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

{"title":"Development of internally-calibrated, direct-detection millimeter-wave radiometers for high-resolution remote sensing of wet-tropospheric path delay","authors":"Victoria D. Hadel, S. Reising, X. Bosch-Lluis, P. Kangaslahti, S. Padmanabhan, C. Parashare, Shannon T. Brown, A. Tanner, O. Montes","doi":"10.1109/USNC-URSI-NRSM.2014.6928044","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928044","url":null,"abstract":"Current satellite ocean altimeters include nadir-viewing, co-located 18-34 GHz microwave radiometers to measure wet-tropospheric path delay. Due to the large antenna footprint sizes at these frequencies, the accuracy of wet path retrievals is substantially degraded within 40 km of coastlines, and retrievals are not provided over land. A viable approach to improve their capability is to add wide-band millimeter-wave window channels in the 90-180 GHz band, thereby achieving finer spatial resolution for a fixed antenna size. In this context, the upcoming Surface Water and Ocean Topography (SWOT) mission is in formulation and planned for launch in late 2020 to improve satellite altimetry to meet the science needs of both oceanography and hydrology and to transition satellite altimetry from the open ocean into the coastal zone and over inland water. To address wet-path delay in these regions, the addition of 90-180 GHz millimeter-wave window-channel radiometers to current Jason-class 18-34 GHz radiometers is expected to improve retrievals of wet-tropospheric delay in coastal areas and to enhance the potential for over-land retrievals.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"38 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":"124161011","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":"RadioAstron observations of pulsars and interstellar scattering","authors":"C. Gwinn, M. Popov, T. Smirnova, V. Shishov, J. Anderson, A. Andrianov, N. Bartel, S. Buchner, A. Deller, W. Hankey, S. Horiuchi, M. Johnson, B. Joshi, N. Kardashev, R. Karuppusamy, M. Kramer, J. McCallum, C. Phillips, J. Quick, J. Reynolds, A. Rudnitsky, E. Safutdinov, V. Soglasnov, A. Tzioumis, J. Zensus, V. Zhuravlev","doi":"10.1109/USNC-URSI-NRSM.2014.6928129","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928129","url":null,"abstract":"Summary form only given. We describe RadioAstron observations directed to understand interstellar scattering by studies of pulsars. The RadioAstron project is an international collaborative mission involving a free-flying satellite, Spektr-R, carrying a 10-m space radio telescope on an elliptical orbit around the Earth. This space telescope performs radio astronomical observations, using very long baseline interferometry (VLBI) techniques in conjunction with ground-based VLBI networks. The orbit of Spektr-R evolves with time. It has an apogee between 280,000 and 350,000 km, a perigee between 7,000 and 80,000 km, a period of 8 to 9 days, and an initial inclination of 51°. RadioAstron operates at the standard radio astronomical wavelengths of 1.19 to 1.63 cm (K-band), 6.2 cm (C-band), 18 cm (L-band), and 92 cm (P-band). As compact radio emitters, pulsars display a variety of observables useful for inferring properties of the material responsible for interstellar scattering. In particular, scattering in the interstellar plasma convolves the time series of electric field emitted at the pulsar with a impulse-response function. This impulse-response function changes over a lateral scale at the observer plane, typically over a scale of an Earth diameter. This variation can be sampled directly only by observations with telescopes separated by this scale, as for example by the space radio telescope aboard Spektr-R and an Earth telescope. We present results of space-Earth VLBI observations of pulsar B0950+08 and the Vela pulsar, at Pand L-band. Individual pulses of both are detected on space-Earth baselines. Pulsar B0950+08 lies within the Local Bubble and is weakly scattered. Its scattering shows similarities to that of intra-day variable extragalactic sources. The Vela pulsar is strongly scattered, by its enclosing supernova remnant. We discuss observations, results,and their interpretation in terms of interstellar scattering for both pulsars.","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":"131496693","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":"Transient plasma analyzer for hypervelcoty impact experiments","authors":"D. Lauben, S. Close, A. Goel, P. Tarantino","doi":"10.1109/USNC-URSI-NRSM.2014.6928073","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928073","url":null,"abstract":"We describe a novel flat panel electrostatic Transient Plasma Analyzer (TPA) designed for Cubesat-based measurements of micrometeoroid hypervelocity impact (HVI) plasma plumes from intentional targets.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"20 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":"125544777","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":"THz impulse radar for medical imaging","authors":"E. Brown, S. Sung, W. Grundfest, Z. Taylor","doi":"10.1109/USNC-URSI-NRSM.2014.6928150","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928150","url":null,"abstract":"The THz impulse radar is an “RF-inspired” sensor system that has performed remarkably well since its development nearly six years ago. It was developed for ex vivo skin-burn imaging, and has since shown great promise in the sensitive detection of hydration levels in soft tissues of several types, including in vivo rabbit cornea and partial and full thickness burns in rat models. An intriguing aspect of the impulse radar is its hybrid architecture which combines the high-peak-power of photoconductive switches with the high-responsivity and -bandwidth (RF and video) of Schottky-diode rectifiers. The result is a very sensitive sensor system which is quasi-coherent in the sense that its signal-to-noise ratio varies approximately linear with the integration time, but the phase information is discarded, which is beneficial in mitigating the effects of clutter and speckle. This talk will summarize studies done on the optimization of THz impulse radar using optical (Gaussian-beam) and large-signal-processing (MATLAB) analysis. A system-performance example will be presented for corneal hydration sensing, and the inherent affordability of this system compared to existing THz spectrometric (time- and frequency-domain) instruments will be emphasized. This architecture may be optimal in medical imaging applications where the presence of water is a defining disease/injury feature.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"68 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":"115000292","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":"Modeling sprite streamer initiation from an unstable sprite halo front","authors":"Ningyu Liu, J. Dwyer","doi":"10.1109/USNC-URSI-NRSM.2014.6928012","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928012","url":null,"abstract":"Summary form only given. High-speed videos have shown that sprite streamers either form out of dark background in the lower ionosphere or appear to be initiated from inhomogeneities at the bottom of a sprite halo [e.g., Cummer et al., GRL, 33, L04104, 2006; McHarg et al., GRL, 34, L06804, 2007; Stenbaek-Nielsen et al., GRL, 34, L11105, 2007]. On the other hand, modeling studies have concluded that inhomogeneities in the lower ionosphere are required for sprite streamer initiation at both overbreakdown [e.g., Qin et al., JGR, 116, A06305, 2011] and subbreakdown conditions [e.g., Liu et al., PRL, 109, 025002, 2012; Kosar et al., JGR, 117, A08328, 2012].","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":"129535982","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":"Ducted millimeter wave propagation over rough seas using PWE","authors":"F. Ryan","doi":"10.1109/USNC-URSI-NRSM.2014.6928026","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928026","url":null,"abstract":"Summary form only given. Microwave and millimeter wave propagation over rough sea surfaces is dominated by the effects of coherent multipath interference between direct and surface reflected paths. In addition, the omnipresent near surface atmospheric refractivity ducting creates additional multipath phenomena. The prediction of the propagated 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 and presence of foam, 4) surface waves (for vertical polarization), and 5) boundary effects which lead to non-planar wave fields near the air-sea interface. One technique that is capable of handling both the refractivity ducting and rough sea surface phenomena is the parabolic wave equation (PWE) method. This presentation will describe a PWE code based upon a rotated, split-step Green's function (SSGF) algorithm used to model maritime RF propagation over rough seas. In contrast to other PWE methods which employ a Miller-Brown type rough surface reflection coefficient, the SSGF technique directly propagates the EM fields over a stochastic realization of a rough sea surface generated from convolution of a surface wave spectrum with a 2-D Gaussian random field. Nonlinear corrections are then applied to produce an oceanographically correct sea surface having non-zero kurtosis and skewness. The surface wave spectrum used includes both wind waves (gravity and capillary) as well as swell. The surface wave spectrum utilizes a wave action method allowing for synthesis of both fully developed (i.e. open ocean) and young seas. The 2-D sea surface is time varying and the local vertical acceleration is used to synthesize breaking wave white water foam patches having different dielectric constant than the sea water. The rotated coordinate system used by the SSGF PWE method is conformal to the rough sea surface. Coverage diagram examples will be shown of millimeter wave (Ka,Ku-band) propagation under ducting conditions over varying types of seas including wind waves and swell for varying wind speeds. Both the spatial and the spectral (angleof-arrival) EM fields for within and cross-duct geometries will be shown.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"10 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":"130642307","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":"Sub-5km baseline tomography for fine-scale auroral measurements","authors":"M. Hirsch, J. Semeter, H. Dahlgren, Chhavi Goenka, H. Akbari, D. Hampton","doi":"10.1109/USNC-URSI-NRSM.2014.6928074","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928074","url":null,"abstract":"Auroral morphologies are a direct result of the specific energy levels driving the optical emissions as well as the spreading of wave energy. The emphasis of the present work is on identifying apparent auroral feature motion in both the B|| and B⊥ dimensions in order to uncover the physical model responsible for wave spreading under the given electron beam excitation. The auroral B|| dimension is known to experience a change in shape and peak optical emission for given electron beam energies, and forward models have been previously established for these phenomena. The transverse proper motion of auroral features is related to spreading of energy in the B⊥ direction. Several theories have been advanced to explain the auroral transverse proper motion, but previous observational efforts have been limited to temporal scales on the order of a second. Our new observational facility is capable of simultaneously resolving features to the decameter scale spatially and millisecond scale temporally-a capability not available until now thanks to recent advances in Electron-Multiplying Charge Coupled Device (EMCCD) technology that are triggerable with sub-millisecond accuracy from GPS-disciplined trigger sources. We can thereby combine multiple simultaneous 2D optical observations with arbitrarily physical separation to take tightly time-synchronized observations of extremely faint optical phenomena for tomographic inversion.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"222 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":"134430974","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":"Argus: A W-band 16-pixel focal plane array for the Green Bank Telescope","authors":"K. Devaraj, S. Church, K. Cleary, D. Frayer, R. Gawande, P. Goldsmith, J. Gundersen, A. Harris, P. Kangaslahti, A. Readhead, R. Reeves, L. Samoska, M. Sieth, P. Voll","doi":"10.1109/USNC-URSI-NRSM.2014.6928110","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928110","url":null,"abstract":"We are building Argus, a 16-pixel square-packed focal plane array that will cover the 75-115.3 GHz frequency range on the Robert C. Byrd Green Bank Telescope (GBT). The primary research area for Argus is the study of star formation within our Galaxy and nearby galaxies. Argus will map key molecules that trace star formation, including carbon monoxide (CO) and hydrogen cyanide (HCN). An additional key science area is astrochemistry, which will be addressed by observing complex molecules in the interstellar medium, and the study of formation of solar systems, which will be addressed by identifying dense pre-stellar cores and by observing comets in our solar system. Argus has a highly scalable architecture and will be a technology path finder for larger arrays. The array is modular in construction, which will allow easy replacement of malfunctioning and poorly performing components.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"50 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":"134461319","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":"L-band radar backscattering from a mature corn canopy: Effect of cobs","authors":"R. Lang, S. Seker, Q. Zhao, M. Kurum, M. Ogut, P. O’neill, M. Cosh","doi":"10.1109/USNC-URSI-NRSM.2014.6928036","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6928036","url":null,"abstract":"The effect of cobs on radar backscatter from a mature corn canopy is considered. In the past, a number of papers have modeled the backscattering properties of corn plants when the cobs are not present. It has been shown by O'Neill et al. [1] that the cob can constitute as much as one third of the total biomass of a mature corn plant. The position of the cob close to the stalk and the lack of knowledge of its dielectric properties make it difficult to model. These difficulties have been overcome with the aid of advanced numerical analysis tools and new biophysical measurements of the corn.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"23 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":"132623561","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":"Numerical study of source localization using the TDOA method","authors":"Mengna Yang, D. Jackson, Zubiao Xiong, Ji Chen, Jeffery T. Williams","doi":"10.1109/USNC-URSI-NRSM.2014.6927992","DOIUrl":"https://doi.org/10.1109/USNC-URSI-NRSM.2014.6927992","url":null,"abstract":"The time difference of arrival (TDOA) positioning method is a classic method that is used to determine the unknown location of a transmitting wireless terminal, based on the time differences in the signals that are received at different receivers. In this research the method is studied for two- dimensional (2-D) problems for simplicity, for an electromagnetic dipole source radiating a carrier wave that is modulated by a baseband signal. By maximizing the cross-correlation between the signals arriving at any two receivers, the TDOA between these two receivers is estimated. In principle, only three receivers are needed for source localization in 2-D problems in the absence of noise, using the TDOA between any two pairs of receivers. The source is then constrained to lie at the intersection of two hyperbolas, arising from these two pair of receivers. Localization in the presence of noise is usually based on minimizing the square error between the measured TDOA between all possible pairs of receivers (multiplied by the speed of light) and the difference in distances between the estimated transmitter location and the corresponding pair of receivers.","PeriodicalId":277196,"journal":{"name":"2014 United States National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM)","volume":"5 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":"114232686","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}