range applications. On the other hand for military applications IR-imaging sensors are widely used which suffer even more from adverse transmission properties of the atmosphere. Application of multichannel techniques as polarimetry, multifrequency techniques and interferometry are also done with more ease due to compactness of the hardware and simplicity of processing. As there exist no data which would allow to investigate the potential of multifrequency polarimetric and interferometric mmW-SAR the Millimeterwave Experimental Multifrequency Polarimetric High Resolution Interferometric Imaging System was installed into an aircraft C-160 `Transall' to gather respective data over different land scenarios. The off-line evaluation of the radar data starts with off-line track, calibration and reformatting procedures. Afterwards synthetic aperture processing is applied to these data to generate radar images for co- and cross-polarization at 35 GHz and 94 GHz. As already mentioned above, SAR-processing at millimeterwavelengths requires a considerable lower amount of sophistication in comparison with algorithms applied at lower radar-frequencies. This can mainly be attributed to the short aperture length at mm-wave frequencies

  20. Reflection nebulae in the Galactic center: soft X-ray imaging polarimetry

    NASA Astrophysics Data System (ADS)

    Marin, F.; Muleri, F.; Soffitta, P.; Karas, V.; Kunneriath, D.

    2015-04-01

    Context. The origin of irradiation and fluorescence of the 6.4 keV bright giant molecular clouds surrounding Sgr A∗, the central supermassive black hole of our Galaxy, remains enigmatic despite numerous attempts to decipher it with spectroscopic and timing analyses. Aims: Testing the theory of a past active period of Sgr A∗ requires opening a new observational window: X-ray polarimetry. In this paper, we aim to show how modern imaging polarimeters could revolutionize our understanding of the Galactic center (GC). Methods: Through Monte Carlo modeling, we produced a 4-8 keV polarization map of the GC. We focused on the polarimetric signature produced by Sgr B1, Sgr B2, G0.11-0.11, Bridge E, Bridge D, Bridge B2, MC2, MC1, Sgr C3, Sgr C2, and Sgr C1. We estimated the resulting polarization that arises from these scattering targets, included polarized flux dilution by the diffuse plasma emission detected toward the GC, and simulated the polarization map that modern polarimetric detectors would obtain assuming the performances of a mission prototype. Results: The eleven reflection nebulae we investigated present a variety of polarization signatures, ranging from nearly unpolarized to highly polarized (~77%) fluxes. Their polarization position angle is found to be normal to the scattering plane, as expected from previous studies. A major improvement in our simulation is the addition of a diffuse, unpolarized plasma emission that strongly affects soft X-ray polarized fluxes. The dilution factor is in the range 50%-70%, making the observation of the Bridge structure unlikely even in the context of modern polarimetry. The best targets are the Sgr B and Sgr C complexes and the G0.11-0.11 cloud, arranged in the order of decreasing detectability. Conclusions: An exploratory observation of a few hundred kilo-seconds of the Sgr B complex would allow a significant detection of the polarization and be sufficient to derive indications of the primary radiation source. A more

  1. Radio Days.

    ERIC Educational Resources Information Center

    Sanderson, Neil

    1998-01-01

    Thousands of today's high school students run FM radio stations at school, carrying on a tradition that began 50 years ago. Radio helps students learn to work with others and develop a strong sense of responsibility. A sidebar gives advice on starting a high school radio station. (MLF)

  2. Snapshot linear-Stokes imaging spectropolarimeter using division-of-focal-plane polarimetry and integral field spectroscopy

    PubMed Central

    Mu, Tingkui; Pacheco, Shaun; Chen, Zeyu; Zhang, Chunmin; Liang, Rongguang

    2017-01-01

    In this paper, the design and experimental demonstration of a snapshot linear-Stokes imaging spectropolarimeter (SLSIS) is presented. The SLSIS, which is based on division-of-focal-plane polarimetry with four parallel linear polarization channels and integral field spectroscopy with numerous slit dispersive paths, has no moving parts and provides video-rate Stokes-vector hyperspectral datacubes. It does not need any scanning in the spectral, spatial or polarization dimension and offers significant advantages of rapid reconstruction without heavy computation during post-processing. The principle and the experimental setup of the SLSIS are described in detail. The image registration, Stokes spectral reconstruction and calibration procedures are included, and the system is validated using measurements of tungsten light and a static scene. The SLSIS’s snapshot ability to resolve polarization spectral signatures is demonstrated using measurements of a dynamic scene. PMID:28191819

  3. Snapshot linear-Stokes imaging spectropolarimeter using division-of-focal-plane polarimetry and integral field spectroscopy

    NASA Astrophysics Data System (ADS)

    Mu, Tingkui; Pacheco, Shaun; Chen, Zeyu; Zhang, Chunmin; Liang, Rongguang

    2017-02-01

    In this paper, the design and experimental demonstration of a snapshot linear-Stokes imaging spectropolarimeter (SLSIS) is presented. The SLSIS, which is based on division-of-focal-plane polarimetry with four parallel linear polarization channels and integral field spectroscopy with numerous slit dispersive paths, has no moving parts and provides video-rate Stokes-vector hyperspectral datacubes. It does not need any scanning in the spectral, spatial or polarization dimension and offers significant advantages of rapid reconstruction without heavy computation during post-processing. The principle and the experimental setup of the SLSIS are described in detail. The image registration, Stokes spectral reconstruction and calibration procedures are included, and the system is validated using measurements of tungsten light and a static scene. The SLSIS’s snapshot ability to resolve polarization spectral signatures is demonstrated using measurements of a dynamic scene.

  4. Firefighters' Radios

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Public Technology Inc. asked for NASA assistance to devise the original firefighter's radio. Good short-range radio communications are essential during a fire to coordinate hose lines, rescue victims, and otherwise increase efficiency. Useful firefighting tool is lower cost, more rugged short range two-way radio. Inductorless electronic circuit replaced inductances and coils in radio circuits with combination of transistors and other low-cost components. Substitution promises reduced circuit size and cost. Enhanced electrical performance made radio more durable and improved maintainability by incorporating modular construction.

  5. IXPE - The Imaging X-Ray Polarimetry Explorer

    NASA Technical Reports Server (NTRS)

    Ramsey, Brian

    2014-01-01

    The Imaging X-ray Polarimetry Explorer (IXPE) is a Small Explorer Mission that will be proposed in response to NASA's upcoming Announcement of Opportunity. IXPE will transform our understanding of the most energetic and exotic astrophysical objects, especially neutron stars and black holes, by measuring the linear polarization of astronomical objects as a function of energy, time and, where relevant, position. As the first dedicated polarimetry observatory IXPE will add a new dimension to the study of cosmic sources, enlarging the observational phase space and providing answers to fundamental questions. IXPE will feature x-ray optics fabricated at NASA/MSFC and gas pixel focal plane detectors provided by team members in Italy (INAF and INFN). This presentation will give an overview of the proposed IXPE mission, detailing the payload configuration, the expected sensitivity, and a typical observing program.

  6. HST Polarimetry of the 3C 273 Jet

    NASA Astrophysics Data System (ADS)

    Clautice, Devon; Perlman, Eric S.; Sparks, William B.; Biretta, John A.; O'Dea, Christopher P.; Baum, Stefi Alison; Cheung, Chi C.; Birkinshaw, Mark; Worrall, Diana M.; Martel, Andre; Urry, C. Megan; Stawarz, Lukasz; Coppi, Paolo S.; Uchiyama, Yasunobu; Cara, Mihai; Meisenheimer, Klaus; Begelman, Mitchell C.

    2017-01-01

    We present preliminary results using HST polarimetry of the jet of 3C 273. Polarization is a critical parameter for understanding jet flows, and has proven essential in characterizing the physics of FR I jets; high-quality HST polarimetry has been done for just two other FR II jets previously. Our recent work on two quasar jets, where we measured high optical polarization in the brightest X-ray knots, has favored the synchrotron emission model over the alternative IC/CMB model for their optical to X-ray emission. These new observations of 3C 273 allow for the determination of the magnetic field structure and confirmation of which emission mechanisms are operating to create its optical to X-ray emission, and will allow us to greatly advance modeling efforts for this jet and nail down its kinetic power, a key unknown parameter for understanding quasars and their cosmological effects.

  7. Solar Polarimetry - from Turbulent Magnetic Fields to Sunspots

    NASA Astrophysics Data System (ADS)

    Kleint, Lucia

    2016-07-01

    Polarimetric measurements are essential to investigate the solar magnetic field. Scattering polarization and the Hanle effect allow us to probe the turbulent magnetic field and the still open questions of its strength and variability. Directed magnetic fields can be detected via the Zeeman effect. To derive their orientation and strength, so-called inversion codes are used, which iteratively modify a model atmosphere and calculate the resulting polarization profiles that are then compared to the observations. While photospheric polarimetry is well-established, chromospheric polarimetry is still in its infancy, especially because it requires a treatment in non-LTE, making it a complex non-linear problem. But some of the most important open questions concern the strength and geometry of the chromospheric magnetic field. In this talk, I will review different polarimetric analysis techniques and recent advances in magnetic field measurements going from the small scales of turbulent magnetic fields to changes of magnetic fields in an active region during flares.

  8. XIPE The X-ray Imaging Polarimetry Explorer

    NASA Astrophysics Data System (ADS)

    Soffitta, Paolo

    2016-07-01

    XIPE (the X-ray Imaging Polarimetry Explorer) is now in the study phase for ESA M4 down-selection in mid-2017. XIPE will be operated as a conventional X-ray observatory but providing polarimetry simultaneously to the usual imaging, temporal and spectral information. 75 % of the time will be available through a competitive Guest Observer Program This is made possible by its unique payload configuration consisting of three GPDs at the focus of three large, albeit low-weight, X-ray telescopes and fitting in the Vega launcher. In this talk I will review the major aspects involved with this kind of measurement, the scientific target, the mission and payload profile of XIPE.

  9. Angle-Resolved Polarimetry of Antenna-Mediated Fluorescence

    NASA Astrophysics Data System (ADS)

    Mohtashami, Abbas; Osorio, Clara I.; Koenderink, A. Femius

    2015-11-01

    Optical phase-array antennas can be used to control not only the angular distribution but also the polarization of fluorescence from quantum emitters. The emission pattern of the resulting system is determined by the properties of the antenna, the properties of the emitters, and the strength of the antenna-emitter coupling. Here we show that Fourier polarimetry can be used to characterize these three contributions. To this end, we measure the angle- and Stokes-parameter-resolved emission of bullseye plasmon antennas as well as spiral antennas excited by an ensemble of emitters. We estimate the average antenna-emitter coupling on the basis of the degree of polarization and determine the effect of anisotropy in the intrinsic emitter orientation on polarization of the resulting emission pattern. Our results provide not only new insights into the behavior of bullseye and spiral antennas but also demonstrate the potential of Fourier polarimetry when characterizing antenna-mediated fluorescence.

  10. Noble Gas Polarimetry Using Rb EPR Frequency Shifts

    NASA Astrophysics Data System (ADS)

    Ma, Z. L.; Jeong, K.; Houghtby, E.; Paskvan, T.; Limes, M. E.; Saam, B.

    2014-05-01

    EPR frequency shifts of optically polarized alkali-metal atoms can be exploited for polarimetry of noble-gas nuclei polarized by spin-exchange optical pumping. Our group recently measured the enhancement factor κ0 = 493 for Rb-129Xe, which characterizes the electron wave-function overlap during collisions and is crucial to the calibration of the frequency-shift for 129Xe polarimetry. This type of polarimetry is useful in several applications involving optically polarized 129Xe; our particular motivation is an in situ measurement of absolute 129Xe polarization within the optical pumping cell of a flow-through 129Xe polarizer. This application has some particular challenges, and we have initially observed some unexpected shifts in the 87Rb EPR frequency measurement on board the polarizer. In effort to disentangle these apparent systematic effects, we have constructed a separate experiment to characterize Rb EPR shifts for both 3He and 129Xe in sealed cells. We present results and analysis of these experiments and discuss implications for using this method in flow-through polarizers. NSF PHY-0855482

  11. Turbid medium polarimetry in biomedical imaging and diagnosis

    NASA Astrophysics Data System (ADS)

    Ghosh, N.; Banerjee, A.; Soni, J.

    2011-06-01

    Studies on polarization properties of scattered light from a random medium like biological tissue have received considerable attention because polarization can be used as an effective tool to discriminate against multiply scattered light (acting as a gating mechanism) and thus can facilitate high resolution imaging through tissue. Further, the polarization properties of scattered light from tissue contain wealth of morphological and functional information of potential biomedical importance. However, in a complex random medium like tissue, numerous complexities due to multiple scattering and simultaneous occurrences of many scattering and polarization events present formidable challenges both in terms of accurate measurements and in terms of analysis of the tissue polarimetry signal. Several studies have therefore been conducted in the recent past to develop appropriate measurement procedures, suitable light propagation models and polarimetry signal analysis methods to overcome these difficulties. In this review, we focus on some of the recent key developments in this area. Specifically, we describe variety of theoretical and experimental tools, illustrated with selected results, aimed at evaluating the prospect of turbid medium polarimetry for both biomedical imaging and diagnosis.

  12. XIPE: the x-ray imaging polarimetry explorer

    NASA Astrophysics Data System (ADS)

    Soffitta, P.; Bellazzini, R.; Bozzo, E.; Burwitz, V.; Castro-Tirado, A.; Costa, E.; Courvoisier, T.; Feng, H.; Gburek, S.; Goosmann, R.; Karas, V.; Matt, G.; Muleri, F.; Nandra, K.; Pearce, M.; Poutanen, J.; Reglero, V.; Sabau Maria, D.; Santangelo, A.; Tagliaferri, G.; Tenzer, C.; Vink, J.; Weisskopf, M. C.; Zane, S.; Agudo, I.; Antonelli, A.; Attina, P.; Baldini, L.; Bykov, A.; Carpentiero, R.; Cavazzuti, E.; Churazov, E.; Del Monte, E.; De Martino, D.; Donnarumma, I.; Doroshenko, V.; Evangelista, Y.; Ferreira, I.; Gallo, E.; Grosso, N.; Kaaret, P.; Kuulkers, E.; Laranaga, J.; Latronico, L.; Lumb, D. H.; Macian, J.; Malzac, J.; Marin, F.; Massaro, E.; Minuti, M.; Mundell, C.; Ness, J. U.; Oosterbroek, T.; Paltani, S.; Pareschi, G.; Perna, R.; Petrucci, P.-O.; Pinazo, H. B.; Pinchera, M.; Rodriguez, J. P.; Roncadelli, M.; Santovincenzo, A.; Sazonov, S.; Sgro, C.; Spiga, D.; Svoboda, J.; Theobald, C.; Theodorou, T.; Turolla, R.; Wilhelmi de Ona, E.; Winter, B.; Akbar, A. M.; Allan, H.; Aloisio, R.; Altamirano, D.; Amati, L.; Amato, E.; Angelakis, E.; Arezu, J.; Atteia, J.-L.; Axelsson, M.; Bachetti, M.; Ballo, L.; Balman, S.; Bandiera, R.; Barcons, X.; Basso, S.; Baykal, A.; Becker, W.; Behar, E.; Beheshtipour, B.; Belmont, R.; Berger, E.; Bernardini, F.; Bianchi, S.; Bisnovatyi-Kogan, G.; Blasi, P.; Blay, P.; Bodaghee, A.; Boer, M.; Boettcher, M.; Bogdanov, S.; Bombaci, I.; Bonino, R.; Braga, J.; Brandt, W.; Brez, A.; Bucciantini, N.; Burderi, L.; Caiazzo, I.; Campana, R.

    2016-07-01

    XIPE, the X-ray Imaging Polarimetry Explorer, is a mission dedicated to X-ray Astronomy. At the time of writing XIPE is in a competitive phase A as fourth medium size mission of ESA (M4). It promises to reopen the polarimetry window in high energy Astrophysics after more than 4 decades thanks to a detector that efficiently exploits the photoelectric effect and to X-ray optics with large effective area. XIPE uniqueness is time-spectrally-spatially- resolved X-ray polarimetry as a breakthrough in high energy astrophysics and fundamental physics. Indeed the payload consists of three Gas Pixel Detectors at the focus of three X-ray optics with a total effective area larger than one XMM mirror but with a low weight. The payload is compatible with the fairing of the Vega launcher. XIPE is designed as an observatory for X-ray astronomers with 75 % of the time dedicated to a Guest Observer competitive program and it is organized as a consortium across Europe with main contributions from Italy, Germany, Spain, United Kingdom, Poland, Sweden.

  13. Surface geometry of protoplanetary disks inferred from near-infrared imaging polarimetry

    SciTech Connect

    Takami, Michihiro; Hasegawa, Yasuhiro; Gu, Pin-Gao; Karr, Jennifer L.; Chapillon, Edwige; Tang, Ya-Wen; Muto, Takayuki; Dong, Ruobing; Hashimoto, Jun; Kusakabe, Nobuyuki; Akiyama, Eiji; Kwon, Jungmi; Itoh, Youchi; Carson, Joseph; Follette, Katherine B.; Mayama, Satoshi; Sitko, Michael; Janson, Markus; Grady, Carol A.; Kudo, Tomoyuki; and others

    2014-11-01

    We present a new method of analysis for determining the surface geometry of five protoplanetary disks observed with near-infrared imaging polarimetry using Subaru-HiCIAO. Using as inputs the observed distribution of polarized intensity (PI), disk inclination, assumed properties for dust scattering, and other reasonable approximations, we calculate a differential equation to derive the surface geometry. This equation is numerically integrated along the distance from the star at a given position angle. We show that, using these approximations, the local maxima in the PI distribution of spiral arms (SAO 206462, MWC 758) and rings (2MASS J16042165-2130284, PDS 70) are associated with local concave-up structures on the disk surface. We also show that the observed presence of an inner gap in scattered light still allows the possibility of a disk surface that is parallel to the light path from the star, or a disk that is shadowed by structures in the inner radii. Our analysis for rings does not show the presence of a vertical inner wall as often assumed in studies of disks with an inner gap. Finally, we summarize the implications of spiral and ring structures as potential signatures of ongoing planet formation.

  14. Nanotube Radio

    NASA Astrophysics Data System (ADS)

    Jensen, Kenneth; Weldon, Jeff; Garcia, Henry; Zettl, Alex

    2008-03-01

    We have constructed a fully functional, fully integrated radio receiver from a single carbon nanotube. The nanotube serves simultaneously as all essential components of a radio: antenna, tunable band-pass filter, amplifier, and demodulator. A direct current voltage source, as supplied by a battery, powers the radio. Using carrier waves in the commercially relevant 40-400 MHz range and both frequency and amplitude modulation techniques, we demonstrate successful music and voice reception.

  15. Radio Science

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Radio science experiments use electromagnetic waves to probe or study the solar system. Three major research areas were identified within this discipline: radio astronomy, radar astronomy, and celestial mechanics. Radio astronomy (or radiometry) is the detection and measurement of naturally produced radio frequency emissions. Sources include surfaces, atmospheres, rings, and plasmas. Radar astronomy is the observation of man-made signals after their interaction with a target. Both imaging and non-imaging results. Celestial mechanics includes all studies related to the motions of (and gravity fields of) bodies within the solar system. These should not be considered rigid separations, but aid in the discussion of the data sets.

  16. A Detector for Cosmic Microwave Background Polarimetry

    NASA Technical Reports Server (NTRS)

    Wollack, E.; Cao, N.; Chuss, D.; Hsieh, W.-T.; Moseley, S. Harvey; Stevenson, T.; U-yen, K.

    2008-01-01

    We present preliminary design and development work on polarized detectors intended to enable Cosmic Microwave Background polarization measurements that will probe the first moments of the universe. The ultimate measurement will be challenging, requiring background-limited detectors and good control of systematic errors. Toward this end, we are integrating the beam control of HE-11 feedhorns with the sensitivity of transition-edge sensors. The coupling between these two devices is achieved via waveguide probe antennas and superconducting microstrip lines. This implementation allows band-pass filters to be incorporated on the detector chip. We believe that a large collection of single-mode polarized detectors will eventually be required for the reliable detection of the weak polarized signature that is expected to result from gravitational waves produced by cosmic inflation. This focal plane prototype is an important step along the path to this detection, resulting in a capability that will enable various future high performance instrument concepts.

  17. Active Galaxy Unification in the Era of X-Ray Polarimetry

    NASA Technical Reports Server (NTRS)

    Dorodnitsyn, A.; Kallman, T.

    2010-01-01

    Active galactic nuclei (AGNs), Seyfert galaxies, and quasars are powered by luminous accretion and often accompanied by winds that are powerful enough to affect the AGN mass budget, and whose observational appearance bears an imprint of processes that are happening within the central parsec around the black hole (BH). One example of such a wind is the partially ionized gas responsible for X-ray and UV absorption (warm absorbers). Here, we show that such gas will have a distinct signature when viewed in polarized X-rays. Observations of such polarization can test models for the geometry of the flow and the gas responsible for launching and collimating it. We present calculations that show that the polarization depends on the hydrodynamics of the flow, the quantum mechanics of resonance-line scattering, and the transfer of polarized X-ray light in the highly ionized moving gas. The results emphasize the three-dimensional nature of the wind for modeling spectra. We show that the polarization in the 0.1-10 keV energy range is dominated by the effects of resonance lines. We predict a 5%-25% X-ray polarization signature of type-2 objects in this energy range. These results are generalized to flows that originate from a cold torus-like structure, located approximately 1 pc from the BH, which wraps the BH and is ultimately responsible for the apparent dichotomy between type 1 and type 2 AGNs. Such signals will be detectable by future dedicated X-ray polarimetry space missions, such as the NASA Gravity and Extreme Magnetism Small Explorer SMEX, "GEMS" Swank et al. (2008).

  18. ACTIVE GALAXY UNIFICATION IN THE ERA OF X-RAY POLARIMETRY

    SciTech Connect

    Dorodnitsyn, A.; Kallman, T.

    2010-03-10

    Active galactic nuclei (AGNs), Seyfert galaxies, and quasars are powered by luminous accretion and often accompanied by winds that are powerful enough to affect the AGN mass budget, and whose observational appearance bears an imprint of processes that are happening within the central parsec around the black hole (BH). One example of such a wind is the partially ionized gas responsible for X-ray and UV absorption (warm absorbers). Here, we show that such gas will have a distinct signature when viewed in polarized X-rays. Observations of such polarization can test models for the geometry of the flow and the gas responsible for launching and collimating it. We present calculations that show that the polarization depends on the hydrodynamics of the flow, the quantum mechanics of resonance-line scattering, and the transfer of polarized X-ray light in the highly ionized moving gas. The results emphasize the three-dimensional nature of the wind for modeling spectra. We show that the polarization in the 0.1-10 keV energy range is dominated by the effects of resonance lines. We predict a 5%-25% X-ray polarization signature of type-2 objects in this energy range. These results are generalized to flows that originate from a cold torus-like structure, located {approx}1 pc from the BH, which wraps the BH and is ultimately responsible for the apparent dichotomy between type 1 and type 2 AGNs. Such signals will be detectable by future dedicated X-ray polarimetry space missions, such as the NASA Gravity and Extreme Magnetism Small Explorer.

  19. College Radio.

    ERIC Educational Resources Information Center

    Sauls, Samuel J.

    As with commercial stations, the underlying premise of the college radio station is to serve the community, whether it be the campus community or the community at large, but in unique ways often geared to underserved niches of the population. Much of college radio's charm lies in its unpredictable nature and constant mutations. The stations give…

  20. Radio astronomy

    NASA Technical Reports Server (NTRS)

    Taylor, R. M.; Manchester, R. N.

    1980-01-01

    The activities of the Deep Space Network in support of radio and radar astronomy operations during July and August 1980 are reported. A brief update on the OSS-sponsored planetary radio astronomy experiment is provided. Also included are two updates, one each from Spain and Australia on current host country activities.

  1. Radio stars.

    PubMed

    Hjellming, R M; Wade, C M

    1971-09-17

    Up to the present time six classes of radio stars have been established. The signals are almost always very faint and drastically variable. Hence their discovery has owed as much to serendipity as to the highly sophisticated equipment and techniques that have been used. When the variations are regular, as with the pulsars, this characteristic can be exploited very successfully in the search for new objects as well as in the detailed study of those that are already known. The detection of the most erratically variable radio stars, the flare stars and the x-ray stars, is primarily a matter of luck and patience. In the case of the novas, one at least knows where and oughly when to look for radio emission. A very sensitive interferometer is clearly the best instrument to use in the initial detection of a radio star. The fact that weak background sources are frequently present makes it essential to prove that the position of a radio source agrees with that of a star to within a few arc seconds. The potential of radio astronomy for the study of radio stars will not be realized until more powerful instruments than those that are available today can be utilized. So far, we have been able to see only the most luminous of the radio stars.

  2. Signatures of AGN feedback

    NASA Astrophysics Data System (ADS)

    Wylezalek, D.; Zakamska, N.

    2016-06-01

    Feedback from active galactic nuclei (AGN) is widely considered to be the main driver in regulating the growth of massive galaxies. It operates by either heating or driving the gas that would otherwise be available for star formation out of the galaxy, preventing further increase in stellar mass. Observational proof for this scenario has, however, been hard to come by. We have assembled a large sample of 133 radio-quiet type-2 and red AGN at 0.1signatures are hosted in galaxies that are more `quenched' considering their stellar mass than galaxies with weaker outflow signatures. This correlation is only seen in AGN host galaxies with SFR >100 M_{⊙} yr^{-1} where presumably the coupling of the AGN-driven wind to the gas is strongest. This observation is consistent with the AGN having a net suppression, or `negative' impact, through feedback on the galaxies' star formation history.

  3. Probing Inflation via Cosmic Microwave Background Polarimetry

    NASA Technical Reports Server (NTRS)

    Chuss, David T.

    2008-01-01

    The Cosmic Microwave Background (CMB) has been a rich source of information about the early Universe. Detailed measurements of its spectrum and spatial distribution have helped solidify the Standard Model of Cosmology. However, many questions still remain. Standard Cosmology does not explain why the early Universe is geometrically flat, expanding, homogenous across the horizon, and riddled with a small anisotropy that provides the seed for structure formation. Inflation has been proposed as a mechanism that naturally solves these problems. In addition to solving these problems, inflation is expected to produce a spectrum of gravitational waves that will create a particular polarization pattern on the CMB. Detection of this polarized signal is a key test of inflation and will give a direct measurement of the energy scale at which inflation takes place. This polarized signature of inflation is expected to be -9 orders of magnitude below the 2.7 K monopole level of the CMB. This measurement will require good control of systematic errors, an array of many detectors having the requisite sensitivity, and a reliable method for removing polarized foregrounds, and nearly complete sky coverage. Ultimately, this measurement is likely to require a space mission. To this effect, technology and mission concept development are currently underway.

  4. Compact Polarimetry in a Low Frequency Spaceborne Context

    NASA Technical Reports Server (NTRS)

    Truong-Loi, M-L.; Freeman, A.; Dubois-Fernandez, P.; Pottier, E.

    2011-01-01

    Compact polarimetry has been shown to be an interesting alternative mode to full polarimetry when global coverage and revisit time are key issues. It consists on transmitting a single polarization, while receiving on two. Several critical points have been identified, one being the Faraday rotation (FR) correction and the other the calibration. When a low frequency electromagnetic wave travels through the ionosphere, it undergoes a rotation of the polarization plane about the radar line of sight for a linearly polarized wave, and a simple phase shift for a circularly polarized wave. In a low frequency radar, the only possible choice of the transmit polarization is the circular one, in order to guaranty that the scattering element on the ground is illuminated with a constant polarization independently of the ionosphere state. This will allow meaningful time series analysis, interferometry as long as the Faraday rotation effect is corrected for the return path. In full-polarimetric (FP) mode, two techniques allow to estimate the FR: Freeman method using linearly polarized data, and Bickel and Bates theory based on the transformation of the measured scattering matrix to a circular basis. In CP mode, an alternate procedure is presented which relies on the bare surface scattering properties. These bare surfaces are selected by the conformity coefficient, invariant with FR. This coefficient is compared to other published classifications to show its potential in distinguishing three different scattering types: surface, doublebounce and volume. The performances of the bare surfaces selection and FR estimation are evaluated on PALSAR and airborne data. Once the bare surfaces are selected and Faraday angle estimated over them, the correction can be applied over the whole scene. The algorithm is compared with both FP techniques. In the last part of the paper, the calibration of a CP system from the point of view of classical matrix transformation methods in polarimetry is

  5. Crystallographic Mapping of Guided Nanowires by Second Harmonic Generation Polarimetry

    PubMed Central

    2017-01-01

    The growth of horizontal nanowires (NWs) guided by epitaxial and graphoepitaxial relations with the substrate is becoming increasingly attractive owing to the possibility of controlling their position, direction, and crystallographic orientation. In guided NWs, as opposed to the extensively characterized vertically grown NWs, there is an increasing need for understanding the relation between structure and properties, specifically the role of the epitaxial relation with the substrate. Furthermore, the uniformity of crystallographic orientation along guided NWs and over the substrate has yet to be checked. Here we perform highly sensitive second harmonic generation (SHG) polarimetry of polar and nonpolar guided ZnO NWs grown on R-plane and M-plane sapphire. We optically map large areas on the substrate in a nondestructive way and find that the crystallographic orientations of the guided NWs are highly selective and specific for each growth direction with respect to the substrate lattice. In addition, we perform SHG polarimetry along individual NWs and find that the crystallographic orientation is preserved along the NW in both polar and nonpolar NWs. While polar NWs show highly uniform SHG along their axis, nonpolar NWs show a significant change in the local nonlinear susceptibility along a few micrometers, reflected in a reduction of 40% in the ratio of the SHG along different crystal axes. We suggest that these differences may be related to strain accumulation along the nonpolar wires. We find SHG polarimetry to be a powerful tool to study both selectivity and uniformity of crystallographic orientations of guided NWs with different epitaxial relations. PMID:28094977

  6. Active Polarimetry for Orbital Debris Identification

    NASA Astrophysics Data System (ADS)

    Pasqual, M.; Cahoy, C.

    We present the results of polarimetric measurements that may help remotely identify orbital debris fragments, thereby extending current space surveillance capabilities. A bench-top polarimeter (wavelength 1064 nm) was used to experimentally determine the polarimetric Bidirectional Reflectance Distribution Function (BRDF) of several common spacecraft materials and coatings, including glossy white paint, matte black paint, black Kapton®, silver Teflon®, aluminum, and titanium. Analysis of these measurements allowed us to estimate each material's Mueller matrix and associated polarimetric properties as a function of the incident angle and (bistatic) in-plane scatter angle. Results revealed notable trends in the materials' polarimetric signatures. Specifically, the materials exhibited mostly weak diattenuation (D < 0.5) in all scatter directions, except for Kapton® and the two paints (D > 0.5 in the forward scatter direction). In terms of retardance (R), silver Teflon® exhibited a finite range of values (R = 30 to 120º) in all directions, while the other materials acted as mirrors (R = 180º) in the back scatter direction and had the full range of behavior (R = 0 to 180º) in the forward scatter direction. Finally, in terms of depolarization power (Delta), glossy white paint was a nearly perfect depolarizer (Delta = 1) in the back scatter direction, but sharply lost depolarization power (Delta = 0) at specular reflection. All other materials were mostly weak depolarizers (Delta < 0.5) in all scatter directions. These experimental findings may be used to develop requirements for a polarimetric laser radar that can interrogate debris fragments, identify their constituent materials, and infer their masses and other characteristics of interest.

  7. Photometry and polarimetry. [optical properties of Titan atmosphere

    NASA Technical Reports Server (NTRS)

    Veverka, J.

    1974-01-01

    A review of available information on the photometry, polarimetry, and narrow band spectrophotometry of Titan discusses five major categories: (1) brightness and color as a function of orbital position; (2) brightness and color as a function of solar phase angle; (3) geometric and bond albedo; (4) reflectance as a function of wavelength; and (5) polarization as a function of solar phase angle. It is concluded that a Saturn-like cloud model may be required to explain the sum of polarimetric and photometric observations.

  8. The Deuteron Beam Polarimetry at Nuclotron-NICA

    NASA Astrophysics Data System (ADS)

    Ladygin, V. P.; Kurilkin, P. K.; Isupov, A. Yu.; Janek, M.; Reznikov, S. G.

    2016-02-01

    The current deuteron beam polarimetry at Nuclotron is provided by the Internal Target polarimeter based on the use of the asymmetry in dp- elastic scattering at large angles in the c.m.s. at 270 MeV. The calibration of the existing deuteron beam polarimeter at Internal Target in the wide energy range will allow to obtain the accuracy of the vector and tensor beam polarization values of about 3-5%. Further upgrade of low energy and extracted beam polarimeters is discussed.

  9. Planet imaging polarimetry with the solar telescope GREGOR

    NASA Astrophysics Data System (ADS)

    Gisler, Daniel; Berkefeld, Thomas; Berdyugina, Svetlana

    2016-07-01

    Polarimetry of planets and planetary systems provide unique information on physics and chemistry of planetary atmospheres. We have built a new instrument, GREGOR Planet Polarimeter (GPP), which includes fast polarimetric modulation, high-rate readout CCD, and adaptive optics. It operates at the solar telescope GREGOR on Tenerife, Canary Islands, and it benefits from the possibility to calibrate the entire optical train after the secondary mirror. Here we present the instrument design, performance tests, and first scientific data. This research is supported by the ERC Advanced Grant HotMol.

  10. Moving Toward Polarimetry with the Event Horizon Telescope

    NASA Astrophysics Data System (ADS)

    Kosowsky, Michael; Fish, V. L.; Doeleman, S.; Johnson, M.; Lu, R.; Marrone, D. P.; Moran, J. M.; Plambeck, R. L.; Wardle, J. F.; EHT Collaboration

    2014-01-01

    The Event Horizon Telescope (EHT) project aims to develop millimeter and submillimeter VLBI to achieve angular resolution of tens of microarcseconds, comparable to the event horizons of nearby supermassive black holes. A major challenge for polarimetry at these scales is instrumental cross-talk, which introduces spurious linear polarization that can easily overwhelm the intrinsic signal. We demonstrate a new method for correcting the instrumental response, based on Markov Chain Monte Carlo simulations and other non-linear fitting methods. We will present preliminary polarimetric results on several EHT targets. Future EHT observations will provide a new window into the rich magnetic structures of their innermost cores.

  11. Radio Pulsars

    NASA Astrophysics Data System (ADS)

    Beskin, V. S.; Chernov, S. V.; Gwinn, C. R.; Tchekhovskoy, A. A.

    2015-10-01

    Almost 50 years after radio pulsars were discovered in 1967, our understanding of these objects remains incomplete. On the one hand, within a few years it became clear that neutron star rotation gives rise to the extremely stable sequence of radio pulses, that the kinetic energy of rotation provides the reservoir of energy, and that electromagnetic fields are the braking mechanism. On the other hand, no consensus regarding the mechanism of coherent radio emission or the conversion of electromagnetic energy to particle energy yet exists. In this review, we report on three aspects of pulsar structure that have seen recent progress: the self-consistent theory of the magnetosphere of an oblique magnetic rotator; the location, geometry, and optics of radio emission; and evolution of the angle between spin and magnetic axes. These allow us to take the next step in understanding the physical nature of the pulsar activity.

  12. Electron Polarimetry at Low Energies in Hall C at Jefferson Lab

    SciTech Connect

    Gaskell, David J.

    2013-11-01

    Although the majority of Jefferson Lab experiments require multi-GeV electron beams, there have been a few opportunities to make electron beam polarization measurements at rather low energies. This proceedings will discuss some of the practical difficulties encountered in performing electron polarimetry via Mo/ller scattering at energies on the order of a few hundred MeV. Prospects for Compton polarimetry at very low energies will also be discussed. While Mo/ller scattering is likely the preferred method for electron polarimetry at energies below 500 MeV, there are certain aspects of the polarimeter and experiment design that must be carefully considered.

  13. VizieR Online Data Catalog: Near-infrared imaging polarimetry of GGD 27 (Kwon+, 2016)

    NASA Astrophysics Data System (ADS)

    Kwon, J.; Tamura, M.; Hough, J. H.; Nagata, T.; Kusakabe, N.; Saito, H.

    2016-08-01

    Observations in the direction of GGD 27 IRS were carried out using the SIRPOL imaging polarimeter at the Infrared Survey Facility (IRSF) 1.4m telescope at SAAO in South Africa. The Facility enables deep wide-field (7.7'x7.7' at a scale of 0.453"/pixel) simultaneous imaging polarimetry in the JHKs bands. Linear polarimetry was performed on the night of 2006 March 14. Circular polarimetry observations of the GGD 27 IRS regions were made on the nights of 2008 July 24 and 2014 March 21. (2 data files).

  14. Radio Astronomy

    NASA Technical Reports Server (NTRS)

    Wolken, P. R.; Shaffer, R. D.

    1983-01-01

    Deep Space Network (DSN) 26- and 64-meter antenna stations were utilized in support of Radio Astronomy Experiment Selection Panel experiments. Within a time span of 10 days, in May 1983 (267.75 hours total), nine RAES experiments were supported. Most of these experiments involved multifacility interferometry using Mark 3 data recording terminals and as many as six non-DSN observatories. Investigations of black holes, quasars, galaxies, and radio sources are discussed.

  15. Determination of foveal location using scanning laser polarimetry

    PubMed Central

    VanNasdale, Dean A.; Elsner, Ann E.; Weber, Anke; Miura, Masahiro; Haggerty, Bryan P.

    2009-01-01

    The fovea is the retinal location responsible for our most acute vision. There are several methods used to localize the fovea, but the fovea is not always easily identifiable. Landmarks used to determine the foveal location are variable in normal subjects and localization becomes even more difficult in instances of retinal disease. In normal subjects, the photoreceptor axons that make up the Henle fiber layer are cylindrical and the radial orientation of these fibers is centered on the fovea. The Henle fiber layer exhibits form birefringence, which predictably changes polarized light in scanning laser polarimetry imaging. In this study 3 graders were able to repeatably identify the fovea in 35 normal subjects using near infrared image types with differing polarization content. There was little intra-grader, inter-grader, and inter-image variability in the graded foveal position for 5 of the 6 image types examined, with accuracy sufficient for clinical purposes. This study demonstrates that scanning laser polarimetry imaging can localize the fovea by using structural properties inherent in the central macula. PMID:19757960

  16. X-ray Polarimetry. A tool for Fundamental Physics

    NASA Astrophysics Data System (ADS)

    Costa, Enrico

    2016-07-01

    X-ray Polarimetry is a window about to be disclosed in Astrophysics. From an extended literature, we expect a significant step forward in the understanding of astrophysical systems emitting X-rays. This includes the study of physics in extreme conditions and, in particular, of General Relativity and Quantum Electrodynamics in extreme conditions. An even more ambitious target could be the search for effects of propagation on long distances as predicted from some theories of New Physics. An example is the rotation of the polarization angle proportional to the distance and to the square of Energy predicted by some specifications of Loop Quantum Gravity. Another example is the change of the polarization status of the flux of far-away sources by the photon-Axion Like Particle conversion in domain-like intergalactic magnetic fields. In absence of a solid picture of the status of polarization of X-ray sources in their reference frame the viability of such measurements is only matter of conjectures. But we can already select a set of presumably polarized sources (within the AGN zoo) or of totally unpolarized sources (such as clusters) and evaluate the sensitivity to such measurements with a sensitive mission of polarimetry like XIPE under study by ESA.

  17. Use of polarimetry to measure the current profile in MTX

    SciTech Connect

    Nevins, W.M.; Hooper, E.B.; Bernstein, I.B.

    1987-07-14

    It is possible in principle to measure the poloidal magnetic field profile, and hence, the profile of the plasma current measuring the change in the polarization of a sequence of microwave beams that pass through the plasma. Actual measurements of the plasma current profile would be very interesting in connection with Lower-Hybrid (or EC) current drive experiments since this would provide direct information on modification of the current profile by the application of rf power. A microwave polarimetry diagnostic on MTX as part of the microwave interferometer is being considered. This diagnostic would be constructed in collaboration with Neville Luhmann and Tony Peebles at UCLA. The diagnostic would utilize the multicord far-infrared interferometer which is designed to operate at a base wavelength of 0.185 mm. This paper reviews the understanding of the physics issues raised by this diagnostic, concurring with Luhmann and Peebles' conclusion that the polarimetry measurements would be easier at longer wavelengths. An increase of only a factor of 2 in the wavelength would make a substantial difference since the signal to be measured goes as lambda/sup 4/. Hence, in this paper operation at longer wavelengths (0.337 mm and 0.447 mm) in addition to operation at 0.119 and 0.185 mm will be considered.

  18. Optimum modulation and demodulation matrices for solar polarimetry.

    PubMed

    del Toro Iniesta, J C; Collados, M

    2000-04-01

    Both temporal and/or spatial modulation are mandatory in current solar polarimetry [Appl. Opt. 24, 3893 (1985); 26, 3838 (1987)]. The modulating and demodulating processes are mathematically described by matrices O and D, respectively, on whose structure the accuracy of Stokes parameter measurements depend. We demonstrate, based on the definition of polarimetric efficiency [Instituto de Astrofísica de Canarias Internal Report (1994); ASP Conf. Ser. 184, 3 (1999)], that the maximum efficiencies of an ideal polarimeter are unity for Stokes I and for (Q(2) + U(2) + V(2))(1/2) and that this occurs if and only if O(T)O is diagonal; given a general (possibly nonideal) modulation matrix O, the optimum demodulation matrix turns out to be D = (O(T)O)(-1)O(T); and the maximum efficiencies in the nonideal case are given by the rms value of the column elements of matrix O and are reached by modulation matrices such that O(T)O is diagonal. From these analytical results we distill two recipes useful in the practical design of polarimeters. Their usefulness is illustrated by discussing cases of currently available solar polarimeters. Although specifically devoted to solar polarimetry, the results here may be applied in practically all other branches of science for which polarimetric measurements are needed.

  19. Illumination invariance and shadow compensation via spectro-polarimetry technique

    NASA Astrophysics Data System (ADS)

    Ibrahim, Izzati; Yuen, Peter; Hong, Kan; Chen, Tong; Soori, Umair; Jackman, James; Richardson, Mark

    2012-10-01

    A major problem for obtaining target reflectance via hyperspectral imaging systems is the presence of illumination and shadow effects. These factors are common artefacts, especially when dealing with a hyperspectral imaging system that has sensors in the visible to near infrared region. This region is known to have highly scattered and diffuse radiance that can modify the energy recorded by the imaging system. A shadow effect will lower the target reflectance values due to the small radiant energy impinging on the target surface. Combined with illumination artefacts, such as diffuse scattering from the surrounding targets, background or environment, the shape of the shadowed target reflectance will be altered. We propose a new method to compensate for illumination and shadow effects on hyperspectral imageries by using a polarization technique. This technique, called spectro-polarimetry, estimates the direct and diffuse irradiance based on two images taken with and without a polarizer. The method is then evaluated using a spectral similarity measure, angle and distance metric. The results of indoor and outdoor tests have shown that using the spectro-polarimetry technique can improve the spectral constancy between shadow and full illumination spectra.

  20. Intrinsic coincident linear polarimetry using stacked organic photovoltaics.

    PubMed

    Roy, S Gupta; Awartani, O M; Sen, P; O'Connor, B T; Kudenov, M W

    2016-06-27

    Polarimetry has widespread applications within atmospheric sensing, telecommunications, biomedical imaging, and target detection. Several existing methods of imaging polarimetry trade off the sensor's spatial resolution for polarimetric resolution, and often have some form of spatial registration error. To mitigate these issues, we have developed a system using oriented polymer-based organic photovoltaics (OPVs) that can preferentially absorb linearly polarized light. Additionally, the OPV cells can be made semitransparent, enabling multiple detectors to be cascaded along the same optical axis. Since each device performs a partial polarization measurement of the same incident beam, high temporal resolution is maintained with the potential for inherent spatial registration. In this paper, a Mueller matrix model of the stacked OPV design is provided. Based on this model, a calibration technique is developed and presented. This calibration technique and model are validated with experimental data, taken with a cascaded three cell OPV Stokes polarimeter, capable of measuring incident linear polarization states. Our results indicate polarization measurement error of 1.2% RMS and an average absolute radiometric accuracy of 2.2% for the demonstrated polarimeter.

  1. Optical polarimetry: Instrumentation and applications; Proceedings of the Seminar, San Diego, Calif., August 23, 24, 1977

    NASA Technical Reports Server (NTRS)

    Azzam, R. M. A. (Editor); Coffeen, D. L.

    1977-01-01

    Instrumentation used in optical polarimetry is discussed with reference to high-resolution spectropolarimetry, an orbiter cloud photopolarimeter, X-ray polarimeters, and the design of a self-nulling ellipsometer. Consideration is given to surface and thin-film ellipsometry noting studies of electrochemical surface layers, surface anisotropy, polish layers on infrared window materials, and anodic films. Papers on biological, chemical, and physical polarimetry are presented including birefringence in biological materials, vibrational optical activity, and the optical determination of the thermodynamic phase diagram of a metamagnet. Remote sensing is discussed in terms of polarization imagery, the optical polarimetry of particulate surfaces, and techniques and applications of elliptical polarimetry in astronomy and atmospheric studies.

  2. X-ray gamma-ray polarimetry small satellite PolariS

    NASA Astrophysics Data System (ADS)

    Hayashida, Kiyoshi; Yonetoku, Daisuke; Gunji, Shuichi; Tamagawa, Toru; Mihara, Tatehiro; Mizuno, Tsunefumi; Takahashi, Hiromitsu; Dotani, Tadayasu; Kubo, Hidetoshi; Yatsu, Yoichi; Tokanai, Fuyuku; Nakamori, Takeshi; Shibata, Shinpei; Hayato, Asami; Furuzawa, Akihiro; Kishimoto, Yuji; Kitamoto, Shunji; Toma, Kenji; Sadamoto, Masaaki; Yoshinaga, Keigo; Kim, Juyong; Ide, Shunichiro; Kamitsukasa, Fumiyoshi; Anabuki, Naohisa; Tsunemi, Hiroshi; Katagiri, Jun; Sugimoto, Juri

    2014-07-01

    PolariS (Polarimetry Satellite) is a Japanese small satellite mission dedicated to polarimetry of X-ray and γ-ray sources. The primary aim of the mission is to perform hard X-ray (10-80 keV) polarimetry of sources brighter than 10 mCrab. For this purpose, PolariS employs three hard X-ray telescopes and scattering type imaging polarimeters. PolariS will measure the X-ray polarization for tens of sources including extragalactic ones mostly for the first time. The second purpose of the mission is γ-ray polarimetry of transient sources, such as γ-ray bursts (GRBs). Wide field polarimeters based on similar concept as that used in the IKAROS/GAP but with higher sensitivity will be used, and polarization measurement of 10 GRBs per year is expected.

  3. A Study of Laser System Requirements for Application in Beam Diagnostics And Polarimetry at the ILC

    SciTech Connect

    Dixit, S.; Delerue, N.; Foster, B.; Howell, D.F.; Peach, K.; Quelch, G.; Qureshi, M.; Reichold, A.; Hirst, G.; Ross, I.; Urakawa, J.; Soskov, V.; Variola, A.; Zomer, F.; Blair, G.A.; Boogert, S.T.; Boorman, G.; Bosco, A.; Driouichi, C.; Karataev, P.; Brachmann, A.; /SLAC

    2007-02-12

    Advanced laser systems will be essential for a range of diagnostics devices and polarimetry at the ILC. High average power, high beam quality, excellent stability and reliability will be crucial in order to deliver the information required to attain the necessary ILC luminosity as well as for efficient polarimetry. The key parameters are listed together with the R & D required to achieve the necessary laser system performance.

  4. Near-infrared polarimetry of the edge-on galaxy NGC 891

    SciTech Connect

    Montgomery, J. D.; Clemens, D. P. E-mail: clemens@bu.edu

    2014-05-01

    The edge-on galaxy NGC 891 was probed using near-infrared (NIR) imaging polarimetry in the H band (1.6 μm) with the Mimir instrument on the 1.8 m Perkins Telescope. Polarization was detected with a signal-to-noise ratio greater than three out to a surface brightness of 18.8 mag arcsec{sup –2}. The unweighted average and dispersion in polarization percentage (P) across the full disk were 0.7% and 0.3%, respectively, and the same quantities for polarization position angle (P.A.) were 12° and 19°, respectively. At least one polarization null point, where P falls nearly to zero, was detected in the northeast disk but not the southwest disk. Several other asymmetries in P between the northern and southern disk were found and may be related to spiral structure. Profiles of P and P.A. along the minor axis of NGC 891 suggest a transition from magnetic (B) field tracing dichroic polarization near the disk mid-plane to scattering dominated polarization off the disk mid-plane. A comparison between NIR P.A. and radio (3.6 cm) synchrotron polarization P.A. values revealed similar B-field orientations in the central-northeast region, which suggests that the hot plasma and cold, star-forming interstellar medium may share a common B-field. Disk-perpendicular polarizations previously seen at optical wavelengths are likely caused by scattered light from the bright galaxy center and are unlikely to be tracing poloidal B-fields in the outer disk.

  5. Four Stokes parameter radio frequency polarimetry of a flare from AD Leonis

    NASA Technical Reports Server (NTRS)

    Spangler, S. R.; Rankin, J. M.; Shawhan, S. D.

    1974-01-01

    Observations of the four Stokes parameters of a 430 MHz flare from the UV Ceti-type star AD Leonis are presented. The maximum amplitude of the event was 0.52 flux units and the durations at one-half and one-tenth maximum were 12 and 40 seconds, respectively. The degree of circular polarization at maximum intensity was approximately 56 percent and was later observed to be as high as 92 percent. Linear polarization was also observed at a level of about 21 percent at flare maximum which allowed an upper limit of 440 radians - sq m to be placed on the rotation measure.

  6. Radio astronomy

    NASA Technical Reports Server (NTRS)

    Kellermann, Kenneth I.; Heeschen, David; Backer, Donald C.; Cohen, Marshall H.; Davis, Michael; Depater, Imke; Deyoung, David; Dulk, George A.; Fisher, J. R.; Goss, W. Miller

    1991-01-01

    The following subject areas are covered: (1) scientific opportunities (millimeter and sub-millimeter wavelength astronomy; meter to hectometer astronomy; the Sun, stars, pulsars, interstellar masers, and extrasolar planets; the planets, asteroids, and comets; radio galaxies, quasars, and cosmology; and challenges for radio astronomy in the 1990's); (2) recommendations for new facilities (the millimeter arrays, medium scale instruments, and small-scale projects); (3) continuing activities and maintenance, upgrading of telescopes and instrumentation; (4) long range programs and technology development; and (5) social, political, and organizational considerations.

  7. Wave propagation and earth satellite radio emission studies

    NASA Technical Reports Server (NTRS)

    Yeh, K. C.; Liu, C. H.; Flaherty, B. J.

    1974-01-01

    Radio propagation studies of the ionosphere using satellite radio beacons are described. The ionosphere is known as a dispersive, inhomogeneous, irregular and sometimes even nonlinear medium. After traversing through the ionosphere the radio signal bears signatures of these characteristics. A study of these signatures will be helpful in two areas: (1) It will assist in learning the behavior of the medium, in this case the ionosphere. (2) It will provide information of the kind of signal characteristics and statistics to be expected for communication and navigational satellite systems that use the similar geometry.

  8. Chromatographic detection of sugar cane samples via polarimetry.

    NASA Astrophysics Data System (ADS)

    López, Juan Carlos; Fajer, Victor; Rodríguez, Carlos W.; Naranjo, Salvador; Mora, Luis; Ravelo, Justo; Cossio, Gladys; Avila, Norma

    2004-03-01

    The combination of molecular exclusion cromatography with the laser polarimetry has become a powerful technique to separate and evaluate some carbohydrates of sugar cane plants. In the following work it has been obtained chromatograms of carbohydrates standards, which has been used as comparison patterns in the studies of the juice quality in different cane varieties of different physiological stadiums and stress conditions. By means of the employment of this technique, it has also been determined the influence of carbohydrates of medium molecular mass in the determination of the apparent sucrose in the routine sugar analysis. On the other hand, discreet determination of the fractions causes time consuming and a troublesome manipulation. In the present work some modifications to the system are shown, obtaining a small volume sample (less than 1 ml) and angular readings on line, avoiding the employment of fraction collectors.

  9. The Imaging X-Ray Polarimetry Explorer (IXPE)

    NASA Technical Reports Server (NTRS)

    Weisskopf, Martin C.; Ramsey, Brian; O’Dell, Stephen; Tennant, Allyn; Elsner, Ronald; Soffita, Paolo; Bellazzini, Ronaldo; Costa, Enrico; Kolodziejczak, Jeffery; Kaspi, Victoria; Mulieri, Fabio; Marshall, Herman; Matt, Giorgio; Romani, Roger

    2016-01-01

    The Imaging X-ray Polarimetry Explorer (IXPE) is an exciting international collaboration for a scientific mission that dramatically brings together the unique talents of the partners to expand observation space by simultaneously adding polarization measurements to the array of source properties currently measured (energy, time, and location). IXPE uniquely brings to the table polarimetric imaging. IXPE will thus open new dimensions for understanding how X-ray emission is produced in astrophysical objects, especially systems under extreme physical conditions-such as neutron stars and black holes. Polarization singularly probes physical anisotropies-ordered magnetic fields, aspheric matter distributions, or general relativistic coupling to black-hole spin-that are not otherwise measurable. Hence, IXPE complements all other investigations in high-energy astrophysics by adding important and relatively unexplored information to the parameter space for studying cosmic X-ray sources and processes, as well as for using extreme astrophysical environments as laboratories for fundamental physics.

  10. Division B Commission 25: Astronomical Photometry and Polarimetry

    NASA Astrophysics Data System (ADS)

    Walker, Alistair; Adelman, Saul; Milone, Eugene; Anthony-Twarog, Barbara; Bastien, Pierre; Chen, Wen Ping; Howell, Steve; Knude, Jens; Kurtz, Donald; Magalhães, Antonio Mario; Menzies, John; Smith, Allyn; Volk, Kevin

    2016-04-01

    Commission 25 (C25) deals with the techniques and issues involved with the measurement of optical and infrared radiation intensities and polarization from astronomical sources. As such, in recent years attention has focused on photometric standard stars, atmospheric extinction, photometric passbands, transformation between systems, nomenclature, and observing and reduction techniques. At the start of the trimester C25 changed its name from Stellar Photometry and Polarization to Astronomical Photometry and Polarization so as to explicitly include in its mandate particular issues arising from the measurement of resolved sources, given the importance of photometric redshifts of distant galaxies for many of the large photometric surveys now underway. We begin by summarizing commission activities over the 2012-2014 period, follow with a report on Polarimetry, continue with Photometry topics that have been of interest to C25 members, and conclude with a Vision for the Future.

  11. Nano-fabricated pixelated micropolarizer array for visible imaging polarimetry

    SciTech Connect

    Zhang, Zhigang; Cheng, Teng; Qiu, Kang; Zhang, Qingchuan E-mail: wgchu@nanoctr.cn; Wu, Xiaoping; Dong, Fengliang; Chu, Weiguo E-mail: wgchu@nanoctr.cn

    2014-10-15

    Pixelated micropolarizer array (PMA) is a novel concept for real-time visible imaging polarimetry. A 320 × 240 aluminum PMA fabricated by electron beam lithography is described in this paper. The period, duty ratio, and depth of the grating are 140 nm, 0.5, and 100 nm, respectively. The units are standard square structures and the metal nanowires of the grating are collimating and uniformly thick. The extinction ratio of 75 and the maximum polarization transmittance of 78.8% demonstrate that the PMA is suitable for polarization imaging. When the PMA is applied to real-time polarization imaging, the degree of linear polarization image and the angle of linear polarization image are calculated from a single frame image. The polarized target object is highlighted from the unpolarized background, and the surface contour of the target object can be reflected by the polarization angle.

  12. Uncertainty in hydrological signatures

    NASA Astrophysics Data System (ADS)

    Westerberg, I. K.; McMillan, H. K.

    2015-09-01

    Information about rainfall-runoff processes is essential for hydrological analyses, modelling and water-management applications. A hydrological, or diagnostic, signature quantifies such information from observed data as an index value. Signatures are widely used, e.g. for catchment classification, model calibration and change detection. Uncertainties in the observed data - including measurement inaccuracy and representativeness as well as errors relating to data management - propagate to the signature values and reduce their information content. Subjective choices in the calculation method are a further source of uncertainty. We review the uncertainties relevant to different signatures based on rainfall and flow data. We propose a generally applicable method to calculate these uncertainties based on Monte Carlo sampling and demonstrate it in two catchments for common signatures including rainfall-runoff thresholds, recession analysis and basic descriptive signatures of flow distribution and dynamics. Our intention is to contribute to awareness and knowledge of signature uncertainty, including typical sources, magnitude and methods for its assessment. We found that the uncertainties were often large (i.e. typical intervals of ±10-40 % relative uncertainty) and highly variable between signatures. There was greater uncertainty in signatures that use high-frequency responses, small data subsets, or subsets prone to measurement errors. There was lower uncertainty in signatures that use spatial or temporal averages. Some signatures were sensitive to particular uncertainty types such as rating-curve form. We found that signatures can be designed to be robust to some uncertainty sources. Signature uncertainties of the magnitudes we found have the potential to change the conclusions of hydrological and ecohydrological analyses, such as cross-catchment comparisons or inferences about dominant processes.

  13. The Radio JOVE Project - Shoestring Radio Astronomy

    NASA Technical Reports Server (NTRS)

    Thieman, J.; Flagg, R.; Greenman, W.; Higgins, C.; Reyes, F.; Sky, J.

    2010-01-01

    Radio JOVE is an education and outreach project intended to give students and other interested individuals hands-on experience in learning radio astronomy. They can do this through building a radio telescope from a relatively inexpensive kit that includes the parts for a receiver and an antenna as well as software for a computer chart recorder emulator (Radio Skypipe) and other reference materials

  14. What X-ray polarimetry can teach us about the central supermassive black hole of the Milky Way galaxy

    NASA Astrophysics Data System (ADS)

    Marin, Frédéric; Karas, Vladimir; Muleri, Fabio; Soffitta, Paolo; Kunneriath, Devaky

    2016-07-01

    Was Sgr A*, the central supermassive black hole of our own Galaxy, a low luminosity AGN in the past? Despite numerous attempts with spectroscopic and timing analyses, the question remains opened as the origin of irradiation and fluorescence of the 6.4 keV bright giant molecular clouds surrounding Sgr A* is still debated. A possible interpretation, based on Compton scattering processes, implies that the high X-ray luminosity of the nebulae arise from reprocessing of a past outburst of Sgr A*. If true, the reflection nebulae should show strong scattering-induced polarization signatures. Detecting such imprints requires opening a new observational window: X-ray polarimetry. In this presentation, I will summarize the results from past and present polarimetric simulations of the Galactic Center in order to show how a future X-ray polarimeter equipped with imaging detectors, such as XIPE (ESA M4) or IXPE (NASA-SMEX), could prove or rejected the hypothesis of the past active phase of Sgr A*.

  15. Space Telecommunications Radio System STRS Cognitive Radio

    NASA Technical Reports Server (NTRS)

    Briones, Janette C.; Handler, Louis M.

    2013-01-01

    Radios today are evolving from awareness toward cognition. A software defined radio (SDR) provides the most capability for integrating autonomic decision making ability and allows the incremental evolution toward a cognitive radio. This cognitive radio technology will impact NASA space communications in areas such as spectrum utilization, interoperability, network operations, and radio resource management over a wide range of operating conditions. NASAs cognitive radio will build upon the infrastructure being developed by Space Telecommunication Radio System (STRS) SDR technology. This paper explores the feasibility of inserting cognitive capabilities in the NASA STRS architecture and the interfaces between the cognitive engine and the STRS radio. The STRS architecture defines methods that can inform the cognitive engine about the radio environment so that the cognitive engine can learn autonomously from experience, and take appropriate actions to adapt the radio operating characteristics and optimize performance.

  16. XIPE: the X-ray imaging polarimetry explorer

    NASA Astrophysics Data System (ADS)

    Soffitta, Paolo; Barcons, Xavier; Bellazzini, Ronaldo; Braga, João; Costa, Enrico; Fraser, George W.; Gburek, Szymon; Huovelin, Juhani; Matt, Giorgio; Pearce, Mark; Poutanen, Juri; Reglero, Victor; Santangelo, Andrea; Sunyaev, Rashid A.; Tagliaferri, Gianpiero; Weisskopf, Martin; Aloisio, Roberto; Amato, Elena; Attiná, Primo; Axelsson, Magnus; Baldini, Luca; Basso, Stefano; Bianchi, Stefano; Blasi, Pasquale; Bregeon, Johan; Brez, Alessandro; Bucciantini, Niccoló; Burderi, Luciano; Burwitz, Vadim; Casella, Piergiorgio; Churazov, Eugene; Civitani, Marta; Covino, Stefano; Curado da Silva, Rui Miguel; Cusumano, Giancarlo; Dadina, Mauro; D'Amico, Flavio; De Rosa, Alessandra; Di Cosimo, Sergio; Di Persio, Giuseppe; Di Salvo, Tiziana; Dovciak, Michal; Elsner, Ronald; Eyles, Chris J.; Fabian, Andrew C.; Fabiani, Sergio; Feng, Hua; Giarrusso, Salvatore; Goosmann, René W.; Grandi, Paola; Grosso, Nicolas; Israel, Gianluca; Jackson, Miranda; Kaaret, Philip; Karas, Vladimir; Kuss, Michael; Lai, Dong; Rosa, Giovanni La; Larsson, Josefin; Larsson, Stefan; Latronico, Luca; Maggio, Antonio; Maia, Jorge; Marin, Frédéric; Massai, Marco Maria; Mineo, Teresa; Minuti, Massimo; Moretti, Elena; Muleri, Fabio; O'Dell, Stephen L.; Pareschi, Giovanni; Peres, Giovanni; Pesce, Melissa; Petrucci, Pierre-Olivier; Pinchera, Michele; Porquet, Delphine; Ramsey, Brian; Rea, Nanda; Reale, Fabio; Rodrigo, Juana Maria; Różańska, Agata; Rubini, Alda; Rudawy, Pawel; Ryde, Felix; Salvati, Marco; de Santiago, Valdivino Alexandre; Sazonov, Sergey; Sgró, Carmelo; Silver, Eric; Spandre, Gloria; Spiga, Daniele; Stella, Luigi; Tamagawa, Toru; Tamborra, Francesco; Tavecchio, Fabrizio; Teixeira Dias, Teresa; van Adelsberg, Matthew; Wu, Kinwah; Zane, Silvia

    2013-12-01

    Abstract X-ray polarimetry, sometimes alone, and sometimes coupled to spectral and temporal variability measurements and to imaging, allows a wealth of physical phenomena in astrophysics to be studied. X-ray polarimetry investigates the acceleration process, for example, including those typical of magnetic reconnection in solar flares, but also emission in the strong magnetic fields of neutron stars and white dwarfs. It detects scattering in asymmetric structures such as accretion disks and columns, and in the so-called molecular torus and ionization cones. In addition, it allows fundamental physics in regimes of gravity and of magnetic field intensity not accessible to experiments on the Earth to be probed. Finally, models that describe fundamental interactions (e.g. quantum gravity and the extension of the Standard Model) can be tested. We describe in this paper the X-ray Imaging Polarimetry Explorer (XIPE), proposed in June 2012 to the first ESA call for a small mission with a launch in 2017. The proposal was, unfortunately, not selected. To be compliant with this schedule, we designed the payload mostly with existing items. The XIPE proposal takes advantage of the completed phase A of POLARIX for an ASI small mission program that was cancelled, but is different in many aspects: the detectors, the presence of a solar flare polarimeter and photometer and the use of a light platform derived by a mass production for a cluster of satellites. XIPE is composed of two out of the three existing JET-X telescopes with two Gas Pixel Detectors (GPD) filled with a He-DME mixture at their focus. Two additional GPDs filled with a 3-bar Ar-DME mixture always face the Sun to detect polarization from solar flares. The Minimum Detectable Polarization of a 1 mCrab source reaches 14 % in the 2-10 keV band in 105 s for pointed observations, and 0.6 % for an X10 class solar flare in the 15-35 keV energy band. The imaging capability is 24 arcsec Half Energy Width (HEW) in a Field of

  17. Multichroic Bolometric Detector Architecture for Cosmic Microwave Background Polarimetry Experiments

    NASA Astrophysics Data System (ADS)

    Suzuki, Aritoki

    Characterization of the Cosmic Microwave Background (CMB) B-mode polarization signal will test models of inflationary cosmology, as well as constrain the sum of the neutrino masses and other cosmological parameters. The low intensity of the B-mode signal combined with the need to remove polarized galactic foregrounds requires a sensitive millimeter receiver and effective methods of foreground removal. Current bolometric detector technology is reaching the sensitivity limit set by the CMB photon noise. Thus, we need to increase the optical throughput to increase an experiment's sensitivity. To increase the throughput without increasing the focal plane size, we can increase the frequency coverage of each pixel. Increased frequency coverage per pixel has additional advantage that we can split the signal into frequency bands to obtain spectral information. The detection of multiple frequency bands allows for removal of the polarized foreground emission from synchrotron radiation and thermal dust emission, by utilizing its spectral dependence. Traditionally, spectral information has been captured with a multi-chroic focal plane consisting of a heterogeneous mix of single-color pixels. To maximize the efficiency of the focal plane area, we developed a multi-chroic pixel. This increases the number of pixels per frequency with same focal plane area. We developed multi-chroic antenna-coupled transition edge sensor (TES) detector array for the CMB polarimetry. In each pixel, a silicon lens-coupled dual polarized sinuous antenna collects light over a two-octave frequency band. The antenna couples the broadband millimeter wave signal into microstrip transmission lines, and on-chip filter banks split the broadband signal into several frequency bands. Separate TES bolometers detect the power in each frequency band and linear polarization. We will describe the design and performance of these devices and present optical data taken with prototype pixels and detector arrays. Our

  18. Imaging polarimetry of class I young stellar objects

    NASA Astrophysics Data System (ADS)

    Lucas, P. W.; Roche, P. F.

    1998-09-01

    We present near-infrared imaging polarimetry of three class I young stellar objects in the Taurus-Auriga dark cloud. We use Monte Carlo simulations to analyse the flux distributions and polarization patterns of these three sources and five others from an earlier paper. In addition, we present high-resolution polarimetry of HL Tau using the shift and add technique. Most young stellar objects in the sample display sharp, unresolved, peaks in the scattered light distribution. This is most simply explained by a strong concentration of matter in the centre, which we model by applying the rho~r^-1.5 power law throughout the envelope. In terms of the Ulrich/Terebey, Shu and Cassen solution for the late stages of contraction of an initially spherical non-magnetic cloud, this corresponds to r_c<10 au. However, this almost spherically symmetric density distribution is inconsistent with observations of flattened, disc-like structures, so we conclude that this solution is not appropriate and different initial conditions apply. The multiple-scattering models with spherical grains do not reproduce some features of the observed polarization patterns, in particular the broad regions of aligned vectors seen in some sources. We interpret this as evidence for elongated aligned grains. The weak wavelength dependence of nebular morphology shows that the dust grains in circumstellar envelopes obey a much shallower extinction law than interstellar grains in the near-infrared, which we describe by the opacity ratio kappa(J/K)=1.8+/-0.3, compared to the interstellar value of 3.25. We place an upper limit on albedo of omega<0.6 from 1.25 to 2.2 μm and we find 0.1<0.4. With the addition of two more observables derived from the observed degrees of linear and circular polarization, we identify five

  19. RADIO ALTIMETERS

    DOEpatents

    Bogle, R.W.

    1960-11-22

    A radio ranging device is described which utilizes a superregenerative oscillator having alternate sending and receiving phases with an intervening ranging interval between said phases, means for varying said ranging interval, means responsive to an on-range noise reduction condition for stopping said means for varying the ranging interval and indicating means coupled to the ranging interval varying means and calibrated in accordance with one-half the product of the ranging interval times the velocity of light whereby the range is indicated.

  20. Polarimetry of grains in the coma of P/Halley. II - Interpretation

    NASA Astrophysics Data System (ADS)

    Dollfus, A.

    1989-04-01

    Physical properties of solid grains in the coma of P/Halley were derived on the basis of optical polarimetry data on the coma continuum obtained by Dollfus and Suchail (1987) and by an analysis of relevant polarization measurements recorded throughout the world. Results of polarimetry in the visible light indicate the presence of large particles, very rough and dark. These rather rough grains are mixed with the cloud of small particles analyzed with the spacecraft impact detectors. The presence of circular and deviated linear polarizations on some areas in the coma indicates elongated grains oriented by gas streams or jets, either in the population of small particles or among the large flakes. It is speculated that the source of the Brownlee particles and of the large grains assumed to produce the zodiacal light are the large cometary fluffy aggregates which are identified by polarimetry, after transportation inward in the solar system by the Poynting-Robertson effect.

  1. Polarimetry of SN 2014J in M82 as a Probe of Its Dusty Environment

    NASA Astrophysics Data System (ADS)

    Wang, Lifan

    2014-10-01

    Late time polarimetry can effectively probe the circumstellar (CS) dust environment of SNe Ia. We propose to acquire imaging polarimetry of SN 2014J at three epochs between 200-400 days after the SN explosion. The delayed light from optical maximum may be scattered into the line of sight and reveal the scattering dust through polarization. Light echoes from interstellar dust at very large distances (> 10pc) from the SN will not be highly polarized in these observations due to the small scattering angle involved. Polarimetry at late time is thus an unambegeous probe of CS dust very close to the SN (at distances ~ 1 light year). Observations of the illusive CS matter is critical in constraining the progenitor systems of SNIa.

  2. Digital Signature Management.

    ERIC Educational Resources Information Center

    Hassler, Vesna; Biely, Helmut

    1999-01-01

    Describes the Digital Signature Project that was developed in Austria to establish an infrastructure for applying smart card-based digital signatures in banking and electronic-commerce applications. Discusses the need to conform to international standards, an international certification infrastructure, and security features for a public directory…

  3. Separation of finite electron temperature effect on plasma polarimetry.

    PubMed

    Imazawa, Ryota; Kawano, Yasunori; Kusama, Yoshinori

    2012-12-01

    This study demonstrates the separation of the finite electron temperature on the plasma polarimetry in the magnetic confined fusion plasma for the first time. Approximate solutions of the transformed Stokes equation, including the relativistic effect, suggest that the orientation angle, θ, and ellipticity angle, ε, of polarization state have different dependency on the electron density, n(e), and the electron temperature, T(e), and that the separation of n(e) and T(e) from θ and ε is possible in principle. We carry out the equilibrium and kinetic reconstruction of tokamak plasma when the central electron density was 10(20) m(-3), and the central electron temperatures were 5, 10, 20, and 30 keV. For both cases when a total plasma current, I(p), is known and when I(p) is unknown, the profiles of plasma current density, j(φ), n(e), and T(e) are successfully reconstructed. The reconstruction of j(φ) without the information of I(p) indicates the new method of I(p) measurement applicable to steady state operation of tokamak.

  4. Separation of finite electron temperature effect on plasma polarimetry

    SciTech Connect

    Imazawa, Ryota; Kawano, Yasunori; Kusama, Yoshinori

    2012-12-15

    This study demonstrates the separation of the finite electron temperature on the plasma polarimetry in the magnetic confined fusion plasma for the first time. Approximate solutions of the transformed Stokes equation, including the relativistic effect, suggest that the orientation angle, {theta}, and ellipticity angle, {epsilon}, of polarization state have different dependency on the electron density, n{sub e}, and the electron temperature, T{sub e}, and that the separation of n{sub e} and T{sub e} from {theta} and {epsilon} is possible in principle. We carry out the equilibrium and kinetic reconstruction of tokamak plasma when the central electron density was 10{sup 20} m{sup -3}, and the central electron temperatures were 5, 10, 20, and 30 keV. For both cases when a total plasma current, I{sub p}, is known and when I{sub p} is unknown, the profiles of plasma current density, j{sub {phi}}, n{sub e}, and T{sub e} are successfully reconstructed. The reconstruction of j{sub {phi}} without the information of I{sub p} indicates the new method of I{sub p} measurement applicable to steady state operation of tokamak.

  5. Observational Aspects of Hard X-ray Polarimetry

    NASA Astrophysics Data System (ADS)

    Chattopadhyay, Tanmoy

    2016-04-01

    Sensitive polarization measurements in X-ray may address a wealth of astrophysical phenomena, which so far remain beyond our understanding through available X-ray spectroscopic, imaging, and timing studies. Though scientific potential of X-ray polarimetry was realized long ago, there has not been any significant advancement in this field for the last four decades since the birth of X-ray astronomy. The only successful polarization measurement in X-rays dates back to 1976, when a Bragg polarimeter onboard OSO-8 measured polarization of Crab nebula. Primary reason behind the lack in progress is its extreme photon hungry nature, which results in poor sensitivity of the polarimeters. Recently, in the last decade or so, with the advancement in detection technology, X-ray polarimetry may see a significant progress in near future, especially in soft X-rays with the invention of photoelectron tracking polarimeters. Though photoelectric polarimeters are expected to provide sensitive polarization measurements of celestial X-ray sources, they are sensitive only in soft X-rays, where the radiation from the sources is dominated by thermal radiation and therefore expected to be less polarized. On the other hand, in hard X-rays, sources are ex-pected to be highly polarized due to the dominance of nonthermal emission over its thermal counterpart. Moreover, polarization measurements in hard X-rays promises to address few interesting scientific issues regarding geometry of corona for black hole sources, emission mechanism responsible for the higher energy peak in the blazars, accretion geometry close to the magnetic poles in accreting neutron star systems and acceleration mechanism in solar flares. Compton polarimeters provide better sensitivity than photoelectric polarimeters in hard X-rays with a broad energy band of operation. Recently, with the development of hard X-ray focusing optics e.g. NuSTAR, Astro-H, it is now possible to conceive Compton polarimeters at the focal plane

  6. UBVR POLARIMETRY OF EVOLVED CARBON STARS NEAR THE GALACTIC EQUATOR

    SciTech Connect

    Lopez, J. M.; Hiriart, D. E-mail: hiriart@astrosen.unam.mx

    2011-07-15

    We present polarimetry and photometry in the UBVR bands of nine low Galactic latitude carbon stars (|b{sup II} | {<=} 15{sup 0}) over a period of one year: V384 Per, ST Cam, S Aur, CL Mon, HV Cas, Y Tau, TT Cyg, U Cyg, and V1426 Cyg. We have corrected the observed values for the effects of extinction and polarization by the interstellar medium to obtain the intrinsic polarization and photometry of the stars. All the observed objects present polarization in at least two bands. There is a statistical correlation between the temporal mean polarization (p) at each filter band and the IR color K - [12] with the redder stars tending to be more polarized. A related trend is found between polarization and mass-loss rate in gas. The degree of polarization increases with the mass-loss rate at around M-dot{sub gas}{approx}3.6x10{sup -7} M{sub sun} yr{sup -1}. We found two stars-TT Cyg and ST Cam-that increase polarization with decreasing mass-loss rate below this value. Multiple observations of TT Cyg, U Cyg, and V1426 Cyg during the campaign show no correlation between polarization and luminosity in any of the UBVR bands. Therefore, the distribution of the scatterers shall vary with time in a very irregular way.

  7. K-space polarimetry of bullseye plasmon antennas.

    PubMed

    Osorio, Clara I; Mohtashami, Abbas; Koenderink, A Femius

    2015-04-30

    Surface plasmon resonators can drastically redistribute incident light over different output wave vectors and polarizations. This can lead for instance to sub-diffraction sized nanoapertures in metal films that beam and to nanoparticle antennas that enable efficient conversion of photons between spatial modes, or helicity channels. We present a polarimetric Fourier microscope as a new experimental tool to completely characterize the angle-dependent polarization-resolved scattering of single nanostructures. Polarimetry allows determining the full Stokes parameters from just six Fourier images. The degree of polarization and the polarization ellipse are measured for each scattering direction collected by a high NA objective. We showcase the method on plasmonic bullseye antennas in a metal film, which are known to beam light efficiently. We find rich results for the polarization state of the beamed light, including complete conversion of input polarization from linear to circular and from one helicity to another. In addition to uncovering new physics for plasmonic groove antennas, the described technique projects to have a large impact in nanophotonics, in particular towards the investigation of a broad range of phenomena ranging from photon spin Hall effects, polarization to orbital angular momentum transfer and design of plasmon antennas.

  8. Polarization in a snap: imaging polarimetry with micropolarizer arrays

    NASA Astrophysics Data System (ADS)

    Vorobiev, Dmitry; Ninkov, Zoran; Gartley, Michael

    2014-05-01

    Polarization, flux, and the spectral energy distribution of light are the fundamental parameters that we measure in order to infer properties of the sources of electromagnetic radiation, such as intensity, temperature, chemical composition and physical geometry. Recently, the fabrication of microgrid polarizer arrays (MPAs) facilitated the development of a new class of division-of-focal plane polarimeters. These devices are capable of measuring the degree and angle of polarization across a scene with a single exposure. We present the design of the Rochester Institute of Technology Polarization Imaging Camera (RITPIC), a snapshot polarimeter for visible and near-infrared remote sensing applications. RITPIC is a compact, light-weight and mechanically robust imaging polarimeter that is deployable on terrestrial, naval, airborne and space-based platforms. RITPIC is developed using commercially available components and is capable of fast cadence imaging polarimetry of a wide variety of scenes. We derive the expected performance of RITPIC using the first high resolution 3D finite-difference time-domain (FDTD) models of these hybrid focal planes and simulated observations of synthetic scenes rendered with the Digital Imaging and Remote Sensing Image Generation (DIRSIG) model. Furthermore, we explore applications in remote sensing for which RITPIC, and devices like it, provide unique advantages.

  9. Imaging Polarimetry With Polarization-Sensitive Focal Planes

    NASA Astrophysics Data System (ADS)

    Vorobiev, Dmitry; Ninkov, Z.

    2014-01-01

    We present a compact, lightweight, snapshot imaging polarimeter designed for operation in the near-infrared (NIR) and mid-infrared (MIR). Flux, polarization and spectral energy distribution are the fundamental measurements through which we infer properties of the sources of radiation such as intensity, temperature, chemical composition, emission mechanisms and structure. In recent decades, many scientific fields that utilize radiometry and spectroscopy have benefited from revolutionary improvements in instrumentation, for example, charge-coupled devices, hybridized infrared arrays, multi-object spectrometers and adaptive optics. Advances in polarimetric instrumentation have been more modest. Recently, the fabrication of microgrid polarizer arrays (MGPAs), facilitated the development of polarization-sensitive focal planes. These devices have inherent capability to measure the degree and angle of polarization across a scene (i.e., imaging polarimetry) instantaneously, without the need for multiple exposures and moving optics or multiple detectors. MGPA-based devices are compact, lightweight, and mechanically robust and perfectly suited for deployment on space-based and airborne platforms. We describe the design, operation and expected performance of MGPA-based imaging polarimeters and identify the applications for which these polarimeters are best suited.

  10. Cryocup - Compact spherical neutron polarimetry device for small angle measurement

    NASA Astrophysics Data System (ADS)

    Wang, Tianhao

    In my thesis I describe my research work of developing a compact device for Spherical Neutron Polarimetry (SNP) measurements at small neutron scattering angles. The thesis first introduced the purpose of this research project, which is developing an easy to use and maintain version of an advanced neutron experiment technique (SNP). After the introduction, the design principle and construction detail of the prototype device is demonstrated. The design principle is based on our finite element simulation of the device's magnetic field profile, and is later verified by the performance test experiment. The prototype device is tested at the SESAME neutron beamline at Indiana University and the HB-2D beamline at Oak Ridge National laboratory. The performance test data are analyzed and proof that the design is successful and the prototype is capable of perform accurate SNP measurement. Based on the test result, the prototype device is utilized to perform SNP measurement on two types of magnetic film sample: Permalloy and Metglas. Combined with other characterization method such as SQUID and MFM, I study the magnetization of these two samples both at zero magnetic field environment and in external field. The SNP data provided by the prototype device is discussed in the thesis and provide detailed information about the magnetization, which is also not accessible through other method. In the end, the possible improvement and the future application of the device is discussed.

  11. Photometry and polarimetry of Saturn's rings from Pioneer Saturn

    NASA Technical Reports Server (NTRS)

    Esposito, L. W.; Dilley, J. P.; Fountain, J. W.

    1980-01-01

    A profile of the average normal optical depth for Saturn's rings between 1.22 and 2.35 Saturn radii is examined. In the A and B rings, horizontal inhomogeneities make these values deceptive. A thinner component of the B ring with an optical depth below 0.08 covers up to 4% of its surface area. In the A ring, the more transparent component covers more than 7% of its area and has an optical depth greater than 0.10. These thinner parts of the rings would rarely be apparent from earth based observations. The particles of the C ring are larger than 15 microns and differ from those of the B and A rings. The C ring is either homogeneous with high albedo and forward scattering phase functions, or shows a gradient in albedo with distance from Saturn. Polarimetry of Saturn's ring provides only an upper limit (below 15%) which is consistent with ground-based predictions. Polarization in the outer A ring is negative.

  12. Arecibo 1418 MHz Polarimetry and Morphological Classification of 95 Pulsars

    NASA Astrophysics Data System (ADS)

    Weitz, K. A.; Weisberg, J. M.; Dawson, B. R.; Despotes, J. T.; Morgan, J. J.; Zink, E. C.; Cordes, J. M.; Lundgren, S. C.; Backer, D. C.

    1995-12-01

    The classification of pulsars allows for the organization of groups of objects which share common features. These classes can then be studied for further correlations, providing insight into a variety of emission and evolutionary questions. Most classification systems are based on the analysis of polarized profiles over a wide frequency range. We gathered polarization data on over one hundred pulsars at 1418 MHz in fifteen observing sessions from 1989 to 1993, using the 305 meter Arecibo telescope. A 20 MHz digital multichannel correlation polarimeter was employed on-line. The multifrequency channels were then dedispersed before summing. All data for each individual pulsar were then calibrated and combined into one full Stokes parameter profile. This process led to polarized average pulse profiles for ninety-five of the pulsars. We used the Rankin (1983) system as the basis for our morphological classifications of the 95 pulsars. In Rankin's model, the frequency evolution of the polarized characteristics of each pulse component is assessed in order to distinguish core from hollow cone emission beams. We studied our 1418 MHz data and all other published polarimetry on each pulsar in order to determine the morphological classifications. We present the polarized profiles and discuss the morphological classifications for these 95 pulsars.

  13. Probing the Galactic center with X-ray polarimetry

    NASA Astrophysics Data System (ADS)

    Marin, F.; Karas, V.; Kunneriath, D.; Muleri, F.; Soffitta, P.

    2014-12-01

    The Galactic center (GC) holds the closest-to-Earth supermassive black hole (SMBH), which makes it the best laboratory to study the close environment of extremely massive compact objects. Polarimetry is sensitive to geometry of the source, which makes it a particularly suitable technique to probe the medium surrounding the GC SMBH. The detection of hard X-ray spectra and prominent iron Kα fluorescence features coincident with localized gas clouds (e.g. Sgr B2, Sgr C) is known for nearly twenty years now and is commonly associated with a past outburst of the SMBH whose radiation is reprocessing onto the so-called ``reflection nebulae''. Since scattering leads to polarization, the re-emitted signal from the giant molecular clouds in the first 100 pc of the GC is expected to be polarized. X-ray polarization measurement is thus particularly adapted to probe the origin of the diffuse X-ray emission from the GC reflection nebulae and reveal the past activity of the central SMBH. In this research note, we summarize the results from past and current polarimetric simulations in order to show how a future X-ray polarimeter equipped with imaging detectors could improve our understanding of high-energy astrophysics.

  14. Quantifying Stress on Grasses Using Polarimetry and Infrared Spectrometry

    NASA Astrophysics Data System (ADS)

    Chavarria, Rose; Noonchester, Eric; Deantonio, Michael

    2004-10-01

    Spectrographic data has been used to analyze the effects of stress on turf. Studies have been done using IR and visible light. To our knowledge, polarimetry has not been studied and could yield information that is not available using the standard measurements. Grass and other crops absorb moisture from the ground. This moisture causes the plants to exhibit a high degree of specular reflectivity. It is a well known law of physics that at a certain angle (referred to as Brewster's angle) all of the light specularly reflected from the surface of a material will have an electric field that oscillates in the plane of the surface. If a subtraction is made between photographic images taken through two polarizers (one horizontal and the other vertical), the remainder is a measurement of the amount of specular reflection. The expectation is that as plants are stressed, the degree of specular reflection will change in such a way as to detect and quantify the amount of stress. We will be correleating the infrared spectrographic data with the polarimetric data in this study.

  15. Mapping the Upper Subsurface of MARS Using Radar Polarimetry

    NASA Technical Reports Server (NTRS)

    Carter, L. M.; Rincon, R.; Berkoski, L.

    2012-01-01

    Future human exploration of Mars will require detailed knowledge of the surface and upper several meters of the subsurface in potential landing sites. Likewise, many of the Planetary Science Decadal Survey science goals, such as understanding the history of Mars climate change, determining how the surface was altered through processes like volcanism and fluvial activity, and locating regions that may have been hospitable to life in the past, would be significantly advanced through mapping of the upper meters of the surface. Synthetic aperture radar (SAR) is the only remote sensing technique capable of penetrating through meters of material and imaging buried surfaces at high (meters to tens-of-meters) spatial resolution. SAR is capable of mapping the boundaries of buried units and radar polarimetry can provide quantitative information about the roughness of surface and subsurface units, depth of burial of stratigraphic units, and density of materials. Orbital SAR systems can obtain broad coverage at a spatial scale relevant to human and robotic surface operations. A polarimetric SAR system would greatly increase the safety and utility of future landed systems including sample caching.

  16. Mid-IR Imaging and Polarimetry of Highly Evolved Objects

    NASA Astrophysics Data System (ADS)

    Jurgenson, C. A.; Stencel, R. E.; Theil, D. S.

    2001-12-01

    We present imaging and polarimetry observation results at selected mid-IR wavelengths taken with the University of Denver's TNTCAM2 at the Wyoming Infrared Observatory's 2.3 m aperture telescope. Post AGB objects include the luminous blue variable AFGL 2298, CW Leo and R CrB. Planetary Nebulae include the Butterfly Nebula M 2-9 and NGC 7027. The characteristics of spectral emission distribution, dust emissivity and magnetic field orientation based on spatial intensity distribution and polarization will be discussed. The objects were chosen for their advanced state of stellar evolution and evidence of resolved nebular structure. In reconstructing our chopped and nodded images, we used a constrained least squares technique called the projected Landweber Method based on work done by Bertero et al. PASP (2000) 112;1121-1137 and the adaptation of the technique by Linz et al. A&A 2002 (in preparation). We acknowledge helpful conversations with Craig Smith, and support for this work from NSF grant AST 9724506, and from the estate of William Herschel Womble.

  17. Impulsive phase solar flare X-ray polarimetry

    NASA Technical Reports Server (NTRS)

    Chanan, Gary; Emslie, A. Gordon; Novick, Robert

    1986-01-01

    The pioneering observational work in solar flare X-ray polarimetry was done in a series of satellite experiments by Tindo and his collaborators in the Soviet Union; initial results showed high levels of polarization in X-ray flares (up to 40%), although of rather low statistical significance, and these were generally interpreted as evidence for strong beaming of suprathermal electrons in the flare energy release process. However, the results of the polarimeter flown by the Columbia Astrophysics Laboratory as part of the STS-3 payload on the Space Shuttle by contrast showed very low levels of polarization. The largest value (observed during the impulsive phase of a single event) was 3.4% + or - 2.2%. At the same time but independent of the observational work, Leach and Petrosian (1983) showed that the high levels of polarization in the Tindo results were difficult to understand theoretically, since the electron beam is isotropized on an energy loss timescale. A subsequent comparison by Leach, Emslie, and Petrosian (1985) of the impulsive phase STS-3 result and the above theoretical treatment shows that the former is consistent with several current models and that a factor of approximately 3 improvement in sensitivity is needed to distinguish properly among the possibilities.

  18. Astrophysical implications and observational prospects of X-ray polarimetry

    NASA Technical Reports Server (NTRS)

    Meszaros, P.; Novick, R.; Szentgyorgyi, A.; Chanan, G. A.; Weisskopf, M. C.

    1988-01-01

    X-ray polarimetry is a prime tool for investigating the physics of compact objects, which has not been adequately exploited thus far. However, current low-cost technology and modest launch requirements could provide a large number of positive observations with a sensitivity factor at least 100 greater than 10 years ago.The amount of astrophysical information potentially to be gained from this is enormous. The introduction of polarimetric information (direction and degree) would bring a quantum jump in the parameter space used to investigate compact objects, from the current two (spectra and time variability) to four independent parameters that models need to satisfy. This should greatly improve our ability to discriminate between various possible models. Such observations could lead to an elucidation of the rotation-powered and accretion-powered pulsar radiation mechanisms, could help clinch the identification of black hole canditates, and could decide between thermal and nonthermal AGN radiation models, as well as pin down the geometry of the accretion flows in both galactic and extragalactic sources.

  19. RADIO FLARES FROM GAMMA-RAY BURSTS

    SciTech Connect

    Kopač, D.; Mundell, C. G.; Kobayashi, S.; Virgili, F. J.; Harrison, R.; Japelj, J.; Gomboc, A.; Guidorzi, C.; Melandri, A.

    2015-06-20

    We present predictions of centimeter and millimeter radio emission from reverse shocks (RSs) in the early afterglows of gamma-ray bursts (GRBs) with the goal of determining their detectability with current and future radio facilities. Using a range of GRB properties, such as peak optical brightness and time, isotropic equivalent gamma-ray energy, and redshift, we simulate radio light curves in a framework generalized for any circumburst medium structure and including a parameterization of the shell thickness regime that is more realistic than the simple assumption of thick- or thin-shell approximations. Building on earlier work by Mundell et al. and Melandri et al. in which the typical frequency of the RS was suggested to lie at radio rather than optical wavelengths at early times, we show that the brightest and most distinct RS radio signatures are detectable up to 0.1–1 day after the burst, emphasizing the need for rapid radio follow-up. Detection is easier for bursts with later optical peaks, high isotropic energies, lower circumburst medium densities, and at observing frequencies that are less prone to synchrotron self-absorption effects—typically above a few GHz. Given recent detections of polarized prompt gamma-ray and optical RS emission, we suggest that detection of polarized radio/millimeter emission will unambiguously confirm the presence of low-frequency RSs at early time.

  20. Optically faint radio sources: reborn AGN?

    NASA Astrophysics Data System (ADS)

    Filho, M. E.; Brinchmann, J.; Lobo, C.; Antón, S.

    2011-12-01

    We present our discovery of several relatively strong radio sources in the field-of-view of SDSS galaxy clusters that have no optical counterparts down to the magnitude limits of the SDSS. The optically faint radio sources appear as double-lobed or core-jet objects in the FIRST radio images and have projected angular sizes ranging from 0.5 to 1.0 arcmin. We followed-up these sources with near-infrared imaging using the wide-field imager HAWK-I on the VLT. We detected Ks-band emitting regions, about 1.5 arcsec in size and coincident with the centers of the radio structures, in all sources, with magnitudes in the range 17-20 mag. We used spectral modelling to characterize the sample sources. In general, the radio properties are similar to those observed in 3CRR sources but the optical-radio slopes are consistent with those of moderate to high redshift (z < 4) gigahertz-peaked spectrum sources. Our results suggest that these unusual objects are galaxies whose black hole has been recently re-ignited but that retain large-scale radio structures, which are signatures of previous AGN activity.

  1. Radio Jove: Jupiter Radio Astronomy for Citizens

    NASA Astrophysics Data System (ADS)

    Higgins, Charles; Thieman, J. R.; Flagg, R.; Reyes, F. J.; Sky, J.; Greenman, W.; Brown, J.; Typinski, D.; Ashcraft, T.; Mount, A.

    2014-01-01

    Radio JOVE is a hands-on educational activity that brings the radio sounds of the Sun, Jupiter, the Milky Way Galaxy, and terrestrial radio noise to students, teachers, and the general public. Participants may build a simple radio telescope kit, make scientific observations, and interact with professional radio observatories in real-time over the Internet. Our website (http://radiojove.gsfc.nasa.gov) includes science information, construction manuals, observing guides, and education resources for teachers and students. Radio Jove is continually expanding its participants with over 1800 kits sold to more than 70 countries worldwide. Recently some of our most dedicated observers have upgraded their Radio Jove antennas to semi-professional observatories. We have spectrographs and wide band antennas, some with 8 MHz bandwidth and some with dual polarization capabilities. In an effort to add to the science literature, these observers are coordinating their efforts to pursue some basic questions about Jupiter’s radio emissions (radio source locations, spectral structure, long term changes, etc.). We can compare signal and ionosphere variations using the many Radio Jove observers at different locations. Observers are also working with members of the Long Wavelength Array Station 1 (LWA1) radio telescope to coordinate observations of Jupiter; Radio Jove is planning to make coordinated observations while the Juno Mission is active beginning in 2015. The Radio Jove program is overviewed, its hardware and software are highlighted, recent sample observations are shown, and we demonstrate that we are capable of real citizen science.

  2. Polarimetry diagnostic on OMEGA EP using a 10-ps, 263-nm probe beam

    SciTech Connect

    Davies, A. Haberberger, D.; Boni, R.; Ivancic, S.; Brown, R.; Froula, D. H.

    2014-11-15

    A polarimetry diagnostic was built and characterized for magnetic-field measurements in laser-plasma experiments on the OMEGA EP laser. This diagnostic was built into the existing 4ω (263-nm) probe system that employs a 10-ps laser pulse collected with an f/4 imaging system. The diagnostic measures the rotation of the probe beam's polarization. The polarimeter uses a Wollaston prism to split the probe beam into orthogonal polarization components. Spatially localized intensity variations between images indicate polarization rotation. Magnetic fields can be calculated by combining the polarimetry data with the measured plasma density profile obtained from angular filter refractometry.

  3. Learning radio astronomy by doing radio astronomy

    NASA Astrophysics Data System (ADS)

    Vaquerizo Gallego, J. A.

    2011-11-01

    PARTNeR (Proyecto Académico con el Radio Telescopio de NASA en Robledo, Academic Project with the NASA Radio Telescope at Robledo) is an educational program that allows high school and undergraduate students to control a 34 meter radio telescope and conduct radio astronomical observations via the internet. High-school teachers who join the project take a course to learn about the science of radio astronomy and how to use the antenna as an educational resource. Also, teachers are provided with learning activities they can do with their students and focused on the classroom implementation of the project within an interdisciplinary framework. PARTNeR provides students with firsthand experience in radio astronomy science. Thus, remote radio astronomical observations allow students to learn with a first rate scientific equipment the basics of radio astronomy research, aiming to arouse scientific careers and positive attitudes toward science. In this contribution we show the current observational programs and some recent results.

  4. UV Signature Mutations †

    PubMed Central

    2014-01-01

    Sequencing complete tumor genomes and exomes has sparked the cancer field's interest in mutation signatures for identifying the tumor's carcinogen. This review and meta-analysis discusses signatures and their proper use. We first distinguish between a mutagen's canonical mutations – deviations from a random distribution of base changes to create a pattern typical of that mutagen – and the subset of signature mutations, which are unique to that mutagen and permit inference backward from mutations to mutagen. To verify UV signature mutations, we assembled literature datasets on cells exposed to UVC, UVB, UVA, or solar simulator light (SSL) and tested canonical UV mutation features as criteria for clustering datasets. A confirmed UV signature was: ≥60% of mutations are C→T at a dipyrimidine site, with ≥5% CC→TT. Other canonical features such as a bias for mutations on the non-transcribed strand or at the 3' pyrimidine had limited application. The most robust classifier combined these features with criteria for the rarity of non-UV canonical mutations. In addition, several signatures proposed for specific UV wavelengths were limited to specific genes or species; non-signature mutations induced by UV may cause melanoma BRAF mutations; and the mutagen for sunlight-related skin neoplasms may vary between continents. PMID:25354245

  5. An archaeal genomic signature

    NASA Technical Reports Server (NTRS)

    Graham, D. E.; Overbeek, R.; Olsen, G. J.; Woese, C. R.

    2000-01-01

    Comparisons of complete genome sequences allow the most objective and comprehensive descriptions possible of a lineage's evolution. This communication uses the completed genomes from four major euryarchaeal taxa to define a genomic signature for the Euryarchaeota and, by extension, the Archaea as a whole. The signature is defined in terms of the set of protein-encoding genes found in at least two diverse members of the euryarchaeal taxa that function uniquely within the Archaea; most signature proteins have no recognizable bacterial or eukaryal homologs. By this definition, 351 clusters of signature proteins have been identified. Functions of most proteins in this signature set are currently unknown. At least 70% of the clusters that contain proteins from all the euryarchaeal genomes also have crenarchaeal homologs. This conservative set, which appears refractory to horizontal gene transfer to the Bacteria or the Eukarya, would seem to reflect the significant innovations that were unique and fundamental to the archaeal "design fabric." Genomic protein signature analysis methods may be extended to characterize the evolution of any phylogenetically defined lineage. The complete set of protein clusters for the archaeal genomic signature is presented as supplementary material (see the PNAS web site, www.pnas.org).

  6. Twin Signature Schemes, Revisited

    NASA Astrophysics Data System (ADS)

    Schäge, Sven

    In this paper, we revisit the twin signature scheme by Naccache, Pointcheval and Stern from CCS 2001 that is secure under the Strong RSA (SRSA) assumption and improve its efficiency in several ways. First, we present a new twin signature scheme that is based on the Strong Diffie-Hellman (SDH) assumption in bilinear groups and allows for very short signatures and key material. A big advantage of this scheme is that, in contrast to the original scheme, it does not require a computationally expensive function for mapping messages to primes. We prove this new scheme secure under adaptive chosen message attacks. Second, we present a modification that allows to significantly increase efficiency when signing long messages. This construction uses collision-resistant hash functions as its basis. As a result, our improvements make the signature length independent of the message size. Our construction deviates from the standard hash-and-sign approach in which the hash value of the message is signed in place of the message itself. We show that in the case of twin signatures, one can exploit the properties of the hash function as an integral part of the signature scheme. This improvement can be applied to both the SRSA based and SDH based twin signature scheme.

  7. ATCA monitoring in support of RadioAstron observations of high brightness temperature AGN

    NASA Astrophysics Data System (ADS)

    Bignall, Hayley; Macquart, Jean-Pierre; McCallum, Jamie Nigel; Cimo, Giuseppe; Jauncey, David; Gurvits, Leonid; Reynolds, Cormac; Schnitzeler, Dominic; Hodgson, Jeffrey; Kovalev, Yuri; Shabala, Stanislav; Koay, Jun Yi

    2014-10-01

    AGN radio emission is thought to be produced by synchrotron emission of relativistic electrons that is Doppler boosted through relativistic bulk motion. Inverse Compton scattering imposes a theoretical limit of 10^12 K on the brightness temperature of synchrotron radiation in the rest frame of the emitting plasma. It is well known that a number of AGN exceed this by 2 orders of magnitude, but the extent of the excess is unknown since measurements only place lower bounds on the actual brightness temperature in many cases. With VLBI including the RadioAstron 10 m space radio telescope, we can make direct measurements of extreme brightness temperatures. Total flux density monitoring of RadioAstron targets is essential to determine the effect of interstellar scintillation (ISS) on the Space VLBI visibilities. Furthermore, by measuring the scintillation timescale and amplitude around the time of the RadioAstron observations, we can use the angular size determined by measurements with RadioAstron to "calibrate" the interstellar scattering -- in particular the distance to the scattering medium -- and then use ISS to directly investigate the physics of ultracompact jets in unprecedented detail. For the majority of sources, accurate flux density monitoring over more than a day is required to achieve these goals. Here we propose to continue ATCA flux density monitoring in support of the RadioAstron AGN Survey observations. As a bonus, broadband polarimetry with the ATCA provides another handle on the physical conditions in the AGN.

  8. ATCA monitoring in support of RadioAstron-LBA observations of high brightness temperature AGN

    NASA Astrophysics Data System (ADS)

    Bignall, Hayley; Macquart, Jean-Pierre; McCallum, Jamie Nigel; Cimo, Giuseppe; Jauncey, David; Gurvits, Leonid; Reynolds, Cormac; Schnitzeler, Dominic; Hodgson, Jeffrey; Kovalev, Yuri; Shabala, Stanislav

    2014-04-01

    AGN radio emission is thought to be produced by synchrotron emission of relativistic electrons that is Doppler boosted through relativistic bulk motion. Inverse Compton scattering imposes a theoretical limit of 10^12 K on the brightness temperature of synchrotron radiation in the rest frame of the emitting plasma. It is well known that a number of AGN exceed this by 2 orders of magnitude, but the extent of the excess is unknown since measurements only place lower bounds on the actual brightness temperature in many cases. With VLBI including the RadioAstron 10 m space radio telescope, we can make direct measurements of extreme brightness temperatures. Total flux density monitoring of RadioAstron targets is essential to determine the effect of interstellar scintillation (ISS) on the Space VLBI visibilities. Furthermore, by measuring the scintillation timescale and amplitude around the time of the RadioAstron observations, we can use the angular size determined by measurements with RadioAstron to "calibrate" the interstellar scattering -- in particular the distance to the scattering medium -- and then use ISS to directly investigate the physics of ultracompact jets in unprecedented detail. For the majority of sources, accurate flux density monitoring over more than a day is required to achieve these goals. Here we propose to undertake ATCA flux density monitoring in support of the RadioAstron AGN Survey observations. As a bonus, broadband polarimetry with the ATCA provides another handle on the physical conditions in the AGN.

  9. Tracking the CME-driven shock wave on 2012 March 5 and radio triangulation of associated radio emission

    SciTech Connect

    Magdalenić, J.; Marqué, C.; Mierla, M.; Zhukov, A. N.; Rodriguez, L.; Krupar, V.; Maksimović, M.; Cecconi, B.

    2014-08-20

    We present a multiwavelength study of the 2012 March 5 solar eruptive event, with an emphasis on the radio triangulation of the associated radio bursts. The main points of the study are reconstruction of the propagation of shock waves driven by coronal mass ejections (CMEs) using radio observations and finding the relative positions of the CME, the CME-driven shock wave, and its radio signatures. For the first time, radio triangulation is applied to different types of radio bursts in the same event and performed in a detailed way using goniopolarimetric observations from STEREO/Waves and WIND/Waves spacecraft. The event on 2012 March 5 was associated with a X1.1 flare from the NOAA AR 1429 situated near the northeast limb, accompanied by a full halo CME and a radio event comprising long-lasting interplanetary type II radio bursts. The results of the three-dimensional reconstruction of the CME (using SOHO/LASCO, STEREO COR, and HI observations), and modeling with the ENLIL cone model suggest that the CME-driven shock wave arrived at 1 AU at about 12:00 UT on March 7 (as observed by SOHO/CELIAS). The results of radio triangulation show that the source of the type II radio burst was situated on the southern flank of the CME. We suggest that the interaction of the shock wave and a nearby coronal streamer resulted in the interplanetary type II radio emission.

  10. Space- and Ground-based Coronal Spectro-Polarimetry

    NASA Astrophysics Data System (ADS)

    Fineschi, Silvano; Bemporad, Alessandro; Rybak, Jan; Capobianco, Gerardo

    This presentation gives an overview of the near-future perspectives of ultraviolet and visible-light spectro-polarimetric instrumentation for probing coronal magnetism from space-based and ground-based observatories. Spectro-polarimetric imaging of coronal emission-lines in the visible-light wavelength-band provides an important diagnostics tool of the coronal magnetism. The interpretation in terms of Hanle and Zeeman effect of the line-polarization in forbidden emission-lines yields information on the direction and strength of the coronal magnetic field. As study case, this presentation will describe the Torino Coronal Magnetograph (CorMag) for the spectro-polarimetric observation of the FeXIV, 530.3 nm, forbidden emission-line. CorMag - consisting of a Liquid Crystal (LC) Lyot filter and a LC linear polarimeter - has been recently installed on the Lomnicky Peak Observatory 20cm Zeiss coronagraph. The preliminary results from CorMag will be presented. The linear polarization by resonance scattering of coronal permitted line-emission in the ultraviolet (UV)can be modified by magnetic fields through the Hanle effect. Space-based UV spectro-polarimeters would provide an additional tool for the disgnostics of coronal magnetism. As a case study of space-borne UV spectro-polarimeters, this presentation will describe the future upgrade of the Sounding-rocket Coronagraphic Experiment (SCORE) to include the capability of imaging polarimetry of the HI Lyman-alpha, 121.6 nm. SCORE is a multi-wavelength imager for the emission-lines, HeII 30.4 nm and HI 121.6 nm, and visible-light broad-band emission of the polarized K-corona. SCORE has flown successfully in 2009. This presentation will describe how in future re-flights SCORE could observe the expected Hanle effect in corona with a HI Lyman-alpha polarimeter.

  11. Kinetic inductance detectors for CMB polarimetry at 100 GHz

    NASA Astrophysics Data System (ADS)

    Lowitz, Amy E.

    Kinetic inductance detectors (KIDs) are a promising technology for astronomical observations over a wide range of wavelengths in the mm and submm regime. Simple fabrication, in as little as one lithographic layer, and passive frequency-domain multiplexing, with readout of up to ˜1000 pixels on a single line with a single cold amplifier, make KIDs an attractive solution for high pixel-count detector arrays. Described in this dissertation is the design, fabrication, and testing of a 20-pixel prototype array of kinetic inductance detectors intended for cosmic microwave background (CMB) polarimetry in a band centered at 3 mm (100 GHz), which is an important band for CMB observations from the ground. We first show that the theoretical performance of idealized KIDs rivals that of their primary competitor detector technology, superconducting transition edge sensors (TESs). Next, we describe the design process, which employed both simulation and semianalytic calculations to optimize the resonant frequencies and optical coupling. Where a specific observing scenario was required to motivate design choices, we have used the QUBIC telescope, a bolometric interferometer designed to study the CMB polarization anisotropy initially from Alto Chorillos, Argentina and later from Dome C, Antarctica. Finally, we describe the fabrication and testing of three prototype arrays made with different materials and geometries. In two iterations of the device geometry, we demonstrate response to mm-wave illumination and improvements in control of pixel center frequencies and coupling quality factors. Additionally, we find that molybdenum is not well-suited to mm-wave KIDs because of excessive thermal dissipation resulting from double-gap behavior of superconducting molybdenum. Titanium nitride trilayers perform better, but exhibit complex and poorly-understood non-Mattis-Bardeen behavior. The superconducting properties of this material will need to be better understood before it can be used

  12. Are there molecular signatures?

    SciTech Connect

    Bennett, W.P.

    1995-10-01

    This report describes molecular signatures and mutational spectrum analysis. The mutation spectrum is defined as the type and location of DNA base change. There are currently about five well documented cases. Mutations and radon-associated tumors are discussed.

  13. Meteor signature interpretation

    SciTech Connect

    Canavan, G.H.

    1997-01-01

    Meteor signatures contain information about the constituents of space debris and present potential false alarms to early warnings systems. Better models could both extract the maximum scientific information possible and reduce their danger. Accurate predictions can be produced by models of modest complexity, which can be inverted to predict the sizes, compositions, and trajectories of object from their signatures for most objects of interest and concern.

  14. Rapid Mueller matrix polarimetry imaging based on four photoelastic modulators with no moving parts (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Gribble, Adam; Alali, Sanaz; Vitkin, Alex

    2016-03-01

    Polarized light has many applications in biomedical imaging. The interaction of a biological sample with polarized light reveals information about its composition, both structural and functional. For example, the polarimetry-derived metric of linear retardance (birefringence) is dependent on tissue structural organization (anisotropy) and can be used to diagnose myocardial infarct; circular birefringence (optical rotation) can measure glucose concentrations. The most comprehensive type of polarimetry analysis is to measure the Mueller matrix, a polarization transfer function that completely describes how a sample interacts with polarized light. To derive this 4x4 matrix it is necessary to observe how a tissue interacts with different polarizations. A well-suited approach for tissue polarimetry is to use photoelastic modulators (PEMs), which dynamically modulate the polarization of light. Previously, we have demonstrated a rapid time-gated Stokes imaging system that is capable of characterizing the state of polarized light (the Stokes vector) over a large field, after interacting with any turbid media. This was accomplished by synchronizing CCD camera acquisition times relative to two PEMs using a field-programmable gate array (FPGA). Here, we extend this technology to four PEMs, yielding a polarimetry system that is capable of rapidly measuring the complete sample Mueller matrix over a large field of view, with no moving parts and no beam steering. We describe the calibration procedure and evaluate the accuracy of the measurements. Results are shown for tissue-mimicking phantoms, as well as initial biological samples.

  15. A Green Fabry-Perot Cavity for Jefferson Lab Hall A Compton Polarimetry

    SciTech Connect

    Rakhman, Abdurahim; Souder, Paul; Nanda, Sirish

    2009-08-04

    A green laser (CW, 532 nm) based Fabry-Perot cavity for high precision Compton Polarimetry is under development in Hall A of the Jefferson Laboratory. In this paper, we present the principle and the preliminary studies for our test cavity.

  16. A New Method for Precision Cold Neutron Polarimetry Using a 3He Spin Filter

    PubMed Central

    Wietfeldt, F. E.; Gentile, T. R.

    2005-01-01

    We present a new method for precision measurement of the capture flux polarization of a polychromatic (white), continuous cold neutron beam, polarized by a 3He spin filter. This method allows an in situ measurement and does not require knowledge of the neutron beam wavelength distribution. We show that a polarimetry precision of 0.1 % is possible. PMID:27308141

  17. A New Method for Precision Cold Neutron Polarimetry Using a (3)He Spin Filter.

    PubMed

    Wietfeldt, F E; Gentile, T R

    2005-01-01

    We present a new method for precision measurement of the capture flux polarization of a polychromatic (white), continuous cold neutron beam, polarized by a (3)He spin filter. This method allows an in situ measurement and does not require knowledge of the neutron beam wavelength distribution. We show that a polarimetry precision of 0.1 % is possible.

  18. Polarization information processing and software system design for simultaneously imaging polarimetry

    NASA Astrophysics Data System (ADS)

    Wang, Yahui; Liu, Jing; Jin, Weiqi; Wen, Renjie

    2015-08-01

    Simultaneous imaging polarimetry can realize real-time polarization imaging of the dynamic scene, which has wide application prospect. This paper first briefly illustrates the design of the double separate Wollaston Prism simultaneous imaging polarimetry, and then emphases are put on the polarization information processing methods and software system design for the designed polarimetry. Polarization information processing methods consist of adaptive image segmentation, high-accuracy image registration, instrument matrix calibration. Morphological image processing was used for image segmentation by taking dilation of an image; The accuracy of image registration can reach 0.1 pixel based on the spatial and frequency domain cross-correlation; Instrument matrix calibration adopted four-point calibration method. The software system was implemented under Windows environment based on C++ programming language, which realized synchronous polarization images acquisition and preservation, image processing and polarization information extraction and display. Polarization data obtained with the designed polarimetry shows that: the polarization information processing methods and its software system effectively performs live realize polarization measurement of the four Stokes parameters of a scene. The polarization information processing methods effectively improved the polarization detection accuracy.

  19. The Radio Amateur's Handbook.

    ERIC Educational Resources Information Center

    Blakeslee, Douglas, Ed.

    The objectives of this basic reference work for the radio amateur are to present radio theory and practice in terms of application and to reflect both the fundamentals and the rapidly-advancing technology of radio communications so that the radio amateur will have a guide to what is practical, meaningful, proven, and useful. Twenty-three chapters…

  20. The Frequency Spectrum Radio.

    ERIC Educational Resources Information Center

    Howkins, John, Ed.

    1979-01-01

    This journal issue focuses on the frequency spectrum used in radio communication and on the World Administrative Radio Conference, sponsored by the International Telecommunication Union, held in Geneva, Switzerland, in the fall of 1979. Articles describe the World Administrative Radio Conference as the most important radio communication conference…

  1. Nonperturbative measurement of the local magnetic field using pulsed polarimetry for fusion reactor conditions (invited).

    PubMed

    Smith, Roger J

    2008-10-01

    A novel diagnostic technique for the remote and nonperturbative sensing of the local magnetic field in reactor relevant plasmas is presented. Pulsed polarimetry [Patent No. 12/150,169 (pending)] combines optical scattering with the Faraday effect. The polarimetric light detection and ranging (LIDAR)-like diagnostic has the potential to be a local B(pol) diagnostic on ITER and can achieve spatial resolutions of millimeters on high energy density (HED) plasmas using existing lasers. The pulsed polarimetry method is based on nonlocal measurements and subtle effects are introduced that are not present in either cw polarimetry or Thomson scattering LIDAR. Important features include the capability of simultaneously measuring local T(e), n(e), and B(parallel) along the line of sight, a resiliency to refractive effects, a short measurement duration providing near instantaneous data in time, and location for real-time feedback and control of magnetohydrodynamic (MHD) instabilities and the realization of a widely applicable internal magnetic field diagnostic for the magnetic fusion energy program. The technique improves for higher n(e)B(parallel) product and higher n(e) and is well suited for diagnosing the transient plasmas in the HED program. Larger devices such as ITER and DEMO are also better suited to the technique, allowing longer pulse lengths and thereby relaxing key technology constraints making pulsed polarimetry a valuable asset for next step devices. The pulsed polarimetry technique is clarified by way of illustration on the ITER tokamak and plasmas within the magnetized target fusion program within present technological means.

  2. Development of X-ray spectroscopic polarimetry with bent Si crystals and CFRP substrate

    NASA Astrophysics Data System (ADS)

    Iizuka, Ryo; Izumiya, Takanori; Tsuboi, Yohko

    2016-07-01

    The light from celestial objects includes four important quantities; images, time variation, energy spectrum, and polarization. In the field of X-ray astronomy, the capabilities of the former three have remarkably developed. On the other hand, the progress for the polarimetry is considerably delayed because of technical difficulties. In order to make a breakthrough in the field of X-ray polarimetry, we have developed a new type of optics for X-ray polarimetry. The system is collecting Bragg crystal with large area and very high sensitivity for the polarization dedicated to Fe-K lines. We adopt the 400 re ection of Si(100) crystals with high sensitivity for the polarization around Fe-K lines (6 7 keV), and bent the crystals with the wide X-ray band and high S/N ratio. Furthermore, to install small area of CCD to non-focal plane, it also has the spectroscopic capability with the better resolution than that of general X-ray CCD. Our previous development was to bent Si crystals to the cylindrical shape of circle and parabola with the DLC deposition. However, for the better optics for the X-ray polarimetry, the shape should be the paraboloid of revolution to collect X-rays with high S/N ratio. We searched for the method to bent the Si crystals to the shape of the paraboloid of revolution. We devised the method to mold the crystal and the CFRP substrate simultaneously pushed to the sophisticated foundation with the paraboloid of revolution. We developed the prototype of about 8 inch in radius of one-quater size. The crystals was also bent in the circumferential direction. Therefore, the image capability examined with optical parallel beam is 0.6 degree. In this thesis, we discussed the new design for X-ray spectroscopic polarimetry, the evaluation of image capability.

  3. Invisibly Sanitizable Signature without Pairings

    NASA Astrophysics Data System (ADS)

    Yum, Dae Hyun; Lee, Pil Joong

    Sanitizable signatures allow sanitizers to delete some pre-determined parts of a signed document without invalidating the signature. While ordinary sanitizable signatures allow verifiers to know how many subdocuments have been sanitized, invisibly sanitizable signatures do not leave any clue to the sanitized subdocuments; verifiers do not know whether or not sanitizing has been performed. Previous invisibly sanitizable signature scheme was constructed based on aggregate signature with pairings. In this article, we present the first invisibly sanitizable signature without using pairings. Our proposed scheme is secure under the RSA assumption.

  4. The Physics of the Jets of Powerful Radio Galaxies and Quasars

    NASA Astrophysics Data System (ADS)

    Perlman, Eric

    2014-10-01

    We propose HST polarimetry of the jet of 3C 273. Polarization is a critical parameter for understanding jet flows, and only HST has the resolution and capability to perform this measurement. The data will confirm which mechanisms are operating to create its optical and X-ray emission, and will show locations where the magnetic fields are being structured by shocks and shears. This will greatly advance modeling efforts for this jet and nail down its kinetic power, a key unknown parameter for understanding quasars and their cosmological effects. Comparison with in-hand radio and ground-based near-IR (AO) optical polarimetry at matched resolution will measure the flow speed in the plasma as a function of particle energy, in the same way as in our analysis of our earlier HST polarimetry data on low-power jets. This proposal builds on our observations of two other quasar jets, where we measured high polarization in the X-ray brightest knots, and so showed that their optical and X-ray emission is most likely due to the synchrotron model, since the alternative, IC/CMB model fails to match those objects' steep radio spectra and modest variability, and requires exceptionally fast flows (Gamma>30) at hundreds of kpc and super-Eddington kinetic power. The proposed observations will provide much stronger constraints because this iconic jet, because of its brightness, exceptional angular separation from the core and low redshift (z=0.158). Our modelling techniques will also provide much information on the jet's internal structure, including shocks and the sites of particle acceleration.

  5. Radio frequency detection assembly and method for detecting radio frequencies

    SciTech Connect

    Cown, Steven H.; Derr, Kurt Warren

    2010-03-16

    A radio frequency detection assembly is described and which includes a radio frequency detector which detects a radio frequency emission produced by a radio frequency emitter from a given location which is remote relative to the radio frequency detector; a location assembly electrically coupled with the radio frequency detector and which is operable to estimate the location of the radio frequency emitter from the radio frequency emission which has been received; and a radio frequency transmitter electrically coupled with the radio frequency detector and the location assembly, and which transmits a radio frequency signal which reports the presence of the radio frequency emitter.

  6. Gas and radio galaxies: a story of love and hate

    NASA Astrophysics Data System (ADS)

    Morganti, Rafaella

    2011-07-01

    Gas in radio galaxies is an important component that plays different roles. Gas can feed the AGN and make it active but dense gas can also be an obstacle for radio jets and (temporarily) destroy their flow. The characteristics of the different phases of gas in the circumnuclear regions of active nuclei hold clear signatures of the influences that the black hole activity has on its surroundings. I will review these effects based on some recent results obtained in the study of neutral hydrogen and CO. In particular, I will concentrate on the effects of radio jets in generating the strong negative feedback of the kind invoked in current scenarios for galaxy evolution.

  7. Polarimetry of an intermediate-age open cluster: NGC 5617

    NASA Astrophysics Data System (ADS)

    Orsatti, A. M.; Feinstein, C.; Vergne, M. M.; Martínez, R. E.; Vega, E. I.

    2010-04-01

    Aims: We present polarimetric observations in the UBVRI bands of 72 stars located in the direction of the medium age open cluster NGC 5617. Our intention is to use polarimetry as a tool in membership identification, by building on previous investigations intended mainly to determine the cluster's general characteristics rather than provide membership suitable for studies such as stellar content and metallicity, as well as study the characteristics of the dust lying between the Sun and the cluster. Methods: The obsevations were carried out using the five-channel photopolarimeter of the Torino Astronomical Observatory attached to the 2.15 m telescope at the Complejo Astronómico El Leoncito (CASLEO; Argentina). Results: We are able to add 32 stars to the list of members of NGC 5617, and review the situation for others listed in the literature. In particular, we find that five blue straggler stars in the region of the cluster are located behind the same dust as the member stars are and we confirm the membership of two red giants. The proposed polarimetric memberships are compared with those derived by photometric and kinematical methods, with excellent results. Among the observed stars, we identify 10 with intrinsic polarization in their light. NGC 5617 can be polarimetrically characterized with Pmax = 4.40 % and θv = 73.1 deg. The spread in polarization values for the stars observed in the direction of the cluster seems to be caused by the uneven distribution of dust in front of the cluster's face. Finally, we find that in the direction of the cluster, the interstellar medium is apparently free of dust, from the Sun's position up to the Carina-Sagittarius arm, where NGC 5617 seems to be located at its farthest border. Based on observations obtained at Complejo Astronómico El Leoncito, operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina and the Universities of La Plata, Córdoba, and San Juan.

  8. Practical quantum digital signature

    NASA Astrophysics Data System (ADS)

    Yin, Hua-Lei; Fu, Yao; Chen, Zeng-Bing

    2016-03-01

    Guaranteeing nonrepudiation, unforgeability as well as transferability of a signature is one of the most vital safeguards in today's e-commerce era. Based on fundamental laws of quantum physics, quantum digital signature (QDS) aims to provide information-theoretic security for this cryptographic task. However, up to date, the previously proposed QDS protocols are impractical due to various challenging problems and most importantly, the requirement of authenticated (secure) quantum channels between participants. Here, we present the first quantum digital signature protocol that removes the assumption of authenticated quantum channels while remaining secure against the collective attacks. Besides, our QDS protocol can be practically implemented over more than 100 km under current mature technology as used in quantum key distribution.

  9. The Dominion Radio Astrophysical Observatory

    NASA Astrophysics Data System (ADS)

    Landecker, T. L.

    1996-05-01

    The DRAO Synthesis Telescope has been designed for imaging with excellent sensitivity to extended structure of low surface-brightness. Able to map HI emission with an angular resolution of 1(') , it is a research tool for investigations of the ISM in our own and nearby galaxies. The telescope operates simultaneously in three bands: the 21-cm HI line, and 1420 and 408 MHz continuum. Seven antennas of diameter 8.5m cover EW baselines from 13m to 600m. Field of view at 1420 and 408 MHz is ~ 2(deg) and ~ 8(deg) ; angular resolution is 1(') and 3.5(') EW, extended by cosecdelta NS. The spectral line correlator has 256 channels, with overall bandwidths from 0.125 to 4 MHz ( ~ 26 to ~ 840 kms(-1) in the HI line). Polarimetry is a standard facility at 1420 MHz continuum. The principal project of the Synthesis Telescope is the DRAO Galactic Plane Survey, a systematic mapping from l=75(deg) to l=145(deg) , -3.5(deg}radio continuum images at 151 MHz (MRAO, Cambridge), and 232 and 327 MHz (BAO, Beijing). Taken together, the data will portray the most important constituents of the ISM as a basis for research into the many interactive processes, on small and large scales, among its phases and components. The DRAO 26-m Telescope provides HI data on large structures for incorporation into Synthesis Telescope images. It is equipped for spectroscopy from 1.3 to 1.7 GHz and at the 6.6 GHz transition of CH_3OH. The solar flux density at 2800 MHz is measured daily and transmitted automatically to many scientific and commercial users. Data are further distributed by NOAA, Boulder, CO, and are available on WWW. The ``Penticton 2800 MHz Solar Flux'' is considered a standard index of solar activity; the 50-year database has a

  10. Factor models for cancer signatures

    NASA Astrophysics Data System (ADS)

    Kakushadze, Zura; Yu, Willie

    2016-11-01

    We present a novel method for extracting cancer signatures by applying statistical risk models (http://ssrn.com/abstract=2732453) from quantitative finance to cancer genome data. Using 1389 whole genome sequenced samples from 14 cancers, we identify an "overall" mode of somatic mutational noise. We give a prescription for factoring out this noise and source code for fixing the number of signatures. We apply nonnegative matrix factorization (NMF) to genome data aggregated by cancer subtype and filtered using our method. The resultant signatures have substantially lower variability than those from unfiltered data. Also, the computational cost of signature extraction is cut by about a factor of 10. We find 3 novel cancer signatures, including a liver cancer dominant signature (96% contribution) and a renal cell carcinoma signature (70% contribution). Our method accelerates finding new cancer signatures and improves their overall stability. Reciprocally, the methods for extracting cancer signatures could have interesting applications in quantitative finance.

  11. Current signature sensor

    NASA Technical Reports Server (NTRS)

    Perotti, Jose M. (Inventor); Lucena, Angel (Inventor); Ihlefeld, Curtis (Inventor); Burns, Bradley (Inventor); Bassignani, Karin E. (Inventor)

    2005-01-01

    A solenoid health monitoring system uses a signal conditioner and controller assembly in one embodiment that includes analog circuitry and a DSP controller. The analog circuitry provides signal conditioning to the low-level raw signal coming from a signal acquisition assembly. Software running in a DSP analyzes the incoming data (recorded current signature) and determines the state of the solenoid whether it is energized, de-energized, or in a transitioning state. In one embodiment, the software identifies key features in the current signature during the transition phase and is able to determine the health of the solenoid.

  12. Current Signature Sensor

    NASA Technical Reports Server (NTRS)

    Perotti, Jose M. (Inventor); Lucena, Angel (Inventor); Ihlefeld, Curtis (Inventor); Burns, Bradley (Inventor); Bassignani, Mario (Inventor); Bassignani, Karin E. (Inventor)

    2005-01-01

    A solenoid health monitoring system uses a signal conditioner and controller assembly in one embodiment that includes analog circuitry and a DSP controller. The analog circuitry provides signal conditioning to the low-level raw signal coming from a signal acquisition assembly. Software running in a DSP analyzes the incoming data (recorded current signature) and determines the state of the solenoid whether it is energized, de-energized, or in a transitioning state. In one embodiment, the software identifies key features in the current signature during the transition phase and is able to determine the health of the solenoid.

  13. High Energy Emission from Quasar Jets: HST polarimetry, X-ray and Gamma-ray Emission and the IC/CMB hypothesis

    NASA Astrophysics Data System (ADS)

    Perlman, Eric S.; Georganopoulos, Markos; Meyer, Eileen T.; Cara, Mihai

    2015-01-01

    One of the unique legacies of the Chandra X-ray Observatory is the discovery of X-ray emission from a large number of extragalactic jets (over 100 are now known). In less powerful, FR I radio jets this emission is generally understood to be synchrotron emission from the highest energy electrons, requiring in situ particle acceleration, but the nature of the high-energy emission from the more powerful quasar jets is less well constrained. In quasar jets, the emission extends for tens to hundreds of kiloparsecs, and the observed X-rays are harder and at a higher flux than expected from an extrapolation of the radio to optical spectrum. Over the last 15 years, a persistent debate has arisen as to the nature of this emission, with the leading model being inverse-Comptonization of the Cosmic Microwave Background radiation. This explanation requires the jet to be relativistic out to hundreds of kiloparsecs from the nucleus, and requires an electron spectrum that extends to very low Lorentz factors. The combination of these two results in a very high kinetic power, very close to or over the Eddington limit if the electron spectrum continues to gamma ~ 1. We discuss recent work with HST polarimetry and the X-ray to gamma-ray spectrum that we believe makes it necessary to re-examine the IC/CMB hypothesis. In many quasar jets, the optical and X-ray emission is joined by a single spectral component, and HST polarimetry in that high-energy component is detecting high polarizations, making it difficult to explain the high-energy emission via the IC/CMB hypothesis. So far, this has been found in 2 jets (PKS 1136-135, Cara et al. 2013, and 1150+497), with observations of a third (3C 273) scheduled for January. In addition, IC/CMB of the highest energy synchrotron photons predicts that we should be detecting GeV gamma-ray emission from the extended jets (Georganopoulos et al. 2006, Meyer & Georganopoulos 2014). These lines of evidence have made the IC/CMB hypothesis very unlikely

  14. Radio Monitoring of Protoplanetary Discs

    NASA Astrophysics Data System (ADS)

    Ubach, Catarina; Tahli Maddison, Sarah; Wright, Chris M.; Wilner, David J.; Lommen, Dave J. P.; Koribalski, Baerbel

    2015-01-01

    We present new results from a radio monitoring survey conducted with ATCA where we measured the flux variability for 11 protoplanetary disks in the Chameoleon and Lupus star forming regions at 7 and 15 mm and 3+6 cm. We determined the source of the excess flux and discuss its effect on grain growth to cm-size pebbles. We found that for most targets the 7 mm flux variability is consistent with the presence of thermal free-free emission and that the targets with excess emission above thermal dust emission also have signatures of grain growth to cm-size pebbles. Our results indicate that the presence of other emission mechanisms does not seem to negatively affect the grain growth process.

  15. Extended Cyclostationary Signatures for OFDM in the Presence of Hardware Imperfections

    NASA Astrophysics Data System (ADS)

    Schmitz, Johannes; Zivkovic, Milan; Mathar, Rudolf

    2012-09-01

    Cyclostationary signatures have been shown to be an effective method for OFDM network synchronization and Cognitive Radio coordination. In this article, an extended method that utilizes cyclostationary signatures for signal parameter identification of OFDM-based Cognitive Radio nodes is presented. The scenario, implemented on a GNU Radio based evaluation platform, shows how different signal parameters, e.g. carrier frequency, occupied bandwidth and the used modulation scheme can be identified at the receiver side using the described approach. A major drawback of cyclostationary detection in OFDM systems is its sensitivity to frequency offset and sampling rate mismatches between oscillators at the transmitter and the receiver. An analytical model that characterizes this impairments is derived, followed by a discussion of implementation issues and the performance evaluation of proposed cyclostationary signature detection, both in a simulation environment and through RF experiments.

  16. Resonance and Radio

    ERIC Educational Resources Information Center

    Starrett, Malin J.

    2008-01-01

    The science and technology of radio receives little attention in contemporary education. This article discusses ways to explore the basic operating principles of radio. (Contains 4 figures, 3 footnotes, and 2 notes.)

  17. A Signature Style

    ERIC Educational Resources Information Center

    Smiles, Robin V.

    2005-01-01

    This article discusses Dr. Amalia Amaki and her approach to art as her signature style by turning everyday items into fine art. Amaki is an assistant professor of art, art history, and Black American studies at the University of Delaware. She loves taking unexpected an object and redefining it in the context of art--like a button, a fan, a faded…

  18. Commercial Radio as Communication.

    ERIC Educational Resources Information Center

    Rothenbuhler, Eric W.

    1996-01-01

    Compares the day-to-day work routines of commercial radio with the principles of a theoretical communication model. Illuminates peculiarities of the conduct of communication by commercial radio. Discusses the application of theoretical models to the evaluation of practicing institutions. Offers assessments of commercial radio deriving from…

  19. Extragalactic Radio Sources

    ERIC Educational Resources Information Center

    Kellerman, Kenneth I.

    1973-01-01

    Discusses new problems arising from the growing observational data through radio telescope arrays, involving the origin of radio sources, apparent superluminal velocities, conversion of radio sources to relativistic particles, and the nature of compact opaque and extended transparent sources. New physics may be needed to answer these cosmological…

  20. Internal Magnetic Field, Temperature and Density Measurements on Magnetized HED plasmas using Pulsed Polarimetry

    SciTech Connect

    Smith, Roger J.

    2016-10-20

    The goals were to collaborate with the MSX project and make the MSX platform reliable with a performance where pulsed polarimetry would be capable of adding a useful measurement and then to achieve a first measurement using pulsed polarimetry. The MSX platform (outside of laser blow off plasmas adjacent to magnetic fields which are low beta) is the only device that can generate high beta magnetized collisionless supercritical shocks, and with a large spatial size of ~10 cm. Creating shocks at high Mach numbers and investigating the dynamics of the shocks was the main goal of the project. The MSX shocks scale to astrophysical magnetized shocks and potentially throw light on the generation of highly energetic particles via a mechanism like the Fermi process.

  1. Metrology of replicated diffractive optics with Mueller polarimetry in conical diffraction.

    PubMed

    Novikova, Tatiana; De Martino, Antonello; Bulkin, Pavel; Nguyen, Quang; Drévillon, Bernard; Popov, Vladimir; Chumakov, Alexander

    2007-03-05

    The feasibility of metrological characterization of the one-dimensional (1D) holographic gratings, used in the nanoimprint molding tool fabrication step, by spectroscopic Mueller polarimetry in conical diffraction is investigated. The studied samples correspond to two different steps of the replicated diffraction grating fabrication process. We characterized master gratings that consist of patterned resist layer on chromium-covered glass substrate and complementary (replica) gratings made of nickel. The profiles of the gratings obtained by fitting the experimental spectra of Mueller matrix coefficients taken at different azimuthal angles were confirmed by atomic force microscopy (AFM) measurements. The calculated profiles of corresponding master and replica gratings are found to be complementary. We conclude that the Mueller polarimetry, as a fast and non-contact optical characterization technique, can provide the basis for the metrology of the molding tool fabrication step in the nanoimprint technique.

  2. Chiral cavity ring down polarimetry: Chirality and magnetometry measurements using signal reversals

    SciTech Connect

    Bougas, Lykourgos; Sofikitis, Dimitris; Katsoprinakis, Georgios E.; Spiliotis, Alexandros K.; Rakitzis, T. Peter; Tzallas, Paraskevas; Loppinet, Benoit

    2015-09-14

    We present the theory and experimental details for chiral-cavity-ring-down polarimetry and magnetometry, based on ring cavities supporting counterpropagating laser beams. The optical-rotation symmetry is broken by the presence of both chiral and Faraday birefringence, giving rise to signal reversals which allow rapid background subtractions. We present the measurement of the specific rotation at 800 nm of vapors of α-pinene, 2-butanol, and α-phellandrene, the measurement of optical rotation of sucrose solutions in a flow cell, the measurement of the Verdet constant of fused silica, and measurements and theoretical treatment of evanescent-wave optical rotation at a prism surface. Therefore, these signal-enhancing and signal-reversing methods open the way for ultrasensitive polarimetry measurements in gases, liquids and solids, and at surfaces.

  3. A MSE Polarimetry diagnostic for the measurement of radial electric fields on the HSX stellarator

    NASA Astrophysics Data System (ADS)

    Dobbins, T. J.; Kumar, S. T. A.; Anderson, F. S. B.; Anderson, D. T.

    2016-10-01

    The radial electric field in HSX has been measured using the Charge Exchange Recombination Spectroscopy. These impurity ion flow measurements could not resolve a large positive radial electric field (40-50 kV/m) near the core of the HSX plasma, predicted by neoclassical codes. A dual PEM (Photo Elastic Modulator) MSE polarimetry system has been designed for direct measurement of the radial electric field in the HSX plasma. The polarimetry design has been optimized to get a maximum change in polarization angle from an electric field while still providing good spatial resolution. It is expected that a radial electric field as small as 7 kV/m can be detected. The initial results of the system on an available port will be presented. The choice and design of the optics for the optimal viewing port will also be presented. This work is supported by US DOE Grant DE-FG02-93ER54222.

  4. Factors controlling the manual and automated extraction of image information using imaging polarimetry

    NASA Astrophysics Data System (ADS)

    Duggin, Michael J.

    2004-07-01

    The factors governing the extraction of useful information from polarimetric images depend upon the image acquisition and analytical methodologies being used, and upon systematic and environmental variations present during the acquisition process. The acquisition process generally occurs with foreknowledge of the analysis to be used. Broadly, interactive image analysis and automated image analysis are two different procedures: in each case, there are technical challenges. Imaging polarimetry is more complex than other imaging methodologies, and produces an increased dimensionality. However, there are several potential broad areas of interactive (manual) and automated remote sensing in which imaging polarimetry can provide useful additional information. A review is presented of the factors controlling feature discrimination, of metrics that are used, and of some proposed directions for future research.

  5. Combining polarimetry and spectropolarimetry techniques in diagnostics of cancer changes in biological tissues

    NASA Astrophysics Data System (ADS)

    Yermolenko, Sergey; Ivashko, Pavlo; Gruia, Ion; Gruia, Maria; Peresunko, Olexander; Zelinska, Natalia; Voloshynskyi, Dmytro; Fedoruk, Olexander; Zimnyakov, Dmitry; Alonova, Marina

    2015-02-01

    The aim of the study is combining polarimetry and spectropolarimetry techniques for identifying the changes of opticalgeometrical structure in different kinds of biotissues with solid tumours. It is researched that a linear dichroism appears in biotissues (human esophagus, muscle tissue of rats, human prostate tissue, cervical smear) with cancer diseases, magnitude of which depends on the type of the tissue and on the time of cancer process development.

  6. Gemini planet imager observational calibration XII: photometric calibration in the polarimetry mode

    NASA Astrophysics Data System (ADS)

    Hung, Li-Wei; Bruzzone, Sebastian; Millar-Blanchaer, Maxwell A.; Wang, Jason J.; Arriaga, Pauline; Metchev, Stanimir; Fitzgerald, Michael P.; Sivaramakrishnan, Anand; Perrin, Marshall D.

    2016-08-01

    The Gemini Planet Imager (GPI) is a high-contrast instrument specially designed for direct imaging and spectroscopy of exoplanets and debris disks. GPI can also operate as a dual-channel integral field polarimeter. The instrument primarily operates in a coronagraphic mode which poses an obstacle for traditional photometric calibrations since the majority of on-axis starlight is blocked. To enable accurate photometry relative to the occulted central star, a diffractive grid in a pupil plane is used to create a set of faint copies, named satellite spots, of the occulted star at specified locations and relative intensities in the field of view. We describe the method we developed to perform the photometric calibration of coronagraphic observations in polarimetry mode using these fiducial satellite spots. With the currently available data, we constrain the calibration uncertainty to be <13%, but the actual calibration uncertainty is likely to be lower. We develop the associated calibration scripts in the GPI Data Reduction Pipeline, which is available to the public. For testing, we use it to photometrically calibrate the HD 19467 B and β Pic b data sets taken in the H-band polarimetry mode. We measure the calibrated flux of HD 19467 B and β Pic b to be 0:078+/-0:011 mJy and 4:87+/-0:73 mJy, both agreeing with other measurements found in the literature. Finally, we explore an alternative method which performs the calibration by scaling the photometry in polarimetry mode to the photometrically calibrated response in spectroscopy mode. By comparing the reduced observations in raw units, we find that observations in polarimetry mode are 1:03 0:01 brighter than those in spectroscopy mode.

  7. ON THE COMBINATION OF IMAGING-POLARIMETRY WITH SPECTROPOLARIMETRY OF UPPER SOLAR ATMOSPHERES DURING SOLAR ECLIPSES

    SciTech Connect

    Qu, Z. Q.; Deng, L. H.; Dun, G. T.; Chang, L.; Zhang, X. Y.; Cheng, X. M.; Qu, Z. N.; Xue, Z. K.; Ma, L.; Allington-Smith, J.; Murray, G.

    2013-09-01

    We present results from imaging polarimetry (IP) of upper solar atmospheres during a total solar eclipse on 2012 November 13 and spectropolarimetry of an annular solar eclipse on 2010 January 15. This combination of techniques provides both the synoptic spatial distribution of polarization above the solar limb and spectral information on the physical mechanism producing the polarization. Using these techniques together we demonstrate that even in the transition region, the linear polarization increases with height and can exceed 20%. IP shows a relatively smooth background distribution in terms of the amplitude and direction modified by solar structures above the limb. A map of a new quantity that reflects direction departure from the background polarization supplies an effective technique to improve the contrast of this fine structure. Spectral polarimetry shows that the relative contribution to the integrated polarization over the observed passband from the spectral lines decreases with height while the contribution from the continuum increases as a general trend. We conclude that both imaging and spectral polarimetry obtained simultaneously over matched spatial and spectral domains will be fruitful for future eclipse observations.

  8. Near-infrared Circular and Linear Polarimetry of Monoceros R2

    NASA Astrophysics Data System (ADS)

    Kwon, Jungmi; Tamura, Motohide; Hough, James H.; Nagata, Tetsuya; Kusakabe, Nobuhiko

    2016-09-01

    We have conducted simultaneous JHK s -band imaging circular and linear polarimetry of the Monoceros R2 (Mon R2) cluster. We present results from deep and wide near-infrared linear polarimetry of the Mon R2 region. Prominent and extended polarized nebulosities over the Mon R2 field are revisited, and an infrared reflection nebula associated with the Mon R2 cluster and two local reflection nebulae, vdB 67 and vdB 69, is detected. We also present results from deep imaging circular polarimetry in the same region. For the first time, the observations show relatively high degrees of circular polarization (CP) in Mon R2, with as much as approximately 10% in the K s band. The maximum CP extent of a ring-like nebula around the Mon R2 cluster is approximately 0.60 pc, while that of a western nebula, around vdB 67, is approximately 0.24 pc. The extended size of the CP is larger than those seen in the Orion region around IRc2, while the maximum degree of CP of ∼10% is smaller than those of ∼17% seen in the Orion region. Nonetheless, both the CP size and degree of this region are among the largest in our infrared CP survey of star-forming regions. We have also investigated the time variability of the degree of the polarization of several infrared sources and found possible variations in three sources.

  9. Systematic comparison between line integrated densities measured with interferometry and polarimetry at JET

    SciTech Connect

    Brombin, M.; Zilli, E.; Giudicotti, L.; Boboc, A.; Collaboration: JET-EFDA Contributors

    2009-06-15

    A systematic comparison between the line integrated electron density derived from interferometry and polarimetry at JET has been carried out. For the first time the reliability of the measurements of the Cotton-Mouton effect has been analyzed for a wide range of main plasma parameters and the possibility to evaluate the electron density directly from polarimetric data has been studied. The purpose of this work is to recover the interferometric data with the density derived from the measured Cotton-Mouton effect, when the fringe jump phenomena occur. The results show that the difference between the line integrated electron density from interferometry and polarimetry is with one fringe (1.143x10{sup 19} m{sup -2}) for more than 90% of the cases. It is possible to consider polarimetry as a satisfactory alternative method to interferometry to measure the electron density and it could be used to recover interferometric signal when a fringe jumps occurs, preventing difficulties for the real-time control of many experiments at the JET machine.

  10. Hard X-ray Polarimetry With Wide Band Laue Lens Telescopes

    NASA Astrophysics Data System (ADS)

    Caroli, E.

    2011-09-01

    Polarimetry is today considered a key observational parameter which can be used to help solve important scientific issues that are still open in the hard X-ray domain (above 10 keV). Therefore the ability to perform high sensitivity polarisation measurements has become a mandatory requirement for the next generation of space telescopes operating in this energy range. In particular the development of new high energy focusing optics, such as wide band Laue lenses operating from ~60 keV up to several hundred keV, with their 50-100 times better sensitivity with respect to current instrumentation, opens a real possibility to make hard X-ray polarimetry an almost standard measurement. Hard X-ray polarimetry can be performed using highly segmented focal plane detectors operated as scattering polarimeters. In this work we summarize results obtained by our group in a series of experiments with CZT/CdTe pixel detector prototypes operating as scattering polarimeters in the range between ~100-700 keV as well as Montecarlo evaluations of the achievable performance in polarisation measurements for Laue lens telescopes using focal planes based on CdTe/CZT pixel detectors.

  11. Power spectra trends in imaging polarimetry of outdoor solar illuminated scenes

    NASA Astrophysics Data System (ADS)

    Kupinski, Meredith; Chipman, Russell

    2016-05-01

    The 1=∫2 power law (where ∫ is spatial frequency) characterizes the spatial power spectrum of non-polarimetric images of outdoor scenes when averaged over an appropriately large ensemble. This empirical result has been repeatedly verified in diverse imaging applications. In this work we compare the ensemble-averaged power spectrum of radiance and polarized radiance images. Outdoor scenes have been imaged over the past three-years using JPL's Ground-based Multiangle SpectroPolarimetric Imager (Ground-MSPI)[1] at the University of Arizona (UA). Ground-MSPI is an eight-band spectropolarimetric camera mounted on a rotating gimbal to acquire pushbroom imagery of solar illuminated outdoor landscapes. This Ground-MSPI image library offers a unique opportunity to quantify the statistical trends between polarimetric and non-polarimetric measurements. From power spectrum analysis of 1,975 images in our collection we report that the magnitude of the 1=∫-exponent is lower for the polarized radiance image than the corresponding radiance image. This result quantifies the contrast mechanism difference for imaging polarimetry, indicates higher spatial frequency content in passive polarimetry of outdoor environments, and supports the assertion that polarimetry offers unique detection capabilities.

  12. Polarimetry as a tool to find and characterise habitable planets orbiting white dwarfs

    NASA Astrophysics Data System (ADS)

    Fossati, Luca; Bagnulo, Stefano; Haswell, Carole A.; Patel, Manish R.; Busuttil, Richard; Kowalski, Piotr M.; Shukyak, Denis V.; Sterzik, Michael F.; Valyavin, Gennady

    2015-10-01

    There are several ways planets can survive the giant phase of the host star, hence one can consider the case of Earth-like planets orbiting white dwarfs. As a white dwarf cools from 6000 K to 4000 K, a planet orbiting at 0.01 AU from the star would remain in the continuous habitable zone (CHZ) for about 8 Gyr. Polarisation due to a terrestrial planet in the CHZ of a cool white dwarf (CWD) is 102 (104) times larger than it would be in the habitable zone of a typical M-dwarf (Sun-like star). Polarimetry is thus a powerful tool to detect close-in planets around white dwarfs. Multi-band polarimetry would also allow one to reveal the presence of a planet atmosphere, even providing a first characterisation. With current facilities a super-Earth-sized atmosphereless planet is detectable with polarimetry around the brightest known CWD. Planned future facilities render smaller planets detectable, in particular by increasing the instrumental sensitivity in the blue. Preliminary habitability study show also that photosynthetic processes can be sustained on Earth-like planets orbiting CWDs and that the DNA-weighted UV radiation dose for an Earth-like planet in the CHZ is less than the maxima encountered on Earth, hence white dwarfs are compatible with the persistence of complex life from the perspective of UV irradiation.

  13. Low Radio Frequency Picosatellite Missions

    NASA Astrophysics Data System (ADS)

    Jones, Dayton L.

    2014-06-01

    The dramatic advances in cubesat and other picosatellite capabilities are opening the door for scientifically important observations at low radio frequencies. Because simple antennas are effective at low frequencies, and receiver technology allows low mass and low power instruments, these observations are an ideal match for very small spacecraft. A workshop on cubesat missions for low frequency radio astronomy was held at the Kiss Institute for Space Sciences, Caltech, to explore mission concepts involving one up to hundreds of picosatellites. One result from this workshop was that there are opportunities for viable missions throughout this large range. For example, the sky-integrated spectral signature of highly redshifted neutral hydrogen from the dark ages and cosmic dawn epochs can be measured by a single antenna on a single spacecraft. There are challenging issues of calibration, foreground removal, and RF interference that need to be solved, but the basic concept is appealingly simple. At the other extreme, imaging of angular structure in the high-redshift hydrogen signal will require an interferometer array with a very large number of antennas. In this case the primary requirement is a sufficiently low individual spacecraft mass that hundreds can be launched affordably. The technical challenges for large arrays are long-term relative station keeping and high downlink data rates. Missions using several to a few tens of picosatellites can image and track bright sources such as solar and planetary radio bursts, and will provide essential validation of technologies needed for much larger arrays.This work has been carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

  14. Wake Signature Detection

    NASA Astrophysics Data System (ADS)

    Spedding, Geoffrey R.

    2014-01-01

    An accumulated body of quantitative evidence shows that bluff-body wakes in stably stratified environments have an unusual degree of coherence and organization, so characteristic geometries such as arrays of alternating-signed vortices have very long lifetimes, as measured in units of buoyancy timescales, or in the downstream distance scaled by a body length. The combination of pattern geometry and persistence renders the detection of these wakes possible in principle. It now appears that identifiable signatures can be found from many disparate sources: Islands, fish, and plankton all have been noted to generate features that can be detected by climate modelers, hopeful navigators in open oceans, or hungry predators. The various types of wakes are reviewed with notes on why their signatures are important and to whom. A general theory of wake pattern formation is lacking and would have to span many orders of magnitude in Reynolds number.

  15. SMAWT Signature Test

    DTIC Science & Technology

    1974-10-01

    were generally inversely proportional to the size assesments of the flash and smoke . Table 26 shows the percent of change in average judgments of...Average Time of Gunner’s View Obscuration by Smoke During Firings From the Wood Line .. .. ..... ..... ...... ..... .. 18 7. Average Obscuration Times...of Gunner’s View Obscuration by Smoke - Grass Line 19 8. Normalized Comparisons of the Relative Grades Assigned to Systems Signature Components

  16. Polarimetry of Solar System Objects: Observations vs. Models

    NASA Astrophysics Data System (ADS)

    Yanamandra-Fisher, P. A.

    2014-04-01

    The overarching goals for the remote sensing and robotic exploration of planetary systems are: (1) understanding the formation of planetary systems and their diversity; and (2) search for habitability. Since all objects have unique polarimetric signatures inclusion of spectrophotopolarimetry as a complementary approach to standard techniques of imaging and spectroscopy, provides insight into the scattering properties of the planetary media. Specifically, linear and circular polarimetric signatures of the object arise from different physical processes and their study proves essential to the characterization of the object. Linear polarization of reflected light by various solar system objects provides insight into the scattering characteristics of atmospheric aerosols and hazes? and surficial properties of atmosphereless bodies. Many optically active materials are anisotropic and so their scattering properties differ with the object's principal axes (such as dichroic or birefringent materials) and are crystalline in structure instead of amorphous, (eg., the presence of olivines and silicates in cometary dust and circumstellar disks? Titan, etc.). Ices (water and other species) are abundant in the system indicated in their near - infrared spectra. Gas giants form outside the frost line (where ices condense), and their satellites and ring systems exhibit signature of water ice? clathrates, nonices (Si, C, Fe) in their NIR spectra and spectral dependence of linear polarization. Additionally, spectral dependence of polarization is important to separate the macroscopic (bulk) properties of the scattering medium from the microscopic (particulate) properties of the scattering medium. Circular polarization, on the other hand, is indicative of magnetic fields and biologically active molecules, necessary for habitability. These applications suffer from lack of detailed observations, instrumentation, dedicated missions and numericalretrieval methods. With recent discoveries and

  17. Polarimetry of optically selected BL Lacertae candidates from the SDSS

    NASA Astrophysics Data System (ADS)

    Heidt, J.; Nilsson, K.

    2011-05-01

    We present and discuss polarimetric observations of 182 targets drawn from an optically selected sample of 240 probable BL Lac candidates out of the SDSS compiled by Collinge et al. (2005, AJ, 129, 2542). In contrast to most other BL Lac candidate samples extracted from the SDSS, its radio- and/or X-ray properties have not been taken into account for its derivation. Thus, because its selection is based on optical properties alone, it may be less prone to selection effects inherent in other samples derived at different frequencies, so it offers a unique opportunity to extract the first unbiased BL Lac luminosity function that is suitably large in size. We found 124 out of 182 targets (68%) to be polarized, 95 of the polarized targets (77%) to be highly polarized (>4%). The low-frequency peaked BL Lac candidates in the sample are on average only slightly more polarized than the high-frequency peaked ones. Compared to earlier studies, we found a high duty cycle in high polarization (˜ 66+2-14% to be >4% polarized) in high-frequency peaked BL Lac candidates. This may come from our polarization analysis, which minimizes the contamination by host galaxy light. No evidence of radio-quiet BL Lac objects in the sample was found. Our observations show that the probable sample of BL Lac candidates of Collinge et al. (2005) indeed contains a large number of bona fide BL Lac objects. High S/N spectroscopy and deep X-ray observations are required to construct the first luminosity function of optically selected BL Lac objects and to test more stringently for any radio-quiet BL Lac objects in the sample. Based on observations collected with the NTT on La Silla (Chile) operated by the European Southern Observatory in the course of the observing proposal 082.B-0133.Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA), operated jointly by the Max-Planck-Institut für Astronomie and the Instituto de Astrofisica de Andalucia (CSIC).Based on observations

  18. Knowledge Signatures for Information Integration

    SciTech Connect

    Thomson, Judi; Cowell, Andrew J.; Paulson, Patrick R.; Butner, R. Scott; Whiting, Mark A.

    2003-10-25

    This paper introduces the notion of a knowledge signature: a concise, ontologically-driven representation of the semantic characteristics of data. Knowledge signatures provide programmatic access to data semantics while allowing comparisons to be made across different types of data such as text, images or video, enabling efficient, automated information integration. Through observation, which determines the degree of association between data and ontological concepts, and refinement, which uses the axioms and structure of the domain ontology to place the signature more accurately within the context of the domain, knowledge signatures can be created. A comparison of such signatures for two different pieces of data results in a measure of their semantic separation. This paper discusses the definition of knowledge signatures along with the design and prototype implementation of a knowledge signature generator.

  19. POLARIMETRY WITH THE GEMINI PLANET IMAGER: METHODS, PERFORMANCE AT FIRST LIGHT, AND THE CIRCUMSTELLAR RING AROUND HR 4796A

    SciTech Connect

    Perrin, Marshall D.; Duchene, Gaspard; Graham, James R.; Kalas, Paul G.; Millar-Blanchaer, Max; Fitzgerald, Michael P.; Chilcote, Jeffrey; Wiktorowicz, Sloane J.; Dillon, Daren; Gavel, Donald; Macintosh, Bruce; Bauman, Brian; Cardwell, Andrew; Goodsell, Stephen; Hartung, Markus; Hibon, Pascale; De Rosa, Robert J.; Doyon, René; Dunn, Jennifer; Erikson, Darren; and others

    2015-02-01

    We present the first results from the polarimetry mode of the Gemini Planet Imager (GPI), which uses a new integral field polarimetry architecture to provide high contrast linear polarimetry with minimal systematic biases between the orthogonal polarizations. We describe the design, data reduction methods, and performance of polarimetry with GPI. Point-spread function (PSF) subtraction via differential polarimetry suppresses unpolarized starlight by a factor of over 100, and provides sensitivity to circumstellar dust reaching the photon noise limit for these observations. In the case of the circumstellar disk around HR 4796A, GPI's advanced adaptive optics system reveals the disk clearly even prior to PSF subtraction. In polarized light, the disk is seen all the way in to its semi-minor axis for the first time. The disk exhibits surprisingly strong asymmetry in polarized intensity, with the west side ≳ 9 times brighter than the east side despite the fact that the east side is slightly brighter in total intensity. Based on a synthesis of the total and polarized intensities, we now believe that the west side is closer to us, contrary to most prior interpretations. Forward scattering by relatively large silicate dust particles leads to the strong polarized intensity on the west side, and the ring must be slightly optically thick in order to explain the lower brightness in total intensity there. These findings suggest that the ring is geometrically narrow and dynamically cold, perhaps shepherded by larger bodies in the same manner as Saturn's F ring.

  20. Polarimetry with the Gemini Planet Imager: methods, performance at first light, and the circumstellar ring around HR 4796A

    SciTech Connect

    Perrin, Marshall D.; Duchene, Gaspard; Millar-Blanchaer, Max; Fitzgerald, Michael P.; Graham, James R.; Wiktorowicz, Sloane J.; Kalas, Paul G.; Macintosh, Bruce; Bauman, Brian; Cardwell, Andrew; Chilcote, Jeffrey; De Rosa, Robert J.; Dillon, Daren; Doyon, René; Dunn, Jennifer; Erikson, Darren; Gavel, Donald; Goodsell, Stephen; Hartung, Markus; Hibon, Pascale; Ingraham, Patrick; Kerley, Daniel; Konapacky, Quinn; Larkin, James E.; Maire, Jérôme; Marchis, Franck; Marois, Christian; Mittal, Tushar; Morzinski, Katie M.; Oppenheimer, B. R.; Palmer, David W.; Patience, Jennifer; Poyneer, Lisa; Pueyo, Laurent; Rantakyrö, Fredrik T.; Sadakuni, Naru; Saddlemyer, Leslie; Savransky, Dmitry; Soummer, Rémi; Sivaramakrishnan, Anand; Song, Inseok; Thomas, Sandrine; Wallace, J. Kent; Wang, Jason J.; Wolff, Schuyler G.

    2015-01-28

    We present the first results from the polarimetry mode of the Gemini Planet Imager (GPI), which uses a new integral field polarimetry architecture to provide high contrast linear polarimetry with minimal systematic biases between the orthogonal polarizations. We describe the design, data reduction methods, and performance of polarimetry with GPI. Point spread function subtraction via di erential polarimetry suppresses unpolarized starlight by a factor of over 100, and provides sensitivity to circumstellar dust reaching the photon noise limit for these observations. In the case of the circumstellar disk around HR 4796A, GPI's advanced adaptive optics system reveals the disk clearly even prior to PSF subtraction. In polarized light, the disk is seen all the way in to its semi-minor axis for the first time. The disk exhibits surprisingly strong asymmetry in polarized intensity, with the west side ≳ 9 times brighter than the east side despite the fact that the east side is slightly brighter in total intensity. Based on a synthesis of the total and polarized intensities, we now believe that the west side is closer to us, contrary to most prior interpretations. Forward scattering by relatively large silicate dust particles leads to the strong polarized intensity on the west side, and the ring must be slightly optically thick in order to explain the lower brightness in total intensity there. These findings suggest that the ring is geometrically narrow and dynamically cold, perhaps shepherded by larger bodies in the same manner as Saturn's F ring.

  1. Polarimetry with the Gemini Planet Imager. Methods, performance at first light, and the circumstellar ring around HR 4796A

    SciTech Connect

    Perrin, Marshall D.; Duchene, Gaspard; Millar-Blanchaer, Max; Fitzgerald, Michael P.; Graham, James R.; Wiktorowicz, Sloane J.; Kalas, Paul G.; Macintosh, Bruce; Bauman, Brian; Cardwell, Andrew; Chilcote, Jeffrey; De Rosa, Robert J.; Dillon, Daren; Doyon, René; Dunn, Jennifer; Erikson, Darren; Gavel, Donald; Goodsell, Stephen; Hartung, Markus; Hibon, Pascale; Ingraham, Patrick; Kerley, Daniel; Konapacky, Quinn; Larkin, James E.; Maire, Jérôme; Marchis, Franck; Marois, Christian; Mittal, Tushar; Morzinski, Katie M.; Oppenheimer, B. R.; Palmer, David W.; Patience, Jennifer; Poyneer, Lisa; Pueyo, Laurent; Rantakyrö, Fredrik T.; Sadakuni, Naru; Saddlemyer, Leslie; Savransky, Dmitry; Soummer, Rémi; Sivaramakrishnan, Anand; Song, Inseok; Thomas, Sandrine; Wallace, J. Kent; Wang, Jason J.; Wolff, Schuyler G.

    2015-01-28

    We report he first results from the polarimetry mode of the Gemini Planet Imager (GPI), which uses a new integral field polarimetry architecture to provide high contrast linear polarimetry with minimal systematic biases between the orthogonal polarizations. We describe the design, data reduction methods, and performance of polarimetry with GPI. Point-spread function (PSF) subtraction via differential polarimetry suppresses unpolarized starlight by a factor of over 100, and provides sensitivity to circumstellar dust reaching the photon noise limit for these observations. In the case of the circumstellar disk around HR 4796A, GPI’s advanced adaptive optics system reveals the disk clearly even prior to PSF subtraction. In polarized light, the disk is seen all the way in to its semi-minor axis for the first time. The disk exhibits surprisingly strong asymmetry in polarized intensity, with the west side ≳9 times brighter than the east side despite the fact that the east side is slightly brighter in total intensity. Based on a synthesis of the total and polarized intensities, we now believe that the west side is closer to us, contrary to most prior interpretations. Forward scattering by relatively large silicate dust particles leads to the strong polarized intensity on the west side, and the ring must be slightly optically thick in order to explain the lower brightness in total intensity there. In conclusion, these findings suggest that the ring is geometrically narrow and dynamically cold, perhaps shepherded by larger bodies in the same manner as Saturn’s F ring.

  2. Polarimetry with the Gemini Planet Imager: Methods, Performance at First Light, and the Circumstellar Ring around HR 4796A

    NASA Astrophysics Data System (ADS)

    Perrin, Marshall D.; Duchene, Gaspard; Millar-Blanchaer, Max; Fitzgerald, Michael P.; Graham, James R.; Wiktorowicz, Sloane J.; Kalas, Paul G.; Macintosh, Bruce; Bauman, Brian; Cardwell, Andrew; Chilcote, Jeffrey; De Rosa, Robert J.; Dillon, Daren; Doyon, René; Dunn, Jennifer; Erikson, Darren; Gavel, Donald; Goodsell, Stephen; Hartung, Markus; Hibon, Pascale; Ingraham, Patrick; Kerley, Daniel; Konapacky, Quinn; Larkin, James E.; Maire, Jérôme; Marchis, Franck; Marois, Christian; Mittal, Tushar; Morzinski, Katie M.; Oppenheimer, B. R.; Palmer, David W.; Patience, Jennifer; Poyneer, Lisa; Pueyo, Laurent; Rantakyrö, Fredrik T.; Sadakuni, Naru; Saddlemyer, Leslie; Savransky, Dmitry; Soummer, Rémi; Sivaramakrishnan, Anand; Song, Inseok; Thomas, Sandrine; Wallace, J. Kent; Wang, Jason J.; Wolff, Schuyler G.

    2015-02-01

    We present the first results from the polarimetry mode of the Gemini Planet Imager (GPI), which uses a new integral field polarimetry architecture to provide high contrast linear polarimetry with minimal systematic biases between the orthogonal polarizations. We describe the design, data reduction methods, and performance of polarimetry with GPI. Point-spread function (PSF) subtraction via differential polarimetry suppresses unpolarized starlight by a factor of over 100, and provides sensitivity to circumstellar dust reaching the photon noise limit for these observations. In the case of the circumstellar disk around HR 4796A, GPI's advanced adaptive optics system reveals the disk clearly even prior to PSF subtraction. In polarized light, the disk is seen all the way in to its semi-minor axis for the first time. The disk exhibits surprisingly strong asymmetry in polarized intensity, with the west side >~ 9 times brighter than the east side despite the fact that the east side is slightly brighter in total intensity. Based on a synthesis of the total and polarized intensities, we now believe that the west side is closer to us, contrary to most prior interpretations. Forward scattering by relatively large silicate dust particles leads to the strong polarized intensity on the west side, and the ring must be slightly optically thick in order to explain the lower brightness in total intensity there. These findings suggest that the ring is geometrically narrow and dynamically cold, perhaps shepherded by larger bodies in the same manner as Saturn's F ring.

  3. Cyclostationary approaches for spatial RFI mitigation in radio astronomy

    NASA Astrophysics Data System (ADS)

    Hellbourg, Grégory; Weber, Rodolphe; Capdessus, Cécile; Boonstra, Albert-Jan

    2012-01-01

    Radio astronomical observations are increasingly corrupted by radio frequency interferences (RFIs), and real time filtering algorithms are becoming essential. In this article, it is shown how spatial processing techniques can limit the impact of the incoming RFIs for phased array radio telescopes. The proposed approaches are based on estimation of the RFI spatial signature. It requires the diagonalization of either the classic correlation matrix or the cyclic correlation matrix of the array. Different diagonalization techniques are compared. Then, RFI detection and RFI filtering techniques are illustrated through simulations on data acquired with the Low Frequency Array Radio telescope, LOFAR. The originality of the study is the use of the cyclostationarity property, in order to improve the spatial separation between cosmic sources and RFIs.

  4. Radio frequency interference mitigation using deep convolutional neural networks

    NASA Astrophysics Data System (ADS)

    Akeret, J.; Chang, C.; Lucchi, A.; Refregier, A.

    2017-01-01

    We propose a novel approach for mitigating radio frequency interference (RFI) signals in radio data using the latest advances in deep learning. We employ a special type of Convolutional Neural Network, the U-Net, that enables the classification of clean signal and RFI signatures in 2D time-ordered data acquired from a radio telescope. We train and assess the performance of this network using the HIDE &SEEK radio data simulation and processing packages, as well as early Science Verification data acquired with the 7m single-dish telescope at the Bleien Observatory. We find that our U-Net implementation is showing competitive accuracy to classical RFI mitigation algorithms such as SEEK's SUMTHRESHOLD implementation. We publish our U-Net software package on GitHub under GPLv3 license.

  5. Dominion Radio Astrophysical Observatory

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    The Dominion Radio Astrophysical Observatory began operating in 1959, and joined the NATIONAL RESEARCH COUNCIL in 1970. It became part of the Herzberg Institute of Astrophysics in 1975. The site near Penticton, BC has a 26 m radio telescope, a seven-antenna synthesis telescope on a 600 m baseline and two telescopes dedicated to monitoring the solar radio flux at 10.7 cm. This part of the Institu...

  6. Radio determination satellite service

    NASA Astrophysics Data System (ADS)

    Briskman, Robert D.

    1990-07-01

    The capabilities and measured performance of a geosynchronous satellite-based service called the radio determination satellite service (RDSS), which operates at radio frequencies allocated by the International Telecommunications Union (ITU) and is licensed in the United States by the Federal Communications Commission (FCC), are discussed. Plans for both improvement in capability and expansion to nearly global coverage are described. Since RDSS can also provide radio navigation, some comparisons of this service with the Global Positioning System (GPS) are made.

  7. Signatures of nonthermal melting

    PubMed Central

    Zier, Tobias; Zijlstra, Eeuwe S.; Kalitsov, Alan; Theodonis, Ioannis; Garcia, Martin E.

    2015-01-01

    Intense ultrashort laser pulses can melt crystals in less than a picosecond but, in spite of over thirty years of active research, for many materials it is not known to what extent thermal and nonthermal microscopic processes cause this ultrafast phenomenon. Here, we perform ab-initio molecular-dynamics simulations of silicon on a laser-excited potential-energy surface, exclusively revealing nonthermal signatures of laser-induced melting. From our simulated atomic trajectories, we compute the decay of five structure factors and the time-dependent structure function. We demonstrate how these quantities provide criteria to distinguish predominantly nonthermal from thermal melting. PMID:26798822

  8. Signature CERN-URSS

    SciTech Connect

    2006-01-24

    Le DG W.Jentschke souhaite la bienvenue à l'assemblée et aux invités pour la signature du protocole entre le Cern et l'URSS qui est un événement important. C'est en 1955 que 55 visiteurs soviétiques ont visité le Cern pour la première fois. Le premier DG au Cern, F.Bloch, et Mons.Amaldi sont aussi présents. Tandis que le discours anglais de W.Jentschke est traduit en russe, le discours russe de Mons.Morozov est traduit en anglais.

  9. Radio data transmission for SCADA

    SciTech Connect

    Frasier, W.E. )

    1989-09-01

    Enron has used such wireless systems as meteor burst radio, 952 MHz multiple address radio, VSAT and L-band satellite, cellular radio and ACSB radio. The company's experience with meteor burst radio communications is discussed in this paper. It indicates good system reliability and consequently all back-up telephone lines have been removed from sites using this system.

  10. Development of a tunable filter for coronal polarimetry

    NASA Astrophysics Data System (ADS)

    Tomczyk, S.; Mathew, S. K.; Gallagher, D.

    2016-07-01

    Measuring magnetic fields in the solar corona is crucial to understanding and predicting the Sun's generation of space weather that affects communications, GPS systems, space flight, and power transmission. The Coronal Solar Magnetism Observatory Large Coronagraph (COSMO LC) is a proposed 1.5 m aperture coronagraph designed to synoptically observe magnetic fields and plasma properties in the large-scale corona to improve our understanding of solar processes that cause space weather. The LC will observe coronal emission lines over the wavelength range from 500 to 1100 nm with a field of view of 1° and a spatial resolution of 2 arcsec. A spectral resolution greater than 8000 over the wavelength range is needed to resolve the polarization signatures of magnetic fields in the emission line profiles. The aperture and field of view of the LC set an étendue requirement of 1.39 m2 deg2 for the postfocus instrumentation. We find that a tunable wide-field birefringent filter using Lithium Niobate crystals can meet the étendue and spectral resolution requirements for the LC spectrometer. We have tested a number of commercially available crystals and verify that crystals of the required size and birefringence uniformity are available. We also evaluate electro-optical tuning of a Lithium Niobate birefringent filter by the application of high voltage. This tunable filter represents a key enabling technology for the COSMO LC.

  11. Magnetism Matters: Coronal Magnetometry Using Multi-Wavelength Polarimetry

    NASA Astrophysics Data System (ADS)

    Gibson, Sarah E.

    2015-08-01

    The solar coronal magnetic field is key both to solving fundamental problems in solar physics such as coronal heating and solar wind acceleration, and to predicting the internal magnetic structure and thus space-weather impact of coronal mass ejections. I will describe the current state of the art in coronal magnetometry, and present results from the Coronal Multichannel Polarimeter (CoMP) at Mauna Loa Solar Observatory (MLSO), which since 2011 has taken polarimetric observations of the solar corona in the near-infrared on a near-daily basis. I will discuss work in progress that utilizes forward modeling to synthesize polarimetric data at multiple heights and vantage points, and at wavelengths from radio to infrared to visible to ultraviolet. The goal is to use such synthetic testbeds to determine the ideal set of observations for constraining the coronal magnetic field, and to establish a Data-Optimized Coronal Field Model (DOC-FM) that efficiently incorporates these data into global magnetic models. This work will provide essential tools and motivation for the planning and implementation of future coronal polarimetric projects and missions spanning a broad range of wavelengths.

  12. Advanced spectral signature discrimination algorithm

    NASA Astrophysics Data System (ADS)

    Chakravarty, Sumit; Cao, Wenjie; Samat, Alim

    2013-05-01

    This paper presents a novel approach to the task of hyperspectral signature analysis. Hyperspectral signature analysis has been studied a lot in literature and there has been a lot of different algorithms developed which endeavors to discriminate between hyperspectral signatures. There are many approaches for performing the task of hyperspectral signature analysis. Binary coding approaches like SPAM and SFBC use basic statistical thresholding operations to binarize a signature which are then compared using Hamming distance. This framework has been extended to techniques like SDFC wherein a set of primate structures are used to characterize local variations in a signature together with the overall statistical measures like mean. As we see such structures harness only local variations and do not exploit any covariation of spectrally distinct parts of the signature. The approach of this research is to harvest such information by the use of a technique similar to circular convolution. In the approach we consider the signature as cyclic by appending the two ends of it. We then create two copies of the spectral signature. These three signatures can be placed next to each other like the rotating discs of a combination lock. We then find local structures at different circular shifts between the three cyclic spectral signatures. Texture features like in SDFC can be used to study the local structural variation for each circular shift. We can then create different measure by creating histogram from the shifts and thereafter using different techniques for information extraction from the histograms. Depending on the technique used different variant of the proposed algorithm are obtained. Experiments using the proposed technique show the viability of the proposed methods and their performances as compared to current binary signature coding techniques.

  13. Multimodal signature modeling of humans

    NASA Astrophysics Data System (ADS)

    Cathcart, J. Michael; Kocher, Brian; Prussing, Keith; Lane, Sarah; Thomas, Alan

    2010-04-01

    Georgia Tech been investigating method for the detection of covert personnel in traditionally difficult environments (e.g., urban, caves). This program focuses on a detailed phenomenological analysis of human physiology and signatures with the subsequent identification and characterization of potential observables. Both aspects are needed to support the development of personnel detection and tracking algorithms. The difficult nature of these personnel-related problems dictates a multimodal sensing approach. Human signature data of sufficient and accurate quality and quantity do not exist, thus the development of an accurate signature model for a human is needed. This model should also simulate various human activities to allow motion-based observables to be exploited. This paper will describe a multimodal signature modeling approach that incorporates human physiological aspects, thermoregulation, and dynamics into the signature calculation. This approach permits both passive and active signatures to be modeled. The focus of the current effort involved the computation of signatures in urban environments. This paper will discuss the development of a human motion model for use in simulating both electro-optical signatures and radar-based signatures. Video sequences of humans in a simulated urban environment will also be presented; results using these sequences for personnel tracking will be presented.

  14. Search for High Rotation Measures in Extragalactic Radio Sources I. Multi-Channel Observations at 10 GHz

    NASA Astrophysics Data System (ADS)

    Inoue, M.; Tabara, H.; Kato, T.; Aizu, K.

    1995-12-01

    Multi-channel polarimetry has been performed to detect high rotation measure (RM) at 3 cm using the Nobeyama 45-m telescope. The high RM candidates of 96 radio sources were selected to be observed, and RMs of 35 sources were derived from the observations. Since the four channels are set contiguously from 2.84 cm to 3.31 cm, |RM| can be derived uniquely up to 15000 rad m(-2) by this polarimeter. We found that there exist sources with RM of several thousands rad m(-2) . In fact, 5 sources have |RM| > 1000 rad m(-2) . On the other hand, all sources observed are well within this system limits, and therefore we suggest the observed upper limit of |RM| is around 5000 rad m(-2) for extragalactic radio sources, even taken into account the redshift of sources.

  15. Determination of D-lactide content in lactide stereoisomeric mixture using gas chromatography-polarimetry.

    PubMed

    Feng, Lidong; Bian, Xinchao; Chen, Zhiming; Xiang, Sheng; Liu, Yanlong; Sun, Bin; Li, Gao; Chen, Xuesi

    2017-03-01

    An analytical method has been proposed to quantify the D-lactide content in a lactide stereoisomeric mixture using combined gas chromatography and polarimetry (GC- polarimetry). As for a lactide stereoisomeric mixture, meso-lactide can be determined quantitatively using GC, but D- and L-lactides cannot be separated by the given GC system. The composition of a lactide stereoisomeric mixture is directly relative to its specific optical rotation. The specific optical rotations of neat L-lactide were obtained in different solutions, which were -266.3° and -298.8° in dichloromethane (DCM) and toluene solutions at 20°C, respectively. Therefore, for a lactide sample, the D-lactide content could be calculated based on the meso-lactide content obtained from GC and the specific optical rotations of the sample and neat L-lactide obtained from polarimetry. The effects of impurities and temperature on the test results were investigated, respectively. When the total content of impurities was not more than 1.0%, the absolute error for determining D-lactide content was less than 0.10% in DCM and toluene solutions. When the D-lactide content was calculated according to the specific optical rotation of neat L-lactide at 20°C, the absolute error caused by the variation in temperature of 20±15°C was not more than 0.2 and 0.7% in DCM and toluene solutions, respectively, and thus usually could be ignored in a DCM solution. When toluene was used as a solvent for the determination of D-lactide content, a temperature correction for specific optical rotations could be introduced and would ensure the accuracy of results. This method is applicable to the determination of D-lactide content in lactide stereoisomeric mixtures. The standard deviation (STDEV) of the measurements is less than 0.5%, indicating that the precision is suitable for this method.

  16. Stabilized radio frequency quadrupole

    DOEpatents

    Lancaster, Henry D.; Fugitt, Jock A.; Howard, Donald R.

    1984-01-01

    A long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator.

  17. Stabilized radio frequency quadrupole

    DOEpatents

    Lancaster, H.D.; Fugitt, J.A.; Howard, D.R.

    1984-12-25

    Disclosed is a long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator. 5 figs.

  18. Amateur Radio Satellite Communications.

    ERIC Educational Resources Information Center

    Koch, David P.

    The Amateur Radio Satellite Communications project had, as its goal, the assembly of an amateur radio satellite station in a high school physics classroom. Specific objectives were to provide: (1) a special source of interest as a motivator for attracting students and building public relations; (2) a center of interest as a motivator for the study…

  19. Planetary foreshock radio emissions

    NASA Astrophysics Data System (ADS)

    Kuncic, Zdenka; Cairns, Iver H.

    2005-07-01

    The electron foreshock regions upstream of Earth's bow shock and upstream of traveling interplanetary shocks are known to be propitious sites for a variety of energetic particle and plasma wave phenomena, including radio emissions. A quantitative theoretical model has been developed for radio emissions associated with the terrestrial foreshock and for type II radio bursts associated with interplanetary shocks. Here, we generalize this model and apply it to other planetary foreshocks. We present predictions for the levels of planetary foreshock radio emissions and compare these with observations by past and present space missions. One key result is that Mercury can be a strong source of foreshock radio emissions, and this prediction may be testable with the anticipated BepiColombo space mission. Although the terrestrial foreshock radio emissions are the most detectable with existing instruments, our results predict that they are the second strongest in absolute terms, following the Jovian foreshock emissions. Indeed, we predict that the radio instrument on board Ulysses should have detected Jovian foreshock radio emissions, and we suggest that there is some evidence in the data to support this. We also suggest that Cassini was potentially capable of detecting foreshock emissions from Venus during its gravity-assist flybys and may possibly be capable of detecting foreshock emissions from Saturn under favorable solar wind conditions.

  20. Radio Astronomy for Amateurs

    NASA Astrophysics Data System (ADS)

    Quinn, N.; Murdin, P.

    2003-04-01

    Karl Jansky is considered the father of RADIOASTRONOMY. During the 1930s, Jansky worked for the Bell Telephone Laboratories studying the origin of static noise from thunderstorms. During the course of this work he discovered that some signals had an extraterrestrial origin. However, it was Grote Reber, a professional radio engineer and radio amateur, who carried out further investigations. In 1937...

  1. The Radio Jove Project

    NASA Technical Reports Server (NTRS)

    Thieman, J. R.

    2010-01-01

    The Radio love Project is a hands-on education and outreach project in which students, or any other interested individuals or groups build a radio telescope from a kit, operate the radio telescope, transmit the resulting signals through the internet if desired, analyze the results, and share the results with others through archives or general discussions among the observers. Radio love is intended to provide an introduction to radio astronomy for the observer. The equipment allows the user to observe radio signals from Jupiter, the Sun, the galaxy, and Earth-based radiation both natural and man-made. The project was started through a NASA Director's Discretionary Fund grant more than ten years ago. it has continued to be carried out through the dedicated efforts of a group of mainly volunteers. Dearly 1500 kits have been distributed throughout the world. Participation can also be done without building a kit. Pre-built kits are available. Users can also monitor remote radio telescopes through the internet using free downloadable software available through the radiosky.com website. There have been many stories of prize-winning projects, inspirational results, collaborative efforts, etc. We continue to build the community of observers and are always open to new thoughts about how to inspire the observers to still greater involvement in the science and technology associated with Radio Jove.

  2. Writing for Radio.

    ERIC Educational Resources Information Center

    Tupper, Marianna S.

    1995-01-01

    Describes a 24-hour commercial radio station simulation class project for eighth-grade language arts. Students wrote their own scripts, chose music and were disc jockeys on their own music and talk shows, and prepared news and traffic reports. Guest speakers from actual commercial radio came in to discuss issues such as advertising, censorship,…

  3. Film, Radio, and Television.

    ERIC Educational Resources Information Center

    Hardesty, Carolyn, Ed.

    1990-01-01

    This journal issue covers the history of film, radio, and television in Iowa. The first article, "When Pictures and Sound Came to Iowa," summarizes the origin of movies and radio and their early beginnings in Iowa. Using old photographs and measurement charts, the viewing, reading, and listening habits of young people in 1950 and 1958…

  4. The MESA polarimetry chain and the status of its double scattering polarimeter

    NASA Astrophysics Data System (ADS)

    Aulenbacher, K.; Bartolomé, P. Aguar; Molitor, M.; Tioukine, V.

    2013-11-01

    We plan to have two independent polarimetry systems at MESA based on totally different physical processes. A first one tries to minimize the systematic uncertainties in double polarized Mo/ller scattering, which is to be achieved by stored hydrogen atoms in an atomic trap (Hydro-Mo/ller-Polarimeter). The other one relies on the equality of polarizing and analyzing power which allows to measure the effective analyzing power of a polarimeter with very high accuracy. Since the status of Hydro-Mo/ller is presented in a separate paper we concentrate on the double scattering polarimeter in this article.

  5. Terahertz spectroscopic polarimetry of generalized anisotropic media composed of Archimedean spiral arrays: Experiments and simulations

    NASA Astrophysics Data System (ADS)

    Aschaffenburg, Daniel J.; Williams, Michael R. C.; Schmuttenmaer, Charles A.

    2016-05-01

    Terahertz time-domain spectroscopic polarimetry has been used to measure the polarization state of all spectral components in a broadband THz pulse upon transmission through generalized anisotropic media consisting of two-dimensional arrays of lithographically defined Archimedean spirals. The technique allows a full determination of the frequency-dependent, complex-valued transmission matrix and eigenpolarizations of the spiral arrays. Measurements were made on a series of spiral array orientations. The frequency-dependent transmission matrix elements as well as the eigenpolarizations were determined, and the eigenpolarizations were found be to elliptically corotating, as expected from their symmetry. Numerical simulations are in quantitative agreement with measured spectra.

  6. Lunar studies. [involving polarimetry and a microfiche data base for lunar photographs

    NASA Technical Reports Server (NTRS)

    Ingersoll, A. P.

    1974-01-01

    Two research projects to classify lunar photographic images are reported. The feasibility of using polarimetry to study large scale features on the moon was investigated. A system was built that measured polarization by subtracting two film images taken through perpendicular Polaroid filters, however, no new boundaries were discovered in the pictures which are not already discernable in ordinary photographs. The present status and equipment of a microfiche library system which would allow easy access to selected lunar photographs from all space missions is also reported.

  7. The MESA polarimetry chain and the status of its double scattering polarimeter

    SciTech Connect

    Aulenbacher, K.; Bartolomé, P. Aguar; Molitor, M.; Tioukine, V.

    2013-11-07

    We plan to have two independent polarimetry systems at MESA based on totally different physical processes. A first one tries to minimize the systematic uncertainties in double polarized Mo/ller scattering, which is to be achieved by stored hydrogen atoms in an atomic trap (Hydro-Mo/ller-Polarimeter). The other one relies on the equality of polarizing and analyzing power which allows to measure the effective analyzing power of a polarimeter with very high accuracy. Since the status of Hydro-Mo/ller is presented in a separate paper we concentrate on the double scattering polarimeter in this article.

  8. Prospects for x-ray polarimetry measurements of magnetic fields in magnetized liner inertial fusion plasmas

    SciTech Connect

    Lynn, Alan G. Gilmore, Mark

    2014-11-15

    Magnetized Liner Inertial Fusion (MagLIF) experiments, where a metal liner is imploded to compress a magnetized seed plasma may generate peak magnetic fields ∼10{sup 4} T (100 Megagauss) over small volumes (∼10{sup −10}m{sup 3}) at high plasma densities (∼10{sup 28}m{sup −3}) on 100 ns time scales. Such conditions are extremely challenging to diagnose. We discuss the possibility of, and issues involved in, using polarimetry techniques at x-ray wavelengths to measure magnetic fields under these extreme conditions.

  9. Outer planet Grand Tour missions photometry/polarimetry experiment critical components study

    NASA Technical Reports Server (NTRS)

    Pellicori, S. F.; Russell, E. E.; Watts, L. A.

    1972-01-01

    Work performed during this effort was limited to two primary areas of technical concern: optical design optimization, and sensor selection. An optical system concept was established, and various system components were evaluated through experimental test sequences. Photodetectors were investigated for the applicability in meeting OPGT requirements as constrained by the photometry/polarimetry team directives. The most promising (gallium arsenide PMT) was further experimentally tested to ascertain its behavior with respect to anticipated environmental conditions. Results of testing and summary of the preceding tradeoff study effort are presented.

  10. Imaging polarimetry and retinal blood vessel quantification at the epiretinal membrane

    NASA Astrophysics Data System (ADS)

    Miura, Masahiro; Elsner, Ann E.; Cheney, Michael C.; Usui, Masahiko; Iwasaki, Takuya

    2007-05-01

    We evaluated a polarimetry method to enhance retinal blood vessels masked by the epiretinal membrane. Depolarized light images were computed by removing the polarization retaining light reaching the instrument and were compared with parallel polarized light images, average reflectance images, and the corresponding images at 514 nm. Contrasts were computed for retinal vessel profiles for arteries and veins. Contrasts were higher in the 514 nm images in normal eyes but higher in the depolarized light image in the eyes with epiretinal membranes. Depolarized light images were useful for examining the retinal vasculature in the presence of retinal disease.

  11. Kramers-Kronig relations in modulation polarimetry diagnostics of glass-ceramics

    NASA Astrophysics Data System (ADS)

    Dudar, B. V.; Matyash, I. E.; Minailova, I. A.; Mishchuk, O. N.; Serdega, B. K.

    2016-10-01

    It has been found that, in an aluminosilicate glass-ceramic sample cut from a massive ingot, there is a correlation of the residual stress with the temperature gradient. The magnitude and coordinate dependence of the stress along the temperature gradient have been determined from the stress-induced linear birefringence measured by the modulation polarimetry technique. Its functional relationship has been established in the form of the Poisson equation with the heterogeneity of the composition due to the preparation conditions. It has been shown that, in the absence of a temperature gradient, the birefringence and dichroism related by the Kramers-Kronig relation play the role of thermodynamic variables.

  12. Radio efficiency of pulsars

    SciTech Connect

    Szary, Andrzej; Melikidze, George I.; Gil, Janusz; Zhang, Bing; Xu, Ren-Xin E-mail: zhang@physics.unlv.edu

    2014-03-20

    We investigate radio emission efficiency, ξ, of pulsars and report a near-linear inverse correlation between ξ and the spin-down power, E-dot , as well as a near-linear correlation between ξ and pulsar age, τ. This is a consequence of very weak, if any, dependences of radio luminosity, L, on pulsar period, P, and the period derivative, P-dot , in contrast to X-ray or γ-ray emission luminosities. The analysis of radio fluxes suggests that these correlations are not due to a selection effect, but are intrinsic to the pulsar radio emission physics. We have found that, although with a large variance, the radio luminosity of pulsars is ≈10{sup 29} erg s{sup –1}, regardless of the position in the P-- P-dot diagram. Within such a picture, a model-independent statement can be made that the death line of radio pulsars corresponds to an upper limit in the efficiency of radio emission. If we introduce the maximum value for radio efficiency into the Monte Carlo-based population syntheses we can reproduce the observed sample using the random luminosity model. Using the Kolmogorov-Smirnov test on a synthetic flux distribution reveals a high probability of reproducing the observed distribution. Our results suggest that the plasma responsible for generating radio emission is produced under similar conditions regardless of pulsar age, dipolar magnetic field strength, and spin-down rate. The magnetic fields near the pulsar surface are likely dominated by crust-anchored, magnetic anomalies, which do not significantly differ among pulsars, leading to similar conditions for generating electron-positron pairs necessary to power radio emission.

  13. Signature CERN-URSS

    ScienceCinema

    None

    2016-07-12

    Le DG W.Jentschke souhaite la bienvenue à l'assemblée et aux invités pour la signature du protocole entre le Cern et l'URSS qui est un événement important. C'est en 1955 que 55 visiteurs soviétiques ont visité le Cern pour la première fois. Le premier DG au Cern, F.Bloch, et Mons.Amaldi sont aussi présents. Tandis que le discours anglais de W.Jentschke est traduit en russe, le discours russe de Mons.Morozov est traduit en anglais.

  14. Signatures of aging revisited

    SciTech Connect

    Drell, S.; Jeanloz, R.; Cornwall, J.; Dyson, F.; Eardley, D.

    1998-03-18

    This study is a follow-on to the review made by JASON during its 1997 Summer Study of what is known about the aging of critical constituents, particularly the high explosives, metals (Pu, U), and polymers in the enduring stockpile. The JASON report (JSR-97-320) that summarized the findings was based on briefings by the three weapons labs (LANL, LLNL, SNL). They presented excellent technical analyses covering a broad range of scientific and engineering problems pertaining to determining signatures of aging. But the report also noted: `Missing, however, from the briefings and the written documents made available to us by the labs and DOE, was evidence of an adequately sharp focus and high priorities on a number of essential near-term needs of maintaining weapons in the stockpile.

  15. Landsat Signature Development Program

    NASA Technical Reports Server (NTRS)

    Hall, R. N.; Mcguire, K. G.; Bland, R. A.

    1976-01-01

    The Landsat Signature Development Program, LSDP, is designed to produce an unsupervised classification of a scene from a Landsat tape. This classification is based on the clustering tendencies of the multispectral scanner data processed from the scene. The program will generate a character map that, by identifying each of the general classes of surface features extracted from the scene data with a specific line printer symbol, indicates the approximate locations and distributions of these general classes within the scene. Also provided with the character map are a number of tables each of which describes either some aspect of the spectral properties of the resultant classes, some inter-class relationship, the incidence of picture elements assigned to the various classes in the character map classification of the scene, or some significant intermediate stage in the development of the final classes.

  16. Multisensors signature prediction workbench

    NASA Astrophysics Data System (ADS)

    Latger, Jean; Cathala, Thierry

    2015-10-01

    Guidance of weapon systems relies on sensors to analyze targets signature. Defense weapon systems also need to detect then identify threats also using sensors. The sensors performance is very dependent on conditions e.g. time of day, atmospheric propagation, background ... Visible camera are very efficient for diurnal fine weather conditions, long wave infrared sensors for night vision, radar systems very efficient for seeing through atmosphere and/or foliage ... Besides, multi sensors systems, combining several collocated sensors with associated algorithms of fusion, provide better efficiency (typically for Enhanced Vision Systems). But these sophisticated systems are all the more difficult to conceive, assess and qualify. In that frame, multi sensors simulation is highly required. This paper focuses on multi sensors simulation tools. A first part makes a state of the Art of such simulation workbenches with a special focus on SE-Workbench. SEWorkbench is described with regards to infrared/EO sensors, millimeter waves sensors, active EO sensors and GNSS sensors. Then a general overview of simulation of targets and backgrounds signature objectives is presented, depending on the type of simulation required (parametric studies, open loop simulation, closed loop simulation, hybridization of SW simulation and HW ...). After the objective review, the paper presents some basic requirements for simulation implementation such as the deterministic behavior of simulation, mandatory to repeat it many times for parametric studies... Several technical topics are then discussed, such as the rendering technique (ray tracing vs. rasterization), the implementation (CPU vs. GP GPU) and the tradeoff between physical accuracy and performance of computation. Examples of results using SE-Workbench are showed and commented.

  17. Signatures of dark matter

    NASA Astrophysics Data System (ADS)

    Baltz, Edward Anthony

    It is well known that most of the mass in the universe remains unobserved save for its gravitational effect on luminous matter. The nature of this ``dark matter'' remains a mystery. From measurements of the primordial deuterium abundance, the theory of big bang nucleosynthesis predicts that there are not enough baryons to account for the amount of dark matter observed, thus the missing mass must take an exotic form. Several promising candidates have been proposed. In this work I will describe my research along two main lines of inquiry into the dark matter puzzle. The first possibility is that the dark matter is exotic massive particles, such as those predicted by supersymmetric extensions to the standard model of particle physics. Such particles are generically called WIMPs, for weakly interacting massive particles. Focusing on the so-called neutralino in supersymmetric models, I discuss the possible signatures of such particles, including their direct detection via nuclear recoil experiments and their indirect detection via annihilations in the halos of galaxies, producing high energy antiprotons, positrons and gamma rays. I also discuss signatures of the possible slow decays of such particles. The second possibility is that there is a population of black holes formed in the early universe. Any dark objects in galactic halos, black holes included, are called MACHOs, for massive compact halo objects. Such objects can be detected by their gravitational microlensing effects. Several possibilities for sources of baryonic dark matter are also interesting for gravitational microlensing. These include brown dwarf stars and old, cool white dwarf stars. I discuss the theory of gravitational microlensing, focusing on the technique of pixel microlensing. I make predictions for several planned microlensing experiments with ground based and space based telescopes. Furthermore, I discuss binary lenses in the context of pixel microlensing. Finally, I develop a new technique for

  18. Index of Spectrum Signature Data

    DTIC Science & Technology

    1985-05-01

    Frederick Research Corporation. Alexandria. VA 163 AN/APG-030 Radar Receiver Heasureaents Electromagnetic Coapatibilitv Analysis Center, US Navv Marine ... Electromagnetic Compatibility Characteristics of the W 86 Gun Fire Control Svstem. Naval HEapons Lab, Dahlgren, VA 501 Partial Spectrum Signature...ECAC-I-IO-(SS) DEPARTMENT OF DEFENSE Electromagnetic Compatibility Analysis Center Annapolis, Maryland 21402 INDEX OF SPECTRUM SIGNATURE DATA

  19. Cell short circuit, preshort signature

    NASA Technical Reports Server (NTRS)

    Lurie, C.

    1980-01-01

    Short-circuit events observed in ground test simulations of DSCS-3 battery in-orbit operations are analyzed. Voltage signatures appearing in the data preceding the short-circuit event are evaluated. The ground test simulation is briefly described along with performance during reconditioning discharges. Results suggest that a characteristic signature develops prior to a shorting event.

  20. Radio-Mode Feedback in Massive Galaxies at Redshift 0 < z < 1

    NASA Astrophysics Data System (ADS)

    Sadler, Elaine M.; Croom, Scott M.; Ching, John H. Y.; Johnston, Helen M.; Cannon, Russell D.; Mauch, Tom

    2010-05-01

    We have carried out a large observational study of the radio luminosities, stellar populations, and environments of massive galaxies over the redshift range 0 < z < 1. Radio jets powered by an accreting central black hole are common in massive galaxies, and there is a large class of “optically quiet AGN,” with radio emission but no optical/IR signature of black-hole accretion. The central black holes in these galaxies are probably accreting in a radiatively inefficient mode, and our results suggest that “radio-mode feedback” as described by Croton et al. is likely to occur in all masssive early-type galaxies at z < 0.8. While it appears that radio-loud AGN occur episodically in all massive early-type galaxies, we also identify a sub-population of galaxies with powerful radio sources and a prominent younger (~ 108 yr) stellar population that may have undergone recent mergers.

  1. RECOILING SUPERMASSIVE BLACK HOLES IN SPIN-FLIP RADIO GALAXIES

    SciTech Connect

    Liu, F. K.; Wang Dong; Chen Xian

    2012-02-20

    Numerical relativity simulations predict that coalescence of supermassive black hole (SMBH) binaries leads not only to a spin flip but also to a recoiling of the merger remnant SMBHs. In the literature, X-shaped radio sources are popularly suggested to be candidates for SMBH mergers with spin flip of jet-ejecting SMBHs. Here we investigate the spectral and spatial observational signatures of the recoiling SMBHs in radio sources undergoing black hole spin flip. Our results show that SMBHs in most spin-flip radio sources have mass ratio q {approx}> 0.3 with a minimum possible value q{sub min} {approx_equal} 0.05. For major mergers, the remnant SMBHs can get a kick velocity as high as 2100 km s{sup -1} in the direction within an angle {approx}< 40 Degree-Sign relative to the spin axes of remnant SMBHs, implying that recoiling quasars are biased to be with high Doppler-shifted broad emission lines while recoiling radio galaxies are biased to large apparent spatial off-center displacements. We also calculate the distribution functions of line-of-sight velocity and apparent spatial off-center displacements for spin-flip radio sources with different apparent jet reorientation angles. Our results show that the larger the apparent jet reorientation angle is, the larger the Doppler-shifting recoiling velocity and apparent spatial off-center displacement will be. We investigate the effects of recoiling velocity on the dust torus in spin-flip radio sources and suggest that recoiling of SMBHs would lead to 'dust-poor' active galactic nuclei. Finally, we collect a sample of 19 X-shaped radio objects and for each object give the probability of detecting the predicted signatures of recoiling SMBH.

  2. Comparative Polarimetry of Comets 103P/Hartley 2, 9P/Tempel 1, and C/2009 P1 (Garradd)

    NASA Astrophysics Data System (ADS)

    Kiselev, N. N.; Rosenbush, V. K.; Afanasiev, V. L.; Blinov, D. A.; Kolesnikov, S. V.; Zaitsev, S. V.

    2012-05-01

    The results of polarimetry of comets 103P/Hartley 2 and 9P/Tempel 1 obtained during the EPOXI mission encounter and DEEP IMPACT mission respectively and comet C/2009 P1 (Garradd) during its approach to the Earth in 2011-2012 are presented.

  3. In Vivo Glucose Monitoring Using Dual-Wavelength Polarimetry to Overcome Corneal Birefringence in the Presence of Motion

    PubMed Central

    Malik, Bilal H.; Gresham, Vincent C.; Coté, Gerard L.

    2012-01-01

    Abstract Objective Over the past 35 years considerable research has been performed toward the investigation of noninvasive and minimally invasive glucose monitoring techniques. Optical polarimetry is one noninvasive technique that has shown promise as a means to ascertain blood glucose levels through measuring the glucose concentrations in the anterior chamber of the eye. However, one of the key limitations to the use of optical polarimetry as a means to noninvasively measure glucose levels is the presence of sample noise caused by motion-induced time-varying corneal birefringence. Research Design and Methods In this article our group presents, for the first time, results that show dual-wavelength polarimetry can be used to accurately detect glucose concentrations in the presence of motion-induced birefringence in vivo using New Zealand White rabbits. Results In total, nine animal studies (three New Zealand White rabbits across three separate days) were conducted. Using the dual-wavelength optical polarimetric approach, in vivo, an overall mean average relative difference of 4.49% (11.66 mg/dL) was achieved with 100% Zone A+B hits on a Clarke error grid, including 100% falling in Zone A. Conclusions The results indicate that dual-wavelength polarimetry can effectively be used to significantly reduce the noise due to time-varying corneal birefringence in vivo, allowing the accurate measurement of glucose concentration in the aqueous humor of the eye and correlating that with blood glucose. PMID:22691020

  4. LUPUS I observations from the 2010 flight of the Balloon-borne large aperture submillimeter telescope for polarimetry

    SciTech Connect

    Matthews, Tristan G.; Chapman, Nicholas L.; Novak, Giles; Ade, Peter A. R.; Hargrave, Peter C.; Nutter, David; Angilè, Francesco E.; Devlin, Mark J.; Klein, Jeffrey; Benton, Steven J.; Fissel, Laura M.; Gandilo, Natalie N.; Netterfield, Calvin B.; Chapin, Edward L.; Fukui, Yasuo; Gundersen, Joshua O.; Korotkov, Andrei L.; Moncelsi, Lorenzo; Mroczkowski, Tony K.; Olmi, Luca; and others

    2014-04-01

    The Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol) was created by adding polarimetric capability to the BLAST experiment that was flown in 2003, 2005, and 2006. BLASTPol inherited BLAST's 1.8 m primary and its Herschel/SPIRE heritage focal plane that allows simultaneous observation at 250, 350, and 500 μm. We flew BLASTPol in 2010 and again in 2012. Both were long duration Antarctic flights. Here we present polarimetry of the nearby filamentary dark cloud Lupus I obtained during the 2010 flight. Despite limitations imposed by the effects of a damaged optical component, we were able to clearly detect submillimeter polarization on degree scales. We compare the resulting BLASTPol magnetic field map with a similar map made via optical polarimetry. (The optical data were published in 1998 by J. Rizzo and collaborators.) The two maps partially overlap and are reasonably consistent with one another. We compare these magnetic field maps to the orientations of filaments in Lupus I, and we find that the dominant filament in the cloud is approximately perpendicular to the large-scale field, while secondary filaments appear to run parallel to the magnetic fields in their vicinities. This is similar to what is observed in Serpens South via near-IR polarimetry, and consistent with what is seen in MHD simulations by F. Nakamura and Z. Li.

  5. Momentum Resolved Radio Frequency Spectroscopy in Trapped Fermi Gases

    SciTech Connect

    Chen Qijin; Levin, K.

    2009-05-15

    We address recent momentum-resolved radio frequency (rf) spectroscopy experiments, showing how they yield more stringent tests than other comparisons with theory, associated with the ultracold Fermi gases. We demonstrate that, by providing a clear dispersion signature of pairing, they remove the ambiguity plaguing the interpretation of previous rf experiments. Our calculated spectral intensities are in semiquantitative agreement with the data. Even in the presence of a trap, the spectra are predicted to exhibit two BCS-like branches.

  6. 75 FR 10439 - Cognitive Radio Technologies and Software Defined Radios

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-08

    ... COMMISSION 47 CFR Part 2 Cognitive Radio Technologies and Software Defined Radios AGENCY: Federal... implement security features in software defined radios (SDRs). While, the Commission dismisses this petition... Order 1. On March 17, 2005, the Commission adopted the Cognitive Radio Report and Order, 70 FR...

  7. Radio broadcasting via satellite

    NASA Astrophysics Data System (ADS)

    Helm, Neil R.; Pritchard, Wilbur L.

    1990-10-01

    Market areas offering potential for future narrowband broadcast satellites are examined, including international public diplomacy, government- and advertising-supported, and business-application usages. Technical issues such as frequency allocation, spacecraft types, transmission parameters, and radio receiver characteristics are outlined. Service and system requirements, advertising revenue, and business communications services are among the economic issues discussed. The institutional framework required to provide an operational radio broadcast service is studied, and new initiatives in direct broadcast audio radio systems, encompassing studies, tests, in-orbit demonstrations of, and proposals for national and international commercial broadcast services are considered.

  8. WIDE-FIELD INFRARED POLARIMETRY OF THE ρ OPHIUCHI CLOUD CORE

    SciTech Connect

    Kwon, Jungmi; Tamura, Motohide; Kusakabe, Nobuhiko; Hough, James H.; Nakajima, Yasushi; Nishiyama, Shogo; Nagata, Tetsuya; Kandori, Ryo

    2015-09-15

    We conducted wide and deep simultaneous JHK{sub s}-band imaging polarimetry of the ρ Ophiuchi cloud complex. Aperture polarimetry in the JHK{sub s} band was conducted for 2136 sources in all three bands, of which 322 sources have significant polarizations in all the JHK{sub s} bands and have been used for a discussion of the core magnetic fields. There is a positive correlation between degrees of polarization and H − K{sub s} color up to H − K{sub s} ≈ 3.5. The magnetic field structures in the core region are revealed up to at least A{sub V} ≈ 47 mag and are unambiguously defined in each sub-region (core) of Oph-A, Oph-B, Oph-C, Oph-E, Oph-F, and Oph-AC. Their directions, degrees of polarization, and polarization efficiencies differ but their changes are gradual; thus, the magnetic fields appear to be connected from core to core, rather than as a simple overlap of the different cloud core components. Comparing our results with the large-scale field structures obtained from previous optical polarimetric studies, we suggest that the magnetic field structures in the core were distorted by the cluster formation in this region, which may have been induced by shock compression due to wind/radiation from the Scorpius–Centaurus association.

  9. Time-resolved Polarimetry of the Superluminous SN 2015bn with the Nordic Optical Telescope

    NASA Astrophysics Data System (ADS)

    Leloudas, Giorgos; Maund, Justyn R.; Gal-Yam, Avishay; Pursimo, Tapio; Hsiao, Eric; Malesani, Daniele; Patat, Ferdinando; de Ugarte Postigo, Antonio; Sollerman, Jesper; Stritzinger, Maximilian D.; Wheeler, J. Craig

    2017-03-01

    We present imaging polarimetry of the superluminous supernova SN 2015bn, obtained over nine epochs between ‑20 and +46 days with the Nordic Optical Telescope. This was a nearby, slowly evolving Type I superluminous supernova that has been studied extensively and for which two epochs of spectropolarimetry are also available. Based on field stars, we determine the interstellar polarization in the Galaxy to be negligible. The polarization of SN 2015bn shows a statistically significant increase during the last epochs, confirming previous findings. Our well-sampled imaging polarimetry series allows us to determine that this increase (from ∼0.54% to ≳1.10%) coincides in time with rapid changes that took place in the optical spectrum. We conclude that the supernova underwent a “phase transition” at around +20 days, when the photospheric emission shifted from an outer layer, dominated by natal C and O, to a more aspherical inner core, dominated by freshly nucleosynthesized material. This two-layered model might account for the characteristic appearance and properties of Type I superluminous supernovae.

  10. Venusian Upper Hazes Observed with an Imaging-Polarimetry System HOPS

    NASA Astrophysics Data System (ADS)

    Satoh, T.; Enomoto, T.; Nakatani, Y.; Nakakushi, T.

    2013-12-01

    Physical properties of the aerosols in the Venusian upper atmosphere can be deduced by measuring linear polarization of reflected sunlight (after single or multiple scattering by the media). The aerosols in the Venusian atmosphere are highly variable, as demonstrated by the findings of numerous sub-micron haze particles in the polar region (Pioneer Venus observations, in Kawabata et al. [1980]). Two dimensional maps of linear polarization over the planetary disc are advantageous as such maps allow us to selectively investigate local features (equatorial, mid-latitude, or polar regions). To monitor and characterize the recent status of the Venusian upper hazes, we carry out a long-term monitoring program with HOPS (Hida Optical Polarimetry System) at the Hida Observatory, University of Kyoto. HOPS is a traditional two-beam polarimetry instrument, with a Wollaston prism and a half-wave retarder (super-achromatic). The observing wavelengths are 930, 647 (650), 548 (546), and 438 nm (latest filters are in the parentheses). In this paper, we report the observing results from 2012 runs (May, August, and October) plus 2013 runs (July and August). These data covers the solar phase angles 40 to 130 degrees. Some of polarization standard stars were also observed to calibrate the data. The phase angle dependence, as well as the wavelength dependence of the polarization of Venus will be presented with possible interpretation of the recent status.

  11. Assembly and test of the gas pixel detector for X-ray polarimetry

    NASA Astrophysics Data System (ADS)

    Li, H.; Feng, H.; Muleri, F.; Bellazzini, R.; Minuti, M.; Soffitta, P.; Brez, A.; Spandre, G.; Pinchera, M.; Sgró, C.; Baldini, L.; She, R.; Costa, E.

    2015-12-01

    The gas pixel detector (GPD) dedicated for photoelectric X-ray polarimetry is selected as the focal plane detector for the ESA medium-class mission concept X-ray Imaging and Polarimetry Explorer (XIPE). Here we show the design, assembly, and preliminary test results of a small GPD for the purpose of gas mixture optimization needed for the phase A study of XIPE. The detector is assembled in house at Tsinghua University following a design by the INFN-Pisa group. The improved detector design results in a good uniformity for the electric field. Filled with pure dimethyl ether (DME) at 0.8 atm, the measured energy resolution is 18% at 6 keV and inversely scales with the square root of the X-ray energy. The measured modulation factor is well consistent with that from simulation, up to ~0.6 above 6 keV. The residual modulation is found to be 0.30 ± 0.15 % at 6 keV for the whole sensitive area, which can be translated into a systematic error of less than 1% for polarization measurement at a confidence level of 99%. The position resolution of the detector is about 80 μm in FWHM, consistent with previous studies and sufficient for XIPE requirements.

  12. The use of laterally graded multilayer mirrors for soft x-ray polarimetry

    NASA Astrophysics Data System (ADS)

    Marshall, Herman L.; Schulz, Norbert S.; Windt, David L.; Gullikson, Eric M.; Craft, Marshall; Blake, Eric; Ross, Connor

    2015-09-01

    We present continued development of laterally graded multilayer mirrors (LGMLs) for a telescope design capable of measuring linear X-ray polarization over a broad spectral band. The multilayer-coated mirrors are used as Bragg reflectors at the Brewster angle. By matching to the dispersion of a spectrometer, one may take advantage of high multilayer reflectivities and achieve modulation factors near 100%. In Phase II of the polarimetry beam- line development, we demonstrated that the system provides 100% polarized X-rays at 0.525 keV (Marshall et al. 2013). In Phase III of the polarimetry beam-line development, we installed an LGML in the source to polarize a wide range of energies between 0.15 and 0.70 keV (Marshall et al. 2014). Here, we present results from continued development of the LGMLs to improve reflectivity in the band of interest, a blazed reflection grating that is suitable for a small flight instrument, and a new detector with a directly deposited optical blocking filter. We also present updated plans for a suborbital rocket experiment designed to detect a polarization level of better than 10% for an active galactic nucleus.

  13. Exploiting the Photoelectric effect for X-ray Polarimetry using Time Projection Chamber

    NASA Technical Reports Server (NTRS)

    Jahoda, Keith; Black, Kevin; Deines-Jones, Philip; Hill, Joanne; Swank, Jean

    2008-01-01

    The promise of photoelectric X-ray polarimetry has now been realized in laboratory demonstrations and may soon be used for astrophysical observations. Photoelectric polarimetry in gas filled proportional counters achieves high sensitivity through a combination of broad band width and good modulation. The band can be tuned by careful choice of gas composition and pressure. The measurements rely on imaging the tracks of photoelectrons. The initial direction of each track carries information about the electric field of the X-ray photon, and an ensemble of such measurements thus measures the net polarization of the source. A novel readout geometry using time projection chambers (TPC) allows deep (i.e. high efficiency) detectors, albeit without the ability to image the sky. Polarimeters which exploit the TPC geometry can be optimized for use behind telescopes, to study faint persistent sources, or as wide field of view instruments, designed to study bright transient events such as gamma-ray bursts or solar flares. We present the conceptual design of both types of TPC polarimeter. Recent laboratory results demonstrate that these polarimeters can achieve substantial gains in the polarization sensitivity achievable in experiments of modest size.

  14. Polarimetry of the polarized hydrogen deuteride HDice target under an electron beam

    SciTech Connect

    Laine, Vivien E.

    2013-10-01

    The study of the nucleon structure has been a major research focus in fundamental physics in the past decades and still is the main research line of the Thomas Jefferson National Accelerator Facility (Jefferson Lab). For this purpose and to obtain statistically meaningful results, having both a polarized beam and a highly efficient polarized target is essential. For the target, this means high polarization and high relative density of polarized material. A Hydrogen Deuteride (HD) target that presents both such characteristics has been developed first at Brookhaven National Lab (BNL) and brought to the Hall B of Jefferson Lab in 2008. The HD target has been shown to work successfully under a high intensity photon beam (BNL and Jefferson Lab). However, it remained to be seen if the target could stand an electron beam of reasonably high current (nA). In this perspective, the target was tested for the first time in its frozen spin mode under an electron beam at Jefferson Lab in 2012 during the g14 experiment. This dissertation presents the principles and usage procedures of this HD target. The polarimetry of this target with Nuclear Magnetic Resonance (NMR) during the electron beam tests is also discussed. In addition, this dissertation also describes another way to perform target polarimetry with the elastic scattering of electrons off a polarized target by using data taken on helium-3 during the E97-110 experiment that occurred in Jefferson Lab's Hall A in 2003.

  15. THE X-RAY POLARIZATION SIGNATURE OF QUIESCENT MAGNETARS: EFFECT OF MAGNETOSPHERIC SCATTERING AND VACUUM POLARIZATION

    SciTech Connect

    Fernandez, Rodrigo; Davis, Shane W.

    2011-04-01

    In the magnetar model, the quiescent non-thermal soft X-ray emission from anomalous X-ray pulsars and soft gamma repeaters is thought to arise from resonant Comptonization of thermal photons by charges moving in a twisted magnetosphere. Robust inference of physical quantities from observations is difficult, because the process depends strongly on geometry, and current understanding of the magnetosphere is not very deep. The polarization of soft X-ray photons is an independent source of information, and its magnetospheric imprint remains only partially explored. In this paper, we calculate how resonant cyclotron scattering would modify the observed polarization signal relative to the surface emission, using a multidimensional Monte Carlo radiative transfer code that accounts for the gradual coupling of polarization eigenmodes as photons leave the magnetosphere. We employ a globally twisted, self-similar, force-free magnetosphere with a power-law momentum distribution, assume a blackbody spectrum for the seed photons, account for general relativistic light deflection close to the star, and assume that vacuum polarization dominates the dielectric properties of the magnetosphere. The latter is a good approximation if the pair multiplicity is not much larger than unity. Phase-averaged polarimetry is able to provide a clear signature of the magnetospheric reprocessing of thermal photons and to constrain mechanisms generating the thermal emission. Phase-resolved polarimetry, in addition, can characterize the spatial extent and magnitude of the magnetospheric twist angle at {approx}100 stellar radii, and discern between uni- or bidirectional particle energy distributions, almost independently of every other parameter in the system. We discuss prospects for detectability with the Gravity and Extreme Magnetism (GEMS) mission.

  16. Planck intermediate results. XLV. Radio spectra of northern extragalactic radio sources

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Aller, H. D.; Aller, M. F.; Arnaud, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Burigana, C.; Calabrese, E.; Catalano, A.; Chiang, H. C.; Christensen, P. R.; Clements, D. L.; Colombo, L. P. L.; Couchot, F.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Dickinson, C.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Eriksen, H. K.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Galeotta, S.; Galli, S.; Ganga, K.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gruppuso, A.; Gurwell, M. A.; Hansen, F. K.; Harrison, D. L.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Hildebrandt, S. R.; Hobson, M.; Hornstrup, A.; Hovatta, T.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Järvelä, E.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maino, D.; Mandolesi, N.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Max-Moerbeck, W.; Meinhold, P. R.; Melchiorri, A.; Mennella, A.; Migliaccio, M.; Mingaliev, M.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Nati, F.; Natoli, P.; Nieppola, E.; Noviello, F.; Novikov, D.; Novikov, I.; Pagano, L.; Pajot, F.; Paoletti, D.; Partridge, B.; Pasian, F.; Pearson, T. J.; Perdereau, O.; Perotto, L.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Pratt, G. W.; Ramakrishnan, V.; Rastorgueva-Foi, E. A.; S Readhead, A. C.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Richards, J. L.; Ristorcelli, I.; Rocha, G.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Savelainen, M.; Savini, G.; Scott, D.; Sotnikova, Y.; Stolyarov, V.; Sunyaev, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tammi, J.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tornikoski, M.; Tristram, M.; Tucci, M.; Türler, M.; Valenziano, L.; Valiviita, J.; Valtaoja, E.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L. A.; Wehrle, A. E.; Wehus, I. K.; Yvon, D.; Zacchei, A.; Zonca, A.

    2016-12-01

    Continuum spectra covering centimetre to submillimetre wavelengths are presented for a northern sample of 104 extragalactic radio sources, mainly active galactic nuclei, based on four-epoch Planck data. The nine Planck frequencies, from 30 to 857 GHz, are complemented by a set of simultaneous ground-based radio observations between 1.1 and 37 GHz. The single-survey Planck data confirm that the flattest high-frequency radio spectral indices are close to zero, indicating that the original accelerated electron energy spectrum is much harder than commonly thought, with power-law index around 1.5 instead of the canonical 2.5. The radio spectra peak at high frequencies and exhibit a variety of shapes. For a small set of low-z sources, we find a spectral upturn at high frequencies, indicating the presence of intrinsic cold dust. Variability can generally be approximated by achromatic variations, while sources with clear signatures of evolving shocks appear to be limited to the strongest outbursts.

  17. Searching for Topological Defect Dark Matter via Nongravitational Signatures

    NASA Astrophysics Data System (ADS)

    Stadnik, Y. V.; Flambaum, V. V.

    2014-10-01

    We propose schemes for the detection of topological defect dark matter using pulsars and other luminous extraterrestrial systems via nongravitational signatures. The dark matter field, which makes up a defect, may interact with standard model particles, including quarks and the photon, resulting in the alteration of their masses. When a topological defect passes through a pulsar, its mass, radius, and internal structure may be altered, resulting in a pulsar "quake." A topological defect may also function as a cosmic dielectric material with a distinctive frequency-dependent index of refraction, which would give rise to the time delay of a periodic extraterrestrial light or radio signal, and the dispersion of a light or radio source in a manner distinct to a gravitational lens. A topological defect passing through Earth may alter Earth's period of rotation and give rise to temporary nonzero electric dipole moments for an electron, proton, neutron, nuclei and atoms.

  18. Superfine Structure of Jovian Millisecond Radio Bursts

    NASA Astrophysics Data System (ADS)

    Rucker, H. O.; Litvinenko, G.; Taubenschuss, U.; Leitner, M.; Lecacheux, A.; Konovalenko, A.

    2004-05-01

    Jupiter decameter (DAM) radio emission mainly consists of wide-band radio storms with time scales in seconds (L-bursts) and milliseconds (S-bursts), the latter comprising a series of short pulses with duration of a few to tens of milliseconds, and strongly controlled by the satellite Io. First in-depth analysis of the subpulse structure was made by Carr and Reyes (1999) with the discovery of successive deep envelope modulations, with time resolution better than 30 microseconds, and during these subpulse periods the discovery of phase coherence. Recent observations by means of the newly developed waveform receiver (at present unsurpassed in spectral resolution) and connected to the decameter world-largest radio telescope UTR-2 (Kharkov) yielded waveform measurements of Jovian S-bursts which have been analyzed by the wavelet analysis method. Main outcome of the present investigation is the detection of clear signatures of microsecond modulations, providing evidence of a superfine burst structure with the following parameters: a) instantaneous frequency band of one separated microsecond pulse of 100 to 300 kHz, b) time duration of one separated micropulse of 6 to 15 microseconds, and c) time interval between closest subsequent microsecond pulses of 5 to 25 microseconds. The apparent frequency drift of a millisecond burst evidently results from sequentially decreasing frequencies of subsequent subpulses, each representing an island of phase coherent gyrating electron bunches.

  19. Polarimetry with the Gemini Planet Imager. Methods, performance at first light, and the circumstellar ring around HR 4796A

    DOE PAGES

    Perrin, Marshall D.; Duchene, Gaspard; Millar-Blanchaer, Max; ...

    2015-01-28

    We report he first results from the polarimetry mode of the Gemini Planet Imager (GPI), which uses a new integral field polarimetry architecture to provide high contrast linear polarimetry with minimal systematic biases between the orthogonal polarizations. We describe the design, data reduction methods, and performance of polarimetry with GPI. Point-spread function (PSF) subtraction via differential polarimetry suppresses unpolarized starlight by a factor of over 100, and provides sensitivity to circumstellar dust reaching the photon noise limit for these observations. In the case of the circumstellar disk around HR 4796A, GPI’s advanced adaptive optics system reveals the disk clearly evenmore » prior to PSF subtraction. In polarized light, the disk is seen all the way in to its semi-minor axis for the first time. The disk exhibits surprisingly strong asymmetry in polarized intensity, with the west side ≳9 times brighter than the east side despite the fact that the east side is slightly brighter in total intensity. Based on a synthesis of the total and polarized intensities, we now believe that the west side is closer to us, contrary to most prior interpretations. Forward scattering by relatively large silicate dust particles leads to the strong polarized intensity on the west side, and the ring must be slightly optically thick in order to explain the lower brightness in total intensity there. In conclusion, these findings suggest that the ring is geometrically narrow and dynamically cold, perhaps shepherded by larger bodies in the same manner as Saturn’s F ring.« less

  20. Eratosthenes via Ham Radio

    ERIC Educational Resources Information Center

    Koser, John F.

    1975-01-01

    A secondary geology class used Eratosthenes' method for measuring the circumference of the earth by comparing their measurements of the shadow of a vertical rod to the measurements made by another person contacted by ham radio. (MLH)

  1. Unveiling the radio cosmos

    NASA Astrophysics Data System (ADS)

    Vanderlinde, Keith

    2017-02-01

    Using a radio telescope with no moving parts, the dark energy speeding up the expansion of the Universe can be probed in unprecedented detail, says Keith Vanderlinde, on behalf of the CHIME collaboration.

  2. Fast Radio Bursts

    NASA Astrophysics Data System (ADS)

    Kaspi, Victoria M.

    2017-01-01

    Fast Radio Bursts (FRBs) are a recently discovered phenomenon consisting of short (few ms) bursts of radio waves that have dispersion measures that strongly suggest an extragalactic and possibly cosmological origin. Current best estimates for the rate of FRBs is several thousand per sky per day at radio frequencies near 1.4 GHz. Even with so high a rate, to date, fewer than 20 FRBs have been reported, with one source showing repeated bursts. In this talk I will describe known FRB properties including what is known about the lone repeating source, as well as models for the origin of these mysterious events. I will also describe the CHIME radio telescope, currently under construction in Canada. Thanks to its great sensitivity and unprecedented field-of-view, CHIME promises major progress on FRBs.

  3. Signatures of AGN feedback

    NASA Astrophysics Data System (ADS)

    Wylezalek, Dominika; Zakamska, Nadia L.; MaNGA-GMOS Team

    2017-01-01

    Feedback from actively accreting SMBHs (Active Galactic Nuclei, AGN) is now widely considered to be the main driver in regulating the growth of massive galaxies. Observational proof for this scenario has, however, been hard to come by. Many attempts at finding a conclusive observational proof that AGN may be able to quench star formation and regulate the host galaxies' growth have shown that this problem is highly complex.I will present results from several projects that focus on understanding the power, reach and impact of feedback processes exerted by AGN. I will describe recent efforts in our group of relating feedback signatures to the specific star formation rate in their host galaxies, where our results are consistent with the AGN having a `negative' impact through feedback on the galaxies' star formation history (Wylezalek+2016a,b). Furthermore, I will show that powerful AGN-driven winds can be easily hidden and not be apparent in the integrated spectrum of the galaxy. This implies that large IFU surveys, such as the SDSS-IV MaNGA survey, might uncover many previously unknown AGN and outflows that are potentially very relevant for understanding the role of AGN in galaxy evolution (Wylezalek+2016c)!

  4. Statistical clumped isotope signatures

    PubMed Central

    Röckmann, T.; Popa, M. E.; Krol, M. C.; Hofmann, M. E. G.

    2016-01-01

    High precision measurements of molecules containing more than one heavy isotope may provide novel constraints on element cycles in nature. These so-called clumped isotope signatures are reported relative to the random (stochastic) distribution of heavy isotopes over all available isotopocules of a molecule, which is the conventional reference. When multiple indistinguishable atoms of the same element are present in a molecule, this reference is calculated from the bulk (≈average) isotopic composition of the involved atoms. We show here that this referencing convention leads to apparent negative clumped isotope anomalies (anti-clumping) when the indistinguishable atoms originate from isotopically different populations. Such statistical clumped isotope anomalies must occur in any system where two or more indistinguishable atoms of the same element, but with different isotopic composition, combine in a molecule. The size of the anti-clumping signal is closely related to the difference of the initial isotope ratios of the indistinguishable atoms that have combined. Therefore, a measured statistical clumped isotope anomaly, relative to an expected (e.g. thermodynamical) clumped isotope composition, may allow assessment of the heterogeneity of the isotopic pools of atoms that are the substrate for formation of molecules. PMID:27535168

  5. Packet Radio for Library Automation.

    ERIC Educational Resources Information Center

    Brownrigg, Edwin B.; And Others

    1984-01-01

    This tutorial on packet radio (communication system using radio and digital packet-switching technology) highlights radio transmission of data, brief history, special considerations in applying packet radio to library online catalogs, technology, defining protocol at physical and network levels, security, geographic coverage, and components. (A…

  6. Soldier’s Radio

    DTIC Science & Technology

    1992-02-14

    individual soldier. "t’s primary use is by individuals in squads or small units, but may also be used to interconnect into local and wide area...Velopilnq the concept for the Soldier’s Radio. The operation of the SR can be partitioned into two areas. The architecture required to provide intra- squad ... SQUAD CONMECTrVITY The basic radio ccmmunications architectures suitable for :cnsideration for the SR intra- squad operations include the Net, .tar

  7. The Radio JOVE Project

    NASA Astrophysics Data System (ADS)

    Garcia, L.; Thieman, J.; Higgins, C.

    1999-09-01

    Radio JOVE is an interactive educational activity which brings the radio sounds of Jupiter and the Sun to students, teachers, and the general public. This is accomplished through the construction of a simple radio telescope kit and the use of a real-time radio observatory on the Internet. Our website (http://radiojove.gsfc.nasa.gov/) will contain science information, instruction manuals, observing guides, and education resources for students and teachers. Our target audience is high school science classes, but subjects can be tailored to college undergraduate physics and astronomy courses or even to middle school science classes. The goals of the project are: 1) Educate people about planetary and solar radio astronomy, space physics, and the scientific method 2) Provide teachers and students with a hands-on radio astronomy exercise as a science curriculum support activity by building and using a simple radio telescope receiver/antenna kit 3) Create the first ever online radio observatory which provides real-time data for those with internet access 4) Allow interactions among participating schools by facilitating exchanges of ideas, data, and observing experiences. Our current funding will allow us to impact 100 schools by partially subsidizing their participation in the program. We expect to expand well beyond this number as publicity and general interest increase. Additional schools are welcome to fully participate, but we will not be able to subsidize their kit purchases. We hope to make a wide impact among the schools by advertising through appropriate newsletters, space grant consortia, the INSPIRE project (http://image.gsfc.nasa.gov/poetry/inspire/), electronic links, and science and education meetings. We would like to acknoledge support from the NASA/GSFC Director's Discretionary Fund, the STScI IDEAS grant program and the NASA/GSFC Space Science Data Operations Office.

  8. Radio observations of solar eclipse.

    NASA Astrophysics Data System (ADS)

    Liu, Yuying; Fu, Qijun

    1998-09-01

    For radio astronomy, a solar eclipse provides an opportunity for making solar radio observations with high one-dimension spatial resolution. The radio observation of a solar eclipse has played an important role in solar radio physics. Some important factors for radio observation of a solar eclipse are introduced and analysed. Solar eclipse radio observation has also played an important role in the progress of solar radio atronomy in China. The solar eclipses of 1958, 1968, 1980 and 1987, which were observed in China, are introduced, and the main results of these observations are briefly shown.

  9. Astrometry of southern radio sources.

    PubMed

    White, G L; Jauncey, D L; Harvey, B R; Savage, A; Gulkis, S; Preston, R A; Peterson, B A; Reynolds, J E; Nicolson, G D; Malin, D F

    1991-01-01

    An overview is presented of a number of astrometry and astrophysics programs based on radio sources from the Parkes 2.7 GHz catalogues. The programs cover the optical identification and spectroscopy of flat-spectrum Parkes sources and the determination of their milliarc-second radio structures and positions. Work is also in progress to tie together the radio and Hipparcos positional reference frames. A parallel program of radio and optical astrometry of southern radio stars is also under way.

  10. Intrusion detection using secure signatures

    DOEpatents

    Nelson, Trent Darnel; Haile, Jedediah

    2014-09-30

    A method and device for intrusion detection using secure signatures comprising capturing network data. A search hash value, value employing at least one one-way function, is generated from the captured network data using a first hash function. The presence of a search hash value match in a secure signature table comprising search hash values and an encrypted rule is determined. After determining a search hash value match, a decryption key is generated from the captured network data using a second hash function, a hash function different form the first hash function. One or more of the encrypted rules of the secure signatures table having a hash value equal to the generated search hash value are then decrypted using the generated decryption key. The one or more decrypted secure signature rules are then processed for a match and one or more user notifications are deployed if a match is identified.

  11. Retail applications of signature verification

    NASA Astrophysics Data System (ADS)

    Zimmerman, Thomas G.; Russell, Gregory F.; Heilper, Andre; Smith, Barton A.; Hu, Jianying; Markman, Dmitry; Graham, Jon E.; Drews, Clemens

    2004-08-01

    The dramatic rise in identity theft, the ever pressing need to provide convenience in checkout services to attract and retain loyal customers, and the growing use of multi-function signature captures devices in the retail sector provides favorable conditions for the deployment of dynamic signature verification (DSV) in retail settings. We report on the development of a DSV system to meet the needs of the retail sector. We currently have a database of approximately 10,000 signatures collected from 600 subjects and forgers. Previous work at IBM on DSV has been merged and extended to achieve robust performance on pen position data available from commercial point of sale hardware, achieving equal error rates on skilled forgeries and authentic signatures of 1.5% to 4%.

  12. Ballastic signature identification systems study

    NASA Technical Reports Server (NTRS)

    Reich, A.; Hine, T. L.

    1976-01-01

    The results are described of an attempt to establish a uniform procedure for documenting (recording) expended bullet signatures as effortlessly as possible and to build a comprehensive library of these signatures in a form that will permit the automated comparison of a new suspect bullet with the prestored library. The ultimate objective is to achieve a standardized format that will permit nationwide interaction between police departments, crime laboratories, and other interested law enforcement agencies.

  13. Fast radio bursts: the last sign of supramassive neutron stars

    NASA Astrophysics Data System (ADS)

    Falcke, Heino; Rezzolla, Luciano

    2014-02-01

    Context. Several fast radio bursts have been discovered recently, showing a bright, highly dispersed millisecond radio pulse. The pulses do not repeat and are not associated with a known pulsar or gamma-ray burst. The high dispersion suggests sources at cosmological distances, hence implying an extremely high radio luminosity, far larger than the power of single pulses from a pulsar. Aims: We suggest that a fast radio burst represents the final signal of a supramassive rotating neutron star that collapses to a black hole due to magnetic braking. The neutron star is initially above the critical mass for non-rotating models and is supported by rapid rotation. As magnetic braking constantly reduces the spin, the neutron star will suddenly collapse to a black hole several thousand to million years after its birth. Methods: We discuss several formation scenarios for supramassive neutron stars and estimate the possible observational signatures making use of the results of recent numerical general-relativistic calculations. Results: While the collapse will hide the stellar surface behind an event horizon, the magnetic-field lines will snap violently. This can turn an almost ordinary pulsar into a bright radio "blitzar": accelerated electrons from the travelling magnetic shock dissipate a significant fraction of the magnetosphere and produce a massive radio burst that is observable out to z > 0.7. Only a few per cent of the neutron stars need to be supramassive in order to explain the observed rate. Conclusions: We suggest the intriguing possibility that fast radio bursts might trace the solitary and almost silent formation of stellar mass black holes at high redshifts. These bursts could be an electromagnetic complement to gravitational-wave emission and reveal a new formation and evolutionary channel for black holes and neutron stars that are not seen as gamma-ray bursts. If supramassive neutron stars are formed at birth and not by accretion, radio observations of these

  14. Radio data archiving system

    NASA Astrophysics Data System (ADS)

    Knapic, C.; Zanichelli, A.; Dovgan, E.; Nanni, M.; Stagni, M.; Righini, S.; Sponza, M.; Bedosti, F.; Orlati, A.; Smareglia, R.

    2016-07-01

    Radio Astronomical Data models are becoming very complex since the huge possible range of instrumental configurations available with the modern Radio Telescopes. What in the past was the last frontiers of data formats in terms of efficiency and flexibility is now evolving with new strategies and methodologies enabling the persistence of a very complex, hierarchical and multi-purpose information. Such an evolution of data models and data formats require new data archiving techniques in order to guarantee data preservation following the directives of Open Archival Information System and the International Virtual Observatory Alliance for data sharing and publication. Currently, various formats (FITS, MBFITS, VLBI's XML description files and ancillary files) of data acquired with the Medicina and Noto Radio Telescopes can be stored and handled by a common Radio Archive, that is planned to be released to the (inter)national community by the end of 2016. This state-of-the-art archiving system for radio astronomical data aims at delegating as much as possible to the software setting how and where the descriptors (metadata) are saved, while the users perform user-friendly queries translated by the web interface into complex interrogations on the database to retrieve data. In such a way, the Archive is ready to be Virtual Observatory compliant and as much as possible user-friendly.

  15. Quantum messages with signatures forgeable in arbitrated quantum signature schemes

    NASA Astrophysics Data System (ADS)

    Kim, Taewan; Choi, Jeong Woon; Jho, Nam-Su; Lee, Soojoon

    2015-02-01

    Even though a method to perfectly sign quantum messages has not been known, the arbitrated quantum signature scheme has been considered as one of the good candidates. However, its forgery problem has been an obstacle to the scheme becoming a successful method. In this paper, we consider one situation, which is slightly different from the forgery problem, that we use to check whether at least one quantum message with signature can be forged in a given scheme, although all the messages cannot be forged. If there are only a finite number of forgeable quantum messages in the scheme, then the scheme can be secured against the forgery attack by not sending forgeable quantum messages, and so our situation does not directly imply that we check whether the scheme is secure against the attack. However, if users run a given scheme without any consideration of forgeable quantum messages, then a sender might transmit such forgeable messages to a receiver and in such a case an attacker can forge the messages if the attacker knows them. Thus it is important and necessary to look into forgeable quantum messages. We show here that there always exists such a forgeable quantum message-signature pair for every known scheme with quantum encryption and rotation, and numerically show that there are no forgeable quantum message-signature pairs that exist in an arbitrated quantum signature scheme.

  16. Simulating realistic predator signatures in quantitative fatty acid signature analysis

    USGS Publications Warehouse

    Bromaghin, Jeffrey F.

    2015-01-01

    Diet estimation is an important field within quantitative ecology, providing critical insights into many aspects of ecology and community dynamics. Quantitative fatty acid signature analysis (QFASA) is a prominent method of diet estimation, particularly for marine mammal and bird species. Investigators using QFASA commonly use computer simulation to evaluate statistical characteristics of diet estimators for the populations they study. Similar computer simulations have been used to explore and compare the performance of different variations of the original QFASA diet estimator. In both cases, computer simulations involve bootstrap sampling prey signature data to construct pseudo-predator signatures with known properties. However, bootstrap sample sizes have been selected arbitrarily and pseudo-predator signatures therefore may not have realistic properties. I develop an algorithm to objectively establish bootstrap sample sizes that generates pseudo-predator signatures with realistic properties, thereby enhancing the utility of computer simulation for assessing QFASA estimator performance. The algorithm also appears to be computationally efficient, resulting in bootstrap sample sizes that are smaller than those commonly used. I illustrate the algorithm with an example using data from Chukchi Sea polar bears (Ursus maritimus) and their marine mammal prey. The concepts underlying the approach may have value in other areas of quantitative ecology in which bootstrap samples are post-processed prior to their use.

  17. Classification of agricultural fields using time series of dual polarimetry TerraSAR-X images

    NASA Astrophysics Data System (ADS)

    Mirzaee, S.; Motagh, M.; Arefi, H.; Nooryazdan, M.

    2014-10-01

    Due to its special imaging characteristics, Synthetic Aperture Radar (SAR) has become an important source of information for a variety of remote sensing applications dealing with environmental changes. SAR images contain information about both phase and intensity in different polarization modes, making them sensitive to geometrical structure and physical properties of the targets such as dielectric and plant water content. In this study we investigate multi temporal changes occurring to different crop types due to phenological changes using high-resolution TerraSAR-X imagers. The dataset includes 17 dual-polarimetry TSX data acquired from June 2012 to August 2013 in Lorestan province, Iran. Several features are extracted from polarized data and classified using support vector machine (SVM) classifier. Training samples and different features employed in classification are also assessed in the study. Results show a satisfactory accuracy for classification which is about 0.91 in kappa coefficient.

  18. Measurement of parameters of polarization in the living human eye using imaging polarimetry.

    PubMed

    Bueno, J M

    2000-01-01

    An imaging polarimeter using liquid-crystal variable retarders (Bueno, J. M., Artal, P. (1999). Double-pass imaging polarimetry in the human eye. Optics Letters, 24, 64-66) has been used to study the parameters of polarization in the living human eye. Retardation introduced by birefringent structures of the eye has been calculated by using a spatially resolved collection of Mueller matrices obtained from series of 16 double-pass retinal images. Results for images with a 2-mm pupil diameter show that although the retardation introduced by the eye in a double-pass varies among individuals, at the central cornea the slow axis is directed along the upper-temporal to lower-nasal line and the ellipticity is close to zero, which indicates the presence of linear birefringence. As pupil size increased, the measured retardation also increased, while ocular birefringence remained linear and azimuthal angle changed without a clear tendency.

  19. Rapid full Mueller matrix imaging polarimetry based on the hybrid phase modulation technique

    NASA Astrophysics Data System (ADS)

    Han, Chien-Yuan; Du, Cheng-You; Jhou, Jhe-Yi

    2017-01-01

    In this work, we present a novel method of Mueller matrix imaging polarimetry, which comprises dual liquid crystal variable retarders at the polarization generation portion and a photoelastic modulator at the polarization analysis portion. The light source can be operated either in the continuous mode, which provides an in-situ calibration process for the liquid crystal variable retarders, or in the pulse mode to deduce the full two-dimensional Mueller matrix with 16 images from the camera. We measured the Mueller matrix images of air as a standard test, as well as a quarter wave plate to determine its azimuthal angle and phase retardation by the polar decomposition technique. Finally, the decomposed Mueller matrix images of a biopolymer specimen with the conformational change produced by heat treatment are presented.

  20. A Pair Production Telescope for Medium-Energy Gamma-Ray Polarimetry

    SciTech Connect

    Hunter , Stanley D.; Bloser, Peter F.; Depaola, Gerardo O.; Dion, Michael P.; DeNolfo, Georgia A.; Hanu, Andrei; Iparraguirre, Marcos; Legere, Jason; Longo, Francesco; McConnell, Mark L.; Nowicki, Suzanne F.; Ryan, James M.; Son, Seunghee; Stecker, Floyd W.

    2014-08-01

    We describe the science motivation and development of a pair production telescope for medium-13 energy gamma-ray polarimetry. Our instrument concept, the Advanced Energetic Pair Telescope 14 (AdEPT), takes advantage of the Three-Dimensional Track Imager, a low-density gaseous time 15 projection chamber, to achieve angular resolution within a factor of two of the pair production 16 kinematics limit (~0.6° at 70 MeV), continuum sensitivity comparable with the Fermi-LAT front 17 detector (<3×10-6 MeV cm-2 s-1 at 70 MeV), and minimum detectable polarization less than 10% 18 for a 10 millicrab source in 106 seconds.

  1. On-chip polarimetry for high-throughput screening of nanoliter and smaller sample volumes

    NASA Technical Reports Server (NTRS)

    Bornhop, Darryl J. (Inventor); Dotson, Stephen (Inventor); Bachmann, Brian O. (Inventor)

    2012-01-01

    A polarimetry technique for measuring optical activity that is particularly suited for high throughput screening employs a chip or substrate (22) having one or more microfluidic channels (26) formed therein. A polarized laser beam (14) is directed onto optically active samples that are disposed in the channels. The incident laser beam interacts with the optically active molecules in the sample, which slightly alter the polarization of the laser beam as it passes multiple times through the sample. Interference fringe patterns (28) are generated by the interaction of the laser beam with the sample and the channel walls. A photodetector (34) is positioned to receive the interference fringe patterns and generate an output signal that is input to a computer or other analyzer (38) for analyzing the signal and determining the rotation of plane polarized light by optically active material in the channel from polarization rotation calculations.

  2. Merged vector gratings recorded in a photocrosslinkable polymer liquid crystal film for polarimetry

    SciTech Connect

    Sasaki, Tomoyuki Wada, Takumi; Noda, Kohei; Ono, Hiroshi; Kawatsuki, Nobuhiro

    2014-01-14

    A merged vector grating, which is holographically fabricated in an anisotropic medium by irradiation with interference light with intensity modulation and polarization modulation, was designed to detect the polarization of light. The merged vector grating is recorded by the interference of two elliptically polarized beams with equal intensities, parallel azimuths, equal ellipticities, and different directions of rotation. We clarified theoretically that the Stokes parameters of the incident light beam are described by the diffraction efficiency of the merged vector grating. Also, to apply this property to formation of a polarimeter without any moving parts or mechanisms, two merged vector gratings with different grating vectors were recorded in a photocrosslinkable polymer liquid crystal film by angle-multiplexed holography. By investigation of the diffraction properties of the gratings obtained, we demonstrated the applicability of the merged vector gratings for use in polarimetry.

  3. Interaction between Faraday rotation and Cotton-Mouton effects in polarimetry modeling for NSTX

    SciTech Connect

    Zhang, J.; Crocker, N. A.; Carter, T. A.; Kubota, S.; Peebles, W. A.

    2010-10-15

    The evolution of electromagnetic wave polarization is modeled for propagation in the major radial direction in the National Spherical Torus Experiment with retroreflection from the center stack of the vacuum vessel. This modeling illustrates that the Cotton-Mouton effect-elliptization due to the magnetic field perpendicular to the propagation direction-is shown to be strongly weighted to the high-field region of the plasma. An interaction between the Faraday rotation and Cotton-Mouton effects is also clearly identified. Elliptization occurs when the wave polarization direction is neither parallel nor perpendicular to the local transverse magnetic field. Since Faraday rotation modifies the polarization direction during propagation, it must also affect the resultant elliptization. The Cotton-Mouton effect also intrinsically results in rotation of the polarization direction, but this effect is less significant in the plasma conditions modeled. The interaction increases at longer wavelength and complicates interpretation of polarimetry measurements.

  4. Optical contrast enhancement of high-resolution ocular fundus imaging in vivo using polarimetry

    NASA Astrophysics Data System (ADS)

    Yang, Hansheng; Rao, Xuejun; Zhang, Yudong

    2007-11-01

    The adaptive optics (AO) retina imaging was performed with contrast enhancement by characterizing polarization parameters of the living retina. A removable pair of polarization state generating unit near the optical source and analysis unit near the CCD camera was incorporated into the basic 37-channle deformable mirror AO microscopic ophthalmoscope. Double-pass imaging polarimetry of the human eye was carried out, then incomplete Mueller matrix was calculated and analyzed to optimize the retina imaging condition using polarized light, which caused the subretinal structures with different polarization properties to emerge from the scattering light background, so the contrast of the image can be substantially enhanced. This method is demonstrated briefly and its validity was tested in the laboratory. The high-resolution images of ocular fundus are compared with 8-frame-averaging images we obtained prior to this method. The experiment results now show improved visualization of fundus structures to some extent without greatly sacrificing image resolution.

  5. High-resolution space-shuttle polarimetry for farm crop classification

    NASA Technical Reports Server (NTRS)

    Egan, Walter G.; Israel, S.; Johnson, W. R.; Whitehead, V. S.

    1992-01-01

    A significant advance is reported in imaging the polarimetry of a terrestrial area of earth located along the Mississippi River near New Madrid, Missouri. Color imagery was obtained with twin Hasselblad cameras with mutually perpendicular polarization analyzers. Digitization of the imagery in three colors (red, green, and blue) was accomplished at the Johnson Space Center Video Digital Analysis System Laboratory, Houston, Texas. A ground resolution of 80-90 m was achieved in the high-resolution imagery. Percent polarization was superior to photometry for recognition and characterization of farm crops such as rice, milo, cotton, and soybeans and of fallow areas. Statistical analyses of the percent-polarization data permit a unique classification of crops. Atmospheric effects may be deduced. Space-shuttle window distortion and viewing angle-sun geometry must be taken into account in analyzing the data.

  6. Mueller matrix group theory formalism for tissue imaging polarimetry contrast increase.

    PubMed

    Fanjul-Vélez, Felix; Samperio-García, David; Pereda-Cubián, David; Arce-Diego, José L

    2007-01-01

    Optical characterization techniques provide a new approach to diagnostic imaging, with features such as a noninvasive or nonionizing character, as long as a resolution improvement. Intensity based measurements could be not enough for certain cases, and polarization information should be also used as a contrast parameter. Imaging polarimetry could be useful in many biomedical applications like dermatology or ophthalmology. Furthermore, it could be applied to the study of internal tissues through the use of optical fiber endoscopes, much less invasive that conventional biopsy. In this work the use of polarization parameters like the entropy factor, polarization components crosstalks or linear and circular polarization degrees is proposed as a way of improving tissue imaging contrast.

  7. Spectro-Imaging Polarimetry of the Local Corona During Solar Eclipse

    NASA Astrophysics Data System (ADS)

    Qu, Z. Q.; Dun, G. T.; Chang, L.; Murray, G.; Cheng, X. M.; Zhang, X. Y.; Deng, L. H.

    2017-02-01

    Results are presented from spectro-imaging polarimetry of radiation from the local solar corona during the 2013 total solar eclipse in Gabon. This polarimetric observation was performed from 516.3 nm to 532.6 nm using a prototype Fiber Arrayed Solar Optical Telescope (FASOT). A polarimetric noise level on the order of 10^{-3} results from a reduced polarimetric optical switching demodulation (RPOSD) procedure for data reduction. It is revealed that the modality of fractional linear polarization profiles of the green coronal line shows a diversity, which may indicate complex mechanisms. The polarization degree can approach 3.2 % above the continuum polarization level on a scale of 1500 km, and the nonuniform spatial distribution in amplitude and polarization direction is found even within a small field of view of 7500 km. All of this implies that the coronal polarization is highly structured and complex even on a small scale.

  8. Nanotwin Detection and Domain Polarity Determination via Optical Second Harmonic Generation Polarimetry.

    PubMed

    Ren, Ming-Liang; Agarwal, Rahul; Nukala, Pavan; Liu, Wenjing; Agarwal, Ritesh

    2016-07-13

    We demonstrate that optical second harmonic generation (SHG) can be utilized to determine the exact nature of nanotwins in noncentrosymmetric crystals, which is challenging to resolve via conventional transmission electron or scanned probe microscopies. Using single-crystalline nanotwinned CdTe nanobelts and nanowires as a model system, we show that SHG polarimetry can distinguish between upright (Cd-Te bonds) and inverted (Cd-Cd or Te-Te bonds) twin boundaries in the system. Inverted twin boundaries are generally not reported in nanowires due to the lack of techniques and complexity associated with the study of the nature of such defects. Precise characterization of the nature of defects in nanocrystals is required for deeper understanding of their growth and physical properties to enable their application in future devices.

  9. PRECISE ABSOLUTE ASTROMETRY FROM THE VLBA IMAGING AND POLARIMETRY SURVEY AT 5 GHz

    SciTech Connect

    Petrov, L.

    2011-09-15

    We present accurate positions for 857 sources derived from the astrometric analysis of 16 eleven-hour experiments from the Very Long Baseline Array imaging and polarimetry survey at 5 GHz (VIPS). Among the observed sources, positions of 430 objects were not previously determined at milliarcsecond-level accuracy. For 95% of the sources the uncertainty of their positions ranges from 0.3 to 0.9 mas, with a median value of 0.5 mas. This estimate of accuracy is substantiated by the comparison of positions of 386 sources that were previously observed in astrometric programs simultaneously at 2.3/8.6 GHz. Surprisingly, the ionosphere contribution to group delay was adequately modeled with the use of the total electron content maps derived from GPS observations and only marginally affected estimates of source coordinates.

  10. X-ray polarimetry and new prospects in high-energy astrophysics

    NASA Astrophysics Data System (ADS)

    Sgrò, C.

    2016-07-01

    Polarimetry is universally recognized as one of the new frontiers in X-ray astrophysics. It is a powerful tool to investigate a variety of astrophysical processes, as well as a mean to study fundamental physics in space. A renewed interest is testified by dedicated missions approved for phase A by ESA and NASA. The main advance is the availability of a gas pixel detector that is able to add polarization measurement to imaging and spectroscopy, and can be used at the focus of a conventional X-ray optics. The detector exploits the photoelectric effect in gas and a finely segmented ASIC as a collecting anode. In this work I will describe in detail the experimental technique and the detector concept, and illustrate the scientific prospects of these new missions.

  11. A Pair Production Telescope for Medium-Energy Gamma-Ray Polarimetry

    NASA Technical Reports Server (NTRS)

    Hunter, Stanley D.; Bloser, Peter F.; Depaola, Gerardo; Dion, Michael P.; DeNolfo, Georgia A.; Hanu, Andrei; Iparraguirre, Marcos; Legere, Jason; Longo, Francesco; McConnell, Mark L.; Nowicki, Suzanne F.; Ryan, James M.; Son, Seunghee; Stecker, Floyd W.

    2014-01-01

    We describe the science motivation and development of a pair production telescope for medium-energy (approximately 5-200 Mega electron Volts) gamma-ray polarimetry. Our instrument concept, the Advanced Energetic Pair Telescope (AdEPT), takes advantage of the Three-Dimensional Track Imager, a low-density gaseous time projection chamber, to achieve angular resolution within a factor of two of the pair production kinematics limit (approximately 0.6 deg at 70 Mega electron Volts), continuum sensitivity comparable with the Fermi-LAT front detector (is less than 3 x 10(exp -6) Mega electron Volts per square centimeter per second at 70 Mega electron Volts), and minimum detectable polarization less than 10% for a 10 milliCrab source in 10(exp 6) s.

  12. High-Sensitivity X-ray Polarimetry with Amorphous Silicon Active-Matrix Pixel Proportional Counters

    NASA Technical Reports Server (NTRS)

    Black, J. K.; Deines-Jones, P.; Jahoda, K.; Ready, S. E.; Street, R. A.

    2003-01-01

    Photoelectric X-ray polarimeters based on pixel micropattern gas detectors (MPGDs) offer order-of-magnitude improvement in sensitivity over more traditional techniques based on X-ray scattering. This new technique places some of the most interesting astronomical observations within reach of even a small, dedicated mission. The most sensitive instrument would be a photoelectric polarimeter at the focus of 2 a very large mirror, such as the planned XEUS. Our efforts are focused on a smaller pathfinder mission, which would achieve its greatest sensitivity with large-area, low-background, collimated polarimeters. We have recently demonstrated a MPGD polarimeter using amorphous silicon thin-film transistor (TFT) readout suitable for the focal plane of an X-ray telescope. All the technologies used in the demonstration polarimeter are scalable to the areas required for a high-sensitivity collimated polarimeter. Leywords: X-ray polarimetry, particle tracking, proportional counter, GEM, pixel readout

  13. Significance Analysis of Prognostic Signatures

    PubMed Central

    Beck, Andrew H.; Knoblauch, Nicholas W.; Hefti, Marco M.; Kaplan, Jennifer; Schnitt, Stuart J.; Culhane, Aedin C.; Schroeder, Markus S.; Risch, Thomas; Quackenbush, John; Haibe-Kains, Benjamin

    2013-01-01

    A major goal in translational cancer research is to identify biological signatures driving cancer progression and metastasis. A common technique applied in genomics research is to cluster patients using gene expression data from a candidate prognostic gene set, and if the resulting clusters show statistically significant outcome stratification, to associate the gene set with prognosis, suggesting its biological and clinical importance. Recent work has questioned the validity of this approach by showing in several breast cancer data sets that “random” gene sets tend to cluster patients into prognostically variable subgroups. This work suggests that new rigorous statistical methods are needed to identify biologically informative prognostic gene sets. To address this problem, we developed Significance Analysis of Prognostic Signatures (SAPS) which integrates standard prognostic tests with a new prognostic significance test based on stratifying patients into prognostic subtypes with random gene sets. SAPS ensures that a significant gene set is not only able to stratify patients into prognostically variable groups, but is also enriched for genes showing strong univariate associations with patient prognosis, and performs significantly better than random gene sets. We use SAPS to perform a large meta-analysis (the largest completed to date) of prognostic pathways in breast and ovarian cancer and their molecular subtypes. Our analyses show that only a small subset of the gene sets found statistically significant using standard measures achieve significance by SAPS. We identify new prognostic signatures in breast and ovarian cancer and their corresponding molecular subtypes, and we show that prognostic signatures in ER negative breast cancer are more similar to prognostic signatures in ovarian cancer than to prognostic signatures in ER positive breast cancer. SAPS is a powerful new method for deriving robust prognostic biological signatures from clinically annotated

  14. Comets at radio wavelengths

    NASA Astrophysics Data System (ADS)

    Crovisier, Jacques; Bockelée-Morvan, Dominique; Colom, Pierre; Biver, Nicolas

    2016-11-01

    Comets are considered as the most primitive objects in the Solar System. Their composition provides information on the composition of the primitive solar nebula, 4.6 Gyr ago. The radio domain is a privileged tool to study the composition of cometary ices. Observations of the OH radical at 18 cm wavelength allow us to measure the water production rate. A wealth of molecules (and some of their isotopologues) coming from the sublimation of ices in the nucleus have been identified by observations in the millimetre and submillimetre domains. We present an historical review on radio observations of comets, focusing on the results from our group, and including recent observations with the Nançay radio telescope, the IRAM antennas, the Odin satellite, the Herschel space observatory, ALMA, and the MIRO instrument aboard the Rosetta space probe.

  15. High redshift radio galaxies

    NASA Technical Reports Server (NTRS)

    Mccarthy, Patrick J.

    1993-01-01

    High redshift galaxies that host powerful radio sources are examined. An overview is presented of the content of radio surveys: 3CR and 3CRR, 4C and 4C/USS, B2/1 Jy, MG, MRC/1Jy, Parkes/PSR, B3, and ESO Key-Project. Narrow-line radio galaxies in the visible and UV, the source of ionization and excitation of the emission lines, emission-line luminosities, morphology of the line-emitting gas, physical properties and energetics, kinematics of the line-emitting gas, and implications from the emission lines are discussed. The morphologies and environments of the host galaxies, the alignment effect, and spectral energy distributions and ages are also examined.

  16. Radio coverage statistics.

    PubMed

    Lynn, W

    1984-01-01

    The Clearinghouse on Development Communication surveyed 135 countries in Asia, Africa, Europe, North and South America, for U.S.A.I.D., to determine the number of radio and television broadcast stations and receivers. Some of the data were obtained from the World Factbook, the World Radio and TV Handbook, and the World Radio and T.V. Facts and Figures, from 1979 to 1981. In those countries where stations are privately owned, audience surveys are often available. In 2 out of 3 developing countries, however, stations are government owned, and no such information is available. Numbers of receivers can sometimes be ascertained from receiver license applications. There is a need for more complete information on broadcast demographics, listening and viewing patterns by the community of world development program personnel.

  17. Radio frequency spectrum management

    NASA Astrophysics Data System (ADS)

    Sujdak, E. J., Jr.

    1980-03-01

    This thesis is a study of radio frequency spectrum management as practiced by agencies and departments of the Federal Government. After a brief introduction to the international agency involved in radio frequency spectrum management, the author concentrates on Federal agencies engaged in frequency management. These agencies include the National Telecommunications and Information Administration (NTIA), the Interdepartment Radio Advisory Committee (IRAC), and the Department of Defense (DoD). Based on an analysis of Department of Defense frequency assignment procedures, recommendations are given concerning decentralizing military frequency assignment by delegating broader authority to unified commanders. This proposal includes a recommendation to colocate the individual Service frequency management offices at the Washington level. This would result in reduced travel costs, lower manpower requirements, and a common tri-Service frequency management data base.

  18. Planetary radio waves

    NASA Technical Reports Server (NTRS)

    Goertz, C. K.

    1986-01-01

    Three planets, the earth, Jupiter and Saturn are known to emit nonthermal radio waves which require coherent radiation processes. The characteristic features (frequency spectrum, polarization, occurrence probability, radiation pattern) are discussed. Radiation which is externally controlled by the solar wind is distinguished from internally controlled radiation which only originates from Jupiter. The efficiency of the externally controlled radiation is roughly the same at all three planets (5 x 10 to the -6th) suggesting that similar processes are active there. The maser radiation mechanism for the generation of the radio waves and general requirements for the mechanism which couples the power generator to the region where the radio waves are generated are briefly discussed.

  19. Imaging Polarimetry of the 67P/Churyumov-Gerasimenko with ACS: Supporting the Rosetta Mission

    NASA Astrophysics Data System (ADS)

    Hines, Dean

    2014-10-01

    We propose ACS/WFC imaging polarimetry of Comet 67P/Churyumov-Gerasimenko (hereafter 67P), in support of the Rosetta mission, to place stringent constraints on dust particles in the coma. Our observations bracket the period when Rosetta operates closest to 67P, and will deploy the Philae lander. Fortunately, this occurs when the comet phase angle is well centered in the negative-polarization branch (12-15 degrees), enabling the different materials within the coma to be mapped using their polarization response, providing information on comet heterogeneity, and on the size, shape/structure, composition, or orientation of the particles. Our results will compare directly with in-situ measurements from Rosetta, placing strong constraints on material on small scales near and at the nucleus, and on larger scales within the coma. During the encounter, 67P will subtend only about 4-5", so ground-based observations would only provide one or two "polarimetric resolution elements" across the coma, at most. Laser AO systems can provide higher spatial resolution, but do not have visible wavelength polarimetry modes. In addition to our high spatial resolution requirement, this exciting period in the Rosetta mission coincides with the end of the visibility window from Earth, with 67P only visible for around 45 minutes between the end of astronomical twilight and reaching 2 airmasses in mid-November for ground-based telescopes. The necessary S/N could not be achieved by polarimeters on even the largest ground-based telescopes during this window. HST/ACS is the only asset capable of achieving our objectives during this once-in-a-lifetime opportunity.

  20. Error quantification of polarimetry-based precipitation estimates from X-band radars

    NASA Astrophysics Data System (ADS)

    Behnke, K. K.; Diederich, M.; Troemel, S.; Ryzhkov, A.; Simmer, C.

    2012-12-01

    Although theory and derived methods for radar polarimetry advanced considerably during the past decades, the quantitative estimation of precipitation from these measurements is still subject to various error sources. Therefore an integrated quantification of estimated polarimetric moments uncertainties including their projection into rainfall rates is indispensable. Besides improved hydrometeor typing and raindrop size discrimination, polarimetric moments allow for the correction of attenuation and beam blockage which are major challenges for the derivation of reliable rainfall estimates especially at shorter wavelengths like X-band. Moreover, polarimetry provides for a multitude of rainfall estimators appropriate for different precipitation regimes and types. This study concentrates on the performance of the estimators R(Z) with Z, the attenuation and beam blockage corrected reflectivity factor at horizontal polarization, R(KDP) with KDP, the specific differential phase, a combination of both estimators, and finally, R(A) using the specific attenuation A derived with the ZPHI method. We analyze observations of the operational German polarimetric X-band twin radar system BoXPol (Bonn) and JüXPol (Jülich) with both radars separated by about 50 km. The large spatial overlap of the mutual observation areas and several in-situ rain measurements in the same area constitute an ideal testbed for our study. We present two approaches for quantifying the error in resulting rain rates. The first approach is based on a statistical evaluation of particle concentration Nw and mean drop diameter Dm analyzed from long-term disdrometer observations in the BoXPol/JüXPol region. The different estimator performances are analyzed by comparison of the retrieved rain rates with rain gauge observations in relation to the ranges of Nw observed during different synoptic conditions. In the second approach, the estimated drop size distributions are used to simulate the polarimetric moments

  1. Laser Guide Star Adaptive Optics Polarimetry of Three Herbig Ae/Be Stars

    NASA Astrophysics Data System (ADS)

    Perrin, M. D.; Gavel, D. T.; Gates, E. L.; Graham, J. R.; Kalas, P.; Larwood, J. D.; Lloyd, J. P.; Max, C. E.; Pennington, D. M.

    2003-12-01

    We have obtained high spatial resolution near-IR imaging polarimetry of several Herbig Ae/Be stars using the Laser Guide Star adaptive optics (AO) system at Lick Observatory. We present here our observations of three of these objects: LkHα 198, LkHα 225, and LkHα 233. Herbig Ae/Be stars are young intermediate-mass stars, whose detailed nature is not as well understood as that of the lower-mass T Tauri stars. AO polarimetry enables us to probe circumstellar dust and outflows at high spatial resolution and dynamic range; the use of the Lick Observatory/LLNL laser guide star system enables observations of these distant and heavily visually extincted targets which could not otherwise be observed with AO. We find a bipolar structure ˜ 10 arcsec in extent oriented north-south surrounding LkHα 198, perpendicular to a dark lane suggestive of an edge-on circumstellar disk. The infrared companion 6 arcsec north illuminates nebulosity oriented in the NW-SE direction and may be the best candidate for driving CO outflow in the region. The two stellar components of the binary LkHα 225 show complex circumstellar structures that resemble tidal arms. Our polarimetric observations establish that the material is illuminated in scattered light from LkHa 225 and is thus physically associated with the binary. The observed morphology may be explained by tidal interactions between circumstellar disks during a close encounter of these stars. LkHα 233 presents a narrow, unpolarized lane separating its characteristic X-shaped reflection nebulosity. This dark lane is oriented perpendicular to a jet and the bipolar cavity and may represent an optically thick circumstellar disk that blocks our direct view of the star at wavelengths shorter than 2.2 micron. This work has been supported by the NSF Center for Adaptive Optics.

  2. Scattered and Reflected Light Polarimetry as a Diagnostic of Multibeam Hohlraum Physics

    NASA Astrophysics Data System (ADS)

    Turnbull, David

    2015-11-01

    Scattered light provides a window into the complex laser-plasma interactions and hydrodynamics occurring within indirect-drive inertial confinement fusion (ICF) hohlraums. Understanding hohlraum physics is an important part of developing improved targets and increasing the likelihood of ignition. Measurements of the scattered light power and spectrum are routinely made on each cone of beams at the National Ignition Facility (NIF) in order to correct for coupling losses due to laser-plasma instabilities. The additional ability to probe scattered light polarization on a 30° incidence beam was recently added, which has produced a number of discoveries regarding multibeam hohlraum physics. One particularly important insight is that the polarizations of an incident beam and its backscatter are affected by amplitude and phase modulations induced by crossing laser beams. The revised theory describing this optical wave mixing has recently been validated by conducting a two beam pump-probe experiment under carefully controlled conditions. This effect could be utilized more generally to produce ultrafast, damage-resistant, and tunable laser-plasma wave plates, polarizers, or other photonic devices. It also enables remote polarimetry-based probing of plasma conditions such as electron temperature. To extract more quantitative feedback about crossed-beam energy transfer (CBET) from the polarimetry data in ICF experiments at the NIF, the diagnostic has been upgraded to measure the complete Stokes vector with temporal resolution. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  3. Retrieving Vegetation Parameters and Soil Reflection Coefficients with P-band SAR Polarimetry

    NASA Astrophysics Data System (ADS)

    Alemohammad, S. H.; Konings, A. G.; Jagdhuber, T.; Entekhabi, D.

    2015-12-01

    Photosynthetic activity of plants is highly dependent on the water available to the plant through its roots. Therefore, measuring the root-zone-soil-moisture across large spatial scales is of great importance for crop monitoring and yield estimation as well as hydrological and ecological modeling. Unlike L-band instruments, which are sensitive to only a few centimeters of the top soil layer, P-band Synthetic Aperture Radar (SAR) instruments have a penetration depth that can be used to retrieve soil moisture profiles in depths of several tens of centimeters (depending on soil texture and moisture content). NASA's Airborne Microwave Observatory of Subcanopy and Subsurface (AirMOSS) mission is designed to study the application of P-band SAR measurements for monitoring root-zone-soil-moisture. In this study, we introduce a new framework to retrieve vegetation parameters and smooth-surface soil reflection coefficients using SAR polarimetry and the fully polarimetric covariance matrix of the backscattering signal from AirMOSS observations. The retrieved soil reflectivities (both horizontally and vertically -polarized) can then be used to estimate the soil moisture profile. The retrieval model takes into account contributions from surface, dihedral and volume scattering coming from the vegetation and soil components, and does not require prior vegetation parameters. This approach reduces the dependency of the retrieval on allometry-based vegetation models with large numbers of uncertain parameters. The performance of this method will be validated using observations from AirMOSS field campaigns in July 2013 over Harvard Forest in Massachusetts, USA. This will enable a quality assessment of the polarimetry-based retrieval of the soil reflectivities and the estimated root-zone-soil-moisture profiles.

  4. Lateral distribution of radio emission and its dependence on air shower longitudinal development

    SciTech Connect

    Kalmykov, Nikolai N.; Konstantinov, Andrey A. E-mail: elan1980@mail.ru

    2012-12-01

    The lateral distribution function (LDF) of radio emission from an extensive air shower is considered as the basic signature sensitive to the shower longitudinal development and, as a consequence, to the mass of a primary cosmic ray's particle that initiated a given shower. The peculiarities in the LDF's structure as well as their sensitivity to the height of shower maximum are investigated and explained.

  5. Radio Emission from Supernovae

    SciTech Connect

    Weiler, Kurt W.; Panagia, Nino; Sramek, Richard A.; Van Dyk, Schuyler D.; Stockdale, Christopher J.; Kelley, Matthew T.

    2009-05-03

    Study of radio supernovae over the past 27 years includes more than three dozen detected objects and more than 150 upper limits. From this work it is possible to identify classes of radio properties, demonstrate conformance to and deviations from existing models, estimate the density and structure of the circumstellar material and, by inference, the evolution of the presupernova stellar wind, and reveal the last stages of stellar evolution before explosion. It is also possible to detect ionized hydrogen along the line of sight, to demonstrate binary properties of the presupernova stellar system, and to detect dumpiness of the circumstellar material.

  6. Radio Observations of Meteors.

    PubMed

    Millman, P M

    1954-08-27

    To summarize, we find that the radio technique of meteor observation enables us to extend the systematic recording of meteor rates down to the 9th or 10th magnitude; to determine satisfactory heights and velocities on a scale previously impossible; to calculate the orbits of meteor showers and individual meteors, in particular those that appear only in the daytime; and to study wind drift and fine structure in the ionosphere. The radio observations have quite definitely indicated that down to the 9th magnitude, corresponding to particles approximately 1 mm in diameter, meteors are members of the solar system and do not come from interstellar space.

  7. Sensors Locate Radio Interference

    NASA Technical Reports Server (NTRS)

    2009-01-01

    After receiving a NASA Small Business Innovation Research (SBIR) contract from Kennedy Space Center, Soneticom Inc., based in West Melbourne, Florida, created algorithms for time difference of arrival and radio interferometry, which it used in its Lynx Location System (LLS) to locate electromagnetic interference that can disrupt radio communications. Soneticom is collaborating with the Federal Aviation Administration (FAA) to install and test the LLS at its field test center in New Jersey in preparation for deploying the LLS at commercial airports. The software collects data from each sensor in order to compute the location of the interfering emitter.

  8. Radio astronomy with microspacecraft

    NASA Technical Reports Server (NTRS)

    Collins, D.

    2001-01-01

    A dynamic constellation of microspacecraft in lunar orbit can carry out valuable radio astronomy investigations in the frequency range of 30kHz--30MHz, a range that is difficult to explore from Earth. In contrast to the radio astronomy ivestigations that have flown on individual spacecraft, the four microspacecraft together with a carrier spacecraft, which transported them to lunar orbit, form an interferometer with far superior angular resolution. Use of microspacecraft allows the entire constellation to be launched with a Taurus-class vehicle. Also distinguishing this approach is that the Moon is used as needed to shield the constellation from RF interference from the Earth and Sun.

  9. Signature molecular descriptor : advanced applications.

    SciTech Connect

    Visco, Donald Patrick, Jr.

    2010-04-01

    In this work we report on the development of the Signature Molecular Descriptor (or Signature) for use in the solution of inverse design problems as well as in highthroughput screening applications. The ultimate goal of using Signature is to identify novel and non-intuitive chemical structures with optimal predicted properties for a given application. We demonstrate this in three studies: green solvent design, glucocorticoid receptor ligand design and the design of inhibitors for Factor XIa. In many areas of engineering, compounds are designed and/or modified in incremental ways which rely upon heuristics or institutional knowledge. Often multiple experiments are performed and the optimal compound is identified in this brute-force fashion. Perhaps a traditional chemical scaffold is identified and movement of a substituent group around a ring constitutes the whole of the design process. Also notably, a chemical being evaluated in one area might demonstrate properties very attractive in another area and serendipity was the mechanism for solution. In contrast to such approaches, computer-aided molecular design (CAMD) looks to encompass both experimental and heuristic-based knowledge into a strategy that will design a molecule on a computer to meet a given target. Depending on the algorithm employed, the molecule which is designed might be quite novel (re: no CAS registration number) and/or non-intuitive relative to what is known about the problem at hand. While CAMD is a fairly recent strategy (dating to the early 1980s), it contains a variety of bottlenecks and limitations which have prevented the technique from garnering more attention in the academic, governmental and industrial institutions. A main reason for this is how the molecules are described in the computer. This step can control how models are developed for the properties of interest on a given problem as well as how to go from an output of the algorithm to an actual chemical structure. This report

  10. e-POP Radio Science Using Amateur Radio Transmissions

    NASA Astrophysics Data System (ADS)

    Frissell, N. A.; Perry, G. W.; Miller, E. S.; Shovkoplyas, A.; Moses, M. L.; James, H. G.; Yau, A. W.

    2015-12-01

    A major component of the enhanced Polar Outflow Probe (e-POP) Radio Receiver Instrument (RRI) mission is to utilize artificially generated radio emissions to study High Frequency (HF) radio wave propagation in the ionosphere. In the North American and European sectors, communications between amateur radio operators are a persistent and abundant source source of HF transmissions. We present the results of HF radio wave propagation experiments using amateur radio transmissions as an HF source for e-POP RRI. We detail how a distributed and autonomously operated amateur radio network can be leveraged to study HF radio wave propagation as well as the structuring and dynamics of the ionosphere over a large geographic region. In one case, the sudden disappearance of nearly two-dozen amateur radio HF sources located in the midwestern United States was used to detect a enhancement in foF2 in that same region. We compare our results to those from other more conventional radio instruments and models of the ionosphere to demonstrate the scientific merit of incorporating amateur radio networks for radio science at HF.

  11. A Cosmic Train Wreck: JVLA Radio Observations of the HST Frontier Fields Cluster Abell 2744

    NASA Astrophysics Data System (ADS)

    Pearce, Connor; Van Weeren, Reinout J.; Jones, Christine; Forman, William R.; Ogrean, Georgiana A.; Andrade-Santos, Felipe; Kraft, Ralph P.; Dawson, William; Brüggen, Marcus; Roediger, Elke; Bulbul, Esra; Mroczkowski, Tony

    2016-01-01

    The galaxy cluster mergers observed in the HST Frontier Fields represent some of the most energetic events in the Universe. Major cluster mergers leave distinct signatures in the ICM in the form of shocks, turbulence, and diffuse cluster radio sources. These diffuse radio sources, so-called radio relics and halos, provide evidence for the acceleration of relativistic particles and the presence of large scale magnetic fields in the ICM. Observations of these halos and relics allow us to (i) study the physics of particle acceleration and its relation with shocks and turbulence in the ICM and (ii) constrain the dynamical evolution of the merger eventsWe present Jansky Very Large Array 1-4 GHz observations of the Frontier cluster Abell 2744. We confirm the presence of the known giant radio halo and radio relic via our deep radio images. Owing to the much greater sensitivity of the JVLA compared to previous observations, we are able to detect a previously unobserved long Mpc-size filament of synchrotron emission to the south west of the cluster core. We also present a radio spectral index image of the diffuse cluster emission to test the origin of the radio relic and halo, related to the underlying particle acceleration mechanism. Finally, we carry out a search for radio emission from the 'jellyfish' galaxies in A2744 to estimate their star formation rate. These highly disturbed galaxies are likely influenced by the cluster merger event, although the precise origin of these galaxies is still being debated.

  12. 2D image of local density and magnetic fluctuations from line-integrated interferometry-polarimetry measurements

    NASA Astrophysics Data System (ADS)

    Lin, L.; Ding, W. X.; Brower, D. L.

    2014-11-01

    Combined polarimetry-interferometry capability permits simultaneous measurement of line-integrated density and Faraday effect with fast time response (˜1 μs) and high sensitivity. Faraday effect fluctuations with phase shift of order 0.05° associated with global tearing modes are resolved with an uncertainty ˜0.01°. For physics investigations, local density fluctuations are obtained by inverting the line-integrated interferometry data. The local magnetic and current density fluctuations are then reconstructed using a parameterized fit of the polarimetry data. Reconstructed 2D images of density and magnetic field fluctuations in a poloidal cross section exhibit significantly different spatial structure. Combined with their relative phase, the magnetic-fluctuation-induced particle transport flux and its spatial distribution are resolved.

  13. Imaging of the magnetic field structure in megagauss plasmas by combining pulsed polarimetry with an optical Kerr effect shutter technique

    SciTech Connect

    Smith, R. J.

    2010-10-15

    Pulsed polarimetry in combination with a high speed photographic technique based on the optical Kerr effect is described. The backscatter in a pulsed polarimeter is directed through a scattering cell and photographed using an {approx}1 ps shutter, essentially freezing the intensity pattern. The image provides both the local electron density and magnetic field distributions along and transverse to the laser sightline. Submillimeter spatial resolution is possible for probing wavelengths in the visible due to the high densities and strong optical activity. Pulsed polarimetry is thereby extended to centimeter-sized plasmas with n{sub e}>10{sup 19}-10{sup 20} cm{sup -3} and B>20-100 T (MG) produced by multiterawatt, multimega-ampere electrical drivers, wire Z pinches, and liner imploded magnetized plasmas.

  14. Imaging polarimetry of the potentially planet-forming circumstellar disk HD 142527: The NaCo view

    NASA Astrophysics Data System (ADS)

    Canovas, H.; Ménard, F.; Hales, A.; Jordán, A.; Schreiber, M. R.; Casassus, S.; Gledhill, T. M.; Pinte, C.

    2014-10-01

    HD 142527 is a unique protoplanetary disk in terms of planet formation. Its high accretion rate combined with its huge inner gap and short age make of it an ideal candidate for harboring forming planets. ALMA cycle-0 observations revealed gap crossing gas streams and showed that the millimeter-sized dust particles are distributed in a horse-shoe shape. Here we present our recent H- and Ks-band imaging polarimetry data of HD 142527 obtained with VLT/NaCo. By means of polarimetry, we remove most of the stellar light, directly imaging the disk's inner regions. Our observations allow us to constrain the dust properties (size and porosity) on the surface of the outer disk. We also detect two regions of the disk with low emission (``nulls") both in polarized and unpolarized light. Intriguingly, one of these nulls is azimuthally coincident with the maximum of the horse-shoe shape detected by ALMA.

  15. Prism beamswitch for radio telescopes.

    PubMed

    Payne, J M; Ulich, B L

    1978-12-01

    A dielectric prism and switching mechanism have been constructed for beamswitching a Cassegrain radio telescope. Spatially extended radio sources may be mapped without significant confusion utilizing the sensitivity and stability inherent in the conventional Dicke radiometer.

  16. Signature Visualization of Software Binaries

    SciTech Connect

    Panas, T

    2008-07-01

    In this paper we present work on the visualization of software binaries. In particular, we utilize ROSE, an open source compiler infrastructure, to pre-process software binaries, and we apply a landscape metaphor to visualize the signature of each binary (malware). We define the signature of a binary as a metric-based layout of the functions contained in the binary. In our initial experiment, we visualize the signatures of a series of computer worms that all originate from the same line. These visualizations are useful for a number of reasons. First, the images reveal how the archetype has evolved over a series of versions of one worm. Second, one can see the distinct changes between version. This allows the viewer to form conclusions about the development cycle of a particular worm.

  17. Graph Analytics for Signature Discovery

    SciTech Connect

    Hogan, Emilie A.; Johnson, John R.; Halappanavar, Mahantesh; Lo, Chaomei

    2013-06-01

    Within large amounts of seemingly unstructured data it can be diffcult to find signatures of events. In our work we transform unstructured data into a graph representation. By doing this we expose underlying structure in the data and can take advantage of existing graph analytics capabilities, as well as develop new capabilities. Currently we focus on applications in cybersecurity and communication domains. Within cybersecurity we aim to find signatures for perpetrators using the pass-the-hash attack, and in communications we look for emails or phone calls going up or down a chain of command. In both of these areas, and in many others, the signature we look for is a path with certain temporal properties. In this paper we discuss our methodology for finding these temporal paths within large graphs.

  18. Measurement of sniper infrared signatures

    NASA Astrophysics Data System (ADS)

    Kastek, M.; Dulski, R.; Trzaskawka, P.; Bieszczad, G.

    2009-09-01

    The paper presents some practical aspects of sniper IR signature measurements. Description of particular signatures for sniper and background in typical scenarios has been presented. We take into consideration sniper activities in open area as well as in urban environment. The measurements were made at field test ground. High precision laboratory measurements were also performed. Several infrared cameras were used during measurements to cover all measurement assumptions. Some of the cameras are measurement class devices with high accuracy and speed. The others are microbolometer cameras with FPA detector similar to those used in real commercial counter-sniper systems. The registration was made in SWIR and LWIR spectral bands simultaneously. An ultra fast visual camera was also used for visible spectra registration. Exemplary sniper IR signatures for typical situation were presented.

  19. SOFIA Mid-infrared Imaging1 and CSO Submillimeter Polarimetry Observations of G034.43+00.24 MM1

    NASA Astrophysics Data System (ADS)

    Jones, T. J.; Gordon, Michael; Shenoy, Dinesh; Gehrz, R. D.; Vaillancourt, John E.; Krejny, M.

    2016-06-01

    We present 11.1 to 37.1 μm imaging observations of the very dense molecular cloud core MM1 in G034.43+00.24 using FORCAST on SOFIA and submillimeter (submm) polarimetry using SHARP on the Caltech Submillimeter Observatory. We find that at the spatial resolution of SOFIA, the point-spread function (PSF) of MM1 is consistent with being a single source, as expected based on millimeter (mm) and submm observations. The spectral energy distributions (SEDs) of MM1 and MM2 have a warm component at the shorter wavelengths not seen in mm and submm SEDs. Examination of H(1.65 μm) stellar polarimetry from the Galactic Plane Infrared Polarization Survey shows that G034 is embedded in an external magnetic field aligned with the Galactic Plane. The SHARP polarimetry at 450 μm shows a magnetic field geometry in the vicinity of MM1 that does not line up with either the Galactic Plane or the mean field direction inferred from the CARMA interferometric polarization map of the central cloud core, but is perpendicular to the long filament in which G034 is embedded. The CARMA polarimetry does show evidence for grain alignment in the central region of the cloud core, and thus does trace the magnetic field geometry near the embedded Class 0 YSO. Based in part on observations made with the NASA/DLR Stratospheric Observatory for Infrared Astronomy (SOFIA). SOFIA is jointly operated by the Universities Space Research Association, Inc. (USRA), under NASA contract NAS2-97001, and the Deutsches SOFIA Institut (DSI) under DLR contract 50 OK 0901 to the University of Stuttgart.

  20. Svetloe Radio Astronomical Observatory

    NASA Technical Reports Server (NTRS)

    Smolentsev, Sergey; Rahimov, Ismail

    2013-01-01

    This report summarizes information about the Svetloe Radio Astronomical Observatory activities in 2012. Last year, a number of changes took place in the observatory to improve some technical characteristics and to upgrade some units to their required status. The report provides an overview of current geodetic VLBI activities and gives an outlook for the future.

  1. Zelenchukskaya Radio Astronomical Observatory

    NASA Technical Reports Server (NTRS)

    Smolentsev, Sergey; Dyakov, Andrei

    2013-01-01

    This report summarizes information about Zelenchukskaya Radio Astronomical Observatory activities in 2012. Last year a number of changes took place in the observatory to improve some technical characteristics and to upgrade some units to the required status. The report provides an overview of current geodetic VLBI activities and gives an outlook for the future.

  2. RADIO RANGING DEVICE

    DOEpatents

    Nieset, R.T.

    1961-05-16

    A radio ranging device is described. It utilizes a super regenerative detector-oscillator in which echoes of transmitted pulses are received in proper phase to reduce noise energy at a selected range and also at multiples of the selected range.

  3. Community Radio in Canada.

    ERIC Educational Resources Information Center

    Canadian Broadcasting Corp., Ottawa (Ontario).

    Results are presented of a survey of 20 community radio organizations operating in Canada. For each of the 20 agencies, information is provided relating to: (1) the name and address of the organization; (2) the name and population of the community served; (3) the station's call letters, frequency, and power; (4) the date of the station's license;…

  4. Radio Channel Simulator (RCSM)

    SciTech Connect

    2007-01-31

    This is a simulation package for making site specific predictions of radio signal strength. The software computes received power at discrete grid points as a function of the transmitter location and propagation environment. It is intended for use with wireless network simulation packages and to support wireless network deployments.

  5. Albanian: Basic Radio Communications.

    ERIC Educational Resources Information Center

    Defense Language Inst., Washington, DC.

    This volume has been designed as a supplement to a course in Albanian developed by the Defense Language Institute. The emphasis in this text is placed on radio communications instruction. The volume is divided into five exercises, each of which contains a vocabulary, dictation, and an air-to-ground communications procedure conducted in Albanian…

  6. Torun Radio Astronomy Observatory

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    Torun Center for Astronomy is located at Piwnice, 15 km north of Torun, Poland. A part of the Faculty of Physics and Astronomy of the Nicolaus Copernicus University, it was created by the union of Torun Radio Astronomy Observatory (TRAO) and the Institute of Astronomy on 1 January 1997....

  7. Educational Broadcasting--Radio.

    ERIC Educational Resources Information Center

    Ahamed, Uvais; Grimmett, George

    This manual is intended for those who must conduct educational radio broadcasting training courses in Asia-Pacific countries without the resources of experienced personnel, as well as for individuals to use in self-learning situations. The selection of material has been influenced by the need to use broadcasting resources effectively in programs…

  8. The origin, evolution and signatures of primordial magnetic fields

    NASA Astrophysics Data System (ADS)

    Subramanian, Kandaswamy

    2016-07-01

    The universe is magnetized on all scales probed so far. On the largest scales, galaxies and galaxy clusters host magnetic fields at the micro Gauss level coherent on scales up to ten kpc. Recent observational evidence suggests that even the intergalactic medium in voids could host a weak  ˜  10-16 Gauss magnetic field, coherent on Mpc scales. An intriguing possibility is that these observed magnetic fields are a relic from the early universe, albeit one which has been subsequently amplified and maintained by a dynamo in collapsed objects. We review here the origin, evolution and signatures of primordial magnetic fields. After a brief summary of magnetohydrodynamics in the expanding universe, we turn to magnetic field generation during inflation and phase transitions. We trace the linear and nonlinear evolution of the generated primordial fields through the radiation era, including viscous effects. Sensitive observational signatures of primordial magnetic fields on the cosmic microwave background, including current constraints from Planck, are discussed. After recombination, primordial magnetic fields could strongly influence structure formation, especially on dwarf galaxy scales. The resulting signatures on reionization, the redshifted 21 cm line, weak lensing and the Lyman-α forest are outlined. Constraints from radio and γ-ray astronomy are summarized. Astrophysical batteries and the role of dynamos in reshaping the primordial field are briefly considered. The review ends with some final thoughts on primordial magnetic fields.

  9. Statistical Studies of Ground-Based Optical Lightning Signatures

    NASA Astrophysics Data System (ADS)

    Hunt, C. R.; Nemzek, R. J.; Suszcynsky, D. M.

    2005-12-01

    Most extensive optical studies of lightning have been conducted from orbit, and the statistics of events collected from earth are relatively poorly documented. The time signatures of optical power measured in the presence of clouds are inevitably affected by scattering,which can distort the signatures by extending and delaying the amplitude profile in time. We have deployed two all-sky photodiode detectors, one in New Mexico and one in Oklahoma, which are gathering data alongside electric field change monitors as part of the LANL EDOTX Great Plains Array. Preliminary results show that the photodiode is sensitive to approximately 50% or more of RF events detected at ranges of up to 30 km, and still has some sensitivity at ranges in excess of 60 km (distances determined by the EDOTX field-change array). The shapes of events within this range were assessed, with focus on rise time, width, peak power, and their correlation to corresponding electric field signatures, and these are being compared with published on-orbit and ground-based data. Initial findings suggest a mean characteristic width (ratio of total detected optical energy to peak power) of 291 +/- 12 microseconds and a mean delay between the RF signal peak and optical peak of 121 +/- 17 microseconds. These values fall between prior ground-based measurements of direct return stroke emissions, and scattering-dominated on-orbit measurements. This work will promote better understanding of the correspondence between radio and optical measurements of lightning.

  10. Textural signatures for wetland vegetation

    NASA Technical Reports Server (NTRS)

    Whitman, R. I.; Marcellus, K. L.

    1973-01-01

    This investigation indicates that unique textural signatures do exist for specific wetland communities at certain times in the growing season. When photographs with the proper resolution are obtained, the textural features can identify the spectral features of the vegetation community seen with lower resolution mapping data. The development of a matrix of optimum textural signatures is the goal of this research. Seasonal variations of spectral and textural features are particularly important when performing a vegetations analysis of fresh water marshes. This matrix will aid in flight planning, since expected seasonal variations and resolution requirements can be established prior to a given flight mission.

  11. Ballistic Signature Identification System Study

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The first phase of a research project directed toward development of a high speed automatic process to be used to match gun barrel signatures imparted to fired bullets was documented. An optical projection technique has been devised to produce and photograph a planar image of the entire signature, and the phototransparency produced is subjected to analysis using digital Fourier transform techniques. The success of this approach appears to be limited primarily by the accuracy of the photographic step since no significant processing limitations have been encountered.

  12. Community Control of Local Radio.

    ERIC Educational Resources Information Center

    Lewis, Peter M.

    This study was designed to determine to what extent local communities control the local radio which serves them, by what formal mechanisms their control is secured, and the underlying assumptions and goals which govern the practice of the professionals who have charge of the facilities. Two British radio stations, BBC Radio Bristol and the…

  13. Ham Radio is Mir Magic.

    ERIC Educational Resources Information Center

    Evans, Gary

    1997-01-01

    Presents a classroom activity in which students communicated with U.S. and Russian astronauts via ham radio while they were in orbit on the space station Mir. Gives suggestions for other ham radio classroom activities as well as names of organizations, publications, and grant programs that teachers can access to help in bring ham radio into their…

  14. Radio: Your Publics Are Listening!

    ERIC Educational Resources Information Center

    Marx, Gary

    The purpose of this booklet is to provide school board members, administrators, teachers, and others interested in education with an understanding of radio, how it works, and how school systems can take advantage of the communications possibilities offered by radio. After providing background information on radio as a mass communications medium…

  15. Collaborative Beamfocusing Radio (COBRA)

    NASA Astrophysics Data System (ADS)

    Rode, Jeremy P.; Hsu, Mark J.; Smith, David; Husain, Anis

    2013-05-01

    A Ziva team has recently demonstrated a novel technique called Collaborative Beamfocusing Radios (COBRA) which enables an ad-hoc collection of distributed commercial off-the-shelf software defined radios to coherently align and beamform to a remote radio. COBRA promises to operate even in high multipath and non-line-of-sight environments as well as mobile applications without resorting to computationally expensive closed loop techniques that are currently unable to operate with significant movement. COBRA exploits two key technologies to achieve coherent beamforming. The first is Time Reversal (TR) which compensates for multipath and automatically discovers the optimal spatio-temporal matched filter to enable peak signal gains (up to 20 dB) and diffraction-limited focusing at the intended receiver in NLOS and severe multipath environments. The second is time-aligned buffering which enables TR to synchronize distributed transmitters into a collaborative array. This time alignment algorithm avoids causality violations through the use of reciprocal buffering. Preserving spatio-temporal reciprocity through the TR capture and retransmission process achieves coherent alignment across multiple radios at ~GHz carriers using only standard quartz-oscillators. COBRA has been demonstrated in the lab, aligning two off-the-shelf software defined radios over-the-air to an accuracy of better than 2 degrees of carrier alignment at 450 MHz. The COBRA algorithms are lightweight, with computation in 5 ms on a smartphone class microprocessor. COBRA also has low start-up latency, achieving high accuracy from a cold-start in 30 ms. The COBRA technique opens up a large number of new capabilities in communications, and electronic warfare including selective spatial jamming, geolocation and anti-geolocation.

  16. Software-defined radar and waveforms for studying micro-Doppler signatures

    NASA Astrophysics Data System (ADS)

    Liu, Baokun; Chen, Rachel

    2014-05-01

    In this paper, we investigate the use of software defined radar (SDR) to analyze the micro-Doppler signatures. The first SDR we use is based on the Universal Software Radio Peripheral (USRP) and GNU Radio, and another SDR which has several operation modes is based on field-programmable gate arrays (FPGA). Typically, the USRP-based SDR is not optimized for radar applications due to its narrow bandwidth and time-varying additional delay caused by USRP components and operating system. The FPGA-based SDR is more suitable for applications where high-resolution range information is required. Our studies indicate that both of the SDR systems are capable of producing the micro-Doppler signatures. System design challenges and measurement results will be discussed in detail.

  17. The importance of Radio Quiet Zone (RQZ) for radio astronomy

    NASA Astrophysics Data System (ADS)

    Umar, Roslan; Abidin, Zamri Zainal; Ibrahim, Zainol Abidin

    2013-05-01

    Most of radio observatories are located in isolated areas. Since radio sources from the universe is very weak, astronomer need to avoid radio frequency interference (RFI) from active spectrum users and radio noise produced by human made (telecommunication, mobile phone, microwave user and many more. There are many observatories around the world are surrounded by a Radio Quiet Zone (RQZ), which is it was set up using public or state laws. A Radio Quiet Zone normally consists of two areas: an exclusive area in which totally radio emissions are forbidden, with restrictions for residents and business developments, and a larger (radius up to 100 km above) coordination area where the power of radio transmission limits to threshold levels. Geographical Information System (GIS) can be used as a powerful tool in mapping large areas with varying RQZ profiles. In this paper, we report the initial testing of the usage of this system in order to identify the areas were suitable for Radio Quiet Zone. Among the important parameters used to develop the database for our GIS are population density, information on TV and telecommunication (mobile phones) transmitters, road networks (highway), and contour shielding. We will also use other information gathered from on-site RFI level measurements on selected 'best' areas generated by the GIS. The intention is to find the best site for the purpose of establishing first radio quiet zones for radio telescope in Malaysia.

  18. Accurate radio and optical positions for southern radio sources

    NASA Technical Reports Server (NTRS)

    Harvey, Bruce R.; Jauncey, David L.; White, Graeme L.; Nothnagel, Axel; Nicolson, George D.; Reynolds, John E.; Morabito, David D.; Bartel, Norbert

    1992-01-01

    Accurate radio positions with a precision of about 0.01 arcsec are reported for eight compact extragalactic radio sources south of -45-deg declination. The radio positions were determined using VLBI at 8.4 GHz on the 9589 km Tidbinbilla (Australia) to Hartebeesthoek (South Africa) baseline. The sources were selected from the Parkes Catalogue to be strong, flat-spectrum radio sources with bright optical QSO counterparts. Optical positions of the QSOs were also measured from the ESO B Sky Survey plates with respect to stars from the Perth 70 Catalogue, to an accuracy of about 0.19 arcsec rms. These radio and optical positions are as precise as any presently available in the far southern sky. A comparison of the radio and optical positions confirms the estimated optical position errors and shows that there is overall agreement at the 0.1-arcsec level between the radio and Perth 70 optical reference frames in the far south.

  19. Improved method of signature extraction

    NASA Technical Reports Server (NTRS)

    Christianson, D.; Gordon, M.; Kistler, R.; Kriegler, F. J.; Lampert, S.; Marshall, R. E.; Mclaughlin, R.; Smith, V.

    1977-01-01

    System promises capability of rapidly processing large amounts of data generated by currently available and planned multispectral sensors, such as those utilized on aircraft and spacecraft. Techniques developed for system, greatly decrease operator time required for signature extraction from multispectral data base.

  20. Topological Signatures for Population Admixture

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Topological Signatures for Population AdmixtureDeniz Yorukoglu1, Filippo Utro1, David Kuhn2, Saugata Basu3 and Laxmi Parida1* Abstract Background: As populations with multi-linear transmission (i.e., mixing of genetic material from two parents, say) evolve over generations, the genetic transmission...

  1. MK 66 Rocket Signature Reduction

    DTIC Science & Technology

    1982-04-01

    Indian Head, Maryland. ’The objec- tive of the study was to reduce the visible signature of the rocket motor. The rocket motor used for demonstration tests...15 6. Actual Emmiissions . . . . . . ........... . 16 7. Human Eye Adjusted Emmissions ..................... .. 16 8. Cross...altered. Additives are commonly used in gun propellants for elimination of muzzle flash. Their use in tactical rockets has been very limited, and

  2. Disaster relief through composite signatures

    NASA Astrophysics Data System (ADS)

    Hawley, Chadwick T.; Hyde, Brian; Carpenter, Tom; Nichols, Steve

    2012-06-01

    A composite signature is a group of signatures that are related in such a way to more completely or further define a target or operational endeavor at a higher fidelity. This paper builds on previous work developing innovative composite signatures associated with civil disasters, including physical, chemical and pattern/behavioral. For the composite signature approach to be successful it requires effective data fusion and visualization. This plays a key role in both preparedness and the response and recovery which are critical to saving lives. Visualization tools enhance the overall understanding of the crisis by pulling together and analyzing the data, and providing a clear and complete analysis of the information to the organizations/agencies dependant on it for a successful operation. An example of this, Freedom Web, is an easy-to-use data visualization and collaboration solution for use in homeland security, emergency preparedness, situational awareness, and event management. The solution provides a nationwide common operating picture for all levels of government through a web based, map interface. The tool was designed to be utilized by non-geospatial experts and is easily tailored to the specific needs of the users. Consisting of standard COTS and open source databases and a web server, users can view, edit, share, and highlight information easily and quickly through a standard internet browser.

  3. MODELING OF GYROSYNCHROTRON RADIO EMISSION PULSATIONS PRODUCED BY MAGNETOHYDRODYNAMIC LOOP OSCILLATIONS IN SOLAR FLARES

    SciTech Connect

    Mossessian, George; Fleishman, Gregory D.

    2012-04-01

    A quantitative study of the observable radio signatures of the sausage, kink, and torsional magnetohydrodynamic (MHD) oscillation modes in flaring coronal loops is performed. Considering first non-zero order effect of these various MHD oscillation modes on the radio source parameters such as magnetic field, line of sight, plasma density and temperature, electron distribution function, and the source dimensions, we compute time-dependent radio emission (spectra and light curves). The radio light curves (of both flux density and degree of polarization) at all considered radio frequencies are then quantified in both time domain (via computation of the full modulation amplitude as a function of frequency) and in Fourier domain (oscillation spectra, phases, and partial modulation amplitude) to form the signatures specific to a particular oscillation mode and/or source parameter regime. We found that the parameter regime and the involved MHD mode can indeed be distinguished using the quantitative measures derived in the modeling. We apply the developed approach to analyze radio burst recorded by Owens Valley Solar Array and report possible detection of the sausage mode oscillation in one (partly occulted) flare and kink or torsional oscillations in another flare.

  4. Fluctuation dynamos and their Faraday rotation signatures

    NASA Astrophysics Data System (ADS)

    Bhat, Pallavi; Subramanian, Kandaswamy

    2013-03-01

    Turbulence is ubiquitous in many astrophysical systems like galaxies, galaxy clusters and possibly even the filaments in the intergalactic medium. We study fluctuation dynamo action in turbulent systems focusing on one observational signature, the random Faraday rotation measure (RM) from radio emission of background sources seen through the intermittent magnetic field generated by such a dynamo. We simulate the fluctuation dynamo in periodic boxes up to resolutions of 5123, with varying fluid and magnetic Reynolds numbers, and measure the resulting random RMs. We show that even though the magnetic field generated is intermittent, it still allows for contributions to the RM to be significant. When the dynamo saturates, the rms value of RM is of the order of 40-50 per cent of the value expected in a model where fields of strength Brms uniformly fill cells of the largest turbulent eddy but are randomly oriented from one cell to another. This level of RM dispersion is obtained across different values of magnetic Reynolds number and Prandtl number explored. We also use the random RMs to probe the structure of the generated fields to distinguish the contribution from intense and diffuse field regions. We find that the strong field regions (say with B > 2Brms) contribute only of the order of 15-20 per cent to the RM. Thus, rare structures do not dominate the RM; rather, the general `sea' of volume filling fluctuating fields are the dominant contributors. We also show that the magnetic integral scale, Lint, which is directly related to the RM dispersion, increases in all the runs, as Lorentz forces become important to saturate the dynamo. It appears that due to the ordering effect of the Lorentz forces, Lint of the saturated field tends to a modest fraction, 1/2-1/3 of the integral scale of the velocity field, for all our runs. These results are then applied to discuss the Faraday rotation signatures of fluctuation dynamo generated fields in young galaxies, galaxy

  5. Microwave-Spectral Signatures Would Reveal Concealed Objects

    NASA Technical Reports Server (NTRS)

    Arndt, G.; Ngo, P.; Carl, J. R.; Byerly, K.; Stolarcyzk, L.

    2004-01-01

    A proposed technique for locating concealed objects (especially small antipersonnel land mines) involves the acquisition and processing of spectral signatures over broad microwave frequency bands. This technique was conceived to overcome the weaknesses of older narrow- band electromagnetic techniques like ground-probing radar and low-frequency electromagnetic induction. Ground-probing radar is susceptible to false detections and/or interference caused by rocks, roots, air pockets, soil inhomogeneities, ice, liquid water, and miscellaneous buried objects other than those sought. Moreover, if the radar frequency happens to be one for which the permittivity of a sought object matches the permittivity of the surrounding soil or there is an unfavorable complex-amplitude addition of the radar reflection at the receiver, then the object is not detected. Low-frequency electromagnetic induction works well for detecting metallic objects, but the amounts of metal in plastic mines are often too small to be detectable. The potential advantage of the proposed technique arises from the fact that wideband spectral signatures generally contain more relevant information than do narrow-band signals. Consequently, spectral signatures could be used to make better decisions regarding whether concealed objects are present and whether they are the ones sought. In some cases, spectral signatures could provide information on the depths, sizes, shapes, and compositions of objects. An apparatus to implement the proposed technique (see Figure 1) could be assembled from equipment already in common use. Typically, such an apparatus would include a radio-frequency (RF) transmitter/receiver, a broad-band microwave antenna, and a fast personal computer loaded with appropriate software. In operation, the counter would be turned on, the antenna would be aimed at the ground or other mass suspected to contain a mine or other sought object, and the operating frequency would be swept over the band of

  6. Space-borne polarimetric SAR sensors or the golden age of radar polarimetry

    NASA Astrophysics Data System (ADS)

    Pottier, E.

    2010-06-01

    SAR Polarimetry represents an active area of research in Active Earth Remote Sensing. This interest is clearly supported by the fact that nowadays there exists, or there will exist in a very next future, a non negligible quantity of launched Polarimetric SAR Spaceborne sensors. The ENVISAT satellite, developed by ESA, was launched on March 2002, and was the first Spaceborne sensor offering an innovative dualpolarization Advanced Synthetic Aperture Radar (ASAR) system operating at C-band. The second Polarimetric Spaceborne sensor is ALOS, a Japanese Earth-Observation satellite, developed by JAXA and was launched in January 2006. This mission includes an active L-band polarimetric radar sensor (PALSAR) whose highresolution data may be used for environmental and hazard monitoring. The third Polarimetric Spaceborne sensor is TerraSAR-X, a new German radar satellite, developed by DLR, EADS-Astrium and Infoterra GmbH, was launched on June 2007. This sensor carries a dual-polarimetric and high frequency X-Band SAR sensor that can be operated in different modes and offers features that were not available from space before. At least, the Polarimetric Spaceborne sensor, developed by CSA and MDA, and named RADARSAT-2 was launched in December 2007 The Radarsat program was born out the need for effective monitoring of Canada’s icy waters, and some Radarsat-2 capabilities that benefit sea- and river ice applications are the multi-polarization options that will improve ice-edge detection, ice-type discrimination and structure information. The many advances in these different Polarimetric Spaceborne platforms were developed to respond to specific needs for radar data in environmental monitoring applications around the world, like : sea- and river-ice monitoring, marine surveillance, disaster management, oil spill detection, snow monitoring, hydrology, mapping, geology, agriculture, soil characterisation, forestry applications (biomass, allometry, height…), urban mapping etc

  7. Block truncation signature coding for hyperspectral analysis

    NASA Astrophysics Data System (ADS)

    Chakravarty, Sumit; Chang, Chein-I.

    2008-08-01

    This paper introduces a new signature coding which is designed based on the well-known Block Truncation Coding (BTC). It comprises of bit-maps of the signature blocks generated by different threshold criteria. Two new BTC-based algorithms are developed for signature coding, to be called Block Truncation Signature Coding (BTSC) and 2-level BTSC (2BTSC). In order to compare the developed BTC based algorithms with current binary signature coding schemes such as Spectral Program Analysis Manager (SPAM) developed by Mazer et al. and Spectral Feature-based Binary Coding (SFBC) by Qian et al., three different thresholding functions, local block mean, local block gradient, local block correlation are derived to improve the BTSC performance where the combined bit-maps generated by these thresholds can provide better spectral signature characterization. Experimental results reveal that the new BTC-based signature coding performs more effectively in characterizing spectral variations than currently available binary signature coding methods.

  8. AIDS radio triggers.

    PubMed

    Elias, A M

    1991-07-01

    In April 1991, the Ethnic Communities' Council of NSW was granted funding under the Community AIDS Prevention and Education Program through the Department of Community Services and Health, to produce a series of 6x50 second AIDS radio triggers with a 10-second tag line for further information. The triggers are designed to disseminate culturally-sensitive information about HIV/AIDS in English, Italian, Greek, Spanish, Khmer, Turkish, Macedonian, Serbo-Croatian, Arabic, Cantonese, and Vietnamese, with the goal of increasing awareness and decreasing the degree of misinformation about HIV/AIDS among people of non-English-speaking backgrounds through radio and sound. The 6 triggers cover the denial that AIDS exists in the community, beliefs that words and feelings do not protect one from catching HIV, encouraging friends to be compassionate, compassion within the family, AIDS information for a young audience, and the provision of accurate and honest information on HIV/AIDS. The triggers are slated to be completed by the end of July 1991 and will be broadcast on all possible community, ethnic, and commercial radio networks across Australia. They will be available upon request in composite form with an information kit for use by health care professionals and community workers.

  9. MULTIMOMENT RADIO TRANSIENT DETECTION

    SciTech Connect

    Spitler, L. G.; Cordes, J. M.; Chatterjee, S.; Stone, J.

    2012-04-01

    We present a multimoment technique for signal classification and apply it to the detection of fast radio transients in incoherently dedispersed data. Specifically, we define a spectral modulation index in terms of the fractional variation in intensity across a spectrum. A signal whose intensity is distributed evenly across the entire band has a lower modulation index than a spectrum whose intensity is localized in a single channel. We are interested in broadband pulses and use the modulation index to excise narrowband radio frequency interference by applying a modulation index threshold above which candidate events are removed. The technique is tested both with simulations and using data from known sources of radio pulses (RRAT J1928+15 and giant pulses from the Crab pulsar). The method is generalized to coherent dedispersion, image cubes, and astrophysical narrowband signals that are steady in time. We suggest that the modulation index, along with other statistics using higher order moments, should be incorporated into signal detection pipelines to characterize and classify signals.

  10. The Askaryan Radio Array

    NASA Astrophysics Data System (ADS)

    Hoffman, Kara D.

    2013-01-01

    Ultra high energy cosmogenic neutrinos could be most efficiently detected in dense, radio frequency (RF) transparent media via the Askaryan effect. Building on the expertise gained by RICE, ANITA and IceCube's radio extension in the use of the Askaryan effect in cold Antarctic ice, we are currently developing an antenna array known as ARA (The Askaryan Radio Array) to be installed in boreholes extending 200 m below the surface of the ice near the geographic South Pole. The unprecedented scale of ARA, which will cover a fiducial area of ~ 100 square kilometers, was chosen to ensure the detection of the flux of neutrinos suggested by the observation of a drop in high energy cosmic ray flux consistent with the GZK cutoff by HiRes and the Pierre Auger Observatory. Funding to develop the instrumentation and install the first prototypes has been granted, and the first components of ARA were installed during the austral summer of 2010-2011. Within 3 years of commencing operation, the full ARA will exceed the sensitivity of any other instrument in the 0.1-10 EeV energy range by an order of magnitude. The primary goal of the ARA array is to establish the absolute cosmogenic neutrino flux through a modest number of events. This information would frame the performance requirements needed to expand the array in the future to measure a larger number of neutrinos with greater angular precision in order to study their spectrum and origins.

  11. Partially Blind Signatures Based on Quantum Cryptography

    NASA Astrophysics Data System (ADS)

    Cai, Xiao-Qiu; Niu, Hui-Fang

    2012-12-01

    In a partially blind signature scheme, the signer explicitly includes pre-agreed common information in the blind signature, which can improve the availability and performance. We present a new partially blind signature scheme based on fundamental properties of quantum mechanics. In addition, we analyze the security of this scheme, and show it is not possible to forge valid partially blind signatures. Moreover, the comparisons between this scheme and those based on public-key cryptography are also discussed.

  12. 48 CFR 4.102 - Contractor's signature.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 1 2011-10-01 2011-10-01 false Contractor's signature. 4... ADMINISTRATIVE MATTERS Contract Execution 4.102 Contractor's signature. (a) Individuals. A contract with an... be signed by that individual, and the signature shall be followed by the individual's typed,...

  13. Workshop on Radio Transients

    NASA Astrophysics Data System (ADS)

    Croft, Steve; Gaensler, Bryan

    2012-04-01

    abstract-type="normal">SummaryWe are entering a new era in the study of variable and transient radio sources. This workshop discussed the instruments and the strategies employed to study those sources, how they are identified and classified, how results from different surveys can be compared, and how radio observations tie in with those at other wavelengths. The emphasis was on learning what common ground there is between the plethora of on-going projects, how methods and code can be shared, and how best practices regarding survey strategy could be adopted. The workshop featured the four topics below. Each topic commenced with a fairly brief introductory talk, which then developed into discussion. By way of preparation, participants had been invited to upload and discuss one slide per topic to a wiki ahead of the workshop. 1. Telescopes, instrumentation and survey strategy. New radio facilities and on-going projects (including upgrades) are both studying the variability of the radio sky, and searching for transients. The discussion first centred on the status of those facilities, and on projects with a time-domain focus, both ongoing and planned, before turning to factors driving choices of instrumentation, such as phased array versus single pixel feeds, the field of view, spatial and time resolution, frequency and bandwidth, depth, area, and cadence of the surveys. 2. Detection, pipelines, and classification. The workshop debated (a) the factors that influence decisions to study variability in the (u,v) plane, in images, or in catalogues, (b) whether, and how much, pipeline code could potentially be shared between one project and another, and which software packages are best for different approaches, (c) how data are stored and later accessed, and (d) how transients and variables are defined and classified. 3. Statistics, interpretation, and synthesis. It then discussed how (i) the choice of facility and strategy and (ii) detection and classification schemes

  14. Signatures of topological Josephson junctions

    NASA Astrophysics Data System (ADS)

    Peng, Yang; Pientka, Falko; Berg, Erez; Oreg, Yuval; von Oppen, Felix

    2016-08-01

    Quasiparticle poisoning and diabatic transitions may significantly narrow the window for the experimental observation of the 4 π -periodic dc Josephson effect predicted for topological Josephson junctions. Here, we show that switching-current measurements provide accessible and robust signatures for topological superconductivity which persist in the presence of quasiparticle poisoning processes. Such measurements provide access to the phase-dependent subgap spectrum and Josephson currents of the topological junction when incorporating it into an asymmetric SQUID together with a conventional Josephson junction with large critical current. We also argue that pump-probe experiments with multiple current pulses can be used to measure the quasiparticle poisoning rates of the topological junction. The proposed signatures are particularly robust, even in the presence of Zeeman fields and spin-orbit coupling, when focusing on short Josephson junctions. Finally, we also consider microwave excitations of short topological Josephson junctions which may complement switching-current measurements.

  15. Polarization signatures of airborne particulates

    NASA Astrophysics Data System (ADS)

    Raman, Prashant; Fuller, Kirk A.; Gregory, Don A.

    2013-07-01

    Exploratory research has been conducted with the aim of completely determining the polarization signatures of selected particulates as a function of wavelength. This may lead to a better understanding of the interaction between electromagnetic radiation and such materials, perhaps leading to the point detection of bio-aerosols present in the atmosphere. To this end, a polarimeter capable of measuring the complete Mueller matrix of highly scattering samples in transmission and reflection (with good spectral resolution from 300 to 1100 nm) has been developed. The polarization properties of Bacillus subtilis (surrogate for anthrax spore) are compared to ambient particulate matter species such as pollen, dust, and soot. Differentiating features in the polarization signatures of these samples have been identified, thus demonstrating the potential applicability of this technique for the detection of bio-aerosol in the ambient atmosphere.

  16. Signatures of a shadow biosphere.

    PubMed

    Davies, Paul C W; Benner, Steven A; Cleland, Carol E; Lineweaver, Charles H; McKay, Christopher P; Wolfe-Simon, Felisa

    2009-03-01

    Astrobiologists are aware that extraterrestrial life might differ from known life, and considerable thought has been given to possible signatures associated with weird forms of life on other planets. So far, however, very little attention has been paid to the possibility that our own planet might also host communities of weird life. If life arises readily in Earth-like conditions, as many astrobiologists contend, then it may well have formed many times on Earth itself, which raises the question whether one or more shadow biospheres have existed in the past or still exist today. In this paper, we discuss possible signatures of weird life and outline some simple strategies for seeking evidence of a shadow biosphere.

  17. Radio quiet, please! - protecting radio astronomy from interference

    NASA Astrophysics Data System (ADS)

    van Driel, W.

    2011-06-01

    The radio spectrum is a finite and increasingly precious resource for astronomical research, as well as for other spectrum users. Keeping the frequency bands used for radio astronomy as free as possible of unwanted Radio Frequency Interference (RFI) is crucial. The aim of spectrum management, one of the tools used towards achieving this goal, includes setting regulatory limits on RFI levels emitted by other spectrum users into the radio astronomy frequency bands. This involves discussions with regulatory bodies and other spectrum users at several levels - national, regional and worldwide. The global framework for spectrum management is set by the Radio Regulations of the International Telecommunication Union, which has defined that interference is detrimental to radio astronomy if it increases the uncertainty of a measurement by 10%. The Radio Regulations are revised every three to four years, a process in which four organisations representing the interests of the radio astronomical community in matters of spectrum management (IUCAF, CORF, CRAF and RAFCAP) participate actively. The current interests and activities of these four organisations range from preserving what has been achieved through regulatory measures, to looking far into the future of high frequency use and giant radio telescope use.

  18. The extreme behavior of the radio-loud narrow-line Seyfert 1 galaxy J0849+5108

    SciTech Connect

    Maune, Jeremy D.; Eggen, Joseph R.; Miller, H. Richard; Marshall, Kevin; Readhead, Anthony C. S.; Hovatta, Talvikki; King, Oliver

    2014-10-10

    Simultaneous radio, optical (both photometry and polarimetry), X-ray, and γ-ray observations of the radio-loud narrow-line Seyfert 1 (RL-NLSy1) galaxy J0849+5108 are presented. A massive three-magnitude optical flare across five nights in 2013 April is detected, along with associated flux increases in the γ-ray, infrared, and radio regimes; no comparable event was detected in the X-rays, though this may be due to poor coverage. A spectral energy distribution (SED) for the object using quasi-simultaneous data centered on the optical flare is compared to the previously published SEDs for the object by D'Ammando et al. The flare event coincided with a high degree of optical polarization. High amplitude optical microvariability is clearly detected, and is found to be of comparable amplitude when the object is observed in both faint and bright states. The object is also seen to undergo rapid shifts in polarization in both degree and electric vector position angle within a single night. J0849+5108 appears to show even more extreme variability than that previously reported for the similar object J0948+0022. These observations appear to support the growing claim that some RL-NLSy1 galaxies constitute a sub-class of blazar-like active galactic nuclei.

  19. Moøller polarimetry with polarized atomic hydrogen at MESA

    SciTech Connect

    Bartolomé, P. Aguar; Aulenbacher, K.; Tyukin, V.

    2013-11-07

    A new generation of parity violation (PV) electron scattering experiments are planned to be carried out at the Institut für Kernphysik in Mainz. These experiments will be performed at low energies of 100-200 MeV using the new accelerator MESA (Mainz Energy recovering Superconducting Accelerator). One of the main challenges of such experiments is to achieve an accuracy in beam polarization measurements that must be below 0.5%. This very high accuracy can be reached using polarized atomic hydrogen gas, stored in an ultra-cold magnetic trap, as the target for electron beam polarimetry based on Mo/ller scattering. Electron spin-polarized atomic hydrogen can be stored at high densities of 10{sup 16} cm{sup −2}, over relatively long time periods, in a high magnetic field (8T) and at low temperatures (0.3K). The gradient force splits the ground state of the hydrogen into four states with different energies. Atoms in the low energy states are trapped in the strong magnetic field region whereas the high energy states are repelled and pumped away. The physics of ultra-cold atomic hydrogen in magnetic traps and the status of the Mainz Hydro-Mo/ller project will be presented.

  20. Moøller polarimetry with polarized atomic hydrogen at MESA

    NASA Astrophysics Data System (ADS)

    Bartolomé, P. Aguar; Aulenbacher, K.; Tyukin, V.

    2013-11-01

    A new generation of parity violation (PV) electron scattering experiments are planned to be carried out at the Institut für Kernphysik in Mainz. These experiments will be performed at low energies of 100-200 MeV using the new accelerator MESA (Mainz Energy recovering Superconducting Accelerator). One of the main challenges of such experiments is to achieve an accuracy in beam polarization measurements that must be below 0.5%. This very high accuracy can be reached using polarized atomic hydrogen gas, stored in an ultra-cold magnetic trap, as the target for electron beam polarimetry based on Mo/ller scattering. Electron spin-polarized atomic hydrogen can be stored at high densities of 1016 cm-2, over relatively long time periods, in a high magnetic field (8T) and at low temperatures (0.3K). The gradient force splits the ground state of the hydrogen into four states with different energies. Atoms in the low energy states are trapped in the strong magnetic field region whereas the high energy states are repelled and pumped away. The physics of ultra-cold atomic hydrogen in magnetic traps and the status of the Mainz Hydro-Mo/ller project will be presented.

  1. The use of laterally graded multilayer mirrors for soft X-ray polarimetry

    NASA Astrophysics Data System (ADS)

    Marshall, Herman L.; Schulz, Norbert S.; Windt, David L.; Gullikson, Eric M.; Blake, Eric; Getty, Dan; McInturff, Zane

    2014-07-01

    ABSTRACT We present continued development of laterally graded multilayer mirrors (LGMLs) for a telescope design capable of measuring linear X-ray polarization over a broad spectral band. The multilayer-coated mirrors are used as Bragg re ectors at the Brewster angle. By matching to the dispersion of a spectrometer, one may take advantage of high multilayer re ectivities and achieve modulation factors over 50% over the entire 0.2-0.8 keV band. In Phase II of the polarimetry beam-line development, we demonstrated that the system provides 100% polarized X-rays at 0.525 keV (Marshall et al. 2013). Here, we present results from phase III of our development, where a LGML is used at the source and laterally manipulated in order to select and polarize X-rays from emission lines for a variety of source anodes. The beam-line will then provide the capability to test polarimeter components across the 0.15-0.70 keV band. We also present plans for a suborbital rocket experiment designed to detect a polarization level of better than 10% for an active galactic nucleus.

  2. High-Contrast Near-Infrared Imaging Polarimetry of the Protoplanetary Disk around RY Tau

    NASA Technical Reports Server (NTRS)

    Takami, Michihiro; Karr, Jennifer L.; Hashimoto, Jun; Kim, Hyosun; Wisenewski, John; Henning, Thomas; Grady, Carol; Kandori, Ryo; Hodapp, Klaus W.; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Chou, Mei-yin; Itoh, Yoichi; Momose, Mumetake; Mayama, Satoshi; Currie, Thayne; Follette, Katherine B.; Kwon, Jungmi; Abe, Lyu; Brandner, Wolfgang; Brandt, Timothy D.; Carson, Joseph; Egner, Sebastian E.; McElwain, Michael W.; Serabyn, Eugene

    2013-01-01

    We present near-infrared coronagraphic imaging polarimetry of RY Tau. The scattered light in the circumstellar environment was imaged at H-band at a high resolution (approx. 0.05) for the first time, using Subaru-HiCIAO. The observed polarized intensity (PI) distribution shows a butterfly-like distribution of bright emission with an angular scale similar to the disk observed at millimeter wavelengths. This distribution is offset toward the blueshifted jet, indicating the presence of a geometrically thick disk or a remnant envelope, and therefore the earliest stage of the Class II evolutionary phase. We perform comparisons between the observed PI distribution and disk models with: (1) full radiative transfer code, using the spectral energy distribution (SED) to constrain the disk parameters; and (2) monochromatic simulations of scattered light which explore a wide range of parameters space to constrain the disk and dust parameters. We show that these models cannot consistently explain the observed PI distribution, SED, and the viewing angle inferred by millimeter interferometry. We suggest that the scattered light in the near-infrared is associated with an optically thin and geometrically thick layer above the disk surface, with the surface responsible for the infrared SED. Half of the scattered light and thermal radiation in this layer illuminates the disk surface, and this process may significantly affect the thermal structure of the disk.

  3. HIGH-CONTRAST NEAR-INFRARED IMAGING POLARIMETRY OF THE PROTOPLANETARY DISK AROUND RY TAU

    SciTech Connect

    Takami, Michihiro; Karr, Jennifer L.; Kim, Hyosun; Chou, Mei-Yin; Hashimoto, Jun; Kandori, Ryo; Kusakabe, Nobuhiko; Kwon, Jungmi; Wisniewski, John; Henning, Thomas; Brandner, Wolfgang; Grady, Carol A.; Hodapp, Klaus W.; Kudo, Tomoyuki; Itoh, Yoichi; Momose, Munetake; Mayama, Satoshi; Currie, Thayne; Follette, Katherine B.; Abe, Lyu; and others

    2013-08-01

    We present near-infrared coronagraphic imaging polarimetry of RY Tau. The scattered light in the circumstellar environment was imaged at the H band at a high resolution ({approx}0.''05) for the first time, using Subaru/HiCIAO. The observed polarized intensity (PI) distribution shows a butterfly-like distribution of bright emission with an angular scale similar to the disk observed at millimeter wavelengths. This distribution is offset toward the blueshifted jet, indicating the presence of a geometrically thick disk or a remnant envelope, and therefore the earliest stage of the Class II evolutionary phase. We perform comparisons between the observed PI distribution and disk models with (1) full radiative transfer code, using the spectral energy distribution (SED) to constrain the disk parameters; and (2) monochromatic simulations of scattered light which explore a wide range of parameters space to constrain the disk and dust parameters. We show that these models cannot consistently explain the observed PI distribution, SED, and the viewing angle inferred by millimeter interferometry. We suggest that the scattered light in the near-infrared is associated with an optically thin and geometrically thick layer above the disk surface, with the surface responsible for the infrared SED. Half of the scattered light and thermal radiation in this layer illuminates the disk surface, and this process may significantly affect the thermal structure of the disk.

  4. Broad Band Polarimetry with the Soft Gamma-ray Detector on board Hitomi (ASTRO-H)

    NASA Astrophysics Data System (ADS)

    Mizuno, Tsunefumi

    2016-07-01

    X-ray and gamma-ray polarization can arise from synchrotron emission in ordered magnetic fields, photon propagation in extremely strong magnetic fields and anisotropic Compton scattering. Polarization measurement provides vital information (often inaccessible even with the current best imaging instruments) on magnetic field and accretion disk around astrophysical objects, hence is a powerful probe to investigate emission mechanism and geometries of the sources. The Soft Gamma-ray Detector (SGD) on board Hitomi (ASTRO-H) satellite is a highly-sensitive spectrometer in the 40-600 keV energy band. Since the SGD is a Si/CdTe Compton camera surrounded by a thick BGO shield, it also works as a very sensitive polarimeter in wide energy range. We have verified the SGD polarization measurement capability through extensive beam tests at a synchrotron facility SPring-8 in 2008 (Takeda et al. 2010) and 2015 (Katsuta et al. in preparation). In addition, we have examined possible sciences provided by the SGD polarimetry based on the expected performance (Coppi et al. 2014). In this contribution, we will present the SGD instrumentation, the latest beam test results and expected sciences provided by the polarization measurements. The results based on the initial observations will also be reported.

  5. Near-infrared Imaging Polarimetry of GGD 27: Circular Polarization and Magnetic Field Structures

    NASA Astrophysics Data System (ADS)

    Kwon, Jungmi; Tamura, Motohide; Hough, James H.; Nagata, Tetsuya; Kusakabe, Nobuhiko; Saito, Hiro

    2016-06-01

    Near-infrared imaging polarimetry in the J, H, and K s bands was carried out for GGD 27 in the dark cloud Lynds 291. Details of an infrared reflection nebula associated with the optical nebulosity GGD 27 and the infrared nebula GGD 27 IRS are presented. Aperture photometry of 1263 point-like sources, detected in all three bands, was used to classify them based on a color-color diagram, and the linear polarization of several hundred sources was determined, with the latter used to map the magnetic field structure around GGD 27. This field, around GGD 27 IRS, appears to be associated with the extended CO outflow of IRAS 18162-2048 however, there are partly distorted or bent components in the field. The Chandrasekhar-Fermi method gives an estimate of the magnetic field strength as ˜90 μG. A region associated with GGD 27 IRS is discovered to have a circular polarization in the range of ˜2%-11% in the K s band. The circular polarization has an asymmetric positive/negative pattern and extends out to ˜ 120″ or 1.0 pc. The circular and linear polarization patterns are explained as resulting from a combination of dense inner and fainter outer lobes, suggesting episodic outflow.

  6. Quantitative spectral light scattering polarimetry for monitoring fractal growth pattern of Bacillus thuringiensis bacterial colonies

    NASA Astrophysics Data System (ADS)

    Banerjee, Paromita; Soni, Jalpa; Ghosh, Nirmalya; Sengupta, Tapas K.

    2013-02-01

    It is of considerable current interest to develop various methods which help to understand and quantify the cellular association in growing bacterial colonies and is also important in terms of detection and identification of a bacterial species. A novel approach is used here to probe the morphological structural changes occurring during the growth of the bacterial colony of Bacillus thuringiensis under different environmental conditions (in normal nutrient agar, in presence of glucose - acting as additional nutrient and additional 3mM arsenate as additional toxic material). This approach combines the quantitative Mueller matrix polarimetry to extract intrinsic polarization properties and inverse analysis of the polarization preserving part of the light scattering spectra to determine the fractal parameter H (Hurst exponent) using Born approximation. Interesting differences are observed in the intrinsic polarization parameters and also in the Hurst exponent, which is a measurement of the fractality of a pattern formed by bacteria while growing as a colony. These findings are further confirmed with optical microscopic studies of the same sample and the results indicate a very strong and distinct dependence on the environmental conditions during growth, which can be exploited to quantify different bacterial species and their growth patterns.

  7. Electron kinetic effects on interferometry and polarimetry in high temperature fusion plasmas

    NASA Astrophysics Data System (ADS)

    Mirnov, V. V.; Brower, D. L.; Den Hartog, D. J.; Ding, W. X.; Duff, J.; Parke, E.

    2013-11-01

    At anticipated high electron temperatures in ITER, the effects of electron thermal motion on phase measurements made by the toroidal interferometer/polarimeter (TIP) and poloidal polarimeter (PoPola) diagnostics will be significant and must be precisely treated or the measurement accuracy will fail to meet the specified requirements for ITER operation. We calculate electron thermal corrections to the interferometric phase and polarization state of an electromagnetic wave propagating along tangential and poloidal chords (Faraday and Cotton-Mouton polarimetry) and incorporate them into the Stokes vector equation for evolution of polarization. Although these corrections are small at electron temperatures Te ≃ 1 keV, they become sizable at Te ⩾ 10 keV. The precision of the previous lowest order linear in the τ = Te/mec2 model may be insufficient; we present a more precise model with τ2-order corrections to satisfy the high accuracy required for ITER TIP and PoPola diagnostics. Proper treatment of temperature effects will ensure more accurate interpretation of interferometric and polarimetric measurements in fusion devices like ITER and DEMO. The use of precise analytic expressions is especially important for burning plasmas where various interferometric techniques will be used for direct real time feedback control of device operations with time resolution ˜1 ms to regulate the rate of the thermonuclear burn and monitor/control the safety factor profile.

  8. Far-field method for the characterisation of three-dimensional fields: vectorial polarimetry

    NASA Astrophysics Data System (ADS)

    Rodríguez, O.; Lara, D.; Dainty, C.

    2010-06-01

    The first attempt to completely characterise a three-dimensional field was done by Ellis and Dogariu with excellent results reported [1] . However, their method is based on near-field techniques, which limits its range of applications. In this work, we present an alternative far-field method for the characterisation of the three-dimensional field that results from the interaction of a tightly focused three-dimensional field [2] with a sub-resolution specimen. Our method is based on the analysis of the scattering-angle-resolved polarisation state distribution across the exit pupil of a high numerical aperture (NA) collector lens using standard polarimetry techniques. Details of the method, the experimental setup built to verify its capabilities, and numerical and first experimental evidence demonstrating that the method allows for high sensitivit y on sub-resolution displacements of a sub-resolution specimen shall be presented [3]. This work is funded by Science Foundation Ireland grant No. 07/IN.1/I906 and Shimadzu Corporation, Japan. Oscar Rodríguez is grateful to the National Council for Science and Technology (CONACYT, Mexico) for the Ph D scholarship 177627.

  9. Optical diagnosis of dengue virus infected human blood using Mueller matrix polarimetry

    NASA Astrophysics Data System (ADS)

    Anwar, Shahzad; Firdous, Shamaraz

    2016-08-01

    Currently dengue fever diagnosis methods include capture ELISAs, immunofluorescence tests, and hemagglutination assays. In this study optical diagnosis of dengue virus infection in the whole blood is presented utilizing Mueller matrix polarimetry. Mueller matrices of about 50 dengue viral infected and 25 non-dengue healthy blood samples were recorded utilizing light source from 500 to 700 nm with scanning step of 10 nm. Polar decomposition of the Mueller matrices for all the blood samples was performed that yielded polarization properties including depolarization, diattenuation, degree of polarization, retardance and optical activity, out of which, depolarization index clusters up the diseased and healthy in to different separate groups. The average depolarized light in the case of dengue infection in the whole blood at 500 nm is 18%, whereas for the healthy blood samples it is 13.5%. This suggests that depolarization index of polarized light at the wavelengths of 500, 510, 520, 530 and 540 nm, we find that in case of depolarization index values are higher for dengue viral infection as compared to normal samples. This technique can effectively be used for the characterization of the dengue virus infected at an early stage of disease.

  10. Phenological tracking og agricultural feilds investigated by using dual polarimetry tanDEM-X images

    NASA Astrophysics Data System (ADS)

    Mirzaee, S.; Motagh, M.; Arefi, H.; Nooryazdan, A.

    2015-04-01

    Remote sensing plays a key role in monitoring and assessing environmental changes. Because of its special imaging characteristics such as high-resolution, capabilities to obtain data in all weather conditions and sensitivity to geometrical and dielectric properties of the features, Synthetic Aperture Radar (SAR) technology has become a powerful technique to detect small scale changes related to earth surface.SAR images contain the information of both phase and intensity in different modes like single, dual and full polarimetric states which are important in order to extract information about various targets. In this study we investigate phenological changes in an agricultural region using high-resolution X-band SAR data. The case study is located in Doroud region of Lorestan province, west of Iran. The purpose is to investigate the ability of copolar and interferometric coherence extracted from TanDEM-X dual polarimetry (HH/VV) in bistatic StripMap mode for tracking the phenological changes of crops during growing season. The data include 11 images acquired between 12.06.2012 and 02.11.2012 and 6 images acquired between 30.05.2013 and 04.08.2013 in the CoSSC format. Results show that copolar coherence is almost able to follow phenological changes but interferometric coherence has a near constant behaviour with fluctuations mainly related to baseline variations.

  11. THE LEGACY OF SCUPOL: 850 {mu}m IMAGING POLARIMETRY FROM 1997 TO 2005

    SciTech Connect

    Matthews, Brenda C.; McPhee, Christie A.; Fissel, Laura M.; Curran, Rachel L.

    2009-05-15

    SCUPOL, the polarimeter for SCUBA on the James Clerk Maxwell Telescope, was the most prolific thermal imaging polarimeter built to date. Between 1997 and 2005, observations of 104 regions were made at 850 {mu}m in the mapping mode. The instrument has produced {approx}50 refereed journal publications, and that number is still growing. We have systematically re-reduced all imaging polarimetry made in the standard 'jiggle-map' mode from the SCUBA archive (2800+ individual observations) to produce a catalog of SCUPOL images and tables. We present the results of our analysis with figures and data tables produced for all 83 regions where significant polarization was detected. In addition, the reduced data cubes and data tables can be accessed online. In many cases, the data included in this paper have been previously published elsewhere. However, this publication includes unpublished data sets, in whole or in part, toward 39 regions, including cores in {rho} Ophiuchus, Orion's OMC-2 region, several young stellar objects, and the galaxy M87.

  12. Complete time-resolved polarimetry of scattered light at the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Turnbull, David; Ayers, Shannon; Bell, Perry; Chow, Robert; Frieders, Gene; Hibbard, Robin L.; Michel, Pierre; Ralph, Joseph E.; Ross, James S.; Stanley, Joel R.; Vickers, James L.; Zeid, Ziad M.; Moody, John D.

    2015-08-01

    The 3ω scattered light polarimetry diagnostic in the 30° incidence cone backscatter diagnostic at the National Ignition Facility (NIF) is being upgraded to measure the full time-resolved Stokes vector. Previously, the diagnostic had a single channel capable of diagnosing the time-integrated balance of the horizontal and vertical polarizations. Two additional channels were added - one that measures the balance of the 45° and 135° projections, and another that measures the right- and left-circular polarizations - and together the three complete the Stokes vector measurement. A division-of-aperture scheme is employed in which three nearby portions of the near field are sampled simultaneously. Time resolution is obtained by relaying an image of the measured regions onto a set of fibers coupled to diodes. The new diagnostic will be capable of measuring scattered light signals <≍ .1GW with ≍ 120ps time resolution. This will allow more rigorous evaluation of earlier indications that backscatter polarization can serve as a quantitative diagnostic of crossed-beam energy transfer in indirect-drive inertial confinement fusion experiments. It will also be used to diagnose Faraday rotation induced by magnetic fields in collisionless shock and turbulent dynamo experiments later this year.

  13. Birefringence of the central cornea in children assessed with scanning laser polarimetry

    NASA Astrophysics Data System (ADS)

    Irsch, Kristina; Shah, Ashesh A.

    2012-08-01

    Corneal birefringence is a well-known confounding factor with all polarization-sensitive technology used for retinal scanning and other intraocular assessment. It has been studied extensively in adults, but little is known regarding age-related differences. Specifically, no information is available concerning corneal birefringence in children. For applications that are geared towards children, such as retinal birefringence scanning for strabismus screening purposes, it is important to know the expected range of both corneal retardance and azimuth in pediatric populations. This study investigated central corneal birefringence in children (ages three and above), by means of scanning laser polarimetry (GDx-VCC™, Carl Zeiss Meditec, Inc.). Children's measures of corneal retardance and azimuth were compared with those obtained in adults. As with previous studies in adults, corneal birefringence was found to vary widely in children, with corneal retardance ranging from 10 to 77 nm, and azimuth (slow axis) ranging from -11° to 71° (measured nasally downward). No significant differences in central corneal birefringence were found between children and adults, nor were significant age-related differences found in general. In conclusion, establishing knowledge of the polarization properties of the central cornea in children allows better understanding, exploitation, or bypassing of these effects in new polarization-sensitive pediatric ophthalmic applications.

  14. OPTICAL IMAGING POLARIMETRY OF THE LkCa 15 PROTOPLANETARY DISK WITH SPHERE ZIMPOL

    SciTech Connect

    Thalmann, C.; Quanz, S. P.; Schmid, H. M.; Garufi, A.; Meyer, M. R.; and others

    2015-08-01

    We present the first optical (590–890 nm) imaging polarimetry observations of the pre-transitional protoplanetary disk around the young solar analog LkCa 15, addressing a number of open questions raised by previous studies. We detect the previously unseen far side of the disk gap, confirming the highly off-centered scattered-light gap shape that was postulated from near-infrared imaging, at odds with the symmetric gap inferred from millimeter interferometry. Furthermore, we resolve the inner disk for the first time and trace it out to 30 AU. This new source of scattered light may contribute to the near-infrared interferometric signal attributed to the protoplanet candidate LkCa 15 b, which lies embedded in the outer regions of the inner disk. Finally, we present a new model for the system architecture of LkCa 15 that ties these new findings together. These observations were taken during science verification of SPHERE ZIMPOL and demonstrate this facility’s performance for faint guide stars under adverse observing conditions.

  15. Determination of cloud coverage of Earth-like exoplanets by polarimetry

    NASA Astrophysics Data System (ADS)

    Rossi, Loïc; Stam, Daphne M.

    2016-10-01

    The properties of clouds in atmospheres of exoplanets will play a key role in the processes determining their radiative balance and climate.They also complicate the detection of chemical species in the atmospheres by flattening the spectra or by creating degeneracies between observables (Kitzmann et al. 2011, Line and Parmentier 2016).Polarimetry promises to be a powerful tool to detect and study exoplanets (Stam et al. 2004). The polarisation of the light scattered by the atmospheres of those planets contains a lot of information about the vertical structure of the atmosphere and about the composition of the clouds (Karalidi et al. 2012) and has already been very successful in the retrieval of atmospheric properties of Venus (Rossi et al. 2015, 2016 in prep).We will show that the degree of polarization of the light scattered by a cloudy exoplanet can be used to discriminate between different types of cloud coverage and to quantify the amount of cloud coverage on the planetary scale. We simulated the disk-integrated polarization of light scattered by exoplanets with various patchy cloud patterns, subsolar clouds and polar cusps. We show that flux and polarization can be used to differentiate between patchy and polar clouds. Observations at various wavelengths in the visible range and of different Stokes parameters would allow to differentiate between cloud coverage and cloud top altitudes.We also propose an observational strategy that could help to retrieve orbital parameters and percentage of cloud coverage with minor ambiguities.

  16. Pulsed Polarimetry and magnetic sensing on the Magnetized Shock Experiment (MSX)

    NASA Astrophysics Data System (ADS)

    Smith, R. J.; Hutchinson, T. M.; Weber, T. E.; Taylor, S. F.; Hsu, S. C.

    2014-10-01

    MSX is uniquely positioned to generate the conditions for collision-less magnetized supercritical shocks with Alvenic Mach numbers (MA) of the order 10 and higher. Significant operational strides have been made in forming plasmas over wide parameter ranges: (Te + Ti) of 10-200 eV, average neof 5-60×10+21 m-3, speeds up to 150 km/s and fields up to 1T with a highest plasma flow MA of 5 to date. The MSX plasma is unique in regards to large plasma size of 10 cm and average β higher than 0.8 making the FRC and the magnetized shock structure candidates for the application of Pulsed Polarimetry, a polarization sensitive Lidar technique. The shock dynamics are presently being investigated using internal probes, interferometry and imaging. Internal probe results and an assessment of the shock parameters will dictate the use of the UW pulsed polarimeter system in which internal ne, Teand B are to be measured. Recent results will be presented. Supported by DOE Office of Fusion Energy Sciences Funding DE-FOA-0000755.

  17. Laser guide star adaptive optics imaging polarimetry of Herbig Ae/Be stars

    NASA Astrophysics Data System (ADS)

    Perrin, Marshall D.; Graham, James R.; Kalas, Paul; Lloyd, James P.; Max, Claire E.; Gavel, Donald T.; Pennington, Deanna M.; Gates, Elinor L.

    2004-10-01

    Current and future large telescopes depend critically on laser guide star adaptive optics (LGS AO) to achieve their scientific goals. However, there are still relatively few scientific results reported from existing LGS AO systems. We present some of the first science results from the Lick Observatory sodium beacon LGS AO system. We achieve high sensitivity to light scattered in the circumstellar enviroment of Herbig Ae/Be stars on scales of 100-200 AU by coupling the LGS AO system to a near-infrared (J,H,Ks bands) dual channel imaging polarimeter. We describe the design, implementation, and performance of this instrument. The dominant noise source near bright stars in AO images is a "seeing halo" of uncorrected speckles, and since these speckles are unpolarized, dual-channel polarimetry achieves a significant contrast gain. Our observations reveal a wide range of morphologies, including bipolar nebulosities with and without outflow-evacuated cavities and disk-mediated interaction among members of a binary. These data suggest that the evolutionary picture developed for the lower-mass T Tauri stars is also relevant to the Herbig Ae/Be stars, and demonstrate the ability of LGS AO systems to enhance the scientific capabilities of even modest sized telescopes.

  18. Spectroscopic Polarimetry of Light scattered by Surface Roughness and Textured Films in Nanotechnologies

    NASA Astrophysics Data System (ADS)

    Ferrieu, F.

    2009-09-01

    The Effective Medium Approximation, (EMA), theory validate the thin films optical metrology in most cases when considering surface roughness. A scaling condition exist between the light wavelengths as compared to thin films roughness. In earlier papers, D. Ramsey and later P. I. Rovira and R. W. Collins, S. F. Nee, had shown however that poly crystaline and textured films could induce light scattering, affecting deeply the SE results. Exhaustives studies in the literature, detail the Mueller matrices properties through optical entropy and depolarization. It has been applied in rather different fields. The mathematical basis, describing depolarizing systems, developped by S. R. Cloude, are an important issue. In the visible range optics, complementary applications exist for thin grating films, surface scatterometry and biological turbid media The optical entropy provides a very powerful analysis technique yielding important surface parameters such as depolarization and roughness, differentiating roughness character, enabling even scatterer's classification. As first results presented here, in thin films characterization for nanotechnologies materials, spectroscopic polarimetry specifies surface properties and films textures through an entropy concept. An ultraviolet extended range of present polarimeters set up for imaging and quality control, should be a promising enhancement compare to the present bidirectionals reflectance distribution function (BRDF) and haze ultraviolet wafer analysis of wafer in conventional processes.

  19. PoGOLite - a circumpolar balloon-borne mission for hard X-ray polarimetry

    NASA Astrophysics Data System (ADS)

    Pearce, Mark

    Mark Pearce For the PoGOLite Collaboration. KTH Royal Institute of Technology, Dept. of Physics, Stockholm, Sweden. pearce@kth.se Abstract Emission processes in astrophysical systems can yield polarised hard X-rays. The orientation of the polarisation plane is a powerful probe of the physical environment around compact astrophysical sources. Despite the wealth of sources accessible to polarisation measurements, and the importance of these measurements, it is 40 years since the last dedicated mission for X-ray polarimetry of point sources. PoGOLite is a balloon-borne hard X-ray polarimeter operating in the 25-100 keV energy band. Polarisation is determined using coincident Compton scattering and photo-absorption in a segmented array of plastic scintillators surrounded by a BGO anticoincidence system and a polyethylene neutron shield. PoGOLite was launched from the Esrange Space Center on July 12th 2013 with the Crab nebula and pulsar as primary observation targets. The mission was terminated on July 25th after an almost complete circumpolar flight. The PoGOLite mission was conducted as a collaboration between Swedish, Japanese, Russian and US scientific teams. The PoGOLite circumpolar mission will be reviewed and the outcome of the 2013 flight discussed.

  20. Ex vivo characterization of normal and adenocarcinoma colon samples by Mueller matrix polarimetry

    NASA Astrophysics Data System (ADS)

    Ahmad, Iftikhar; Ahmad, Manzoor; Khan, Karim; Ashraf, Sumara; Ahmad, Shakil; Ikram, Masroor

    2015-05-01

    Mueller matrix polarimetry along with polar decomposition algorithm was employed for the characterization of ex vivo normal and adenocarcinoma human colon tissues by polarized light in the visible spectral range (425-725 nm). Six derived polarization metrics [total diattenuation (DT), retardance (RT), depolarization (ΔT), linear diattenuation (DL), retardance (δ), and depolarization (ΔL)] were compared for normal and adenocarcinoma colon tissue samples. The results show that all six polarimetric properties for adenocarcinoma samples were significantly higher as compared to the normal samples for all wavelengths. The Wilcoxon rank sum test illustrated that total retardance is a good candidate for the discrimination of normal and adenocarcinoma colon samples. Support vector machine classification for normal and adenocarcinoma based on the four polarization properties spectra (ΔT, ΔL, RT,and δ) yielded 100% accuracy, sensitivity, and specificity, while both DT and D showed 66.6%, 33.3%, and 83.3% accuracy, sensitivity, and specificity, respectively. The combination of polarization analysis and given classification methods provides a framework to distinguish the normal and cancerous tissues.

  1. Polarimetry of Pinctada fucata nacre indicates myostracal layer interrupts nacre structure

    PubMed Central

    Jones, Joshua A.; D'Addario, Anthony J.; Galvez, Enrique J.

    2017-01-01

    The inner layer of many bivalve and gastropod molluscs consists of iridescent nacre, a material that is structured like a brick wall with bricks consisting of crystalline aragonite and mortar of organic molecules. Myostracal layers formed during shell growth at the point of muscle attachment to the shell can be found interspersed within the nacre structure. Little has been done to examine the effect the myostracal layer has on subsequent nacre structure. Here we present data on the structure of the myostracal and nacre layers from a bivalve mollusc, Pinctada fucata. Scanning electron microscope imaging shows the myostracal layer consists of regular crystalline blocks. The nacre before the layer consists of tablets approximately 400 nm thick, while after the myostracal layer the tablets are approximately 500 nm thick. A new technique, imaging polarimetry, indicates that the aragonite crystals within the nacre following the myostracal layer have greater orientation uniformity than before the myostracal layer. The results presented here suggest a possible interaction between the myostracal layer and subsequent shell growth. PMID:28386442

  2. Chromospheric polarimetry through multiline observations of the 850-nm spectral region

    NASA Astrophysics Data System (ADS)

    Quintero Noda, C.; Shimizu, T.; Katsukawa, Y.; de la Cruz Rodríguez, J.; Carlsson, M.; Anan, T.; Oba, T.; Ichimoto, K.; Suematsu, Y.

    2017-02-01

    Future solar missions and ground-based telescopes aim to understand the magnetism of the solar chromosphere. We performed a supporting study in Quintero Noda et al. focused on the infrared Ca II 8542 Å line and we concluded that it is one of the best candidates because it is sensitive to a large range of atmospheric heights, from the photosphere to the middle chromosphere. However, we believe that it is worth trying to improve the results produced by this line observing additional spectral lines. In that regard, we examined the neighbourhood solar spectrum looking for spectral lines which could increase the sensitivity to the atmospheric parameters. Interestingly, we discovered several photospheric lines which greatly improve the photospheric sensitivity to the magnetic field vector. Moreover, they are located close to a second chromospheric line which also belongs to the Ca II infrared triplet, i.e. the Ca II 8498 Å line, and enhances the sensitivity to the atmospheric parameters at chromospheric layers. We conclude that the lines in the vicinity of the Ca II 8542 Å line not only increase its sensitivity to the atmospheric parameters at all layers, but also they constitute an excellent spectral window for chromospheric polarimetry.

  3. Application of Mueller polarimetry in conical diffraction for critical dimension measurements in microelectronics.

    PubMed

    Novikova, Tatiana; De Martino, Antonello; Ben Hatit, Sami; Drévillon, Bernard

    2006-06-01

    Fast and efficient metrology tools are required in microelectronics for control of ever-decreasing feature sizes. Optical techniques such as spectroscopic ellipsometry (SE) and normal incidence reflectometry are widely used for this task. In this work we investigate the potential of spectral Mueller polarimetry in conical diffraction for the characterization of 1D gratings, with particular emphasis on small critical dimensions (CDs). Mueller matrix spectra were taken in the visible (450-700 nm) wavelength range on a photoresist grating on a Si substrate with 70/240 nm CD/period nominal values, set at nine different azimuthal angles. These spectra were fitted with a rigorous coupled-wave analysis (RCWA) algorithm by using different models for the grating profile (rectangular and trapezoidal, with or without rounded corners). A detailed study of the stability and consistency of the optimal CD values, together with the variation of the merit function (the mean square deviation D2) around these values, clearly showed that for a given wavelength range, this technique can decouple some critical parameters (e.g., top and bottom CDs, left and right sidewall projections) much more efficiently than the usual SE.

  4. Evaluating Glaucomatous Retinal Nerve Fiber Damage by GDx VCC Polarimetry in Taiwan Chinese Population

    PubMed Central

    Chen, Hsin-Yi; Huang, Mei-Ling; Huang, Wei-Cheng

    2010-01-01

    Purpose To study the capability of scanning laser polarimetry with variable corneal compensation (GDx VCC) to detect differences in retinal nerve fiber layer thickness between normal and glaucomatous eyes in a Taiwan Chinese population. Methods This study included 44 normal eyes and 107 glaucomatous eyes. The glaucomatous eyes were divided into three subgroups on the basis of its visual field defects (early, moderate, severe). Each subject underwent a GDx-VCC exam and visual field testing. The area under the receiver-operating characteristic curve (AROC) of each relevant parameter was used to differentiate normal from each glaucoma subgroup, respectively. The correlation between visual field index and each parameter was evaluated for the eyes in the glaucoma group. Results For normal vs. early glaucoma, the parameter with the best AROC was Nerve fiber indicator (NFI) (0.942). For normal vs. moderate glaucoma, the parameter showing the best AROC was NFI (0.985). For normal vs. severe glaucoma, the parameter that had the best AROC was NFI (1.000). For early vs. moderate glaucoma, the parameter with the best AROC was NFI (0.732). For moderate vs. severe, the parameter showing the best AROC was temporal-superior-nasal-inferior-temporal average (0.652). For early vs. severe, the parameter with the best AROC was NFI (0.852). Conclusions GDx-VCC-measured parameters may serve as a useful tool to distinguish normal from glaucomatous eyes; in particular, NFI turned out to be the best discriminating parameter.

  5. Laboratory test of a polarimetry imaging subtraction system for the high-contrast imaging

    NASA Astrophysics Data System (ADS)

    Dou, Jiangpei; Ren, Deqing; Zhu, Yongtian; Zhang, Xi; Li, Rong

    2012-09-01

    We propose a polarimetry imaging subtraction test system that can be used for the direct imaging of the reflected light from exoplanets. Such a system will be able to remove the speckle noise scattered by the wave-front error and thus can enhance the high-contrast imaging. In this system, we use a Wollaston Prism (WP) to divide the incoming light into two simultaneous images with perpendicular linear polarizations. One of the images is used as the reference image. Then both the phase and geometric distortion corrections have been performed on the other image. The corrected image is subtracted with the reference image to remove the speckles. The whole procedure is based on an optimization algorithm and the target function is to minimize the residual speckles after subtraction. For demonstration purpose, here we only use a circular pupil in the test without integrating of our apodized-pupil coronagraph. It is shown that best result can be gained by inducing both phase and distortion corrections. Finally, it has reached an extra contrast gain of 50-times improvement in average, which is promising to be used for the direct imaging of exoplanets.

  6. Nonlinear analysis of dynamic signature

    NASA Astrophysics Data System (ADS)

    Rashidi, S.; Fallah, A.; Towhidkhah, F.

    2013-12-01

    Signature is a long trained motor skill resulting in well combination of segments like strokes and loops. It is a physical manifestation of complex motor processes. The problem, generally stated, is that how relative simplicity in behavior emerges from considerable complexity of perception-action system that produces behavior within an infinitely variable biomechanical and environmental context. To solve this problem, we present evidences which indicate that motor control dynamic in signing process is a chaotic process. This chaotic dynamic may explain a richer array of time series behavior in motor skill of signature. Nonlinear analysis is a powerful approach and suitable tool which seeks for characterizing dynamical systems through concepts such as fractal dimension and Lyapunov exponent. As a result, they can be analyzed in both horizontal and vertical for time series of position and velocity. We observed from the results that noninteger values for the correlation dimension indicates low dimensional deterministic dynamics. This result could be confirmed by using surrogate data tests. We have also used time series to calculate the largest Lyapunov exponent and obtain a positive value. These results constitute significant evidence that signature data are outcome of chaos in a nonlinear dynamical system of motor control.

  7. Radio emision from supernova remnants

    NASA Astrophysics Data System (ADS)

    Dubner, G.

    2016-06-01

    The vast majority of supernova remnants (SNRs) in our Galaxy and nearby galaxies have been discovered through radio observations, and only a very small number of the SNRs catalogued in the Milky Way have not been detected in the radio band, or are poorly defined by current radio observations. The study of the radio emission from SNRs is an excellent tool to investigate morphological characteristics, marking the location of shock fronts and contact discontinuities; the presence, orientation and intensity of the magnetic field; the energy spectrum of the emitting particles; and the dynamical consequences of the interaction with the circumstellar and interstellar medium. I will review the present knowledge of different important aspects of radio remnants and their impact on the interstellar gas. Also, new radio studies of the Crab Nebula carried out with the Karl Jansky Very Large Array (JVLA) at 3 GHz and with ALMA at 100 GHz, will be presented.

  8. Uzaybimer Radio Telescope Control System

    NASA Astrophysics Data System (ADS)

    Balbay, R.; Öz, G. K.; Arslan, Ö.; Özeren, F. F.; Küçük, İ.

    2016-12-01

    A 13 meters former NATO radar is being converted into a radio telescope. The radio telescope is controlled by a system which has been developed at UZAYBİMER. The Telescope Control System(TCS) has been designed using modern industrial systems. TCS has been developed in LabView platform in which works Windows embedded OS. The position feedback used on radio telescopes is an industrial EtherCAT standard. ASCOM library is used for astronomical calculations.

  9. Radio Emission from Binary Stars

    NASA Astrophysics Data System (ADS)

    Hjellming, R.; Murdin, P.

    2000-11-01

    Stellar radio emission is most common in double star systems where each star provides something essential in producing the large amounts of radio radiation needed for it to be detectable by RADIO TELESCOPES. They transfer mass, supply energy or, when one of the stars is a NEUTRON STAR or BLACK HOLE, have the strong gravitational fields needed for the energetic particles and magnetic fields needed...

  10. The properties of radio ellipticals

    NASA Astrophysics Data System (ADS)

    Sparks, W. B.; Disney, M. J.; Wall, J. V.; Rodgers, A. W.

    1984-03-01

    The authors present optical and additional radio data for the bright galaxies of the Disney & Wall survey. These data form the basis of a statistical comparison of the properties of radio elliptical galaxies to radio-quiet ellipticals. The correlations may be explained by the depth of the gravitational potential well in which the galaxy resides governing the circumstances under which an elliptical galaxy rids itself of internally produced gas.

  11. HerMES: disentangling active galactic nuclei and star formation in the radio source population

    NASA Astrophysics Data System (ADS)

    Rawlings, J. I.; Page, M. J.; Symeonidis, M.; Bock, J.; Cooray, A.; Farrah, D.; Guo, K.; Hatziminaoglou, E.; Ibar, E.; Oliver, S. J.; Roseboom, I. G.; Scott, Douglas; Seymour, N.; Vaccari, M.; Wardlow, J. L.

    2015-10-01

    We separate the extragalactic radio source population above ˜50 μJy into active galactic nuclei (AGN) and star-forming sources. The primary method of our approach is to fit the infrared spectral energy distributions (SEDs), constructed using Spitzer/IRAC (Infrared Array Camera) and Multiband Imaging Photometer for Spitzer (MIPS) and Herschel/SPIRE photometry, of 380 radio sources in the Extended Chandra Deep Field-South. From the fitted SEDs, we determine the relative AGN and star-forming contributions to their infrared emission. With the inclusion of other AGN diagnostics such as X-ray luminosity, Spitzer/IRAC colours, radio spectral index and the ratio of star-forming total infrared flux to k-corrected 1.4 GHz flux density, qIR, we determine whether the radio emission in these sources is powered by star formation or by an AGN. The majority of these radio sources (60 per cent) show the signature of an AGN at some wavelength. Of the sources with AGN signatures, 58 per cent are hybrid systems for which the radio emission is being powered by star formation. This implies that radio sources which have likely been selected on their star formation have a high AGN fraction. Below a 1.4 GHz flux density of 1 mJy, along with finding a strong contribution to the source counts from pure star-forming sources, we find that hybrid sources constitute 20-65 per cent of the sources. This result suggests that hybrid sources have a significant contribution, along with sources that do not host a detectable AGN, to the observed flattening of the source counts at ˜1 mJy for the extragalactic radio source population.

  12. Radio-loud and Radio-quiet QSOs

    NASA Astrophysics Data System (ADS)

    Kellermann, K. I.; Condon, J. J.; Kimball, A. E.; Perley, R. A.; Ivezić, Željko

    2016-11-01

    We discuss 6 GHz JVLA observations covering a volume-limited sample of 178 low-redshift (0.2< z< 0.3) optically selected quasi-stellar objects (QSOs). Our 176 radio detections fall into two clear categories: (1) about 20% are radio-loud QSOs (RLQs) with spectral luminosities of {L}6≳ {10}23.2 {{W}} {{Hz}}-1 that are primarily generated in the active galactic nucleus (AGN) responsible for the excess optical luminosity that defines a bona fide QSO; and (2) the remaining 80% that are radio-quiet QSOs (RQQs) that have {10}21≲ {L}6≲ {10}23.2 {{W}} {{Hz}}-1 and radio sizes ≲ 10 {kpc}, and we suggest that the bulk of their radio emission is powered by star formation in their host galaxies. “Radio-silent” QSOs ({L}6≲ {10}21 {{W}} {{Hz}}-1) are rare, so most RQQ host galaxies form stars faster than the Milky Way; they are not “red and dead” ellipticals. Earlier radio observations did not have the luminosity sensitivity of {L}6≲ {10}21 {{W}} {{Hz}}-1 that is needed to distinguish between such RLQs and RQQs. Strong, generally double-sided radio emission spanning \\gg 10 {kpc} was found to be associated with 13 of the 18 RLQ cores with peak flux densities of {S}{{p}}> 5 {mJy} {{beam}}-1 ({log}(L)≳ 24). The radio luminosity function of optically selected QSOs and the extended radio emission associated with RLQs are both inconsistent with simple “unified” models that invoke relativistic beaming from randomly oriented QSOs to explain the difference between RLQs and RQQs. Some intrinsic property of the AGNs or their host galaxies must also determine whether or not a QSO appears radio-loud.

  13. RADIO FREQUENCY ATTENUATOR

    DOEpatents

    Giordano, S.

    1963-11-12

    A high peak power level r-f attenuator that is readily and easily insertable along a coaxial cable having an inner conductor and an outer annular conductor without breaking the ends thereof is presented. Spaced first and second flares in the outer conductor face each other with a slidable cylindrical outer conductor portion therebetween. Dielectric means, such as water, contact the cable between the flares to attenuate the radio-frequency energy received thereby. The cylindrical outer conductor portion is slidable to adjust the voltage standing wave ratio to a low level, and one of the flares is slidable to adjust the attenuation level. An integral dielectric container is also provided. (AFC)

  14. Packet Radio Communications Project

    DTIC Science & Technology

    1974-12-01

    init.ate any pending DMA channel I/O now possible as a result of the completed DMA I/O operation. For example, if the packet transmision has been...keyboard and printer b. Binary data record I/O fo/from the tape media c. Scan for unsolicited keyboard input 2-12 Software description of experimental...the station and transmit to the station packets input on the radio receivers. The goal is to provide a transparent packet transfer media to

  15. Radio frequency strain monitor

    NASA Technical Reports Server (NTRS)

    Heyman, Joseph S. (Inventor); Rogowski, Robert S. (Inventor); Holben, Jr., Milford S. (Inventor)

    1989-01-01

    A radio frequency strain monitor includes a voltage controlled oscillator for generating an oscillating signal that is input into a propagation path. The propagation path is preferably bonded to the surface of a structure to be monitored and produces a propagated signal. A phase difference between the oscillating and propagated signals is detected and maintained at a substantially constant value which is preferably a multiple of 90.degree. by changing the frequency of the oscillating signal. Any change in frequency of the oscillating signal provides an indication of strain in the structure to which the propagation path is bonded.

  16. Lunar Farside Radio Lab

    NASA Astrophysics Data System (ADS)

    Maccone, Claudio

    2005-03-01

    It is proposed that the Farside of the Moon should be protected legally against man-made radio pollution and uncontrolled exploitation. In fact, only by establishing a radiotelescope on the Farside of the Moon it will finally be possible to cope with the Radio Frequency Interference (RFI) that is now increasingly plaguing all of Radioastronomy, Bioastronomy and Search for Extraterrestrial Intelligence (SETI) Searches done from the surface of the Earth. It is suggested to partition the Farside into 3 sectors, each 60°wide, to ensurethe creation of a future “Lunar Farside Radio Lab” inside crater Daedalus (at 180°E) with our planned Radiotelescope (in practice a Phased Array),complete freedom to exploit the Nearside as well as the four Lagrangian points L1, L3, L4 and L5 of the Earth Moon system by allowing even some International Space Stations to be located there. It is also claimed, however, thatthe “opposite” Lagrangian point L2 should possibly be kept free of spacecrafts that would flood the Farside by the RFI they produce. Realistically, it might be difficult to comply with the latter request in view of the far-future development of a Space Base located there in order to depart towards the Asteroids and the Outer Planets at very reduced fuel consumption. A more reasonable request about any future space station located at the Earth Moon L2 point is thus that this future space station should be shielded to prevent its RFI from reaching the Farside of the Moon.A number of further astrophysical, astronautical and technical issues could just be highlighted in this study and deserve much more elaboration. To mention a few:the precise size of the “Quiet Cone” extending into space above the Farside of the Moon. Also, the experimental measurement of how quiet this Cone actually is by letting a radiometer orbit the Moon (see the web site www.rli.it);the mathematical modelling of the weak ionosphere of the Moon and its possible diffraction effects at very

  17. Solar radio emission

    NASA Technical Reports Server (NTRS)

    Goldman, M. V.; Smith, D. F.

    1981-01-01

    Active areas of both observational and theoretical research in which rapid progress is being made are discussed. These include: (1) the dynamic spectrum or frequency versus time plot; (2) physical mechanisms in the development of various types of bursts; (3) microwave type 1, 2, 3, and moving type 4 bursts; (4) bursts caused by trapped electrons; (5) physics of type 3bursts; (6) the physics of type 2 bursts and their related shocks; (7) the physics of both stationary and moving traps and associated type 1 and moving type 4 bursts; and (8) the status of the field of solar radio emission.

  18. Severely comminuted radius fracture presenting as a signature patterned injury.

    PubMed

    Jain, Saurabh; Rajan, Sunil; Srivastava, Abhishek

    2016-01-01

    Dilemma still prevails, regarding the exact management of mangled extremity injuries between limb salvage versus amputation, each having there own set of complications. We here present a case of severely comminuted fractures of radius (bag of bones) along with the multiple criss-cross shaped lacerated wounds on the forearm and wrist presenting as a "signature pattern injury" caused by entrapment of the limb in the concrete mixer. MESS score of patient was 8, a score valid for amputation, but contrary, we successfully salvaged the patient's limb with use of radio-carpal distracter. Management of mangled injuries should be individualized, with due consideration to the mechanism and force of injury, associated injuries, and the patient profile.

  19. Severely comminuted radius fracture presenting as a signature patterned injury

    PubMed Central

    Jain, Saurabh; Rajan, Sunil; Srivastava, Abhishek

    2016-01-01

    Dilemma still prevails, regarding the exact management of mangled extremity injuries between limb salvage versus amputation, each having there own set of complications. We here present a case of severely comminuted fractures of radius (bag of bones) along with the multiple criss-cross shaped lacerated wounds on the forearm and wrist presenting as a “signature pattern injury” caused by entrapment of the limb in the concrete mixer. MESS score of patient was 8, a score valid for amputation, but contrary, we successfully salvaged the patient's limb with use of radio-carpal distracter. Management of mangled injuries should be individualized, with due consideration to the mechanism and force of injury, associated injuries, and the patient profile. PMID:27053813

  20. Searches for electromagnetic signatures of gravitational wave sources

    NASA Astrophysics Data System (ADS)

    Soares-Santos, Marcelle

    2017-01-01

    Motivated by the exciting prospect of new wealth of information that will arise from observations of gravitational and electromagnetic radiation from the same astrophysical phenomena, our community has performed a broad range of follow-up programs for LIGO/Virgo events. In this talk, I present an overview of this effort, including results of searches for signatures of the first two LIGO-triggered binary black hole mergers in the 2015-2016 observing campaign, when multiple facilities reported searches in gamma/X-rays, optical, infra-red, and radio wavelengths. I will also discuss plans for upcoming observing campaigns and long term prospects for this exciting emerging field: multi-messenger astrophysics with gravitational waves.

  1. Observations of Solar Radio Transients

    NASA Astrophysics Data System (ADS)

    Paige, Giorla

    2011-05-01

    A low frequency radio telescope has been recently been constructed on the campus of the The College of New Jersey (TCNJ) and has begun conducting observations at 20MHz as part of NASA'a Radio Jove program. This instrument is capable of observations of solar radio emission including strong prompt radio emission associated with solar burst events. We will discuss solar observations conducted with this instrument as well as an effort to conduct coincident observations with the Eight-meter-wavelength Transient Array (ETA) and the Long Wavelength Array (LWA).

  2. Internet Resources for Radio Astronomy

    NASA Astrophysics Data System (ADS)

    Andernach, H.

    A subjective overview of Internet resources for radio-astronomical information is presented. Basic observing techniques and their implications for the interpretation of publicly available radio data are described, followed by a discussion of existing radio surveys, their level of optical identification, and nomenclature of radio sources. Various collections of source catalogues and databases for integrated radio source parameters are reviewed and compared, as well as the web interfaces to interrogate the current and ongoing large-area surveys. Links to radio observatories with archives of raw (uv-) data are presented, as well as services providing images, both of individual objects or extracts (``cutouts'') from large-scale surveys. While the emphasis is on radio continuum data, a brief list of sites providing spectral line data, and atomic or molecular information is included. The major radio telescopes and surveys under construction or planning are outlined. A summary is given of a search for previously unknown optically bright radio sources, as performed by the students as an exercise, using Internet resources only. Over 200 different links are mentioned and were verified, but despite the attempt to make this report up-to-date, it can only provide a snapshot of the situation as of mid-1998.

  3. Remote Sensing and Modeling of Polarimetric Signatures of Solar System Objects

    NASA Astrophysics Data System (ADS)

    Yanamandra-Fisher, P. A.

    2011-12-01

    Polarimetry is currently enjoying a rejuvenation in planetary, astrophysical and exobiology applications from characterization of various solar system objects (planetary atmospheres, comets, satellites, ring systems, asteroids, dust, etc.) to detection and characterization of exoplanets and identification of biological markers. Although ground-based observations of the planets and their satellites are restricted to small phase angles, important results have been obtained with polarimetry. Incident starlight is linearly polarized by planetary atmospheres due to multiple light scattering by atmospheric aerosols and hazes (sulphuric acid on Venus; dust storms and ice clouds on Mars; variations in hydrocarbon hazes from equator to poles on Jupiter, Saturn, Neptune and Uranus). In Saturn's rings, anisotropic multiple scattering effects are observed and exhibit variations often in few days or weeks, with mutual interactions and gravitational resulting in organized structures. The curves of polarization for atmosphereless Solar System objects (such as the Moon, planetary satellites and asteroids) are diagnostic of the micro-texture of the surface, and demonstrate that most of them have their surfaces covered with a regolith of fine material, a function of particle size and regolith packing density. These properties are a function of the composition of the parent bodies. An example is the recent discovery of a class of large inversion angle asteroids, displaying spinel features in their spectra and indicative of the oldest surfaces in the Solar System. Linear and circular polarization of comets provides information about the composition and wavelength dependence of the dust, indicative of new, active comets vs. older comets. Measuring the degree of linear polarization can diagnose physical conditions of the scattering surface and is complementary to photometry and spectroscopy for the remote analysis of small solar system objects. In addition, measuring the linear

  4. Optical emission in the radio lobes of radio galaxies. II - New observations of 21 radio lobes

    NASA Astrophysics Data System (ADS)

    Crane, P.; Tyson, J. A.; Saslaw, W. C.

    1983-02-01

    The authors report new identifications of optical emission associated with the radio lobes of double radio galaxies. Optical emission is present in the outer radio structure of the sources 3C 219, 3C 244.1, 3C 247, 3C 252, 3C 268.2, 3C 321, 3C 319, 3C 337, and possibly in 3C 330. The authors have not found emission to the detection limit of V ≡ 24 in the sources 3C 79, 3C 173.1, 3C 223, 3C 325, and 3C 381. Of the 21 separate sources in optical studies of extended lobes of radio galaxies reported to date, 16 radio sources observed so far show significant optical emission within one or both lobes, while in 11 of these the optical object is within 2arcsec of the radio peak.

  5. The Extragalactic Radio Background

    NASA Technical Reports Server (NTRS)

    Kogut, A.; Fixsen, D. J.; Levin, S. M.; Limon, M.; Lubin, P. M.; Seiffert, M.; Singal, J.; Villela, T.; Wollack, E.; Wuensche, C. A.

    2011-01-01

    The existence of an isotropic component of the high-latitude radio sky has been recognized for nearly fifty years, but has typically been assumed to be Galactic in origin. We use recent radio observations to test whether the observed high-latitude component could originate within either an extended Galactic halo or a more local "bubble" structure. The lack of significant polarization from the isotropic component, combined with the lack of significant correlation with the Galactic far-infrared emission, rule out an origin within the Galaxy. We conclude that an extragalactic origin is the only viable alternative for the bulk of the isotropic high-latitude emission. The extragalactic component is 2-3 times brighter than local (Galactic) emission towards the Galactic poles and is consistent with a power law in frequency with amplitude T(sub r) = 24.1 plus or minus 2.1 K and spectral index beta = -2.599 plus or minus 0.036 evaluated at reference frequency 310 MHz.

  6. Basic equations of radar polarimetry and its solutions - The characteristic radar polarization states for the coherent and partially polarized cases

    NASA Astrophysics Data System (ADS)

    Boerner, Wolfgang-Martin; Yan, Wei-Ling; Xi, An-Qing

    1990-10-01

    A comprehensive overview of the basic principles of radar polarimetry is presented. The relevant fundamental field equations are first provided in order to introduce the polarization state formulations of electromagnetic waves in the frequency domain, including the Jones and the Stokes vector formalism and its presentation on the Poincare sphere and on relevant map projections. In the next step, the scattering matrices (S) and (M) are given together with change of polarization bases transformation operators, and the optimal polarization states are determined for the coherent and partially coherent cases.

  7. Forensic handwriting examiners' expertise for signature comparison.

    PubMed

    Sita, Jodi; Found, Bryan; Rogers, Douglas K

    2002-09-01

    This paper reports on the performance of forensic document examiners (FDEs) in a signature comparison task that was designed to address the issue of expertise. The opinions of FDEs regarding 150 genuine and simulated questioned signatures were compared with a control group of non-examiners' opinions. On the question of expertise, results showed that FDEs were statistically better than the control group at accurately determining the genuineness or non-genuineness of questioned signatures. The FDE group made errors (by calling a genuine signature simulated or by calling a simulated signature genuine) in 3.4% of their opinions while 19.3% of the control group's opinions were erroneous. The FDE group gave significantly more inconclusive opinions than the control group. Analysis of FDEs' responses showed that more correct opinions were expressed regarding simulated signatures and more inconclusive opinions were made on genuine signatures. Further, when the complexity of a signature was taken into account, FDEs made more correct opinions on high complexity signatures than on signatures of lower complexity. There was a wide range of skill amongst FDEs and no significant relationship was found between the number of years FDEs had been practicing and their correct, inconclusive and error rates.

  8. An Optical and X-Ray Examination of Two Radio Supernova Remnant Candidates in 30 Doradus

    NASA Astrophysics Data System (ADS)

    Chu, You-Hua; Gruendl, Robert A.; Chen, C.-H. Rosie; Lazendic, Jasmina S.; Dickel, John R.

    2004-11-01

    The giant H II region 30 Doradus is known for its violent internal motions and bright diffuse X-ray emission, suggesting the existence of supernova remnants (SNRs), but no nonthermal radio emission has been detected. Recently, Lazendic et al. compared the Hα/Hβ and radio/Hα ratios and suggested two small radio sources to be nonthermal and thus SNR candidates; however, no optical or X-ray counterparts were detected. We have used high-resolution optical images and high-dispersion spectra to examine the morphological, spectral, and kinematic properties of these two SNR candidates and still find no optical evidence supporting their identification as SNRs. We have also determined the X-ray luminosities of these SNR candidates and find them 1-3 orders of magnitude lower than those commonly seen in young SNRs. High extinction can obscure optical and X-ray signatures of an SNR, but would prohibit the use of a high radio/Hα ratio to identify nonthermal radio emission. We suggest that the SNR candidate MCRX J053831.8-690620 is associated with a young star-forming region; while the radio emission originates from the obscured star-forming region, the observed optical emission is dominated by the foreground. We suggest that the SNR candidate MCRX J053838.8-690730 is associated with a dust/molecular cloud, which obscures some optical emission but not the radio emission.

  9. Is lightning a possible source of the radio emission on HAT-P-11b?

    NASA Astrophysics Data System (ADS)

    Hodosán, G.; Rimmer, P. B.; Helling, Ch.

    2016-09-01

    Lightning induced radio emission has been observed on Solar system planets. There have been many attempts to observe exoplanets in the radio wavelength, however, no unequivocal detection has been reported. Lecavelier des Etangs et al. carried out radio transit observations of the exoplanet HAT-P-11b, and suggested that a small part of the radio flux can be attributed to the planet. Here, we assume that this signal is real, and study if this radio emission could be caused by lightning with similar energetic properties like in the Solar system. We find that a lightning storm with 3.8 × 106 times larger flash densities than the Earth-storms with the largest lightning activity is needed to produce the observed signal from HAT-P-11b. The optical emission of such thunderstorm would be comparable to that of the host star. We show that HCN produced by lightning chemistry is observable 2-3 yr after the storm, which produces signatures in the L (3.0-4.0 μm) and N (7.5-14.5 μm) infrared bands. We conclude that it is unlikely that the observed radio signal was produced by lightning, however, future, combined radio and infrared observations may lead to lightning detection on planets outside the Solar system.

  10. The evolution of radio-loud active galactic nuclei as a function of black hole spin

    NASA Astrophysics Data System (ADS)

    Garofalo, D.; Evans, D. A.; Sambruna, R. M.

    2010-08-01

    Recent work on the engines of active galactic nuclei jets suggests that their power depends strongly and perhaps counter-intuitively on black hole spin. We explore the consequences of this on the radio-loud population of active galactic nuclei and find that the time evolution of the most powerful radio galaxies and radio-loud quasars fits into a picture in which black hole spin varies from retrograde to prograde with respect to the accreting material. Unlike the current view, according to which jet powers decrease in tandem with a global downsizing effect, we argue for a drop in jet power resulting directly from the paucity of retrograde accretion systems at lower redshift z caused by a continuous history of accretion dating back to higher z. In addition, the model provides simple interpretations for the basic spectral features differentiating radio-loud and radio-quiet objects, such as the presence or absence of disc reflection, broadened iron lines and signatures of disc winds. We also briefly describe our models' interpretation of microquasar state transitions. We highlight our result that the most radio-loud and most radio-quiet objects both harbour highly spinning black holes but in retrograde and prograde configurations, respectively.

  11. Genetic signatures of heroin addiction.

    PubMed

    Chen, Shaw-Ji; Liao, Ding-Lieh; Shen, Tsu-Wang; Yang, Hsin-Chou; Chen, Kuang-Chi; Chen, Chia-Hsiang

    2016-08-01

    Heroin addiction is a complex psychiatric disorder with a chronic course and a high relapse rate, which results from the interaction between genetic and environmental factors. Heroin addiction has a substantial heritability in its etiology; hence, identification of individuals with a high genetic propensity to heroin addiction may help prevent the occurrence and relapse of heroin addiction and its complications. The study aimed to identify a small set of genetic signatures that may reliably predict the individuals with a high genetic propensity to heroin addiction. We first measured the transcript level of 13 genes (RASA1, PRKCB, PDK1, JUN, CEBPG, CD74, CEBPB, AUTS2, ENO2, IMPDH2, HAT1, MBD1, and RGS3) in lymphoblastoid cell lines in a sample of 124 male heroin addicts and 124 male control subjects using real-time quantitative PCR. Seven genes (PRKCB, PDK1, JUN, CEBPG, CEBPB, ENO2, and HAT1) showed significant differential expression between the 2 groups. Further analysis using 3 statistical methods including logistic regression analysis, support vector machine learning analysis, and a computer software BIASLESS revealed that a set of 4 genes (JUN, CEBPB, PRKCB, ENO2, or CEBPG) could predict the diagnosis of heroin addiction with the accuracy rate around 85% in our dataset. Our findings support the idea that it is possible to identify genetic signatures of heroin addiction using a small set of expressed genes. However, the study can only be considered as a proof-of-concept study. As the establishment of lymphoblastoid cell line is a laborious and lengthy process, it would be more practical in clinical settings to identify genetic signatures for heroin addiction directly from peripheral blood cells in the future study.

  12. Infrared signatures for remote sensing

    SciTech Connect

    McDowell, R.S.; Sharpe, S.W.; Kelly, J.F.

    1994-04-01

    PNL`s capabilities for infrared and near-infrared spectroscopy include tunable-diode-laser (TDL) systems covering 300--3,000 cm{sup {minus}1} at <10-MHz bandwidth; a Bruker Fourier-transform infrared (FTIR) spectrometer for the near- to far-infrared at 50-MHz resolution; and a stable line-tunable, 12-w cw CO{sub 2} laser. PNL also has a beam expansion source with a 12-cm slit, which provides a 3-m effective path for gases at {approximately}10 K, giving a Doppler width of typically 10 MHz; and long-path static gas cells (to 100 m). In applying this equipment to signatures work, the authors emphasize the importance of high spectral resolution for detecting and identifying atmospheric interferences; for identifying the optimum analytical frequencies; for deriving, by spectroscopic analysis, the molecular parameters needed for modeling; and for obtaining data on species and/or bands that are not in existing databases. As an example of such spectroscopy, the authors have assigned and analyzed the C-Cl stretching region of CCl{sub 4} at 770--800 cm{sup {minus}1}. This is an important potential signature species whose IR absorption has remained puzzling because of the natural isotopic mix, extensive hot-band structure, and a Fermi resonance involving a nearby combination band. Instrument development projects include the IR sniffer, a small high-sensitivity, high-discrimination (Doppler-limited) device for fence-line or downwind monitoring that is effective even in regions of atmospheric absorption; preliminary work has achieved sensitivities at the low-ppb level. Other work covers trace species detection with TDLs, and FM-modulated CO{sub 2} laser LIDAR. The authors are planning a field experiment to interrogate the Hanford tank farm for signature species from Rattlesnake Mountain, a standoff of ca. 15 km, to be accompanied by simultaneous ground-truthing at the tanks.

  13. Signature of anisotropic bubble collisions

    SciTech Connect

    Salem, Michael P.

    2010-09-15

    Our universe may have formed via bubble nucleation in an eternally inflating background. Furthermore, the background may have a compact dimension--the modulus of which tunnels out of a metastable minimum during bubble nucleation--which subsequently grows to become one of our three large spatial dimensions. When in this scenario our bubble universe collides with other ones like it, the collision geometry is constrained by the reduced symmetry of the tunneling instanton. While the regions affected by such bubble collisions still appear (to leading order) as disks in an observer's sky, the centers of these disks all lie on a single great circle, providing a distinct signature of anisotropic bubble nucleation.

  14. Spectroscopic signature for ferroelectric ice

    NASA Astrophysics Data System (ADS)

    Wójcik, Marek J.; Gług, Maciej; Boczar, Marek; Boda, Łukasz

    2014-09-01

    Various forms of ice exist within our galaxy. Particularly intriguing type of ice - ‘ferroelectric ice' was discovered experimentally and is stable in temperatures below 72 K. This form of ice can generate enormous electric fields and can play an important role in planetary formation. In this letter we present Car-Parrinello simulation of infrared spectra of ferroelectric ice and compare them with spectra of hexagonal ice. Librational region of the spectra can be treated as spectroscopic signature of ice XI and can be of help to identify ferroelectric ice in the Universe.

  15. Satellite signatures in SLR observations

    NASA Technical Reports Server (NTRS)

    Appleby, G. M.

    1993-01-01

    We examine the evidence for the detection of satellite-dependent signatures in the laser range observations obtained by the UK single-photon Satellite Laser Ranging (SLR) System models of the expected observation distributions from Ajisai and Lageos are developed from the published satellite spread functions and from the characteristics of the SLR System and compared with the observations. The effects of varying return strengths are discussed using the models and by experimental observations of Ajisai, during which a range of return levels from single to multiple photons is achieved. The implications of these results for system-dependent center for mass corrections are discussed.

  16. Observational Signatures of Magnetic Reconnection

    NASA Technical Reports Server (NTRS)

    Savage, Sabrina

    2014-01-01

    Magnetic reconnection is often referred to as the primary source of energy release during solar flares. Directly observing reconnection occurring in the solar atmosphere, however, is not trivial considering that the scale size of the diffusion region is magnitudes smaller than the observational capabilities of current instrumentation, and coronal magnetic field measurements are not currently sufficient to capture the process. Therefore, predicting and studying observationally feasible signatures of the precursors and consequences of reconnection is necessary for guiding and verifying the simulations that dominate our understanding. I will present a set of such observations, particularly in connection with long-duration solar events, and compare them with recent simulations and theoretical predictions.

  17. Gut microbiota signatures of longevity.

    PubMed

    Kong, Fanli; Hua, Yutong; Zeng, Bo; Ning, Ruihong; Li, Ying; Zhao, Jiangchao

    2016-09-26

    An aging global population poses substantial challenges to society [1]. Centenarians are a model for healthy aging because they have reached the extreme limit of life by escaping, surviving, or delaying chronic diseases [2]. The genetics of centenarians have been extensively examined [3], but less is known about their gut microbiotas. Recently, Biagi et al.[4] characterized the gut microbiota in Italian centenarians and semi-supercentenarians. Here, we compare the gut microbiota of Chinese long-living people with younger age groups, and with the results from the Italian population [4], to identify gut-microbial signatures of healthy aging.

  18. Space Telecommunications Radio Architecture (STRS)

    NASA Technical Reports Server (NTRS)

    Reinhart, Richard C.

    2006-01-01

    A software defined radio (SDR) architecture used in space-based platforms proposes to standardize certain aspects of radio development such as interface definitions, functional control and execution, and application software and firmware development. NASA has charted a team to develop an open software defined radio hardware and software architecture to support NASA missions and determine the viability of an Agency-wide Standard. A draft concept of the proposed standard has been released and discussed among organizations in the SDR community. Appropriate leveraging of the JTRS SCA, OMG's SWRadio Architecture and other aspects are considered. A standard radio architecture offers potential value by employing common waveform software instantiation, operation, testing and software maintenance. While software defined radios offer greater flexibility, they also poses challenges to the radio development for the space environment in terms of size, mass and power consumption and available technology. An SDR architecture for space must recognize and address the constraints of space flight hardware, and systems along with flight heritage and culture. NASA is actively participating in the development of technology and standards related to software defined radios. As NASA considers a standard radio architecture for space communications, input and coordination from government agencies, the industry, academia, and standards bodies is key to a successful architecture. The unique aspects of space require thorough investigation of relevant terrestrial technologies properly adapted to space. The talk will describe NASA s current effort to investigate SDR applications to space missions and a brief overview of a candidate architecture under consideration for space based platforms.

  19. Safety and Special Radio Services.

    ERIC Educational Resources Information Center

    Federal Communications Commission, Washington, DC.

    Numerous radio stations across the nation perform nonbroadcast services in areas ranging from aviation, forestry protection, and telephone maintenance to amateur and citizen radio. These services can be grouped in four general categories: (1) safety, (2) industry, (3) land transportation, and (4) miscellaneous purposes. This bulletin briefly…

  20. Frequency Allocation; The Radio Spectrum.

    ERIC Educational Resources Information Center

    Federal Communications Commission, Washington, DC.

    The Federal Communications Commission (FCC) assigns segments of the radio spectrum to categories of users, and specific frequencies within each segment to individual users. Since demand for channel space exceeds supply, the process is complex. The radio spectrum can be compared to a long ruler: the portion from 10-540 kiloHertz has been set aside…

  1. Stabilized radio-frequency quadrupole

    DOEpatents

    Lancaster, H.D.; Fugitt, J.A.; Howard, D.R.

    1982-09-29

    A long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator.

  2. The future for radio astronomy

    NASA Astrophysics Data System (ADS)

    Breton, Rene P.; Hassall, Tom

    2013-12-01

    THE TRANSIENT UNIVERSE Rene P Breton and Tom Hassall argue that, while radio astronomy has always involved transient phenomena, exploration of this part of the electromagnetic spectrum has been falling behind because of the lack of data. But the advent of a new generation of radio telescopes such as LOFAR, could change that.

  3. Audiences for Contemporary Radio Formats.

    ERIC Educational Resources Information Center

    Lull, James T.; And Others

    A radio audience survey of 110 sample geographic clusters in the Santa Barbara, California, area served a twofold purpose: the construction of a demographic profile of audience types according to radio format choices, and the identification and analysis of various audience subgroups. A skip interval technique of these geographic clusters resulted…

  4. The Radio Phenomenon in Italy.

    ERIC Educational Resources Information Center

    Faenza, Roberto

    One in a series of studies of experiments in new audiovisual techniques in Europe and the situations in some member countries, this paper traces the development of radio in Italy. Opposing views about radio broadcasting (public monopoly vs. freedom of broadcasting) are examined, and the various political and legal aspects of communications in…

  5. Radio imaging of a type IVM radio burst on the 14th of August 2010

    SciTech Connect

    Bain, H. M.; Krucker, S.; Saint-Hilaire, P.; Raftery, C. L.

    2014-02-10

    Propagating coronal mass ejections (CMEs) are often accompanied by burst signatures in radio spectrogram data. We present Nançay Radioheliograph observations of a moving source of broadband radio emission, commonly referred to as a type IV radio burst (type IVM), which occurred in association with a CME on the 14th of August 2010. The event was well observed at extreme ultraviolet (EUV) wavelengths by SDO/AIA and PROBA2/SWAP, and by the STEREO SECCHI and SOHO LASCO white light (WL) coronagraphs. The EUV and WL observations show the type IVM source to be cospatial with the CME core. The observed spectra is well fitted by a power law with a negative slope, which is consistent with optically thin gyrosynchrotron emission. The spectrum shows no turn over at the lowest Nançay frequencies. By comparing simulated gyrosynchrotron spectra with Nançay Radioheliograph observations, and performing a rigorous parameter search we are able to constrain several key parameters of the underlying plasma. Simulated spectra found to fit the data suggest a nonthermal electron distribution with a low energy cutoff of several tens to 100 keV, with a nonthermal electron density in the range 10{sup 0}-10{sup 2} cm{sup –3}, in a magnetic field of a few Gauss. The nonthermal energy content of the source is found to contain 0.001%-0.1% of the sources thermal energy content. Furthermore, the energy loss timescale for this distribution equates to several hours, suggesting that the electrons could be accelerated during the CME initiation or early propagation phase and become trapped in the magnetic structure of the CME core without the need to be replenished.

  6. 78 FR 32165 - Commercial Radio Operators; Correction

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-29

    ... COMMISSION 47 CFR Part 0 Commercial Radio Operators; Correction AGENCY: Federal Communication Commission... rules concerning radio operator licenses for maritime and aviation in order to reduce administrative...) Administers the Commission's commercial radio operator program (part 13 of this chapter); the...

  7. Galaxy clusters: Radio relics from fossil electrons

    NASA Astrophysics Data System (ADS)

    Johnston-Hollitt, Melanie

    2017-01-01

    The detection of a tailed radio galaxy in a galaxy cluster conjoined to a region of diffuse radio emission confirms that radio galaxies provide the energetic electrons needed to explain the origin of this enigmatic emission.

  8. Quantum broadcasting multiple blind signature with constant size

    NASA Astrophysics Data System (ADS)

    Xiao, Min; Li, Zhenli

    2016-09-01

    Using quantum homomorphic signature in quantum network, we propose a quantum broadcasting multiple blind signature scheme. Different from classical signature and current quantum signature schemes, the multi-signature proposed in our scheme is not generated by simply putting the individual signatures together, but by aggregating the individual signatures based on homomorphic property. Therefore, the size of the multi-signature is constant. Furthermore, based on a wide range of investigation for the security of existing quantum signature protocols, our protocol is designed to resist possible forgery attacks against signature and message from the various attack sources and disavowal attacks from participants.

  9. Bio-signatures of Planet Earth from Spectropolarimetry

    NASA Astrophysics Data System (ADS)

    Sterzik, M. F.; Bagnulo, S.; Emde, C.

    2015-10-01

    Polarimetry is routinely used to characterise the surfaces of bodies in our solar system. In the near future, polarisation measurements of the starlight reflected by exoplanets will become a common and powerful tool to constrain the atmospheres and the surface properties of other worlds.

  10. Radio characteristics of galactic nuclei

    NASA Astrophysics Data System (ADS)

    Condon, J. J.

    1986-02-01

    Radio characteristics of galactic nuclei, providing such unique information as spectral data on source variability, and the long-term history of the central engine and its duration of activity and total energy, are reviewed. The compact radio source characteristics are complicated by orientation-dependent relativistic beaming and by refractive focusing in the interstellar medium. Incoherent synchrotron radiation is thought to be the emission mechanism, with the result that synchrotron self-absorption in compact sources hides the central engine from direct radio observation. However, the history revealed by the extended jets and lobes of radio galaxies and quasars favors a single massive object not supported by radiation pressure, either a spinar or a black hole, as the energy source in radio-galaxy nuclei.

  11. Radio outburst of BL Lacertae

    NASA Astrophysics Data System (ADS)

    Buemi, C. S.; Leto, P.; Trigilio, C.; Umana, G.; Giroletti, M.; Orienti, M.; Raiteri, C. M.; Villata, M.; Bach, U.

    2013-04-01

    We report on extremely high radio flux of BL Lacertae at 43 and 8 GHz. Observations at 43 GHz with the 32 m radio telescope in Noto (Italy) revealed a flux density of 10.5 +/- 0.2 Jy on 2013 April 10.65, while observations at 8 GHz with the 32 m radio telescope in Medicina (Italy) detected a flux density of 8.2 +/- 0.7 Jy on April 12.22. These extremely high radio fluxes show that the radio activity likely correlated to the strong optical, near-infrared, and gamma-ray activity of 2011-2012 (see ATels #4028, #4031, #4155, #4271, #4277, #4349, #4565, #4600), and X-ray activity of late 2012 (ATels #4557, #4627), is far to be exhausted.

  12. Tracing the Magnetic Field of IRDC G028.23-00.19 Using NIR Polarimetry

    NASA Astrophysics Data System (ADS)

    Hoq, Sadia; Clemens, D. P.; Guzmán, Andrés E.; Cashman, Lauren R.

    2017-02-01

    The importance of the magnetic (B) field in the formation of infrared dark clouds (IRDCs) and massive stars is an ongoing topic of investigation. We studied the plane-of-sky B field for one IRDC, G028.23-00.19, to understand the interaction between the field and the cloud. We used near-IR background starlight polarimetry to probe the B field and performed several observational tests to assess the field importance. The polarimetric data, taken with the Mimir instrument, consisted of H-band and K-band observations, totaling 17,160 stellar measurements. We traced the plane-of-sky B-field morphology with respect to the sky-projected cloud elongation. We also found the relationship between the estimated B-field strength and gas volume density, and we computed estimates of the normalized mass-to-magnetic flux ratio. The B-field orientation with respect to the cloud did not show a preferred alignment, but it did exhibit a large-scale pattern. The plane-of-sky B-field strengths ranged from 10 to 165 μG, and the B-field strength dependence on density followed a power law with an index consistent with 2/3. The mass-to-magnetic flux ratio also increased as a function of density. The relative orientations and relationship between the B field and density imply that the B field was not dynamically important in the formation of the IRDC. The increase in mass-to-flux ratio as a function of density, though, indicates a dynamically important B field. Therefore, it is unclear whether the B field influenced the formation of G28.23. However, it is likely that the presence of the IRDC changed the local B-field morphology.

  13. Selective optical scattering characterisation of tissue malignancy using Mueller matrix polarimetry: a simulation study

    NASA Astrophysics Data System (ADS)

    Fathima, Adeeba; Sujatha, N.

    2016-04-01

    Quantitative Mueller polarimetry optically characterizes a medium and is reflected upon by the ultrastructural changes in it. Tissue morphology changes occur during advent of diseases like cancer neoplasia. This alters the Mueller matrix characterizing the tissue as an optical element. The nucleus size undergoes an approximate doubling during the development of cancer. Cell crowding during cancer increases the number density of the nuclei per unit volume. Modeling the cell nuclei as main scattering centers, a systematic computational study on how Mueller matrix elements vary for an increase in scatterer size and number density is performed. Simulation on polarized light transport of wavelength 633nm through a slab of size 3 mm comprising of spherical scatterers in a medium of refractive index 1.33 is carried out. Light propagation is modeled using Monte Carlo method and meridian plane method is adopted for tracking the polarization state change. The stokes vector of the outgoing light is tracked to calculate the Mueller matrix images of the light backscattered from the slab. The Mueller matrix elements as well as depolarization factors are derived. The depolarization index increases with scatterer size. Along with nucleus size, change in the cell number density is also expected in the different stages of the cancer growth. Volume fraction of the scatterers in medium is varied as an indicator of this number density change. Behavior of Mueller matrix with respect to change in scattering coefficient due to variation in scatterer size and volume fraction is studied. It is observed that the depolarization index derived from Mueller matrix has selective discrimination towards the change in scattering coefficient caused due to size change and volume fraction change respectively.

  14. Imaging polarimetry of comet 73P/Schwassmann-Wachmann 3 main fragments during its 2006 apparition

    NASA Astrophysics Data System (ADS)

    Hadamcik, E.; Levasseur-Regourd, A. C.

    2016-04-01

    We have observed the dust ejected by parts of the nucleus (so-called fragments or components) of comet 73 P/Schwassmann-Wachmann 3 during seven consecutive nights from 2006, April 27 to May 3 by imaging polarimetry using the 0.8 m telescope at OHP (Observatoire de Haute-Provence, France). Three fragments were observed, B and C main fragments on all nights and G fragment on two nights at 24 h interval. Fragment C, which almost behaves as a normal comet, presents some night-to-night evolution on polarization maps together with some sunward-jets morphology. Fragment B, as noticed by numerous observers, continues to fragment, with clues to the presence of large secondary fragments, tailward on the intensity images; an increase of activity is noticed on May 2. Jets and fans are observed sunward, with a larger extension in fragment C than in B. Fragment G is fainter and, as fragment B, it continues to fragment. A short sunward jet is detected on the rotational gradient image together with an important tailward structure. The integrated polarization for the two main fragments is typical of polarization of high-Pmax comets. An important evolution is observed from night-to-night on the polarization maps. Fragment C presents, in two nights at 48 h interval, a lower polarization in the inner coma, neither observed in the intermediate night nor later. A high polarization is also observed on the two sides of the lower polarization regions. In fragment B, the regions around the secondary fragments have a higher polarization than the surrounding coma, They are easily detected in the treated intensity images. As usually, the polarization increases when the phase angle increases. Numerous observers have found similar chemical compositions for the two main fragments together with differences in their optical properties, suggesting heterogeneities in the physical properties during the aggregation of the original nucleus and/or changes after the ejection of dust particles.

  15. Spotting the misaligned outflows in NGC 1068 using X-ray polarimetry

    NASA Astrophysics Data System (ADS)

    Goosmann, R. W.; Matt, G.

    2011-08-01

    We model the expected X-ray polarization induced by complex reprocessing in the active nucleus of the Seyfert 2 galaxy NGC 1068. Recent analysis of infrared interferometry observations suggests that the ionized outflows ejected by the central engine are not aligned with the symmetry axis of the obscuring torus. This conclusion was obtained by extrapolating the apparent orientation of the narrow-line region to the inner parts of the ionization cones. We show that future measurements of the soft X-ray polarization vector unambiguously determine the orientation of the ionization cones. Furthermore, X-ray polarimetry across a broad photon energy range may independently verify the misalignment between the ionization cones and the axis of the torus. To model the expected polarization percentage and position angle, we apply the radiative transfer code STOKES. Reprocessing of the primary X-ray radiation takes place in the accretion disc, the surrounding equatorial torus and the inclined, ionized outflows. We also examine additional equatorial scattering occurring in between the accretion disc and the inner surfaces of the torus. Radiative coupling between the different reprocessing components is computed coherently. The resulting polarization properties depend on the optical depth of the reprocessing regions and on the viewing angle of the observer. We show that even under unfavourable conditions the misalignment of the outflows with respect to the torus axis can be determined from a rotation of the polarization position angle between softer and harder X-rays. We argue that the misalignment of the outflows with respect to the torus axis in NGC 1068 may be constrained by a future X-ray mission if equipped with a broad-band polarimeter.

  16. Prospects of 3D mapping of the Galactic Centre clouds with X-ray polarimetry

    NASA Astrophysics Data System (ADS)

    Marin, F.; Karas, V.; Kunneriath, D.; Muleri, F.

    2014-07-01

    Despite past panchromatic observations of the innermost part of the Milky Way, the overall structure of the Galactic Centre (GC) remains enigmatic in terms of geometry. In this paper, we aim to show how polarimetry can probe the three-dimensional position of the molecular material in the central ˜100 pc of the GC. We investigate a model where the central supermassive black hole Sgr A* is radiatively coupled to a fragmented circumnuclear disc (CND), an elliptical twisted ring representative of the central molecular zone (CMZ), and the two main, bright molecular clouds Sgr B2 and Sgr C. 8-35 keV integrated polarization mapping reveals that Sgr B2 and Sgr C, situated at the two sides of the CMZ, present the highest polarization degrees (66.5 and 47.8 per cent, respectively), both associated with a polarization position angle ψ = 90° (normal to the scattering plane). The CND shows a lower polarization degree, 1.0 per cent with ψ = -20.5°, tracing the inclination of the CND with respect to the Galactic plane. The CMZ polarization is spatially variable. We also consider a range of spatial locations for Sgr A* and the reprocessing media, and investigate how the modelled three-dimensional geometry influences the resulting GC polarization. The two reflection nebulae are found to always produce high polarization degrees (≫10 per cent). We show that a 500 ks observation with a broad-band polarimeter could constrain the location and the morphology of the scattering material with respect to the emitting source, revealing the past activity of Sgr A*.

  17. Exploring the Dynamic Radio Sky

    NASA Astrophysics Data System (ADS)

    Mooley, Kunal P.; Hallinan, Gregg; Frail, Dale A.; Myers, Steven T.; Kulkarni, Shrinivas R.; Bourke, Stephen; Horesh, Assaf

    2015-01-01

    Most of what is currently known about slow radio transients (supernovae, gamma-ray bursts, tidal disruption events, stellar flares, etc.) has come via radio follow-up of objects identified by synoptic telescopes at optical, X-ray or gamma-ray wavelengths. However, with the ability to capture obscured, unbeamed and magnetically-driven phenomena, radio surveys offer unique discovery strong diagnostic for cosmic transients. For the first time, we are systematically exploring the dynamic radio sky on timescales between one day to several years using multi-epoch large surveys with the Karl G. Jansky Array (VLA). We have carried out surveys in the COSMOS deep field as well as wide fields like Stripe 82. I have developed a unique infrastructure for near-real-time calibration, imaging, transient search, transient vetting, rapid multiwavelength follow-up, and contemporaneous optical surveys to better characterize radio transient phenomena. A large part of my thesis includes the commissioning of a new observing mode at the VLA: On-The-Fly Mosaicking. This mode has significantly improved the survey efficiency of the VLA, and it is a driver for VLASS, the future all-sky survey planned with this telescope. Through our radio surveys we have discovered several fascinating transients that are unique to the radio. These surveys have established the VLA as an efficient transient discovery machine. My thesis has enormous implications for how to design efficient transient surveys for the next generation of radio interferometer facilities like ASKAP, MeerKAT, WSRT/Apertif and LOFAR. My work has also provided answers to key problems such as the rates of transients, demographics of variability of radio sources including AGN, and false-positive foreground for future searches for the radio counterparts of gravitational-wave (GW) sources.

  18. The Radio Language Arts Project: adapting the radio mathematics model.

    PubMed

    Christensen, P R

    1985-01-01

    Kenya's Radio Language Arts Project, directed by the Academy for Educational Development in cooperation with the Kenya Institute of Education in 1980-85, sought to teach English to rural school children in grades 1-3 through use of an intensive, radio-based instructional system. Daily 1/2 hour lessons are broadcast throughout the school year and supported by teachers and print materials. The project further was aimed at testing the feasibility of adaptation of the successful Nicaraguan Radio Math Project to a new subject area. Difficulties were encountered in articulating a language curriculum with the precision required for a media-based instructional system. Also a challenge was defining the acceptable regional standard for pronunciation and grammar; British English was finally selected. An important modification of the Radio Math model concerned the role of the teacher. While Radio Math sought to reduce the teacher's responsibilities during the broadcast, Radio Language Arts teachers played an important instructional role during the English lesson broadcasts by providing translation and checks on work. Evaluations of the Radio language Arts Project suggest significant gains in speaking, listening, and reading skills as well as high levels of satisfaction on the part of parents and teachers.

  19. Radio frequency coaxial feedthrough

    DOEpatents

    Owens, Thomas L.

    1989-01-17

    An improved radio frequency coaxial transmission line vacuum feed-through provided based on the use of a half-wavelength annular dielectric pressure barrier disk, or multiple disks comprising an effective half wavelength structure to eliminate reflections from the barrier surfaces. Gas-tight seals are formed about the outer and inner diameter surfaces of the barrier disk using a sealing technique which generates radial forces sufficient to form seals by forcing the conductor walls against the surfaces of the barrier disks in a manner which does not deform the radii of the inner and outer conductors, thereby preventing enhancement of the electric field at the barrier faces which limits voltage and power handling capabilities of a feedthrough.

  20. Radio Seeing Monitor Interferometer

    NASA Astrophysics Data System (ADS)

    Hiriart, David; Valdez, Jorge; Zaca, Placido; Medina, José L.

    2002-10-01

    A two-element interferometer for monitoring atmospheric phase fluctuations (radio seeing) is presented; this uses the unmodulated beacon signal at 11.715 GHz from a geostationary satellite. The system measures phase differences on the signal received by two small antennas separated by 50 m. The system incorporates the best features from previous designs: a heterodyne phase-lock receiver and an IQ demodulator system. Phase fluctuations measured at this frequency may be extrapolated to millimetric and submillimetric wavelengths since the atmosphere is not dispersive at these frequencies. The instrument has been tested at the Observatory San Pedro Martir (Mexico) at 2800 m above sea level. The final destination of the instrument is Cerro la Negra (Mexico), where the Large Millimeter Telescope is under construction, at an altitude of 4600 m.

  1. Radio pulsar disk electrodynamics

    NASA Technical Reports Server (NTRS)

    Michel, F. C.

    1983-01-01

    Macroscopic physics are discussed for the case of a disk close to an isolated, magnetized, rotating neutron star that acts as a Faraday disk dynamo, while the disk acts as both a load and a neutral sheet. This sheet allows the polar cap current to return to the neutron star, splitting a dipolar field into two monopolar halves. The dominant energy loss is from the stellar wind torque, and the next contribution is dissipation in the auroral zones, where the current returns to the star in a 5 cm-thick sheet. The disk itself may be a source of visible radiation comparable to that in pulsed radio frequency emission. As the pulsar ages, the disk expands and narrows into a ring which, it is suggested, may lead to a cessation of pulsed emission at periods of a few sec.

  2. Visual signatures in video visualization.

    PubMed

    Chen, Min; Botchen, Ralf P; Hashim, Rudy R; Weiskopf, Daniel; Ertl, Thomas; Thornton, Ian M

    2006-01-01

    Video visualization is a computation process that extracts meaningful information from original video data sets and conveys the extracted information to users in appropriate visual representations. This paper presents a broad treatment of the subject, following a typical research pipeline involving concept formulation, system development, a path-finding user study, and a field trial with real application data. In particular, we have conducted a fundamental study on the visualization of motion events in videos. We have, for the first time, deployed flow visualization techniques in video visualization. We have compared the effectiveness of different abstract visual representations of videos. We have conducted a user study to examine whether users are able to learn to recognize visual signatures of motions, and to assist in the evaluation of different visualization techniques. We have applied our understanding and the developed techniques to a set of application video clips. Our study has demonstrated that video visualization is both technically feasible and cost-effective. It has provided the first set of evidence confirming that ordinary users can be accustomed to the visual features depicted in video visualizations, and can learn to recognize visual signatures of a variety of motion events.

  3. SETI reloaded: Next generation radio telescopes, transients and cognitive computing

    NASA Astrophysics Data System (ADS)

    Garrett, Michael A.

    2015-08-01

    The Search for Extra-terrestrial Intelligence (SETI) using radio telescopes is an area of research that is now more than 50 years old. Thus far, both targeted and wide-area surveys have yet to detect artificial signals from intelligent civilisations. In this paper, I argue that the incidence of co-existing intelligent and communicating civilisations is probably small in the Milky Way. While this makes successful SETI searches a very difficult pursuit indeed, the huge impact of even a single detection requires us to continue the search. A substantial increase in the overall performance of radio telescopes (and in particular future wide-field instruments such as the Square Kilometre Array - SKA), provide renewed optimism in the field. Evidence for this is already to be seen in the success of SETI researchers in acquiring observations on some of the world's most sensitive radio telescope facilities via open, peer-reviewed processes. The increasing interest in the dynamic radio sky, and our ability to detect new and rapid transient phenomena such as Fast Radio Bursts (FRB) is also greatly encouraging. While the nature of FRBs is not yet fully understood, I argue they are unlikely to be the signature of distant extra-terrestrial civilisations. As astronomers face a data avalanche on all sides, advances made in related areas such as advanced Big Data analytics, and cognitive computing are crucial to enable serendipitous discoveries to be made. In any case, as the era of the SKA fast approaches, the prospects of a SETI detection have never been better.

  4. A TYPE II RADIO BURST WITHOUT A CORONAL MASS EJECTION

    SciTech Connect

    Su, W.; Cheng, X.; Ding, M. D.; Chen, P. F.; Sun, J. Q. E-mail: dmd@nju.edu.cn

    2015-05-10

    Type II radio bursts are thought to be a signature of coronal shocks. In this paper, we analyze a short-lived type II burst that started at 07:40 UT on 2011 February 28. By carefully checking white-light images, we find that the type II radio burst is not accompanied by a coronal mass ejection, only by a C2.4 class flare and narrow jet. However, in the EUV images provided by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, we find a wave-like structure that propagated at a speed of ∼600 km s{sup −1} during the burst. The relationship between the type II radio burst and the wave-like structure is, in particular, explored. For this purpose, we first derive the density distribution under the wave by the differential emission measure method, which is used to restrict the empirical density model. We then use the restricted density model to invert the speed of the shock that produces the observed frequency drift rate in the dynamic spectrum. The inverted shock speed is similar to the speed of the wave-like structure. This implies that the wave-like structure is most likely a coronal shock that produces the type II radio burst. We also examine the evolution of the magnetic field in the flare-associated active region and find continuous flux emergence and cancellation taking place near the flare site. Based on these facts, we propose a new mechanism for the formation of the type II radio burst, i.e., the expansion of the strongly inclined magnetic loops after reconnecting with a nearby emerging flux acts as a piston to generate the shock wave.

  5. Radio Astronomy Explorer /RAE/. I - Observations of terrestrial radio noise.

    NASA Technical Reports Server (NTRS)

    Herman, J. R.; Caruso, J. A.; Stone, R. G.

    1973-01-01

    Radio Astronomy Explorer (RAE) I data are analyzed to establish characteristics of HF terrestrial radio noise at an altitude of about 6000 km. Time and frequency variations in amplitude of the observed noise well above cosmic noise background are explained on the basis of temporal and spatial variations in ionospheric critical frequency coupled with those in noise source distributions. It is shown that terrestrial radio noise regularly breaks through the ionosphere and reaches RAE with magnitudes 15 dB and more above cosmic noise background, on frequencies above the F-layer critical frequency.

  6. Secure Obfuscation for Encrypted Group Signatures

    PubMed Central

    Fan, Hongfei; Liu, Qin

    2015-01-01

    In recent years, group signature techniques are widely used in constructing privacy-preserving security schemes for various information systems. However, conventional techniques keep the schemes secure only in normal black-box attack contexts. In other words, these schemes suppose that (the implementation of) the group signature generation algorithm is running in a platform that is perfectly protected from various intrusions and attacks. As a complementary to existing studies, how to generate group signatures securely in a more austere security context, such as a white-box attack context, is studied in this paper. We use obfuscation as an approach to acquire a higher level of security. Concretely, we introduce a special group signature functionality-an encrypted group signature, and then provide an obfuscator for the proposed functionality. A series of new security notions for both the functionality and its obfuscator has been introduced. The most important one is the average-case secure virtual black-box property w.r.t. dependent oracles and restricted dependent oracles which captures the requirement of protecting the output of the proposed obfuscator against collision attacks from group members. The security notions fit for many other specialized obfuscators, such as obfuscators for identity-based signatures, threshold signatures and key-insulated signatures. Finally, the correctness and security of the proposed obfuscator have been proven. Thereby, the obfuscated encrypted group signature functionality can be applied to variants of privacy-preserving security schemes and enhance the security level of these schemes. PMID:26167686

  7. Input apparatus for dynamic signature verification systems

    DOEpatents

    EerNisse, Errol P.; Land, Cecil E.; Snelling, Jay B.

    1978-01-01

    The disclosure relates to signature verification input apparatus comprising a writing instrument and platen containing piezoelectric transducers which generate signals in response to writing pressures.

  8. New insights into the study of magnetic field in the clumpy torus of AGN using near-infrared polarimetry

    NASA Astrophysics Data System (ADS)

    Lopez-Rodriguez, E.; Packham, C.; Young, S.; Elitzur, M.; Levenson, N. A.; Mason, R. E.; Almeida, C. Ramos; Alonso-Herrero, A.; Jones, T. J.; Perlman, E.

    2013-10-01

    We present J, H and Kn imaging polarimetry of IC5063. NIR polarimetry observations may advance our understanding of the mechanisms of polarisation and hence magnetic field strength in the torus of AGN. In these proceedings we summarize the polarisation results of the central 1.2″ aperture (~263 pc) of IC5063. We present a simple polarising model to account for various mechanisms of polarisation in the central regions of IC5063. The model is consistent with dichroic absorption from diffuse stellar emission through dust in the nuclear bulge and electron scattering as dominant mechanisms of polarisation at J and H. Dichroic absorption from aligned dust grains within the torus of IC5063 is dominant at Kn with a visual extinction of Av = 48±2 mag by the torus. Through the use of various components to the central engine of IC5063, we estimated the intrinsic polarisation from dichroic absorption to be . The dust grain alignment mechanism is assumed to be produced by paramagnetic relaxation. In this case, the intrinsic polarisation, , and the visual extinction by the torus, Av, are related with the magnetic field strength. The magnetic field strength is estimated to be in the range of 12-128 mG, for the physical conditions and environments of the gas and dust in the NIR emitting regions of the torus of IC5063.

  9. A demonstration test of the dual-beam polarimetry differential imaging system for the high-contrast observation

    NASA Astrophysics Data System (ADS)

    Dou, Jiangpei; Ren, Deqing; Zhu, Yongtian; Wang, Xue; Zhang, Xi; Li, Rong

    2012-09-01

    We propose a dual-beam polarimetry differential imaging test system that can be used for the direct imaging of the exoplanets. The system is composed of a liquid crystal variable retarder (LCVR) in the pupil to switch between two orthogonal polarized states, and a Wollaston prism (WP) that will be inserted before the final focal focus of the system to create two polarized images for the differential subtraction. Such a system can work separately or be integrated in the coronagraph system to enhance the high-contrast imaging. To demonstrate the feasibility of the proposed system, here we show the initial test result both with and without integrating our developed coronagraph. A unique feature for this system is that each channel can subtract with itself by using the retarder to rotate the planet's polarization orientation, which has the best performance according to our lab test results. Finally, it is shown that the polarimetry differential imaging system is a promising technique and can be used for the direct imaging observation of reflected lights from the exoplanets.

  10. Radar Polarimetric Techniques in Target Signature Characterisation.

    NASA Astrophysics Data System (ADS)

    Sampath, Venkatesh

    Les techniques polarimetriques servent a determiner les coefficients complexes de retrodiffusion des cibles radar pour toute combinaison de polarisations transmise et recue. Lorsque les champs electriques sont utilises, on doit considerer quatre coefficients en tout, regroupes dans une matrice appelee la matrice de retrodiffusion. Cette matrice contient beaucoup de renseignements sur la cible (en particulier sa symetrie, ses dimensions, la diposition et la separation de ses points brillants, etc). Sa connaissance est donc fondamentale et si chacun de ses coefficients peut etre calcule pour une combinaison donnee de polarisation, on peut reconstituer cette matrice et en faire ressortir toute l'information qu'elle contient sur l'objet en question. De plus, en disposant de techniques de polarimetrie, on peut retrouver cette matrice pour n'importe quelle combinaison de polarisation des antennes en transmission et reception.

  11. Signatures of lightning activity in seismic records

    NASA Astrophysics Data System (ADS)

    Kiszely, Márta; Bór, József; Mónus, Péter; Betz, Hans-Dieter

    2014-05-01

    A thunderstorm with intense lightning activity swept through Hungary on 28th August, 2013 between 00:00-09:00 UTC from the west towards north-east. Characteristic signal patterns could be observed in the time series recorded by seismometers in Hungary during the time the thunderstorm was close to a recording station. The signal patterns occurred coherently both in the vertical and in the horizontal seismic records. The patterns are composed of a sharp spike and a longer lasting disturbance which followed the spike after a gap of several seconds. This disturbance was of increased amplitude and lasted for up to a few tens of seconds. Detection times of spikes in the seismic records were compared to occurrence times of lightning strokes in the thunderstorm. Information on the occurrence time, polarity, type (CG or IC), peak current, and geographical location (including height estimation for IC events) of lightning strokes was provided by the LINET lightning detection network which uses magnetic loop antennas sensitive in the VLF-LF radio bands. A single lightning stroke could be unambiguously associated with each spike in the seismic records. This one-to-one correspondence suggests that the spike was caused by the electromagnetic shock wave from the lightning return stroke. The longer lasting disturbance is, on the other hand, most probably the signature of the subsequent air pressure wave which induced ground waves, too. In more than half of the examined cases, the time between the spike and the detection of a wave packet (peak amplitude) in the disturbance matched the expected propagation time of sound waves between the source location given by LINET and the seismic station. The direct sound wave associated wave packet, however, was not always the first arriving one in the seismic disturbance which suggests that coupling of sound waves and ground waves may not only occur at the seismic detector. The poster shows case studies of lightning associated seismic records

  12. Radio studies of extragalactic supernovae.

    PubMed

    Weiler, K W; Sramek, R A; Panagia, N

    1986-03-14

    Some exploding stars (supernovae) are powerful emitters of centimeter radio radiation. Detailed observations have shown that these supernovae quickly become detectable in the radio range, first at shorter wavelengths (higher frequencies) and later at progressively longer and longer wavelengths (lower frequencies). This part of the phenomenon appears to be well explained by a monotonic decrease in the amount of ionized material surrounding the radio-emitting regions as the shock from the explosion travels outward. The radio emission itself is of a nonthermal, synchrotron origin, as is the case in most bright cosmic radio sources. Once the absorption effects become negligible, the radio intensity declines with time until reaching the detection limit of the telescope. Models suggest that the absorbing material originates in a dense wind of matter lost by the supernova progenitor star, or by its companion if it is in a binary system, in the last stages of evolution before the explosion. The synchrotron radio emission can be generated either externally by the shock wave from the explosion propagating through this same high density stellar wind or internally by a rapidly rotating neutron star, which is the collapsed core of the exploded star. Present results appear to favor the former model for at least the first several years after the supernova explosion, although the latter model remains viable.

  13. Radio emission in Mercury magnetosphere

    NASA Astrophysics Data System (ADS)

    Varela, J.; Reville, V.; Brun, A. S.; Pantellini, F.; Zarka, P.

    2016-10-01

    Context. Active stars possess magnetized wind that has a direct impact on planets that can lead to radio emission. Mercury is a good test case to study the effect of the solar wind and interplanetary magnetic field (IMF) on radio emission driven in the planet magnetosphere. Such studies could be used as proxies to characterize the magnetic field topology and intensity of exoplanets. Aims: The aim of this study is to quantify the radio emission in the Hermean magnetosphere. Methods: We use the magnetohydrodynamic code PLUTO in spherical coordinates with an axisymmetric multipolar expansion for the Hermean magnetic field, to analyze the effect of the IMF orientation and intensity, as well as the hydrodynamic parameters of the solar wind (velocity, density and temperature), on the net power dissipated on the Hermean day and night side. We apply the formalism derived by Zarka et al. (2001, Astrophys. Space Sci., 277, 293), Zarka (2007, Planet. Space Sci., 55, 598) to infer the radio emission level from the net dissipated power. We perform a set of simulations with different hydrodynamic parameters of the solar wind, IMF orientations and intensities, that allow us to calculate the dissipated power distribution and infer the existence of radio emission hot spots on the planet day side, and to calculate the integrated radio emission of the Hermean magnetosphere. Results: The obtained radio emission distribution of dissipated power is determined by the IMF orientation (associated with the reconnection regions in the magnetosphere), although the radio emission strength is dependent on the IMF intensity and solar wind hydro parameters. The calculated total radio emission level is in agreement with the one estimated in Zarka et al. (2001, Astrophys. Space Sci., 277, 293) , between 5 × 105 and 2 × 106 W.

  14. VLA Observations of Solar Decimetric Spike Bursts: Direct Signature of Accelerated Electrons in Reconnection Outflow Region

    NASA Astrophysics Data System (ADS)

    Chen, B.; Bastian, T.; Gary, D. E.

    2014-12-01

    Solar decimetric spike bursts, which appear in a radio dynamic spectrum as a cluster of short-lived and narrowband brightenings, have been suggested as a possible signature of many, "elementary" particle accelerations at or near a magnetic reconnection site. Their dynamic spectral feature can be potentially used to diagnose important parameters of the reconnection site such as plasma density and spatial size of the fragmentation. Yet direct observational evidence supporting this scenario has been elusive mainly due to the lack of imaging observations. The upgraded Karl G. Jansky Very Large Array (VLA) provides the first opportunity of performing simultaneous radio imaging and dynamic spectroscopy, which allows radio sources to be imaged at every spatio-temporal pixel in the dynamic spectrum. Here we report Jansky VLA observations of decimetric spike bursts recorded during an eruptive solar limb flare. Combined with EUV and X-ray data from SDO and RHESSI, we show that the spike bursts coincide spatially with a loop-top hard X-ray source, which are located in a region where supra-arcade downflows meet the underlying hot, EUV/X-ray loops. We interpret the observed spike bursts as a direct signature of non-thermal electrons accelerated by turbulences and/or shocks in the reconnection outflow region.

  15. Radio protection zone evaluation at the Dominion Radio Astrophysical Observatory

    NASA Astrophysics Data System (ADS)

    Tapping, Ken

    Increasing use of the radio spectrum by licensed and unlicensed devices, together with the encroachment of housing developments are an issue facing many radio observatories, including the Dominion Radio Astrophysical Observatory (DRAO), located near Penticton in Southern British Columbia. A joint study by Industry Canada (Canada's national spectrum manager), and the National Research Council (Operator of DRAO) is currently in progress to examine protection zone needs and the reliability of the definitions of the zone, and the general level of background noise from growing local communities. The objectives are to produce a definition of a protection zone that is useful in spectrum management to protect the observatory, and to establish how much local community development is acceptable if the observatory is to remain a viable location for radio astronomical observations. This presentation will summarize the results so far in this ongoing study.

  16. Radio Search For Extrasolar Planets

    NASA Astrophysics Data System (ADS)

    Zarka, P.

    Theoretical justification and ongoing observational efforts in view of detecting radio emissions from extrasolar planets will be presented. On the "prediction" side, a heuris- tic scaling law has been established relating the radio output of any magnetized flow- obstacle system to the incident magnetic energy flux on the obstacle. Its confirmation by the observation of radio emission from extrasolar planets would help to understand the energy budget of such a system. On the "detection" side, specific procedures have been developed for interference mitigation and weak burst detection.

  17. Recurrent Activity in Radio Galaxies

    SciTech Connect

    Jamrozy, Marek; Konar, Chiranjib; Machalski, Jerzy; Mack, Karl-Heinz; Saikia, Dhruba; Siemiginowska, Aneta; Stawarz, Lukasz; /KIPAC, Menlo Park /Jagiellonian U.

    2007-10-15

    One of the outstanding issues concerning extragalactic radio sources is the total duration of their active phase and the possible existence of duty cycles of their nuclear activity. A duty cycle can be recognized if there is a mechanism which preserves the information of past activity for a sufficiently long time after a new activity has started up. If a new cycle starts before the radio lobes created during a former activity period have faded, we can recognize this by the observations of a young radio source embedded in an old relic structure.

  18. Searches for Fast Radio Transients

    NASA Astrophysics Data System (ADS)

    Cordes, J. M.; McLaughlin, M. A.

    2003-10-01

    We discuss optimal detection of fast radio transients from astrophysical objects while taking into account the effects of propagation through intervening ionized media, including dispersion, scattering, and scintillation. Our analysis applies to the giant-pulse phenomenon exhibited by some pulsars, for which we show examples, and to radio pulses from other astrophysical sources, such as prompt radio emission from gamma-ray burst sources and modulated signals from extraterrestrial civilizations. We estimate scintillation parameters for extragalactic sources that take into account scattering both in the host galaxy and in foreground Galactic plasma.

  19. The Helios radio astronomy experiment

    NASA Technical Reports Server (NTRS)

    Kayser, S.; Stone, R.

    1984-01-01

    Radio bursts traveling between the Sun and the Earth were tracked by radio astronomy experiments on Helios 1 and 2. A relatively short dipole antenna with a well-defined toroidal reception pattern was flown. The antenna spins in the ecliptic at 60.3 rpm and 2 frequencies are measured in each revolution. The signal analysis determines the strength of the signal, the direction of the source in the ecliptic, and the degree of modulation, and estimates source size. The experiments provide three-dimensional direction finding in space. They extend the radio frequency window beyond what is observable on Earth, and offer a long triangulation baseline.

  20. Study of interacting CMEs and DH type II radio bursts

    NASA Astrophysics Data System (ADS)

    Prasanna Subramanian, S.; Shanmugaraju, A.

    2013-04-01

    The subject of interaction between the Corona Mass Ejections (CMEs) is important in the concept of space-weather studies. In this paper, we analyzed a set of 15 interacting events taken from the list compiled by Manoharan et al. (in J. Geophys. Res. 109:A06109, 2004) and their associated DH type II radio bursts. The pre and primary CMEs, and their associated DH type II bursts are identified using the SOHO/LASCO catalog and Wind/WAVES catalog, respectively. All the primary CMEs are associated with shocks and interplanetary CMEs. These CMEs are found to be preceded by secondary slow CMEs. Most of primary CMEs are halo type CME and much faster (Mean speed = 1205 km s-1) than the pre CME (Mean speed = 450 km s-1). The average delay between the pre and primary CMEs, drift rate of DH type IIs and interaction height are found to be 211 min, 0.878 kHz/s and 17.87 Ro, respectively. The final observed distance (FOD) of all pre CMEs are found to be less than 15 Ro and it is seen that many of the pre CMEs got merged with the primary CMEs, and, they were not traced as separate CMEs in the LASCO field of view. Some radio signatures are identified for these events in the DH spectrum around the time of interaction. The interaction height obtained from the height-time plots of pre and primary CMEs is found to have correlations with (i) the time delay between the two CMEs and (ii) the central frequency of emission in the radio signatures in the DH spectrum around the time of interaction. The centre frequency of emission in the DH spectrum around the time of interaction seems to decrease when the interaction height increases. This result is compared with an interplanetary density model of Saito et al. (in Solar Phys. 55:121, 1977).