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Sample records for hf radar sea

  1. The study of single station inverting the sea surface current by HF ground wave radar based on adjoint assimilation technology

    Science.gov (United States)

    Han, Shuzong; Yang, Hua; Xue, Wenhu; Wang, Xingchi

    2017-06-01

    This paper introduces the assimilation technology in an ocean dynamics model and discusses the feasibility of inverting the sea surface current in the detection zone by assimilating the sea current radial velocity detected by single station HF ground wave radar in ocean dynamics model. Based on the adjoint assimilation and POM model, the paper successfully inverts the sea surface current through single station HF ground wave radar in the Zhoushan sea area. The single station HF radar inversion results are also compared with the bistatic HF radar composite results and the fixed point measured results by Annderaa current meter. The error analysis shows that acquisition of flow velocity and flow direction data from the single station HF radar based on adjoint assimilation and POM model is viable and the data obtained have a high correlation and consistency with the flow field observed by HF radar.

  2. Surface current dynamics under sea breeze conditions observed by simultaneous HF radar, ADCP and drifter measurements

    Science.gov (United States)

    Sentchev, Alexei; Forget, Philippe; Fraunié, Philippe

    2017-02-01

    Ocean surface boundary layer dynamics off the southern coast of France in the NW Mediterranean is investigated by using velocity observations by high-frequency (HF) radars, surface drifting buoys and a downward-looking drifting acoustic Doppler current profiler (ADCP). The analysis confirms that velocities measured by HF radars correspond to those observed by an ADCP at the effective depth z f = k -1, where k is wavenumber of the radio wave emitted by the radar. The radials provided by the radars were in a very good agreement with in situ measurements, with the relative errors of 1 and 9 % and root mean square (RMS) differences of 0.02 and 0.04 m/s for monostatic and bistatic radar, respectively. The total radar-based velocities appeared to be slightly underestimated in magnitude and somewhat biased in direction. At the end of the survey period, the difference in the surface current direction, based on HF radar and ADCP data, attained 10°. It was demonstrated that the surface boundary layer dynamics cannot be reconstructed successfully without taking into the account velocity variation with depth. A significant misalignment of ˜30° caused by the sea breeze was documented between the HF radar (HFR-derived) surface current and the background current. It was also found that the ocean response to a moderate wind forcing was confined to the 4-m-thick upper layer. The respective Ekman current attained the maximum value of 0.15 m/s, and the current rotation was found to be lagging the wind by approximately 40 min, with the current vector direction being 15-20° to the left of the wind. The range of velocity variability due to wind forcing was found comparable with the magnitude of the background current variability.

  3. Application of ESPRIT in Broad Beam HF Ground Wave Radar Sea Surface Current Mapping

    Institute of Scientific and Technical Information of China (English)

    Liu Dan-hong; Wu Xiong-bin; Wen Bi-yang; Cheng Feng

    2004-01-01

    HF surface wave radar system OSMAR2000 is a broad-beam sea-state detecting radar. ESPRIT (Estimation of Signal Parameters via Rotational Invariance Technique) algorithm is proposed to apply in DOA (direction of arrival) determination of sea echoes. The algorithm of ESPRIT is briefly introduced first. Then discussions are made on the technique for application in the OSMAR2000 framework. Numerical simulation results are presented to demonstrate the feasibility of radial current mapping based on this method. The algorithm manifests significant performance and computational advantages compared with that of MUSIC. Data acquired by OSMAR2000 are processed to give radial current map and the synthesized vector currents are compared with the in-situ measurement with traditional means. The results show the validity of ESPRIT application in DOA determination for broad-beam radar.

  4. Surface Circulation in the Iroise Sea (W. Brittany) from High Resolution HF Radar Mapping

    Science.gov (United States)

    2013-01-01

    ratios and also a real data set from the radar experiment in Bodega Bay, northern Cal- ifornia, in the Gulf of Lion, western Mediterranean (Sentchev et...2005. HF radar observations of surface circula- tion off Bodega Bay (northern California, USA). J. Geophys. Res. 110, C10020. doi:10.1029

  5. CALYPSO: a new HF RADAR network to monitor sea surface currents in the Malta-Sicily channel (Mediterranean sea)

    Science.gov (United States)

    Cosoli, S.; Ciraolo, G.; Drago, A.; Capodici, F.; Maltese, A.; Gauci, A.; Galea, A.; Azzopardi, J.; Buscaino, G.; Raffa, F.; Mazzola, S.; Sinatra, R.

    2016-12-01

    Located in one of the main shipping lanes in the Mediterranean Sea, and in a strategic region for oil extraction platforms, the Malta-Sicily channel is exposed to significant oil spill risks. Shipping and extraction activities constitute a major threat for marine areas of relevant ecological value in the area, and impacts of oil spills on the local ecosystems and the economic activities, including tourism and fisheries, can be dramatic. Damages would be even more devastating for the Maltese archipelago, where marine resources represent important economic assets. Additionally, North Africa coastal areas are also under threat, due to their proximity to the Malta-Sicily Channel. Prevention and mitigation measures, together with rapid-response and decision-making in case of emergency situations, are fundamental steps that help accomplishing the tasks of minimizing risks and reducing impacts to the various compartments. Thanks to state-of-art technology for the monitoring of sea-surface currents in real-time under all sea-state conditions, the CALYPSO network of High-Frequency Radars represents an essential and invaluable tool for the specific purpose. HF radars technology provide a unique tool to track surface currents in near-real time, and as such the dispersion of pollutants can be monitored and forecasted and their origin backtracked, for instance through data assimilation into ocean circulation models or through short-term data-driven statistical forecasts of ocean currents. The network is constituted of four SeaSonde systems that work in the 13.5MHz frequency band. The network is operative since August 2012 and has been extensively validated using a variety of independent platforms and devices, including current meter data and drifting buoys. The latter provided clear evidences of the reliability of the collected data as for tracking the drifting objects. Additionally, data have provided a new insight into the oceanographic characteristics of the region

  6. Gap Filling of the CALYPSO HF Radar Sea Surface Current Data through Past Measurements and Satellite Wind Observations

    Directory of Open Access Journals (Sweden)

    Adam Gauci

    2016-01-01

    Full Text Available High frequency (HF radar installations are becoming essential components of operational real-time marine monitoring systems. The underlying technology is being further enhanced to fully exploit the potential of mapping sea surface currents and wave fields over wide areas with high spatial and temporal resolution, even in adverse meteo-marine conditions. Data applications are opening to many different sectors, reaching out beyond research and monitoring, targeting downstream services in support to key national and regional stakeholders. In the CALYPSO project, the HF radar system composed of CODAR SeaSonde stations installed in the Malta Channel is specifically serving to assist in the response against marine oil spills and to support search and rescue at sea. One key drawback concerns the sporadic inconsistency in the spatial coverage of radar data which is dictated by the sea state as well as by interference from unknown sources that may be competing with transmissions in the same frequency band. This work investigates the use of Machine Learning techniques to fill in missing data in a high resolution grid. Past radar data and wind vectors obtained from satellites are used to predict missing information and provide a more consistent dataset.

  7. Correction of inertial oscillations by assimilation of HF radar data in a model of the Ligurian Sea

    Science.gov (United States)

    Vandenbulcke, Luc; Beckers, Jean-Marie; Barth, Alexander

    2016-11-01

    This article aims at analyzing if high-frequency radar observations of surface currents allow to improve model forecasts in the Ligurian Sea, where inertial oscillations are a dominant feature. An ensemble of ROMS models covering the Ligurian Sea, and nested in the Mediterranean Forecasting System, is coupled with two WERA high-frequency radars. A sensitivity study allows to determine optimal parameters for the ensemble filter. By assimilating observations in a single point, the obtained correction shows that the forecast error covariance matrix represents the inertial oscillations, as well as large- and meso-scale processes. Furthermore, it is shown that the velocity observations can correct the phase and amplitude of the inertial oscillations. Observations are shown to have a strong effect during approximately half a day, which confirms the importance of using a high temporal observation frequency. In general, data assimilation of HF radar observations leads to a skill score of about 30% for the forecasts of surface velocity.

  8. Correction of inertial oscillations by assimilation of HF radar data in a model of the Ligurian Sea

    Science.gov (United States)

    Vandenbulcke, Luc; Beckers, Jean-Marie; Barth, Alexander

    2017-01-01

    This article aims at analyzing if high-frequency radar observations of surface currents allow to improve model forecasts in the Ligurian Sea, where inertial oscillations are a dominant feature. An ensemble of ROMS models covering the Ligurian Sea, and nested in the Mediterranean Forecasting System, is coupled with two WERA high-frequency radars. A sensitivity study allows to determine optimal parameters for the ensemble filter. By assimilating observations in a single point, the obtained correction shows that the forecast error covariance matrix represents the inertial oscillations, as well as large- and meso-scale processes. Furthermore, it is shown that the velocity observations can correct the phase and amplitude of the inertial oscillations. Observations are shown to have a strong effect during approximately half a day, which confirms the importance of using a high temporal observation frequency. In general, data assimilation of HF radar observations leads to a skill score of about 30% for the forecasts of surface velocity.

  9. Surface current measurements in Juan de Fuca Strait using the SeaSonde HF [high frequency] radar

    Energy Technology Data Exchange (ETDEWEB)

    Hodgins, D.O.

    1994-09-01

    The shore-based SeaSonde high-frequency (HF) radar was deployed for three weeks in summer 1993 to measure surface currents in the Strait of Georgia, British Columbia. Experimental objectives included documenting the complex flow regime generated by large tides and the brackish plume of the Fraser River, and determining the radar performance under low-wind, low-salinity conditions. The radar data showed that surface flows are dominated by the plume jet formed by the Fraser River outflow, giving rise to recurring, energetic eddies with scales of 8-12 km, strong flow meanders, and convergent fronts. These features were continuously modulated by the along-channel tidal flows. Comparisons with a detailed numerical model hindcast gave good correlation between observed and predicted flow fields, especially at tidal and low frequencies. Radar return was found to be correlated with local winds and radar performance was independent of salinity variations in the plume. Synthetic aperture radar (SAR) provides a map of the radar scattering characteristics of the ocean surface on a capillary wave scale. ERS-1 satellite and airborne SAR images for July 28, 1993 were obtained and surface features were examined in the context of the HF radar current fields. Results show that SAR images alone cannot reliably provide the dynamical data required in this region by oil spill models. Under certain conditions, however, the radar imagery offers valuable physical information on phenomena affecting oil slick development. Interpretation of SAR imagery in conjunction with other remote sensing information would offer more quantitative prediction data. 28 refs., 334 figs., 1 tab.

  10. Assimilation of HF radar data in a regional model of the Ligurian Sea

    Science.gov (United States)

    Vandenbulcke, Luc; Barth, Alexander; Beckers, Jean-Marie

    2015-04-01

    An ensemble of ROMS models with 1/60 degree resolution, covering the Ligurian Sea, and nested in the Mediterranean Forecasting System, is coupled with two WERA high-frequency radars run by the NATO Undersea Research Center (now CMRE). The following perturbations are applied to the members of the ensemble: the wind forcing field, the open sea boundary conditions, and a supplementary term in the momentum equation. An ensemble Kalman (EnKF) filter is then used to assimilate hourly-averaged radial currents into the model. A observation operator extracts the corresponding model radial currents from the model currents, then smooths them in the azimuthal direction as a function of distance to the radar. The observations are spatially dense, and not uncorrelated to one another, which is approximated in our experiment by increasing the observation error variance. Different cases are run, with the estimation vector containing the model state (in which case it is called the state vector) or multiple model states at different time steps. In the latter case, the filter is closely related to the Ensemble Smoother and the Asynchronous EnKF. The impact of different parameters is studied: the correlation length of the localization function, the (experimentally determined) total observational error, the stochastic perturbation in the momentum equation, the assimilation window length, etc. The update vector generated by the data assimilation scheme is analyzed to examine whether inertial oscillations are present and corrected. The model surface temperature is also compared with satellite images in order to assess the impact of assimilating one variable (surface currents) on another one (surface temperature).

  11. The Relationship Between Sea Breeze Forcing and HF Radar-Derived Surface Currents in Monterey Bay

    Science.gov (United States)

    2014-06-01

    and Mr. Richard Lind, to whom I owe great appreciation. I would like to thank Mr. Mike Cook again for making me an expert in Matlab . He also assisted...such as aircraft, lidar , radiosondes and wind profilers, have been used over the years to measure the horizontal and vertical movement of sea breeze...useful, and it was made easy due to the existing MATLAB HFR_Progs toolbox. Using harmonic analysis for winds was not a common idea, but it provided

  12. European coordination for coastal HF radar data in EMODnet Physics

    Science.gov (United States)

    Mader, Julien; Novellino, Antonio; Gorringe, Patrick; Griffa, Annalisa; Schulz-Stellenfleth, Johannes; Montero, Pedro; Montovani, Carlo; Ayensa, Garbi; Vila, Begoña; Rubio, Anna; Sagarminaga, Yolanda

    2015-04-01

    Historically, joint effort has been put on observing open ocean, organizing, homogenizing, sharing and reinforcing the impact of the acquired information based on one technology: ARGO with profilers Argo floats, EuroSites, ESONET-NoE, FixO3 for deep water platforms, Ferrybox for stations in ships of opportunities, and GROOM for the more recent gliders. This kind of networking creates synergies and makes easier the implementation of this source of data in the European Data exchange services like EMODnet, ROOSs portals, or any applied services in the Blue economy. One main targeted improvement in the second phase of EMODnet projects is the assembling of data along coastline. In that sense, further coordination is recommended between platform operators around a specific technology in order to make easier the implementation of the data in the platforms (4th EuroGOOS DATAMEQ WG). HF radar is today recognized internationally as a cost-effective solution to provide high spatial and temporal resolution current maps (depending on the instrument operation frequency, covering from a few kilometres offshore up to 200 km) that are needed for many applications for issues related to ocean surface drift or sea state characterization. Significant heterogeneity still exists in Europe concerning technological configurations, data processing, quality standards and data availability. This makes more difficult the development of a significant network for achieving the needed accessibility to HF Radar data for a pan European use. EuroGOOS took the initiative to lead and coordinate activities within the various observation platforms by establishing a number of Ocean Observing Task Teams such as HF-Radars. The purpose is to coordinate and join the technological, scientific and operational HF radar communities at European level. The goal of the group is on the harmonization of systems requirements, systems design, data quality, improvement and proof of the readiness and standardization of

  13. Joint Efforts Towards European HF Radar Integration

    Science.gov (United States)

    Rubio, A.; Mader, J.; Griffa, A.; Mantovani, C.; Corgnati, L.; Novellino, A.; Schulz-Stellenfleth, J.; Quentin, C.; Wyatt, L.; Ruiz, M. I.; Lorente, P.; Hartnett, M.; Gorringe, P.

    2016-12-01

    During the past two years, significant steps have been made in Europe for achieving the needed accessibility to High Frequency Radar (HFR) data for a pan-European use. Since 2015, EuroGOOS Ocean Observing Task Teams (TT), such as HFR TT, are operational networks of observing platforms. The main goal is on the harmonization of systems requirements, systems design, data quality, improvement and proof of the readiness and standardization of HFR data access and tools. Particular attention is being paid by HFR TT to converge from different projects and programs toward those common objectives. First, JERICO-NEXT (Joint European Research Infrastructure network for Coastal Observatory - Novel European eXpertise for coastal observaTories, H2020 2015 Programme) will contribute on describing the status of the European network, on seeking harmonization through exchange of best practices and standardization, on developing and giving access to quality control procedures and new products, and finally on demonstrating the use of such technology in the general scientific strategy focused by the Coastal Observatory. Then, EMODnet (European Marine Observation and Data Network) Physics started to assemble HF radar metadata and data products within Europe in a uniform way. This long term program is providing a combined array of services and functionalities to users for obtaining free of charge data, meta-data and data products on the physical conditions of European sea basins and oceans. Additionally, the Copernicus Marine Environment Monitoring Service (CMEMS) delivers from 2015 a core information service to any user related to 4 areas of benefits: Maritime Safety, Coastal and Marine Environment, Marine Resources, and Weather, Seasonal Forecasting and Climate activities. INCREASE (Innovation and Networking for the integration of Coastal Radars into EuropeAn marine SErvices - CMEMS Service Evolution 2016) will set the necessary developments towards the integration of existing European

  14. Tsunami Arrival Detection with High Frequency (HF Radar

    Directory of Open Access Journals (Sweden)

    Donald Barrick

    2012-05-01

    Full Text Available Quantitative real-time observations of a tsunami have been limited to deep-water, pressure-sensor observations of changes in the sea surface elevation and observations of sea level fluctuations at the coast, which are essentially point measurements. Constrained by these data, models have been used for predictions and warning of the arrival of a tsunami, but to date no system exists for local detection of an actual incoming wave with a significant warning capability. Networks of coastal high frequency (HF-radars are now routinely observing surface currents in many countries. We report here on an empirical method for the detection of the initial arrival of a tsunami, and demonstrate its use with results from data measured by fourteen HF radar sites in Japan and USA following the magnitude 9.0 earthquake off Sendai, Japan, on 11 March 2011. The distance offshore at which the tsunami can be detected, and hence the warning time provided, depends on the bathymetry: the wider the shallow continental shelf, the greater this time. We compare arrival times at the radars with those measured by neighboring tide gauges. Arrival times measured by the radars preceded those at neighboring tide gauges by an average of 19 min (Japan and 15 min (USA The initial water-height increase due to the tsunami as measured by the tide gauges was moderate, ranging from 0.3 to 2 m. Thus it appears possible to detect even moderate tsunamis using this method. Larger tsunamis could obviously be detected further from the coast. We find that tsunami arrival within the radar coverage area can be announced 8 min (i.e., twice the radar spectral time resolution after its first appearance. This can provide advance warning of the tsunami approach to the coastline locations.

  15. Improvements on Signal Processing for HF Radar

    Institute of Scientific and Technical Information of China (English)

    LIU Yongtan; SHEN Yiying

    2001-01-01

    In this paper improvements on signalprocessing are achieved to enhance the performancesof H-F radar system, being unobtainable by the con-ventional signal processing. Using the improved sig-nal processing both high range resolution and longcoherent integration time may be obtained for goodbenefit to the target resolution and weak signal de-tection. Modification to the unmatched correspon-dence between range delay samples and range resolu-tion ceils saves an additional accumulation loss in therange processing. Finally, comparisons between theimproved and the conventional signal processing aregiven by numerical simulation.

  16. HF Radar observations of the Dardanelles outflow current in North Eastern Aegean using validated WERA HF radar data

    Directory of Open Access Journals (Sweden)

    Z. KOKKINI

    2015-01-01

    Full Text Available A two-site WERA HF radar station was installed in November 2009 at the eastern coast of Lemnos Island in North Aegean Sea, aiming to monitor the surface inflow of Black Sea waters exiting from the Dardanelles Strait, as well as to constitute a coastal management tool for incidents of oil-pollution or save-and-rescue operations. Strong interference by foreign transmissions is a source of noise deteriorating the quality of the backscattered signal, thus significantly reducing the HF radar’s effective data return rate. In order to ameliorate this problem, further quality-control and data gap interpolating procedures have been developed and applied, to be used in addition to the procedures incorporated and used by the manufacturer’s signal processing software. The second-level processing involves traditional despiking in the temporal domain, preceding Empirical Orthogonal Function analysis. The latter is used not only to filter high-frequency noise but also to fill data gaps in time and space. The data reconstruction procedure has been assessed via comparison of (a HF radial with CODE-type drifter radial velocities as well as (b HF-derived virtual drifter tracks with actual drifter tracks. The main circulation features and their variability, as revealed by the reconstructed fields, are presented.

  17. HF Radar observations of the Dardanelles outflow current in North Eastern Aegean using validated WERA HF radar data

    Directory of Open Access Journals (Sweden)

    Z. KOKKINI

    2014-12-01

    Full Text Available A two-site WERA HF radar station was installed in November 2009 at the eastern coast of Lemnos Island in North Aegean Sea, aiming to monitor the surface inflow of Black Sea waters exiting from the Dardanelles Strait, as well as to constitute a coastal management tool for incidents of oil-pollution or save-and-rescue operations. Strong interference by foreign transmissions is a source of noise deteriorating the quality of the backscattered signal, thus significantly reducing the HF radar’s effective data return rate. In order to ameliorate this problem, further quality-control and data gap interpolating procedures have been developed and applied, to be used in addition to the procedures incorporated and used by the manufacturer’s signal processing software. The second-level processing involves traditional despiking in the temporal domain, preceding Empirical Orthogonal Function analysis. The latter is used not only to filter high-frequency noise but also to fill data gaps in time and space. The data reconstruction procedure has been assessed via comparison of (a HF radial with CODE-type drifter radial velocities as well as (b HF-derived virtual drifter tracks with actual drifter tracks. The main circulation features and their variability, as revealed by the reconstructed fields, are presented.

  18. Toward an european Med HF-radar coastal monitoring

    Science.gov (United States)

    Molcard, A.; Fraunie, P.

    2010-12-01

    The monitoring of coastal areas through HF radar is developping in the european Mediterranean coasts, through national and international projects. Surface current maps may be used for process studies, forecast correction through assimilation, or for practical applications in transport studies (jellyfish, oil-spill, search-and-rescue operations). Results of radar campaigns in the North-western Mediterranean (evidence of mesoscale eddy in the Gulf of Lions and identification of dynamical structures by FSLE in the Ligurian Sea) are shown, as well as techniques for current reconstruction using a single site. A new inter-regional european project started in summer 2010, regrouping 5 countries for an integrated oil-spill coastal awarness network is presented.

  19. Surface current measurements in the Juan de Fuca strait using the SeaSonde hf radar. Report series No. EE-149

    Energy Technology Data Exchange (ETDEWEB)

    Hodgins, D.O.

    1994-12-31

    SeaSonde is an integrated data acquisition and processing system for remotely mapping ocean surface currents, based on coastal ocean dynamics application radar (CODAR) principles. This demonstration project was begun in June 1992 to collect surface current information in the more sheltered, but tidally active waters of the Straits of Juan de Fuca and Georgia. Two radar units spanning the strait between Victoria and Port Angeles were deployed, and a series of tests with real-time data transmission to Seaconsult`s office in Vancouver were carried out. This report discusses the data collected in July 1992. In addition to the radar data collection program, four days of Orion buoy drifts were carried out, as well as deployment of a woodchip slick to simulate oil-on-water motion during one of the drifter experiments. These drifts were targeted for the coverage area of the radars.

  20. An Investigation of Alternatives to MUSIC for Direction Finding in Oceanographic HF Radars

    Science.gov (United States)

    Emery, B. M.; Washburn, L.

    2016-12-01

    Of the many potential instruments and observing systems, only HF radar comes closest to matching the spatial and temporal scales needed to fully reveal dynamics of the coastal ocean. However two problems with HF radars limit their usefulness: 1) a specified error model and 2) gaps in radial coverage (of otherwise functioning radars). The growth of post processing methods applied to HF radar data illustrates the need to improve this aspect of these systems. Meanwhile, decades of work in radar processing and direction finding (DF) from outside of oceanography have received little attention. To fully realize the potential of these systems we apply simulation based evaluations of alternative DF and radar processing techniques. The simulations use as inputs surface currents from a high resolution regional ocean model (ROMS). Preliminary results suggest that Maximum Likelihood (ML) based DF methods may have advantages for oceanographic HF radars, particularly at low SNR. Investigation is ongoing, with the overall goal of improved ocean current measurements from SeaSondes as well as uniform linear arrays such as WERA and LERA.

  1. Test of HF Ground Wave Radar OSMAR2000 at the Eastern China Sea%高频地波雷达的东海试验

    Institute of Scientific and Technical Information of China (English)

    吴世才; 杨子杰; 文必洋; 石振华; 田建生; 高火涛; 吴雄斌

    2001-01-01

    “高频地波雷达海洋环境监测技术”是由武汉大学主持的国家“863”计划海洋领域的重大课题,本课题组研制了两套高频地波雷达OSMAR2000,并于1999年底,在浙江省舟山市朱家尖和宁波市象山分别建立了两个雷达实验站,进行了一年的现场自检试验和与传统海洋测量仪器的对比验证试验.试验结果表明,雷达探测海流和海风的距离达到200 km, 探测浪高的距离达到120 km,系统整体性能达到国外同类雷达20世纪90年代后期先进水平.%The Radio Wave Propagation and Remote Sensing Laboratory of Wuhan University has successfully managed The HF Ground Wave Radar Technique in Monitoring Ocean Environment, one of the key marine projects in the national 863 plans of China. Two sets of HF ground wave radar systems named OSMAR2000 had been developed and deployed at Zhujiajian,Zhoushan city and Xiangshan,Ningbo city of Zhejiang Province, where the radar's self-test experiments and verification tests against in-situ measurements by traditional marine instruments were carried out and lasted for one year. The results indicate that OSMAR2000's detecting coverage is 200km for currents and wind, and 120km for waves. OSMAR 2000 adopts FMICW wave form. Phased array is used both for transmitting and receiving.MUSIC and MVM algorithms are applied to achieve high resolution in current bearing determination.The integrated capacity of OSMAR2000 is believed to have reached the advanced level of the late 1990's.

  2. Coastal Ocean State Estimates and Forecasts based on HF Radar Data

    Science.gov (United States)

    Stanev, E. V.; Schulz-Stellenfleth, J.; Staneva, J.; Seemann, J.

    2012-04-01

    Coastal Observing System for Northern and Arctic Seas (COSYNA) collects near real-time HF radar data, which are used in parallel with numerical models to provide continuously state estimates and coastal ocean forecasts. The forecasting suite includes nested 3-D hydrodynamic models running in data-assimilation mode, which are forced with an up-to-date meteorological forecast data. This paper reviews a new method focussed on intra-tidal time scales combining radial surface currents measurements from three HF radars in the German Bight with a priori information from the hydrodynamic model. The example provided in this study is considered as a step towards developing new coastal ocean products.

  3. HF Over-the-Horizon Radar System Performance Analysis

    Science.gov (United States)

    2007-09-01

    target detection technique and radar equations are applied. Chapter V uses PROPLAB model simulation to bring in the principle of raytracing and... RADAR SYSTEM PERFORMANCE ANALYSIS by Bin-Yi Liu September 2007 Thesis Co-Advisors: Phillip E. Pace Jeffrey B. Knorr THIS PAGE...Thesis 4. TITLE AND SUBTITLE HF Over-the-Horizon Radar System Performance Analysis 6. AUTHOR(S) Bin-Yi Liu 5. FUNDING NUMBERS 7. PERFORMING

  4. Polarization Diversity for HF Ground Wave Radar

    Institute of Scientific and Technical Information of China (English)

    QIAO Xiaolin; JIN Ming

    2001-01-01

    A new method of single sample polar-ization filtering is proposed.The algorithm is fast andsuitable for the polarization processing of stationaryor nonstationary polarized disturbed signals with oneor more independent sources of disturbance.An HFground wave polarimetric radar with the ability of ra-dio disturbance suppression is then introduced.Somenumerical results demonstrate the effectiveness of sin-gle sample polarization filtering method for groundwave polarimetric radar.

  5. Potential Use of HF Radar for Tsunami Detection in the Central and Eastern Mediterranean

    Science.gov (United States)

    Cokacar, Tulay; Necmioglu, Ocal; Ozer, Ceren

    2016-04-01

    Today, HF radar is recognized as internationally cost-effective and efficient solution to provide near-real time measurements that cover a large area continuously over time for ocean hazards warning and long term ocean monitoring studies such as, seasonal forecasts of climate, hurricanes, s torm surges and large-scale ocean circulation changes. These radar systems recently became an operational tool in coastal monitoring worldwide. They are used for many operational applications that include ship detection, tracking, guidance, distribution of pollutants, fishery and oceanography. HF radar data used for the tsunami warnings, can also be used for the other purposes and be of potential interest to wide application area users and stakeholders. Moreover multi user applications will ensure the system is maintained operationally over the long term. Hence the system is cost effective also with regards to maintenance. New algorithms allow useful detection and verification for tsunami detection. While technical monitoring capacity and the algorithms for tsunami detection is improved significantly, further studies are required to obtain complete wave height determination. We analysed the available technology and algorithms for the purpose of tsunami detection in the central-eastern Mediterranean and its connected Seas (Aegean and Black Sea). Since the study area is characterized by narrow continental shelf area, the HF radar observation for the purpose of tsunami detection is possible in restricted areas. While extensive continental shelves in the northeastern Black Sea and along the coast of Tunisia in the central Mediterranean let tsunami detection 2.5 hours before tsunami waves hit the coast, the detection is possible around 1 hr or less in advance for the remaining basins with wide continental shelf areas. The bathymetric structure is important for deciding the applicability of HF radar systems for the tsunami detection in continental shelf areas, which can be covered by

  6. First HF radar measurements of summer mesopause echoes at SURA

    Directory of Open Access Journals (Sweden)

    A. N. Karashtin

    Full Text Available HF sounding of the mesosphere was first carried out at SURA in summer 1994 at frequencies in the range 8–9 MHz using one of the sub-arrays of the SURA heating facility. The observations had a range resolution of 3 km. Almost all measurements indicated the presence of strong radar returns from altitudes between 83 and 90 km with features very similar to VHF measurements of mesopause summer echoes at mid-latitudes and polar mesopause summer echoes. In contrast to VHF observations, HF mesopause echoes are almost always present.

  7. First HF radar measurements of summer mesopause echoes at SURA

    Science.gov (United States)

    Karashtin, A. N.; Shlyugaev, Y. V.; Abramov, V. I.; Belov, I. F.; Berezin, I. V.; Bychkov, V. V.; Eryshev, E. B.; Komrakov, G. P.

    1997-07-01

    HF sounding of the mesosphere was first carried out at SURA in summer 1994 at frequencies in the range 8-9 MHz using one of the sub-arrays of the SURA heating facility. The observations had a range resolution of 3 km. Almost all measurements indicated the presence of strong radar returns from altitudes between 83 and 90 km with features very similar to VHF measurements of mesopause summer echoes at mid-latitudes and polar mesopause summer echoes. In contrast to VHF observations, HF mesopause echoes are almost always present.

  8. Waves study in the Gulf of Naples by HF radar and buoy measurements

    Science.gov (United States)

    Saviano, Simona; Kalampokis, Alkiviadis; Uttieri, Marco; Zambianchi, Enrico

    2016-04-01

    An HF radar (25 MHz SeaSonde manufactured by CODAR Ocean Sensors Ltd.) has been operating in the Gulf of Naples (GoN) (Southeastern Tyrrhenian Sea) since 2004. HF radars use first-order echoes to determine surface currents, while second-order ones can be exploited to estimate the main parameters characterizing the wave field: wave direction, significant height (hs) and period (ps). Waves were studied in the GoN at three radar sites over a range cell located between 5 and 6 km from the coast. This choice, based upon preliminary sensitivity studies, allowed us to analyze the surface gravity wave field over an area of the basin where the depth is deep enough to avoid breaking, but at the same time close to the coast where the sea echo intensity is sufficiently high to ensure good data quality. The data acquired in the reference year 2012 are compared with the measurements collected over the same period by a directional waverider buoy installed offshore Capri island and managed by the Civil Protection Department of the Campania Region. The analysis aims at investigating the accuracy and the seasonal patterns of the wave parameters, showing the different responses of the wave field in different sectors of the GoN, and at verifying the agreement between the recordings of the two platforms. In addition, a coastal storm is studied to test the responsiveness of HF radars in critical environmental conditions. This work is a contribution to the Flagship Project RITMARE - The Italian Research for the Sea.

  9. Radar for Mapping Sea Ice

    Science.gov (United States)

    Barath, F. T.; Jordan, R. L.

    1983-01-01

    X-band system has 100-m2 resolution. Wide swath imaging radar of synthetic aperature type transmits signal to ground station for subsequent processing into imagery. Concept meets functional requirements for continuously mapping sea ice in north and south polar regions.

  10. Signal processing technique for randomly discontinuous spectra HF radar waveforms

    Institute of Scientific and Technical Information of China (English)

    张东坡; 刘兴钊

    2004-01-01

    A major problem with all high frequency (HF) radars is a relatively poor range resolution available due to many interference sources. To avoid the interferences in frequency domain and operate with wideband, the randomly discontinuous spectra (RDS) signal is employed. However, it results in high range sidelobes when matching the reflected echo, which is much more difficult for target detection. A new signal processing technique that is radically different from the conventional technique to lower range sidelobes is introduced. This method is based on suppressing the selfclutter of the radar range ambiguity function (AF) by mismatched filtering. An effective algorithm is adopted to solve the filter coefficients. Simulation results show that the peak sidelobe level can be reduced to -30dB and the achievable system bandwidth is about 400KHz. The technique is adaptable to practical radar systems and applicable for other realtime signal processing.

  11. Analysis of one year of HF radar data acquired in the German Bight

    Science.gov (United States)

    Schulz-Stellenfleth, J.; Stanev, E. V.; Seemann, J.

    2012-04-01

    Surface current measurements are taken on a pre-operational basis by three HF radar stations in the German Bight. This area is very shallow and dominated by tides. The HF radar is part of the COSYNA system, which aims at the implementation of an integrated observing system for the North Sea. The radars provide meridional and zonal current components at intervals of 20 minutes in areas where at least two stations overlap and only radial components elswhere. An analysis of the radar observations is performed for a data set of one year. A tidal decompositions is carried out to identify dominating constituents for different areas. Furthermore, the two dimensional surface current dynamics is analysed using tidal ellipses parameters.The generation of overtides in the shallow water areas is demonstrated. Different factors driving this mechanism are discussed. A closer look at the neap/spring tide cycle provides insight into the relative role of bottom friction processes. The relation between the inclination of tidal ellipses and bathymetric features is studied in this context as well. Current, salinity and temperature profile measurements taken at the offshore platform FINO-3 are used in addition to study stratification effects. The impact of the meteo forcing is investigated based on several case studies such as storm events and rapid changes of wind direction. For this purpose residual currents are estimated from the radar data. Finally the divergence of the observed current fields is analysed and the relation to water level dynamics is discussed. The study is meant to support the ongoing work on data assimilation and quality control within COSYNA. The relevance of the presented analysis for this work is explained and illustrated. The work is of value for the optimisation of HF radar system setups in other regions as well.

  12. Characterizing the surface circulation in the Ebro Delta using a HF radar data-model approach

    Science.gov (United States)

    Lorente Jimenez, Pablo; Piedracoba Varela, Silvia; Soto-Navarro, Javier; Garcia-Sotillo, Marcos; Alvarez Fanjul, Enrique

    2016-04-01

    One year-long (2014) quality-controlled current observations from a CODAR SeaSonde High Frequency (HF) radar network deployed in the Ebro Delta (northwestern Mediterranean) were combined with operational products provided by a regional ocean forecasting system named IBI (Iberia-Biscay-Ireland) in order to comprehensively portray the ocean state and its variability. First, accurate HF radar data were used as benchmark for the rigorous validation of IBI performance by means of the computation of skill metrics and quality indicators. The analysis of the monthly averaged current maps for 2014 showed that IBI properly captured the prevailing dynamic features of the coastal circulation observed by the HF radar, according to the resemblance of circulation patterns and the eddy kinetic energy spatial distribution. The model skill assessment was completed with an exploration of dominant modes of variability both in time and space. The EOF analysis confirmed that the modeled surface current field evolved in space and time according to three significantly dominant modes of variability which accounted for the 49.2% of the total variance, in close agreement with the results obtained for the HF radar (46.1%). The response of the subtidal surface current field to prevalent wind regimes in the study area was examined in terms of induced circulation structures by performing a conditional averaging approach. This data-model synergistic approach has proved to be valid to operationally monitor and describe the complex coastal circulation in Ebro Delta despite the observed model drawbacks in terms of reduced energy content in surface currents and some inaccuracies in the wind-driven low frequency response. This integrated methodology constitutes a powerful tool for improving operational ocean forecasting systems at European level within the frame of the Copernicus Marine Environment Monitoring Service (CMEMS). It also facilitates high-stakes decision-making for coastal management and

  13. Nightside studies of coherent HF Radar spectral width behaviour

    Directory of Open Access Journals (Sweden)

    E. E. Woodfield

    Full Text Available A previous case study found a relationship between high spectral width measured by the CUTLASS Finland HF radar and elevated electron temperatures observed by the EISCAT and ESR incoherent scatter radars in the post-midnight sector of magnetic local time. This paper expands that work by briefly re-examining that interval and looking in depth at two further case studies. In all three cases a region of high HF spectral width (>200 ms-1 exists poleward of a region of low HF spectral width (<200 ms-1. Each case, however, occurs under quite different geomagnetic conditions. The original case study occurred during an interval with no observed electrojet activity, the second study during a transition from quiet to active conditions with a clear band of ion frictional heating indicating the location of the flow reversal boundary, and the third during an isolated sub-storm. These case studies indicate that the relationship between elevated electron temperature and high HF radar spectral width appears on closed field lines after 03:00 magnetic local time (MLT on the nightside. It is not clear whether the same relationship would hold on open field lines, since our analysis of this relationship is restricted in latitude. We find two important properties of high spectral width data on the nightside. Firstly the high spectral width values occur on both open and closed field lines, and secondly that the power spectra which exhibit high widths are both single-peak and multiple-peak. In general the regions of high spectral width (>200 ms-1 have more multiple-peak spectra than the regions of low spectral widths whilst still maintaining a majority of single-peak spectra. We also find that the region of ion frictional heating is collocated with many multiple-peak HF spectra. Several mechanisms for the generation of high spectral width have been proposed which would produce multiple-peak spectra, these are discussed in relation to

  14. Modification of polarization filtering technique in HF ground wave radar

    Institute of Scientific and Technical Information of China (English)

    Zhang Guoyi; Tan Zhongji; Wang Jiantao

    2006-01-01

    The polarization filter using three orthogonal linear polarization antennas can suppress more disturbances than the polarization filter using two orthogonal linear polarization antennas in HF ground wave radar. But the algorithm of the threedimension filter is relatively complicated and not suitable for real-time processing. It can't use linear and nonlinear polarization vector translation technique directly. A modified polarization filter which is simple and has same suppressing ability as the three-dimension polarization filter is given. It only has half parameters of the primary one. Some problems about estimation of polarization parameters and selection of disturbances are discussed. A method of holding the phase of radar backscatter signal constantly is put forward so that unstationary disturbance signal can be processed.

  15. Quality assurance and control issues for HF radar wave and current measurements

    Science.gov (United States)

    Wyatt, Lucy

    2015-04-01

    HF radars are now widely used to provide surface current measurements over wide areas of the coastal ocean for scientific and operational applications. In general data quality is acceptable for these applications but there remain issues that impact on the quantity and quality of the data. These include problems with calibration and interference which impact on both phased array (e.g. WERA, Pisces) and direction-finding (e.g. SeaSonde) radars. These same issues and others (e.g. signal-to-noise, in-cell current variability, antenna sidelobes) also impact on the quality and quantity of wave data that can be obtained. These issues will be discussed in this paper, illustrated with examples from deployments of WERA, Pisces and SeaSonde radars in the UK, Europe, USA and Australia. These issues involve both quality assurance (making sure the radars perform to spec and the software is fully operational) and in quality control (identifying problems with the data due to radar hardware or software performance issues and flagging these in the provided data streams). Recommendations for the former, and current practice (of the author and within the Australian Coastal Ocean Radar Network, ACORN*) for the latter, will be discussed. The quality control processes for wave measurement are not yet as well developed as those for currents and data from some deployments can be rather noisy. Some new methods, currently under development by SeaView Sensing Ltd and being tested with ACORN data, will be described and results presented. *ACORN is a facility of the Australian Integrated Marine Observing System, IMOS. IMOS is a national collaborative research infrastructure, supported by Australian Government. It is led by University of Tasmania in partnership with the Australian marine and climate science community.

  16. Analysis of Sea Spikes in Radar Sea Clutter Data

    NARCIS (Netherlands)

    Melief, H.W.; Greidanus, H.; Genderen, P. van; Hoogeboom, P.

    2006-01-01

    Abstract—In this paper three sets of high-resolution, coherent, and polarimetric radar sea clutter data are analyzed and compared with radar sea clutter models. The nature of the data allows a thorough analysis of the power, polarization and velocity of the sea clutter. It is shown that these

  17. Analysis of Sea Spikes in Radar Sea Clutter Data

    NARCIS (Netherlands)

    Melief, H.W.; Greidanus, H.; Genderen, P. van; Hoogeboom, P.

    2006-01-01

    Abstract—In this paper three sets of high-resolution, coherent, and polarimetric radar sea clutter data are analyzed and compared with radar sea clutter models. The nature of the data allows a thorough analysis of the power, polarization and velocity of the sea clutter. It is shown that these quanti

  18. Towards the creation of a multi-institutional HF Radar Network in the Gulf of Mexico.

    Science.gov (United States)

    Flores-vidal, X.; Flament, P. J.; Durazo, R.; Navarro, L. F.; Salles, P.; Alvarez, P.; Carrillo, L.; Kurczyn, J. A.; Ulloa, M. J.; Rodriguez, I.; Toro Valencia, V. G.; Marin, M.; Perales, H.; Sanay, R.

    2016-12-01

    The Gulf of Mexico is source of important resources for both Mexico and USA, its beaches and coasts bring economical resources for these countries through the generation of jobs on the fisheries, touristic and industrial sectors. However, systematic monitoring is still necessary to evaluate its health and dynamics. This work is part of a multi-institutional project named "Implementation of oceanographic observational networks (physical, geochemical and ecological) to generate scenarios for possible contingencies related to the exploration and production of hydrocarbons in the deep waters of the Gulf of Mexico" (funded by SENER-CONACyT) which is an unprecedented Mexican joint effort to better understand the dynamics in the Gulf of Mexico. We will present the first actions towards the creation of the Mexican multi-Institutional HF Radar Network, which will allow us to synoptically map in real time the sea surface currents up to 200 km offshore. We expect to attract collaborations with the active or ongoing USA HF radar stations and institutions along the Gulf of Mexico, as well as to share methodologies and to evaluate standard data formats. The Radar Network in the Gulf of Mexico is planned to be active during 2017-2018, and it is expected to be permanent.

  19. Surface Current Measurements In Terra Nova Bay By Hf Radar

    Science.gov (United States)

    Flocco, D.; Falco, P.; Wadhams, P.; Spezie, G.

    We present the preliminary results of a field experiment carried out within frame- work of the CLIMA project of the Italian National Programme for Antarctic Research (PNRA) and in cooperation with the Scott Polar Research Institute of Cambridge. Dur- ing the second period (02/12/1999-23/01/2000) of the XV Italian expedition a coastal radar was used to characterize the current field in the area of Terra Nova Bay (TNB). One of the aims of the CLIMA (Climatic Long-term Interactions for the Mass balance in Antarctica) project is to determine the role of the polynya in the sea ice mass bal- ance, water structure and local climate. The OSCR-II experiment was planned in order to provide surface current measurements in the area of TNB polynya, one of the most important coastal polynya of the Ross Sea. OSCR (Ocean Surface Current Radar) is a shore based, remote sensing system designed to measure sea surface currents in coastal waters. Two radar sites (a master and a slave) provide with radial current mea- surements; data combined from both sites yield the total current vector. Unfortunately the master and slave stations did not work together throughout the whole period of the experiment. A description of the experiment and a discussion of the results, will be proposed.

  20. Dual HF radar study of the subauroral polarization stream

    Directory of Open Access Journals (Sweden)

    R. A. Makarevich

    2008-01-01

    Full Text Available The dual HF radars comprising the Tasman International Geophysical Environment Radar (TIGER system often observe localized high-velocity F-region plasma flows (≥1500 m/s in the midnight sector (20:00–02:00 MLT at magnetic latitudes as low as Λ=60° S. The flow channels exhibit large variability in the latitudinal extent and electric field strength, and are similar to the subauroral polarization stream or SAPS, a plasma convection feature thought to be related to the polarization electric field due to the charge separation during substorm and storm development. In this study, the 2-D plasma drift velocity within the channel is derived for each of the two TIGER radars from the maximum velocities measured in all 16 radar beams within the latitudinally narrow channel, and the time variation of the subauroral electric field is examined near substorm onset. It is demonstrated that the flow channel often does not have a clear onset, rather it manifests differently in different phases of its evolution and can persist for at least two substorm cycles. During the growth phase the electric fields within the flow channel are difficult to distinguish from those of the background auroral convection but they start to increase near substorm onset and peak during the recovery phase, in contrast to what has been reported previously for auroral convection which peaks just before the substorm onset and falls sharply at the substorm onset. The response times to substorm onset range from −5 to +40 min and show some dependence on the substorm location with longer delays observed for substorms eastward of the radars' viewing area. The propagation velocity of the high-velocity region is also investigated by comparing the observations from the two closely-spaced TIGER radars. The observations are consistent with the notion that the polarization electric field is established with the energetic ions drifting westward and equatorward from the initial substorm

  1. Wave parameters comparisons between High Frequency (HF) radar system and an in situ buoy: a case study

    Science.gov (United States)

    Fernandes, Maria; Alonso-Martirena, Andrés; Agostinho, Pedro; Sanchez, Jorge; Ferrer, Macu; Fernandes, Carlos

    2015-04-01

    The coastal zone is an important area for the development of maritime countries, either in terms of recreation, energy exploitation, weather forecasting or national security. Field measurements are in the basis of understanding how coastal and oceanic processes occur. Most processes occur over long timescales and over large spatial ranges, like the variation of mean sea level. These processes also involve a variety of factors such as waves, winds, tides, storm surges, currents, etc., that cause huge interference on such phenomena. Measurement of waves have been carried out using different techniques. The instruments used to measure wave parameters can be very different, i.e. buoys, ship base equipment like sonar and satellites. Each equipment has its own advantage and disadvantage depending on the study subject. The purpose of this study is to evaluate the behaviour of a different technology available and presently adopted in wave measurement. In the past few years the measurement of waves using High Frequency (HF) Radars has had several developments. Such a method is already established as a powerful tool for measuring the pattern of surface current, but its use in wave measurements, especially in the dual arrangement is recent. Measurement of the backscatter of HF radar wave provides the raw dataset which is analyzed to give directional data of surface elevation at each range cell. Buoys and radars have advantages, disadvantages and its accuracy is discussed in this presentation. A major advantage with HF radar systems is that they are unaffected by weather, clouds or changing ocean conditions. The HF radar system is a very useful tool for the measurement of waves over a wide area with real-time observation, but it still lacks a method to check its accuracy. The primary goal of this study was to show how the HF radar system responds to high energetic variations when compared to wave buoy data. The bulk wave parameters used (significant wave height, period and

  2. HF omnidirectional spectral CW auroral radar (HF-OSCAR) at very high latitude. Part 1: Technique

    Science.gov (United States)

    Olesen, J. K.; Jacobsen, K. E.; Stauning, P.; Henriksen, S.

    1983-12-01

    An HF system for studies of very high latitude ionospheric irregularities was described. Radio aurora from field-aligned E-region irregularities of the Slant E Condition type were discussed. The complete system combines an ionosonde, a 12 MHz pulse radar and a 12 MHz bistatic CW Doppler-range set-up. The two latter units use alternately a 360 deg rotating Yagi antenna. High precision oscillators secure the frequency stability of the Doppler system in which the received signal is mixed down to a center frequency of 500 Hz. The Doppler shift range is max + or - 500 Hz. The received signal is recorded in analog form on magnetic tape and may be monitored visually and audibly. Echo range of the CW Doppler signal is obtained by a 150 Hz amplitude modulation of the transmitted signal and phase comparison with the backscattered signal.

  3. Finland HF and Esrange MST radar observations of polar mesosphere summer echoes

    Directory of Open Access Journals (Sweden)

    T. Ogawa

    Full Text Available Peculiar near range echoes observed in summer with the SuperDARN HF radar in Finland are presented. The echoes were detected at four frequencies of 9, 11, 13 and 15 MHz at slant ranges of 105–250 km for about 100 min. Interferometer measurements indicate that the echoes are returned from 80–100 km altitudes with elevation angles of 20°–60°. Echo power (< 16 dB, Doppler velocity (between –30 and + 30 ms-1 and spectral width (< 60 ms-1 fluctuate with periods of several to 20 min, perhaps due to short–period atmospheric gravity waves. When the HF radar detected the echoes, a vertical incidence MST radar, located at Esrange in Sweden (650 km north of the HF radar site, observed polar mesosphere summer echoes (PMSE at altitudes of 80–90 km. This fact suggests that the near range HF echoes are PMSE at HF band, although both radars did not probe a common volume. With increasing radar frequency, HF echo ranges are closer to the radar site and echo power becomes weaker. Possible mechanisms to explain these features are discussed.

    Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; thermospheric dynamics; waves and tides; instruments and techniques

  4. Estimation of detection threshold in multiple ship target situations with HF ground wave radar

    Institute of Scientific and Technical Information of China (English)

    Li Hongbo; Shen Yiying; Liu Yongtan

    2007-01-01

    A credible method of calculating the detection threshold is presented for the multiple target situations,which appear frequently in the lower Doppler velocity region during the surveillance of sea with HF ground wave radar. This method defines a whole-peak-outlier elimination (WPOE) criterion, which is based on in-peak-samples correlation of each target echo spectra, to trim off the target signals and abnormal disturbances with great amplitude from the complex spectra. Therefore, cleaned background noise samples are obtained to improve the accuracy and reliability of noise level estimation. When the background noise is nonhomogeneous, the detection samples are limited and often occupied heavily with outliers. In this case, the problem that the detection threshold is overvalued can be solved. In applications on experimental data, it is verified that this method can reduce the miss alarm rate of signal detection effectively in multiple target situations as well as make the adaptability of the detector better.

  5. STRING: A new drifter for HF radar validation.

    Science.gov (United States)

    Rammou, Anna-Maria; Zervakis, Vassilis; Bellomo, Lucio; Kokkini, Zoi; Quentin, Celine; Mantovani, Carlo; Kalampokis, Alkiviadis

    2015-04-01

    High-Frequency radars (HFR) are an effective mean of remotely monitoring sea-surface currents, based on recording the Doppler-shift of radio-waves backscattered on the sea surface. Validation of HFRs' measurements takes place via comparisons either with in-situ Eulerian velocity data (usually obtained by surface current-meters attached on moorings) or to Lagrangian velocity fields (recorded by surface drifters). The most common surface drifter used for this purpose is the CODE-type drifter (Davis, 1985), an industry-standard design to record the vertical average velocity of the upper 1 m layer of the water column. In this work we claim that the observed differences between the HFR-derived velocities and Lagrangian measurements can be attributed not just to the different spatial scales recorded by the above instruments but also due to the fact that while the HFR-derived velocity corresponds to exponentially weighted vertical average of the velocity field from the surface to 1 m depth (Stewart and Joy, 1974) the velocity estimated by the CODE drifters corresponds to boxcar-type weighted vertical average due to the orthogonal shape of the CODE drifters' sails. After analyzing the theoretical behavior of a drifter under the influence of wind and current, we proceed to propose a new design of exponentially-shaped sails for the drogues of CODE-based drifters, so that the HFR-derived velocities and the drifter-based velocities will be directly comparable, regarding the way of vertically averaging the velocity field.The new drifter, codenamed STRING, exhibits identical behavior to the classical CODE design under relatively homogeneous conditions in the upper 1 m layer, however it is expected to follow a significantly different track in conditions of high vertical shear and stratification. Thus, we suggest that the new design is the instrument of choice for validation of HFR installations, as it can be used in all conditions and behaves identically to CODEs when vertical

  6. Sea clutter scattering, the K distribution and radar performance

    CERN Document Server

    Ward, Keith; Watts, Simon

    2013-01-01

    Sea Clutter: Scattering, the K Distribution and Radar Performance, 2nd Edition gives an authoritative account of our current understanding of radar sea clutter. Topics covered include the characteristics of radar sea clutter, modelling radar scattering by the ocean surface, statistical models of sea clutter, the simulation of clutter and other random processes, detection of small targets in sea clutter, imaging ocean surface features, radar detection performance calculations, CFAR detection, and the specification and measurement of radar performance. The calculation of the performance of pract

  7. Water exchange between Algeciras Bay and the Strait of Gibraltar: A study based on HF coastal radar

    Science.gov (United States)

    Chioua, J.; Dastis, C.; González, C. J.; Reyes, E.; Mañanes, R.; Ruiz, M. I.; Álvarez, E.; Yanguas, F.; Romero, J.; Álvarez, O.; Bruno, M.

    2017-09-01

    This study analyses the water mass exchanges at subinertial scale between Algeciras Bay and the adjacent Strait of Gibraltar. The mechanisms triggering this exchange process is investigated with the aid of recently-acquired data on surface currents obtained using a system of HF coastal radars deployed on the eastern side of the Strait, and remotely-sensed images of sea surface temperature (SST) and chlorophyll from the MODIS sensor of the Aqua satellite. HF radar data on surface currents are analyzed by the application of real empirical orthogonal function (EOF) decomposition, which produces three EOF modes explaining more than 70% of the variance of the surface currents at the mouth of the Bay (modes 2, 3, and 6). Mode 2 is related to the fluctuations of the Atlantic Jet in the central zone of the Strait, mainly due to a combined effect of the atmospheric pressure fluctuations in the Western Mediterranean Sea and local wind in the eastern side of the Strait; mode 3 is related to the coastal currents induced by zonal wind forcing on the north-western coast of the Strait and Alboran Sea; and mode 6 seems to be related to water transport induced by winds blowing with a significant north component into and out of the Bay.

  8. Arctic and Antarctic polar mesosphere summer echoes observed with oblique incidence HF radars: analysis using simultaneous MF and VHF radar data

    Directory of Open Access Journals (Sweden)

    T. Ogawa

    2004-12-01

    Full Text Available Polar mesosphere summer echoes (PMSEs have been well studied using vertical incidence VHF radars at northern high-latitudes. In this paper, two PMSE events detected with the oblique incidence SuperDARN HF radars at Hankasalmi, Finland (62.3° N and Syowa Station, Antarctica (69.0° S, are analyzed, together with simultaneous VHF and medium-frequency (MF radar data. Altitude resolutions of the HF radars in the mesosphere and the lower thermosphere are too poor to know exact PMSE altitudes. However, a comparison of Doppler velocity from the HF radar and neutral wind velocity from the MF radar shows that PMSEs at the HF band appeared at altitudes within 80-90km, which are consistent with those from previous vertical incidence HF-VHF radar results. The HF-VHF PMSE occurrences exhibit a semidiurnal behavior, as observed by other researchers. It is found that in one event, PMSEs occurred when westward semidiurnal winds with large amplitude at 85-88km altitudes attained a maximum. When the HF-VHF PMSEs were observed at distances beyond 180km from MF radar sites, the MF radars detected no appreciable signatures of echo enhancement.

    Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; thermospheric dynamics; waves and tides

  9. Evidence of Polar Mesosphere Summer Echoes Observed by SuperDARN SANAE HF Radar in Antarctica

    OpenAIRE

    Olakunle Ogunjobi; Venkataraman Sivakumar; Judy Ann Elizabeth Stephenson; and William Tafon Sivla

    2015-01-01

    We report on the polar mesosphere summer echoes (PMSE) occurrence probability over SANAE (South African National Antarctic Expedition) IV, for the first time. A matching coincidence method is described and implemented for PMSE extraction from SuperDARN (Super Dual Auroral Radar Network) HF radar. Several SuperDARN-PMSE characteristics are studied during the summer period from years 2005 - 2007. The seasonal and interannual SuperDARN-PMSE variations in relation to the mesospheric neutral winds...

  10. Artificial Ionization and UHF Radar Response Associated with HF Frequencies near Electron Gyro-Harmonics (Invited)

    Science.gov (United States)

    Watkins, B. J.; Fallen, C. T.; Secan, J. A.

    2013-12-01

    We present new results from O-mode ionospheric heating experiments at the HAARP facility in Alaska to demonstrate that the magnitude of artificial ionization production is critically dependent on the choice of HF frequency near gyro-harmonics. For O-mode heating in the lower F-region ionosphere, typically about 200 km altitude, artificial ionization enhancements are observed in the lower ionosphere (about 150 - 220 km) and also in the topside ionosphere above about 500 km. Lower ionosphere density enhancements are inferred from HF-enhanced ion and plasma-line signals observed with UHF radar. Upper ionospheric density enhancements have been observed with TEC (total electron content) experiments by monitoring satellite radio beacons where signal paths traverse the HF-modified ionosphere. Both density enhancements and corresponding upward plasma fluxes have also been observed in the upper ionosphere via in-situ satellite observations. The data presented focus mainly on observations near the third and fourth gyro-harmonics. The specific values of the height-dependent gyro-harmonics have been computed from a magnetic model of the field line through the HF heated volume. Experiments with several closely spaced HF frequencies around the gyro-harmonic frequency region show that the magnitude of the lower-ionosphere artificial ionization production maximizes for HF frequencies about 1.0 - 1.5 MHz above the gyro-harmonic frequency. The response is progressively larger as the HF frequency is increased in the frequency region near the gyro-harmonics. For HF frequencies that are initially greater than the gyro-harmonic value the UHF radar scattering cross-section is relatively small, and non-existent or very weak signals are observed; as the signal returns drop in altitude due to density enhancements the HF interaction region passes through lower altitudes where the HF frequency is less than the gyro-harmonic value, for these conditions the radar scattering cross-section is

  11. The use of radar for bathymetry in shallow seas

    NARCIS (Netherlands)

    Greidanus, H.

    1997-01-01

    The bottom topography in shallow seas can be observed by air- and space borne radar. The paper reviews the radar imaging mechanism, and discusses the possibilities and limitations for practical use of radar in bathymetric applications, including the types of radar instruments available for this

  12. Improving Navigation information for the Rotterdam Harbour access through a 3D Model and HF radar

    Science.gov (United States)

    Schroevers, Marinus

    2015-04-01

    The Port of Rotterdam is one of the largest harbours in the world and a gateway to Europe. For the access to Rotterdam harbour, information on hydrodynamic and meteorological conditions is of vital importance for safe and swift navigation. This information focuses on the deep navigation channel in the shallow foreshore, which accommodates large seagoing vessels. Due to a large seaward extension of the Port of Rotterdam area in 2011, current patterns have changed. A re-evaluation of the information needed, showed a need for an improved accuracy of the cross channel currents and swell, and an extended forecast horizon. To obtain this, new information system was designed based on a three dimensional hydrodynamic model which produces a 72 hour forecast. Furthermore, the system will assimilate HF radars surface current to optimize the short term forecast. The project has started in 2013 by specifying data needed from the HF radar. At the same time (temporary) buoys were deployed to monitor vertical current profiles. The HF radar will be operational in July 2015, while the model development starts beginning 2015. A pre operational version of the system is presently planned for the end of 2016. A full operational version which assimilates the HF radar data is planned for 2017.

  13. E-region decameter-scale plasma waves observed by the dual TIGER HF radars

    Directory of Open Access Journals (Sweden)

    B. A. Carter

    2009-01-01

    Full Text Available The dual Tasman International Geospace Environment Radar (TIGER HF radars regularly observe E-region echoes at sub-auroral magnetic latitudes 58°–60° S including during geomagnetic storms. We present a statistical analysis of E-region backscatter observed in a period of ~2 years (late 2004–2006 by the TIGER Bruny Island and Unwin HF radars, with particular emphasis on storm-time backscatter. It is found that the HF echoes normally form a 300-km-wide band at ranges 225–540 km. In the evening sector during geomagnetic storms, however, the HF echoes form a curved band joining to the F-region band at ~700 km. The curved band lies close to the locations where the geometric aspect angle is zero, implying little to no refraction during geomagnetic storms, which is an opposite result to what has been reported in the past. The echo occurrence, Doppler velocity, and spectral width of the HF echoes are examined in order to determine whether new HF echo types are observed at sub-auroral latitudes, particularly during geomagnetic storms. The datasets of both TIGER radars are found to be dominated by low-velocity echoes. A separate population of storm-time echoes is also identified within the datasets of both radars with most of these echoes showing similar characteristics to the low-velocity echo population. The storm-time backscatter observed by the Bruny Island radar, on the other hand, includes near-range echoes (r<405 km that exhibit some characteristics of what has been previously termed the High Aspect angle Irregularity Region (HAIR echoes. We show that these echoes appear to be a storm-time phenomenon and further investigate this population by comparing their Doppler velocity with the simultaneously measured F- and E-region irregularity velocities. It is suggested that the HAIR-like echoes are observed only by HF radars with relatively poor geometric aspect angles when electron density is low and when the electric field is particularly

  14. On the collocation between dayside auroral activity and coherent HF radar backscatter

    Directory of Open Access Journals (Sweden)

    J. Moen

    Full Text Available The 2D morphology of coherent HF radar and optical cusp aurora has been studied for conditions of predominantly southward IMF conditions, which favours low-latitude boundary layer reconnection. Despite the variability in shape of radar cusp Doppler spectra, the spectral width criterion of > 220 m s–1 proves to be a robust cusp discriminator. For extended periods of well-developed radar backscatter echoes, the equatorward boundary of the > 220 m s–1 spectral width enhancement lines up remarkably well with the equatorward boundary of the optical cusp aurora. The spectral width boundary is however poorly determined during development and fading of radar cusp backscatter. Closer inspection of radar Doppler profile characteristics suggests that a combination of spectral width and shape may advance boundary layer identification by HF radar. For the two December days studied the onset of radar cusp backscatter occurred within pre-existing 630.0 nm cusp auroral activity and appear to be initiated by sunrise, i.e. favourable radio wave propagation conditions had to develop. Better methods are put forward for analysing optical data, and for physical interpretation of HF radar data, and for combining these data, as applied to detection, tracking, and better understanding of dayside aurora. The broader motivation of this work is to develop wider use by the scientific community, of results of these techniques, to accelerate understanding of dynamic high-latitude boundary-processes. The contributions in this work are: (1 improved techniques of analysis of observational data, yielding meaningfully enhanced accuracy for deduced cusp locations; (2 a correspondingly more pronounced validation of correlation of boundary locations derived from the observational data set; and (3 a firmer physical rationale as to why the good correlation observed should theoretically be expected.

    Key words: Ionosphere (ionospheric

  15. Experimental Research of HF Passive Radar Based on DRM Digital AM Broadcasting

    Directory of Open Access Journals (Sweden)

    Wan Xian-rong

    2012-03-01

    Full Text Available This paper gives the experimental research of HF Passive Bistatic Radar (HFPBR based on Digital Radio Mondiale (DRM digital AM broadcasting that have been first carried out in China, using the newly-developed all-digital active/passive integrated HF surface wave radar system. The principle, key techniques, experimental equipment, and preliminary results are introduced about this new radar system. Based on analysis of the measurement data, experimental results under different scenarios including surface-wave, sky-wave, and hybrid sky-surface propagation modes are presented, which have proved, for the first time worldwide, the technical feasibility of using DRM broadcasting signal for over-the-horizon detection by field experiment and formed the theoretical and experimental basis for the further development of HFPBR.

  16. Radar Backscatter Study of Sea Ice.

    Science.gov (United States)

    1980-02-01

    in controlling the "state" of the ice ( temperatura and salinity) are shown in Figure 4.3-79. The salinity profile is a typical irregular c-shaped...the University of Kansas to provide well- controlled systematic studies to relate radar backscatter return to sea ice and to pin down some of the...34..,. : . - " ... ,. -.. .... .. .. ... ,,, ... ... _ ., ’.. . . , 72. Profiles of the parameters most important in controlling the "state" of the ice (temperature and salinity

  17. Mid-latitude E-region bulk motions inferred from digital ionosonde and HF radar measurements

    Directory of Open Access Journals (Sweden)

    J. Delloue

    2004-11-01

    Full Text Available In the mid-latitude E-region there is now evidence suggesting that neutral winds play a significant role in driving the local plasma instabilities and electrodynamics inside sporadicE layers. Neutral winds can be inferred from coherent radar backscatter measurements of the range-/azimuth-time-intensity (RTI/ATI striations of quasi-periodic (QP echoes, or from radar interferometer/imaging observations. In addition, neutral winds in the E-region can be estimated from angle-of-arrival ionosonde measurements of sporadic-E layers. In the present paper we analyse concurrent ionosonde and HF coherent backscatter observations obtained when a Canadian Advanced Digital Ionosonde (CADI was operated under a portion of the field-of-view of the Valensole high frequency (HF radar. The Valensole radar, a mid-latitude radar located in the south of France with a large azimuthal scanning capability of 82° (24° E to 58° W, was used to deduce zonal bulk motions of QP echoing regions using ATI analysis. The CADI was used to measure angle-of-arrival information in two orthogonal horizontal directions and thus derive the motion of sporadic-E patches drifting with the neutral wind. This paper compares the neutral wind drifts of the unstable sporadic-E patches as determined by the two instruments. The CADI measurements show a predominantly westward aligned motion, but the measured zonal drifts are underestimated relative to those observed with the Valensole radar.

  18. Validation of the CUTLASS HF radar gravity wave observing capability using EISCAT CP-1 data

    Directory of Open Access Journals (Sweden)

    N. F. Arnold

    Full Text Available Quasi-periodic fluctuations in the returned ground-scatter power from the SuperDARN HF radars have been linked to the passage of medium-scale gravity waves. We have applied a technique that extracts the first radar range returns from the F-region to study the spatial extent and characteristics of these waves in the CUTLASS field-of-view. Some ray tracing was carried out to test the applicability of this method. The EISCAT radar facility at Tromsø is well within the CUTLASS field-of-view for these waves and provides a unique opportunity to assess independently the ability of the HF radars to derive gravity wave information. Results from 1st March, 1995, where the EISCAT UHF radar was operating in its CP-1 mode, demonstrate that the radars were in good agreement, especially if one selects the electron density variations measured by EISCAT at around 235 km. CUTLASS and EISCAT gravity wave observations complement each other; the former extends the spatial field of view considerably, whilst the latter provides detailed vertical information about a range of ionospheric parameters.

    Key words. Ionosphere (ionosphere – atmosphere interactions · Meteorology and atmospheric dynamics (thermospheric dynamics · Radio science (ionospheric propagations

  19. Interpolation of the Radial Velocity Data from Coastal HF Radars

    Science.gov (United States)

    2013-01-01

    similar to the ones used in [20] for OMA processing of HFR observations in the Bodega Bay. The coordinate system is rotated clockwise (north is on...geometry of the 3-radar experiment in the Bodega Bay conducted in spring and summer of 2003 (Fig. 1). In the second series real data acquired on...July 30, 2003 in the Bodega Bay and offshore the coast of Brittany has been used. 2.2.1. Experiments with Simulated Data Simulated data experiments

  20. Integrated Monitoring of the Soya Warm Current Using HF Ocean Radars, Satellite Altimeters, Coastal Tide Gauges, and a Bottom-Mounted ADCP

    Science.gov (United States)

    Ebuchi, N.; Fukamachi, Y.; Ohshima, K. I.; Wakatsuchi, M.

    2007-12-01

    The Soya Warm Current (SWC) is a coastal boundary current, which flows along the coast of Hokkaido in the Sea of Okhotsk. The SWC flows into the Sea of Okhotsk from the Sea of Japan through the Soya/La Perouse Strait, which is located between Hokkaido, Japan, and Sakhalin, Russia. It supplies warm, saline water in the Sea of Japan to the Sea of Okhotsk and largely affects the ocean circulation and water mass formation in the Sea of Okhotsk, and local climate, environment and fishery in the region. However, the SWC has never been continuously monitored due to the difficulties involved in field observations related to, for example, severe weather conditions in the winter, political issues at the border strait, and conflicts with fishing activities in the strait. Detailed features of the SWC and its variations have not yet been clarified. In order to monitor variations in the SWC, three HF ocean radar stations were installed around the strait. The radar covers a range of approximately 70 km from the coast. It is shown that the HF radars clearly capture seasonal and subinertial variations of the SWC. The velocity of the SWC reaches its maximum, approximately 1 m/s, in summer, and weakens in winter. The velocity core is located 20 to 30 km from the coast, and its width is approximately 50 km. The surface transport by the Soya Warm Current shows a significant correlation with the sea level difference along the strait, as derived from coastal tide gauge records. The cross-current sea level difference, which is estimated from the sea level anomalies observed by the Jason-1 altimeter and a coastal tide gauge, also exhibits variation in concert with the surface transport and along-current sea level difference.

  1. Beam Forming HF Radar Beam Pattern Measurements and Phase Offset Calibration Using a UAV

    Science.gov (United States)

    Cahl, D.; Voulgaris, G.

    2016-12-01

    It has been shown that measuring antenna patterns for direction finding radars improves surface current measurements. For beam forming radars, the beam pattern of the receive array is assumed to be similar to that derived using theoretical calculations. However, local environmental conditions may lead to deviations (i.e., larger sidelobes and beamwidth) from this idealized beam pattern. This becomes particularly important for wave measurements that are sensitive to interference from sidelobes. Common techniques for beam forming HF radar phase calibration include "cross calibration", using a secondary beam forming site as the signal source, or calibration using a ship. The former method is limited to only one direction; on straight coastlines this is often at a large angle from the radar bore site where the beam width and uncertainty in phase calibration might be large. The latter technique requires chartering a ship with an appropriate reflector or transmitter, or the identification of ships of opportunity. Recent advances in UAV technology combined with an easement of FAA restrictions (Part 107) allows phase calibrations and beam pattern measurements to be completed on an HF radar site using a small transmitter attached to a UAV. This presentation describes the use of a UAV and the development of a method for beam forming phase calibration and beam pattern measurements. This method uses the UAV as a moving signal source to provide true sidelobe and beamwidth measurements. Results are shown from a calibration carried out at a beam forming (WERA) radar site (8.3 MHz) located in Georgetown, SC and are compared with results from a cross calibration. Phase calibrations acquired by the UAV showed a dependence on azimuthal angle from the radar bore site. Also, the beam patterns obtained were found to be narrower than those derived using the stationary source method. The effect of the new phase values derived using this method on the accuracy of radial velocities will be

  2. US Integrated Ocean Observing System HF Radar Network: National Applications and International Implementation

    Science.gov (United States)

    Harlan, J.

    2016-12-01

    The US Integrated Ocean Observing System (IOOS), a partnership of academic institutions and Federal agencies, within NOAA National Ocean Service (NOS), operates the nation's only high-frequency (HF) radar network providing near-real-time 2-D maps of ocean of surface currents speed and direction. This system supports US Coast Guard search and rescue operations, NOAA response to oil spills, port navigation and tracking of harmful algal bloom. In the research realm, the data are helping to understand oceanographic processes such as the warm water mass off of the west coast of the US and are routinely ingested into oceanographic models and are used for research into tsunami detection. A key component of the network is the data management system that ingests and distributes hourly data from radars throughout US coastal areas as well as Canada and Mexico, comprising nearly 150 radars. HF radar operators outside the US have adopted the data file formats that were developed by the US IOOS and these data are displayed publicly in near-real-time. To enhance the utility of HF radar data to end-users in all parts of the globe, operational products are needed. Recently in the US, quasi-operational products have been developed, or are under development, including: 2-D maps in AWIPS-II, tidal analysis and prediction from NOS Center for Operational Oceanographic Products & Services (CO-OPS), tsunami detection algorithms led by National Tsunami Warning Center, and significant wave height pilot project. These products will be highlighted and potential for international use discussed.

  3. HF Radar Signal Processing Based on Tomographic Imaging and CS Technique

    Directory of Open Access Journals (Sweden)

    Qiang Yang

    2014-01-01

    Full Text Available This study presents the application of a spotlight-mode synthetic aperture radar (SAR imaging technique to the problem of high probablity target detection in high frequency (HF radar system, attempting to improve its spatial resolution. The effects of finite aperture on resolution, sampling constraints and reconstruction over a complete angular range of 360 degrees are discussed. A Convolution Back Projection (CBP algorithm has been applied to image reconstruction. In order to solve the range limitation of aspect angle with one radar-carrying platform, we collect data over a larger azimuthal range by making multi-aspect observations. Each straight line is a sub aperture over which we can perform the CBP algorithm. When we demand higher resolution for stationary target, it will cause blur with longer data acquisition time. Thus the application of the traditional imaging algorithm is limited. Compressed Sensing (CS has recently attracted much interest as it can reduce the number of samples without compromising the imaging quality. Within this motivation, we discuss the applicability of CS and present the application constraint for HF radar system.

  4. On determining the noon polar cap boundary from SuperDARN HF radar backscatter characteristics

    Directory of Open Access Journals (Sweden)

    M. Pinnock

    Full Text Available Previous work has shown that ionospheric HF radar backscatter in the noon sector can be used to locate the footprint of the magnetospheric cusp particle precipitation. This has enabled the radar data to be used as a proxy for the location of the polar cap boundary, and hence measure the flow of plasma across it to derive the reconnection electric field in the ionosphere. This work used only single radar data sets with a field of view limited to ~2 h of local time. In this case study using four of the SuperDARN radars, we examine the boundary determined over 6 h of magnetic local time around the noon sector and its relationship to the convection pattern. The variation with longitude of the latitude of the radar scatter with cusp characteristics shows a bay-like feature. It is shown that this feature is shaped by the variation with longitude of the poleward flow component of the ionospheric plasma and may be understood in terms of cusp ion time-of-flight effects. Using this interpretation, we derive the time-of-flight of the cusp ions and find that it is consistent with approximately 1 keV ions injected from a subsolar reconnection site. A method for deriving a more accurate estimate of the location of the open-closed field line boundary from HF radar data is described.

    Key words: Ionosphere (ionosphere–magnetosphere interactions; plasma convection · Magnetospheric physics (magnetopause · cusp · and boundary layers

  5. Height dependence of the observed spectrum of radar backscatter from HF-induced ionospheric Langmuir turbulence

    Science.gov (United States)

    Fejer, J. A.; Sulzer, M. P.; Djuth, F. T.

    1991-09-01

    Results are presented of observations of the spectrum of the 430-MHz radar backscatter from HF-induced Langmuir turbulence with height discrimination. During very stable ionospheric conditions under which the height of the below-threshold backscatter spectrum changed by less than 300 m during a 7-min period, a 20-s-long temporary increase in the HF power from 3 MW ERP to 38-MW-equivalent-radiated HF power is found to result in subsequent strong above-threshold spectra extending to heights up to 1200 m greater than the height of the below-threshold spectrum for more than a minute. The generation of irregularities in the plasma density during the 20 s of enhanced HF power is suggested as a possible cause of this persistence of strong above-threshold spectra at greater heights. The initial temporal evolution of the backscatter spectrum from Langmuir turbulence after the start of HF transmissions is observed for different heights. The observational results are compared with the predictions of existing theories of Langmuir turbulence.

  6. A classification of spectral populations observed in HF radar backscatter from the E region auroral electrojets

    Directory of Open Access Journals (Sweden)

    S. E. Milan

    Full Text Available Observations of HF radar backscatter from the auroral electrojet E region indicate the presence of five major spectral populations, as opposed to the two predominant spectral populations, types I and II, observed in the VHF regime. The Doppler shift, spectral width, backscatter power, and flow angle dependencies of these five populations are investigated and described. Two of these populations are identified with type I and type II spectral classes, and hence, are thought to be generated by the two-stream and gradient drift instabilities, respectively. The remaining three populations occur over a range of velocities which can greatly exceed the ion acoustic speed, the usual limiting velocity in VHF radar observations of the E region. The generation of these spectral populations is discussed in terms of electron density gradients in the electrojet region and recent non-linear theories of E region irregularity generation.

    Key words. Ionosphere (ionospheric irregularities

  7. A statistical survey of dayside pulsed ionospheric flows as seen by the CUTLASS Finland HF radar

    Directory of Open Access Journals (Sweden)

    K. A. McWilliams

    Full Text Available Nearly two years of 2-min resolution data and 7- to 21-s resolution data from the CUTLASS Finland HF radar have undergone Fourier analysis in order to study statistically the occurrence rates and repetition frequencies of pulsed ionospheric flows in the noon-sector high-latitude ionosphere. Pulsed ionospheric flow bursts are believed to be the ionospheric footprint of newly reconnected geomagnetic field lines, which occur during episodes of magnetic flux transfer to the terrestrial magnetosphere - flux transfer events or FTEs. The distribution of pulsed ionospheric flows were found to be well grouped in the radar field of view, and to be in the vicinity of the radar signature of the cusp footprint. Two thirds of the pulsed ionospheric flow intervals included in the statistical study occurred when the interplanetary magnetic field had a southward component, supporting the hypothesis that pulsed ionospheric flows are a reconnection-related phenomenon. The occurrence rate of the pulsed ionospheric flow fluctuation period was independent of the radar scan mode. The statistical results obtained from the radar data are compared to occurrence rates and repetition frequencies of FTEs derived from spacecraft data near the magnetopause reconnection region, and to ground-based optical measurements of poleward moving auroral forms. The distributions obtained by the various instruments in different regions of the magnetosphere were remarkably similar. The radar, therefore, appears to give an unbiased sample of magnetopause activity in its routine observations of the cusp footprint.

    Key words: Magnetospheric physics (magnetosphere-ionosphere interactions; plasma convection; solar wind-magnetosphere interactions

  8. Surface circulation patterns at the southeastern Bay of Biscay: new observations from HF radar data

    Science.gov (United States)

    Solabarrieta, L.; Rubio, A.; Medina, R.; Paduan, J. D.; Castanedo, S.; Fontán, A.; Cook, M.; González, M.

    2012-12-01

    A CODAR Seasonde High Frequency (HF) radar network has been operational since the beginning of 2009 for the oceanic region of the Basque Country, Spain (south-eastern Bay of Biscay, Atlantic Ocean). It forms part of the Basque operational data acquisition system, established by the Directorate of Emergency Attention and Meteorology of the Basque Government. It is made up of two antennas, at the capes Higer (43d 23.554' N, 1d 47.745' W) and Matxitxako (43d 7.350' N, 2d 45.163' W), emitting at 4.525 MHz frequency and 30 kHz bandwidth. This system provides hourly surface currents with 5.12 km spatial resolution, covering 10,000 km2. Space- and time-covering measurements have been available in the study area since 2009. The data contribute considerably to the study of surface current patterns and the main physical processes in the area. Additional applications relate to security of navigation, maritime rescue, validation and improvement of numerical models, etc. For comparison with other validation studies and to obtain an estimate of the performance of the Basque system, statistical and spectral analysis of the surface currents obtained through the HF radar and different in-situ platforms have been conducted. The analyses show values of comparison between the different measuring systems consistent with those done by other authors (Paduan and Rosenfeld, 1996; Kaplan et al., 2005). The radar is able to reproduce the time evolution of the currents with a reasonable accuracy; likewise, the main three spectral peaks (inertial, semidiurnal and diurnal) are well resolved. In this context, the aim of this work is to show the HF radar ability to measure accurately the surface currents in the south-eastern Bay of Biscay and to study the ocean circulation in the area (figures 1 and 2). Surface current patterns are analysed and described for the period 2009-2011, for different timescales. A clear seasonality at a large-scale has been observed in accordance with previous work

  9. Eddies on the boundary between the Kuroshio current and coastal waters observed by HF ocean surface radar

    Science.gov (United States)

    Nadai, A.

    2016-02-01

    The HF ocean surface radar (HFOSR) is one of the powerful tools to measure the ocean current parameters like surface currents. Three observations of the Kuroshio current in the Tokara straight using HFOSR had done by the National Institute of Information and Comunications Technology (NICT: the former name is the Communications Research Laboratory). The first-order echoes on Doppler spectra of HFOSR shows broaden and splitting shape in the region of the border between the Kuroshio currents and coastal waters. The surface velocity maps show the existence of eddy on the border. The investigation of the mechanism of broadening first order-echoes by Nadai (2006) revealed that the modulation of wave fields from surface currents like eddy is the cause of broadening and the measured current fields also influenced the modulated wave fields. Moreover, Nadai (2006) also suggested that the influence is able to reduce using the average of two radial velocities extracted by the first-order echoes. In this paper, the results of current field observation around the border between the Kuroshio current and coastal waters are presented. Many small scale eddies are observed at the border of the Kuroshio current and coastal waters. The typical radius of the eddies is about 10km. Usury the observation of such a small scale eddy is difficult, but the eddies with same scale are observed by airborne synthetic aperture radar in the same area at different time. The eddies shows strong rotation as the typical tangential speed is about 1m/s. While the typical speed of the Kuroshio current is about 1.5m/s, the typical speed of the eddy movements is about 0.7m/s. No eddies generated in the radar coverage, but one or two eddies entered in the radar coverage a day. Therefore the origin of these eddies will exist in the upstream area of the radar coverage. Using the compensation method for the influence of the modulated wave field suggested by Nadai (2006), the eddies shows weak divergence. It is

  10. Reflectivity Model of Low Grazing Angle Radar Sea Clutter

    Institute of Scientific and Technical Information of China (English)

    FENG Sheng; CHEN Jie; CAI Tao; TU Xu-yan

    2005-01-01

    The commonly used reflectivity models of radar sea clutter are summarized. Among these models, the adjusted Barton model and the adjusted Morchin model are compared. From the analysis result, the γ-p reflectivity model is presented for low grazing angle radar sea clutter by the adjustment of the original Barton reflectivity model. The model takes into account radar frequency, grazing angle, sea condition, and polarization property. The influences of these factors on the proposed model are analyzed. The model absorbs the merits from commonly used reflectivity models for sea clutter. It introduces several researchers' opinions, and extends them. And it accounts for the reflectivity at arbitrary radar frequency from VHF to X-band, arbitrary low grazing angle, arbitrary sea condition and different polarization property. One of the main results is the proposed γ-p reflectivity model can reflect the influence of polarization on sea clutter reflectivity to some extent. The proposed γ-p reflectivity model of low-angle radar-sea clutter is validated by comparing the simulated and statistically experimental data.

  11. Signal processing techniques for phase-coded HF-VHF radars

    Directory of Open Access Journals (Sweden)

    J. A. Baskaradas

    2003-06-01

    Full Text Available HF-VHF radar techniques are easy to employ and commonly used in geophysical applications. They include deep radio soundings, used for probing the ionosphere, stratosphere-mesosphere measurement, weather forecast and radio-glaciology. Fast algorithms and powerful processors facilitate the development of several kinds of low power radars, but the reduction of the transmitted power has to be compensated by on-line processing of an encoded signal to maintain a favorable signal-to-noise ratio suitable for detection. Moreover, radars have to reconstruct return echoes with different travel times due to various origins (multi-path, adjacent objects, etc.. Such needs can be accomplished by means of signal phase coding and one of the most attractive is the reversal phase code. The composite echo signal must be processed to extract the physical information useful for the measurement considered. In this paper some algorithms used for on-line processing of phase-coded signals will be described, both in time and frequency domain.

  12. UHF Radar observations at HAARP with HF pump frequencies near electron gyro-harmonics and associated ionospheric effects

    Science.gov (United States)

    Watkins, Brenton; Fallen, Christopher; Secan, James

    Results for HF modification experiments at the HAARP facility in Alaska are presented for experiments with the HF pump frequency near third and fourth electron gyro-harmonics. A UHF diagnostic radar with range resolution of 600 m was used to determine time-dependent altitudes of scattering from plasma turbulence during heating experiments. Experiments were conducted with multiple HF frequencies stepped by 20 kHz above and below the gyro-harmonic values. During times of HF heating the HAARP facility has sufficient power to enhance large-scale ionospheric densities in the lower ionosphere (about 150-200 km altitude) and also in the topside ionosphere (above about 350 km). In the lower ionosphere, time-dependent decreases of the altitude of radar scatter result from electron density enhancements. The effects are substantially different even for relatively small frequency steps of 20 kHz. In all cases the time-varying altitude decrease of radar scatter stops about 5-10 km below the gyro-harmonic altitude that is frequency dependent; we infer that electron density enhancements stop at this altitude where the radar signals stop decreasing with altitude. Experiments with corresponding total electron content (TEC) data show that for HF interaction altitudes above about 170 km there is substantial topside electron density increases due to upward electron thermal conduction. For lower altitudes of HF interaction the majority of the thermal energy is transferred to the neutral gas and no significant topside density increases are observed. By selecting an appropriate HF frequency a little greater than the gyro-harmonic value we have demonstrated that the ionospheric response to HF heating is a self-oscillating mode where the HF interaction altitude moves up and down with a period of several minutes. If the interaction region is above about 170 km this also produces a continuously enhanced topside electron density and upward plasma flux. Experiments using an FM scan with the HF

  13. A New Range Sidelobe Suppression Technique for Randomly Intermittent Spectra HF Radar Signal

    Institute of Scientific and Technical Information of China (English)

    ZHANG Dong-po; LIU Xing-zhao

    2005-01-01

    The randomly intermittent spectra (RIS) signal is employed to combat spectrum congestion in radar and other radio services to evade the external interferences in high-frequency (HF) and ultrahigh-frequency (UHF)bands. However, the spectra discontinuity of the signal gets rise to high range sidelobes when matching the refleeted echo, which is much more difficult for targets detection. So it is indispensable to investigate the technique for sidelobes suppression of the range profile when RIS signal is utilized, This paper introduced a new processing technique based on time domain filtering to lower the range sidelobes. A robust and effetive algorithm is adopted to solve the coefficients of the filter, and the restriction on the desired response of the filter is derived. The simulation results show that the peak range sidelobe can be reduced to -27 dB from -9.5 dB while the frequency band span (FBS) is 200 kHz.

  14. HF Doppler radar observations of sporadic E at an Indian low latitude station, Visakhapatnam

    Directory of Open Access Journals (Sweden)

    M. S. S. R. K. N Sarma

    2009-02-01

    Full Text Available 5.5 MHz HF Doppler radar observations of Sporadic E over an Indian low latitude station, Visakhapatnam (17.7° N, 83.3° E and Dip 20° with 10 s resolution showed quasi-periodic variations of the echo strength and Doppler velocity variations with periods of a few minutes to a few tens of minutes. The echo strength and Doppler velocity variations with time in different range bins of the ES echo showed variations which are some times similar and some times significantly different in successive range bins at intervals of 7.5 km. The ES echo occurs with the height of maximum echo strength in the range of 100 km to 120 km and some times at 130 km. The altitude variation of the average Doppler velocity is highly variable and the height of maximum echo strength is not the same as the height of maximum Doppler velocity. Observations of ES echoes at different times of the day are presented to bring out the differences between the day and night time ES echoes. The relationship between Radar and ES parameters derived from Ionograms is poorer than that of mid latitudes which is quite consistent with the expectations based on gradient drift instability.

  15. HF radar observations of a quasi-biennial oscillation in midlatitude mesospheric winds

    Science.gov (United States)

    Malhotra, Garima; Ruohoniemi, J. M.; Baker, J. B. H.; Hibbins, R. E.; McWilliams, K. A.

    2016-11-01

    The equatorial quasi-biennial oscillation (QBO) is known to be an important source of interannual variability in the middle- and high-latitude stratosphere. The influence of the QBO on the stratospheric polar vortex in particular has been extensively studied. However, the impact of the QBO on the winds of the midlatitude mesosphere is much less clear. We have applied 13 years (2002-2014) of data from the Saskatoon Super Dual Auroral Radar Network HF radar to show that there is a strong QBO signature in the midlatitude mesospheric zonal winds during the late winter months. We find that the Saskatoon mesospheric winds are related to the winds of the equatorial QBO at 50 hPa such that the westerly mesospheric winds strengthen when QBO is easterly, and vice versa. We also consider the situation in the late winter Saskatoon stratosphere using the European Centre for Medium-Range Weather Forecasts ERA-Interim reanalysis data set. We find that the Saskatoon stratospheric winds between 7 hPa and 70 hPa weaken when the equatorial QBO at 50 hPa is easterly, and vice versa. We speculate that gravity wave filtering from the QBO-modulated stratospheric winds and subsequent opposite momentum deposition in the mesosphere plays a major role in the appearance of the QBO signature in the late winter Saskatoon mesospheric winds, thereby coupling the equatorial stratosphere and the midlatitude mesosphere.

  16. Evidence of Polar Mesosphere Summer Echoes Observed by SuperDARN SANAE HF Radar in Antarctica

    Directory of Open Access Journals (Sweden)

    Olakunle Ogunjobi

    2015-01-01

    Full Text Available We report on the polar mesosphere summer echoes (PMSE occurrence probability over SANAE (South African National Antarctic Expedition IV, for the first time. A matching coincidence method is described and implemented for PMSE extraction from SuperDARN (Super Dual Auroral Radar Network HF radar. Several SuperDARN-PMSE characteristics are studied during the summer period from years 2005 - 2007. The seasonal and interannual SuperDARN-PMSE variations in relation to the mesospheric neutral winds are studied and presented in this paper. The occurrence probability of SuperDARN-PMSE on the day-to-day scale show, predominantly, diurnal variation, with a broader peak between 12 - 14 LT and distinct minimum of 22 LT. The SuperDARN-PMSE occurrence probability rate is high in the summer solstice. Seasonal variations show a connection between the SuperDARN-PMSE occurrence probability rate and mesospheric temperature from SABER (Sounding of the Atmosphere using Broadband Emission Radiometry. The seasonal trend for both meridional and zonal winds is very stable year-to-year. Analysis of the neutral wind variations indicates the importance of pole-to-pole circulations in SuperDARN-PMSE generation.

  17. PMSE long term observations using SuperDARN SANAE HF radar measurements

    Directory of Open Access Journals (Sweden)

    Olakunle Ogunjobi

    2017-01-01

    Full Text Available It is known that the presence of nanometre-scale ice particles and neutral air turbulence in the Polar summer mesosphere modify the D-region plasma, resulting in strong backscatter. These strong backscatters are referred to as Polar Mesosphere Summer Echoes (PMSE. Although studies on PMSE have been ongoing for over three decades, aspects revealed by various instruments are still the subject of discussion. As a sequel to the paper by Ogunjobi et al. (2015, we report on the long term trends and variations in PMSE occurrence probability from Super Dual Auroral Radar Network (SuperDARN high frequency (HF radar measurements over the South African National Antarctic Expedition IV (SANAE IV. In this current paper, a simple multiple-filter technique is employed to obtain the occurrence probability rate for SuperDARN-PMSE during the summer periods for the years 1998 - 2007. The SuperDARN-PMSE occurrence probability rate in relation to geomagnetic activity is examined. The mesospheric neutral winds and temperature trends during these periods, are further studied and presented in this paper. Both the monthly and diurnal variations in occurrence are consistent with previous reports, confirming the presence of PMSE from SuperDARN SANAE IV radar measurements and the influence of pole to pole mesospheric transport circulation. The special mesospheric mean flow observed prior to the year 2002 is ascribed to the influence of solar activity. The SuperDARN-PMSE occurrence probability peaks with lowered geomagnetic activity. These present results support the hypothesis that the particle precipitation also plays an important role in SuperDARN-PMSE occurrence.

  18. A comparison of optical and coherent HF radar backscatter observations of a post-midnight aurora

    Directory of Open Access Journals (Sweden)

    S. E. Milan

    Full Text Available A poleward-progressing 630 nm optical feature is observed between approximately 0100 UT and 0230 UT (0400 MLT to 0530 MLT by a meridian-scanning photometer (MSP located at Ny Ålesund, Svalbard. Simultaneous coherent HF radar measurements indicate a region of poleward-expanding backscatter with rapid sunward plasma flow velocity along the MSP meridian. Spatial maps of the backscatter indicate a stationary backscatter feature aligned obliquely with respect to the MSP meridian, which produces an impression of poleward-expansion as the MSP progresses to later MLT. Two interpretations of the observations are possible, depending on whether the arc system is considered to move (time-dependent or to be stationary in time and apparent motion is produced as the MSP meridian rotates underneath it (time-independent. The first interpretation is as a poleward motion of an east-west aligned auroral arc. In this case the appearance of the region of backscatter is not associated with the optical feature, though the velocities within it are enhanced when the two are co-located. The second interpretation is as a polar arc or theta aurora, common features of the polar cap under the prevailing IMF northwards conditions. In this case the backscatter appears as an approximately 150 km wide region adjacent to the optical arc. In both interpretations the luminosity of the optical feature appears related to the magnitude of the plasma flow velocity. The optical features presented here do not generate appreciable HF coherent backscatter, and are only identifiable in the backscatter data as a modification of the flow by the arc electrodynamics.

  19. CUTLASS HF radar observations of high-velocity E-region echoes

    Directory of Open Access Journals (Sweden)

    M. V. Uspensky

    Full Text Available A short event of high-velocity E-region echo observations by the Pykkvibaer HF radar is analysed to study echo parameters and the echo relation to the Farley-Buneman plasma instability. The echoes were detected in several beams aligned closely to the magnetic L-shell direction. Two echo groups were identified: one group corresponded to the classical type 1 echoes with velocities close to the nominal ion-acoustic speed of 400 ms1 , while the other group had significantly larger velocities, of the order of 700 ms1 . The mutual relationship between the echo power, Doppler velocity, spectral width and elevation angles for these two groups was studied. Plotting of echo parameters versus slant range showed that all ~700 ms1 echoes originated from larger heights and distances of 500–700 km, while all ~400 ms1 echoes came from lower heights and from farther distances; 700–1000 km. We argue that both observed groups of echoes occurred due to the Farley-Buneman plasma instability excited by strong ( ~70 mVm1 and uniformly distributed electric fields. We show that the echo velocities for the two groups were different because the echoes were received from different heights. Such a separation of echo heights occurred due to the differing amounts of ionospheric refraction at short and large ranges. Thus, the ionospheric refraction and related altitude modulation of ionospheric parameters are the most important factors to consider, when various characteristics of E-region decametre irregularities are derived from HF radar measurements.

    Key words. Ionosphere (ionospheric irregularities; plasma waves and instabilities; polar ionosphere

  20. Study on the impact of sudden stratosphere warming in the upper mesosphere-lower thermosphere regions using satellite and HF radar - [Article

    CSIR Research Space (South Africa)

    Mbatha, N

    2010-01-01

    Full Text Available The occurrence of sudden stratospheric warming (SSW) excites disturbances in the mesosphere-lower thermospheric (MLT) wind and temperature. Here, researchers have examined the high frequency (HF) radar wind data from the South African National...

  1. Comparison of D-region Doppler drift winds measured by the SuperDARN Finland HF radar over an annual cycle using the Kiruna VHF meteor radar

    Directory of Open Access Journals (Sweden)

    N. F. Arnold

    Full Text Available The SuperDARN chain of oblique HF radars has provided an opportunity to generate a unique climatology of horizontal winds near the mesopause at a number of high latitude locations, via the Doppler shifted echoes from sources of ionisation in the D-region. Ablating meteor trails form the bulk of these targets, but other phenomena also contribute to the observations. Due to the poor vertical resolution of the radars, care must be taken to reduce possible biases from sporadic-E layers and Polar Mesospheric Summer echoes that can affect the effective altitude of the geophysical parameters being observed. Second, there is strong theoretical and observational evidence to suggest that the radars are picking up echoes from the backward looking direction that will tend to reduce the measured wind strengths. The effect is strongly frequency dependent, resulting in a 20% reduction at 12 MHz and a 50% reduction at 10 MHz. A comparison of the climatologies observed by the Super-DARN Finland radar between September 1999 and September 2000 and that obtained from the adjacent VHF meteor radar located at Kiruna is also presented. The agreement between the two instruments was very good. Extending the analysis to the SuperDARN Iceland East radar indicated that the principles outlined above could be applied successfully to the rest of the SuperDARN network.

    Key words. Ionosphere (ionosphere-atmosphere interactions; instruments and techniques – Meteorology and atmospheric dynamics (waves and tides

  2. Morning sector drift-bounce resonance driven ULF waves observed in artificially-induced HF radar backscatter

    Directory of Open Access Journals (Sweden)

    L. J. Baddeley

    Full Text Available HF radar backscatter, which has been artificially-induced by a high power RF facility such as the EISCAT heater at Tromsø, has provided coherent radar ionospheric electric field data of unprecedented temporal resolution and accuracy. Here such data are used to investigate ULF wave processes observed by both the CUTLASS HF radars and the EISCAT UHF radar. Data from the SP-UK-OUCH experiment have revealed small-scale (high azimuthal wave number, m -45 waves, predominantly in the morning sector, thought to be brought about by the drift-bounce resonance processes. Conjugate observations from the Polar CAM-MICE instrument indicate the presence of a non-Maxwellian ion distribution function. Further statistical analysis has been undertaken, using the Polar TIMAS instrument, to reveal the prevalence and magnitude of the non-Maxwellian energetic particle populations thought to be responsible for generating these wave types.

    Key words. Ionosphere (active experiments; wave-particle interactions Magnetospheric physics (MHD waves and instabilities

  3. Comparison between real drifter's trajectories and simulated trajectories using HF radar data, in the Bay of Biscay

    Science.gov (United States)

    Solabarrieta, Lohitzune; Cook, Michael; Paduan, Jeffrey; Sergey, Frolov; Rubio, Anna; Fontán, Almudena; Castanedo, Sonia; Gonzalez, Manuel; Medina, Raúl; Fernández, Vicente; Charria, Guillaume

    2013-04-01

    A High Frequency (HF) radar network is operational since the beginning of 2009 for the oceanic region of the Basque Country, Spain (south-eastern part of the Bay of Biscay, Atlantic Ocean). It forms part of the Basque operational data acquisition system, established by the Directorate of Emergency Attention and Meteorology of the Basque Government. It is made up of two antennas emitting at 40 kHz broadband and 4.5 MHz frequency and covering a 150 km range with 5 km radial and 5° angular resolutions. Hourly space- and time-covering measurements are contributing considerably to the study of surface current patterns and the main physical processes in the area. Additional applications relate, for example, to security of navigation, maritime rescue, validation and improvement of numerical models and trajectories prediction. Since 2009, different drifters have been deployed in the study area. Since the radar has been proved to reproduce the time evolution of the currents through comparison with moored buoys with a reasonable accuracy, the aim of this work is to evaluate the capabilities of the system to reproduce the trajectories of a set of drifters available in the study area. To make trajectory simulations, we will use HF radar total velocities, surface velocities obtained from EOF (Empirical Orthogonal Function) analysis of the whole radar data set, forecast velocities for 48 hours and also OMA (Open-Boundary Modal Analysis) derived current velocities.

  4. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during April 2015 (NCEI Accession 0138389)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  5. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during May 2015 (NCEI Accession 0138488)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  6. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during March 2015 (NCEI Accession 0138305)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  7. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Hawaii, North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during July 2016 (NCEI Accession 0156405)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  8. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during January 2015 (NCEI Accession 0137088)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  9. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during May 2016 (NCEI Accession 0154390)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  10. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during February 2016 (NCEI Accession 0145802)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  11. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during January 2016 (NCEI Accession 0144289)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  12. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during June 2015 (NCEI Accession 0138584)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  13. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during December 2015 (NCEI Accession 0141107)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  14. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during September 2015 (NCEI Accession 0138948)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  15. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Hawaii, North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during August 2016 (NCEI Accession 0156626)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  16. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during April 2016 (NCEI Accession 0151734)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  17. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during November 2015 (NCEI Accession 0139553)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  18. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during October 2015 (NCEI Accession 0139156)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  19. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Hawaii, North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during June 2016 (NCEI Accession 0155984)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  20. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during February 2015 (NCEI Accession 0137265)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  1. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during July 2015 (NCEI Accession 0138671)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  2. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during August 2015 (NCEI Accession 0138776)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  3. Surface ocean velocities obtained by HF radar from stations located along coastal waters of Antarctica, Hawaii, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico and western US during March 2016 (NCEI Accession 0148080)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The archival package contains ocean surface radial velocities collected from High frequency (HF) radar stations. NDBC, which with SIO assembles data from the IOOS HF...

  4. On auroral dynamics observed by HF radar: 1. Equatorward edge of the afternoon-evening diffuse luminosity belt

    Directory of Open Access Journals (Sweden)

    M. Uspensky

    Full Text Available Observations and modelling are presented which illustrate the ability of the Finland CUTLASS HF radar to monitor the afternoon-evening equatorward auroral boundary during weak geomagnetic activity. The subsequent substorm growth phase development was also observed in the late evening sector as a natural continuation of the preceding auroral oval dynamics. Over an 8 h period the CUTLASS Finland radar observed a narrow (in range and persistent region of auroral F- and (later E-layer echoes which gradually moved equatorward, consistent with the auroral oval diurnal rotation. This echo region corresponds to the subvisual equatorward edge of the diffuse luminosity belt (SEEL and the ionospheric footprint of the inner boundary of the electron plasma sheet. The capability of the Finland CUTLASS radar to monitor the E-layer SEEL-echoes is a consequence of the nearly zero E-layer rectilinear aspect angles in a region 5–10° poleward of the radar site. The F-layer echoes are probably the boundary blob echoes. The UHF EISCAT radar was in operation and observed a similar subvisual auroral arc and an F-layer electron density enhancement when it appeared in its antenna beam.

    Key words: Ionsophere (ionospheric irregularities · Magnetospheric physics (auroral phenomena; magnetosphere–ionosphere interactions

  5. Refractivity estimation from radar sea clutter

    Institute of Scientific and Technical Information of China (English)

    Huang Si-Xun; Zhao Xiao-Feng; Sheng Zheng

    2009-01-01

    This paper addresses the problem of estimating lower atmospheric refractivity under the nonstandard propagation conditions frequently encountered in low altitude maritime radar applications. The vertical structure of the refractive environment is modeled by using a five-parameter model, and the horizontal structure is modeled as range-independent. The electromagnetic propagation in the troposphere is simulated by using a split-step fast Fourier transform based on parabolic approximation to the wave equation. A global search marked as a modified genetic algorithm (MGA) for the 5 environmental parameters is performed by using a genetic algorithm (GA) integrated with a simulated annealing technique. The retrieved results from simulated runs demonstrate the ability of this method to make atmospheric refractivity estimations. A comparison with the classical GA and the Bayesian Markov Chain Monte Carlo (Bayesian-MCMC) technique shows that the MGA can not only shorten the inverse time but also improve the inverse precision. For real data cases, the inversion values do not match the reference data very well. The inverted profile, however, can be used to synoptically describe the real refractive structure.

  6. Joint observations of a traveling ionospheric disturbance with the Paratunka OMTI camera and the Hokkaido HF radar

    Directory of Open Access Journals (Sweden)

    A. Koustov

    2009-06-01

    Full Text Available On 10 September 2007 between 10:00 and 14:00 UT, the OMTI all-sky imager at Paratunka (Kamchatka, Russia, GLAT~52° observed the onset and south-western progression of a localized depletion region in the airglow intensity. The perturbation, while being stretched in the NW-SE direction, crossed the entire field of view of the camera. During the event, the Hokkaido SuperDARN HF radar was monitoring echoes in the Paratunka longitudinal sector. It was detecting a localized band of ground scatter echoes progressing equatorward synchronously with the motion of the optical perturbation. It is suggested that both features resulted from the onset and south-western progression of a localized region with enhanced electric field that influenced the distribution of the plasma density in the ionosphere. Modeling of the HF ground scatter dynamics based on numerical ray tracing demonstrated qualitative consistency with the observations.

  7. Wind influence on surface current variability in the Ibiza Channel from HF Radar

    Science.gov (United States)

    Lana, Arancha; Marmain, Julien; Fernández, Vicente; Tintoré, Joaquin; Orfila, Alejandro

    2016-04-01

    Surface current variability is investigated using 2.5 years of continuous velocity measurements from an high frequency radar (HFR) located in the Ibiza Channel (Western Mediterranean Sea). The Ibiza Channel is identified as a key geographical feature for the exchange of water masses but still poorly documented. Operational, quality controlled, HFR derived velocities are provided by the Balearic Islands Coastal Observing and Forecasting System (SOCIB). They are assessed by performing statistical comparisons with current-meter, ADCP, and surface lagrangian drifters. HFR system does not show significant bias, and its accuracy is in accordance with previous studies performed in other areas. The main surface circulation patterns are deduced from an EOF analysis. The first three modes represent almost 70 % of the total variability. A cross-correlation analysis between zonal and meridional wind components and the temporal amplitudes of the first three modes reveal that the first two modes are mainly driven by local winds, with immediate effects of wind forcing and veering following Ekman effect. The first mode (37 % of total variability) is the response of meridional wind while the second mode (24 % of total variability) is linked primarily with zonal winds. The third and higher order modes are related to mesoscale circulation features. HFR derived surface transport presents a markedly seasonal variability being mostly southwards. Its comparison with Ekman-induced transport shows that wind contribution to the total surface transport is on average around 65 %.

  8. Mapping ionospheric backscatter measured by the SuperDARN HF radars – Part 1: A new empirical virtual height model

    Directory of Open Access Journals (Sweden)

    T. K. Yeoman

    2008-05-01

    Full Text Available Accurately mapping the location of ionospheric backscatter targets (density irregularities identified by the Super Dual Auroral Radar Network (SuperDARN HF radars can be a major problem, particularly at far ranges for which the radio propagation paths are longer and more uncertain. Assessing and increasing the accuracy of the mapping of scattering locations is crucial for the measurement of two-dimensional velocity structures on the small and meso-scale, for which overlapping velocity measurements from two radars need to be combined, and for studies in which SuperDARN data are used in conjunction with measurements from other instruments. The co-ordinates of scattering locations are presently estimated using a combination of the measured range and a model virtual height, assuming a straight line virtual propagation path. By studying elevation angle of arrival information of backscatterred signals from 5 years of data (1997–2001 from the Saskatoon SuperDARN radar we have determined the actual distribution of the backscatter target locations in range-virtual height space. This has allowed the derivation of a new empirical virtual height model that allows for a more accurate mapping of the locations of backscatter targets.

  9. Inversion for atmosphere duct parameters using real radar sea clutter

    Science.gov (United States)

    Sheng, Zheng; Fang, Han-Xian

    2012-02-01

    This paper addresses the problem of estimating the lower atmospheric refractivity (M profile) under nonstandard propagation conditions frequently encountered in low altitude maritime radar applications. The vertical structure of the refractive environment is modeled using five parameters and the horizontal structure is modeled using five parameters. The refractivity model is implemented with and without a priori constraint on the duct strength as might be derived from soundings or numerical weather-prediction models. An electromagnetic propagation model maps the refractivity structure into a replica field. Replica fields are compared with the observed clutter using a squared-error objective function. A global search for the 10 environmental parameters is performed using genetic algorithms. The inversion algorithm is implemented on the basis of S-band radar sea-clutter data from Wallops Island, Virginia (SPANDAR). Reference data are from range-dependent refractivity profiles obtained with a helicopter. The inversion is assessed (i) by comparing the propagation predicted from the radar-inferred refractivity profiles with that from the helicopter profiles, (ii) by comparing the refractivity parameters from the helicopter soundings with those estimated. This technique could provide near-real-time estimation of ducting effects.

  10. Inversion for atmosphere duct parameters using real radar sea clutter

    Institute of Scientific and Technical Information of China (English)

    Sheng Zheng; Fang Han-Xian

    2012-01-01

    This paper addresses the problem of estimating the lower atmospheric refractivity (M profile) under nonstandard propagation conditions frequently encountered in low altitude maritime radar applications.The vertical structure of the refractive environment is modeled using five parameters and the horizontal structure is modeled using five parameters.The refractivity model is implemented with and without a priori constraint on the duct strength as might be derived from soundings or numerical weather-prediction models.An electromagnetic propagation model maps the refractivity structure into a replica field.Replica fields are compared with the observed clutter using a squared-error objective function.A global search for the 10 environmental parameters is performed using genetic algorithms.The inversion algorithm is implemented on the basis of S-band radar sea-clutter data from Wallops Island,Virginia (SPANDAR).Reference data are from range-dependent refractivity profiles obtained with a helicopter. The inversion is assessed (i) by comparing the propagation predicted from the radar-inferred refractivity profiles with that from the helicopter profiles,(ii) by comparing the refractivity parameters from the helicopter soundings with those estimated.This technique could provide near-real-time estimation of ducting effects.

  11. A Polarization Technique for Mitigating Low Grazing Angle Radar Sea Clutter

    Science.gov (United States)

    2017-03-03

    A Polarization Technique for Mitigating Low-Grazing-Angle Radar Sea Clutter Molly K. Crane MIT Lincoln Laboratory Lexington, MA 02420 Email...MA 02420 Email: mabel.ramirez@ll.mit.edu Abstract—Traditional detection schemes in conventional mar- itime surveillance radars may suffer serious...effective means of enhancing target detection in sea clutter, MIT Lincoln Laboratory (MIT LL) collected a fully polarimetric X-band radar dataset on

  12. Space Radar Image of Jerusalem and the Dead Sea

    Science.gov (United States)

    1994-01-01

    This space radar image shows the area surrounding the Dead Sea along the West Bank between Israel and Jordan. This region is of major cultural and historical importance to millions of Muslims, Jews and Christians who consider it the Holy Land. The yellow area at the top of the image is the city of Jericho. A portion of the Dead Sea is shown as the large black area at the top right side of the image. The Jordan River is the white line at the top of the image which flows into the Dead Sea. Jerusalem, which lies in the Judaean Hill Country, is the bright, yellowish area shown along the left center of the image. Just below and to the right of Jerusalem is the town of Bethlehem. The city of Hebron is the white, yellowish area near the bottom of the image. The area around Jerusalem has a history of more than 2,000 years of settlement and scientists are hoping to use these data to unveil more about this region's past. The Jordan River Valley is part of an active fault and rift system that extends from southern Turkey and connects with the east African rift zone. This fault system has produced major earthquakes throughout history and some scientists theorize that an earthquake may have caused the fall of Jericho's walls. The Dead Sea basin is formed by active earthquake faulting and contains the lowest place on the Earth's surface at about 400 meters (1,300 feet) below sea level. It was in caves along the northern shore of the Dead Sea that the Dead Sea Scrolls were found in 1947. The blue and green areas are generally regions of undeveloped hills and the dark green areas are the smooth lowlands of the Jordan River valley. This image is 73 kilometers by 45 kilometers (45 miles by 28 miles) and is centered at 31.7 degrees north latitude, 35.4 degrees east longitude. North is toward the upper left. The colors are assigned to different radar frequencies and polarizations as follows: red is L-band, horizontally transmitted and vertically received; green is L-band, horizontally

  13. Morphologie radar de fonds marins Radar Morphology of Some Sea Floors

    Directory of Open Access Journals (Sweden)

    Wadsworth A.

    2006-11-01

    Full Text Available Les radars latéraux sont des instruments de télédétection, fournissant des images de la surface terrestre survolée par pratiquement tout temps, c'est-à-dire de jour ou de nuit, par temps clair ou à travers de la brume, du brouillard, des nuages ou de la pluie. Dans le cadre de l'utilisation de ces instruments pour l'acquisition de données en mer, afin de quantifier les vagues ou la houle, des visualisations annexes, involontaires à l'origine, ont été réalisées. C'est le cas, par exemple, de certains fonds marins, que l'on peut voirlorsque quelques éléments opérationnels sont bien choisis. De plus, une certaine idée de leur morphologie peut être atteinte. Divers exemples sont présentés dans le cas de faibles fonds. Une approche des causes de cette visualisation est proposée, les grandes limites en sont fixées. Side-looking radars are remote-sensing instruments providing images of the ground surface overflown in almost all weather, i. e. day or night, with clear weather or through mist, fog, clouds or rain. These equipments, previously used to quantify sea waves and swell produced, in sonie cases, a noise which was later understood as being a signal, an expression of sea bottom features. This is the case, for example, for sonie sea floors which can be seenwhen a few operational elements have been carefully chosen. Likewise, some idea of the morphology of sea floors can be obtained. This article gives different examples for shallow depths. An approach to the causes of this visualization is proposed, and the major limitations are determined.

  14. Surface circulation at the Strait of Gibraltar: A combined HF radar and high resolution model study

    Science.gov (United States)

    Soto-Navarro, Javier; Lorente, Pablo; Álvarez Fanjul, Enrique; Carlos Sánchez-Garrido, Jose; García-Lafuente, Jesús

    2016-03-01

    Observations from a high frequency radar system and outputs from a high resolution operational ocean model working at the Strait of Gibraltar have been analyzed and compared during the period February 2013 to September 2014 in order to evaluate their capability to resolve the surface circulation of the region. The description of the mean circulation patterns has been statistically assessed, showing good agreement, particularly in the central region of the strait corresponding with the Atlantic Jet (AJ) stream, although some short scale features are not reproduced by the model. In the frequency domain very high concordance is observed. Tidal maps of diurnal and semidiurnal constituents are in good agreement with previous observations. The analysis of the model and radar response to the wind forcing reveals that the low resolution of the model wind-forcing field and its deeper superficial level smoothes the wind effect on the simulated currents. The first three EOF modes account for the 86% of model and radar variances. The coincidence between the observed and simulated patterns is very significant for the first two modes, which account for the mean velocity field and the latitudinal shifting of the AJ consequence of the flow-topography interaction. The third mode captures the wind-induced circulation, and greater discrepancies are found in this case. Results underline the complementary character of both systems: radar observations improve the model description, resolving short scale processes, while the model completes the radar information when the time or spatial coverage is poorer.

  15. MEASURING SEA ICE DRIFT VIA CROSS-CORRELATION OF RADAR ICE IMAGES

    Institute of Scientific and Technical Information of China (English)

    SUN He-quan; SHEN Yong-ming; Qiu Da-hong

    2004-01-01

    The motion of sea ice has a great effect on winter navigation, and oil field exploration in the Bohai Sea. It is very important to measure the ice drift accurately and efficiently. As a practical technique, radar imagery has been used for sea ice monitoring and forecasting for a long time. Combining with the radar imagery and cross-correlation technique, a new measurement method based on the cross-correlation of radar ice images is specified in this paper to obtain full field measurement of sea ice drift. The theory and fast implementation of cross-correlation are presented briefly in the paper, including the filtering method to modify the invalid vectors. To show deeply the validity of the present method, the velocity maps of sea ice drift are provided in the paper, which are calculated from the radar images grabbed in the Liaodong Gulf. The comparison with the traditional tracing method is also conducted.

  16. IonRayTrace: An HF Propagation Model for Communications and Radar Applications

    Science.gov (United States)

    2014-12-01

    this report was performed by the Atmospheric Propagation Branch (Code 55280), Space and Naval Warfare Systems Center Pacific (SSC Pacific), San Diego...the 2- to 7-MHz (red), 7- to 12-MHz (green), and 12- to 17-MHz (blue) bands ..................... 9 1 1. OVERVIEW The Advanced Refractivity ...density of free electrons (102 to 104 cm-3) and has negligible refractive effect on electromagnetic waves in the HF band [5]. However, in general

  17. Simultaneous PMC and PMSE observations with a ground-basedlidar and SuperDARN HF radar over Syowa Station, Antarctica

    Science.gov (United States)

    Suzuki, Hidehiko; Nakamura, Takuji; Tsutsumi, Masaki; Kawahara, Takuya D.; Ogawa, Tadahiko; Tomikawa, Yoshihiro; Ejiri, Mitsumu K.; Sessai Yukimatu, Akira; Abo, Makoto

    2012-07-01

    A Rayleigh-Raman lidar system had been installed by the 52nd JapaneseAntarctic Research Expedition on February, 2011 at Syowa Station Antarctica(69.0°S, 39.5°E). Polar Mesospheric Cloud (PMC) was detected by the lidar at22:30UT (+3hr for LT) on Feb 4th, 2011, the first day of a routineoperation. This event is the first time to detect PMC over Syowa Station bya lidar. In the same night, SuperDARN HF radar with oblique incidence beamsalso detected Polar Mesosphere Summer Echoes (PMSEs) during 21:30UT to23:00UT. Although these signals were detected at different times andlocations, PMC motion estimated using horizontal wind velocities obtained bya collocated MF radar strongly suggests that they have a common origin (i.e.ice particle). We consider that this event occurred in the end of PMCactivity period at Syowa Station in the austral summer season (2010-2011),since the lidar did not detected any PMC signals on other days in February,2011. This is consistent with satellite-born PMC observations by AIM/CIPSand atmospheric temperature observations by AURA/MLS instruments.

  18. Assessing Evaporation Duct Variability In The Eastern Mediterranean Sea In Support Of Radar And Radio Communications

    Science.gov (United States)

    2016-12-01

    EVAPORATION DUCT VARIABILITY IN THE EASTERN MEDITERRANEAN SEA IN SUPPORT OF RADAR AND RADIO COMMUNICATIONS by Süleyman C. Gürbüz December 2016...MEDITERRANEAN SEA IN SUPPORT OF RADAR AND RADIO COMMUNICATIONS 5. FUNDING NUMBERS 6. AUTHOR(S) Süleyman C. Gürbüz 7. PERFORMING ORGANIZATION NAME(S...IN THE EASTERN MEDITERRANEAN SEA IN SUPPORT OF RADAR AND RADIO COMMUNICATIONS Süleyman C. Gürbüz Lieutenant Junior Grade, Turkish Navy B.S

  19. Optical identification of sea-mines - Gated viewing three-dimensional laser radar

    DEFF Research Database (Denmark)

    Busck, Jens

    2005-01-01

    A gated viewing high accuracy mono-static laser radar has been developed for the purpose of improving the optical underwater sea-mine identification handled by the Navy. In the final stage of the sea-mine detection, classification and identification process the Navy applies a remote operated...... vehicle for optical identification of the bottom seamine. The experimental results of the thesis indicate that replacing the conventional optical video and spotlight system applied by the Navy with the gated viewing two- and three-dimensional laser radar can improve the underwater optical sea......-mine identification. The laser radar has also a number of applications on land, for example, face recognition at several hundred meters range. The main components of the laser radar system are a green pulsed laser and a fast gating intensified CCD camera. The laser radar system innovation is a combination...

  20. Observation of Zenneck-Like Waves over a Metasurface Designed for Launching HF Radar Surface Wave

    Directory of Open Access Journals (Sweden)

    Florent Jangal

    2016-01-01

    Full Text Available Since the beginning of the 20th century a controversy has been continuously revived about the existence of the Zenneck Wave. This wave is a theoretical solution of Maxwell’s equations and might be propagated along the interface between the air and a dielectric medium. The expected weak attenuation at large distance explains the constant interest for this wave. Notably in the High Frequency band such a wave had been thought as a key point to reduce the high attenuation observed in High Frequency Surface Wave Radar. Despite many works on that topic and various experiments attempted during one century, there is still an alternation of statements between its existence and its nonexistence. We report here an experiment done during the optimisation of the transmitting antennas for Surface Wave Radars. Using an infrared method, we visualize a wave having the structure described by Zenneck above a metasurface located on a dielectric slab.

  1. Simultaneous PMC and PMSE observations with a ground-based lidar and SuperDARN HF radar at Syowa Station, Antarctica

    Directory of Open Access Journals (Sweden)

    H. Suzuki

    2013-10-01

    Full Text Available A Rayleigh–Raman lidar system was installed in January 2011 at Syowa Station, Antarctica (69.0° S, 39.6° E. Polar mesospheric clouds (PMCs were detected by lidar at around 22:30 UTC (LT −3 h on 4 February 2011, which was the first day of observation. This was the first detection of PMCs over Syowa Station by lidar. On the same day, a Super Dual Auroral Radar Network (SuperDARN HF radar with oblique-incidence beams detected polar mesospheric summer echoes (PMSE between 21:30 and 23:00 UTC. This event is regarded as the last PMC activity around Syowa Station during the austral summer season (2010–2011, since no other PMC signals were detected by lidar in February 2011. This is consistent with results of PMC and mesopause temperature observations by satellite-born instruments of AIM (Aeronomy of Ice in the Mesosphere/CIPS (Cloud Imaging and Particle Size and AURA/MLS (Microwave Limb Sounder and horizontal wind measurements taken by a separate MF radar. Doppler velocity of PMSE observed by the HF radar showed motion toward Syowa Station (westward. This westward motion is consistent with the wind velocities obtained by the MF radar. However, the PMSE region showed horizontal motion from a north-to-south direction during the PMC event. This event indicates that the apparent horizontal motion of the PMSE region can deviate from neutral wind directions and observed Doppler velocities.

  2. Simultaneous PMC and PMSE observations with a ground-based lidar and SuperDARN HF radar at Syowa Station, Antarctica

    Science.gov (United States)

    Suzuki, H.; Nakamura, T.; Ejiri, M. K.; Ogawa, T.; Tsutsumi, M.; Abo, M.; Kawahara, T. D.; Tomikawa, Y.; Yukimatu, A. S.; Sato, N.

    2013-10-01

    A Rayleigh-Raman lidar system was installed in January 2011 at Syowa Station, Antarctica (69.0° S, 39.6° E). Polar mesospheric clouds (PMCs) were detected by lidar at around 22:30 UTC (LT -3 h) on 4 February 2011, which was the first day of observation. This was the first detection of PMCs over Syowa Station by lidar. On the same day, a Super Dual Auroral Radar Network (SuperDARN) HF radar with oblique-incidence beams detected polar mesospheric summer echoes (PMSE) between 21:30 and 23:00 UTC. This event is regarded as the last PMC activity around Syowa Station during the austral summer season (2010-2011), since no other PMC signals were detected by lidar in February 2011. This is consistent with results of PMC and mesopause temperature observations by satellite-born instruments of AIM (Aeronomy of Ice in the Mesosphere)/CIPS (Cloud Imaging and Particle Size) and AURA/MLS (Microwave Limb Sounder) and horizontal wind measurements taken by a separate MF radar. Doppler velocity of PMSE observed by the HF radar showed motion toward Syowa Station (westward). This westward motion is consistent with the wind velocities obtained by the MF radar. However, the PMSE region showed horizontal motion from a north-to-south direction during the PMC event. This event indicates that the apparent horizontal motion of the PMSE region can deviate from neutral wind directions and observed Doppler velocities.

  3. Remote sensing of the sea by X-band, dual-polarized, coherent weather radar

    Science.gov (United States)

    Forget, Philippe; Saillard, Marc; Testud, Jacques; Le Bouar, Erwan

    2010-05-01

    Remote sensing of the sea surface over large areas with high resolution (<1km) and at high time rate (<1h) is still a challenge that space-borne radiometers and radars can only satisfy. This presentation is an investigation of the use for this purpose of a ground-based, rotating, coherent X-band, dual-polarized (HH-VV) weather radar. We studied the data acquired by such a meteorological device, dedicated to precipitation measurements and operated in South of France at the top of a mountain near the Ligurian Sea. One month of data was considered. We observed that the sea signal often dominated the atmospheric signal despite the only slight inclination from horizontal of the radar beam direction. The radar signals being calibrated for weather application, both atmosphere and ocean radar equations were used to extract the normalized radar cross section (NRCS) of the sea. Other useful experimental parameters provided by the radar were the mean Doppler velocity and, to mask the undesirable rain signals, the polarization ratio. In situ measurements on wind and wave conditions were recorded by an off-shore meteorological buoy. Furthermore, the surface wind field as computed by the meteorological model MM5 over the Ligurian Sea was available at high time and space resolution during the experimental period The main results concern the variation of NRCS and Doppler velocity with wind and wave conditions. In particular, for moderate to strong winds, we generally found a very good correlation between the Doppler velocity field and the wind velocity component along the radar azimuths. The preliminary results obtained in this experiment suggest that operational weather radars can be valuable means to monitor useful wind information over large sea surfaces.

  4. X-Band high range resolution radar measurements of sea surface forward scatter at low grazing angles

    CSIR Research Space (South Africa)

    Smit, JC

    2008-05-01

    Full Text Available Radar measurements of a radar calibration sphere test target suspended in sea surface multipath propagation conditions are reported. Wideband measurements together with high range resolution (HRR) processing were employed to resolve the direct...

  5. Ku-band radar penetration into snow cover Arctic sea ice using airborne data

    OpenAIRE

    Willatt, R.; Laxon, S.; Giles, K.; R. Cullen; Haas, C.; V. Helm

    2011-01-01

    Satellite radar altimetry provides data to monitor winter Arctic sea-ice thickness variability on interannual, basin-wide scales. When using this technique an assumption is made that the peak of the radar return originates from the snow/ice interface. This has been shown to be true in the laboratory for cold, dry snow as is the case on Arctic sea ice during winter. However, this assumption has not been tested in the field. We use data from an airborne normal-incidence Ku-band radar altimeter ...

  6. Near-real-time surface ocean velocities derived from HF radar stations located along coastal waters of Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico, Hawaii and western US during February 2016 (NCEI Accession 0145743)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains near-real-time ocean surface velocities, also known as total vector velocities, derived from HF radar stations. The velocities are...

  7. Near-real-time surface ocean velocities derived from HF radar stations located along coastal waters of Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico, Hawaii and western US during April 2016 (NCEI Accession 0151726)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains near-real-time ocean surface velocities, also known as total vector velocities, derived from HF radar stations. The velocities are...

  8. Near-real-time surface ocean velocities derived from HF radar stations located along coastal waters of Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico, Hawaii and western US during February 2015 (NCEI Accession 0131074)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains near-real-time ocean surface velocities, also known as total vector velocities, derived from HF radar stations. The velocities are...

  9. Near-real-time surface ocean velocities derived from HF radar stations located along coastal waters of Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico, Hawaii and western US during March 2015 (NCEI Accession 0131884)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains near-real-time ocean surface velocities, also known as total vector velocities, derived from HF radar stations. The velocities are...

  10. Near-real-time surface ocean velocities derived from HF radar stations located along coastal waters of Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico, Hawaii and western US during May 2016 (NCEI Accession 0154389)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains near-real-time ocean surface velocities, also known as total vector velocities, derived from HF radar stations. The velocities are...

  11. Near-real-time surface ocean velocities derived from HF radar stations located along coastal waters of Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico, Hawaii and western US during March 2016 (NCEI Accession 0148078)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains near-real-time ocean surface velocities, also known as total vector velocities, derived from HF radar stations. The velocities are...

  12. Near-real-time surface ocean velocities derived from HF radar stations located along coastal waters of Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico, Hawaii and western US during December 2015 (NCEI Accession 0141105)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains near-real-time ocean surface velocities, also known as total vector velocities, derived from HF radar stations. The velocities are...

  13. Near-real-time surface ocean velocities derived from HF radar stations located along coastal waters of Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico, Hawaii and western US during April 2015 (NCEI Accession 0131908)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains near-real-time ocean surface velocities, also known as total vector velocities, derived from HF radar stations. The velocities are...

  14. Near-real-time surface ocean velocities derived from HF radar stations located along coastal waters of Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico, Hawaii and western US during June 2015 (NCEI Accession 0131956)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains near-real-time ocean surface velocities, also known as total vector velocities, derived from HF radar stations. The velocities are...

  15. Near-real-time surface ocean velocities derived from HF radar stations located along coastal waters of Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico, Hawaii and western US during January 2016 (NCEI Accession 0144286)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains near-real-time ocean surface velocities, also known as total vector velocities, derived from HF radar stations. The velocities are...

  16. Near-real-time surface ocean velocities derived from HF radar stations located along coastal waters of Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico, Hawaii and western US during June 2016 (NCEI Accession 0155978)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains near-real-time ocean surface velocities, also known as total vector velocities, derived from HF radar stations. The velocities are...

  17. Near-real-time surface ocean velocities derived from HF radar stations located along coastal waters of Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico, Hawaii and western US during May 2015 (NCEI Accession 0131932)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains near-real-time ocean surface velocities, also known as total vector velocities, derived from HF radar stations. The velocities are...

  18. Near-real-time surface ocean velocities derived from HF radar stations located along coastal waters of Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico, Hawaii and western US during January 2015 (NCEI Accession 0129913)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains near-real-time ocean surface velocities, also known as total vector velocities, derived from HF radar stations. The velocities are...

  19. Ku-Band radar penetration into Snow over Arctic Sea Ice

    DEFF Research Database (Denmark)

    Hendricks, Stefan; Stenseng, Lars; Helm, Veit

    Sea ice freeboard measurements are of great interest for basin-scale ice mass balance monitoring. Typically, laser- and radar-altimeters are used for freeboard retrieval in operational systems such as aircrafts and satellites. For laser beams it can be assumed that the dominant reflector......, if radar altimeters are capable of measuring the distance to the snow-ice interface reliably. We present the results of aircraft campaigns in the Arctic with a scanning laser altimeter and the Airborne SAR/Interferometric Radar Altimeter System (ASIRAS) of the European Space Agency. The elevation...... observations are converted into freeboard profiles, taking the different footprints into account when comparing the two systems. Based on the probability distribution of laser and radar freeboard we discuss the specific characteristics of both systems and the apparent radar penetration over sea ice...

  20. Towards a synthesis of substorm electrodynamics: HF radar and auroral observations

    Directory of Open Access Journals (Sweden)

    A. Grocott

    2006-12-01

    Full Text Available At 08:35 UT on 21 November 2004, the onset of an interval of substorm activity was captured in the southern hemisphere by the Far UltraViolet (FUV instrument on board the IMAGE spacecraft. This was accompanied by the onset of Pi2 activity and subsequent magnetic bays, evident in ground magnetic data from both hemispheres. Further intensifications were then observed in both the auroral and ground magnetic data over the following ~3 h. During this interval the fields-of-view of the two southern hemisphere Tasman International Geospace Enviroment Radars (TIGER moved through the evening sector towards midnight. Whilst initially low, the amount of backscatter from TIGER increased considerably during the early stages of the expansion phase such that by ~09:20 UT an enhanced dusk flow cell was clearly evident. During the expansion phase the equatorward portion of this flow cell developed into a narrow high-speed flow channel, indicative of the auroral and sub-auroral flows identified in previous studies (e.g. Freeman et al., 1992; Parkinson et al., 2003. At the same time, higher latitude transient flow features were observed and as the interval progressed the flow reversal region and Harang discontinuity became very well defined. Overall, this study has enabled the spatial and temporal development of many different elements of the substorm process to be resolved and placed within a simple conceptual framework of magnetospheric convection. Specifically, the detailed observations of ionospheric flows have illustrated the complex interplay between substorm electric fields and associated auroral dynamics. They have helped define the distinct nature of different substorm current systems such as the traditional substorm current wedge and the more equatorward currents associated with polarisation electric fields. Additionally, they have revealed a radar signature of nightside reconnection which provides the promise of quantifying nightside reconnection in a

  1. Sea surface Ka-band radar cross-section from field observations in the Black Sea

    Science.gov (United States)

    Yurovsky, Yury; Kudryavtsev, Vladimir; Grodsky, Semyon; Chapron, Bertrand

    2016-04-01

    An interest in Ka-band radar backscattering from the ocean surface is growing due to better spatial resolution and more accurate Doppler anomaly estimate. But, available empirical models of Ka-band cross-section are quite scarce and sometime controversial. Here we present multi-year (2009-2015) field measurements of Ka-band co-polarized (VV and HH) sea surface normalized radar cross-section (NRCS) from research platform in the Black sea collected in a wide range of observation and sea state conditions. The data are fitted by polynomial function of incidence angle, azimuth and wind speed with accounting for measured radar antenna pattern. This empirical NRCS is compared with published Ka- and Ku-band data. Our Ka-band NRCS is close to Ku-band, but is 5-7 dB higher than 'pioneer' measurements by Masuko et al. (1986). Following the two-scale Bragg paradigm, the NRCS is split into polarized (Bragg) and non-polarized components and analyzed in terms of polarization ratio (VV/HH) and polarization difference (VV-HH) to estimate wave spectra at the Bragg wave number. Non-polarized component dominates at low incidence angles 60°) NRCS azimuth dependency is unimodal (upwind peak) for HH and bimodal (with up- and downwind peaks) for VV polarization. This again can be attributed to different backscattering mechanisms for VV and HH polarizations. With decreasing of incidence angle, up- to downwind ratio tends to 1, and under light wind conditions (4-6 m/s) can be less than 1. The same situation is observed for polarization difference, which reflects Bragg backscattering properties only. This effect can be explained by enhanced roughness on upwind (windward) face of the tilting wave. Retrieval of Bragg roughness properties shows that omni-directional saturation spectra at ~1000 rad/m are 2-3 times higher (0.01 at 10 m/s wind speed) than the spectra obtained from optical measurements of regular sea surface without wave breaking. This suggests that observed difference can arise

  2. An Ionospheric Es Layer Clutter Model and Suppression in HF Surfacewave Radar

    Directory of Open Access Journals (Sweden)

    Yajun Li

    2013-01-01

    Full Text Available This paper based on a fast implemented multiphase screen method using DFT puts forward an ionospheric Es layer clutter model and uses the newly developed dimensionality reduction space-time adaptive processing- (STAP- JDL algorithm to suppress Es layer clutter, which proves the validity of the proposed model. Firstly, the multiphase screen method was analyzed, and a fast algorithm using DFT was proposed. Then, based on the multiphase screen method and thorough simulation, we reached a conclusion of the high-frequency radio wave propagation’s fluctuation characteristics in the ionosphere. According to the results of the analysis, a new Es layer ionospheric clutter model was established and was compared with the measured data and verification was made. Finally, based on the built clutter model, JDL algorithm was applied to the high-frequency surface wave radar ionospheric clutter suppression, using the measured data to verify the validity of the model and algorithm. The simulation results showed that the built model can show the characteristics of the ionospheric Es layer clutter and that the JDL algorithm can suppress ionospheric Es layer clutter quite effectively.

  3. Simulation of the satellite radar altimeter sea ice thickness retrieval uncertainty

    Directory of Open Access Journals (Sweden)

    R. T. Tonboe

    2009-07-01

    Full Text Available Although it is well known that radar waves penetrate into snow and sea ice, the exact mechanisms for radar-altimeter scattering and its link to the depth of the effective scattering surface from sea ice are still unknown. Previously proposed mechanisms linked the snow ice interface, i.e. the dominating scattering horizon, directly with the depth of the effective scattering surface. However, simulations using a multilayer radar scattering model show that the effective scattering surface is affected by snow-cover and ice properties. With the coming Cryosat-2 (planned launch 2009 satellite radar altimeter it is proposed that sea ice thickness can be derived by measuring its freeboard. In this study we evaluate the radar altimeter sea ice thickness retrieval uncertainty in terms of floe buoyancy, radar penetration and ice type distribution using both a scattering model and ''Archimedes' principle''. The effect of the snow cover on the floe buoyancy and the radar penetration and on the ice cover spatial and temporal variability is assessed from field campaign measurements in the Arctic and Antarctic. In addition to these well known uncertainties we use high resolution RADARSAT SAR data to simulate errors due to the variability of the effective scattering surface as a result of the sub-footprint spatial backscatter and elevation distribution sometimes called preferential sampling. In particular in areas where ridges represent a significant part of the ice volume (e.g. the Lincoln Sea the simulated altimeter thickness estimate is lower than the real average footprint thickness. This means that the errors are large, yet manageable if the relevant quantities are known a priori. A discussion of the radar altimeter ice thickness retrieval uncertainties concludes the paper.

  4. Simulation of the satellite radar altimeter sea ice thickness retrieval uncertainty

    Science.gov (United States)

    Tonboe, R. T.; Pedersen, L. T.; Haas, C.

    2009-07-01

    Although it is well known that radar waves penetrate into snow and sea ice, the exact mechanisms for radar-altimeter scattering and its link to the depth of the effective scattering surface from sea ice are still unknown. Previously proposed mechanisms linked the snow ice interface, i.e. the dominating scattering horizon, directly with the depth of the effective scattering surface. However, simulations using a multilayer radar scattering model show that the effective scattering surface is affected by snow-cover and ice properties. With the coming Cryosat-2 (planned launch 2009) satellite radar altimeter it is proposed that sea ice thickness can be derived by measuring its freeboard. In this study we evaluate the radar altimeter sea ice thickness retrieval uncertainty in terms of floe buoyancy, radar penetration and ice type distribution using both a scattering model and ''Archimedes' principle''. The effect of the snow cover on the floe buoyancy and the radar penetration and on the ice cover spatial and temporal variability is assessed from field campaign measurements in the Arctic and Antarctic. In addition to these well known uncertainties we use high resolution RADARSAT SAR data to simulate errors due to the variability of the effective scattering surface as a result of the sub-footprint spatial backscatter and elevation distribution sometimes called preferential sampling. In particular in areas where ridges represent a significant part of the ice volume (e.g. the Lincoln Sea) the simulated altimeter thickness estimate is lower than the real average footprint thickness. This means that the errors are large, yet manageable if the relevant quantities are known a priori. A discussion of the radar altimeter ice thickness retrieval uncertainties concludes the paper.

  5. Characterizing the surface circulation in Ebro Delta (NW Mediterranean) with HF radar and modeled current data

    Science.gov (United States)

    Lorente, P.; Piedracoba, S.; Sotillo, M. G.; Aznar, R.; Amo-Balandron, A.; Pascual, A.; Soto-Navarro, J.; Alvarez-Fanjul, E.

    2016-11-01

    Quality-controlled current observations from a High Frequency radar (HFR) network deployed in the Ebro River Delta (NW Mediterranean) were combined with outputs from IBI operational ocean forecasting system in order to comprehensively portray the ocean state and its variability during 2014. Accurate HFR data were used as benchmark for a rigorous validation of the Iberia-Biscay-Ireland (IBI) regional system, routinely operated in the frame of the Copernicus Marine Environment Monitoring Service (CMEMS). The analysis of skill metrics and monthly averaged current maps showed that IBI reasonably captured the prevailing dynamic features of the coastal circulation previously observed by the HFR, according to the moderate resemblance found in circulation patterns and the spatial distribution of eddy kinetic energy. The model skill assessment was completed with an exploration of dominant modes of spatiotemporal variability. The EOF analysis confirmed that the modeled surface current field evolved both in space and time according to three significantly dominant modes of variability which accounted for the 49.2% of the total variance, in close agreement with the results obtained for HFR (46.1%). The response of the subtidal surface current field to prevailing wind regime in the study area was examined in terms of induced circulation structures and immediacy of reaction by performing a conditional averaging approach and a time-lagged vector correlation analysis, respectively. This observations-model synergistic strategy has proved to be valid to operationally monitor the complex coastal circulation in Ebro Delta despite the observed model drawbacks in terms of reduced energy content in surface currents and some inaccuracies in the wind-driven low frequency response. This integrated methodology aids to improve the prognostic capabilities of IBI ocean forecasting system and also to facilitate high-stakes decision-making for coastal management in the Ebro River Delta marine

  6. Sub-mesoscale Eddies and Their Propagation Paths in Long Bay, SC Observed in HF Radar Surface Currents

    Science.gov (United States)

    Cahl, D.; Voulgaris, G.

    2015-12-01

    Sub-mesoscale eddies on the shoreward front of the Gulf Stream (GS) are thought to play a critical role in controlling cross-shelf transport and momentum flux in the South Atlantic Bight (SAB) but cannot be observed continuously from satellites due to cloud cover. Non-linear eddies have the ability to trap and transport water as they propagate, which make them a potential source of cross-shelf transport. Long Bay, SC, just downstream of the Charleston Bump is the area of highest eddy activity in the SAB. Surface currents in Long Bay have been observed since 2012 using HF radars. The accuracy of three eddy detection methods (Okubo-Weiss, Vector-geometry, Winding-angle) are compared in this area of high shear on the shoreward front of the GS. The Okubo-Weiss parameter does not perform well in this area due to the high shear environment where eddies propagate. The Vector-Geometry method has good successful detection rates but suffers in shape analysis from inaccurate Stream Function contours in this area due to divergent surface currents. The Winding-Angle method performs well and was used to detect eddies and their propagation paths in Long Bay for years 2013 and 2014. Detected eddies propagate predominantly along-shelf, with cyclonic (anticyclonic) eddies propagating downstream (upstream) with respect the GS. Few eddies with the ability to trap and transport water propagating in the across-shelf direction were observed, leading to the conclusion that most of the influence of these eddies is confined to the shoreward front of the GS, near the shelf break.

  7. Waveform analysis of airborne synthetic aperture radar altimeter over Arctic sea ice

    Directory of Open Access Journals (Sweden)

    M. Zygmuntowska

    2013-03-01

    Full Text Available Sea ice thickness is one of the most sensitive variables in the Arctic climate system. In order to quantify changes in sea ice thickness, CryoSat was launched in 2010 carrying a Ku-band Radar Altimeter (SIRAL designed to measure sea ice freeboard with a few centimeters accuracy. The instrument uses the synthetic aperture radar technique providing signals with a resolution of about 300 m along track. In this study, airborne Ku-band radar altimeter data over different sea ice types has been analyzed. A set of parameters has been defined to characterize the difference in strength and width of the returned power waveforms. With a Bayesian based method it is possible to classify about 80% of the waveforms by three parameters: maximum of the returned power echo, the trailing edge width and pulse peakiness. Furthermore, the radar power echo maximum can be used to minimize the rate of false detection of leads compared to the widely used Pulse Peakiness parameter. The possibility to distinguish between different ice types and open water allows to improve the freeboard retrieval and the conversion into sea ice thickness where surface type dependent values for the sea ice density and snow load can be used.

  8. Sea ice thickness measurement and its underside morphol-ogy analysis using radar penetration in the Arctic Ocean

    Institute of Scientific and Technical Information of China (English)

    SUN; Bo; (孙; 波); WEN; Jiahong; (温家洪); HE; Maobing; (何茂兵); KANG; Jiancheng; (康建成); LUO; Yuzhong; (罗宇忠); LI; Yuansheng; (李院生)

    2003-01-01

    Based on radar penetrating measurements and analysis of sea ice in the Arctic Ocean, the potential of radar wave to measure sea ice thickness and map the morphology of the underside of sea ice is investigated. The results indicate that the radar wave can penetrate Arctic summer sea ice of over 6 m in thickness; and the propagation velocity of the radar wave in sea ice is in the range of 0.142 m·ns-1 to 0.154 m·ns-1. The radar images display the roughness and micro-relief variation of sea ice bottom surface. These features are closely related to sea ice types, which show that radar survey may be used to identify and classify ice types. Since radar images can simultaneously display the linear profile features of both the upper surface and the underside of sea ice, we use these images to quantify their actual linear length discrepancy. A new length factor is suggested in relation to the actual linear length discrepancy in linear profiles of sea ice, which may be useful in the further study of the area difference between the upper surface and bottom surface of sea ice.

  9. Measurements of sea ice thickness and its subice morphology analysis using ice-penetration radar in the Arctic Ocean

    Institute of Scientific and Technical Information of China (English)

    孙波; 邓新生; 康建成; 罗宇忠; 温家洪; 李院生

    2003-01-01

    Based on radar penetrating measurements and analysis of sea ice in the Arctic Ocean, The potential of radar wave to measure sea ice thickness and map the morphology of the underside of sea ice is investigated.The results indicate that the radar wave can penetrate Arctic summer sea ice of over 6 meters thick; and the propagation velocity of the radar wave in sea ice is in the range of 0.142 m*ns-1 to 0.154 m*ns-1.The radar images display the roughness and micro-relief variation of sea ice bottom surface.These features are closely related to sea ice types, which show that radar survey may be used to identify and classify ice types.Since radar images can simultaneously display the linear profile features of both the upper surface and the underside of sea ice, we use these images to quantify their actual linear length discrepancy.A new length factor is suggested in relation to the actual linear length discrepancy in linear profiles of sea ice, which may be useful in further study of the area difference between the upper surface and bottom surface of sea ice.

  10. An Overview of the Bathymetry and Composition of Titan's Hydrocarbon Seas from the Cassini RADAR Altimeter

    Science.gov (United States)

    Mastrogiuseppe, M.; Hayes, A.; Lunine, J. I.; Poggiali, V.; Seu, R.; Hofgartner, J. D.; Lorenz, R. D.; Le Gall, A. A.

    2015-12-01

    The Cassini RADAR's altimetry mode has been successfully used for probing the depth and composition of Titan's hydrocarbons seas. In May 2013, during the spacecraft's 91stflyby of Titan (T91), the instrument demonstrates its capabilities as a radar sounder, presenting a unique opportunity to constrain direct measurements of the depth and composition of Titan's second largest sea, Ligeia Mare. Later, observations of Kraken Mare and Punga Mare were planned and executed in August 2014 (T104) and January 2015 (T108), respectively. While most of the seafloor was not detected at Kraken, suggesting the sea was either too deep or too absorptive in these areas to observe a return from the seafloor, shallow areas near Moray Sinus did return subsurface detections. At Punga Mare, a clear detection of the subsurface was observed with a maximum depth of 120 m along the interrogated track of the sea. We will present an analysis of all three altimetric observations of Titan's mare, as well a re-analysis of altimetry data acquired over southern Ontario Lacus. Depths measurements and liquid composition are obtained using a novel technique which makes use of radar simulations and Monte Carlo based inversions. Finally, we will show that the estimates obtained from the direct measurements described above can be used along with the RADAR's active (i.e. Synthetic Aperture Radar) and passive (Radiometry) modes to generate bathymetry maps of areas not observed by altimetry.

  11. Ku-Band radar penetration into Snow over Arctic Sea Ice

    DEFF Research Database (Denmark)

    Hendricks, Stefan; Stenseng, Lars; Helm, Veit

    Sea ice freeboard measurements are of great interest for basin-scale ice mass balance monitoring. Typically, laser- and radar-altimeters are used for freeboard retrieval in operational systems such as aircrafts and satellites. For laser beams it can be assumed that the dominant reflector is the s......Sea ice freeboard measurements are of great interest for basin-scale ice mass balance monitoring. Typically, laser- and radar-altimeters are used for freeboard retrieval in operational systems such as aircrafts and satellites. For laser beams it can be assumed that the dominant reflector...... is the snow/air interface, whereas radar waves interact with the variable physical properties of the snow cover on the Arctic sea ice. In addition, radar elevation measurements may vary for different retracker algorithms, which determine the track point of the scattered echo power distribution. Since accurate...... knowledge of the reflection horizon is critical for sea ice thickness retrieval, validation data is necessary to investigate the penetration of radar waves into the snow for the upcoming CryoSat-2 mission. Furthermore, the combination of both optical and RF wavelengths might be used to derive snow thickness...

  12. Validation of Airborne FMCW Radar Measurements of Snow Thickness Over Sea Ice in Antarctica

    Science.gov (United States)

    Galin, Natalia; Worby, Anthony; Markus, Thorsten; Leuschen, Carl; Gogineni, Prasad

    2012-01-01

    Antarctic sea ice and its snow cover are integral components of the global climate system, yet many aspects of their vertical dimensions are poorly understood, making their representation in global climate models poor. Remote sensing is the key to monitoring the dynamic nature of sea ice and its snow cover. Reliable and accurate snow thickness data are currently a highly sought after data product. Remotely sensed snow thickness measurements can provide an indication of precipitation levels, predicted to increase with effects of climate change in the polar regions. Airborne techniques provide a means for regional-scale estimation of snow depth and distribution. Accurate regional-scale snow thickness data will also facilitate an increase in the accuracy of sea ice thickness retrieval from satellite altimeter freeboard estimates. The airborne data sets are easier to validate with in situ measurements and are better suited to validating satellite algorithms when compared with in situ techniques. This is primarily due to two factors: better chance of getting coincident in situ and airborne data sets and the tractability of comparison between an in situ data set and the airborne data set averaged over the footprint of the antennas. A 28-GHz frequency modulated continuous wave (FMCW) radar loaned by the Center for Remote Sensing of Ice Sheets to the Australian Antarctic Division is used to measure snow thickness over sea ice in East Antarctica. Provided with the radar design parameters, the expected performance parameters of the radar are summarized. The necessary conditions for unambiguous identification of the airsnow and snowice layers for the radar are presented. Roughnesses of the snow and ice surfaces are found to be dominant determinants in the effectiveness of layer identification for this radar. Finally, this paper presents the first in situ validated snow thickness estimates over sea ice in Antarctica derived from an FMCW radar on a helicopterborne platform.

  13. MF and HF radar techniques for investigating the dynamics and structure of the 50 to 110 km height region: a review

    Science.gov (United States)

    Reid, Iain Murray

    2015-12-01

    The application of medium-frequency (MF) and high-frequency (HF) partial reflection radar to investigate the neutral upper atmosphere is one of the oldest such techniques still regularly in use. The techniques have been continuously improved and remain a robust and reliable method of obtaining wind velocities, turbulence intensities, electron densities, and measurements of atmospheric structure in the mesosphere lower thermosphere (MLT) region (50 to 110 km). In this paper, we review recent developments, discuss the strengths and weaknesses of the technique, and consider possible improvements.

  14. The measurement of sea surface profile with X-band coherent marine radar

    Institute of Scientific and Technical Information of China (English)

    WANG Yunhua; LI Huimin; ZHANG Yanmin; GUO Lixin

    2015-01-01

    The line-of-sight velocity of scattering facets is related to the Doppler signals of X-band coherent marine radar from the oceanic surface. First, the sign Doppler Estimator is applied to estimate the Doppler shift of each radar resolution cell. And then, in terms of the Doppler shift, a retrieval algorithm extracting the vertical displacement of the sea surface has been proposed. The effects induced by radar look-direction and radar spatial resolution are both taken into account in this retrieval algorithm. The comparison between the sea surface spectrum of buoy data and the retrieved spectrum reveals that the function of the radar spatial resolution is equivalent to a low pass filter, impacting especially the spectrum of short gravity waves. The experimental data collected by McMaster IPIX radar are also used to validate the performance of the retrieval algorithm. The derived significant wave height and wave period are compared with the in situ measurements, and the agreement indicates the practicality of the retrieval technology.

  15. Airborne radar surveys of snow depth over Antarctic sea ice during Operation IceBridge

    Science.gov (United States)

    Panzer, B.; Gomez-Garcia, D.; Leuschen, C.; Paden, J. D.; Gogineni, P. S.

    2012-12-01

    Over the last decade, multiple satellite-based laser and radar altimeters, optimized for polar observations, have been launched with one of the major objectives being the determination of global sea ice thickness and distribution [5, 6]. Estimation of sea-ice thickness from these altimeters relies on freeboard measurements and the presence of snow cover on sea ice affects this estimate. Current means of estimating the snow depth rely on daily precipitation products and/or data from passive microwave sensors [2, 7]. Even a small uncertainty in the snow depth leads to a large uncertainty in the sea-ice thickness estimate. To improve the accuracy of the sea-ice thickness estimates and provide validation for measurements from satellite-based sensors, the Center for Remote Sensing of Ice Sheets deploys the Snow Radar as a part of NASA Operation IceBridge. The Snow Radar is an ultra-wideband, frequency-modulated, continuous-wave radar capable of resolving snow depth on sea ice from 5 cm to more than 2 meters from long-range, airborne platforms [4]. This paper will discuss the algorithm used to directly extract snow depth estimates exclusively using the Snow Radar data set by tracking both the air-snow and snow-ice interfaces. Prior work in this regard used data from a laser altimeter for tracking the air-snow interface or worked under the assumption that the return from the snow-ice interface was greater than that from the air-snow interface due to a larger dielectric contrast, which is not true for thick or higher loss snow cover [1, 3]. This paper will also present snow depth estimates from Snow Radar data during the NASA Operation IceBridge 2010-2011 Antarctic campaigns. In 2010, three sea ice flights were flown, two in the Weddell Sea and one in the Amundsen and Bellingshausen Seas. All three flight lines were repeated in 2011, allowing an annual comparison of snow depth. In 2011, a repeat pass of an earlier flight in the Weddell Sea was flown, allowing for a

  16. Effectiveness of WRF wind direction for retrieving coastal sea surface wind from synthetic aperture radar

    DEFF Research Database (Denmark)

    Takeyama, Yuko; Ohsawa, Teruo; Kozai, Katsutoshi;

    2013-01-01

    Wind direction is required as input to the geophysical model function (GMF) for the retrieval of sea surface wind speed from a synthetic aperture radar (SAR) images. The present study verifies the effectiveness of using the wind direction obtained from the weather research and forecasting model...

  17. SIMULATION OF THE Ku-BAND RADAR ALTIMETER SEA ICE EFFECTIVE SCATTERING SURFACE

    DEFF Research Database (Denmark)

    Tonboe, Rasmus; Andersen, Søren; Pedersen, Leif Toudal

    2006-01-01

    A radiative transfer model is used to simulate the sea ice radar altimeter effective scattering surface variability as a function of snow depth and density. Under dry snow conditions without layering these are the primary snow parameters affecting the scattering surface variability. The model...... is initialised with in situ data collected during the May 2004 GreenIce ice camp in the Lincoln Sea (73ºW; 85ºN). Our results show that the snow cover is important for the effective scattering surface depth in sea ice and thus for the range measurement, ice freeboard and ice thickness estimation....

  18. Modeling of oil spreading in a problem of radar multiangle diagnostics of Sea surface pollutions

    Science.gov (United States)

    Matveev, A. Ya.; Kubryakov, A. A.; Boev, A. G.; Bychkov, D. M.; Ivanov, V. K.; Stanichny, S. V.; Tsymbal, V. N.

    2016-12-01

    The possibilities of a multiangle method of radar diagnostics to determine thickness of an oil film on a sea surface by comparing the radar data with the quantitative modeling results obtained using the model of oil spreading dynamics are analyzed. The experimental results of the remote sensing of the Caspian Sea water area near the Neftyanye Kamni oil field by the Envisat-1 synthetic aperture radar (SAR) and the new Floating Objects Tracking System (FOTS) model of oil spreading are used for the analysis. The model allows to calculate the dynamics and change in the mass and size of an oil slick basing only on the available data of satellite measurements and atmospheric reanalysis.The model takes into account the main processes that influence the slick formation (gravity spreading, advective transport, dispersion, emulsification, turbulent mixing, and evaporation). This model is used to calculate the thickness evolution and dynamics of the displacement of oil slicks in the period between two consecutive radar images of this region (0.5-4 days) and to estimate the volumes of oil spilled in the field. The good consistence of the height of the oil film calculated using radar measurements and the modeling results confirms the method's reliability.

  19. Report on Scattering Physics of Multistatic Radar Sea Clutter

    Science.gov (United States)

    2014-05-30

    clutter & targets, and assessing detection schemes using the observations and the results of data analysis. The panel recognises the potential value ...similar (as they should be, since they are based on some of the same data), whilst the GIT model has much smaller values of reflectivity at low sea...When the power is summed over range, averaged over many surface realisations and recalculated at various grazing angles and rms sea surface wave

  20. Comparison of numerical hindcasted severe waves with Doppler radar measurements in the North Sea

    Science.gov (United States)

    Ponce de León, Sonia; Bettencourt, João H.; Dias, Frederic

    2017-01-01

    Severe sea states in the North Sea present a challenge to wave forecasting systems and a threat to offshore installations such as oil and gas platforms and offshore wind farms. Here, we study the ability of a third-generation spectral wave model to reproduce winter sea states in the North Sea. Measured and modeled time series of integral wave parameters and directional wave spectra are compared for a 12-day period in the winter of 2013-2014 when successive severe storms moved across the North Atlantic and the North Sea. Records were obtained from a Doppler radar and wave buoys. The hindcast was performed with the WAVEWATCH III model (Tolman 2014) with high spectral resolution both in frequency and direction. A good general agreement was obtained for integrated parameters, but discrepancies were found to occur in spectral shapes.

  1. A Statistical study of the Doppler spectral width of high-latitude ionospheric F-region echoes recorded with SuperDARN coherent HF radars

    Directory of Open Access Journals (Sweden)

    J.-P. Villain

    Full Text Available The HF radars of the Super Dual Auroral Radar Network (SuperDARN provide measurements of the E × B drift of ionospheric plasma over extended regions of the high-latitude ionosphere. We have conducted a statistical study of the associated Doppler spectral width of ionospheric F-region echoes. The study has been conducted with all available radars from the Northern Hemisphere for 2 specific periods of time. Period 1 corresponds to the winter months of 1994, while period 2 covers October 1996 to March 1997. The distributions of data points and average spectral width are presented as a function of Magnetic Latitude and Magnetic Local Time. The databases are very consistent and exhibit the same features. The most stringent features are: a region of very high spectral width, collocated with the ionospheric LLBL/cusp/mantle region; an oval shaped region of high spectral width, whose equator-ward boundary matches the poleward limit of the Holzworth and Meng auroral oval. A simulation has been conducted to evaluate the geometrical and instrumental effects on the spectral width. It shows that these effects cannot account for the observed spectral features. It is then concluded that these specific spectral width characteristics are the signature of ionospheric/magnetospheric coupling phenomena.

    Key words. Ionosphere (auroral ionosphere; ionosphere-magnetosphere interactions; ionospheric irregularities

  2. Testing sea-level markers observed in ground-penetrating radar data from Feddet, south-eastern Denmark

    DEFF Research Database (Denmark)

    Hede, Mikkel Ulfeldt; Nielsen, Lars; Clemmensen, Lars B;

    2012-01-01

    Ground-penetrating radar (GPR) data have been collected across the modern part (test identification of sea-level markers in GPR data from microtidal depositional environments. Nielsen and Clemmensen (2009) showed...

  3. Ultra-Wideband Radars for Measurements over Land and Sea Ice

    Science.gov (United States)

    Gogineni, S.; Hale, R.; Miller, H. G.; Yan, S.; Rodriguez-Morales, F.; Leuschen, C.; Wang, Z.; Gomez-Garcia, D.; Binder, T.; Steinhage, D.; Gehrmann, M.; Braaten, D. A.

    2015-12-01

    We developed two ultra-wideband (UWB) radars for measurements over the ice sheets in Greenland and Antarctica and sea ice. One of the UWB radars operates over a 150-600 MHz frequency range with a large, cross-track 24-element array. It is designed to sound ice, image the ice-bed interface, and map internal layers with fine resolution. The 24-element array consists of three 8-element sub-arrays. One of these sub-arrays is mounted under the fuselage of a BT-67 aircraft; the other two are mounted under the wings. The polarization of each antenna element can be individually reconfigured depending on the target of interest. The measured inflight VSWR is less than 2 over the operating range. The fuselage sub-array is used both for transmission and reception, and the wing-mounted sub-arrays are used for reception. The transmitter consists of an 8-channel digital waveform generator to synthesize chirped pulses of selectable pulse width, duration, and bandwidth. It also consists of drivers and power amplifiers to increase the power level of each individual channel to about 1 kW and a fast high-power transmit/receive switch. Each receiver consists of a limiter, switches, low-noise and driver amplifiers, and filters to shape and amplify received signals to the level required for digitization. The digital sub-section consists of timing and control sub-systems and 24 14-bit A/D converters to digitize received signals at a rate of 1.6 GSPS. The radar performance is evaluated using an optical delay line to simulate returns from about 2 km thick ice, and the measured radar loop sensitivity is about 215 dB. The other UWB microwave radar operates over a 2-18 GHz frequency range in Frequency-Modulated Continuous Wave (FM-CW) mode. It is designed to sound more than 1 m of snow over sea ice and map internal layers to a depth about 25-40 m in polar firn and ice. We operated the microwave radar over snow-covered sea ice and mapped snow as thin as 5 cm and as thick as 60 cm. We mapped

  4. Radar Backscatter Across the Gulf Stream Sea Surface Temperature Front

    Science.gov (United States)

    Nghiem, S. V.; Li, F. K.; Walsh, E. J.; Lou, S. H.

    1998-01-01

    Ocean backscatter signatures were measured by the Jet Propulsion Laboratory airborne NUSCAT K(sub u)-band scatterometer across the Gulf Stream sea surface temperature front. The measurements were made during the Surface Wave Dynamics Experiment (SWADE) off the coast of Virginia and Maryland in the winter of 1991.

  5. Using particle filter to track horizontal variations of atmospheric duct structure from radar sea clutter

    Directory of Open Access Journals (Sweden)

    X. F. Zhao

    2012-08-01

    Full Text Available This paper addresses the problem of estimating range-varying parameters of the height-dependent refractivity over the sea surface from radar sea clutter. In the forward simulation, the split-step Fourier parabolic equation (PE is used to compute the radar clutter power in the complex refractive environments. Making use of the inherent Markovian structure of the split-step Fourier PE solution, the refractivity from clutter (RFC problem is formulated within a nonlinear recursive Bayesian state estimation framework. Particle filter (PF that is a technique for implementing a recursive Bayesian filter by Monte Carlo simulations is used to track range-varying characteristics of the refractivity profiles. Basic ideas of employing PF to solve RFC problem are introduced. Both simulation and real data results are presented to check up the feasibility of PF-RFC performances.

  6. Sensitivity, uncertainty analyses and algorithm selection for Sea Ice Thickness retrieval from Radar Altimeter

    CERN Document Server

    Djepa, Vera

    2013-01-01

    For accurate forecast of climate change, sea ice mass balance, ocean circulation and sea- atmosphere interactions is required to have long term records of Sea Ice Thickness (SIT). Different approaches have been applied to retrieve SIT and only satellite altimetry, radar or laser, have been proven to provide hemispheric estimates of SIT distribution over a sufficient thickness range. To simplify the algorithm for SIT retrieval from RA, constant ice density has been applied until now, which lead to different results for derived SIT and SID, in dependence on input information for sea ice density and snow depth. The purpose of this paper is to select algorithm for SID and SIT retrieval from RA, using statistical, sensitivity analyses and independent observations of SID from moored ULS, or on Submarine. The impact of ice density and snow depth on accuracy of the retrieved SIT has been examined, applying sensitivity analyses, and the propagated uncertainties have been summarised. Accuracy of algorithms for snow dep...

  7. Lipa, B. et al. Tsunami Arrival Detection with High Frequency (HF Radar. Remote Sens. 2012, 4, 1448-1461

    Directory of Open Access Journals (Sweden)

    Donald Barrick

    2012-11-01

    Full Text Available We neglected to state that the radar data from Tokushima and Anan is owned by the Ministry of Land, Infrastructure, Transport and Tourism, Shikoku Regional Development Bureau, Komatsushima port and airport office, Japan. Lipa et al. [1] describe results on tsunami detection using data measured by two radars located at Tokushima and Anan on the Kii channel. This data is owned by the Ministry of Land, Infrastructure, Transport and Tourism, Shikoku Regional Development Bureau, Komatsushima port and airport office, Japan. Locations of the radars are shown in Figure 4(a,c [1]. Results of the data analysis are given in Section 3.1.2, plotted in Figure 6 and listed in Table 1 [1].

  8. GEOPHYSICS, ASTRONOMY AND ASTROPHYSICS: Refractivity estimation from radar sea clutter

    Science.gov (United States)

    Huang, Si-Xun; Zhao, Xiao-Feng; Sheng, Zheng

    2009-11-01

    This paper addresses the problem of estimating lower atmospheric refractivity under the nonstandard propagation conditions frequently encountered in low altitude maritime radar applications. The vertical structure of the refractive environment is modeled by using a five-parameter model, and the horizontal structure is modeled as range-independent. The electromagnetic propagation in the troposphere is simulated by using a split-step fast Fourier transform based on parabolic approximation to the wave equation. A global search marked as a modified genetic algorithm (MGA) for the 5 environmental parameters is performed by using a genetic algorithm (GA) integrated with a simulated annealing technique. The retrieved results from simulated runs demonstrate the ability of this method to make atmospheric refractivity estimations. A comparison with the classical GA and the Bayesian Markov Chain Monte Carlo (Bayesian-MCMC) technique shows that the MGA can not only shorten the inverse time but also improve the inverse precision. For real data cases, the inversion values do not match the reference data very well. The inverted profile, however, can be used to synoptically describe the real refractive structure.

  9. Hyperspectral and Radar Airborne Imagery over Controlled Release of Oil at Sea

    Directory of Open Access Journals (Sweden)

    Sébastien Angelliaume

    2017-08-01

    Full Text Available Remote sensing techniques are commonly used by Oil and Gas companies to monitor hydrocarbon on the ocean surface. The interest lies not only in exploration but also in the monitoring of the maritime environment. Occurrence of natural seeps on the sea surface is a key indicator of the presence of mature source rock in the subsurface. These natural seeps, as well as the oil slicks, are commonly detected using radar sensors but the addition of optical imagery can deliver extra information such as thickness and composition of the detected oil, which is critical for both exploration purposes and efficient cleanup operations. Today, state-of-the-art approaches combine multiple data collected by optical and radar sensors embedded on-board different airborne and spaceborne platforms, to ensure wide spatial coverage and high frequency revisit time. Multi-wavelength imaging system may create a breakthrough in remote sensing applications, but it requires adapted processing techniques that need to be developed. To explore performances offered by multi-wavelength radar and optical sensors for oil slick monitoring, remote sensing data have been collected by SETHI (Système Expérimental de Télédection Hyperfréquence Imageur, the airborne system developed by ONERA (the French Aerospace Lab, during an oil spill cleanup exercise carried out in 2015 in the North Sea, Europe. The uniqueness of this dataset lies in its high spatial resolution, low noise level and quasi-simultaneous acquisitions of different part of the EM spectrum. Specific processing techniques have been developed to extract meaningful information associated with oil-covered sea surface. Analysis of this unique and rich dataset demonstrates that remote sensing imagery, collected in both optical and microwave domains, allows estimating slick surface properties such as the age of the emulsion released at sea, the spatial abundance of oil and the relative concentration of hydrocarbons remaining on

  10. Hyperspectral and Radar Airborne Imagery over Controlled Release of Oil at Sea

    Science.gov (United States)

    Angelliaume, Sébastien; Ceamanos, Xavier; Viallefont-Robinet, Françoise; Baqué, Rémi; Déliot, Philippe

    2017-01-01

    Remote sensing techniques are commonly used by Oil and Gas companies to monitor hydrocarbon on the ocean surface. The interest lies not only in exploration but also in the monitoring of the maritime environment. Occurrence of natural seeps on the sea surface is a key indicator of the presence of mature source rock in the subsurface. These natural seeps, as well as the oil slicks, are commonly detected using radar sensors but the addition of optical imagery can deliver extra information such as thickness and composition of the detected oil, which is critical for both exploration purposes and efficient cleanup operations. Today, state-of-the-art approaches combine multiple data collected by optical and radar sensors embedded on-board different airborne and spaceborne platforms, to ensure wide spatial coverage and high frequency revisit time. Multi-wavelength imaging system may create a breakthrough in remote sensing applications, but it requires adapted processing techniques that need to be developed. To explore performances offered by multi-wavelength radar and optical sensors for oil slick monitoring, remote sensing data have been collected by SETHI (Système Expérimental de Télédection Hyperfréquence Imageur), the airborne system developed by ONERA (the French Aerospace Lab), during an oil spill cleanup exercise carried out in 2015 in the North Sea, Europe. The uniqueness of this dataset lies in its high spatial resolution, low noise level and quasi-simultaneous acquisitions of different part of the EM spectrum. Specific processing techniques have been developed to extract meaningful information associated with oil-covered sea surface. Analysis of this unique and rich dataset demonstrates that remote sensing imagery, collected in both optical and microwave domains, allows estimating slick surface properties such as the age of the emulsion released at sea, the spatial abundance of oil and the relative concentration of hydrocarbons remaining on the sea surface

  11. Hyperspectral and Radar Airborne Imagery over Controlled Release of Oil at Sea.

    Science.gov (United States)

    Angelliaume, Sébastien; Ceamanos, Xavier; Viallefont-Robinet, Françoise; Baqué, Rémi; Déliot, Philippe; Miegebielle, Véronique

    2017-08-02

    Remote sensing techniques are commonly used by Oil and Gas companies to monitor hydrocarbon on the ocean surface. The interest lies not only in exploration but also in the monitoring of the maritime environment. Occurrence of natural seeps on the sea surface is a key indicator of the presence of mature source rock in the subsurface. These natural seeps, as well as the oil slicks, are commonly detected using radar sensors but the addition of optical imagery can deliver extra information such as thickness and composition of the detected oil, which is critical for both exploration purposes and efficient cleanup operations. Today, state-of-the-art approaches combine multiple data collected by optical and radar sensors embedded on-board different airborne and spaceborne platforms, to ensure wide spatial coverage and high frequency revisit time. Multi-wavelength imaging system may create a breakthrough in remote sensing applications, but it requires adapted processing techniques that need to be developed. To explore performances offered by multi-wavelength radar and optical sensors for oil slick monitoring, remote sensing data have been collected by SETHI (Système Expérimental de Télédection Hyperfréquence Imageur), the airborne system developed by ONERA (the French Aerospace Lab), during an oil spill cleanup exercise carried out in 2015 in the North Sea, Europe. The uniqueness of this dataset lies in its high spatial resolution, low noise level and quasi-simultaneous acquisitions of different part of the EM spectrum. Specific processing techniques have been developed to extract meaningful information associated with oil-covered sea surface. Analysis of this unique and rich dataset demonstrates that remote sensing imagery, collected in both optical and microwave domains, allows estimating slick surface properties such as the age of the emulsion released at sea, the spatial abundance of oil and the relative concentration of hydrocarbons remaining on the sea surface.

  12. HF radar transmissions that deviate from great-circle paths: new insight from e-POP RRI

    Science.gov (United States)

    Perry, G. W.; Miller, E. S.; James, H. G.; Howarth, A. D.; St-Maurice, J. P.; Yau, A. W.

    2016-12-01

    Significant deviations of SuperDARN radar transmissions from their expected great-circle paths have been detected at ionospheric altitudes using the Radio Receiver Instrument (RRI) on the Enhanced Polar Outflow Probe (e-POP). Experiments between SuperDARN Rankin Inlet and e-POP RRI were conducted at similar local times over consecutive days. Customized experiment modes which incorporated the agile frequency switching capabilities of each system were used. The RRI measurements show deviations of radar transmissions from their expected paths by as much as 2 or 3 SuperDARN beam widths, equivalent to 6° - 10° in bearing from Rankin Inlet. The deviations displayed a dependence on the radar carrier frequency and a day-to-day variability, suggesting that the deviations were transient in nature. We will discuss the deviations in the context of 3D ray trace modeling and measurements from the Resolute Bay Incoherent Scatter Radar - North (RISR-N). The latter provided diagnostic information of the ionosphere along the ray path between RRI and Rankin Inlet during the experiments.

  13. Spatial and temporal variations of small-scale plasma turbulence parameters in the equatorial electrojet: HF and VHF radar observational results

    Directory of Open Access Journals (Sweden)

    G. Manju

    2005-06-01

    Full Text Available The spatial and temporal variations of various parameters associated with plasma wave turbulence in the equatorial electrojet (EEJ at the magnetic equatorial location of Trivandrum (8.5° N, 77° E; dip 0.5° N are studied for the first time, using co-located HF (18MHz and VHF (54.95MHz coherent backscatter radar observations (daytime in the altitude region of 95-110km, mostly on magnetically quiet days. The derived turbulence parameters are the mean electron density irregularity strength (δn/n, anomalous electron collision frequency (νe* and the corrected east-west electron drift velocity (Vey. The validity of the derived parameters is confirmed using radar data at two different frequencies and comparing with in-situ measurements. The behaviour of δn/n in relation to the backscattered power during weak and strong EEJ conditions is also examined to understand the growth and evolution of turbulence in the electrojet.

  14. A flux transfer event observed at the magnetopause by the Equator-S spacecraft and in the ionosphere by the CUTLASS HF radar

    Directory of Open Access Journals (Sweden)

    D. A. Neudegg

    Full Text Available Observations of a flux transfer event (FTE have been made simultaneously by the Equator-S spacecraft near the dayside magnetopause whilst corresponding transient plasma flows were seen in the near-conjugate polar ionosphere by the CUTLASS Finland HF radar. Prior to the occurrence of the FTE, the magnetometer on the WIND spacecraft ~226 RE upstream of the Earth in the solar wind detected a southward turning of the interplanetary magnetic field (IMF which is estimated to have reached the subsolar magnetopause ~77 min later. Shortly afterwards the Equator-S magnetometer observed a typical bipolar FTE signature in the magnetic field component normal to the magnetopause, just inside the magnetosphere. Almost simultaneously the CUTLASS Finland radar observed a strong transient flow in the F region plasma between 78° and 83° magnetic latitude, near the ionospheric region predicted to map along geomagnetic field lines to the spacecraft. The flow signature (and the data set as a whole is found to be fully consistent with the view that the FTE was formed by a burst of magnetopause reconnection.

    Key words. Interplanetary physics (ionosphere-magnetosphere interaction · Magnetospheric physics (magnetopause · cusp · and boundary layers; solar wind-magnetosphere interactions

  15. Water mass circulation and weathering inputs in the Labrador Sea based on coupled Hf-Nd isotope compositions and rare earth element distributions

    Science.gov (United States)

    Filippova, Alexandra; Frank, Martin; Kienast, Markus; Rickli, Jörg; Hathorne, Ed; Yashayaev, Igor M.; Pahnke, Katharina

    2017-02-01

    The Labrador Sea is one of the key areas for deep water formation driving the Atlantic thermohaline circulation and thus plays an important role in Northern Hemisphere climatic fluctuations. In order to better constrain the overturning processes and the origins of the distinct water masses, combined dissolved Hf-Nd isotopic compositions and rare earth element (REE) distribution patterns were obtained from four water depth profiles along a section across the Labrador Sea. These were complemented by one surface sample off the southern tip of Greenland, three shallow water samples off the coast of Newfoundland, and two deep water samples off Nova Scotia. Although light REEs are markedly enriched in the surface waters off the coast of Newfoundland compared to north Atlantic waters, the REE concentration profiles are essentially invariant throughout the water column across the Labrador Sea. The hafnium concentrations of surface waters exhibit a narrow range between 0.6 and 1 pmol/kg but are not significantly higher than at depth. Neodymium isotope signatures (ɛNd) vary from unradiogenic values between -16.8 and -14.9 at the surface to more radiogenic values near -11.0 at the bottom of the Labrador Sea mainly reflecting the advection of the Denmark Strait Overflow Water and North East Atlantic Deep Water, the signatures of which are influenced by weathering contributions from Icelandic basalts. Unlike Nd, water column radiogenic Hf isotope signatures (ɛHf) are more variable representing diverse weathering inputs from the surrounding landmasses. The least radiogenic seawater ɛHf signatures (up to -11.7) are found in surface waters close to Greenland and near the Canadian margin. This reflects the influence of recirculating Irminger Current Waters, which are affected by highly unradiogenic inputs from Greenland. A three to four ɛHf unit difference is observed between Denmark Strait Overflow Water (ɛHf ∼ -4) and North East Atlantic Deep Water (ɛHf ∼ -0

  16. Testing sea-level markers observed in ground-penetrating radar data from Feddet, south-eastern Denmark

    DEFF Research Database (Denmark)

    Hede, Mikkel Ulfeldt; Nielsen, Lars; Clemmensen, Lars B

    2012-01-01

    Ground-penetrating radar (GPR) data have been collected across the modern part (sea-level markers in GPR data from microtidal depositional environments. Nielsen and Clemmensen (2009) showed that iden......Ground-penetrating radar (GPR) data have been collected across the modern part (... that identified downlap points in GPR data from Anholt (an island in the Kattegat Sea, Denmark) can be interpreted to mark sea level at the time of deposition. The data presented here support this hypothesis. The GPR reflection data have been acquired with shielded 250 MHz Sensors & Software antennae along...

  17. Design Considerations for a Dual-Frequency Radar for Sea Spray Measurement in Hurricanes

    Science.gov (United States)

    Esteban-Fernandez, Daniel; Durden, Stephen L.; Chaubell, Julian; Cooper, Kenneth B.

    2010-01-01

    Over the last few years, researchers have determined that sea spray from breaking waves can have a large effect on the magnitude and distribution of the air-sea energy flux at hurricane-force wind speeds. Characterizing the fluxes requires estimates of the height-dependent droplet size distribution (DSD). Currently, the few available measurements have been acquired with spectrometer probes, which can provide only flight-level measurements. As such, in-situ measurement of near-surface droplet fluxes in hurricanes with these instruments is, at best, extremely challenging, if at all possible. This paper describes an airborne dual-wavelength radar profiler concept to retrieve the DSD of sea spray.

  18. Mapping of sea ice and measurement of its drift using aircraft synthetic aperture radar images

    Science.gov (United States)

    Leberl, F.; Bryan, M. L.; Elachi, C.; Farr, T.; Campbell, W.

    1979-01-01

    Side-looking radar images of Arctic sea ice were obtained as part of the Arctic Ice Dynamics Joint Experiment. Repetitive coverages of a test site in the Arctic were used to measure sea ice drift, employing single images and blocks of overlapping radar image strips; the images were used in conjunction with data from the aircraft inertial navigation and altimeter. Also, independently measured, accurate positions of a number of ground control points were available. Initial tests of the method were carried out with repeated coverages of a land area on the Alaska coast (Prudhoe). Absolute accuracies achieved were essentially limited by the accuracy of the inertial navigation data. Errors of drift measurements were found to be about + or - 2.5 km. Relative accuracy is higher; its limits are set by the radar image geometry and the definition of identical features in sequential images. The drift of adjacent ice features with respect to one another could be determined with errors of less than + or - 0.2 km.

  19. The estimation of lower refractivity uncertainty from radar sea clutter using the Bayesian-MCMC method

    Institute of Scientific and Technical Information of China (English)

    Sheng Zheng

    2013-01-01

    The estimation of lower atmospheric refractivity from radar sea clutter (RFC) is a complicated nonlinear optimization problem.This paper deals with the RFC problem in a Bayesian framework.It uses the unbiased Markov Chain Monte Carlo (MCMC) sampling technique,which can provide accurate posterior probability distributions of the estimated refractivity parameters by using an electromagnetic split-step fast Fourier transform terrain parabolic equation propagation model within a Bayesian inversion framework.In contrast to the global optimization algorithm,the Bayesian-MCMC can obtain not only the approximate solutions,but also the probability distributions of the solutions,that is,uncertainty analyses of solutions.The Bayesian-MCMC algorithm is implemented on the simulation radar sea-clutter data and the real radar seaclutter data.Reference data are assumed to be simulation data and refractivity profiles are obtained using a helicopter.The inversion algorithm is assessed (i) by comparing the estimated refractivity profiles from the assumed simulation and the helicopter sounding data; (ii) the one-dimensional (1D) and two-dimensional (2D) posterior probability distribution of solutions.

  20. Reconstruction of the sea surface elevation from the analysis of the data collected by a wave radar system

    Science.gov (United States)

    Ludeno, Giovanni; Soldovieri, Francesco; Serafino, Francesco; Lugni, Claudio; Fucile, Fabio; Bulian, Gabriele

    2016-04-01

    X-band radar system is able to provide information about direction and intensity of the sea surface currents and dominant waves in a range of few kilometers from the observation point (up to 3 nautical miles). This capability, together with their flexibility and low cost, makes these devices useful tools for the sea monitoring either coastal or off-shore area. The data collected from wave radar system can be analyzed by using the inversion strategy presented in [1,2] to obtain the estimation of the following sea parameters: peak wave direction; peak period; peak wavelength; significant wave height; sea surface current and bathymetry. The estimation of the significant wave height represents a limitation of the wave radar system because of the radar backscatter is not directly related to the sea surface elevation. In fact, in the last period, substantial research has been carried out to estimate significant wave height from radar images either with or without calibration using in-situ measurements. In this work, we will present two alternative approaches for the reconstruction of the sea surface elevation from wave radar images. In particular, the first approach is based on the basis of an approximated version of the modulation transfer function (MTF) tuned from a series of numerical simulation, following the line of[3]. The second approach is based on the inversion of radar images using a direct regularised least square technique. Assuming a linearised model for the tilt modulation, the sea elevation has been reconstructed as a least square fitting of the radar imaging data[4]. References [1]F. Serafino, C. Lugni, and F. Soldovieri, "A novel strategy for the surface current determination from marine X-band radar data," IEEE Geosci.Remote Sens. Lett., vol. 7, no. 2, pp. 231-235, Apr. 2010. [2]Ludeno, G., Brandini, C., Lugni, C., Arturi, D., Natale, A., Soldovieri, F., Serafino, F. (2014). Remocean System for the Detection of the Reflected Waves from the Costa

  1. Bathymetry and Composition of Titan's Hydrocarbon Seas from the Cassini RADAR Altimeter

    Science.gov (United States)

    Mastrogiuseppe, Marco; Hayes, Alex; Poggiali, Valerio; Lunine, Jonathan; Seu, Roberto; Hofgartner, Jason; Le Gall, Alice; Lorenz, Ralph

    2016-04-01

    The Cassini RADAR's altimetry mode has been successfully used for probing the depth and composition of Titan's hydrocarbons seas. In May 2013, during the spacecraft's T91 flyby of Titan, the instrument demonstrated its capabilities as a radar sounder, presenting a unique opportunity to constraint the depth and composition of Titan's second largest sea, Ligeia Mare. Later, observations of Kraken Mare and Punga Mare were planned and executed in August 2014 (T104) and January 2015 (T108), respectively. While most of the seafloor was not detected at Kraken, suggesting the sea was either too deep or too absorptive in these areas to observe a return from the seafloor, shallow areas near Moray Sinus did show subsurface reflections. At Punga Mare, a clear detection of the subsurface was observed with a maximum depth of 120 m along the radar altimetry transect. Herein we present a re-analysis of altimetry data acquired over Ligeia Mare and, earlier in the Cassini mission (in December 2008 during T49), over the southern Ontario Lacus. Depths measurements and liquid composition are obtained using a novel technique which makes use of radar simulations and Monte Carlo-based inversions. Simulation is based on a two-layer model, where the surface is represented by a specular reflection and the seafloor is modeled using a facet-based synthetic surface, including thermal noise, speckle effects, analog to digital conversion (ADC), block adaptive quantization (BAQ), and allows for possible receiver saturation. This new analysis provides an update to the Ku-band attenuation (the Cassini RADAR operates at a wavelength of 2 cm) and results in a new estimate for loss tangent and composition. We found a value of specific attenuation of the liquid equal to 0.14±0.02 dB/m and 0.2±0.1 dB/m, which is equivalent to a loss tangent of 4.4±0.9x10^-5 and 7±3x10^-5 for Ligeia Mare and Ontario Lacus, respectively. Assuming that Titan's liquid bodies are composed by a ternary mixture of methane

  2. Arctic sea surface height variability and change from satellite radar altimetry and GRACE, 2003-2014

    Science.gov (United States)

    Armitage, Thomas W. K.; Bacon, Sheldon; Ridout, Andy L.; Thomas, Sam F.; Aksenov, Yevgeny; Wingham, Duncan J.

    2016-06-01

    Arctic sea surface height (SSH) is poorly observed by radar altimeters due to the poor coverage of the polar oceans provided by conventional altimeter missions and because large areas are perpetually covered by sea ice, requiring specialized data processing. We utilize SSH estimates from both the ice-covered and ice-free ocean to present monthly estimates of Arctic Dynamic Ocean Topography (DOT) from radar altimetry south of 81.5°N and combine this with GRACE ocean mass to estimate steric height. Our SSH and steric height estimates show good agreement with tide gauge records and geopotential height derived from Ice-Tethered Profilers. The large seasonal cycle of Arctic SSH (amplitude ˜5 cm) is dominated by seasonal steric height variation associated with seasonal freshwater fluxes, and peaks in October-November. Overall, the annual mean steric height increased by 2.2 ± 1.4 cm between 2003 and 2012 before falling to circa 2003 levels between 2012 and 2014 due to large reductions on the Siberian shelf seas. The total secular change in SSH between 2003 and 2014 is then dominated by a 2.1 ± 0.7 cm increase in ocean mass. We estimate that by 2010, the Beaufort Gyre had accumulated 4600 km3 of freshwater relative to the 2003-2006 mean. Doming of Arctic DOT in the Beaufort Sea is revealed by Empirical Orthogonal Function analysis to be concurrent with regional reductions in the Siberian Arctic. We estimate that the Siberian shelf seas lost ˜180 km3 of freshwater between 2003 and 2014, associated with an increase in annual mean salinity of 0.15 psu yr-1. Finally, ocean storage flux estimates from altimetry agree well with high-resolution model results, demonstrating the potential for altimetry to elucidate the Arctic hydrological cycle.

  3. High-Resolution Radar Scattering Characteristics of a Disturbed Sea Surface and Floating Debris

    Science.gov (United States)

    1977-07-29

    theoretically and experimentally. Oil drums, logs, and aluminum-covered plastic gallon milk bottles were considered and measured. A comparison of the echoing...covered plastic bottle ,38 N R tEPO R1 8 131 0 DBSM L LJ v ’ da) B 6 GH1 0 DSM -- DBSM ib) 9.2 GHz Ils Fig. 29 - Vertically polarized return from wave...j2 ’ NRL Report 8131 (~High-Resolution Radar Scattering Characteristics of a Disturbed Sea Surface and Floating Debris B. L. LEWIS. J. P. HANSEN. 1

  4. An Adaptive Objective Function for Evaporation Duct Estimations from Radar Sea Echo

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jin-Peng; WU Zhen-Sen; WANG Bo

    2011-01-01

    In the process of atmospheric refractivity estimation from radar sea echo, the objective function that calculates the match between the predicted and observed field plays an important role. To reduce the effect of noises from long ranges on the objective function, we present a selection method of final ranges for inversion. An adaptive objective function is introduced with a linear distance weight added to the least squares error function(LSEF).Through an evaporation duct height(EDH) retrieving process, the performance of the adaptive objective function is evaluated. The result illustrates that the present method performs better than the LSEF in EDH inversions from clutters with different clutter-to-noise ratios.

  5. The structure of turbulence in the middle and lower atmosphere seen by and deduced from MF, HF and VHF radar, with special emphasis on small-scale features and anisotropy

    Directory of Open Access Journals (Sweden)

    W. K. Hocking

    Full Text Available An overview of the turbulent structures seen by MF, HF and VHF radars in the troposphere, stratosphere and mesosphere is presented, drawing on evidence from previous radar measurements, in situ studies, laboratory observations, observations at frequencies other than those under focus, and modelling studies. We are particularly interested in structures at scales less than one radar pulse length, and smaller than the beam width, and especially the degree of anisotropy of turbulence at these scales. Previous radar observations are especially important in regard to the degree of anisotropy, and we highlight the role that these studies have had in furthering our understanding in this area. The contrasts and similarities between the models of anisotropic turbulence and specular reflection are considered. The need for more intense studies of anisotropy at MF, HF and VHF is especially highlighted, since this is an area in which these radars can make important contributions to the understanding of atmospheric turbulence.

    Key words. Meteorology and atmospheric dynamics (turbulence – Atmospheric composition and structure (instruments and techniques – History of geophysics (atmospheric sciences

  6. Air-Sea Spray Airborne Radar Profiler Characterizes Energy Fluxes in Hurricanes

    Science.gov (United States)

    Durden, Stephen L.; Esteban-Fermandez, D.

    2010-01-01

    A report discusses ASAP (Air-sea Spray Airborne Profiler), a dual-wavelength radar profiler that provides measurement information about the droplet size distribution (DSD) of sea-spray, which can be used to estimate heat and moisture fluxes for hurricane research. Researchers have recently determined that sea spray can have a large effect on the magnitude and distribution of the air-sea energy flux at hurricane -force wind speeds. To obtain information about the DSD, two parameters of the DSD are required; for example, overall DSD amplitude and DSD mean diameter. This requires two measurements. Two frequencies are used, with a large enough separation that the differential frequency provides size information. One frequency is 94 GHz; the other is 220 GHz. These correspond to the Rayleigh and Mie regions. Above a surface wind speed of 10 m/ s, production of sea spray grows exponentially. Both the number of large droplets and the altitude they reach are a function of the surface wind speed.

  7. Effects of surface roughness on sea ice freeboard retrieval with an Airborne Ku-Band SAR radar altimeter

    DEFF Research Database (Denmark)

    Hendricks, Stefan; Stenseng, Lars; Helm, Veit

    2010-01-01

    Results from two years of the CryoSat Validation Experiment (CryoVEx) over sea ice in the western Arctic Ocean are presented. The estimation of freeboard, the height of sea ice floating above the water level, is one the main goals of the CryoSat-2 mission of the European Space Agency (ESA) in order...... to investigate sea ice volume changes on an Arctic wide scale. Freeboard retrieval requires precise radar range measurements to the ice surface, therefore we investigate the penetration of the Ku-Band radar waves into the overlying snow cover as well as the effects of sub-footprint-scale surface roughness using...... of the airborne validation dataset, since the radar overestimates the amount of open water and thin ice as well the freeboard of heavy ice deformation zones....

  8. Near-real-time surface ocean velocities derived from HF radar stations located along coastal waters of North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico, Hawaii and western US during July 2016 (NCEI Accession 0156399)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains near-real-time ocean surface velocities, also known as total vector velocities, derived from HF radar stations. The velocities are...

  9. Near-real-time surface ocean velocities derived from HF radar stations located along coastal waters of North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico, Hawaii and western US during July 2015 (NCEI Accession 0131976)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains near-real-time ocean surface velocities, also known as total vector velocities, derived from HF radar stations. The velocities are...

  10. Near-real-time surface ocean velocities derived from HF radar stations located along coastal waters of North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico, Hawaii and western US during August 2015 (NCEI Accession 0131989)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains near-real-time ocean surface velocities, also known as total vector velocities, derived from HF radar stations. The velocities are...

  11. Near-real-time surface ocean velocities derived from HF radar stations located along coastal waters of North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico, Hawaii and western US during October 2015 (NCEI Accession 0138228)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains near-real-time ocean surface velocities, also known as total vector velocities, derived from HF radar stations. The velocities are...

  12. Near-real-time surface ocean velocities derived from HF radar stations located along coastal waters of North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico, Hawaii and western US during August 2016 (NCEI Accession 0156623)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains near-real-time ocean surface velocities, also known as total vector velocities, derived from HF radar stations. The velocities are...

  13. Near-real-time surface ocean velocities derived from HF radar stations located along coastal waters of North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico, Hawaii and western US during November 2015 (NCEI Accession 0139551)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains near-real-time ocean surface velocities, also known as total vector velocities, derived from HF radar stations. The velocities are...

  14. Near-real-time surface ocean velocities derived from HF radar stations located along coastal waters of North Slope Alaska, Puerto Rico/Virgin Islands, eastern US/Gulf of Mexico, Hawaii and western US during September 2015 (NCEI Accession 0137285)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains near-real-time ocean surface velocities, also known as total vector velocities, derived from HF radar stations. The velocities are...

  15. Integrating ground-penetrating radar and borehole data from a Wadden Sea barrier island

    DEFF Research Database (Denmark)

    Nielsen, Lars; Møller, I.; Nielsen, L. H.

    2009-01-01

    Sea level rise may have large implications for low-gradient barrier coastal systems. This problem motivated an integrated ground-penetrating radar (GPR) and sedimentological study of the Rømø Wadden Sea barrier island. Crossing W-E and N-S-oriented 100 MHz GPR reflection profiles with a total...... signals varies between 7 and 15 m in the interior of the island where the shallow subsurface is not influenced by saltwater intrusion or fine-grained salt marsh sediments. Analysis of common midpoint reflection data constrains the radar wave velocity distribution in the subsurface and facilitates depth...

  16. Main sea clutter characteristics impacting small slow moving targets detection by marine radars

    Directory of Open Access Journals (Sweden)

    O. D. Mrachkovskiy

    2013-04-01

    Full Text Available Searching of the sea clutter mathematical model is carried out in this paper. It is suitable to create based on it algorithm for small slow moving targets detection by marine radars. The compound Gaussian model for modeling sea clutter amplitude stochastic distribution is selected as a result of the sources analysis, because it was confirmed by most of researches. The discussed in the literature model based on chaos theory is choosen as perspective alternative for stochastic model; its advantage of using it for such problems solution must be definitively proved or denied. It was proposed many different distributions for high resolution sea clutter amplitude data modeling. The most frequently reported in the literature are K, Log-Normal and Weibull distributions. K distribution belonging to a compound-Gaussian model has the most significant theoretical and experimental background. This distribution choice is physically explained basing on the processes taking place when electromagnetic waves scattered from capillarity and gravity sea waves create a composed echo. Signal representing this echo is the product of two random components, called texture and speckle. Texture is the result of scattering from gravity waves, has a Gamma pdf (in case of K distribution and corresponds to slow-varying large-scale structure. Speckle is the result of scattering from isolated scatterers (capillarity waves, has a Rayleigh pdf and corresponds to rapid varying small-scale structure. So, K distribution envelope is a compound distribution consisting of a locally Rayleigh distribution speckle whose mean is modulated by a gamma distribution texture. All researches consider Rayleigh pdf for speckle. The lognormal, generalized Gaussian, inverse gamma and some other distributions were proposed for the texture. Due to literature analyses it is seen that texture distribution depends on radar range resolution, but strong dependence is not proved. Some scientists modified K

  17. Mapping sea ice using reflected GNSS signals in a bistatic radar system

    Science.gov (United States)

    Chew, Clara; Zuffada, Cinzia; Shah, Rashmi; Mannucci, Anthony

    2016-04-01

    Global Navigation Satellite System (GNSS) signals can be used as a kind of bistatic radar, with receivers opportunistically recording ground-reflected signals transmitted by the GNSS satellites themselves. This technique, GNSS-Reflectometry (GNSS-R), has primarily been explored using receivers flown on aircraft or balloons, or in modeling studies. Last year's launch of the TechDemoSat-1 (TDS-1) satellite represents an enormous opportunity to investigate the potential of using spaceborne GNSS receivers to sense changes in the land and ocean surface. Here, we examine the ability of reflected GNSS signals to estimate sea ice extent and sea ice age, as well as comment on the possibility of using GNSS-R to detect leads and polynyas within the ice. In particular, we quantify how the peak power of Delay Doppler Maps (DDMs) generated within the GNSS receiver responds as the satellite flies over the Polar Regions. To compute the effective peak power of each DDM, we first normalize the peak power of the DDM by the noise floor. We also correct for antenna gain, range, and incidence angle. Once these corrections are made, the effective peak power across DDMs may be used as a proxy for changes in surface permittivity and surface roughness. We compare our calculations of reflected power to existing sea ice remote sensing products such as data from the SSMI/S as well as Landsat imagery. Our analysis shows that GNSS reflections are extremely sensitive to the sea ice edge, with increases in reflected power of more than 10 dB relative to reflected power over the open ocean. As the sea ice ages, it thickens and roughens, and reflected power decreases, though it does not decrease below the power over the open ocean. Given the observed sensitivity of GNSS reflections to small features over land and the sensitivity to the sea ice edge, we hypothesize that reflection data could help map the temporal evolution of leads and polynyas.

  18. About uncertainties in sea ice thickness retrieval from satellite radar altimetry: results from the ESA-CCI Sea Ice ECV Project Round Robin Exercise

    Science.gov (United States)

    Kern, S.; Khvorostovsky, K.; Skourup, H.; Rinne, E.; Parsakhoo, Z. S.; Djepa, V.; Wadhams, P.; Sandven, S.

    2014-03-01

    One goal of the European Space Agency Climate Change Initiative sea ice Essential Climate Variable project is to provide a quality controlled 20 year long data set of Arctic Ocean winter-time sea ice thickness distribution. An important step to achieve this goal is to assess the accuracy of sea ice thickness retrieval based on satellite radar altimetry. For this purpose a data base is created comprising sea ice freeboard derived from satellite radar altimetry between 1993 and 2012 and collocated observations of snow and sea ice freeboard from Operation Ice Bridge (OIB) and CryoSat Validation Experiment (CryoVEx) air-borne campaigns, of sea ice draft from moored and submarine Upward Looking Sonar (ULS), and of snow depth from OIB campaigns, Advanced Microwave Scanning Radiometer aboard EOS (AMSR-E) and the Warren Climatology (Warren et al., 1999). An inter-comparison of the snow depth data sets stresses the limited usefulness of Warren climatology snow depth for freeboard-to-thickness conversion under current Arctic Ocean conditions reported in other studies. This is confirmed by a comparison of snow freeboard measured during OIB and CryoVEx and snow freeboard computed from radar altimetry. For first-year ice the agreement between OIB and AMSR-E snow depth within 0.02 m suggests AMSR-E snow depth as an appropriate alternative. Different freeboard-to-thickness and freeboard-to-draft conversion approaches are realized. The mean observed ULS sea ice draft agrees with the mean sea ice draft computed from radar altimetry within the uncertainty bounds of the data sets involved. However, none of the realized approaches is able to reproduce the seasonal cycle in sea ice draft observed by moored ULS satisfactorily. A sensitivity analysis of the freeboard-to-thickness conversion suggests: in order to obtain sea ice thickness as accurate as 0.5 m from radar altimetry, besides a freeboard estimate with centimetre accuracy, an ice-type dependent sea ice density is as mandatory

  19. Comparison of space borne radar altimetry and airborne laser altimetry over sea ice in the Fram Strait

    DEFF Research Database (Denmark)

    Giles, K.A.; Hvidegaard, Sine Munk

    2006-01-01

    This paper describes the first comparison of satellite radar and airborne laser altimetry over sea ice. In order to investigate the differences between measurements from the two different instruments we explore the statistical properties of the data and determine reasonable scales in space and ti...

  20. Trace metal speciation and bioavailability in surface waters of the Black Sea coastal area evaluated by HF-PLM and DGT.

    Science.gov (United States)

    Slaveykova, Vera I; Karadjova, Irina B; Karadjov, Metody; Tsalev, Dimiter L

    2009-03-15

    Trace metal speciation in seawater from the Bulgarian Black Sea coast was studied in situ by hollow fiber permeation liquid membrane (HF-PLM) and by diffusion gradients in thin-film gels (DGT). The concentrations of Cd, Cu, Ni, and Pb determined by HF-PLM were lower than those measured by DGT, in agreement with their analytical windows, e.g., free metal ions provided by the HF-PLM and dynamic (mobile and labile) species by the DGT. The obtained suite of data was further used to evaluate the bioavailability of these metals to the microorganisms, which was then compared with experimental results of metal uptake to green microalga Chlorella salina. Uptake fluxes of the Cd, Cu, Ni, and Pb to C. salina, were predicted from the measured HF-PLM concentrations and laboratory experimentation in artificial seawater, in agreement with theoretical considerations. The HF-PLM and DGT appear to be promising analytical techniques for speciation and bioavailability studies in complex environmental media and allow improved understanding of the role of different chemical species in metal bioavailability (and impact) in seawaters.

  1. Evaluation of second-order texture parameters for sea ice classification from radar images

    Science.gov (United States)

    Shokr, Mohammed E.

    1991-06-01

    With the advent of airborne and spaceborne synthetic aperture radar (SAR) systems, sea ice classification from SAR images has become an important research subject. Since gray tone alone has proven to be of limited capability in differentiating ice types, texture has naturally become an attractive avenue to explore. Accordingly, performance of texture quantification parameters as related to their ability to discriminate ice types has to be examined. SAR image appearance depends on radar parameters involved in the image construction procedures from the doppler history record. Therefore the feasibility of using universal texture/ice type relationships that hold for all combinations of radar parameters also has to be investigated. To that end, imagery data from three different SAR systems were used in this study. Five conventional texture parameters, derived from the gray level co-occurrence matrix (GLCM), were examined. Two of them were modified to ensure their invariant character under linear gray tone transformations. Results indicated that all parameters were highly correlated. The parameters did not, in general, vary with the computational variables used in generating co-occurrence matrices. Ice types can be identified uniquely by the mean value of any texture parameter. The relatively high variability of texture parameters, however, confuses ice discrimination, particularly of smoother ice types. Ice classification was conducted using a per-pixel maximum likelihood supervised scheme. When texture was combined with gray tone, the overall average classification accuracy was improved. Texture was successful in improving the classification accuracy of multiyear ice but was less promising in discriminating first-season ice types. The best two GLCM texture parameters, according to the computed overall average classification accuracies, were the inverse difference moment and the entropy. A brief description of GLCM texture parameters as related to ice's physical

  2. Oil Detection In and Under Sea Ice Using Ground-Penetrating Radar

    Science.gov (United States)

    Steinbronn, L.; Bradford, J.; Liberty, L.; Dickins, D.; Brandvik, P. J.

    2007-12-01

    Marine oil spills can occur in the Arctic due to pipeline breaks or leaks and spills from storage or production facilities. Depending on the time of year and scenario, a portion or all of the spill may become trapped under and/or encapsulated within the sea ice sheet. The current methods for locating spilled oil include visually inspecting drilled ice cores or sending divers under the ice. Speed is a key issue in oil clean-up. A non-invasive method of detecting oil quickly and reliably would greatly facilitate the clean-up and lessen the impact on the environment. First-year ice thicknesses of 0.5-2.0 m, typical of the Arctic region, can be well-resolved using radar. Oil film thicknesses can range from a few mm to 20 cm depending on the ice-water interface topography. For typical conditions a frequency of 500 MHz gives a 1/4 wavelength limit of 7 cm; therefore a typical spill scenario is a thin-bed problem for ground-penetrating radar (GPR). Interference due to thin-beds may cause amplitude, phase and frequency anomalies in the reflected wavelet. In April 2006, SINTEF conducted a contained oil-spill under natural Arctic sea ice conditions in a fjord on Svalbard. Using data collected during that experiment from a 500 MHz antenna and complex trace analysis we computed the instantaneous frequency, instantaneous phase and the envelope function and found significant differences in the data before and after the oil was inserted. These results demonstrated the potential of GPR to be a practical system for oil in ice detection under certain conditions. As a follow-on to the 2006 project, we have undertaken a detailed modeling effort to estimate GPR response to specific variables, such as ice and oil thicknesses, ice salinity and temperature.

  3. Holocene relative sea level variations at the spit system Feddet (Denmark) resolved by ground-penetrating radar and geomorphological data

    DEFF Research Database (Denmark)

    Hede, Mikkel Ulfeldt; Bendixen, Mette; Clemmensen, Lars B;

    Estimates of Holocene sea-level variations have been presented in a range of studies based on different approaches, including interpretation of internal beach ridge characteristics from ground-penetrating radar (GPR) and geomorphological data. We present GPR data and geomorphological observations...... of sea level variation and vertical land movement in southern Scandinavia in response to unloading after the last glaciation. We have tested the validity of downlap points, which marks the transition from beach to upper shoreface as sea-level markers. The test is based on comparative analyses...

  4. A MIMO FMCW radar approach to HFSWR

    Science.gov (United States)

    Hinz, J. O.; Zölzer, U.

    2011-07-01

    In this paper we propose one possible approach how to apply the concept of multiple-input multiple-output (MIMO) to monostatic Frequency Modulated Continuous Wave (FMCW) High-Frequency Surface Wave Radar (HFSWR) in a maritime environment. Common tasks for a HFSWR are sea-state monitoring and ship detection, where our focus is on ship detection. A limiting factor in HFSWR is the available bandwidth, which is inversely proportional to the range resolution capability of the radar and typical below 100 kHz. The question is how to extend or combine a conventional single-input multiple-output (SIMO) FMCW phased-array type radar with stretch processing and the colocated MIMO concept to "reuse" the very limited HF radar band resources. Another important question to answer is how MIMO FMCW waveforms can be separated at the receiver.

  5. About the consistency between Envisat and CryoSat-2 radar freeboard retrieval over Antarctic sea ice

    Directory of Open Access Journals (Sweden)

    S. Schwegmann

    2015-09-01

    Full Text Available Knowledge about Antarctic sea-ice volume and its changes over the past decades has been sparse due to the lack of systematic sea-ice thickness measurements in this remote area. Recently, first attempts have been made to develop a sea-ice thickness product over the Southern Ocean from space-borne radar altimetry and results look promising. Today, more than 20 years of radar altimeter data are potentially available for such products. However, data come from different sources, and the characteristics of individual sensors differ. Hence, it is important to study the consistency between single sensors in order to develop long and consistent time series over the potentially available measurement period. Here, the consistency between freeboard measurements of the Radar Altimeter 2 on-board Envisat and freeboard measurements from the Synthetic-Aperture Interferometric Radar Altimeter on-board CryoSat-2 is tested for their overlap period in 2011. Results indicate that mean and modal values are comparable over the sea-ice growth season (May–October and partly also beyond. In general, Envisat data shows higher freeboards in the seasonal ice zone while CryoSat-2 freeboards are higher in the perennial ice zone and near the coasts. This has consequences for the agreement in individual sectors of the Southern Ocean, where one or the other ice class may dominate. Nevertheless, over the growth season, mean freeboard for the entire (regional separated Southern Ocean differs generally by not more than 2 cm (5 cm, except for the Amundsen/Bellingshausen Sea between Envisat and CryoSat-2, and the differences between modal freeboard lie generally within ±10 cm and often even below.

  6. Observation of melt onset on multiyear Arctic sea ice using the ERS 1 synthetic aperture radar

    Science.gov (United States)

    Winebrenner, D. P.; Nelson, E. D.; Colony, R.; West, R. D.

    1994-01-01

    We present nearly coincident observations of backscattering from the Earth Remote-Sensing Satellite (ERS) 1 synthetic aperture radar (SAR) and of near-surface temperature from six drifting buoys in the Beaufort Sea, showing that the onset of melting in snow on multiyear sea ice is clearly detectable in the SAR data. Melt onset is marked by a clean, steep decrease in the backscattering cross section of multiyear ice at 5.3 GHz and VV polarization. We investigate the scattering physics responsible for the signature change and find that the cross section decrease is due solely to the appearance of liquid water in the snow cover overlying the ice. A thin layer of moist snow is sufficient to cause the observed decrease. We present a prototype algorithm to estimate the date of melt onset using the ERS 1 SAR and apply the algorithm first to the SAR data for which we have corresponding buoy temperatures. The melt onset dates estimated by the SAR algorithm agree with those obtained independently from the temperature data to within 4 days or less, with the exception of one case in which temperatures oscillated about 0 C for several weeks. Lastly, we apply the algorithm to the entire ERS 1 SAR data record acquired by the Alaska SAR Facility for the Beaufort Sea north of 73 deg N during the spring of 1992, to produce a map of the dates of melt onset over an area roughly 1000 km on a side. The progression of melt onset is primarily poleward but shows a weak meridional dependence at latitudes of approximately 76 deg-77 deg N. Melting begins in the southern part of the study region on June 13 and by June 20 has progressed to the northermost part of the region.

  7. Observation of melt onset on multiyear Arctic sea ice using the ERS 1 synthetic aperture radar

    Science.gov (United States)

    Winebrenner, D. P.; Nelson, E. D.; Colony, R.; West, R. D.

    1994-01-01

    We present nearly coincident observations of backscattering from the Earth Remote-Sensing Satellite (ERS) 1 synthetic aperture radar (SAR) and of near-surface temperature from six drifting buoys in the Beaufort Sea, showing that the onset of melting in snow on multiyear sea ice is clearly detectable in the SAR data. Melt onset is marked by a clean, steep decrease in the backscattering cross section of multiyear ice at 5.3 GHz and VV polarization. We investigate the scattering physics responsible for the signature change and find that the cross section decrease is due solely to the appearance of liquid water in the snow cover overlying the ice. A thin layer of moist snow is sufficient to cause the observed decrease. We present a prototype algorithm to estimate the date of melt onset using the ERS 1 SAR and apply the algorithm first to the SAR data for which we have corresponding buoy temperatures. The melt onset dates estimated by the SAR algorithm agree with those obtained independently from the temperature data to within 4 days or less, with the exception of one case in which temperatures oscillated about 0 C for several weeks. Lastly, we apply the algorithm to the entire ERS 1 SAR data record acquired by the Alaska SAR Facility for the Beaufort Sea north of 73 deg N during the spring of 1992, to produce a map of the dates of melt onset over an area roughly 1000 km on a side. The progression of melt onset is primarily poleward but shows a weak meridional dependence at latitudes of approximately 76 deg-77 deg N. Melting begins in the southern part of the study region on June 13 and by June 20 has progressed to the northermost part of the region.

  8. Synthetic range profiling, ISAR imaging of sea vessels and feature extraction, using a multimode radar to classify targets: initial results from field trials

    CSIR Research Space (South Africa)

    Abdul Gaffar, MY

    2011-04-01

    Full Text Available -based classification of small to medium sized sea vessels in littoral condition. The experimental multimode radar is based on an experimental tracking radar that was modified to generate SRP and ISAR images in both search and tracking modes. The architecture...

  9. Comparison of sea-level measurements using microwave radar and subsurface pressure gauge deployed in Mandovi estuary in Goa, Central West Coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Mehra, P.; Agarvadekar, Y.; Luis, R.; Nadaf, L.

    measurement of atmospheric pressure along with sub-bottom absolute pressure gauge. The radar gauge has advantages over other type of gauges with regard to easy installation, maintenance and also sea level measurements are absolute and could be given precedence...

  10. CBSIT 2009: Airborne Validation of Envisat Radar Altimetry and In Situ Ice Camp Measurements Over Arctic Sea Ice

    Science.gov (United States)

    Connor, Laurence; Farrell, Sinead; McAdoo, David; Krabill, William; Laxon, Seymour; Richter-Menge, Jacqueline; Markus, Thorsten

    2010-01-01

    The past few years have seen the emergence of satellite altimetry as valuable tool for taking quantitative sea ice monitoring beyond the traditional surface extent measurements and into estimates of sea ice thickness and volume, parameters that arc fundamental to improved understanding of polar dynamics and climate modeling. Several studies have now demonstrated the use of both microwave (ERS, Envisat/RA-2) and laser (ICESat/GLAS) satellite altimeters for determining sea ice thickness. The complexity of polar environments, however, continues to make sea ice thickness determination a complicated remote sensing task and validation studies remain essential for successful monitoring of sea ice hy satellites. One such validation effort, the Arctic Aircraft Altimeter (AAA) campaign of2006. included underflights of Envisat and ICESat north of the Canadian Archipelago using NASA's P-3 aircraft. This campaign compared Envisat and ICESat sea ice elevation measurements with high-resolution airborne elevation measurements, revealing the impact of refrozen leads on radar altimetry and ice drift on laser altimetry. Continuing this research and validation effort, the Canada Basin Sea Ice Thickness (CBSIT) experiment was completed in April 2009. CBSIT was conducted by NOAA. and NASA as part of NASA's Operation Ice Bridge, a gap-filling mission intended to supplement sea and land ice monitoring until the launch of NASA's ICESat-2 mission. CBIST was flown on the NASA P-3, which was equipped with a scanning laser altimeter, a Ku-band snow radar, and un updated nadir looking photo-imaging system. The CB5IT campaign consisted of two flights: an under flight of Envisat along a 1000 km track similar to that flown in 2006, and a flight through the Nares Strait up to the Lincoln Sea that included an overflight of the Danish GreenArc Ice Camp off the coast of northern Greenland. We present an examination of data collected during this campaign, comparing airborne laser altimeter measurements

  11. Maritime target and sea clutter measurements with a coherent Doppler polarimetric surveillance radar

    NARCIS (Netherlands)

    Smith, A.J.E.; Gelsema, S.J.; Kester, L.J.H.M.; Melief, H.W.; Premel Cabic, G.; Theil, A.; Woudenberg, E.

    2002-01-01

    Doppler polarimetry in a surveillance radar for the maritime surface picture is considered. This radar must be able to detect low-RCS targets in littoral environments. Measurements on such targets have been conducted with a coherent polarimetric measurement radar in March 2001 and preliminary

  12. Maritime target and sea clutter measurements with a coherent Doppler polarimetric surveillance radar

    NARCIS (Netherlands)

    Smith, A.J.E.; Gelsema, S.J.; Kester, L.J.H.M.; Melief, H.W.; Premel Cabic, G.; Theil, A.; Woudenberg, E.

    2002-01-01

    Doppler polarimetry in a surveillance radar for the maritime surface picture is considered. This radar must be able to detect low-RCS targets in littoral environments. Measurements on such targets have been conducted with a coherent polarimetric measurement radar in March 2001 and preliminary result

  13. The ISMAR high frequency coastal radar network: Monitoring surface currents for management of marine resources

    DEFF Research Database (Denmark)

    Carlson, Daniel Frazier

    2015-01-01

    The Institute of Marine Sciences (ISMAR) of the National Research Council of Italy (CNR) established a High Frequency (HF) Coastal Radar Network for the measurement of the velocity of surface currents in coastal seas. The network consists of four HF radar systems located on the coast of the Gargano...... of geospatial data, a netCDF architecture has been defined on the basis of the Radiowave Operators Working Group (US ROWG) recommendations and compliant to the Climate and Forecast (CF) Metadata Conventions CF-1.6. The hourly netCDF files are automatically attached to a Thematic Real-time Environmental...... by the ISMAR HF radar network are presently used in a number of applications, ranging from oil spill and SAR to fishery and coastal management applications....

  14. Studies of medium scale travelling ionospheric disturbances using TIGER SuperDARN radar sea echo observations

    Directory of Open Access Journals (Sweden)

    L.-S. He

    2004-12-01

    Full Text Available

    Seasonal and diurnal variations in the direction of propagation of medium-scale travelling ionospheric disturbances (MSTIDs have been investigated by analyzing sea echo returns detected by the TIGER SuperDARN radar located in Tasmania (43.4° S, 147.2° E geographic; –54.6°Λ. A strong dependency on local time was found, as well as significant seasonal variations. Generally, the propagation direction has a northward (i.e. equatorward component. In the early morning hours the direction of propagation is quite variable throughout the year. It then becomes predominantly northwest and changes to northeast around 09:00 LT. In late fall and winter it changes back to north/northwest around 15:00 LT. During the other seasons, northward propagation is very obvious near dawn and dusk, but no significant northward propagation is observed at noon.

    It is suggested that the variable propagation direction in the morning is related to irregular magnetic disturbances that occur at this local time. The changes in the MSTID propagation directions near dawn and dusk are generally consistent with changes in ionospheric electric fields occurring at these times and is consistent with dayside MSTIDs being generated by the Lorentz force.

    Key words. Ionosphere (ionospheric disturbances; wave propagation; ionospheric irregularities; signal processing

  15. A parameter inversion for sea bridge based on high-resolution polarimetric synthetic aperture radar

    Institute of Scientific and Technical Information of China (English)

    LIU Genwang; ZHANG Jie; ZHANG Xi; MENG Junmin; WANG Guoyu

    2016-01-01

    Each reflection return of a bridge over water is displayed as wide stripe in a high-resolution synthetic aperture radar (SAR) image, which lead to difficulties in a parameter inversion. Therefore, a method of bridge parameter inversion is proposed for high-resolution full polarimetric SAR (PolSAR). First, the single, double and triple-bounce returns from each component of the bridge are distinguished by the polarization scattering features. Then the reasons which lead to the backscatter echoes of the bridge over water being displayed as stripes are analyzed, using a principle of microwave reflection, as well as an extraction method for each reflection return, and a parameter retrieval method is obtained. Finally, the parameters of the bridge, including the height (top and bottom surfaces of the sea bridge), width, thickness, span, and height of the bridge tower, are retrieved using full polarimetric AIRSAR data. When a comparison of the measured data is completed, the results indicate that the proposed method can invert the parameters with a high accuracy, and that the inversion error of the bridge height (bottom surface) is only 1.3%. Moreover, the results also show that for the high-resolution SAR, the C and L-band images have the same ability in regards to parameter retrieval.

  16. Hourly surface currents measured by High Frequency (HF) Wellen radars (WERA) off western Oahu, Hawaii, from September 2002 to May 2003 (NODC Accession 0013113)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A pair of High Frequency Wellen radars (WERA) shore-based at southwest Oahu (Ko'Olina) and northwest Oahu (Kaena), Hawaii measured surface currents over a nine-month...

  17. Reconstruction and future prediction of the sea surface from radar observations

    NARCIS (Netherlands)

    Wijaya, Andreas Parama; Naaijen, P.; Andonowati, A.; van Groesen, Embrecht W.C.

    2015-01-01

    For advanced offshore engineering applications the prediction with available nautical X-band radars of phase-resolved incoming waves is very much desired. At present, such radars are already used to detect averaged characteristics of waves, such as the peak period, significant wave height, wave dire

  18. FMCW radar system for detection and classification of small vessels in high sea state conditions

    NARCIS (Netherlands)

    Wasselin, J.-P.; Mazuel, S.; Itcia, E.; Huizing, A.G.; Theil, A.

    2012-01-01

    The ROCKWELL COLLINS France radar department is currently developing a FMCW radar system for the detection and the classification of small maritime targets in the frame of the SISMARIS, SARGOS & I2C projects. Several test campaigns have been conducted since 2009 to develop a sensor as well as an

  19. Cassini RADAR observations of lakes and seas in the Northern Polar region of Titan: Bathymetry and Composition

    Science.gov (United States)

    Mastrogiuseppe, Marco; Hayes, Alex; Poggiali, Valerio; Lunine, Jonathan; Seu, Roberto; Hofgartner, Jason; Le Gall, Alice; Lorenz, Ralph; Mitri, Giuseppe

    2017-04-01

    Recent observations by the Cassini spacecraft has revealed its RADAR to be an invaluable tool for investigating Titan's seas and lakes. The T91 (May 2013) observation of Ligeia Mare, Titan's second largest sea, has demonstrated the capabilities of the RADAR, in its altimeter mode, to measure depth, composition and seafloor topography. The 104 (August 2014) observation provided similar data over the largest sea, Kraken Mare, and the T108 (January 2015) flyby acquired an altimetry pass over Punga Mare. The T49 (December 2007) altimetry pass over Ontario Lacus, the largest southern liquid body, has also been processed to retrieve subsurface echoes. Cassini's final flyby of Titan, T126 (April 2017), is the next and unique opportunity to observe an area in the Northern Polar region of Titan, where several small - medium size (5 - 30 km) lakes are present and have been previously imaged by Cassini. In our presentation, we will report the integrated results of these investigations and discuss them in the overall context of Titan's hydrologic cycle.

  20. The impact of snow depth, snow density and ice density on sea ice thickness retrieval from satellite radar altimetry: results from the ESA-CCI Sea Ice ECV Project Round Robin Exercise

    Science.gov (United States)

    Kern, S.; Khvorostovsky, K.; Skourup, H.; Rinne, E.; Parsakhoo, Z. S.; Djepa, V.; Wadhams, P.; Sandven, S.

    2015-01-01

    We assess different methods and input parameters, namely snow depth, snow density and ice density, used in freeboard-to-thickness conversion of Arctic sea ice. This conversion is an important part of sea ice thickness retrieval from spaceborne altimetry. A data base is created comprising sea ice freeboard derived from satellite radar altimetry between 1993 and 2012 and co-locate observations of total (sea ice + snow) and sea ice freeboard from the Operation Ice Bridge (OIB) and CryoSat Validation Experiment (CryoVEx) airborne campaigns, of sea ice draft from moored and submarine upward looking sonar (ULS), and of snow depth from OIB campaigns, Advanced Microwave Scanning Radiometer (AMSR-E) and the Warren climatology (Warren et al., 1999). We compare the different data sets in spatiotemporal scales where satellite radar altimetry yields meaningful results. An inter-comparison of the snow depth data sets emphasizes the limited usefulness of Warren climatology snow depth for freeboard-to-thickness conversion under current Arctic Ocean conditions reported in other studies. We test different freeboard-to-thickness and freeboard-to-draft conversion approaches. The mean observed ULS sea ice draft agrees with the mean sea ice draft derived from radar altimetry within the uncertainty bounds of the data sets involved. However, none of the approaches are able to reproduce the seasonal cycle in sea ice draft observed by moored ULS. A sensitivity analysis of the freeboard-to-thickness conversion suggests that sea ice density is as important as snow depth.

  1. Sea-ice deformation state from synthetic aperture radar imagery - Part I: comparison of C- and L-band and different polarization

    DEFF Research Database (Denmark)

    Dierking, Wolfgang; Dall, Jørgen

    2007-01-01

    In this paper, we present a quantitative comparison of L- and C-band airborne synthetic aperture radar imagery acquired at like- and cross-polarizations over deformed sea ice under winter conditions. The parameters characterizing the deformation state of the ice are determined at both radar bands...... and at different polarizations. The separation of deformed and level ice is based on a target detection technique. The threshold is set such that image pixels with intensities equal to or larger than the highest 2% of the level-ice intensity distribution are classified as deformed ice, independent of the radar...... are very sensitive to the radar frequency. Aeral fractions are larger, and average distances are smaller at L-band than at C-band because of the much higher intensity contrast between the deformed and level ice at L-band. The differences between polarizations at one radar band are smaller but not always...

  2. Antenna Pattern Measurements for Oceanographic Radars Using Small Aerial Drones

    Science.gov (United States)

    Washburn, L.; Romero, E.; Johnson, C.; Emery, B.; Gotschalk, C.

    2016-12-01

    We describe a method employing small, quadrotor drone aircraft for antenna pattern measurements (APMs) of high-frequency (HF) oceanographic radars used for observing ocean surface currents. During APMs, the drones carry small radio signal sources in circular arcs centered on receive antenna arrays at HF radar sites, similarly to conventional boat-based APMs. Previous studies have shown that accurate surface current measurements using HF radar require APMs. In the absence of APMs so-called "ideal" antenna patterns are assumed and these can differ substantially from measured patterns. Typically APMs are obtained using small research vessels, an expensive procedure requiring sea-going technicians, a vessel, and other equipment necessary to support small boat operations. Adverse sea conditions and obstacles in the water can limit the ability of small vessels to conduct APMs. In contrast, drones can successfully conduct APMs at much lower cost and in a broader range of sea states with comparable accuracy. Drone-based patterns can extend farther shoreward since they are not affected by the surf zone and thereby expand the range of bearings over which APMs are conducted. We describe recent progress in the use of drones for APMs including: (1) evaluation of the accuracy APM flight trajectories; (2) estimates of radial velocity components due to deviation of flight paths from circular arcs; and (3) the effects of altitude with respect to ground wave versus direct signal propagation. Use of drones simplifies APMs and it is hoped that this will lead to more frequent APMs and improved surface current measurements from HF radar networks.

  3. Assimilation of HF Radar Observations in the Chesapeake-Delaware Bay Region Using the Navy Coastal Ocean Model (NCOM) and the Four-Dimensional Variational (4DVAR) Method

    Science.gov (United States)

    2015-01-01

    Forget G, Kohl A, Terrill E. Assessing 40 -VAR for dynamical mapping of coastal high-frequency radar in San Diego . Dyn Allnos Oceans 2009;48:175-97...Mon Weather Rev 20 14;142(4): 1509- 24. 10. Roarty H, Glenn S, Kohut J, Gong D, Handel E, Rivera E, et at. Operation and applica- tion of a regional

  4. Radar Signature Calculation Facility

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: The calculation, analysis, and visualization of the spatially extended radar signatures of complex objects such as ships in a sea multipath environment and...

  5. An Ultra-Wideband, Microwave Radar for Measuring Snow Thickness on Sea Ice and Mapping Near-Surface Internal Layers in Polar Firn

    Science.gov (United States)

    Panzer, Ben; Gomez-Garcia, Daniel; Leuschen, Carl; Paden, John; Rodriguez-Morales, Fernando; Patel, Azsa; Markus, Thorsten; Holt, Benjamin; Gogineni, Prasad

    2013-01-01

    Sea ice is generally covered with snow, which can vary in thickness from a few centimeters to >1 m. Snow cover acts as a thermal insulator modulating the heat exchange between the ocean and the atmosphere, and it impacts sea-ice growth rates and overall thickness, a key indicator of climate change in polar regions. Snow depth is required to estimate sea-ice thickness using freeboard measurements made with satellite altimeters. The snow cover also acts as a mechanical load that depresses ice freeboard (snow and ice above sea level). Freeboard depression can result in flooding of the snow/ice interface and the formation of a thick slush layer, particularly in the Antarctic sea-ice cover. The Center for Remote Sensing of Ice Sheets (CReSIS) has developed an ultra-wideband, microwave radar capable of operation on long-endurance aircraft to characterize the thickness of snow over sea ice. The low-power, 100mW signal is swept from 2 to 8GHz allowing the air/snow and snow/ ice interfaces to be mapped with 5 c range resolution in snow; this is an improvement over the original system that worked from 2 to 6.5 GHz. From 2009 to 2012, CReSIS successfully operated the radar on the NASA P-3B and DC-8 aircraft to collect data on snow-covered sea ice in the Arctic and Antarctic for NASA Operation IceBridge. The radar was found capable of snow depth retrievals ranging from 10cm to >1 m. We also demonstrated that this radar can be used to map near-surface internal layers in polar firn with fine range resolution. Here we describe the instrument design, characteristics and performance of the radar.

  6. Regional characteristics of sea ice thickness in Canadian shelf and Arctic Archipelago measured by Ground Penetrating Radar

    Institute of Scientific and Technical Information of China (English)

    LI Tao; ZHAO Jinping; JIAO Yutian; HOU Jiaqiang; MU Longjiang

    2015-01-01

    Ground Penetrating Radar (GPR) measurements of sea ice thickness including undeformed ice and ridged ice were carried out in the central north Canadian Archipelago in spring 2010. Results have shown a significant spatial heterogeneity of sea ice thickness across the shelf. The undeformed multi-year fast ice of (2.05±0.09) m thick was investigated southern inshore zone of Borden island located at middle of the observational section, which was the observed maximum thickness in the field work. The less thick sea ice was sampled across a flaw lead with the thicknesses of (1.05±0.11) m for the pack ice and (1.24±0.13) m for the fast ice. At the northernmost spot of the section, the undeformed multi-year pack ice was (1.54±0.22) m thick with a ridged ice of 2.5 to 3 m, comparing to the multi-year fast ice with the thickness of (1.67±0.16) m at the southernmost station in the Prince Gustaf Adolf Sea.

  7. Inversion of X-band nautical radar data for sea-state monitoring: a new technique to estimate the surface currents

    Science.gov (United States)

    Serafino, F.; Lugni, C.; Raffa, F.; Soldovieri, F.

    2009-04-01

    The inversion of X-band marine images sequences allows obtaining the sea state parameter estimation and the reconstruction of the wave height evolution [1-4]. This result is possible tanks to the fact that the backscattering from the sea is "visible", under some conditions, on the marine radar images. These radar signatures, that typically are suppressed because represent a noise (clutter) for the navigation, are the "useful signal" to be processed in order to achieve information about the sea state: peak wave length, period and direction, current speed and direction and the evolution of surface elevation. The backscattering phenomena is due to the Bragg resonance with ocean waves of wavelengths similar to those of the transmitted electromagnetic waves. In particular, the longer waves modulate the backscattering phenomenon and thus they become visible in the "radar" images. As a consequence, the radar image is not a direct representation of the sea state and thus a processing procedure is needed in order to reconstruct the sea state. After a Fourier Transform of the data, a spectral filter is used to erase all the undesired phenomenon via a dispersion relation. The use of the Modulation Transfer Function (MTF) allows the passage from the radar spectrum to sea spectrum; finally, the resulting spectrum is Fourier transformed to return to the space-time domain. A key step of the whole procedure is the generation of the spectral filter. To built the filter the surface currents have to be estimated, if they are not correctly determined the results of the overall inversion are quite poor. This drawback is further increased when the values of the surface current become high or the data are acquired by a moving vessel, since the problem of the determination of the current is quite complicated and particular attention needs the filtering procedure. This work presents an innovative procedure able to estimate the free-surface current values with high accuracy compared to the

  8. High Frequency Radar Locations in the United States as of February 2016.

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset show the point locations of High Frequency (HF) radar systems across the US. HF radars measure the speed and direction of ocean surface currents in near...

  9. Excitation thresholds of field-aligned irregularities and associated ionospheric hysteresis at very high latitudes observed using SPEAR-induced HF radar backscatter

    Directory of Open Access Journals (Sweden)

    D. M. Wright

    2009-07-01

    Full Text Available On 10 October 2006 the SPEAR high power radar facility was operated in a power-stepping mode where both CUTLASS radars were detecting backscatter from the SPEAR-induced field-aligned irregularities (FAIs. The effective radiated power of SPEAR was varied from 1–10 MW. The aim of the experiment was to investigate the power thresholds for excitation (Pt and collapse (Pc of artificially-induced FAIs in the ionosphere over Svalbard. It was demonstrated that FAI could be excited by a SPEAR ERP of only 1 MW, representing only 1/30th of SPEAR's total capability, and that once created the irregularities could be maintained for even lower powers. The experiment also demonstrated that the very high latitude ionosphere exhibits hysteresis, where the down-going part of the power cycle provided a higher density of irregularities than for the equivalent part of the up-going cycle. Although this second result is similar to that observed previously by CUTLASS in conjunction with the Tromsø heater, the same is not true for the equivalent incoherent scatter measurements. The EISCAT Svalbard Radar (ESR failed to detect any hysteresis in the plasma parameters over Svalbard in stark contract with the measurements made using the Tromsø UHF.

  10. Comparison of CryoSat-2 and ENVISAT radar freeboard over Arctic sea ice: toward an improved Envisat freeboard retrieval

    Science.gov (United States)

    Guerreiro, Kevin; Fleury, Sara; Zakharova, Elena; Kouraev, Alexei; Rémy, Frédérique; Maisongrande, Philippe

    2017-09-01

    Over the past decade, sea-ice freeboard has been monitored with various satellite altimetric missions with the aim of producing long-term time series of ice thickness. While recent studies have demonstrated the capacity of the CryoSat-2 mission (2010-present) to provide accurate freeboard measurements, the current estimates obtained with the Envisat mission (2002-2012) still require some large improvements. In this study, we first estimate Envisat and CryoSat-2 radar freeboard by using the exact same processing algorithms. We then analyse the freeboard difference between the two estimates over the common winter periods (November 2010-April 2011 and November 2011-March 2012). The analysis of along-track data and gridded radar freeboard in conjunction with Envisat pulse-peakiness (PP) maps suggests that the discrepancy between the two sensors is related to the surface properties of sea-ice floes and to the use of a threshold retracker. Based on the relation between the Envisat pulse peakiness and the radar freeboard difference between Envisat and CryoSat-2, we produce a monthly CryoSat-2-like version of Envisat freeboard. The improved Envisat data set freeboard displays a similar spatial distribution to CryoSat-2 (RMSD = 1.5 cm) during the two ice growth seasons and for all months of the period of study. The comparison of the altimetric data sets with in situ ice draught measurements during the common flight period shows that the improved Envisat data set (RMSE = 12-28 cm) is as accurate as CryoSat-2 (RMSE = 15-21 cm) and much more accurate than the uncorrected Envisat data set (RMSE = 178-179 cm). The comparison of the improved Envisat radar freeboard data set is then extended to the rest of the Envisat mission to demonstrate the validity of PP correction from the calibration period. The good agreement between the improved Envisat data set and the in situ ice draught data set (RMSE = 13-32 cm) demonstrates the potential of the PP correction to produce accurate

  11. Comparison of CryoSat-2 and ENVISAT radar freeboard over Arctic sea ice: toward an improved Envisat freeboard retrieval

    Directory of Open Access Journals (Sweden)

    K. Guerreiro

    2017-09-01

    Full Text Available Over the past decade, sea-ice freeboard has been monitored with various satellite altimetric missions with the aim of producing long-term time series of ice thickness. While recent studies have demonstrated the capacity of the CryoSat-2 mission (2010–present to provide accurate freeboard measurements, the current estimates obtained with the Envisat mission (2002–2012 still require some large improvements. In this study, we first estimate Envisat and CryoSat-2 radar freeboard by using the exact same processing algorithms. We then analyse the freeboard difference between the two estimates over the common winter periods (November 2010–April 2011 and November 2011–March 2012. The analysis of along-track data and gridded radar freeboard in conjunction with Envisat pulse-peakiness (PP maps suggests that the discrepancy between the two sensors is related to the surface properties of sea-ice floes and to the use of a threshold retracker. Based on the relation between the Envisat pulse peakiness and the radar freeboard difference between Envisat and CryoSat-2, we produce a monthly CryoSat-2-like version of Envisat freeboard. The improved Envisat data set freeboard displays a similar spatial distribution to CryoSat-2 (RMSD  =  1.5 cm during the two ice growth seasons and for all months of the period of study. The comparison of the altimetric data sets with in situ ice draught measurements during the common flight period shows that the improved Envisat data set (RMSE  =  12–28 cm is as accurate as CryoSat-2 (RMSE  =  15–21 cm and much more accurate than the uncorrected Envisat data set (RMSE  =  178–179 cm. The comparison of the improved Envisat radar freeboard data set is then extended to the rest of the Envisat mission to demonstrate the validity of PP correction from the calibration period. The good agreement between the improved Envisat data set and the in situ ice draught data set (RMSE

  12. The application of the multifractal cross-correlation analysis methods in radar target detection within sea clutter

    Science.gov (United States)

    Xi, Caiping; Zhang, Shuning; Xiong, Gang; Zhao, Huichang; Yang, Yonghong

    2017-02-01

    Many complex systems generate multifractal time series which are long-range cross-correlated. This paper introduces three multifractal cross-correlation analysis methods, such as multifractal cross-correlation analysis based on the partition function approach (MFXPF), multifractal detrended cross-correlation analysis (MFDCCA) methods based on detrended fluctuation analysis (MFXDFA) and detrended moving average analysis (MFXDMA), which only consider one moment order. We do comparative analysis of the artificial time series (binomial multiplicative cascades and Cantor sets with different probabilities) by these methods. Then we do a feasibility test of the fixed threshold target detection within sea clutter by applying the multifractal cross-correlation analysis methods to the IPIX radar sea clutter data. The results show that it is feasible to use the method of the fixed threshold based on the multifractal feature parameter Δf(α) by the MFXPF and MFXDFA-1 methods. At last, we give the main conclusions and provide a valuable reference on how to choose the multifractal algorithms, the detection parameters and the target detection methods within sea clutter in practice.

  13. Study on the impact of sudden stratosphere warming in the upper mesosphere-lower thermosphere regions using satellite and HF radar measurements [Conference paper

    CSIR Research Space (South Africa)

    Mbatha, N

    2009-07-01

    Full Text Available successive positions in increments of 3.25˚, giving an azimuth extent of ~52˚ boxshadowdwn The meteor trail echoes occur predominantly in and below the lower E region (~95 km) [Hussey et al.,2000], thus acquisition of the winds in meteor region... is accomplished by using data from the first several range gates of the radar boxshadowdwn The backscatter at this distance is primarily due to meteors, and thus a nominal height of 90-95 km is assumed SAIP conference 2009 [UKZN] 10/28/2009 boxshadowdwn...

  14. Sea Ice Deformation State From Synthetic Aperture Radar Imagery - Part II: Effects of Spatial Resolution and Noise Level

    DEFF Research Database (Denmark)

    Dierking, Wolfgang; Dall, Jørgen

    2008-01-01

    . The areal fraction at C-band remains constant. The retrieved average distance between deformation features increases both at C- and L-bands, as the image resolution gets coarser. The influence of noise becomes noticeable if its level is equal or larger than the average intensity backscattered from the level......C- and L-band airborne synthetic aperture radar (SAR) imagery acquired at like- and cross-polarization over sea ice under winter conditions is examined with the objective to study the discrimination between level ice and ice deformation features. High-resolution low-noise data were analysed....... The signal-to-noise ratio is varied between typical noise levels for airborne imagery and satellite data. Areal fraction of deformed ice and average deformation distance are determined for each image product. At L-band, the retrieved values of the areal fraction get larger as the image resolution is degraded...

  15. Volcanic and Tectonic Activity in the Red Sea Region (2004-2013): Insights from Satellite Radar Interferometry and Optical Imagery

    KAUST Repository

    Xu, Wenbin

    2015-04-01

    Studying recent volcanic and tectonic events in the Red Sea region is important for improving our knowledge of the Red Sea plate boundary and for regional geohazard assessments. However, limited information has been available about the past activity due to insufficient in-situ data and remoteness of some of the activity. In this dissertation, I have used satellite remote sensing to derive new information about several recent volcanic and tectonic events in the Red Sea region. I first report on three volcanic eruptions in the southern Red Sea, the 2007-8 Jebel at Tair eruption and the 2011-12 & 2013 Zubair eruptions, which resulted in formation of two new islands. Series of high- resolution optical images were used to map the extent of lava flows and to observe and analyze the growth and destructive processes of the new islands. I used Interferometric Synthetic Aperture Radar (InSAR) data to study the evolution of lava flows, to estimate their volumes, as well as to generate ground displacements maps, which were used to model the dikes that fed the eruptions. I then report on my work of the 2009 Harrat Lunayyir dike intrusion and the 2004 Tabuk earthquake sequence in western Saudi Arabia. I used InSAR observations and stress calculations to study the intruding dike at Harrat Lunayyir, while I combined InSAR data and Bayesian estimation to study the Tabuk earthquake activity. The key findings of the thesis are: 1) The recent volcanic eruptions in the southern Red Sea indicate that the area is magmatically more active than previously acknowledged and that a rifting episode has been taken place in the southern Red Sea; 2) Stress interactions between an ascending dike intrusion and normal faulting on graben-bounding faults above the dike can inhibit vertical propagation of magma towards the surface; 3) InSAR observations can improve locations of shallow earthquakes and fault model uncertainties are useful to associate earthquake activity with mapped faults; 4). The

  16. Sea-Based X-Band (SBX) Radar Vessel Maintenance and Repair. Draft Environmental Assessment

    Science.gov (United States)

    2011-02-14

    which is a primary port of entry for Honda, Acura, Volkswagen , Isuzu, Mitsubishi Fuso, and Hino Motors vehicles; and Tenth Avenue Marine Terminal...approximately 3 months. The SBX 8 Radar Vessel would be accompanied by its support vessel (the motor vessel Dove, shown in 9 Figure 2-1). The...road motor vehicles and other mobile sources (California Air Resources Board, 2010). Military aircraft and ship activities over and offshore of San

  17. High-Resolution Mapping of Sea Ice, Icebergs and Growlers in Kongsfjorden, Svalbard, using Ground Based Radar, Satellite, and UAV

    Science.gov (United States)

    Lauknes, T. R.; Rouyet, L.; Solbø, S. A.; Sivertsen, A.; Storvold, R.; Akbari, V.; Negrel, J.; Gerland, S.

    2016-12-01

    The dynamics of sea ­ice has a well­ recognized role in the climate system and its extent and evolution is impacted by the global warming. In addition, calving of icebergs and growlers at the tidewater glacier fronts is a component of the mass loss in polar regions. Understanding of calving and ice ­ocean interaction, in particular at tidewater glacier front remains elusive, and a problematic uncertainty in climate change projections. Studying the distribution, volumetry and motion of sea ­ice, icebergs and growlers is thus essential to understand their interactions with the environment in order to be able to predict at short­term their drifts, e.g. to mitigate the risk for shipping, and at longer term the multiple relations with climate changes. Here, we present the results from an arctic fieldwork campaign conducted in Kongsfjorden, Svalbard in April 2016, where we used different remote sensing instruments to observe dynamics of sea ice, icebergs, and growlers. We used a terrestrial radar system, imaging the study area every second minute during the observation period. At the front of the Kronebreen glacier, calving events can be detected and the drift of the generated icebergs and growlers tracked with unprecedented spatial and temporal resolution. During the field campaign, we collected four Radarsat-2 quad-pol images, that will be used to classify the different types of sea ice. In addition, we used small unmanned aircraft (UAS) instrumented with high resolution cameras capturing HD video and still pictures. This allows to map and measure the size of icebergs and ice floes. Such information is essential to validate sensitivity and detection limits from the ground and satellite based measurements.

  18. Integration of WERA Ocean Radar into Tsunami Early Warning Systems

    Science.gov (United States)

    Dzvonkovskaya, Anna; Helzel, Thomas; Kniephoff, Matthias; Petersen, Leif; Weber, Bernd

    2016-04-01

    High-frequency (HF) ocean radars give a unique capability to deliver simultaneous wide area measurements of ocean surface current fields and sea state parameters far beyond the horizon. The WERA® ocean radar system is a shore-based remote sensing system to monitor ocean surface in near real-time and at all-weather conditions up to 300 km offshore. Tsunami induced surface currents cause increasing orbital velocities comparing to normal oceanographic situation and affect the measured radar spectra. The theoretical approach about tsunami influence on radar spectra showed that a tsunami wave train generates a specific unusual pattern in the HF radar spectra. While the tsunami wave is approaching the beach, the surface current pattern changes slightly in deep water and significantly in the shelf area as it was shown in theoretical considerations and later proved during the 2011 Japan tsunami. These observed tsunami signatures showed that the velocity of tsunami currents depended on a tsunami wave height and bathymetry. The HF ocean radar doesn't measure the approaching wave height of a tsunami; however, it can resolve the surface current velocity signature, which is generated when tsunami reaches the shelf edge. This strong change of the surface current can be detected by a phased-array WERA system in real-time; thus the WERA ocean radar is a valuable tool to support Tsunami Early Warning Systems (TEWS). Based on real tsunami measurements, requirements for the integration of ocean radar systems into TEWS are already defined. The requirements include a high range resolution, a narrow beam directivity of phased-array antennas and an accelerated data update mode to provide a possibility of offshore tsunami detection in real-time. The developed software package allows reconstructing an ocean surface current map of the area observed by HF radar based on the radar power spectrum processing. This fact gives an opportunity to issue an automated tsunami identification message

  19. Snow Radar Derived Surface Elevations and Snow Depths Multi-Year Time Series over Greenland Sea-Ice During IceBridge Campaigns

    Science.gov (United States)

    Perkovic-Martin, D.; Johnson, M. P.; Holt, B.; Panzer, B.; Leuschen, C.

    2012-12-01

    This paper presents estimates of snow depth over sea ice from the 2009 through 2011 NASA Operation IceBridge [1] spring campaigns over Greenland and the Arctic Ocean, derived from Kansas University's wideband Snow Radar [2] over annually repeated sea-ice transects. We compare the estimates of the top surface interface heights between NASA's Atmospheric Topographic Mapper (ATM) [3] and the Snow Radar. We follow this by comparison of multi-year snow depth records over repeated sea-ice transects to derive snow depth changes over the area. For the purpose of this paper our analysis will concentrate on flights over North/South basin transects off Greenland, which are the closest overlapping tracks over this time period. The Snow Radar backscatter returns allow for surface and interface layer types to be differentiated between snow, ice, land and water using a tracking and classification algorithm developed and discussed in the paper. The classification is possible due to different scattering properties of surfaces and volumes at the radar's operating frequencies (2-6.5 GHz), as well as the geometries in which they are viewed by the radar. These properties allow the returns to be classified by a set of features that can be used to identify the type of the surface or interfaces preset in each vertical profile. We applied a Support Vector Machine (SVM) learning algorithm [4] to the Snow Radar data to classify each detected interface into one of four types. The SVM algorithm was trained on radar echograms whose interfaces were visually classified and verified against coincident aircraft data obtained by CAMBOT [5] and DMS [6] imaging sensors as well as the scanning ATM lidar. Once the interface locations were detected for each vertical profile we derived a range to each interface that was used to estimate the heights above the WGS84 ellipsoid for direct comparisons with ATM. Snow Radar measurements were calibrated against ATM data over areas free of snow cover and over GPS

  20. Realtime generation of K-Distributed sea clutter for hardware in the loop radar evaluation

    CSIR Research Space (South Africa)

    Van der Merwe, Johannes R

    2016-10-01

    Full Text Available This paper proposes a practical implementation for the generation of real-time K-Distributed correlated sea-clutter in firmware. The method uses a dual cumulative distribution function (CDF) based look-up method to transpose a complex uniformly...

  1. NOAA high resolution sea surface winds data from Synthetic Aperture Radar (SAR) on the RADARSAT-2 satellite

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Synthetic Aperture Radar (SAR)-derived high resolution wind products are calculated from high resolution SAR images of normalized radar cross section (NRCS) of the...

  2. The relationship between the microwave radar cross section and both wind speed and stress: Model function studies using Frontal Air-Sea Interaction Experiment data

    Science.gov (United States)

    Weissman, David E.; Davidson, Kenneth L.; Brown, Robert A.; Friehe, Carl A.; Li, Fuk

    1994-01-01

    The Frontal Air-Sea Interaction Experiment (FASINEX) provided a unique data set with coincident airborne scatterometer measurements of the ocean surface radar cross section (RCS)(at Ku band) and near-surface wind and wind stress. These data have been analyzed to study new model functions which relate wind speed and surface friction velocity (square root of the kinematic wind stress) to the radar cross section and to better understand the processes in the boundary layer that have a strong influence on the radar backscatter. Studies of data from FASINEX indicate that the RCS has a different relation to the friction velocity than to the wind speed. The difference between the RCS models using these two variables depends on the polarization and the incidence angle. The radar data have been acquired from the Jet Propulsion Laboratory airborne scatterometer. These data span 10 different flight days. Stress measurements were inferred from shipboard instruments and from aircraft flying at low altitudes, closely following the scatterometer. Wide ranges of radar incidence angles and environmental conditions needed to fully develop algorithms are available from this experiment.

  3. Characterization of seepage surfaces from Space-borne radar interferometry stacking techniques, Southern Dead Sea area, Jordan

    Science.gov (United States)

    Tessari, Giulia; Closson, Damien; Abou Karaki, Najib; Atzori, Simone; Fiaschi, Simone; Floris, Mario; Pasquali, Paolo; Riccardi, Paolo

    2014-05-01

    The Dead Sea is a terminal lake located in a pull-apart basin of the Dead Sea Transform fault zone. It is the lowest emerged place on Earth at about -428 m bsl. Since the 1960s, the over-pumping of its tributaries leads to a decrease in the water level. Eventually, it became more pronounced decades after decades. In 2014, it is more than 1m/year. The overall drop is around 33 m. With salinity ten times greater than the ocean water one, the lake body and its underground lateral extensions act as a high density layer over which the fresh ground waters are in hydrostatic equilibrium. The slope of the interface between saline and fresh waters is ten times shallower than normally expected near the ocean. According to a number of wells along the Jordanian Dead Sea coast, the water table level does not drop at the same speed than the Dead Sea. An increasingly important gradient is constantly being created along the coastal zone. In many places, the fresh ground waters move very rapidly towards the base level to compensate for the imbalance. This statement is supported by a body of observations: a) appearance of vegetation (Tamarisk) in arid areas (precipitation: 50 to 70 mm/year) dominated by salt deposits such as the Lisan peninsula; b) presence of submarine circular collapses visible along the coast. Their diameters decreasing with distance from the shore line; c) appearances of springs and recurring landslides along the coast. With the exception of the submarine features, all these elements are located in the land strip that emerged progressively from the 1960s, 33 m in elevation, ranging from a few decameters up to several kilometers wide. In many places, the surface is characterized by superficial seepages causing subtle to very pronounced subsidence, and sinkholes. In this contribution, we show that advanced differential radar interferometry techniques applied to ERS, ENVISAT and COSMO-SkyMed images stacks are able to underscore the most affected places. The mapping

  4. Determination of Backscatter Characteristics of Sea Ice Using Synthetic Aperture Radar Data.

    Science.gov (United States)

    1981-03-01

    removed on 79-3-6, to the locations shown in Figure 5. A-15 untera Figure A-7 Typical snow cover on shorefast ice, 79-3-4. Fluff layer is quite dry, has...in Table II. ii Table B-i GROUND TRUTH DATA SHIP AREA -Sea Cakes -Small floes-2-20m -Ocean swell & pulp ice -first year fast ice -iceberg SITE 3 -first

  5. Pulse-to-pulse correlation in CryoSat SAR mode radar altimeter echoes from the sea surface

    Science.gov (United States)

    Smith, W. H.

    2012-12-01

    Serial correlation among successive radar echoes returned from the ocean surface is an important design constraint in satellite altimetry. Walsh [1974, 1982] established the conventional wisdom. Taking the radar footprint to be a uniformly radiating disk, he derived a theoretically expected echo decorrelation time of about 0.5 milliseconds. Following Walsh, ocean altimeters usually employ a pulse repetition frequency (PRF) around 2 kHz, in order to obtain statistically independent echoes at (so it is thought) the maximum possible rate. CryoSat, designed for ranging to ice surfaces, employs a PRF of 18.2 kHz in its SAR mode. CryoSat SAR echo sequences over ocean surfaces can be used to empirically determine the ocean echo decorrelation, and thus to test Walsh's model. Such a test is presented in this paper. The analysis begins by forming the ensemble average of complex cross products of pairs of echoes separated by a time lag L * PRI, where the pulse repetition interval (PRI) is 55 microseconds and the echo lag L runs from 0 to 32. The L = 0 case yields the conventional pulse-limited waveform, which is used to determine the sea state in each ensemble average. The averages of lagged echo cross products reveal the complex coherency, with sampling in both slow time (lag, L), and fast time (range, sampled in waveform gates). Data from many areas and sea states are analyzed, and the results are explained using a simple theory approximating the complex coherency expected from a Gaussian radar pulse. This theory generalizes the classical Brown [1977] waveform model to lagged echo cross products, and generalizes Walsh's work to the case of footprints with non-uniform illumination and diffuse edges. Phase is due to vertical motion of the antenna. Amplitude variations in fast time are due to horizontal motion of the antenna, and are independent of wave height; their functional form confirms Brown's assumption that scattering is independent of azimuth. In slow time, the

  6. The 2007-8 volcanic eruption on Jebel at Tair island (Red Sea) observed by satellite radar and optical images

    KAUST Repository

    Xu, Wenbin

    2014-01-31

    We use high-resolution optical images and Interferometric Synthetic Aperture Radar (InSAR) data to study the September 2007-January 2008 Jebel at Tair eruption. Comparison of pre- and post-eruption optical images reveals several fresh ground fissures, a new scoria cone near the summit, and that 5.9 ± 0.1 km2 of new lava covered about half of the island. Decorrelation in the InSAR images indicates that lava flowed both to the western and to the northeastern part of the island after the start of the eruption, while later lavas were mainly deposited near the summit and onto the north flank of the volcano. From the InSAR data, we also estimate that the average thickness of the lava flows is 3.8 m, resulting in a bulk volume of around 2.2 × 107 m3. We observe no volcano-wide pre- or post-eruption uplift, which suggests that the magma source may be deep. The co-eruption interferograms, on the other hand, reveal local and rather complex deformation. We use these observations to constrain a tensile dislocation model that represents the dike intrusion that fed the eruption. The model results show that the orientation of the dike is perpendicular to the Red Sea rift, implying that the local stresses within the volcanic edifice are decoupled from the regional stress field. © 2014 Springer-Verlag Berlin Heidelberg.

  7. Duct heights inferred from radar sea clutter using proper orthogonal bases

    Science.gov (United States)

    Fountoulakis, Vasileios; Earls, Christopher

    2016-10-01

    Maritime electromagnetic (EM)-based communication and detection systems are strongly influenced by meteorological conditions, as they can cause anomalous electromagnetic propagation within the surface layer. To predict the performance of such systems, detailed knowledge of the refractivity profile is required. In recent years, refractivity from clutter (RFC) methods has been developed to estimate this refractivity profile by measuring radar clutter return from the rough ocean surface. The current work proposes an RFC framework that utilizes a novel surrogate model for EM propagation. The surrogate model is based on an offline created library of sparsely sampled field data of clutter returns, compressed into proper orthogonal bases, and indexed on specific surface layer refractive parameters. By exploiting the Riemannian manifold structure of the space that proper orthogonal bases occur in, we are able to interpolate among them. This, then, enables us to use the surrogate model in an inverse problem setting, whose goal is to uncover in situ maritime EM propagation conditions efficiently. We demonstrate the feasibility of our proposed surrogate model-based RFC approach for evaporation duct by testing it with field data obtained from an experimental campaign.

  8. Improving the Accuracy of Coastal Sea Surface Heights by Retracking Decontaminated Radar Altimetry Waveforms

    Science.gov (United States)

    Huang, Zhengkai; Wang, Haihong; Luo, Zhicai

    2017-04-01

    Due to the complex coastal topography and energetic ocean dynamics effect, the return echoes are contaminated while the satellite footprint approaches or leaves the coastline. Specular peaks are often induced in the trailing edges of contaminated waveforms, thus leading the error in the determination of the leading edge and associated track offset in the waveform retracking process. We propose an improved algorithm base on Tseng's modification method to decontaminated coastal (0-7 km from coastline) waveforms, thus improving both the utilization and precision of coastal sea surface height (SSH). Using the Envisat/Jason-2 SGDR data, the shortcoming of Tseng's method is pointed out and the novel algorithm is proposed by revising the strategy of selecting reference waveform and determining weight for removing outlier. The reference waveform of the decontaminated technology is closer to the real waveform of the offshore area, which avoids the over-modification problem of Tseng method. The sea-level measurements from tide gauge station and geoid height from EGM2008 model were used to validate the retracking strategy. Experimental results show that decontaminated waveform was more suitable than original and Tseng modified waveform and has uniform performance in both compare to the tide gauge and geoid. The retrieved altimetry data in the 0-1km and 1-7km coastal zone indicate that threshold retracker with decontaminated waveform have STD of 73.8cm and 33cm as compared with in situ gauge data,which correspond to 62.1% and 58% in precession compared to the unretracked altimetry measurements. The retracked SSHs are better in two coastal (0-1 km and 1-7km) zones, which have STD of 11.9cm and 22.7cm as compared with geoid height. Furthermore, the comparisons shows that the precision of decontaminated technology improve 0.3cm and 3.3cm than the best result of PISTACH product in coastal sea. This work is supported by the National Natural Science Foundation of China (Grant Nos

  9. Study on the Detectability of the Sky-Surface Wave Hybrid Radar

    Directory of Open Access Journals (Sweden)

    Hou Chengyu

    2014-01-01

    Full Text Available Working in the HF (high-frequency band and the transmitter and receiver locating separately, the sky-surface wave hybrid radar both has the capabilities of the OTHR (over-the-horizon radar and the advantage of the bistatic radar. As the electromagnetic wave will be disturbed by the ionosphere, interfered by the sea clutter and attenuated by the sea surface, the detectability of this radar system is more complex. So, in this paper, we will discuss the problem detailedly. First of all, the radar equation is deduced based on the propagation of the electromagnetic wave. Then, how to calculate the effect of the ionosphere and the propagation loss is discussed. And an example based on the radar equation is given. At last, the ambiguity function is used to analyze the range and velocity resolution. From the result, we find that the resolution has relation with the location of the target and the height of reflection point of the ionosphere. But compared with the location, the effect of the ionospheric height can be ignored.

  10. Wind turbine clutter mitigation in coastal UHF radar.

    Science.gov (United States)

    Yang, Jing; Pan, Chao; Wang, Caijun; Jiang, Dapeng; Wen, Biyang

    2014-01-01

    Coastal UHF radar provides a unique capability to measure the sea surface dynamic parameters and detect small moving targets, by exploiting the low energy loss of electromagnetic waves propagating along the salty and good conducting ocean surface. It could compensate the blind zone of HF surface wave radar at close range and reach further distance than microwave radars. However, its performance is susceptible to wind turbines which are usually installed on the shore. The size of a wind turbine is much larger than the wavelength of radio waves at UHF band, which results in large radar cross section. Furthermore, the rotation of blades adds time-varying Doppler frequency to the clutter and makes the suppression difficult. This paper proposes a mitigation method which is based on the specific periodicity of wind turbine clutter and performed mainly in the time-frequency domain. Field experimental data of a newly developed UHF radar are used to verify this method, and the results prove its effectiveness.

  11. Behavior Subtraction applied to radar

    NARCIS (Netherlands)

    Rossum, W.L. van; Caro Cuenca, M.

    2014-01-01

    An algorithm developed for optical images has been applied to radar data. The algorithm, Behavior Subtraction, is based on capturing the dynamics of a scene and detecting anomalous behavior. The radar application is the detection of small surface targets at sea. The sea surface yields the expected s

  12. Sea ice layer exploration with Very High Frequency radar echoes%甚高频雷达回波对海冰的检测

    Institute of Scientific and Technical Information of China (English)

    赵耀

    2013-01-01

    Based on the time domain Mueller matrix solution, a method for Very High Frequency(VHF, 30 MHz-300 MHz) radar pulse penetration on sea ice is developed. The polarimetric radar pulse echoes contain echoes from top and bottom interfaces, volumetric scattering of air-bubbles and interface-volume interactions. By changing model parameters such as the layer thickness, salinity, dielectric constant and interfacial roughness, the radar pulse echoes on sea ice are numerically simulated to verify the feasibility of the proposed method. The results demonstrate that the model can be used to explore sea ice, and the information such as depth and other structure properties can be inversed and estimated.%通过推导海冰层的全极化脉冲波时域 Mueller矩阵解,提出空基甚高频(VHF,30 MHz~300 MHz)雷达窄脉冲检测海冰层的方法。海冰层的雷达脉冲极化回波主要由海冰上下两层随机粗糙面、海冰层中空气泡的体散射以及面-体相互作用几种散射机制的回波组成。通过改变海冰的特征参数(海冰层厚、含盐量、介电常数、界面粗糙度等),对海冰雷达回波进行数值模拟来验证本文提出的方法是否可行。结果表明,本模型可用于检测海冰,对海冰的层厚和分层结构进行反演或者估算。

  13. A synthetic aperture radar sea surface distribution estimation by n-order Bézier curve and its application in ship detection

    Institute of Scientific and Technical Information of China (English)

    LANG Haitao; ZHANG Jie; WANG Yiduo; ZHANG Xi; MENG Junmin

    2016-01-01

    To dates, most ship detection approaches for single-pol synthetic aperture radar (SAR) imagery try to ensure a constant false-alarm rate (CFAR). A high performance ship detector relies on two key components: an accurate estimation to a sea surface distribution and a fine designed CFAR algorithm. First, a novel nonparametric sea surface distribution estimation method is developed based onn-order Bézier curve. To estimate the sea surface distribution usingn-order Bézier curve, an explicit analytical solution is derived based on a least square optimization, and the optimal selection also is presented to two essential parameters, the ordern of Bézier curve and the numberm of sample points. Next, to validate the ship detection performance of the estimated sea surface distribution, the estimated sea surface distribution byn-order Bézier curve is combined with a cell averaging CFAR (CA-CFAR). To eliminate the possible interfering ship targets in background window, an improved automatic censoring method is applied. Comprehensive experiments prove that in terms of sea surface estimation performance, the proposed method is as good as a traditional nonparametric Parzen window kernel method, and in most cases, outperforms two widely used parametric methods, K and G0 models. In terms of computation speed, a major advantage of the proposed estimation method is the time consuming only depended on the numberm of sample points while independent of imagery size, which makes it can achieve a significant speed improvement to the Parzen window kernel method, and in some cases, it is even faster than two parametric methods. In terms of ship detection performance, the experiments show that the ship detector which constructed by the proposed sea surface distribution model and the given CA-CFAR algorithm has wide adaptability to different SAR sensors, resolutions and sea surface homogeneities and obtains a leading performance on the test dataset.

  14. The use of radar for bathymetry assessment

    NARCIS (Netherlands)

    Aardoom, J.H.; Greidanus, H.S.F.

    1998-01-01

    The bottom topography in shallow seas can be observed by air- and spaceborne imaging radar. Bathymetric information derived from radar data is limited in accuracy, but radar has a good spatial coverage. The accuracy can be increased by assimilating the radar imagery into existing or insitu gathered

  15. The use of radar for bathymetry assessment

    NARCIS (Netherlands)

    Aardoom, J.H.; Greidanus, H.S.F.

    1998-01-01

    The bottom topography in shallow seas can be observed by air- and spaceborne imaging radar. Bathymetric information derived from radar data is limited in accuracy, but radar has a good spatial coverage. The accuracy can be increased by assimilating the radar imagery into existing or insitu gathered

  16. Radar sea clutter power modeling under the atmospheric duct propagation conditions∗%大气波导条件下雷达海杂波功率仿真*

    Institute of Scientific and Technical Information of China (English)

    赵小峰; 黄思训

    2013-01-01

      考虑近海面大气折射率垂直梯度的变化,采用曲面波频谱估计方法(CWSE)计算掠射角,并结合修正的GIT海表反射率模型和雷达距离方程对大气波导条件下雷达海杂波功率进行仿真,最后通过数值实验及与实测数据比较,验证了CWSE方法的可行性。%Taking into account the variations of the refractivity gradient near the sea surface, We have used the curved wave spectral esti-mation (CWSE) technique to calculate the grazing angle. CWSE combined with the modified GIT reflectivity model and radar range equation, the radar sea clutter power modeling is performed under the atmospheric duct propagation conditions. Finally, the validation of CWSE is tested through numerical experiments and comparisons with the real measurement data.

  17. Phase I for the Use of TOPEX-Poseidon and Jason-1 Radar Altimetry to Monitor Coastal Wetland Inundation and Sea Level Rise in Coastal Louisiana

    Science.gov (United States)

    Brozen, Madeline; Batina, Matthew; Parker, Stephen; Brooks, Christopher

    2010-01-01

    The objective of the first phase of this project was to determine the feasibility of applying satellite altimetry data to monitor sea level rise and inundation within coastal Louisiana. Global sea level is rising, and coastal Louisiana is subsiding. Therefore, there is a need to monitor these trends over time for coastal restoration and hazard mitigation efforts. TOPEX/POSEIDON and Jason-data are used for global sea level estimates and have also been demonstrated successfully in water level studies of lakes, river basins, and floodplains throughout the world. To employ TOPEX/POSEIDON and Jason-1 data in coastal regions, the numerous steps involved in processing the data over non-open ocean areas must be assessed. This project outlined the appropriate methodology for processing non-open ocean data, including retracking and atmospheric corrections. It also inventoried the many factors in coastal land loss including subsidence, sea level rise, coastal geomorphology, and salinity levels, among others, through a review of remote sensing and field methods. In addition, the project analyzed the socioeconomic factors within the Coastal Zone as compared to the rest of Louisiana. While sensor data uncertainty must be addressed, it was determined that it is feasible to apply radar altimetry data from TOPEX/POSEIDON and Jason 1 to see trends in change within Coastal Louisiana since

  18. A practical algorithm for the retrieval of floe size distribution of Arctic sea ice from high-resolution satellite Synthetic Aperture Radar imagery

    Directory of Open Access Journals (Sweden)

    Byongjun Hwang

    2017-07-01

    Full Text Available In this study, we present an algorithm for summer sea ice conditions that semi-automatically produces the floe size distribution of Arctic sea ice from high-resolution satellite Synthetic Aperture Radar data. Currently, floe size distribution data from satellite images are very rare in the literature, mainly due to the lack of a reliable algorithm to produce such data. Here, we developed the algorithm by combining various image analysis methods, including Kernel Graph Cuts, distance transformation and watershed transformation, and a rule-based boundary revalidation. The developed algorithm has been validated against the ground truth that was extracted manually with the aid of 1-m resolution visible satellite data. Comprehensive validation analysis has shown both perspectives and limitations. The algorithm tends to fail to detect small floes (mostly less than 100 m in mean caliper diameter compared to ground truth, which is mainly due to limitations in water-ice segmentation. Some variability in the power law exponent of floe size distribution is observed due to the effects of control parameters in the process of de-noising, Kernel Graph Cuts segmentation, thresholds for boundary revalidation and image resolution. Nonetheless, the algorithm, for floes larger than 100 m, has shown a reasonable agreement with ground truth under various selections of these control parameters. Considering that the coverage and spatial resolution of satellite Synthetic Aperture Radar data have increased significantly in recent years, the developed algorithm opens a new possibility to produce large volumes of floe size distribution data, which is essential for improving our understanding and prediction of the Arctic sea ice cover

  19. Lunar Radar Cross Section at Low Frequency

    Science.gov (United States)

    Rodriguez, P.; Kennedy, E. J.; Kossey, P.; McCarrick, M.; Kaiser, M. L.; Bougeret, J.-L.; Tokarev, Y. V.

    2002-01-01

    Recent bistatic measurements of the lunar radar cross-section have extended the spectrum to long radio wavelength. We have utilized the HF Active Auroral Research Program (HAARP) radar facility near Gakona, Alaska to transmit high power pulses at 8.075 MHz to the Moon; the echo pulses were received onboard the NASA/WIND spacecraft by the WAVES HF receiver. This lunar radar experiment follows our previous use of earth-based HF radar with satellites to conduct space experiments. The spacecraft was approaching the Moon for a scheduled orbit perturbation when our experiment of 13 September 2001 was conducted. During the two-hour experiment, the radial distance of the satellite from the Moon varied from 28 to 24 Rm, where Rm is in lunar radii.

  20. Large phased-array radars

    Science.gov (United States)

    Brookner, Eli, Dr.

    1988-12-01

    Large phased-array radars can play a very important part in arms control. They can be used to determine the number of RVs being deployed, the type of targeting of the RVs (the same or different targets), the shape of the deployed objects, and possibly the weight and yields of the deployed RVs. They can provide this information at night as well as during the day and during rain and cloud covered conditions. The radar can be on the ground, on a ship, in an airplane, or space-borne. Airborne and space-borne radars can provide high resolution map images of the ground for reconnaissance, of anti-ballistic missile (ABM) ground radar installations, missile launch sites, and tactical targets such as trucks and tanks. The large ground based radars can have microwave carrier frequencies or be at HF (high frequency). For a ground-based HF radar the signal is reflected off the ionosphere so as to provide over-the-horizon (OTH) viewing of targets. OTH radars can potentially be used to monitor stealth targets and missile traffic.

  1. Investigation and Development of Data-Driven D-Region Model for HF Systems Impacts

    Science.gov (United States)

    Eccles, J. V.; Rice, D.; Sojka, J. J.; Hunsucker, R. D.

    2002-01-01

    Space Environment Corporation (SEC) and RP Consultants (RPC) are to develop and validate a weather-capable D region model for making High Frequency (HF) absorption predictions in support of the HF communications and radar communities. The weather-capable model will assimilate solar and earth space observations from NASA satellites. The model will account for solar-induced impacts on HF absorption, including X-rays, Solar Proton Events (SPE's), and auroral precipitation. The work plan includes: I . Optimize D-region model to quickly obtain ion and electron densities for proper HF absorption calculations. 2. Develop indices-driven modules for D-region ionization sources for low, mid, & high latitudes including X-rays, cosmic rays, auroral precipitation, & solar protons. (Note: solar spectrum & auroral modules already exist). 3. Setup low-cost monitors of existing HF beacons and add one single-frequency beacon. 4. Use PENEX HF-link database with HF monitor data to validate D-region/HF absorption model using climatological ionization drivers. 5. Develop algorithms to assimilate NASA satellite data of solar, interplanetary, and auroral observations into ionization source modules. 6. Use PENEX HF-link & HF-beacon data for skill score comparison of assimilation versus climatological D-region/HF absorption model. Only some satellites are available for the PENEX time period, thus, HF-beacon data is necessary. 7. Use HF beacon monitors to develop HF-link data assimilation algorithms for regional improvement to the D-region/HF absorption model.

  2. Sensitivity of CryoSat-2 Arctic sea-ice freeboard and thickness on radar-waveform interpretation

    DEFF Research Database (Denmark)

    Ricker, R.; Hendricks, S.; Helm, V.

    2014-01-01

    as the height of the ice surface above the sea level. Accurate CryoSat-2 range measurements over open water and the ice surface of the order of centimetres are necessary to achieve the required accuracy of the freeboard-to-thickness conversion. Besides uncertainties of the actual sea-surface height and limited...... of sea-ice freeboard and higher-level products that arise from the choice of the retracker threshold only, independent of the uncertainties related to snow and ice properties. Our study shows that the choice of retracker thresholds does have a significant impact on magnitudes of estimates of sea...... of roughly 0.06-0.12 m. Furthermore we obtain a significant rise of 0.02-0.15m of freeboard from March 2013 to November 2013 in the area for multiyear sea ice north of Greenland and Canada. Since this is unlikely, it gives rise to the assumption that applying different retracker thresholds depending...

  3. Holocene relative sea level variations at the spit system Feddet (Denmark) resolved by ground-penetrating radar and geomorphological data

    DEFF Research Database (Denmark)

    Hede, Mikkel Ulfeldt; Bendixen, Mette; Clemmensen, Lars B;

    collected across beach ridge deposits from Feddet, eastern Denmark, and resolve past relative sea level with a relatively high precision. Feddet is a spit located in Faxe Bay (western part of the Baltic Sea) close to the current 0-isobase of isostatic rebound and is considered a key locality for studies...... in both the present beach face and upper shoreface deposits and in the interpreted beach face and upper shoreface GPR reflections. The break point marks the present transition from beach to upper shoreface and coincides with actual sea level within a few centimetres. Furthermore, our observations indicate...... that downlap points of deposits formed under both relatively high and low water levels are preserved and are identified in GPR reflection data. Thus, records of these sea-level markers constrain the local relative sea level history during the Holocene. Downlap points identified in GPR data across other...

  4. New method to implement digital down converter in radar system

    Institute of Scientific and Technical Information of China (English)

    Ma Zhigang; Wen Biyang; Zhou Hao; Bai Liyun

    2005-01-01

    Digital down converter (DDC) is the main part of the next generation high frequency (HF) radar. In order to realize the single chip integrations of digital receiver hardware in the next generation HF Radar, a new design for DDC by using FPGA is presented. Some important and practical applications are given in this paper, and the result can prove the validity. Because we can adjust the parameters freely according to our need, the DDC system can be adapted to the next generation HF radar system.

  5. The accuracy of using the spectral width boundary measured in off-meridional SuperDARN HF radar beams as a proxy for the open-closed field line boundary

    Science.gov (United States)

    Chisham, G.; Freeman, M. P.; Sotirelis, T.; Greenwald, R. A.

    2005-10-01

    Determining reliable proxies for the ionospheric signature of the open-closed field line boundary (OCB) is crucial for making accurate measurements of magnetic reconnection. This study compares the latitudes of spectral width boundaries (SWBs) measured by different beams of the Goose Bay radar of the Super Dual Auroral Radar Network (SuperDARN), with the latitudes of OCBs determined using the low-altitude Defense Meteorological Satellite Program (DMSP) spacecraft, in order to determine whether the accuracy of the SWB as a proxy for the ionospheric projection of the OCB depends on the line-of-sight direction of the radar beam. The latitudes of SWBs and OCBs were identified using automated algorithms applied to 5 years (1997 2001) of data measured in the 1000 1400 magnetic local time (MLT) range. Six different Goose Bay radar beams were used, ranging from those aligned in the geomagnetic meridional direction to those aligned in an almost zonal direction. The results show that the SWB is a good proxy for the OCB in near-meridionally-aligned beams but becomes progressively more unreliable for beams greater than 4 beams away from the meridional direction. We propose that SWBs are identified at latitudes lower than the OCB in the off-meridional beams due to the presence of high spectral width values that result from changes in the orientation of the beams with respect to the gradient in the large-scale ionospheric convection pattern. Keywords. Ionosphere (Instruments and techniques; Plasma convection) Magnetospheric physics (Magnetopause, cusp and boundary layers)

  6. ExtraHF survey

    DEFF Research Database (Denmark)

    Piepoli, Massimo F; Binno, Simone; Corrà, Ugo

    2015-01-01

    AIMS: In heart failure (HF), exercise training programmes (ETPs) are a well-recognized intervention to improve symptoms, but are still poorly implemented. The Heart Failure Association promoted a survey to investigate whether and how cardiac centres in Europe are using ETPs in their HF patients...... of evidence on safety or benefit was cited. When implemented, an ETP was proposed to all HF patients in only 55% of the centres, with restriction according to severity or aetiology. CONCLUSIONS: With respect to previous surveys, there is evidence of increased availability of ETPs in HF in Europe, although too...

  7. Monitoring of sinkholes and subsidence affecting the Jordanian coast of the Dead Sea through Synthetic Aperture Radar data and last generation Sentinel-1 data

    Science.gov (United States)

    Tessari, Giulia; Riccardi, Paolo; Lecci, Daniele; Pasquali, Paolo; Floris, Mario

    2017-04-01

    Since the mid-1980s the coast of the Dead Sea is affected by sinkholes occurring over and around the emerged mud and salt flats. Strong subsidence and landslides also affect some segments of the coast. Nowadays, several thousands of sinkholes attest that the degradation of the Dead Sea coast is worsening. Furthermore, soil deformations are interesting the main streets running along both the Israeli and Jordanian sides of the Dead Sea. These hazards are due to the dramatic dropping of the Dead Sea level, characterized by an increasing rate from about 60 cm/yr in the 1970s up to 1 m/yr in the 2000s, which provokes a lowering of the fresh-saline groundwater interface, replacing the hypersaline groundwater with fresh water and causing a consequent erosion of the subsurface salt layers. Subsidence, sinkholes, river erosion and landslides damage bridges, roads, dikes, houses, factories worsening this ongoing disaster. One of the most emblematic effects is the catastrophic collapse of a 12-km newly constructed dyke, located on the Lisan Peninsula (Jordan), occurred in 2000. Differential Interferometric Synthetic Aperture Radar (DInSAR) techniques and Advanced stacking DInSAR techniques (A-DInSAR) were applied to investigate sinkholes and subsidence affecting the Jordanian coast of the Dead Sea. The use of SAR data already proof to be efficient on the risk management of the area, allowing to identify a vulnerable portion of an Israeli highway, averting a possible collapse. Deformation analysis has been focused on the Ghor Al Haditha area and Lisan peninsula, located in the South-Eastern part of the lake coast. The availability of a huge database of SAR data, since the beginning of the 90s, allowed to observe the evolution of the displacements which are damaging this area. Furthermore, last generation Sentinel-1 data, acquired by the ESA mission, were processed to obtain information about the recent evolution of the subsidence and sinkholes affecting the study area, from

  8. A wave energy resource assessment in the China's seas based on multi-satellite merged radar altimeter data

    Institute of Scientific and Technical Information of China (English)

    WAN Yong; ZHANG Jie; MENG Junmin; WANG Jing

    2015-01-01

    Wave energy resources are abundant in both offshore and nearshore areas of the China's seas. A reliable assessment of the wave energy resources must be performed before they can be exploited. First, for a water depth in offshore waters of China, a parameterized wave power density model that considers the effects of the water depth is introduced to improve the calculating accuracy of the wave power density. Second, wave heights and wind speeds on the surface of the China's seas are retrieved from an AVISO multi-satellite altim-eter data set for the period from 2009 to 2013. Three mean wave period inversion models are developed and used to calculate the wave energy period. Third, a practical application value for developing the wave energy is analyzed based on buoy data. Finally, the wave power density is then calculated using the wave field data. Using the distribution of wave power density, the energy level frequency, the time variability indexes, the to-tal wave energy and the distribution of total wave energy density according to a wave state, the offshore wave energy in the China's seas is assessed. The results show that the areas of abundant and stable wave energy are primarily located in the north-central part of the South China Sea, the Luzon Strait, southeast of Taiwan in the China's seas; the wave power density values in these areas are approximately 14.0–18.5 kW/m. The wave energy in the China’s seas presents obvious seasonal variations and optimal seasons for a wave energy utilization are in winter and autumn. Except for very coastal waters, in other sea areas in the China's seas, the energy is primarily from the wave state with 0.5 m≤Hs≤4 m, 4 s≤Te≤10 s whereHs is a significant wave height andTe is an energy period; within this wave state, the wave energy accounts for 80% above of the total wave energy. This characteristic is advantageous to designing wave energy convertors (WECs). The practical application value of the wave energy is higher

  9. Science requirements for free-flying imaging radar (FIREX) experiment for sea ice, renewable resources, nonrenewable resources and oceanography

    Science.gov (United States)

    Carsey, F.

    1982-01-01

    A future bilateral SAR program was studied. The requirements supporting a SAR mission posed by science and operations in sea-ice-covered waters, oceanography, renewable resources, and nonrenewable resources are addressed. The instrument, mission, and program parameters were discussed. Research investigations supporting a SAR flight and the subsequent overall mission requirements and tradeoffs are summarized.

  10. The Precision Expandable Radar Calibration Sphere (PERCS) With Applications for Laser Imaging and Ranging

    Science.gov (United States)

    2008-09-01

    HF facilities such as HAARP in Alaska, EISCAT in Norway, and Arecibo in Puerto Rico; (3) the chain of high latitude SuperDARN radars used for auroral...DF arrays, ground HF transmitters such as the Navy relocatable over the horizon radar (ROTHR) and the Air Force/Navy HAARP system would be employed...United States and Australia; (2) high power HF facilities such as HAARP in Alaska, EISCAT in Norway, and Arecibo in Puerto Rico; (3) the chain of high

  11. Effect of High-Frequency Sea Waves on Wave Period Retrieval from Radar Altimeter and Buoy Data

    Directory of Open Access Journals (Sweden)

    Xifeng Wang

    2016-09-01

    Full Text Available Wave periods estimated from satellite altimetry data behave differently from those calculated from buoy data, especially in low-wind conditions. In this paper, the geometric mean wave period T a is calculated from buoy data, rather than the commonly used zero-crossing wave period T z . The geometric mean wave period uses the fourth moment of the wave frequency spectrum and is related to the mean-square slope of the sea surface measured using altimeters. The values of T a obtained from buoys and altimeters agree well (root mean square difference: 0.2 s only when the contribution of high-frequency sea waves is estimated by a wavenumber spectral model to complement the buoy data, because a buoy cannot obtain data from waves having wavelengths that are shorter than the characteristic dimension of the buoy.

  12. Generation of ionospheric ducts by the HAARP HF heater

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, J A; Pradipta, R; Burton, L M; Labno, A; Lee, M C [Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Watkins, B J; Fallen, C [University of Alaska Fairbanks, Fairbanks, AK 99775 (United States); Kuo, S P [New York University, Brooklyn, NY 11201 (United States); Burke, W J [Air Force Research Laboratory, Hanscom AFB, MA 01731 (United States); Mabius, D; See, B Z, E-mail: mclee@mit.edu [Boston University, Boston, MA 02215 (United States)

    2010-12-15

    We report an investigation of ionospheric ducts having the shape of large plasma sheets, generated by vertically transmitted HAARP HF heater waves in several experiments conducted in Gakona, Alaska. Theory predicts that O-mode heater wave-created ionospheric ducts form parallel-plate waveguides within the meridional plane, and those generated by the X-mode heater waves are orthogonal to the meridional plane. Our theoretical prediction is supported by measurements of ionosonde data (namely ionograms), range-time-intensity (RTI) plots of UHF and HF backscatter radars, as well as magnetometer data analyses. When these plasma sheets experienced ExB drifts, they were intercepted by the HAARP UHF radar and seen as slanted stripes in the RTI plots. This striking feature was also observed in our earlier experiments using the Arecibo UHF radar.

  13. Quantum radar

    CERN Document Server

    Lanzagorta, Marco

    2011-01-01

    This book offers a concise review of quantum radar theory. Our approach is pedagogical, making emphasis on the physics behind the operation of a hypothetical quantum radar. We concentrate our discussion on the two major models proposed to date: interferometric quantum radar and quantum illumination. In addition, this book offers some new results, including an analytical study of quantum interferometry in the X-band radar region with a variety of atmospheric conditions, a derivation of a quantum radar equation, and a discussion of quantum radar jamming.This book assumes the reader is familiar w

  14. Ground-Based Midcourse Defense (GMD) Sea-Based X-Band Radar (SBX) Placement and Operation, Adak, Alaska

    Science.gov (United States)

    2005-08-03

    can swim freely in the ocean and includes fish, squids, and marine mammals. Most species of nektonic animals live near the sea surface, where food is...living in rural areas of Alaska are partially or wholly dependent on the harvesting of natural resources for food and other living necessities. To...emissions time of up to 5 hours per day. The main beam would be GMO SBX Placement and Operation at Adak, Alaska EA 4-11 constantly moving and would

  15. Synchro Controller of Radar on FPGA

    Institute of Scientific and Technical Information of China (English)

    JiangTie-zhen; ShiZhen-hua; WuShi-cai

    2003-01-01

    This paper mainly represents the realization of synchro controller based on the programmable logic devices FPGA by request of HF ground wave radar synchro controller under the instance of making the best of the virtues of FPGA.This design introduces the data communication between PC and synchro controller by I2C Bus, which can carry the synchronous signals' parameters to RAM of synchro controller,then according to the theory that the result of comparing counter value with signals' parameters is the needed wave,we produce all waves HF ground wave radar needs, moreover all waves are produced timesharing in order to save resources.

  16. Synchro Controller of Radar on FPGA

    Institute of Scientific and Technical Information of China (English)

    Jiang Tie-zhen; Shi Zhen-huat; Wu Shi-cai

    2003-01-01

    This paper mainly represents the realization of synchro controller based on the programmable logic devices FPGA by request of HF ground wave radar synchro controller under the instance of making the best of the virtues of FPGA.This design introduces the data communication between PC and synchro controller by I2C Bus, which can carry the syn-chronous signals' parameters to RAM of synchro controller,then according to the theory that the result of comparing counter value with signals' parameters is the needed wave,we produce all waves HF ground wave radar needs, moreover all waves are produced time-sharing in order to save re-sources.

  17. 基于SEA的雷达组网探测能力评估%Radar Netting Detection Capability Evaluation Based on SEA

    Institute of Scientific and Technical Information of China (English)

    杨龙坡; 熊家军

    2011-01-01

    对空中目标的探测能力是评估雷达组网作战效能的一项重要的基础性指标,为了客观评估雷达组网的探测能力,提出了一种基于SEA的评估方法,建立了评估的性能量度,构建了系统映射和使命映射的数学模型,并进行了仿真计算.仿真结果表明了该方法的可行性和有效性.%The detection capability of radar netting is the fundamental index to evaluate its operational effectiveness. In order to evaluate the detection capability objectively, a method based on system effectiveness analysis ( SEA) is proposed. The measure of performance, the mathematical model of the system mapping and the mission mapping are built. Simulation result indicates the feasibility and validity of the method.

  18. Radar Chart

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Radar Chart collection is an archived product of summarized radar data. The geographic coverage is the 48 contiguous states of the United States. These hourly...

  19. In Pursuit of Nearshore Wave Characteristics- Implementation and Validation of a Shallow Water Correction for High Frequency Radars along the New Jersey Coast

    Science.gov (United States)

    Livermont, E. A.

    2014-12-01

    Within the U.S., coastal ocean current mapping with HF radar has matured to the point where it is now considered an essential component of regional ocean observing systems. A Mid-Atlantic HF radar network now provides high-resolution coverage within five localized networks, which are linked together to cover the full range of the Mid-Atlantic coast. While the primary focus of these networks has been on offshore current mapping observations, a long-term objective has been to develop and evaluate nearshore waves and currents. Of particular interest is the height of ocean waves that play a crucial role in engineering projects, ship navigation and design, vessel traffic control as well as shoreline protection, beach erosion, and mitigation of oil spills and ocean pollution. The radars owned by Rutgers University cover the coastline of New Jersey at multiple frequencies from 4.5 to 25 MHz. Their echoes contain information on both currents and waves from deep water up into the shallow coastal zone, providing an excellent archive for this study. Radar sea-echo spectra consist of dominant first-order peaks surrounded with lower-energy second-order structures. Present analysis methods assume that the waves do not interact with the ocean floor. The assumption of deep water is often invalid close to the coast and for broad continental shelves, and is particularly inadequate to describe the second-order sea-echo used to give information on ocean waves. Additionally, second-order echo is often only visible above the noise floor at close ranges. In this paper, a shallow water spectral theory is implemented at four locations on the New Jersey coast- Strathmere, Wildwood, Brant Beach, and Sea Bright. The corrected wave characteristics extracted from the HF radars were then compared to several in situ wave measurements. The first three sites—Strathmere, Wildwood and Brant Beach—were validated against two long-term (1999-2007) wave gauges deployed by Stevens Institute of

  20. First 100 ms of HF modification at Tromso, Norway

    Science.gov (United States)

    Djuth, F. T.; Isham, B.; Rietveld, M. T.; Hagfors, T.; La Hoz, C.

    Experiments were performed with the high-power high-frequency HF facility at Troms o Norway to test theoretical predictions for the excitation of ion and Langmuir oscillations in the ionosphere The principal diagnostic of wave-plasma interactions was the VHF radar at the European Incoherent Scatter EISCAT facility High resolution radar techniques were used to monitor the temporal development of the ion and Langmuir oscillations HF pulses 100 ms in duration were periodically transmitted into a smooth background F region plasma Measurements of the radar backscatter spectra show that all key spectral features predicted by strong Langmuir turbulence SLT theory modified Zakharov model are simultaneously present in the plasma and that their evolution is in agreement with theoretical expectations However several new features have been observed that cannot be anticipated by current theory because of limitations in the electric field strength within the simulations The experimental results reinforce the notion that new theoretical developments are needed to accommodate the large HF electric fields produced at Troms o and HAARP Gakona Alaska and to treat the electron acceleration process in a self-consistent fashion The F region response to two HF effective radiated power levels sim 58 MW and sim 125 MW was investigated at Troms o These ERP values include absorptive losses resulting from the sunlit D region In general the results at 58 MW ERP and 125 MW ERP are consistent with many of the SLT

  1. Radar Fundamentals, Presentation

    OpenAIRE

    Jenn, David

    2008-01-01

    Topics include: introduction, radar functions, antennas basics, radar range equation, system parameters, electromagnetic waves, scattering mechanisms, radar cross section and stealth, and sample radar systems.

  2. Radar Fundamentals, Presentation

    OpenAIRE

    Jenn, David

    2008-01-01

    Topics include: introduction, radar functions, antennas basics, radar range equation, system parameters, electromagnetic waves, scattering mechanisms, radar cross section and stealth, and sample radar systems.

  3. Radar equations for modern radar

    CERN Document Server

    Barton, David K

    2012-01-01

    Based on the classic Radar Range-Performance Analysis from 1980, this practical volume extends that work to ensure applicability of radar equations to the design and analysis of modern radars. This unique book helps you identify what information on the radar and its environment is needed to predict detection range. Moreover, it provides equations and data to improve the accuracy of range calculations. You find detailed information on propagation effects, methods of range calculation in environments that include clutter, jamming and thermal noise, as well as loss factors that reduce radar perfo

  4. Modern Radar Techniques for Geophysical Applications: Two Examples

    Science.gov (United States)

    Arokiasamy, B. J.; Bianchi, C.; Sciacca, U.; Tutone, G.; Zirizzotti, A.; Zuccheretti, E.

    2005-01-01

    The last decade of the evolution of radar was heavily influenced by the rapid increase in the information processing capabilities. Advances in solid state radio HF devices, digital technology, computing architectures and software offered the designers to develop very efficient radars. In designing modern radars the emphasis goes towards the simplification of the system hardware, reduction of overall power, which is compensated by coding and real time signal processing techniques. Radars are commonly employed in geophysical radio soundings like probing the ionosphere; stratosphere-mesosphere measurement, weather forecast, GPR and radio-glaciology etc. In the laboratorio di Geofisica Ambientale of the Istituto Nazionale di Geofisica e Vulcanologia (INGV), Rome, Italy, we developed two pulse compression radars. The first is a HF radar called AIS-INGV; Advanced Ionospheric Sounder designed both for the purpose of research and for routine service of the HF radio wave propagation forecast. The second is a VHF radar called GLACIORADAR, which will be substituting the high power envelope radar used by the Italian Glaciological group. This will be employed in studying the sub glacial structures of Antarctica, giving information about layering, the bed rock and sub glacial lakes if present. These are low power radars, which heavily rely on advanced hardware and powerful real time signal processing. Additional information is included in the original extended abstract.

  5. 基于K分布舰载雷达海杂波仿真方法研究%Study on Simulation Method of Ship-Borne Radar Sea Clutter Based on K Distribution

    Institute of Scientific and Technical Information of China (English)

    曹艳霞; 李国君

    2016-01-01

    海杂波的仿真对杂波环境下舰载雷达性能的研究具有重要意义。介绍了海杂波仿真的有关概念,研究了基于 K 分布海杂波的建模及实现方法,建立了一个较为准确的舰载雷达海杂波幅度分布模型和功率谱模型,最后以 Matlab 为平台给予了仿真实现,仿真数据与理论曲线吻合较好,仿真算法有效可行。结果表明,该方法可以有效地模拟舰载雷达海杂波特性,为雷达信号处理器的设计奠定了基础,该方法具有较高的估计精度和很好的工程实用性,对于雷达海杂波建模与仿真及其背景下目标检测研究具有现实意义。%Simulation of sea clutter will benefit the research on ship-borne radar performance in the clut-ter environment.The essential of simulation of the sea clutter is introduced,and the modeling and realizing methods of ship borne radar sea clutter based on K-distribution are researched.The amplitude distribution model and power spectrum model are exactly established.At last,the simulation is performed with Matlab. The simulation data tallies with the theory curve well,and the simulation algorithm is feasible.The results demonstrate that this method can simulate sea clutter of ship-borne radar effectively,and lay a foundation for designing radar signal processor.This method is of high estimation precision and perfect engineering practica-bility.This conclusion is quite reasonable and applicable in the research on target detection under sea clutter background.

  6. Modern HF Communications.

    Science.gov (United States)

    1983-05-01

    vertically directed pulRe,’ radar , measures the delay time of the reflected siqnals in the frequency ranqe 1-20 MHz. This delay time is converted to a...qensitive and sophisticated iH or UHF- radars which detect weak reflections from plasma irregularit ies. There are ooil a few such installations in operation...terms of a few measurable parameeprs, so that the raytracing through the simplified model ionosphere yields realistic signal characteristics, for

  7. Observations of HF backscatter decay rates from HAARP generated FAI

    Science.gov (United States)

    Bristow, W. A.; Hysell, D. L.

    2016-12-01

    Suitable experiments at the High-frequency Active Auroral Research Program (HAARP) facilities in Gakona, Alaska, create a region of ionospheric Field-Aligned Irregularities (FAI) that produces strong radar backscatter observed by the SuperDARN radar on Kodiak Island, Alaska. Creation of FAI in HF ionospheric modification experiments has been studied by a number of authors who have developed a rich theoretical background. The decay of the irregularities, however, has not been so widely studied yet it has the potential for providing estimates of the parameters of natural irregularity diffusion, which are difficult measure by other means. Hysell, et al. [1996] demonstrated using the decay of radar scatter above the Sura heating facility to estimate irregularity diffusion. A large database of radar backscatter from HAARP generated FAI has been collected over the years. Experiments often cycled the heater power on and off in a way that allowed estimates of the FAI decay rate. The database has been examined to extract decay time estimates and diffusion rates over a range of ionospheric conditions. This presentation will summarize the database and the estimated diffusion rates, and will discuss the potential for targeted experiments for aeronomy measurements. Hysell, D. L., M. C. Kelley, Y. M. Yampolski, V. S. Beley, A. V. Koloskov, P. V. Ponomarenko, and O. F. Tyrnov, HF radar observations of decaying artificial field aligned irregularities, J. Geophys. Res. , 101, 26,981, 1996.

  8. Observations of HF backscatter decay rates from HAARP generated FAI

    Science.gov (United States)

    Bristow, William; Hysell, David

    2016-07-01

    Suitable experiments at the High-frequency Active Auroral Research Program (HAARP) facilities in Gakona, Alaska, create a region of ionospheric Field-Aligned Irregularities (FAI) that produces strong radar backscatter observed by the SuperDARN radar on Kodiak Island, Alaska. Creation of FAI in HF ionospheric modification experiments has been studied by a number of authors who have developed a rich theoretical background. The decay of the irregularities, however, has not been so widely studied yet it has the potential for providing estimates of the parameters of natural irregularity diffusion, which are difficult measure by other means. Hysell, et al. [1996] demonstrated using the decay of radar scatter above the Sura heating facility to estimate irregularity diffusion. A large database of radar backscatter from HAARP generated FAI has been collected over the years. Experiments often cycled the heater power on and off in a way that allowed estimates of the FAI decay rate. The database has been examined to extract decay time estimates and diffusion rates over a range of ionospheric conditions. This presentation will summarize the database and the estimated diffusion rates, and will discuss the potential for targeted experiments for aeronomy measurements. Hysell, D. L., M. C. Kelley, Y. M. Yampolski, V. S. Beley, A. V. Koloskov, P. V. Ponomarenko, and O. F. Tyrnov, HF radar observations of decaying artificial field aligned irregularities, J. Geophys. Res. , 101, 26,981, 1996.

  9. Planetary Radar

    Science.gov (United States)

    Neish, Catherine D.; Carter, Lynn M.

    2015-01-01

    This chapter describes the principles of planetary radar, and the primary scientific discoveries that have been made using this technique. The chapter starts by describing the different types of radar systems and how they are used to acquire images and accurate topography of planetary surfaces and probe their subsurface structure. It then explains how these products can be used to understand the properties of the target being investigated. Several examples of discoveries made with planetary radar are then summarized, covering solar system objects from Mercury to Saturn. Finally, opportunities for future discoveries in planetary radar are outlined and discussed.

  10. Frederiksberg HF kursus

    DEFF Research Database (Denmark)

    Lindstrøm, Maria Duclos

    2008-01-01

    Notatet bygger på et interviewmateriale med dimitterede HF-kursister 3 måneder efter endt eksamen. Notatet undersøger dels, hvad der har hjulpet til at gennemføre, dels hvad der har været negativt og vanskeligt ved uddannelsen. Endvidere belyser notatet hvad kursisterne oplever at tage med fra de...

  11. Aspects of HF radio propagation

    Directory of Open Access Journals (Sweden)

    Stephane Saillant

    2009-06-01

    .

    c Development of inversion techniques enabling backscatter ionograms obtained by an HF radar to be used

    to estimate the ionospheric electron density profile. This development facilitates the operation of over the horizon

    HF radars by enhancing the frequency management aspects of the systems.

    d Various propagation prediction techniques have been tested against measurements made over the trough

    path mentioned above, and also over a long-range path between Cyprus and the UK.

    e The effect of changes in the levels of ionospheric disturbances on the operational availability at various

    data throughput rates has been examined for the trough path mentioned earlier.

    The topics covered in this paper are necessarily brief, and the reader is referred to full papers referenced


  12. Feasibility of sea ice typing with synthetic aperture radar (SAR): Merging of Landsat thematic mapper and ERS 1 SAR satellite imagery

    Science.gov (United States)

    Steffen, Konrad; Heinrichs, John

    1994-01-01

    Earth Remote-Sensing Satellite (ERS) 1 synthetic aperture radar (SAR) and Landsat thematic mapper (TM) images were acquired for the same area in the Beaufort Sea, April 16 and 18, 1992. The two image pairs were colocated to the same grid (25-m resolution), and a supervised ice type classification was performed on the TM images in order to classify ice free, nilas, gray ice, gray-white ice, thin first-year ice, medium and thick first-year ice, and old ice. Comparison of the collocated SAR pixels showed that ice-free areas can only be classified under calm wind conditions (less than 3 m/s) and for surface winds greater than 10 m/s based on the backscattering coefficient alone. This is true for pack ice regions during the cold months of the year where ice-free areas are spatially limited and where the capillary waves that cause SAR backscatter are dampened by entrained ice crystals. For nilas, two distinct backscatter classes were found at -17 dB and at -10 dB. The higher backscattering coefficient is attributed to the presence of frost flowers on light nilas. Gray and gray-white ice have a backscatter signature similar to first-year ice and therefore cannot be distinguished by SAR alone. First-year and old ice can be clearly separated based on their backscattering coefficient. The performance of the Geophysical Processor System ice classifier was tested against the Landsat derived ice products. It was found that smooth first-year ice and rough first-year ice were not significantly different in the backscatter domain. Ice concentration estimates based on ERS 1 C band SAR showed an error range of 5 to 8% for high ice concentration regions, mainly due to misclassified ice-free and smooth first-year ice areas. This error is expected to increase for areas of lower ice concentration. The combination of C band SAR and TM channels 2, 4, and 6 resulted in ice typing performance with an estimated accuracy of 90% for all seven ice classes.

  13. Illumination of the Air Environment Using Radiation of HF Broadcast Stations

    Science.gov (United States)

    Lutsenko, V. I.; Lutsenko, I. V.; Popov, I. V.

    2015-06-01

    We consider the possibility of using illumination of the HF broadcast stations for location of air objects. The relationships for estimation of the detection range are obtained and requirements for the degree of suppression of a direct signal from the broadcast station are determined. Spectral characteristics of the signals from HF broadcast stations are studied experimentally for different polarizations of the received radiation. The possibility of air object detection using the Doppler effect is shown. Theoretical estimates of the radar cross section of air objects for different polarizations of the incident radiation are given. It is found experimentally that the radar cross section is about the same for the vertical and horizontal polarizations.

  14. 微波雷达海洋回波多普勒频谱的数值仿真%Numerical Simulation of Doppler Spectrum of Sea Echo for Microwave Radar

    Institute of Scientific and Technical Information of China (English)

    陈泽宗; 金燕; 陈曦; 范林刚

    2013-01-01

    研究了微波与海面相互作用的散射机理,在Plant等人研究成果的基础上对多普勒频谱仿真模型进行改进和完善.根据Bragg散射原理、复合表面理论和线性波理论,引入不同极化机制下的NRCS,给出多普勒频谱的谱型、幅度和时域变化特征,比较分析了不同海况下的仿真结果.%An improved numerical simulation method of Doppler Spectrum of sea echo for ground-based microwave wave radar is presented based on a study of scattering mechanism of microwave with ocean surface and some research results by W.J.Plant et al.According to the theories of Bragg scattering,composite surface,linear wave,and the expressions for NRCS of different polarization types,the characteristics of Doppler spectrum is displayed in shape,amplitude and time domain,and Doppler spectra of different ocean conditions are compared and qualitatively analyzed.Accordingly,it can be concluded that the simulation results reflect actual ocean environment and accord with objective law,which provides significant theoretical model for oceanographic observation by microwave wave radar and information extraction of sea state,especially parameters of wind,wave and current.

  15. Comparison of sea-level measurements between microwave radar and subsurface pressure gauge deployed at select locations along the coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Mehra, P.; Desai, R.G.P.; Joseph, A.; VijayKumar, K.; Agarvadekar, Y.; Luis, R.; Nadaf, L.

    Sea-level data are obtained from several remote and coastal locations using absolute pressure gauges deployed at known level, known as chart datum. However, to yield correct sea-level measurements from absolute pressure measurements, it is necessary...

  16. National High Frequency Radar Network (hfrnet) and Pacific Research Efforts

    Science.gov (United States)

    Hazard, L.; Terrill, E. J.; Cook, T.; de Paolo, T.; Otero, M. P.; Rogowski, P.; Schramek, T. A.

    2016-12-01

    The U.S. High Frequency Radar Network (HFRNet) has been in operation for over ten years with representation from 31 organizations spanning academic institutions, state and local government agencies, and private organizations. HFRNet currently holds a collection from over 130 radar installations totaling over 10 million records of surface ocean velocity measurements. HFRNet is a primary example of inter-agency and inter-institutional partnerships for improving oceanographic research and operations. HF radar derived surface currents have been used in several societal applications including coastal search and rescue, oil spill response, water quality monitoring and marine navigation. Central to the operational success of the large scale network is an efficient data management, storage, access, and delivery system. The networking of surface current mapping systems is characterized by a tiered structure that extends from the individual field installations to local regional operations maintaining multiple sites and on to centralized locations aggregating data from all regions. The data system development effort focuses on building robust data communications from remote field locations (sites) for ingestion into the data system via data on-ramps (Portals or Site Aggregators) to centralized data repositories (Nodes). Centralized surface current data enables the aggregation of national surface current grids and allows for ingestion into displays, management tools, and models. The Coastal Observing Research and Development Center has been involved in international relationships and research in the Philippines, Palau, and Vietnam. CORDC extends this IT architecture of surface current mapping data systems leveraging existing developments and furthering standardization of data services for seamless integration of higher level applications. Collaborations include the Philippine Atmospheric Geophysical and Astronomical Services Administration (PAGASA), The Coral Reef Research

  17. Tsunami Detection by High-Frequency Radar Beyond the Continental Shelf

    Science.gov (United States)

    Grilli, Stéphan T.; Grosdidier, Samuel; Guérin, Charles-Antoine

    2016-12-01

    Where coastal tsunami hazard is governed by near-field sources, such as submarine mass failures or meteo-tsunamis, tsunami propagation times may be too small for a detection based on deep or shallow water buoys. To offer sufficient warning time, it has been proposed to implement early warning systems relying on high-frequency (HF) radar remote sensing, that can provide a dense spatial coverage as far offshore as 200-300 km (e.g., for Diginext Ltd.'s Stradivarius radar). Shore-based HF radars have been used to measure nearshore currents (e.g., CODAR SeaSonde® system; http://www.codar.com/), by inverting the Doppler spectral shifts, these cause on ocean waves at the Bragg frequency. Both modeling work and an analysis of radar data following the Tohoku 2011 tsunami, have shown that, given proper detection algorithms, such radars could be used to detect tsunami-induced currents and issue a warning. However, long wave physics is such that tsunami currents will only rise above noise and background currents (i.e., be at least 10-15 cm/s), and become detectable, in fairly shallow water which would limit the direct detection of tsunami currents by HF radar to nearshore areas, unless there is a very wide shallow shelf. Here, we use numerical simulations of both HF radar remote sensing and tsunami propagation to develop and validate a new type of tsunami detection algorithm that does not have these limitations. To simulate the radar backscattered signal, we develop a numerical model including second-order effects in both wind waves and radar signal, with the wave angular frequency being modulated by a time-varying surface current, combining tsunami and background currents. In each "radar cell", the model represents wind waves with random phases and amplitudes extracted from a specified (wind speed dependent) energy density frequency spectrum, and includes effects of random environmental noise and background current; phases, noise, and background current are extracted from

  18. Weather Radar Stations

    Data.gov (United States)

    Department of Homeland Security — These data represent Next-Generation Radar (NEXRAD) and Terminal Doppler Weather Radar (TDWR) weather radar stations within the US. The NEXRAD radar stations are...

  19. Modeling and simulation of the sea clutter for telemetry and control radars in Hainan launch site%海南发射场测控雷达海杂波建模与仿真

    Institute of Scientific and Technical Information of China (English)

    周敏; 蔡红维; 阮航; 龚建泽

    2015-01-01

    海南发射场雷达测控设备工作时面临着较严重的海杂波影响,为此需要建立准确的海杂波模型,研究和掌握海杂波的性质。研究了球不变随机过程法(SIRP)产生相参相关 K 分布海杂波的仿真模型;其中,采用了基于复倒谱的方法来产生相关高斯随机序列;最后,开展了仿真实验。结果表明,本方法模拟产生的海杂波在概率分布和功率谱特性上与理论值都吻合,说明该方法是准确和有效的。该方法对开展海杂波条件下测控雷达检测性能研究和杂波抑制方法研究都有重要意义。%Sea clutters impact seriously on the performance of telemetry and control radars in Hainan launch site.There-fore,it is necessary to establish a correct mathematical model to research the characteristics of the sea clutters.The sim-ulation model for generating coherent correlated K-distributed sea clutters based on SIRP is researched,and the correla-ted Gaussian series are generated by a method based on the complex cestrum technology.Finally,the coherent correlated K-distributed sea clutters are generated by computer simulations.Results show that the probability distribution and the power spectrum density of the simulated sea clutters match well with the expected theoretical results,which proves that the method is correct and valid.The proposed method will benefit researches on radar detection performance analysis and clutter suppression technologies.

  20. Pulsed inductive HF laser

    Energy Technology Data Exchange (ETDEWEB)

    Razhev, A M; Kargapol' tsev, E S [Institute of Laser Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk (Russian Federation); Churkin, D S; Demchuk, S V [Novosibirsk State University, Novosibirsk (Russian Federation)

    2016-03-31

    We report the results of experimentally investigated dependences of temporal, spectral and spatial characteristics of an inductive HF-laser generation on the pump conditions. Gas mixtures H{sub 2} – F{sub 2}(NF{sub 3} or SF6{sub 6}) and He(Ne) – H{sub 2} – F{sub 2}(NF{sub 3} or SF{sub 6}) were used as active media. The FWHM pulse duration reached 0.42 μs. This value corresponded to a pulsed power of 45 kW. For the first time, the emission spectrum of an inductive HF laser was investigated, which consisted of seven groups of bands with centres around the wavelengths of 2732, 2736, 2739, 2835, 2837, 2893 and 2913 nm. The cross section profile of the laser beam was a ring with a diameter of about 20 mm and width of about 5 mm. Parameters of laser operation in the repetitively pulsed regime were sufficiently stable. The amplitude instability of light pulses was no greater than 5% – 6%. (lasers)

  1. Bistatic radar

    CERN Document Server

    Willis, Nick

    2004-01-01

    Annotation his book is a major extension of a chapter on bistatic radar written by the author for the Radar Handbook, 2nd edition, edited by Merrill Skolnik. It provides a history of bistatic systems that points out to potential designers the applications that have worked and the dead-ends not worth pursuing. The text reviews the basic concepts and definitions, and explains the mathematical development of relationships, such as geometry, Ovals of Cassini, dynamic range, isorange and isodoppler contours, target doppler, and clutter doppler spread.Key Features * All development and analysis are

  2. HF Detecting Radar and Communication Frequency Selection System

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Real time communication (RTC) frequency selecting system is used to the maximum usable frequency (MUF) between two communication points, then finds the best frequency between 0. 85 MUF and 1.0MUF. Determination of electric wave delay is mostly introduced, and of MUF values, the form of frequencycontrolling code and relative interface circuits in the frequency selecting system are introduced in detail.

  3. The Influence of Wind on HF Radar Surface Current Forecasts

    Science.gov (United States)

    2008-12-01

    9 1. Ekman , 1905 .........................................................................................9 2. McNally, Luther and...x THIS PAGE INTENTIONALLY LEFT BLANK xi LIST OF FIGURES Figure 1. Ekman Spiral. – The angle between the wind and the surface current is 45º... Paul Jessen Terry Rago Superv. Gen. Eng. Robert Wyland I also appreciate the Oceanography and Meteorology/Oceanography students

  4. In-situ Calibration Methods for Phased Array High Frequency Radars

    Science.gov (United States)

    Flament, P. J.; Flament, M.; Chavanne, C.; Flores-vidal, X.; Rodriguez, I.; Marié, L.; Hilmer, T.

    2016-12-01

    HF radars measure currents through the Doppler-shift of electromagnetic waves Bragg-scattered by surface gravity waves. While modern clocks and digital synthesizers yield range errors negligible compared to the bandwidth-limited range resolution, azimuth calibration issues arise for beam-forming phased arrays. Sources of errors in the phases of the received waves can be internal to the radar system (phase errors of filters, cable lengths, antenna tuning) and geophysical (standing waves, propagation and refraction anomalies). They result in azimuthal biases (which can be range-dependent) and beam-forming side-lobes (which induce Doppler ambiguities). We analyze the experimental calibrations of 17 deployments of WERA HF radars, performed between 2003 and 2012 in Hawaii, the Adriatic, France, Mexico and the Philippines. Several strategies were attempted: (i) passive reception of continuous multi-frequency transmitters on GPS-tracked boats, cars, and drones; (ii) bi-static calibrations of radars in mutual view; (iii) active echoes from vessels of opportunity of unknown positions or tracked through AIS; (iv) interference of unknown remote transmitters with the chirped local oscillator. We found that: (a) for antennas deployed on the sea shore, a single-azimuth calibration is sufficient to correct phases within a typical beam-forming azimuth range; (b) after applying this azimuth-independent correction, residual pointing errors are 1-2 deg. rms; (c) for antennas deployed on irregular cliffs or hills, back from shore, systematic biases appear for some azimuths at large incidence angles, suggesting that some of the ground-wave electromagnetic energy propagates in a terrain-following mode between the sea shore and the antennas; (d) for some sites, fluctuations of 10-25 deg. in radio phase at 20-40 deg. azimuthal period, not significantly correlated among antennas, are omnipresent in calibrations along a constant-range circle, suggesting standing waves or multiple paths in

  5. Advances in Ice Penetrating Radar

    Science.gov (United States)

    Paden, J. D.

    2016-12-01

    Radars have been employed for ice remote sensing since the mid-twentieth century. The original application in radioglaciology was to obtain ice thickness: an essential parameter in ice flux calculations and boundary condition in ice flow models. Later, radars were used to estimate basal conditions and track laterally persistent features in the ice. The Center for Remote Sensing of Ice Sheet's recent hardware advances include multichannel systems and radar suites covering the usable frequency spectrum. These advances coupled with increased interest in the polar regions result in a concomitant exponential growth in data. We focus on a few results that have come from these changes. Multichannel radar systems improved clutter rejection and enabled 3D imaging. Using computer vision algorithms, we have automated the process of extracting the ice bottom surface in 3D imagery for complex topographies including narrow glacier channels where the ice surface and ice bottom merge together within the 3D images. We present results of wide swath imaging which have enabled narrow, 2-3 km wide, glacier channels to be fully imaged in a single pass. When radar data are available across the frequency spectrum, we have the ability to enhance target detection and measure frequency dependent properties. For example, we can couple HF sounder measurements in warmer ice where scattering attenuates and hides the signal of interest with VHF sounder measurements in cooler ice which have much improved resolution from a single flight line. We present examples of improved bed detection with coupled HF and VHF imagery in a temperate to cold ice transition that show the strong frequency dependence of englacial scattering. To handle the increased data rate, we developed a standard processing chain and data product for CReSIS radar systems, including legacy systems. Application specific GIS tools are an essential part and enable us to merge other data products during data analysis. By using imagery

  6. Radar detection

    CERN Document Server

    DiFranco, Julius

    2004-01-01

    This book presents a comprehensive tutorial exposition of radar detection using the methods and techniques of mathematical statistics. The material presented is as current and useful to today's engineers as when the book was first published by Prentice-Hall in 1968 and then republished by Artech House in 1980. The book is divided into six parts.

  7. HF Interference, Procedures and Tools (Interferences HF, procedures et outils)

    Science.gov (United States)

    2007-06-01

    such sources. The existing HF background noise possibly may be increased via ground wave and/or sky wave propagation. Increase of the existing HF...télécommunications filaires à large bande. Les télécommunications via le réseau électrique courant, dites PowerLine Communications (PLT ou PLC) et diverses...cumulative de nombreuses sources de même type. Le bruit de fond HF existant risque d’être augmenté par propagation de l’onde terrestre et/ou aérienne

  8. The impact of snow depth, snow density and ice density on sea ice thickness retrieval from satellite radar altimetry: results from the ESA-CCI Sea Ice ECV Project Round Robin Exercise

    DEFF Research Database (Denmark)

    Kern, S.; Khvorostovsky, K.; Skourup, H.

    2015-01-01

    sonar (ULS), and of snow depth from OIB campaigns, Advanced Microwave Scanning Radiometer (AMSR-E) and the Warren climatology (Warren et al., 1999). We compare the different data sets in spatiotemporal scales where satellite radar altimetry yields meaningful results. An inter-comparison of the snow...

  9. Integration and Validation of Avian Radars (IVAR)

    Science.gov (United States)

    2011-07-01

    elected to locate the Ra serve as the destination for streaming, storing, and redistributing data applications, including the Radar Fusion Engine (RFE...from a study location documented targets being tracked throughout a full, 360° field-of-view. Methods We elected to use the SEA AR-1 radar located...which are less than 10 m from the cart, are there to warn pedestrians of the obstruction on the sidewalk . 267 268 Figure 6-126. eBirdRad

  10. Polar Remote Sensing by CryoSat-type Radar Altimetry

    DEFF Research Database (Denmark)

    Stenseng, Lars

    observations, but the thickness and thereby the mass of the sea-ice is subject to large uncertainties. Satellite observations of the icecaps are also affected by errors in the margin zones, where the largest changes takes place. The development of a new type of radar altimeter, named the SAR altimeter....... Furthermore, a method has been developed to separate radar signals returned by ice floes from radar signals returned from the sea between the ice floes. When heights measured over ice floes and heights measured over ocean can be separated, the height by which the ice floe is above the sea surface can...

  11. Limitations of Radar Coordinates

    OpenAIRE

    Bini, Donato; Lusanna, Luca; Mashhoon, Bahram

    2004-01-01

    The construction of a radar coordinate system about the world line of an observer is discussed. Radar coordinates for a hyperbolic observer as well as a uniformly rotating observer are described in detail. The utility of the notion of radar distance and the admissibility of radar coordinates are investigated. Our results provide a critical assessment of the physical significance of radar coordinates.

  12. Marburg Hemorrhagic Fever (Marburg HF)

    Science.gov (United States)

    ... CDC Cancel Submit Search The CDC Marburg hemorrhagic fever (Marburg HF) Note: Javascript is disabled or is ... first recognized in 1967, when outbreaks of hemorrhagic fever occurred simultaneously in laboratories in Marburg and Frankfurt, ...

  13. Ocean wave parameters and spectrum estimated from single and dual high-frequency radar systems

    Science.gov (United States)

    Hisaki, Yukiharu

    2016-09-01

    The high-frequency (HF) radar inversion algorithm for spectrum estimation (HIAS) can estimate ocean wave directional spectra from both dual and single radar. Wave data from a dual radar and two single radars are compared with in situ observations. The agreement of the wave parameters estimated from the dual radar with those from in situ observations is the best of the three. In contrast, the agreement of the wave parameters estimated from the single radar in which no Doppler spectra are observed in the cell closest to the in situ observation point is the worst among the three. Wave data from the dual radar and the two single radars are compared. The comparison of the wave heights estimated from the single and dual radars shows that the area sampled by the Doppler spectra for the single radar is more critical than the number of Doppler spectra in terms of agreement with the dual-radar-estimated wave heights. In contrast, the comparison of the wave periods demonstrates that the number of Doppler spectra observed by the single radar is more critical for agreement of the wave periods than the area of the Doppler spectra. There is a bias directed to the radar position in the single radar estimated wave direction.

  14. Estimation of past sea-level variations based on ground-penetrating radar mapping of beach-ridges - preliminary results from Feddet, Faxe Bay, eastern Denmark

    DEFF Research Database (Denmark)

    Hede, Mikkel Ulfeldt; Nielsen, Lars; Clemmensen, Lars B

    2011-01-01

    Estimates of past sea-level variations based on different methods and techniques have been presented in a range of studies, including interpretation of beach ridge characteristics. In Denmark, Holocene beach ridge plains have been formed during the last c. 7700 years, a period characterised by both...... (i.e. sea-level) at the time of deposition. Combining the variations in height of the downlaps (in meters above present mean sea-level) with optically stimulated luminescence dating techniques provides estimates of relative sealevel at specific times....... been chosen as a key-locality in this project, as it is located relatively close to the current 0-isobase of isostatic rebound. GPR reflection data have been acquired with shielded 250 MHz Sensors & software antennae along a number of profile lines across beach ridge and swale structures of the Feddet...

  15. Hf Transition Probabilities and Abundances

    CERN Document Server

    Lawler, J E; Labby, Z E; Sneden, C; Cowan, J J; Ivans, I I

    2006-01-01

    Radiative lifetimes from laser-induced fluorescence measurements, accurate to about +/- 5 percent, are reported for 41 odd-parity levels of Hf II. The lifetimes are combined with branching fractions measured using Fourier transform spectrometry to determine transition probabilities for 150 lines of Hf II. Approximately half of these new transition probabilities overlap with recent independent measurements using a similar approach. The two sets of measurements are found to be in good agreement for measurements in common. Our new laboratory data are applied to refine the hafnium photospheric solar abundance and to determine hafnium abundances in 10 metal-poor giant stars with enhanced r-process abundances. For the Sun we derive log epsilon (Hf) = 0.88 +/- 0.08 from four lines; the uncertainty is dominated by the weakness of the lines and their blending by other spectral features. Within the uncertainties of our analysis, the r-process-rich stars possess constant Hf/La and Hf/Eu abundance ratios, log epsilon (Hf...

  16. RADAR PPI Scope Overlay

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — RADAR PPI Scope Overlays are used to position a RADAR image over a station at the correct resolution. The archive maintains several different RADAR resolution types,...

  17. Advances in bistatic radar

    CERN Document Server

    Willis, Nick

    2007-01-01

    Advances in Bistatic Radar updates and extends bistatic and multistatic radar developments since publication of Willis' Bistatic Radar in 1991. New and recently declassified military applications are documented. Civil applications are detailed including commercial and scientific systems. Leading radar engineers provide expertise to each of these applications. Advances in Bistatic Radar consists of two major sections: Bistatic/Multistatic Radar Systems and Bistatic Clutter and Signal Processing. Starting with a history update, the first section documents the early and now declassified military

  18. Moving Target Indication for Multi-channel Airborne Radar Systems

    NARCIS (Netherlands)

    Lidicky, L.

    2010-01-01

    Moving target indication (MTI) using radar is of great interest in civil and military applications. Its uses include airborne or space-borne surveillance of ground moving vehicles (cars, trains) or ships at sea, for instance. Airborne (space-borne) radar offers several advantages when compared to op

  19. Research at the Stanford Center for Radar Astronomy

    Science.gov (United States)

    1972-01-01

    The research is reported in the applications of radar and radio techniques to the study of the solar system, and to space programs. Experiments reported include: bistatic-radar on Apollo missions, development of an unmanned geophysical observatory in the Antartic, Bragg scattering probes of sea states, characteristics of dense solar wind disturbances, and satellite communications for Alaska.

  20. Moving Target Indication for Multi-channel Airborne Radar Systems

    NARCIS (Netherlands)

    Lidicky, L.

    2010-01-01

    Moving target indication (MTI) using radar is of great interest in civil and military applications. Its uses include airborne or space-borne surveillance of ground moving vehicles (cars, trains) or ships at sea, for instance. Airborne (space-borne) radar offers several advantages when compared to op

  1. External calibration technique of millimeter-wave cloud radar

    Science.gov (United States)

    Wen, Tao; Zhao, Zeng-Liang; Yao, Zhi-Gang; Han, Zhi-Gang; Guo, Lin-Da

    2016-10-01

    The millimeter-wave cloud radar can provide a large number of fine and reliable information for the inversion of cloud macro and micro parameters. A key link of using the millimeter-wave cloud radar to detect the cloud is that the radar must be calibrated. Due to the precision components and severe environment of millimeter-wave cloud radar, subtle changes may take place in the operation process of cloud radar, unless the cloud radar is calibrated regularly. Although the calibration system inside the cloud radar can track and monitor the main working parameters and correct the detection results, it fails to consider the characteristics of the antenna and the mutual influence among different components of cloud radar. Therefore, the external calibration for cloud radar system is very important. Combined with the actual situation of cloud radar under domestic onboard platform, this paper builds a complete external calibration technique process of cloud radar based on the calm sea, providing the theoretical support for the external calibration experiments of the airborne and even satellite-borne millimeter-wave cloud radar developed by our country.

  2. Radar-to-Radar Interference Suppression for Distributed Radar Sensor Networks

    OpenAIRE

    Wen-Qin Wang; Huaizong Shao

    2014-01-01

    Radar sensor networks, including bi- and multi-static radars, provide several operational advantages, like reduced vulnerability, good system flexibility and an increased radar cross-section. However, radar-to-radar interference suppression is a major problem in distributed radar sensor networks. In this paper, we present a cross-matched filtering-based radar-to-radar interference suppression algorithm. This algorithm first uses an iterative filtering algorithm to suppress the radar-to-radar ...

  3. Hardware in the loop testing and evaluation of seaborne search radars

    CSIR Research Space (South Africa)

    Strydom, JJ

    2012-09-01

    Full Text Available as the texture component of sea clutter. The shorter wavelengths are responsible for the speckle component of sea clutter. The comparative figures below show the “spikiness” of the sea clutter measured during low and high sea state conditions using an X... test environment is also more repeatable, thus allowing several radars to be evaluated under very similar conditions. DRFM based test environments enable the characterisation of a radar system’s target detection, target tracking...

  4. Doppler characteristics of sea clutter.

    Energy Technology Data Exchange (ETDEWEB)

    Raynal, Ann Marie; Doerry, Armin Walter

    2010-06-01

    Doppler radars can distinguish targets from clutter if the target's velocity along the radar line of sight is beyond that of the clutter. Some targets of interest may have a Doppler shift similar to that of clutter. The nature of sea clutter is different in the clutter and exo-clutter regions. This behavior requires special consideration regarding where a radar can expect to find sea-clutter returns in Doppler space and what detection algorithms are most appropriate to help mitigate false alarms and increase probability of detection of a target. This paper studies the existing state-of-the-art in the understanding of Doppler characteristics of sea clutter and scattering from the ocean to better understand the design and performance choices of a radar in differentiating targets from clutter under prevailing sea conditions.

  5. Phenomena induced by powerful HF pumping towards magnetic zenith with a frequency near the F-region critical frequency and the third electron gyro harmonic frequency

    Directory of Open Access Journals (Sweden)

    N. F. Blagoveshchenskaya

    2009-01-01

    Full Text Available Multi-instrument observational data from an experiment on 13 October 2006 at the EISCAT/HEATING facility at Tromsø, Norway are analysed. The experiment was carried out in the evening hours when the electron density in the F-region dropped, and the HF pump frequency fH was near and then above the critical frequency of the F2 layer. The distinctive feature of this experiment is that the pump frequency was just below the third electron gyro harmonic frequency, while both the HF pump beam and UHF radar beam were directed towards the magnetic zenith (MZ. The HF pump-induced phenomena were diagnosed with several instruments: the bi-static HF radio scatter on the London-Tromsø-St. Petersburg path, the CUTLASS radar in Hankasalmi (Finland, the European Incoherent Scatter (EISCAT UHF radar at Tromsø and the Tromsø ionosonde (dynasonde. The results show thermal electron excitation of the HF-induced striations seen simultaneously from HF bi-static scatter and CUTLASS radar observations, accompanied by increases of electron temperature when the heater frequency was near and then above the critical frequency of the F2 layer by up to 0.4 MHz. An increase of the electron density up to 25% accompanied by strong HF-induced electron heating was observed, only when the heater frequency was near the critical frequency and just below the third electron gyro harmonic frequency. It is concluded that the combined effect of upper hybrid resonance and gyro resonance at the same altitude gives rise to strong electron heating, the excitation of striations, HF ray trapping and extension of HF waves to altitudes where they can excite Langmuir turbulence and fluxes of electrons accelerated to energies that produce ionization.

  6. Ocean wave imaging mechanism by imaging radar

    Institute of Scientific and Technical Information of China (English)

    何宜军

    2000-01-01

    Analytical representations of the high frequency spectra of ocean wave and its variation due to the variation of ocean surface current are derived from the wave-number spectrum balance equation. The ocean surface imaging formulation of real aperture radar (RAR) is given using electromagnetic wave backscattering theory of ocean surface and the modulations of ocean surface winds, currents and their variations to RAR are described. A general representation of the phase modulation induced by the ocean surface motion is derived according to standard synthetic aperture radar (SAR) imaging theory. The detectability of ocean current and sea bottom topography by imaging radar is discussed. The results constitute the theoretical basis for detecting ocean wave fields, ocean surface winds, ocean surface current fields, sea bottom topography, internal wave and so on.

  7. Observation and theory of the radar aurora

    Energy Technology Data Exchange (ETDEWEB)

    Sahr, J.D.

    1990-01-01

    Plasma density irregularities occurring near the Aurora Borealis cause scattering of HF, VHF, and UHF radio waves. Analysis of the resulting radar signal provides great detail about the spatial and temporal characteristics of these auroral E region irregularities. Observations are presented of the radar aurora from recent campaigns in northern Sweden. After reviewing the basic theory and observations of auroral electrojet irregularities, a simple nonlinear fluid theory of electrojet ion-acoustic waves is introduced, and reduced to a form of the three-wave interaction equations. This theory provides a simple mechanism for excitation of linearly stable waves at large aspect and flow angles, as well as a prediction of the power spectra that a coherent scatter radar should observe. In addition, this theory may be able to account for type 3 waves without resorting to ion gyro modes, such as the electrostatic ion-cyclotron wave. During the course of the research a simple new radar transmitting mode and signal processing algorithm was generated which very simply solves a frequency aliasing problem that often occurs in CUPRI auroral radar studies. Several new radar data analysis routines were developed, including the principally cross-beam image and scatter plots of the second versus first moments of the power spectrum of the irregularities. Analysis of vertical interferometer data shows that type 3 waves originate at ordinary electrojet altitudes, not in the upper E region, from which it is concluded that the electrostatic ion-cyclotron mode does not generate type 3 waves. The measured height of type 3 waves and other spectral analyses provide support for the pure ion-acoustic theory of type 3 waves. Suggestions are offered for hardware improvements to the CUPRI radar, new experiments to test new and existing theories.

  8. Ionosonde Studies of Field-Aligned Irregularities during High-Power HF Heating at Arecibo,

    Science.gov (United States)

    1988-02-01

    September 1981 ionospheric HF heating campaign at Arecibo have been simulated using simplified ionospheric models -’ and analytic raytracing techniques. The...R given by R = ((h )2 -(V ))/6B) NR h6B is the radar range of the oblique echoes and h ERT the virtual height of the overhead ionization measured at...However, the conditions of the Arecibo experiment are such that various simplifications can be made, including the adoption of analytic raytracing

  9. Adaptive radar resource management

    CERN Document Server

    Moo, Peter

    2015-01-01

    Radar Resource Management (RRM) is vital for optimizing the performance of modern phased array radars, which are the primary sensor for aircraft, ships, and land platforms. Adaptive Radar Resource Management gives an introduction to radar resource management (RRM), presenting a clear overview of different approaches and techniques, making it very suitable for radar practitioners and researchers in industry and universities. Coverage includes: RRM's role in optimizing the performance of modern phased array radars The advantages of adaptivity in implementing RRMThe role that modelling and

  10. Radar and ARPA manual

    CERN Document Server

    Bole, A G

    2013-01-01

    Radar and ARPA Manual focuses on the theoretical and practical aspects of electronic navigation. The manual first discusses basic radar principles, including principles of range and bearing measurements and picture orientation and presentation. The text then looks at the operational principles of radar systems. Function of units; aerial, receiver, and display principles; transmitter principles; and sitting of units on board ships are discussed. The book also describes target detection, Automatic Radar Plotting Aids (ARPA), and operational controls of radar systems, and then discusses radar plo

  11. Surface Contour Radar (SCR) contributions to FASINEX

    Science.gov (United States)

    Walsh, E. J.

    1988-01-01

    The SCR was asked to participate in the Frontal Air-Sea Interaction Experiment (FASINEX) to provide directional wave spectra. The NASA P-3 carrying the SCR, the Radar Ocean Wave Spectrometer, and the Airborne Oceanographic Lidar was one of five aircrafts and two ocean research ships participating in this coordinated study of the air sea interaction in the vicinity of a sea surface temperature front near 28 deg N, 70 deg W. Analysis of data from the February 1986 experiment is still ongoing, but results already submitted for publication strengthen the hypothesis that off-nadir radar backscatter is closely correlated to wind stress. The SCR provided valuable information on the directional wave spectrum and its spatial variation.

  12. Environmentally friendly HF (DF) lasers

    Science.gov (United States)

    Apollonov, V. V.

    2016-08-01

    Dedicated to the 100th anniversary of the birth of Academician A M Prokhorov, this paper reviews the physics of self-sustained volume discharge without preionization—self-initiated volume discharge (SIVD)—in the working mixtures of non-chain hydrofluoride HF (deuterofluoride (DF)) lasers. The dynamics of SIVD in discharge gaps with different geometries is thoroughly described. The mechanisms for the restriction of current density in a diffuse channel in electric discharges in SF6 and SF6 based mixtures (which determines whether SIVD is possible) are proposed and analyzed using simple models. The most probable mechanisms are the electron impact dissociation of SF6 and other mixture components, electron-ion recombination and electron attachment to vibrationally excited SF6 molecules. Starting from a comparative analysis of the rate coefficients of these processes, it is shown that electron-ion recombination is capable of compensating for electron detachment from negative ions via electron impact. It is also established that SIVD is not only observed in SF6, but also in other strongly electronegative gases. The factors that determine the uniformity of the active medium in non-chain HF (DF) lasers are analyzed. Some special features of non-chain HF (DF) lasers with different apertures operating are carefully examined. Consideration is given to the problem of increasing the aperture and discharge volume of non-chain HF (DF) lasers. Based on our experimental results, the possibility of increasing the energy of such lasers to ~1 kJ and above is shown.

  13. Principles of modern radar systems

    CERN Document Server

    Carpentier, Michel H

    1988-01-01

    Introduction to random functions ; signal and noise : the ideal receiver ; performance of radar systems equipped with ideal receivers ; analysis of the operating principles of some types of radar ; behavior of real targets, fluctuation of targets ; angle measurement using radar ; data processing of radar information, radar coverage ; applications to electronic scanning antennas to radar ; introduction to Hilbert spaces.

  14. Passive MIMO Radar Detection

    Science.gov (United States)

    2013-09-01

    cumulative distribution function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 CORA COvert RAdar...PaRaDe), developed by the Insti- tute of Electronic Systems at the Warsaw University of Technology [59, 60]; COvert RAdar ( CORA ), developed by the German

  15. Weather Radar Impact Zones

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — These data represent an inventory of the national impacts of wind turbine interference with NEXRAD radar stations. This inventory was developed by the NOAA Radar...

  16. Application of in situ observations, high frequency radars, and ocean color, to study suspended matter, particulate carbon, and dissolved organic carbon fluxes in coastal waters of the Barents Sea - the NORDFLUX project

    Science.gov (United States)

    Stramska, Malgorzata; Yngve Børsheim, Knut; Białogrodzka, Jagoda; Cieszyńska, Agata; Ficek, Dariusz; Wereszka, Marzena

    2016-04-01

    There is still a limited knowledge about suspended and dissolved matter fluxes transported from coastal regions into the open sea regions in the Arctic. The land/sea interface is environmentally important and sensitive to climate change. Important biogeochemical material entering the oceans (including carbon) passes through this interface, but too little is known about the efficiency of this transport. Our goal in the NORDFLUX program is to improve quantitative understanding of the environmental feedbacks involved in these processes through an interdisciplinary study with innovative in situ observations. Completed work includes two in situ experiments in the Norwegian fiord (Porsangerfjorden) in the summers of 2014 and 2015. Experiments used research boat for collection of water samples and in situ bio-optical data, an autonomous glider, mooring with T S sensors, and a high frequency radar system. We have used these data to derive spatial maps of water temperature, salinity, surface currents, chlorophyll fluorescence, dissolved organic matter (DOM) fluorescence, and inherent optical properties (IOPs) of the water. The interpretation of these data in terms of suspended matter concentration and composition is possible by in situ 'calibrations' using water samples from discrete hydrographic stations. Total suspended matter (TSM), particulate carbon (POC and PIC), and dissolved organic carbon (DOC) concentrations together with measured water currents will allow us to estimate reservoirs and fluxes. Concentrations and fluxes will be related to physical conditions and meteorological data. An important aspect of this project is the work on regional ocean color algorithms. Global ocean color (OC) algorithms currently used by NASA do not perform sufficiently well in coastal Case 2 waters. Our data sets will allow us to derive such local algorithms. We will then use these algorithms for interpretation of OC data in terms of TSM concentrations and composition and DOC. After

  17. Digital LPI Radar Detector

    OpenAIRE

    Ong, Peng Ghee; Teng, Haw Kiad

    2001-01-01

    Approved for public release; distribution is unlimited The function of a Low Probability ofIntercept (LPI) radar is to prevent its interception by an Electronic Support (ES) receiver. This objective is generally achieved through the use of a radar waveform that is mismatched to those waveforms for which an ES receiver is tuned. This allows the radar to achieve a processing gain, with respect to the ES receiver, that is equal to the time-bandwidth product ofthe radar waveform. This...

  18. Network radar countermeasure systems integrating radar and radar countermeasures

    CERN Document Server

    Jiang, Qiuxi

    2016-01-01

    This is the very first book to present the network radar countermeasure system. It explains in detail the systematic concept of combining radar and radar countermeasures from the perspective of the information acquisition of target location, the optimization of the reconnaissance and detection, the integrated attack of the signals and facilities, and technological and legal developments concerning the networked system. It achieves the integration of the initiative and passivity, detection and jamming. The book explains how the system locates targets, completes target identification, tracks targets and compiles the data.

  19. Deep Stochastic Radar Models

    OpenAIRE

    Wheeler, Tim Allan; Holder, Martin; Winner, Hermann; Kochenderfer, Mykel

    2017-01-01

    Accurate simulation and validation of advanced driver assistance systems requires accurate sensor models. Modeling automotive radar is complicated by effects such as multipath reflections, interference, reflective surfaces, discrete cells, and attenuation. Detailed radar simulations based on physical principles exist but are computationally intractable for realistic automotive scenes. This paper describes a methodology for the construction of stochastic automotive radar models based on deep l...

  20. Radar: Human Safety Net

    Science.gov (United States)

    Ritz, John M.

    2016-01-01

    Radar is a technology that can be used to detect distant objects not visible to the human eye. A predecessor of radar, called the telemobiloscope, was first used to detect ships in the fog in 1904 off the German coast. Many scientists have worked on the development and refinement of radar (Hertz with electromagnetic waves; Popov with determining…

  1. Radar and wind turbines; Radar en windturbines

    Energy Technology Data Exchange (ETDEWEB)

    Van Doorn, H.

    2010-03-15

    In the last years the developments of wind parks were hampered because of their possible effect on the radar for observation of air traffic. Work is currently being done on a new assessment model for wind turbines under the auspices of the steering group National Security for the military radar systems. Air traffic control Netherlands (LVNL) will look at the options for civil radars to join in. [Dutch] In de afgelopen jaren zijn windparkontwikkelingen onder meer belemmerd vanwege mogelijke effecten op radar voor de waarneming van luchtverkeer. Onder auspicien van de stuurgroep Nationale Veiligheid voor de militaire radarsystemen op land wordt gewerkt aan een nieuw beoordelingsmodel voor windturbines. De Luchtverkeersleiding Nederland (LVNL) zal bezien in hoeverre de civiele radars hierbij kunnen aansluiten.

  2. Observability of fine-scale ocean dynamics in the northwestern Mediterranean Sea

    Science.gov (United States)

    Morrow, Rosemary; Carret, Alice; Birol, Florence; Nino, Fernando; Valladeau, Guillaume; Boy, Francois; Bachelier, Celine; Zakardjian, Bruno

    2017-01-01

    Technological advances in the recent satellite altimeter missions of Jason-2, SARAL/AltiKa and CryoSat-2 have improved their signal-to-noise ratio, allowing us to observe finer-scale ocean processes with along-track data. Here, we analyse the noise levels and observable ocean scales in the northwestern Mediterranean Sea, using spectral analyses of along-track sea surface height from the three missions. Jason-2 has a higher mean noise level with strong seasonal variations, with higher noise in winter due to the rougher sea state. SARAL/AltiKa has the lowest noise, again with strong seasonal variations. CryoSat-2 is in synthetic aperture radar (SAR) mode in the Mediterranean Sea but with lower-resolution ocean corrections; its statistical noise level is moderate with little seasonal variation. These noise levels impact on the ocean scales we can observe. In winter, when the mixed layers are deepest and the submesoscale is energetic, all of the altimeter missions can observe wavelengths down to 40-50 km (individual feature diameters of 20-25 km). In summer when the submesoscales are weaker, SARAL can detect ocean scales down to 35 km wavelength, whereas the higher noise from Jason-2 and CryoSat-2 blocks the observation of scales less than 50-55 km wavelength. This statistical analysis is completed by individual case studies, where filtered along-track altimeter data are compared with co-located glider and high-frequency (HF) radar data. The glider comparisons work well for larger ocean structures, but observations of the smaller, rapidly moving dynamics are difficult to co-locate in space and time (gliders cover 200 km in a few days, altimetry in 30 s). HF radar surface currents at Toulon measure the meandering Northern Current, and their good temporal sampling shows promising results in comparison to co-located SARAL altimetric currents. Techniques to separate the geostrophic component from the wind-driven ageostrophic flow need further development in this coastal

  3. Pulse Doppler radar

    CERN Document Server

    Alabaster, Clive

    2012-01-01

    This book is a practitioner's guide to all aspects of pulse Doppler radar. It concentrates on airborne military radar systems since they are the most used, most complex, and most interesting of the pulse Doppler radars; however, ground-based and non-military systems are also included. It covers the fundamental science, signal processing, hardware issues, systems design and case studies of typical systems. It will be a useful resource for engineers of all types (hardware, software and systems), academics, post-graduate students, scientists in radar and radar electronic warfare sectors and milit

  4. Understanding radar systems

    CERN Document Server

    Kingsley, Simon

    1999-01-01

    What is radar? What systems are currently in use? How do they work? This book provides engineers and scientists with answers to these critical questions, focusing on actual radar systems in use today. It is a perfect resource for those just entering the field, or as a quick refresher for experienced practitioners. The book leads readers through the specialized language and calculations that comprise the complex world of radar engineering as seen in dozens of state-of-the-art radar systems. An easy to read, wide ranging guide to the world of modern radar systems.

  5. Polarimetric radars and polarimetric SAR data in tasks of detection and identification of marine oil pollution

    Science.gov (United States)

    Sineva, A. A.; Ivanov, A. Yu.

    2016-12-01

    Detecting and distinguishing different kinds of oil pollution, including spills of crude oil on the sea surface, is one important problem of modern remote sensing. The wide use of imaging radars is not always effective. In this review paper, the main principles and methods of polarization radar imaging and radar data processing are discussed based on present theoretical and experimental approaches and ideas. The efficiency of polarimetric methods for oil-spill detection and accurate identification on the sea surface is demonstrated as well. As is shown, modern methods of multipolarimetric radar-signal processing is a powerful means for improving oil-pollution detection and discrimination algorithms.

  6. Multidimensional radar picture

    Science.gov (United States)

    Waz, Mariusz

    2010-05-01

    In marine navigation systems, the three-dimensional (3D) visualization is often and often used. Echosonders and sonars working in hydroacustic systems can present pictures in three dimensions. Currently, vector maps also offer 3D presentation. This presentation is used in aviation and underwater navigation. In the nearest future three-dimensional presentation may be obligatory presentation in displays of navigation systems. A part of these systems work with radar and communicates with it transmitting data in a digital form. 3D presentation of radar picture require a new technology to develop. In the first step it is necessary to compile digital form of radar signal. The modern navigation radar do not present data in three-dimensional form. Progress in technology of digital signal processing make it possible to create multidimensional radar pictures. For instance, the RSC (Radar Scan Converter) - digital radar picture recording and transforming tool can be used to create new picture online. Using RSC and techniques of modern computer graphics multidimensional radar pictures can be generated. The radar pictures mentioned should be readable for ECDIS. The paper presents a method for generating multidimensional radar picture from original signal coming from radar receiver.

  7. A thirty second isomer in Hf-171

    NARCIS (Netherlands)

    Campbell, P; Billowes, J; Cochrane, ECA; Cooke, JL; Cooper, TG; Dendooven, P; Evans, DE; Grant, IS; Griffith, JAR; Honkanen, A; Huhta, M; Oinonen, M; Pearson, MR; Penttila, H; Persson, B.L.; Richardson, DS; Tungate, G; Wheeler, PD; Zybert, L; Aysto, J

    1997-01-01

    An isomer has been detected in Hf-171 with a half-life of T-1/2 = 29.5(9) s. The state was populated in the Yb-170(alpha,3n)Hf-171m reaction at a beam energy of E-alpha = 50 MeV in an on-line ion guide isotope separator. The isomeric Hf-17lm(+) beam was extracted from the ion guide, mass-analysed an

  8. Simultaneous Multi-angle Radar Observations of Langmuir Turbulence Excited by RF Ionospheric Interactions at HAARP

    Science.gov (United States)

    Sheerin, J. P.; Rayyan, N.; Watanabe, N.; Watkins, B. J.; Bristow, W. A.; Bernhardt, P. A.

    2013-10-01

    The high power HAARP HF transmitter is employed to generate and study strong Langmuir turbulence (SLT) in the interaction region of overdense ionospheric plasma. Diagnostics included the Modular UHF Ionospheric Radar (MUIR) sited at HAARP, the SuperDARN-Kodiak HF radar, and HF receivers to record stimulated electromagnetic emissions (SEE). Dependence of diagnostic signals on HAARP HF parameters, including pulselength, duty-cycle, aspect angle, and frequency were recorded. Short pulse, low duty cycle experiments demonstrate control of artificial field-aligned irregularities (AFAI) and isolation of ponderomotive effects. Among the effects observed and studied are: SLT spectra including cascade, collapse, and co-existence spectra and an outshifted plasma line under certain ionospheric conditions. High time resolution studies of the temporal evolution of the plasma line reveal the appearance of an overshoot effect on ponderomotive timescales. Bursty turbulence is observed in the collapse and cascade lines. For the first time, simultaneous multi-angle radar measurements of plasma line spectra are recorded demonstrating marked dependence on aspect angle with the strongest interaction region observed displaced southward of the HF zenith pointing angle. Numerous measurements of the outshifted plasma line are observed. Experimental results are compared to previous high latitude experiments and predictions from recent modeling efforts.

  9. The study of multilayers Fe/Hf and Ni/Hf by slow positron beam technique

    Science.gov (United States)

    Tashiro, Mutsumi; Nakajyo, Terunobu; Murashige, Yusuke; Koizumi, Tomoya; Kanazawa, Ikuzo; Komori, Fumio; Soe, We-Hyo; Yamamoto, Ryoichi; Ito, Yasuo

    1997-05-01

    The S-parameters versus the incident positron energy are measured in the Ni/Hf multilayer, thin Hf film, thin Fe film and the bilayer Fe/Hf. We have analyzed the change in vacancy-type defects in these multilayers and thin films with the deposition temperature in the MBE system.

  10. Bright prospects for radar detection of Europa's ocean

    Science.gov (United States)

    Aglyamov, Yury; Schroeder, Dustin M.; Vance, Steven D.

    2017-01-01

    The surface of Europa has been hypothesized to include an ice regolith layer from hundreds of meters to kilometers in thickness. However, contrary to previous claims, it does not present a significant obstacle to searching for Europa's ocean with radar sounding. This note corrects prior volume scattering loss analyses and expands them to includes observational and thermo-mechanical constraints on pore size and regolith depth. This provides a more physically realistic range of potential ice-regolith volume-scattering losses for radar sounding observations of Europa's ice shell in the HF and VHF frequency bands. We conclude that, for the range of physical processes and material properties observed or hypothesized for Europa, volume scattering losses are not likely to pose a major obstacle to radar penetration.

  11. Phased-array radar design application of radar fundamentals

    CERN Document Server

    Jeffrey, Thomas

    2009-01-01

    Phased-Array Radar Design is a text-reference designed for electrical engineering graduate students in colleges and universities as well as for corporate in-house training programs for radar design engineers, especially systems engineers and analysts who would like to gain hands-on, practical knowledge and skills in radar design fundamentals, advanced radar concepts, trade-offs for radar design and radar performance analysis.

  12. Long-term sea level change in the Malaysian seas from multi-mission altimetry data

    NARCIS (Netherlands)

    Din, A.H.; Omar, K.M.; Naeije, M.C.; Ses, S.

    2012-01-01

    The long-term sea level change during 1993 to 2008 was investigated in the Malaysian seas from satellite altimetry data of the TOPEX, JASON-1, ERS-1, ERS-2 and ENVISAT missions. Sea level data retrieval and reduction were carried out using the radar altimeter database system (RADS). In RADS data pro

  13. HF radiation emitted by chaotic leader processes

    Science.gov (United States)

    Mäkelä, J. S.; Edirisinghe, M.; Fernando, M.; Montaño, R.; Cooray, V.

    2007-04-01

    This paper presents direct measurements of narrowband 10 MHz HF radiation from so-called “chaotic leaders” associated with subsequent return strokes. Although the term is controversial and poorly defined, we find that more than 30% of subsequent strokes in close lightning flashes contain electric field characteristics that are best described as “chaotic”. In earlier studies, return strokes have consistently been observed to be the strongest sources of HF radiation, but the results for leader processes are less consistent. We also observe return strokes to be the main HF emitter, and the leaders before the first return stroke in a flash sequence also emit HF though somewhat less intensely. The leaders preceding subsequent strokes typically emit little or no HF radiation, whether they are dart or dart-stepped leaders. However, it was observed that the presence of a chaotic component increases the leader HF intensity dramatically Defining the HF intensity unequivocally can be problematic for processes like chaotic leaders which have a combination of continuous and impulsive phenomena. Two time-domain methods were used to measure the HF intensity, the peak energy and the RMS energy. In the frequency domain these correspond to the energy spectral density (ESD) and power spectral density (PSD), respectively. It was found that the methods are not necessarily compatible. Thus, it is suggested that to clarify future work, leader processes should be characterized by the PSD rather than the ESD.

  14. Doppler radar physiological sensing

    CERN Document Server

    Lubecke, Victor M; Droitcour, Amy D; Park, Byung-Kwon; Singh, Aditya

    2016-01-01

    Presents a comprehensive description of the theory and practical implementation of Doppler radar-based physiological monitoring. This book includes an overview of current physiological monitoring techniques and explains the fundamental technology used in remote non-contact monitoring methods. Basic radio wave propagation and radar principles are introduced along with the fundamentals of physiological motion and measurement. Specific design and implementation considerations for physiological monitoring radar systems are then discussed in detail. The authors address current research and commercial development of Doppler radar based physiological monitoring for healthcare and other applications.

  15. HfS, Hyperfine Structure Fitting Tool

    CERN Document Server

    Estalella, Robert

    2016-01-01

    HfS is a tool to fit the hyperfine structure of spectral lines, with multiple velocity components. The HfS_nh3 procedures included in HfS fit simultaneously the hyperfine structure of the NH$_3$ (J,K)= (1,1) and (2,2) transitions, and perform a standard analysis to derive $T_\\mathrm{ex}$, NH$_3$ column density, $T_\\mathrm{rot}$, and $T_\\mathrm{k}$. HfS uses a Monte Carlo approach for fitting the line parameters. Especial attention is paid to the derivation of the parameter uncertainties. HfS includes procedures that make use of parallel computing for fitting spectra from a data cube.

  16. Combined radar and telemetry system

    Energy Technology Data Exchange (ETDEWEB)

    Rodenbeck, Christopher T.; Young, Derek; Chou, Tina; Hsieh, Lung-Hwa; Conover, Kurt; Heintzleman, Richard

    2017-08-01

    A combined radar and telemetry system is described. The combined radar and telemetry system includes a processing unit that executes instructions, where the instructions define a radar waveform and a telemetry waveform. The processor outputs a digital baseband signal based upon the instructions, where the digital baseband signal is based upon the radar waveform and the telemetry waveform. A radar and telemetry circuit transmits, simultaneously, a radar signal and telemetry signal based upon the digital baseband signal.

  17. The physical basis for estimating wave-energy spectra with the radar ocean-wave spectrometer

    Science.gov (United States)

    Jackson, Frederick C.

    1987-01-01

    The derivation of the reflectivity modulation spectrum of the sea surface for near-nadir-viewing microwave radars using geometrical optics is described. The equations required for the derivation are presented. The derived reflectivity modulation spectrum provides data on the physical basis of the radar ocean-wave spectrometer measurements of ocean-wave directional spectra.

  18. Radar illusion via metamaterials

    Science.gov (United States)

    Jiang, Wei Xiang; Cui, Tie Jun

    2011-02-01

    An optical illusion is an image of a real target perceived by the eye that is deceptive or misleading due to a physiological illusion or a specific visual trick. The recently developed metamaterials provide efficient approaches to generate a perfect optical illusion. However, all existing research on metamaterial illusions has been limited to theory and numerical simulations. Here, we propose the concept of a radar illusion, which can make the electromagnetic (EM) image of a target gathered by radar look like a different target, and we realize a radar illusion device experimentally to change the radar image of a metallic target into a dielectric target with predesigned size and material parameters. It is well known that the radar signatures of metallic and dielectric objects are significantly different. However, when a metallic target is enclosed by the proposed illusion device, its EM scattering characteristics will be identical to that of a predesigned dielectric object under the illumination of radar waves. Such an illusion device will confuse the radar, and hence the real EM properties of the metallic target cannot be perceived. We designed and fabricated the radar illusion device using artificial metamaterials in the microwave frequency, and good illusion performances are observed in the experimental results.

  19. Java Radar Analysis Tool

    Science.gov (United States)

    Zaczek, Mariusz P.

    2005-01-01

    Java Radar Analysis Tool (JRAT) is a computer program for analyzing two-dimensional (2D) scatter plots derived from radar returns showing pieces of the disintegrating Space Shuttle Columbia. JRAT can also be applied to similar plots representing radar returns showing aviation accidents, and to scatter plots in general. The 2D scatter plots include overhead map views and side altitude views. The superposition of points in these views makes searching difficult. JRAT enables three-dimensional (3D) viewing: by use of a mouse and keyboard, the user can rotate to any desired viewing angle. The 3D view can include overlaid trajectories and search footprints to enhance situational awareness in searching for pieces. JRAT also enables playback: time-tagged radar-return data can be displayed in time order and an animated 3D model can be moved through the scene to show the locations of the Columbia (or other vehicle) at the times of the corresponding radar events. The combination of overlays and playback enables the user to correlate a radar return with a position of the vehicle to determine whether the return is valid. JRAT can optionally filter single radar returns, enabling the user to selectively hide or highlight a desired radar return.

  20. Determination of radar MTF

    Energy Technology Data Exchange (ETDEWEB)

    Chambers, D. [Lawrence Livermore National Lab., CA (United States)

    1994-11-15

    The ultimate goal of the Current Meter Array (CMA) is to be able to compare the current patterns detected with the array with radar images of the water surface. The internal wave current patterns modulate the waves on the water surface giving a detectable modulation of the radar cross-section (RCS). The function relating the RCS modulations to the current patterns is the Modulation Transfer Function (MTF). By comparing radar images directly with co-located CMA measurements the MTF can be determined. In this talk radar images and CMA measurements from a recent experiment at Loch Linnhe, Scotland, will be used to make the first direct determination of MTF for an X and S band radar at low grazing angles. The technical problems associated with comparing radar images to CMA data will be explained and the solution method discussed. The results suggest the both current and strain rate contribute equally to the radar modulation for X band. For S band, the strain rate contributes more than the current. The magnitude of the MTF and the RCS modulations are consistent with previous estimates when the wind is blowing perpendicular to the radar look direction.

  1. Aspects of Radar Polarimetry

    OpenAIRE

    Lüneburg, Ernst

    2002-01-01

    This contribution is a tutorial introduction to the phenomenological theory of radar polarimetry for the coherent scatter case emphasizing monostatic backscattering and forward scattering (transmission). Characteristic similarities and differences between radar polarimetry and optical polarimetry and the role of linear and antilinear operators (time-reversal) are pointed out and typical polarimetric invariants are identified.

  2. The Cloud Radar System

    Science.gov (United States)

    Racette, Paul; Heymsfield, Gerald; Li, Lihua; Tian, Lin; Zenker, Ed

    2003-01-01

    Improvement in our understanding of the radiative impact of clouds on the climate system requires a comprehensive view of clouds including their physical dimensions, dynamical generation processes, and detailed microphysical properties. To this end, millimeter vave radar is a powerful tool by which clouds can be remotely sensed. The NASA Goddard Space Flight Center has developed the Cloud Radar System (CRS). CRS is a highly sensitive 94 GHz (W-band) pulsed-Doppler polarimetric radar that is designed to fly on board the NASA high-altitude ER-2 aircraft. The instrument is currently the only millimeter wave radar capable of cloud and precipitation measurements from above most all clouds. Because it operates from high-altitude, the CRS provides a unique measurement perspective for cirrus cloud studies. The CRS emulates a satellite view of clouds and precipitation systems thus providing valuable measurements for the implementation and algorithm validation for the upcoming NASA CloudSat mission that is designed to measure ice cloud distributions on the global scale using a spaceborne 94 GHz radar. This paper describes the CRS instrument and preliminary data from the recent Cirrus Regional Study of Tropical Anvils and Cirrus Layers - Florida Area Cirrus Experiment (CRYSTAL-FACE). The radar design is discussed. Characteristics of the radar are given. A block diagram illustrating functional components of the radar is shown. The performance of the CRS during the CRYSTAL-FACE campaign is discussed.

  3. Property Analysis and Suppression Method of Real Measured Sea Spikes

    Directory of Open Access Journals (Sweden)

    Huang Yong

    2015-06-01

    Full Text Available In case of high-resolution, low grazing angle, high sea state, and horizontal transmitting, horizontal receiving polarization, the radar returns are strengthened, resulting in sea spikes. The sea spikes have the characteristics of high amplitudes, nonstationary, and non-Gaussian, which have a strong impact on the radar detection of weak marine moving targets. This study proposes a method for sea clutter suppression. Firstly, based on the sea spikes identification and selection method, the amplitude, temporal correlation, Doppler spectrum, and fractional power spectrum properties of sea spikes are analyzed. Secondly, the data to be detected are chosen by selecting the background clutter with minimum mean power, which can also eliminate the sea spikes. Correspondingly, sea clutter is suppressed with improved Signal-to-Clutter Ratio (SCR. Finally, the results of experiment with real radar data verify the effectiveness of the proposed method.

  4. Micropower impulse radar imaging

    Energy Technology Data Exchange (ETDEWEB)

    Hall, M.S.

    1995-11-01

    From designs developed at the Lawrence Livermore National Laboratory (LLNL) in radar and imaging technologies, there exists the potential for a variety of applications in both public and private sectors. Presently tests are being conducted for the detection of buried mines and the analysis of civil structures. These new systems use a patented ultra-wide band (impulse) radar technology known as Micropower Impulse Radar (GPR) imaging systems. LLNL has also developed signal processing software capable of producing 2-D and 3-D images of objects embedded in materials such as soil, wood and concrete. My assignment while at LLNL has focused on the testing of different radar configurations and applications, as well as assisting in the creation of computer algorithms which enable the radar to scan target areas of different geometeries.

  5. Principles of modern radar radar applications

    CERN Document Server

    Scheer, James A

    2013-01-01

    Principles of Modern Radar: Radar Applications is the third of the three-volume seriesof what was originally designed to be accomplished in one volume. As the final volumeof the set, it finishes the original vision of a complete yet bounded reference for radartechnology. This volume describes fifteen different system applications or class ofapplications in more detail than can be found in Volumes I or II.As different as the applications described, there is a difference in how these topicsare treated by the authors. Whereas in Volumes I and II there is strict adherence tochapter format and leve

  6. NOAA Laboratory for Satellite Altimetry Sea Level Rise Products: Global and regional sea level time series and trend maps for the major ocean basins and marginal seas, based on measurements from satellite radar altimeters, from 1992-12-17 to 2016-09-15 (NCEI Accession 0125535)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains global and regional mean sea level time series and trend maps calculated on a continual basis since December 1992 by Laboratory for...

  7. Studies of Plasma Instability Process Excited by Ground Based High Power HF (Heating) Facilities

    Science.gov (United States)

    2007-11-02

    the altitude z = 285 km. Night time plasma line intensities were observed to be enhanced by a factor 10 ÷ 100 extended to altitude below 250 km. When HF...waves, whose wave vector is directed toward the radar, and the phase velocity vph is equal to the velocity of suprathermal electrons v vph =(1/2) λr...averaged and in final form depends on two scalar factors only: full power density P absorbed by fast electrons in the acceleration layer, and characteristic

  8. HF Transverse Segmentation and Tagging Jet Capability

    CERN Document Server

    Doroshkevich, E A; Kuleshov, Sergey

    1998-01-01

    So called tagging jets and pile-up were simulated for the optimisation of the HF segmentation. The energy resolution, angular resolution and efficiency of jet reconstruction are defined for different calorimeter segmentation.

  9. Collisional quenching of highly rotationally excited HF

    CERN Document Server

    Yang, Benhui; Forrey, R C; Stancil, P C; Balakrishnan, N

    2015-01-01

    Collisional excitation rate coefficients play an important role in the dynamics of energy transfer in the interstellar medium. In particular, accurate rotational excitation rates are needed to interpret microwave and infrared observations of the interstellar gas for nonlocal thermodynamic equilibrium line formation. Theoretical cross sections and rate coefficients for collisional deexcitation of rotationally excited HF in the vibrational ground state are reported. The quantum-mechanical close-coupling approach implemented in the nonreactive scattering code MOLSCAT was applied in the cross section and rate coefficient calculations on an accurate 2D HF-He potential energy surface. Estimates of rate coefficients for H and H$_2$ colliders were obtained from the HF-He collisional data with a reduced-potential scaling approach. The calculation of state-to-state rotational quenching cross sections for HF due to He with initial rotational levels up to $j=20$ were performed for kinetic energies from 10$^{-5}$ to 15000...

  10. Microhardness evaluation alloys Hf-Si-B; Avaliacao de microdureza de ligas Hf-Si-B

    Energy Technology Data Exchange (ETDEWEB)

    Gigolotti, Joao Carlos Janio; Costa, Eliane Fernandes Brasil [Centro Universitario de Volta Redonda (UNIFOA), Volta Redonda, RJ (Brazil); Nunes, Carlos Angelo; Rocha, Elisa Gombio; Coelho, Gilberto Carvalho, E-mail: carlosjanio@uol.com.br, E-mail: eliane-costabrasi@hotmail.com, E-mail: cnunes@demar.eel.usp.br, E-mail: elisarocha@alunos.eel.usp.br, E-mail: coelho@demar.eel.usp.br [Universidade de Sao Paulo (USP), Lorena, SP (Brazil)

    2014-08-15

    The technological advance has generated increasing demand for materials that can be used under high temperature, what includes intermetallic MR-Si-B (MR = refractory metal) alloys with multiphase structures, that can also be applied in oxide environments. Thus, this work had for objective the micro hardness study of the Hf-Si-B system alloys, heat treated at 1600 deg C, in the Hf rich region. Hf-Si-B alloys had been produced with blades of Hf (min. 99.8%), Si (min. 99.998%) and B (min. 99.5%), in the voltaic arc furnace and heat treated at 1600 deg C under argon atmosphere. The relationship of the phases had been previously identified by X-ray diffraction and contrast in backscattered electron imaging mode. The alloys had their hardness analyzed by method Vickers (micro hardness) with load of 0.05 kgf and 0.2 kgf and application time of 20 s. The results, obtained from the arithmetic mean of measurements for each alloy on the heterogeneous region, showed a mean hardness of 11.08 GPA, with small coefficient of variation of 3.8%. The borides HfB2 (19.34 GPa) e HfB - 11.76 GPa, showed the hardness higher than the silicides Hf2Si (8.57 GPa), Hf5Si3 (9.63 GPa), Hf3Si2 (11.66 GPa), Hf5Si4 (10.00 GPa), HfSi (10.02 GPa) e HfSi2 (8.61 GPa). (author)

  11. Progress of KOERI Tsunami Warning System for the Eastern Mediterranean, Aegean and Black Seas

    Science.gov (United States)

    Necmioglu, Ocal; Meral Ozel, Nurcan; Ozer Sozdinler, Ceren; Yilmazer, Mehmet; Cokacar, Tulay; Comoglu, Mustafa; Pinar, Ali; Kekovali, Kivanc

    2016-04-01

    This presentation provides a progress report on the activities of the Bogazici University / Kandilli Observatory and Earthquake Research Institute - Regional Earthquake and Tsunami Monitoring Center (KOERI-RETMC) which provides services as a Candidate Tsunami Service Provider (CTSP) of ICG/NEAMTWS in the Eastern Mediterranean, Aegean and Black Seas since 1 July 2012. KOERI continues to operate 178 BB and 97 strong motion and 6 short period sensors and the regional coverage includes 77 stations from GFZ and additional 16 stations through bilateral agreements. One radar-type tide-gauge has been installed in Fethiye within the framework of "Inexpensive Device for Sea-Level Measurement" (IDSL) initiative offered as donation by the EC/JRC and planning is in progress for the possible installation of three more IDSLs in selected locations in the Aegean Sea coast of Turkey. The capabilities and the limitations of HF Radar technology for the purpose of tsunami detection in the Eastern Mediterranean has been identified and the maturity and the applicability of these systems for the possible use under the Tsunami Warning System has been determined. The development of the TsuComp as a user-friendly interface to be used in the assessment of tsunamigenic potential and as a single-point entry for message dissemination has been finalized. The work towards the creation of Tsunami Inundation Maps at the Tsunami Forecast Points in Turkey is near finalization. This work is partially funded by project ASTARTE - Assessment, Strategy And Risk Reduction for Tsunamis in Europe - FP7-ENV2013 6.4-3, Grant 603839. The authors would like to thank EC/JRC and Mr. Alessandro Annunziato for their continuous support in the operational activities of RETMC and IDSL initiative.

  12. Radar cross section

    CERN Document Server

    Knott, Gene; Tuley, Michael

    2004-01-01

    This is the second edition of the first and foremost book on this subject for self-study, training, and course work. Radar cross section (RCS) is a comparison of two radar signal strengths. One is the strength of the radar beam sweeping over a target, the other is the strength of the reflected echo sensed by the receiver. This book shows how the RCS ?gauge? can be predicted for theoretical objects and how it can be measured for real targets. Predicting RCS is not easy, even for simple objects like spheres or cylinders, but this book explains the two ?exact? forms of theory so well that even a

  13. Radar and electronic navigation

    CERN Document Server

    Sonnenberg, G J

    2013-01-01

    Radar and Electronic Navigation, Sixth Edition discusses radar in marine navigation, underwater navigational aids, direction finding, the Decca navigator system, and the Omega system. The book also describes the Loran system for position fixing, the navy navigation satellite system, and the global positioning system (GPS). It reviews the principles, operation, presentations, specifications, and uses of radar. It also describes GPS, a real time position-fixing system in three dimensions (longitude, latitude, altitude), plus velocity information with Universal Time Coordinated (UTC). It is accur

  14. Suppression of Clutter Near Port by S-Band Radar

    Science.gov (United States)

    Ishii, Seishiro; Sayama, Syuji

    It was reported that various radar clutters obey a Weibull distribution under certain conditions. To suppress such Weibull-distributed clutter, a new adaptive method was proposed by the present authors. In this method, the parameters of the Weibull distribution and the threshold level for an adaptive Constant False Alarm Rate (CFAR) detector are determined by calculating the variance after it passed through a logarithmic amplifier. To apply this new method to practical problems observed by an S-band radar, computer simulation were made for a finite number of samples in order to obtain the CFAR maintenance in Weibull radar clutter which was including sea clutter and ground clutter from a variety of terrain near the port. Finally an improvement value of target-to-clutter ratio 49.5dB was obtained for the detection of ships embedded in sea clutter near the port.

  15. Low-elevation monopulse radar and tracking simulator (LEMRATS)

    Science.gov (United States)

    Conte, Jeffrey E.; Groves, Gordon W.; Blair, W. Dale

    1996-06-01

    A simulation program is presented for studying the problem of tracking a low- flying target over the sea with an amplitude comparison monopulse radar. The simulation models the essential physical and logical processes involved in the tracking environment, which include specular and diffuse reflections from a spherical sea surface, target RCS scintillation, channel noise. Realistic monopulse angle measurements are generated by means of a four-lobe antenna model. The simulator allows easy substitution of the default radar-pointing and tracking algorithms by alternatives that the user may construct. Target trajectories and radar size, height, and frequency can be selected to study of the relative merits of various trade-offs. A common application is to put the simulator under the control of a driver that carries out multiple Monte Carlo experiments to test different parameter sets.

  16. Oil Spill Dectection by Imaging Radars: Challenges and Pitfalls

    Science.gov (United States)

    Alpers, Werner; Zeng, Kan; Tang, DanLing

    2016-08-01

    Criteria for discriminating between radar signatures of oil films and oil-spill look-alikes visible on synthetic aperture radar (SAR) images of the sea surface are critically reviewed. The main challenge in oil spill detection using SAR is to discriminate between mineral oil films and biogenic slicks originating from secretions (exudations) of biota in the water column. The claim that oil spill detection algorithms based on measuring 1) the reduction of the normalized radar cross section (NRCS), 2) the differences in the geometry and shape of the surface films, and 3) the differences in texture have a high success rate is questioned. Furthermore, it is questioned that polarimetric SAR data are of great help for discriminating between mineral oil films and biogenic slicks. However, differences in the statistical behavior of the radar backscattering is expected due to the fact that, other than monomolecular biogenic surface films, mineral oil films can form multi-layers.

  17. Detecting weather radar clutter using satellite-based nowcasting products

    DEFF Research Database (Denmark)

    Jensen, Thomas B.S.; Gill, Rashpal S.; Overgaard, Søren

    2006-01-01

    for the detecting and removal of clutter. Naturally, the improved spatio-temporal resolution of the Meteosat Second Generation sensors, coupled with its increased number of spectral bands, is expected to yield even better detection accuracies. Weather radar data from three C-band Doppler weather radars...... Application Facility' of EUMETSAT and is based on multispectral images from the SEVIRI sensor of the Meteosat-8 platform. Of special interest is the 'Precipitating Clouds' product, which uses the spectral information coupled with surface temperatures from Numerical Weather Predictions to assign probabilities...... by the resolution of the radar data. Subsequently, a supervised classifier was developed based on training data selected by a weather radar expert. Results of classification of data from several different meteorological events are shown. Cases of widespread sea clutter caused by anomalous propagation are especially...

  18. Weather radars – the new eyes for offshore wind farms?

    DEFF Research Database (Denmark)

    Trombe, Pierre-Julien; Pinson, Pierre; Vincent, Claire Louise

    2014-01-01

    Offshore wind fluctuations are such that dedicated prediction and control systems are needed for optimizing the management of wind farms in real-time. In this paper, we present a pioneer experiment – Radar@Sea – in which weather radars are used for monitoring the weather at the Horns Rev offshore...... inputs to prediction systems for anticipating changes in the wind fluctuation dynamics, generating improved wind power forecasts and developing specific control strategies. However, integrating weather radar observations into automated decision support systems is not a plug-and-play task...... observed at Horns Rev and (iv) we discuss the future perspectives for weather radars in wind energy. Copyright © 2013 John Wiley & Sons, Ltd....

  19. Modeling radar backscatter from breaking waves on the surface

    NARCIS (Netherlands)

    Melief, H.W.; Greidanus, H.S.F.; Hoogeboom, P.; Genderen, P. van

    2003-01-01

    A model for describing radar sea clutter is proposed. It consists of two parts, an oceanographic and an electromagnetic one. The former contains swell, small capillary and gravity waves as well as breaking wave events. The latter combines ray tracing, Bragg scattering and the Method of Moments. It i

  20. Wind Profiling Radar

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Clutter present in radar return signals as used for wind profiling is substantially removed by carrying out a Daubechies wavelet transformation on a time series of...

  1. Imaging Radar Polarimetry

    Science.gov (United States)

    vanZyl, J. J.; Zebker, H. A.

    1993-01-01

    In this paper, we review the state of the art in imaging radar polarimetry, examine current developments in sensor technology and implementation for recording polarimetric measurements, and describe techniques and areas of application for the new remote sensing data.

  2. Radar Landmass Simulation Computer Programming (Interim Report).

    Science.gov (United States)

    RADAR SCANNING, TERRAIN), (*NAVAL TRAINING, RADAR OPERATORS), (*FLIGHT SIMULATORS, TERRAIN AVOIDANCE), (* COMPUTER PROGRAMMING , INSTRUCTION MANUALS), PLAN POSITION INDICATORS, REAL TIME, DISPLAY SYSTEMS, RADAR IMAGES, SIMULATION

  3. Comparison and error analysis of remotely measured waveheight by high frequency ground wave radar

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    High frequency ground wave radar (HFGWR) has unique advantage in the survey of dynamical factors, such as sea surface current, sea wave, and sea surface wind in marine conditions in coastal sea area.Compared to marine satellite remote sensing, it involves lower cost, has higher measuring accuracy and spatial resolution and sampling frequency. High frequency ground wave radar is a new land based remote sensing instrument with superior vision and greater application potentials. This paper reviews the development history and application status of high frequency wave radar, introduces its remote-sensing principle and method to inverse offshore fluid, and wave and wind field. Based on the author's "863 Project", this paper recounts comparison and verification of radar remote-sensing value, the physical calibration of radar-measured data and methods to control the quality of radar-sensing data. The authors discuss the precision of radar-sensing data's inversing on offshore fluid field and application of the assimilated data on assimilation.

  4. Downhole pulse radar

    Science.gov (United States)

    Chang, Hsi-Tien

    1987-09-28

    A borehole logging tool generates a fast rise-time, short duration, high peak-power radar pulse having broad energy distribution between 30 MHz and 300 MHz through a directional transmitting and receiving antennas having barium titanate in the electromagnetically active region to reduce the wavelength to within an order of magnitude of the diameter of the antenna. Radar returns from geological discontinuities are sampled for transmission uphole. 7 figs.

  5. An Overview on Development of Passive Radar Based on the Low Frequency Band Digital Broadcasting and TV Signals

    Directory of Open Access Journals (Sweden)

    Wan Xian-rong

    2012-06-01

    Full Text Available Starting from the detection principle and characteristics of passive radar, this paper describes the development of passive radar based on the low frequency band (HF/VHF/UHF digital broadcasting and TV signal. Based on the radio coverage ratio and technical features of digital broadcasting and TV signals, the research status in abroad, especially in Europe, is introduced at first, on experimental systems, technical parameters, and comparative experiments. Then the latest development of passive radars, in different frequency bands in China, both theory and experimental study are presented. Followed is the commentary on the key techniques and problems of Digital Broadcasting-based Passive Radar (DBPR, including the waveform’s properties and its modification, reference signal extraction, multipath clutter rejection, target detection, tracking, and fusion as well as real-time signal processing. Finally, the prospects of development and application of this kind of passive radar are discussed.

  6. Laser radar technology and applications; Proceedings of the Meeting, Quebec, Canada, June 3-5, 1986

    Science.gov (United States)

    Cruickshank, James M.; Harney, Robert C.

    1986-01-01

    Various papers on laser radar technology and applications are presented. The topics considered include: eye-safe solid lasers for lidar applications, practical DF laser for ranging applications, ultrafast surface barrier photodetectors, performance analyses for peak-detecting laser radars, multiple scattering for laser beams propagating in a layered atmosphere, laser radar cross section of objects immersed in the earth's atmosphere, measurements of pulse coherence in mode-locked TEA-CO2 lasers, and single longitudinal mode operation of a continuously tunable high pressure TE-CO2. Also discussed are: amplitude-modulated laser system for distance and displacement measurement, minilaser rangefinder, laser docking system radar flight experiment, improved optical resonator for laser radars, design of frequency-stable TEA-CO2 lasers, HgCdTe photodiodes for heterodyne applications, acoustooptic spectrum analyzer for laser radar applications, laser cloud mapper and its applications, scanning lidar bathymeter for water depth measurement, and fluorescence lidar for land and sea remote sensing.

  7. First results of HF radio science with e-POP RRI and SuperDARN

    Science.gov (United States)

    Perry, G. W.; James, H. G.; Gillies, R. G.; Howarth, A.; Hussey, G. C.; McWilliams, K. A.; White, A.; Yau, A. W.

    2017-01-01

    The first results from coordinated experiments between the Radio Receiver Instrument (RRI) on the Enhanced Polar Outflow Probe (e-POP) and the Super Dual Auroral Radar Network (SuperDARN) Saskatoon high frequency (HF) radar are examined for a conjunction on 8 July 2014. e-POP, a payload on the CAScade, Smallsat and IOnospheric Polar Explorer spacecraft, was located at 380 km altitude, approximately 10° north (geographic) and 2° west of Saskatoon, Canada, moving in a southeast direction. We use a matched filter technique to extract individual received SuperDARN pulses from the RRI data stream. The pulses show characteristics of propagation through the F region ionosphere: they are heavily dispersed, they show significant pulse-to-pulse variability in magnitude, and there is clear evidence that they experienced multipath propagation. We calculate the polarization parameters of the pulses and use them to identify magnetoionic phenomena such as mode-splitting and single-mode fading. These first RRI results provide compelling insight into HF radio wave propagation and show RRI's potential to significantly advance radio science.

  8. Detection of Small Sea-Surface Targets with a Search Lidar

    NARCIS (Netherlands)

    Heuvel, J.C. van den; Bekman, H.H.P.T.; Putten, F.J.M.; Cohen, L.A.

    2007-01-01

    Naval operations in the littoral have to deal with the threat of small sea-surface targets. These targets have a low radar cross-section and low velocity, which makes them hard to detect by radar in the presence of sea clutter. Typical threats include periscopes, jet skies, FIAC’s, and speedboats. S

  9. Detection of Small Sea-Surface Targets with a Search Lidar

    NARCIS (Netherlands)

    Heuvel, J.C. van den; Bekman, H.H.P.T.; Putten, F.J.M.; Cohen, L.A.

    2007-01-01

    Naval operations in the littoral have to deal with the threat of small sea-surface targets. These targets have a low radar cross-section and low velocity, which makes them hard to detect by radar in the presence of sea clutter. Typical threats include periscopes, jet skies, FIAC’s, and speedboats.

  10. Detection of Small Sea-Surface Targets with a Search Lidar

    NARCIS (Netherlands)

    Heuvel, J.C. van den; Bekman, H.H.P.T.; Putten, F.J.M.; Cohen, L.A.

    2007-01-01

    Naval operations in the littoral have to deal with the threat of small sea-surface targets. These targets have a low radar cross-section and low velocity, which makes them hard to detect by radar in the presence of sea clutter. Typical threats include periscopes, jet skies, FIAC’s, and speedboats. S

  11. Insights into factors contributing to the observability of a submarine at periscope depth by modern radar, Part 2: EM simulation of mast RCS in a realistic sea surface environment

    CSIR Research Space (South Africa)

    Smit, JC

    2012-09-01

    Full Text Available and some insights gained are described in. The current paper presents the results of a subsequent computational electromagnetic (CEM) simulation investigation of a simplified mast model in a realistic sea surface environment. The results illustrate some...

  12. Using of standard marine radar for determination of a water surface and an atmosphere near-surface layer parameters

    Science.gov (United States)

    Bogatov, Nikolay A.; Bakhanov, Victor V.; Ermoshkin, Aleksei V.; Kazakov, Vasily I.; Kemarskaya, Olga N.; Titov, Victor I.; Troitskaya, Yulia I.

    2014-10-01

    At present time radar methods of the seas and oceans diagnostics are actively developing. Using of the radar stations based on satellites and planes allows to receive information on a sea surface and a atmosphere near-surface layer with coverage of big water surface areas independently of day time. The developed methods of satellite radio images processing can be applied to marine radar stations. In Institute of Applied Physics RAS works on sea surface diagnostics systems development on the basis of standard marine radar are actively conducted. Despite smaller coverage of the territory in comparison with satellite data, marine radar have possibility to record spatially temporary radar images and to receive information on a surrounding situation quickly. This work deals with results of the researches which were conducted within the international expedition in the Atlantic Ocean in the autumn of 2012 on a route Rotterdam (Netherlands) - Ushuaya (Argentina) - Antarctica — Ushuaya. During this expedition a complex measurements of a sea surface, a atmosphere near-surface layer parameters and subsurface currents in the wide range of hydroweather conditions, including the storm were carried out. The system developed in IAP RAS on the basis of a marine radar ICOM MR-1200RII and the ADC (Analog Digital Converter) block for data recording on the personal computer was used. Display of a non-uniform near-surface current on sea surface radar images in storm conditions is shown. By means of the high-speed anemometer and meteorological station the measurements of the atmosphere parameters were carried out. Comparison of the anemometer data with calculated from radar images is carried out. Dependence of radar cross section from wind speed in the wide range of wind speeds, including storm conditions is investigated. Possibility of marine radar using for surface waves intensity and ice situation estimates also as icebergs detection is shown.

  13. Temperate Ice Depth-Sounding Radar

    Science.gov (United States)

    Jara-Olivares, V. A.; Player, K.; Rodriguez-Morales, F.; Gogineni, P.

    2008-12-01

    Glaciers in several parts of the world are reported to be retreating and thinning rapidly over the last decade. Radar instruments can be used to provide a wealth of information regarding the internal and basal conditions of large and small ice masses. These instruments typically operate in the VHF and UHF regions of the electromagnetic spectrum. For temperate-ice sounding, however, the high water content produces scattering and attenuation in propagating radar waves at VHF and UHF frequencies, which significantly reduce the penetration depths. Radars operating in the HF band are better suited for systematic surveys of the thickness and sub-glacial topography of temperate-ice regions. We are developing a dual-frequency Temperate-Ice-Depth Sounding Radar (TIDSoR) that can penetrate through water pockets, thus providing more accurate measurements of temperate ice properties such as thickness and basal conditions. The radar is a light-weight, low power consumption portable system for surface-based observations in mountainous terrain or aerial surveys. TIDSoR operates at two different center frequencies: 7.7 MHz and 14 MHz, with a maximum output peak power of 20 W. The transmit waveform is a digitally generated linear frequency-modulated chirp with 1 MHz bandwidth. The radar can be installed on aircrafts such as the CReSIS UAV [1], DCH-6 (Twin Otter), or P-3 Orion for aerial surveys, where it could be supported by the airplane power system. For surface based experiments, TIDSoR can operate in a backpack configuration powered by a compact battery system. The system can also be installed on a sled towed by a motorized vehicle, in which case the power supply can be replaced by a diesel generator. The radar consists of three functional blocks: the digital section, the radio-frequency (RF) section, and the antenna, and is designed to weigh less than 2 kg, excluding the power supply. The digital section generates the transmit waveforms as well as timing and control signals

  14. A barrier radar concept

    Science.gov (United States)

    Marshall, J.; Ball, C.; Weissman, I.

    A description is given of a low power, light-weight radar that can be quickly set up and operated on batteries for extended periods of time to detect airborne intruders. With low equipment and operating costs, it becomes practical to employ a multiplicity of such radars to provide an unbroken intrusion fence over the desired perimeter. Each radar establishes a single transmitted fan beam extending vertically from horizon to horizon. The beam is generated by a two-face array antenna built in an A-frame configuration and is shaped, through phasing of the array elements, to concentrate the transmitter power in a manner consistent with the expected operating altitude ceiling of the targets of interest. The angular width of this beam in the dimension transverse to the fan depends on the radar transmission frequency and the antenna aperture dimension, but is typically wide enough so that a target at the maximum altitude or range will require tens of seconds to pass through the beam. A large number of independent samples of radar data will thus be available to provide many opportunities for target detection.

  15. General concepts of modern HF communications

    Science.gov (United States)

    Aarons, Jules

    Both conceptual and hardware advancements have led to substantial systems developments in military HF communications; the former encompass coding and error correction techniques for security, in order to minimize propagation and interference, while the latter prominently include digital equipment permitting the selection of a frequency for a particular path and propagation mode, as well as modulation selection. Propagation-related advancements involve better statistical models as well as advancements in short-term forecasting methods responsive to changes in solar-geophysical parameters. Adaptive HF systems have been developed for meteor-scatter radio communications.

  16. Research on Multi-Layer Distributed HF Radio Network Structure

    Institute of Scientific and Technical Information of China (English)

    Hui Dai; Chun-Jiang Wang; Quan Yu

    2008-01-01

    High frequency (HF) transmission is an important communication techniques. However, conventional point-to-point transmission can be easily destroyed, which limits its utilization in practice. HF networking communication has the capability against demolishment. The network structure is one of the key factors for HF networking communication. In this paper, a novel analysis method of the network connectedness based on the eigenvalue is derived, and a multi-layer distributed HF radio network structure is proposed. Both the theore tical analysis and the computer simulation results verify that the application of the proposed network structure in the HF radio communication can improve the anti demolishment ability of the HF network efficiently.

  17. Polarimetric C-Band SAR Observations of Sea Ice in the Greenland Sea

    DEFF Research Database (Denmark)

    Thomsen, Bjørn Bavnehøj; Nghiem, S.V.; Kwok, R.

    1998-01-01

    The fully polarimetric EMISAR acquired C-band radar signatures of sea ice in the Greenland Sea during a campaign in March 1995. The authors present maps of polarimetric signatures over an area containing various kinds of ice and discuss the use of polarimetric SAR for identification of ice types...

  18. Airport Surveillance Radar : Model 8 -

    Data.gov (United States)

    Department of Transportation — The Airport Surveillance Radar Model 8 (ASR-8) is a short-range (60 nautical mile (nmi)), analog radar system used to detect and report the presence and location of...

  19. Airport Surveillance Radar : Model 7 -

    Data.gov (United States)

    Department of Transportation — The Airport Surveillance Radar Model 7 (ASR-7) is a short-range (60 nautical miles (nmi)) analog radar system used to detect and report the presence and location of...

  20. Radar for tracer particles

    CERN Document Server

    Ott, Felix; Huang, Kai

    2016-01-01

    We introduce a radar system capable of tracking a $5$mm spherical target continuously in three dimensions. The $10$GHz (X-band) radar system has a transmission power of $1$W and operates in the near field of the horn antennae. By comparing the phase shift of the electromagnetic wave traveling through the free space with an IQ-Mixer, we obtain the relative movement of the target with respect to the antennae. From the azimuth and inclination angles of the receiving antennae obtained in the calibration, we reconstruct the target trajectory in a three-dimensional Cartesian system. Finally, we test the tracking algorithm with target moving in circular as well as in pendulum motions, and discuss the capability of the radar system.

  1. Localizing Ground-Penetrating Radar

    Science.gov (United States)

    2014-11-01

    ing Ground-Penetrating Radar (LGPR) uses very high frequency (VHF) radar reflections of underground features to generate base- line maps and then...Innovative ground- penetrating radar that maps underground geological features provides autonomous vehicles with real-time localization. Localizing...NOV 2014 2. REPORT TYPE 3. DATES COVERED 00-00-2014 to 00-00-2014 4. TITLE AND SUBTITLE Localizing Ground-Penetrating Radar 5a. CONTRACT NUMBER

  2. Mode S Baseline Radar Tracking.

    Science.gov (United States)

    1982-11-01

    range units and 20 azimuth units) overlaying the position of the beacon reports. In the cases analyzed where beacon reports were not radar reinforced ...82/53 j~ C ~ 7 C _ _ _ _ _ _ 4. Title end Su.btitle 5. Neget at. November 1982 MDDE S BASELINE RADAR TRACKIN4G 6. Poelin Orgeuianti.. Cede ACT-100...Ground Clutter 33 Mode S/ARTS III 100-Scan False Radar Track Summary 74 34 Percent Beacon Radar Reinforcement 77 vii INTRODUCTION PURPOSE. The purpose of

  3. Systems and Methods for Radar Data Communication

    Science.gov (United States)

    Bunch, Brian (Inventor); Szeto, Roland (Inventor); Miller, Brad (Inventor)

    2013-01-01

    A radar information processing system is operable to process high bandwidth radar information received from a radar system into low bandwidth radar information that may be communicated to a low bandwidth connection coupled to an electronic flight bag (EFB). An exemplary embodiment receives radar information from a radar system, the radar information communicated from the radar system at a first bandwidth; processes the received radar information into processed radar information, the processed radar information configured for communication over a connection operable at a second bandwidth, the second bandwidth lower than the first bandwidth; and communicates the radar information from a radar system, the radar information communicated from the radar system at a first bandwidth.

  4. Noise Radar Technology Basics

    Science.gov (United States)

    2006-12-01

    poursuite, estimation Doppler, polarimétrie, interférométrie, sondage du sol ou profilage de la sous- surface , détection, imagerie SAR (radar à synthèse...mesure de distance et d’estimation Doppler. Deux récepteurs de traitement cohérent, soit le récepteur de corrélation et le récep- teur de traitement DSP... traitement spectral double) des échos radar sont décrits et une estimation de leur portée est présentée. Les capacités LPI (faible probabilité

  5. Ground penetrating radar

    CERN Document Server

    Daniels, David J

    2004-01-01

    Ground-penetrating radar has come to public attention in recent criminal investigations, but has actually been a developing and maturing remote sensing field for some time. In the light of recent expansion of the technique to a wide range of applications, the need for an up-to-date reference has become pressing. This fully revised and expanded edition of the best-selling Surface-Penetrating Radar (IEE, 1996) presents, for the non-specialist user or engineer, all the key elements of this technique, which span several disciplines including electromagnetics, geophysics and signal processing. The

  6. Human walking estimation with radar

    NARCIS (Netherlands)

    Dorp, Ph. van; Groen, F.C.A.

    2003-01-01

    Radar can be used to observe humans that are obscured by objects such as walls. These humans cannot be visually observed. The radar measurements are used to animate an obscured human in virtual reality. This requires detailed information about the motion. The radar measurements give detailed informa

  7. Radar Test Range Design Considerations.

    Science.gov (United States)

    1980-04-29

    radar cross section associated with dihedral and trihedral corner reflectors is highly dependent upon the squareness or alignment of the...slightly misaligned. We now show how the radar cross section for dihedral and trihedral corner reflectors depends upon their surface misalignment. All...coefficients, p and q, for the dihedral corner reflector , one must consider the radar cross section

  8. Status Of Imaging Radar Polarimetry

    Science.gov (United States)

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

    1991-01-01

    Report pulls together information on imaging radar polarimetry from a variety of sources. Topics include theory, equipment, and experimental data. Reviews state of the art, examines current applicable developments in radar equipment, describes recording and processing of radar polarimetric measurements, and discusses interpretation and application of resulting polarimetric images.

  9. Human walking estimation with radar

    NARCIS (Netherlands)

    Dorp, Ph. van; Groen, F.C.A.

    2003-01-01

    Radar can be used to observe humans that are obscured by objects such as walls. These humans cannot be visually observed. The radar measurements are used to animate an obscured human in virtual reality. This requires detailed information about the motion. The radar measurements give detailed

  10. Coded continuous wave meteor radar

    OpenAIRE

    2015-01-01

    The concept of coded continuous wave meteor radar is introduced. The radar uses a continuously transmitted pseudo-random waveform, which has several advantages: coding avoids range aliased echoes, which are often seen with commonly used pulsed specular meteor radars (SMRs); continuous transmissions maximize pulse compression gain, allowing operation with significantly lower peak transmit power; the temporal resolution can be changed after ...

  11. Systematic Comparison of HF CMOS Transconductors

    NARCIS (Netherlands)

    Klumperink, Eric A.M.; Nauta, Bram

    2003-01-01

    Transconductors are commonly used as active elements in high-frequency (HF) filters, amplifiers, mixers, and oscillators. This paper reviews transconductor design by focusing on the V-I kernel that determines the key transconductor properties. Based on bandwidth considerations, simple V-I kernels wi

  12. Electron impact on vibrationally cold {{HF}}^{+}

    Science.gov (United States)

    Cristian Stroe, Marius; Fifirig, Magda

    2016-12-01

    The dissociative recombination and vibrational excitation processes induced by electron impact on vibrationally cold {{HF}}+ are investigated in the framework of the multichannel quantum defect theory for electron energies below 1 eV. The thermal rate coefficients for the electron temperature range from 10 to 5000 K are reported.

  13. ORIGIN OF EXCESS (176)Hf IN METEORITES

    DEFF Research Database (Denmark)

    Thrane, Kristine; Connelly, James Norman; Bizzarro, Martin

    2010-01-01

    After considerable controversy regarding the (176)Lu decay constant (lambda(176)Lu), there is now widespread agreement that (1.867 +/- 0.008) x 10(-11) yr(-1) as confirmed by various terrestrial objects and a 4557 Myr meteorite is correct. This leaves the (176)Hf excesses that are correlated with...

  14. The SeaWinds Scatterometer Instrument

    Science.gov (United States)

    Wu, C.; Graf, J.; Freilich, M.; Long, D.; Spencer, M.; Tsai, W.; Lisman, D.; Winn, C.

    1994-01-01

    The SeaWinds scatterometer instrument is currently being developed by NASA/JPL, as part of the NASA EOS Program, for flight on the Hapanese ADEOS II mission in 1999. This Ku-band radar scatterometer will infer surface wind speed and direction by measuring the radar normalized backscatter cross-section over several different azimuth angles. This paper presents the design characteristics of and operational approach to the instrument itself.

  15. The Newcastle meteor radar

    Science.gov (United States)

    Keay, Colin

    1987-01-01

    A brief history and development of the Newcastle Meteor Radar system is given. Also described are its geographical coordinates and its method of operation. The initial objective when the project was commenced was to develop an entirely digital analyzer capable of recognizing meteor echo signals and recording as many of their parameters as possible. This objective was achieved.

  16. Compressive CFAR radar detection

    NARCIS (Netherlands)

    Anitori, L.; Otten, M.P.G.; Rossum, W.L. van; Maleki, A.; Baraniuk, R.

    2012-01-01

    In this paper we develop the first Compressive Sensing (CS) adaptive radar detector. We propose three novel architectures and demonstrate how a classical Constant False Alarm Rate (CFAR) detector can be combined with ℓ1-norm minimization. Using asymptotic arguments and the Complex Approximate Messag

  17. Compressive CFAR Radar Processing

    NARCIS (Netherlands)

    Anitori, L.; Rossum, W.L. van; Otten, M.P.G.; Maleki, A.; Baraniuk, R.

    2013-01-01

    In this paper we investigate the performance of a combined Compressive Sensing (CS) Constant False Alarm Rate (CFAR) radar processor under different interference scenarios using both the Cell Averaging (CA) and Order Statistic (OS) CFAR detectors. Using the properties of the Complex Approximate Mess

  18. Synthetic Aperture Radar Interferometry

    Science.gov (United States)

    Rosen, P. A.; Hensley, S.; Joughin, I. R.; Li, F.; Madsen, S. N.; Rodriguez, E.; Goldstein, R. M.

    1998-01-01

    Synthetic aperture radar interferometry is an imaging technique for measuring the topography of a surface, its changes over time, and other changes in the detailed characteristics of the surface. This paper reviews the techniques of interferometry, systems and limitations, and applications in a rapidly growing area of science and engineering.

  19. Spaceborne Radar Study

    Science.gov (United States)

    1974-06-28

    via either the oomm beam or the omnichannel . Satellite instrumentation data are sent to the ground station following every radar signal transmission...If comm beam contact is lost, the instrumentation data are sent via the omnichannel transmitter on command of the ground station. There are six ways

  20. An overview of high-latitude hf induced aurora from EISCAT

    Science.gov (United States)

    Kosch, M.; Gustavsson, B.; Rietveld, M.

    The EISCAT HF facility is capable of transmitting over 200 MW into the ionosphere below 5.423 MHz using the low-gain antenna array. Over 1000 MW above 5.423 MHz is available using the high-gain antenna array. During O-mode pumping in the hours after sunset, F-region electrons can be accelerated sufficiently to excite the oxygen atoms and nitrogen molecules, resulting in observable optical emissions at 844.6 (O), 630 (O1D), 557.7 (O1S) and 427.8 (N2) nm above EISCAT. Initial success came in February 1999 with optical recordings by ALIS (Auroral Large Imaging System) from various Swedish locations south of EISCAT and DASI (Digital All-Sky Imager) from Skibotn, Norway, 50 km south-east of EISCAT. Several observations have features unique to high latitudes. Novel discoveries include: (1) Very large electron temperature enhancements of a few 1000 K, which maximise along the magnetic field line direction (2) Ion temperature enhancements of a few 100 K accompanied by large ion outflows, (3) The optical emission usually appears near the magnetic field line direction regardless of the HF transmitter beam pointing direction, (4) The optical emission appears below the HF pump reflection altitude as well as the upper-hybrid resonance height, (5) The optical emission and HF coherent radar backscatter disappears when pumping on the 3rd, 4th or 5th gyro-harmonic frequency, (6) The first artificial optical observations at 844.6 (O) and 427.8 (N2) nm and (7) Annular optical structures, which subsequently collapse into blobs.

  1. Radar Observations of Asteroids

    Science.gov (United States)

    Ostro, S. J.

    2003-05-01

    During the past 25 years, radar investigations have provided otherwise unavailable information about the physical and dynamical properties of more than 200 asteroids. Measurements of the distribution of echo power in time delay and Doppler frequency provide two-dimensional images with spatial resolution as fine as a decameter. Sequences of delay-Doppler images can be used to produce geologically detailed three-dimensional models, to define the rotation state precisely, to constrain the internal density distribution, and to estimate the trajectory of the object's center of mass. Radar wavelengths (4 to 13 cm) and the observer's control of transmitted and received polarizations make the observations sensitive to near-surface bulk density and macroscopic structure. Since delay-Doppler positional measurements are orthogonal to optical angle measurements and typically have much finer fractional precision, they are powerful for refining orbits and prediction ephemerides. Radar astrometry can add decades or centuries to the interval over which an asteroid's close Earth approaches can accurately be predicted and can significantly refine collision probability estimates based on optical astrometry alone. In the highly unlikely case that a small body is on course for an Earth collision in this century, radar reconnaissance would almost immediately distinguish between an impact trajectory and a near miss and would dramatically reduce the difficulty and cost of any effort to prevent the collision. The sizes and rotation periods of radar-detected asteroids span more than four orders of magnitude. These observations have revealed both stony and metallic objects, elongated and nonconvex shapes as well as nearly featureless spheroids, small-scale morphology ranging from smoother than the lunar regolith to rougher than the rockiest terrain on Mars, craters and diverse linear structures, non-principal-axis spin states, contact binaries, and binary systems.

  2. Off-shore Wind Atlas of the Central Aegean Sea: A simple comparison of NCEP/NCAR RE-analysis data, QuickSCAT and ENVISAT Synthetic Aperture Radar (SAR) by use of Wind Atlas Method

    DEFF Research Database (Denmark)

    Bingöl, Ferhat; Hasager, Charlotte Bay; Karagali, Ioanna

    2012-01-01

    Offshore wind energy is progressing rapidly in many parts of the world including Europe. While our understanding of offshore wind is growing parallel to that, most of the offshore wind development is located in shallow or transitional waters. Deep, open sea was never preferred by developers due t...

  3. Space radar image of Mauna Loa, Hawaii

    Science.gov (United States)

    1995-01-01

    This image of the Mauna Loa volcano on the Big Island of Hawaii shows the capability of imaging radar to map lava flows and other volcanic structures. Mauna Loa has erupted more than 35 times since the island was first visited by westerners in the early 1800s. The large summit crater, called Mokuaweoweo Caldera, is clearly visible near the center of the image. Leading away from the caldera (towards top right and lower center) are the two main rift zones shown here in orange. Rift zones are areas of weakness within the upper part of the volcano that are often ripped open as new magma (molten rock) approaches the surface at the start of an eruption. The most recent eruption of Mauna Loa was in March and April 1984, when segments of the northeast rift zones were active. If the height of the volcano was measured from its base on the ocean floor instead of from sea level, Mauna Loa would be the tallest mountain on Earth. Its peak (center of the image) rises more than 8 kilometers (5 miles) above the ocean floor. The South Kona District, known for cultivation of macadamia nuts and coffee, can be seen in the lower left as white and blue areas along the coast. North is toward the upper left. The area shown is 41.5 by 75 kilometers (25.7 by 46.5 miles), centered at 19.5 degrees north latitude and 155.6 degrees west longitude. The image was acquired by the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/ X-SAR) aboard the space shuttle Endeavour on its 36th orbit on October 2, 1994. The radar illumination is from the left of the image. The colors in this image were obtained using the following radar channels: red represents the L-band (horizontally transmitted and received); green represents the L-band (horizontally transmitted, vertically received); blue represents the C-band (horizontally transmitted, vertically received). The resulting color combinations in this radar image are caused by differences in surface roughness of the lava flows. Smoother flows

  4. The effect of plasma density structure on HF radio wave propagation at auroral and polar latitudes measured by e-POP

    Science.gov (United States)

    Perry, G. W.; James, H. G.; Gillies, R.; McWilliams, K. A.; St-Maurice, J. P.; Yau, A. W.

    2015-12-01

    One of the scientific objectives of the enhanced Polar Outflow Probe (e-POP) Radio Receiver Instrument (RRI) is to study ionospheric density structure and its impact on High Frequency (HF) radio wave propagation. We present a survey of several ePOP RRI transits through isolated beams of the Super Dual Auroral Radar Network (SuperDARN) Saskatoon and Rankin Inlet radars. It reveals that the spreading of a SuperDARN beam beyond its nominal azimuthal beam width of 3.24° is a common occurrence at auroral and polar latitudes. Furthermore, on multiple occasions, lateral deviations of a beam's power peak by several beam widths was measured, indicating the presence of significant plasma density gradients along the ray path. The e-POP RRI measurements illustrate that our understanding and recognition of plasma density gradients and their influence on HF radio wave propagation is limited. We report on the results of employing HF ray tracing techniques to quantify the impact of ionospheric structuring on HF radio wave propagation, and consider the source of the gradients contributing to the spreading of the SuperDARN beams.

  5. 2006 Fynmeet sea clutter measurement trial: Datasets

    CSIR Research Space (South Africa)

    Herselman, PLR

    2007-09-06

    Full Text Available 3000 3200 3400 3600 -30 -25 -20 -15 -10 -5 0 5 10 15 Experiment Summary Value Radar Setup Value Type Sea Clutter Tx Frequency 9.125 GHz Date 31-Jul-2006 PRF 5 kHz Start Time 15:45:38.468 Tracking Range 2300 m Duration 183090 PRI's (36.6178 s... 15 Experiment Summary Value Radar Setup Value Type Sea Clutter Tx Frequency 9.125 GHz Date 31-Jul-2006 PRF 5 kHz Start Time 15:46:15.103 Tracking Range 2300 m Duration 212925 PRI's (42.5848 s) Range Extend 1440 m (96 gates), 15 m res...

  6. An MSK Radar Waveform

    Science.gov (United States)

    Quirk, Kevin J.; Srinivasan, Meera

    2012-01-01

    The minimum-shift-keying (MSK) radar waveform is formed by periodically extending a waveform that separately modulates the in-phase and quadrature- phase components of the carrier with offset pulse-shaped pseudo noise (PN) sequences. To generate this waveform, a pair of periodic PN sequences is each passed through a pulse-shaping filter with a half sinusoid impulse response. These shaped PN waveforms are then offset by half a chip time and are separately modulated on the in-phase and quadrature phase components of an RF carrier. This new radar waveform allows an increase in radar resolution without the need for additional spectrum. In addition, it provides self-interference suppression and configurable peak sidelobes. Compared strictly on the basis of the expressions for delay resolution, main-lobe bandwidth, effective Doppler bandwidth, and peak ambiguity sidelobe, it appears that bi-phase coded (BPC) outperforms the new MSK waveform. However, a radar waveform must meet certain constraints imposed by the transmission and reception of the modulation, as well as criteria dictated by the observation. In particular, the phase discontinuity of the BPC waveform presents a significant impediment to the achievement of finer resolutions in radar measurements a limitation that is overcome by using the continuous phase MSK waveform. The phase continuity, and the lower fractional out-of-band power of MSK, increases the allowable bandwidth compared with BPC, resulting in a factor of two increase in the range resolution of the radar. The MSK waveform also has been demonstrated to have an ambiguity sidelobe structure very similar to BPC, where the sidelobe levels can be decreased by increasing the length of the m-sequence used in its generation. This ability to set the peak sidelobe level is advantageous as it allows the system to be configured to a variety of targets, including those with a larger dynamic range. Other conventionally used waveforms that possess an even greater

  7. Shipboard Survey Near the Philippines with a Coherent X-Band Radar

    Science.gov (United States)

    2008-02-26

    IGARSS 2008 TALK MEASURING AND MODELING THE NORMALIZED RADAR CROSS SECTION OF THE SEA FOR BACKSCATTER William J. Plant, William C. Keller, Kenneth...Hayes, Gene Chatham Applied Physics Laboratory, University of Washington, Seattle, WA, USA plant,apl.washington.edu The normalized radar cross section ...Here we take tentative steps toward a statistical 5 model of backscatter from a random distribution of dihedral corner reflectors which may represent

  8. Satellite radar altimetry over ice. Volume 1: Processing and corrections of Seasat data over Greenland

    Science.gov (United States)

    Zwally, H. Jay; Brenner, Anita C.; Major, Judith A.; Martin, Thomas V.; Bindschadler, Robert A.

    1990-01-01

    The data-processing methods and ice data products derived from Seasat radar altimeter measurements over the Greenland ice sheet and surrounding sea ice are documented. The corrections derived and applied to the Seasat radar altimeter data over ice are described in detail, including the editing and retracking algorithm to correct for height errors caused by lags in the automatic range tracking circuit. The methods for radial adjustment of the orbits and estimation of the slope-induced errors are given.

  9. Application of the JPDA-UKF to HFSW Radars for Maritime Situational Awareness

    Science.gov (United States)

    2012-07-01

    paper preliminary results from the NATO Under- sea Research Centre ( NURC ) Battlespace Preparation 2009 (BP09) HFWS Radar experiment, which took place...information about the NURC HFSW-radar experiment are provided. The MTT is described in Section III. Experimental results are reported in Section IV...EXPERIMENT RESULTS In this section the MTT has been tested on a subset of the NURC BP09 experiment data set. Data from the Palmaria and San Rossore WERA

  10. REMPI Spectroscopy of HfF

    CERN Document Server

    Loh, Huanqian; Yahn, Tyler S; Looser, Herbert; Field, Robert W; Cornell, Eric A

    2012-01-01

    The spectrum of electronic states at 30000--33000 cm$^{-1}$ in hafnium fluoride has been studied using (1+1) resonance-enhanced multi-photon ionization (REMPI) and (1+1$'$) REMPI. Six $\\Omega' = 3/2$ and ten $\\Pi_{1/2}$ vibronic bands have been characterized. We report the molecular constants for these bands and estimate the electronic energies of the excited states using a correction derived from the observed isotope shifts. When either of two closely spaced $\\Pi_{1/2}$ electronic states is used as an intermediate state to access autoionizing Rydberg levels, qualitatively distinct autoionization spectra are observed. The intermediate state-specificity of the autoionization spectra bodes well for the possibility of using a selected $\\Pi_{1/2}$ state as an intermediate state to create ionic HfF$^+$ in various selected quantum states, an important requirement for our electron electric dipole moment (eEDM) search in HfF$^+$.

  11. Plasma modifications induced by an X-mode HF heater wave in the high latitude F region of the ionosphere

    Science.gov (United States)

    Blagoveshchenskaya, N. F.; Borisova, T. D.; Yeoman, T. K.; Rietveld, M. T.; Häggström, I.; Ivanova, I. M.

    2013-12-01

    We presented experimental results of strong plasma modifications induced by X-mode powerful HF radio waves injected towards the magnetic zenith into the high latitude F region of the ionosphere. The experiments were conducted in 2009-2011 using the EISCAT Heating facility, UHF incoherent scatter radar and the EISCAT ionosonde at Tromsø, Norway; and the CUTLASS SuperDARN HF coherent radar at Hankasalmi, Finland. The results showed that the X-mode HF pump wave can generate strong small-scale artificial field aligned irregularities (AFAIs) in the F region of the high-latitude ionosphere. These irregularities, with spatial scales across the geomagnetic field of the order of 9-15 m, were excited when the heater frequency (fH) was above the ordinary-mode critical frequency (foF2) by 0.1-1.2 MHz. It was found that the X-mode AFAIs appeared between 10 s and 4 min after the heater is turned on. Their decay time varied over a wide range between 3 min and 30 min. The excitation of X-mode AFAIs was accompanied by electron temperature (Te) enhancements and an increase in the electron density (Ne) depending on the effective radiated power (ERP). Under ERPs of about 75-180 MW the Te enhances up to 50% above the background level and an increase in Ne of up to 30% were observed. Dramatic changes in the Te and Ne behavior occurred at effective radiated powers of about 370-840 MW, when the Ne and Te values increased up to 100% above the background ones. It was found that AFAIs, Ne and Te enhancements occurred, when the extraordinary-mode critical frequency (fxF2) lied in the frequency range fH-fce/2≤fxF2≤fH+fce/2, where fce is the electron gyrofrequency. The strong Ne enhancements were observed only in the magnetic field-aligned direction in a wide altitude range up to the upper limit of the UHF radar measurements. In addition, the maximum value of Ne is about 50 km higher than the Te enhancement peak. Such electron density enhancements (artificial ducts) cannot be explained by

  12. Digitally Driven Antenna for HF Transmission

    Science.gov (United States)

    2010-09-01

    the 1-MHz carrier signal. This signal is then fed into the base terminals of an NPN/ PNP transistor pair arranged in a push–pull configura- tion. A dual...negative voltage connected to the collector terminal of the PNP transistor . Since it was not possible to explicitly simulate the radia- tion of the time...complementary pair of switching transistors is driven with a pulsewidth modulated HF signal, eliminating the requirement for a frequency-dependent

  13. RFID UHF i HF w bibliotekach

    Directory of Open Access Journals (Sweden)

    Gładysz Bartłomiej

    2015-06-01

    Full Text Available The potential of the innovative Radio Frequency Identification (RFID technology to be applied for support, acceleration and automation of the circulation process of library collection is presented. Technology basics, and hardware and software components are described. Two different radio standards used in libraries are compared. The goal is to present the potential of RFID technology for libraries, to highlight the differences and to build a basis for further consideration of UHF and HF alternatives.

  14. Radar cross-sectional study using noise radar

    Science.gov (United States)

    Freundorfer, A. P.; Siddiqui, J. Y.; Antar, Y. M. M.

    2015-05-01

    A noise radar system is proposed with capabilities to measure and acquire the radar cross-section (RCS) of targets. The proposed system can cover a noise bandwidth of near DC to 50 GHz. The noise radar RCS measurements were conducted for selective targets like spheres and carpenter squares with and without dielectric bodies for a noise band of 400MHz-5000MHz. The bandwidth of operation was limited by the multiplier and the antennae used.

  15. Morphology and possible origins of near-range oblique HF backscatter at high and midlatitudes

    Science.gov (United States)

    Ponomarenko, Pavlo, V.; Iserhienrhien, Blessing; St.-Maurice, Jean-Pierre

    2016-06-01

    High-frequency radars (HF, ˜10-20 MHz) forming the Super Dual Auroral Radar Network (SuperDARN) regularly observe returns from very close ranges of ≤300-400 km (near-range echoes, NREs). These echoes are conventionally attributed to backscatter from meteor trails, but other sources of NRE have been invoked, including polar mesospheric summer echoes (PMSE), and non-field-aligned E region irregularities leading to high-aspect ionospheric returns. In order to relate NRE to a particular mechanism, it is essential to establish beforehand their spatiotemporal trends with respect to season, local time, and latitude. Systematic information of this kind is generally lacking from the literature, so we attempt to fill the gap by performing a statistical analysis of such echoes observed by five radars covering midlatitudes to polar latitudes over all seasons and local times. We detected two major echo populations which were observed at each radar site: (i) a nightside-early morning returns representing the well-known meteor backscatter and (ii) a midsummer population centered near the local noon. At high latitudes the summer daytime echoes are usually interpreted as PMSE, but the observed population extends to much lower latitudes and is centered well above the conventional PMSE height range. We hypothesize that this population could be related to neutral turbulence in the lower E region. In addition, there was a pronounced evening population restricted to the auroral region which we provisionally attribute to irregularities generated by the precipitating energetic particles and strong electric fields.

  16. Realistic simulations of tsunami detection by High-Frequency Radar in British Columbia, Canada

    Science.gov (United States)

    Grilli, Stéphan; Shelby, Michael; Grilli, Annette; Lado Insua, Tania; Guérin, Charles-Antoine

    2016-04-01

    A promising technique for long-range detection of tsunamis is the use of shore-based High Frequency (HF) surface wave radars, also simply referred to as oceanographic radars. These over-the-horizon radars are routinely used for real-time monitoring of ocean surface currents up to a 70-80 km range, based on the Doppler shift the latter cause in ocean waves at the radar Bragg frequency. Quite recently there has been convincing numerical and experimental evidence that oceanographic radars can also be used to detect tsunami-induced surface currents. However, these need to be at least 0.15-0.20 m/s to be detectable, when considering environmental noise and background currents (from tide and mesoscale circulation). This limits the actual detection of tsunami currents to the near range, that is essentially to the continental shelf over which tsunami currents become strong enough; in many cases this does not leave enough time to issue an efficient warning, unless there is a wide shelf. In recent work, some of the authors have proposed a detection algorithm that does not have this limitation and can detect an approaching tsunami in deeper water, beyond the continental shelf. This algorithm does not require "inverting" currents, but instead is based on spatial correlations of the raw signals recorded at two distant radar cells along the same wave ray, shifted in time by the tsunami propagation time along the ray. An elevated correlation would indicate the presence of a tsunami. We apply this algorithm to a realistic tsunami case study conducted, using a state-of-the-art long wave model, for sources (both seismic and landslide) and bathymetry off of Vancouver Island, BC. The propagation time between different radar cells is calculated with a Geometrical Optics approach using the Eikonal equation. This requires first determining wave rays' intersections with radar cells and computing a connectivity matrix between the latter. A model simulating the radar backscattered signal in

  17. Netted LPI RADARs

    Science.gov (United States)

    2011-09-01

    easier and, since they cover most of the space around the antenna, can expose it easily at various bearings ). Typical sidelobe levels for conventional...modern radar systems results in an electro- magnetic environment where the receiver should expect very few pulses. Staggered PRF and frequency agility...detector, a logarithmic amplitude compressor , and a signal encoder. All subunits are digitally controlled by computer as to frequency, sweep rate, and

  18. Imaging synthetic aperture radar

    Science.gov (United States)

    Burns, Bryan L.; Cordaro, J. Thomas

    1997-01-01

    A linear-FM SAR imaging radar method and apparatus to produce a real-time image by first arranging the returned signals into a plurality of subaperture arrays, the columns of each subaperture array having samples of dechirped baseband pulses, and further including a processing of each subaperture array to obtain coarse-resolution in azimuth, then fine-resolution in range, and lastly, to combine the processed subapertures to obtain the final fine-resolution in azimuth. Greater efficiency is achieved because both the transmitted signal and a local oscillator signal mixed with the returned signal can be varied on a pulse-to-pulse basis as a function of radar motion. Moreover, a novel circuit can adjust the sampling location and the A/D sample rate of the combined dechirped baseband signal which greatly reduces processing time and hardware. The processing steps include implementing a window function, stabilizing either a central reference point and/or all other points of a subaperture with respect to doppler frequency and/or range as a function of radar motion, sorting and compressing the signals using a standard fourier transforms. The stabilization of each processing part is accomplished with vector multiplication using waveforms generated as a function of radar motion wherein these waveforms may be synthesized in integrated circuits. Stabilization of range migration as a function of doppler frequency by simple vector multiplication is a particularly useful feature of the invention; as is stabilization of azimuth migration by correcting for spatially varying phase errors prior to the application of an autofocus process.

  19. The Radar Roadmap

    Science.gov (United States)

    2013-01-01

    LIMITATION OF ABSTRACT Same as Report ( SAR ) 18. NUMBER OF PAGES 25 19a. NAME OF RESPONSIBLE PERSON a. REPORT unclassified b. ABSTRACT unclassified c...ABSTRACT Same as Report ( SAR ) 18. NUMBER OF PAGES 25 19a. NAME OF RESPONSIBLE PERSON a. REPORT unclassified b. ABSTRACT unclassified c. THIS PAGE...object bistatic radars. The former allows high resolution without the use of pulse compression techniques and the latter promises cheaper systems by

  20. Radar Investigations of Asteroids

    Science.gov (United States)

    Ostro, S.

    2004-05-01

    Radar investigations have provided otherwise unavailable information about the physical and dynamical properties of about 230 asteroids. Measurements of the distribution of echo power in time delay (range) and Doppler frequency (line-of-sight velocity) provide two-dimensional images with spatial resolution as fine as a decameter. Sequences of delay-Doppler images can be used to produce geologically detailed three-dimensional models, to define the rotation state precisely, to constrain the internal density distribution, and to estimate the trajectory of the object's center of mass. Radar wavelengths (4 to 13 cm) and the observer's control of transmitted and received polarizations make the observations sensitive to near-surface bulk density and macroscopic structure. Since delay-Doppler measurements are orthogonal to optical angle measurements and typically have much finer fractional precision, they are powerful for refining orbits and prediction ephemerides. Such astrometric measurements can add decades or centuries to the interval over which an asteroid's close Earth approaches can accurately be predicted and can significantly refine collision probability estimates based on optical astrometry alone. In the highly unlikely case that a small body is on course for an Earth collision in this century, radar reconnaissance would almost immediately distinguish between an impact trajectory and a near miss and would dramatically reduce the difficulty and cost of any effort to prevent the collision. The sizes and rotation periods of radar-detected asteroids span more than four orders of magnitude. The observations have revealed both stony and metallic objects, elongated and nonconvex shapes as well as nearly featureless spheroids, small-scale morphology ranging from smoother than the lunar regolith to rougher than the rockiest terrain on Mars, craters and diverse linear structures, non-principal-axis spin states, contact binaries, and binary systems.

  1. Radar clutter classification

    Science.gov (United States)

    Stehwien, Wolfgang

    1989-11-01

    The problem of classifying radar clutter as found on air traffic control radar systems is studied. An algorithm based on Bayes decision theory and the parametric maximum a posteriori probability classifier is developed to perform this classification automatically. This classifier employs a quadratic discriminant function and is optimum for feature vectors that are distributed according to the multivariate normal density. Separable clutter classes are most likely to arise from the analysis of the Doppler spectrum. Specifically, a feature set based on the complex reflection coefficients of the lattice prediction error filter is proposed. The classifier is tested using data recorded from L-band air traffic control radars. The Doppler spectra of these data are examined; the properties of the feature set computed using these data are studied in terms of both the marginal and multivariate statistics. Several strategies involving different numbers of features, class assignments, and data set pretesting according to Doppler frequency and signal to noise ratio were evaluated before settling on a workable algorithm. Final results are presented in terms of experimental misclassification rates and simulated and classified plane position indicator displays.

  2. Nordic Snow Radar Experiment

    Science.gov (United States)

    Lemmetyinen, Juha; Kontu, Anna; Pulliainen, Jouni; Vehviläinen, Juho; Rautiainen, Kimmo; Wiesmann, Andreas; Mätzler, Christian; Werner, Charles; Rott, Helmut; Nagler, Thomas; Schneebeli, Martin; Proksch, Martin; Schüttemeyer, Dirk; Kern, Michael; Davidson, Malcolm W. J.

    2016-09-01

    The objective of the Nordic Snow Radar Experiment (NoSREx) campaign was to provide a continuous time series of active and passive microwave observations of snow cover at a representative location of the Arctic boreal forest area, covering a whole winter season. The activity was a part of Phase A studies for the ESA Earth Explorer 7 candidate mission CoReH2O (Cold Regions Hydrology High-resolution Observatory). The NoSREx campaign, conducted at the Finnish Meteorological Institute Arctic Research Centre (FMI-ARC) in Sodankylä, Finland, hosted a frequency scanning scatterometer operating at frequencies from X- to Ku-band. The radar observations were complemented by a microwave dual-polarization radiometer system operating from X- to W-bands. In situ measurements consisted of manual snow pit measurements at the main test site as well as extensive automated measurements on snow, ground and meteorological parameters. This study provides a summary of the obtained data, detailing measurement protocols for each microwave instrument and in situ reference data. A first analysis of the microwave signatures against snow parameters is given, also comparing observed radar backscattering and microwave emission to predictions of an active/passive forward model. All data, including the raw data observations, are available for research purposes through the European Space Agency and the Finnish Meteorological Institute. A consolidated dataset of observations, comprising the key microwave and in situ observations, is provided through the ESA campaign data portal to enable easy access to the data.

  3. Overview and Prospects of Research on Sea Clutter Property Cognition

    Directory of Open Access Journals (Sweden)

    Ding Hao

    2016-10-01

    Full Text Available Sea clutter is one of the main limiting factors influencing the target detection performance of nautical radars. The physical mechanism of sea clutter is complex with an abundance of influencing factors, and the non-Gaussian as well as non-stationarity behavior is significant. Thus, research into sea clutter property cognition is complicated and has to be systematic. Based on research that concentrates on experimental data, this paper reviews and summarizes the research developments in sea clutter property cognition. It concentrates on the properties that are of most interest for target detection algorithms: amplitude distribution, spectra, correlation, and non-stationarity and nonlinearity. The main research results are also concluded. Based on this, four aspects of problems that need further exploration are highlighted and include the following: further analysis of sea clutter influencing factors; the game problem between sea clutter precision modeling and the requirements of detection algorithms; and the property cognition between radar target and sea clutter.

  4. Interdisciplinary Earth Science Applications Using Satellite Radar Altimetry

    Science.gov (United States)

    Kuo, C.; Shum, C.; Lee, H.; Dai, C.; Yi, Y.

    2012-12-01

    Satellite altimetry was conceived as a space geodetic concept for ocean surface topography mapping in the NASA-sponsored 1969 Williamstown, MA Conference, and was tested as part of the passive and active radar payload (S192), along with a radiometer and a scatterometer, on Skylab-1 in May 14, 1973. Since then, numerous radar and laser satellite altimetry missions orbiting/flying-by the Earth, Mars, Mercury, Titan and the Moon have been launched, evolving from the original scientific objective of marine gravity field mapping to a geodetic tool to address interdisciplinary Earth and planetary sciences. The accuracy of the radar altimeter has improved from 0.9 m RMS for the S-192 Skylab Ku-band compressed-pulse altimeter, to 2 cm RMS (2 second average) for the dual-frequency pulse-limited radar altimetry and associated sensors onboard TOPEX/POSEIDON. Satellite altimetry has evolved into a unique cross-disciplinary geodetic tool in addressing contemporary Earth science problems including sea-level rise, large-scale general ocean circulation, ice-sheet mass balance, terrestrial hydrology, and bathymetry. Here we provide a concise review and describe specific results on the additional recent innovative and unconventional applications of interdisciplinary science research using satellite radar altimetry, including geodynamics, land subsidence, snow depth, wetland and cold region hydrology.

  5. Deflating British Radar Myths of World War II

    Science.gov (United States)

    1997-03-01

    this interference was well enough known for scientists to theorize how to use this interference. In 1900, Nikola Tesla suggested a wireless system...which would use reflected radio waves to locate objects and even to measure their distance. Tesla explained the concept of radar as, “When we raise...of a moving object such as a vessel at sea.” Unfortunately, Tesla was considered an anarchist and was never given funding for his ideas. His ideas

  6. Detection of Weather Radar Clutter

    DEFF Research Database (Denmark)

    Bøvith, Thomas

    2008-01-01

    Weather radars provide valuable information on precipitation in the atmosphere but due to the way radars work, not only precipitation is observed by the weather radar. Weather radar clutter, echoes from non-precipitating targets, occur frequently in the data, resulting in lowered data quality....... Especially in the application of weather radar data in quantitative precipitation estimation and forecasting a high data quality is important. Clutter detection is one of the key components in achieving this goal. This thesis presents three methods for detection of clutter. The methods use supervised...... and precipitating and non-precipitating clouds. Another method uses the difference in the motion field of clutter and precipitation measured between two radar images. Furthermore, the direction of the wind field extracted from a weather model is used. The third method uses information about the refractive index...

  7. FMWC Radar for Breath Detection

    DEFF Research Database (Denmark)

    Suhr, Lau Frejstrup; Tafur Monroy, Idelfonso; Vegas Olmos, Juan José

    We report on the experimental demonstration of an FMCW radar operating in the 25.7 - 26.6 GHz range with a repetition rate of 500 sweeps per second. The radar is able to track the breathing rate of an adult human from a distance of 1 meter. The experiments have utilized a 50 second recording window...... to accurately track the breathing rate. The radar utilizes a saw tooth modulation format and a low latency receiver. A breath tracking radar is useful both in medical scenarios, diagnosing disorders such as sleep apnea, and for home use where the user can monitor its health. Breathing is a central part of every...... radar chip which, through the use of a simple modulation scheme, is able to measure the breathing rate of an adult human from a distance. A high frequency output makes sure that the radar cannot penetrate solid obstacles which is a wanted feature in private homes where people therefore cannot measure...

  8. Radar techniques using array antennas

    CERN Document Server

    Wirth, Wulf-Dieter

    2013-01-01

    Radar Techniques Using Array Antennas is a thorough introduction to the possibilities of radar technology based on electronic steerable and active array antennas. Topics covered include array signal processing, array calibration, adaptive digital beamforming, adaptive monopulse, superresolution, pulse compression, sequential detection, target detection with long pulse series, space-time adaptive processing (STAP), moving target detection using synthetic aperture radar (SAR), target imaging, energy management and system parameter relations. The discussed methods are confirmed by simulation stud

  9. The importance of elevation angle measurements in HF radar investigations of the ionosphere

    Science.gov (United States)

    Greenwald, Raymond A.; Frissell, Nathaniel; de Larquier, Sebastien

    2017-03-01

    We evaluate the performance of three methods for determining the ground range and refractive index of ionospheric scattering volumes. Each method uses the same equivalent path analysis with the latter parameter derived through the additional use of Snell's law. Two of these methods make their predictions using the group range and a virtual height model for each scattering volume; the third method uses the group range and the elevation angle of the ray. The effectiveness of each of these methods is evaluated using ray tracing through a simulated reference ionosphere. Ray tracings provide determinations of the initial elevation angle and group range of the transmitted signal and the ground range and refractive index of the scattering volume. The first pair of parameters is used as inputs to the geolocation methods, and the second pair becomes part of a data set against which the predictions of the geolocation methods are evaluated. We find that the geolocation methods using virtual height models change the initial elevation angle to a value that is consistent with their virtual height model but inconsistent with ray tracing. Consequently, predictions of ground range and refractive index from methods using virtual height models are rarely consistent with predictions from ray tracing. In contrast, the third method uses the initial elevation angle from ray tracing and yields accurate predictions in the bottomside ionosphere. Two modifications were made to this method to extend the agreement between it and ray tracing to all backscattered signals.

  10. PMSE long term observations using SuperDARN SANAE HF radar measurements

    National Research Council Canada - National Science Library

    Olakunle Ogunjobi; Venkataraman Sivakumar; Judy Ann Elizabeth Stephenson; Zolile Mtumela

    2017-01-01

    .... These strong backscatters are referred to as Polar Mesosphere Summer Echoes (PMSE). Although studies on PMSE have been ongoing for over three decades, aspects revealed by various instruments are still the subject of discussion...

  11. Proximal Ignimbrite Geometry on Santorini, Greece Using Ground Penetrating Radar

    Science.gov (United States)

    Stasiuk, M. V.; Russell, J. K.; Hill, G. J.; Druitt, T. H.

    2001-12-01

    Ground penetrating radar (GPR) surveys on Santorini, Greece, are used to constrain the 3-dimensional geometry of the near-surface pyroclastic deposits produced by the 3.6 ka caldera-forming Minoan eruption. Specifically, the results elucidate deposit structures at the south end of the island. More than 2.4 km of radar survey data were collected at a measurement spacing of 0.5-1.0 m, using the common offset reflection method (3 m offset) and radar frequencies of 50 and 100 MHz. Imaging depths of the raw data were typically small (caldera rim while phase 4 gradually thickens. The GPR results suggest that the flows were more energetic than the previous model implied, and too energetic to bulk deposit in the subaerial, proximal area. Most of the mass of pyroclastics swept down the slope and into the sea, leaving behind only thin veneers. The velocity reduction caused by a combination of the phase 4 flow thickening as it passed over the ancient sea cliffs, and by entering the sea, caused the flow to switch to a strongly depositional mode resulting in a thickened deposit. An implication of these results is that most of the Minoan pyroclastic flow deposits on Santorini, apart from those near and on the outer coast, were emplaced aggradationally.

  12. Analysis of sea-surface radar signatures by means of wavelet-based edge detection and detection of regularities; Analyse von Radarsignaturen der Meeresoberflaeche mittels auf Wavelets basierender Kantenerkennung und Regularitaetsbestimmung

    Energy Technology Data Exchange (ETDEWEB)

    Wolff, U. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Gewaesserphysik

    2000-07-01

    The derivation and implementation of an algorithm for edge detection in images and for the detection of the Lipschitz regularity in edge points are described. The method is based on the use of the wavelet transform for edge detection at different resolutions. The Lipschitz regularity is a measure that characterizes the edges. The description of the derivation is first performed in one dimension. The approach of Mallat is formulated consistently and proved. Subsequently, the two-dimensional case is addressed, for which the derivation, as well as the description of the algorithm, is analogous. The algorithm is applied to detect edges in nautical radar images using images collected at the island of Sylt. The edges discernible in the images and the Lipschitz values provide information about the position and nature of spatial variations in the depth of the seafloor. By comparing images from different periods of measurement, temporal changes in the bottom structures can be localized at different resolutions and interpreted. The method is suited to the monitoring of coastal areas. It is an inexpensive way to observe long-term changes in the seafloor character. Thus, the results of this technique may be used by the authorities responsible for coastal protection to decide whether measures should be taken or not. (orig.)

  13. Detection of Transionospheric SuperDARN HF Waves by the Radio Receiver Instrument on the enhanced Polar Outflow Probe Satellite

    Science.gov (United States)

    Gillies, R. G.; Yau, A. W.; James, H. G.; Hussey, G. C.; McWilliams, K. A.

    2014-12-01

    The enhanced Polar Outflow Probe (ePOP) Canadian small-satellite was launched in September 2013. Included in this suite of eight scientific instruments is the Radio Receiver Instrument (RRI). The RRI has been used to measure VLF and HF radio waves from various ground and spontaneous ionospheric sources. The first dedicated ground transmission that was detected by RRI was from the Saskatoon Super Dual Auroral Radar Network (SuperDARN) radar on Nov. 7, 2013 at 14 MHz. Several other passes over the Saskatoon SuperDARN radar have been recorded since then. Ground transmissions have also been observed from other radars, such as the SPEAR, HAARP, and SURA ionospheric heaters. However, the focus of this study will be on the results obtained from the SuperDARN passes. An analysis of the signal recorded by the RRI provides estimates of signal power, Doppler shift, polarization, absolute time delay, differential mode delay, and angle of arrival. By comparing these parameters to similar parameters derived from ray tracing simulations, ionospheric electron density structures may be detected and measured. Further analysis of the results from the other ground transmitters and future SuperDARN passes will be used to refine these results.

  14. Electron-ion temperature ratio estimations in the summer polar mesosphere when subject to HF radio wave heating

    Science.gov (United States)

    Pinedo, H.; La Hoz, C.; Havnes, O.; Rietveld, M.

    2014-10-01

    We have inferred the electron temperature enhancements above mesospheric altitudes under Polar Mesospheric Summer Echoes (PMSE) conditions when the ionosphere is exposed to artificial HF radio wave heating. The proposed method uses the dependence of the radar cross section on the electron-to-ion temperature ratio to infer the heating factor from incoherent scatter radar (ISR) power measurements above 90 km. Model heating temperatures match our ISR estimations between 90 and 130 km with 0.94 Pearson correlation index. The PMSE strength measured by the MORRO MST radar is about 50% weaker during the heater-on period when the modeled electron-to-ion mesospheric temperature is approximately 10 times greater than the unperturbed value. No PMSE weakening is found when the mesospheric temperature enhancement is by a factor of three or less. The PMSE weakening and its absence are consistent with the modeled mesospheric electron temperatures. This consistency supports to the proposed method for estimating mesospheric electron temperatures achieved by independent MST and ISR radar measurements.

  15. Reconfigurable L-Band Radar

    Science.gov (United States)

    Rincon, Rafael F.

    2008-01-01

    The reconfigurable L-Band radar is an ongoing development at NASA/GSFC that exploits the capability inherently in phased array radar systems with a state-of-the-art data acquisition and real-time processor in order to enable multi-mode measurement techniques in a single radar architecture. The development leverages on the L-Band Imaging Scatterometer, a radar system designed for the development and testing of new radar techniques; and the custom-built DBSAR processor, a highly reconfigurable, high speed data acquisition and processing system. The radar modes currently implemented include scatterometer, synthetic aperture radar, and altimetry; and plans to add new modes such as radiometry and bi-static GNSS signals are being formulated. This development is aimed at enhancing the radar remote sensing capabilities for airborne and spaceborne applications in support of Earth Science and planetary exploration This paper describes the design of the radar and processor systems, explains the operational modes, and discusses preliminary measurements and future plans.

  16. Active Modification of VHF and HF PMSE during the 2009 EISCAT Campaign

    Science.gov (United States)

    Mahmoudian, A.; Scales, W.; Kosch, M.; Singer, A.; Rietveld, M. T.

    2009-12-01

    Polar Mesospheric Summer Echoes (PMSE) are strong echoes that have been typically observed in the frequency range from 50MHz to 1.3GHz and in the altitude about 85Km. The PMSE is produced by scattering from electron irregularities due to electron charging on the irregular subvisible mesospheric dust layer. The radar echoes occur at half the radar wavelength therefore the wavelength of the irregularities are roughly in the range of 10cm to 10m. In recent experiments, the EISCAT ground based ionospheric heating facility was used to produce an artificial enhancement in electron temperature in dust layer.Important information can be obtained from temporal behavior of the electron irregularities during turn on or turn off the radio wave heating. Considering the temporal behavior of electron irregularities during heating process provides diagnostic information about dust layer. In the first part of the presentation, the radar data obtained during an experimental campaign at the European Incoherent Scatter Scientific Association (EISCAT) facility in Tromso, Norway in July 2009 is discussed. The measurement was set up with 3 minutes heating cycle in which the heater is on for 40 seconds to increase electron temperature in the specific area in the ionosphere and after 40 seconds, the heater is turned off. At the same time the scatter radar signal also is recorded to analyze temporal behavior during turn on and turn off of the heater. Radar scattering at 224 MHz (VHF) and 7.953 MHz (HF) frequency bands was observed. Modulation in the PMSE is observed. In the second part of the presentation, a computational model is used to provide interpretation of the data. A one dimensional computational model is used to study PMSE during radio wave heating. There are different parameters which vary with temperature such electron-neutral collision frequency, recombination coefficient and dust charging process. The model includes ions, electrons and dust. The ions and electrons are treated

  17. Tsunami Detection by High Frequency Radar Beyond the Continental Shelf: II. Extension of Time Correlation Algorithm and Validation on Realistic Case Studies

    Science.gov (United States)

    Grilli, Stéphan T.; Guérin, Charles-Antoine; Shelby, Michael; Grilli, Annette R.; Moran, Patrick; Grosdidier, Samuel; Insua, Tania L.

    2017-08-01

    In past work, tsunami detection algorithms (TDAs) have been proposed, and successfully applied to offline tsunami detection, based on analyzing tsunami currents inverted from high-frequency (HF) radar Doppler spectra. With this method, however, the detection of small and short-lived tsunami currents in the most distant radar ranges is challenging due to conflicting requirements on the Doppler spectra integration time and resolution. To circumvent this issue, in Part I of this work, we proposed an alternative TDA, referred to as time correlation (TC) TDA, that does not require inverting currents, but instead detects changes in patterns of correlations of radar signal time series measured in pairs of cells located along the main directions of tsunami propagation (predicted by geometric optics theory); such correlations can be maximized when one signal is time-shifted by the pre-computed long wave propagation time. We initially validated the TC-TDA based on numerical simulations of idealized tsunamis in a simplified geometry. Here, we further develop, extend, and apply the TC algorithm to more realistic tsunami case studies. These are performed in the area West of Vancouver Island, BC, where Ocean Networks Canada recently deployed a HF radar (in Tofino, BC), to detect tsunamis from far- and near-field sources, up to a 110 km range. Two case studies are considered, both simulated using long wave models (1) a far-field seismic, and (2) a near-field landslide, tsunami. Pending the availability of radar data, a radar signal simulator is parameterized for the Tofino HF radar characteristics, in particular its signal-to-noise ratio with range, and combined with the simulated tsunami currents to produce realistic time series of backscattered radar signal from a dense grid of cells. Numerical experiments show that the arrival of a tsunami causes a clear change in radar signal correlation patterns, even at the most distant ranges beyond the continental shelf, thus making an

  18. Mapping of sea bottom topography

    Science.gov (United States)

    Calkoen, C. J.; Wensink, G. J.; Hesselmans, G. H. F. M.

    1992-01-01

    Under suitable conditions the bottom topography of shallow seas is visible in remote sensing radar imagery. Two experiments were performed to establish which remote sensing technique or combination yields optimal imaging of bottom topography and which hydro-meteorological conditions are favorable. A further goal is to gain experience with these techniques. Two experiments were performed over an area in the North Sea near the measuring platform Meetpost Noordwijk (MPN). The bottom topography in the test area is dominated by sand waves. The crests of the sand waves are perpendicular to the coast line and the dominating (tidal-)current direction. A 4x4 sq km wide section of the test area was studied in more detail. The first experiment was undertaken on 16 Aug. 1989. During the experiment the following remote sensing instruments were used: Landsat-Thematic Mapper, and NASA/JPL Airborne Imaging Radar (AIR). The hydro-meteorological conditions; current, wind, wave, and air and water temperature were monitored by MPN, a ship of Rijkswaterstaat (the OCTANS), and a pitch-and-roll WAVEC-buoy. The second experiment took place on 12 July 1992. During this experiment data were collected with the NASA/JPL polarimetric synthetic aperture radar (SAR), and a five-band helicopter-borne scatterometer. Again the hydro-meteorological conditions were monitored at MPN and the OCTANS. Furthermore, interferometric radar data were collected.

  19. 超高频雷达海洋表面流的探测结果与分析%Results and analysis of surface current based on UHF radar

    Institute of Scientific and Technical Information of China (English)

    文必洋; 李艳; 侯义东; 杨静

    2016-01-01

    近岸海域地形、海流复杂,而超高频雷达系统具有较高距离分辨率、小发射功率的特点,波长介于高频电磁波和微波之间,能同时提取海浪毛细波与重力波信息,与波浪作用比较敏感,能实现近海海洋动力参数的精细测量.不同于高频雷达回波谱,超高频雷达回波中一阶峰、二阶峰展宽严重并混叠在一起,难以划分一阶峰区域,因此,文中系统设计采用数字波束形成进行流速方位提取.雷达反演的流速结果与浮标数据的相关系数为0.88,但是均方根误差很大.通过分析,得出海洋表面流速不仅受到潮汐效应、地球自转的影响,当地风速在很大程度上也会影响表面流速的结论.%Ultra high frequency(UHF)radar has the characteristics of high range resolution and low-power,which can extract information of both capillary wave and gravity wave with the wavelength be-tween high frequency and microwave.It is possible to obtain precise monitoring of the coastal ocean dy-namics parameters by UHF radar,though the offshore topography and ocean surface current are complex. UHF radar is different from HF radar,since the first-order peak and second-order spectrum are indistin-guishable in the sea echo spectrum.It is difficult to extract first-order peak,therefore,multiple signal classification algorithm (MUSIC)is unavailable and digital beam-forming(DBF)is used in extracting the radial velocity.After a month,the radar and buoy datais highly correlated with a coefficient of 0.88,how-ever,the root mean square error is large.The results show that the velocity of the ocean surface is influ-enced not only by the tidal effect and the rotationof the earth,but also by the local wind speed.

  20. On the radar cross section (RCS) prediction of vehicles moving on the ground

    Energy Technology Data Exchange (ETDEWEB)

    Sabihi, Ahmad [Department of Mathematical Sciences, Sharif University of Technology, Tehran (Iran, Islamic Republic of)

    2014-12-10

    As readers should be aware, Radar Cross Section depends on the factors such as: Wave frequency and polarization, Target dimension, angle of ray incidence, Target’s material and covering, Type of radar system as monostatic or bistatic, space in which contains target and propagating waves, and etc. Having moved or stationed in vehicles can be effective in RCS values. Here, we investigate effective factors in RCS of moving targets on the ground or sea. Image theory in electromagnetic applies to be taken into account RCS of a target over the ground or sea.

  1. SIMULATION STUDY OF IMAGING OF UNDERWATER BOTTOM TOPOGRAPHY BY SYNTHETIC APERTURE RADAR

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Interaction between current and underwater bottom topography modulates roughness of the sea surface, which in turn yields variation of the radar scattering echo. By using the mechanism, this paper presents a simulation model for Synthetic Aperture Radar (SAR) imaging of underwater bottom topography. The numerical simulations experiments were made using the Princeton Ocean Model (POM) and analytical expression theory of SAR Image in Mischief sea area. It is concluded that the SAR image is better visual when water depth of underwater bottom topography is shallow or gradient of underwater bottom topography is high.

  2. Removing interfering clutter associated with radar pulses that an airborne radar receives from a radar transponder

    Science.gov (United States)

    Ormesher, Richard C.; Axline, Robert M.

    2008-12-02

    Interfering clutter in radar pulses received by an airborne radar system from a radar transponder can be suppressed by developing a representation of the incoming echo-voltage time-series that permits the clutter associated with predetermined parts of the time-series to be estimated. These estimates can be used to estimate and suppress the clutter associated with other parts of the time-series.

  3. Dynamic Singularity Spectrum Distribution of Sea Clutter

    Science.gov (United States)

    Xiong, Gang; Yu, Wenxian; Zhang, Shuning

    2015-12-01

    The fractal and multifractal theory have provided new approaches for radar signal processing and target-detecting under the background of ocean. However, the related research mainly focuses on fractal dimension or multifractal spectrum (MFS) of sea clutter. In this paper, a new dynamic singularity analysis method of sea clutter using MFS distribution is developed, based on moving detrending analysis (DMA-MFSD). Theoretically, we introduce the time information by using cyclic auto-correlation of sea clutter. For transient correlation series, the instantaneous singularity spectrum based on multifractal detrending moving analysis (MF-DMA) algorithm is calculated, and the dynamic singularity spectrum distribution of sea clutter is acquired. In addition, we analyze the time-varying singularity exponent ranges and maximum position function in DMA-MFSD of sea clutter. For the real sea clutter data, we analyze the dynamic singularity spectrum distribution of real sea clutter in level III sea state, and conclude that the radar sea clutter has the non-stationary and time-varying scale characteristic and represents the time-varying singularity spectrum distribution based on the proposed DMA-MFSD method. The DMA-MFSD will also provide reference for nonlinear dynamics and multifractal signal processing.

  4. Comparison of sea-ice freeboard distributions from aircraft data and cryosat-2

    DEFF Research Database (Denmark)

    Ricker, Robert; Hendricks, Stefan; Helm, Veit

    2012-01-01

    highly accurate range measurements. During the CryoSat Validation Experiment (CryoVEx) 2011 in the Lincoln Sea Cryosat-2 underpasses were accomplished with two aircraft which carried an airborne laser scanner, a radar altimeter and an electromagnetic induction device for direct sea ice thickness...... retrieval. Both aircraft flew in close formation at the same time of a CryoSat-2 overpass. This is a study about the comparison of the sea-ice freeboard distribution of laser scanner and radar altimeter measurements with the CryoSat-2 product within the multi-year sea ice region of the Lincoln Sea in spring...

  5. Ray-Trace of an Abnormal Radar Echo Using Geographic Information System

    Directory of Open Access Journals (Sweden)

    Chi-Nan Chen

    2009-01-01

    Full Text Available Weather radar plays a key role in natural disaster mitigation just as surveillance radar does in detecting objects that threaten homeland security. Both together comprise an instrumental part of radar observation. Therefore, quality control of the data gathered through radar detection is extremely important. However, radar waves propagate in the atmosphere, and an anomalous echo can occur if there are significant discontinuities in temperature and humidity in the lower boundary layer. The refractive curvature of the earth makes some errors in observation inevitable. On the night of July 3, 2003, Next Generation Radar (NEXRAD weather radar detected an abnormal echo. The Weather Research and Forecast (WRF model was utilized to simulate the atmospheric conditions. Radar propagation was simulated using the Advanced Refractivity Engineering Prediction System (AREPS as well as the GIS. The results show the feasibility of establishing an abnormal propagation early-warning system and extending the application of the GIS in serving as the foundation of a Common Operation Picture (COP. Furthermore, the parameters of the boundary layer near the sea's surface in the numerical weather forecasting model need remodification.Defence Science Journal, 2009, 59(1, pp.63-72, DOI:http://dx.doi.org/10.14429/dsj.59.1487

  6. HF Propagation Directions Observed by the e-POP Radio Receiver Instrument

    Science.gov (United States)

    James, H. G.; Perry, G. W.

    2016-12-01

    We have investigated high-frequency (HF) propagation direction measurements by the e-POP Radio Receiver Instrument (RRI) on the CASSIOPE spacecraft. The measurement of the direction of arrival (DOA) of electromagnetic waves propagating in the ionosphere is a desirable technique for the analysis of both spontaneous emissions and waves emitted by ground transmitters. In the case of detection of waves launched by HF radars, DOA evidence at low earth orbit close to regions of (coherent) backscatter may help to understand the details of the physics of scatter of radar waves, by the examination of waves both incident on and scattered by irregularities of density. The RRI has been used to observe direct transmissions from the ground for evaluation of a DOA detection algorithm. Signals are detected with two orthogonal 6-m distributed dipoles on RRI working at frequencies up to about 18 MHz. When ground sources emit electric-field polarisation of one of the Ordinary (O) and Extraordinary (X) cold-plasma modes, the DOA of transmissions propagating near the bore sight of the RRI crossed dipoles can be determined. In the instance of transversely polarized transmissions from a SuperDARN source, the emissions are the sum of the two cold-plasma modes and we depend on differential refraction to temporally resolve the pulsed transmissions into two modes for DOA measurement by the RRI. DOA information can help to confirm the existence of horizontal density gradients that can bend rays away from the great-circle beam paths traditionally assumed in the SuperDARN fields of view.

  7. Radar foundations for imaging and advanced concepts

    CERN Document Server

    Sullivan, Roger

    2004-01-01

    Through courses internally taught at IDA, Dr. Roger Sullivan has devised a book that brings readers fully up to speed on the most essential quantitave aspects of general radar in order to introduce study of the most exciting and relevant applications to radar imaging and advanced concepts: Synthetic Aperture Radar (4 chapters), Space-time Adaptive Processing, moving target indication (MTI), bistatic radar, low probability of intercept (LPI) radar, weather radar, and ground-penetrating radar. Whether you're a radar novice or experienced professional, this is an essential refer

  8. Broadview Radar Altimetry Toolbox

    Science.gov (United States)

    Mondéjar, Albert; Benveniste, Jérôme; Naeije, Marc; Escolà, Roger; Moyano, Gorka; Roca, Mònica; Terra-Homem, Miguel; Friaças, Ana; Martinho, Fernando; Schrama, Ernst; Ambrózio, Américo; Restano, Marco

    2016-07-01

    The universal altimetry toolbox, BRAT (Broadview Radar Altimetry Toolbox) which can read all previous and current altimetry missions' data, incorporates now the capability to read the upcoming Sentinel-3 L1 and L2 products. ESA endeavoured to develop and supply this capability to support the users of the future Sentinel-3 SAR Altimetry Mission. BRAT is a collection of tools and tutorial documents designed to facilitate the processing of radar altimetry data. This project started in 2005 from the joint efforts of ESA (European Space Agency) and CNES (Centre National d'Études Spatiales), and it is freely available at http://earth.esa.int/brat. The tools enable users to interact with the most common altimetry data formats. The BratGUI is the front-end for the powerful command line tools that are part of the BRAT suite. BRAT can also be used in conjunction with MATLAB/IDL (via reading routines) or in C/C++/Fortran via a programming API, allowing the user to obtain desired data, bypassing the data-formatting hassle. BRAT can be used simply to visualise data quickly, or to translate the data into other formats such as NetCDF, ASCII text files, KML (Google Earth) and raster images (JPEG, PNG, etc.). Several kinds of computations can be done within BRAT involving combinations of data fields that the user can save for posterior reuse or using the already embedded formulas that include the standard oceanographic altimetry formulas. The Radar Altimeter Tutorial, that contains a strong introduction to altimetry, shows its applications in different fields such as Oceanography, Cryosphere, Geodesy, Hydrology among others. Included are also "use cases", with step-by-step examples, on how to use the toolbox in the different contexts. The Sentinel-3 SAR Altimetry Toolbox shall benefit from the current BRAT version. While developing the toolbox we will revamp of the Graphical User Interface and provide, among other enhancements, support for reading the upcoming S3 datasets and

  9. GNSS-R Sea/Land and Sea/Ice Transition Dtetectiond from TDS-1 DDMs

    Science.gov (United States)

    Schiavulli, D.; Frappart, F.; Darrozes, J.; Ramilien, G.; Nunziata, F.; Migliaccio, M.

    2016-08-01

    In this paper, Global Navigation Satellite System (GNSS) Reflectometry, GNSS-R, Delay-Doppler Maps (DDMs) are processed to provide added value products for imaging remote sensing. In particular, actual DDMs collected by the UK TechDemoSat- 1 sensor are processed in order to reconstruct the Normalized Radar Cross section field for marine scenarios including non homogeneous elements, i.e. sea/land and sea/ice transition. The result consists of a radar image of the observed scene able to complement data provided by sensors dedicated to imaging remote sensing.

  10. Weather Radar Technology Development

    Science.gov (United States)

    1990-08-15

    Preparation). MISCELLANEOUS Donaldson Jr, R.J., 1987: "Significance of the 40th Anniversary Conference." Address at the Battan Memorial and 40th Anni - versary...Bergen and Albers (1987). They have achieved -37 -29 -25 -6 4 7 magnificent results for reducing general -35 -28 -19 -7 -3 4 ambiguity. 283 284 285 3.2... Albers , 1988: Two- and the National Severe Storms Laboratory S-band three-dimensional de-aliasing of Doppler radar in Norman, Oklahoma. For three

  11. Radar scattering of linear dunes and mega-yardangs: Application to Titan

    Science.gov (United States)

    Paillou, Philippe; Seignovert, Benoît; Radebaugh, Jani; Wall, Stephen

    2016-05-01

    The Ku-band (13.8 GHz - 2.2 cm) RADAR instrument onboard the Cassini-Huygens spacecraft has revealed the richness of the surface of Titan, as numerous seas, lakes, rivers, cryo-volcanic flows and vast dune fields have been discovered. Linear dunes are a major geomorphological feature present on Titan, covering up to 17% of its surface, mainly in equatorial regions. However, the resolution of the RADAR instrument is not good enough to allow a detailed study of the morphology of these features. In addition, other linear wind-related landforms, such as mega-yardangs (linear wind-abraded ridges formed in cohesive rocks), are likely to present a comparable radar signature that could be confused with the one of dunes. We conducted a comparative study of the radar radiometry of both linear dunes and mega-yardangs, based on representative terrestrial analogues: the linear dunes located in the Great Sand Sea in western Egypt and in the Namib Desert in Namibia, and the mega-yardangs observed in the Lut Desert in eastern Iran and in the Borkou Desert in northern Chad. We analysed the radar scattering of both terrestrial linear dunes and mega-yardangs, using high-resolution radar images acquired by the X-band (9.6 GHz - 3.1 cm) sensor of the TerraSAR-X satellite. Variations seen in the radar response of dunes are the result of a contrast between the dune and interdune scattering, while for mega-yardangs these variations are the result of a contrast between ridges and erosion valleys. We tested a simple surface scattering model, with parameters derived from the local topography and surface roughness estimates, to accurately reproduce the radar signal variations for both landforms. It appears that we can discriminate between two types of dunes - bare interdunes as in Egypt and sand-covered interdunes as in Namibia, and between two types of mega-yardangs - young yardangs as in Iran and older ones as in Chad. We applied our understanding of the radar scattering to the analysis of

  12. Terahertz radar cross section measurements

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Heiselberg, Henning; Jepsen, Peter Uhd

    2010-01-01

    We perform angle- and frequency-resolved radar cross section (RCS) measurements on objects at terahertz frequencies. Our RCS measurements are performed on a scale model aircraft of size 5-10 cm in polar and azimuthal configurations, and correspond closely to RCS measurements with conventional radar...

  13. Performance indicators modern surveillance radar

    NARCIS (Netherlands)

    Nooij, P.N.C.; Theil, A.

    2014-01-01

    Blake chart computations are widely employed to rank detection coverage capabilities of competitive search radar systems. Developed for comparable 2D radar systems with a mechanically rotating reflector antenna, it was not necessary to regard update rate and plot quality in Blake's chart. To

  14. Measuring human behaviour with radar

    NARCIS (Netherlands)

    Dorp, Ph. van

    2001-01-01

    The paper presents human motion measurements with the experimental Frequency Modulated Continuous Wave(FMCW) radar at TNO-FEL. The aim of these measurements is to analyse the Doppler velocity spectrum of humans. These analysis give insight in measuring human behaviour with radar for security applica

  15. Imaging with Synthetic Aperture Radar

    CERN Document Server

    Massonnet, Didier

    2008-01-01

    Describing a field that has been transformed by the recent availability of data from a new generation of space and airborne systems, the authors offer a synthetic geometrical approach to the description of synthetic aperture radar, one that addresses physicists, radar specialists, as well as experts in image processing.  

  16. Performance indicators modern surveillance radar

    NARCIS (Netherlands)

    Nooij, P.N.C.; Theil, A.

    2014-01-01

    Blake chart computations are widely employed to rank detection coverage capabilities of competitive search radar systems. Developed for comparable 2D radar systems with a mechanically rotating reflector antenna, it was not necessary to regard update rate and plot quality in Blake's chart. To charact

  17. Synthetic Aperture Radar - Hardware Development

    Directory of Open Access Journals (Sweden)

    V. Rosner

    2009-06-01

    Full Text Available Experimental real and synthetic aperture radar are developed from the base-band digital unit to the analogue RF parts, based on solid state units, using pulse compression for radar imaging. Proper QPSK code is found for matched filter.

  18. Generation of whistler waves by continuous HF heating of the upper ionosphere

    Science.gov (United States)

    Vartanyan, A.; Milikh, G. M.; Eliasson, B.; Najmi, A. C.; Parrot, M.; Papadopoulos, K.

    2016-07-01

    Broadband VLF waves in the frequency range 7-10 kkHz and 15-19 kHz, generated by F region CW HF ionospheric heating in the absence of electrojet currents, were detected by the DEMETER satellite overflying the High Frequency Active Auroral Research Program (HAARP) transmitter during HAARP/BRIOCHE campaigns. The VLF waves are in a frequency range corresponding to the F region lower lybrid (LH) frequency and its harmonic. This paper aims to show that the VLF observations are whistler waves generated by mode conversion of LH waves that were parametrically excited by HF-pump-plasma interaction at the upper hybrid layer. The paper discusses the basic physics and presents a model that conjectures (1) the VLF waves observed at the LH frequency are due to the interaction of the LH waves with meter-scale field-aligned striations—generating whistler waves near the LH frequency; and (2) the VLF waves at twice the LH frequency are due to the interaction of two counterpropagating LH waves—generating whistler waves near the LH frequency harmonic. The model is supported by numerical simulations that show good agreement with the observations. The (Detection of Electromagnetic Emissions Transmitted from Earthquake Regions results and model discussions are complemented by the Kodiak radar, ionograms, and stimulated electromagnetic emission observations.

  19. Systematic Study on Triaxial Superdeformed Bands of Hf Isotopes

    Institute of Scientific and Technical Information of China (English)

    ZHANG Da-Li; DING Bin-Gang

    2009-01-01

    Properties of the triaxial superdeformed (TSD) bands of Hf isotopes are investigated systematically within the supersymmetry scheme including many-body interactions and a perturbation possessing the SO(5) (or SU(5)) symmetry on the rotational symmetry. Quantitatively good results of the γ-ray energies, the dynamical moments of inertia,and the spin of the TSD bands in Hf isotopes are obtained. It shows that this approach is quite powerful in describing the properties of the triaxial superdeformation in Hf isotopes.

  20. Determining Energy Distributions of HF-Accelerated Electrons at HAARP

    Science.gov (United States)

    2015-11-18

    AFRL-AFOSR-VA-TR-2015-0383 Determining energy distributions of HF-accelerated electrons at HAARP Christopher Fallen University of Alaska Fairbanks...2012 - 11/14/2015 4. TITLE AND SUBTITLE Determining energy distributions of HF-accelerated electrons at HAARP 5a. CONTRACT NUMBER FA9550-12-1-0424...transmitted from the High-frequency Active Auroral Research Program ( HAARP ) transmitter in Alaska. For a given fixed HF-plasma interaction altitude

  1. Physics of the Geospace Response to Powerful HF Radio Waves

    Science.gov (United States)

    2012-10-31

    studies of the response of the Earth’s space plasma to high-power HF radio waves from the High-frequency Active Auroral Research Program ( HAARP ...of HF heating and explored to simulate artificial ducts. DMSP- HAARP experiments revealed that HF-created ion outflows and artificial density ducts...in the topside ionosphere appeared faster than predicted by the models, pointing to kinetic (suprathermal) effects. CHAMP/GRACE- HAARP experiments

  2. Radar image registration and rectification

    Science.gov (United States)

    Naraghi, M.; Stromberg, W. D.

    1983-01-01

    Two techniques for radar image registration and rectification are presented. In the registration method, a general 2-D polynomial transform is defined to accomplish the geometric mapping from one image into the other. The degree and coefficients of the polynomial are obtained using an a priori found tiepoint data set. In the second part of the paper, a rectification procedure is developed that models the distortion present in the radar image in terms of the radar sensor's platform parameters and the topographic variations of the imaged scene. This model, the ephemeris data and the digital topographic data are then used in rectifying the radar image. The two techniques are then used in registering and rectifying two examples of radar imagery. Each method is discussed as to its benefits, shortcomings and registration accuracy.

  3. A radar image time series

    Science.gov (United States)

    Leberl, F.; Fuchs, H.; Ford, J. P.

    1981-01-01

    A set of ten side-looking radar images of a mining area in Arizona that were aquired over a period of 14 yr are studied to demonstrate the photogrammetric differential-rectification technique applied to radar images and to examine changes that occurred in the area over time. Five of the images are rectified by using ground control points and a digital height model taken from a map. Residual coordinate errors in ground control are reduced from several hundred meters in all cases to + or - 19 to 70 m. The contents of the radar images are compared with a Landsat image and with aerial photographs. Effects of radar system parameters on radar images are briefly reviewed.

  4. PEMISAHAN Zr – Hf SECARA SINAMBUNG MENGGUNAKAN MIXER SETTLER

    Directory of Open Access Journals (Sweden)

    Dwi Biyantoro

    2017-01-01

    Full Text Available ABSTRAK PEMISAHAN Zr – Hf SECARA SINAMBUNG MENGGUNAKANMIXER SETTLER. Telah dilakukan pemisahanZr – Hf secara sinambung menggunakan pengaduk pengenap (mixer settler 16 stage. Larutan umpan adalah zirkon nitrat dengan kadar Zr = 30786 ppm dan Hf = 499 ppm. Ekstraktan dipakai adalah solven 60 % TBP dalam kerosen dan larutan scrubbingyang dipakai adalah asam nitrat 1 M. Umpan masuk pada stageke 5 dikontakkan secara berlawanan arah dengan solven masuk pada stage ke 16 dan larutan scrubbing masuk pada stage ke 1. Tujuan penelitian ini adalah memisahkan unsur Zr dan Hf dari hasil olah pasir zirkon menggunakan solven TBP dengan alat mixer settler16 stage. Analisis umpan dan hasil proses pemisahan untuk zirkonium (Zr dilakukan dengan menggunakan alat pendar sinar-X, sedangkananalisis unsur hafnium (Hf menggunakan Analisis Pengaktifan Neutron (APN. Parameter penelitian dilakukan dengan variasi keasaman asam nitrat dalam umpan dan variasi waktu pada berbagai laju pengadukan. Hasil penelitian pemisahan unsur Zr dengan Hf diperolehkondisi optimum pada keasaman umpan 4 N HNO3, keseimbangan dicapai setelah 3jam dan laju pengadukan 3300 rpm. Hasil ekstrak  unsur zirkon (Zr diperoleh kadar sebesar 28577 ppm dengan efisiensi 92,76 % serta kadar pengotor hafnium (Hf sebesar 95 ppm. Kata Kunci: pemisahan Zr, Hf, ekstraksi, mixer settler, alat pendar sinar-X, APN. ABSTRACT SEPARATION of Zr - Hf CONTINUOUSLY USE THE MIXER SETTLER. Separation of Zr - Hf continuously using mixer settler 16 stage has been done. The feed solution is zircon nitrate concentration of Zr = 30786 ppm  and Hf = 499 ppm. As the solvent used extractant 60 % TBP in 40 % kerosene. Nitric acid solution used srubbing 1 M. The feed entered into stage to 5 is contacted with solvents direction on the stage to 16 and the scrubbing solution enter the stage to 1. The purpose of this study is to separate Zr and Hf of the results from the process of zircon sand using solvent TBP using 16 stage

  5. Mitigating Doppler shift effect in HF multitone data modem

    Science.gov (United States)

    Sonlu, Yasar

    1989-09-01

    Digital communications over High Frequency (HF) radio channels are getting important in recent years. Current HF requirements are for data transmission at rates 2.4 kbps or more to accommodate computer data links and digital secure voice. HF modems which were produced to meet these speeds are, serial modems and parallel modems. On the other hand, the HF sky-wave communication medium, the ionosphere, has some propagation problems such as multipath and Doppler shift. The effect of Doppler shift in a parallel modem which employs Differential Quadrature Phase Shift Keying (DQPSK) modulation is considered and a correction method to mitigate the Doppler Shift effect is introduced.

  6. Epitaxial Thin Films of Y doped HfO2

    Science.gov (United States)

    Serrao, Claudy; Khan, Asif; Ramamoorthy, Ramesh; Salahuddin, Sayeef

    Hafnium oxide (HfO2) is one of a few metal oxides that is thermodynamically stable on silicon and silicon oxide. There has been renewed interest in HfO2 due to the recent discovery of ferroelectricity and antiferroelectricity in doped HfO2. Typical ferroelectrics - such as strontium bismuth tantalate (SBT) and lead zirconium titanate (PZT) - contain elements that easily react with silicon and silicon oxide at elevated temperatures; therefore, such ferroelectrics are not suited for device applications. Meanwhile, ferroelectric HfO2 offers promise regarding integration with silicon. The stable phase of HfO2 at room temperature is monoclinic, but HfO2 can be stabilized in the tetragonal, orthorhombic or even cubic phase by suitable doping. We stabilized Y-doped HfO2 thin films using pulsed laser deposition. The strain state can be controlled using various perovskite substrates and controlled growth conditions. We report on Y-doped HfO2 domain structures from piezo-response force microscopy (PFM) and structural parameters via X-ray reciprocal space maps (RSM). We hope this work spurs further interest in strain-tuned ferroelectricity in doped HfO2.

  7. Microstructural characterization of as-cast hf-b alloys

    Directory of Open Access Journals (Sweden)

    João Carlos Jânio Gigolotti

    2012-04-01

    Full Text Available An accurate knowledge of several metal-boron phase diagrams is important to evaluation of higher order systems such as metal-silicon-boron ternaries. The refinement and reassessment of phase diagram data is a continuous work, thus the reevaluation of metal-boron systems provides the possibility to confirm previous data from an investigation using higher purity materials and better analytical techniques. This work presents results of rigorous microstructural characterization of as-cast hafnium-boron alloys which are significant to assess the liquid composition associated to most of the invariant reactions of this system. Alloys were prepared by arc melting high purity hafnium (minimum 99.8% and boron (minimum 99.5% slices under argon atmosphere in water-cooled copper crucible with non consumable tungsten electrode and titanium getter. The phases were identified by scanning electron microscopy, using back-scattered electron image mode and X-ray diffraction. In general, a good agreement was found between our data and those from the currently accepted Hafnium-Boron phase diagram. The phases identified are αHfSS and B-RhomSS, the intermediate compounds HfB and HfB2 and the liquide L. The reactions are the eutectic L ⇔ αHfSS + HfB and L ⇔ HfB2 + B-Rhom, the peritectic L + HfB2 ⇔ HfB and the congruent formation of HfB2.

  8. A DFT study of temperature dependent dissociation mechanism of HF in HF(H2O)7 cluster

    Indian Academy of Sciences (India)

    Swatantra K Yadav; Hirdyesh Mishra; Ashwani K Tiwari

    2015-10-01

    We report a Density Functional Theoretical (DFT) study of dissociation of Hydrogen Fluoride (HF) in HF(H2O)7 cluster, using B3LYP functional and empirical exchange correlation functional M06-2X along with 6-31+G(d,p) basis set. Dissociation constant, KRP, of HF dissociation and pKa values of HF in cluster at various temperatures have been reported. It has been found that both KRP and pKa are highly dependent on temperature. The variation of pKa with temperature suggests that HF is strong acid at lower temperatures. Our study also reveals that HF is a stronger acid in water cluster than in bulk water. Further, the results obtained by DFT calculations have been compared with the earlier reported results obtained from Monte Carlo (MC) simulation. It is found that DFT results are qualitatively consistent with the results of MC simulation but quantitatively different.

  9. 100 years of radar

    CERN Document Server

    Galati, Gaspare

    2016-01-01

    This book offers fascinating insights into the key technical and scientific developments in the history of radar, from the first patent, taken out by Hülsmeyer in 1904, through to the present day. Landmark events are highlighted and fascinating insights provided into the exceptional people who made possible the progress in the field, including the scientists and technologists who worked independently and under strict secrecy in various countries across the world in the 1930s and the big businessmen who played an important role after World War II. The book encourages multiple levels of reading. The author is a leading radar researcher who is ideally placed to offer a technical/scientific perspective as well as a historical one. He has taken care to structure and write the book in such a way as to appeal to both non-specialists and experts. The book is not sponsored by any company or body, either formally or informally, and is therefore entirely unbiased. The text is enriched by approximately three hundred ima...

  10. Hf-W chronometry of primitive achondrites

    Science.gov (United States)

    Schulz, T.; Münker, C.; Mezger, K.; Palme, H.

    2010-03-01

    Metal segregation and silicate melting on asteroids are the most incisive differentiation events in the early evolution of planetary bodies. The timing of these events can be constrained using the short-lived 182Hf- 182W radionuclide system. Here we present new 182Hf- 182W data for major types of primitive achondrites including acapulcoites, winonaites and one lodranite. These meteorites are of particular interest because they show only limited evidence for partial melting of silicates and are therefore intermediate between chondrites and achondrites. For acapulcoites we derived a 182Hf- 182W age of Δ tCAI = 4.1 +1.2/ -1.1 Ma. A model age for winonaite separates calculated from the intercept of the isochron defines an age of Δ tCAI = 4.8 +3.1/ -2.6 Ma (assuming a bulk Hf/W ratio of ˜1.2). Both ages most likely define primary magmatic events on the respective parent bodies, such as melting of metal, although metal stayed in place and did not segregate to form a core. A later thermal event is responsible for resetting of the winonaite isochron, yielding an age of Δ tCAI = 14.3 +2.7/ -2.2 Ma, significantly younger than the model age. Assuming a co-genetic relationship between winonaites and silicates present in IAB iron meteorites (based on oxygen isotope composition) and including data by Schulz et al. (2009), a common parent body chronology can be established. Magmatic activity occurred between ˜1.5 and 5 Ma after CAIs. More than 5 Ma later, intensive thermal metamorphism has redistributed Hf-W. Average cooling rates calculated for the winonaite/IAB parent asteroid range between ˜35 and ˜4 K/Ma, most likely reflecting different burial depths. Cooling rates obtained for acapulcoites were ˜40 K/Ma to ˜720 K and then ˜3 K/Ma to ˜550 K. Accretion and subsequent magmatism on the acapulcoite parent body occurred slightly later if compared to most achondrite parent bodies (e.g., angrites, ureilites and eucrites), in this case supporting the concept of an inverse

  11. Pressure induced novel compounds in the Hf-O system from first-principles calculations

    OpenAIRE

    2015-01-01

    Using first-principles evolutionary simulations, we have systematically investigated phase stability in the Hf-O system at pressure up to 120 GPa. New compounds Hf5O2, Hf3O2, HfO and HfO3 are discovered to be thermodynamically stable at certain pressure ranges and a new stable high-pressure phase is found for Hf2O with space group Pnnm and anti-CaCl2-type structure. Both P62m-HfO and P4m2-Hf2O3 show semimetallic character. Pnnm-HfO3 shows interesting structure, simultaneously containing oxide...

  12. Ferroelectricity of nondoped thin HfO2 films in TiN/HfO2/TiN stacks

    Science.gov (United States)

    Nishimura, Tomonori; Xu, Lun; Shibayama, Shigehisa; Yajima, Takeaki; Migita, Shinji; Toriumi, Akira

    2016-08-01

    We report on the impact of TiN interfaces on the ferroelectricity of nondoped HfO2. Ferroelectric properties of nondoped HfO2 in TiN/HfO2/TiN stacks are shown in capacitance-voltage and polarization-voltage characteristics. The Curie temperature is also estimated to be around 500 °C. The ferroelectricity of nondoped HfO2 clearly appears by thinning HfO2 film down to ˜35 nm. We directly revealed in thermal treatments that the ferroelectric HfO2 film on TiN was maintained by covering the top surface of HfO2 with TiN, while it was followed by a phase transition to the paraelectric phase in the case of the open surface of HfO2. Thus, it is concluded that the ferroelectricity in nondoped HfO2 in this study was mainly driven by both of top and bottom TiN interfaces.

  13. Radar signature acquisition using an indigenously designed noise radar system

    Science.gov (United States)

    Freundorfer, A. P.; Siddiqui, J. Y.; Antar, Y. M. M.; Thayaparan, T.

    2011-06-01

    A new design of a noise radar system is proposed with capabilities to measure and acquire the radar signature of various targets. The proposed system can cover a noise bandwidth of near DC to 30 GHz. The noise radar signature measurements were conducted for selective targets like spheres and carpenter squares with and without dielectric bodies for a noise band of 400MHz-3000MHz. The bandwidth of operation was limited by the multiplier and the antennae used. The measured results of the target signatures were verified with the simulation results.

  14. A comparison of field-line resonances observed at the Goose Bay and Wick radars

    Directory of Open Access Journals (Sweden)

    G. Provan

    Full Text Available Previous observations with the Goose Bay HF coherent-scatter radar have revealed structured spectral peaks at ultra-low frequencies. The frequencies of these spectral peaks have been demonstrated to be extremely consistent from day to day. The stability of these spectral peaks can be seen as evidence for the existence of global magnetospheric cavity modes whose resonant frequencies are independent of latitude. Field-line resonances occur when successive harmonics of the eigenfrequency of the magnetospheric cavity or waveguide match either the first harmonic eigenfrequency of the geomagnetic field lines or higher harmonics of this frequency. Power spectra observed at the SABRE VHF coherent-scatter radar at Wick, Scotland, during night and early morning are revealed to show similarly clearly structured spectral peaks. These spectral peaks are the result of local field-line resonances due to Alfvén waves standing on magnetospheric field lines. A comparison of the spectra observed by the Goose Bay and Wick radars demonstrate that the frequencies of the field-line resonances are, on average, almost identical, despite the different latitudinal ranges covered by the two radars. Possible explanations for the similarity of the signatures on the two radar systems are discussed.

  15. Characterization of Synthetic Aperture Radar Image Features of the Ocean as a Function of Wind Speed and High Frequency Radar Products

    Science.gov (United States)

    2012-06-01

    the next sections, the method to obtain surface currents from CODAR-type HF radar is described. The process of attaining calibrated and geocoded SAR...n.d.). It’s not the same as geocoding , but does allow the user to have a reasonable interpretation of the SAR image before taking further steps...of a scene and the tilt of the satellite sensor (NEST User Manual, n.d.). The final product is a geocoded image in the projection chosen by the

  16. Contrast validation test for retrieval method of high frequency ground wave radar

    Institute of Scientific and Technical Information of China (English)

    WANG Hailong; GUO Peifang; HAN Shuzong; XIE Qiang; ZHOU Liangming

    2005-01-01

    In this paper, on the basis of the working principles of high frequency ground wave radar for retrieval of ocean wave and sea wind elements were used to systematically study the data obtained from contrast validation test in Zhoushan sea area of Zhejiang Province on Oct. 2000, to validate the accuracy of OSMAR2000for wave and wind parameters, and to analyze the possible error caused when using OSMAR2000 to retrieve ocean parameters.

  17. Radar, Insect Population Ecology, and Pest Management

    Science.gov (United States)

    Vaughn, C. R. (Editor); Wolf, W. (Editor); Klassen, W. (Editor)

    1979-01-01

    Discussions included: (1) the potential role of radar in insect ecology studies and pest management; (2) the potential role of radar in correlating atmospheric phenomena with insect movement; (3) the present and future radar systems; (4) program objectives required to adapt radar to insect ecology studies and pest management; and (5) the specific action items to achieve the objectives.

  18. Radar signal analysis and processing using Matlab

    CERN Document Server

    Mahafza, Bassem R

    2008-01-01

    Offering radar-related software for the analysis and design of radar waveform and signal processing, this book provides comprehensive coverage of radar signals and signal processing techniques and algorithms. It contains numerous graphical plots, common radar-related functions, table format outputs, and end-of-chapter problems. The complete set of MATLAB[registered] functions and routines are available for download online.

  19. Finishing and Commissioning the New Arecibo HF Facility

    Science.gov (United States)

    Sulzer, M. P.; Gonzalez, S. A.

    2011-12-01

    , one is excited 120 degrees ahead, and the other 120 degrees behind. The two elements in each crossed pair must have currents shifted by 90 degrees. In most systems all the elements excited 90 degrees apart are also spatially orthogonal. That is not the case in this array; modeling results showed better array performance with this geometry. Recent analysis shows that it might be necessary to excite the transmitters at 90 degrees plus or minus some offset in order to achieve 90 degrees in the antenna currents. We must make the measurements to determine the size of this offset. The electrical substation that provides power to the transmitters and the heat exchangers providing cooling is complete. Wiring of the power to the transmitters is nearly complete; we are beginning the commissioning of the transmitters. Four one MW generators have been installed; we have tested the power system with the 430 MHz transmitter and the site together. This system provides a flexible complete way to power the planetary radar, the HF facility, and site backup,as well as the 430 transmitter if required. The commissioning tasks that we complete in the next few months will affect the scientific usefulness of the facility, especially in the first campaign. It is important that we bring up the system in an efficient and orderly fashion.

  20. Air and spaceborne radar systems an introduction

    CERN Document Server

    Lacomme, Philippe; Hardange, Jean-Philippe; Normant, Eric

    2001-01-01

    A practical tool on radar systems that will be of major help to technicians, student engineers and engineers working in industry and in radar research and development. The many users of radar as well as systems engineers and designers will also find it highly useful. Also of interest to pilots and flight engineers and military command personnel and military contractors. """"This introduction to the field of radar is intended for actual users of radar. It focuses on the history, main principles, functions, modes, properties and specific nature of modern airborne radar. The book examines radar's