Sample records for digital hf radar

  1. WAVE-DRIVEN SURFACE FROM HF RADAR

    E-print Network

    Miami, University of

    FEATURE INTERNAL CURRENTS WAVE-DRIVEN SURFACE FROM HF RADAR By Lynn K. Shay Observations from-fre- quency (HF) radar have revealed that not only are the low-frequency and tidal currents resolved of the horizontal flow structure from HF radar pro- vides the spatial context for moored and ship- based

  2. HF radar measurements of long ocean waves

    Microsoft Academic Search

    B. J. Lipa; D. E. Barrick; J. W. Maresca

    1981-01-01

    Sea-echo data from three separate narrow-beam HF radar experiments on the Pacific Ocean are analyzed here by techniques presented in Lipa and Barrick (1980). Only those wave spectral components whose periods exceeded 10 s were included. Close agreement of radar-deduced wave field parameters with surface observations confirms the validity of the second-order theoretical solution for the echo Doppler spectrum, upon

  3. HF radar data assimilation in the Monterey Bay area

    Microsoft Academic Search

    Jeffrey D. Paduan; Igor Shulman

    2004-01-01

    The utility of high-frequency (HF) radar data for improving numerical circulation model predictions is evaluated. Comparisons of the statistical properties of the (CODAR-type) HF radar data and the observed wind indicate a strong correlation between the dominant alongshore, upwelling-favoring wind-forcing and HF radar-derived surface currents along the central California coastline. Because inadequate knowledge of the wind stress is probably a

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

    NASA Astrophysics Data System (ADS)

    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 HFR data access and tools. In this context, a coordinated action between EuroGOOS HF Radar Task Team and EMODnet Physics has been pushed to achieve a pilot integration of the data from existing HF radar systems, with the following operational objectives: definition of needed metadata; standardization for data format and QC; recommendation for the implementation of HF radar data in Regional and European Portals. This coordinated action for organizing and creating links between operators of HF radar platforms will benefit to the implementation of this key information in the European Marine Observation Data Network.

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

    E-print Network

    Paris-Sud XI, Université de

    Validation of the CUTLASS HF radar gravity wave observing capability using EISCAT CP-1 data N. F-scatter power from the SuperDARN HF radars have been linked to the passage of medium-scale gravity waves. We of the HF radars to derive gravity wave information. Results from 1st March, 1995, where the EISCAT UHF

  6. On the accuracy of HF radar surface current measurements: Intercomparisons with ship-based sensors

    Microsoft Academic Search

    R. D. Chapman; L. K. Shay; H. C. Graber; J. B. Edson; A. Karachintsev; C. L. Trump; D. B. Ross

    1997-01-01

    High-frequency (HF) radar systems can provide periodic, two-dimensional, vector current estimates over an area approaching 1000 km . As the use of these HF systems has gained wider acceptance, a number of attempts have been made to estimate the accuracy of such systems. However, comparisons of HF radar current estimates with in situ sensors are difficult to interpret since HF

  7. Digital Array Radar panel development

    Microsoft Academic Search

    William Chappell; Caleb Fulton

    2010-01-01

    The Army Digital Array Radar (DAR) project's goal is to demonstrate how wide-bandgap semiconductor technology, highly-integrated transceivers, and the ever-increasing capabilities of commercial digital components can be leveraged to provide new capabilities and enhanced performance in future low-cost phased array systems. A 16-element, S-band subarray has been developed with panel-integrated, plastic-packaged gallium-nitride (GaN) amplifiers, multi-channel transceiver ICs, and digitization at

  8. Experimental HF radar trial of real-time STAP

    Microsoft Academic Search

    Giuseppe Fabrizio; David Holdsworth; Alfonso Farina

    2007-01-01

    An alternative multi-static HF radar architecture, known as the Forward-Based Receiver Augmentation (FBRA) system, has been developed and tested by the Defence Science and Technology Organization [1]. The experimental system has performed beyond expectations in a number of trials involving targets of interest. This is not only due to the impressive hardware capabilities, but also the advanced signal processing for

  9. HF radar in French Mediterranean Sea: an element of MOOSE Mediterranean Ocean Observing System on Environment

    E-print Network

    Boyer, Edmond

    HF radar in French Mediterranean Sea: an element of MOOSE Mediterranean Ocean Observing System for the MOOSE program. 2 HF RADAR DEPLOYMENT IN NORTH WESTERN MEDITERRANEAN SEA The chosen sites for this HF , Pascal Guterman2 , Karim Bernardet2 1 Mediterranean Institute of Oceanography (MIO, UM 110, USTV

  10. A bistatic HF radar for current mapping and robust ship tracking

    Microsoft Academic Search

    D. B. Trizna

    2008-01-01

    A bistatic HF radar has been developed for application to ocean current mapping and ship vector tracking. The radar can operate in a multi-frequency mode, so that it can map ocean current vertical shear and can provide more robust ship tracks than single frequency HF radars. This tracking robustness is achieved by avoiding target fading due to echo nulls from

  11. Measuring Antenna Patterns for Ocean Surface Current HF Radars with Ships of Opportunity

    E-print Network

    California at Santa Barbara, University of

    Measuring Antenna Patterns for Ocean Surface Current HF Radars with Ships of Opportunity BRIAN M-finding HF radars from ships of opportunity. Positions obtained from the Automatic Identification System (AIS) are used to identify signals backscattered from ships in ocean current radar data. These signals and ship

  12. A Nested Multi-static HF Radar Testbed for the New York Bight and Beyond

    Microsoft Academic Search

    J. T. Kohut; S. M. Glenn; H. J. Roarty; O. M. Schofield

    2007-01-01

    Surface currents are envisioned to be an integral component of the Integrated Ocean Observing System (IOOS) and High Frequency (HF) radar technologies provide the means to measure these data across multiple scales. The Rutgers University Coastal Ocean Observation Lab (COOL) has continuously operated a nested network of HF radars since 1998 as part of a sustained coastal observatory centered on

  13. HF radar observations of small-scale surface current variability in the Straits of Florida

    E-print Network

    Miami, University of

    HF radar observations of small-scale surface current variability in the Straits of Florida A. B-frequency Wellen radar (WERA), transmitting at 16.045 MHz, was deployed along the eastern Florida Shelf current measurements within the radar footprint along the shelf break at 86-m depth. The shallowest ADCP

  14. Measurements of near surface ocean currents using HF radar

    NASA Astrophysics Data System (ADS)

    Laws, Kenneth Evans

    High Frequency (HF) radar is unique both in its ability to probe the ocean currents within the top few meters below the surface and to provide synoptic current maps covering thousands of square kilometers. This work focuses on the evaluation of ocean current measurement techniques, using the multi-frequency coastal radar (MCR), a system that operates on four frequencies (4.8, 6.8, 13.4 and 21.8 MHz) concurrently. Two methods of data processing, traditional beam forming and a direction finding approach, MUltiple SIgnal Characterization (MUSIC), are compared. Simulations and comparisons using real data are used to evaluate the application of MUSIC to the MCR and to design modifications to improve its performance. Uncertainties in the radar measurements as a function of radar operating frequency, sea state parameters and data processing method are estimated. Results show MUSIC to be applicable to the MCR and to outperform beam forming, particularly for the lower frequencies, over most of the real and simulated experiments examined. High resolution ocean wave spectral energy measurements are used to estimate the effect of Stokes drift on MCR measurements. The effect is shown to be small in magnitude relative to the expected errors in the MCR measurements and highly correlated with the wind. Although results show a correlation between the MCR measurements and the expected Stokes drift effect, the correlations could be the result of wind stress-induced currents. Using assumptions as to the form of the vertical current profile, estimates of the near-surface vertical shear are obtained from the MCR data. Analysis of the shear estimates casts doubt on the validity of a near-surface, logarithmic current profile for the open ocean. Further analysis of vertical shear estimates yields an estimate of the ocean current magnitude at the sea surface that is in agreement with the commonly accepted value of about 3% of the wind speed. Results of this work demonstrate a significant advantage to using MUSIC direction finding over conventional beam forming in limited aperture, multi-frequency radar applications and improve the MCR's shear measurement capability.

  15. HF surface wave radar for oceanography - a review of activities in Germany

    Microsoft Academic Search

    Klaus-Werner Gurgel; Heinz-Hennann Essen; Thomas Schlick

    2003-01-01

    The remote sensing group of the University of Hamburg is working in the field of HF radar since 1980. For the start three CODAR systems have been purchased from NOAA\\/ERL (developed by D. Barrick's NOAA group). Based on 16 years of experience a new system called WEllen RAdar (WERA) has been designed at the University of Hamburg in 1996. The

  16. Extraction of sea state from HF radar sea echo: Mathematical theory and modeling

    Microsoft Academic Search

    Belinda J. Lipa; Donald E. Barrick

    1986-01-01

    directional ocean waveheight spectrum and surface current, using a dimensionless mathematical formulation. In this paper, we describe the simulation of narrow- and broad-beam radar sea-echo from both deep and shallow water, discussing the effect of ocean surface currents, including vertical and horizontal current shear. This paper provides the mathematical tools for the modeling of common experimental situations in HF radar

  17. From AESA radar to digital radar for surface-based applications

    Microsoft Academic Search

    Odile Adrian; Surface Radar

    2009-01-01

    This paper describes how Thales surface radar product policy is evolving from active electronically steered antenna (AESA) radar to digital radar in order to improve its capabilities when operating in challenging electromagnetic environments. It shows how digital receiver technology (with an analogue-to-digital converter behind every receive antenna element) tailored for the digital beam forming array application is a key enabling

  18. Digital Frequency Synthesizer For Radar Astronomy

    NASA Technical Reports Server (NTRS)

    Sadr, Ramin; Satorius, Edgar; Robinett, J. Loris, Jr.; Olson, Erlend

    1992-01-01

    Report discusses conceptual digital frequency synthesizer part of programmable local oscillator in radar-astronomy system. Phase must remain continuous during adjustments of frequency, phase noise must be low, and spectral purity must be high. Discusses theory of operation in some mathematical detail and presents new analysis of spectral purity of output.

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

    NASA Astrophysics Data System (ADS)

    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 significantly increased and strong signals persist while the high-power HF is present . Simultaneous observations of topside TEC measurements and lower-ionosphere UHF radar observations suggest there is an optimum altitude region to heat the lower F-region in order to produce topside ionosphere density enhancements. The observations are dependent on HF power levels and we show several examples where heating results are only observed for the high-power levels attainable with the HAARP facility.

  20. Extraction of wave parameters from measured HF radar sea-echo Doppler spectra

    Microsoft Academic Search

    Donald E. Barrick

    1977-01-01

    Computerized techniques for extracting rms wave height and dominant wave period from HF radar sea-echo Doppler spectra are derived. Earlier theoretical models for first- and second-order sea backscatter (derived elsewhere) are employed to obtain the simple, closed-form inversion equations giving these two radar-deduced quantities. The results are general in that no specific models for the radial or azimuthal form of

  1. Backtracking drifting objects using surface currents from high-frequency (HF) radar technology

    NASA Astrophysics Data System (ADS)

    Abascal, Ana Julia; Castanedo, Sonia; Fernández, Vicente; Medina, Raúl

    2012-07-01

    In this work, the benefits of high-frequency (HF) radar ocean observation technology for backtracking drifting objects are analysed. The HF radar performance is evaluated by comparison of trajectories between drifter buoys versus numerical simulations using a Lagrangian trajectory model. High-resolution currents measured by a coastal HF radar network combined with atmospheric fields provided by numerical models are used to backtrack the trajectory of two dataset of surface-drifting buoys: group I (with drogue) and group II (without drogue). A methodology based on optimization methods is applied to estimate the uncertainty in the trajectory simulations and to optimize the search area of the backtracked positions. The results show that, to backtrack the trajectory of the buoys in group II, both currents and wind fields were required. However, wind fields could be practically discarded when simulating the trajectories of group I. In this case, the optimal backtracked trajectories were obtained using only HF radar currents as forcing. Based on the radar availability data, two periods ranging between 8 and 10 h were selected to backtrack the buoy trajectories. The root mean squared error (RMSE) was found to be 1.01 km for group I and 0.82 km for group II. Taking into account these values, a search area was calculated using circles of RMSE radii, obtaining 3.2 and 2.11 km2 for groups I and II, respectively. These results show the positive contribution of HF radar currents for backtracking drifting objects and demonstrate that these data combined with atmospheric models are of value to perform backtracking analysis of drifting objects.

  2. The effects of sea clutter on the performance of HF Surface Wave Radar in ship detection

    Microsoft Academic Search

    Hank Leong; A. Ponsford

    2008-01-01

    This paper presents a study of the effects of sea clutter on the performance of HF surface wave radar (HFSWR), operating in the band between 3 and 5 MHz, in the detection of two classes of ships: large freighters with gross registered tonnage (GRT) in the order of several tens of thousands of tons and small vessels with a GRT

  3. Gigabit Networking: Digitized Radar Data Transfer and Beyond

    E-print Network

    Jayasumana, Anura P.

    ) and Digital Sky projects [12]. VMS is a 3-D simulator that allows users to see, move and even feel molecularGigabit Networking: Digitized Radar Data Transfer and Beyond Sangeetha L. Bangolae, Anura P facilities that were inaccessible in the past due to limited bandwidths. VCHILL project for digitized radar

  4. Ion acoustic HF radar echoes at high latitudes and far ranges

    NASA Astrophysics Data System (ADS)

    Lacroix, P. J.; Moorcroft, D. R.

    2001-12-01

    Using data taken over 18 months with the Iceland East (CUT-LASS/Iceland) Super Dual Auroral Radar Network (SuperDARN) HF radar we have made a statistical study of a class of echoes which occur at ranges typically associated with F region echoes, but which have Doppler speeds near the ion acoustic speed Cs typical of E region echoes [Milan et al., 1997]. Comparison of the seasonal, diurnal, and range distributions of these echoes with the predictions of propagation models show that these are, indeed, E region echoes, differing in morphology from similar echoes at nearer ranges mainly because of the propagation conditions which are required to observe them. For the particular radar geometry of this study, conventional theory predicts that the effects of ionospheric gradients will result in phase velocities (radar Doppler velocities) which differ significantly from Cs, in disagreement with these observations. However, the observations are consistent with a new nonlinear theory of St.-Maurice and Hamza [2001].

  5. APQ-102 imaging radar digital image quality study

    NASA Technical Reports Server (NTRS)

    Griffin, C. R.; Estes, J. M.

    1982-01-01

    A modified APQ-102 sidelooking radar collected synthetic aperture radar (SAR) data which was digitized and recorded on wideband magnetic tape. These tapes were then ground processed into computer compatible tapes (CCT's). The CCT's may then be processed into high resolution radar images by software on the CYBER computer.

  6. The effect of the Interplanetary Magnetic Field (IMF) on HF radar scattering volume electron densities

    NASA Astrophysics Data System (ADS)

    Gillies, R.; Yau, A. W.; Hussey, G. C.; Sofko, G. J.

    2012-12-01

    The Cascade Small-Sat and Ionospheric Polar Explorer (CASSIOPE) satellite will be launched in late 2012 with a suite of eight scientific instruments comprising the enhanced Polar Outflow Probe (ePOP). The Radio Receiver Instrument (RRI) will be used in conjunction with Super Dual Auroral Radar Network (SuperDARN) radars for detailed studies of the radar scattering volume. The Doppler velocities that are measured by the SuperDARN radars tend to be underestimated because the refractive index in the scattering volume is not known and, therefore, not taken into account when the velocities are calculated. A technique using frequency shifts made by the SuperDARN radars to study the electron density of the radar scattering volume has been developed. These scattering volume electron density values have been calculated for various parameters from SuperDARN frequency shifting data. This study focuses on the dependence of the Interplanetary Magnetic Field (IMF) on the scattering volume electron density results. The dependence of the average scattering volume electron density at different times and locations for various IMF orientations has been determined. This study allows improvements to be made to SuperDARN velocity measurements for various conditions and provides insight into the physics of the coherent scattering process. Finally, the upcoming launch of the ePOP satellite is anticipated to further confirm these results. The instruments on ePOP satellite will provide in situ high resolution measurements of the scattering volumes of the HF radars.

  7. Compact Digital Receiver Development for Radar Based Remote Sensing

    Microsoft Academic Search

    M. Yearyl; R. Kelleyl; J. Meierl; S. Ongl; R. Palmer

    2008-01-01

    This paper is the first of a series of publications that discusses the design and implementation of an inexpensive, nearly all-digital FPGA-based radar receiver which can be used in a variety of applications including single\\/dual-polarization weather radar, sidelobe cancellation, a subarray module for a digital beam-forming phased-array radar, and other applications where a compact, low-power, low-cost receiver is needed. The

  8. Statistical patterns of high-latitude convection obtained from Goose Bay HF radar observations

    Microsoft Academic Search

    J. M. Ruohoniemi; R. A. Greenwald

    1996-01-01

    We have derived patterns that describe the statistical interplanetary magnetic field (IMF) dependencies of ionospheric convection in the high-latitude region of the northern hemisphere. The observations of plasma motion were made with the HF coherent backscatter radar located at Goose Bay, Labrador, over the period September 1987 to June 1993. The area covered by the measurements extended poleward of 65øA

  9. Variational assimilation of HF radar surface currents in a coastal ocean model off Oregon

    NASA Astrophysics Data System (ADS)

    Yu, Peng; Kurapov, Alexander L.; Egbert, Gary D.; Allen, John S.; Kosro, P. Michael

    2012-06-01

    The impact of assimilation of sea surface velocity fields observed by a set of high-frequency (HF) radars is studied using a three-dimensional ocean circulation model configured along the Oregon coast. The study period is June-July 2008 featuring upwelling and separation of the coastal currents into the adjacent interior ocean. The nonlinear model is based on the Regional Ocean Modeling System (ROMS) and the data assimilation (DA) component on the AVRORA system utilizing the representer-based variational algorithm. Assimilation proceeds in a series of 3-day windows, providing an analysis solution in each window and a 3-day forecast into the next window. Experiments with two different initial condition error covariances are compared (one is dynamically balanced, based on the linearized equation of state, temperature-salinity relation, and geostrophic and thermal wind balance relations and the other is multivariate unbalanced). While the assimilation impact is statistically better in the case of the balanced covariance, the case with the unbalanced covariance also provides sensible improvement in terms of surface velocity and sea surface temperature (SST) model-data forecast statistics. The analysis of representer functions shows that even if the initial condition error covariance is unbalanced, the correction fields at the model initial time are partially balanced after each dynamical field is smoothed independently, due to inherent dynamical properties of the adjoint model. Assimilation of the HF radar surface currents improves not only surface velocity forecasts, but also geometry of the upwelling SST front and the sea surface height (SSH) slope near the coast, as verified against unassimilated satellite SSH and SST data. The assimilation also alters the latitudinal distribution of the time-averaged offshore transport. Combined HF radar velocity and other observations, e.g., altimetry, is needed to better constrain surface geostrophic currents in the entire model domain, including the area not covered by the HF radar data.

  10. Trajectory prediction using HF radar surface currents: Monte Carlo simulations of prediction uncertainties

    Microsoft Academic Search

    David S. Ullman; James O'Donnell; Josh Kohut; Todd Fake; Arthur Allen

    2006-01-01

    An important aspect of particle trajectory modeling in the ocean is the assessment of the uncertainty in the final particle position. Monte Carlo particle trajectory simulations using surface currents derived from standard-range and long-range CODAR HF radar systems were performed using random-walk and random-flight models of the unresolved velocities. Velocity statistics for these models were derived from the covariance functions

  11. MF\\/HF multistatic mid-ocean radar experiments in support of SWOTHR (Surface-Wave Over-The-Horizon Radar)

    Microsoft Academic Search

    Alan A. Burns; Daniel S. Naar

    1989-01-01

    A shoreline based multistatic MF\\/HF radar experiment was fielded in a mid-ocean environment with the objectives of evaluating and demonstrating several aspects of the surface-wave over-the-horizon radar (SWOTHR) concept. Data were collected at 2.8 and 7.8 MHz. A-4 aircraft were used on cooperative targets, whose calculated radar cross reactions were -15 dBsm at 2.8 MHz. An A-4 flying at 300

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

    Microsoft Academic Search

    M. Uspensky; P. Eglitis; H. Opgenoorth; G. Starkov; T. Pulkkinen; R. Pellinen

    2001-01-01

    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

  13. Traveling Ionospheric Disturbance Characteristics Over Texas Using the TIDDBIT HF Doppler Radar

    NASA Astrophysics Data System (ADS)

    Wene, G.; Crowley, G.; Fessler, B.; Bronn, J.

    2004-05-01

    Atmospheric gravity waves (AGW) are generated by numerous lower atmospheric processes, such as storms, and by auroral processes in the ionosphere. At ionospheric heights, the motion of the neutral gas in the AGW sets the ionosphere into motion. The waves displace the isoionic contours, resulting in a travelling ionospheric disturbance (TID). TIDs can be thought of as traveling corrugations in the ionosphere, and they can seriously affect HF radio communications and surveillance systems. Consequently, one of the most sensitive methods for detecting transient changes in the ionosphere is the HF Doppler technique operating in the 3-10 MHz band. A simple Doppler system consists of a CW (continuous wave) radio transmitter and receiver, which are highly frequency-stable. When a HF radio wave is reflected from the ionosphere, movement of the reflection point during passage of a TID produces a change in phase path and a Doppler shift proportional to the time rate of change of the phase path. The Doppler system is sensitive to motions of the ionospheric reflection point, and it therefore provides an accurate measure of both the TID and AGW periods. Similarly, because the TID velocity is determined simply from triangulation using the time-delays between perturbations at different reflection points, the TID velocities are also an accurate estimate of the underlying gravity wave horizontal and vertical trace velocities. HF Doppler systems have advantages over all other techniques for the measurement of TID characteristics. They are more amenable to analysis than data from ionosonde chains, and their time resolution (30 sec) is much higher than that of ionosondes . Unlike total electron content (TEC) methods, which respond to height-integrated TID effects, the HF Doppler radar responds to TIDs at the altitude of the radio reflection point. Finally, HF Doppler systems have low power consumption, so that both spatial and temporal resolution can be maintained for many days without the costs that would be associated with an incoherent-scatter radar. SwRI recently designed, built and deployed an HF Doppler sounding system for three months, in Texas, to investigate TIDs. The TIDDBIT radar consisted of three transmitters (Austin, Uvalde and St. Hedwig) and a receiver in San Antonio, Texas. Using cross-spectral analysis and triangulation of the TIDDBIT signals, TID speeds and azimuths were obtained for each wave frequency. We provide a synoptic survey of the TID characteristics observed over Texas during January-March 2002. Such a system would be of great utility for the study of gravity wave seeding of low latitude ionospheric irregularities.

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

    SciTech Connect

    Fejer, J.A. (Univ. of California, San Diego, La Jolla (United States)); Sulzer, M.P. (National Astronomy and Ionosphere Center, Arecibo (Puerto Rico)); Djuth, F.T. (Geospace Research, Los Angeles, CA (United States))

    1991-09-01

    Observations of the spectrum of 430-MHz radar backscatter from HF-induced Langmuir turbulence with height discrimination are described. During very stable ionospheric conditions under which the height of the below-threshold backscatter spectrum had 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 resulted 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 was observed for different heights. The observational results are compared with the predictions of existing theories of Langmuir turbulence.

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

    NASA Astrophysics Data System (ADS)

    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 shear is insignificant. Finally, we present results from three experiments using both drifter types in HFR-covered regions of the Eastern Mediterranean. More experiments are planned, incorporating design improvements dictated by the results of the preliminary field tests. This work was held in the framework of the project "Specifically Targeted for Radars INnovative Gauge (STRING)", funded by the Greek-French collaboration programme "Plato".

  16. DIGITAL VISION he advent of phased array radars and space-time adaptive processing has given radar

    E-print Network

    Nehorai, Arye

    © DIGITAL VISION T he advent of phased array radars and space-time adaptive processing has given radar designers the ability make radars adaptable on receive. The current state of radar technolo- gy of pairs of complementary sequences. Shortly thereafter, Welti proposed to use Golay sequences in radar

  17. Long-term observations of meteor winds by the SuperDARN HF radar network

    NASA Astrophysics Data System (ADS)

    Talaat, Elsayed; Ruohoniemi, J. Michael; McCubbin, Elizabeth; Azeem, S. M. Irfan; Greenwald, Raymond

    2012-07-01

    The HF Super Dual Auroral Radar Network (SuperDARN) radars detect a category of backscatter that is due to meteor trails in the mesosphere. The motion of the neutral atmosphere can be inferred and applied to the study of atmospheric tides and planetary waves. The current configurations of longitudinal radar chains in the northern and southern hemispheres have accumulated mesospheric wind measurements continuously since the last solar cycle maximum while the archives of some of the radars span more than a solar cycle. We have analyzed the occurrence of mesospheric tides, planetary wave, and gravity wave activity in the meteor wind data over long periods at several radar stations in both hemispheres. Understanding the behavior of planetary waves and tides is not only crucial to characterizing mesopause variability but also transport in the mesosphere and lower thermosphere. in the mesosphere and lower thermosphere. We examine the seasonal and inter-annual variations of the diurnal, semidiurnal and terdiurnal tides, and planetary waves. We find connections to the quasi-biennial oscillation and to sudden stratospheric warming (SSW) events. We present examples of intensified planetary wave activity that occurred during SSWs. Additionally, we examine the variability in tidal and planetary wave activity over the past solar cycle and correlations with lower atmospheric phenomena and other datasets.

  18. Validation of HF Radar ocean surface currents in the Ibiza Channel using lagrangian drifters, moored current meter and underwater gliders

    NASA Astrophysics Data System (ADS)

    Lana, Arancha; Fernández, Vicente; Orfila, Alejandro; Troupin, Charles; Tintoré, Joaquín

    2015-04-01

    SOCIB High Frequency (HF) radar is one component of a multi-platform system located in the Balearic Islands and made up of Lagrangian platforms (profilers and drifting buoys), fixed stations (sea-level, weather, mooring and coastal), beach monitoring (camera), gliders, a research vessel as well as an ocean forecast system (waves and hydrodynamics). The HF radar system overlooks the Ibiza Channel, known as a 'choke point" where Atlantic and Mediterranean water masses interact and where meridional exchanges of water mass properties between the Balearic and the Algerian sub-basins take place. In order to determine the reliability of surface velocity measurements in this area, a quality assessment of the HF Radar is essential. We present the results of several validation experiments performed in the Ibiza Channel in 2013 and 2014. Of particular interest is an experiment started in September 2014 when a set of 13 surface drifters with different shapes and drogue lengths were released in the area covered by the HF radar. The drifter trajectories can be examined following the SOCIB Deployment Application (DAPP): http://apps.socib.es/dapp. Additionally, a 1-year long time series of surface currents obtained from a moored surface current-meter located in the Ibiza Channel, inside the area covered by the HF radar, was also used as a useful complementary validation exercise. Direct comparison between both radial surface currents from each radar station and total derived velocities against drifters and moored current meter velocities provides an assessment of the HF radar data quality at different temporal periods and geographical areas. Statistics from these comparisons give good correlation and low root-mean-square deviation. The results will be discussed for different months, geographical areas and types of surface drifters and wind exposure. Moreover, autonomous underwater glider constitutes an additional source of information for the validation of the observed velocity structures and some statistics will be presented.

  19. Digital Doppler radial velocity data compared objectively with digital reflectivity radar data

    E-print Network

    Beaver, Thomas Foster

    1980-01-01

    DIGITAL DOPPLER RADIAL VELOCI1'( DATA COI'IVARED OBJECTIVELY MITII DIGITAL REFLECTIVITY RADAR DATA A Thes1s by THOFIAS FOSTER BEAVER Submitted to the Graduate College of Texas A8M University in partial fulfillment of the requirement... for the degree of MASTER GF SCIENCE May 1980 Major Subject: Meteorology DIGITAL DOPPLER RADIAL VELOCITY DATA COMPARED OBJECTIVELY WITH DIGITAL REFLECTIVITY RADAR DATA A Thesis by THOMAS FOSTER BEAVER Approved as to style and content by: Dr. Vance E. er...

  20. HF Radar for Long-Range Monitoring of Ionospheric Irregularities in the Equatorial Region

    NASA Astrophysics Data System (ADS)

    Pedersen, T. R.; Parris, R. T.; Dao, E. V.

    2014-12-01

    Ionospheric instabilities associated with plasma bubbles in the equatorial region are one of the major space weather impacts, creating scintillation that affects satellite communications and navigation as well as spread-F and propagation effects on lower frequency systems. Coherent scatter radars can be used to detect the presence of irregularities at a scale size corresponding to half the wavelength of the radar when the raypaths are perpendicular to the magnetic field. A number of vertical incidence radars operating in the VHF range near the magnetic equator use this effect to map out vertical irregularity structure in bubbles, while at high latitudes in both the northern and more recently southern hemisphere, HF radars in the SuperDARN network have successfully used refraction along near-horizontal paths to reach perpendicularity with the near-vertical magnetic field and map out ionospheric convection and irregularity structure over fields of view thousands of km across. In the equatorial region, perpendicularity can be obtained anywhere within a near-vertical plane even without refraction, although refraction can be used to achieve long ranges after one or more reflections from the earth's surface and bottomside ionosphere. This potentially provides a means of detecting and monitoring equatorial plasma bubbles over the oceans from long ranges using a small number of ground-based sites. We discuss the possible echoes that could be detected by such a system, the likely propagation modes and characteristics, and means of obtaining and utilizing elevation angle information to correctly locate distant plasma bubbles.

  1. Characteristics of medium-scale traveling ionospheric disturbances observed near the Antarctic Peninsula by HF radar

    NASA Astrophysics Data System (ADS)

    Grocott, A.; Hosokawa, K.; Ishida, T.; Lester, M.; Milan, S. E.; Freeman, M. P.; Sato, N.; Yukimatu, A. S.

    2013-09-01

    We present a survey of medium-scale traveling ionospheric disturbances (MSTIDs) observed by a Super Dual Auroral Radar Network HF radar located in the Falkland Islands between May 2010 and April 2011. The radar has a field of view that overlooks the Antarctic Peninsula, a known hot spot of gravity wave activity. We present observations of radar ground-backscatter data, in which the signatures of MSTIDs are manifested as structured enhancements in echo power. Observed periods were in the range 30-80 min, corresponding to frequencies of 0.2-0.6 mHz. Wavelengths were generally in the range 200-800 km and phase speeds in the range 100-300 m s-1. These values are within the ranges typically associated with medium-scale gravity waves. We find a primary population of northward (equatorward) propagating MSTIDs, which demonstrate an association with enhanced solar wind-magnetosphere coupling and a smaller, westward propagating population, that could be associated with atmospheric gravity waves excited by winds over the Andean and Antarctic Peninsula mountains or by the high winds of the Antarctic Polar Vortex.

  2. Observations of very-high-latitude ionospheric irregularities with the Goose Bay HF (high frequency) radar

    SciTech Connect

    Greenwald, R.A.; Baker, K.B.

    1985-06-07

    The Goose Bay HF radar is a sophisticated instrument capable of providing detailed information on very-high-latitude E- and F-region ionospheric electron-density irregularities which act as a source of clutter on OTH radar systems. Through the use of two parallel phased-array antennas, this instrument is able to image the location of these irregularities within a three-dimensional volume covering much of northeastern Canada and Greenland. It is also capable of following the temporal variability of these irregularities as well as determining unambiguously the Doppler shift and broadening of radar signals scattered by them. This paper presents initial results with a single phased-array antenna, which represent typical examples of the spatial intensity distribution of these irregularities at different local times. Examples are presented of Doppler spectra of the irregularities at different local times. Data of this type are of appreciable value in ascertaining the techniques that must be utilized to improve clutter mitigation on high-latitude radar systems.

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

    NASA Astrophysics Data System (ADS)

    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.

  4. Kilometric irregularities in the E and R regions of the daytime equatorial ionosphere observed by a high resolution HF radar

    SciTech Connect

    Blanc, E.; Mercandalli, B. [Laboratorie de Detection et de Geophysique, Bruyeres le Chatel (France)] [Laboratorie de Detection et de Geophysique, Bruyeres le Chatel (France); Houngninou, E.

    1996-03-15

    The authors describe results from a vertically oriented HF radar operated in the Ivory Coast, which studied irregularities in the E and F regions of the equatorial ionosphere. The authors report on irregularity observations at heights consistent with the equatorial electrojet, and at heights above the electrojet, and into the F1 layer. They observe irregularities into the F region in this work. The radar operated in the frequency range from 1 to 8 MHz.

  5. HF radar signatures of the cusp and low-latitude boundary layer

    NASA Technical Reports Server (NTRS)

    Baker, K. B.; Dudeney, J. R.; Greenwald, R. A.; Pinnock, M.; Newell, P. T.; Rodger, A. S.; Mattin, N.; Meng, C.-I.

    1995-01-01

    Continuous ground-based observations of ionospheric and magnetospheric regions are critical to the Geospace Environmental Modeling (GEM) program. It is therefore important to establish clear intercalibrations between different ground-based instruments and satellites in order to clearly place the ground-based observations in context with the corresponding in situ satellite measurements. HF-radars operating at high latitudes are capable of observing very large spatial regions of the ionosphere on a nearly continuous basis. In this paper we report on an intercalibration study made using the Polar Anglo-American Conjugate Radar Experiment radars located at Goose Bay, Labrador, and Halley Station, Antarctica, and the Defense Meteorological Satellite Program (DMSP) satellites. The DMSP satellite data are used to provide clear identifications of the ionospheric cusp and the low-latitude boundary layer (LLBL). The radar data for eight cusp events and eight LLBL events have been examined in order to determine a radar signature of these ionospheric regions. This intercalibraion indicates that the cusp is always characterized by wide, complex Doppler power spectra, whereas the LLBL is usually found to have spectra dominated by a single component. The distribution of spectral widths in the cusp is of a generally Gaussian form with a peak at about 220 m/s. The distribution of spectral widths in the LLBL is more like an exponential distribution, with the peak of the distribution occurring at about 50 m/s. There are a few cases in the LLBL where the Doppler power spectra are strikingly similar to those observed in the cusp.

  6. Currents, Tides and Waves measured by an HF Radar in the Gulf of Naples

    NASA Astrophysics Data System (ADS)

    Falco, Pierpaolo; Buonocore, Berardino; Cianelli, Daniela; Di Lemma, Roberta; Giordano, Alberto; Iermano, Ilaria; Kalampokis, Alkiviadis; Saviano, Simona; Uttieri, Marco; Zambardino, Giovanni; Zambianchi, Enrico

    2015-04-01

    An HF radar has been operating in the Gulf of Naples (Southeastern Tyrrhenian Sea) since 2004. The system is a SeaSonde manufactured by CODAR Ocean Sensors Ltd. Three mono-static radar units working at about 25 Mhz ensure the surface current mapping over nearly the entire Gulf of Naples area. The grid resolution is 1 Km with a range of approximately 40 Km. From continuous observations of the surface current fields several characteristics of the surface circulation were assessed. One of the most prominent evidences is the wind field forcing of the surface current, which determines different but recurrent circulation patterns affecting the transport and the off-in shore exchanges. The analysis of long and continuous current observations has revealed significant tidal currents. Previous studies regarding the tide magnitude in the Southern Tyrrhenian Sea showed a very limited tidal contribution to the current field. The determination of tidal current in the Gulf of Naples has pointed out a prevalent diurnal contribution and intensity values up to a maximum of 10 cm/s. Waves are one of the most important elements in a coastal management framework. HF radar may provide an estimate of the main parameters characterizing the wave field: wave direction, significant height and period. Waves were studied in the Gulf of Naples 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 Gulf where the depth is not too shallow and the sea echo intensity is sufficiently high to ensure good data quality. A pluriannual wave observation time series was studied in order to depict typical seasonal patterns.

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

    NASA Astrophysics Data System (ADS)

    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 frequency increasing near the gyro-harmonic value were conducted. The FM scan rate was sufficiently slow that the electron density was approximately in an equilibrium state. For these experiments the altitude of the HF interaction follows a near straight line downward parallel to the altitude-dependent gyro-harmonic level.

  8. The Long Wavelength Array (LWA): A Large HF/VHF Array for Solar Physics, Ionospheric Science, and Solar Radar

    E-print Network

    Ellingson, Steven W.

    The Long Wavelength Array (LWA): A Large HF/VHF Array for Solar Physics, Ionospheric Science for solar physics and space weather investigations, through its ability to characterize a diverse range, and Solar Radar A Ground-Based Instrument Paper for the 2010 NRC Decadal Survey of Solar and Space

  9. Recent results from a nested multi-static HF radar network for the NorthEast Observing System (NEOS)

    Microsoft Academic Search

    J. T. Kohut; S. M. Glenn; H. J. Roarty

    2003-01-01

    Summary form only given. Anested HF radar network has been deployed along the New Jersey coast as part of the New Jersey Shelf Observing System (NJSOS) and the larger regional NorthEast Observing System (NEOS). A 25 MHz standard system (range about 50 km) setup for continuous operation since 1999 includes two sites in Brant Beach and Brigantine, New Jersey. A

  10. HF (HIGH FREQUENCY) RADAR MEASUREMENTS OF CIRCULATION IN THE EASTERN STRAIT OF JUAN DE FUCA NEAR PROTECTION ISLAND (JULY, 1979)

    EPA Science Inventory

    During July 1979 the surface currents in the Eastern Strait of Juan de Fuca were mapped with a High Frequency (HF) radar system (CODAR). These currents were measured simultaneously over several hundred square kilometers continuously for five days. The strong tidal currents and es...

  11. Intercomparison of an ADCP, ADP, standard and long-range HF radar: influence of horizontal and vertical shear

    Microsoft Academic Search

    H. Roarty; J. Kohut; S. Glenn

    2003-01-01

    A nested HF radar network has been deployed along the New Jersey coast as part of the New Jersey Shelf Observing System (NJSOS). A standard range (about 50 km) system setup for continuous operation since 1999 includes two sites in Brant Beach and Brigantine, New Jersey. A second longer range system (about 170 km) includes four New Jersey sites set

  12. Interferometric evidence for the observation of ground backscatter originating behind the CUTLASS coherent HF radars

    NASA Astrophysics Data System (ADS)

    Milan, S. E.; Jones, T. B.; Robinson, T. R.; Thomas, E. C.; Yeoman, T. K.

    1997-01-01

    Interferometric techniques allow the SuperDARN coherent HF radars to determine the elevation angles of returned backscatter, giving information on the altitude of the scatter volume, in the case of ionospheric backscatter, or the reflection altitude, in the case of ground backscatter. Assumptions have to be made in the determination of elevation angles, including the direction of arrival, or azimuth, of the returned signals, usually taken to be the forward look-direction (north) of the radars, specified by the phasing of the antenna arrays. It is shown that this assumption is not always valid in the case of ground backscatter, and that significant returns can be detected from the backward look-direction of the radars. The response of the interferometer to backscatter from behind the radar is modelled and compared with observations. It is found that ground backscatter from a field-of-view that is the mirror image of the forward-looking field-of-view is a common feature of the observations, and this interpretation successfully explains several anomalies in the received backscatter. Acknowledgements. The authors are grateful to Prof. D. J. Southwood (Imperial College, London), J. C. Samson (University of Alberta, Edmonton), L. J. Lanzerotti (AT&T Bell Laboratories), A. Wolfe (New York City Technical College) and to Dr. M. Vellante (University of LÁquila) for helpful discussions. They also thank Dr. A. Meloni (Istituto Nazionale di Geofisica, Roma) who made available geomagnetic field observations from LÁquila Geomagnetic Observatory. This research activity at LÁquila is supported by MURST (40% and 60% contracts) and by GIFCO/CNR. Topical Editor K.-H. Glaßmeier thanks C. Waters and S. Fujita for their help in evaluating this paper.-> Correspondence to :P. Francia->

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

    NASA Astrophysics Data System (ADS)

    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 direction) were obtained during 2013 and 2014 from one 13.5 MHz CODAR SeaSonde radar station from Hydrographic Institute, located in Espichel Cape (Portugal). These data were compared with those obtained from one wave buoy Datawell Directional Waverider, also from Hydrographic Institute, moored inbound Sines (Portugal) at 100 m depth. For this first approach, was assumed that all the waves are in a deep water situation. Results showed that during high energetic periods, the HF radar system revealed a good correlation with wave buoy data following the bulk wave parameters gradient variations.

  14. Performance Analysis of Pulse Doppler Digital Radars with Application to the Shuttle Ku-Band System

    Microsoft Academic Search

    W. K. Alem; C. L. Weber

    1978-01-01

    The performance of a class of pulse Doppler radars with a digitally implemented signal processing unit is investigated. TheKuband rendezvous radar onboard the Shuttle Orbiter is a pulse Doppler radar which is in this class. The detection capability is first presented. A unified analysis of digital radar tracking loops is presented which employs logarithmic discriminants. The results are applied to

  15. 74. Transmitter building no. 102, view of radar digital test ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    74. Transmitter building no. 102, view of radar digital test and maintenance cabinet area control panel and date storage system showing ampex tape storage devices. - Clear Air Force Station, Ballistic Missile Early Warning System Site II, One mile west of mile marker 293.5 on Parks Highway, 5 miles southwest of Anderson, Anderson, Denali Borough, AK

  16. Digital technique for generating synthetic aperture radar images

    Microsoft Academic Search

    W. J. van de Lindt

    1977-01-01

    This paper describes a digital processing method applicable to a synthetic aperture radar, to be carried by the space shuttle or by satellites. The method uses an earth-fixed coordinate system in which corrective procedures are invoked to compensate for errors introduced by the satellite motion, earth curvature, and wavefront curvature. Among the compensations discussed are those of the coordinate system,

  17. Radar shadow detection in synthetic aperture radar images using digital elevation model and projections

    NASA Astrophysics Data System (ADS)

    Prasath, V. B. Surya; Haddad, Oussama

    2014-01-01

    Synthetic aperture radar (SAR) images are currently widely used in target recognition tasks. In this work, we propose an automatic approach for radar shadow detection and extraction from SAR images utilizing geometric projections along with the digital elevation model (DEM), which corresponds to the given georeferenced SAR image. First, the DEM is rotated into the radar geometry, so that each row would match that of a radar line of sight. Next, we extract the shadow regions by processing row by row until the image is covered fully. We test the proposed shadow detection approach on different DEMs and simulated one-dimensional signals and two-dimensional hills and valleys modeled by various variance-based Gaussian functions. Experimental results indicate that the proposed algorithm produces good results in detecting shadows in SAR images with high resolution.

  18. Subinertial and seasonal variations in the Soya Warm Current revealed by HF ocean radars, coastal tide gauges, and bottom-mounted ADCP

    Microsoft Academic Search

    Naoto Ebuchi; Yasushi Fukamachi; Kay I. Ohshima; Masaaki Wakatsuchi

    2009-01-01

    Subinertial and seasonal variations in the Soya Warm Current (SWC) are investigated using data obtained by high frequency\\u000a (HF) ocean radars, coastal tide gauges, and a bottom-mounted acoustic Doppler current profiler (ADCP). The HF radars clearly\\u000a captured the seasonal variations in the surface current fields of the SWC. Almost the same seasonal cycle was repeated in\\u000a the period from August

  19. Evaluation of two algorithms for a network of coastal HF radars in the Mid-Atlantic Bight

    NASA Astrophysics Data System (ADS)

    Kohut, Josh; Roarty, Hugh; Randall-Goodwin, Evan; Glenn, Scott; Lichtenwalner, C. Sage

    2012-06-01

    The National High Frequency (HF) Surface Current Mapping Radar Network is being developed as a backbone system within the U.S. Integrated Ocean Observing System. This paper focuses on the application of HF radar-derived surface current maps to U.S. Coast Guard Search and Rescue operations along the Mid-Atlantic coast of the USA. In that context, we evaluated two algorithms used to combine maps of radial currents into a single map of total vector currents. In situ data provided by seven drifter deployments and four bottom-mounted current meters were used to (1) evaluate the well-established unweighted least squares (UWLS) and the more recently adapted optimal interpolation (OI) algorithms and (2) quantify the sensitivity of the OI algorithm to varying decorrelation scales and error thresholds. Results with both algorithms were shown to depend on the location within the HF radar data footprint. The comparisons near the center of the HF radar coverage showed no significant difference between the two algorithms. The most significant distinction between the two was seen in the drifter trajectories. With these simulations, the weighting of radial velocities by distance in the OI implementation was very effective at reducing both the distance between the actual drifter and the cluster of simulated particles as well as the scale of the search area that encompasses them. In this study, the OI further reduced the already improved UWLS-based search areas by an additional factor of 2. The results also indicated that the OI output was relatively insensitive to the varying decorrelation scales and error thresholds tested.

  20. Three-Frequency Nonlinear Heterodyne Detection. 2: Digital Communications and Pulsed Radar

    E-print Network

    Teich, Malvin C.

    Three-Frequency Nonlinear Heterodyne Detection. 2: Digital Communications and Pulsed Radar Malvin Carl Teich and Rainfield Y. Yen Part 1 of this paper [Appl. Opt. 14,666 (1975)]dealt with the cw radar the technique for a number of specificpulsed radar and digital communications applications. Both the vacuum

  1. Characterization of HF Propagation for Digital Audio Broadcasting

    NASA Technical Reports Server (NTRS)

    Vaisnys, Arvydas

    1997-01-01

    The purpose of this presentation is to give a brief overview of some propagation measurements in the Short Wave (3-30 MHz) bands, made in support of a digital audio transmission system design for the Voice of America. This task is a follow on to the Digital Broadcast Satellite Radio task, during which several mitigation techniques would be applicable to digital audio in the Short Wave bands as well, in spite of the differences in propagation impairments in these two bands. Two series of propagation measurements were made to quantify the range of impairments that could be expected. An assessment of the performance of a prototype version of the receiver was also made.

  2. Digital meteorological radar data compared with digital infrared data from a geostationary meteorological satellite 

    E-print Network

    Henderson, Rodney Stuart

    1979-01-01

    , for providing the satellite data and advice regarding its use. Mr. Ray McAnelly, for his generation of the digital radar data used in this study, Mr. T. O. Haig, also of the Space Science and Engineering Center, for information on the McIDAS system. Mrs... (Continued) CHAPTER Page 4. Basic Characteristics of In'rared Satellite Data. 5. McIDAS Data 6. Data Reduction and Display 26 27 29 IV. COMPARISON OF DIGITAL RADAR AND SATELLITE DATA 38 1. The Ba sis for the Comparison 2. First Tilt...

  3. Assessing SARAL/AltiKa delayed-time Ssalto/Duacs data in the coastal zone: comparisons with HF radar observations in the Ibiza Channel

    NASA Astrophysics Data System (ADS)

    Pascual, Ananda; Lana, Arancha; Troupin, Charles; Ruiz, Simón; Faugère, Yannice; Escudier, Romain; Tintoré, Joaquín

    2015-04-01

    We present an initial assessment of SARAL/AltiKa Ssalto/Duacs data in the coastal band. The study focuses on the Ibiza Channel where the north-south water exchanges play a key role in controlling the circulation variability in the Western Mediterranean at a wide range of scales. In this area, the track 16 of SARAL/AltiKa intercepts the domain covered by a coastal high-frequency (HF) radar system, which provides hourly surface currents, with a range up to 60 km. We evaluate the performance of the new altimeter when compared to the HF radar surface velocity fields. The Ssalto/Duacs delayed-time along-track products evidence the emerging capabilities of SARAL/AltiKa in the coastal zone: data are retrieved at a distance of only 7 km from the coast. Additionally, SARAL/AltiKa derived velocities reveal coherent mesoscale features among the different cycles and with reasonable agreement with HF radar fields (significant correlations of 0.54). Root mean square (rms) differences between the estimated SARAL and the HF radar velocities are of about 13 cm/s, which the same magnitude of the altimetric rms (14 cm/s) and slightly larger than HF radar (10 cm/s). These results are consistent with recent studies in other parts of the ocean applying similar approaches to Topex/Poseidon and Jason-1 missions and using dedicated coastal-oriented altimeter corrections.

  4. Surface circulation in the Strait of Gibraltar: a comparison study between HF radar and high resolution model data.

    NASA Astrophysics Data System (ADS)

    Soto-Navarro, Javier; Lorente, Pablo; Álvarez-Fanjul, Enrique; Ruiz-Gil de la Serna, M. Isabel

    2015-04-01

    Surface currents from the HF radar system deployed by Puertos del Estado (PdE) at the Strait of Gibraltar and an operational high resolution configuration of the MIT global circulation model, implemented in the strait area in the frame of the SAMPA project, have been analyzed and compared in the period February 2013 - September 2014. The comparison have been carried out in the time and frequency domains, by statistical a geophysical (tide ellipses, wind forcing, EOF) methods. Results show good agreement between both current fields in the strait axis, with correlation around 0.6 (reaching 0.9 in the low frequency band). Higher discrepancies are found in the boundaries of the domain, due to the differences in the meridional components, likely related to the sparser and less accurate radar measurements in these areas. Rotary spectral analysis show a very good agreement between both systems, which is reflected in a very similar and realistic representation of the main tide constituents (M2, S2 and K1). The wind forced circulation pattern, of special interest in the mouth of the Bay of Algeciras, is also precisely represented by radar and model. Finally, the spatial patterns of the first four EOF modes of both fields are rather close, reinforcing the previous results. As conclusion, the analysis points out the proper representation of the surface circulation of the area performed by the PdE HF radar system and the SAMPA model. However, weak and strong points are found in both, stressing the importance of having two complementary tools in the area.

  5. Performance analysis of pulse Doppler digital radars with application to the Shuttle Ku-band system

    Microsoft Academic Search

    W. K. Alem; C. L. Weber

    1978-01-01

    A pulse Doppler digital radar is one of the primary components of the Ku-band integrated radar and communication equipment on the Space Shuttle. The performance of the Ku-band rendezvous radar to be used on the Space Shuttle is analyzed in four parts. First an overall functional block diagram description is presented to illustrate the signal processing in the detection and

  6. Validation of Orthorectified Interferometric Radar Imagery and Digital Elevation Models

    NASA Technical Reports Server (NTRS)

    Smith Charles M.

    2004-01-01

    This work was performed under NASA's Verification and Validation (V&V) Program as an independent check of data supplied by EarthWatch, Incorporated, through the Earth Science Enterprise Scientific Data Purchase (SDP) Program. This document serves as the basis of reporting results associated with validation of orthorectified interferometric interferometric radar imagery and digital elevation models (DEM). This validation covers all datasets provided under the first campaign (Central America & Virginia Beach) plus three earlier missions (Indonesia, Red River: and Denver) for a total of 13 missions.

  7. Sub-auroral flow shear observed by King Salmon HF radar and RapidMAG

    NASA Astrophysics Data System (ADS)

    Hori, T.; Kikuchi, T.; Tsuji, Y.; Shinbori, A.; Ohtaka, T.; Kunitake, M.; Watari, S.; Nagatsuma, T.; Troshichev, O. A.

    2010-12-01

    We examine in detail the evolution of ionospheric flow shears in the sub-auroral region associated with alternate northward/southward turnings of the IMF. The flow shear structures are often observed in the dusk sector by the SuperDARN King Salmon (KSR) HF radar. Interestingly, some of those show the eastward (westward) flow on the lower (higher) latitude side, respectively, opposite to the typical polarity of the dusk convection cell. In those flow shear events, the IMF has a weak but persistent southward component (~ -1 to -3 nT) before onset of flow shears and following decreases of the southward IMF or even northward turning appear to cause the flow shears. The ground magnetograms provided by the Russian Auroral and Polar Ionospheric Disturbance Magnetometers (RapidMAG) show gradual increases (abrupt declines) of the H-component in association with the increases (decreases) of the merging electric field, respectively, derived from the simultaneous solar wind-IMF observations. The fairly coherent increases (decreases) of the H-component over the wide range of local time (afternoon to evening) indicate development (decay) of the large-scale DP2 current system. A detailed analysis on the 2-D convection structure near the lower latitude edge of the dusk convection cell shows that the ionospheric plasma generally flows westward there and has a larger speed with increasing latitude particularly during increases of the merging electric field. However, once the southward IMF decreases or even shifts to northward and thereby the merging electric field goes down, the region of westward flow moves toward higher latitudes and instead an eastward flow emerges there, forming a flow shear of the counterclockwise sense. This indicates that a downward field-aligned current (FAC), which is the Region-2 (R2) sense on the dusk side, flows into the flow shear region. Subsequently the convection returns to a westward flow again upon increases of the merging electric field due to the southward turning of IMF. A likely interpretation of these observations would be as follows: The R2 convection cell associated with a downward FAC is overwhelmed by the DP2 convection under the southward IMF. As the DP2 cell weakens rapidly, however, the R2 cell is still driven for a while by the partial ring current with its slowly decaying nature, resulting in the emergence of the R2 sense flow shear in the ionosphere. In other words, the ionospheric convection structure is controlled by the dynamic balance between that driven by the Region-1 FAC (the dusk DP2 cell) and that by the R2 FAC. The radar observation also reveals that those changes of convection structure take place rather quickly (~several min), very sensitive even to small variations of the merging electric field.

  8. Elliptical storm cell modeling of digital radar data

    NASA Technical Reports Server (NTRS)

    Altman, F. J.

    1972-01-01

    A model for spatial distributions of reflectivity in storm cells was fitted to digital radar data. The data were taken with a modified WSR-57 weather radar with 2.6-km resolution. The data consisted of modified B-scan records on magnetic tape of storm cells tracked at 0 deg elevation for several hours. The MIT L-band radar with 0.8-km resolution produced cross-section data on several cells at 1/2 deg elevation intervals. The model developed uses ellipses for contours of constant effective-reflectivity factor Z with constant orientation and eccentricity within a horizontal cell cross section at a given time and elevation. The centers of the ellipses are assumed to be uniformly spaced on a straight line, with areas linearly related to log Z. All cross sections are similar at different heights (except for cell tops, bottoms, and splitting cells), especially for the highest reflectivities; wind shear causes some translation and rotation between levels. Goodness-of-fit measures and parameters of interest for 204 ellipses are considered.

  9. Digital Radar-Signal Processors Implemented in FPGAs

    NASA Technical Reports Server (NTRS)

    Berkun, Andrew; Andraka, Ray

    2004-01-01

    High-performance digital electronic circuits for onboard processing of return signals in an airborne precipitation- measuring radar system have been implemented in commercially available field-programmable gate arrays (FPGAs). Previously, it was standard practice to downlink the radar-return data to a ground station for postprocessing a costly practice that prevents the nearly-real-time use of the data for automated targeting. In principle, the onboard processing could be performed by a system of about 20 personal- computer-type microprocessors; relative to such a system, the present FPGA-based processor is much smaller and consumes much less power. Alternatively, the onboard processing could be performed by an application-specific integrated circuit (ASIC), but in comparison with an ASIC implementation, the present FPGA implementation offers the advantages of (1) greater flexibility for research applications like the present one and (2) lower cost in the small production volumes typical of research applications. The generation and processing of signals in the airborne precipitation measuring radar system in question involves the following especially notable steps: The system utilizes a total of four channels two carrier frequencies and two polarizations at each frequency. The system uses pulse compression: that is, the transmitted pulse is spread out in time and the received echo of the pulse is processed with a matched filter to despread it. The return signal is band-limited and digitally demodulated to a complex baseband signal that, for each pulse, comprises a large number of samples. Each complex pair of samples (denoted a range gate in radar terminology) is associated with a numerical index that corresponds to a specific time offset from the beginning of the radar pulse, so that each such pair represents the energy reflected from a specific range. This energy and the average echo power are computed. The phase of each range bin is compared to the previous echo by complex conjugate multiplication to obtain the mean Doppler shift (and hence the mean and variance of the velocity of precipitation) of the echo at that range.

  10. A Digital Array Radar with a Hierarchical System Architecture Caleb Fulton, Patrick Clough, Vijay Pai, and William Chappell

    E-print Network

    A Digital Array Radar with a Hierarchical System Architecture Caleb Fulton, Patrick Clough, Vijay -- A digital array radar system prototype is pre sented that makes use of a hierarchical digital backend for future radars that fully embrace the concept of lowcost inte gration in a panelized platform

  11. Characteristics of daytime mid-latitude travelling ionospheric disturbances observed over the Antarctic peninsular with HF radar

    NASA Astrophysics Data System (ADS)

    Grocott, A.; Hosokawa, K.; Ishida, T.; Lester, M.; Milan, S. E.; Sato, N.; Yukimatu, A. S.

    2012-12-01

    We present a survey of travelling ionospheric disturbances (TIDs) observed by an HF radar located in the Falkland Islands between March 2010 and September 2011. The radar has a field of view that overlooks the Antarctic peninsular, a known hotspot of gravity wave activity. We present observations of radar ground backscatter data, in which the signatures of TIDs are manifest as structured enhancements in received backscattered power. Often, multiple TID signals are observed during an interval of observations and we discuss a new approach to their interpretation. Observed periods were in the range 30 - 60 minutes, corresponding to frequencies of 0.3 - 0.6 mHz. Wavelengths were generally in the range 250 - 400 km and phase speeds in the range 50 - 200 m/s. These values are within the ranges typically associated with medium-scale gravity waves. We discuss these results in terms of seasonal and diurnal variations, as well as in terms of their relationship to the local topography and large-scale geomagnetic activity.

  12. Perturbed Angular Correlation of the stretched cascade in the decay of 180mHf using a digital spectrometer

    NASA Astrophysics Data System (ADS)

    Jäger, Markus; Butz, Tilman

    2012-05-01

    We report on the measurement of the nuclear quadrupole interaction (NQI) at Hf sites using the nuclear probe 180mHf in HfF4·HF·2H2O at 300 K by exploiting all possible start quanta in the stretched cascade with a digital Time Differential Perturbed Angular Correlation (TDPAC) spectrometer. With conventional spectrometers, multiple prompt start signals would paralyze the router. The gain in coincidence rate is about a factor of 5 compared to a conventional spectrometer using a single start only. With multiple starts 180mHf is a promising new isomeric nuclear probe in TDPAC experiments. As an additional feature we implemented the possibility to measure up to four cascades simultaneously in order to save data collection time or to measure isobaric contaminations like 111mCd and 111In.

  13. Seasonal variation of a coastal jet in the Long Island Sound outflow region based on HF radar and Doppler current observations

    Microsoft Academic Search

    D. S. Ullman; D. L. Codiga

    2004-01-01

    Surface current (HF radar) and velocity profile observations, obtained as part of the Front-Resolving Observational Network with Telemetry (FRONT) project over an approximately 2-year period, are used to describe the seasonal variability of a coastal jet in the Long Island Sound outflow region. The jet is observed in an area of the continental shelf where surface thermal fronts are frequently

  14. Seasonal variation of a coastal jet in the Long Island Sound outflow region based on HF radar and Doppler current observations

    Microsoft Academic Search

    D. S. Ullman; D. L. Codiga

    2004-01-01

    Surface current (HF radar) and velocity prole observations, obtained as part of the Front Resolving Observational Network with Telemetry (FRONT) project over an approximately 2-year period, are used to describe the seasonal variability of a coastal jet in the Long Island Sound outo w region. The jet is observed in an area of the con- tinental shelf where surface thermal

  15. A combined QC methodology in Ebro Delta HF radar system: real time web monitoring of diagnostic parameters and offline validation of current data

    NASA Astrophysics Data System (ADS)

    Lorente, Pablo; Piedracoba, Silvia; Soto-Navarro, Javier; Ruiz, Maria Isabel; Alvarez Fanjul, Enrique

    2015-04-01

    Over recent years, special attention has been focused on the development of protocols for near real-time quality control (QC) of HF radar derived current measurements. However, no agreement has been worldwide achieved to date to establish a standardized QC methodology, although a number of valuable international initiatives have been launched. In this context, Puertos del Estado (PdE) aims to implement a fully operational HF radar network with four different Codar SeaSonde HF radar systems by means of: - The development of a best-practices robust protocol for data processing and QC procedures to routinely monitor sites performance under a wide variety of ocean conditions. - The execution of validation works with in-situ observations to assess the accuracy of HF radar-derived current measurements. The main goal of the present work is to show this combined methodology for the specific case of Ebro HF radar (although easily expandable to the rest of PdE radar systems), deployed to manage Ebro River deltaic area and promote the conservation of an important aquatic ecosystem exposed to a severe erosion and reshape. To this aim, a web interface has been developed to efficiently monitor in real time the evolution of several diagnostic parameters provided by the manufacturer (CODAR) and used as indicators of HF radar system health. This web, updated automatically every hour, examines sites performance on different time basis in terms of: - Hardware parameters: power and temperature. - Radial parameters, among others: Signal-to-Noise Ratio (SNR), number of radial vectors provided by time step, maximum radial range and bearing. - Total uncertainty metrics provided by CODAR: zonal and meridional standard deviations and covariance between both components. - Additionally, a widget embedded in the web interface executes queries against PdE database, providing the chance to compare current time series observed by Tarragona buoy (located within Ebro HF radar spatial domain) and those measured by the closest radar grid point. A thorough analysis of the temporal evolution of the aforementioned parameters allows to define the standard thresholds for each site within which they are considered to be running optimally. In contrast, a site performance could be categorized as sub-optimal if an erratic and/or anomalous behavior is persistently detected in radial parameters values, related to a significant discrepancy from the mean and clearly outside the limits defined by the associated standard deviations. Consequently, a three colored-based alert system is activated according to each site's current status: green (OK), yellow (acceptable, but issue detected) and red (KO). Since this approach is constrained by the fact that it can not state the intrinsic quality of surface current data, a complementary validation analysis is required: HF radar-derived radial and total vectors are compared with observations from a current meter installed in Tarragona buoy. This validation, conducted for the entire 2014, aims to complete the proposed methodology through the exploration of the existence of bearing errors and the evaluation of intrinsic uncertainties related to HF radar technology by means of objective quality indicators.

  16. Mapping near-inertial variability in the SE Bay of Biscay from HF radar data and two offshore moored buoys

    NASA Astrophysics Data System (ADS)

    Rubio, A.; Reverdin, G.; Fontán, A.; González, M.; Mader, J.

    2011-10-01

    HF radar surface current data together with data from two operational offshore oceanographic buoys located over the slope are used to map the variability associated with the near-inertial waves, during a target year (2009), in the SE Bay of Biscay. The results obtained show the complex 4D distribution of inertial oscillations in this area. We find a very pronounced horizontal structure across the area with ranges of a factor 5 in near-inertial kinetic energy. This pattern presents also strong seasonal variability, with a peak in KE closer to the shelf-break in summer, whereas winter maximum is weaker and located further to the north-east. The mooring data indicate more trapping near the surface in summer. These patterns are discussed in relation to the known seasonal differences in atmospheric/buoyancy forcing and the characteristics of the sub-inertial surface velocity field.

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

    E-print Network

    Paris-Sud XI, Université de

    appreciable HF coherent backscatter, and are only identi®able in the backscatter data as a modi., 1995) are designed to employ backscatter from high- latitude ®eld-aligned ionospheric plasma density observations is of interest, not only as a multi-instrument investigation of large-scale geophysical processes

  18. Digital beam forming on transmit and receive with an AESA FMCW radar

    Microsoft Academic Search

    C. M. Lievers; W. L. van Rossum; A. P. M. Maas; A. G. Huizing

    2007-01-01

    This paper describes an active electronically scanned array (AESA) FMCW radar with eight transceivers. Each transceiver has its own Direct Digital Synthesizer (DDS) for signal generation which enables digital beam forming on transmit as well as on receive. The coherent operation of the eight transceivers and the capability to perform digital beam forming on transmit and receive is demonstrated.

  19. Performance analysis of pulse Doppler digital radars with application to the Shuttle Ku-band system

    NASA Technical Reports Server (NTRS)

    Alem, W. K.; Weber, C. L.

    1978-01-01

    A pulse Doppler digital radar is one of the primary components of the Ku-band integrated radar and communication equipment on the Space Shuttle. The performance of the Ku-band rendezvous radar to be used on the Space Shuttle is analyzed in four parts. First an overall functional block diagram description is presented to illustrate the signal processing in the detection and the tracking modes. The detection capabilities and limitations of the radar are investigated taking all of the system losses into account. A new unified analysis of digital radar tracking loops is developed which takes into consideration the effects of a scintillating target and receiver front end noise. The behavior of the radar is discussed in the presence of thermal noise, amplitude scintillation, and target glint.

  20. Digital elevation models of the Moon from Earth-based radar interferometry

    Microsoft Academic Search

    Jean-Luc Margot; Donald B. Campbell; Raymond F. Jurgens; Martin A. Slade

    2000-01-01

    Three-dimensional (3D) maps of the nearside and polar regions of the Moon can be obtained with an Earth-based radar interferometer. This paper describes the theoretical background, experimental setup, and processing techniques for a sequence of observations performed with the Goldstone Solar System Radar in 1997. These data provide radar imagery and digital elevation models of the polar areas and other

  1. A short-term predictive system for surface currents from a rapidly deployed coastal HF radar network

    NASA Astrophysics Data System (ADS)

    Barrick, Donald; Fernandez, Vicente; Ferrer, Maria I.; Whelan, Chad; Breivik, Øyvind

    2012-05-01

    In order to address the need for surface trajectory forecasts following deployment of coastal HF radar systems during emergency-response situations (e.g., search and rescue, oil spill), a short-term predictive system (STPS) based on only a few hours data background is presented. First, open-modal analysis (OMA) coefficients are fitted to 1-D surface currents from all available radar stations at each time interval. OMA has the effect of applying a spatial low-pass filter to the data, fills gaps, and can extend coverage to areas where radial vectors are available from a single radar only. Then, a set of temporal modes is fitted to the time series of OMA coefficients, typically over a short 12-h trailing period. These modes include tidal and inertial harmonics, as well as constant and linear trends. This temporal model is the STPS basis for producing up to a 12-h current vector forecast from which a trajectory forecast can be derived. We show results of this method applied to data gathered during the September 2010 rapid-response demonstration in northern Norway. Forecasted coefficients, currents, and trajectories are compared with the same measured quantities, and statistics of skill are assessed employing 16 24-h data sets. Forecasted and measured kinetic variances of the OMA coefficients typically agreed to within 10-15%. In one case where errors were larger, strong wind changes are suspected and examined as the cause. Sudden wind variability is not included properly within the STPS attack we presently employ and will be a subject for future improvement.

  2. Digital signal processing techniques in a monopulse tracking radar

    Microsoft Academic Search

    U. Fazio; F. Ambrosioni; C. Debonis

    1979-01-01

    A description of a special-purpose Signal Processor is given. Since the Processor is highly flexible, it can be applied in a wide range of modern ground or ship-borne tracking radars, such as, Fire Control Radar for rockets or for conventional artillery (ground or anti-aircraft), Instrumentation Radar, and Tracking Radar for Command to line-of-sight missile guidance. Illustrated are the three main

  3. Digital Doppler radial velocity data compared objectively with digital reflectivity radar data 

    E-print Network

    Beaver, Thomas Foster

    1980-01-01

    sn sn &4 &0 KILO NIETHBS IVEST OF I'iSSL FIG. 21. 3-km CAVM, 18D5-1812 CDT, 1 May 1977 (1-km grid), Doppler data. 48 2N 28 6- 4 1O 0 14 18 O g 22 26 3O E O 38 I I 0 I I 1 I "~ I I I v I I I I f 1 I I ~~~ J~ 76 72 68... (Member) Dr. G en N. Wi cams (Member) Dr. Kenneth C. Brun s ge (Head of Department) May 1980 ABSTRACT Digital Doppler Radial Velocity Data Compared Objectively with Digital Reflectivity Radar Data. (May 1980) Thomas Foster Beaver, B. S. , Grove...

  4. Assessing the fidelity of surface currents from a coastal ocean model and HF radar using drifting buoys in the Middle Atlantic Bight

    NASA Astrophysics Data System (ADS)

    Kuang, Liang; Blumberg, Alan F.; Georgas, Nickitas

    2012-08-01

    The rapid expansion of urbanization along the world's coastal areas requires a more comprehensive and accurate understanding of the coastal ocean. Over the past several decades, numerical ocean circulation models have tried to provide such insight, based on our developing understanding of physical ocean processes. The systematic establishment of coastal ocean observation systems adopting cutting-edge technology, such as high frequency (HF) radar, satellite sensing, and gliders, has put such ocean model predictions to the test, by providing comprehensive observational datasets for the validation of numerical model forecasts. The New York Harbor Observing and Prediction System (NYHOPS) is a comprehensive system for understanding coastal ocean processes on the continental shelf waters of New York and New Jersey. To increase confidence in the system's ocean circulation predictions in that area, a detailed validation exercise was carried out using HF radar and Lagrangian drifter-derived surface currents from three drifters obtained between March and October 2010. During that period, the root mean square (RMS) differences of both the east-west and north-south currents between NYHOPS and HF radar were approximately 15 cm s-1. Harmonic analysis of NYHOPS and HF radar surface currents shows similar tidal ellipse parameters for the dominant M2 tide, with a mean difference of 2.4 cm s-1 in the semi-major axis and 1.4 cm s-1 in the semi-minor axis and 3° in orientation and 10° in phase. Surface currents derived independently from drifters along their trajectories showed that NYHOPS and HF radar yielded similarly accurate results. RMS errors when compared to currents derived along the trajectory of the three drifters were approximately 10 cm s-1. Overall, the analysis suggests that NYHOPS and HF radar had similar skill in estimating the currents over the continental shelf waters of the Middle Atlantic Bight during this time period. An ensemble-based set of particle tracking simulations using one drifter which was tracked for 11 days showed that the ensemble mean separation generally increases with time in a linear fashion. The separation distance is not dominated by high frequency or short spatial scale wavelengths suggesting that both the NYHOPS and HF radar currents are representing tidal and inertial time scales correctly and resolving some of the smaller scale eddies. The growing ensemble mean separation distance is dominated by errors in the mean flow causing the drifters to slowly diverge from their observed positions. The separation distance for both HF radar and NYHOPS stays below 30 km after 5 days, and the two technologies have similar tracking skill at the 95 % level. For comparison, the ensemble mean distance of a drifter from its initial release location (persistence assumption) is estimated to be greater than 70 km in 5 days.

  5. Characterizing the coastal dynamics behaviour within the Gulf of Naples using modelling, HF radar and in situ measurements

    NASA Astrophysics Data System (ADS)

    Iermano, Ilaria; Cianelli, Daniela; Falco, Pierpaolo; Uttieri, Marco; Zambianchi, Enrico

    2013-04-01

    The integration of numerical models in coastal observatories represents a current challenge for the scientific community, constituting a frontier both for research purposes and for a variety of practical applications, ranging from coastal protection to search and rescue activities, or support to engineering works and operational structures. Here we present the monitoring network installed in the Gulf of Naples, our recent advances in coastal and in-situ observations and the integrated ocean-atmosphere modelling approach, through connections to the state of the art and still opened research issues that will be the challenges for the next years. Currently, the monitoring network of the Gulf of Naples is composed of moored instrumentation and a HF radar system composed of three antennas that provide hourly data of surface currents for the entire Gulf at a spatial resolution of 1 km. The ocean model configuration is a ROMS (Regional Ocean Modeling System)-based code, configured on the region (~13-15E, 40-42N). The increasing availability of long-term observations, the large dataset recently acquired in sea-truth campaigns and numerical output from meteorological and ocean models allow us to use these integrated tools to characterize the coastal dynamics processes, and thus provide quantitative support to decision makers in the field of management strategy on oil spill and search and rescue operations, vulnerability of coasts and correct management strategies of the environmental heritage. This talk presents diverse scientific issues recently addressed by the DiSAm (University of Naples Parthenope) in the broad activity of developing and tuning of the oceanic components of modeling system. We will show some numerical model results in the Gulf of Naples basin in response to high resolution atmospheric forcing provided by the SKIRON model focusing mainly on the seasonal circulation and on the mesoscale and submesoscale variability associated with the current system of the basin. A particular attention is devoted to the analysis of the fate of waters originated inside the Gulf and in the Tyrrhenian Sea, which circulate in the area, giving insights as to the water renewal mechanisms of individual subareas. The results of simulations are compared with eulerian synoptic measurements of surface currents provided by the HF radar system installed on the Gulf's coasts, showing a very good agreement between the two data sets.

  6. Variability in the air-sea interaction patterns and timescales within the south-eastern Bay of Biscay, as observed by HF radar data

    NASA Astrophysics Data System (ADS)

    Fontán, A.; Esnaola, G.; Sáenz, J.; González, M.

    2013-04-01

    Two high-frequency (HF) radar stations were installed on the coast of the south-eastern Bay of Biscay in 2009, providing high spatial and temporal resolution and large spatial coverage of currents in the area for the first time. This has made it possible to quantitatively assess the air-sea interaction patterns and timescales for the period 2009-2010. The analysis was conducted using the Barnett-Preisendorfer approach to canonical correlation analysis (CCA) of reanalysis surface winds and HF radar-derived surface currents. The CCA yields two canonical patterns: the first wind-current interaction pattern corresponds to the classical Ekman drift at the sea surface, whilst the second describes an anticyclonic/cyclonic surface circulation. The results obtained demonstrate that local winds play an important role in driving the upper water circulation. The wind-current interaction timescales are mainly related to diurnal breezes and synoptic variability. In particular, the breezes force diurnal currents in waters of the continental shelf and slope of the south-eastern Bay. It is concluded that the breezes may force diurnal currents over considerably wider areas than that covered by the HF radar, considering that the northern and southern continental shelves of the Bay exhibit stronger diurnal than annual wind amplitudes.

  7. Variability in the air-sea interaction patterns and time-scales within the Southeastern Bay of Biscay, as observed by HF radar data

    NASA Astrophysics Data System (ADS)

    Fontán, A.; Esnaola, G.; Sáenz, J.; González, M.

    2012-08-01

    Two high frequency (HF) radar stations were installed on the Southeastern Bay of Biscay in 2009, providing high spatial and temporal resolution and large spatial coverage currents for the first time in the area. This has enabled to determine quantitatively the air-sea interaction patterns and time-scales for the period 2009-2010. The analysis was conducted by using the Barnett-Preisendorfer approach to canonical correlation analysis (CCA) of reanalysis surface winds and HF radar-derived currents. The results reveal that the CCA yields two canonical patterns. The first wind-current interaction pattern corresponds to the classical Ekman drift at sea surface, whilst the second describes an anticyclonic/cyclonic surface circulation. The results obtained demonstrate that the local winds play an important role in driving the upper water circulation. The wind-current interaction time-scales are mainly related to diurnal breezes and synoptic variability. In particular, the breezes force diurnal currents in the continental shelf and slope of the Southeastern Bay. It is concluded that the breezes may force diurnal currents over considerably wider areas than that covered by the HF radar, considering that the northern and southern continental shelves of the Bay exhibit stronger diurnal than annual wind amplitudes.

  8. HF radar detection of infrasonic waves generated in the ionosphere by the 28 March 2005 Sumatra earthquake

    NASA Astrophysics Data System (ADS)

    Bourdillon, Alain; Occhipinti, Giovanni; Molinié, Jean-Philippe; Rannou, Véronique

    2014-03-01

    Surface waves generated by earthquakes create atmospheric waves detectable in the ionosphere using radio waves techniques: i.e., HF Doppler sounding, GPS and altimeter TEC measurements, as well as radar measurements. We present observations performed with the over-the-horizon (OTH) radar NOSTRADAMUS after the very strong earthquake (M=8.6) that occurred in Sumatra on March 28, 2005. An original method based on the analysis of the RTD (Range-Time-Doppler) image is suggested to identify the multi-chromatic ionospheric signature of the Rayleigh wave. The proposed method presents the advantage to preserve the information on the range variation and time evolution, and provides comprehensive results, as well as easy identification of the waves. In essence, a Burg algorithm of order 1 is proposed to compute the Doppler shift of the radar signal, resulting in sensitivity as good as obtained with higher orders. The multi-chromatic observation of the ionospheric signature of Rayleigh wave allows to extrapolate information coherent with the dispersion curve of Rayleigh waves, that is, we observe two components of the Rayleigh waves with estimated group velocities of 3.8 km/s and 3.6 km/s associated to 28 mHz (T~36 s) and 6.1 mHz (T~164 s) waves, respectively. Spectral analysis of the RTD image reveals anyway the presence of several oscillations at frequencies between 3 and 8 mHz clearly associated to the transfer of energy from the solid-Earth to the atmosphere, and nominally described by the normal modes theory for a complete planet with atmosphere. Oscillations at frequencies larger than 8 mHz are also observed in the spectrum but with smaller amplitudes. Particular attention is pointed out to normal modes 0S29 and 0S37 which are strongly involved in the coupling process. As the proposed method is frequency free, it could be used not only for detection of ionospheric perturbations induced by earthquakes, but also by other natural phenomena as well as volcanic explosions and particularly tsunamis, for future oceanic monitoring and tsunami warning systems.

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

    NASA Astrophysics Data System (ADS)

    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).

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

    NASA Astrophysics Data System (ADS)

    Grocott, A.; Lester, M.; Parkinson, M. L.; Yeoman, T. K.; Dyson, P. L.; Devlin, J. C.; Frey, H. U.

    2006-12-01

    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 way which has already proved extremely successful in studies of the dayside magnetosphere.

  11. Digital signal processing in binary phase coded CW multistatic radar

    Microsoft Academic Search

    R. Norland

    2003-01-01

    Electronic countermeasures (ECM) and homing anti-radiation missiles (ARM) pose a threat to the operability of radar. One solution to counteract the threat and continue operating radar is to separate the transmitter and receiver and spread the emitted signal in both frequency and space. The Norwegian Defence Research Establishment (FFI) has developed a low power, bistatic, coherent, spread spectrum and continuous

  12. Advanced ground-penetrating radar for digital soil mapping

    Microsoft Academic Search

    S. Lambot; J. Minet; K. Z. Jadoon; E. Slob; H. Vereecken

    2009-01-01

    Sustainable and optimal agricultural and environmental management of water and land resources particularly relies on the description and understanding of soil water distribution and dynamics at different scales. We present an advanced ground penetrating radar (GPR) method for mapping the shallow soil water content and unsaturated hydraulic properties at the field scale. The radar system is based on vector network

  13. Digitized dual wavelength radar data from a Texas thunderstorm 

    E-print Network

    Radlein, Robin Ann

    1977-01-01

    ) Antenna beam width~8(horizontal) ](vertical) 0 ' 5 5 1 54 1 54 0 5 5 1 54 1 ~ 52 Antenna Gain, G~ db Minimum detectable signal, dhm 2 3 -6 Radar Constant, C, w km m mm 40 5 -107 5 1 0089%10 40 3 -107 5 8, 609%10 13 radar beam... of the most important tools for the detection of severe local storms such as tornadoes~ hailstorms~ and severe thunderstorms The usefulness of early radars was limited~ however, by the capacity of the operator to recognize the type and severity of a storm...

  14. A STATUS REPORT ON THE RF AND DIGITAL COMPONENTS OF THE MULTICHANNEL RECEIVER DEVELOPMENT AT THE NATIONAL WEATHER RADAR TESTBED

    Microsoft Academic Search

    M. Yeary; J. Crain; A. Zahrai; R. Kelley; J. Meier; Y. Zhang; I. Ivic; C. Curtis; R. Palmer; T.-Y. Yu; G. Zhang; R. Doviak; P. Chilson; M. Xue; Q. Xu

    This paper describes the status of a project that will simultaneously digitize the radar signals coming from eight channels on the phased array antenna at the Na- tional Weather Radar Testbed (NWRT) in Norman, Ok- lahoma. At the current time, a single-channel digital receiver is operational on this S-band radar to mimic the current WSR-88D capability. The multi-channel dig- ital

  15. High Frequency (HF) upgrade study for the Canadian Regional Operations Control Center (ROCC) AWACS Digital Information Link (RADIL) project

    NASA Astrophysics Data System (ADS)

    Wickwire, Kenneth

    1995-04-01

    The Regional Operations Control Center AWACS Digital Information Link/Rapidly Deployable Integrated Command and Control System (RADIL/RADIC) System Program Office, Canadian RADIL Program, has acquired high-frequency (HF) radio equipment for two Canadian ground stations under the RADIL Project. This equipment will allow those stations to carry out Tactical Digital Information Link (TADIL) A data transmissions assisted by MIL-STD-188-141A automatic link establishment (ALE). The MITRE Corporation has been tasked to study whether U.S. TADIL stations should be equipped with similar HF-ALE modems. This report analyzes the improvements in performance over northern links that can be expected from the addition of ALE to the TADIL A system. Since there is only a small amount of data on ALE-assisted digital communications in northern regions, the analysis combines a probabilistic approach to comparison of ALE and conventional linking techniques with actual HF propagation data from links in Canada, Iceland, and Norway. The report also assesses the risks to effective communications of using an ALE-TADIL A system in the north and recommends several improvements in hardware and software that can lower those risks.

  16. Accuracy Assessment of a Digital Height Model Derived from Airborne Synthetic Aperture Radar Measurements

    Microsoft Academic Search

    Alfred Kleusberg; Hans-georg Klaedtke

    1999-01-01

    Abstract: A digital height model (DHM) derived from airborne interferometric synthetic aperture Radar (InSAR) covering about140 kmwas compared to the elevations of Trigonometric Points, the DHM of the state of Baden-Wrttemberg (DHMBa-W), and GPS derived elevations.

  17. An atlas of November 1978 synthetic aperture radar digitized imagery for oil spill studies

    NASA Technical Reports Server (NTRS)

    Maurer, H. E.; Oderman, W.; Crosswell, W. F.

    1982-01-01

    A data set is described which consists of digitized synthetic aperture radar (SAR) imagery plus correlative data and some preliminary analysis results. This data set should be of value to experimenters who are interested in the SAR instrument and its application to the detection and monitoring of oil on water and other distributed targets.

  18. Global digital topography mapping with a synthetic aperture scanning radar altimeter

    Microsoft Academic Search

    C. Elachi; K. E. Im; F. Li; E. Rodriguez

    1990-01-01

    Global digital topography data of the land surface is of importance in a variety of geoscientific and application disciplines. Such a database, with a spatial resolution of 150 to 500 m and height accuracy of 5 m or better can be acquired from an orbiting platform using a synthetic aperture scanning radar altimeter. Near-global coverage can be achieved within 14

  19. Tornado identification from analyses of digital radar data

    E-print Network

    Pittman, Donald Wayne

    1976-01-01

    . There are two somewhat different types of BWERs: those of long persistence with a 5-10 km dia- meter and those of short duration with a diameter of only 1 -5 km. A dual-doppler radar study of the smaller-scale phenomena by M Carthy et al. revealed dynamics...

  20. Global search and rescue - A new concept. [orbital digital radar system with passive reflectors

    NASA Technical Reports Server (NTRS)

    Sivertson, W. E., Jr.

    1976-01-01

    A new terrestrial search and rescue concept is defined embodying the use of simple passive radiofreqeuncy reflectors in conjunction with a low earth-orbiting, all-weather, synthetic aperture radar to detect, identify, and position locate earth-bound users in distress. Users include ships, aircraft, small boats, explorers, hikers, etc. Airborne radar tests were conducted to evaluate the basic concept. Both X-band and L-band, dual polarization radars were operated simultaneously. Simple, relatively small, corner-reflector targets were successfully imaged and digital data processing approaches were investigated. Study of the basic concept and evaluation of results obtained from aircraft flight tests indicate an all-weather, day or night, global search and rescue system is feasible.

  1. Spectral analysis, digital integration, and measurement of low backscatter in coherent laser radar

    NASA Technical Reports Server (NTRS)

    Vaughan, J. M.; Callan, R. D.; Bowdle, D. A.; Rothermel, J.

    1989-01-01

    A method of surface acoustic wave (SAW) spectral analysis and digital integration that has been used previously in coherent CW laser work with CO2 lasers at 10.6 microns is described. Expressions are derived for the signal to noise ratio in the measured voltage spectrum with an approximation for the general case and rigorous treatment for the low signal case. The atmospheric backscatter data accumulated by the airborne LATAS (laser true airspeed) coherent laser radar system are analyzed.

  2. Global digital topography mapping with a synthetic aperture scanning radar altimeter

    NASA Technical Reports Server (NTRS)

    Elachi, C.; Im, K. E.; Rodriguez, E.

    1990-01-01

    Global digital topography data of the land surface is of importance in a variety of geoscientific and application disciplines. Such a database, with a spatial resolution of 150 to 500 m and height accuracy of 5 m or better can be acquired from an orbiting platform using a synthetic aperture scanning radar altimeter. Near-global coverage can be achieved within 14 days from an orbiting platform in a polar or near-polar orbit.

  3. Hf phased-array radar for studying small-scale structure in the high-latitude ionosphere

    Microsoft Academic Search

    R. A. Greenwald; K. B. Baker; R. A. Hutchins; C. Hanuise

    1985-01-01

    Since October 1983, a new coherent backscatter radar has been in operation at Goose Bay, Labrador, for the purpose of studying small-scale electron density structure in the high-latitude ionosphere. This radar operates over a frequency band that extends from 8 to 20 MHz, and it uses an electronically phased array of 16 log-periodic antennas for both transmission and reception. The

  4. Radar

    Microsoft Academic Search

    James R. Zimbelman; Kenneth S. Edgett

    1994-01-01

    Over 1,000,000 km2 of the equatorial surface of Mars west of the Arsia Mons volcano displays no 3.5-cm radar echo to the very low level of the radar system noise for the Very Large Array; the area displaying this unique property has been terms \\

  5. Digital radar-gram processing for water pipelines leak detection

    NASA Astrophysics Data System (ADS)

    García-Márquez, Jorge; Flores, Ricardo; Valdivia, Ricardo; Carreón, Dora; Malacara, Zacarías; Camposeco, Arturo

    2006-02-01

    Ground penetrating radars (GPR) are useful underground exploration devices. Applications are found in archaeology, mine detection, pavement evaluation, among others. Here we use a GPR to detect by an indirect way, the anomalies caused by the presence of water in the neighborhood of an underground water pipeline. By Fourier transforming a GPR profile map we interpret the signal as spatial frequencies, instead of the temporal frequencies, that composes the profile map. This allows differentiating between signals returning from a standard subsoil feature from those coming back from anomalous zones. Facilities in Mexican cities are commonly buried up to 2.5 m. Their constituent materials are PVC, concrete or metal, typically steel. GPRs are ultra-wide band devices; leak detection must be an indirect process since echoes due to the presence of underground zones with high moisture levels are masked by dense reflections (clutter). In radargrams the presence of water is visualized as anomalies in the neighborhood of the facility. Enhancement of these anomalies will give us the information required to detect leaks.

  6. An airborne digital processor for radar scatterometer data

    E-print Network

    Yeadon, David Steven

    1977-01-01

    the binary rep- resentation of aircraft attitude parameters. These parameters are avail- able from the ADC. Unfortunately, the ADC format is incompatible with the digital processor format. Generally, the ADC format presents the data in a serial bit pulse... four-bit BCD representa- tion. The other two codes both use the Air Data Ac uisition S stem (ASO-90) format, wherein each word consists of six bits. The first bit (the index bit) is always a logical ONE. The last bit is the parity bit for that word...

  7. Occurrence characteristics of subauroral westward plasma flows and lowest speed threshold of SAPS observed by the SuperDARN Hokkaido HF radar

    NASA Astrophysics Data System (ADS)

    Nagano, H.; Nishitani, N.; Hori, T.

    2014-12-01

    Westward rapid plasma flows in the ionosphere at subauroral latitudes are called "Sub-Auroral Polarization Stream (SAPS) [Foster and Burke, 2002]". SAPS is a manifestation of the Magnetosphere-Ionosphere (M-I) coupling. Therefore, it is important to know occurrence characteristics of SAPS in order to understand the details of M-I coupling system. As a result of the present analysis of SAPS using the SuperDARN Hokkaido HF radar, Kataoka et al. [2009] reported that positions of SAPS shifts toward lower latitude with decreasing Dst index. We investigate the characteristics of SAPS, with focus on the relationship between occurrence characteristics of SAPS and a variety of solar wind and geomagnetic parameters, using the SuperDARN Hokkaido HF radar with a field of view covering Far East Russia, which has been in operation since 2006. In particular, we identify the lowest limit of SAPS speed, which has not been discussed in the previous literatures. This is to examine the lowest threshold of electric field to generate SAPS as a result of M-I coupling. In order to investigate SAPS occurrence characteristics comprehensively, we analyzed events with wider ranges of velocity and MLAT than those in the previous studies. As a result of statistical analysis, we found two categories of westward flows that were reasonably separated with a speed threshold of ~150-200 m/s. For the faster flows above the threshold there is a clear correlation between MLAT and Dst index, whereas for the slower flows there is no such correlation. Similar correlation is found for MLT and AL index as well. The faster flows are considered to be SAPS, whereas the slower flows are probably associated with midlatitude F-region ionospheric irregularities not directly related to storms / substorms.

  8. Digital tapped delay lines for HWIL testing of matched filter radar receivers

    NASA Astrophysics Data System (ADS)

    Olson, Richard F.; Braselton, William J.; Mohlere, Richard D.

    2009-05-01

    Matched filter processing for pulse compression of phase coded waveforms is a classic method for increasing radar range measurement resolution. A generic approach for simulating high resolution range extended radar scenes in a Hardware in the Loop (HWIL) test environment is to pass the phase coded radar transmit pulse through an RF tapped delay line comprised of individually amplitude- and phase-weighted output taps. In the generic approach, the taps are closely spaced relative to time intervals equivalent to the range resolution of the compressed radar pulse. For a range-extended high resolution clutter scene, the increased number of these taps can make an analog implementation of an RF tapped delay system impractical. Engineers at the U.S. Army Aviation and Missile Research, Development and Engineering Center (AMRDEC) have addressed this problem by transferring RF tapped delay line signal operations to the digital domain. New digital tapped delay line (DTDL) systems have been designed and demonstrated which are physically compact compared to analog RF TDLs, leverage low cost FPGA and data converter technology, and may be readily expanded using open slots in a VME card cage. In initial HWIL applications, the new DTDLs have been shown to produce better dynamic range in pulse compressed range profiles than their analog TDL predecessors. This paper describes the signal requirements and system architecture for digital tapped delay lines. Implementation, performance, and HWIL simulation integration issues for AMRDEC's first generation DTDLs are addressed. The paper concludes with future requirements and plans for ongoing DTDL technology development at AMRDEC.

  9. Modern Radar Techniques for Geophysical Applications: Two Examples

    NASA Technical Reports Server (NTRS)

    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.

  10. The Long Wavelength Array (LWA): A Large HF\\/VHF Array for Solar Physics, Ionospheric Science, and Solar Radar

    Microsoft Academic Search

    N. Kassim; S. White; P. Rodriquez; J. Hartman; B. Hicks; J. Lazio; K. Stewart; J. Craig; G. Taylor; C. Cormier; V. Romero; F. Jenet

    2010-01-01

    The Long Wavelength Array (LWA), currently under construction in New Mexico, will be an imaging HF\\/VHF interferometer providing a new approach for studying the Sun-Earth environment from the surface of the sun to the Earth's ionosphere. The LWA will be a powerful tool for solar physics and space weather investigations, through its ability to characterize a diverse range of low-frequency,

  11. An analysis of the data collection modes of a digital weather radar system with respect to significant severe weather features 

    E-print Network

    Neyland, Michael Arthur

    1978-01-01

    LIST OF ACROBYMS EWER CAPPI CAZM DVIP PPI bounded weak echo region constant altitude plan position indi. cator constant altitude reflectivity map digital video integrator and processor plan position indicator. minimum detectable signal PRF... of radar, it was recognized that the device could locate and tracR areas of severe weather and precipitation. Since that time, radar has come to be considered one of the most important tools available to the meteoro- logist for the detection of severe...

  12. Multiple-site investigation of the properties of an HF radio channel and the ionosphere using Digital Radio Mondiale broadcasting

    NASA Astrophysics Data System (ADS)

    Mlynarczyk, Janusz; Koperski, Piotr; Kulak, Andrzej

    2012-01-01

    The Digital Radio Mondiale (DRM), one of the new digital radio broadcasting standards, has been designed to overcome typical short wave radio channel difficulties, such as the multipath propagation and fast temporal changes of the received signal level, both related to the properties of the ionosphere along the path of propagation. In particular, some of the RF carriers used in the applied COFDM transmission technique serve to estimate the current state of the radio channel to enable the proper demodulation of the received signal.We have been detecting such RF carriers on select frequency channels (standard DRM broadcast) using a network of recording stations located in different parts of Poland in order to collect data on the HF radio channel. We have been also evaluating the usefulness of this procedure in providing information on the current state of the ionosphere in the refraction region between the transmitter and receivers. When the DRM system becomes more widespread, this method can supplement data that comes from the ionosondes, since it does not require much financial resources and the receivers can be easily scattered over a large area. This paper presents a set of experimental data and its analysis.

  13. Observational evidence of mesoscale variability of the Northern Current (North-Western Mediterranean Sea): a combined study via gliders, HF RADAR, surface drifters, and vessel data

    NASA Astrophysics Data System (ADS)

    Bellomo, Lucio; Berta, Maristella; Pietro Gasparini, Gian; Griffa, Annalisa; Gatimu Magaldi, Marcello; Marmain, Julien; Molcard, Anne; Vetrano, Anna; Béguery, Laurent; Borghini, Mireno

    2013-04-01

    Results from a combined observational effort put forth in December 2011 are here presented. The focus is on the mesoscale variability of the Northern Current (NC), the branch of the general North-Western Mediterranean cyclonic circulation extending from the Ligurian to the Catalan Sea (Albérola et al., Oceanologica Acta, vol. 18, n. 2, 1995). The study area, located between the Ligurian Sea and the Gulf of Lions, includes the part of French coast between Nice and Toulon, where only a few hydrographic data have been collected in the past. Dynamic instabilities of the NC, observed and reported in literature (Picco et al., Ocean Science, vol. 6, 2010), make this region particularly important, with consequences in the recirculation of the Ligurian Gyre and in the NC intrusions in the Gulf of Lions (Millot and Wald, Oceanologica Acta, vol. 3, n. 4, 1980). This works aims at providing experimental evidence of the effects that mesoscale exerts on the NC dynamics via an innovative and complementary data set. Two Slocum Gliders (a Shallow and a Deep one), both equipped with CTD and dissolved oxygen sensors, sampled the area within 70 km from the coast for about 20 days. The shallow one (200 m) realized six transects describing a "W"-shaped pattern from Nice to Toulon, whereas the deep one (1000 m) performed repeated cross-current sections off Toulon. Concurrent observations were obtained via: a) CTD and both Lowered and Vessel-Mounted ADCP transects obtained during a 5-day oceanographic cruise on board of the Research Vessel Urania; b) repeated deployments of surface drifters; c) a continuously-recording High Frequency (HF) RADAR which measures surface currents off Toulon in a 40 × 25 km2 region with high resolution both in space (2 km) and in time (1 hour). The combined use of data from the shallow glider and the ship-based ADCP measurements reveals the presence of an instability of the offshore front of the NC. Its location is confirmed by high-resolution satellite images in the same period and by the trajectories of the drifters. The instability is thought to evolve in a filament which detaches from the main branch and moves eastward, participating to the recirculation of the Ligurian Gyre. Data from the deep glider and the HF RADAR are used to assess the temporal evolution of the NC front in the region off Toulon. The analysis shows that the surface front is here eroded during the observational period. Possible reasons include a) the blowing of Mistral and/or Tramontane, which are the strongest and most persistent winds of the region, with associated offshore Ekman transport and mixing; b) buoyancy loss which induce convective cells at the surface; c) simply lateral advection as the HF RADAR synoptic view reveals that the front is often interrupted or modified because of instabilities.

  14. Digital Terrestrial Video Broadcast Interference Suppression in Forward-Looking Ground Penetrating Radar Systems

    NASA Astrophysics Data System (ADS)

    Rial, F. I.; Mendez-Rial, Roi; Lawadka, Lukasz; Gonzalez-Huici, Maria A.

    2014-11-01

    In this paper we show how radio frequency interference (RFI) generated by digital video broadcasting terrestrial and digital audio broadcasting transmitters can be an important noise source for forward-looking ground penetrating radar (FLGPR) systems. Even in remote locations the average interference power sometimes exceeds ultra-wideband signals by many dB, becoming the limiting factor in the system sensitivity. The overall problem of RFI and its impact in GPR systems is briefly described and several signal processing approaches to removal of RFI are discussed. These include spectral estimation and coherent subtraction algorithms and various filter approaches which have been developed and applied by the research community in similar contexts. We evaluate the performance of these methods by simulating two different scenarios submitted to real RFI acquired with a FLGPR system developed at the Fraunhofer Institute for High Frequency Physics and Radar Techniques (FHR), (GER). The effectiveness of these algorithms in removing RFI is presented using some performance indices after suppression.

  15. New evidences of ocean surface current processes in the SE Bay of Biscay, using HF radar data

    NASA Astrophysics Data System (ADS)

    Solabarrieta, Lohitzune; Rubio, Anna; Cardenas, Mar; Méndez, Fernando J.; Esnaola, Ganix; Castanedo, Sonia; Ferrer, Luis; Medina, Raul

    2015-04-01

    High Frequency Radar (HFR) data in the south-eastern Bay of Biscay (Atlantic Ocean) offer, since 2009, a new approach to the temporal and spatial variability of the ocean surface processes in the area. Past studies have already described the main characteristics of the surface and subsurface water circulation over the shelf and slope. As they were mainly based upon punctual in time or in space in-situ measurements, the 5 year-long hourly HFR-derived velocity fields analyzed here, contribute considerably to the understanding of surface current patterns in the HFR footprint area. New evidence is given, over different time-scales, on the main ocean surface processes, in an area where surface currents show marked temporal and spatial variability. With cyclonic (anticyclonic) patterns during winter (summer) months, the analysis of lowpass ?ltered currents shows that a key component of this seasonal variability is associated with the surface signature of the Iberian Poleward Current (IPC). Clearly intensi?ed over the upper part of the slope, this current circulates eastward off the Spanish coast and northward over the French shelves and slopes in winter. In order to complete the previous descriptions, a K-means clustering technique, has been applied to HFR and wind data (from the Weather Research and Forecasting model). The results of the K-means analysis offer a deeper insight into the surface circulation patterns together with the wind patterns, after analyzing the occurrence probabilities of the radar current groups into the wind groups. In addition, a composite analysis based on a daily-scale winter-time series of the IPC for the 2009-2012 period deduced from satellite SST data and the low-passed surface currents, allows to identify the surface currents residuals related to the IPC. This HFR network offers data operationally, being, nowadays a key component of the Basque Ocean Observing System, and highly valuable for operational purposes.

  16. Integration of radar altimeter, precision navigation, and digital terrain data for low-altitude flight

    NASA Technical Reports Server (NTRS)

    Zelenka, Richard E.

    1992-01-01

    Avionic systems that depend on digitized terrain elevation data for guidance generation or navigational reference require accurate absolute and relative distance measurements to the terrain, especially as they approach lower altitudes. This is particularly exacting in low-altitude helicopter missions, where aggressive terrain hugging maneuvers create minimal horizontal and vertical clearances and demand precise terrain positioning. Sole reliance on airborne precision navigation and stored terrain elevation data for above-ground-level (AGL) positioning severely limits the operational altitude of such systems. A Kalman filter is presented which blends radar altimeter returns, precision navigation, and stored terrain elevation data for AGL positioning. The filter is evaluated using low-altitude helicopter flight test data acquired over moderately rugged terrain. The proposed Kalman filter is found to remove large disparities in predicted AGL altitude (i.e., from airborne navigation and terrain elevation data) in the presence of measurement anomalies and dropouts. Previous work suggested a minimum clearance altitude of 220 ft AGL for a near-terrain guidance system; integration of a radar altimeter allows for operation of that system below 50 ft, subject to obstacle-avoidance limitations.

  17. Applications of digital radar in the analysis of severe local storms

    E-print Network

    Vogel, John Everett

    1973-01-01

    values to 100 n mi, thus 21ogr = 4. Using a value of 0. 9 for K (Greene, 1971) and the value of C 2 obtained earlier, we have log CK = -10. 5. 2 (7) 11 DIGITAL RADAR DATA FORMAT op IE A. /+~ +~ Eb g Q PV THRESHOlD LEVEL OF V INTEGERS- (dbm ) ~ I... faeae5903z 9S 1570862 'I '1 5 5 I 'I l 5 2 2 I I 2 2 4 9%54904022 122 0 '791'19&TT2 16 9049474'I 12 40000%sf? 22 14 16 90le444\\t33Z 10 'I e00 122 99 443?l 113 SI& 144 127 75 25 15 0 D 377. ?1310 4'I 39Z I'I 315. '13 lal 2'I *4 3 37 3'I 4 o o...

  18. The application of the ADSP-21020 40-bit floating point DSP microprocessor in a digital Doppler radar

    SciTech Connect

    Robinson, S.H.; Morrison, R.E.

    1991-08-26

    A continuous wave doppler radar system has been designed which is portable, easily deployable and can be remotely controlled. The system is immune to ground clutter and is used for wind speed detection and direction determination. Nearly real time digital signal processing is performed by an Analog Devices ADSP-21020, a 40-bit floating point Digital Signal Processing (DSP) microprocessor. This paper provides an overview of the design of the system including the radio frequency (RF) to digital interface. The various DSP detection algorithms are discussed and compared to system performance and sensitivity. Finally, DSP performance is compared to the performance of an earlier system using Analog Device's ADSP-2100. 6 refs.

  19. Space Plasma Exploration by Active Radar (SPEAR): an overview of a future radar facility

    E-print Network

    Paris-Sud XI, Université de

    Space Plasma Exploration by Active Radar (SPEAR): an overview of a future radar facility D. M is a new polar cap HF radar facility which is to be deployed on Svalbard. The principal capabilities of SPEAR will include the generation of arti®cial plasma irregularities, operation as an `all-sky' HF radar

  20. Frequency diversity wideband digital receiver and signal processor for solid-state dual-polarimetric weather radars

    NASA Astrophysics Data System (ADS)

    Mishra, Kumar Vijay

    The recent spate in the use of solid-state transmitters for weather radar systems has unexceptionably revolutionized the research in meteorology. The solid-state transmitters allow transmission of low peak powers without losing the radar range resolution by allowing the use of pulse compression waveforms. In this research, a novel frequency-diversity wideband waveform is proposed and realized to extenuate the low sensitivity of solid-state radars and mitigate the blind range problem tied with the longer pulse compression waveforms. The latest developments in the computing landscape have permitted the design of wideband digital receivers which can process this novel waveform on Field Programmable Gate Array (FPGA) chips. In terms of signal processing, wideband systems are generally characterized by the fact that the bandwidth of the signal of interest is comparable to the sampled bandwidth; that is, a band of frequencies must be selected and filtered out from a comparable spectral window in which the signal might occur. The development of such a wideband digital receiver opens a window for exciting research opportunities for improved estimation of precipitation measurements for higher frequency systems such as X, Ku and Ka bands, satellite-borne radars and other solid-state ground-based radars. This research describes various unique challenges associated with the design of a multi-channel wideband receiver. The receiver consists of twelve channels which simultaneously downconvert and filter the digitized intermediate-frequency (IF) signal for radar data processing. The product processing for the multi-channel digital receiver mandates a software and network architecture which provides for generating and archiving a single meteorological product profile culled from multi-pulse profiles at an increased data date. The multi-channel digital receiver also continuously samples the transmit pulse for calibration of radar receiver gain and transmit power. The multi-channel digital receiver has been successfully deployed as a key component in the recently developed National Aeronautical and Space Administration (NASA) Global Precipitation Measurement (GPM) Dual-Frequency Dual-Polarization Doppler Radar (D3R). The D3R is the principal ground validation instrument for the precipitation measurements of the Dual Precipitation Radar (DPR) onboard the GPM Core Observatory satellite scheduled for launch in 2014. The D3R system employs two broadly separated frequencies at Ku- and Ka-bands that together make measurements for precipitation types which need higher sensitivity such as light rain, drizzle and snow. This research describes unique design space to configure the digital receiver for D3R at several processing levels. At length, this research presents analysis and results obtained by employing the multi-carrier waveforms for D3R during the 2012 GPM Cold-Season Precipitation Experiment (GCPEx) campaign in Canada.

  1. Hardware description ADSP-21020 40-bit floating point DSP as designed in a remotely controlled digital CW Doppler radar

    SciTech Connect

    Morrison, R.E.; Robinson, S.H.

    1991-01-01

    A continuous wave Doppler radar system has been designed which is portable, easily deployed, and remotely controlled. The heart of this system is a DSP/control board using Analog Devices ADSP-21020 40-bit floating point digital signal processor (DSP) microprocessor. Two 18-bit audio A/D converters provide digital input to the DSP/controller board for near real time target detection. Program memory for the DSP is dual ported with an Intel 87C51 microcontroller allowing DSP code to be up-loaded or down-loaded from a central controlling computer. The 87C51 provides overall system control for the remote radar and includes a time-of-day/day-of-year real time clock, system identification (ID) switches, and input/output (I/O) expansion by an Intel 82C55 I/O expander. 5 refs., 8 figs., 2 tabs.

  2. Comparative analyses for the prediction of streamflow from small watershed by use of digitized radar data 

    E-print Network

    Braatz, Dean Thomas

    1973-01-01

    characteristics of the WSR-57. Table 2. Characteristics of the WSR-57 weather radar used by NSSL. (Source: NWS, NOAA) Band Wavelength Peak power Pulse repetition frequency (PRF) Pulse length Minimum detectable signal Beam wid th Antenna gain Normal scan... on radar data, After several years of development, the automatic radar- signal processing and data communication system is undergoing evaluation during the testing period of the D/RADEX as to its operational performance. Basically, each automatic...

  3. HF radio oceanography — A review

    Microsoft Academic Search

    Donald E. Barrick

    1978-01-01

    The understanding and utilization of HF radar sea-echo have enjoyed steady progress since the experimental discovery of the underlying radar\\/sea interaction process over two decades ago. The agreement of theory with measured data confirms the correctness of currently accepted explanations for both the first-order and second-order portions of the sea-echo Doppler spectrum in terms of the wave-height directional spectrum. Furthermore,

  4. In-flight detection of errors for enhanced aircraft flight safety and vertical accuracy improvement using digital terrain elevation data with an inertial navigation system, global positioning system and radar altimeter

    Microsoft Academic Search

    Robert Anthony Gray

    1999-01-01

    This dissertation discusses integration architectures using digital terrain elevation data (DTED) with an inertial navigation system (INS), a global positioning system (GPS) and a radar altimeter. Two integration architectures are considered: DTED with INS, GPS and radar altimeter for aircraft vertical accuracy improvement during the final approach; and DTED with kinematic GPS (KGPS) and a radar altimeter for enhanced aircraft

  5. A general statistical instrument theory of atmospheric and ionospheric radars

    SciTech Connect

    Woodman, R.F. (Instituto Geofisico del Peru, Lima (Peru))

    1991-05-01

    Some basic functional relationships between the statistics of the signals received in a radar and the statistics of the density fluctuations of a scattering medium are derived. They vary in their degree of generality, but they are all very general in scope. They include monostatic and bistatic radars scattering from either atmospheric, ionospheric, or meteorological media. They are valid for refractive and slightly dispersive media, so they can also be used for HF ionospheric radars. They include the effects of filtering, including receiver filtering, pulse compression coding and decoding schemes, and coherent integration, or any alternative linear digital filtering scheme. Functional relationships to include cross-correlation schemes, such as Faraday rotation experiments and interferometers, are included. Some simplified expressions are derived for frequently encountered situations, where different approximations can be made. These simplified expressions cover a large number of radar techniques currently in use for atmospheric and ionospheric applications.

  6. Integration of radar altimeter, precision navigation, and digital terrain data for low-altitude flight

    NASA Technical Reports Server (NTRS)

    Zelenka, Richard E.

    1992-01-01

    A Kalman filter for the integration of a radar altimeter into a terrain database-dependent guidance system was developed. Results obtained from a low-altitude helicopter flight test data acquired over moderately rugged terrain showed that the proposed Kalman filter removes large disparities in predicted above-ground-level (AGL) altitude in the presence of measurement anomalies and dropouts. Integration of a radar altimeter makes it possible to operate a near-terrain guidance system at or below 50 ft (subject to obstacle-avoidance limitations), whereas without radar altimeter integration, a minimum clearance altitude of 220 AGL is needed, as is suggested by previous work.

  7. Digital Map Products from the Cassini RADAR in the NASA Planetary Data System

    NASA Astrophysics Data System (ADS)

    Kirk, R. L.; Becker, T. L.; Garcia, P.; Barrett, J. M.; Stiles, B. W.; Legall, A.; Janssen, M. A.; Wye, L.; Zebker, H. A.; Cassini RADAR Science Team

    2010-03-01

    A new set of Titan maps, made from Cassini RADAR prime mission data, will be delivered early in 2010. Consistent presentation of diverse data sets in simple projections with extensive indexing should greatly facilitate comparative Titan research.

  8. A Digital Interface for Imagery and Control of a Navico\\/Lowrance Broadband Radar

    Microsoft Academic Search

    Adrian Dabrowski; Sebastian Busch; Roland Stelzer

    \\u000a The paper describes a method to establish compatibility between an autonomous surface vessel control system and a Navico Broadband\\u000a Radar BR24. The solution obtains radar imagery and control of the antenna unit over its standard Ethernet interface, making\\u000a the proprietary controller unit optional. It presents devices, software and methods used for empirical protocol analysis and\\u000a documents the findings. Protocol details

  9. A digital elevation model of the Greenland Ice Sheet derived from combined laser and radar altimetry data

    NASA Astrophysics Data System (ADS)

    Fredenslund Levinsen, Joanna; Smith, Ben; Sørensen, Louise S.; Forsberg, René

    2014-05-01

    When estimating elevation changes of ice-covered surfaces from radar altimetry, it is important to correct for slope-induced errors. They cause the reflecting point of the pulse to move up-slope and thus return estimates in the wrong coordinates. Slope-induced errors can be corrected for by introducing a Digital Elevation Model (DEM). In this work, such a DEM is developed for the Greenland Ice Sheet using a combination of Envisat radar and ICESat laser altimetry. If time permits, CryoSat radar altimetry will be included as well. The reference year is 2010 and the spatial resolution 2.5 x 2.5 km. This is in accordance with the results obtained in the ESA Ice Sheets CCI project showing that a 5 x 5 km grid spacing is reasonable for ice sheet-wide change detection (Levinsen et al., 2013). Separate DEMs will be created for the given data sets, and the geostatistical spatial interpolation method collocation will be used to merge them, thus adjusting for potential inter-satellite biases. The final DEM is validated with temporally and spatially agreeing airborne lidar data acquired in the NASA IceBridge and ESA CryoVex campaigns. The motivation for developing a new DEM is based on 1) large surface changes presently being observed, and mainly in margin regions, hence necessitating updated topography maps for accurately deriving and correcting surface elevation changes, and 2) although radar altimetry is subject to surface penetration of the signal into the snowpack, data is acquired continuously in time. This is not the case with e.g. ICESat, where laser altimetry data were obtained in periods of active lasers, i.e. three times a year with a 35-day repeat track. Previous DEMs e.g. have 2007 as the nominal reference year, or they are built merely from ICESat data. These have elevation errors as small as 10 cm, which is lower than for Envisat and CryoSat. The advantage of an updated DEM consisting of combined radar and laser altimetry therefore is the possibility of achieving a high spatial and temporal coverage, as well as the opportunity to continuously map surface changes relative to an updated topography and slopes. References: Levinsen, J. F., Khvorostovsky, K., Ticconi, F., Shepherd, A., Forsberg, R., Sørensen, L. S., Muir, A., Pie, N., Felikson, D., Flament, T., Hurkmans, R., Moholdt, G., Gunter, B., Lindenbergh, R. C., and Kleinherenbrink, M.: ESA's Ice Sheets CCI: validation and inter-comparison of surface elevation changes derived from laser and radar altimetry over Jakobshavn Isbræ, Greenland - Round Robin results, The Cryosphere Discuss., 7, 5433-5460, 2013.

  10. Evaluation of high frequency radar wave measurement

    Microsoft Academic Search

    L. R Wyatt; S. P Thompson; R. R Burton

    1999-01-01

    The spatial coverage, temporal availability and spectral and parameter accuracy of wave measurements using radars operating at the upper end of the high frequency (HF) radio band are discussed. The two radars used are the Ocean Surface Current Radar (OSCR) developed in the UK and the Wellen Radar (WERA) developed in Germany. The measurements show that useful accuracy is obtainable

  11. An analysis of HF radar measured surface currents to determine tidal, wind-forced, and seasonal circulation in the Gulf of the Farallones, California, United States

    Microsoft Academic Search

    Matt K. Gough; Newell Garfield; Erika McPhee-Shaw

    2010-01-01

    A complete year of hourly 3 km resolution high-frequency radar measured surface currents covering the Gulf of the Farallones were analyzed with the following three primary objectives: (1) describe the seasonal surface circulation, (2) identify tidal currents, and (3) determine the influence of wind forcing. Three predominant seasonal circulation regimes were identified: relaxation, storm, and upwelling. The relaxation period exhibited

  12. Low resolution radar digital interface. [with data recorder for precipitation measurements

    NASA Technical Reports Server (NTRS)

    1973-01-01

    This document describes the design and operation of a low resolution radar data recording system for precipitation measurements. This system records a full azimuth scan on seven track magnetic tapes every five minutes. It is designed to operate on a continuous basis with operator intervention required only for changing tape reels and calibration.

  13. Using X-band Weather Radar Measurements to Monitor the Integrity of Digital Elevation Models for Synthetic Vision Systems

    NASA Technical Reports Server (NTRS)

    Young, Steve; UijtdeHaag, Maarten; Sayre, Jonathon

    2003-01-01

    Synthetic Vision Systems (SVS) provide pilots with displays of stored geo-spatial data representing terrain, obstacles, and cultural features. As comprehensive validation is impractical, these databases typically have no quantifiable level of integrity. Further, updates to the databases may not be provided as changes occur. These issues limit the certification level and constrain the operational context of SVS for civil aviation. Previous work demonstrated the feasibility of using a realtime monitor to bound the integrity of Digital Elevation Models (DEMs) by using radar altimeter measurements during flight. This paper describes an extension of this concept to include X-band Weather Radar (WxR) measurements. This enables the monitor to detect additional classes of DEM errors and to reduce the exposure time associated with integrity threats. Feature extraction techniques are used along with a statistical assessment of similarity measures between the sensed and stored features that are detected. Recent flight-testing in the area around the Juneau, Alaska Airport (JNU) has resulted in a comprehensive set of sensor data that is being used to assess the feasibility of the proposed monitor technology. Initial results of this assessment are presented.

  14. Monthly and seasonal occurrences of potential flash flood-producing rains determined from Manually Digitized Radar data

    NASA Technical Reports Server (NTRS)

    Wilson, G. S.

    1980-01-01

    An analysis is conducted of a small 4-year climatological data base of Manually Digitized Radar (MDR) data to infer the monthly and seasonal distributions of the relative frequency of occurrence of potential flash flood-producing rains over the Central and Eastern U.S. Some possible meteorological mechanisms for producing potential flash flooding rains are discussed in terms of the relative maxima and minima in the monthly and seasonal frequency distributions over the MDR network. Frequencies were found to be generally higher in more southern locations and lower farther north in all months and seasons. However, most locations experienced an annual cycle in the frequency of occurrence with maxima in summer and minima in winter. In given seasons and months, local areas of maximum and minimum occurrences may be related to quasi-stationary meteorological processes that trigger and organize intense convection over a common area.

  15. Interferometric synthetic aperture radar and the Data Collection System Digital Terrain Elevation Demonstration

    Microsoft Academic Search

    Robert Heidelbach; R. Bolus; J. Chadwick

    1994-01-01

    Digital Terrain Elevations (DTE) that can be rapidly generated, and that have better fidelity and accuracy than Digital Terrain Elevation Data (DTED) Levels 1 or 2, would be extremely beneficial to Department of Defense (DOD) military operations, civil works programs, and various commercial applications. As a result, the Advanced Research Projects Agency (ARPA), along with the U.S. Army Topographic Engineering

  16. The Shuttle Radar Topography Mission

    Microsoft Academic Search

    Tom G. Farr; Paul A. Rosen; Edward Caro; Robert Crippen; Riley Duren; Scott Hensley; Michael Kobrick; Mimi Paller; Ernesto Rodriguez; Ladislav Roth; David Seal; Scott Shaffer; Joanne Shimada; Jeffrey Umland; Marian Werner; Michael Oskin; Douglas Burbank; Douglas Alsdorf

    2007-01-01

    The Shuttle Radar Topography Mission produced the most complete, highest-resolution digital elevation model of the Earth. The project was a joint endeavor of NASA, the National Geospatial-Intelligence Agency, and the German and Italian Space Agencies and flew in February 2000. It used dual radar antennas to acquire interferometric radar data, processed to digital topographic data at 1 arc sec resolution.

  17. Multidimensional radar picture

    NASA Astrophysics Data System (ADS)

    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.

  18. Solid state transmitters for modern radar applications

    Microsoft Academic Search

    Donald J. Hoft; Fuat Agi

    1986-01-01

    To exemplify the advancing state-of-the-art in radar SS transmitters, this paper describes in some detail three major systems covering a broad range of frequencies: HF, UHF and L-band, which utilize SS transmitters. At HF a 200 kW CW transmitter is described which is applicable in an over-the-horizon radar application; at UHF the Pave Paws (AN\\/FPS-115) long-range phased array radar transmitter

  19. Applications of digital radar in the analysis of severe local storms 

    E-print Network

    Vogel, John Everett

    1973-01-01

    ) and Wilk and Gray (1970). A block diagram describing the acquisition, recording, and processing of the signals received by the NSSL, WSR-57 radar i. s shown in Fig. 1. As shown in the diagram, the target echo is detected and processed generally... gain Pulse length Beam width Wavelength Pulse repeti. tion frequency Minimum detectable signal 450 kw 7. 079 x 10 3 1. 20 x 10 m 3 2. 0 deg 1. 04 x 10 m -1 164 sec -110 dbm STC PRE-AMP LOG IF [ Signai Averogs~ng VIDEO AMPLIFIER 200...

  20. Real-time signal construction and digital quadrature modulation for pulse Doppler radar clutter

    NASA Astrophysics Data System (ADS)

    Liang, Zhiheng; Xu, Jiaxiang; Chen, Xunda

    2001-08-01

    The signal processors in pulse Doppler radar can detect the target signal which is spectrally separated from clutter, even if the signal is -60 dB weaker or more than main- lobe clutter, so in missile hardware-in-the-loop it is required that the noise resulted by clutter reconstruction architecture should be -60 dB lower than main-lobe clutter. Because of the restriction, a new method of clutter reconstruction with specific power spectrum is proposed, which include conversion from power spectrum to vector spectrum, randomization of phase, inverse Fourier transform, and then windowing and overlapping the series time domain sequence, which guarantee the expectation value and variance of random sequence continuously. The simulation results demonstrate that by applying the method, the ratio of signal to noise is increased from 30 dB to 60 dB.

  1. Monitoring of Ground Movement and Generation of Digital Elevation Models Using Interferometric Synthetic Aperture Radar (InSAR) Data

    NASA Astrophysics Data System (ADS)

    Panda, B. B.

    2013-12-01

    Interferometric synthetic aperture radar (InSAR) has the potential for measuring deformation of the earth's surface with very high accuracy and for the development of digital elevation models. Both capabilities are of high relevance for ground movement assessment. In addition, when archived raw data is available (post 1992), recent historic movement may be quantifiable. InSAR utilizes satellite-based data acquired at two different times along orbits of a similar trajectory to detect changes in the ground surface elevation. This technique can be used to monitor ground movement for rectangular areas as large as 100 kilometers on a side. Knowledge of topography, geology, trends and mechanics of existing ground movement is required for successful interpretation of InSAR data. The detection of ground surface deformation in terrain of high slope relief terrain is difficult. For ground deformation mapping by means of InSAR it is necessary to separate the motion-related and the topographic phase contributions. This is achieved by using a low resolution digital elevation model (DEM) during the processing of InSAR data. The application of InSAR technology to mining areas provides monitoring of not only the active mine areas but also the adjacent regions that has been affected by mining. Thus InSAR technique proves to be an essential ground monitoring methods in future for mining areas. The results from the InSAR analysis are compared with data from a ground-based monitoring system comprised of measured survey prisms for an open pit mine in Canada. InSAR analysis provided the location of the stable site for relocating the crusher which was affected by movement of pit slope. The presentation will show the application of InSAR technology to various mines in USA and Canada. Besides subsidence evaluation, InSAR data is also used to generate digital elevation models (DEM) and digital terrain models (DTM). The DEM and DTM derived from InSAR data for a mine in Canada is compared with the survey and LIDAR data to demonstrate the applicability of InSAR data to model surface topography.

  2. ATM-0838219 Mid-Latitude SuperDARN Radar Infrastructure

    E-print Network

    Shepherd, Simon

    into the Kansas soil. The PI has a go with help from a very nervous assistant. View of the first radar site ATM-0838219 Mid-Latitude SuperDARN Radar Infrastructure for the Study of Ionospheric-Latitude Radar Chain Field of views from the completed chain of eight HF SuperDARN radars located at mid

  3. Opening and closing of sea ice leads - Digital measurements from synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Fily, M.; Rothrock, D. A.

    1990-01-01

    An algorithm that uses two sequential SAR digital images to measure the opening and closing of sea ice leads is introduced. The methods used to analyze the SAR images is described, including the mesh of tie points and the classification of leads and ice. The results of the anaylsis are compared with independent manual measurements, showing that the cells covering each lead are best interpreted as opening or closing in a group, rather than individually. Also, consideration is given to an automated algorithm for grouping cells, the possibility of simplifying the method, and the relationship between the opening and closing measurements and the theory of their parametric relation to mean deformation.

  4. The Arecibo Observatory as an MST radar

    NASA Technical Reports Server (NTRS)

    Woodman, R. F.

    1983-01-01

    The radars and other systems at the Arecibo Observatory were designed and built, originally, for incoherent-scatter and radio-astronomy research. More recently, important additions have been made for planetary radar and artificial RF heating of the ionosphere. Although designed and built for a different application, these systems have shown to be very powerful tools for tropospheric, stratospheric and mesospheric research. The Observatory at present has two main radars: one at 430 and the other at 2380 MHz. In addition, 50-MHz MST radar work has been done using portable transmitters brought to the Observatory for this purpose. This capability will become permanent with the recent acquisition of a transmitter at this frequency. Furthermore, control and data processing systems have been developed to use the powerful HF transmitter and antennas of the HF-heating facility as an HF bistatic radar. A brief description of the four radars available at the Observatory is presented.

  5. A new 1 km Digital Elevation Model of the Antarctic Derived From Combined Satellite Radar and Laser Data

    NASA Astrophysics Data System (ADS)

    Griggs, J. A.; Bamber, J. L.; Gomez-Dans, J. L.

    2008-12-01

    Digital elevation models (DEMs) of Antarctica have been derived, previously, from satellite radar altimetry (SRA) and limited terrestrial data. Near the ice sheet margins and in areas of steep relief the SRA data tend to have relatively poor coverage and accuracy. To remedy this and to extend the coverage beyond the latitudinal limit of the SRA missions (81.5° S) we have combined laser altimeter measurements from the Geosciences Laser Altimeter System onboard ICESat with SRA data from the geodetic phase of ERS-1. The former provide decimetre vertical accuracy but poor spatial coverage. The latter have excellent spatial coverage but poorer vertical accuracy. By combining the radar and laser data using an optimal approach we have maximised the vertical accuracy and spatial resolution of the DEM and minimised the number of grid cells with an interpolated elevation estimate. We assessed the optimum resolution for producing a DEM which was found to be 1 km. This resulted in just under 35% of grid cells having an interpolated value. The accuracy of the final DEM was assessed using a suite of independent airborne altimeter data. The RMS error in the new DEM was found to be roughly half that of the best previous 5 km resolution, SRA-derived DEM, with marked improvements in the steeper marginal and mountainous areas and between 81.5 and 86° S. RMS differences varied from 4.84 m over the Siple Coast region of West Antarctica to 29.28 m when compared to a more limited dataset over the Antarctic Peninsula. The airborne data sets were used to produce an error map for the DEM by developing a multiple linear regression model based on the variables known to influence errors in the DEM. Errors were found to correlate highly with surface slope, roughness and density of satellite data points. Errors ranged from typically sim1 m over the ice shelves to about 4-10 m for the majority of the grounded ice sheet. In the steeply sloping margins and mountain ranges the estimated error is several 10's m. Slightly less than 7% of the area covered by the satellite data had an estimated random error greater than 20 m.

  6. A new digital elevation model of the Antarctic derived from combined satellite radar altimter and GLAS data

    NASA Astrophysics Data System (ADS)

    Bamber, J. L.; Gomez-Dans, J. L.

    2005-12-01

    Digital elevation models (DEMs) of Antarctica have been derived, previously, from satellite radar altimetry (SRA) and limited terrestrial data of relatively poor vertical accuracy. Near the ice sheet margins and in other areas of steep relief the SRA data tend to have both poor coverage and accuracy. To remedy this and to extend the coverage south of the latitudinal limit of the SRA missions (81.5° S) we have combined laser altimeter measurements from the Geosciences Laser Altimeter System onboard ICESat with SRA data from the geodetic phase of the ERS-1 satellite mission. The former provide decimetre vertical accuracy but with poor spatial coverage: they have, for example, an across-track spacing of about 20 km at 70° S. The latter have excellent spatial coverage away from steep relief (across-track spacing by contrast is 2.8 km at 70° S) but a poorer vertical accuracy. By combining the radar and laser data using an optimal approach we have maximised the vertical accuracy and spatial resolution of the DEM and minimised the number of grid cells with an interpolated elevation estimate. A slope-dependent bias, however, exists between the laser and radar altimeter height estimates due to the different footprint sizes of the two instruments and the way the SRA data were processed. We have calculated and removed the bias (which was found to be a function of surface slope) from the SRA data and merged them with the laser data by weighting them as a function of their RMS error. We assessed the optimum resolution for producing a DEM based on a trade-off between increased resolution and increased interpolation of grid cells. The optimum resolution was found to be 2 km, which resulted in less than 40% of cells being interpolated (i.e. cells where no measurements exist). At resolutions smaller than this the percentage of interpolated cells rapidly increases. The resolution is also a trade-off between the along and across-track spacing of the data, which varies with latitude. It reflects the spatial resolution justified by the global data coverage. Thus, close to the latitudinal limit of ICESat (86° S) a higher resolution could be justified. The accuracy of the final DEM was assessed using independent airborne laser altimeter data for a high relief region of West Antarctica. The DEM contains a wealth of information related to ice flow. This is particularly apparent for the two largest ice shelves-the Filchner-Ronne and Ross-where the effect of flow of ice streams and outlet glaciers can be traced as far as the calving fronts. Rifts are clearly visible as are the surface expression of subglacial lakes and other basal features. At this resolution, surface roughness, related to subglacial topography, is also discernable.

  7. Decoders for MST radars

    NASA Technical Reports Server (NTRS)

    Woodman, R. F.

    1983-01-01

    Decoding techniques and equipment used by MST radars are described and some recommendations for new systems are presented. Decoding can be done either by software in special-purpose (array processors, etc.) or general-purpose computers or in specially designed digital decoders. Both software and hardware decoders are discussed and the special case of decoding for bistatic radars is examined.

  8. Performance Evaluation of SeaSonde High-Frequency Radar for Vessel Detection

    E-print Network

    , demonstrating that ships can be detected and tracked by multistatic HF radar in a multiship environment whileP A P E R Performance Evaluation of SeaSonde High-Frequency Radar for Vessel Detection A U T H O R A C T High-frequency (HF) surface wave radar has been identified to be a gap-filling technology

  9. Target identification from radar signatures

    Microsoft Academic Search

    R. Strattan

    1978-01-01

    Modern high resolution radar techniques and real time digital signal processing advances indicate the feasibility of extracting characteristic features of aircraft targets from their radar signatures. Two basic approaches have been suggested. The low frequency approach utilizes harmonically related radar frequencies with wavelengths comparable to the target dimensions. The microwave approach utilizes spread spectrum techniques to achieve high range resolution.

  10. Radar data processing and analysis

    NASA Technical Reports Server (NTRS)

    Ausherman, D.; Larson, R.; Liskow, C.

    1976-01-01

    Digitized four-channel radar images corresponding to particular areas from the Phoenix and Huntington test sites were generated in conjunction with prior experiments performed to collect X- and L-band synthetic aperture radar imagery of these two areas. The methods for generating this imagery are documented. A secondary objective was the investigation of digital processing techniques for extraction of information from the multiband radar image data. Following the digitization, the remaining resources permitted a preliminary machine analysis to be performed on portions of the radar image data. The results, although necessarily limited, are reported.

  11. The Shuttle Radar Topography Mission

    NASA Astrophysics Data System (ADS)

    Farr, Tom G.; Rosen, Paul A.; Caro, Edward; Crippen, Robert; Duren, Riley; Hensley, Scott; Kobrick, Michael; Paller, Mimi; Rodriguez, Ernesto; Roth, Ladislav; Seal, David; Shaffer, Scott; Shimada, Joanne; Umland, Jeffrey; Werner, Marian; Oskin, Michael; Burbank, Douglas; Alsdorf, Douglas

    2007-06-01

    The Shuttle Radar Topography Mission produced the most complete, highest-resolution digital elevation model of the Earth. The project was a joint endeavor of NASA, the National Geospatial-Intelligence Agency, and the German and Italian Space Agencies and flew in February 2000. It used dual radar antennas to acquire interferometric radar data, processed to digital topographic data at 1 arc sec resolution. Details of the development, flight operations, data processing, and products are provided for users of this revolutionary data set.

  12. Radar in transition

    NASA Astrophysics Data System (ADS)

    Barton, D. K.

    1984-12-01

    It is pointed out that radar engineers, at the end of 1984, find their field in transition between the conventional designs of the post War II era and the digitally controlled, solid-state systems which will be in place for the year 2000. The U.S. Navy has two major phased array radar systems in operation, including the rotating three-dimensional (3D) AN/SPS-48, and the phased-scanned AN/SPY-1 (Aegis) radars. The Aegis represents a major step beyond the conventional 3D and mechanical fire-control radars. However, it requires a special ship, dedicated to its use. Attention is given to questions regarding an extension of the application of Aegis technology to other U.S. Navy applications and to other navies, an ambitious solid-state radar program in the UK, and Army radars.

  13. Passive radar in the high frequency band

    Microsoft Academic Search

    Giuseppe Fabrizio; Fabiola Colone; Pierfrancesco Lombardo; Alfonso Farina

    2008-01-01

    Passive radar systems using emitters of opportunity for target detection and tracking have received significant interest recently, especially those which exploit frequency modulated (FM) radio stations and TV transmitters as signal sources. This paper is concerned with passive radar systems that utilize signal sources in the high frequency (HF) band (3-30 MHz), where due to long-distance ionospheric propagation, the transmitter

  14. National IOOS High Frequency Radar Search and Rescue Project Jack Harlan, NOAA IOOS Program, Silver Spring, MD

    E-print Network

    code (originally developed at SIO) and providing near-real-time HF radar data to ASA, developersNational IOOS High Frequency Radar Search and Rescue Project Jack Harlan, NOAA IOOS Program, Silver have begun an effort to extend the use of high frequency (HF) radar for U.S. Coast Guard (USCG) search

  15. Temperate Ice Depth-Sounding Radar

    NASA Astrophysics Data System (ADS)

    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. It also digitizes the output signal from the receiver and stores the data in binary format using a portable computer. The RF-section consists of a high- power transmitter and a low-noise receiver with digitally controlled variable gain. The antenna is time-shared between the transmitter and receiver by means of a transmit/receive (T/R) switch. In regards to the antenna, we have made a survey study of various electrically small antennas (ESA) to choose the most suitable radiating structure for this application. Among the different alternatives that provide a good trade-off between electrical performance and small size, we have adopted an ESA dipole configuration for airborne platforms and a half-wavelength radiator for the surface-based version. The airborne antenna solution is given after studying the geometry of the aerial vehicle and its fuselage contribution to the antenna radiation pattern. Dipoles are made of 11.6 mm diameter cables (AWG 0000) or printed patches embedded into the aircraft fuselage, wings, or both. The system is currently being integrated and tested. TIDSoR is expected to be deployed during the spring 2008 either in Alaska or Greenland for surface based observations. In this paper, we will discuss our design considerations and current progress towards the development of this radar system. [1] Center for Remote Sensing of Ice Sheets (Cresis), Sept 2008, [Online]. Available: http://www.cresis.ku.edu

  16. Solid state transmitters for modern radar applications

    NASA Astrophysics Data System (ADS)

    Hoft, Donald J.; Agi, Fuat

    To exemplify the advancing state-of-the-art in radar SS transmitters, this paper describes in some detail three major systems covering a broad range of frequencies: HF, UHF and L-band, which utilize SS transmitters. At HF a 200 kW CW transmitter is described which is applicable in an over-the-horizon radar application; at UHF the Pave Paws (AN/FPS-115) long-range phased array radar transmitter (over 0.5 megawatt PK power per face) is presented; and finally at L-band an 80 kW pulsed transmitter for shipboard and ATC surveillance applications is described.

  17. Lunar Radar Cross Section at Low Frequency

    NASA Technical Reports Server (NTRS)

    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.

  18. Large phased-array radars

    SciTech Connect

    Brookner, D.E.

    1988-12-15

    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.

  19. Large phased-array radars

    NASA Astrophysics Data System (ADS)

    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.

  20. Cassini Radar hardware technologies

    SciTech Connect

    Wheeler, K.; Renick, P. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States)

    1996-03-01

    The hardware development portion of the Cassini Radar task is complete. The flight model Digital Assembly and Energy Storage Assembly have been integrated and tested, as has the engineering/qualification model Radio Frequency Electronics Assembly. Integration of the flight model Radio Frequency Electronics Assembly is ready to begin. The intent of this paper is to describe some of the more interesting technologies implemented in the electronics to achieve the requirements of the Cassini Radar experiment. {copyright} {ital 1996 American Institute of Physics.}

  1. Terminal Doppler weather radar

    Microsoft Academic Search

    M. Michelson; W. W. Shrader; J. G. Wieler

    1990-01-01

    The terminal Doppler weather radar (TDWR) system, now under development, will provide automatic detection of microbursts and low-level wind shear. This paper discusses the TDWR performance parameters and describes its structural elements, including the antenna subsystem, the transmitter, the receiver\\/exciter, the digital signal processor, and the radar product generator\\/remote monitoring subsystem. Attention is also given to the processes of the

  2. Radio Science, Volume ???, Number , Pages 112, Passive over-the-horizon radar with WWV and the first

    E-print Network

    Ellingson, Steven W.

    as a relatively powerful bistatic, HF radar, capable of monitoring the entire visible sky. In this paper, we monostatic and bistatic radar systems, ionosondes have been and continue to be used to sound the ionosphere

  3. High-frequency radar observations of ocean surface currents.

    PubMed

    Paduan, Jeffrey D; Washburn, Libe

    2013-01-01

    This article reviews the discovery, development, and use of high-frequency (HF) radio wave backscatter in oceanography. HF radars, as the instruments are commonly called, remotely measure ocean surface currents by exploiting a Bragg resonant backscatter phenomenon. Electromagnetic waves in the HF band (3-30 MHz) have wavelengths that are commensurate with wind-driven gravity waves on the ocean surface; the ocean waves whose wavelengths are exactly half as long as those of the broadcast radio waves are responsible for the resonant backscatter. Networks of HF radar systems are capable of mapping surface currents hourly out to ranges approaching 200 km with a horizontal resolution of a few kilometers. Such information has many uses, including search and rescue support and oil-spill mitigation in real time and larval population connectivity assessment when viewed over many years. Today, HF radar networks form the backbone of many ocean observing systems, and the data are assimilated into ocean circulation models. PMID:22809196

  4. A new 1 km digital elevation model of the Antarctic derived from combined satellite radar and laser data Part 1: Data and methods

    NASA Astrophysics Data System (ADS)

    Bamber, J. L.; Gomez-Dans, J. L.; Griggs, J. A.

    2008-11-01

    Digital elevation models (DEMs) of Antarctica have been derived, previously, from satellite radar altimetry (SRA) and limited terrestrial data. Near the ice sheet margins and in other areas of steep relief the SRA data tend to have relatively poor coverage and accuracy. To remedy this and to extend the coverage beyond the latitudinal limit of the SRA missions (81.5° S) we have combined laser altimeter measurements from the Geosciences Laser Altimeter System onboard ICESat with SRA data from the geodetic phase of the ERS-1 satellite mission. The former provide decimetre vertical accuracy but with poor spatial coverage. The latter have excellent spatial coverage but a poorer vertical accuracy. By combining the radar and laser data using an optimal approach we have maximised the vertical accuracy and spatial resolution of the DEM and minimised the number of grid cells with an interpolated elevation estimate. We assessed the optimum resolution for producing a DEM based on a trade-off between resolution and interpolated cells, which was found to be 1 km. This resulted in just under 35% of grid cells having an interpolated value. The accuracy of the final DEM was assessed using a suite of independent airborne altimeter data and used to produce an error map. The RMS error in the new DEM was found to be roughly half that of the best previous 5 km resolution, SRA-derived DEM, with marked improvements in the steeper marginal and mountainous areas and between 81.5 and 86° S. The DEM contains a wealth of information related to ice flow. This is particularly apparent for the two largest ice shelves the Filchner-Ronne and Ross where the surface expression of flow of ice streams and outlet glaciers can be traced from the grounding line to the calving front. The surface expression of subglacial lakes and other basal features are also illustrated. We also use the DEM to derive new estimates of balance velocities and ice divide locations.

  5. A new 1 km digital elevation model of the Antarctic derived from combined satellite radar and laser data - Part 1: Data and methods

    NASA Astrophysics Data System (ADS)

    Bamber, J. L.; Gomez-Dans, J. L.; Griggs, J. A.

    2009-05-01

    Digital elevation models (DEMs) of the whole of Antarctica have been derived, previously, from satellite radar altimetry (SRA) and limited terrestrial data. Near the ice sheet margins and in other areas of steep relief the SRA data tend to have relatively poor coverage and accuracy. To remedy this and to extend the coverage beyond the latitudinal limit of the SRA missions (81.5° S) we have combined laser altimeter measurements from the Geosciences Laser Altimeter System onboard ICESat with SRA data from the geodetic phase of the ERS-1 satellite mission. The former provide decimetre vertical accuracy but with poor spatial coverage. The latter have excellent spatial coverage but a poorer vertical accuracy. By combining the radar and laser data using an optimal approach we have maximised the vertical accuracy and spatial resolution of the DEM and minimised the number of grid cells with an interpolated elevation estimate. We assessed the optimum resolution for producing a DEM based on a trade-off between resolution and interpolated cells, which was found to be 1 km. This resulted in just under 32% of grid cells having an interpolated value. The accuracy of the final DEM was assessed using a suite of independent airborne altimeter data and used to produce an error map. The RMS error in the new DEM was found to be roughly half that of the best previous 5 km resolution, SRA-derived DEM, with marked improvements in the steeper marginal and mountainous areas and between 81.5 and 86° S. The DEM contains a wealth of information related to ice flow. This is particularly apparent for the two largest ice shelves - the Filchner-Ronne and Ross - where the surface expression of flow of ice streams and outlet glaciers can be traced from the grounding line to the calving front. The surface expression of subglacial lakes and other basal features are also illustrated. We also use the DEM to derive new estimates of balance velocities and ice divide locations.

  6. Radar sector blanker

    NASA Astrophysics Data System (ADS)

    Hall, Roger B.

    1994-03-01

    A radar sector blanker comprises in analog-to-digital converter and a sector controller unit. The analog-to-digital converter receives the analog synchro voltages describing the positioning of a radar antenna and changes these voltages into binary-coded decimal (BCD) information. The sector controller unit comprises a portable housing, a controller system, and a power supply. The controller system includes an OFF comparator circuit, an ON comparator circuit, an S-R latch, and a solid-state switch. Each comparator circuit comprises three cascaded transistor-transistor logic (TTL) integrated chips. The power supply gives a direct-current voltage to the solid-state switch and the TTL chips. The sector blanker blocks transmission for a predetermined rotational region or sector of a radar system.

  7. Digital Base Band Converter As Radar Vlbi Backend / Dbbc K? Ciparošanas Sist?ma Radara Vlbi Nov?rojumiem

    NASA Astrophysics Data System (ADS)

    Tuccari, G.; Bezrukovs, Vl.; Nechaeva, M.

    2012-12-01

    A digital base band converter (DBBC) system has been developed by the Istituto di Radioastronomia (Noto, Italy) for increasing the sensitivity of European VLBI Network (EVN) by expanding the full observed bandwidth using numerical methods. The output data rate of this VLBI-backend is raised from 1 to 4 Gbps for each radiotelescope. All operations related to the signal processing (frequency translation, amplification, frequency generation with local oscillators, etc.) are transferred to the digital domain, which allows - in addition to well-known advantages coming from digital technologies - achieving better repeatability, precision, simplicity, etc. The maximum input band of DBBC system is 3.5 GHz, and the instantaneous bandwidth is up to 1 GHz for each radio frequency/intermediate frequency (RF/IF) out of the eight possible. This backend is a highly powerful platform for other radioastronomy applications, and a number of additional so-called personalities have been developed and used. This includes PFB (polyphase filter bank) receivers and Spectra for high resolution spectroscopy. An additional new development with the same aim - to use the DBBC system as a multi-purpose backend - is related to the bi-static radar observations including Radar VLBI. In such observations it is possible to study the population of space debris, with detection of even centimetre class fragments. A powerful transmitter is used to illuminate the sky region to be analyzed, and the echoes coming from known or unknown objects are reflected to one or more groundbased telescopes thus producing a single-dish or interferometric detection. The DBBC Radar VLBI personality is able to realize a high-resolution spectrum analysis, maintaining in the central area the echo signal at the expected frequency including the Doppler shift of frequency. For extremely weak signals a very large integration time is needed, so for this personality different input parameters are provided. The realtime information can then allow exploring easily the desired range of search for unknown or not fully determined orbit objects. These features make Radar VLBI personality most useful in the space debris measurements. DBBC sist?ma izstr?d?ta Noto Radioastronomijas instit?t?. Sist?mas galvenaisuzdevums - palielin?t visa Eiropas VLBI t?kla jut?bu - realiz?ts, palielinotvisas nov?rojam?s joslas platumu un pielietojot ciparu sign?lu apstr?des metodes.Izejas datu pl?sma palielin?ta no 1 l?dz 4 Gbps katram radioteleskopam un visasoper?cijas, kas saist?tas ar sign?lu apstr?di (frekvences p?rveidošana, pastiprin?jums,iekš?jie ?eneratori, utt.), realiz?tas digit?l? form?, kas ?auj ieg?t noz?m?gusuzlabojumus atk?rtojam?b?, precizit?t?, vienk?rš?b?, nemaz neminot visp?rzin?m?spriekšroc?bas, ko nodrošina digit?lo tehnolo?iju izmantošana. Maksim?l? ieejassign?la frekven?u josla ir 3.5 GHz, un moment?nais joslas platums ir l?dz 1 GHz uzkatru no asto?iem iesp?jamajiem RF/IF kan?liem. Š? datu re?istr?cijas sist?ma ir?oti veiktsp?j?ga platforma ne tikai EVN, bet ar? citiem radioastronomijas pielietojumiem,un papildus tiek izstr?d?ta vesela virkne programmat?ras pakot?u, kasv?l vair?k paplašina sist?mas funkcionalit?ti. Tas ietver PFB (Polif?zes FiltruBanka) uztv?r?jus "Spectra”, kas piem?roti augstas izš?irtsp?jas spektroskopijasvajadz?b?m. Papildus realiz?ts jaunas programmat?ras risin?jums, ar m?r?iizmantot DBBC sist?mu k? daudzfunkcion?lu datu ciparošanas iek?rtu, kasizmantojama bistatiskiem radara nov?rojumiem, tai skait? ar? rad

  8. A theoretical model for the temporal evolution of HF-enhanced plasma lines

    NASA Technical Reports Server (NTRS)

    Kuo, S. P.; Ho, A. Y.; Lee, M. C.; Djuth, F. T.

    1990-01-01

    The HF-enhanced plasma lines (HFPLs) observed in the Arecibo heating experiments refer to the radar returns at frequencies near the sum and difference of the radar frequency and the HF-heatear frequency. Those enhanced spectral lines are caused by backscatter of radar signals from parametrically excited plasma waves having a wavenumber of 18 n. A nonlinear theory was developed to describe the temporal evolution of those specified plasma waves and their originating altitude interval of HFPLs observed at Arecibo, Puerto Rico are explained. The theoretical resultsagree well with the observation (Djuth and Sulzer, 1989).

  9. A theoretical model for the temporal evolution of HF-enhanced plasma lines

    NASA Astrophysics Data System (ADS)

    Kuo, S. P.; Ho, A. Y.; Lee, M. C.; Djuth, F. T.

    1990-10-01

    The HF-enhanced plasma lines (HFPLs) observed in the Arecibo heating experiments refer to the radar returns at frequencies near the sum and difference of the radar frequency and the HF-heatear frequency. Those enhanced spectral lines are caused by backscatter of radar signals from parametrically excited plasma waves having a wavenumber of 18 n. A nonlinear theory was developed to describe the temporal evolution of those specified plasma waves and their originating altitude interval of HFPLs observed at Arecibo, Puerto Rico are explained. The theoretical resultsagree well with the observation (Djuth and Sulzer, 1989).

  10. UNDERSTANDING HF CHANNEL SIMULATOR REQUIREMENTS IN ORDER TO REDUCE HF MODEM PERFORMANCE MEASUREMENT VARIABILITY

    Microsoft Academic Search

    W. N. Furman; J. W. Nieto

    SUMMARY This paper begins with a brief overview of the HF channel and the mechanisms that hinder both analog and digital communications. Next the paper examines the Watterson channel model and describes the constituent parts common to most channel simulator implementations. This is followed by an overview of standards and documents which address various aspects of simulator implementations utilized for

  11. An analysis of the data collection modes of a digital weather radar system with respect to significant severe weather features

    E-print Network

    Neyland, Michael Arthur

    1978-01-01

    10 ' r (9a) (9b) Finally, the value of Z is given by e 3 The digital system produces log P rather than log P . Wilk aud Kessler (1970) developed an equation whrch correct- Eq (7), but the correction is usually less than 1 dB. (01P +21ogr+w) 2..., ubstituting Eq (6) into Eq (5) we get log Z = 2 log r + log P + 9. 0 e3 r log Z = 2 log r + log P + 10. 1 e10 r (7a) (7b) The digital value of P is converted to its dBm equivalent (always r negative) through the use of calibration data for each...

  12. Simultaneous measurements of HF-enhanced plasma waves and artificial field-aligned irregularities at Arecibo

    SciTech Connect

    Noble, S.T. (Rice Univ., Houston, TX (USA)); Djuth, F.T. (Aerospace Corp., Los Angeles, CA (USA))

    1990-09-01

    Two radar systems with beams intersecting in the HF-modified F region were used to simultaneously measure HF-enhanced plasma lines (HFPLs) and artificial geomagnetic field-aligned irregularities (AFAIs). The Arecibo 430-MHz radar was used for the HFPL observations, and a portable 49.92-MHz backscatter radar was deployed on the island of Guadeloupe to monitor the AFAIs. The experiment was desgined to examine the degree to which HF-induced plasma turbulence influences the development of AFAIs. When the HF beam is stepped up in power, sustained HFPLs and AFAIs are first observed at the same HF power level, indicating that ponderomotively driven instabilities may be involved in the early time development of AFAIs. As the HF power is increased, the HFPL backscatter power begins to saturate at {approximately}70 MW effective radiated power (ERP). However, the backscatter from AFAIs is linearly dependent on HF power, even at the highest (120 MW ERP) HF power levels available at Arecibo. This suggests that additional processes may contribute to the development of AFAIs. For example, ponderomotively driven instabilities may give rise to weak geomagnetic field-aligned irregularities that are subsequently driven unstable by processes excited near the upper hybrid resonance. It is also likely that AFAIs greatly impact the development of HF-induced plasma turbulence at late times (>1 s) following HF turn-on. Once the ionosphere is preconditioned by high-power HF modifications, AFAIs and HFPLs can be simultaneously sustained at a much lower HF power level than that needed to originally excite them. The nature of the preconditioning process is currently not well understood. New theoretical initiatives are clearly needed to guide future experimental activity in this area.

  13. Multichannel Receiver Design, Instrumentation, and First Results at the National Weather Radar Testbed

    Microsoft Academic Search

    Mark Yeary; Gerald Crain; Allen Zahrai; Christopher D. Curtis; John Meier; Redmond Kelley; Igor R. Ivic; Robert D. Palmer; Richard J. Doviak; G. Zhang; Tian-You Yu

    2012-01-01

    When the National Weather Radar Testbed (NWRT) was installed in 2004, a single-channel digital receiver was implemented so that the radar could mimic typical Weather Surveillance Radar (WSR) version 1988 Doppler (WSR-88D) capability. This, however, left unused eight other channels, built into the antenna. This paper describes the hardware instrumentation of a recently completed project that digitizes the radar signals

  14. Radar frequency radiation

    NASA Astrophysics Data System (ADS)

    Malowicki, E.

    1981-11-01

    A method is presented for the determination of radar frequency radiation power densities that the PAVE PAWS radar system could produce in its air and ground environment. The effort was prompted by the concern of the people in the vicinity of OTIS AFB MA and BEALE AFB CA about the possible radar frequency radiation hazard of the PAVE PAWS radar. The method is based on the following main assumptions that: (a) the total field can be computed as the vector summation of the individual fields due to each antenna element; (b) the individual field can be calculated using distances for which the field point is in the far field of the antenna element. An RFR computer program was coded for the RADC HE 6180 digital computer and exercised to calculate the radiation levels in the air and ground space for the present baseline and the possible Six DB and 10 DB growth systems of the PAVE PAWS radar system at OTIS AFB MA. The average radiation levels due to the surveillance fence were computed for three regions: in the air space in front of the radar, at the radar hazard fence at OTIS AFB MA and at representative ground points in the OTIS AFB vicinity. It was concluded that the radar frequency radiation of PAVE PAWS does not present a hazard to personnel provided there is no entry to the air hazard zone or to the area within the hazard fence. The method developed offers a cost effective way to determine radiation levels from a phased array radar especially in the near field and transition regions.

  15. Subsurface Radar Sounding of the Jovian Moon Ganymede

    Microsoft Academic Search

    Lorenzo Bruzzone; Giovanni Alberti; Claudio Catallo; Adamo Ferro; Wlodek Kofman; Roberto Orosei

    2011-01-01

    This paper provides an overview of the Europa Jupiter System Mission (EJSM) and of its scientific objectives, focusing the attention on the subsurface radar (SSR) instru- ment included in the model payload of the Jupiter Ganymede Orbiter (JGO). The SSR instrument is a radar sounder system at low frequency (HF\\/VHF band) designed to penetrate the sur- face of Ganymede icy

  16. g-factors of rotational states in176Hf,177Hf, and180Hf

    NASA Astrophysics Data System (ADS)

    Alfter, I.; Bodenstedt, E.; Knichel, W.; Schüth, J.; Vianden, R.

    1996-12-01

    g-factors of rotational states in176Hf and180Hf were measured with the twelve detector IPAC-apparatus of our laboratory [1]. The natural radioactivity 3.78·1010y176Lu and the 5.5 h isomer180mHf were used which populate the ground-state rotational bands of176Hf and180Hf. The integral rotations of ?-? directional correlations in strong external magnetic fields and in static hyperfine fields of (Lu?Hf)Fe2 and HfFe2 were observed. The following results were obtained: ^{176} Hf: ( {4_1^ + } ) = + 0.334( {38} ) \\ ^{180} Hf: ( {2_1^ + } ) = + 0.305( {14} ) \\ ( {4_1^ + } ) = + 0.358( {43} ) \\ {{ ( {6_1^ + } )} / {( {4_1^ + } )}} = + 0.95( {12} ) \\ . The hyperfine field in (Lu?Hf)Fe2 was calibrated by observing the integral rotation of the 9/2- first excited state of177Hf populated in the decay of 6.7d177Lu. The g-factor of this state was redetermined in an external magnetic field as ^{177} Hf: ( {{9 {/ {2^ - }}} ) = + 0.228( 7 ) . Finally the g-factor of the 2{1/+} state of176Hf was derived from the measured g(2{1/+}) of180Hf by use of the precisely known ratio g(2{1/+},176Hf)/ g(2{1/+},180Hf) [2] as ^{176} Hf: ( {2_1^ + } ) = + 0.315( {30} ).

  17. Near field focusing algorithm for high frequency ground penetration imaging radar

    Microsoft Academic Search

    Russell D. Brown; E. Douglas Lynch; David W. Mokry; James M. VanDamme; Richard A. Schneible; Michael C. Wicks

    1999-01-01

    Ground penetrating radar has been successfully used for imaging stratigraphic structures. The goal of our ground penetrating radar program is to provide a capability for strategic subsurface target detection for military applications. This paper describes an experimental approach to high frequency (HF) radar sub-surface profiling, and the results obtained from signal and data processing for deep tunnel detection. Ongoing experiments

  18. Phosphate Lu–Hf geochronology

    Microsoft Academic Search

    Gry H. Barfod; Olga Otero; Francis Albarède

    2003-01-01

    Igneous, metamorphic and biogenic apatite contains Lu and Hf in proportions that make this mineral suitable for dating by the 176Lu–176Hf method. We present a new method for separation of Lu and Hf from apatite that involves a single extraction column step for Hf and a second exchange column step for Lu. This procedure allows rapid sample processing prior to

  19. Application of ground-penetrating radar, digital optical borehole images, and cores for characterization of porosity hydraulic conductivity and paleokarst in the Biscayne aquifer, southeastern Florida, USA

    USGS Publications Warehouse

    Cunningham, K.J.

    2004-01-01

    This paper presents examples of ground-penetrating radar (GPR) data from two study sites in southeastern Florida where karstic Pleistocene platform carbonates that comprise the unconfined Biscayne aquifer were imaged. Important features shown on resultant GPR profiles include: (1) upward and lateral qualitative interpretative distribution of porosity and hydraulic conductivity; (2) paleotopographic relief on karstic subaerial exposure surfaces; and (3) vertical stacking of chronostratigraphic high-frequency cycles (HFCs). These characteristics were verified by comparison to rock properties observed and measured in core samples, and identified in digital optical borehole images. Results demonstrate that an empirical relation exists between measured whole-core porosity and hydraulic conductivity, observed porosity on digital optical borehole images, formation conductivity, and GPR reflection amplitudes-as porosity and hydraulic conductivity determined from core and borehole images increases, formation conductivity increases, and GPR reflection amplitude decreases. This relation allows for qualitative interpretation of the vertical and lateral distribution of porosity and hydraulic conductivity within HFCs. Two subtidal HFCs in the uppermost Biscayne aquifer have significantly unique populations of whole-core porosity values and vertical hydraulic conductivity values. Porosity measurements from one cycle has a median value about two to three times greater than the values from the other HFC, and median values of vertical hydraulic-conductivity about three orders of magnitude higher than the other HFC. The HFC with the higher porosity and hydraulic conductivity values is shown as a discrete package of relatively low-amplitude reflections, whereas the HFC characterized by lower porosity and hydraulic-conductivity measurements is expressed by higher amplitude reflections. Porosity and hydraulic-conductivity values measured from whole-core samples, and vuggy porosity identified on digital borehole images from shallowing-upward, peritidal HFCs show that the highest porosity occurs at the base of the cycles, moderate porosity at the middle of the cycles, and lowest porosity occurs at the top of cycles. Hydraulic conductivity is also highest at the base of the peritidal cycles and lowest in the middle to upper parts of cycles. This change in porosity and hydraulic conductivity from bottom to top is visible as an upward variation in reflection amplitude on GPR profiles-lowest amplitudes at the base and highest at the cycle tops. This study demonstrates that GPR can be used to show the qualitative distribution of porosity and hydraulic conductivity within a cycle-stratigraphic framework composed of carbonate HFCs. The distribution of porosity and hydraulic conductivity within HFCs is related to depositional textures. The upward and lateral patterns of the rock facies within the HFCs can be translated to geophysical-log properties and radar facies configurations that could aid in interpretation and prediction of ground-water flow through a carbonate aquifer. ?? 2003 Elsevier B.V. All rights reserved.

  20. Accuracy assessment of interferometric digital elevation models derived from the Shuttle Radar Topography Mission X- and C-band data in a test area with rolling topography and moderate forest cover

    NASA Astrophysics Data System (ADS)

    Kocak, G.; Buyuksalih, Gurcan; Oruc, M.

    2005-03-01

    In February 2000, the Shuttle Radar Topography Mission (SRTM) mapped large areas of the global landmass using two radar systems operating simultaneously in X and C band. The radar mapping instrument consisted of modified versions of the SIR-C C-band and X-band radars flown on the shuttle in 1994. Modifications included a 60-m retractable boom, with C-band and X-band receive-only antennas attached to the boom's end. High-accuracy metrology systems were added to measure position and attitude of the shuttle and the positions of the boom antennas. The dual apertures at each band form radar interferometers suitable for making high-accuracy topographic maps of the Earth. The C-band data set is being processed by JPL for the archives of the National Imagery and Mapping Agency and the National Aeronautics and Space Administration. The X-band data set is processed and distributed at DLR, Germany. This paper deals with the accuracy assessments of the interferometric DEMs derived from the X- and C-band synthetic aperture radar systems over a testfield with rolling topography and moderate forest cover using the reference DEM digitized from the topographic maps of 1:25,000 scale. Obtained results for the two interferometric DEMs are similar and lie in the range of 10-11 m. The accuracy of SRTM X- and C-band DEMs was also checked against ground control points measured by differential GPS, and the rms height errors were found to be about 9 m, which confirms the results based on the reference DEM.

  1. Radar Entomology

    NSDL National Science Digital Library

    0000-00-00

    Radar tracking used to profile insect migration, mating and flight patterns. Many links to various pages include current workers in radar entomology, historical uses of the technology, and many images.

  2. Radar principles

    NASA Technical Reports Server (NTRS)

    Sato, Toru

    1989-01-01

    Discussed here is a kind of radar called atmospheric radar, which has as its target clear air echoes from the earth's atmosphere produced by fluctuations of the atmospheric index of refraction. Topics reviewed include the vertical structure of the atmosphere, the radio refractive index and its fluctuations, the radar equation (a relation between transmitted and received power), radar equations for distributed targets and spectral echoes, near field correction, pulsed waveforms, the Doppler principle, and velocity field measurements.

  3. A radar image time series

    NASA Technical Reports Server (NTRS)

    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. Radar image registration and rectification

    NASA Technical Reports Server (NTRS)

    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.

  5. A model for high frequency radar auroral clutter

    NASA Astrophysics Data System (ADS)

    Elkins, T. J.

    1980-03-01

    A model is developed to permit estimation of the effects of irregularities in the auroral ionosphere in producing clutter experienced by Over-The Horizon radars operating at high geomagnetic latitudes. The model is used on various sources of data, including auroral radar (HF, VHF, UHF), vertical incidence ionosondes, satellite particle detectors, and optical sensors (ground-based and satellite-borne). The model addresses both the amplitude and Doppler components of auroral radar clutter and also the effect of ionospheric refraction that is extremely important at high frequencies. Consideration is given to the question of predictability of the effects of auroral clutter on HF radar systems. An important component of the model is the incorporation of data from the Polar Fox II experiment conducted for the purpose of evaluating auroral clutter effects on OTH radars.

  6. Surface M2 tidal currents along the North Carolina shelf observed with a high-frequency radar

    E-print Network

    Shay, Lynn K. "Nick"

    Surface M2 tidal currents along the North Carolina shelf observed with a high-frequency radar over the continental shelf of Duck, North Carolina, was explored using surface current observations measured by a high-frequency (HF) radar. The Ocean Surface Current Radar (OSCR) was deployed at the U

  7. Radar: the evolution since World War II

    Microsoft Academic Search

    R. Strong

    2005-01-01

    Modern radar design has benefited from the evolution of specialized digital processing, allowing high resolution ground mapping, target identification, and target tracking under many conditions. Air-to-air interception makes use of complex decision processes to select from many modes that depend on the clutter backgrounds and flight profiles. Today's multimode radars provide this information for each task while minimizing distractions. Fire

  8. The AN\\/GSC10 (KATHRYN) Variable Rate Data Modem for HF Radio

    Microsoft Academic Search

    M. Zimmerman; A. Kirsch

    1967-01-01

    The AN\\/GSC-10 (KATHRYN) is a new modem equipment for digital data transmission on HF radio circuits. Its unique modulation technique provides a wide range of signal redundancy and data rate to allow optimum performance over the correspondingly wide range of propagation conditions characteristic of HF radio. Efficient detection is achieved at all levels of redundancy by utilizing a fully coherent

  9. Spaceborne radar

    NASA Technical Reports Server (NTRS)

    Moore, R. K.; Eckerman, J.; Meneghini, R.; Atlas, D.; Boerner, W. M.; Cherry, S.; Clark, J. F.; Doviak, R. J.; Goldhirsh, J.; Lhermitte, R. M.

    1981-01-01

    The spaceborne radar panel considered how radar could be used to measure precipitation from satellites. The emphasis was on how radar could be used with radiometry (at microwave, visible (VIS), and infrared (IR) wavelengths) to reduce the uncertainties of measuring precipitation with radiometry alone. In addition, the fundamental electromagnetic interactions involved in the measurements were discussed to determine the key work areas for research and development to produce effective instruments. Various approaches to implementing radar systems on satellites were considered for both shared and dedicated instruments. Finally, a research and development strategy was proposed for establishing the parametric relations and retrieval algorithms required for extracting precipitation information from the radar and associated radiometric data.

  10. HF channel modeling for real-time packet transmission

    Microsoft Academic Search

    Mehdi Rostami; Joao Angeja; Joao Tavares; Antonio Navarro

    2003-01-01

    The recent rapid growth of multimedia communications has efficiently allowed delivering different services, formats and contents over an enormous variety of digital networks with IP acting as an integration protocol. The main objective of this research work is to evaluate the performance of an high frequency (HF) wireless network for transporting multimedia services according to UDP\\/IP protocol stack. Besides, allowing

  11. Surveillance radars - State of the art, research and perspectives

    NASA Astrophysics Data System (ADS)

    Farina, A.; Galati, G.

    1985-08-01

    An assessment is made of the signal processing techniques currently employed by ground-based surveillance radars, and a projection is made of those techniques that are likely to be applied to such radars in the future. Further applications of such techniques in such diverse fields as multistatic and dispersed radars, AEW, and space-based radars are also considered. Attention is given to prospective technological advancements that will facilitate radar systems' future dealings with antiradiation missiles and stealth aircraft, which may include digital beam forming, adaptivity, and high resolution multidimensional processing and target classification. The advantages of multistatic radar are examined in detail.

  12. An integrated radar imaging system for the STAR2 aircraft

    Microsoft Academic Search

    B. Akam; R. Deane; M. Sartori; R. Lowry; B. Mercer

    1988-01-01

    A commercial lightweight, real-time digital synthetic-aperture radar (SAR) known as STAR-2 (sea-lice and terrain assessment radar) is described. The SAR system consists of the MacDonald Dettwiler integrated radar imaging system (IRIS) and is carried aboard a small executive twin-turboprop aircraft. The IRIS makes extensive use of digital electronics to provide data of high radiometric and geometric quality, in real time.

  13. Auroral backscatter observed at HF from Ottawa

    SciTech Connect

    Montbriand, L.E.

    1988-10-01

    Bistatic HF radar recordings of auroral scattering sources north of Ottawa are reported. Doppler frequency spreads over + or - 100 Hz were obtained at least 35 percent of the time. The peak of the Doppler frequency distribution was sometimes shifted from zero by as much as 50 Hz, and significant contributions often occurred at Doppler frequencies greater than 150 Hz. Signals received simultaneously on both arms of a two-arm direction-finding array were used to identify the specific elevations and bearings of the backscatter signals. A detailed study of a particular hour-long period is reported, and a large number of 'apparent' auroral backscatter sources are identified. The source regions, probably located in the F layer, were elongated mainly in the north-south direction and extended over at least 3 deg of latitude. North-south corridors were found between such sources in which echo returns were either absent or very weak. 14 references.

  14. Meridian Digital Telephones and Options

    E-print Network

    Maxwell, Bruce D.

    Meridian Digital Telephones and Options M2006 M2008/M2008HF M2616 M2216ACD M2016S Secure Set Quick Digital Telephone Your Meridian Digital Telephone provides easy access to a wide range of business features. Your telephone system administrator assigns features to your feature keys, and provides you

  15. Use of the Hualien, Taiwan, dynasonde for surveillance of HF environmental radio and positioning of transmitting stations

    NASA Astrophysics Data System (ADS)

    Tsai, L.-C.; Chen, G. H.; Tian, M. H.; Zhang, Y.

    2012-04-01

    Since 2010, a 2nd generation NOAA HF radars, also referred as dynasonde, has been built at Hualien (23.89 N, 121.55 E), Taiwan. The Hualien dynasonde has a new design of ionospheric radar of fully digitizing the complex signal records and using multiple parallel receiver channels for simultaneous measurements of signals from multiple spaced receiving antennas. The Hualien dynasonde utilizes interferometric sounding pulse patterns and a receiving antenna array (including eight receivers connected to different spaced dipole antennas) to receive not only ionospherical echoes but also environmental radio signals. We have applied the Hermite normal form method to solve the phase-measurement aliasing and least squares problem and improve measurements of radio angles of arrival (AOA). The further ray-tracing experiments can be used for the study of radio wave propagation in the ionosphere. In this study we present a numerical and step by step ray-tracing method on a phenomenological ionospheric electron density model, the TaiWan Ionospheric Model (TWIM), which is constructed from the FormoSat3 / Constellation Observing System for Meteorology, Ionosphere and Climate (FS3/COSMIC) ionospheric radio occultation data and global ionosonde foF2 data. The three-dimensional TWIM consists of vertically-fitted ?-Chapman-type layers, with distinct F2, F1, E, and D layers, for which the layer parameters such as peak density, peak density height, and scale height are represented by surface spherical harmonics. This way the continuity of Ne and its derivatives is maintained. The methodology is successfully applied to a practical HF transmitter for oblique incidence ray tracing. Then, the AOA data will be used for backward ray tracing in the TWIM model and be used to determine ground-based transmitting station position.

  16. Longitudinal and seasonal variations in the occurrence of sunrise undulation at the dip equator: A study using Trivandrum and Jicamarca Digital Ionosonde and Jicamarca Incoherent Scatter radar measurements

    NASA Astrophysics Data System (ADS)

    Ambili, K. M.; St-Maurice, Jean-Pierre; Choudhary, Raj Kumar

    At night, the absence of photo ionization in combination with sustained downward plasma motion means that the F region can be severely depleted at the magnetic equator at the end of the night. As a result, there can be, at sunrise, a sudden upward jump in altitude of the F region peak which is then followed by a quick descent in association with the downward motion of the photo ionization production peak. This constitutes what has been described as the equatorial sunrise undulation. Its anecdotal existence has been reported over Jicamarca (120 S, 76.90 W, 1.70 S dip-latitude) while it has been seen repeatedly over Trivandrum (8.470 N, 76.920 E, 0.170 S dip latitude), India, particularly during equinox conditions. Seasonal variations in the occurrence of sunrise undulation in the F-region peak height (hmF2) at two longitudinally separated geomagnetic equatorial stations, namely Jicamarca and Trivandrum are being presented. Measurements from Digital ionosondes, located at these two stations, have been used in this study. A fast descends in hmF2 after the local F region sunrise was quite visible at both the stations. The frequency of occurrence of sunrise undulation at Trivandrum, however, was high compared to the same at Jicamarca. There were noticeable differences in the seasonal occurrence of sunrise undulation at the two places. While it was observed throughout the year at Trivandrum, there was a distinct seasonal preference of occurrence at Jicamarca, at least in the year 2010, a low solar active period. Its frequency of occurrence at Jicamarca was high during winter (June) solstice, low during equinox (March) and had almost negligible occurrence during summer solstice (December). We show that (1) plasma density during sunrise at Jicamarca on average was twice as much as at Trivandrum, and (2) average height of hmF2 during night at Jicamarca was higher (~100km ) during equinox and solstice months compared to the same at Trivandrum. Our results suggest that the background density plays an important role in the observation of a sunrise undulation in the F region peak which itself is quite sensitive to the electric field seen by the plasma between sunset and sunrise. Using incoherent backscatter radar data from Jicamarca we show that the sunrise undulation can be masked when remnant plasma from the previous night does not come down to low enough altitude. We argue that this is the reason behind the lack of sunrise undulations in December at Jicamarca, given the fact that there is often very strong plasma uplift in the evening at that time of year. Thus the seasonal and longitudinal variation of sunrise ionosphere is a proxy to understand the electro-dynamical features of the night before.

  17. Tracking the velocity and position of offshore vessels and floating objects with HF Doppler transponders

    Microsoft Academic Search

    MICHAEL W. EVANS; TOM M. GEORGES; B. Weber

    1981-01-01

    Experiments with a high-frequency (HF) Doppler radar and a frequency-shifting transponder show that the velocity and position of ships or floating objects can be tracked without the need for accurate differential-position measurements. Maximum-entropy spectral analysis permits tracking during rapid maneuvers using sampling times as short as 4 s.

  18. Evaluating Radial Current Measurements from CODAR High-Frequency Radars with Moored Current Meters

    Microsoft Academic Search

    Brian M. Emery; Libe Washburn; Jack A. Harlan

    2004-01-01

    The performance of a network of five CODAR (Coastal Ocean Dynamics Application Radar) SeaSonde high- frequency (HF) radars, broadcasting near 13 MHz and using the Multiple Signal Classification (MUSIC) algorithm for direction finding, is described based on comparisons with an array of nine moorings in the Santa Barbara Channel and Santa Maria basin deployed between June 1997 and November 1999.

  19. Radar test range design considerations

    NASA Astrophysics Data System (ADS)

    Sofianos, D.

    1980-04-01

    This report presents considerations for and the preliminary design of a synthetic aperture RADAR (SAR) test range. The purpose is to present a methodology and conceptual design for a Flexible Test Bed (FTB) digital processor operational test. The objectives of this operational test are to: (1) determine whether the processor modifications improved image quality, (2) establish a processor performance baseline, and (3) determine whether the system will attain desired levels of probability of detection. It is assumed that SAI would develop a test design while GAC will fabricate and install the required radar test range.

  20. Digital communications study

    NASA Technical Reports Server (NTRS)

    Boorstyn, R. R.

    1973-01-01

    Research is reported dealing with problems of digital data transmission and computer communications networks. The results of four individual studies are presented which include: (1) signal processing with finite state machines, (2) signal parameter estimation from discrete-time observations, (3) digital filtering for radar signal processing applications, and (4) multiple server queues where all servers are not identical.

  1. Integrated photonic analog-to-digital converters

    E-print Network

    Khilo, Anatol (Anatol M.)

    2011-01-01

    Accurate conversion of wideband multi-GHz analog signals into the digital domain has long been a target of analog-to-digital converter (ADC) developers, driven by applications in radar systems, software radio, medical ...

  2. FPGA implementation of a software-defined radar processor

    NASA Astrophysics Data System (ADS)

    Suarez, Hernan; Zhang, Yan Rockee

    2013-05-01

    A unified digital pulse compression processor is introduced as a radar-application-specific-processor (RASP) architecture for the next generation of adaptive radar. Based on traditional pulse compression matched filter and correlation receiver, the processor integrates specific designs to handle waveform diversities, which includes random noise waveforms, as well as digital transceiver self-reconfiguration for adaptive radars. Initial prototype of this processor is implemented with the latest Xilinx FPGA device and tested with an RF spaceborne radar transceiver testbed. Initial validation results show the effectiveness of real-time processing and engineering concepts.

  3. Using radar image simulation to assess relative geometric distortions inherent in radar imagery

    NASA Technical Reports Server (NTRS)

    Kaupp, V. H.; Macdonald, H. C.; Waite, W. P.

    1981-01-01

    A unique method for observing the relative contributions of backscatter and propagation effects is afforded by radar image simulation. Digital terrain data are used in modeling radar image formation. Backscatter and propagation effects are modeled separately. These are incorporated serially and the image expression of each is noted. Sequences of images are presented illustrating these effects over a range of slopes and angles of incidence. The conclusions reached are that at angles of incidence that are smaller than the average slope of the terrain in a region, propagation phenomena predominate. As the angle of incidence increases beyond this, the radar image portrays an increasingly faithful representation of the backscatter from the ground. It is also demonstrated that digital simulation affords an important tool for evaluating complex interactions between the ground and radar, for training users in radar image interpretation, and for selecting optimum sensor parameters for particular applications.

  4. Ionospheric decontamination and sea clutter suppression for HF skywave Radars

    Microsoft Academic Search

    Kun Lu; Xingzhao Liu; Yongtan Liu

    2005-01-01

    In this paper, a cascaded correction and suppression method of reducing ionospheric phase path contamination and sea clutter to enable detection of targets travelling at speeds near the Bragg Doppler is addressed. The Hankel rank reduction (HRR) technique based on singular value decomposition (SVD) has been used to estimate the ionospheric phase distortion and suppress the sea clutter. Simulation results

  5. SBRAS — an advanced simulator of spaceborne radar

    Microsoft Academic Search

    Min Wang; Diannong Liang; Haifeng Huang; Zhen Dong

    2007-01-01

    An application-oriented spaceborne radar advanced simulator (SBRAS) is presented in this paper. SBRAS is initiated by the technical and economical requirements to verify formation-flying distributed satellites synthetic aperture radar (SAR) scheme and simplify the instrument hardware design. The simulator develops a full flow of signal processing including formation design, SAR raw data simulation of nature scene, imaging, InSAR processing, digital

  6. Wideband OFDM system for radar and communications

    Microsoft Academic Search

    Dmitriy Garmatyuk; Jonathan Schuerger; Kyle Kauffman; Scott Spalding

    2009-01-01

    This paper describes the design and architectural composition of a radar system built on OFDM platform. The radar signal is generated digitally by forming an arbitrary-length vector of OFDM sub-carrier amplitudes and translating it in analog format via 1000 Ms\\/s D\\/A conversion. The resultant baseband signal has a bandwidth of 500 MHz, and variable number and composition of sub-carriers, which

  7. Marburg Hemorrhagic Fever (Marburg HF)

    MedlinePLUS

    ... chronological list of known cases and outbreaks. Marburg hemorrhagic fever (Marburg HF) Topics Transmission How do people get Marburg hemorrhagic fever? Signs and Symptoms What are the signs and ...

  8. Suppression of sidelobe scatterers in an AESA FMCW radar

    Microsoft Academic Search

    W. L. van Rossum; C. M. Lievers; A. P. M. Maas; A. G. Huizing

    2008-01-01

    This paper describes an active electronically scanned array (AESA) FMCW radar with eight transceivers. Each transceiver has its own direct digital synthesizer (DDS) for signal generation which enables digital beam forming on transmit as well as on receive. The coherent operation of the eight transceivers and the capability to perform digital beam forming on transmit and receive is demonstrated. Also

  9. Half life of 175Hf.

    PubMed

    Fang, Kaihong; Wang, Dawei; Yang, Shaobo; Zhao, Jiangtao; Peng, Haibo; Wang, Qiang; Wang, Tieshan

    2012-10-01

    This work measured the half life of radioisotope (175)Hf, which was produced by neutron activation method at the ZF-300-II Intense Neutron Generator in Lanzhou University. The half life of (175)Hf, measured by ?-ray spectrometry using a well calibrated GEM-60P coaxial High Purity Germanium (HPGe) detector, has been found to be 70.65±0.19 days. The present result agrees with the literature data well, while the accuracy was improved. PMID:22871434

  10. The Italian involvement in Cassini radar

    NASA Astrophysics Data System (ADS)

    Nirchio, F.; Pernice, B.; Borgarelli, L.; Dionisio, C.

    1991-12-01

    The Radio Frequency Electronic Subsystem (RFES) of the Cassini radar is described. The requirements of the Cassini radar are summarized. The design parameters taken into consideration in developing the RFES are described. The RFES interfaces with the High Gain Antenna (HGA) for signal transmission and reception. The operational parameters of the Cassini radar are presented. The front end electronics (FEE), microwave receiver (MR), high power amplifier (HPA), frequency generator (FG), digital chip generator (DCG), Chirp Up Converter and Amplifier (CUCA) and power supply of the RFES are described.

  11. Highly Integrated Radar Sensor-on-Chip

    NASA Astrophysics Data System (ADS)

    Mende, Ralph

    2012-05-01

    A highly integrated 24 GHz radar sensor is presented, based on a Radio Frequency Integrated Circuit (RFIC) which was specifically developed for a Frequency Modulated Shift Keying (FMSK) based Radar system design. Antenna, waveform, the Radio Frequency (RF) and Digital Signal Processor (DSP) module, the software design, cost and performance aspects will be described. The significant technical and economical advantages of the implemented Silicon-Germanium (SiGe) Bipolar CMOS (BiCMOS) transceiver are demonstrated. Some automotive and other applications based on this technology and new radar system design will be explained.

  12. RADAR PRINCIPLES I Introduction

    E-print Network

    Sato, Toru

    ) bands. Antenna size of weather radarsis a few to about ten metersin diameter, but an} atmospheric radar atmospheric radars have antennas witli dialneter of 10- 300 in. Weather radars cover a wide horizontal areaRADAR PRINCIPLES I Introduction Radar is a general technique, willcli has a wide range

  13. Limitations of Radar Coordinates

    E-print Network

    Donato Bini; Luca Lusanna; Bahram Mashhoon

    2004-12-17

    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.

  14. Hf isotope constraints on mantle evolution

    Microsoft Academic Search

    Vincent J. M Salters; William M White

    1998-01-01

    The similarity of the Lu–Hf and Sm–Nd isotope system during most mantle differentiation processes makes the combination of 176Hf\\/177Hf and 143Nd\\/144Nd a very sensitive indicator of a select number of processes. This paper present new Hf-isotope data for a large number of ocean islands and examines the Hf–Nd–Pb isotope relations of oceanic volcanics. Except for HIMU islands, St. Helena and

  15. FPGA based Ultra-Wideband pseudo-noise radar

    Microsoft Academic Search

    Amutha Jayakumar; Asha Durafe

    2011-01-01

    A high accuracy experimental platform for Ultra Wide Band (UWB) PN radar performance evaluation has been created. This PN radar platform could be used for the applications such as unmanned- aerial-vehicle anti-collision and short-range distance measurement etc (3). It includes compact size X-band radar transceiver, baseband signal processing in FPGA, high speed analog to digital converter (ADC), and Matlab tools.

  16. TRMM radar

    NASA Technical Reports Server (NTRS)

    Okamoto, Kenichi

    1993-01-01

    The results of a conceptual design study and the performance of key components of the Bread Board Model (BBM) of the Tropical Rainfall Measuring Mission (TRMM) radar are presented. The radar, which operates at 13.8 GHz and is designed to meet TRMM mission objectives, has a minimum measurable rain rate of 0.5 mm/h with a range resolution of 250 m, a horizontal resolution of about 4 km, and a swath width of 220 km. A 128-element active phased array system is adopted to achieve contiguous scanning within the swath. The basic characteristics of BBM were confirmed by experiments. The development of EM started with the cooperation of NASDA and CRL.

  17. Satellite remote sensing of landscape freeze/thaw state dynamics for complex Topography and Fire Disturbance Areas Using multi-sensor radar and SRTM digital elevation models

    NASA Technical Reports Server (NTRS)

    Podest, Erika; McDonald, Kyle; Kimball, John; Randerson, James

    2003-01-01

    We characterize differences in radar-derived freeze/thaw state, examining transitions over complex terrain and landscape disturbance regimes. In areas of complex terrain, we explore freezekhaw dynamics related to elevation, slope aspect and varying landcover. In the burned regions, we explore the timing of seasonal freeze/thaw transition as related to the recovering landscape, relative to that of a nearby control site. We apply in situ biophysical measurements, including flux tower measurements to validate and interpret the remotely sensed parameters. A multi-scale analysis is performed relating high-resolution SAR backscatter and moderate resolution scatterometer measurements to assess trade-offs in spatial and temporal resolution in the remotely sensed fields.

  18. Nearshore Applications of Marine Radar 15 June 2006

    E-print Network

    Haller, Merrick

    wave and weather conditions 2.2 Marine radar wave imaging system 12 Radar properties and data collection parameters Nyquist wavenumber and frequency Data collection nomenclature Image stability of in situ wave and weather conditions 3.2 Data Collection Parameters 45 Digital collection parameters Data

  19. FPGA based Architecture for Radar's STC, FTC and Gain modules

    Microsoft Academic Search

    Joaquín García; Gilberto Viveros; René Cumplido

    Recent innovations like reconfigurable computing have allowed to easy experiment new architectures that support a wide range of applications for Digital Signal Processing (DSP). Field Programmable Gate Array (FPGA) provides a cheap platform for research and development. Radar signal processing is widely used for civil and military proposes. Radar's systems operate on Real-Time basis. This paper presents an architecture that

  20. R69-15 Microwave Radar and Electronic Environment Simulator

    Microsoft Academic Search

    C. W. Schisler

    1969-01-01

    In this paper the author describes the design, development, and application of a general-purpose radar and electromagnetic environment simulator, controlled by digital and analog computers. This simulator is being used at the White Sands Missile Range (WSMR) to provide direct synthesis of radar systems and their electromagnetic environment operating concurrently with missile flight simulators, range instrumentation simulations, and related test-range

  1. Countering stealth with passive, multi-static, low frequency radars

    Microsoft Academic Search

    H. Kuschel; J. Heckenbach; S. Mu?ller; R. Appel

    2010-01-01

    The potential of passive, multi-static radars as covert sensors for the detection of low flying, stealth air targets are illustrated by multi-static RCS analysis, coverage simulations for low flight levels and measurement results obtained with an experimental passive radar using digital audio broadcast signals (DAB). The measurement sensor is described and future perspectives are pointed out.

  2. INTEGRATED CONTROL OF COMBINED SEWER REGULATORS USING WEATHER RADAR

    EPA Science Inventory

    Integrated operation was simulated of ten dynamic combined sewer regulators on a Montreal interceptor. Detailed review of digital recording weather radar capabilities indicated that it is potentially the best rainfall estimation means for accomplishing the runoff prediction that ...

  3. Forest Canopy Characterization and Vegetation Penetration Assessment with SpaceBorne Radar

    Microsoft Academic Search

    Marc Imhoff; Michael Story; Charles Vermillion; Faruq Khan; Fabian Polcyn

    1986-01-01

    Synthetic Aperture Radar (SAR) images from the- National Aeronautics and Space Administration's Shuttle Imaging Radar-B (SIR-B) Mission were used to analyze the effects of radar incidence angle on information content and vegetation penetration. Three SAR data sets using incidence angles of 26°, 46°, and 58° were acquired over the mangrove jungles of Southern Bangladesh. The data sets were digitally processed

  4. Metrology, attitude, and orbit determination for spaceborne interferometric synthetic aperture radar

    Microsoft Academic Search

    Riley M. Duren; Ed Wong; Bill Breckenridge; Scott Shaffer; Courtney Duncan; Eldred F. Tubbs; Phil M. Salomon

    1998-01-01

    The Shuttle Radar Topography Mission (SRTM), scheduled for an 11 day Space Shuttle flight in 1999, will use an Interferometric Synthetic Aperture Radar instrument to produce a near-global digital elevation map of the earth's land surface with 16 m absolute vertical height accuracy at 30 meter postings. SRTM will achieve the required interferometric baseline by extending a receive-only radar antenna

  5. Radar image processing module development program, phase 3

    NASA Technical Reports Server (NTRS)

    1977-01-01

    The feasibility of using charge coupled devices in an IPM for processing synthetic aperture radar signals onboard the NASA Convair 990 (CV990) aircraft was demonstrated. Radar data onboard the aircraft was recorded and processed using a CCD sampler and digital tape recorder. A description of equipment and testing was provided. The derivation of the digital presum filter was documented. Photographs of the sampler/tape recorder, real time display and circuit boards in the IPM were also included.

  6. Radar studies related to the earth resources program. [remote sensing programs

    NASA Technical Reports Server (NTRS)

    Holtzman, J.

    1972-01-01

    The radar systems research discussed is directed toward achieving successful application of radar to remote sensing problems in such areas as geology, hydrology, agriculture, geography, forestry, and oceanography. Topics discussed include imaging radar and evaluation of its modification, study of digital processing for synthetic aperture system, digital simulation of synthetic aperture system, averaging techniques studies, ultrasonic modeling of panchromatic system, panchromatic radar/radar spectrometer development, measuring octave-bandwidth response of selected targets, scatterometer system analysis, and a model Fresnel-zone processor for synthetic aperture imagery.

  7. Estimation of planetary surface roughness by HF sounder observation

    NASA Astrophysics Data System (ADS)

    Kobayashi, T.; Ono, T.

    Japanese Martian exploration project "Nozomi" was to carry out several science missions. Plasma Wave Sounder, one of those onboard missions, was an HF sounder to study Martian plasma environment, and Martian surface with the altimetry mode (Oya and Ono, 1998) as well. The altimetry mode observation was studied by means of computer simulations utilizing the KiSS code which had been originally designed to simulate the SELENE Lunar Radar Sounder, a spaceborne HF GPR, based on Kirchhoff approximation theory (Kobayashi, Oya and Ono, 2002). We found an empirical power law for the standard deviation of observed altitudes over Gaussian random rough surfaces: it varies in proportion to the square of the RMS gradient of the surface ?{2} hRMS{?_0, where hRMS and ?_0 are the RMS height of the surface and the correlation distance of the surface, respectively. We applied Geometrical optics to understand this empirical power law, and derived a square power law for the standard deviation of the observed altitude. Our Geometrical optics model assumed the followings: 1) the observed surface is a Gaussian random rough surface, 2) the mean surface is a flat horizontal plane, 3) the observed surface echo is the back scattering echoes, 4) the observed altitude is the mean value of the apparent range of those back scattering echoes. These results imply that HF sounder may be utilized to measure the surface roughness of planetary bodies in terms of the RMS gradient of the surface. Refrence: H. Oya and T. Ono, A new altimeter for Mars land shape observations utilizing the ionospheric sounder system onboard the Planet-B spacecraft, Earth Planets Space, Vol. 50, pp.229-234, 1998 T. Kobayashi, H. Oya, and T. Ono, A-scope analysis of subsurface radar sounding of lunar mare region, Earth Planets Space, Vol. 54, pp.973-982, 2002

  8. Radar: The Cassini Titan Radar Mapper

    Microsoft Academic Search

    C. Elachi; M. D. Allison; L. Borgarelli; P. Encrenaz; E. Im; M. A. Janssen; W. T. K. Johnson; R. L. Kirk; R. D. Lorenz; J. I. Lunine; D. O. Muhleman; S. J. Ostro; G. Picardi; F. Posa; C. G. Rapley; L. E. Roth; R. Seu; L. A. Soderblom; S. Vetrella; S. D. Wall; C. A. Wood; H. A. Zebker

    2004-01-01

    The Cassini RADAR instrument is a multimode 13.8 GHz multiple-beam sensor that can operate as a synthetic-aperture radar (SAR) imager, altimeter, scatterometer, and radiometer. The principal objective of the RADAR is to map the surface of Titan. This will be done in the imaging, scatterometer, and radiometer modes. The RADAR altimeter data will provide information on relative elevations in selected

  9. Future Trends in Automotive Radar \\/ Imaging Radar

    Microsoft Academic Search

    J. Wenger

    1998-01-01

    There is a growing interest of car manufacturers in sensors monitoring the car's surrounding area in order to improve safety systems from mere crash survival to crash prediction or prevention by early detection of hazardous situations. Therefore radar sensors have been intensively investigated for many years. A large variety of radar based vehicular sensors have been developed. Narrow-beam radars are

  10. Radar echo processing with partitioned de-ramp

    DOEpatents

    Dubbert, Dale F.; Tise, Bertice L.

    2013-03-19

    The spurious-free dynamic range of a wideband radar system is increased by apportioning de-ramp processing across analog and digital processing domains. A chirp rate offset is applied between the received waveform and the reference waveform that is used for downconversion to the intermediate frequency (IF) range. The chirp rate offset results in a residual chirp in the IF signal prior to digitization. After digitization, the residual IF chirp is removed with digital signal processing.

  11. Vegetation height estimation from Shuttle Radar Topography Mission and National Elevation Datasets

    Microsoft Academic Search

    Josef Kellndorfer; Wayne Walker; Leland Pierce; Craig Dobson; Jo Ann Fites; Carolyn Hunsaker; John Vona; Michael Clutter

    2004-01-01

    A study was conducted to determine the feasibility of obtaining estimates of vegetation canopy height from digital elevation data collected during the 2000 Shuttle Radar Topography Mission (SRTM). The SRTM sensor mapped 80% of the Earth's land mass with a C-band Interferometric Synthetic Aperture Radar (InSAR) instrument, producing the most complete digital surface map of Earth. Due to the relatively

  12. Signature of 3-4 day planetary waves in the equatorial ionospheric F layer height and medium frequency radar winds over Tirunelveli (8.7oN)

    NASA Astrophysics Data System (ADS)

    Sundararaman, Sathishkumar

    Signature of 3-4 day planetary waves in the equatorial ionospheric F layer height and medium frequency radar winds over Tirunelveli (8.7oN) S. Sathishkumar1, R. Dhanya1, K. Emperumal1, D. Tiwari2, S. Gurubaran1 and A. Bhattacharyya2 1. Equatorial Geophysical Research Laboratory, Indian Institute of Geomagnetism, Tirunelveli, India 2. Indian Institute of Geomagnetism, Navi Mumbai, India Email: sathishmaths@gmail.com Abstract The equatorial atmosphere-ionosphere system has been studied theoretically and observationally in the past. In the equatorial atmosphere, oscillations with periods of 3-4 days are often observed in the medium frequency (MF) radar over Tirunelveli (8.7oN, 77.8oE, 1.34oN geomag. lat.). Earlier observations show the clear evidence that these waves can propagate from the stratosphere to ionosphere. A digital ionosonde has been providing useful information on several ionospheric parameters from the same site. Simultaneous observations of mesospheric winds using medium frequency radar and F-layer height (h'F) from ionosonde reveal that the 3-4 day wave was evident in both the component during the 01 June 2007 and 31 July 2007. The 3-4 day wave could have an important role in the day to day variability of the equatorial ionosphere evening uplift. Results from an extensive analysis that is being carried out in the direction of 3-4 day wave present in the ionosphere will be presented.

  13. Soviet oceanographic synthetic aperture radar (SAR) research

    SciTech Connect

    Held, D.N.; Gasparovic, R.F.; Mansfield, A.W.; Melville, W.K.; Mollo-Christensen, E.L.; Zebker, H.A.

    1991-01-01

    Radar non-acoustic anti-submarine warfare (NAASW) became the subject of considerable scientific investigation and controversy in the West subsequent to the discovery by the Seasat satellite in 1978 that manifestations of underwater topography, thought to be hidden from the radar, were visible in synthetic aperture radar (SAR) images of the ocean. In addition, the Seasat radar produced images of ship wakes where the observed angle between the wake arms was much smaller than expected from classical Kelvin wake theory. These observations cast doubt on the radar oceanography community's ability to adequately explain these phenomena, and by extension on the ability of existing hydrodynamic and radar scattering models to accurately predict the observability of submarine-induced signatures. If one is of the opinion that radar NAASW is indeed a potentially significant tool in detecting submerged operational submarines, then the Soviet capability, as evidenced throughout this report, will be somewhat daunting. It will be shown that the Soviets have extremely fine capabilities in both theoretical and experimental hydrodynamics, that Soviet researchers have been conducting at-sea radar remote sensing experiments on a scale comparable to those of the United States for several years longer than we have, and that they have both an airborne and spaceborne SAR capability. The only discipline that the Soviet Union appears to be lacking is in the area of digital radar signal processing. If one is of the opinion that radar NAASW can have at most a minimal impact on the detection of submerged submarines, then the Soviet effort is of little consequence and poses not threat. 280 refs., 31 figs., 12 tabs.

  14. Observation and theory of the radar aurora

    SciTech Connect

    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.

  15. Auxiliary signal processing system for a multiparameter radar

    NASA Technical Reports Server (NTRS)

    Chandrasekar, V.; Gray, G. R.; Caylor, I. J.

    1993-01-01

    The design of an auxiliary signal processor for a multiparameter radar is described with emphasis on low cost, quick development, and minimum disruption of radar operations. The processor is based around a low-cost digital signal processor card and personal computer controller. With the use of such a concept, an auxiliary processor was implemented for the NCAR CP-2 radar during a 1991 summer field campaign and allowed measurement of additional polarimetric parameters, namely, the differential phase and the copolar cross correlation. Sample data are presented from both the auxiliary and existing radar signal processors.

  16. Radar frequency radiation

    Microsoft Academic Search

    E. Malowicki

    1981-01-01

    A method is presented for the determination of radar frequency radiation power densities that the PAVE PAWS radar system could produce in its air and ground environment. The effort was prompted by the concern of the people in the vicinity of OTIS AFB MA and BEALE AFB CA about the possible radar frequency radiation hazard of the PAVE PAWS radar.

  17. GMTI MIMO radar

    Microsoft Academic Search

    D. W. Bliss; K. W. Forsythe; S. K. Davis; G. S. Fawcett; D. J. Rabideau; L. L. Horowitz; S. Kraut

    2009-01-01

    Multiple-input multiple-output (MIMO) extensions to radar systems enable a number of advantages compared to traditional approaches. These advantages include improved angle estimation and target detection. In this paper, MIMO ground moving target indication (GMTI) radar is addressed. The concept of coherent MIMO radar is introduced. Comparisons are presented comparing MIMO GMTI and traditional radar performance. Simulations and theoretical bounds for

  18. Spaceborne weather radar

    Microsoft Academic Search

    Robert Meneghini; Toshiaki Kozu

    1990-01-01

    The present work on the development status of spaceborne weather radar systems and services discusses radar instrument complementarities, the current forms of equations for the characterization of such aspects of weather radar performance as surface and mirror-image returns, polarimetry, and Doppler considerations, and such essential factors in spaceborne weather radar design as frequency selection, scanning modes, and the application of

  19. Wind shear radar simulation

    NASA Technical Reports Server (NTRS)

    Britt, Charles L.

    1988-01-01

    Viewgraphs used in a presentation on wind shear radar simulation are given. Information on a microburst model of radar reflectivity and wind velocity, radar pulse output, the calculation of radar return, microburst power spectrum, and simulation plans are given. A question and answer session is transcribed.

  20. An analysis of simulated stereo radar imagery

    NASA Technical Reports Server (NTRS)

    Pisaruck, M. A.; Kaupp, V. H.; Macdonald, H. C.; Waite, W. P.

    1983-01-01

    Simulated stereo radar imagery is used to investigate parameters for a spaceborne imaging radar. Incidence angles ranging from small to intermediate to large are used with three digital terrain model areas which are representative of relatively flat, moderately rough, and mountainous terrain. The simulated radar imagery was evaluated by interpreters for ease of stereo perception and information content, and rank order within each class of terrain. The interpreter's results are analyzed for trends between the height of a feature and either parallax or vertical exaggeration for a stereo pair. A model is developed which predicts the amount of parallax (or vertical exaggeration) an interpreter would desire for best stereo perception of a feature of a specific height. Results indicate the selection of angle of incidence and stereo intersection angle depend upon the relative relief of the terrain. Examples of the simulated stereo imagery are presented for a candidate spaceborne imaging radar having four selectable angles of incidence.

  1. Processing for spaceborne synthetic aperture radar imagery

    NASA Technical Reports Server (NTRS)

    Lybanon, M.

    1973-01-01

    The data handling and processing in using synthetic aperture radar as a satellite-borne earth resources remote sensor is considered. The discussion covers the nature of the problem, the theory, both conventional and potential advanced processing techniques, and a complete computer simulation. It is shown that digital processing is a real possibility and suggests some future directions for research.

  2. Shuttle imaging radar-C science plan

    NASA Technical Reports Server (NTRS)

    1986-01-01

    The Shuttle Imaging Radar-C (SIR-C) mission will yield new and advanced scientific studies of the Earth. SIR-C will be the first instrument to simultaneously acquire images at L-band and C-band with HH, VV, HV, or VH polarizations, as well as images of the phase difference between HH and VV polarizations. These data will be digitally encoded and recorded using onboard high-density digital tape recorders and will later be digitally processed into images using the JPL Advanced Digital SAR Processor. SIR-C geologic studies include cold-region geomorphology, fluvial geomorphology, rock weathering and erosional processes, tectonics and geologic boundaries, geobotany, and radar stereogrammetry. Hydrology investigations cover arid, humid, wetland, snow-covered, and high-latitude regions. Additionally, SIR-C will provide the data to identify and map vegetation types, interpret landscape patterns and processes, assess the biophysical properties of plant canopies, and determine the degree of radar penetration of plant canopies. In oceanography, SIR-C will provide the information necessary to: forecast ocean directional wave spectra; better understand internal wave-current interactions; study the relationship of ocean-bottom features to surface expressions and the correlation of wind signatures to radar backscatter; and detect current-system boundaries, oceanic fronts, and mesoscale eddies. And, as the first spaceborne SAR with multi-frequency, multipolarization imaging capabilities, whole new areas of glaciology will be opened for study when SIR-C is flown in a polar orbit.

  3. Venus surface imaging from orbital radar data

    Microsoft Academic Search

    Iu. V. Kornienko; D. G. Stankevich; O. T. Basilevskii; Iu. G. Shkuratov

    1982-01-01

    Visual images of the Venusian surface for the region corresponding to the landing site of Veneras 11-14 (between latitudes -17 and +41 deg and longitudes 250-330 deg) have been obtained on the basis of radar studies conducted by the Pioneer Venus Orbiter. The images, which include several axonometric projections and a stereoscopic pair, have been generated by a digital imaging

  4. Radio HF precursors of Earthquakes

    NASA Astrophysics Data System (ADS)

    Ruzhin, Yu.; Nomicos, C.; Vallianatos, F.; Shpakovsky, V.

    The high frequency (HF) earthquake electromagnetic precursors (40-55MHz band) were recorded by the four electromagnetic stations a few days (hours) prior the event associated with earthquakes with magnitude more than 5.0 at Crete Island. These experiments were performed continuously during 1998-2002 and specific peculiarities are found. This is underhorizon epicenter position for main part of events under question. Another unusual result is that such HF preseismic radio noise-like signals are responsible for seaquakes too. We made conclusion about developing of some thunderstorm-like charged clouds activity in atmosphere before the seismic event. As result of our analysis and interpretation of the available data of continuous observations on a network of Crete island we should state here, that in an atmosphere above the sea on the eve of earthquake at heights of 0.1-10 km the spatially distributed spots of sporadic charged clouds are occurred and the conditions for the electrical discharges in an atmosphere are created which can serve a source of HF radio-emission registered by Crete network. The atmosphere theory relations are used to model a corresponding to an anomalous event emissions generation observed on the Crete. The supposed mechanism of preseismic electricity generation is the model of convection carrier started in an atmosphere. It is governed by the horizontal gradient of air temperature. The occurrence of electrical charges in a surface of the sea and transportation them further on heights up to 10 km in our model occurs due to sporadic energy injections that allocated within bottom of the sea as gases and heat. The dimensions of width and height govern the size of atmosphere convection cells in the earthquake preparation area. These dimensions of the sporadic spots are close to 3 km each as it is derived from shadow geometry and spectral fluctuations of HF signal. Based on experience of Crete HF precursors observation the method for satellite mapping of HF emission (40-55MHz band) as part of VULKAN project for early warning of natural hazards are discussed.

  5. KAGUYA Lunar Radar Sounder (LRS) observation of lunar surface echo and its calibration

    NASA Astrophysics Data System (ADS)

    Kobayashi, Takao; Ryeol Lee, Seung

    2015-04-01

    Lunar Radar Sounder (LRS) is an HF radar of which the center frequency of transmitted pulse is 5 MHz. LRS was installed to KAGUYA which flew to the Moon in 2007. During the operation period of 19 months, LRS performed radar sounding observation from the orbit at the nominal altitude of 100 km to cover whole surface of the Moon with its foot print. The total number of LRS observations (pulse transmissions) exceeded 10^8. We extracted the nadir surface echo out of each observation which made a surface echo map of the Moon, i.e. a mosaic image of the Moon of an HF frequency (5 MHz). The observed surface echoes carry information regarding lunar surface and that of shallow subsurface (near-surface) whose depth scale is smaller than the range resolution of the LRS (~ 150 m in vacuum). An inversion algorithm is applied to extract such information. However, inversion algorithms often assume a simple model of Fresnel reflection. One should remove the effect of surface roughness from the LRS data before practicing inversion. For this purpose, we carried out simulation of LRS observation to evaluate the surface roughness effect on the LRS data quantitatively. The simulation is based on Kirchhoff approximation theory. Digital Elevation Model (DEM) of KAGUYA Terrain Camera (TC) mission was used in the simulation to simulate the actual lunar terrain. LRS observation simulation was performed in the range from -90 to 70 degrees in longitude and in the range from -30 to 70 degrees in latitude at every 0.1 degree interval in both directions. The simulation revealed 1) LRS surface echo observation is sensible to the surface terrain: even wrinkle ridges and small craters are well recognized in the mosaic image of simulation surface echo map. 2) Little difference was found in the mosaic image of an old mare surface and a young mare surface. 3) However, apparent difference was found in the shape of the distribution functions of echo intensity of an old mare surface and a young mare surface. We used the simulation result to remove the surface roughness effect on the LRS data to obtain the plane surface echo intensity. The resultant data revealed 1) Highland surface presents weak echo intensity than mare surface. 2) Young mare surface presents more intense echo than old mare surface. 3) Some areas in maria presents significantly weak echo than surrounding mare surface. These findings are attributed to the property of near-surface subsurface. Our inversion found that the young mare surface material has larger permittivity than the old mare surface material.

  6. Current Structure Variations Detected by High-Frequency Radar and Vector-Measuring Current Meters

    Microsoft Academic Search

    Lynn K. Shay; Steven J. Lentz; Hans C. Graber; Brian K. Haus

    1998-01-01

    Ocean surface current measurements from high-frequency (HF) radar are assessed by comparing these data to near-surface current observations from 1 to 30 October 1994 at two moored subsurface current meter arrays (20 and 25 m) instrumented with vector-measuring current meters (VMCMs) and Seacat sensors during the Duck94 experiment. A dual-station ocean surface current radar (OSCR) mapped the current fields at

  7. Radar investigation of barium releases over Arecibo Observatory, Puerto Rico

    NASA Technical Reports Server (NTRS)

    Djuth, Frank T.

    1995-01-01

    The NASA Combined Release and Radiation Effects Satellite (CRRES) El Coqui rocket campaign was successfully carried out in Puerto Rico during the period 18 May through 12 July 1992. This report describes five chemical release experiments in the upper ionosphere supported by Geospace Research, Inc. during the El Coqui campaign. Additional spin-off science is also discussed. The El Coqui releases are designated AA-1 (rocket 36-082), AA-2 (rocket 36-081), AA-3b (rocket 36-064), AA-4 (rocket 36-065), and AA-7 (rocket 36-083). Particular attention is paid to releases AA-2 and AA-4. These two experiments involved the illumination of ionospheric release regions with powerful high-frequency (HF) radio waves transmitted from the Arecibo HF facility. In the AA-2 experiment, microinstabilities excited by the HF wave in a Ba(+) plasma were examined. This release yielded a smooth plasma cloud that helped clarify several fundamental issues regarding the physics of wave plasma instabilities. During AA-2 extremely strong HF-induced Langmuir turbulence was detected with the Arecibo 430 MHz radar. CF3Br was released in the AA-4 study to create an ionospheric hole that focused the HF beam. This experiment successfully explored wave-plasma coupling in an O(+) ionosphere under conditions of very high HF electric field strengths.

  8. Pulse compression hardware decoding techniques for MST radars

    Microsoft Academic Search

    M. P. Sulzer; R. F. Woodman

    1985-01-01

    The techniques for decoding in hardware received signals transmitted by phase-coded mesospherestratosphere-troposphere (MST) radars are reviewed. The designs consist of digital and analog types which resemble filters or correlators in their operation. A new analog design is presented, and a discussion of the choice between hardware and software decoding is given. The number of bits required for digital coherent integrators

  9. Radar Range Sidelobe Reduction Using Adaptive Pulse Compression Technique

    NASA Technical Reports Server (NTRS)

    Li, Lihua; Coon, Michael; McLinden, Matthew

    2013-01-01

    Pulse compression has been widely used in radars so that low-power, long RF pulses can be transmitted, rather than a highpower short pulse. Pulse compression radars offer a number of advantages over high-power short pulsed radars, such as no need of high-power RF circuitry, no need of high-voltage electronics, compact size and light weight, better range resolution, and better reliability. However, range sidelobe associated with pulse compression has prevented the use of this technique on spaceborne radars since surface returns detected by range sidelobes may mask the returns from a nearby weak cloud or precipitation particles. Research on adaptive pulse compression was carried out utilizing a field-programmable gate array (FPGA) waveform generation board and a radar transceiver simulator. The results have shown significant improvements in pulse compression sidelobe performance. Microwave and millimeter-wave radars present many technological challenges for Earth and planetary science applications. The traditional tube-based radars use high-voltage power supply/modulators and high-power RF transmitters; therefore, these radars usually have large size, heavy weight, and reliability issues for space and airborne platforms. Pulse compression technology has provided a path toward meeting many of these radar challenges. Recent advances in digital waveform generation, digital receivers, and solid-state power amplifiers have opened a new era for applying pulse compression to the development of compact and high-performance airborne and spaceborne remote sensing radars. The primary objective of this innovative effort is to develop and test a new pulse compression technique to achieve ultrarange sidelobes so that this technique can be applied to spaceborne, airborne, and ground-based remote sensing radars to meet future science requirements. By using digital waveform generation, digital receiver, and solid-state power amplifier technologies, this improved pulse compression technique could bring significant impact on future radar development. The novel feature of this innovation is the non-linear FM (NLFM) waveform design. The traditional linear FM has the limit (-20 log BT -3 dB) for achieving ultra-low-range sidelobe in pulse compression. For this study, a different combination of 20- or 40-microsecond chirp pulse width and 2- or 4-MHz chirp bandwidth was used. These are typical operational parameters for airborne or spaceborne weather radars. The NLFM waveform design was then implemented on a FPGA board to generate a real chirp signal, which was then sent to the radar transceiver simulator. The final results have shown significant improvement on sidelobe performance compared to that obtained using a traditional linear FM chirp.

  10. Geostatistical analysis of ground-penetrating radar data: A means of describing spatial variation in the subsurface

    Microsoft Academic Search

    Jane Rea; Rosemary Knight

    1998-01-01

    We have investigated the use of ground-penetrating radar (GFR) as a means of characterizing the heterogeneity of the subsurface. Radar data were collected at several sites in southwestern British Columbia underlain by glaciodeltaic sediments. A cliff face study was conducted in which geostatistical analysis of a digitized photograph of the face and the radar image of the face showed excellent

  11. Radar images analysis for scattering surfaces characterization

    NASA Astrophysics Data System (ADS)

    Piazza, Enrico

    1998-10-01

    According to the different problems and techniques related to the detection and recognition of airplanes and vehicles moving on the Airport surface, the present work mainly deals with the processing of images gathered by a high-resolution radar sensor. The radar images used to test the investigated algorithms are relative to sequence of images obtained in some field experiments carried out by the Electronic Engineering Department of the University of Florence. The radar is the Ka band radar operating in the'Leonardo da Vinci' Airport in Fiumicino (Rome). The images obtained from the radar scan converter are digitized and putted in x, y, (pixel) co- ordinates. For a correct matching of the images, these are corrected in true geometrical co-ordinates (meters) on the basis of fixed points on an airport map. Correlating the airplane 2-D multipoint template with actual radar images, the value of the signal in the points involved in the template can be extracted. Results for a lot of observation show a typical response for the main section of the fuselage and the wings. For the fuselage, the back-scattered echo is low at the prow, became larger near the center on the aircraft and than it decrease again toward the tail. For the wings the signal is growing with a pretty regular slope from the fuselage to the tips, where the signal is the strongest.

  12. Ultrawideband radar clutter measurements of forested terrain, 1991--1992

    SciTech Connect

    Sheen, D.M.; Severtsen, R.H.; Prince, J.M.; Davis, K.C.; Collins, H.D.

    1993-06-01

    The ultrawideband (UWB) radar clutter measurements project was conducted to provide radar clutter data for new ultrawideband radar systems which are currently under development. A particular goal of this project is to determine if conventional narrow band clutter data may be extrapolated to the UWB case. This report documents measurements conducted in 1991 and additional measurements conducted in 1992. The original project consisted of clutter measurements of forested terrain in the Olympic National Forest near Sequim, WA. The impulse radar system used a 30 kW peak impulse source with a 2 Gigasample/second digitizer to form a UHF (300--1000 MHz) ultrawideband impulse radar system. Additional measurements were conducted in parallel using a Systems Planning Corporation (SPC) step-chirp radar system. This system utilized pulse widths of 1330 nanoseconds over a bandwidth of 300--1000 MHz to obtain similar resolution to the impulse system. Due to the slow digitizer data throughput in the impulse radar system, data collection rates were significantly higher using the step-chirp system. Additional forest clutter measurements were undertaken in 1992 to increase the amount of data available, and especially to increase the amount of data from the impulse radar system.

  13. Imaging Radar Applications in the Death Valley Region

    NASA Technical Reports Server (NTRS)

    Farr, Tom G.

    1996-01-01

    Death Valley has had a long history as a testbed for remote sensing techniques (Gillespie, this conference). Along with visible-near infrared and thermal IR sensors, imaging radars have flown and orbited over the valley since the 1970's, yielding new insights into the geologic applications of that technology. More recently, radar interferometry has been used to derive digital topographic maps of the area, supplementing the USGS 7.5' digital quadrangles currently available for nearly the entire area. As for their shorter-wavelength brethren, imaging radars were tested early in their civilian history in Death Valley because it has a variety of surface types in a small area without the confounding effects of vegetation. In one of the classic references of these early radar studies, in a semi-quantitative way the response of an imaging radar to surface roughness near the radar wavelength, which typically ranges from about 1 cm to 1 m was explained. This laid the groundwork for applications of airborne and spaceborne radars to geologic problems in and regions. Radar's main advantages over other sensors stems from its active nature- supplying its own illumination makes it independent of solar illumination and it can also control the imaging geometry more accurately. Finally, its long wavelength allows it to peer through clouds, eliminating some of the problems of optical sensors, especially in perennially cloudy and polar areas.

  14. Remorque RADAR Description technique

    E-print Network

    Heurteaux, Yanick

    ANNEXE: Remorque RADAR Description technique Le but de la remorque est de transporter un RADAR et pour héberger l'électronique radar et son opérateur. Caractéristiques générales de la remorque : · PTC'un côté, une baie de l'autre. Un hublot sur le toit et une baie donnant sur la partie RADAR. Un plafonnier

  15. UWB RADAR Receiver Architecture

    Microsoft Academic Search

    Nuno Paulino; Adolfo Steiger Garção; João Goes

    this chapter describes the operation of a radar system. The differences and advantages of using UWB signals in the radar system,\\u000a over traditional narrow band signals, are discussed. The radar equation, usually defined for narrow band signals, is redefined\\u000a for UWB signals. This new radar equation is used to analyze the echo signals from targets with basic shapes, resulting in

  16. Cassini Titan Radar Mapper

    Microsoft Academic Search

    CHARLES ELACHI; E. Im; L. E. Roth; C. L. Werner

    1991-01-01

    The Cassini Titan Radar Mapper is a multimode radar instrument designed to probe the optically inaccessible surface of Titan, Saturn's largest moon. The instrument is to be included in the payload of the Cassini Saturn Mission, scheduled for launch in 1995. The individual modes of Cassini Radar Mapper will allow topographic mapping and surface imaging at few hundred meters resolution.

  17. Lunar radar backscatter studies

    NASA Technical Reports Server (NTRS)

    Thompson, T. W.

    1979-01-01

    The lunar surface material in the Plato area is characterized using Earth based visual, infrared, and radar signatures. Radar scattering in the lunar regolith with an existing optical scattering computer program is modeled. Mapping with 1 to 2 km resolution of the Moon using a 70 cm Arecibo radar is presented.

  18. High power HF modification: Geophysics

    NASA Astrophysics Data System (ADS)

    Carlson, Herbert C., Jr.

    1990-10-01

    As the electric field and power density of radio frequency (RF) radiation increases continuously in a plasma, the response of the plasma to the incident energy changes discontinuously. This follows from a complex of competing physical processes, each generally with its own power dependent threshold, and plasma instabilities each with its own growth and decay rate. Nonlinear power dependencies, boundary condition dependencies on past histories of the plasma conditions, dependence on proximity to plasma resonances, and nonlinear mixing in the plasma to up and down convert with respect to resonances, all conspire to make experimental guidance invaluable to theoretical development. The experiment ahs demonstrated that with increasing HF power one passes the threshold of detectability sequentially from: passive transmission, to cross-modulation, to thermal bulk heating, to parametric and other instabilities with plasma structuring and stimulated electromagnetic radiation, to electron acceleration and airglow, to reported stimulated ionization. The RF propagation and emission environment is affected through the VLF to GHz range by lensing, scattering, modulation, and simulated emission. The optical background and emission character is affected over a very wide spectrum by electron impact and temperature enhancement altering translational, rotational and vibrational temperatures (as well as raising fine structure population distribution questions). A set of geophysical effects are address over this range, and participation is invited in anticipation of what effects lie beyond the next threshold (of ionospheric response to higher HF illumination). The exciting upgrade of the Heater at Tromso and emerging new HF modifier plans in the U.S. are partial motivation for such conjecture.

  19. Observation and Simulation of Small Earthquake Tsunami in Okinawa by Using Ocean Radar

    NASA Astrophysics Data System (ADS)

    Takahashi, T.; Konuma, T.; Kojima, S.

    2008-12-01

    The present tsunami warning systems use seismic waves to detect tsunamis. To upgrade the systems, new detecting method by using the ocean radar has been studied. NiCT has observed an ocean current in Okinawa with the HF ocean radar installed in Ishigaki Island and Yonaguni Island. A small earthquake of Mw 6.0 occurred in the observing region on April 4, 2007 and generated a very weak tsunami. In this study, the Doppler spectrums of the ocean radar data and the simulated tsunami propagation are computed and compared.

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

    NASA Astrophysics Data System (ADS)

    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.

  1. Evaluating radial component current measurements from CODAR high frequency radars and moored in situ current meters

    E-print Network

    California at Santa Barbara, University of

    near Pt. Sal (FBK), Pt. Arguello (ARG), Pt. Conception (PTC), Refugio Beach (RFG), and Coal Oil Point, and up to ~9o differences in flow directions. 1. INTRODUCTION We installed the first HF radar at Coal Oil a simple flow field and measured bearing errors, showing up to 15% differences in computed flow speeds

  2. Radar Meteorology Tutorial

    NSDL National Science Digital Library

    McNoldy, Brian

    Brian McNoldy at Multi-community Environmental Storm Observatory (MESO) educates the public about the use of radar in meteorology in this pdf document. After reading about the history of radar, visitors can find out how radar can detect storms by transmitting a high-power beam of radiation. Students can learn how scatter, absorption, frequencies, scan angles, and moments impact the radar display. With the help of many example images, the author also discusses how to interpret the images collected. At the end of the online document, visitors can learn about the characteristics and capabilities of NEXRAD WSR-88D, the radar used throughout the United States.

  3. Design and simulation of a scatterometer processor using digital filtering techniques

    E-print Network

    Galka, Walter

    1975-01-01

    -Chairmen of Advisory Committee: Dr. John W. Rouse, Jr. Dr. Jo W. Howze This report describes two digital filtering methods by which scatterometer data can be reprocessed. The processors are designed to operate on sampled data from a Doppler radar scatterometer... The Radar Scatterometer. Scope of this Report II. THE RYAN 13. 3 GHz DOPPLER RADAR SCATTEROMERER. 7 The Doppler Scatterometer. The Analog Processor The Digital Processor. III. DIGITAL FILTER DESIGN. Introduction The K-Transform. 13 19 24 24 26...

  4. Magellan - Radar performance and data products

    NASA Astrophysics Data System (ADS)

    Pettengill, Gordon H.; Ford, Peter G.; Johnson, William T. K.; Raney, R. Keith; Soderblom, Laurence A.

    1991-04-01

    The Magellan Venus orbiter carries only one scientific instrument: a 12.6-centimeter-wavelength radar system shared among three data-taking modes. The synthetic-aperture mode images radar echoes from the Venus surface at a resolution of between 120 and 300 meters, depending on spacecraft altitude. In the altimetric mode, relative height measurement accuracies may approach 5 meters, depending on the terrain's roughness, although orbital uncertainties place a floor of about 50 meters on the absolute uncertainty. In areas of extremely rough topography, accuracy is limited by the inherent line-of-sight radar resolution of about 88 meters. The maximum elevation observed to date, corresponding to a planetary radius of 6062 kilometers, lies within Maxwell Mons. When used as a thermal emission radiometer, the system can determine surface emissivities to an absolute accuracy of about 0.02. Mosaicked and archival digital data products will be released in compact disk (CDROM) format.

  5. The Apollo Lunar Sounder radar system

    NASA Technical Reports Server (NTRS)

    Porcello, L. J.; Zelenka, J. S.; Adams, G. F.; Jackson, P. L.; Jordan, R. L.; Phillips, R. J.; Brown, W. E., Jr.; Ward, S. H.

    1974-01-01

    The objectives of the Apollo 17 Lunar Sounder Experiment (ALSE) were to detect subsurface geologic structures, to generate a continuous lunar profile, and to image the moon at radar wavelengths. A three-wavelength synthetic-aperture radar (SAR) operating at 60, 20, and 2 m wavelengths was designed to attain these objectives. The design choices reflected a balance of scientific requirements versus Apollo mission and hardware constraints. The radar data from the lunar mission were recorded on photographic film in a conventional SAR format, and were returned to earth for processing. A combination of optical and digital processing and exploitation techniques was applied to the scientific interpretation of the data. Some preliminary results from the lunar mission have been obtained.

  6. A transceiver module of the Mu radar

    NASA Technical Reports Server (NTRS)

    Kato, S.; Ogawa, T.; Tsuda, T.; Sato, T.; Kimura, I.; Fukao, S.

    1983-01-01

    The transceiver (TR) module of a middle and upper atmospheric radar is described. The TR module used in the radar is mainly composed of two units: a mixer (MIX unit) and a power amplifier (PA unit). The former generates the RF wave for transmission and converts the received echo to the IF signal. A 41.5-MHz local signal fed to mixers passes through a digitally controlled 8-bit phase shifter which can change its value up to 1,000 times in a second, so that the MU radar has the ability to steer its antenna direction quickly and flexibly. The MIX unit also contains a buffer amplifier and a gate for the transmitting signal and preamplifier for the received one whose noise figure is less than 5 dB. The PA unit amplifies the RF signal supplied from the MIX unit up to 63.7 dBm (2350 W), and feeds it to the crossed Yagi antenna.

  7. Magellan: Radar performance and data products

    USGS Publications Warehouse

    Pettengill, G.H.; Ford, P.G.; Johnson, W.T.K.; Raney, R.K.; Soderblom, L.A.

    1991-01-01

    The Magellan Venus orbiter carries only one scientific instrument: a 12.6-centimeter-wavelength radar system shared among three data-taking modes. The syntheticaperture mode images radar echoes from the Venus surface at a resolution of between 120 and 300 meters, depending on spacecraft altitude. In the altimetric mode, relative height measurement accuracies may approach 5 meters, depending on the terrain's roughness, although orbital uncertainties place a floor of about 50 meters on the absolute uncertainty. In areas of extremely rough topography, accuracy is limited by the inherent line-of-sight radar resolution of about 88 meters. The maximum elevation observed to date, corresponding to a planetary radius of 6062 kilometers, lies within Maxwell Mons. When used as a thermal emission radiometer, the system can determine surface emissivities to an absolute accuracy of about 0.02. Mosaicked and archival digital data products will be released in compact disk (CDROM) format.

  8. space Radar Image of Long Valley, California

    NASA Technical Reports Server (NTRS)

    1994-01-01

    An area near Long Valley, California, was mapped by the Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar aboard the space shuttle Endeavor on April 13, 1994, during the first flight of the radar instrument, and on October 4, 1994, during the second flight of the radar instrument. The orbital configurations of the two data sets were ideal for interferometric combination -- that is overlaying the data from one image onto a second image of the same area to create an elevation map and obtain estimates of topography. Once the topography is known, any radar-induced distortions can be removed and the radar data can be geometrically projected directly onto a standard map grid for use in a geographical information system. The 50 kilometer by 50 kilometer (31 miles by 31 miles) map shown here is entirely derived from SIR-C L-band radar (horizontally transmitted and received) results. The color shown in this image is produced from the interferometrically determined elevations, while the brightness is determined by the radar backscatter. The map is in Universal Transverse Mercator (UTM) coordinates. Elevation contour lines are shown every 50 meters (164 feet). Crowley Lake is the dark feature near the south edge of the map. The Adobe Valley in the north and the Long Valley in the south are separated by the Glass Mountain Ridge, which runs through the center of the image. The height accuracy of the interferometrically derived digital elevation model is estimated to be 20 meters (66 feet) in this image. Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves, allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3 cm). The multi-frequency data will be used by the international scientific community to better understand the global environment and how it is changing. The SIR-C/X-SAR data, complemented by aircraft and ground studies, will give scientists clearer insights into those environmental changes which are caused by nature and those changes which are induced by human activity. SIR-C was developed by NASA's Jet Propulsion Laboratory. X-SAR was developed by the Dornier and Alenia Spazio companies for the German space agency, Deutsche Agentur fuer Raumfahrtangelegenheiten (DARA), and the Italian space agency, Agenzia Spaziale Italiana (ASI), with the Deutsche Forschungsanstalt fuer Luft und Raumfahrt e.V.(DLR), the major partner in science, operations and data processing of X-SAR.

  9. THE 1988 YELLOWSTONE FIRES OBSERVED BY IMAGING RADARS

    Microsoft Academic Search

    Eric Rignot; Don G. Despain; Francesco Holecz

    In 1988, nearly half a million hectares of forest burned in the Greater Yellowstone Area. Six years later, the burned areas were still visible in the dual-polarization radar images acquired by the Spaceborne Imaging Radar C (SIR-C) at both C- (5.6 cm wavelength) and L-band (24 cm) frequency. The data were georeferenced, rectified and calibrated using a digital topographic model

  10. HF Radio Wave Propagation in the Ionosphere Observed with the ePOP RRI (Radio Receiver Instrument) -- SuperDARN Experiment

    NASA Astrophysics Data System (ADS)

    Hussey, G. C.; Gillies, R. G.; Ridley, C. G.; Yau, A. W.; McWilliams, K. A.; Sofko, G. J.

    2014-12-01

    The Radio Receiver Instrument (RRI) on the enhanced Polar Outflow Probe (ePOP) scientific payload of the recently launched CSA (Canadian Space Agency) CASSIOPE (Cascade Demonstrator Small-Sat and Ionospheric Polar Explorer) satellite mission and the Super Dual Auroral Radar Network (SuperDARN) of HF radars have successfully executed a number of experiments since the launch of ePOP in late September, 2013. This presentation investigates the propagation delays and timing associated with HF radio waves transversing the plasma in the terrestrial ionosphere. Both the relative and absolute timing of the co-ordinated SuperDARN-RRI experiments will be presented. This knowledge is essential for interpreting HF radio wave propagation effects such as range accuracy, mode-splitting and timing, Doppler shift, and delayed 'echo' signatures, for example.

  11. Haloviruses HF1 and HF2: evidence for a recent and large recombination event.

    PubMed

    Tang, Sen-Lin; Nuttall, Stewart; Dyall-Smith, Mike

    2004-05-01

    Haloviruses HF1 and HF2 were isolated from the same saltern pond and are adapted to hypersaline conditions, where they infect a broad range of haloarchaeal species. The HF2 genome has previously been reported. The complete sequence of the HF1 genome has now been determined, mainly by PCR and primer walking. It was 75,898 bp in length and was 94.4% identical to the HF2 genome but about 1.8 kb shorter. A total of 117 open reading frames and five tRNA-like genes were predicted, and their database matches and characteristics were similar to those found in HF2. A comparison of the predicted restriction digest patterns based on nucleotide sequence with the observed restriction digest patterns of viral DNA showed that, unlike the case for HF2, some packaged HF1 DNA had cohesive termini. Except for a single base change, HF1 and HF2 were identical in sequence over the first 48 kb, a region that includes the early and middle genes. The remaining 28 kb of HF1 showed many differences from HF2, and the similarity of the two genomes over this late gene region was 87%. The abrupt shift in sequence similarity around 48 kb suggests a recent recombination event between either HF1 or HF2 and another HF-like halovirus that has swapped most of the right-end 28 kb. This example indicates there is a high level of recombination among viruses that live in this extreme environment. PMID:15090523

  12. Haloviruses HF1 and HF2: Evidence for a Recent and Large Recombination Event

    PubMed Central

    Tang, Sen-Lin; Nuttall, Stewart; Dyall-Smith, Mike

    2004-01-01

    Haloviruses HF1 and HF2 were isolated from the same saltern pond and are adapted to hypersaline conditions, where they infect a broad range of haloarchaeal species. The HF2 genome has previously been reported. The complete sequence of the HF1 genome has now been determined, mainly by PCR and primer walking. It was 75,898 bp in length and was 94.4% identical to the HF2 genome but about 1.8 kb shorter. A total of 117 open reading frames and five tRNA-like genes were predicted, and their database matches and characteristics were similar to those found in HF2. A comparison of the predicted restriction digest patterns based on nucleotide sequence with the observed restriction digest patterns of viral DNA showed that, unlike the case for HF2, some packaged HF1 DNA had cohesive termini. Except for a single base change, HF1 and HF2 were identical in sequence over the first 48 kb, a region that includes the early and middle genes. The remaining 28 kb of HF1 showed many differences from HF2, and the similarity of the two genomes over this late gene region was 87%. The abrupt shift in sequence similarity around 48 kb suggests a recent recombination event between either HF1 or HF2 and another HF-like halovirus that has swapped most of the right-end 28 kb. This example indicates there is a high level of recombination among viruses that live in this extreme environment. PMID:15090523

  13. An update on the multi-channel phased array Weather Radar at the National Weather Radar Testbed

    Microsoft Academic Search

    M. Yeary; G. Crain; A. Zahrai; R. Kelley; J. Meier; Y. Zhang; I. Ivic; C. Curtis; R. Palmer; T.-Y. Yu; R. Doviak

    2011-01-01

    The first phased array radar dedicated to weather observation and analysis is now instrumented with eight, simultaneous digital receivers. The multi-channel receiver will collect signals from the sum, azimuth-difference, elevation- difference, and five broad-beamed auxiliary channels. The multi-channel receiver will allow the direct implementation of interferometry techniques to estimate crossbeam wind, shear and turbulence within a radar resolution volume. Access

  14. Dependence of spectral width of polar cap HF echoes upon electric field

    NASA Astrophysics Data System (ADS)

    Koustov, A. V.; Shalimov, S.; Kozlovsky, A.

    2010-12-01

    The EISCAT Svalbard Radar (ESR) monitors plasma parameters in the ionospheric region that is frequently located near the polar cap boundary. The SuperDARN radar at Hankasalmi, Finland detects coherent echoes from this region and these echoes typically show increased spectral width. We consider data of joint ESR and SuperDARN observations to show that the spectral width of HF echoes tends to increase with the electric field. This relationship is explained in terms of non-linear evolution of the ExB gradient drift instability with energy cascade from hundred of meters wavelengths to meter wavelengths. We assume that non-linearly generated, relatively strong decameter waves (seen by the Hankasalmi radar) decay through three-wave interaction with shorter wavelengths and estimate that the decameter waves/irregularities decay time is determined by the parameters of the shorter wavelength structures. We associate the decameter wave decay time with the correlation time, and thus the spectral width, of HF echoes.

  15. Dependence of spectral width of ionospheric F region HF echoes on electric field

    NASA Astrophysics Data System (ADS)

    Kozlovsky, A.; Shalimov, S.; Koustov, A. V.; Lukianova, R.; Turunen, T.

    2011-07-01

    The EISCAT Svalbard radar (ESR) monitors plasma parameters in the ionospheric region that is frequently located near the polar cap boundary. The SuperDARN radar at Hankasalmi, Finland, detects coherent echoes from this region, and these echoes typically show increased spectral width. We consider data of joint ESR and SuperDARN observations to show that the spectral width of HF echoes tends to increase with the ionospheric electric field. This relationship is explained in terms of nonlinear evolution of the E × B gradient drift instability with energy cascade from hundreds of meter wavelengths to meter wavelengths. We assume that decameter waves (seen by the Hankasalmi radar) with relatively large amplitude decay through a three-wave interaction with shorter wavelengths and estimate that the decay time of the decameter waves/irregularities is determined by the parameters of the shorter-wavelength structures. We associate the decameter wave decay time with the correlation time, and thus the spectral width, of HF echoes.

  16. Do you have a radar bill in your pocket?

    NSDL National Science Digital Library

    National Council of Teachers of Mathematics (NCTM)

    2002-01-01

    This activity introduces students to radar bills (currency that has serial numbers that read the same forward and backward) and challenges them to estimate how frequently radar bills occur. The activity, part of the Figure This! collection of 80 math challenges emphasizing math in the real world, explains how symmetry and repeating patterns are important to mathematicians, scientists, and artists. The Hint tells students that our currency has eight-digit serial numbers, and the solution provides a table that shows the relationship between the number of digits in a serial number and the number of radar bills. Related questions ask students to solve similar problems with serial numbers that contain different numbers of digits. Answers to all questions and links to additional resources are provided. Copyright 2005 Eisenhower National Clearinghouse

  17. Optical and ionospheric phenomena at EISCAT under continuous X-mode HF pumping

    NASA Astrophysics Data System (ADS)

    Blagoveshchenskaya, N. F.; Borisova, T. D.; Kosch, M.; Sergienko, T.; Brändström, U.; Yeoman, T. K.; Häggström, I.

    2014-12-01

    We present experimental results from multiinstrument observations in the high-latitude ionospheric F2 layer at the EISCAT (European Incoherent Scatter Scientific Association) heating facility. The results come from a set of experiments, when an X-polarized HF pump wave at high heater frequencies (fH > 6.0 MHz) was injected into the F region of the ionosphere toward the magnetic zenith. Experiments were carried out under quiet magnetic conditions with an effective radiated power of 458-548 MW. HF pumping was produced at different heater frequencies, away from electron gyroharmonic frequencies, and different durations of heater pulses. We show the first experimental evidence of the excitation of artificial optical emissions at red (630 nm) and green (557.7 nm) lines in the high-latitude ionospheric F2 layer induced by an X-polarized HF pump wave. Intensities at red and green lines varied in the range 110-950 R and 50-350 R, respectively, with a ratio of green to red line of 0.35-0.5. The results of optical observations are compared with behaviors of the HF-enhanced ion and plasma lines from EISCAT UHF incoherent scatter radar data and small-scale field-aligned artificial irregularities from Cooperative UK Twin Located Auroral Sounding System observations. It was found that the X-mode radio-induced optical emissions coexisted with HF-enhanced ion and plasma lines and strong artificial field-aligned irregularities throughout the whole heater pulse. It is indicative that parametric decay or oscillating two-stream instabilities were not quenched by fully established small-scale field-aligned artificial irregularities excited by an X-mode HF pump wave.

  18. Multistatic radar systems signal processing

    Microsoft Academic Search

    I. Bradaric; G. T. Capraro; D. D. Weiner; M. C. Wicks

    2006-01-01

    In this paper, a multistatic radar system with multiple receivers and one transmitter is analyzed. We address the rules for selecting the weights for fusing multiple receivers in order to meet pre-specified performance goals. A multistatic radar ambiguity function is used to relate different radar performance measures to system parameters such as radar geometry and radar waveforms. Simulations are used

  19. Rendezvous radar for the orbital maneuvering vehicle

    NASA Technical Reports Server (NTRS)

    Locke, John W.; Olds, Keith; Parks, Howard

    1991-01-01

    This paper describes the development of the Rendezvous Radar Set (RRS) for the Orbital Maneuvering Vehicle (OMV) for the National Aeronautics and Space Administration (NASA). The RRS was to be used to locate, and then provide vectoring information to, target satellites (or Shuttle or Space Station) to aid the OMV in making a minimum-fuel-consumption approach and rendezvous. The RRS design is that of an X-Band, all solid-state, monopulse tracking, frequency hopping, pulse-Doppler radar system. The development of the radar was terminated when the OMV prime contract to TRW was terminated by NASA. At the time of the termination, the development was in the circuit design stage. The system design was virtually completed, the PDR had been held. The RRS design was based on Motorola's experiences, both in the design and production of radar systems for the US Army and in the design and production of hi-rel communications systems for NASA space programs. Experience in these fields was combined with the latest digital signal processor and micro-processor technology to design a light-weight, low-power, spaceborne radar. The antenna and antenna positioner (gimbals) technology developed for the RRS is now being used in the satellite-to-satellite communication link design for Motorola's Iridium telecommunications system.

  20. Rendezvous radar for the orbital maneuvering vehicle

    NASA Astrophysics Data System (ADS)

    Locke, John W.; Olds, Keith; Parks, Howard

    This paper describes the development of the Rendezvous Radar Set (RRS) for the Orbital Maneuvering Vehicle (OMV) for the National Aeronautics and Space Administration (NASA). The RRS was to be used to locate, and then provide vectoring information to, target satellites (or Shuttle or Space Station) to aid the OMV in making a minimum-fuel-consumption approach and rendezvous. The RRS design is that of an X-Band, all solid-state, monopulse tracking, frequency hopping, pulse-Doppler radar system. The development of the radar was terminated when the OMV prime contract to TRW was terminated by NASA. At the time of the termination, the development was in the circuit design stage. The system design was virtually completed, the PDR had been held. The RRS design was based on Motorola's experiences, both in the design and production of radar systems for the US Army and in the design and production of hi-rel communications systems for NASA space programs. Experience in these fields was combined with the latest digital signal processor and micro-processor technology to design a light-weight, low-power, spaceborne radar. The antenna and antenna positioner (gimbals) technology developed for the RRS is now being used in the satellite-to-satellite communication link design for Motorola's Iridium telecommunications system.

  1. RFI suppression for ultra wideband radar

    Microsoft Academic Search

    T. Miller; L. Potter; J. McCorkle

    1997-01-01

    An estimate-and-subtract algorithm is presented for the real-time digital suppression of radio frequency interference (RFI) in ultrawideband (UWB) synthetic aperture radar (SAR) systems used for foliage- and ground-penetrating imaging. The algorithm separately processes fixed- and variable-frequency interferers. Excision of estimated targets greatly reduces bias in RFI estimates, thereby reducing target energy loss and sidelobe levels in SAR imagery. Performance is

  2. A fully photonics-based coherent radar system.

    PubMed

    Ghelfi, Paolo; Laghezza, Francesco; Scotti, Filippo; Serafino, Giovanni; Capria, Amerigo; Pinna, Sergio; Onori, Daniel; Porzi, Claudio; Scaffardi, Mirco; Malacarne, Antonio; Vercesi, Valeria; Lazzeri, Emma; Berizzi, Fabrizio; Bogoni, Antonella

    2014-03-20

    The next generation of radar (radio detection and ranging) systems needs to be based on software-defined radio to adapt to variable environments, with higher carrier frequencies for smaller antennas and broadened bandwidth for increased resolution. Today's digital microwave components (synthesizers and analogue-to-digital converters) suffer from limited bandwidth with high noise at increasing frequencies, so that fully digital radar systems can work up to only a few gigahertz, and noisy analogue up- and downconversions are necessary for higher frequencies. In contrast, photonics provide high precision and ultrawide bandwidth, allowing both the flexible generation of extremely stable radio-frequency signals with arbitrary waveforms up to millimetre waves, and the detection of such signals and their precise direct digitization without downconversion. Until now, the photonics-based generation and detection of radio-frequency signals have been studied separately and have not been tested in a radar system. Here we present the development and the field trial results of a fully photonics-based coherent radar demonstrator carried out within the project PHODIR. The proposed architecture exploits a single pulsed laser for generating tunable radar signals and receiving their echoes, avoiding radio-frequency up- and downconversion and guaranteeing both the software-defined approach and high resolution. Its performance exceeds state-of-the-art electronics at carrier frequencies above two gigahertz, and the detection of non-cooperating aeroplanes confirms the effectiveness and expected precision of the system. PMID:24646997

  3. Apollo experience report: Lunar module landing radar and rendezvous radar

    NASA Technical Reports Server (NTRS)

    Rozas, P.; Cunningham, A. R.

    1972-01-01

    A developmental history of the Apollo lunar module landing and rendezvous radar subsystems is presented. The Apollo radar subsystems are discussed from initial concept planning to flight configuration testing. The major radar subsystem accomplishments and problems are discussed.

  4. MIMO radar, SIMO radar, and IFIR radar: a P. P. Vaidyanathan and Piya Pal

    E-print Network

    Vaidyanathan, P. P.

    MIMO radar, SIMO radar, and IFIR radar: a comparison P. P. Vaidyanathan and Piya Pal Dept and SIMO radar systems for the case where the transmitter and receiver are collocated. The simplicity of the application allows one to see clearly where the advantages of MIMO radar come from, and what the tradeoffs are

  5. Radar performance improvement

    Microsoft Academic Search

    G. R. Little

    1976-01-01

    The AN\\/APQ-153 fire control radar modified to provide angle tracking was evaluated for improved performance. The frequency agile modifications are discussed along with the range-rate improvement modifications, and the radar to computer interface. A parametric design and comparison of noncoherent and coherent radar systems are presented. It is shown that the shuttle rendezvous range and range-rate requirements can be made

  6. Caribbean Radar Cases

    NSDL National Science Digital Library

    2014-09-14

    This module presents radar case studies taken from events in the Caribbean that highlight radar signatures of severe weather. These cases include examples of deep convection, squall lines, bow echoes, tornadoes, and heavy rain resulting in flooding. Each case study includes a discussion of the conceptual models of each type of event as a review before showing the radar signatures and allowing the learner to analyze each one.

  7. Performance of CSMA and TDMA protocols for break-in channel access in a frequency hopping (FH) narrowband high frequency (HF) blocked channel environment

    Microsoft Academic Search

    Y. Hong; D. Miller

    1993-01-01

    Military systems often require multiple communication mode capabilities, such as teletype, facsimile, digital data, and digital voice, as well as some network layer functions such as break-in and late network entry. Channel assignment for these network layer functions, called service functions, is strictly an overhead from a communication point of view. In a narrowband (3 kHz) high frequency (HF) channel

  8. Improved HF183 Quantitative Real-Time PCR Assay for Characterization of Human Fecal Pollution in Ambient Surface Water Samples

    PubMed Central

    Green, Hyatt C.; Haugland, Richard A.; Varma, Manju; Millen, Hana T.; Borchardt, Mark A.; Field, Katharine G.; Walters, William A.; Knight, R.; Sivaganesan, Mano; Kelty, Catherine A.

    2014-01-01

    Quantitative real-time PCR (qPCR) assays that target the human-associated HF183 bacterial cluster within members of the genus Bacteroides are among the most widely used methods for the characterization of human fecal pollution in ambient surface waters. In this study, we show that a current TaqMan HF183 qPCR assay (HF183/BFDrev) routinely forms nonspecific amplification products and introduce a modified TaqMan assay (HF183/BacR287) that alleviates this problem. The performance of each qPCR assay was compared in head-to-head experiments investigating limits of detection, analytical precision, predicted hybridization to 16S rRNA gene sequences from a reference database, and relative marker concentrations in fecal and sewage samples. The performance of the modified HF183/BacR287 assay is equal to or improves upon that of the original HF183/BFDrev assay. In addition, a qPCR chemistry designed to combat amplification inhibition and a multiplexed internal amplification control are included. In light of the expanding use of PCR-based methods that rely on the detection of extremely low concentrations of DNA template, such as qPCR and digital PCR, the new TaqMan HF183/BacR287 assay should provide more accurate estimations of human-derived fecal contaminants in ambient surface waters. PMID:24610857

  9. Accuracy and resolution of shuttle radar topography mission data Bridget Smith and David Sandwell

    E-print Network

    Sandwell, David T.

    ascending and descending C-band swaths from the Shuttle interferometer were processed into a digitalAccuracy and resolution of shuttle radar topography mission data Bridget Smith and David Sandwell provided by the Shuttle Radar Topography Mission (SRTM) through spectral comparisons with the National

  10. The Design of a High Performance MMW Radar System for Autonomous Land Vehicle Navigation

    Microsoft Academic Search

    S. Clark; H. Durrant Whyte

    This paper describes the design of a high performance 77GHz millimetre wave radar, signal processing and control system for use in autonomous vehicle navigation. The radar front end and intermediate frequency components are described together with a method of distinguishing pre-placed target beacons from other reflectors using the polarisation of the reflected signal. Digital signal processing hardware is described which

  11. A New Implementation of the Mellin Transform and its Application to Radar Classification of Ships

    Microsoft Academic Search

    Philip E. Zwicke; Imre Kiss

    1983-01-01

    A modified Mellin transform for digital implementation is developed and applied to range radar profiles of naval vessels. The scale invariance property of the Mellin transform provides a means for extracting features from the profiles which are insensitive to the aspect angle of the radar. Past implementations of the Mellin transform based on the FFT have required exponential sampling, interpolation,

  12. Equatorial radar system

    NASA Technical Reports Server (NTRS)

    Rukao, S.; Tsuda, T.; Sato, T.; Kato, S.

    1989-01-01

    A large clear air radar with the sensitivity of an incoherent scatter radar for observing the whole equatorial atmosphere up to 1000 km altitude is now being designed in Japan. The radar, called the Equatorial Radar, will be built in Pontianak, Kalimantan Island, Indonesia (0.03 N, 109.3 E). The system is a 47 MHz monostatic Doppler radar with an active phased array configuration similar to that of the MU radar in Japan, which has been in successful operation since 1983. It will have a PA product of more than 5 x 10(9) sq. Wm (P = average transmitter power, A = effective antenna aperture) with sensitivity more than 10 times that of the MU radar. This system configuration enables pulse-to-pulse beam steering within 25 deg from the zenith. As is the case of the MU radar, a variety of sophisticated operations will be made feasible under the supervision of the radar controller. A brief description of the system configuration is presented.

  13. The Invisible Radar Triangle

    NSDL National Science Digital Library

    2014-09-18

    Students learn about radar imaging and its various military and civilian applications that include recognition and detection of human-made targets, and the monitoring of space, deforestation and oil spills. They learn how the concepts of similarity and scaling are used in radar imaging to create three-dimensional models of various targets. Students apply the critical attributes of similar figures to create scale models of a radar imaging scenario using infrared range sensors (to emulate radar functions) and toy airplanes (to emulate targets). They use technology tools to measure angles and distances, and relate the concept of similar figures to real-world applications.

  14. Generalized radar/radiometry imaging problems

    E-print Network

    Genève, Université de

    Paper Generalized radar/radiometry imaging problems Ivan Prudyus, Sviatoslav Voloshynovskiy, Andriy- ing simulation based on radar, synthetic aperture radar (SAR) and radiometry systems are presented systems, synthetic aperture radar, spatio-temporal imaging. 1. Introduction Resolution of radar

  15. Development of a 1310-nm, Coherent Laser Radar with RF Pulse Compression Christopher Allen, Yanki Cobanoglu, Sekken Kenny Chong, Sivaprasad Gogineni

    E-print Network

    Kansas, University of

    on the current state of this system in this paper. SYSTEM OVERVIEW Our hybrid RF/laser radar system marries fiberDevelopment of a 1310-nm, Coherent Laser Radar with RF Pulse Compression Christopher Allen, Yanki, coherent laser radar (lidar) that uses traditional RF pulse compression and digital signal processing

  16. Digital Optical Circuit Technology

    NASA Technical Reports Server (NTRS)

    Dove, B. L. (editor)

    1985-01-01

    The Proceedings for the 48th Meeting of the AGARD Avionics Panel contain the 18 papers presented a Technical Evaluation Report, and discussions that followed the presentations of papers. Seven papers were presented in the session devoted to optical bistability. Optical logic was addressed by three papers. The session on sources, modulators and demodulators presented three papers. Five papers were given in the final session on all optical systems. The purpose of this Specialists' Meeting was to present the research and development status of digital optical circuit technology and to examine its relevance in the broad context of digital processing, communication, radar, avionics and flight control systems implementation.

  17. Combined observations of rock mass movements using satellite SAR interferometry, differential GPS, airborne digital

    E-print Network

    Kääb, Andreas

    interferometry, differential GPS, airborne digital photogrammetry, and airborne photography interpretation Tazio of combined remote sensing observations from satellite and airborne microwave and optical sensors synthetic aperture radar (SAR) interferometry, differential GPS, and airborne digital photogrammetry

  18. Radar cross calibration investigation TAMU radar polarimeter calibration measurements

    NASA Technical Reports Server (NTRS)

    Blanchard, A. J.; Newton, R. W.; Bong, S.; Kronke, C.; Warren, G. L.; Carey, D.

    1982-01-01

    A short pulse, 20 MHz bandwidth, three frequency radar polarimeter system (RPS) operates at center frequencies of 10.003 GHz, 4.75 GHz, and 1.6 GHz and utilizes dual polarized transmit and receive antennas for each frequency. The basic lay-out of the RPS is different from other truck mounted systems in that it uses a pulse compression IF section common to all three RF heads. Separate transmit and receive antennas are used to improve the cross-polarization isolation at each particular frequency. The receive is a digitally controlled gain modulated subsystem and is interfaced directly with a microprocesser computer for control and data manipulation. Antenna focusing distance, focusing each antenna pair, rf head stability, and polarization characteristics of RPS antennas are discussed. Platform and data acquisition procedures are described.

  19. Wind Turbine Clutter Mitigation in Coastal UHF Radar

    PubMed Central

    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. PMID:24550709

  20. Wind turbine clutter mitigation in coastal UHF radar.

    PubMed

    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. PMID:24550709

  1. Ground validation of Dual Precipitation Radar (DPR) on GPM by rapid scan Phased Array weahter Radar (PAR)

    NASA Astrophysics Data System (ADS)

    Hirano, Y.; Mega, T.; Shimamura, S.; Wu, T.; Kikuchi, H.; Ushio, T.; Yoshikawa, E.; Chandra, C. V.

    2014-12-01

    The core observatory satellite of the Global Precipitation Measurement (GPM) mission was launched on February 27th 2014. The Dual-frequency Precipitation Radar (DPR) on the GPM core observatory is the succession of the TRMM Precipitation Radar (PR). The DPR consists of a Ku-band precipitation radar and a Ka-band precipitation radar. The DPR is expected to be more sensitive than the PR especially in the measurement of light rainfall and snowfall in high latitude regions. Because of the difference of spatial and temporal resolutions, Space Radar (SR) and conventional type of Ground Radar (GR) are hard to compare.The SR observes each point of earth in short time, for example one footprint is an observation in some microseconds. Rain-gauge measurements have accurate rainfall rate, but rain-gage observes small area and accumulated rainfall in some minutes. The conventional GR can cover a wide area, however, a volume scan requires several minutes. The Phased Array weather Radar (PAR) is developed by Osaka University, Toshiba, and NICT. The PAR is a weather-radar on X-band within 100m range sampling. High spatial and temporal resolution is achieved by the PAR with pulse compression and the digital beam-forming technique. The PAR transmits a wide beam and receives narrow beams by using digital beam forming. Then, the PAR observes many elevation angles from a single pulse. The time of each volume scan is 10-30 seconds in operation, typically 30 seconds. The study shows comparisons between the DPR and the PAR by more similar spatial and temporal resolution. The rainfall region of DPR is similar to the one of PAR. Correlation coefficient of both radar reflectivity suggests more than 0.8 in the 20km range of PAR. As a result, it is considered that DPR can observe with high accuracy. We present the case study which DPR overpassed the PAR observation region in detail.

  2. The EISCAT Svalbard radar: A case study in modern incoherent scatter radar system design

    NASA Astrophysics Data System (ADS)

    Wannberg, G.; Wolf, I.; Vanhainen, L.-G.; Koskenniemi, K.; RöTtger, J.; Postila, M.; Markkanen, J.; Jacobsen, R.; Stenberg, A.; Larsen, R.; Eliassen, S.; Heck, S.; Huuskonen, A.

    1997-11-01

    The EISCAT (European incoherent scatter) Svalbard radar (ESR) was officially inaugurated on August 22, 1996. This event marked the successful completion on schedule of the first phase of the EISCAT Svalbard radar project. In contrast to previous incoherent scatter radars, the ESR system design was adapted to make use of commercial off-the-shelf TV transmitter hardware, thereby reducing design risk, lead times, and cost to a minimum. Commercial hardware is also used in the digital signal processing system. Control and monitoring are performed by distributed, networked VME systems. Thanks to modern reflector antenna design methods and extreme efforts to reduce the receiver noise contribution, the system noise temperature is only 70 K, thus making the ESR about 30% faster than the much more powerful EISCAT UHF radar in F region experiments! Once the transmitter power is increased to 1 MW, it will become about 2-3 times faster than the UHF radar. State-of-the-art exciter and receiver hardware has been developed in-house to accommodate the special requirements introduced by operating the radar at the exceptionally high duty cycle of 25%. The RF waveform is generated by a system based on four switchable direct digital synthesizers. Continuous monitoring of the transmitted RF waveform by the receiver system allows removal of klystron-induced spurious Doppler effects from the data. Intermediate-frequency sampling at 7.5 MHz is employed, followed by fully digital channel separation, signal detection, and postdetection filtering in six parallel receiver channels. Radar codes for both E and F layer observation have been designed and perfected. So far, more than 40 hours of good quality ionospheric data have been collected and analyzed in terms of plasma parameters. While the tragic loss of the Cluster mission suddenly changed the plans and dispositions of a majority of the ESR user community, the radar has still been in high demand since its inauguration. It is now being operated by EISCAT staff on a campaign basis, to provide ground-based support data for a number of other magnetospheric satellites, notably Polar and FAST, and will be opened to the EISCAT user community for special program operations later in 1997.

  3. Statistical gamma transitions in {sup 174}Hf

    SciTech Connect

    Farris, L.P.; Cizewski, J.A.; Brinkman, M.J.; Henry, R.G.; Lee, C.S. [Rutgers--the State Univ., New Brunswick, NJ (United States); Khoo, T.L.; Janssens, R.V.F.; Moore, E.F.; Carpenter, M.P.; Ahmad, I.; Lauritsen, T. [Argonne National Lab., IL (United States); Kolata, J.J.; Beard, K.B.; Ye, D.; Garg, U. [Notre Dame Univ., IN (United States); Kaplan, M.S.; Saladin, J.X.; Winchell, D. [Pittsburgh Univ., PA (United States)

    1992-08-01

    Statistical spectrum extracted from the {sup 172}Yb({alpha},2n){sup 174}Hf reaction was fit with Monte Carlo simulations using a modified GDR E1 strength function and several formulations of the level density.

  4. Statistical gamma transitions in sup 174 Hf

    SciTech Connect

    Farris, L.P.; Cizewski, J.A.; Brinkman, M.J.; Henry, R.G.; Lee, C.S. (Rutgers--the State Univ., New Brunswick, NJ (United States)); Khoo, T.L.; Janssens, R.V.F.; Moore, E.F.; Carpenter, M.P.; Ahmad, I.; Lauritsen, T. (Argonne National Lab., IL (United States)); Kolata, J.J.; Beard, K.B.; Ye, D.; Garg, U. (Notre Dame Univ., IN (United States)); Kaplan, M.S.; Saladin, J.X.; Winchell, D. (Pittsburgh Univ., PA (Un

    1992-01-01

    Statistical spectrum extracted from the {sup 172}Yb({alpha},2n){sup 174}Hf reaction was fit with Monte Carlo simulations using a modified GDR E1 strength function and several formulations of the level density.

  5. Java Radar Analysis Tool

    NASA Technical Reports Server (NTRS)

    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.

  6. Noncooperative rendezvous radar system

    NASA Technical Reports Server (NTRS)

    1974-01-01

    A fire control radar system was developed, assembled, and modified. The baseline system and modified angle tracking system are described along with the performance characteristics of the baseline and modified systems. Proposed changes to provide additional techniques for radar evaluation are presented along with flight test data.

  7. Phased-array radars

    Microsoft Academic Search

    Eli Brookner

    1985-01-01

    The operating principles, technology, and applications of phased-array radars are reviewed and illustrated with diagrams and photographs. Consideration is given to the antenna elements, circuitry for time delays, phase shifters, pulse coding and compression, and hybrid radars combining phased arrays with lenses to alter the beam characteristics. The capabilities and typical hardware of phased arrays are shown using the US

  8. Determination of radar MTF

    SciTech Connect

    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.

  9. Active radar stealth device

    Microsoft Academic Search

    R. N. Cain; Albert J. Corda

    1991-01-01

    This patent discloses an active radar stealth device mounted on a host platform for minimizing the radar cross-section of the host platform. A coating which is essentially microwave transparent is attached to the surface of a host platform and is exposed to an incident microwave field. A plurality of detector\\/emitter pairs contained within the coating detect and actively cancel, respectively,

  10. Nd-Hf isotope systematics around Antarctica

    NASA Astrophysics Data System (ADS)

    van de Flierdt, T.; Roy, M.; Hemming, S. R.; Goldstein, S. L.; Abouchami, W.

    2004-12-01

    The motivation to study Nd-Hf systematics around Antarctica is twofold. First of all, a wide range of bedrock ages and lithologies are found around the perimeter of the Antarctic continent, ranging from Archean basement terrains to recent volcanics. However, in Nd-Hf isotope space Antarctica remains one of the poorly known regions of the world's continents. A first order characterization of Nd and Hf isotopes in the detrital fraction of marine sediments will fill this gap and will put additional constraints on Antarctic bedrock geology and isotope systematics. Preliminary data indicate a range of Nd isotopes from -1 to -19 and a range of Hf isotopes from -2 to -20. These values reflect the variable Antarctic provenance and follow local geology. The lowest values are found in the Indian Ocean sector close to Archean outcrops and the highest values are observed in the Pacific sector close to young bedrock ages in the region between the Ross Sea and the Antarctic Peninsula. In Nd-Hf isotope space the new data scatter around the terrestrial correlation line. Two samples from the Indian sector display more radiogenic Hf isotopes for a given Nd isotopic composition, pointing towards potentially different Nd-Hf isotope systematics for the sediments with old provenance. Second, detrital inputs from Antarctica get dispersed into the Antarctic Circumpolar Current (ACC). The ACC is the connection between the Pacific, Atlantic, and Indian Oceans and distributes deep waters formed in the North Atlantic as well as exports deep water generated at sites around Antarctica. It is however not known whether there exists significant transfer of dissolved Nd and Hf from the Antarctic continent to the ACC and ultimately to the world's ocean. An improved understanding of the composition of Southern Ocean water masses and their dependence on inputs from the Antarctic continent and deep water sources on the Antarctic shelf is an important precondition to unravel past global circulation patterns and material inputs to the ocean. We will present new Hf isotope data for ferromanganese nodules from the ACC, which will be compared with existing Nd isotope data. Preliminary results indicate a small range in Hf isotopes for the Pacific sector of the ACC (3.9 to 4.5), which is almost indistinguishable within the analytical error and matches with what would have been predicted from Nd-Hf isotope systematics in seawater.

  11. Thermochemistry of Hf-zirconolite, CaHfTi{sub 2}O{sub 7}

    SciTech Connect

    Putnam, R.L.; Navrotsky, A.; Woodfield, B.F.; Shapiro, J.L.; Stevens, R.; Boerio-Goates, J.

    1999-07-01

    The formation enthalpy, {minus}3,752.3 {+-} 4.7 kJ/mol, of Hf-zirconolite, CaHfTi{sub 2}O{sub 7} was obtained using high temperature oxide-melt solution calorimetry. Combined with heat capacity data obtained using low temperature adiabatic calorimetry the authors report the heat capacity (Cp) and the standard molar formation energetics for Hf-zirconolite from T = 298.15 K to T = 1,500 K. Comparison of Hf-zirconolite with Zr-zirconolite is made.

  12. Battlefield digitization with Discoverer II

    Microsoft Academic Search

    David A. Whelan; John J. Koss

    1999-01-01

    Discover II is a technology demonstration program to develop an demonstrate an affordable space-based radar (SBR) with High Range Resolution Ground Moving Target Indication, SAR imaging capabilities and Digitized Terrain Elevation Data (DTED) that will revolutionize surveillance and precision geolocation support to the tactical warfighter. The near- continuous, global access provided by the objective Discoverer II concept, in combination with

  13. Advances in HF parallel tone modem technology

    Microsoft Academic Search

    G. J. Luhowy

    1988-01-01

    The author describes the HF modem, which contains a 75 to 2400 bps 39-tone waveform, a robust 75-bps direct-spread waveform, and two independent 45-1200-bps binary frequency-shift-keyed (FSK) waveforms. The availability of powerful new microprocessors permits economic implementation of complex signal-processing sizes. Improved signaling techniques and potent error-correcting codes allow greatly improved performance on the HF channel. Measured performance data taken

  14. Looking at Radar Images

    NSDL National Science Digital Library

    These activities pertain to the value of the different types of images, including a false color mosaic, a Compressed Stokes image, a vegetation map and key, and various ground photographs. Students are given specific directions on how to decide what features of a radar image indicate such structures as upland forest, clear-cut areas, and roads. In a second activity, students look at the radar images to see if they can produce a vegetation map similar to the one they have been given. The third activity introduces 15 Decade Volcanoes that pose a particular threat to humans. Using the Decade Volcanoes as examples, students view radar images of volcanoes that occur around the world. The final exercise is aimed at helping students distinguish the differences between radar image data and visible photographs. Students will look at radar data and photographs of three sites taken by the astronauts.

  15. Spaceborne weather radar

    NASA Technical Reports Server (NTRS)

    Meneghini, Robert; Kozu, Toshiaki

    1990-01-01

    The present work on the development status of spaceborne weather radar systems and services discusses radar instrument complementarities, the current forms of equations for the characterization of such aspects of weather radar performance as surface and mirror-image returns, polarimetry, and Doppler considerations, and such essential factors in spaceborne weather radar design as frequency selection, scanning modes, and the application of SAR to rain detection. Attention is then given to radar signal absorption by the various atmospheric gases, rain drop size distribution and wind velocity determinations, and the characteristics of clouds, as well as the range of available estimation methods for backscattering, single- and dual-wavelength attenuation, and polarimetric and climatological characteristics.

  16. Micropower impulse radar imaging

    SciTech Connect

    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.

  17. Low-frequency noise in submicrometer MOSFETs with HfO2, HfO2\\/Al2O3 and HfAlOx gate stacks

    Microsoft Academic Search

    Bigang Min; Siva Prasad Devireddy; Zeynep Çelik-Butler; Fang Wang; Ania Zlotnicka; Hsing-Huang Tseng; Philip J. Tobin

    2004-01-01

    Low-frequency noise measurements were performed on p- and n-channel MOSFETs with HfO2, HfAlOx and HfO2\\/Al2O3 as the gate dielectric materials. The gate length varied from 0.135 to 0.36 ?m with 10.02 ?m gate width. The equivalent oxide thicknesses were: HfO2 23 Å, HfAlOx 28.5 Å and HfO2\\/Al2O3 33 Å. In addition to the core structures with only about 10 Å

  18. Browse > Conferences> Radar Conference, 2008. RADAR ... INDEX TERMS

    E-print Network

    Préaux, Jean-Philippe

    Browse > Conferences> Radar Conference, 2008. RADAR ... INDEX TERMS REFERENCES CITING DOCUMENTS Force, MorphoAnalysis in Signal Process. Lab., Salon-de-Provence This paper appears in: Radar Conference, 2008. RADAR '08. IEEE Issue Date: 26-30 May 2008 On page(s): 1 - 5 Location: Rome ISSN: 1097-5659 Print

  19. Error Distribution and Diversity Performance of a Frequency-Differential PSK HF Modem

    Microsoft Academic Search

    G. Porter

    1968-01-01

    A 4800-bit\\/s digital data modem is operated over a simulated HF channel to determine the bit-error rate and error distributions of the received serial binary data stream. The measured error distributions for multipath-limited conditions are compared with back-to-back operation and theoretically determined random distributions, and are also used to evaluate forward acting error correction assuming half-rate random error-correcting block codes.

  20. Pulse compression hardware decoding techniques for MST radars

    Microsoft Academic Search

    M. P. Sulzer; R. F. Woodman

    1985-01-01

    The techniques for decoding in hardware received signals transmitted by phase-coded mesosphere-stratosphere-troposphere (MST) radars are reviewed. The designs consist of digital and analog types which resemble filters or correlators in their operation. A new analog design is presented, and a discussion of the choice between hardware and software decoding is given. The number of bits required for digital coherent integrators

  1. Use and Interpretation of Radar

    NSDL National Science Digital Library

    John Nielsen-Gammon

    1996-01-01

    This undergraduate meteorology tutorial from Texas A&M University discusses the basic principles of operation of weather radars, describes how to interpret radar mosaics, and discusses the use of radar in weather forecasting. Students learn the relationship between range and elevation and how to use radar images and mosaics in short-range forecasting.

  2. Ground-penetrating radar methods

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ground-penetrating radar geophysical methods are finding greater and greater use in agriculture. With the ground-penetrating radar (GPR) method, an electromagnetic radio energy (radar) pulse is directed into the subsurface, followed by measurement of the elapsed time taken by the radar signal as it ...

  3. Radar remote sensing in biology

    USGS Publications Warehouse

    Moore, Richard K.; Simonett, David S.

    1967-01-01

    The present status of research on discrimination of natural and cultivated vegetation using radar imaging systems is sketched. The value of multiple polarization radar in improved discrimination of vegetation types over monoscopic radars is also documented. Possible future use of multi-frequency, multi-polarization radar systems for all weather agricultural survey is noted.

  4. Time-frequency analysis of synthetic aperture radar signals

    SciTech Connect

    Johnston, B.

    1996-08-01

    Synthetic aperture radar (SAR) has become an important tool for remote sensing of the environment. SAR is a set of digital signal processing algorithms that are used to focus the signal returned to the radar because radar systems in themselves cannot produce the high resolution images required in remote sensing applications. To reconstruct an image, several parameters must be estimated and the quality of output image depends on the degree of accuracy of these parameters. In this thesis, we derive the fundamental SAR algorithms and concentrate on the estimation of one of its critical parameters. We show that the common technique for estimating this particular parameter can sometimes lead to erroneous results and reduced quality images. We also employ time-frequency analysis techniques to examine variations in the radar signals caused by platform motion and show how these results can be used to improve output image quality.

  5. Model for optimal parallax in stereo radar imagery

    NASA Technical Reports Server (NTRS)

    Pisaruck, M. A.; Kaupp, V. H.; Macdonald, H. C.; Waite, W. P.

    1984-01-01

    Simulated stereo radar imagery is used to investigate parameters for a spaceborne imaging radar. Incidence angles ranging from small to intermediate to large are used with three digital terrain model areas which are representative of relatively flat, moderately rough, and mountaneous terrain. The simulated radar imagery was evaluated by interpreters for ease of stereo perception and information content, and rank ordered within each class of terrain. The interpreter's results are analyzed for trends between the height of a feature and either parallax or vertical exaggeration for a stereo pair. A model is developed which predicts the amount of parallax (or vertical exaggeration) an interpreter would desire for best stereo perception of a feature of a specific height. Results indicate the selection of angle of incidence and stereo intersection angle depend upon the relief of the terrain. Examples of the simulated stereo imagery are presented for a candidate spaceborne imaging radar having four selectable angles of incidence.

  6. DBF technique for the space synchronization of bistatic (multistatic) radars

    Microsoft Academic Search

    Shujie Zhao; Fulu Geng; Ruyun Gao; Changrong Xie; Xudong Ma; Jianchun Chen

    1991-01-01

    The space synchronization is one of the key techniques of bistatic(multistatic) radars. The concept and main parameters in implementing the space synchronization by pulse chasing with digital beam forming (DBF) technique are discussed. A implementation scheme as well as some of the test results of a prototype are also given in this paper.

  7. Multi-instrument coordinated observations of auroral dynamics at EISCAT Svalbard and Sondrestrom Radar sites

    NASA Astrophysics Data System (ADS)

    Bhatt, A.; Stromme, A.; Häggström, I.; Samara, M.; Michell, R. G.; Labelle, J. W.; Broughton, M.; Lanchester, B. S.

    2011-12-01

    A multi-instrument campaign to observe auroral dynamics was conducted during February 7-10, 2011 at the EISCAT Svalbard Radar (ESR) in Norway and the Sondrestrom radar in Greenland. This campaign involved measurements of incoherent scatter spectra from both the radars, optical observations of aurora on both sites, and auroral radio emissions measured with a spectrum analyzer and with an LF/MF/HF interferometer at Sondrestrom. In this paper, we will present data from this coordinated study, focusing on correlations of plasma line enhancements and any NEIALs events with other datasets during auroral precipitation periods and substorm onsets. We will also present a comparative analysis of the same event reflected in two radars with very different wavelengths.

  8. HF Accelerated Electron Fluxes, Spectra, and Ionization

    NASA Astrophysics Data System (ADS)

    Carlson, Herbert C.; Jensen, Joseph B.

    2014-12-01

    Wave particle interactions, an essential aspect of laboratory, terrestrial, and astrophysical plasmas, have been studied for decades by transmitting high power HF radio waves into Earth's weakly ionized space plasma, to use it as a laboratory without walls. Application to HF electron acceleration remains an active area of research (Gurevich in Usp Fizicheskikh Nauk 177(11):1145-1177, 2007) today. HF electron acceleration studies began when plasma line observations proved (Carlson et al. in J Atmos Terr Phys 44:1089-1100, 1982) that high power HF radio wave-excited processes accelerated electrons not to ~eV, but instead to -100 times thermal energy (10 s of eV), as a consequence of inelastic collision effects on electron transport. Gurevich et al (J Atmos Terr Phys 47:1057-1070, 1985) quantified the theory of this transport effect. Merging experiment with theory in plasma physics and aeronomy, enabled prediction (Carlson in Adv Space Res 13:1015-1024, 1993) of creating artificial ionospheres once ~GW HF effective radiated power could be achieved. Eventual confirmation of this prediction (Pedersen et al. in Geophys Res Lett 36:L18107, 2009; Pedersen et al. in Geophys Res Lett 37:L02106, 2010; Blagoveshchenskaya et al. in Ann Geophys 27:131-145, 2009) sparked renewed interest in optical inversion to estimate electron spectra in terrestrial (Hysell et al. in J Geophys Res Space Phys 119:2038-2045, 2014) and planetary (Simon et al. in Ann Geophys 29:187-195, 2011) atmospheres. Here we present our unpublished optical data, which combined with our modeling, lead to conclusions that should meaningfully improve future estimates of the spectrum of HF accelerated electron fluxes. Photometric imaging data can significantly improve detection of emissions near ionization threshold, and confirm depth of penetration of accelerated electrons many km below the excitation altitude. Comparing observed to modeled emission altitude shows future experiments need electron density profiles to derive more accurate HF electron flux spectra.

  9. Investigation of the differences in stability of the OCxxxHF and COxxxHF complexes

    SciTech Connect

    Curtiss, L.A.; Pochatko, D.J.; Reed, A.E.; Weinhold, F.

    1985-03-15

    The structure and energetics of the isomeric H-bonded complexes OCxxxHF and COxxxHF have been investigated by ab initio molecular orbital theory and by natural bond orbital analysis. Only with the inclusion of electron correlation is a significant preference for the experimentally observed OCxxxHF isomer found. The large effect of correlation upon the relative stability of the two isomers is apparently entirely an electrostatic effect caused by the correlation-induced sign reversal of the dipole moment of CO. Nevertheless, a molecular multipole expansion is found inadequate to account for the principal features of these H-bonded complexes and their relative stability. Contrary to a recent study, we find that ''charge transfer'' effects are highly significant contributions to the binding in these complexes. The differences in stability of OCxxxHF and COxxxHF are attributed primarily to differences in the interaction of carbon and oxygen lone pairs of CO donating into the unfilled antibond on HF, i.e., to differences in n/sub C/..-->..sigma/sub HF/( and n/sub O/..-->..sigma/sub HF/( matrix elements.

  10. Spaceborne laser radar.

    PubMed

    Flom, T

    1972-02-01

    Laser radar systems are being developed to acquire and track targets in applications such as the rendezvous and docking of two spacecraft. To search effectively for and locate a target using a narrow laser beam, a scanning system is needed. This paper describes a scan technique whereby a narrow laser beam is synchronously scanned with an equally narrow receiver field-of-view without the aid of mechanical gimbals. Equations are developed in order to examine the maximum acquisition and tracking rates, and the maximum target range for a scanning laser radar system. A recently built prototype of a small, lightweight, low-power-consuming scanning laser radar is described. PMID:20111497

  11. Radar transmitter procedures

    NASA Astrophysics Data System (ADS)

    1993-03-01

    This ITOP outlines the test methods used in evaluating the performance and characteristics of general types of radar transmitters to include single or variable frequency transmitters. The test methods serve as a guide in determining the overall efficiency of such equipment as a function of their design and their recorded performance. This ITOP is limited to methods for measuring the performance of the radar transmitter under test as a major component. Some performance aspects of the transmitter can be tested only when configured as part of a total radar system.

  12. AUTOMATIC GENERATION OF BALD EARTH DIGITAL ELEVATION MODELS FROM DIGITAL SURFACE MODELS CREATED USING AIRBORNE IFSAR

    Microsoft Academic Search

    Yandong Wang; Bryan Mercer; Vincent C. Tao; Jayanti Sharma; Scott Crawford

    This paper presents a novel approach for the automatic generation of 'bald-earth' digital elevation models (DEMs) from digital surface models (DSMs) created using STAR-3i - the Intermap Interferometric Synthetic Aperture Radar (IFSAR) system. The method uses a hierarchical surface fitting technique to yield bald earth DEMs. It first generates a hierarchy of images from the original DSMs, and bald earth

  13. Earth resources shuttle imaging radar. [systems analysis and design analysis of pulse radar for earth resources information system

    NASA Technical Reports Server (NTRS)

    1975-01-01

    A report is presented on a preliminary design of a Synthetic Array Radar (SAR) intended for experimental use with the space shuttle program. The radar is called Earth Resources Shuttle Imaging Radar (ERSIR). Its primary purpose is to determine the usefulness of SAR in monitoring and managing earth resources. The design of the ERSIR, along with tradeoffs made during its evolution is discussed. The ERSIR consists of a flight sensor for collecting the raw radar data and a ground sensor used both for reducing these radar data to images and for extracting earth resources information from the data. The flight sensor consists of two high powered coherent, pulse radars, one that operates at L and the other at X-band. Radar data, recorded on tape can be either transmitted via a digital data link to a ground terminal or the tape can be delivered to the ground station after the shuttle lands. A description of data processing equipment and display devices is given.

  14. Radar - The Future

    NASA Astrophysics Data System (ADS)

    Warwick, G.

    1985-02-01

    Progress in civil and military radar units since the invention of radar in 1935 is summarized, noting the trend to multipurpose units. The earliest systems functioned at 10 cm, then 3 cm after development of a cavity magnetron to provide power for shorter wavelengths. Military needs are driving improvements in three-dimensional scanning capabilities, Primarily to locate aircraft in the presence of ground clutter and sea surface scattering. Autonomous, separate transmitter and receiver units are being tested. Lengthening ground-based radar wavelengths to tens of meters will permit over-the-horizon sensing with backscattering, ionospheric bounce, or induction of a potential in the sea surface as the possible techniques. Mode S monopulse radars will permit transponder queries between small and large aircraft. Finally, pulse Doppler SAR systems may afford terrain recognition with no corroborating data except an expert systems data base.

  15. Caribbean Radar Products

    NSDL National Science Digital Library

    2014-09-14

    This module provides examples of radar imagery from various locations in the Caribbean to demonstrate the different types of images available. Also, examples of different meteorological and non meteorological features are presented to show features seen in island locations.

  16. Millimeter Waves Ballistic Radar

    Microsoft Academic Search

    A. N. Zubkov; V. S. Gavrilov; Ya. M. Kempa; Z. V. Dufanets; N. A. Naumets

    2006-01-01

    Solid-state Doppler millimeter waves ballistic radar designed for measuring of exterior and interior ballistic parameters of highly dynamical faint objects is developed. The coherence characteristics of transmit-receive module are supported by the floating heterodyne oscillation behavior

  17. Soil moisture detection from radar imagery of the Phoenix, Arizona test site

    NASA Technical Reports Server (NTRS)

    Cihlar, J.; Ulaby, F. T.; Mueller, R.

    1975-01-01

    The Environmental Research Institute of Michigan (ERIM) dual-polarization X and L band radar was flown to acquire radar imagery over the Phoenix (Arizona) test site. The site was covered by a north-south pass and an east-west pass. Radar response to soil moisture was investigated. Since the ERIM radar does not have accurately measured antenna patterns, analysis of the L band data was performed separately for each of several strips along the flight line, each corresponding to a narrow angle of incidence. For the NS pass, good correlation between the radar return and mositure content was observed for each of the two nearest (to nadir) angular ranges. At higher angular ranges, no correlation was observed. The above procedure was not applied to the EW pass due to flight path misalignments. The results obtained stress the importance of radar calibration, the digitization process, and the angle of incidence.

  18. Active radar stealth device

    NASA Astrophysics Data System (ADS)

    Cain, R. N.; Corda, Albert J.

    1991-07-01

    This patent discloses an active radar stealth device mounted on a host platform for minimizing the radar cross-section of the host platform. A coating which is essentially microwave transparent is attached to the surface of a host platform and is exposed to an incident microwave field. A plurality of detector/emitter pairs contained within the coating detect and actively cancel, respectively, the microwave field at each respective detector/emitter pair.

  19. Phased-array radars

    NASA Astrophysics Data System (ADS)

    Brookner, E.

    1985-02-01

    The operating principles, technology, and applications of phased-array radars are reviewed and illustrated with diagrams and photographs. Consideration is given to the antenna elements, circuitry for time delays, phase shifters, pulse coding and compression, and hybrid radars combining phased arrays with lenses to alter the beam characteristics. The capabilities and typical hardware of phased arrays are shown using the US military systems COBRA DANE and PAVE PAWS as examples.

  20. Multiresolution GMTI radar

    Microsoft Academic Search

    J. R. Guerci; A. O. Steinhardt

    2003-01-01

    The detection and tracking of ground moving vehicles from airborne radar can be challenging at slow target velocities due to the close space-time (angle-Doppler) proximity of strong competing mainbeam clutter. Moreover, in complex non-stationary clutter environments, conventional space-time adaptive processing (STAP) cannot be relied upon to provide precision ing. In this paper, we re-examine GMTI radar from a multiresolution perspective

  1. Weather Radar Network Design

    Microsoft Academic Search

    Francesc Junyent; V. Chandrasekar

    2008-01-01

    The Engineering Research Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) is investigating the use of dense networks of short-range radars for weather sensing. A first test-bed of this new paradigm is currently deployed in southwest Oklahoma. The potential benefits of closely deployed, overlapping, short-range weather radars are easy to see intuitively amounting to a greater ability to measure

  2. Doppler Radar Technology

    NSDL National Science Digital Library

    This resource provides an introduction to the function and uses of the The National Weather Service's (NWS) Weather Surveillance Doppler Radar (WSR-88D). Topics include the components of the system, an overview of the products and overlays the system creates, and some example images with captions explaining what is being shown. There are also links to radar meteorology tutorials and to information on training to use the system and interpret its imagery.

  3. Radar network characterization

    Microsoft Academic Search

    Francesc Junyent; V. Chandrasekar

    2007-01-01

    The use of dense networks of small radars for weather sensing is being investigated by the Engineering Research Center for Collaborative Adaptive Sensing of the Atmosphere, with a first test-bed of this new paradigm well underway. The potential benefits of closely-deployed, overlapping, short-range weather radars are easy to see intuitively, and can be summarized as a greater ability to mitigate

  4. HF Propagation Effects Caused by an Artificial Plasma Cloud in the Ionosphere

    NASA Astrophysics Data System (ADS)

    Joshi, D. R.; Groves, K. M.; McNeil, W. J.; Caton, R. G.; Parris, R. T.; Pedersen, T. R.; Cannon, P. S.; Angling, M. J.; Jackson-Booth, N. K.

    2014-12-01

    In a campaign carried out by the NASA sounding rocket team, the Air Force Research Laboratory (AFRL) launched two sounding rockets in the Kwajalein Atoll, Marshall Islands, in May 2013 known as the Metal Oxide Space Cloud (MOSC) experiment to study the interactions of artificial ionization and the background plasma and measure the effects on high frequency (HF) radio wave propagation. The rockets released samarium metal vapor in the lower F-region of the ionosphere that ionized forming a plasma cloud that persisted for tens of minutes to hours in the post-sunset period. Data from the experiments has been analyzed to understand the impacts of the artificial ionization on HF radio wave propagation. Swept frequency HF links transiting the artificial ionization region were employed to produce oblique ionograms that clearly showed the effects of the samarium cloud. Ray tracing has been used to successfully model the effects of the ionized cloud. Comparisons between observations and modeled results will be presented, including model output using the International Reference Ionosphere (IRI), the Parameterized Ionospheric Model (PIM) and PIM constrained by electron density profiles measured with the ALTAIR radar at Kwajalein. Observations and modeling confirm that the cloud acted as a divergent lens refracting energy away from direct propagation paths and scattering energy at large angles relative to the initial propagation direction. The results confirm that even small amounts of ionized material injected in the upper atmosphere can result in significant changes to the natural propagation environment.

  5. HF Radio Wave Production of Artificial Ionospheres

    NASA Astrophysics Data System (ADS)

    Carlson, Herbert

    In 1993 it was predicted that artificial ionospheres would be produced by high power HF radio waves, once HF transmitters approached a GWatt ERP. When that threshold was very recently achieved, such production was indeed detected and published at two high latitude high power HF facilities. Here we review: the first-principles logic behind that prediction, which aspects of such production are critically dependent on magnetic latitude, and which aspects of such production depend only on physical parameters independent of latitude. These distinctions follow directly from decomposition of the problem of ionization production into its components of: radio-wave propagation, wave-particle interactions, electron transport, and quantitative elastic/inelastic cross-sections. We outline this analysis to show that, within the context of early observations, the production of ionization is inevitable, and only a question of competing instability thresholds, and scale of ionization production. This illustrates complimentary aeronomy and plasma physics to advance understanding of both.

  6. The Shuttle Radar Topography Mission: A Global DEM

    NASA Technical Reports Server (NTRS)

    Farr, Tom G.; Kobrick, Mike

    2000-01-01

    Digital topographic data are critical for a variety of civilian, commercial, and military applications. Scientists use Digital Elevation Models (DEM) to map drainage patterns and ecosystems, and to monitor land surface changes over time. The mountain-building effects of tectonics and the climatic effects of erosion can also be modeled with DEW The data's military applications include mission planning and rehearsal, modeling and simulation. Commercial applications include determining locations for cellular phone towers, enhanced ground proximity warning systems for aircraft, and improved maps for backpackers. The Shuttle Radar Topography Mission (SRTM) (Fig. 1), is a cooperative project between NASA and the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense. The mission is designed to use a single-pass radar interferometer to produce a digital elevation model of the Earth's land surface between about 60 degrees north and south latitude. The DEM will have 30 m pixel spacing and about 15 m vertical errors.

  7. 2-D inner-shelf current observations from a single VHF WEllen RAdar (WERA) station

    USGS Publications Warehouse

    Voulgaris, G.; Kumar, N.; Gurgel, K.-W.; Warner, J.C.; List, J.H.

    2011-01-01

    The majority of High Frequency (HF) radars used worldwide operate at medium to high frequencies (8 to 30 MHz) providing spatial resolutions ranging from 3 to 1.5 km and ranges from 150 to 50 km. This paper presents results from the deployment of a single Very High Frequency (VHF, 48 MHz) WEllen RAdar (WERA) radar with spatial resolution of 150 m and range 10-15 km, used in the nearshore off Cape Hatteras, NC, USA. It consisted of a linear array of 12 antennas operating in beam forming mode. Radial velocities were estimated from radar backscatter for a variety of wind and nearshore wave conditions. A methodology similar to that used for converting acoustically derived beam velocities to an orthogonal system is presented for obtaining 2-D current fields from a single station. The accuracy of the VHF radar-derived radial velocities is examined using a new statistical technique that evaluates the system over the range of measured velocities. The VHF radar velocities showed a bias of 3 to 7 cm/s over the experimental period explainable by the differences in radar penetration and in-situ measurement height. The 2-D current field shows good agreement with the in-situ measurements. Deviations and inaccuracies are well explained by the geometric dilution analysis. ?? 2011 IEEE.

  8. Radar MeteorologyRadar Meteorology Feb 20, 1941 10 cm (S-band) radar used to track rain showers (Ligda)

    E-print Network

    Rutledge, Steven

    Radar MeteorologyRadar Meteorology Feb 20, 1941 10 cm (S-band) radar used to track rain showers similar observations in the early 1940's (U.S. Air Corps meteorologists receiving "radar" training at MIT in 1943 First operational weather radar, Panama, 1943 Science of radar meteorology born from WWII research

  9. On the potentials of passive, multistatic, low frequency radars to counter stealth and detect low flying targets

    Microsoft Academic Search

    H. Kuschel; J. Heckenbach; S. Muller; R. Appel

    2008-01-01

    The potentials of passive, multi-static radars as covert sensors for the detection of low flying, stealth air targets are illustrated by multi-static RCS analysis, coverage simulations for low flight levels and measurement results obtained with an experimental passive radar using digital audio broadcast signals (DAB). The measurement sensor is described and future perspectives are pointed out.

  10. Digital Libraries

    NSDL National Science Digital Library

    Heather

    2008-09-29

    This projects introduces digital libraries, digital initiatives, search techniques, and the Instructional Architect Review Rubric. Digital Library Information : The Scope of the Digital Library D-Lib Journal article, 1998 2008 Joint Conference on Digital Libraries (JCDL) Annual meeting devoted to Digital Libraries Initiatives : Digital Libraries Initiative The Initiative's focus is to dramatically advance the means to collect, store, and organize information in digital forms, and make it available for searching, retrieval, and processing via communication networks -- all in ...

  11. Weather Radar and Instrumentation: Laboratory Modules

    NSDL National Science Digital Library

    These 16 radar education modules, developed for the Weather Radar and Instrumentation Curriculum at the University of Oklahoma, provide hands-on instruction for beginning, intermediate, or advanced students to learn about radar systems, especially weather radar. Topics include hardware, weather radar, adaptive systems, advanced hydrometeors, applications of weather radar, and atmospheric interpretations. The modules may be downloaded.

  12. Inversion to estimate ocean wave directional spectrum from high-frequency radar

    NASA Astrophysics Data System (ADS)

    Hisaki, Yukiharu

    2015-04-01

    An high-frequency (HF) radar observes ocean surface currents and waves by radiating HF radio waves to the sea surface and analyzing the backscattered signals. Ocean wave spectrum is estimated from the first- and the second-order scattering of Doppler spectra by the inversion. The estimation of ocean surface currents is robust, because the surface currents can be derived from the peak Doppler frequency of the first-order scattering in the Doppler spectrum. The method to estimate ocean wave spectra is complicated and the second-order scattering in the Doppler spectrum is fragile, which is affected by the noise in the Doppler spectrum. A new method to estimate ocean wave spectra from HF radar is developed. This method is the extension of Hisaki (1996, 2005, 2006, 2009, 2014). The new method can be applied to both the single radar and dual radar array case, while the previous methods can be applied only the single radar case (Hisaki, 2005, 2006, 2009, 2014) or dual radar case (Hisaki, 1996). Ocean wave spectra are estimated in the regular grid cells, while wave spectra are estimated on the polar grids points with the origin of the radar position in the previous method for single radar case. The governing equations for wave estimation are the integral equations which relate the wave spectrum to the Doppler spectrum, and the energy balance equation under the assumption of stationarity. The regularization constraints in the horizontal space and the wave frequency-direction space are also used for the estimation. The unknowns, which are spectral values, surface wind speeds and directions, are estimated by seeking the minimum of the objective function, which is defined as the sum of weighted squares of the equations. The signal to noise ratio in the Doppler spectrum for wave estimation must be high. We selected the Doppler spectra using the SOM (Self organization map ) analysis method. The method will be demonstrated by comparing with in-situ observed data, in which only the Doppler spectrum from the single radar can be available.

  13. Ultrawideband imaging radar based on OFDM: system simulation analysis

    NASA Astrophysics Data System (ADS)

    Garmatyuk, Dmitriy

    2006-05-01

    Orthogonal frequency division-multiplexing (OFDM) is rapidly emerging as a preferred method of UWB signaling in commercial applications aimed mainly at low-power, high data-rate communications. This paper explores the possibility of applying OFDM to use in imaging radar technology. Ultra-wideband nature of the signal provides for high resolution of the radar, whereas usage of multi-sub-carrier method of modulation allows for dynamic spectrum allocation. Robust multi-path performance of OFDM signals and heavy reliance of transceiver design on digital processors easily implemented in modern VLSI technology make a number of possible applications viable, e.g.: portable high-resolution indoor radar/movement monitoring system; through-the-wall/foliage synthetic aperture imaging radar with a capability of image transmission/broadcasting, etc. Our work is aimed to provide a proof-of-concept simulation scenario to explore numerous aspects of UWB-OFDM radar imaging through evaluating range and cross-range imaging performance of such a system with an eventual goal of software-defined radio (SDR) implementation. Stripmap SAR topology was chosen for modeling purposes. Range/cross-range profiles were obtained along with full 2-D images for multi-target in noise scenarios. Model set-up and results of UWB-OFDM radar imaging simulation study using Matlab/Simulink modeling are presented and discussed in this paper.

  14. Fiber optic coherent laser radar 3D vision system

    NASA Astrophysics Data System (ADS)

    Sebastian, Richard L.; Clark, Robert B.; Simonson, Dana L.; Slotwinski, Anthony R.

    1994-01-01

    Recent advances in fiber optic component technology and digital processing components have enabled the development of a new 3D vision system based upon a fiber optic FMCW coherent laser radar. The approach includes a compact scanner with no moving parts capable of randomly addressing all pixels. The system maintains the immunity to lighting and surface shading conditions which is characteristic of coherent laser radar. The random pixel addressability allows concentration of scanning and processing on the active areas of a scene, as is done by the human eye-brain system.

  15. Fiber optic coherent laser radar 3d vision system

    SciTech Connect

    Sebastian, R.L.; Clark, R.B.; Simonson, D.L. [and others

    1994-12-31

    Recent advances in fiber optic component technology and digital processing components have enabled the development of a new 3D vision system based upon a fiber optic FMCW coherent laser radar. The approach includes a compact scanner with no moving parts capable of randomly addressing all pixels. The system maintains the immunity to lighting and surface shading conditions which is characteristic of coherent laser radar. The random pixel addressability allows concentration of scanning and processing on the active areas of a scene, as is done by the human eye-brain system.

  16. Imaging Radar in the Mojave Desert-Death Valley Region

    NASA Technical Reports Server (NTRS)

    Farr, Tom G.

    2001-01-01

    The Mojave Desert-Death Valley region has had a long history as a test bed for remote sensing techniques. Along with visible-near infrared and thermal IR sensors, imaging radars have flown and orbited over the area since the 1970's, yielding new insights into the geologic applications of these technologies. More recently, radar interferometry has been used to derive digital topographic maps of the area, supplementing the USGS 7.5' digital quadrangles currently available for nearly the entire area. As for their shorter-wavelength brethren, imaging radars were tested early in their civilian history in the Mojave Desert-Death Valley region because it contains a variety of surface types in a small area without the confounding effects of vegetation. The earliest imaging radars to be flown over the region included military tests of short-wavelength (3 cm) X-band sensors. Later, the Jet Propulsion Laboratory began its development of imaging radars with an airborne sensor, followed by the Seasat orbital radar in 1978. These systems were L-band (25 cm). Following Seasat, JPL embarked upon a series of Space Shuttle Imaging Radars: SIRA (1981), SIR-B (1984), and SIR-C (1994). The most recent in the series was the most capable radar sensor flown in space and acquired large numbers of data swaths in a variety of test areas around the world. The Mojave Desert-Death Valley region was one of those test areas, and was covered very well with 3 wavelengths, multiple polarizations, and at multiple angles. At the same time, the JPL aircraft radar program continued improving and collecting data over the Mojave Desert Death Valley region. Now called AIRSAR, the system includes 3 bands (P-band, 67 cm; L-band, 25 cm; C-band, 5 cm). Each band can collect all possible polarizations in a mode called polarimetry. In addition, AIRSAR can be operated in the TOPSAR mode wherein 2 antennas collect data interferometrically, yielding a digital elevation model (DEM). Both L-band and C-band can be operated in this way, with horizontal resolution of about 5 m and vertical errors less than 2 m. The findings and developments of these earlier investigations are discussed.

  17. Microphysical cross validation of spaceborne radar and ground polarimetric radar

    Microsoft Academic Search

    V. Chandrasekar; Steven M. Bolen; Eugenio Gorgucci

    2003-01-01

    Ground-based polarimetric radar observations along the beam path of the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR), matched in resolution volume and aligned to PR measurements, are used to estimate the parameters of a gamma raindrop size distribution (RSD) model along the radar beam in the presence of rain. The PR operates at 13.8 GHz, and its signal returns

  18. RADAR: THE CASSINI TITAN RADAR MAPPER C. ELACHI1,

    E-print Network

    RADAR: THE CASSINI TITAN RADAR MAPPER C. ELACHI1, , M. D. ALLISON2 , L. BORGARELLI3 , P. ENCRENAZ4; Accepted in final form 3 June 1999) Abstract. The Cassini RADAR instrument is a multimode 13.8 GHz multiple coefficient as low as -40 dB. 1. Introduction The Cassini spacecraft, launched on October 15, 1997, carries

  19. Minimum radar cross section bounds for passive radar responsive tags

    Microsoft Academic Search

    P. Bidigare; T. Stevens; B Correll; M. Beauvais

    2004-01-01

    A common problem in ground moving target indication (GMTI) radar is detecting a target with even a large radar cross section (RCS) when its line-of-sight velocity falls below the minimum detectable velocity (MDV) for that radar system. In a cooperative scenario, a target may employ a tagging device, which can shift or spread its Doppler signature to become more detectable.

  20. Characteristics of HfO2/Hf-based bipolar resistive memories

    NASA Astrophysics Data System (ADS)

    Jinshun, Bi; Zhengsheng, Han

    2015-06-01

    Nano-scale Hf/HfO2-based resistive random-access-memory (RRAM) devices were fabricated. The cross-over between top and bottom electrodes of RRAM forms the metal–insulator–metal sandwich structure. The electrical responses of RRAM are studied in detail, including forming process, SET process and RESET process. The correlations between SET voltage and RESET voltage, high resistance state and low resistance state are discussed. The electrical characteristics of RRAM are in a strong relationship with the compliance current in the SET process. The conduction mechanism of nano-scale Hf/HfO2-based RRAM can be explained by the quantum point contact model. Project supported by the National Natural Science Foundation of China (Nos. 11179003, 61176095).

  1. Microwave emissions from police radar 

    E-print Network

    Fink, John Michael

    1994-01-01

    The purpose of this study was to evaluate police officers exposures to microwaves emitted by traffic radar units at the ocular and testicular level. Additionally, comparisons were made of the radar manufacturers published maximum power density...

  2. Venus wind-altitude radar

    NASA Technical Reports Server (NTRS)

    Levanon, N.

    1974-01-01

    A design study on adding a radar altimeter to the Pioneer Venus small probe is review. Block and timing diagrams are provided. The inherent and interface ambiguities, resolution, and data handling logic for radar altimeters are described.

  3. Systems and Methods for Radar Data Communication

    NASA Technical Reports Server (NTRS)

    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. Interactions Among Ionospheric Propagation, HF Modems, and Data Protocols

    E-print Network

    Johnson, Eric E.

    1 Interactions Among Ionospheric Propagation, HF Modems, and Data Protocols Eric E. Johnson New for data communications have been increasingly well-addressed by recent generations of HF data modems-bandwidth channels in mind. In this paper, we explore the interactions among the skywave channel, HF data modems

  5. Self interstitial trapping at Hf impurities in Niobium

    Microsoft Academic Search

    R.-D. Roitzheim; R. Vianden

    1991-01-01

    After electron irradiation at ~ 15 K of Niobium doped with181Hf the trapping of defects at the Hf impurities was observed by means of the perturbed angular correlation method. The results are interpreted as the formation of Hf-Nb mixed dumbbells which are formed at ~ 5 K and are stable up to ~ 80 K.

  6. Aluminothermic preparation of Hf–Ta and Nb–10Hf–1Ti alloys and their characterization

    Microsoft Academic Search

    I. G Sharma; S Majumdar; S. P Chakraborty; A. K Suri

    2003-01-01

    The high temperature materials capable of withstanding high stress levels at elevated temperature together with excellent oxidation resistance have received considerable attention since the emergence of aerospace industries. Alloys such as Nb–10Hf–1Ti and Hf–20 to 30 wt.% Ta are being considered seriously for development to meet the growing demand for aerospace and other high temperature requirements. Currently the alloys are

  7. A review of array radars

    Microsoft Academic Search

    E. Brookner

    1981-01-01

    Achievements in the area of array radars are illustrated by such activities as the operational deployment of the large high-power, high-range-resolution Cobra Dane; the operational deployment of two all-solid-state high-power, large UHF Pave Paws radars; and the development of the SAM multifunction Patriot radar. This paper reviews the following topics: array radars steered in azimuth and elevation by phase shifting

  8. The Clementine Bistatic Radar Experiment

    Microsoft Academic Search

    S. Nozette; C. L. Lichtenberg; P. Spudis; R. Bonner; W. Ort; E. Malaret; M. Robinson; E. M. Shoemaker

    1996-01-01

    During the Clementine 1 mission, a bistatic radar experiment measured the magnitude and polarization of the radar echo versus bistatic angle, beta, for selected lunar areas. Observations of the lunar south pole yield a same-sense polarization enhancement around beta = 0. Analysis shows that the observed enhancement is localized to the permanently shadowed regions of the lunar south pole. Radar

  9. SEASAT Synthetic Aperture Radar Data

    NASA Technical Reports Server (NTRS)

    Henderson, F. M.

    1981-01-01

    The potential of radar imagery from space altitudes is discussed and the advantages of radar over passive sensor systems are outlined. Specific reference is made to the SEASAT synthetic aperture radar. Possible applications include oil spill monitoring, snow and ice reconnaissance, mineral exploration, and monitoring phenomena in the urban environment.

  10. Review of current radar interests

    Microsoft Academic Search

    M. I. Skolnik

    1974-01-01

    Current radar applications and problem areas are reviewed. Air traffic control, aircraft and ship navigation, remote sensing, and law enforcement are some of the applications mentioned. Both the Gemini and the Apollo space vehicles used radar for rendezvous and docking, and Apollo also utilized it for lunar landing. Equipment improvements suggested include better isolation in CW radar, efficient linear transmitters,

  11. A radar tour of Venus

    Microsoft Academic Search

    J. K. Beatty

    1985-01-01

    The surface of Venus is briefly characterized in a summary of results obtained by the Soviet Venera 15 and 16 8-cm synthetic-aperture radars, IR radiometers, and radar altimeters. A series of radar images, mainly from Kotelnikov et al. (1984), are presented and discussed, and the descent vehicles to be released by the two Vega spacecraft as they pass Venus in

  12. Analysis of Random Radar Networks

    E-print Network

    Adve, Raviraj

    a design tradeoff between spatial diversity and interference cancellation for multistatic radar networksAnalysis of Random Radar Networks Rani Daher, Raviraj Adve Department of Electrical and Computer.daher@utoronto.ca, rsadve@comm.utoronto.ca Abstract--We introduce the notion of random radar networks to analyze the effect

  13. Analysis of weather radar return

    Microsoft Academic Search

    D. Payne

    1977-01-01

    A mathematical model of detected clutter from an airborne weather radar of conventional design is developed. The model is the joint probability density of samples of radar return from hydrometeors at the same nominal range and scan angle. It is developed from analysis of the effect on the received signal of the following parameters: inhomogeneous hydrometeor motion, radar frequency stability,

  14. Hydrofluoric Acid (HF) Instructions The CEPSR Clean Room supplies one pound bottles of aqueous HF; their concentration may

    E-print Network

    Kim, Philip

    Hydrofluoric Acid (HF) Instructions The CEPSR Clean Room supplies one pound bottles of aqueous HF solution that resembles water; it is one of the strongest inorganic acids. Exposure to this acid can be no immediate pain or discomfort. HF differs from other acids because the fluoride ion readily penetrates

  15. Spaceborne Imaging Radar Symposium

    NASA Technical Reports Server (NTRS)

    Elachi, C.

    1983-01-01

    An overview of the present state of the art in the different scientific and technological fields related to spaceborne imaging radars was presented. The data acquired with the SEASAT SAR (1978) and Shuttle Imaging Radar, SIR-A (1981) clearly demonstrated the important emphasis in the 80's is going to be on in-depth research investigations conducted with the more flexible and sophisticated SIR series instruments and on long term monitoring of geophysical phenomena conducted from free-flying platforms such as ERS-1 and RADARSAT.

  16. Spaceborne laser radar.

    NASA Technical Reports Server (NTRS)

    Flom, T.

    1972-01-01

    Development of laser systems to acquire and track targets in applications such as the rendezvous and docking of two spacecraft. A scan technique is described whereby a narrow laser beam is simultaneously scanned with an equally narrow receiver field-of-view without the aid of mechanical gimbals. Equations are developed in order to examine the maximum acquisition and tracking rates, and the maximum target range for a scanning laser radar system. A recently built prototype of a small, lightweight, low-power-consuming scanning laser radar is described.

  17. Microwave radar oceanographic investigations

    NASA Technical Reports Server (NTRS)

    Jackson, F. C.

    1988-01-01

    The Radar Ocean Wave Spectrometer (ROWS) technique was developed and demonstrated for measuring ocean wave directional spectra from air and space platforms. The measurement technique was well demonstrated with data collected in a number of flight experiments involving wave spectral comparisons with wave buoys and the Surface Contour Radar (SCR). Recent missions include the SIR-B underflight experiment (1984), FASINEX (1986), and LEWEX (1987). ROWS related activity is presently concentrating on using the aircraft instrument for wave-processes investigations and obtaining the necessary support (consensus) for a satellite instrument development program. Prospective platforms include EOS and the Canadian RADARSAT.

  18. Radar Investigations of Asteroids

    NASA Technical Reports Server (NTRS)

    Ostro, S. J.

    1984-01-01

    Radar investigations of asteroids, including observations during 1984 to 1985 of at least 8 potential targets and continued analyses of radar data obtained during 1980 to 1984 for 30 other asteroids is proposed. The primary scientific objectives include estimation of echo strength, polarization, spectral shape, spectral bandwidth, and Doppler shift. These measurements yield estimates of target size, shape, and spin vector; place constraints on topography, morphology, density, and composition of the planetary surface; yield refined estimates of target orbital parameters; and reveals the presence of asteroidal satellites.

  19. An adaptive digital beamforming network for satellite communication systems

    NASA Astrophysics Data System (ADS)

    Barrett, M.; Fernandez, J.; Lagunas, M. A.; Coromina, F.

    1991-10-01

    The use of adaptive digital beamforming techniques has, until recently, been largely restricted to high performance military radar systems. Recent advances in digital technology, however, have enabled the design of single chip digital beamforming networks. This, coupled with advances in digital signal processor technology, enables complete beamforming systems to be constructed at a lower cost, thus making the application of these techniques to commercial communications systems attractive. The design and development of such an adaptative digital beamforming network are described. The system is being developed as a proof of concept laboratory based demonstrator to enable the feasibility of adaptive digital beamforming techniques for communication systems to be determined. Ultimately, digital beamforming could be used in conjunction with large array antennas for communication satellite systems. This will enable the simultaneous steering of high gain antenna beams in the direction of ground based users and the nulling of unwanted interference sources, such as radar systems, to be performed.

  20. Collisional quenching of highly rotationally excited HF

    NASA Astrophysics Data System (ADS)

    Yang, B.; Walker, K. M.; Forrey, R. C.; Stancil, P. C.; Balakrishnan, N.

    2015-06-01

    Context. 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. Aims: Theoretical cross sections and rate coefficients for collisional deexcitation of rotationally excited HF in the vibrational ground state are reported. Methods: 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 H2 colliders were obtained from the HF-He collisional data with a reduced-potential scaling approach. Results: 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 15 000 cm-1. State-to-state rate coefficients for temperatures between 0.1 and 3000 K are also presented. The comparison of the present results with previous work for lowly-excited rotational levels reveals significant differences. In estimating HF-H2 rate coefficients, the reduced-potential method is found to be more reliable than the standard reduced-mass approach. Conclusions: The current state-to-state rate coefficient calculations are the most comprehensive to date for HF-He collisions. We attribute the differences between previously reported data and our results to differences in the adopted interaction potential energy surfaces. The new He rate coefficients can be used in a variety of applications. The estimated H2 and H collision rates can also augment the smaller datasets previously developed for H2 and electrons. Rate coefficient tables are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/578/A65

  1. Soft X-ray photoemission studies of Hf oxidation

    SciTech Connect

    Suzer, S.; Sayan, S.; Banaszak Holl, M.M.; Garfunkel, E.; Hussain, Z.; Hamdan, N.M.

    2002-02-01

    Soft X-Ray Photoemission Spectroscopy using surface sensitive Synchrotron Radiation has been applied to accurately determine the binding energy shifts and the valence band offset of the HfO2 grown on Hf metal. Charging of oxide films under x-rays (or other irradiation) is circumvented by controlled and sequential in-situ oxidation. Photoemission results show the presence of metallic Hf (from the substrate) with the 4f7/2 binding energy of 14.22 eV, fully oxidized Hf (from HfO2) with the 4f7/2 binding energy of 18.16 eV, and at least one clear suboxide peak. The position of the valence band of HfO2 with respect to the Hf(m) Fermi level is determined as 4.05 eV.

  2. Description, characteristics and testing of the NASA airborne radar

    NASA Technical Reports Server (NTRS)

    Jones, W. R.; Altiz, O.; Schaffner, P.; Schrader, J. H.; Blume, H. J. C.

    1991-01-01

    Presented here is a description of a coherent radar scattermeter and its associated signal processing hardware, which have been specifically designed to detect microbursts and record their radar characteristics. Radar parameters, signal processing techniques and detection algorithms, all under computer control, combine to sense and process reflectivity, clutter, and microburst data. Also presented is the system's high density, high data rate recording system. This digital system is capable of recording many minutes of the in-phase and quadrature components and corresponding receiver gains of the scattered returns for selected spatial regions, as well as other aircraft and hardware related parameters of interest for post-flight analysis. Information is given in viewgraph form.

  3. Preliminary science results from the Shuttle Imaging Radar-B

    NASA Technical Reports Server (NTRS)

    Ruzek, M.

    1985-01-01

    Preliminary results of analyzing digital radar imagery data obtained by the SIR-B aboard the Space Shuttle Challenger STS 41-G are presented. The data cover 5 million square kilometers of the earth surface between 57 deg north and south latitudes. Radar imagery of the same target at different incidence angles was used to classify surfaces by their backscatter response as a function of incidence angle. The SIR-B proved to be useful for collecting multiple incidence angle data sets over a broad range of targets, providing information in the areas of geology, archeology, forestry, agriculture, oceanography, geography, and hydrology. The analysis is also used to optimize radar parameters such as look angle for future missions.

  4. Development of land based radar polarimeter processor system

    NASA Technical Reports Server (NTRS)

    Kronke, C. W.; Blanchard, A. J.

    1983-01-01

    The processing subsystem of a land based radar polarimeter was designed and constructed. This subsystem is labeled the remote data acquisition and distribution system (RDADS). The radar polarimeter, an experimental remote sensor, incorporates the RDADS to control all operations of the sensor. The RDADS uses industrial standard components including an 8-bit microprocessor based single board computer, analog input/output boards, a dynamic random access memory board, and power supplis. A high-speed digital electronics board was specially designed and constructed to control range-gating for the radar. A complete system of software programs was developed to operate the RDADS. The software uses a powerful real time, multi-tasking, executive package as an operating system. The hardware and software used in the RDADS are detailed. Future system improvements are recommended.

  5. Bistatic synthetic aperture radar

    Microsoft Academic Search

    A. M. Horne; G. Yates

    2002-01-01

    Synthetic aperture radar (SAR) is becoming increasingly important in many military ground surveillance and targeting roles because of its ability to operate in all weather, day and night, and to detect, classify and geolocate objects at long stand-off ranges. Bistatic SAR, where the transmitter and receiver are on separate platforms, is seen as a potential means of countering vulnerability. This

  6. Rain radar instrument definition

    NASA Astrophysics Data System (ADS)

    Vincent, Nicolas; Chenebault, J.; Suinot, Noel; Mancini, Paolo L.

    1996-12-01

    As a result of a pre-phase a study, founded by ESA, this paper presents the definition of a spaceborne Rain Radar, candidate instrument for earth explorer precipitation mission. Based upon the description of user requirements for such a dedicated mission, a mission analysis defines the most suitable space segment. At system level, a parametric analysis compares pros and cons of instrument concepts associated with rain rate retrieval algorithms in order to select the most performing one. Several trade-off analysis at subsystem level leads then to the definition of the proposed design. In particular, as pulse compression is implemented in order to increase the radar sensitivity, the selected method to achieve a pulse response with a side-lobe level below--60 dB is presented. Antenna is another critical rain radar subsystem and several designs are com pared: direct radiating array, single or dual reflector illuminated by single or dual feed arrays. At least, feasibility of centralized amplification using TWTA is compared with criticality of Tx/Rx modules for distributed amplification. Mass and power budgets of the designed instrument are summarized as well as standard deviations and bias of simulated rain rate retrieval profiles. The feasibility of a compliant rain radar instrument is therefore demonstrated.

  7. Bistatic radar meteorological satellite

    NASA Technical Reports Server (NTRS)

    Nathanson, F. E.

    1981-01-01

    A technique is discussed that employs a radar transmitter with a moderate size antenna placed in a geosynchronous orbit with either a 0 degree or a low inclination orbit. The reflected signals from the precipitation are then received either on a single beam from a satellite having a beamwidth of about 6 degrees or preferably with a beam that scans the U.S. in a raster pattern with about 0.9 degrees beamwidth. While it would seem that a bistatic system with the transmitter at synchronous altitude and the receivers near the surface would not be a very efficient way of designing a radar system, it is somewhat surprising that the required power and antenna sizes are not that great. Two factors make the meteorological application somewhat more attractive than the bistatic detection of point targets. First, the bistatic reflections of radar signals from precipitation are to a large extent omnidirectional, and while raindrops are spheriods rather than spheres, the relationship of the reflectivity of the rain to rainfall rate can be easily derived. The second reason is that the rain echo signal level is independent of range from a receive only radar, and if the bistatic system works at all, it will work at long ranges.

  8. Weather and radar interactions

    Microsoft Academic Search

    J. P. Booth

    2005-01-01

    This paper discusses the effects of weather on radar system performance. This discussion were based on computer simulations and climatological data. The relationships between frequency and range were explored as they interact with the weather. This effort is being conducted in the RF Technology Division of the Applied Sensors, Guidance, and Electronics Directorate, US Army Aviation and Missile Research, Development,

  9. Distributed aperture OFDM radar

    Microsoft Academic Search

    Byung Wook Jung; R aviraj S. Adve; Joohwan Chun

    2009-01-01

    This paper presents a new method of obtaining frequency diversity using orthogonal frequency division multiplexing (OFDM). Exploiting spatial diversity, the key advantage of a distributed aperture radar, requires orthogonality in, for example, the frequency, time, waveform, dimensions across sensors. This paper focuses on the simplest of these cases; frequency orthogonality. Here we address the key drawback associated with frequency diversity:

  10. Heterogeneous chemistry of HBr and HF

    SciTech Connect

    Hanson, D.R.; Ravishankara, A.R. [Univ. of Colorado, Boulder, CO (United States)

    1992-11-12

    The authors present information on heterogeneous chemistry of HF and HBr on glass and ice surfaces at a temperature of 200K. Their objective is to study whether heterogeneous reactions of these species could be important in the atmospheric chemistry occuring on NAT particles or cloud condensation nuclei, and be a contributor to ozone depletion. HF showed no significant uptake or reactions with ClONO{sub 2} or HOCl. HBr was found to adsorb on these surfaces, and did not exhibit saturation for even relative high concentrations. In addition it showed reactivity with ClONO{sub 2}, Cl{sub 2} and N{sub 2}O{sub 5} on ice surfaces.

  11. 25. Perimeter acquisition radar building room #2M4, (mezzanine), power supply ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    25. Perimeter acquisition radar building room #2M4, (mezzanine), power supply room; computer power supply on left and water flow on right. This room is directly below data processing area (room #318). Sign on right reads: High purity water digital rack - Stanley R. Mickelsen Safeguard Complex, Perimeter Acquisition Radar Building, Limited Access Area, between Limited Access Patrol Road & Service Road A, Nekoma, Cavalier County, ND

  12. Chemical pumping of pure rotational HF lasers

    Microsoft Academic Search

    J. H. Smith; D. W. Robinson

    1981-01-01

    In the reported investigation, pure rotational laser oscillation has been observed in HF, following flash photolysis of various mixtures of trifluoromethyl halide, acetylenic compound, and argon in the ratio of 1:1:100. Specifically, mixtures of CF3I + C2H2, CF3I + CH3C2H, and CF3Br + C2H2 exhibit different patterns of laser intensity, and, further, are markedly different from patterns generated by the

  13. Removal of uranium from aqueous HF solutions

    Microsoft Academic Search

    Howard Pulley; Steven F. Seltzer

    1980-01-01

    This invention is a simple and effective method for removing uranium from aqueous HF solutions containing trace quantities of the same. The method comprises contacting the solution with particulate calcium fluoride to form uranium-bearing particulates, permitting the particulates to settle, and separting the solution from the settled particulates. The CaF.sub.2 is selected to have a nitrogen surface area in a

  14. Removal of uranium from aqueous HF solutions

    Microsoft Academic Search

    H. Pulley; S. F. Seltzer

    1980-01-01

    This invention is a simple and effective method for removing uranium from aqueous HF solutions containing trace quantities of the same. The method comprises contacting the solution with particulate calcium fluoride to form uranium-bearing particulates, permitting the particulates to settle, and separating the solution from the settled particulates. The CaF2 is selected to have a nitrogen surface area in a

  15. Space Radar Image of Long Valley, California - 3D view

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This is a three-dimensional perspective view of Long Valley, California by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar on board the space shuttle Endeavour. This view was constructed by overlaying a color composite SIR-C image on a digital elevation map. The digital elevation map was produced using radar interferometry, a process by which radar data are acquired on different passes of the space shuttle and, which then, are compared to obtain elevation information. The data were acquired on April 13, 1994 and on October 3, 1994, during the first and second flights of the SIR-C/X-SAR radar instrument. The color composite radar image was produced by assigning red to the C-band (horizontally transmitted and vertically received) polarization; green to the C-band (vertically transmitted and received) polarization; and blue to the ratio of the two data sets. Blue areas in the image are smooth and yellow areas are rock outcrops with varying amounts of snow and vegetation. The view is looking north along the northeastern edge of the Long Valley caldera, a volcanic collapse feature created 750,000 years ago and the site of continued subsurface activity. Crowley Lake is off the image to the left. Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves, allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3 cm). The multi-frequency data will be used by the international scientific community to better understand the global environment and how it is changing. The SIR-C/X-SAR data, complemented by aircraft and ground studies, will give scientists clearer insights into those environmental changes which are caused by nature and those changes which are induced by human activity. SIR-C was developed by NASA's Jet Propulsion Laboratory. X-SAR was developed by the Dornier and Alenia Spazio companies for the German space agency, Deutsche Agentur fuer Raumfahrtangelegenheiten (DARA), and the Italian space agency, Agenzia Spaziale Italiana (ASI), with the Deutsche Forschungsanstalt fuer Luft und Raumfahrt e.V.(DLR), the major partner in science, operations and data processing of X-SAR.

  16. Space Radar Image of Long Valley, California in 3-D

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This three-dimensional perspective view of Long Valley, California was created from data taken by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar on board the space shuttle Endeavour. This image was constructed by overlaying a color composite SIR-C radar image on a digital elevation map. The digital elevation map was produced using radar interferometry, a process by which radar data are acquired on different passes of the space shuttle. The two data passes are compared to obtain elevation information. The interferometry data were acquired on April 13,1994 and on October 3, 1994, during the first and second flights of the SIR-C/X-SAR instrument. The color composite radar image was taken in October and was produced by assigning red to the C-band (horizontally transmitted and vertically received) polarization; green to the C-band (vertically transmitted and received) polarization; and blue to the ratio of the two data sets. Blue areas in the image are smooth and yellow areas are rock outcrops with varying amounts of snow and vegetation. The view is looking north along the northeastern edge of the Long Valley caldera, a volcanic collapse feature created 750,000 years ago and the site of continued subsurface activity. Crowley Lake is the large dark feature in the foreground. Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves, allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3 cm). The multi-frequency data will be used by the international scientific community to better understand the global environment and how it is changing. The SIR-C/X-SAR data, complemented by aircraft and ground studies, will give scientists clearer insights into those environmental changes which are caused by nature and those changes which are induced by human activity. SIR-C was developed by NASA's Jet Propulsion Laboratory. X-SAR was developed by the Dornier and Alenia Spazio companies for the German space agency, Deutsche Agentur fuer Raumfahrtangelegenheiten (DARA), and the Italian space agency, Agenzia Spaziale Italiana (ASI), with the Deutsche Forschungsanstalt fuer Luft und Raumfahrt e.v. (DLR), the major partner in science, operations and data processing of X-SAR.

  17. Transformation of electronic properties and structural phase transition from HfN to Hf3N4

    NASA Astrophysics Data System (ADS)

    Huang, H. H.; Fan, Xiaofeng; Hu, C. Q.; Singh, David J.; Jiang, Q.; Zheng, W. T.

    2015-06-01

    We report investigation of the structural phase transition and electronic properties of Hf1?x N (0 ? x ? 0.25) using first principles calculations. The defective NaCl-type structure with Hf vacancies (VHf) is found to be stable over a large phase region. Hf3N4 with the Zr3N4-type structure is only stable in relative small region and readily destabilized when the stoichiometric ratio of N to Hf deviates from 4/3. The electronic and optic properties of Hf1?x N are controlled by the concentration of VHf. The full depletion of excess free electrons from Hf atoms results in the structural phase transition of Hf3N4.

  18. Space Radar Image of Oetzal, Austria

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This is a digital elevation model that was geometrically coded directly onto an X-band seasonal change image of the Oetztal supersite in Austria. The image is centered at 46.82 degrees north latitude and 10.79 degrees east longitude. This image is located in the Central Alps at the border between Switzerland, Italy and Austria, 50 kilometers (31 miles) southwest of Innsbruck. It was acquired by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture aboard the space shuttle Endeavour on April 14, 1994 and on October 5, 1994. It was produced by combining data from these two different data sets. Data obtained in April is green; data obtained in October appears in red and blue, and was used as an enhancement based on the ratio of the two data sets. Areas with a decrease in backscatter from April to October appear in light blue (cyan), such as the large Gepatschferner glacier seen at the left of the image center, and most of the other glaciers in this view. A light blue hue is also visible at the east border of the dark blue Lake Reschensee at the upper left side. This shows a significant rise in the water level. Magenta represents areas with an increase of backscatter from April 10 to October 5. Yellow indicates areas with high radar signal response during both passes, such as the mountain slopes facing the radar. Low radar backscatter signals refer to smooth surface (lakes) or radar grazing areas to radar shadow areas, seen in the southeast slopes. The area is approximately 29 kilometers by 21 kilometers (18 miles by 13.5 miles). The summit of the main peaks reaches elevations of 3,500 to 3,768 meters (xx feet to xx feet)above sea level. The test site's core area is the glacier region of Venter Valley, which is one of the most intensively studied areas for glacier research in the world. Research in Venter Valley (below center)includes studies of glacier dynamics, glacier-climate regions, snowpack conditions and glacier hydrology. About 25 percent of the core test site is covered by glaciers. Corner reflectors are set up for calibration. Five corner reflectors can be seen on the Gepatschferner and two can be seen on the Vernagtferner. Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves, allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3 cm). The multi-frequency data will be used by the international scientific community to better understand the global environment and how it is changing. The SIR-C/X-SAR data, complemented by aircraft and ground studies, will give scientists clearer insights into those environmental changes which are caused by nature and those changes which are induced by human activity. SIR-C was developed by NASA's Jet Propulsion Laboratory. X-SAR was developed by the Dornier and Alenia Spazio companies for the German space agency, Deutsche Agentur fuer Raumfahrtangelegenheiten (DARA), and the Italian space agency, Agenzia Spaziale Italiana (ASI), with the Deutsche Forschungsanstalt fuer Luft und Raumfahrt e.V.(DLR), the major partner in science, operations and data processing of X-SAR.

  19. Detection of Transionospheric SuperDARN HF Waves by the Radio Receiver Instrument on the enhanced Polar Outflow Probe Satellite

    NASA Astrophysics Data System (ADS)

    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.

  20. Electron-ion temperature ratio estimations in the summer polar mesosphere when subject to HF radio wave heating

    NASA Astrophysics Data System (ADS)

    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.

  1. The Shuttle Radar Topography Mission is uncrated in the Multi- Payload Processing Facility

    NASA Technical Reports Server (NTRS)

    1999-01-01

    The Shuttle Radar Topography Mission (SRTM) sits uncovered inside the Multi-Payload Processing Facility. The primary payload on mission STS-99, the SRTM consists of a specially modified radar system that will fly onboard the Space Shuttle during the 11-day mission scheduled for September 1999. This radar system will gather data that will result in the most accurate and complete topographic map of the Earth's surface that has ever been assembled. SRTM is an international project spearheaded by the National Imagery and Mapping Agency and NASA, with participation of the German Aerospace Center DLR. Its objective is to obtain the most complete high-resolution digital topographic database of the Earth.

  2. Radar cross section measurements of a scale model of the space shuttle orbiter vehicle

    NASA Technical Reports Server (NTRS)

    Yates, W. T.

    1978-01-01

    A series of microwave measurements was conducted to determine the radar cross section of the Space Shuttle Orbiter vehicle at a frequency and at aspect angles applicable to re-entry radar acquisition and tracking. The measurements were performed in a microwave anechoic chamber using a 1/15th scale model and a frequency applicable to C-band tracking radars. The data were digitally recorded and processed to yield statistical descriptions useful for prediction of orbiter re-entry detection and tracking ranges.

  3. Alterations of Visual Reaction Time and Short Term Memory in Military Radar Personnel

    PubMed Central

    MORTAZAVI, Seyed Mohammad Javad; TAEB, Shahram; DEHGHAN, Naser

    2013-01-01

    Background Radar transmitters emit high-power radiofrequency radiation by creation of a high-voltage and high-frequency alternating electrical current. Methods: Health effects of occupational exposure to military radar were investigated. Visual reaction time was recorded with a simple blind computer-assisted-visual reaction time test. To assess the short-term memory, modified Wechsler Memory Scale test was performed. Results: The mean +/- SD reaction time in radar works (N=100) and the control group (N=57) were 238.58 +/? 23.47 milliseconds and 291.86 +/? 28.26 milliseconds (P<0.0001), respectively. The scores of forward digit span in radar works and the control group were 3.56 +/? 0.77 and 4.29 +/? 1.06 (P<0.0001), while the scores of backward digit span in radar works and the control group were 2.70 +/? 0.69 and 3.62 +/? 0.95 (P<0.0001). The scores of word recognition in radar works and the control group were 3.37 +/? 1.13 and 5.86 +/? 1.11 (P<0.0001). Finally, the scores of paired words in radar works and the control group were 13.56 +/? 1.78 and 15.21 +/? 2.20 (P<0.0001). It can be concluded that occupational exposures to radar radiations decreases reaction time, which may lead to a better response to different hazards. Conclusion: To the best of our knowledge, this is the first study to show that occupational exposure to radar microwave radiation leads to decreased reaction time and the lower performance of short-term memory. Altogether, these results indicate that occupational exposure to radar microwave radiations may be linked to some non-detrimental and detrimental health effects. PMID:23785684

  4. Monsoon flood boundary delineation and damage assessment using space borne imaging radar and Landsat data

    NASA Technical Reports Server (NTRS)

    Imhoff, Marc L.; Vermillion, C.; Story, M. H.; Choudhury, A. M.; Gafoor, A.

    1987-01-01

    Space-borne synthetic aperture radar (SAR) data acquired by the Shuttle Imaging Radar-B (SIR-B) Program and Landsat Multispectral Scanner Subsystem (MSS) Data from Landsat 4 were used to map flood boundaries for the assessment of flood damage in the Peoples Republic of Bangladesh. The cloud penetrating capabilities of the L-band radar provided a clear picture of the hydrologic conditions of the surface during a period of inclement weather at the end of the wet phase of the 1984 monsoon. The radar image data were digitally processed to geometrically rectify the pixel geometry and were filtered to subdue radar image speckle effects. Contrast enhancement techniques and density slicing were used to create discrete land-cover categories corresponding to surface conditions present at the time of the Shuttle overflight. The radar image classification map was digitally registered to a spectral signature classification map of the area derived from Landsat MSS data collected two weeks prior to the SIR-B mission. Classification accuracy comparisons were made between the radar and MSS classification maps, and flood boundary and flood damage assessment measurements were made with the merged data by adding the classifications and inventorying the land-cover classes inundated at the time of flooding.

  5. Laboratory reproduction of arecibo experimental results: HF wave-enhanced Langmuir waves

    NASA Astrophysics Data System (ADS)

    Lee, M. C.; Riddolls, R. J.; Vilece, K. D.; Dalrymple, N. E.; Rowlands, M. J.; Moriarty, D. T.; Groves, K. M.; Sulzer, M. P.; Kuo, S. P.

    Laboratory experiments at MIT using the Versatile Toroidal Facility (VTF) have produced “cascading” and “frequency-upshifted” spectra of HF wave-enhanced Langmuir waves resembling the spectra observed in Arecibo experiments. The VTF experiments are well-explained using the source mechanism proposed by Kuo and Lee [1992] to interpret observed Langmuir wave spectra at Arecibo, Puerto Rico. This mechanism is referred to as a nonlinear scattering of parametric decay instability (PDI)-excited Langmuir waves by “pre-existing” lower hybrid waves to preferentially produce anti-Stokes (i.e., frequency-upshifted) Langmuir waves. Recent radar spectral observations of anti-Stokes Langmuir waves at Arecibo with improved range and time resolution [Sulzer and Fejer, 1994] can be reasonably understood in terms of this mechanism.

  6. METR 4624--Radar Meteorology SPRING 2012

    E-print Network

    Droegemeier, Kelvin K.

    METR 4624--Radar Meteorology SPRING 2012 Dr. Michael I. Biggerstaff; drdoppler@ou.edu (best method Principles of weather radar and storm observations including: radar system design, em wave propagation, radar&Q, moments of the power spectrum, ground clutter, attenuation, rainfall measurements using radar reflectivity

  7. METR 4624--Radar Meteorology SPRING 2014

    E-print Network

    Droegemeier, Kelvin K.

    METR 4624--Radar Meteorology SPRING 2014 Dr. Michael I. Biggerstaff; drdoppler@ou.edu (best method Principles of weather radar and storm observations including: radar system design, em wave propagation, radar&Q, moments of the power spectrum, ground clutter, attenuation, rainfall measurements using radar reflectivity

  8. Optimum frequency for subsurface-imaging synthetic-aperture radar

    SciTech Connect

    Brock, B.C.; Patitz, W.E.

    1993-05-01

    A subsurface-imaging synthetic-aperture radar (SISAR) has potential for application in areas as diverse as non-proliferation programs for nuclear weapons to environmental monitoring. However, most conventional synthetic-aperture radars operate at higher microwave frequencies which do not significantly penetrate below the soil surface. This study attempts to provide a basis for determining optimum frequencies and frequency ranges which will allow synthetic-aperture imaging of buried targets. Since the radar return from a buried object must compete with the return from surface clutter, the signal-to-clutter ratio is an appropriate measure of performance for a SISAR. A parameter-based modeling approach is used to model the complex dielectric constant of the soil from measured data obtained from the literature. Theoretical random-surface scattering models, based on statistical solutions to Maxwell's equations, are used to model the clutter. These models are combined to estimate the signal-to-clutter ratio for canonical targets buried in several soil configurations. Initial results indicate that the HF spectrum (3--30 MHz), although it could be used to detect certain targets under some conditions, has limited practical value for use with SISAR, while the upper vhf through uhf spectrum ([approximately]100 MHz--1 GHz) shows the most promise for a general purpose SISAR system. Recommendations are included for additional research.

  9. An MSK Radar Waveform

    NASA Technical Reports Server (NTRS)

    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 spectral efficiency than the MSK waveform, such as linear frequency modulation (LFM) and Costas frequency hopping, have a fixed peak sidelobe level that is therefore not configurable, and can be exceeded by high contrast targets. Furthermore, in the case of a multistatic experiment observing a target in motion, self-interference from the transmitter to the receiver is mitigated by the MSK waveform. Waveforms that have delay Doppler coupling, such as LFM, provide no such protection.

  10. Recent Advances in Spaceborne Precipitation Radar Measurement Techniques and Technology

    NASA Technical Reports Server (NTRS)

    Im, Eastwood; Durden, Stephen L.; Tanelli, Simone

    2006-01-01

    NASA is currently developing advanced instrument concepts and technologies for future spaceborne atmospheric radars, with an over-arching objective of making such instruments more capable in supporting future science needs and more cost effective. Two such examples are the Second-Generation Precipitation Radar (PR-2) and the Nexrad-In-Space (NIS). PR-2 is a 14/35-GHz dual-frequency rain radar with a deployable 5-meter, wide-swath scanned membrane antenna, a dual-polarized/dual-frequency receiver, and a realtime digital signal processor. It is intended for Low Earth Orbit (LEO) operations to provide greatly enhanced rainfall profile retrieval accuracy while consuming only a fraction of the mass of the current TRMM Precipitation Radar (PR). NIS is designed to be a 35-GHz Geostationary Earth Orbiting (GEO) radar for providing hourly monitoring of the life cycle of hurricanes and tropical storms. It uses a 35-m, spherical, lightweight membrane antenna and Doppler processing to acquire 3-dimensional information on the intensity and vertical motion of hurricane rainfall.

  11. Incoherent scatter radar directional pattern using radio astronomical observations

    NASA Astrophysics Data System (ADS)

    Medvedev, A. V.; Zavorin, A. V.; Lebedev, V. P.; Lubyshev, B. I.; Nosov, V. E.

    2002-03-01

    The Irkutsk Incoherent Scatter (IS) radar is a unique facility in Russia, designed for geophysical and radio- probing investigations of the upper atmosphere. The range of problems tackled using the radar is quite extensive. Having a high potential and investigative capability, the radar represents an extremely sophisticated engineering facility. A maximum possible knowledge of all performance data of this instrument is necessary for conducting accurate measurements of space environment parameters and for scientific experiments. Of particular interest in this regard is the radar's antenna system. The spatial distribution of the radiation power (directional pattern) of the antenna system is as yet imperfectly understood. Because of the complexity and the unconventional nature of the antenna design, a mathematical simulation and calculation of the directional pattern involves a highly cumbersome task, and the reliability of such calculations is low. The overall worldwide practice shows that the most powerful tool for obtaining the directional pattern characteristics is to measure the variations of the noise power level when various cosmic radio sources traverse the beam. The advancement of digital technology in the present state of the art makes it possible to record large amounts of information needed to construct an accurate spatial distribution of the power received and radiated by the antenna. Results, thus obtained, are useful for correctly selecting the IS radar operation modes.

  12. Target tracking for multistatic radar with transmitter uncertainty

    Microsoft Academic Search

    Sora Choi; Christian R. Berger; David Crouse; Peter Willett; Shengli Zhou

    2009-01-01

    We present a target tracking system for a specific sort of passive radar, that using a Digital Audio\\/Video Broadcast (DAB\\/DVB) network for illuminators of opportunity. The system can measure bi-static range and range-rate. Angular information is assumed here unavailable. The DAB\\/DVB network operates in a single frequency mode; this means the same data stream is broadcast from multiple senders in

  13. Miniature L-Band Radar Transceiver

    NASA Technical Reports Server (NTRS)

    McWatters, Dalia; Price, Douglas; Edelstein, Wendy

    2007-01-01

    A miniature L-band transceiver that operates at a carrier frequency of 1.25 GHz has been developed as part of a generic radar electronics module (REM) that would constitute one unit in an array of many identical units in a very-large-aperture phased-array antenna. NASA and the Department of Defense are considering the deployment of such antennas in outer space; the underlying principles of operation, and some of those of design, also are applicable on Earth. The large dimensions of the antennas make it advantageous to distribute radio-frequency electronic circuitry into elements of the arrays. The design of the REM is intended to implement the distribution. The design also reflects a requirement to minimize the size and weight of the circuitry in order to minimize the weight of any such antenna. Other requirements include making the transceiver robust and radiation-hard and minimizing power demand. Figure 1 depicts the functional blocks of the REM, including the L-band transceiver. The key functions of the REM include signal generation, frequency translation, amplification, detection, handling of data, and radar control and timing. An arbitrary-waveform generator that includes logic circuitry and a digital-to-analog converter (DAC) generates a linear-frequency-modulation chirp waveform. A frequency synthesizer produces local-oscillator signals used for frequency conversion and clock signals for the arbitrary-waveform generator, for a digitizer [that is, an analog-to-digital converter (ADC)], and for a control and timing unit. Digital functions include command, timing, telemetry, filtering, and high-rate framing and serialization of data for a high-speed scientific-data interface. The aforementioned digital implementation of filtering is a key feature of the REM architecture. Digital filters, in contradistinction to analog ones, provide consistent and temperature-independent performance, which is particularly important when REMs are distributed throughout a large array. Digital filtering also enables selection among multiple filter parameters as required for different radar operating modes. After digital filtering, data are decimated appropriately in order to minimize the data rate out of an antenna panel. The L-band transceiver (see Figure 2) includes a radio-frequency (RF)-to-baseband down-converter chain and an intermediate- frequency (IF)-to-RF up-converter chain. Transmit/receive (T/R) switches enable the use of a single feed to the antenna for both transmission and reception. The T/R switches also afford a built-in test capability by enabling injection of a calibration signal into the receiver chain. In order of decreasing priority, components of the transceiver were selected according to requirements of radiation hardness, then compactness, then low power. All of the RF components are radiation-hard. The noise figure (NF) was optimized to the extent that (1) a low-noise amplifier (LNA) (characterized by NF < 2 dB) was selected but (2) the receiver front-end T/R switches were selected for a high degree of isolation and acceptably low loss, regardless of the requirement to minimize noise.

  14. Molecular sieve separation of ground state HF molecules in a non-chain HF laser

    NASA Astrophysics Data System (ADS)

    Ma, Lianying; Zhou, Songqing; Huang, Chao; Cheng, Hongwei; Zhu, Feng

    2015-05-01

    A 3A molecular sieve separation device was designed and mounted in a closed-cycled non-chain HF laser to separate the ground state molecule being produced in discharge region from gas stream in order to improve the stability of laser output energy. Experiments were carried out with several different discharge voltages and gas flow velocities, and the preliminary results show that the molecular sieve separation device could dramatically decrease the decay of output energy of HF laser while improving the laser energy stability.

  15. Radar images of Mars

    NASA Technical Reports Server (NTRS)

    Muhleman, Duane O.; Butler, Bryan J.; Grossman, Arie W.; Slade, Martin A.

    1991-01-01

    VLA radar-reflected flux-density mappings have yielded full disk images of Mars which reveal near-surface features, including a region in the Tharsis volcano area that displayed no echo to the very low level of the radar-system noise. This feature is interpreted as a deposit of dust or ash whose density is less than about 0.5 g/cu cm; it must be several meters thick, and may be much deeper. The most strongly reflecting geological feature was the south polar ice cap, which is interpretable as arising from nearly-pure CO2 or H2O ice, with less than 2 vol pct Martian dust. Only one anomalous reflecting feature was identified outside the Tharsis region.

  16. New weather radar coming

    NASA Astrophysics Data System (ADS)

    Maggs, William Ward

    What would you call the next generation of radar for severe weather prediction? NEXRAD, of course. A prototype for the new system was recently completed in Norman, Okla., and by the early 1990s up to 195 stations around the United States will be tracking dangerous weather and sending faster, more accurate, and more detailed warnings to the public.NEXRAD is being built for the Departments of Commerce, Transportation, and Defense by the Unisys Corporation under a $450 million contract signed in December 1987. Th e system will be used by the National Weather Service, the Federal Aviation Administration (FAA), and the U.S. Air Force and Navy. The NEXRAD radar tower in Norman is expected to be operational in October.

  17. Cognitive processing for nonlinear radar

    NASA Astrophysics Data System (ADS)

    Martone, Anthony; Ranney, Kenneth; Hedden, Abigail; Mazzaro, Gregory; McNamara, David

    2013-05-01

    An increasingly cluttered electromagnetic environment (EME) is a growing problem for radar systems. This problem is becoming critical as the available frequency spectrum shrinks due to growing wireless communication device usage and changing regulations. A possible solution to these problems is cognitive radar, where the cognitive radar learns from the environment and intelligently modifies the transmit waveform. In this paper, a cognitive nonlinear radar processing framework is introduced where the main components of this framework consist of spectrum sensing processing, target detection and classification, and decision making. The emphasis of this paper is to introduce a spectrum sensing processing technique that identifies a transmit-receive frequency pair for nonlinear radar. It will be shown that the proposed technique successfully identifies a transmit-receive frequency pair for nonlinear radar from data collected from the EME.

  18. A review of array radars

    NASA Astrophysics Data System (ADS)

    Brookner, E.

    1981-10-01

    Achievements in the area of array radars are illustrated by such activities as the operational deployment of the large high-power, high-range-resolution Cobra Dane; the operational deployment of two all-solid-state high-power, large UHF Pave Paws radars; and the development of the SAM multifunction Patriot radar. This paper reviews the following topics: array radars steered in azimuth and elevation by phase shifting (phase-phase steered arrays); arrays steered + or - 60 deg, limited scan arrays, hemispherical coverage, and omnidirectional coverage arrays; array radars steering electronically in only one dimension, either by frequency or by phase steering; and array radar antennas which use no electronic scanning but instead use array antennas for achieving low antenna sidelobes.

  19. Outline of the Mu radar

    NASA Technical Reports Server (NTRS)

    Kato, S.

    1983-01-01

    A middle and upper atmospheric radar system is described. The antenna array consists of 25 groups each of which consists of 19 crossed-Yagis with three elements; each antenna has semiconductor transmitter and receiver, called a module, and each group of 19 antennas works as an independent small radar steering its radar beam under the control of a microcomputer. Thus, the total system consists of 25 small radars of this kind, enabling one to do various sophisticated operations with the system. The system is controlled by two other computers, one for radar controlling (HP9835A) and the other for data taking and on-line analysis (VAX11/750). The computer-controlled system is simple in operation for users and reliable in observation. Very quick beam steering (as quick as in a msec) is also possible because of electronic phase-changing of each module output under control of the microcomputer which is further controlled by the radar controller.

  20. Airborne bistatic radar applications

    Microsoft Academic Search

    James A. Foster

    1987-01-01

    Applications of bistatic radar when one or both of the units are airborne are discussed. Scenarios that merit deeper consideration are covert strike and head-on SAR using a stand-off illuminator, either airborne or space-based; area air defense with passive ground-based receivers and stand-off illuminators; an airborne picket line to detect stealth aircraft and missiles; AWACS aircraft providing mutual support in

  1. Radar receiver procedures

    NASA Astrophysics Data System (ADS)

    1990-04-01

    This International Test Operations Procedures (ITOP) outlines the test methods used in evaluating the performance and characteristics of general types of radar receivers to include single or variable frequency receivers. The test methods serve as a guide in determining the overall efficiency of such equipment as a function of their design and their recorded performance. If a conflict exists between the accuracies, frequency, and levels stated in this ITOP and those stated in the appropriate requirements documents, the requirements documents must be used.

  2. Imaging synthetic aperture radar

    DOEpatents

    Burns, Bryan L. (Tijeras, NM); Cordaro, J. Thomas (Albuquerque, NM)

    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.

  3. Shuttle imaging radar experiment

    USGS Publications Warehouse

    Elachi, C.; Brown, W.E.; Cimino, J.B.; Dixon, T.; Evans, D.L.; Ford, J.P.; Saunders, R.S.; Breed, C.; Masursky, H.; McCauley, J.F.; Schaber, G.; Dellwig, L.; England, A.; MacDonald, H.; Martin-Kaye, P.; Sabins, F.

    1982-01-01

    The shuttle imaging radar (SIR-A) acquired images of a variety of the earth's geologic areas covering about 10 million square kilometers. Structural and geomorphic features such as faults, folds, outcrops, and dunes are clearly visible in both tropical and arid regions. The combination of SIR-A and Seasat images provides additional information about the surface physical properties: topography and roughness. Ocean features were also observed, including large internal waves in the Andaman Sea. Copyright ?? 1982 AAAS.

  4. Radar gun hazards

    SciTech Connect

    Not Available

    1991-12-20

    Radar guns - hand-held units used by the law to nail speeders - have been in use since the early '60s. Now they've been accused of causing cancer. Police officers in several states have so far filed eight suits against the manufacturer, claiming that they have contracted rare forms of cancer, such as of the eyelid and the testicle, from frequent proximity to the devices. Spurred by concerns expressed by police groups, researchers at the Rochester Institute of Technology are conducting what they believe to be the first research of its kind in the nation. Last month psychologist John Violanti, an expert in policy psychology and health, sent out a one-page survey to 6,000 active and retired police officers in New York State, asking them about their health and their use of radar guns. Violanti says melanoma, leukemia, and lymph node cancer may be linked to these as well as other electromagnetic devices. The Food and Drug Administration earlier this year issued a warning about radar guns, telling users not to operate them closer than 6 inches from the body. But this may not be a sufficient safeguard since the instruments can give off crisscrossing wave emissions within a police vehicle. The survey will be used to help determine if it would be safer to mount the guns, which are currently either hand-held or mounted on dashboards, outside troopers' cars.

  5. Comet radar explorer

    NASA Astrophysics Data System (ADS)

    Farnham, Tony; Asphaug, Erik; Barucci, Antonella; Belton, Mike; Bockelee-Morvan, Dominique; Brownlee, Donald; Capria, Maria Teresa; Carter, Lynn; Chesley, Steve; Farnham, Tony; Gaskell, Robert; Gim, Young; Heggy, Essam; Herique, Alain; Klaasen, Ken; Kofman, Wlodek; Kreslavsky, Misha; Lisse, Casey; Orosei, Roberto; Plaut, Jeff; Scheeres, Dan

    The Comet Radar Explorer (CORE) is designed to perform a comprehensive and detailed exploration of the interior, surface, and inner coma structures of a scientifically impor-tant Jupiter family comet. These structures will be used to investigate the origins of cometary nuclei, their physical and geological evolution, and the mechanisms driving their spectacular activity. CORE is a high heritage spacecraft, injected by solar electric propulsion into orbit around a comet. It is capable of coherent deep radar imaging at decameter wavelengths, high resolution stereo color imaging, and near-IR imaging spectroscopy. Its primary objective is to obtain a high-resolution map of the interior structure of a comet nucleus at a resolution of ¿100 elements across the diameter. This structure shall be related to the surface geology and morphology, and to the structural details of the coma proximal to the nucleus. This is an ideal complement to the science from recent comet missions, providing insight into how comets work. Knowing the structure of the interior of a comet-what's inside-and how cometary activity works, is required before we can understand the requirements for a cryogenic sample return mission. But more than that, CORE is fundamental to understanding the origin of comets and their evolution in time. The mission is made feasible at low cost by the use of now-standard MARSIS-SHARAD reflec-tion radar imaging hardware and data processing, together with proven flight heritage of solar electric propulsion. Radar flight heritage has been demonstrated by the MARSIS radar on Mars Express (Picardi et al., Science 2005; Plaut et al., Science 2007), the SHARAD radar onboard the Mars Reconnaissance Orbiter (Seu et al., JGR 2007), and the LRS radar onboard Kaguya (Ono et al, EPS 2007). These instruments have discovered detailed subsurface structure to depths of several kilometers in a variety of terrains on Mars and the Moon. A reflection radar deployed in orbit about a comet will enjoy significant simplifying benefits compared to using the same instrument for Mars or lunar radar science: (1) The proximity of operations leads to a much higher signal to noise, as much as +30 dB. (2) The lack of an ionosphere simplifies data modeling and analysis. (3) The body is globally illuminated during every data acquisition, minimizing ambiguity or 'clutter' and allowing for tomographic reconstruction. What is novel is the data processing, where instead of a planar radargram approach we coherently process the data into an image of the deep interior. CORE thus uses a MARSIS-SHARAD heritage radar to make coherent reflection sounding measurements, a 'CAT SCAN' of a comet nucleus. What is unique about this mission compared to the Mars radars mentioned above, is that the target is a finite mass of dirty ice in free space, rather than a sheet of dirty ice draped on a planet surface. The depth of penetration (kilometers), attainable resolution (decameters), and the target materials, are more or less the same. This means that the science story is robust, and the radar implementation is robust. The target is comet 10P/Tempel 2, discovered by Wilhelm Tempel in 1873 and observed on most apparitions since. It has been extensively studied, in part because of interest as a CRAF target in the mid-1980s, and much is known about it. Tempel 2 is one of the largest known comet nuclei, 16×8×8 km (about the same size as Halley) [1] and has rotation period 8.9 hours [3,5,6,7,9]. The spin state is evolving with time, spinning up by ˜10 sec per perihelion pass [5,7]. The comet is active, but not exceedingly so, especially given its size. The water production is measured at ˜ 4 × 1028 mol/sec at its peak [2], a factor of 25 lower than comet Halley, and it is active over only ˜2% of its surface. The dust environment is well known, producing a factor of ˜100 less dust than Halley. Comet References: [1] A'Hearn et al., ApJ 347, 1155, 1989 [2] Feldman and Festou, ACM 1991, p. 171, 1992 [3] Jewitt and Luu, AJ 97, 1766, 1989 [4] Lamy et al., Comets II p 223. 2009 [5] Muel

  6. Spaceborne Imaging Radar Project

    NASA Technical Reports Server (NTRS)

    Herman, Neil

    1986-01-01

    In June of 1985 the Project Initiation Agreement was signed by the Jet Propulsion Laboratory and the NASA Office of Space Science and Applications for the Spaceborne Imaging Radar Project (SIR). The thrust of the Spaceborne Imaging Radar Project is to continue the evolution of synthetic aperture radar (SAR) science and technology developed during SEASAT, SIR-A and SIR-B missions to meet the needs of the Earth Observing System (EOS) in the mid 1990's. As originally formulated, the Project plans were for a reflight of the SIR-B in 1987, the development of a new SAR, SIR-C, for missions in mid 1989 and early 1990, and the upgrade of SIR-C to EOS configuration with a qualification flight aboard the shuttle in the 1993 time frame (SIR-D). However, the loss of the shuttle Challenger has delayed the first manifest for SIR to early 1990. This delay prompted the decision to drop SIR-B reflight plans and move ahead with SIR-C to more effectively utilize this first mission opportunity. The planning for this project is discussed.

  7. Space-based radar handbook

    Microsoft Academic Search

    Leopold J. Cantafio

    1989-01-01

    The design and operation of space-based radar (SBR) systems are discussed in chapters contributed by leading experts. An overview of current and planned SBRs is presented, and particular attention is given to SBR-platform orbits, the ionospheric environment and its effects on SBR detection, space-based SARs, bistatic SBRs, rendezvous radars, radar altimeters for space vehicles, scatterometers and other modest-resolution systems, and

  8. Radar-aeolian roughness project

    NASA Technical Reports Server (NTRS)

    Greeley, Ronald; Dobrovolskis, A.; Gaddis, L.; Iversen, J. D.; Lancaster, N.; Leach, Rodman N.; Rasnussen, K.; Saunders, S.; Vanzyl, J.; Wall, S.

    1991-01-01

    The objective is to establish an empirical relationship between measurements of radar, aeolian, and surface roughness on a variety of natural surfaces and to understand the underlying physical causes. This relationship will form the basis for developing a predictive equation to derive aeolian roughness from radar backscatter. Results are given from investigations carried out in 1989 on the principal elements of the project, with separate sections on field studies, radar data analysis, laboratory simulations, and development of theory for planetary applications.

  9. Overview of Radar Data Compression Valliappa Lakshmanan

    E-print Network

    Lakshmanan, Valliappa

    Overview of Radar Data Compression Valliappa Lakshmanan Cooperative Institute of Mesoscale Meteorological Studies University of Oklahoma & National Severe Storms Laboratory Abstract Radar data is routinely transmitted in real-time from the coterminous United States (CONUS) radar sites and placed

  10. REVIEW ARTICLE Interferometric Synthetic Aperture Radar

    E-print Network

    Kansas, University of

    REVIEW ARTICLE Interferometric Synthetic Aperture Radar Christopher T. Allen Department of Electrical Engineering and Computer Science and Radar Systems and Remote Sensing Laboratory University of Kansas Abstract. This paper provides a brief review of interferometric synthetic aperture radar (In

  11. Combustion synthesis of HfB2Al composites

    Microsoft Academic Search

    H. C. Yi; J. Y. Guigné; T. C. Woodger; J. J. Moore

    1998-01-01

    Combustion synthesis (SHS) of HfB2-Al composite materials with a wide range of HfB2-to-Al ratios corresponding to either metal (Al) or ceramic (HfB2) matrix was carried out with the emphasis on 60 and 70 vol pct Al. The effects of composition and green density of pellets on the combustion characteristics were studied. Combustion temperature, wave velocity, and reaction mode all changed

  12. Combustion synthesis of HfB 2 Al composites

    Microsoft Academic Search

    H. C. Yi; J. Y. Guigné; T. C. Woodger; J. J. Moore

    1998-01-01

    Combustion synthesis (SHS) of HfB2-Al composite materials with a wide range of HfB2-to-Al ratios corresponding to either metal (Al) or ceramic (HfB2) matrix was carried out with the emphasis on 60 and 70 vol pct Al. The effects of composition and green density of pellets\\u000a on the combustion characteristics were studied. Combustion temperature, wave velocity, and reaction mode all changed

  13. Solid-state radar transmitters

    NASA Astrophysics Data System (ADS)

    Ostroff, E. D.; Borkowski, M.; Thomas, H.; Curtis, J.

    The technology and design procedures for introducing transistors into radio transmitters are discussed. The design characteristics of solid-state radar transmitters are described, with emphasis given to power amplifier/modules and devices for summing the output power in space or in an output combiner. Some design issues related to power supplies, pulse waveform amplitude regulation; reliability; and cost; and also considered. Some examples of successful solid-state radar systems are described, including the AN/TPS-59 radar, the AN/SPS-40 system, and the Pave/PAWS phased array radar. Black and white photographs of the different systems are provided.

  14. Digital Preservation.

    ERIC Educational Resources Information Center

    Yakel, Elizabeth

    2001-01-01

    Reviews research on digital preservation issues, including born-digital and digitally recreated documents. Discusses electronic records research; metadata and other standards; electronic mail; Web-based documents; moving images media; selection of materials for digitization, including primary sources; administrative issues; media stability…

  15. Radar Image, Hokkaido, Japan

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The southeast part of the island of Hokkaido, Japan, is an area dominated by volcanoes and volcanic caldera. The active Usu Volcano is at the lower right edge of the circular Lake Toya-Ko and near the center of the image. The prominent cone above and to the left of the lake is Yotei Volcano with its summit crater. The city of Sapporo lies at the base of the mountains at the top of the image and the town of Yoichi -- the hometown of SRTM astronaut Mamoru Mohri -- is at the upper left edge. The bay of Uchiura-Wan takes up the lower center of the image. In this image, color represents elevation, from blue at the lowest elevations to white at the highest. The radar image has been overlaid to provide more details of the terrain. Due to a processing problem, an island in the center of this crater lake is missing and will be properly placed when further SRTM swaths are processed. The horizontal banding in this image is a processing artifact that will be removed when the navigation information collected by SRTM is fully calibrated. This image was acquired by the Shuttle Radar Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched on February 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense (DoD), and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Earth Science Enterprise, Washington, DC. Size: 100 by 150 kilometers (62 by 93 miles) Location: 42.5 deg. North lat., 140.3 deg. East lon. Orientation: North towards upper left Image Data: SRTM Original Data Resolution: SRTM 30 meters (99 feet) Date Acquired: February 17, 2000

  16. Chemical pumping of pure rotational HF lasers

    Microsoft Academic Search

    John H. Smith; Dean W. Robinson

    1981-01-01

    Pure rotational laser oscillation has been observed in HF following flash photolysis of various mixtures of trifluoromethyl halide, acetylenic compound, and argon in the ration of 1:1:100. Specifically, mixtures of CF3I+C2H2, CF3I+CH3C2H, and CF3Br+C2H2 exhibit different patterns of laser intensity, and, further, are markedly different from patterns generated by the known photoelimination system CH2CF2. The above systems show laser intensity

  17. Combustion synthesis of HfB2-Al composites

    NASA Astrophysics Data System (ADS)

    Yi, H. C.; Guigné, J. Y.; Woodger, T. C.; Moore, J. J.

    1998-08-01

    Combustion synthesis (SHS) of HfB2-Al composite materials with a wide range of HfB2-to-Al ratios corresponding to either metal (Al) or ceramic (HfB2) matrix was carried out with the emphasis on 60 and 70 vol pct Al. The effects of composition and green density of pellets on the combustion characteristics were studied. Combustion temperature, wave velocity, and reaction mode all changed drastically with composition and green density. The combustion mechanisms were also studied using temperature profile analysis. The combustion zone can be divided into preflame and main reaction zones, and the width of the latter was much larger than that of the former. It was also found that the combustion reaction was initiated at the melting of the aluminum and consisted of a two-step reaction sequence corresponding to the initial formation of Al3Hf and, subsequently, HfB2 compounds. The formation of Al3Hf triggered the HfB2 formation according to the following reaction mechanism: A1_3 Hf + 2B to HfB_2 + 3A1

  18. Millimeter Wave Cloud Radar (MMCR) Handbook

    SciTech Connect

    KB Widener; K Johnson

    2005-01-30

    The millimeter cloud radar (MMCR) systems probe the extent and composition of clouds at millimeter wavelengths. The MMCR is a zenith-pointing radar that operates at a frequency of 35 GHz. The main purpose of this radar is to determine cloud boundaries (e.g., cloud bottoms and tops). This radar will also report radar reflectivity (dBZ) of the atmosphere up to 20 km. The radar possesses a doppler capability that will allow the measurement of cloud constituent vertical velocities.

  19. Removing interfering clutter associated with radar pulses that an airborne radar receives from a radar transponder

    DOEpatents

    Ormesher, Richard C. (Albuquerque, NM); Axline, Robert M. (Albuquerque, NM)

    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.

  20. Planetary radar studies. [radar mapping of the Moon and radar signatures of lunar and Venus craters

    NASA Technical Reports Server (NTRS)

    Thompson, T. W.; Cutts, J. A.

    1981-01-01

    Progress made in studying the evolution of Venusian craters and the evolution of infrared and radar signatures of lunar crater interiors is reported. Comparison of radar images of craters on Venus and the Moon present evidence for a steady state Venus crater population. Successful observations at the Arecibo Observatory yielded good data on five nights when data for a mix of inner and limb areas were acquired. Lunar craters with radar bright ejects are discussed. An overview of infrared radar crater catalogs in the data base is included.

  1. IONOTOMO: A new approach for ionospheric tomography using OTH radar

    NASA Astrophysics Data System (ADS)

    Rummel, R. F.; Gruber, T.; Ihde, J.; Liebsch, G.; Sideris, M. G.; Rangelova, E. V.; Woodworth, P. L.; Hughes, C. W.; Gerlach, C.

    2011-12-01

    Tomography techniques have been recently developed to reconstruct electron density in the ionosphere. Most of the recent methods are based on the inversion of the Total Electron Content (TEC) measured by ground-based GPS receivers (e.g., Garcia & Crespon). Notwithstanding the high-density of the stations coverage, as a consequence of the high frequency of the GPS signals, the inversion of the TEC-GPS measurements mainly reconstructs the electron density of the F2 region, where the ionosphere reaches the maximum of ionization, neglecting the lower ionosphere regions. Close to the ionospheric tomography by GPS, additional studies in ionospheric tomography explore HF propagation by OTH radar (Fridman and Fridman, 1994; Ruelle and Landeau, 1994; Landeau et al., 1997; Fridman, 1998). Those works are only based on the inversion of the leading edge echo curve, neglecting valuable informations present in the OTH radar data. To overcome those limits, we set up a new ionospheric tomography 3D method, based on ray-tracing theory and achieving the full analysis of over-the-horizon (OTH) radar data. The major advance of our methodology is taking into account, numerically and jointly, not only the speed variation of EM wave induced by the electron density variation but also the perturbation in the raypath, both necessary for the OTH radar inversion. We present here the originality and the advantages of our method with a full set of synthetic benchmark highlighting the sensitivity of our tomography to the plasma heterogeneities. Additionally, we show the possibility to integrate GPS-TEC data as well as satellite TEC occultations to our tomographic method, for a complete joint inversion capable to reconstruct the entire ionosphere. [Fridman and Fridman, 1994] J. Atmos. Terr. Phys., 56, 115-131, 1994. [Ruelle and Landeau, 1994] J. Atmos. Terr. Phys., 56, 103-114, 1994. [Landeau et al., 1997] J. Atm. Solar Terr. Phys., 59, 125-138, 1997. [Fridman, 1998] Radio Sci., 33, 1159-1171, 1998.

  2. Statistical characteristics of simulated radar imagery from bare soil surfaces: Effects of surface roughness and soil moisture variability

    SciTech Connect

    Narayanan, R.M.; Rundquist, D.C. (Univ. of Nebraska, Lincoln, NE (United States)); Pardipuram, R. (Hughes STX Corp., Lanham, MD (United States))

    1994-01-01

    The potential of high-resolution radar imagery to estimate various hydrological parameters, such as soil moisture, has long been recognized. Image simulation is one approach to study the interrelationships between the radar response and the underlying ground parameters. In order to perform realistic simulations, the authors incorporated the effects of naturally occurring spatial variability and spatial correlations of those ground parameters that affect the radar response, primarily surface roughness and soil moisture. Surface roughness and soil moisture images were generated for a hypothetical 100 x 100 m bare soil surface area at 1 m resolution using valid probability distribution and correlation lengths, These values were then used to obtain copolarized radar scattering coefficients at 2 GHz (L band) and 10 GHz (X band) frequencies using appropriate backscatter models, which were then converted to a digital number within 0--255 gray scale in order to generate radar images. The effect of surface roughness variability causes variability in the radar image, which is more apparent under smooth soil conditions. On the other hand, the inherent spatial pattern in soil moisture tends to cause similar patterns in the radar image under rougher soil conditions. The maximum difference between contrast-enhanced mean values of the radar image digital number due to moisture variations occurs at surface roughness values in the 1.5--2.0 cm range.

  3. Digital Sustainability and Digital Repositories

    Microsoft Academic Search

    Kevin Bradley

    The tasks associated with managing and backing up digital data are well known to IT managers, but the mere presence of the data stream is not the only criterion for preserving and maintaining digital content. Digital sustainability recognises that the continuity of digital information goes well beyond basic storing and managing of data and is integrated into the lifecycle of

  4. A digital laser slopemeter

    NASA Astrophysics Data System (ADS)

    Crossingham, Grant James

    This thesis is concerned with the design of a new ocean going instrument to measure the local sea surface profile. The motivation behind this project was the need to investigate oceanographic features that have been observed using imaging radar aboard aircraft and satellites. The measurements made with this instrument will further the understanding of the processes involved in radar backscatter from the ocean surface and will enable further analysis of ocean phenomena detected using imaging radars. With an improved understanding of these processes it will be possible to analyse quantitatively satellite images generated from around the globe. This will allow global environmental monitoring which could lead to improved weather forecasting, pollution control such as oil slick monitoring and surface and subsurface operations. It is believed that radar signals having a wavelength of 10 to 300mm are backscattered from waves on the ocean surface of similar length. Earlier attempts to measure waves including those designed to measure millimetric waves are critically reviewed and an account of the evolution of the design of a new instrument to measure these small waves is presented. This new instrument has been tested in the laboratory, which has demonstrated that a repeatable wave slope measurement accuracy of +/-0.56° has been achieved in static tests. Dynamic tests made using a wave tank have generated a wave slope profile, clearly showing 10mm wavelengths present on the surface. The new Digital Slopemeter is designed to measure the small-scale sea surface roughness for wavelengths in the range 10mm to 224mm. This instrument uses two grids of wavelength shifting fibres to digitally record the slope of a refracted laser beam. The laser beam is rapidly scanned over the sea surface to ensure that the profile of the surface is effectively stationary over a length of 224mm. The wave slope is sampled at 3.5mm intervals along each scan, allowing 7mm wavelengths to be resolved. This efficient measurement of the sea surface roughness enables a real-time display of the data collected. The design of the instrument permits it to be deployed from the bow of a research vessel in moderate seas. This instrument is therefore simple and flexible to deploy.

  5. Super Dual Auroral Radar Network observations of fluctuations in the spectral distribution of near range meteor

    NASA Astrophysics Data System (ADS)

    Upper Mesosphere, Echoes In The; Thermosphere , Lower

    2001-04-01

    The Doppler shifts of meteor echoes measured by the SuperDARN HF radar network have been used in several studies to observe neutral winds in the upper mesosphere and lower thermosphere region. In the absence of accurate height information for individual meteors, it has been necessary to assume a statistical mean meteor layer where the variations in altitude were not correlated to changes in the horizontal winds. Observations of spectral width distribution variations made by the radars allow an independent determination of the systematic error in the height. We have investigated the dependence of this distribution on a number of factors including the radar geometry, diurnal and seasonal cycles, variations in solar UV irradiance and geomagnetic activity. Changes in the altitude of the mean meteor layer observed at different radar ranges provide us with some insight into the structure of the upper mesosphere and the lower thermosphere within which the meteors are being ablated. An examination of the spectral widths, as measured by the CUT-LASS Finland radar, in the days preceding and following a Storm Sudden Commencement in April 1997, illustrates how the spectral properties of the observed region can be affected. The variations in the widths were consistent with model calculations of the changes to the temperature profile over this interval. Further refinements in the determination of the spectral width are outlined for future experiments.

  6. Fpga based L-band pulse doppler radar design and implementation

    NASA Astrophysics Data System (ADS)

    Savci, Kubilay

    As its name implies RADAR (Radio Detection and Ranging) is an electromagnetic sensor used for detection and locating targets from their return signals. Radar systems propagate electromagnetic energy, from the antenna which is in part intercepted by an object. Objects reradiate a portion of energy which is captured by the radar receiver. The received signal is then processed for information extraction. Radar systems are widely used for surveillance, air security, navigation, weather hazard detection, as well as remote sensing applications. In this work, an FPGA based L-band Pulse Doppler radar prototype, which is used for target detection, localization and velocity calculation has been built and a general-purpose Pulse Doppler radar processor has been developed. This radar is a ground based stationary monopulse radar, which transmits a short pulse with a certain pulse repetition frequency (PRF). Return signals from the target are processed and information about their location and velocity is extracted. Discrete components are used for the transmitter and receiver chain. The hardware solution is based on Xilinx Virtex-6 ML605 FPGA board, responsible for the control of the radar system and the digital signal processing of the received signal, which involves Constant False Alarm Rate (CFAR) detection and Pulse Doppler processing. The algorithm is implemented in MATLAB/SIMULINK using the Xilinx System Generator for DSP tool. The field programmable gate arrays (FPGA) implementation of the radar system provides the flexibility of changing parameters such as the PRF and pulse length therefore it can be used with different radar configurations as well. A VHDL design has been developed for 1Gbit Ethernet connection to transfer digitized return signal and detection results to PC. An A-Scope software has been developed with C# programming language to display time domain radar signals and detection results on PC. Data are processed both in FPGA chip and on PC. FPGA uses fixed point arithmetic operations as it is fast and facilitates source requirement as it consumes less hardware than floating point arithmetic operations. The software uses floating point arithmetic operations, which ensure precision in processing at the expense of speed. The functionality of the radar system has been tested for experimental validation in the field with a moving car and the validation of submodules are tested with synthetic data simulated on MATLAB.

  7. Advanced digital SAR processing study

    NASA Technical Reports Server (NTRS)

    Martinson, L. W.; Gaffney, B. P.; Liu, B.; Perry, R. P.; Ruvin, A.

    1982-01-01

    A highly programmable, land based, real time synthetic aperture radar (SAR) processor requiring a processed pixel rate of 2.75 MHz or more in a four look system was designed. Variations in range and azimuth compression, number of looks, range swath, range migration and SR mode were specified. Alternative range and azimuth processing algorithms were examined in conjunction with projected integrated circuit, digital architecture, and software technologies. The advaced digital SAR processor (ADSP) employs an FFT convolver algorithm for both range and azimuth processing in a parallel architecture configuration. Algorithm performace comparisons, design system design, implementation tradeoffs and the results of a supporting survey of integrated circuit and digital architecture technologies are reported. Cost tradeoffs and projections with alternate implementation plans are presented.

  8. Imaging Radar for Ecosystem Studies

    NASA Technical Reports Server (NTRS)

    Waring, Richard H.; Way, JoBea; Hunt, E. Raymond J.; Morrissey, Leslie; Ranson, K. Jon; Weishampel, John F.; Oren, Ram; Franklin, Steven E.

    1996-01-01

    Recently a number of satellites have been launched with radar sensors, thus expanding opportunities for global assessment. In this article we focus on the applications of imaging radar, which is a type of sensor that actively generates pulses of microwaves and, in the interval between sending pulses, records the returning signals reflected back to an antenna.

  9. Rendezvous radar for orbital vehicles

    Microsoft Academic Search

    John W. Locke; Larry D. Casey

    1992-01-01

    In this paper some of the factors which relate to the system design of rendezvous radars are discussed and the system design and the capabilities of the OMV Rendezvous Radar System (RRS) are described. The potential for transferring manufacturing technologies and methods which have been developed for high-volume-production commercial and military hardware systems into the relatively low volume world of

  10. OFDM waveforms for multistatic radars

    Microsoft Academic Search

    Y. Paichard

    2010-01-01

    In this paper, the benefits of OFDM waveforms are analyzed for multistatic radar systems, where several radar stations cooperate in the same frequency band. The signal is coded over a 2D pattern, in the time and the frequency domains, using orthogonal Golay complementary sets derived from Reed-Muller codes. Binary data are also encoded in the signal. The obtained ambiguity and

  11. Frequency diversity in multistatic radars

    Microsoft Academic Search

    Byung Wook Jung; R aviraj S. Adve; Joohwan Chun

    2008-01-01

    This paper presents the model and analysis of a frequency-diverse radar system. Multistatic radar systems provide an inherent spatial diversity by processing signals from different platforms which view a potential target from different aspect angles. By using different frequencies at each platform, an additional diversity gain can be obtained on top of the advantages of spatial diversity. Here, since platforms

  12. Classification algorithms for weather radar

    Microsoft Academic Search

    Felix Yanovsky; Vitaly Marchuk; Yaroslav Ostrovsky; Yulia Averyanova

    2008-01-01

    Theory, measurements, and signal processing applying to the radar remote sensing of weather objects are considered. Algorithms for hydrometeor type and turbulence intensity recognition are developed and analyzed. Particularly, fuzzy logic and neural network approaches are applied for weather radar signal processing.

  13. Space Radar Images of Earth

    NSDL National Science Digital Library

    This collection of images was captured by the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar, which was flown on two flights of the space shuttle Endeavour in 1994. Images are classified into categories for ease in searching: archaeological sites, cities, ecology and agriculture, geology, interferometry, oceans, rivers, snow and ice, and volcanoes.

  14. Radar background signal reduction study

    Microsoft Academic Search

    E. F. Knott; C. J. Ray; M. S. West; R. J. Wohlers

    1980-01-01

    This report summarizes a study whose objective was to identify materials and\\/or techniques to reduce radar background signals for ground plane radar cross section (RCS) ranges. Background signal reduction is essential for improving the accuracy of RCS measurements and the primary application is for operations at the RATSCAT range on the White Sands Missile Range in New Mexico. A survey

  15. Synthetic aperture radar processing with tiered subapertures

    SciTech Connect

    Doerry, A.W. [Sandia National Labs., Albuquerque, NM (United States). Synthetic Aperture Radar Dept.

    1994-06-01

    Synthetic Aperture Radar (SAR) is used to form images that are maps of radar reflectivity of some scene of interest, from range soundings taken over some spatial aperture. Additionally, the range soundings are typically synthesized from a sampled frequency aperture. Efficient processing of the collected data necessitates using efficient digital signal processing techniques such as vector multiplies and fast implementations of the Discrete Fourier Transform. Inherent in image formation algorithms that use these is a trade-off between the size of the scene that can be acceptably imaged, and the resolution with which the image can be made. These limits arise from migration errors and spatially variant phase errors, and different algorithms mitigate these to varying degrees. Two fairly successful algorithms for airborne SARs are Polar Format processing, and Overlapped Subaperture (OSA) processing. This report introduces and summarizes the analysis of generalized Tiered Subaperture (TSA) techniques that are a superset of both Polar Format processing and OSA processing. It is shown how tiers of subapertures in both azimuth and range can effectively mitigate both migration errors and spatially variant phase errors to allow virtually arbitrary scene sizes, even in a dynamic motion environment.

  16. Hand-held imaging laser radar

    NASA Astrophysics Data System (ADS)

    Ricks, Douglas W.; Willhite, H. Wayne

    1997-08-01

    We investigated laser radar technology for tactical intelligence; that is, we wanted to build a camcorder-sized device for information on terrain, and for reconnaissance and surveillance of various targets. Our performance requirements were; field of view 15 mrad by 150 mrad, image resolution 0.15 mrad, range 1 km, range depth resolution 15 cm, and acquisition time one third of a second. We designed imaging devices using two of the most promising technologies that we found. The first imager uses a digital CCD camera with a modulated image intensifier. The laser is a Q- switched, flashlamp-pumped, Nd:YAG laser. THere is no scanner in this system. The range is obtained by a technology similar to classical continuous phase detection. The second imager uses a diode-pumped solid state laser, and fiber optics to relay the image to thirty-two avalanche photo-diodes. The laser beam is split into thirty-two beams and a binary optics scanner is used for scanning between beams. The range is obtained with time-of-flight electronics. BOth imaging system designs meet the basic requirements, and could also be used in automatic target recognition, aimpoint selection, target tracking, obstacle avoidance, and other imaging laser radar applications.

  17. Land subsidence measured by satellite radar altimetry

    NASA Technical Reports Server (NTRS)

    Krabill, W. B.; Brooks, R. L.

    1981-01-01

    Radar altimeter measurements from the GEOS-3 and SEASAT satellites are being evaluated to assess their potential contribution to terrain mapping. The primary evaluation area is the San Joaquin Valley of southern California; 40,000/sq km of the Valley have been mapped at a contour interval of 10 m from the satellite altimeter measurements. The accuracy of the altimeter derived terrain elevations is being assessed by comparison with 1:24,000 and digitized 1:250,000 maps and by intercomparisons at the crossover altimeter intersections. Comparisons of the altimeter derived elevations with historical maps archived at the U.S. Geological Survey confirms the USGS 1926-1972 subsidence contours for this area. Preliminary results from a similar analysis in the Houston-Galveston area of subsidence also demonstrates a capability of measuring land subsidence by satellite altimetry.

  18. Space-based radar handbook

    NASA Astrophysics Data System (ADS)

    Cantafio, Leopold J.

    The design and operation of space-based radar (SBR) systems are discussed in chapters contributed by leading experts. An overview of current and planned SBRs is presented, and particular attention is given to SBR-platform orbits, the ionospheric environment and its effects on SBR detection, space-based SARs, bistatic SBRs, rendezvous radars, radar altimeters for space vehicles, scatterometers and other modest-resolution systems, and thermal control for SBRs. Also considered are the radar cross sections of satellites and other space targets, SBR clutter and interference, space antenna technology, onboard radar-signal processors, space power systems, and SBR structures. Diagrams, drawings, graphs, maps, and tables of numerical data are provided.

  19. 40 CFR 180.1273 - Beauveria bassiana HF23; exemption from the requirement of a tolerance.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 2010-07-01 false Beauveria bassiana HF23; exemption from the...Tolerances § 180.1273 Beauveria bassiana HF23; exemption from the requirement...a tolerance. Residues of Beauveria bassiana HF23 are exempt...

  20. Data Directed Estimation Techniques for Single-Tone HF Modems

    Microsoft Academic Search

    Frank M. Hsu

    1985-01-01

    This paper is concerned with data directed estimation (DDE) techniques for use in single-tone HF modems. The proposed scheme uses least-squares adaptive techniques for dealing with fading and multipath radio HF channels. The DDE is based on direct estimation of channel parameters and data blocks. Training data is imbedded into the transmission in the form of blocks of training bits

  1. Acidizing of Sandstone Reservoirs Using HF and Organic Acids 

    E-print Network

    Yang, Fei

    2012-10-19

    , and illite) were examined to react with formic-HF acid mixtures which contain different concentrations of HF. Coreflood experiments on sandstone cores featured by different mineralogy with dimensions of 1.5 in. x 6 in. were also conducted at a flow rate of 5...

  2. Signal extraction using Compressed Sensing for passive radar with OFDM signals

    Microsoft Academic Search

    Christian R. Berger; Shengli Zhou; Peter Willett

    2008-01-01

    Passive radar is a concept where possibly multiple non-cooperative illuminators are used in a multi-static setup. A freely available signal, like radio or television, is decoded and used to identify moving airborne targets based on their Doppler shift. New digital signals, like Digital Audio\\/Video Broadcast (DAB\\/DVB), are excellent candidates for this scheme, as they are widely available, can be easily

  3. Radar Multi-Targets Real-Time Communication Based on Software Radio

    Microsoft Academic Search

    Hangcheng Han; Jianping An; Weiyu An

    2010-01-01

    According to the modern software radio principle, a programmable general-purpose platform is designed to realize radar multi-targets real-time communication. The receiver is designed based on wideband IF sampling architecture, and cascaded with two digital attenuators. C-band signal is transformed into IF signal through twice conversions. DSP, FPGA, and ARM are used for digital signal processing. Cascaded Integrator-Comb (CIC) filter and

  4. Crystal structure of Si-doped HfO2

    NASA Astrophysics Data System (ADS)

    Zhao, Lili; Nelson, Matthew; Aldridge, Henry; Iamsasri, Thanakorn; Fancher, Chris M.; Forrester, Jennifer S.; Nishida, Toshikazu; Moghaddam, Saeed; Jones, Jacob L.

    2014-01-01

    Si-doped HfO2 was prepared by solid state synthesis of the starting oxides. Using Rietveld refinement of high resolution X-ray diffraction patterns, a substitutional limit of Si in HfO2 was determined as less than 9 at. %. A second phase was identified as Cristobalite (SiO2) rather than HfSiO4, the latter of which would be expected from existing SiO2-HfO2 phase diagrams. Crystallographic refinement with increased Si-dopant concentration in monoclinic HfO2 shows that c/b increases, while ? decreases. The spontaneous strain, which characterizes the ferroelastic distortion of the unit cell, was calculated and shown to decrease with increasing Si substitution.

  5. Improved electrical properties of metal-oxide-semiconductor capacitor with HfTiON gate dielectric by using HfSiON interlayer

    Microsoft Academic Search

    J. P. Xu; F. Ji; C. X. Li; P. T. Lai; J. G. Guan; Y. R. Liu

    2007-01-01

    Metal-oxide-semiconductor (MOS) capacitor with HfTiON\\/HfSiON stack structure as high-k gate dielectric is fabricated, and its electrical properties are compared with those of a similar device with HfTiON only as gate dielectric. Experimental results show that the device with HfTiON\\/HfSiON gate dielectric exhibits better interface properties, lower gate leakage current, and enhanced high-field reliability. All these improvements should be attributed to

  6. An improved radar detection range plotting method based on radar equation

    Microsoft Academic Search

    Li-Wei Wang; Xiao-Song Jiang

    2011-01-01

    In this paper, an improved radar detection range plotting method based on radar equation is proposed. Radar equation can be used to plot the radar detection range in theory from the point of view of energy. But in practice, the condition can not be satisfied. Based on radar equation, this method takes ground reflection, atmospheric refraction, earth curvature and obstacle

  7. STOP-HF: Expanding the role of HF programs into the community

    PubMed Central

    ElMaghawry, Mohamed; ElGuindy, Ahmed

    2014-01-01

    The St Vincent's Screening TO Prevent Heart Failure (STOP-HF) study is a recently published trial that assessed the use of brain natriuretic peptide (BNP) as a screening tool for HF in an at-risk population in reducing newly-diagnosed heart failure and prevalence of significant left ventricular (LV) systolic and/or diastolic dysfunction. The study provides an excellent model to the global community on how to integrate primary care simple screening with secondary and tertiary level targeted diagnostic and therapeutic system. This integration includes screening of high-risk groups, use of a sensitive screening tool, early diagnostic modalities, early therapeutic interventions, and proper assessment of the hard clinical outcomes. However, more studies are needed across multiple sites around the world with different levels of health care services and variable biomarkers to identify higher-risk groups. PMID:25405176

  8. Hf propagation through actively modified ionospheres

    SciTech Connect

    Argo, P.E.; Fitzgerald, T.J.; Wolcott, J.H.; Simons, D.J. (Los Alamos National Lab., NM (USA)); Warshaw, S.; Carlson, R. (Lawrence Livermore National Lab., CA (USA))

    1990-01-01

    We have developed a computer modeling capability to predict the effect of localized electron density perturbations created by chemical releases or high-power radio frequency heating upon oblique, one-hop hf propagation paths. We have included 3-d deterministic descriptions of the depleted or enhanced ionization, including formation, evolution, and drift. We have developed a homing ray trace code to calculate the path of energy propagation through the modified ionosphere in order to predict multipath effects. We also consider the effect of random index of refraction variations using a formalism to calculate the mutual coherence functions for spatial and frequency separations based upon a path integral solution of the parabolic wave equation for a single refracted path through an ionosphere which contains random electron density fluctuations. 5 refs., 8 figs.

  9. Understanding Radar Refractivity: Sources of Uncertainty

    E-print Network

    Droegemeier, Kelvin K.

    Understanding Radar Refractivity: Sources of Uncertainty David Bodine1,2 , Dan Michaud1,2 , Robert Radar Research Center, University of Oklahoma, Norman, OK, USA 3 NOAA/OAR National Severe Storms validation of WSR-88D radar refractiv- ity retrievals, and discusses some challenges to implementing radar

  10. Shuttle rendezvous radar performance: evaluation and simulation

    Microsoft Academic Search

    J. W. Griffin; A. C. Lindberg; T. B. Ahn; P. L. Harton

    1989-01-01

    The authors describe the performance evaluation and simulation of the Ku-band shuttle rendezvous radar. Computer simulation, using the radar cross section for specific spacecraft, provided an estimate of rendezvous radar range performance for that spacecraft. The radar cross section model included smooth metallic surfaces, rough surfaces, and shadowing effects, as well as phase differences due to different path lengths to

  11. Soviet oceanographic synthetic aperture radar (SAR) research

    Microsoft Academic Search

    D. N. Held; R. F. Gasparovic; A. W. Mansfield; W. K. Melville; E. L. Mollo-Christensen; H. A. Zebker

    1991-01-01

    Radar non-acoustic anti-submarine warfare (NAASW) became the subject of considerable scientific investigation and controversy in the West subsequent to the discovery by the Seasat satellite in 1978 that manifestations of underwater topography, thought to be hidden from the radar, were visible in synthetic aperture radar (SAR) images of the ocean. In addition, the Seasat radar produced images of ship wakes

  12. The applicability of GMTI MIMO Radar

    Microsoft Academic Search

    Michael Zatman

    2010-01-01

    MIMO Radar has been proposed as a technique for improving the Minimum Detectable Velocity (MDV) performance of airborne radar systems. However, the increased pulse repetition frequency associated with waveform multiplexing techniques used in GMTI MIMO Radar increases the amount of range ambiguous clutter the radar must suppress, reducing the amount of clutter-free Doppler space available to detect targets and often

  13. Seasat views North America, the Caribbean, and Western Europe with imaging radar

    NASA Technical Reports Server (NTRS)

    Ford, J. P.; Blom, R. G.; Bryan, M. L.; Daily, M.; Dixon, T. H.; Elachi, C.; Xenos, E. C.

    1980-01-01

    Forty-one digitally correlated Seasat synthetic-aperture radar images of land areas in North America, the Caribbean, and Western Europe are presented to demonstrate this microwave orbital imagery. The characteristics of the radar images, the types of information that can be extracted from them, and certain of their inherent distortions are briefly described. Each atlas scene covers an area of 90 X 90 kilometers, with the exception of the one that is the Nation's Capital. The scenes are grouped according to salient features of geology, hydrology and water resources, urban landcover, or agriculture. Each radar image is accompanied by a corresponding image in the optical or near-infrared range, or by a simple sketch map to illustrate features of interest. Characteristics of the Seasat radar imaging system are outlined.

  14. Prototype fiber optic system to remote TRACALS radars

    NASA Astrophysics Data System (ADS)

    Radcliff, J. A.; Becker, K. E.

    1982-06-01

    The transmission mediums currently used to remote Traffic Control and Landing Systems (TRACALS) radars are coaxial cables (coax) or a microwave link. Problems and limitations are encountered in using either medium. Coax is susceptible to electromagnetic interference, moisture, ground loops, lightning and electromagnetic pulse (EMP). Microwave links are susceptible to electromagnetic interference, propagation anomaly, electronic warfare and EMP. The coax remoting system used on the Precision Approach Radar (PAR) is highly susceptible to interference from power lines for runway lights and has a maximum remoting distance of 12,000 ft. Remoting TRACALS radars via a fiber optic system appeared to be a complete solution to the problems listed above. The 1842 EEG conducted a feasiblity study of the use of a FO system to remote a PAR (AFCC Technical Report, 1842 EEG/EEIT-TR-80-9). The AN/FPN-62 radar was used in conducting the study. The study demonstrated that an analog FO system can handle the combined analog/digital, time and frequency multiplexed signals which are passed over the AN/FPN-62 remoting system. A FO system appeared to be a desirable alternative and warranted a full investigation.

  15. Synthetic aperture radar and interferometry development at Sandia National Laboratories

    SciTech Connect

    NONE

    1993-04-01

    Environmental monitoring, earth-resource mapping, and military systems require broad-area imaging at high resolutions. Many times the imagery must be acquired in inclement weather or during night as well as day. Synthetic aperture radar (SAR) provides such a capability. SAR systems take advantage of the long-range propagation characteristics of radar signals and the complex information processing capability of modern digital electronics to provide high resolution imagery. SAR complements photographic and other optical imaging capabilities because of the minimum constrains on time-of-day and atmospheric conditions and because of the unique responses of terrain and cultural targets to radar frequencies. Interferometry is a method for generating a three-dimensional image of terrain. The height projection is obtained by acquiring two SAR images from two slightly differing locations. It is different from the common method of stereoscopic imaging for topography. The latter relies on differing geometric projections for triangulation to define the surface geometry whereas interferometry relies on differences in radar propagation times between the two SAR locations. This paper presents the capabilities of SAR, explains how SAR works, describes a few SAR applications, provides an overview of SAR development at Sandia, and briefly describes the motion compensation subsystem.

  16. Digital redaction 

    E-print Network

    Coquelin, Valerie

    1997-01-01

    in the digitization of historical collections is finding appropriate ways to handle rare inanuscripts, glass plate negatives, bound books and other fragile originals. One of the principal anxieties about digital infor- mation is the fear that obsolescent hardware..., and increasing access possibilities? What shape will the digital libraries of tomorrow take? The terminology "digital library" is in- deed challenged by the vast range of realities it may cover. Libraries are more than just book warehouses. They are social...

  17. Nearshore Processes, Currents and Directional Wave Spectra Monitoring Using Coherent and Non-coherent Imaging Radars

    NASA Astrophysics Data System (ADS)

    Trizna, D.; Hathaway, K.

    2007-05-01

    Two new radar systems have been developed for real-time measurement of near-shore processes, and results are presented for measurements of ocean wave spectra, near-shore sand bar structure, and ocean currents. The first is a non-coherent radar based on a modified version of the Sitex radar family, with a data acquisition system designed around an ISR digital receiver card. The card operates in a PC computer with inputs from a Sitex radar modified for extraction of analogue signals for digitization. Using a 9' antenna and 25 kW transmit power system, data were collected during 2007 at the U.S. Army Corps of Engineers Field Research Facility (FRF), Duck, NC during winter and spring of 2007. The directional wave spectrum measurements made are based on using a sequence of 64 to 640 antenna rotations to form a snapshot series of radar images of propagating waves. A square window is extracted from each image, typically 64 x 64 pixels at 3-m resolution. Then ten sets of 64 windows are submitted to a three-dimensional Fast Fourier Transform process to generate radar image spectra in the frequency-wavenumber space. The relation between the radar image spectral intensity and wave spectral intensity derived from the FRF pressure gauge array was used for a test set of data, in order to establish a modulation transfer function (MTF) for each frequency component. For 640 rotations, 10 of such spectra are averaged for improved statistics. The wave spectrum so generated was compared for extended data sets beyond those used to establish the MTF, and those results are presented here. Some differences between the radar and pressure sensor data that are observed are found to be due to the influence of the wind field, as the radar echo image weakens for light winds. A model is developed to account for such an effect to improve the radar estimate of the directional wave spectrum. The radar ocean wave imagery is severely influenced only by extremely heavy rain-fall rates, so that acceptable quality were assured for most weather conditions on a diurnal basis using a modest tower height. A new coherent microwave radar has recently been developed by ISR and preliminary testing was conducted in the spring of 2007. The radar is based on the Quadrapus four-channel transceiver card, mixed up to microwave frequencies for pulse transmission and back down to base-band for reception. We use frequency-modulated pulse compression methods to obtain 3-m spatial resolution. A standard marine radar pedestal is used to house the microwave components, and rotating radar PPI images similar to marine radar images are obtained. Many of the methods used for the marine radar system have been transferred to the coherent imaging radar. New processing methods applied to the coherent data allow summing of radial velocity images to map mean currents in the near shore zone, such as rip currents. A pair of such radars operating with a few hundred meter separation can be used to map vector currents continuously in the near shore zone and in harbors on a timely basis. Results of preliminary testing of the system will be presented.

  18. Shuttle radar mapping with diverse incidence angles in the rainforest of Borneo

    Microsoft Academic Search

    J. P. FORD; D. J. CASEY

    1988-01-01

    Shuttle Imaging Radar-B (SIR-B) images, obtained at two different incidence angles were analysed for discrimination and mapping of vegetation in the rainforest of Borneo. In an area of coastal lowland three units of forest canopy and two units of open surface cover were distinguished and mapped. The backscatter characteristics of the units were compared and analysed by ratioing digital image

  19. Blind Separation of Human Heartbeats and Breathing by the use of a Doppler Radar Remote Sensing

    Microsoft Academic Search

    Nicolas Petrochilos; Meriam Rezk; Anders Høst-Madsen; Victor Lubecke; Olga Boric-Lubecke

    2007-01-01

    The combined use of a Doppler radar with digital signal pro- cessing technique gives an effective non-invasive remote sensing of heart beat signals. Initial results have showed that the proposed tech- nique is very promising in successfully isolating desired heart beat signals from other mobile objects and other distortion effects char- acterizing the wireless channel. We concentrate in this paper

  20. A Virtual Antenna Beamforming (VAB) Approach for Radar Systems by Using Orthogonal Coding Waveforms

    Microsoft Academic Search

    Hai Deng; Braham Himed

    2009-01-01

    An innovative approach is introduced to form virtual transmitting and receiving radar antenna beams simultaneously by transmitting orthogonal coding waveforms from the antenna elements and digitally processing of their echoes at the receiver. Multiple virtual transmitting-receiving beams can be formed simultaneously by employing an equal number of beamforming filters without increasing transmitting power or antenna gain or resolution loss. The

  1. Digital Citizenship

    ERIC Educational Resources Information Center

    Isman, Aytekin; Canan Gungoren, Ozlem

    2014-01-01

    Era in which we live is known and referred as digital age.In this age technology is rapidly changed and developed. In light of these technological advances in 21st century, schools have the responsibility of training "digital citizen" as well as a good citizen. Digital citizens must have extensive skills, knowledge, Internet and …

  2. IET Radar, Sonar and Navigation Journal, vol 7, no 1, January, pp. 55-66 Saeed Daneshmand1

    E-print Network

    Calgary, University of

    error. This paper is a preprint of a paper accepted by IET Radar, Sonar & Navigation and is subject.org/journals/doc/IEEDRL-home/info/support/copyinf.jsp). When the final version is published, the copy of record will be available at IET Digital Library1 IET Radar, Sonar and Navigation Journal, vol 7, no 1, January, pp. 55-66 Saeed Daneshmand1 , Ali

  3. Testbed for development of a DSP-based signal processing subsystem for an Earth-orbiting radar scatterometer

    NASA Technical Reports Server (NTRS)

    Clark, Douglas J.; Lux, James P.; Shirbacheh, Mike

    2002-01-01

    A testbed for evaluation of general-purpose digital signal processors in earth-orbiting radar scatterometers is discussed. Because general purpose DSP represents a departure from previous radar signal processing techniques used on scatterometers, there was a need to demonstrate key elements of the system to verify feasibility for potential future scatterometer instruments. Construction of the testbed also facilitated identification of an appropriate software development environment and the skills mix necessary to perform the work.

  4. Historical aspects of radar atmospheric dynamics

    NASA Technical Reports Server (NTRS)

    Kato, Susumu

    1989-01-01

    A review of the history of radar techniques which have been applied to atmospheric observation is given. The author starts with ionosphere observation with the ionosonde, symbolizing as it does the earliest history of radar observation, and proceeds to later developments in radar observation such as the use of partial reflection, meteor, and incoherent scatter radars. Mesosphere stratosphere troposphere (MST) radars are discussed in terms of lower atmosphere observation.

  5. Imaging radar applications to mapping and charting

    NASA Technical Reports Server (NTRS)

    Leberl, F.

    1976-01-01

    The paper outlines the major actual and potential radar mapping applications, gives an account of the present state of satellite radar imaging, and reviews the radargrammetric work achieved since 1972. Attention is focused on the mapping methods and accuracy regarding single-image radar mapping, stereo radargrammetry, and mapping from blocks of overlapping imagery. It is recommended that more radargrammetric expertise be applied in radar mapping projects so that full advantage may be taken of the metric information potential of imaging radar.

  6. The Clementine bistatic radar experiment.

    PubMed

    Nozette, S; Lichtenberg, C L; Spudis, P; Bonner, R; Ort, W; Malaret, E; Robinson, M; Shoemaker, E M

    1996-11-29

    During the Clementine 1 mission, a bistatic radar experiment measured the magnitude and polarization of the radar echo versus bistatic angle, beta, for selected lunar areas. Observations of the lunar south pole yield a same-sense polarization enhancement around beta = 0. Analysis shows that the observed enhancement is localized to the permanently shadowed regions of the lunar south pole. Radar observations of periodically solar-illuminated lunar surfaces, including the north pole, yielded no such enhancement. A probable explanation for these differences is the presence of low-loss volume scatterers, such as water ice, in the permanently shadowed region at the south pole. PMID:8929403

  7. The Clementine bistatic radar experiment

    USGS Publications Warehouse

    Nozette, S.; Lichtenberg, C.L.; Spudis, P.; Bonner, R.; Ort, W.; Malaret, E.; Robinson, M.; Shoemaker, E.M.

    1996-01-01

    During the Clementine 1 mission, a bistatic radar experiment measured the magnitude and polarization of the radar echo versus bistatic angle, ??, for selected lunar areas. Observations of the lunar south pole yield a same- sense polarization enhancement around ?? = 0. Analysis shows that the observed enhancement is localized to the permanently shadowed regions of the lunar south pole. Radar observations of periodically solar-illuminated lunar surfaces, including the north pole, yielded no such enhancement. A probable explanation for these differences is the presence of low-loss volume scatterers, such as water ice, in the permanently shadowed region at the south pole.

  8. Space Radar Images of Earth

    NSDL National Science Digital Library

    Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR), part of NASA's Mission to Planet Earth, is studying how our global environment is changing. From the unique vantage point of space, the radar system observes, monitors and assesses large-scale environmental processes with a focus on climate change. The spaceborne data, complemented by aircraft and ground studies, gives scientists highly detailed information that will help them distinguish natural environmental changes from those that are the result of human activity. The images are divided into nine categories for easier viewing.

  9. The Clementine Bistatic Radar Experiment

    NASA Technical Reports Server (NTRS)

    Nozette, S.; Lichtenberg, C. L.; Spudis, P.; Bonner, R.; Ort, W.; Malaret, E.; Robinson, M.; Shoemaker, E. M.

    1996-01-01

    During the Clementine 1 mission, a bistatic radar experiment measured the magnitude and polarization of the radar echo versus bistatic angle, beta, for selected lunar areas. Observations of the lunar south pole yield a same-sense polarization enhancement around beta = 0. Analysis shows that the observed enhancement is localized to the permanently shadowed regions of the lunar south pole. Radar observations of periodically solar-illuminated lunar surfaces, including the north pole, yielded no such enhancement. A probable explanation for these differences is the presence of low-loss volume scatterers, such as water ice, in the permanently shadowed region at the south pole.

  10. Asteroid orbit fitting with radar and angular observations

    NASA Astrophysics Data System (ADS)

    Baturin, A. P.

    2013-12-01

    The asteroid orbit fitting problem using their radar and angular observations has been considered. The problem was solved in a standanrd way by means of minimization of weighted sum of squares of residuals. In the orbit fitting both kinds of radar observa-tions have been used: the observations of time delays and of Doppler frequency shifts. The weight for angular observations has been set the same for all of them and has been determined as inverse mean-square residual obtained in the orbit fitting using just angular observations. The weights of radar observations have been set as inverse squared errors of these observations published together with them in the Minor Planet Center electronical circulars (MPECs). For the orbit fitting some five asteroids have been taken from these circulars. The asteroids have been chosen fulfilling the requirement of more than six radar observations of them to be available. The asteroids are 1950 DA, 1999 RQ36, 2002 NY40, 2004 DC and 2005 EU2. Several orbit fittings for these aster-oids have been done: with just angular observations; with just radar observations; with both angular and radar observations. The obtained results are quite acceptable because in the last case the mean-square angular residuals are approximately equal to the same ones obtained in the fitting with just angular observations. As to radar observations mean-square residuals, the time delay residuals for three asteroids do not exceed 1 ?s, for two others ˜ 10 ?s and the Doppler shift residuals for three asteroids do not exceed 1 Hz, for two others ˜ 10 Hz. The motion equations included perturbations from 9 planets and the Moon using their ephemerides DE422. The numerical integration has been performed with Everhart 27-order method with variable step. All calculations have been exe-cuted to a 34-digit decimal precision (i.e. using 128-bit floating-point numbers). Further, the sizes of confidence ellipsoids of im-proved orbit parameters have been compared. It has been accepted that an indicator of ellipsoid size is a geometric mean of its six semi-axes. A comparison of sizes has shown that confidence ellipsoids obtained in orbit fitting with both angular and radar obser-vations are several times less than ellipsoids obtained with just angular observations.

  11. Power-Stepped HF Cross Modulation Experiments at HAARP

    NASA Astrophysics Data System (ADS)

    Greene, S.; Moore, R. C.; Langston, J. S.

    2013-12-01

    High frequency (HF) cross modulation experiments are a well established means for probing the HF-modified characteristics of the D-region ionosphere. In this paper, we apply experimental observations of HF cross-modulation to the related problem of ELF/VLF wave generation. HF cross-modulation measurements are used to evaluate the efficiency of ionospheric conductivity modulation during power-stepped modulated HF heating experiments. The results are compared to previously published dependencies of ELF/VLF wave amplitude on HF peak power. The experiments were performed during the March 2013 campaign at the High Frequency Active Auroral Research Program (HAARP) Observatory. HAARP was operated in a dual-beam transmission format: the first beam heated the ionosphere using sinusoidal amplitude modulation while the second beam broadcast a series of low-power probe pulses. The peak power of the modulating beam was incremented in 1-dB steps. We compare the minimum and maximum cross-modulation effect and the amplitude of the resulting cross-modulation waveform to the expected power-law dependence of ELF/VLF wave amplitude on HF power.

  12. Airborne bistatic radar applications

    NASA Astrophysics Data System (ADS)

    Foster, James A.

    1987-09-01

    Applications of bistatic radar when one or both of the units are airborne are discussed. Scenarios that merit deeper consideration are covert strike and head-on SAR using a stand-off illuminator, either airborne or space-based; area air defense with passive ground-based receivers and stand-off illuminators; an airborne picket line to detect stealth aircraft and missiles; AWACS aircraft providing mutual support in ECM environments; and passive surveillance of hostile air space using illuminators of opportunity and an airborne receiver. Scenarios considered impractical are bistatic air-to-air missile guidance using an aircraft other than the launch aircraft as illuminator; passive interdiction using illuminators of opportunity; and scenarios involving a ground based illuminator and an aircraft as the receiver.

  13. Radar backscatter modelling

    NASA Astrophysics Data System (ADS)

    Schaber, G. G.; Kozak, R. C.; Gurule, R. L.

    1984-04-01

    The terrain analysis software package was restructured and documentation was added. A program was written to test Johnson Space Center's four band scatterometer data for spurious signals data. A catalog of terrain roughness statistics and calibrated four frequency multipolarization scatterometer data is being published to support the maintenance of Death Valley as a radar backscatter calibration test site for all future airborne and spacecraft missions. Test pits were dug through sand covered terrains in the Eastern Sahara to define the depth and character of subsurface interfaces responsible for either backscatter or specular response in SIR-A imagery. Blocky sandstone bedrock surfaces at about 1 m depth were responsible for the brightest SIR-A returns. Irregular very dense CaCO3 cemented sand interfaces were responsible for intermediate grey tones. Ancient river valleys had the weakest response. Reexamination of SEASAT l-band imagery of U.S. deserts continues.

  14. Fly eye radar or micro-radar sensor technology

    NASA Astrophysics Data System (ADS)

    Molchanov, Pavlo; Asmolova, Olga

    2014-05-01

    To compensate for its eye's inability to point its eye at a target, the fly's eye consists of multiple angularly spaced sensors giving the fly the wide-area visual coverage it needs to detect and avoid the threats around him. Based on a similar concept a revolutionary new micro-radar sensor technology is proposed for detecting and tracking ground and/or airborne low profile low altitude targets in harsh urban environments. Distributed along a border or around a protected object (military facility and buildings, camp, stadium) small size, low power unattended radar sensors can be used for target detection and tracking, threat warning, pre-shot sniper protection and provides effective support for homeland security. In addition it can provide 3D recognition and targets classification due to its use of five orders more pulses than any scanning radar to each space point, by using few points of view, diversity signals and intelligent processing. The application of an array of directional antennas eliminates the need for a mechanical scanning antenna or phase processor. It radically decreases radar size and increases bearing accuracy several folds. The proposed micro-radar sensors can be easy connected to one or several operators by point-to-point invisible protected communication. The directional antennas have higher gain, can be multi-frequency and connected to a multi-functional network. Fly eye micro-radars are inexpensive, can be expendable and will reduce cost of defense.

  15. Radar measurement of the seasonal variation in the velocity of the sunrise terminator

    NASA Astrophysics Data System (ADS)

    Meehan, D. H.

    1990-03-01

    The HF phased-array radar at Bribie Island, Australia, used to measure horizontal movements of the ionosphere, has been calibrated using the known velocity of the sunrise terminator. The seasonal variation in the velocity of the terminator has been resolved, both in magnitud and direction. The technique uses single-station ionospheric sounding, and requires the angle of arrival and Doppler shift of ionospheric echoes to be measured as the terminator passes overhead. Pfister's (1971) theorem allows calculation of the velocity of the reflecting surface. The difference between theory and experiment is less than 3 percent in speed and 2 degrees in direction on average.

  16. DESDynI Quad First Stage Processor - A Four Channel Digitizer and Digital Beam Forming Processor

    NASA Technical Reports Server (NTRS)

    Chuang, Chung-Lun; Shaffer, Scott; Smythe, Robert; Niamsuwan, Noppasin; Li, Samuel; Liao, Eric; Lim, Chester; Morfopolous, Arin; Veilleux, Louise

    2013-01-01

    The proposed Deformation, Eco-Systems, and Dynamics of Ice Radar (DESDynI-R) L-band SAR instrument employs multiple digital channels to optimize resolution while keeping a large swath on a single pass. High-speed digitization with very fine synchronization and digital beam forming are necessary in order to facilitate this new technique. The Quad First Stage Processor (qFSP) was developed to achieve both the processing performance as well as the digitizing fidelity in order to accomplish this sweeping SAR technique. The qFSP utilizes high precision and high-speed analog to digital converters (ADCs), each with a finely adjustable clock distribution network to digitize the channels at the fidelity necessary to allow for digital beam forming. The Xilinx produced FX130T Virtex 5 part handles the processing to digitally calibrate each channel as well as filter and beam form the receive signals. Demonstrating the digital processing required for digital beam forming and digital calibration is instrumental to the viability of the proposed DESDynI instrument. The qFSP development brings this implementation to Technology Readiness Level (TRL) 6. This paper will detail the design and development of the prototype qFSP as well as the preliminary results from hardware tests.

  17. Space Radar Image of West Texas - SAR scan

    NASA Technical Reports Server (NTRS)

    1999-01-01

    This radar image of the Midland/Odessa region of West Texas, demonstrates an experimental technique, called ScanSAR, that allows scientists to rapidly image large areas of the Earth's surface. The large image covers an area 245 kilometers by 225 kilometers (152 miles by 139 miles). It was obtained by the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) flying aboard the space shuttle Endeavour on October 5, 1994. The smaller inset image is a standard SIR-C image showing a portion of the same area, 100 kilometers by 57 kilometers (62 miles by 35 miles) and was taken during the first flight of SIR-C on April 14, 1994. The bright spots on the right side of the image are the cities of Odessa (left) and Midland (right), Texas. The Pecos River runs from the top center to the bottom center of the image. Along the left side of the image are, from top to bottom, parts of the Guadalupe, Davis and Santiago Mountains. North is toward the upper right. Unlike conventional radar imaging, in which a radar continuously illuminates a single ground swath as the space shuttle passes over the terrain, a Scansar radar illuminates several adjacent ground swaths almost simultaneously, by 'scanning' the radar beam across a large area in a rapid sequence. The adjacent swaths, typically about 50 km (31 miles) wide, are then merged during ground processing to produce a single large scene. Illumination for this L-band scene is from the top of the image. The beams were scanned from the top of the scene to the bottom, as the shuttle flew from left to right. This scene was acquired in about 30 seconds. A normal SIR-C image is acquired in about 13 seconds. The ScanSAR mode will likely be used on future radar sensors to construct regional and possibly global radar images and topographic maps. The ScanSAR processor is being designed for 1996 implementation at NASA's Alaska SAR Facility, located at the University of Alaska Fairbanks, and will produce digital images from the forthcoming Canadian RADARSAT satellite. Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves, allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3 cm). The multi-frequency data will be used by the international scientific community to better understand the global environment and how it is changing. The SIR-C/X-SAR data, complemented by aircraft and ground studies, will give scientists clearer insights into those environmental changes which are caused by nature and those changes which are induced by human activity. SIR-C was developed by NASA's Jet Propulsion Laboratory. X-SAR was developed by the Dornier and Alenia Spazio companies for the German space agency, Deutsche Agentur fuer Raumfahrtangelegenheiten (DARA), and the Italian space agency, Agenzia Spaziale Italiana (ASI), with the Deutsche Forschungsanstalt fuer Luft und Raumfahrt e.v.(DLR), the major partner in science, operations, and data processing of X-SAR.

  18. The design of static and mobile HF communication systems

    NASA Astrophysics Data System (ADS)

    Darnell, M.

    1986-03-01

    The lecture deals with more specific aspects of HF communication system design arising from a previous lecture entitled HF system design principles presented as part of AGARD Lecture Series 127 in 1983. The major topics considered are: (1) the design of point-to-point systems; (2) the design of systems involving mobile terminals; (3) system control and frequency management; (4) resistance to interception and disruption. The lecture is intended to provide a technical framework for later lectures covering the more detailed aspects of HF communication system design.

  19. Development and Observation of the Phase Array Radar at X band

    NASA Astrophysics Data System (ADS)

    Ushio, T.; Shimamura, S.; Wu, T.; Kikuchi, H.; Yoshida, S.; Kawasaki, Z.; Mizutani, F.; Wada, M.; Satoh, S.; Iguchi, T.

    2013-12-01

    A new Phased Array Radar (PAR) system for thunderstorm observation has been developed by Toshiba Corporation and Osaka University under a grant of NICT, and installed in Osaka University, Japan last year. It is now well known that rapidly evolving severe weather phenomena (e.g., microbursts, severe thunderstorms, tornadoes) are a threat to our lives particularly in a densely populated area and is closely related to the production of lightning discharges. Over the past decade, mechanically rotating radar systems at the C-band or S-band have been proved to be effective for weather surveillance especially in a wide area more than 100 km in range. However, severe thunderstorm sometimes develops rapidly on the temporal and spatial scales comparable to the resolution limit (-10 min. and -500m) of typical S-band or C-band radar systems, and cannot be fully resolved with these radar systems. In order to understand the fundamental process and dynamics of such fast changing weather phenomena like lightning and tornado producing thunderstorm, volumetric observations with both high temporal and spatial resolution are required. The phased array radar system developed has the unique capability of scanning the whole sky with 100m and 10 to 30 second resolution up to 60 km. The system adopts the digital beam forming technique for elevation scanning and mechanically rotates the array antenna in azimuth direction within 10 to 30 seconds. The radar transmits a broad beam of several degrees with 24 antenna elements and receives the back scattered signal with 128 elements digitizing at each elements. Then by digitally forming the beam in the signal processor, the fast scanning is realized. After the installation of the PAR system in Osaka University, the initial observation campaign was conducted in Osaka urban area with Ku-band Broad Band Radar (BBR) network, C-band weather radar, and lightning location system. The initial comparison with C band radar system shows that the developed PAR system can observe the behavior of the thunderstorm structure in much more detail than any other radar system. The observed high temporal resolution images of the severe thunderstorm and lightning are introduced, showing the potential capabilities of the PAR and lightning location system.

  20. Advanced Borehole Radar for Hydrogeology

    NASA Astrophysics Data System (ADS)

    Sato, M.

    2014-12-01

    Ground Penetrating Radar is a useful tool for monitoring the hydrogeological environment. We have developed GPR systems which can be applied to these purposes, and we will demonstrate examples borehole radar measurements. In order to have longer radar detection range, frequency lower than100MHz has been normally adopted in borehole radar. Typical subsurface fractures of our interests have a few mm aperture and radar resolution is much poorer than a few cm in this frequency range. We are proposing and demonstrating to use radar polarimetry to solve this problem. We have demonstrated that a full-polarimetry borehole radar can be used for characterization of subsurface fractures. Together with signal processing for antenna characteristic compensation to equalize the signal by a dipole antenna and slot antennas, we could demonstrate that polarimetric borehole radar can estimate the surface roughness of subsurface fractures, We believe the surface roughness is closely related to water permeability through the fractures. We then developed a directional borehole radar, which uses optical field sensor. A dipole antenna in a borehole has omni-directional radiation pattern, and we cannot get azimuthal information about the scatterers. We use multiple dipole antennas set around the borehole axis, and from the phase differences, we can estimate the 3-diemnational orientation of subsurface structures. We are using optical electric field sensor for receiver of borehole radar. This is a passive sensor and connected only with optical fibers and does not require any electric power supply to operate the receiver. It has two major advantages; the first one is that the receiver can be electrically isolated from other parts, and wave coupling to a logging cable is avoided. Then, secondary, it can operate for a long time, because it does not require battery installed inside the system. It makes it possible to set sensors in fixed positions to monitor the change of environmental conditions for a long period. We demonstrated this idea using cross- hole borehole radar measurement. We think this method is useful for detecting any changes in hydrogeological situations, which will be useful for subsurface storage such as LNG and nuclear waste.