2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)最新文献

{"title":"Recent results from the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) on the Van Allen Probes","authors":"C. Kletzing","doi":"10.1109/USNC-URSI-NRSM.2014.6928090","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928090","url":null,"abstract":"The physics of the creation, loss, and transport of radiation belt particles is intimately connected to the electric and magnetic fields which mediate these processes. A large range of field and particle interactions are involved in this physics from large-scale ring current ion and magnetic field dynamics to microscopic kinetic interactions of whistler-mode chorus waves with energetic electrons. To measure these kinds of radiation belt interactions, NASA implemented the two-satellite Van Allen Probes mission. As part of the mission, the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) investigation is an integrated set of instruments consisting of a tri-axial fluxgate magnetometer (MAG) and a Waves instrument which includes a tri-axial search coil magnetometer (MSC). These wave measurements include AC electric and magnetic fields from 10Hz to 400 kHz.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"89 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122945676","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An overview of STEREO/WAVES science results","authors":"N. Gopalswamy, P. Makela, S. Yashiro","doi":"10.1109/USNC-URSI-NRSM.2014.6928130","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928130","url":null,"abstract":"Summary form only given. The Radio and Plasma Wave (WAVES) Experiment on the Solar Terrestrial Relations Observatory (STEREO) mission has been tracking heliospheric radio signatures of large-scale energy release on the Sun in the form of radio bursts at frequencies below the ionospheric cutoff. In particular, type III bursts caused by beams of electrons propagating along open magnetic field lines and type II bursts caused by electrons accelerated at shocks driven by coronal mass ejections (CMEs). Occasionally one observes type IV bursts, which are thought to be produced by energetic electrons trapped in flare magnetic structures. In addition, STEREO/WAVES observations provide information on radio enhancement associated with colliding CMEs within the coronagraphic field of view. Most of these radio emissions were also observed by the WAVES experiment on board the Wind spacecraft, but the STEREO/WAVES experiment provides additional information because of the stereoscopic observations. This paper summarizes some of the key results obtained using the STEREO/WAVES observations.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"136 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123587912","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analysis of slant STEC methodologies","authors":"Ben Schilling, R. Calfas, A. Coster, T. Gaussiran, A. Komjathy","doi":"10.1109/USNC-URSI-NRSM.2014.6928066","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928066","url":null,"abstract":"The era of Global Navigation Satellite Systems (GNSS) and burgeoning worldwide receiver networks have increased the fidelity of ionospheric models and capacity of their applications. Precise slant total electron content (STEC) measurements are critical for a plethora of modern applications including precision navigation and geolocation, radio communication, surveillance, and weather modeling. The precision of STEC estimates from dual-frequency Global Positioning System (GPS) data is bounded by carrier phase noise, multipath effects, and systematic errors of estimating satellite and receiver biases (C. Brunini and F. Azpilicueta, Geodesy, 84:293-304). Through a collaborative effort, this presentation investigates precision of STEC estimates by analyzing disparities in STEC derived from International GNSS Service (IGS) GPS data among three independent processing chains: an open source algorithm developed at the Applied Research Laboratories at the University of Texas at Austin (ARL:UT) and algorithms developed at the Jet Propulsion Laboratory (JPL) and Haystack Observatory at the Massachusetts Institute of Technology (MIT). A common data set consisting of RINEX files from nearly 150 IGS stations in early March 2012 was processed by all three algorithms. After removing satellite and receiver biases from the STEC estimates, three ΔSTEC comparisons were analyzed over a period of quiescent ionospheric conditions on March 4th, 2012 and a period following a coronal mass ejection on March 7th, 2012. The debiased ΔSTEC values represent the inherent processing noise due to the Kalman filtering technique of obtaining STEC from dual-frequency GPS observations. Results of the ΔSTEC distributions and impact of the processing error will be presented.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"142 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122914204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A comparison of propagation over rough sea surfaces using MOM and PWE methods","authors":"F. Ryan, J. Johnson, R. Burkholder","doi":"10.1109/USNC-URSI-NRSM.2014.6928022","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928022","url":null,"abstract":"Microwave propagation over rough seas plays an important role in maritime communication and surveillance applications. For propagation between low altitude antennas, the prediction of the electromagnetic fields is complicated by a number of effects including: 1) non-flat rough sea surfaces caused by wind waves and swell, 2) shadowing or blockage of direct-path due to wave crests, 3) finite conductivity surface boundary conditions, 4) surface waves (for vertical polarization), and 5) boundary effects which lead to non-planar wave fields near the air-sea interface. Traditional methods for modeling RF path loss or propagation factor using simple 2-ray geometrical optics models, or even spherical wave models, fail to correctly predict the near surface EM fields. More exact propagation techniques such as integral equation or parabolic wave equation (PWE) methods could be employed to predict the fields, but the veracity of PWE for near surface predictions has often been questioned.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"109 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123832367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"RaPTIR: Radio-wave propagation through ionosphere regions CubeSat mission","authors":"Julio Martin-Hidalgo, C. Swenson, Daniel Farr","doi":"10.1109/USNC-URSI-NRSM.2014.6928030","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928030","url":null,"abstract":"Summary form only given. The ionosphere plays an important role in radio-wave propagation. Lower frequency waves are deflected, and higher frequency waves are degraded in terms of amplitude, phase and polarization. The characteristics of this layer are due largely to solar conditions. The varying solar conditions cause great variability at different daily times, seasons, position and altitudes. Different techniques have been used to measure the ionosphere in the past, but they are limited in spatial coverage and resolution. This paper presents a mission concept for a CubeSat constellation which collects simultaneous measurements from different spatial positions. With this detailed information it will be possible to better understand ionospheric physics and improve associated models.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"112 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124120442","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Manifold-based interference mitigatation","authors":"J. W. K. Chong, A. Gasiewski","doi":"10.1109/USNC-URSI-NRSM.2014.6928043","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928043","url":null,"abstract":"Summary form only given. There is increasing competition for use of the radio spectrum among the fundamental types of spectrum users: `active' users who transmit radio signals, e.g. voice or data communications, radar surveillance, and Earth remote sensing radars; and `passive' users who operate in receive-only mode, e.g. in radio astronomy and passive remote sensing. Both active and passive users need increasing amounts of spectrum usage; the former is driven by the telecommunications industry which continually invents new uses for active systems, while the latter needs increased spectrum to obtain the increased sensitivity required for new studies and services. As such, there is significant potential for passive services to suffer radio frequency interference from active services, even in bands where the passive services are the primary users. This paper discusses the problem of finding a common descriptor language, i.e. a relevant set of parameters to adequately represent a wide range of spectrum users, e.g. Keplerian orbital elements describe the position and velocity of a an Earth-observing satellite. Preliminary results in the modeling of spectrum users in electrospace and determination of competitive hypervolumes will also be presented.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124173486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Scattering of wind turbines - Radar wave propagation analysis in wind farms","authors":"F. Kong, Yan Zhang, R. Palmer","doi":"10.1109/USNC-URSI-NRSM.2014.6927977","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6927977","url":null,"abstract":"Summary form only given. As the wind power industry thrives, more wind turbines are being installed across the country. A large group of wind turbines built next to each other forms a wind farm, which may cause potential EMI (Electromagnetic Interference) to nearby radio devices. Some studies have been performed to investigate this impact on radio applications, mostly on radar, because by far there have been many cases found to have severe impact on radar networks. Modern wind turbines typically have rotor diameter of 80 m to 100 m, hub height at 100 m and tower base diameter at 4 to 5 m. The extremely large physical dimension of wind turbines will result high backscattered RCS (Radar Cross Section) on the orders of 10,000 m2, which may even saturate radar receivers if installed close up. Given the high RCS, wind turbines are generally visible to nearby radar as long as it falls in the LOS. The rotor blades rotate at speed approximately between 15 rpm to 20 rpm. Combined with the blade length, this rotation rate will result extremely high tip speed of more than 100 m/s. The continuous distribution of scatters along the blade results in continuous contamination of Doppler spectrum with possible aliasing effect. Furthermore, this wind turbine clutter effect is non-stationary as the statistics of the return signal varies from scan to scan. Therefore, conventional ground clutter filter has failed to mitigate this recently recognized type of clutter. The isolated clutter effect refers to clutter only detectable within the wind farm area, which has limited effect as long as the locations of the wind farms are known. However, the multi-path scattering mechanism may also result in the multi-path clutter effect, which may extend the clutter contaminated area far beyond the wind farm by creating spurious images of wind turbines. All these effects will be investigated in this study, with actual cases shown. The understanding of the scattering mechanisms of wind turbines may help properly site wind farms and search of effective mitigation solution in general.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125863691","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Radar Holography using compressed sensing for point targets","authors":"Qian Zhu, J. Mathews, R. Volz","doi":"10.1109/USNC-URSI-NRSM.2014.6928072","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928072","url":null,"abstract":"The scientific community has been interested in observing meteors for decades due to the role of meteoriods in studying space weather, the upper atmosphere of the meteor zone, and various aspects of plasma physics. Meteor events detected by single receiver radar system are usually shown in the Range-Time-Intensity (RTI) plot. While we can not acquire meteor information in the cross-range domain with traditional single-receiver detection methods, the Radar Holography is a good alternative. The mathematical basis of radar holography is the fourier transform relationship[Woodman, 1997]. The images of interested targets can be obtained from the scattered electromagnetic field at a finite number of sampling points on the groud (Receiver Array). For point targets, the interested signal is natural sparse and compressible, therefore, by introducing the compressed sensing (CS) concept, we can approximately reconstruct the signal from only a few measurements, which can be less than the number required by the Nyquist-Shannon sampling theorem. However, the sparse approximation based on the CS is a NP-hard optimization problem therefore its solution can not be found easily. It is shown that by satisfying certain reconstruction conditions [Candes et al., 2008], we can approximate the original problem by l1 norm minimization, which is easily solvable by various algorithms. In this paper, we will apply the CS method to radar holography in the range, doppler frequency and cross-range domain for point targets. For modeling, a discrete linear radar signal mode is derived, and the sparse approximation based on CS has been applied. We demonstrate that this approach can provide satisfied resolution in both the temporal and spatial domain by better limiting usual ringing effect.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125910199","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Shedding light on foregrounds with new MWA and PAPER data","authors":"D. Jacobs, J. Bowman","doi":"10.1109/USNC-URSI-NRSM.2014.6928116","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928116","url":null,"abstract":"Summary form only given. Significant effort has recently been turned to the problem of detecting and characterizing intergalactic hydrogen prior to its complete ionization by stars, occurring sometime before t=950Ma (z=6). The distribution of HI, visible in redshifted 21cm radio emission, is one of the few observables into the onset of non-linear structure leading to the birth of the first stars and galaxies. Before it was ionized by stellar UV radiation, HI was found throughout the universe, roughly tracing out the underlying matter distribution and temperature. HI 21cm emission from this epoch (6 <; z <; 12) is redshifted into the VHF radio band (100 <; f <; 200 MHz) and with a observer frequency depending on redshift/distance provides a fully three dimensional view. The emission is expected to have surface brightness of ~25mK with a non-gaussian distribution and most power occurring on scales of 10cMpc. Here we describe how data from PAPER and MWA have significantly tightened our constraints on bright foregrounds, and through comparison, identified some of the most likely sources of error in foreground removal steps. In addition we present early results of an exploration of the redshift and spatial dependence of fainter foreground components identified in the deep PAPER data which has so far given the tightest constraints. Comparing with new MWA observations we seek to separate possible faint foreground contamination from equally likely systematic corruption.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128849356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gyrotropic effects in hyperbolic metamaterials","authors":"M. Othman, C. Guclu, F. Capolino","doi":"10.1109/USNC-URSI-NRSM.2014.6928010","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928010","url":null,"abstract":"Hyperbolic metamaterials (HMs) have recently been one of the most prominent impetus to infrared and optical applications for their broadband spontaneous emission enhancement and super absorption of near fields. It has been shown that plasmonic layers stacked with subwavelength dielectric spacers can be homogenized as a uniaxial electric media, with negative transverse permittivity for a wide range of parameters, which gives rise to a hyperbolic wavevector dispersion characteristics. In this premise, we investigate an HM implementation that utilize thin in-plane anisotropic structures in a multilayer configuration. Such anisotropic materials can be implemented, depending on the desired operating wavelength, using anistropically-patterned metasurfaces, or by exploiting the Hall effect in magnetically-biased metals, semiconductors or graphene sheets. We explore the possibility of observing non-vanishing off-diagonal elements in the effective permittivity tensor, in other words, obtaining an effective gyrotropic and nonreciprocal media with negative transverse permittivity. Moreover, we demonstrate how the propagation wavenumber inside the effective gyrotropic medium can be derived using a transmission line formalism, where a new set of wave solutions is formed as a result of the peculiar coupling between the TE and TM polarizations. We also validate our analysis with the rigorous transfer matrix approach by cascading the multilayers and constructing a four port network that accounts for the mode-coupling, and we show good agreement with the effective medium description in calculating plane wave transmission and reflection spatial spectrum of the multilayer.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"59 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126645721","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}