Note: This page contains sample records for the topic digital hf radar from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

Digital hf radar observations of equatorial spread-F  

SciTech Connect

Modern digital ionosondes, with both direction finding and doppler capabilities can provide large scale pictures of the Spread-F irregularity regions. A morphological framework has been developed that allows interpretation of the hf radar data. A large scale irregularity structure is found to be nightward of the dusk terminator, stationary in the solar reference frame. As the plasma moves through this foehn-wall-like structure it descends, and irregularities may be generated. Localized upwellings, or bubbles, may be produced, and they drift with the background plasma. The spread-F irregularity region is found to be best characterized as a partly cloudy sky, due to the patchiness of the substructures. 13 references, 16 figures.

Argo, P.E.

1984-01-01

2

Results of a bistatic HF radar surface wave sea scatter experiment  

Microsoft Academic Search

We describe a set of HF radar sea scatter experiments that test a new digital receiver in both monostatic and bistatic modes. The University of Miami's OSCR HF radar system was used as a transmitter signal source, and sea echoes were received with both receive systems using different receive antenna arrays. Independent GPS time-coupled rubidium clocks were used to maintain

Dennis Trizna; James Gordon

2002-01-01

3

Wellen Radar (WERA): a new ground-wave HF radar for ocean remote sensing  

Microsoft Academic Search

HF radars can be used to measure surface currents and wave spectra. The Coastal Radar (CODAR) used by the University of Hamburg was designed for current mapping only. It has been operated for 15 field experiments during the past 15 years. Recently, a new HF radar called Wellen Radar (WERA) has been developed at the University of Hamburg. One main

K.-W Gurgel; G Antonischki; H.-H Essen; T Schlick

1999-01-01

4

Application of HF radar currents to oil spill modelling  

Microsoft Academic Search

In this work, the benefits of high-frequency (HF) radar currents for oil spill modeling and trajectory analysis of floating objects are analyzed. The HF radar performance is evaluated by means of comparison between a drifter buoy trajectory and the one simulated using a Lagrangian trajectory model. A methodology to optimize the transport model performance and to calculate the search area

Ana J. Abascal; Sonia Castanedo; Raul Medina; Inigo J. Losada; Enrique Alvarez-Fanjul

2009-01-01

5

CFAR Target Detection Based on Gumbel Distribution for HF Radar  

Microsoft Academic Search

High frequency (HF) radars are capable to detect and track targets at extremely long ranges. But the signal environment that includes external noise, different kinds of clutter and interference will significantly limit the detection and system capability. This paper considers a new approach to solve the target detection problem in a complex HF radar signal environment. It uses conventional constant

A. L. Dzvonkovskaya; H. Rohling

2006-01-01

6

Application of HF radar currents to oil spill modelling.  

PubMed

In this work, the benefits of high-frequency (HF) radar currents for oil spill modeling and trajectory analysis of floating objects are analyzed. The HF radar performance is evaluated by means of comparison between a drifter buoy trajectory and the one simulated using a Lagrangian trajectory model. A methodology to optimize the transport model performance and to calculate the search area of the predicted positions is proposed. This method is applied to data collected during the Galicia HF Radar Experience. This experiment was carried out to explore the capabilities of this technology for operational monitoring along the Spanish coast. Two long-range HF radar stations were installed and operated between November 2005 and February 2006 on the Galician coast. In addition, a drifter buoy was released inside the coverage area of the radar. The HF radar currents, as well as numerical wind data were used to simulate the buoy trajectory using the TESEO oil spill transport model. In order to evaluate the contribution of HF radar currents to trajectory analysis, two simulation alternatives were carried out. In the first one, wind data were used to simulate the motion of the buoy. In the second alternative, surface currents from the HF radar were also taken into account. For each alternative, the model was calibrated by means of the global optimization algorithm SCEM-UA (Shuffled Complex Evolution Metropolis) in order to obtain the probability density function of the model parameters. The buoy trajectory was computed for 24h intervals using a Monte Carlo approach based on the results provided in the calibration process. A bivariate kernel estimator was applied to determine the 95% confidence areas. The analysis performed showed that simulated trajectories integrating HF radar currents are more accurate than those obtained considering only wind numerical data. After a 24h period, the error in the final simulated position improves using HF radar currents. Averaging the information from all the simulated daily periods, the mean search and rescue area calculated using HF radar currents, is reduced by approximately a 62% in comparison with the search area calculated without these data. These results show the positive contribution of HF radar currents for trajectory analysis, and demonstrate that these data combined with atmospheric forecast models, are of value for trajectory analysis of oil spills or floating objects. PMID:18996546

Abascal, Ana J; Castanedo, Sonia; Medina, Raul; Losada, Inigo J; Alvarez-Fanjul, Enrique

2008-11-08

7

RADARC HF ionospheric prediction program for OTH radar  

NASA Astrophysics Data System (ADS)

A model for predicting the performance of an over-the-horizon high frequency (HF) radar is described. The program can also be used for management of an existing radar or for HF broadcasting assessment. When the radar parameters, such as power, antenna, and frequency are given, the program predicts the signal-to-noise, ground clutter-to-noise, ionospheric spread Doppler clutter-to-noise, and received power as a function of range from the radar site. The report is intended to provide the reader with a general description of the prediction model and to show those mathematics and procedures which are upgraded from NRL Report 2226. The procedures should provide the OTH radar engineers with information to execute the program for studies or evaluation of existing or planned radars.

Lucas, D. L.; Prinson, G. S.; Headrick, J. M.; Thomason, J. F.

1993-09-01

8

HF Radar Sea-echo from Shallow Water  

PubMed Central

HF radar systems are widely and routinely used for the measurement of ocean surface currents and waves. Analysis methods presently in use are based on the assumption of infinite water depth, and may therefore be inadequate close to shore where the radar echo is strongest. In this paper, we treat the situation when the radar echo is returned from ocean waves that interact with the ocean floor. Simulations are described which demonstrate the effect of shallow water on radar sea-echo. These are used to investigate limits on the existing theory and to define water depths at which shallow-water effects become significant. The second-order spectral energy increases relative to the first-order as the water depth decreases, resulting in spectral saturation when the waveheight exceeds a limit defined by the radar transmit frequency. This effect is particularly marked for lower radar transmit frequencies. The saturation limit on waveheight is less for shallow water. Shallow water affects second-order spectra (which gives wave information) far more than first-order (which gives information on current velocities), the latter being significantly affected only for the lowest radar transmit frequencies for extremely shallow water. We describe analysis of radar echo from shallow water measured by a Rutgers University HF radar system to give ocean wave spectral estimates. Radar-derived wave height, period and direction are compared with simultaneous shallow-water in-situ measurements.

Lipa, Belinda; Nyden, Bruce; Barrick, Don; Kohut, Josh

2008-01-01

9

Directional sea spectrum determination using HF Doppler radar techniques  

Microsoft Academic Search

Second-order features in HF radar Doppler spectral data are compared with a theoretical model of the radar spectrum. The model is the corner reflector double-scatter model which employs a more realistic directional sea spectrum model than those used in earlier works. It includes a frequency-dependent angular spreading function and assumes the existence of spectral energy over a full360degarising from an

DENNIS B. TRIZNA; JOHN C. MOORE; JAMES M. HEADRICK; ROBERT W. BOGLE

1977-01-01

10

Adaptive remote sensing with HF skywave radar  

NASA Astrophysics Data System (ADS)

Practical issues of skywave radar remote sensing of the ocean surface, such as methods of radar resource management, parameter optimization, data-dependent processing, and real-time implementation of remote sensing capabilities, are discussed. The way in which they are addressed in an operational skywave radar system, the Australian JINDALEE radar, is discussed. Emphasis is placed on adaptivity - the need to adjust the radar operating parameters and processing techniques to match the changing propagation environment and the specific objectives of measurements. The key points that must be taken into consideration are described. The concept of the category 'suitability for detailed analysis' is introduced, and the variability of data quality on the synoptic scale is illustrated.

Anderson, S. J.

1992-04-01

11

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

Microsoft Academic Search

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

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

1997-01-01

12

Bistatic HF radar diagnostics induced field-aligned irregularities  

Microsoft Academic Search

In late March and early April of 1995, an experimental campaign involving the modification of the F2 ionospheric layer took place in Russia and Ukraine. HF pulsed and CW Doppler radar observations of field-aligned irregularities within the region over the Sura heater were made with the UTR-2 radio telescope serving as the receiver. In this paper, some preliminary results of

Y. M. Yampolski; V. S. Beley; S. B. Kascheev; A. V. Koloskov; V. G. Somov; D. L. Hysell; B. Isham; M. C. Kelley

1997-01-01

13

HF radar: A tool for coral reef planning and management  

Microsoft Academic Search

This paper builds on previous research on turbulent kinetic energy concepts in the coral reef domain, and develops it as a management tool. HF ocean radar data from the southern Great Barrier Reef are used to identify times and locations when a critical value of the Simpson-Hunter parameter is exceeded and the water column becomes vertically mixed. When this happens,

Diane D. DiMassa; Malcolm L. Heron; Scott F. Heron

2011-01-01

14

Hard threshold correlation detector for mobile HF Surface Wave Radar  

Microsoft Academic Search

Mobile HF Surface Wave Radar (SWR) can be realized by an offshore distributed receiver array structure which communicates to the central processing unit at the base station via a wireless link. State of the art detectors demand a sophisticated signal processing which can only be done at base station hence making it imperative to transmit raw data form receiver to

Anshu Gupta; Th. Fickenscher

2012-01-01

15

An HF Radar Based Integrated Maritime Surveillance System  

Microsoft Academic Search

Abstract: - In this paper, the physics behind an Integrated Maritime Surveillance system based on HF surface wave,radars (HFSWR) is discussed. Due to the complexity of the system a comprehensive understanding of electromagnetic wave (EM) propagation, antenna design, EM wave – ocean wave interaction, target reflectivity, interference sources and their stochastic behaviours is essential. The success of the system depends,on

Levent Sevgi; Anthony M. Ponsford

16

Results from UHF and HF radar studies of ionospheric interaction experiments at HAARP  

Microsoft Academic Search

High power HF radiowave experiments have begun at the HAARP Ionospheric Research Observatory in Gakona Alaska The SuperDARN HF radar station in Kodiak Alaska is now routinely employed to monitor HF backscatter from irregularities formed in the interaction volume over HAARP A 16-panel prototype of a new UHF radar facility MUIR has recently become operational on the HAARP site Complementary

J. Sheerin; W. Bristow; B. Watkins; S. Oyama; C. Heinselman

2006-01-01

17

Results from UHF and HF Radar Studies of Ionospheric Interaction Experiments at HAARP  

Microsoft Academic Search

High power HF radiowave experiments have begun at the HAARP Ionospheric Research Observatory in Gakona, Alaska. The SuperDARN HF radar station in Kodiak, Alaska is now routinely employed to monitor HF backscatter from irregularities formed in the interaction volume over HAARP. A 16-panel prototype of a new UHF incoherent scatter radar facility, AMISR, has recently become operational on the HAARP

J. P. Sheerin; R. Ilie; E. L. Roesler; W. A. Bristow; B. J. Watkins; S. Oyama

2005-01-01

18

Hokkaido HF radar: progress report on mid-latitude SuperDARN radar in East Asia  

NASA Astrophysics Data System (ADS)

We present a progress report on new HF radar in Hokkaido, northern Japan. The planned Hokkaido radar is located at (43.5°, 143.6°) geographic coordinates and at geomagnetic latitude of ~ 37°, much lower than the existing SuperDARN HF radars. The funding for constructing Hokkaido radar was approved by the government for 2005 fiscal year. It will be the second mid-latitude SuperDARN radar, and the first one in East Asia. The radar can monitor the wide latitudinal range ( 38° to 65° in geomagnetic coordinates), which could not be covered by using the existing radars. Using this radar, we can deal with a wide variety of scientific targets, ranging from the magnetosphere/ionosphere to the thermosphere/mesosphere. In particular, Hokkaido is situated in an excellent location to monitor the energy budget between the polar and middle latitude regions, by collaborating with a wide variety of observation network such as high-latitude SuperDARN, 210° MM network, airglow imager network and Japanese GPS network (GEONET).

Nishitani, N.; Ogawa, T.; Kikuchi, T.

2005-12-01

19

Toward an european Med HF-radar coastal monitoring  

NASA Astrophysics Data System (ADS)

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

Molcard, A.; Fraunie, P.

2010-12-01

20

Digital beamforming for Passive Coherent Location radar  

Microsoft Academic Search

The paper presents digital beamforming for Passive Coherent Location (PCL) radar. The considered circular antenna array is a part of a passive system developed at Warsaw University of Technology. The system is based on FM radio transmitters. The array consists of eight half-wave dipoles arranged in a circular array covering 360deg with multiple beams. The digital beamforming procedure is presented,

Mateusz Malanowski; Krzysztof Kulpa

2008-01-01

21

UHF and HF Radar Studies of Langmuir Turbulence Experiments at HAARP  

Microsoft Academic Search

High power HF transmitters induce a number of plasma instabilities in the interaction region of overdense ionospheric plasma. Radars such as SuperDARN have been used to study artificial field-aligned irregularities (AFAI) created by the high power HF radiowave at the HAARP Ionospheric Observatory, Gakona, AK. A new Modular UHF Ionospheric Radar (MUIR) sited at HAARP, may now be used to

J. P. Sheerin; J. M. Gerres; J. S. Troyer; S. Oyama; B. J. Watkins; J. E. Turnquist; W. A. Bristow; C. J. Heinselman

2006-01-01

22

UHF and HF Radar Studies of Langmuir Turbulence Experiments at HAARP  

Microsoft Academic Search

High power HF transmitters induce a number of plasma instabilities in the interaction region of overdense ionospheric plasma. Radars such as SuperDARN have been used to study artificial field-aligned irregularities (AFAI) created by the high power HF radiowave at the HAARP Ionospheric Observatory, Gakona, AK. A new Modular UHF Ionospheric Radar (MUIR) sited at HAARP, may now be used to

J. P. Sheerin; J. M. Gerres; M. E. Bacon; B. J. Watkins; W. A. Bristow; J. E. Turnquist; S. I. Oyama; C. J. Heinselman

2007-01-01

23

Digital Meteorological Radar Data Compared with Digital Infrared Data from a Geostationary Meteorological Satellite.  

National Technical Information Service (NTIS)

Digital 10 cm radar data were collected using the Texas A&M University weather radar system. The digital radar data were then compared with GOES-East infrared imagery mapped to the digital radar grid projection. Point values of infrared digital count were...

R. S. Henderson

1979-01-01

24

Assessment of WERA long-range HF-radar performance from the user's perspective  

Microsoft Academic Search

Since April 2006, long range (8.3MHz) WERA HF radars have been operated on the Southeastern United States coastline, as part of the U.S. Integrated Ocean Observing System (IOOS) and in particular the national HF Radar network. These radars measure currents operationally, and waves and winds experimentally across the wide continental shelf of Georgia (GA) and South Carolina (SC). Half-hourly data

D. Savidge; J. Amft; A. Gargett; M. Archer; D. Conley; G. Voulgaris; L. Wyatt; K.-W. Gurgel

2011-01-01

25

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

Microsoft Academic Search

HF radar backscatter, which has been artificially- induced by a high power RF facility such as the EISCAT heater at Tromsø, has provided coherent radar ionospheric electric field data of unprecedented temporal resolution and accuracy. Here such data are used to investigate ULF wave processes observed by both the CUTLASS HF radars and the EISCAT UHF radar. Data from the

L. J. Baddeley; T. K. Yeoman; D. M. Wright; J. A. Davies; K. J. Trattner; J. L. Roeder

2002-01-01

26

HF radar observations of ionospheric backscatter during geomagnetically quiet periods  

NASA Astrophysics Data System (ADS)

The quiet-time coherent backscatter from the F-region observed by the Tasman International Geospace Environment Radar (TIGER) Bruny Island HF radar is analysed statistically in order to determine typical trends and controlling factors in the ionospheric echo occurrence. A comparison of the F-region peak density values from the IRI-2007 model and ionosonde measurements in the vicinity of the radar's footprint shows a very good agreement, particularly at subauroral and auroral latitudes, and model densities within the radar's footprint are used in the following analyses. The occurrence of F-region backscatter is shown to exhibit distinct diurnal, seasonal and solar cycle variations and these are compared with model trends in the F-region peak electron density and Pedersen conductance of the underlying ionosphere. The solar cycle effects in occurrence are demonstrated to be strong and more complex than a simple proportionality on a year-to-year basis. The diurnal and seasonal effects are strongly coupled to each other, with diurnal trends exhibiting a systematic gradual variation from month to month that can be explained when both electron density and conductance trends are considered. During the night, the echo occurrence is suggested to be controlled directly by the density conditions, with a direct proportionality observed between the occurrence and peak electron density. During the day, the echo occurrence appears to be controlled by both conductance and propagation conditions. It is shown that the range of echo occurrence values is smaller for larger conductances and that the electron density determines what value the echo occurrence takes in that range. These results suggest that the irregularity production rates are significantly reduced by the highly conducting E layer during the day while F-region density effects dominate during the night.

Kane, T. A.; Makarevich, R. A.; Devlin, J. C.

2012-01-01

27

Improved Reliability Prediction for HF (High Frequency) Digital Voice Transmission.  

National Technical Information Service (NTIS)

A method for predicting the performance of High Frequency (HF) digital voice transmission is described. The method takes into account the effects of multipath propagation and signal processing techniques which exploit the multipath to achieve improved per...

A. Malaga

1989-01-01

28

Detection by HF radar of the Eta Aquarid meteor shower  

NASA Astrophysics Data System (ADS)

The successful observation of the Eta Aquarid meteor shower is reported, demonstrating the value of HF skywave radars operating at frequencies below 15 MHz for meteor detection. The results are consistent with the shower radiant having a diameter of about 6 deg, centered on R.A. = 339 deg, declination = 0 deg. If the cumulative distribution of meteoroidal particles exceeding a lower threshold mass m is described by a power law of the form N(m) = about m exp c, where the exponent c is assumed to equal -1.0 for sporadic meteors, then, by comparison, the particles of the Eta Aquarid shower must belong to a flatter distribution, with c in the range from -1.0 to -0.6.

Thomas, R. M.

1989-07-01

29

Digital Frequency Synthesizer for Radar Astronomy.  

National Technical Information Service (NTIS)

The digital frequency synthesizer (DFS) is an integral part of the programmable local oscillator (PLO) which is being developed for the NASA's Deep Space Network (DSN) and radar astronomy. Here, the theory of operation and the design of the DFS are discus...

R. Sadr E. Satorius L. Robinett E. Olson

1990-01-01

30

Persistent enhancement of the HF pump-induced plasma line measured with a UHF diagnostic radar at HAARP  

Microsoft Academic Search

Plasma lines excited by a powerful, high-frequency (HF) radio wave are studied using data obtained with an ultrahigh frequency (UHF) radar at HAARP (High Frequency Active Auroral Research Program) from 3 to 5 February 2005. Of particular interest is persistent enhancement of the radar backscatter power during HF on at several HF frequencies. The persistent enhancement is induced with the

S. Oyama; B. J. Watkins; F. T. Djuth; M. J. Kosch; P. A. Bernhardt; C. J. Heinselman

2006-01-01

31

HF Ocean Surface Radar Monitoring for Coral Bleaching in the Great Barrier Reef  

Microsoft Academic Search

HF ocean surface radar provides a valuable multi-parameter monitoring technique for the investigation and management of coral bleaching. The physical parameters normally associated with bleaching are temperature and light, which are primarily controlled by insolation, wind, waves and currents. The radar provides a useful monitoring of wind and waves, and is the leading technology for monitoring surface currents. The deployment

M. L. Heron; B. Willis; A. Prytz; P. Cetina-Heredia; Y. Mao; O. Hoegh-Guldberg; W. J. Skirving; S. F. Heron; C. M. Eakin

2006-01-01

32

Storm-time E-region radar backscatter observed by the SuperDARN HF radars  

NASA Astrophysics Data System (ADS)

Storm-time coherent echoes observed by the SuperDARN HF radars in the short ranges corresponding to the E-region backscatter are investigated. Analysis of the spatial distribution of the echoes shows that during storms most of the echoes are detected at locations that are close to the expected locations calculated using a straight-line propagation model (i.e. assuming no radar wave refraction). Analysis of the E layer critical frequency, foE, from one subauroral ionosonde station confirmed that during storms foE typically decreases to lower values as compared with normal conditions. This result suggests that the electron density in the E region is often depleted during storms. The progression of depletion with storm-time and MLT is analysed using several SuperDARN radars separated in longitude. The types of short-range echoes detected during storms are also examined. A new storm-time population of echoes is identified; the echoes exhibit small negative Doppler velocities for a large range of spectral widths. Local ionospheric plasma convection velocity measurements are then used to study the conditions favorable for the generation of these echoes.

Carter, B. A.; Makarevich, R. A.

2008-12-01

33

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

Microsoft Academic Search

HF radar backscatter, which has been artificially-induced by a high power RF facility such as the EISCAT heater at Tromsø, has provided coherent radar ionospheric electric field data of unprecedented temporal resolution and accuracy. Here such data are used to investigate ULF wave processes observed by both the CUTLASS HF radars and the EISCAT UHF radar. Data from the SP-UK-OUCH

L. J. Baddeley; T. K. Yeoman; D. M. Wright; J. A. Davies; K. J. Trattner; J. L. Roeder

2002-01-01

34

Simulation and detection of tsunami signatures in ocean surface currents measured by HF radar  

NASA Astrophysics Data System (ADS)

High-frequency (HF) surface wave radars provide the unique capability to continuously monitor the coastal environment far beyond the range of conventional microwave radars. Bragg-resonant backscattering by ocean waves with half the electromagnetic radar wavelength allows ocean surface currents to be measured at distances up to 200 km. When a tsunami propagates from the deep ocean to shallow water, a specific ocean current signature is generated throughout the water column. Due to the long range of an HF radar, it is possible to detect this current signature at the shelf edge. When the shelf edge is about 100 km in front of the coastline, the radar can detect the tsunami about 45 min before it hits the coast, leaving enough time to issue an early warning. As up to now no HF radar measurements of an approaching tsunami exist, a simulation study has been done to fix parameters like the required spatial resolution or the maximum coherent integration time allowed. The simulation involves several steps, starting with the Hamburg Shelf Ocean Model (HAMSOM) which is used to estimate the tsunami-induced current velocity at 1 km spatial resolution and 1 s time step. This ocean current signal is then superimposed to modelled and measured HF radar backscatter signals using a new modulation technique. After applying conventional HF radar signal processing techniques, the surface current maps contain the rapidly changing tsunami-induced current features, which can be compared to the HAMSOM data. The specific radial tsunami current signatures can clearly be observed in these maps, if appropriate spatial and temporal resolution is used. Based on the entropy of the ocean current maps, a tsunami detection algorithm is described which can be used to issue an automated tsunami warning message.

Gurgel, Klaus-Werner; Dzvonkovskaya, Anna; Pohlmann, Thomas; Schlick, Thomas; Gill, Eric

2011-10-01

35

Digital quadrature demodulation for radar ESM applications  

NASA Astrophysics Data System (ADS)

The feasibility of using digital techniques for coherent demodulation of wideband signals was investigated for application in radar electronic support measures systems. Several different design approaches and analysis methods were considered: a medium bandwidth design with simple Hilbert transformer, a medium bandwidth design with zero direct current offset, and a wide bandwidth matched response design with zero direct current offset. It was found that the processing requirements to achieve good accuracy for pulse and other wideband signals can be minimized through appropriate choice of intermediate frequency, the use of half-band finite impulse response filters, and the application of decimation. This suggests that an application specific integrated circuit implementation of a digital coherent demodulator should have potential cost and performance advantages over existing analog approaches.

Inkol, Robert; Saper, Ron

1992-05-01

36

Design and applications of a versatile HF radar calibration target in low Earth orbit  

NASA Astrophysics Data System (ADS)

High frequency (HF) radars are used to detect ionospheric irregularities, meteor trails, and moving targets. The Precision Expandable Radar Calibration Sphere (PERCS) is a simple radar target in space to help determine the operational parameters of ground HF radars. PERCS will have a known radar cross section that is independent of observation direction within 0.5 dB. The PERCS satellite can be launched in a stowed configuration that has about 1 m in diameter. After launch, the PERCS will expand to a diameter of almost 10 m. Upon expansion, a stable wire frame is formed to act as a radar scatter target in the form of a polyhedral sphere. The simplest version of the sphere has 60 vertices (V60) that are joined to 90 rigid segments. Each segment is hinged so that the PERCS can be folded into a compact package for launch. Analysis of the V60 wire frame with a 10 m diameter shows that the radar cross section (RCS) is nearly independent of viewing angle up to 30 MHz. Another design with 240 vertices produces even better performance. Radar systems will be calibrated using the radar echo data and the precise knowledge of the target RCS, position, and velocity. The PERCS can reflect radar signals from natural targets such as field aligned and current driven irregularities not presently accessible from ground-based radars. The wire frame structure has several advantages over a metalized spheroid "balloon" with (1) much less drag, (2) larger radar cross section, and (3) lower fabrication cost.

Bernhardt, Paul A.; Siefring, Carl L.; Thomason, Joe F.; Rodriquez, Serafin P.; Nicholas, Andrew C.; Koss, Steven M.; Nurnberger, Mike; Hoberman, Chuck; Davis, Matthew; Hysell, David L.; Kelley, Michael C.

2008-02-01

37

Very high latitude F-region irregularities observed by HF-radar backscatter  

Microsoft Academic Search

In February and March, 1982, a coherent scatter HF radar was operated from Cleary, Alaska to observe 7- to 15-m wavelength F-region plasma irregularities near the poleward edge of the auroral zone and in the polar cap. The radar operated for five days from February 25 to March 1 and produced approximately 700,000 Doppler spectra during that time. Of those

K. B. Baker; R. A. Greenwald; R. T. Tsunoda

1983-01-01

38

HF Radar Performance on a Low Energy Environment as Found Using CODAR SeaSonde on the West Florida Shelf  

NASA Astrophysics Data System (ADS)

A network of three CODAR (Coastal Ocean Dynamics Application Radar) SeaSonde HF radars operating at 4.925 MHz has operated on the West Florida Shelf since 2003. HF Radar performance is evaluated in terms of percentage of data returns and RMS differences between the HF radar radial currents and an array of velocity measurements by moored acoustic Doppler current profilers (ADCP). Temporal variation of the radial current coverage is described and possible factors affecting the HF radar observations on this low energy (current and wave) shelf are discussed. Despite the challenge of achieving more backscatter from this low energy shelf, the data quality is good when the acquired HF radial currents are compared with the ADCP top bins. The RMS difference is in the range of 6 - 11 cm/s for hourly and 3 - 6 cm/s for 36-hour low-pass filtered radial currents, respectively.

Liu, Y.; Merz, C. R.; Weisberg, R. H.

2008-12-01

39

Digital image transformation and rectification of spacecraft and radar images  

USGS Publications Warehouse

Digital image transformation and rectification can be described in three categories: (1) digital rectification of spacecraft pictures on workable stereoplotters; (2) digital correction of radar image geometry; and (3) digital reconstruction of shaded relief maps and perspective views including stereograms. Digital rectification can make high-oblique pictures workable on stereoplotters that would otherwise not accommodate such extreme tilt angles. It also enables panoramic line-scan geometry to be used to compile contour maps with photogrammetric plotters. Rectifications were digitally processed on both Viking Orbiter and Lander pictures of Mars as well as radar images taken by various radar systems. By merging digital terrain data with image data, perspective and three-dimensional views of Olympus Mons and Tithonium Chasma, also of Mars, are reconstructed through digital image processing. ?? 1985.

Wu, S. S. C.

1985-01-01

40

The adaptive suppression of interference in HF ground wave radar  

NASA Astrophysics Data System (ADS)

The feasibility of the concept of interference suppression in the high-frequency ground wave radar using adaptive null steering in polarization space is demonstrated. The described system uses a horizontal auxiliary aerial that feeds a least mean squares estimation filter to generate an estimate of the interference affecting the radar's performance. Subtraction of this estimate from the affected radar signal results in suppression of the interference. Skywave interference-to-noise levels were reduced by up to 30 dB. The performance depends upon there being a detectable horizontal component of the interference signal's polarization.

Madden, J. M.

41

The Space-Based Calibration of Optical Systems and HF Radars Using the Precision Expandable Radar Calibration Sphere  

NASA Astrophysics Data System (ADS)

The Precision Expandable Radar Calibration Sphere (PERCS) is designed to provide a relatively simple target in space that can be used to determine the operational parameters of both ground Imaging systems and HF radars. PERCS is a 10 meter diameter wire frame in low earth orbit with corner cube reflectors placed at 60 or more vertices around the wire frame. For optical system calibration, PERCS will provide precisely spaced reflection points on the vertices of a large polyhedron. For HF radar calibration, PERCS will have a known radar cross section that is independent of observation direction within 0.5 dB. Laser satellite tracking will provide accurate orbital position and velocity of PERCS. The PERCS will orbit at 600 km altitude in a high inclination. Because of the wire frame construction, atmospheric drag will be low and the large spherical structure is expected to be available for more than five years. The PERCS satellite will be launched in a stowed configuration that has less than one meter in diameter. After launch, the PERCS will expand to a diameter of almost 10 meters. Hoberman Sphere technology will be used to produce a stable wire-frame to act as a radar scatter target. The sphere is based on a truncated icosahedron commonly known in chemistry as a "buckyball". The 60 vertices (V60) are hinged to be joined to 90 rigid segments. Each segment is hinged so that the PERCS can be folded into a compact package for launch.

Bernhardt, P.

42

Mapping of North Atlantic winds by HF radar sea backscatter interpretation  

Microsoft Academic Search

This work presents preliminary results on attempts to map winds of a storm at long range (500 to 1000 nmi) over a large area (10^{5}mi2) in the North Atlantic from the U. S. Naval Research Laboratory, HF radar research facilities at Chesapeake Beach, Md. [1] It appears that the short time response of the sea surface to local winds can

A. Long; D. Trizna

1973-01-01

43

On the design of integrated HF radar systems for Homeland Security applications  

Microsoft Academic Search

In this paper, HCAC's research and development efforts on the development of integrated and low cost HF radar for coastal surveillance and other Homeland Security applications are summarized. The proposed design incorporates electrically small antenna for rapid deployment, supports operation on floating platforms by using enhanced DSP algorithms to mitigate clutter, incorporates improved propagation modeling to more accurately select optimum

James Baker; Nuri Celik; Nobutaka Omaki; Jill Kobashigawa; Hyoung-Sun Youn; Magdy F. Iskander

2010-01-01

44

Real-time procedures implemented within coastal HF radar system in the northern Adriatic  

Microsoft Academic Search

The paper overviews the performances of the HF radar network installed in the northern Adriatic Sea. The system architecture is designed to work in real-time and delayed modes, but the accent is given on the real-time data acquisition, processing, archiving and presenting on the web. Several minor and the major dropout of the system were reported in 2008, and the

I. Vilibic; V. Dadic; D. Ivankovic; S. Muslim; J. Sepic; H. Mihanovic

2009-01-01

45

Radar scattering statistics for digital terrain models  

NASA Astrophysics Data System (ADS)

The statistic results for a digital terrain model are presented that closely match measurements for 77% of the 189 possible combinations of 7 radar bands, 3 polarizations, and 9 terrain types. The model produces realistic backscatter coefficient values for the scenarios over all incidence angles from normal to grazing. The generator was created using measured data sets reported in the Handbook of Radar Scattering Statistics for Terrain covering L, C, S, X, Ka, Ku, and W frequency bands; HH, HV, and VV polarizations; and soil and rock, shrub, tree, short vegetation, grass, dry snow, wet snow, road surface, and urban area terrain types. The first two statistical moments match published values precisely, and a Chi-Square histogram test failed to reject the generator at a 95% confidence level for the 146 terrain models implemented. A Sea State model provides the grazing angle extension for predictions beyond the available measurements. This work will contain a comprehensive set of plots of mean and standard deviation versus incidence angle.

Wilson, Kelce; Patrick, Dale; Blair, James

2005-05-01

46

The Use of Normal Mode Analysis to Extend HF Radar Coverage Over Enclosed Bays  

NASA Astrophysics Data System (ADS)

A technique referred to as Normal Mode Analysis (NMA) has recently been developed for representing total vector CODAR HF radar data. This technique has been applied to Corpus Christi Bay. These modes satisfy the coastal boundary constraint of no flow normal to the shore, and inherently represent both divergent and rotational flow as two sets of ortho-normal basis functions. The use of NMA allows the measurement of flows in mostly enclosed bays, like Corpus Christi, where wind-driven and tidal currents predominate. Furthermore, it extends the measurement coverage into regions where only one, or even no radar is able to provide coverage. The PDE2D software, which is based on a Finite Element Method, is used to obtain the eigenfunctions for the Corpus Christi Bay. Comparisons are made with the real-time total-vector maps produced by the HF Radar data over the common coverage area.

Aguilar, H.; Miszczak, M. E.; Fitzgerald, R. M.; Barrick, D.

2003-12-01

47

Typical disturbances of the daytime equatorial F region observed with a high-resolution HF radar  

NASA Astrophysics Data System (ADS)

HF radar measurements were performed near the magnetic equator in Africa (Korhogo 9°24'63''N-5°37'38''W) during the International Equatorial Electrojet Year (1993-1994). The HF radar is a high-resolution zenithal radar. It gives ionograms, Doppler spectra and echo parameters at several frequencies simultaneously. This paper presents a comparative study of the daytime ionospheric structures observed during 3 days selected as representative of different magnetic conditions, given by magnetometer measurements. Broad Doppler spectra, large echo width, and amplitude fluctuations revealed small-scale instability processes up to the F-region peak. The height variations measured at different altitudes showed gravity waves and larger-scale disturbances related to solar daytime influence and equatorial electric fields. The possibility of retrieving the ionospheric electric fields from these Doppler or height variation measurements in the presence of the other possible equatorial ionospheric disturbances is discussed.

Blanc, E.; Houngninou:, E.

1998-06-01

48

Improved statistical prediction of surface currents based on historic HF-radar observations  

NASA Astrophysics Data System (ADS)

Accurate short-term prediction of surface currents can improve the efficiency of search-and-rescue operations, oil-spill response, and marine operations. We developed a linear statistical model for predicting surface currents (up to 48 h in the future) based on a short time history of past HF-radar observations (past 48 h) and an optional forecast of surface winds. Our model used empirical orthogonal functions (EOFs) to capture spatial correlations in the HF-radar data and used a linear autoregression model to predict the temporal dynamics of the EOF coefficients. We tested the developed statistical model using historical observations of surface currents in Monterey Bay, California. The predicted particle trajectories separated from particles advected with HF-radar data at a rate of 4.4 km/day. The developed model was more accurate than an existing statistical model (drifter separation of 5.5 km/day) and a circulation model (drifter separation of 8.9 km/day). When the wind forecast was not available, the accuracy of our model degraded slightly (drifter separation of 4.9 km/day), but was still better than existing models. We found that the minimal length of the HF-radar data required to train an accurate statistical model was between 1 and 2 years, depending on the accuracy desired. Our evaluation showed that the developed model is accurate, is easier to implement and maintain than existing statistical and circulation models, and can be relocated to other coastal systems of similar complexity that have a sufficient history of HF-radar observations.

Frolov, Sergey; Paduan, Jeffrey; Cook, Michael; Bellingham, James

2012-07-01

49

Applications of spectral estimation techniques to radar Doppler processing: Simulation and analysis of HF (High-frquency) skywave radar data  

NASA Astrophysics Data System (ADS)

This work is the second paper in a series of studies of the application of spectral estimations techniques to Doppler processing of coherent radar signals. In this work, simulated high-frequency (HF) radar sea scatter time series are generated and processed by use of three different spectral estimation algorithms and the fast Fourier transform (FFT). The sea clutter is simulated by narrowband filtering a wideband Gaussian noise spectrum in the frequency domain, with filter widths appropriate to describe first-order Bragg lines and second-order continuum. Targets are introduced as sinusoids, stepped by 5 dB for eight different echo power values, and stepped in Doppler frequency for four different values relative to the clutter. These simulations identify problems that appear unique to Doppler processing of coherent radar data in the presence of broadband clutter, and are in distinction to the application of spectral estimation to processing in the spatial domain. In the latter case, the spectral contributions are generally narrowly confined in the angular power spectral estimate, and the aim is to separate these contributions in the presence of noise. The HF radar application is concerned with separation of weak targets in the presence of stronger clutter returns, which are relati vely broad compared to the target return. It appears that the Burg maximum entropy method allows the detection of targets in clutter under conditions which the FFT is incapable of detection with any degree of accuracy.

Trizna, D. B.; McNeal, G. D.

1985-12-01

50

Survey of Analog-to Digital Converters for Radar Applications.  

National Technical Information Service (NTIS)

The ever increasing speeds and dynamic ranges of modern radar signal processors require the use of state of the art Analog-to Digital Converter (ADC) technology. In fact, many radar designs are constrained by the lack of ADCs with sufficient speed and/or ...

R. C. Hicks

1991-01-01

51

A Multi-frequency Beam-forming HF Radar for Tsunami Detection  

NASA Astrophysics Data System (ADS)

We discuss a new multi-frequency beam-forming HF radar design for robust detection and tracking of tsunami waves from 200 km distances, providing continuous coverage of the tsunami wave pattern after it impinges on the continental shelf. The method works by mapping ocean currents at long range using traditional HF radar method of radial Bragg line Doppler shift measurements. The tsunami is detected by anomalous spatial patterns of higher than normal Bragg-line shifts due to the large orbital wave of the series of tsunami wave crests as they impinge on the continental shelf. An approach using beam forming of 16 or 32 antenna elements provides an update every five minutes or less, while Direction-of-Arrival method systems using just a few antenna elements inherently require of the order of 30 to 60 minutes for a reliable current map. The multi-frequency radar provides a more robust capability than the single frequency HF radar for at least two reasons. First, because the HF channel user spectrum suffers diurnal variability in channel occupancy due to the ionosphere changing with time of day, low frequencies can become contaminated with user noise, so that maximum range for reliable detection not achieved. Under this condition, one would rely on quiet higher HF frequencies that lie above the Maximum Usable Frequency (MUF) for ionospheric reflection propagation. Alternatively, for daylight operation when low frequency utilization can be used to minimize surface wave propagation loss, the sea state might not be sufficiently active to allow long range coverage needed for reliable detection, due to the lack of ocean wave spectral energy at the Bragg-resonant wave frequency. Thus, single- frequency radars, operating in the 4-6 MHz range to minimize propagation losses to achieve long-range coverage, would suffer due to low wind conditions. The multi-frequency HF radar discussed here allows one to dynamically choose the optimum frequency from a set of 8 to 16, as allowed by local radio frequency allocation authorities, assuming just a single frequency is used at a time. Alternatively, one may choose four to eight frequencies operating simultaneously, to allow the clearest channel and best signal strength channel for enhanced processing. We will discuss the tradeoffs on multiple frequency use versus single optimum frequency use, both using a multi-frequency radar capability. Results of preliminary testing of a prototype system at Duck, NC will also be presented.

Trizna, D. B.

2007-05-01

52

A frequency averaging method to improve sea-state measurements with an HF skywave radar  

NASA Astrophysics Data System (ADS)

A frequency averaging method which can improve the quality of averaged spectra of HF signals scattered by the sea is described. The method is compared to the classical single-frequency pulse-radar. Using the skywave radar of Valensole, France, the statistical independence of signals scattered by the sea at close frequencies is experimentally verified. Spectra of signals reflected by an F2 ionospheric layer are presented to illustrate the method. The possibility of further reducing interference by introducing the method in frequency modulated continuous wave systems is discussed.

Parent, Jacques

1987-04-01

53

Coherent HF radar backscatter characteristics associated with auroral forms identified by incoherent radar techniques: A comparison of CUTLASS and EISCAT observations  

Microsoft Academic Search

Backscatter from decameter-wavelength field-aligned F region irregularities, as measured by the Cooperative UK Twin Located Auroral Sounding System (CUTLASS) Finland HF coherent radar, is compared with common volume plasma parameters and the electric field deduced by the European Incoherent Scatter (EISCAT) UHF incoherent radar system, for a 12 hour period from June 18 to June 19, 1996. During this interval

S. E. Milan; J. A. Davies; M. Lester

1999-01-01

54

Reconfigurable digitally scanned polarimetric L-Band radar  

Microsoft Academic Search

We present the design and initial results from a digitally steered, polarimetric, phased array L-band radar utilizing a novel, high performance architecture. The instrument leverages recent advances in radio frequency and digital signal processing components in order to enable collocated measurements of emission and backscatter in a compact aircraft instrument with no moving parts. The driving methodologies are the minimization

Luko Krnan; Rafael Rincon

2009-01-01

55

Wind-speed inversion from HF radar first-order backscatter signal  

Microsoft Academic Search

Land-based high-frequency (HF) radars have the unique capability of continuously monitoring ocean surface environments at\\u000a ranges up to 200 km off the coast. They provide reliable data on ocean surface currents and under slightly stricter conditions\\u000a can also give information on ocean waves. Although extraction of wind direction is possible, estimation of wind speed poses\\u000a a challenge. Existing methods estimate wind

Wei Shen; Klaus-Werner Gurgel; George Voulgaris; Thomas Schlick; Detlef Stammer

56

Very high latitude F-region irregularities observed by HF-radar backscatter  

Microsoft Academic Search

The results of a five-day scan of 7 to 15 m wavelength F-region plasma irregularities near the poleward edge of the auroral zone and in the polar cap region from February-March, 1982 are reported. Around 70,000 Doppler spectra were obtained, with 10 percent displaying a backscattered power at least 3 dB over background noise. The HF radar unit was located

K. B. Baker; R. A. Greenwald; R. T. Tsunoda

1983-01-01

57

A statistical study of the location and motion of the HF radar cusp  

NASA Astrophysics Data System (ADS)

The large-scale and continuous monitoring of the ionospheric cusp region offered by HF radars has been exploited in order to examine the statistical location and motion of the equatorward edge of the HF radar cusp as a function of the upstream IMF BZ component. Although a considerable scatter is seen, both parameters have a clear influence from the north-south component of the IMF. Excellent agreement is achieved with previous observations from low altitude spacecraft data. The HF radar cusp region is seen to migrate equatorward at a rate of 0.02° min-1 nT-1 under IMF BZ south conditions, but remains static for IMF BZ north. The motion of the cusp implies an addition of magnetic flux of ~ 2 × 104 Wbs-1 nT-1 under IMF BZ south conditions, equivalent to a reconnection voltage of 20 kV nT-1, which is consistent with previous estimates from case studies on both the dayside and nightside regions.

Yeoman, T. K.; Hanlon, P. G.; McWilliams, K. A.

2002-02-01

58

Interpretation of equatorial electrojet irregularities observed with a broad beam HF zenithal radar  

NASA Astrophysics Data System (ADS)

Observations of the equatorial ionosphere were performed in Africa with the radar of the Laboratoire de Détection et de Géophysique near the magnetic equator during the International Equatorial Electrojet Year (1993-1994). This high-resolution zenithal HF radar uses a broad beam antenna, in which complex echo structures are observed. A diversity of irregularities appears in the 100-500 km radar range up to the F region. Some irregularities appear in range-time-intensity diagrams as a parabolic region between 140 and 180 km with a minimum at noon. This region is only observed for radar frequencies between 4 and 5 MHz. At these frequencies, type II irregularities arising from vertical and oblique directions in the 100-140 km range dominate the spectra, and type I irregularities are difficult to clearly identify. Ray tracing and simulations show that type I irregularities are a possible source of the observed parabolic region. Irregularities from the equatorial "150 km region" as observed with the Jicamarca radar appear at slightly higher radar ranges.

Farges, T.; Blanc, E.; Villain, J. P.

1999-09-01

59

Evaluation of the attenuation provided by a radar absorbing material (RAM) coating on an HF wire rope antenna  

Microsoft Academic Search

A shipboard electromagnetic interference (EMI) problem is considered. The use of radar absorbent material (RAM) to reduce unintentional X-band (8-12 GHz) radar reflections from HF wire rope antennas is analyzed. An exact series solution for a lossy-coated circular cylinder was developed and used to determine the effectiveness of the various RAM coatings

Griffin K. Gothard; Broun Hall

1991-01-01

60

Observations of convection vortices in the afternoon sector using the SuperDARN HF radars  

SciTech Connect

Observations of convection vortices using the new SuperDARN HF radars are presented. The velocity field derived from the overlapping fields of view of the new HF radars at Kapuskasing, Ontario, and Saskatoon, Saskatchewan, Canada, often image the portion of the convection pattern near the convection reversal boundary. Observations from near the convection reversal boundary in the afternoon sector of October 22, 1993, showed two convection vortices evolving within the field of view of both radars. The first vortex appeared at about 2120 UT and the second at about 2145 UT: 1446 MLT and 1512 MLT, respectively. The vortices were roughly 900 km in diameter and moved tailward with a velocity of about 600 m/s. At the times the vortices were observed by the radars, ground-based magnetometers of the CANOPUS and MACCS chains show transient deflections of near 100 nT, and the GOES 6 and GOES 7 satellite magnetometers showed significant decreases in the magnetospheric magnetic field strength. Data from the Geotail satellite magnetometer lagged by an appropriate time interval indicated that there were southward turnings of the interplanetary magnetic field that coincided with the decreases of magnetospheric magnetic field strength. The observations differ in many respects from previously published vortex observations. It is theorized that the vortices were caused by the Kelvin-Helmholtz instability at the inner edge of the low-latitude boundary layer. 48 refs.

Bristow, W.A.; Greenwald, R.A.; Sibeck, D.G. [Johns Hopkins Univ., Laurel, MD (United States)] [and others

1995-10-01

61

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

SciTech Connect

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.

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

62

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

NASA Astrophysics Data System (ADS)

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.

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

2012-07-01

63

Characterization of ocean surface current properties from single site HF/VHF radar  

NASA Astrophysics Data System (ADS)

Surface current mapping from HF/VHF coastal radars traditionally requires at least two distant sites. Vector velocities are estimated by combining the radial velocity components measured by the radars. In many circumstances (e.g., failures, interferences, logistics constraints), such a combination is not possible by lack of data from one station. Two methods are evaluated to get information on surface circulation from a single site radar: the Vectorial Reconstruction Method (VRM) for current vector mapping and the Vortex Identification Method (VIM) for detecting eddy-like structures. The VRM assumes a non-divergent horizontal surface current, and the VIM analyzes radial velocities and their radial and orthoradial gradients. These two methods are tested on modeled and measured data sets in the Northwestern Mediterranean Sea where both high-resolution ocean circulation model and radar campaigns are available. The VRM performance is strongly limited by the divergence-free hypothesis which was not satisfied in our real data. The VIM succeeded in detection of vortex in the Gulf of Lions and from an operating single site radar located on the Provence coasts in summer.

Marmain, Julien; Forget, Philippe; Molcard, Anne

2011-11-01

64

Protecting digital avionics systems from high power radar interference  

Microsoft Academic Search

Protecting digital systems from high power radar interference is primarily a task of preventing unwanted RF energy from getting into sensitive semiconductor components. The degree of shielding or filtering required depends upon the RF field values, the sensitivity of the semiconductor components to the RF energy, and the degree of interference or upset that can be tolerated in the system.

J. M. Roe

1977-01-01

65

Implementation of digital pulse doppler radar signal generator and receiver  

Microsoft Academic Search

In this paper, hardware implementation of digital pulse Doppler radar signals generator and receiver based on FPGA is explained. Different performances have been noticed while using CORDIC and Hilbert transform cores for the phase shifter blocks in the implementation of generator and receiver parts. Algorithms are implemented on the Xilinx Virtex-4 FPGA. Required hardware area, resolution and amplitude of Doppler

Emrah Onat; Mahmut Serin

2011-01-01

66

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

67

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

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

68

HF Radar Measurements of the Ionospheric Footprint of the Cusp During the December 2002 Rocket Campaign  

NASA Astrophysics Data System (ADS)

The NASA Cusp rocket Campaign of December 2002 provides a unique combination of in situ and ground-based instrumentation for the investigation of the Earth's cusp. The CUTLASS HF radars provided 2-D convection measurements over the rocket trajectory region during launch from Ny Alesund on December 14. The radars ran in a special mode with high spatial and temporal resolution. Stereo operations allowed a full 16 beam scan to be generated every 48 s, whilst simultaneously a restricted 6 beam scan localized over the trajectory was generated every 18 s. Excellent data coverage was obtained from both radars over almost the entire rocket trajectory, allowing 2-D convection information to be recovered. The remaining SuperDARN array provided the global convection solution at a resolution of 2 min. The spatial and temporal variations of the ionospheric convection flows under the influence of transient magnetopause reconnection processes will be presented, along with an examination of the location and motion of geophysical boundaries derived from radar spectral width.

Yeoman, T. K.; McWilliams, K. A.; Milan, S. E.; Lester, M.

2003-12-01

69

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

SciTech Connect

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.

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

1985-06-07

70

MDR--Processing Manually Digitized Radar Observations.  

National Technical Information Service (NTIS)

MDR computer program reads seven hours of radar observations from the local database and produces three graphics. The graphics are one-, three-, and six-hourly sums of MDR values or rainfall amounts. Convective and stratiform Z-R relations are provided al...

M. R. Peroutka

1983-01-01

71

GPS ionospheric scintillation and HF radar backscatter - A comparison between GISTM network and SuperDARN at high latitudes  

NASA Astrophysics Data System (ADS)

The occurrence of GPS ionospheric scintillation at high latitudes over Scandinavia in 2003 and 2008 is compared with the occurrence of HF radar backscatter from field-aligned irregularities as a function of magnetic local time and geomagnetic latitude for the same two years. The scintillation was observed using GPS Ionospheric Scintillation and TEC Monitors (GISTM) included in a network extending from high to mid latitudes. Both the HF radar backscatter and GPS scintillation predominantly occur in the night portion of the auroral oval and the ionospheric footprint of the cusp. Data subsets for geomagnetically quiet and disturbed periods show the expected shift in latitude of the ionospheric regions both in the occurrence of phase scintillation and the HF radar backscatter from ionospheric irregularities.

Prikryl, Paul; Spogli, Luca; Alfonsi, Lucilla; Romano, Vincenzo; Aquino, Marcio

2010-05-01

72

Wind-speed inversion from HF radar first-order backscatter signal  

NASA Astrophysics Data System (ADS)

Land-based high-frequency (HF) radars have the unique capability of continuously monitoring ocean surface environments at ranges up to 200 km off the coast. They provide reliable data on ocean surface currents and under slightly stricter conditions can also give information on ocean waves. Although extraction of wind direction is possible, estimation of wind speed poses a challenge. Existing methods estimate wind speed indirectly from the radar derived ocean wave spectrum, which is estimated from the second-order sidebands of the radar Doppler spectrum. The latter is extracted at shorter ranges compared with the first-order signal, thus limiting the method to short distances. Given this limitation, we explore the possibility of deriving wind speed from radar first-order backscatter signal. Two new methods are developed and presented that explore the relationship between wind speed and wave generation at the Bragg frequency matching that of the radar. One of the methods utilizes the absolute energy level of the radar first-order peaks while the second method uses the directional spreading of the wind generated waves at the Bragg frequency. For both methods, artificial neural network analysis is performed to derive the interdependence of the relevant parameters with wind speed. The first method is suitable for application only at single locations where in situ data are available and the network has been trained for while the second method can also be used outside of the training location on any point within the radar coverage area. Both methods require two or more radar sites and information on the radio beam direction. The methods are verified with data collected in Fedje, Norway, and the Ligurian Sea, Italy using beam forming HF WEllen RAdar (WERA) systems operated at 27.68 and 12.5 MHz, respectively. The results show that application of either method requires wind speeds above a minimum value (lower limit). This limit is radar frequency dependent and is 2.5 and 4.0 m/s for 27.68 and 12.5 MHz, respectively. In addition, an upper limit is identified which is caused by wave energy saturation at the Bragg wave frequency. Estimation of this limit took place through an evaluation of a year long database of ocean spectra generated by a numerical model (third generation WAM). It was found to be at 9.0 and 11.0 m/s for 27.68 and 12.5 MHz, respectively. Above this saturation limit, conventional second-order methods have to be applied, which at this range of wind speed no longer suffer from low signal-to-noise ratios. For use in operational systems, a hybrid of first- and second-order methods is recommended.

Shen, Wei; Gurgel, Klaus-Werner; Voulgaris, George; Schlick, Thomas; Stammer, Detlef

2012-01-01

73

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

SciTech Connect

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.

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

1996-03-15

74

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

NASA Astrophysics Data System (ADS)

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->

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

1997-01-01

75

HF radar observations of Pc 5 field line resonances in the midnight\\/early morning MLT sector  

Microsoft Academic Search

On a number of occasions The Johns Hopkins University\\/Applied Physics Laboratory HF radar at Goose Bay, Labrador, has observed the effects of field line resonances on the drift velocities of irregularities in the F region of the high-latitude ionosphere. One of the most interesting sets of resonances occurs near midnight MLT and may be associated with shear in the convective

J. M. Ruohoniemi; R. A. Greenwald; K. B. Baker; J. C. Samson

1991-01-01

76

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

Microsoft Academic Search

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

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

2003-01-01

77

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

Microsoft Academic Search

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

H. Roarty; J. Kohut; S. Glenn

2003-01-01

78

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

Microsoft Academic Search

Document the time-evolving 3D structure of NI oscillations in a coastal regionAn effective approach to observe NI oscillations by HF radar and in-situ dataProvide hypotheses on the processes modulating the structure of NI oscillations

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

2011-01-01

79

HF (HIGH FREQUENCY) RADAR MEASUREMENTS OF CIRCULATION IN THE EASTERN STRAIT OF JUAN DE FUCA (AUGUST, 1978)  

EPA Science Inventory

During August, 1978, the surface currents in the Eastern Strait of Juan de Fuca were mapped with a High Frequency (HF) radar system (CODAR). The surface currents were measured simultaneously over several hundred square kilometers at one hour intervals continuously for five days. ...

80

Technology Development of a Compact Radar Digital Receiver  

Microsoft Academic Search

As part of a NASA ESTO funded Instrument Incubator Program (IIP), a Ka-band radar interferometer is currently under development to demonstrate the potential for an ice-surface topography, swath-mapping sensor at transmit powers that are technologically feasible and practical. The proposed system utilizes digital beam forming (DBF) with an antenna array in elevation. Each array element utilizes a dedicated receiver (16

Brandon Heavey; Delwyn Moller; Gregory Sadowy; Jordan Tanabe

81

Digital pulse compression and its application in reducing radar interference  

NASA Astrophysics Data System (ADS)

Pulse compression is a technique which allows improvement in detecting radar targets while preserving a good resolution power at a distance. This technique consists in transmitting a longer coded pulse and receiving it with a filter adapted to the code transmitted. Digital systems of pulse compression can possess a wider variety of codes than analog systems and can use a new code at each transmission. These two advantages are combined to reduce radar noise. The performance of digital pulse compression is evaluated for different types of radar interference. To counter certain types of interference such as replication of code, it is necessary to use a new code at each transmission. Two types of codes are studied: biphase pseudorandom codes and polyphase codes derived from linear frequency modulated signals or chirp. Supplementary methods, such as cumulative detection and coherent integration of a salvo of pulses, are sometimes needed to supress interference residuals. Digital pulse compression was also applied in real time and the results are supported by computer simulations and by tests on an experimental prototype.

Blanchette, Martin

1992-07-01

82

Digital controller for the Wave Propagation Laboratory's VHF and UHF wind-profiling radars  

NASA Astrophysics Data System (ADS)

Principles are described for operation of a digital system that is used to control the operations of a multiple beam stratospheric-tropospheric (ST) radar system. The digital system, referred to as the radar controller, contains the digital logic for generating the necessary pulse sequences for modulation of the radar transmitter, gating the radar's receiver channels, and sequencing the antenna beams. The radar controller also performs digital-to-analog conversion and coherent averaging of the receiver necessary for signal detection in ST radars. The radar controller is controlled internally by a Z80 microprocessor, and the entire system functions as a peripheral device to a host minicomputer. Block diagrams and detailed circuit schematics for all the custom designed electronics are included.

Moran, K.

1984-09-01

83

Improvement of HF coherent radar line-of-sight velocities by estimating the refractive index in the scattering volume using radar frequency shifting  

Microsoft Academic Search

Measurements of ionospheric drift velocities using HF coherent scatter radars, such as SuperDARN, are generally underestimated because the refractive index in the scattering volume has not been taken into account. Refractive index values evaluated from electron density measurements, international reference ionosphere predictions, or elevation angle measurements have been applied to SuperDARN velocities in past studies. However, the SuperDARN velocities so

R. G. Gillies; G. C. Hussey; G. J. Sofko; P. V. Ponomarenko; K. A. McWilliams

2011-01-01

84

Use of 'velocity projection' to estimate the variation of sea-surface height fromHF Doppler radar current measurements  

Microsoft Academic Search

The technique of 'velocity projection' (J. Geophys. Res. 106 (2001) 6973) is used to estimate the sea-surface height field and its change over time from measurements of surface velocity made using a shore-based HF Doppler radar over a3 0? 30-kmregion of the continental shelf located near the m outh of the Chesapeake Bay (USA). Projected current profiles are compared with

G. O. Marmorino; C. Y. Shen; T. E. Evans; G. J. Lindemann; Z. R. Hallock; L. K. Shay

85

Observation by HF radar of the Phillips resonance mechanism for generation of wind waves  

NASA Astrophysics Data System (ADS)

Measurements are reported of directional ocean wave spectra made over 80° of viewing angle by an HF radar, operating in the surface wave mode in an area 22.5 km north of San Clemente Island, California. Ten azimuths from 280° to 360° true bearing were simultaneously measured for 10 wave frequencies ranging from 0.14 Hz (75 m waves) to 0.35 Hz (13 m waves). A Waverider buoy was used to measure omnidirectional energy in the region, and first-order radar Bragg lines were used to determine the spreading of wave energy with angle. Data are presented in which a bimodal spectrum was present: an attenuated spectrum with wave components to 0.10 Hz from a storm at sea at 270° bearing; plus a transient local wind spectrum, stronger in amplitude at the higher frequencies, with wave cutoff near 0.14 Hz, and running from 315° bearing. Just after the onset of local winds, the westerly spectrum fitted a cosine squared spread at the lowest measured frequencies. With the development of local wind, which blew at a 12-14 kn (6-7 m s-1) speed for a period of 12 hours, the wave spectrum spread about the wind direction as cosine thirty-second at the lowest frequencies measured, 0.14 Hz, and cosine sixty-fourth at the highest frequencies measured, 0.35 Hz. For 0.28 Hz waves the Phillips resonance mechanism for wave generation is proposed to explain the twin peaks in amplitude observed, equally spaced either side of the wind direction. These were dominant for the earliest measurement period and still were major contributions for later measurement periods. This mechanism was found to contribute also at the higher wave frequencies, as predicted by theory. Coherence times are derived from the angular widths of the Phillips resonances based on predictions of Stewart and Manton and are found to agree quite well with theory.

Trizna, D. B.; Bogle, R. W.; Moore, J. C.; Howe, C. M.

1980-09-01

86

Surface current response to land-sea breeze circulation in Monterey Bay, California as observed by a new multifrequency HF radar  

Microsoft Academic Search

A new multifrequency (4-25 MHz) HF radar was installed at the Long Marine Laboratory (University of California at Santa Cruz) on the north coast of Monterey Bay CA in July, 1996. This radar is capable of observing near-surface currents at varying depths in the top two meters of the ocean. Observations were made over a three week period in March,

J. F. Vesecky; Calvin C. Teague; Robert G. Onstott; J. M. Daida; Peter Hansen; Dan Fernandez; N. Schnepf; Ken Fischer

1997-01-01

87

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

88

Dragged Neutral --Campaign Observations with Fabry-Perot Interferometers and HF-radars in Alaska--  

NASA Astrophysics Data System (ADS)

In this presentation, we will introduce campaign observations with HF-radars and Fabry-Perot Interferometers in Alaska held on 2000/2001 in cooperated with CRL and GI/UAF. The main purposes of this project are (1) quantitative estimates of response of ion and neutral for the change of IMF Bz, (2)estimation of the role of vertical wind in large scale neutral circulation in the thermosphere, (3) Validity check of vector wind velocity deduced from the method of Conde and Smith [1998]. Locations of instruments are shown in the figure below. Two FPI (Scanning: CRL; All-sky: GI/UAF) are installed at Poker Flat. An all-sky FPI and a scanning FPI are installed at Eagle and Inuvik, respectively. We have got an initial result obtained on Nov. 24, 2000. On the beginning of the observation, 06:14:00UT, the directions of neutral and plasma flow were different from each other. Hereafter the plasma flow kept its direction northwestward from 06:56 to 08:52UT, and the neutral wind was gradually accelerated for the same direction. The plasma flow showed a vortical structure and changed it_fs direction rapidly after 08:52UT, while the neutral wind did not respond to the short-term variation. This result is consistent with many previous works.

Ishii, M.; Bristow, W.; Conde, M.; Smith, R. W.; Krynicki, M.

2001-12-01

89

The shuttle radar topography mission—a new class of digital elevation models acquired by spaceborne radar  

Microsoft Academic Search

For 11 days in February 2000, the Shuttle Radar Topography Mission (SRTM) successfully recorded by interferometric synthetic aperture radar (InSAR) data of the entire land mass of the earth between 60°N and 57°S. The data acquired in C- and X-bands are processed into the first global digital elevation models (DEMs) at 1 arc sec resolution, by NASA-JPL and German aerospace

Bernhard Rabus; Michael Eineder; Achim Roth; Richard Bamler

2003-01-01

90

Modern Radar Techniques for Geophysical Applications: Two Examples.  

National Technical Information Service (NTIS)

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 ...

B. J. Arokiasamy

2005-01-01

91

Observation by HF radar of the Phillips resonance mechanism for generation of wind waves  

SciTech Connect

Measurements are reported of directional ocean wave spectra made over 80/sup 0/ of viewing angle by an HF radar, operating in the surface wave mode in an area 22.5 km north of San Clemente Island, California. Ten azimuths from 280/sup 0/ to 360/sup 0/ true bearing were simultaneously measured for 10 wave frequencies ranging from 0.14 Hz (75 m waves) to 0.35 Hz (13 m waves). A Waverider buoy was used to measure omnidirectional energy in the region, and first-order radar Bragg lines were used to determine the spreading of wave energy with angle. Data are presented in which a bimodal spectrum was present: an attenuated spectrum with wave components to 0.10 Hz from a storm at sea at 270/sup 0/ bearing; plus a transient local wind spectrum, stronger in amplitude at the higher frequencies, with wave cutoff near 0.14 Hz, and running from 315/sup 0/ bearing. Just after the onset of local winds, the westerly spectrum fitted a cosine squared spread at the lowest measured frequencies. With the development of local wind, which blew at a 12--14 kn (6--7 m s/sup -1/) speed for a period of 12 hours, the wave spectrum spread about the wind direction as cosine thirty-second at the lowest frequencies measured, 0.14 Hz, and cosine sixty-fourth at the highest frequencies measured, 0.35 Hz. For 0.28 Hz waves the Phillips resonance mechanism for wave generation is proposed to explain the twin peaks in amplitude observed, equally spaced either side of the wind direction. These were dominant for the earliest measurement period and still were major contributions for later measurement periods. This mechanism was found to contribute also at the higher wave frequencies, as predicted by theory. Coherence times are derived from the angular widths of the Phillips resonances based on predictions of Stewart and Manton and are found to agree quite well with theory.

Trizna, D.B.; Bogle, R.W.; Moore, J.C.; Howe, C.M.

1980-09-20

92

Instantaneous mapping of high-latitude convection with coherent HF radars  

SciTech Connect

Coherent HF radars at Goose Bay (Labrador) and Schefferville (Quebec) are used to study plasma convection in the high-latitude ionosphere. Maps of the two-dimensional flow pattern are obtained by merging simultaneous sets of radial velocity data, each with a time resolution of a few minutes. From a time sequence of such maps the authors have separated the changes in flow due to magnetic local time (MLT) variations over the region of observation, from those due to UT time variations. They study in detail the convection in the early morning sector observed on October 15, 1989, when the interplanetary magnetic field (IMF) reversed from southward to northward. This IMF reversal was not associated with a clear response in the nightside convection but rather with several sudden changes, some of which anticipated the B{sub z} reversal. They suggest that these changes are associated with delayed and superposed ionosphere responses to previous IMF perturbations, or to local effects. After the IMF reversal from south to north observations of westward and southwestward velocities in the 71{degrees}-77{degrees} invariant latitude range are consistent with the earlier simulations for B{sub z} > 0 and B{sub y} < 0. During the period of steady northward IMF after the reversal the convection pattern was observed to reconfigure slowly: a region of large velocities progressively moved poleward, while convection in the low-latitude part of the field of view faded away. These data, combined with particle data from successive passes of the DMSP satellites, provide information on the contraction of the polar cap after the IMF B{sub z} reversal and on the MLT dependency of the velocity at which this contraction occurs. They show that the polar cap contracts more rapidly in the daytime than in the nighttime and more rapidly in the postmidnight sector than in the premidnight sector. 29 refs., 11 figs., 21 tabs.

Hanuise, C. [Universite de Toulon et du Var, La Garde (France); Senior, C. [CNRS, Saint-Maur-des-Fosses (France); Cerisier, J.-C. [CNRS, Saint-Maur-des-Fosses (France)]|[Universite Pierre et Marie Curie, Paris (France); Villian, J.-P. [CNRS, Orleans (France); Greenwald, R.A.; Ruohoniemi, J.M.; Baker, K.B. [Applied Physics lab., Laurel, MD (United States)

1993-10-01

93

Ground-based weather radar compatibility with digital radio-relay microwave systems  

NASA Astrophysics Data System (ADS)

The potential for ground-based weather radar (meteorological radar) interference to digital microwave systems in the common carrier bands of 3700 to 4200 MHz and 5925 to 6425 MHz is examined. Reported cases of interference to microwave common carrier systems from ground-based weather radar systems have increased due to the trend towards digital modulations. Because of this interference, the National Telecommunications and Information Administration, the Federal Communications Commission and the National Spectrum Managers Association formed an informal working group to investigate and document the potential problems. The existing and planned spectrum uses by ground-based weather radars and digital microwave systems are addressed as well as regulations and policy pertaining to their electromagnetic compatibility. Methods to mitigate the interference in both the radar transmitter and microwave receiver are also provided.

Gawthrop, P. E.; Patrick, G. M.

1990-03-01

94

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

Microsoft Academic Search

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

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

2000-01-01

95

A new digital signal processor for Doppler radar cardiopulmonary monitoring system  

Microsoft Academic Search

Remote sensing and monitoring of cardiopulmonary activities based on direct conversion Doppler radar shows promise in medical and security applications. For accurate sensing, demodulation of the quadrature outputs of a direct-conversion Doppler radar is a great challenge. A digital signal processor based on Kalman filtering and principal component combining of quadrature channels is suggested. Rate detection ability and success ratio

Mohammad Shaifur Rahman; Byung-Jun Jang; Ki-Doo Kim

2008-01-01

96

Moving target detection via digital time domain correlation of random noise radar signals  

Microsoft Academic Search

Ultra-wideband random noise radar theoretically has a thumbtack ambiguity function, which cannot be realized due to hardware, processing, and environmental limitations. Velocity estimation using traditional Doppler processing is not practicable for ultra-wideband random noise radar because of the large fractional bandwidth. Through analysis, this paper explores moving target detection using digital correlation processing of random noise signals in the time

James R. Lievsay; Geoffrey A. Akers

2011-01-01

97

38. Perimeter acquisition radar building room #414, digital/electrical repair shop; ...  

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

38. Perimeter acquisition radar building room #414, digital/electrical repair shop; showing work areas available for maintenance and equipment repair - Stanley R. Mickelsen Safeguard Complex, Perimeter Acquisition Radar Building, Limited Access Area, between Limited Access Patrol Road & Service Road A, Nekoma, Cavalier County, ND

98

Surface circulation in the Iroise Sea (western Brittany) derived from high resolution current mapping by HF radars  

NASA Astrophysics Data System (ADS)

The use of high frequency radar (HFR) systems for near-real-time coastal ocean monitoring necessities that short time scale motions of the radar-derived velocities are better understood. While the ocean radar systems are able to describe coastal flow patterns with unprecedented details, the data they produce are often too sparse or gappy for applications such as the identification of coherent structures and fronts or understanding transport and mixing processes. In this study, we address two challenges. First, we report results from the HF radar system (WERA) which is routinely operating since 2006 on the western Brittany coast to monitor surface circulation in the Iroise Sea, over an area extending up to 100 km offshore. To obtain more reliable records of vector current fields at high space and time resolution, the Multiple Signal Classification (MUSIC) direction finding algorithm is employed in conjunction with the variational interpolation (2dVar) of radar-derived velocities. This provides surface current maps at 1 km spacing and time resolution of 20 min. Removing the influence of the sea state on radar-derived current measurements is discussed and performed on some data sequences. Second, we examine in deep continuous 2d velocity records for a number of periods, exploring the different modes of variability of surface currents in the region. Given the extent, duration, and resolution of surface current velocity measurements, new quantitative insights from various time series and spatial analysis on higher frequency kinematics will be discussed. By better characterizing the full spectrum of flow regimes that contribute to the surface currents and their shears, a more complete picture of the circulation in the Iroise Sea can be obtained.

Sentchev, Alexei; Forget, Philippe; Barbin, Yves; Marié, Louis; Ardhuin, Fabrice

2010-05-01

99

The application of high latitude ionosphere radars for space weather research  

Microsoft Academic Search

Ionospheric radars are used to investigate the auroral and polar cap regions, where solar wind-magnetosphere-ionosphere coupling is most evident. There are basically four categories of ground-based radars applied for this purpose: The digital ionosondes, coherent backscatter HF radars (F-region), coherent backscatter VHF and UHF radars (E-region), and incoherent scatter VHF and UHF radars. These systems are briefly described and examples

J. Röttger

2002-01-01

100

Ionospheric and auroral clutter models for HF surface wave and over-the-horizon radar systems  

NASA Astrophysics Data System (ADS)

The detection performance of high frequency surface wave radar (HFSWR) and high frequency over-the-horizon radar (OTHR) systems is heavily influenced by the presence of radar clutter. In HFSWR systems, the clutter has its origins in vertical-incidence ionospheric reflections, whereas in OTHR systems, the origin is Bragg backscatter from plasma structures in the auroral zone. This paper models the spreading of the radar clutter signal in the Doppler and angle-of-arrival domains that arises from forward-scattering effects as the radar pulse propagates through regions of ionospheric plasma irregularities. The models use a geometric optics approach to determine the power spectrum of the radar signal phase. This power spectrum is then used to simulate three-dimensional space-time-range radar data cubes. The accuracy of the models is tested by comparing the simulated data to measured data cubes. As an application, the data are then used to evaluate the performance of the newly developed fast fully adaptive (FFA) space-time adaptive processing (STAP) scheme to improve the extraction of target echoes from a clutter background.

Ravan, M.; Riddolls, R. J.; Adve, R. S.

2012-01-01

101

The digital signal processor for the ALCOR millimeter wave radar  

NASA Astrophysics Data System (ADS)

This report describes the use of an array processor for real time radar signal processing. Pulse compression, range marking, and monopulse error computation are some of the functions that will be performed in the array processor for the millimeter wave ALCOR radar augmentation. Real time software design, processor architecture, and system interfaces are discussed in the report.

Ford, R. A.

1980-11-01

102

Advanced ground-penetrating radar for digital soil mapping  

Microsoft Academic Search

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

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

2009-01-01

103

Digital topography of volcanoes from radar interferometry: an example from Mt Vesuvius, Italy  

Microsoft Academic Search

A new airborne radar technique can generate digital topographic data for volcanoes at a scale of 10 m spatial and 1–5 m vertical, with a swath width of ~6.4 km. Called TOPSAR, the intrument is an interferometric radar flown on the NASA DC-8 aircraft. TOPSAR data permit the quantification of volcano slopes, volumes, and heights, and as such will be

Peter J. Mouginis-Mark; Harold Garbeil

1993-01-01

104

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

NASA Astrophysics Data System (ADS)

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.

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

2011-10-01

105

Modeling and performance of HF/OTH radar target classification systems  

NASA Astrophysics Data System (ADS)

The effects of a class of multipath propagation channels on the performance of a radar target classification system are considered. A Rician frequency-selective fading channel model is used to characterize the effects of the multipath propagation medium and evaluate the performances of radar target classification systems. The performances of classification algorithms that use relative amplitude, relative phase, and absolute amplitude measurements as features are investigated. Performance estimates of the various classification algorithms for interesting sets of channel parameters are obtained by means of Monte Carlo simulations.

Strausberger, Donald J.; Chamberlain, Neil F.; Garber, Frederick D.; Walton, Eric K.

106

Correlated observations of the boundary between polar cap and nightside auroral zone by HF radars and the DMSP satellite  

SciTech Connect

Simultaneous observations from HF radars and the DMSP satellite have been used to relate the ionospheric convection pattern and the nightside precipitation at the polar cap-auroral zone boundary. The convection is eastward in the poleward part of the radars field of view and predominantly westward at lower latitudes. The DMSP-F9 particle spectrograms exhibit energetic precipitating protons at the poleward edge of an inverted V'. The downward H[sup +] flow displays spatial filtering effects with a clear energy-latitude dispersion. Single-particle trajectory simulations in appropriate field models demonstrate that these ions were ejected from the neutral sheet near 120 R[sub E] geocentric distance. Most notably, the simulations reveal significant azimuthal dispersion during transport, and the source region in the magnetotail is found to extend over several Earth radii in the dawn-dusk direction, less energetic particles originating duskward of the high-energy ones. The longitudinal spread of the tail source suggests particle precipitation in the ionosphere over at least one hour magnetic local time. Also, as the downflowing protons travel near the lobeward edge of the plasma sheet, the observations suggest that the convection reversal lies inside the boundary layer plasma sheet (PSBL). 11 refs., 3 figs.

Senior, C.; Cerisier, J.C. (CRPE/CNRS, Saint-Maur-des-Fosses (France)); Hanuise, C. (Universite de Toulon et du Var (France)); Villain, J.P. (LPCE, Orleans La Source (France)); Greenwald, R.G.; Newell, P.T. (John Hopkins Univ., Laurel, MD (United States)); Rich, F.J. (GMG, Bedford, MA (United States))

1994-02-01

107

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

108

Ocean Surface Currents From AVHRR Imagery: Comparison With Land-Based HF Radar Measurements  

Microsoft Academic Search

We focus on inverting the surface temperature (or heat) equation to obtain the surface velocity field in the coastal ocean and compare the results with those from the maximum cross correlation (MCC) technique and with the in situ velocity fields measured by the Rutgers University Coastal Ocean Dynamics Radar (CODAR). When compared with CODAR fields, velocities from the heat equation

Scott R. Chubb; Richard P. Mied; Colin Y. Shen; Wei Chen; Thomas E. Evans; Josh Kohut

2008-01-01

109

Doppler Spectral Characteristics of High Latitude Ionospheric Irregularities: Effect on HF Radars.  

National Technical Information Service (NTIS)

This report considers the Doppler spectral properties of radar signals scattered from high latitude E and F-region ionospheric irregularities. Although the exact mechanism for the production of F-region irregularities is not yet known, it appears that the...

R. A. Greenwald

1981-01-01

110

A compact low cost, high-power broad band SPDT switch for HF and VHF radar  

NASA Astrophysics Data System (ADS)

The high power SPDT (single pole double throw) switch is extremely useful as a building block for forming linear and circular polarized beams in high power radars. It can also be used simply as a switch to route the RF to two different feeder lines. This paper brings out the detailed design and development of a broad band, low loss, SPDT switch for high power applications using vacuum relay. This fabricated unit is comparatively economical as the only purchased item is a vacuum relay. The size is also compact and two outputs are adjacent to each other as per the requirements. The constructed SPDT switch operates well from dc to VHF range (200 MHz) and has an insertion loss of less than 0.5 dB and isolation better than 35 dB up to 200 MHz. This switch has been tested for 120 kW peak power at 53 MHz with the load VSWR of 2:1 without any trace of breakdown and is already connected with the Indian MST Radar system. There are 32 such units in the whole radar system.

Agarwal, Arvind; Sarkar, B. K.

1993-08-01

111

Survey of Analog-To-Digital Converter Technology for Radar Applications.  

National Technical Information Service (NTIS)

A survey was made of 135 Analog-to-Digital Converter (ADC) manufacturers in the United States and the United Kingdom to determine the availability of ADC's for radar applications. This report contains tabulations on the resolution, sample rate, logic fami...

D. W. Burlage E. R. Billam

1978-01-01

112

Instrument-Based Noncontact Doppler Radar Vital Sign Detection System Using Heterodyne Digital Quadrature Demodulation Architecture  

Microsoft Academic Search

In this paper, we present a fast solution to build a Doppler radar system for noncontact vital sign detection (VSD) using instruments that are generally equipped in radio-frequency and communication laboratories. This paper demonstrates the feasibility of conducting research on VSD in ordinary radio-frequency laboratories. The system is designed with a heterodyne digital quadrature demodulation architecture that helps mitigate quadrature

Changzhan Gu; Changzhi Li; Jenshan Lin; Jiang Long; Jiangtao Huangfu; Lixin Ran

2010-01-01

113

An advanced digital signal processor for the HRR polarimetric MMW active guidance radar  

Microsoft Academic Search

Polarimetric CFAR detection procedures are first outlined. An advanced digital signal processor used for MMW polarimetric HRR active precision guiding radar is configured that involves a preamplifier and filter, a spectral analyzer and a DSP-based polarimetric detector\\/discriminator to seek and track ground targets in surface clutter. A fuzzy relative optimal state (FROS) of a processor is conceptualized concerning the compromise

Yong Rin; Benchao Sie; Lui Yongtan

1993-01-01

114

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)

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.

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

2012-08-01

115

Climatology of GPS phase scintillation and HF radar backscatter for the high-latitude ionosphere under solar minimum conditions  

NASA Astrophysics Data System (ADS)

Maps of GPS phase scintillation at high latitudes have been constructed after the first two years of operation of the Canadian High Arctic Ionospheric Network (CHAIN) during the 2008-2009 solar minimum. CHAIN consists of ten dual-frequency receivers, configured to measure amplitude and phase scintillation from L1 GPS signals and ionospheric total electron content (TEC) from L1 and L2 GPS signals. Those ionospheric data have been mapped as a function of magnetic local time and geomagnetic latitude assuming ionospheric pierce points (IPPs) at 350 km. The mean TEC depletions are identified with the statistical high-latitude and mid-latitude troughs. Phase scintillation occurs predominantly in the nightside auroral oval and the ionospheric footprint of the cusp. The strongest phase scintillation is associated with auroral arc brightening and substorms or with perturbed cusp ionosphere. Auroral phase scintillation tends to be intermittent, localized and of short duration, while the dayside scintillation observed for individual satellites can stay continuously above a given threshold for several minutes and such scintillation patches persist over a large area of the cusp/cleft region sampled by different satellites for several hours. The seasonal variation of the phase scintillation occurrence also differs between the nightside auroral oval and the cusp. The auroral phase scintillation shows an expected semiannual oscillation with equinoctial maxima known to be associated with aurorae, while the cusp scintillation is dominated by an annual cycle maximizing in autumn-winter. These differences point to different irregularity production mechanisms: energetic electron precipitation into dynamic auroral arcs versus cusp ionospheric convection dynamics. Observations suggest anisotropy of scintillation-causing irregularities with stronger L-shell alignment of irregularities in the cusp while a significant component of field-aligned irregularities is found in the nightside auroral oval. Scintillation-causing irregularities can coexist with small-scale field-aligned irregularities resulting in HF radar backscatter. The statistical cusp and auroral oval are characterized by the occurrence of HF radar ionospheric backscatter and mean ground magnetic perturbations due to ionospheric currents.

Prikryl, P.; Jayachandran, P. T.; Mushini, S. C.; Chadwick, R.

2011-02-01

116

Measurements of drift velocity of artificial small-scale field-aligned irregularities using multi-position HF radars  

NASA Astrophysics Data System (ADS)

In report the results of multi-position radar measurements of Doppler frequency shift DFS scattered signals by artificial small-scale field-aligned irregularities FAI are presented In measurements two pairs of bistatic configurations HF radars have been used Kaliningrad 54 7 r N 20 6 r E -- SURA 56 1 r N 46 1 r E - IZMIRAN 55 3 r N 37 2 r E path 1 and RVI 55 8 r N 38 3 r E - SURA - Rostov-Don 47 2 r N 39 6 r E path 2 Such geometry of paths has allowed to determine the value and direction of drift velocity of FAI in a plane orthogonal to magnetic field Observations were carried out in March 2005 in the evening hours from 16 00 to 19 00 UT On the first path the probing transmitter operated at frequency 9300 kHz in a pulse mode tau 100 mu s F rep 25 Hz on the second path as the probing transmitter was used the RVI station of precise times which operated at frequency 14996 kHz in continuous carrier mode The heating facility SURA operated in a mode 5 min -- radiation and 5 min - pause on pump wave frequency f p close to critical frequency of F-layer f p le f o F2 According to results of spectral measurements in an operating time of heating facility on both paths scattered signals from artificial small-scale field-aligned irregularities were observed On the basis of DFS measurements of the scattered signal SS we have calculated value V and direction azimuth A of the irregularities drift velocity It is obtained that during moderate disturbance period magnetic

Uryadov, V. P.; Frolov, V. L.; Vertogradov, G. G.; Vertogradov, V. G.; Kim, V. Yu.; Panchenko, V. A.; Polimatidi, V. P.; Ivanov, V. P.

117

A novel digital receiver concept for ISRO's future remote sensing radars  

NASA Astrophysics Data System (ADS)

Technology development related to digital, antenna and RF subsystems for Microwave Radar Sensors like Synthetic Aperture Radar, Scatterometer, Altimeter and Radiometer is one of the major activities under ISRO's microwave remote sensing programme, since 1980s. These technologies are now being gainfully utilized for building ISRO's operational Earth Observation missions involving microwave sensors like Radar Imaging Satellite, RISAT SAR, Oceansat-2 Scatterometer, Megha-Tropiques, MADRAS and Airborne SAR for Disaster Management, DMSAR. Concurrently, advanced technology developments in these fields are underway to meet the major technological challenges of building ISRO's proposed advanced microwave missions like ultra-high resolution SAR's, Synthetic Aperture Radiometer (SARAD), Milli-meter and sub-millimeter wave sounders and SAR Constellations for Disaster management as well as Interferometric, Polarmetric and polarmetric interferometry applications. Also, these hardware are being designed with core radar electronics concept, in which the same RF and digital hardware sub-units / modules will be utilized to build different microwave radar sensors. One of the major and common requirements for all these active and passive microwave sensors is the moderate to highspeed data acquisition and signal processing system. Traditionally, the Data acquisition units for all these radar sensors are implemented as stand-alone units, following the radar receivers. For ISRO's C-band airborne SAR (ASAR) and RISAT high resolution SAR, we have designed and developed High Speed 8-bit ADC based I/Q Digitisers, operating at 30.814 MHz and 250 MHz sampling rates, respectively. With the increasing demand of wide bandwidth and ultra-high resolution in imaging and non-imaging radar systems, the technology trend worldwide is towards a digital receiver, involving bandpass or IF sampling, thus eliminating the need for RF down converters and analog IQ demodulators. In order to evolve a generic configuration for all the microwave sensors, we have initiated design and development of a generic L-band digital receiver, consisting of receiver elements (LNA, digital attenuator and Bandpass filter) followed by Analog-to-Digital Converter. The digitised data can then be output in parallel or serial format. Additionally, a digital signal processor performing tasks like data compression, convolution or correlation and formatting can also be integrated with this generic digital receiver. The front end of the receiver is wide-band, catering to bandwidths of upto 2 GHz while the digitisation rates are also of the order of 1-2 GHz. It is proposed to standardize the design and use this generic receiver for front end data acquisition of all the future microwave sensors. It will meet the digitisation requirements of 500 MHz to 1 GHz for ultra-high resolution (0.25-0.5 meter) SAR as well as direct sampling of the signal around 1.4GHz for L-band Synthetic Aperture Radiometer. After initial prototyping using discrete receiver elements and ultra-high speed 8-bit ADC, it will be taken up as a custom ASIC or multi-chip module consisting of RF MMIC's and a mixed signal ADC ASIC. These designs will be fabricated using InP, GaAs or SiGe process technologies at competent foundries like GATEC, SCL, Infineon/Germany, X-Fab/Germany and Ommic-Philips/France. This novel digital receiver will offer several advantages like flexibility, stability, reduced RF hardware and miniaturisation. This paper describes the ultra-high speed design requirements, configuration details and target specifications and salient features of this generic L-band digital receiver for ISRO's future spaceborne and airborne radar missions. It also addresses the associated signal integrity, EMI/EMC and thermal issues.

Desai, Nilesh; Vachhani, J. G.; Soin, Sumit; Agrawal, Rinku; Rao, C. V. N.; Gujraty, Virendra; Rana, Surindersingh

2006-12-01

118

HF radar observations of Pc 5 field line resonances in the midnight/early morning MLT sector  

SciTech Connect

On a number of occasions The Johns Hopkins University/Applied Physics Laboratory HF radar at Goose Bay, Labrador, has observed the effects of field line resonances on the drift velocities of irregularities in the F region of the high-latitude ionosphere. One of the most interesting sets of resonances occurs near midnight MLT and may be associated with shear in the convective flow in the magnetotail. This paper discusses in detail a particularly clear example which shows field line resonance equatorward of a region of shear flow in the early morning sector. The motions were predominantly in the geomagnetic east-west direction, indicating north-south electric fields. As expected of field line resonance pulsations, these oscillations had pronounced peaks in their latitudinal power distribution. The pulsations could occur simultaneously but remained distinct as the latitude of peak response was observed to vary inversely with the frequency of the pulsation. The authors interpret these features in terms of field line resonance theory and discuss the possible sources of the pulsation energy.

Ruohoniemi, J.M.; Greenwald, R.A.; Baker, K.B. (Johns Hopkins Univ., Laurel, MD (United States)); Samson, J.C. (Univ. of Alberta, Edmonton (Canada))

1991-09-01

119

Water Import of East China Sea through Taiwan Strait as Measured by ADCP on a Ferry and by HF Radars  

NASA Astrophysics Data System (ADS)

East China Sea is surrounded by countries that contains one fourth of the world population. To understand the marine environment and marine ecosystem, one has to know the balance of water transport in and out of East China Sea. Half of the influx to East China Sea is through Taiwan Strait. Unfortunately, the heavy fishing activity resulted the longest current measurement with bottom-mount ADCP across Taiwan Strait is only 2.5 months long. The current in Taiwan Strait were survey with an ADCP installed at the bottom of a ferry boat which provides about 1000 transects in 2009-2011 across Taiwan Strait. The measurement of volume transport Q from Taiwan Strait to East China Sea shows clearly that the variation of Q is mostly by the local wind, Q (Sv) = 0.279 Wa10 + 2.12, where Wa10 is the along strait wind component at 10 m height. This is verified with HF radar measurement from Taiwan.

Liu, Cho-Teng; Matsuno, Takeshi; Chen, Hsien-Wen; Yang, Wen Chang; Ichikawa, Kaoru; Tsai, Wei-Teng; Lee, Chang-Wei

2013-04-01

120

A technique for calculating ionospheric Doppler shifts from standard ionograms suitable for scientific, HF communication, and OTH radar applications  

NASA Astrophysics Data System (ADS)

High-resolution Doppler ionograms taken at 5 min intervals were obtained from a KEL IPS 71 ionosonde operating over a full ionosonde sweep range. The ionograms were converted into true height profiles using the program POLAN. POLAN also produced an equivalent parabolic layer model of best fit to the true height profile. A parabolic layer model of the ionosphere is defined by three parameters, namely, peak height, maximum electron density/critical frequency, and parabolic thickness. Equations for calculating Doppler shift from a time-varying parabolic layer model have long been known but have seen remarkably little use in the absence of suitable input data and a means of verifying the results. This paper shows that these equations can provide an accurate means of calculating ionospheric Doppler shift based on standard ionospheric ionograms taken at a 5 min rate over a 24 h period when compared with actual Doppler measurements. Apart from its scientific interest, the demonstrated technique will prove particularly valuable in deriving Doppler shift and associated signal fading for the real-time control of over-the-horizon radar and HF communication links.

Lynn, K. J. W.

2009-12-01

121

An Evaluation of HF Ionospheric Backscatter Echoes.  

National Technical Information Service (NTIS)

The characteristics of HF radar echoes reflected from ionization irregularities aligned along the lines of force of the earth's magnetic field are discussed. The spatial-geographical extent of ionospheric backscatter echoes is estimated for an HF radar lo...

G. H. Millman

1975-01-01

122

AFOS (Automation of Field Operations and Services) Monitoring of MDR (Manually Digitized Radar) Data Using Flash Flood Guidance,  

National Technical Information Service (NTIS)

The Automation of Field Operations and Services (AFOS) applications program MDRPLT, distributed to the field by the Techniques Development Laboratory (TDL), plots Manually Digitized Radar (MDR) data on local map backgrounds (Newton, 1984). These plots can...

G. A. Norman M. C. Newton

1987-01-01

123

On the spatiotemporal evolution of the ionospheric backscatter during magnetically disturbed periods as observed by the TIGER Bruny Island HF radar  

NASA Astrophysics Data System (ADS)

The Superposed Epoch Analysis (SEA) method is used to examine a 4-year database (2000-2003) of the TIGER Bruny Island radar (MLON=226.78°E, MLAT=55.06°S) measurements to determine typical patterns of the spatiotemporal evolution of ionospheric backscatter during geomagnetically disturbed periods. SEA is performed separately for three disturbance categories: short-, medium-, and long-duration magnetic disturbances, based on the Dst index variation. Prior to SEA, the diurnal, seasonal, and solar cycle effects have been accounted for by subtracting the nominal quiet-time values. It is found that the occurrence of ionospheric HF backscatter exhibited strongest enhancements near t=0 h between 65°S and 70°S MLAT (range of 800-2500 km) during short-duration magnetic disturbance. In contrast, a reduction in echo occurrence first occurred near t=0 h at higher ranges (r?2500 km) and expanded equatorwards during the recovery phase of the magnetic disturbances. This reduction in occurrence became progressively stronger and prolonged for medium- and long-duration magnetic disturbances. These categories also showed clear enhancements in the E-region backscatter (r<765 km) commencing from t=0 h. These observations can be explained by three main factors: (1) an enhancement in the E-region densities due to high-energy particle precipitation during magnetically disturbed periods causing the HF radar waves to refract from smaller altitudes and closer ranges, (2) a variability in the F-region densities associated with magnetic disturbances also affecting the propagation of the HF radar waves, and (3) a short-lived strong enhancement in growth rate of decametre-scale ionospheric irregularities when IMF turned southwards causing the highest echo occurrence near t=0 h during SEA.

Kumar, V. V.; Makarevich, R. A.; Kane, T. A.; Ye, H.; Devlin, J. C.; Dyson, P. L.

2011-08-01

124

Applications of high-frequency radar  

NASA Astrophysics Data System (ADS)

Efforts to extend radar range by an order of magnitude with use of the ionosphere as a virtual mirror started after the end of World War II. A number of HF radar programs were pursued, with long-range nuclear burst and missile launch detection demonstrated by 1956. Successful east coast radar aircraft detect and track tests extending across the Atlantic were conducted by 1961. The major obstacles to success, the large target-to-clutter ratio and low signal-to-noise ratio, were overcome with matched filter Doppler processing. To search the areas that a 2000 nautical mile (3700 km) radar can reach, very complex and high dynamic range processing is required. The spectacular advances in digital processing technology have made truly wide-area surveillance possible. Use of the surface attached wave over the oceans can enable HF radar to obtain modest extension of range beyond the horizon. The decameter wavelengths used by both skywave and surface wave radars require large physical antenna apertures, but they have unique capabilities for air and surface targets, many of which are of resonant scattering dimensions. Resonant scattering from the ocean permits sea state and direction estimation. Military and commercial applications of HF radar are in their infancy.

Headrick, J. M.; Thomason, J. F.

1998-07-01

125

Comparison of the X-TRACK altimetry estimated currents with moored ADCP and HF radar observations on the West Florida Shelf  

NASA Astrophysics Data System (ADS)

The performance of coastal altimetry over a wide continental shelf is assessed using multiple-year ocean current observations by moored Acoustic Doppler Current Profilers (ADCP) and high-frequency (HF) radar on the West Florida Shelf. Across-track, surface geostrophic velocity anomalies, derived from the X-TRACK along-track sea level anomalies are compared with the near surface current vector components from moored ADCP observations at mid shelf. The altimeter-derived velocity anomalies are also directly compared with the HF radar surface current vector radial components that are aligned perpendicular to the satellite track. Preliminary results indicate the potential usefulness of the along-track altimetry data in contributing to descriptions of the surface circulation on the West Florida Shelf and the challenges of such applications. On subtidal time scales, the root-mean-square difference (rmsd) between the estimated and the observed near surface velocity component anomalies is 8-11 cm/s, which is about the same magnitude as the standard deviations of the velocity components themselves. Adding a wind-driven Ekman velocity component generally helps to reduce the rmsd values.

Liu, Yonggang; Weisberg, Robert H.; Vignudelli, Stefano; Roblou, Laurent; Merz, Clifford R.

2012-10-01

126

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

127

Automatic modulation classification of digital modulations in presence of HF noise  

NASA Astrophysics Data System (ADS)

Designing an automatic modulation classifier (AMC) for high frequency (HF) band is a research challenge. This is due to the recent observation that noise distribution in HF band is changing over time. Existing AMCs are often designed for one type of noise distribution, e.g., additive white Gaussian noise. This means their performance is severely compromised in the presence of HF noise. Therefore, an AMC capable of mitigating the time-varying nature of HF noise is required. This article presents a robust AMC method for the classification of FSK, PSK, OQPSK, QAM, and amplitude-phase shift keying modulations in presence of HF noise using feature-based methods. Here, extracted features are insensitive to symbol synchronization and carrier frequency and phase offsets. The proposed AMC method is simple to implement as it uses decision-tree approach with pre-computed thresholds for signal classification. In addition, it is capable to classify type and order of modulation in both Gaussian and non-Gaussian environments.

Alharbi, Hazza; Mobien, Shoaib; Alshebeili, Saleh; Alturki, Fahd

2012-12-01

128

Analysis and characterization of the vertical accuracy of digital elevation models from the Shuttle Radar Topography Mission  

Microsoft Academic Search

The first near-global high-resolution digital elevation model (DEM) of the Earth has recently been released following the successful Shuttle Radar Topography Mission (SRTM) of 2000. This data set will have applications in a wide range of fields and will be especially valuable in the Earth sciences. Prior to widespread dissemination and use, it is important to acquire knowledge regarding the

Giacomo Falorni; Vanessa Teles; Enrique R. Vivoni; Rafael L. Bras; Kevin S. Amaratunga

2005-01-01

129

Theoretical Fundamentals of Radar.  

National Technical Information Service (NTIS)

The book examines the principles of radar, methods of coordinate measurement and scanning and circuits for radar stations of three types: with an operator, a continuous computer installation and a digital computer. It presents the characteristics of radar...

A. A. Korostelev A. V. Petrov N. I. Burenin V. E. Dulevich Y. A. Melnik

1967-01-01

130

47 CFR 73.758 - System specifications for digitally modulated emissions in the HF broadcasting service.  

Code of Federal Regulations, 2011 CFR

...Emission characteristics â(1) Bandwidth and center frequency. A full digitally modulated emission will have a 10 kHz bandwidth with its center frequency at any of the...a digital emission of 5 kHz or 10 kHz bandwidth, next to either a 5 kHz or 10...

2011-10-01

131

47 CFR 73.758 - System specifications for digitally modulated emissions in the HF broadcasting service.  

Code of Federal Regulations, 2012 CFR

...Emission characteristics â(1) Bandwidth and center frequency. A full digitally modulated emission will have a 10 kHz bandwidth with its center frequency at any of the...a digital emission of 5 kHz or 10 kHz bandwidth, next to either a 5 kHz or 10...

2012-10-01

132

Digital signal processing and numerical analysis for radar in geophysical applications  

NASA Astrophysics Data System (ADS)

Numerical solutions for signal processing are described in this work as a contribution to study of echo detection methods for ionospheric sounder design. The ionospheric sounder is a high frequency radar for geophysical applications. The main detection approach has been done by implementing the spread-spectrum techniques using coding methods to improve the radar's range resolution by transmitting low power. Digital signal processing has been performed and the numerical methods were checked. An algorithm was proposed and its computational complexity was calculated.The proposed detection process combines two channels correlations with the local code and calculates threshold (Vt) by statistical evaluation of the background noise to design a detection algorithm. The noisy signals treatment was performed depending on the threshold and echo amplitude. In each case, the detection was improved by using coherent integration. Synthetic signals, close loop and actual echoes, obtained from the Advanced Ionospheric Sounder (AIS-INGV) at Rome Ionospheric Observatory, were used to verify the process.The results showed that, even in highly noisy environments, the echo detection is possible.Given that these are preliminary results, further studies considering data sets corresponding to other geophysical conditions are needed.

Molina, María G.; Cabrera, M. A.; Ezquer, R. G.; Fernandez, P. M.; Zuccheretti, E.

2013-05-01

133

A system for the real time exploitation of digital synthetic aperture radar data  

NASA Astrophysics Data System (ADS)

The Advanced Building Block for Large Area Exploitation (ABLE) is a system designed to demonstrate the feasibility of doing real time synthetic aperture radar exploitation. ABLE has four subsystems, which have the following functions: (1) reception and processing of the phase histories to produce an image; (2) automatic change detection; (3) two-stage exploitation function proper; and (4) production and management of cues, as well as the ancillary management necessary for efficient exploitation. ABLE's major components consist of the Synthetic Aperture Precision Processor High Reliability (SAPPHIRE) digital correlator, the automatic change detection subsystem, the exploitation subsystem, and the exploitation management system. Factors influencing the system engineering are discussed, and the resulting design features are described.

Withman, R. L.

134

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

SciTech Connect

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.

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

1991-08-26

135

A simple method for optimizing radar absorbent material coatings on HF rope antennas for the increased attenuation of unwanted reflections  

Microsoft Academic Search

The research presented here examines the maximum attenuation available from concentric layers of radar absorbing materials (RAM) surrounding an infinitely long perfect electrically conducting circular cylinder. The electrical phenomenology of normally incident transverse magnetic (TM) and transverse electrical (TE) waves associated with backscattered and bistatic behavior is investigated for a frequency range up to 25 GHz. Some of the more

George W. Jarriel; Lloyd S. Riggs; Michael E. Baginski

1997-01-01

136

THE NEW INGV DIGITAL IONOSONDE DESIGN REPORT  

Microsoft Academic Search

The ionosonde is a system which exploits the radar technique: it applies electromagnetic waves with variable frequency in the HF band to measure the io nospheric layers electron density, height and other parameters. This paper is a technical report on the new digital ionosonde (AIS-INGV), which was designed both for research purposes and for the routine serv ice of the

J. Baskaradas Arokiasamy; C. Bianchi; U. Sciacca; G. Tutone; E. Zuccheretti

137

Observations of meteors using over-the-horizon radar  

NASA Astrophysics Data System (ADS)

Over-the-horizon skywave radars operating in the HF band utilize digital techniques for both radar control and signal processing. These radars are also equipped with frequency management subsystems for the selection of appropriate frequencies for meteor detection based on real-time monitoring of the HF signal environment. Results of meteor observations using such a radar are discussed, including the detection of the Eta Aquarid meteor. A large increase in the echo rate caused by sporadic meteors is obtained as frequencies are reduced below 15 MHz and the underdense echo ceiling rises in altitude. Preliminary observations of highly Doppler shifted echoes traveling at meteoric velocities and identified as meteor head echoes, are presented.

Thomas, R. M.; Netherway, D. J.

138

HF RADAR observations of coastal currents induced by the 29-30 September 2009 tsunami South of O’ahu  

NASA Astrophysics Data System (ADS)

A High-Frequency RADAR collected radial current observations at 1.5 km resolution every 15 minutes along O’ahu’s South Shore. Following the arrival of the tsunami generated by the September 29 Samoan earthquake, radial currents fluctuations of up to 4 cm/s were recorded 25-35 km off shore. The bursts of shoreward surface current associated with the tsunami are located at the transition between deep and shallower water on Penguin Bank, a submerged bank extending westward from the Lanai-Molokai group. The RADAR currents and supporting sea level data from other sensors in the area, showed oscillations at a dominant period of 500 sec. excited by the tsunami, which persisted for more than 8 hours after the tsunami’s initial arrival.

Flament, P. J.; Cass, J. L.; Merrifield, M. A.; Gurgel, K.

2009-12-01

139

A 3D Optimal Interpolation Assimilation Scheme of HF Radar Current Data into a Numerical Ocean Model  

NASA Astrophysics Data System (ADS)

In this work a technique for the 3D assimilation of ocean surface current measurements into a numerical ocean model based on data from High Frequency Radar (HFR) systems is presented. The technique is the combination of supplementary forcing on the surface and of and Ekman layer projection of the correction in the depth. Optimal interpolation through BLUE (Best Linear Unbiased Estimator) of the model predicted velocity and HFR observations is computed in order to derive a supplementary forcing applied at the surface boundary. In the depth the assimilation is propagated using an additional Ekman pumping (vertical velocity) based on the correction achieved by BLUE. In this work a HFR data assimilation system for hydrodynamic modelling of Galway Bay in Ireland is developed; it demonstrates the viability of adopting data assimilation techniques to improve the performance of numerical models in regions characterized by significant wind-driven flows. A network of CODAR Seasonde high frequency radars (HFR) deployed within Galway Bay, on the West Coast of Ireland, provides flow measurements adopted for this study. This system provides real-time synoptic measurements of both ocean surface currents and ocean surface waves in regions of the bay where radials from two or more radars intersect. Radar systems have a number of unique advantages in ocean modelling data assimilation schemes, namely, the ability to provide two-dimensional mapping of surface currents at resolutions that capture the complex structure related to coastal topography and the intrinsic instability scales of coastal circulation at a relatively low-cost. The radar system used in this study operates at a frequency of 25MHz which provides a sampling range of 25km at a spatial resolution of 300m.A detailed dataset of HFR observed velocities is collected at 60 minute intervals for a period chosen for comparison due to frequent occurrences of highly-energetic, storm-force events. In conjunction with this, a comprehensive weather station, tide gauge and river monitoring program is conducted. The data are then used to maintain density fields within the model and to force the wind direction and magnitude on flows. The Data Assimilation scheme is then assessed and validated via HFR surface flow measurements.

Ragnoli, Emanuele; Zhuk, Sergiy; Donncha, Fearghal O.; Suits, Frank; Hartnett, Michael

2013-04-01

140

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

NASA Astrophysics Data System (ADS)

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.

Mlynarczyk, Janusz; Koperski, Piotr; Kulak, Andrzej

2012-01-01

141

FMCW channel sounder with digital processing for measuring the coherence of wideband HF radio links  

NASA Astrophysics Data System (ADS)

Multipath propagation, and in particular, the interference between the ordinary and the extraordinary waves, places a fundamental constraint on the performance of wideband HF skywave radio links. Furthermore, the dispersive nature of ionospheric propagation causes phase nonlinearity and hence distortion of narrow pulses. In this paper, an FMCW wideband sounder built for the purposes of characterizing the channel is described. Spectral analysis of the audio output of the sounder via the FFT algorithm is shown to permit measurement of thef amplitude/frequency function, the polarization bandwidth, the fade rate, the fade depth and the distortion of a narrow pulse, all for a desired isolated ionospheric propagation mode. The sounder was used to collect data over an oblique path in the UK. The results of applying the FFT processing technique to the experimental data are presented.

Salous, S.

1986-08-01

142

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

SciTech Connect

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.

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

1991-01-01

143

Topographic constraints on impact crater morphology on Venus from high-resolution stereo synthetic aperture radar digital elevation models  

Microsoft Academic Search

High-resolution digital elevation models (DEMs) derived from Magellan Left-Left Stereo synthetic aperture radar data of Venus for a set of impact craters ranging in rim diameter from 5 to 300 km exhibit depths broadly as expected from theory but with significant departures for both large and small craters. In craters larger than 38 km diameter, rim-floor depth becomes independent of

Christopher G. Cochrane; Richard C. Ghail

2006-01-01

144

Pc 3-4 Pulsations Near the Cusp: Observations using Search Coil Magnetometers and HF Radars on Svalbard  

NASA Astrophysics Data System (ADS)

Pc 3-4 pulsations (f ~10-100 mHz) originating in the ion foreshock upstream of Earth's bow shock due to the interaction between reflected ions and the solar wind frequently are observed in dayside ground magnetometer records at high latitudes. Many early studies noted increased Pc 3-4 wave power in the vicinity of the dayside cusp and inferred entry via the cusp, but later studies have revealed a more complex picture. In this study, we examined power near local noon at Pc 3-4 frequencies observed by search coil magnetometers at three closely-spaced stations on Svalbard (Ny Alesund, Longyearbyen, and Hornsund). Nineteen days with clear band-limited Pc 3-4 wave power near local noon, and thirteen days with only broadband wave power, were selected for which clear cusp signatures were available in data from the Finland SuperDARN radar, which was used to accurately determine the cusp latitude. 3-s resolution fixed- beam mode data from a radar beam viewing over Svalbard also made it possible to determine Pc 3-4 periodicity in regions of the cusp and auroral zone ionosphere that returned sufficient signal. Band-limited (Pc 3-4) and broadband ULF signals in near-noon magnetometer data showed a similar latitude distribution: wave power peaked about 4-5 degrees south of the cusp. Radar backscatter from the cusp showed no evidence of Pc 3-4 modulation in this region during any of these intervals, whereas two intervals of data at lower latitudes did show modulation at Pc 3-4 frequencies. These observations are consistent not with entry via the cusp proper but along field lines equatorward of the cusp which map to the low-latitude boundary layer or outer magnetosphere. Because this location is similar to that observed for the maximum power of traveling convection vortex events / magnetic impulse events (TCVs/MIEs), we suggest that similar physics may play a role in transmitting perturbations from the upstream solar wind into the dayside magnetosphere in both cases.

Engebretson, M. J.; Lu, F.; Posch, J.; Lessard, M. R.; Kim, H.; Wright, D.; Yeoman, T.; Johnson, J.

2008-12-01

145

Structural analysis of the central Columbia Plateau utilizing radar, digital topography, and magnetic data bases  

SciTech Connect

Interest in the Hanford site (Washington) as a nuclear production, power, and waste disposal site has led to generation of a vast quantity of geophysical and remote sensing data sets of the central Columbia Plateau. To data, these various studies, including at least 13 independent magnetic linear and image lineament studies, have not been adequately correlated. Therefore, these studies provide a unique opportunity to compare and contrast the viability of the different geophysical and remote sensing techniques. The geology of the central Columbia Plateau is characterized by subdued topography and limited outcrop, with most of the exposure concentrated in localized folded/faulted mountains (the Yakima folds) and along river canyons. In order to efficiently compare lineament data bases, we have written an automated computer routine that correlated lineaments that are within a user specified distance of each other. The angle between their trends has to be less than an input maximum separation angle. If more than two lineament maps exist for the area, the analyst may also specify the minimum number of times each structure must be seen. The lineament correlation routine was applied to data bases of all aeromagnetic linears as well as lineaments seen on radar and a digital elevation model DEM image. Geologic structures align with a set of three-dimensional planar structures identified with our Geologic Spatial Analysis (GSA) system. The GSA analysis is based upon computer automated detection of valley bottoms as defined by a DEM.

Thiessen, R.L.; Eliason, J.R.; Johnson, L.K.; Brougher, C.W. [Washington State Univ., Pullman, WA (United States). Dept. of Geology; Foley, M.G.; Beaver, D.E. [Pacific Northwest Lab., Richland, WA (United States)

1991-08-01

146

Effects of Stereoscopic 3D Digital Radar Displays on Air Traffic Controller Performance.  

National Technical Information Service (NTIS)

Air traffic controllers are responsible for directing air traffic based upon decisions made from traffic activity depicted on 2Dimensional (2D) radar displays. Controllers must identify aircraft and detect potential conflicts while simultaneously developi...

J. G. Russi

2013-01-01

147

A general statistical instrument theory of atmospheric and ionospheric radars  

SciTech Connect

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.

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

1991-05-01

148

Digital Signal Generator and Receiver design For S-band Radar  

Microsoft Academic Search

The new generation of radar has to be equipped with a high performance exciters and receivers to cope with the threat in an Electronic Warfare scenario. The threat in a complex environment with interfering signals requires a reliable signal generation with proper frequency agility and efficient gain controls in receiver units. This is quite cumbersome to achieve in analog domain.

L. Prakasam; T. Roy; D. Meena

2007-01-01

149

A digital signal processor for Doppler radar sensing of vital signs  

Microsoft Academic Search

A signal processor for the determination of respiration and heart rates in Doppler radar measurements is described. The processor can reliably calculate both rates for a subject at distances as large as 2 m. The rate determination is based on autocorrelation and uses several enhancement techniques, including a center clipper. Several representative results are included to show the future potential

B. Lohman; O. Boric-Lubecke; V. M. Lubecke; P. W. Ong; M. M. Sondhi

2002-01-01

150

Digital Realtime SAR (Synthetic Aperture Radar) Processor for C- and X-Band Applications.  

National Technical Information Service (NTIS)

A flexible hardware concept to handle high speed image processing tasks is applied to a real time SAR-processor covering C-band ERS-1 as well as X-band radar data. The SPECAN-algorithm used in the processor breadboard, the basic hardware processing module...

R. Schotter

1986-01-01

151

Digital ASIC implementation of a video filter for synthetic aperture radar.  

National Technical Information Service (NTIS)

Two GaAs ASICs have been designed and implemented for a synthetic aperture radar which eliminate the dc bias in the sampled video data and increase the signal to noise ratio by summing the data across consecutive bursts. The High Pass Filter and Presummer...

B. L. Remund J. Chow J. Salinas

1991-01-01

152

A digital ASIC implementation of a video filter for synthetic aperture radar  

SciTech Connect

Two GaAs ASICs have been designed and implemented for a synthetic aperture radar which eliminate the dc bias in the sampled video data and increase the signal to noise ratio by summing the data across consecutive bursts. The High Pass Filter and Presummer ASICs process data at a maximum sample rate of 170 MHz and 125 MHz respectively. The chips are fully ECL and TTL compatible. The high pass filter is packaged in GigaBit's standard 132-pin ceramic package, while the presummer is packaged in TriQuint's standard 196-pin ceramic package. The presummer has been successfully tested in a prototype synthetic aperture radar at Sandia National Laboratories. The high pass filter has been successfully tested in a high speed test fixture. These ASICs provide flexibility and low power consumption at data rates previously unattainable with comparable hardware. 1 refs., 4 figs.

Remund, B.L. (Sandia National Labs., Albuquerque, NM (United States)); Chow, J.; Salinas, J. (GigaBit Logic, Newbury Park, CA (United States))

1991-01-01

153

HF radio oceanography — A review  

Microsoft Academic Search

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,

Donald E. Barrick

1978-01-01

154

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

Microsoft Academic Search

On 10 October 2006 the SPEAR high power radar facility was operated in a power-stepping mode where both CUTLASS radars were detecting backscatter from the SPEAR-induced field-aligned irregularities (FAIs). The effective radiated power of SPEAR was varied from 1-10 MW. The aim of the experiment was to investigate the power thresholds for excitation (Pt) and collapse (Pc) of artificially-induced FAIs

D. M. Wright; R. S. Dhillon; T. K. Yeoman; T. R. Robinson; E. C. Thomas; L. J. Baddeley; S. Imber

2009-01-01

155

The Shuttle Radar Topography Mission  

Microsoft Academic Search

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.

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

156

Aspect angle dependence of HF enhanced incoherent backscatter  

Microsoft Academic Search

An HF ionospheric interaction experiment was performed in November and December of 1997 using the EISCAT HF transmitter and 931 and 224 MHz incoherent scatter radars, all co-located near Tromsø, Norway. During this experiment the pointing of the UHF radar was varied in a predetermined and repeating cycle between elevation angles of 90 and 77.2 degrees south, that is, between

B. Isham; M. T. Rietveld; T. Hagfors; C. La Hoz; E. Mishin; W. Kofman; T. B. Leyser; A. P. van Eyken

1999-01-01

157

Design of a Digital Simulation of the Polar Planimeter for Calculating Areas of Echoes from Radar Weather Observations.  

National Technical Information Service (NTIS)

The effort discussed in the report was to fulfill a requirement for expediently analyzing data on radar weather prediction techniques. Data is recorded at various radar stations, which make hourly weather observations on the local weather activity within ...

R. G. Kelley

1968-01-01

158

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

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

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

2010-01-01

159

Advanced HF anti-jam network architecture  

NASA Astrophysics Data System (ADS)

The Hughes HF2000 system was developed using a flexible architecture which utilizes a wideband RF front-end and extensive digital signal processing. The HF2000 antijamming (AJ) mode was field tested via an HF skywave path between Fullerton, CA and Carlsbad, CA (about 100 miles), and it was shown that reliable fast frequency-hopping data transmission is feasible at 2400 b/s without adaptive equalization. The necessary requirements of an HF communication network are discussed, and how the HF2000 AJ mode can be used to support those requirements is shown. The Hughes HF2000 AJ mode system architecture is presented.

Jackson, E. M.; Horner, Robert W.; Cai, Khiem V.

160

Simulation of post-ADC digital beamforming for large aperture array radars  

NASA Astrophysics Data System (ADS)

This paper presents simulations and methods developed to investigate the feasibility of using a Fractional-Sample-Delay (FSD) system in the planned EISCAT_3D incoherent scatter radar. Key requirements include a frequency-independent beam direction over a 30 MHz band centered around 220 MHz, with correct reconstruction of pulse lengths down to 200 ns. The clock jitter from sample to sample must be extremely low for the integer sample delays. The FSD must also be able to delay the 30 MHz wide signal band by 1/1024th of a sample without introducing phase shifts, and it must operate entirely in baseband. An extensive simulation system based on mathematical models has been developed, with inclusion of performance-degrading aspects such as noise, timing error, and bandwidth. Finite Impulse Response (FIR) filters in the baseband of a band-pass-sampled signal have been used to apply true time delay beamforming. It has been confirmed that such use is both possible and well behaved. The target beam-pointing accuracy of 0.06° is achievable using optimized FIR filters with lengths of 36 taps and an 18 bit coefficient resolution. Even though the minimum fractional delay step necessary for beamforming is ˜13.1 ps, the maximum sampling timing error allowed in the array is found to be ? ? 120 ps if the errors are close to statistically independent.

Johansson, G.; Borg, J.; Johansson, J.; Lundberg Nordenvaad, M.; Wannberg, G.

2010-06-01

161

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

NASA Astrophysics Data System (ADS)

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

Wright, D. M.; Dhillon, R. S.; Yeoman, T. K.; Robinson, T. R.; Thomas, E. C.; Baddeley, L. J.; Imber, S.

2009-07-01

162

Shuttle Radar Topography Mission: DLR's Interferometric SAR Processor for the Generation of a Global Digital Elevation Model  

Microsoft Academic Search

The Shuttle Radar Topography Mission (SRTM) will be launched in January 2000. Its intention is the global topographic mapping of the Earth' surface. The data will be acquired by the first space-born single-pass synthetic aperture radar (SAR) interferometer. Within eleven days this mission will map all continents between 60 latitude. The resulting data set is unique in two respects. Firstly,

Nico Adam; Michael Eineder; Helko Breit; Steffen Suchandt

2000-01-01

163

HF, VHF, and UHF systems and technology  

Microsoft Academic Search

A wide variety of unique systems and components inhabits the HF, VHF, and UHF bands. Many communication systems (ionospheric, meteor-burst, and troposcatter) provide beyond-line-of-sight coverage and operate independently of external infrastructure. Broadcasting and over-the-horizon radar also operate in these bands. Magnetic-resonance imaging uses HF\\/VHF signals to see the interior of a human body, and RF heating is used in a

Frederick H. Raab; Robert Caverly; Richard Campbell; Murat Eron; James B. Hecht; Arturo Mediano; Daniel P. Myer; John L. B. Walker

2002-01-01

164

Radar in transition  

NASA Astrophysics Data System (ADS)

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.

Barton, D. K.

1984-12-01

165

HF (High Frequencies) Groundwave and Skywave Propagation.  

National Technical Information Service (NTIS)

The principles of HF ground- and skywave propagation are reviewed with regard to regular conditions as well as anomalous phenomena which may effect the signal characteristics and thus may have an influence on the performance of digital communication syste...

K. Hortenbach

1986-01-01

166

HF groundwave and skywave propagation  

NASA Astrophysics Data System (ADS)

The principles of HF ground- and skywave propagation are reviewed with regard to regular conditions as well as anomalous phenomena which may effect the signal characteristics and thus may have an influence on the performance of digital communication systems. Particular consideration is given to the statistics of signal fading as a basis for system design.

Hortenbach, Klaus-Juergen

1986-10-01

167

Millimeter radar  

Microsoft Academic Search

The paper discusses some of the advantages offered by millimeter waves over microwaves, reviews possible and past millimeter radar applications, and looks at some future millimeter radar systems. The coming millimeter radars include radiometric seekers, radiometers, and high resolution radar for satellite identification. Important problems to be resolved before millimeter radars can be put into production include component capability; radar

S. L. Johnston

1977-01-01

168

Superconductor Digital-RF Receiver Systems  

NASA Astrophysics Data System (ADS)

Digital superconductor electronics has been experiencing rapid maturation with the emergence of smaller-scale, lower-cost communications applications which became the major technology drivers. These applications are primarily in the area of wireless communications, radar, and surveillance as well as in imaging and sensor systems. In these areas, the fundamental advantages of superconductivity translate into system benefits through novel Digital-RF architectures with direct digitization of wide band, high frequency radio frequency (RF) signals. At the same time the availability of relatively small 4K cryocoolers has lowered the foremost market barrier for cryogenically-cooled digital electronic systems. Recently, we have achieved a major breakthrough in the development, demonstration, and successful delivery of the cryocooled superconductor digital-RF receivers directly digitizing signals in a broad range from kilohertz to gigahertz. These essentially hybrid-technology systems combine a variety of superconductor and semiconductor technologies packaged with two-stage commercial cryocoolers: cryogenic Nb mixed-signal and digital circuits based on Rapid Single Flux Quantum (RSFQ) technology, room-temperature amplifiers, FPGA processing and control circuitry. The demonstrated cryocooled digital-RF systems are the world's first and fastest directly digitizing receivers operating with live satellite signals in X-band and performing signal acquisition in HF to L-band at ˜30GHz clock frequencies.

Mukhanov, Oleg A.; Kirichenko, Dmitri; Vernik, Igor V.; Filippov, Timur V.; Kirichenko, Alexander; Webber, Robert; Dotsenko, Vladimir; Talalaevskii, Andrei; Tang, Jia Cao; Sahu, Anubhav; Shevchenko, Pavel; Miller, Robert; Kaplan, Steven B.; Sarwana, Saad; Gupta, Deepnarayan

169

Mid-latitude ionospheric plasma drift: A comparison of digital ionosonde and incoherent scatter radar measurements at Millstone Hill. Ph.D. Thesis  

SciTech Connect

A successful validation of the Digisonde drift technique was performed by comparing local ionospheric plasma drift velocity vectors measured by a Digisonde 256 digital ionosonde and a UHF incoherent scatter radar co-located at Millstone Hill (42 deg N, 71 deg 30` W) in Massachusetts, USA. The Digisonde drift technique uses imaging Doppler interferometry, measuring amplitude and phase Doppler spectra of ionospherically reflected signals across an array of receive antennas and processing these as line of sight ionospheric velocity vectors. Line of sight velocities of sufficient orthogonality are combined to calculate 3 dimensional ionospheric plasma drift vectors with 5 minutes resolution. A total of 145 hours of simultaneous radar and ionosonde drift vectors from 4 experiments are presented and compared. Geographically aligned, bottom side F-region (200-350 km) velocity components measured by each system were correlated. East-west velocities correlate to plus 0.90, north-south components to plus 0.67 and vertical components to plus 0.51. The Digisonde drift technique works best during moderately disturbed nighttime conditions, and those conditions are the emphasis of the work. The relative smoothness of the daytime mid-latitude ionosphere reduces the technique`s ability to measure horizontal drifts.

Bullett, T.W.

1994-12-31

170

Water slope and discharge in the Amazon River estimated using the shuttle radar topography mission digital elevation model  

Microsoft Academic Search

We find that the standard deviation, hence error, of the water surface elevation data from the Shuttle Radar Topography Mission (SRTM) is 5.51 m for basin-wide, regional and local Amazon mainstem reaches. This error implies a minimum reach length of 733km in order to calculate a reliable water-surface slope. Resulting slopes are 1.92 +\\/- 0.19 cm\\/km for Manacapuru, 2.86 +\\/-

Gina LeFavour; Doug Alsdorf

2005-01-01

171

Radar in transition  

Microsoft Academic Search

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,

D. K. Barton

1984-01-01

172

Terminal Doppler weather radar  

Microsoft Academic Search

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

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

1990-01-01

173

Physical and orbital properties of micrometeors observed using the 430 MHz Arecibo observatory radar  

Microsoft Academic Search

Physical and orbital properties of 1200+ radar micrometeors are deduced from more than 8000+ event detections using the 430 MHz Arecibo radar in Puerto Rico. These results are very distinct from classical HF\\/VHF radar observations in that the head-echo (radar scattering from the region immediately surrounding the meteoroid) is always observed, leading uniquely to very accurate Doppler speed determinations. A

Diego Janches

2000-01-01

174

Lunar Radar Cross Section at Low Frequency  

NASA Astrophysics Data System (ADS)

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.

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

2002-01-01

175

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

176

Radar sector blanker  

NASA Astrophysics Data System (ADS)

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.

Hall, Roger B.

1994-03-01

177

Passive Radar.  

National Technical Information Service (NTIS)

The basic ideas and concepts of one of the newest branches of radar, that of passive radar, are discussed. A great deal of attention is devoted to questions of the use of passive radar by the armed forces. The physical fundamentals of passive radar, and t...

A. G. Nikolaev S. V. Pertsov

1975-01-01

178

Alpine snow distribution from-ground based radar measurements compared with a high resolution digital elevation model from ground-based LiDAR observations  

NASA Astrophysics Data System (ADS)

Collection of snow depth and precipitation measurements is exceedingly difficult above treeline in exposed areas of alpine terrain. Variability in surface topography combined with wind can cause large variations in snow depth and snow water equivalent over tens of meters, and precipitation measurements are often unreliable where wind speeds are high. Total snow depth and water equivalent measurements are often not representative in these highly variable snowpacks, while alpine locations often contain a large percentage of the water stored as snow in many watersheds. We use two different ground-based radar systems to measure snow distribution near an alpine weather station at 3719 m (12,200 ft) in SW Colorado at the Center for Snow and Avalanche Studies' Senator Beck Basin Study Area. The spatial distribution of snow is compared with a high resolution digital elevation model derived from ground-based LiDAR observations in snow-free conditions. The length scales of variation in both subsurface topography and snow depth are investigated in the region surrounding the weather station to help place the continuous snow depth observations at the weather station in the context of the snow distribution at the slope scale across this low angle site.

Marshall, H.; Deeb, E. J.; Gleason, A.; Heilig, A.; Finnegan, D. C.; Deems, J. S.; Havens, S.; Kormos, P. R.; Landry, C.; McCreight, J. L.

2011-12-01

179

A comparison of velocity measurements from the CUTLASS Finland radar and the EISCAT UHF system  

Microsoft Academic Search

The CUTLASS Finland radar, which com- prises an integral part of the SuperDARN system of HF coherent radars, provides near continuous observations of high-latitude plasma irregularities within a field-of- view which extends over some four million square kilometres. Within the Finland radar field-of-view lie both the EISCAT mainland and EISCAT Svalbard incoherent scatter radar facilities. Since the CUTLASS Finland radar

J. A. Davies; M. Lester; S. E. Milan; T. K. Yeoman

1999-01-01

180

Radar applications overview  

NASA Astrophysics Data System (ADS)

During the fifty years since its initial development as a means of providing early warning of airborne attacks against allied countries during World War II, radar systems have developed to the point of being highly mobile and versatile systems capable of supporting a wide variety of remote sensing applications. Instead of being tied to stationary land-based sites, radar systems have found their way into highly mobile land vehicles as well as into aircraft, missiles, and ships of all sizes. Of all these applications, however, the most exciting revolution has occurred in the airborne platform arena where advanced technology radars can be found in all shapes and sizes...ranging from the large AWACS and Joint STARS long range surveillance and targeting systems to small millimeter wave multi-spectral sensors on smart weapons that can detect and identify their targets through the use of highly sophisticated digital signal processing hardware and software. This paper presents an overview of these radar applications with the emphasis on modern airborne sensors that span the RF spectrum. It will identify and describe the factors that influence the parameters of low frequency and ultra wide band radars designed to penetrate ground and dense foliage environments and locate within them buried mines, enemy armor, and other concealed or camouflaged weapons of war. It will similarly examine the factors that lead to the development of airborne radar systems that support long range extended endurance airborne surveillance platforms designed to detect and precision-located both small high speed airborne threats as well as highly mobile time critical moving and stationary surface vehicles. The mission needs and associated radar design impacts will be contrasted with those of radar systems designed for high maneuverability rapid acquisition tactical strike warfare platforms, and shorter range cued air-to-surface weapons with integral smart radar sensors.

Greenspan, Marshall

1996-06-01

181

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

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.

Cunningham, K. J.

2004-01-01

182

High-frequency radar observations of ocean surface currents.  

PubMed

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

Paduan, Jeffrey D; Washburn, Libe

2012-09-04

183

Sea backscatter at HF: Interpretation and utilization of the echo  

Microsoft Academic Search

Theories and concepts for utilization of HF sea echo are compared and tested against surface-wave measurements made from San Clemente Island in the Pacific in a joint NRL\\/ITS\\/NOAA experiment. The use of first-order sea echo as a reference target for calibration of HF over-the-horizon radars is established. Features of the higher order Doppler spectrum can be employed to deduce the

DONALD E. BARRICK; JAMES M. HEADRICK; ROBERT W. BOGLE; DOUGLASS D. CROMBIE

1974-01-01

184

Production and Modification of Ionospheric Irregularities by Powerful HF Radio Transmissions.  

National Technical Information Service (NTIS)

Several types of active experiments have been performed with the high power HF heater near Arecibo, Puerto Rico. The temporal behavior of suprathermal electron fluxes was studied by observing the 430 MHz radar backscatter from ionospheric Langmuir waves t...

J. A. Fejer

1990-01-01

185

Array radars - An update. II  

NASA Astrophysics Data System (ADS)

Research aimed at improving array radars is reviewed. Advances in MMICs, the use of HEMT low noise amplifiers for analog and digital circuitry, the application of VHSIC chips to the programmable signal processor of the F-16 airborne fire control radar, Si compiler language, memory chips, and GHz and GaAs logic are discussed. Consideration is given to CMOS gate arrays, floating point chips, a single-chip digital signal processor, systolic array architectures, radiation hardened chips, digital beamforming, distributed beamsteering computers, fiber optics, flat low voltage displays, and adaptive-adaptive array processing.

Brookner, Eli

1987-03-01

186

Terminal Doppler weather radar  

NASA Astrophysics Data System (ADS)

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 base data formation, point target removal, signal-to-noise thresholding, and velocity de-aliasing and to the TDWR algorithms and displays. A schematic diagram of the TDWR system is presented.

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

1990-02-01

187

Passive Radar.  

National Technical Information Service (NTIS)

This book sets forth in brief the physical principles of passive radar, describes the functional diagrams and circuit peculiarities of the apparatus, and offers recommendations for modifying radar receivers to adapt them for receiving natural radio-freque...

A. G. Nikolaev S. V. Pertsov

1975-01-01

188

Avalanche Communications - A Robust HF Relay Technique for Stressed Channels  

Microsoft Academic Search

One of the most challenging communications tasks facing industry at present is that of providing reliable digital traffic over the HF ionospheric channel. The variability of the channel with time and external conditions which effect the isonosphere and the substantial amount of natural and man made interference have made the HF channel relatively unreliable for analog voice communications. The multipath

D. D. McRae

1983-01-01

189

Ionospheric Diagnostics for Skywave Sea-State Radar.  

National Technical Information Service (NTIS)

Ionospheric motions and spatial multipath distort the sea-echo spectra obtained with HF skywave radars. At the SRI-WARF radar, two sweep-frequency ionospheric diagnostics are used on-line to help select frequencies and ranges most likely to be free of suc...

M. Kotaki T. M. Georges

1982-01-01

190

A UHF high power solid state radar transmitter  

Microsoft Academic Search

Attention is given to an all solid state high power radar transmitter. The transmitter is housed in the chief HF cabinet in the rear of the radar antenna. It consists of 16 unit row transmitters. The total peak output power is 18 kW. The power amplifier modules and the combination technique are described. The performance characteristics of Chinese high power

Zhencheng Chen; Hongbing Qian; Guoan Zhou

1991-01-01

191

Studies of HF-induced Strong Plasma Turbulence at the HAARP Ionospheric Observatory  

Microsoft Academic Search

High power HF transmitters may induce a number of plasma instabilities in the interaction region of overdense ionospheric plasma. We report results from our recent experiments using over one gigawatt of HF power (ERP) to generate and study strong Langmuir turbulence (SLT) and particle acceleration at the HAARP Observatory, Gakona, Alaska. Among the effects observed and studied in UHF radar

J. P. Sheerin; N. Adham; R. G. E. Roe; M. R. Keith; B. J. Watkins; W. A. Bristow; P. A. Bernhardt; C. A. Selcher

2010-01-01

192

Ionospheric refraction effects in slant range profiles of auroral HF coherent echoes  

Microsoft Academic Search

The theory of auroral coherent echoes developed for VHF scattering by Uspensky et al. (1988, 1989) is applied to the interpretation of intensity and Doppler velocity slant range profiles of HF radar aurora. The theoretical model includes the effects of irregularity aspect sensitivity, ionospheric refraction of the radar beam, and the reception of signals from different heights. The predicted profiles

M. V. Uspensky; A. V. Kustov; G. J. Sofko; J. A. Koehler; J. P. Villain; C. Hanuise; J. M. Ruohoniemi; P. J. S. Williams

1994-01-01

193

Temporal evolution of the HF-enhanced plasma line in sporadic E  

Microsoft Academic Search

The high-power HF facility at Arecibo has been used to study the excitation of Langmuir waves in midlatitude sporadic E. Measurements of the temporal evolution of the so-called HF-enhanced plasma line (HFPL) were made using the Arecibo 430-MHz radar. After HF turn-on in the plasma the HFPL exhibtis a rapid growth phase followed by a quick overshoot. During periods of

F. T. Djuth; C. A. Gonzales; H. M. Ierkic

1988-01-01

194

HF radio wave acceleration of ionospheric electrons: Analysis of HF-induced optical enhancements  

Microsoft Academic Search

The shape of the HF-pump modified electron energy distribution has long been a central question in the field of ionospheric high-frequency radio wave modification experiments. Here we present estimates of the enhanced differential electron flux, from 1.9 to 100 eV based on optical multiwavelength (6300, 5577, 8446, and 4278 Å) data and 930 MHz incoherent scatter radar measurements of ion

B. Gustavsson; B. Eliasson

2008-01-01

195

Monitoring the F-region peak electron density using HF backscatter interferometry  

NASA Astrophysics Data System (ADS)

High frequency (HF, 10-20 MHz) radars routinely utilize Bragg scatter from plasma fluctuations to monitor ionospheric turbulence. While the propagation of the probing HF radio waves is also strongly affected by the regular structure of the ionosphere, this information is rarely extracted from the data. In the present work we present and test a new technique for estimating the F-region peak electron densities, NmF2, using information about the vertical refraction of HF backscatter echoes that is readily available in the Super Dual Auroral Radar Network (SuperDARN) data set.

Ponomarenko, P. V.; Koustov, A. V.; St.-Maurice, J.-P.; Wiid, J.

2011-11-01

196

Multifrequency observations of Polar Mesosphere Summer Echoes using Alaskan radar facilities: Comparisons and scattering calculations  

NASA Astrophysics Data System (ADS)

We present polar mesospheric radar observations at three frequency bands (MF/HF/VHF) and eight radar frequencies: 2.43, 3.3, 4.53, 4.9, 7.6, 28, 50, and 139 MHz, in order to better understand the well known but still not fully understood Polar Mesosphere Summer Echoes (PMSE). The echo morphology at the different frequencies is described by means of case studies where PMSE events were observed concurrently using at least two radar systems deployed over the Alaskan central region. The identity of MF and HF radar echoes as PMSE is resolved for the first time by means of simultaneous measurements made with VHF radars, the reference sensors employed traditionally for PMSE studies. On the basis of echo duration and radar reflectivity estimates, we suggest that low-power HF radars would be more appropriate for PMSE monitoring. This is confirmed by a radar target analysis of turbulent scattering mechanisms in the polar summer mesosphere. MF radars show highly organized PMSE layers quite often but are more susceptible to ionospheric absorption and higher-altitude returns associated with geomagnetic activity. Both phenomena produce a blanking effect in MF PMSE, which at times can persist for hours. HF and VHF radars are less affected by absorption events, but the PMSE echoes become weaker as the radar frequency increases.

Ramos, Camilo; Kelley, Michael C.; Djuth, Frank T.; Groves, Keith M.; Murayama, Yasuhiro; Kawamura, Seiji; Thorsen, Denise

2009-10-01

197

A new digital all-sky imager experiment for optical auroral studies in conjunction with the Scandinavian twin auroral radar experiment  

Microsoft Academic Search

Studies of the relationship between the optical aurorae and the ionospheric electric fields, as observed by the bi-static Scandinavian twin auroral coherent backscatter radar experiment (STARE) and the tri-static European incoherent backscatter radar facility (EISCAT), are to be undertaken in Scandinavia. For this purpose, an unmanned and fully automatic low-light-level television camera system, coupled to an all-sky lens, has been

M. J. Kosch; T. Hagfors; E. Nielsen

1998-01-01

198

Convergence of ESM sensors and passive covert radar  

Microsoft Academic Search

This paper explains the convergence of ESM sensors and passive covert radar (PCR) by presenting the results of field tests with the application of an experimental wideband digital ESM receiver as a sensor in bistatic configuration for PCR. Exploitation of an a priori unknown radar illumination gives the principal possibility of detecting moving targets. A LPI radar with FMCW signals

Dietmar Matthes

2005-01-01

199

Generation of ionospheric ducts by the HAARP HF heater  

NASA Astrophysics Data System (ADS)

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

Cohen, J. A.; Pradipta, R.; Burton, L. M.; Labno, A.; Lee, M. C.; Watkins, B. J.; Fallen, C.; Kuo, S. P.; Burke, W. J.; Mabius, D.; See, B. Z.

2010-12-01

200

Synthetic Aperture Helicopter Radar Experimental Evaluation Program.  

National Technical Information Service (NTIS)

The purpose of the program is to determine the resolution and MTI performance of a helicopter radar concept employing rotor tip mounted antennas and real-time digital synthetic aperture processing. The approach involves an experimental evaluation of the c...

N. F. Powell

1969-01-01

201

Bistatic radar sea state monitoring field test  

Microsoft Academic Search

Recent advances in understanding the physical phenomena controlling the interaction of electromagnetic energy with the ocean surface have revealed the possiblity of remote measurement of the two-dimensional surface wave height spectrum of the ocean using bistatic radar techniques. The basic feasibility of such a technique operating at frequencies in the HF region (3 to 30 MHz) was examined during previous

G. T. Ruck; G. K. Kirchbaum; J. O. Everly

1975-01-01

202

Radar observables  

NASA Astrophysics Data System (ADS)

A comprehensive account is given of missile design considerations relevant to the prediction, control, and measurement of airframe radar cross sections (RCSs), with a view to the minimization of missile observability. RCS reduction may proceed through airframe shaping to deflect incident radar emissions, as well as through the use of radar-absorbing surface materials and the devision of active radar signal-cancellation methods; some combination of these is often required, due to the deficiencies of any one method. The interaction of all RCS-reduction methods with airframe aerodynamic-design criteria are stressed.

Knott, Eugene F.

203

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

SciTech Connect

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.

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

1990-09-01

204

The meteor radar as a tool for upper atmosphere research  

NASA Astrophysics Data System (ADS)

Meteor radars provide measurements of the upper mesosphere-lower thermosphere neutral wind field by using the reflection of electromagnetic waves from meteor trails. These radars are relatively inexpensive and provide an excellent means of monitoring the mean winds and tides in the 80-100 km region. Recently new techniques have been developed to detect meteor echoes from other ground-based radar systems operating in the HF/VHF frequency range. The meteor echo information augments the data that is routinely collected by these radars. In this paper I will review the meteor radar technique and emphasize new methods of detection of meteor echoes on Mesosphere-Stratosphere-Troposphere (ST/MST) radars and on the Imaging Doppler Interferometer (IDI) radar.

Avery, S. K.

205

Doppler Radar  

Microsoft Academic Search

This paper contains a discussion of the principle of operation of cw doppler search radar systems and an analysis of their performance capabilities, with particular emphasis on the elimination of fixed targets. A comparison of these systems and MTI pulse radar systems is made.

E. J. Barlow

1949-01-01

206

TRMM Radar.  

National Technical Information Service (NTIS)

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...

K. Okamoto

1993-01-01

207

Lightweight SAR GMTI radar technology development  

NASA Astrophysics Data System (ADS)

A small and lightweight dual-channel radar has been developed for SAR data collections. Using standard Displaced Phase Center Antenna (DPCA) radar digital signal processing, SAR GMTI images have been obtained. The prototype radar weighs 5-lbs and has demonstrated the extraction of ground moving targets (GMTs) embedded in high-resolution SAR imagery data. Heretofore this type of capability has been reserved for much larger systems such as the JSTARS. Previously, small lightweight SARs featured only a single channel and only displayed SAR imagery. Now, with the advent of this new capability, SAR GMTI performance is now possible for small UAV class radars.

Kirk, John C.; Lin, Kai; Gray, Andrew; Hseih, Chung; Darden, Scott; Kwong, Winston; Majumder, Uttam; Scarborough, Steven

2013-05-01

208

Trends in radar signal processing  

Microsoft Academic Search

It is thought that the commercial very large scale intergration (VLSI) efforts, along with the military Very High Speed Integrated Circuits (VHSIC) program, will be of overwhelming importance in the future development of digital radar signal processing and data processing. Sucess in VLSI\\/VHSIC goals will also reduce software costs through the use of oversized low-cost signal processor hardware, for example

E. Brookner

1982-01-01

209

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

Microsoft Academic Search

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

V. H. Kaupp; H. C. MacDonald; W. P. Waite

1981-01-01

210

RADAP II, an interim radar data processor  

NASA Astrophysics Data System (ADS)

The RADAP (radar data processor) II system, which is developed by the National Weather Service and is a follow-up of the D/RADEX (Digitized Radar Experiment) is described. RADAP maintains the present automatic digital processing capabilities at the D/RADEX sites and extends these capabilities to include 10 network sites in order to fulfill the digital radar data requirements during the period before the production of the Next-Generation Weather Radar (NEXRAD) systems. Consideration is given to the current and future users of the RADAP II data, to the system capability, operational requirements, and hardware; to the installation schedule, and to the products of RADAP II. RADAP II is used for the continued development and testing of applications software to provide feedback on the operational usefulness of the software which is critical to the successful design and development of the NEXRAD system.

Greene, D. R.; Nilsen, J. D.; Saffle, R. E.; Holmes, D. W.; Hudlow, M. D.; Ahnert, P. R.

211

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  

Microsoft Academic Search

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

Kevin J. Cunningham

2004-01-01

212

Usefulness of synthetic aperture radar (SAR) interferometry for digital elevation model (DEM) generation and estimation of land surface displacement in Jharia coal field area  

Microsoft Academic Search

Land surface displacement is a phenomenon of ground movement, which may occur due to various reasons including unplanned mining. The quantification of land surface displacement through conventional field surveys is based on sparingly distributed point data, which may be insufficient for many applications. A detailed spatial and temporal monitoring of land surface displacements through remote sensing-based synthetic aperture radar (SAR)

Atanu Bhattacharya; Manoj K. Arora; Mukat L. Sharma

2011-01-01

213

Usefulness of synthetic aperture radar (SAR) interferometry for digital elevation model (DEM) generation and estimation of land surface displacement in Jharia coal field area  

Microsoft Academic Search

Land surface displacement is a phenomenon of ground movement, which may occur due to various reasons including unplanned mining. The quantification of land surface displacement through conventional field surveys is based on sparingly distributed point data, which may be insufficient for many applications. A detailed spatial and temporal monitoring of land surface displacements through remote sensing-based synthetic aperture radar (SAR)

Atanu Bhattacharya; Manoj K. Arora; Mukat L. Sharma

2012-01-01

214

Rise and fall of electron temperatures: Ohmic heating of ionospheric electrons from underdense HF radio wave pumping  

Microsoft Academic Search

Here we present electron temperature variations observed with incoherent scatter radar during a European Incoherent Scatter Scientific Association Heating experiment with high-frequency (HF) radio wave transmission at frequencies above the peak ionospheric critical frequency. The electron temperature increased from 2000 K up to 2800 K during the HF transmission periods. During the experiment both pump frequency and polarization were altered

B. Gustavsson; M. T. Rietveld; N. V. Ivchenko; M. J. Kosch

2010-01-01

215

Artificial ionospheric mirrors for radar applications  

NASA Astrophysics Data System (ADS)

Recognition of performance limitations associated with traditional skywave over-the-horizon (OTH) HF radars has led a number of investigators to propose the creation of an Artificial Ionospheric Mirror (AIM) in the upper atmosphere, in order to reflect ground-based radar signals for OTH surveillance. The AIM is produced by beaming sufficient electromagnetic power to the lower ionosphere (around 70 km) to enhance the in situ ionization level to 10(exp 7) to 10(exp 8) electrons/cu cm, thereby providing an ionized layer capable of reflecting radar frequencies of 5 to 90 MHz. A baseline AIM system concept and an associated performance evaluation are presented, based upon the relevant ionization and propagation physics and in the context of air surveillance for the cruise missile threat. Results of the subject indicate that a system using this concept would both complement and enhance the performance of the existing skywave OTH radars.

Short, Robert D.; Wallace, Tom; Stewart, Clayton V.; Lallement, Pierre; Koert, Peter

1990-10-01

216

HF system design  

NASA Astrophysics Data System (ADS)

This lecture is intended to complement the companion lecture dealing with the propagation aspects of HF communications. The major topics covered are as follows: (1) the design of point-to-point systems; (2) the design of systems involving mobile terminals; (3) system control and frequency management; and (4) resistance to interception and disruption. The lecture attempts to show how the propagation effects discussed in the previous lecture on HF groundwave and skywave propagation are taken into account in the design of HF communications systems for various purposes.

Darnell, M.

1986-10-01

217

Principals of Radar and Meteorological Radar Devices.  

National Technical Information Service (NTIS)

Three meteorological radar units are described: the Malachite radiotheodolite with rangefinder attachment, the Meteorite radar station, and the MRL radar station. The principles of operation of these systems are given along with circuit descriptions and e...

O. G. Korol R. D. Chernyak

1973-01-01

218

FPGA implementation of a software-defined radar processor  

NASA Astrophysics Data System (ADS)

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.

Suarez, Hernan; Zhang, Yan Rockee

2013-05-01

219

HAL-3 radar test set  

NASA Astrophysics Data System (ADS)

This paper presents the HAL-3 radar test set (called the set in the following) used to measure the technical specifications of the HAL-3 airborne radar and to maintain it based on tested results. Some new techniques are employed in the set, including sinusoidal pulsewidth modulation (SPWM) in the power supply, digital gyro simulator and automatic test module (ATM) with STD industrial control microprocessor series. The specially designed software implements man-machine interaction with menu in Chinese, selects parameters and operation mode, and controls testing procedures. These techniques may be extensively applied to other automatic test instruments.

Fang, Zhenhe; Zhang, Ming-Xing; Shen, Chang-Hong; Wang, Yi

1994-07-01

220

Basic System Concept for Integrating a 2D and a 3D Radar and Designs of Automatic Detection Systems.  

National Technical Information Service (NTIS)

A basic system concept of digitally integrating any 2D radar and any frequency-scan 3D radar was applied to the SPS-12 and SPS-39 radars, giving a composite coverage with nulls greatly decreased from those of the SPS-12 pattern. Both radars operate in a s...

G. V. Trunk B. H. Cantrell D. F. Queen

1974-01-01

221

Stimulated Emission and Radar Observations of RF-Ionosphere Interaction Experiments at HAARP  

Microsoft Academic Search

High power HF radiowaves launched from ground-based transmitters interact with overdense ionospheric plasma to produce strong nonlinear effects. Where available, VHF\\/UHF radar data reveal several spatial and temporal signatures in the plasma line backscatter indicative of strong turbulence effects at many scales. Stimulated electromagnetic emissions (SEE) which propagate to HF receivers on the ground may provide information complementary to plasma

J. P. Sheerin; J. M. Parzych; J. P. Mills; W. A. Bristow; K. M. Groves

2003-01-01

222

Stimulated emission and radar observations of rf-ionosphere interaction experiments  

Microsoft Academic Search

High power HF radiowaves launched from ground-based transmitters interact with overdense ionospheric plasma to produce strong nonlinear effects. Where available, VHF\\/UHF radar data reveal several spatial and temporal signatures in the plasma line backscatter indicative of strong turbulence effects at many scales. Stimulated electromagnetic emissions (SEE) which propagate to HF receivers on the ground may provide information complementary to plasma

J. Sheerin; W. Bristow; K. Groves

2004-01-01

223

u-factors of rotational states in 176Hf, 177Hf, and 180Hf  

Microsoft Academic Search

g-factors of rotational states in 176Hf and 180Hf were measured with the twelve detector IPAC-apparatus of our laboratory (1). The natural radioactivity 3.78 Æ 1010y 176Lu and the 5.5 h isomer 180.Hf were used which populate the ground-state rotational bands of 176Hf and 180Hf. The integral rotations of c-c directional correlations in strong external magnetic fields and in static hyperfine

I. Alfter; E. Bodenstedt; W. Knichel; J. Schu; R. Vianden

1996-01-01

224

Saturation and hysteresis effects in ionospheric modification experiments observed by the CUTLASS and EISCAT radars  

Microsoft Academic Search

The results of high latitude ionospheric modification experiments utilising the EISCAT heating facility at Tromsø are presented. As a result of the interaction between the high power pump waves and upper hybrid waves in the ionosphere, field-aligned electron density irregularities are artificially excited. Observations of these structures with the CUTLASS coherent HF radars and the EISCAT incoherent UHF radar exhibit

D. M. Wright; J. A. Davies; T. K. Yeoman; T. R. Robinson; H. Shergill

2006-01-01

225

Preliminary performance of SubSurface Radar for the EJSM\\/Laplace mission  

Microsoft Academic Search

The Sub-Surface Radar (SSR) instrument is a core payload for the Jupiter Ganymede Orbiter (JGO) of the EJSM, which is complementary to the Ice Penetrating Radar on board the Jupiter Europa Orbiter (JEO). These instruments work at low frequency (HF\\/VHF band) and are designed to penetrate the surfaces of icy moons of Jupiter. The paper will present a preliminary performance

G. Alberti; S. Mattei; R. Seu; L. Bruzzone; A. Ferro; R. Orosei; A. Olivieri; C. Catallo

2010-01-01

226

A-scope analysis of subsurface radar sounding of lunar mare region  

Microsoft Academic Search

Lunar Radar Sounder (LRS) is a spaceborne HF radar system and is a science mission of Japanese lunar exploration project, SELENE, which is scheduled to be launched in 2005. The primary objective of LRS is to investigate the geologic structure of lunar subsurface from orbit. Computer simulations of LRS observation of lunar mare region have been carried out by utilizing

Takao Kobayashi; Hiroshi Oya; Takayuki Ono

2002-01-01

227

Measurement of ocean wave spectra using narrow-beam HE radar  

Microsoft Academic Search

A data interpretation algorithm is developed to extract ocean wave information from HF radar backscatter observed by a narrow-beam antenna system. The basis of this measurement is the inversion of the integral equation representing the second-order radar cross section of the ocean surface. This equation is numerically inverted by approximating it as a matrix equation and pseudoinverting the kernel matrix

Randy Howell; John Walsh

1993-01-01

228

Remote sensing of wind speed at sea surface level using HF skywave echoes from decametric waves  

NASA Astrophysics Data System (ADS)

Using an HF skywave radar to study the decametric sea waves, it appears that their amplitudes do not saturate as the wind speed increases. A measurement method, based on the Kahma sea wave spectrum, is proposed and radar estimations of the wind speed are compared with in situ measurements performed on board a ship. The rms difference between the two measurements is 2.5m/s and is probably mainly due to the spatial variability in the wind speed.

Gaffard, C.; Parent, J.

1990-04-01

229

Determining {HF} communications channel parameters using {SuperDARN}  

NASA Astrophysics Data System (ADS)

Space weather effects can strongly influence high-frequency (HF) communications by changing the ionospheric environment through which the radiowaves propagate. As many systems utilize HF communications, the ability to make real time assessments of propagation conditions is an important part of space weather monitoring systems. In this paper we present new techniques for measuring HF communications channel parameters using data from SuperDARN radars. These techniques use ground-scatter returns to define the variation in skip distance with frequency. From these data, the maximum usable frequency (MUF) as a function of range is determined and ionospheric critical frequecies are estimated. These calculations are made in near-real time and the results are made available on the world wide web. F region critical frequencies calculated using this method show good agreement with ionosonde data.

Hughes, J. M.; Bristow, W.

2001-12-01

230

Radar resource sharing study  

NASA Astrophysics Data System (ADS)

The Radar Resource Sharing Study was undertaken to evaluate the relative advantages or three candidate technologies for implementing a shared beamformer for a dual band (S and UHF) airborne surveillance radar. The beamformer was required to interface with the two active array apertures and perform the signal combining and distribution functions necessary to produce the receive and transmit beams required for each band. The objective was to compare the three approaches in terms of size, weight, power consumption and hardware sharing, based on 1997 technology projections. The candidate beam-former technologies investigated were Conventional, Digital and Optical beamformers. In the digital and optical cases, technology limitations precluded accomplishing all of the required beamformer functions. Therefore, hybrid approaches which employed each of these technologies to the maximum practical extent were devised. The study commenced in September 1992 and was conducted primarily on the basis of beamformer requirements for monostatic operation. Later the scope was expanded to consider a bistatic receive implementation having significantly different beam requirements.

Gouse, Ronald; Clancy, John

1995-03-01

231

The Italian involvement in Cassini radar  

NASA Astrophysics Data System (ADS)

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.

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

1991-12-01

232

Shipboard Radar.  

National Technical Information Service (NTIS)

The navigational radar 'Stvor' is designed for installation on ships of the shipping fleet and also on marine and river boats of low and medium tonnage. A 'Stvor' station enables ships to navigate in zero visibility -- in fog, at night, etc. Because of it...

1968-01-01

233

Radar Antenna.  

National Technical Information Service (NTIS)

An antenna is described for range-gated, pulse doppler, radar systems. The antenna includes first and second, shortened, half-wave dipoles and first and second reflecting screens. One dipole is fed through a fixed 22 1/2 degree phase-shift network while t...

O. E. Rittenback

1978-01-01

234

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

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

235

Planning of a C-Band Pulse Doppler Radar with Polarization Diversity for Atmospheric Research in the Mesoscale Range.  

National Technical Information Service (NTIS)

Radar system specifications for cloud physics studies are outlined. A semimobile system, comprising computer controlled pulse Doppler radar and digitized signal processing is recommended. Design requirements arising from the need to collect data on type o...

H. Schuster

1982-01-01

236

Multipath track fusion for over-the-horizon radar  

NASA Astrophysics Data System (ADS)

Over-the-horizon skywave radar exploits ionospheric propagation of HF signals to detect targets beyond the line-of-sight horizon. Multiple propagation paths between the radar sites and the target are often encountered, giving multiple resolved detections for a single target. An algorithm for the fusion of multipath tracks is outlined here which accounts for uncertainty in the coordinate registration transformation to ground coordinates. A multihypothesis track association procedure is described which may be appended to existing radar coordinate tracking filters. The probability for each feasible track association hypothesis is computed, and fused estimates for target states in ground coordinates are evaluated for each hypothesis.

Percival, Douglas J.; White, Kruger A.

1997-10-01

237

HF process (hydroforming)  

Microsoft Academic Search

A very comprehensive description is presented of the development of the HF process through the pilot-plant stage. The report included many graphs and tables giving data on various aspects of experimentation for the process, including starting materials, temperatures, pressures, throughputs, yields, composition of products, and amount of circulating gases. Preliminary experiments in small, electrically-heated ovens were used to discover which

Welz

1943-01-01

238

Midlatitude ionospheric HF channel reciprocity: Evidence from the ionospheric oblique incidence sounding experiments  

NASA Astrophysics Data System (ADS)

Ionospheric HF channel reciprocity is investigated at middle latitudes on the basis of ionospheric oblique incidence sounding experiments. Two identical Wuhan Ionospheric Oblique Incidence Sounding Systems (WIOISS), located at Wuhan (30°32'N, 114°21'E) and Wanning (18°58'N, 110°31'E), are used to carry out the campaign. Comparisons of group distance and Doppler shift between Wuhan-Wanning and Wanning-Wuhan HF ionospheric propagation paths indicate that the reciprocity of the ionospheric HF channel is satisfied at midlatitude region. A 3-D ray tracing simulation is also implemented to evaluate the group distances of the two paths. Midlatitude ionospheric HF channel reciprocity, as verified both experimentally and theoretically in the present study, can be useful for HF communication systems and sky wave over-the-horizon radars.

Zhou, Chen; Zhao, Zhengyu; Deng, Feng; Ni, Binbin; Chen, Gang

2010-12-01

239

Mid-latitude Ionospheric HF Channel Reciprocity: Evidence from the Ionospheric Oblique Incidence Sounding Experiments  

NASA Astrophysics Data System (ADS)

The mid-latitude ionospheric HF channel reciprocity is studied in this paper through theoret-ical considerations and ionospheric oblique incidence sounding experiments. The reciprocity of ionospheric HF channel experiments were carried out by using two identical Wuhan Iono-spheric Oblique Incidence Sounding Systems (WIOISS) located in Wuhan (30° 32N, 114° 21E) and Wanning (18° 58N, 110° 31E) respectively. The comparisons of group distance and Doppler shift between Wuhan-Wanning and Wanning-Wuhan HF ionospheric propagation paths show that the reciprocity of ionospheric HF channel is satisfied to some extent. The group dis-tances of two paths are calculated by a 3-D ray tracing simulation as well. The theoretical and experimental results could be widely used for HF communication systems and sky wave over-the-horizon radar.

Zhou, Chen; Zhao, Zhengyu; Zhang, Yuannong

240

The Signal and Interference Environment in Passive Bistatic Radar  

Microsoft Academic Search

We present a review of the properties of some signals that may be used as illuminators of opportunity in passive bistatic radar systems. It is shown that such signals are not ideal for radar purposes, though modern digital modulation formats are to be preferred, since their ambiguity performance is better and in general does not vary with time. However, with

Hugh Griffiths; Chris Baker

2007-01-01

241

Performance of random OFDM radar signals in deception jamming scenarios  

Microsoft Academic Search

The paper examines the performance of randomly generated OFDM waveforms in presence of deception jamming. The scenario of interest uses OFDM waveforms for synthetic aperture radar (SAR) imaging of a target area into which a digital radio frequency memory (DRFM) repeat jammer has been introduced. The jammer attempts to introduce false targets into the final image by replicating the radar

Jonathan Schuerger; Dmitriy Garmatyuk

2009-01-01

242

Low-cost radar surveillance of inland waterways for homeland security applications  

Microsoft Academic Search

Low-cost radar systems have been developed for homeland security missions. These detect and track small maneuvering craft in the water. The systems consist of a conventional marine radar, a capture card that digitizes the radar signals, and a computer that processes them. We have an experimental system that can monitor western Lake Ontario. It runs in real time, with operator

P. Weber; A. Premji; T. J. Nohara; C. Krasnor

2004-01-01

243

Imaging a BQM-74E Target Drone Using Coherent Radar Cross Section Measurements  

Microsoft Academic Search

ince the early 1980s and the advent of the modern computer, digital radar imaging has developed into a mature field. In this article, the specific problem of imaging a rotating target with a stationary radar is reviewed and built upon. The relative motion between the rotating target and the stationary radar can be used to create a circular synthetic aperture

Allen J. Bric

1997-01-01

244

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

Microsoft Academic Search

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

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

1998-01-01

245

Sampling rate influence on detection performance of CFAR algorithms implemented in radar extractor  

Microsoft Academic Search

A radar extractor based on a two-processor digital signal-processing (DSP) card implemented in a standard personal computer (PC) has been developed. A constant false alarm rate (CFAR) processor is applied as a part of radar extractor algorithms. Some particular problems related to the CFAR automatic detection of radar signals are investigated, from theoretical and practical point of view, and given

Miroslav M. Petrovic; Dragan D. Dimitrijevic; Aleksandar T. Kostic

2001-01-01

246

Adaptive Filtering of Radar Images for Autofocus Applications.  

National Technical Information Service (NTIS)

Autofocus techniques are being designed at the Jet Propulsion Laboratory to automatically choose the filter parameters (i.e., the focus) for the digital synthetic aperture radar correlator; currently, processing relies upon interaction with a human operat...

J. A. Stiles V. S. Frost J. S. Gardner D. R. Eland K. S. Shanmugam

1981-01-01

247

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 ...

248

Planning of a C-band pulse Doppler radar with polarization diversity for atmospheric research in the mesoscale range  

NASA Astrophysics Data System (ADS)

A radar system was defined, suitable for research in cloud physics requiring measured values of meteorological parameters relevant to a complete model of the behavior of the observed object in space and time. This problem can be solved using remote sensing methods, especially radar measuring methods. A semimobile system, comprising computer controlled pulse Doppler radar with polarization diversity and digitized radar signal processing is recommended. The fundamental attributes of the radar system are summarized.

Schuster, H.

1981-09-01

249

Auroral backscatter observed at HF from Ottawa  

SciTech Connect

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.

Montbriand, L.E.

1988-10-01

250

Signal Processing for Passive Radar Using OFDM Waveforms  

Microsoft Academic Search

Passive radar is a concept where illuminators of opportunity are used in a multistatic radar setup. New digital signals, like digital audio\\/video broadcast (DAB\\/DVB), are excellent candidates for this scheme, as they are widely available, can be easily decoded to acquire the noise-free signal, and employ orthogonal frequency division multiplex (OFDM). Multicarrier transmission schemes like OFDM use block channel equalization

Christian R. Berger; Bruno Demissie; Jörg Heckenbach; Peter Willett; Shengli Zhou

2010-01-01

251

Multipolarization Radar Images for Geologic Mapping and Vegetation Discrimination  

Microsoft Academic Search

The NASA\\/JPL airborne synthetic aperture radar system produces radar image data simultaneously in four linear polarizations (HH, VV, VH, HV) at 24.6-cm wavelength (L-band), with 10-m resolution, across a swath width of approximately 10 km. The signal data are recorded optically and digitally and annotated in each of the channels to facilitate a completely automated digital correlation. Both standard amplitude,

Diane Evans; Tom Farr; J. P. Ford; Thomas Thompson; C. L. Werner

1986-01-01

252

Impact of different correlation receiving techniques on the imaging performance of UWB random noise radar  

Microsoft Academic Search

Cross correlation receiver is one of the most important parts in a random noise radar system. In this paper, the impact of different correlation receiving techniques on the imaging performance of ultra wideband (UWB) random noise radar is studied. Three types of correlation receivers, namely, the ideal analog correlation receiver, the digital-analog correlation receiver, and the fully digital correlation receiver,

Xiaojian Xu; Ram M. Narayanan

2003-01-01

253

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

Microsoft Academic Search

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

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

2004-01-01

254

Survivable HF communications  

NASA Astrophysics Data System (ADS)

Robust HF uses a noncoherent FSK (frequency-shift-keyed) signal. It uses fast pseudorandom frequency hopping and a rugged modulation format which makes it impervious to multipath, atmospheric, and man-made noise. It is optimized as an antijam system. The robust-HF operating frequency range is 2-30 MHz. The pseudorandom frequency hopping uses variable bandwidth and adapts to the best frequencies between the lowest usable frequency and the maximum usable frequency. The system operates skywave (long distance) or ground wave (up to 100 km, or even more over water). Buried hard antennas have been tested and show almost no degradation in system performance. Robust HF uses powerful error coding with variable code rates and code combining, which automatically adapt according to link conditions. The result is exceptional processing gain. A powerful cyclic redundancy check (CRC) is included to prevent delivery of corrupt data. System bit rates run as high as 600 b/s, with average throughput of about 75 b/s, depending on the code rate.

Randerson, John T.

255

Studies of HF-induced Strong Plasma Turbulence at the HAARP Ionospheric Observatory  

NASA Astrophysics Data System (ADS)

High power HF transmitters may induce a number of plasma instabilities in the interaction region of overdense ionospheric plasma. We report results from our recent experiments using over one gigawatt of HF power (ERP) to generate and study strong Langmuir turbulence (SLT) and particle acceleration at the HAARP Observatory, Gakona, Alaska. Among the effects observed and studied in UHF radar backscatter are: SLT spectra including the outshifted plasma line or free-mode, appearance of a short timescale ponderomotive overshoot effect, collapse, cascade and co-existing spectra, control of artificial field-aligned irregularities (AFAI), the aspect angle dependence of the plasma line spectra, and suprathermal electrons. Mapping the intensity of SLT versus pointing angle, we have discovered a number of regions of strong interaction displaced from the primary HF interaction region. Stimulated electromagnetic emission (SEE) measurements complement radar measurements. Experimental results are compared to previous high latitude experiments and predictions from recent modeling efforts.

Sheerin, J. P.; Adham, N.; Watanabe, N.; Watkins, B. J.; Bristow, W. A.; Selcher, C. A.; Bernhardt, P. A.

2011-11-01

256

ISRO's programmable digital waveform generator  

Microsoft Academic Search

One of the major and common requirements for all active microware sensors is generation of the transmit modulation signal-like chirp\\/LFM signal, MSK, etc., which can be generated by analog or digital means. With the increasing demands of side bandwidth, longer duration chirp signals in radar systems, digital signal generation, and processing has emerged as a preferred alternative. Design and development

S. Gangele; N. M. Desai; R. Senthil Kumar; J. G. Vachhani; V. R. Gujraty

2008-01-01

257

Soviet oceanographic synthetic aperture radar (SAR) research  

SciTech Connect

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.

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

1991-01-01

258

Polarization radar processing technology  

NASA Astrophysics Data System (ADS)

A comprehensive effort is presented involving measurements and performance evaluation for the detection of scatters immersed in a background of natural and man-made clutter using polarization diverse waveforms. The effort spans evaluation from the initial stages of theoretical formulation to processor performance evaluation using real world data. The theoretical approach consists of determining polarimetric statistical properties of the backscatter waveform and the use of these properties to derive the optimum dual polarized S-Band radar system with selectable polarization on both transmit and receive. Recording equipment consists of 12 bit digital in-phase and quadrature channels indexed in time and phase for both polarizations. Several processors utilizing optimum and sub-optimum algorithms were evaluated using simulated and live radar data, and performance results were compared. The processor types include fully adaptive algorithms designed to operate on polarimetric spectral spread waveforms, and several combinations of single channel and polarization diverse receivers with both single and dual transmit polarization. A conventional fixed transmit and receive mode with no spectral processing is included. Comparisons are made between the various processors. The simulated and real data consist of randomly scattered dipoles, spheres, Swerling type scatters, and scatters of opportunity.

Stiefvater, Kenneth C.; Brown, Russell D.; Vannicola, Vincent C.; Wicks, Michael C.

1989-10-01

259

The implementation of radar signal simulator  

Microsoft Academic Search

This article describes a variety of FPGA-based radar signal generator. This system is connected to the host, binding data from the software interface, through the PCI bus transfer stored in the system. Within the FPGA to achieve DDS signal generator, and finally through the digital-analog converter output. Finally, the system resource utilization and the actual results are given.

Fuyang Zhang; Jun Wang; Yuxian Zhang; Pei Wang

2011-01-01

260

Synthetic Aperture Helicopter Radar Experimental Evaluation Program.  

National Technical Information Service (NTIS)

The object of the program is to determine the resolution and MTI performance of a helicopter radar concept employing rotor tip mounted antennas and real-time digital synthetic aperture processing. The present report describes and analyzes the results of s...

N. F. Powell

1969-01-01

261

Thresholded samplers for UWB impulse radar  

Microsoft Academic Search

This paper presents two novel methods for sampling the backscatter in an impulse radar system. The authors have called the two related methods for swept threshold and stochastic resonance sampling. The samplers are simple, mostly digital circuits which are not clocked, but instead utilize continuous-time signal processing. Since fine-pitch CMOS is not very good for analog processing, but instead has

Hakon A. Hjortland; Dag T. Wisland; Tor Sverre Lande; Claus Limbodal; Kjetil Meisal

2007-01-01

262

Radar Ionospheric Impact Mitigation  

Microsoft Academic Search

New ionospheric modeling technology is being developed to improve correction of ionospheric impacts on the performance of ground-based space-surveillance radars (SSRs) in near-real-time. These radars, which detect and track space objects, can experience significant target location errors due to ionospheric delay and refraction of the radar signals. Since these radars must detect and track targets essentially to the radar horizon,

G. Bishop; D. Decker; C. Baker

2006-01-01

263

Observation and theory of the radar aurora  

SciTech Connect

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.

Sahr, J.D.

1990-01-01

264

New algorithm of ground track processing in high-frequency skywave over-the-horizon-B radar  

NASA Astrophysics Data System (ADS)

In this paper, the concept pattern of the recognition tracking coordinate transformation data processor in HF skywave OTH-B radar is described. A new algorithm to determine the ground distance of a moving object from the time delay transformation of HF radar is proposed. Just the probe data obtained from only a single radar station are needed; there is no need to know the midpoint ionospheric data. The calculated ground track is compared with the actual track and the results show that the mean deviation is less than four percent.

Peinan, Jiao

1993-08-01

265

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)

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.

Sundararaman, Sathishkumar

266

Development of onboard software for the Lunar Radar Sounder (LRS) of the SELENE satellite  

NASA Astrophysics Data System (ADS)

The main purpose of the Lunar Radar Sounder Experiment (LRS) onboard the SELENE satellite is to obtain shapes of surface and subsurface structures of the Moon by using an FMCW radar technique in HF frequency range. In addition to the radar experiment, LRS provide the spectrum of plasma waves and solar and planetary radio waves in wide frequency range covering from 10Hz to 30MHz. We have developed onboard software for main CPU and two DSPs to perform the following observations and mission data processing. The sounder pulse whose frequency is swept from 4 to 6MHz in 200?s is transmitted every 50ms. Received echo signal is mixed with local signal whose frequency is swept from 4 to 8MHz in 400?s and converted to a digital dataset with sampling frequency of 6.25MHz. The wave form data of echo signal can be sent in several formats: raw wave form data (SDR-W mode, 492kbps), ensemble average of 8 wave form data (SDR-A, 80kbps), power spectrum (SDR-S mode, 80kbps) and complex Fourier coefficients (SDR-C mode, 80kbps). In SDR-A/S/C mode, onboard FFT calculations and data selections are carried out to reduce transmission data size. Natural plasma waves and radio waves are received and processed by the three subsystems: sounder receiver (20kHz-12.5MHz, SDR), swept frequency receiver (20kHz-30MHz, NPW), and wave form capture receiver (10Hz-1MHz, WFC). The basic function and performance of the LRS have been examined via system function test and system EMC test which started in August, 2003.

Kumamoto, A.; Ono, T.; Lrs Development Team

267

Ti-TiNi-HfNi-Hf Liquidus surface  

Microsoft Academic Search

Physical and chemical analysis methods are used for the first time to examine the Ti-TiNi-HfNi-Hf alloys in the melting-crystallization\\u000a region. The liquidus surface is shown to consist of six fields of primary phase crystallization: ?1, ?, ?, ?, ?, and ?. The largest fields are of ?-and ?-phases. The ?1 ternary phase is formed by peritectic reaction l + ?

O. L. Semenova; L. O. Tret’yachenko; V. M. Petyukh

2007-01-01

268

Determination of Sub-Ice Topography in a Valley Glacier Environment Using Airborne Radar Sounding with Echo Discrimination Techniques  

Microsoft Academic Search

The identification of subsurface radar echoes on Mars in areas where significant surface topography exists will require careful echo source discrimination to avoid misinterpretation. We have developed these techniques for airborne radar sounding data in the Dry Valleys of Antarctica. This effort includes a radar data simulator that utilizes a lidar-generated digital elevation model (DEM) of nearby surface topography to

J. W. Holt; D. D. Blankenship; D. L. Morse; M. E. Peters; S. D. Kempf; B. Johnson

2004-01-01

269

Optimal pollution mitigation in Monterey Bay based on coastal radar data and nonlinear dynamics.  

PubMed

High-frequency (HF) radar technology produces detailed velocity maps near the surface of estuaries and bays. The use of velocity data in environmental prediction, nonetheless, remains unexplored. In this paper, we uncover a striking flow structure in coastal radar observations of Monterey Bay, along the California coastline. This complex structure governs the spread of organic contaminants, such as agricultural runoff which is a typical source of pollution in the bay. We show that a HF radar-based pollution release scheme using this flow structure reduces the impact of pollution on the coastal environment in the bay. We predict the motion of the Lagrangian flow structures from finite-time Lyapunov exponents of the coastal HF velocity data. From this prediction, we obtain optimal release times, at which pollution leaves the bay most efficiently. PMID:17948809

Coulliette, Chad; Lekien, Francois; Paduan, Jeffrey D; Haller, George; Marsden, Jerrold E

2007-09-15

270

Features of ultrawideband radar projecting  

Microsoft Academic Search

The article presents a new approach to ultrawideband (UWB) radar projecting. Some advantages of such radars are shown in comparison with common narrowband radars and some features of UWB radars are considered, which do not allow the use of traditional methods. New methods of UWB radar characteristics calculation and radar systems projecting are suggested. It discusses the range equation, passive

Igor Immoreev; B. Vovshin

1995-01-01

271

Insertion of an acousto-optic range-Doppler processor into an advanced Army radar  

NASA Astrophysics Data System (ADS)

The primary objective of this program is to perform pulse compression in an existing military system using an optical processor. To achieve this objective, an acousto-optic (AO) range- Doppler processor is being developed to interface to an advanced ground-based radar system developed by the U.S. Army Missile Command (MICOM) and replace the function of several digital processor boards currently in the radar. This paper provides an overview of the MICOM radar system, describes the AO range-Doppler processor, the rf and digital electronic interfaces required to achieve real-time operation in the MICOM radar, and system integration issues.

Viveiros, Edward A.; Harrison, Lorna J.; Berinato, Robert J.; Durrett, Rodney A.

1995-06-01

272

Phenomena in the high latitude ionosphere induced by an X-mode HF heater wave  

NASA Astrophysics Data System (ADS)

New experimental results are presented from high power ionospheric modification experiments with the EISCAT/Heating HF facility at Tromsø, Norway. The experiments were conducted in the course of Russian EISCAT HF heating campaigns in 2009 - 2011 using the following diagnostic tools: the EISCAT UHF incoherent scatter radar at Tromsø, the CUTLASS (SuperDARN) HF coherent radar, bi-static HF Doppler radio scatter and the EISCAT ionosonde (dynasonde). The effects on the high-latitude F region of the ionosphere by X-mode powerful HF radio waves injected towards the magnetic zenith (MZ) are analysed. We present the first experimental evidence for strong plasma modifications induced by the X-mode powerful HF radio waves. The distinctive feature of modification experiments is that the heater frequency is choosen by a special way, namely, it is above the ordinary-mode critical frequency but comparable with the extraordinary-mode critical frequency. The results show that the X-mode HF pump wave can generate very strong small-scale artificial field aligned irregularities (AFAIs) in the F-region of the high-latitude ionosphere. These irregularities, with spatial scales across the geomagnetic field of the order of 8 - 15 m, appeared 10 s - 4 min after the heater is turned on. They had the unusually long decay time which varied in a wide range between 3 and 30 min. The generation of the X-mode AFAIs was accompanied by electron temperature (Te) enhancements up to 50 % above the background level and an increase in the electron density (Ne) by up to 30 %. Such electron density enhancements can be attributed to HF-induced ionization production rather than the change of the density distribution due to the thermal diffusion. The analysis of the incoherent backscatter spectra obtained with the EISCAT UHF radar during X-mode HF pumping demonstrated the strongly enhanced ion line shoulders (upshifted and downshifted spectral peaks) observed during the whole 10 min heater-on period, which are unusual for X-mode heating. The possible mechanisms for plasma modifications induced by the X-mode powerful HF radio wave are discussed.

Blagoveshchenskaya, N. F.; Borisova, T. D.; Yeoman, T. K.; Rietveld, M. T.

2011-12-01

273

Goldstone Solar System Radar.  

National Technical Information Service (NTIS)

Planning, direction, experimental design, and coordination of data-acquisition and engineering activities in support of all Goldstone planetary radar astronomy were performed. This work demands familiarity with the various components of a planetary radar ...

R. F. Jurgens

1988-01-01

274

Radar Absorbing Material Design.  

National Technical Information Service (NTIS)

Low observable platforms have extremely low radar cross section specifications that cannot be achieved by shaping alone. The application of radar absorbing material is necessary, in which case the appropriate constitutive parameters and thickness must be ...

C. K. Yuzcelik

2003-01-01

275

Radar, Target and Ranging.  

National Technical Information Service (NTIS)

This Test Operations Procedure (TOP) provides conventional test methods employing conventional test instrumentation for testing conventional radars. Single tests and subtests designed to test radar components, transmitters, receivers, antennas, etc., and ...

1984-01-01

276

Spaceborne Radar Study.  

National Technical Information Service (NTIS)

Three air-defense radar surveillance systems are described, each consisting of active radar satellites capable of operating at earth-synchronous orbit altitude with associated ground control stations. Systems 1 (three satellites) provides a detection fenc...

J. Greene R. Kaplan G. J. McNiff P. Nosal J. L. Schultz

1974-01-01

277

Statistical MIMO Radar.  

National Technical Information Service (NTIS)

Inspired by recent advances in multiple-input multiple-output (MIMO) communications, we introduce the statistical MIMO radar concept. Unlike beamforming, array radar, or STAP, which presuppose a high correlation between signals either transmitted or recei...

A. Haimovich E. Fishler R. Blum D. Chizhik R. Valenzuela

2004-01-01

278

Radar Location Equipment Development Program: Phase I  

SciTech Connect

The work described in this report represents the first phase of a planned three-phase project designed to develop a radar system for monitoring waste canisters stored in a thick layer of bedded salt at the Waste Isolation Pilot Plant near Carlsbad, New Mexico. The canisters will be contained in holes drilled into the floor of the underground waste storage facility. It is hoped that these measurements can be made to accuracies of +-5 cm and +-2/sup 0/, respectively. The initial phase of this project was primarily a feasibility study. Its principal objective was to evaluate the potential effectiveness of the radar method in the planned canister monitoring application. Its scope included an investigation of the characteristics of radar signals backscattered from waste canisters, a test of preliminary data analysis methods, an assessment of the effects of salt and bentonite (a proposed backfill material) on the propagation of the radar signals, and a review of current ground-penetrating radar technology. A laboratory experiment was performed in which radar signals were backscattered from simulated waste canisters. The radar data were recorded by a digital data acquisition system and were subsequently analyzed by three different computer-based methods to extract estimates of canister location and tilt. Each of these methods yielded results that were accurate within a few centimeters in canister location and within 1/sup 0/ in canister tilt. Measurements were also made to determine the signal propagation velocities in salt and bentonite (actually a bentonite/sand mixture) and to estimate the signal attenuation rate in the bentonite. Finally, a product survey and a literature search were made to identify available ground-penetrating radar systems and alternative antenna designs that may be particularly suitable for this unique application. 10 refs., 21 figs., 4 tabs.

Sandness, G.A.; Davis, K.C.

1985-06-01

279

HF ground scatter from the polar cap: Ionospheric propagation and ground surface effects  

NASA Astrophysics Data System (ADS)

In addition to being scattered by the ionospheric field-aligned irregularities, HF radar signals can be reflected by the ionosphere toward the Earth and then scattered back to the radar by the rugged ground surface. These ground scatter (GS) echoes are responsible for a substantial part of the returns observed by HF radars making up the Super Dual Auroral Radar Network (SuperDARN). While a GS component is conventionally used in studying ionosphere dynamics (e.g., traveling ionospheric disturbances, ULF waves), its potential in monitoring the state of the scattering surface remains largely unexploited. To fill this gap, we investigated diurnal and seasonal variation of the ground echo occurrence and location from a poleward-looking SuperDARN radar at Rankin Inlet, Canada. Using colocated ionosonde information, we have shown that seasonal and diurnal changes in the high-latitude ionosphere periodically modulate the overall echo occurrence rate and spatial coverage. In addition, characteristics of GS from a particular geographic location are strongly affected by the state of the underlying ground surface. We have shown that (1) ice sheets rarely produce detectable backscatter, (2) mountain ranges are the major source of GS as they can produce echoes at all seasons of the year, and (3) sea surface becomes a significant source of GS once the Arctic sea ice has melted away. Finally, we discuss how the obtained results can expand SuperDARN abilities in monitoring both the ionosphere and ground surface.

Ponomarenko, P. V.; St. Maurice, J.-P.; Hussey, G. C.; Koustov, A. V.

2010-10-01

280

Controlling radar signature  

SciTech Connect

Low observable technologies for military and tactical aircraft are reviewed including signature-reduction techniques and signal detection/jamming. Among the applications considered are low-signature sensors and the reduction of radar cross section in conjunction with radar-absorbing structures and materials. Technologies for reducing radar cross section are shown to present significant technological challenges, although they afford enhanced aircraft survivability.

Foulke, K.W. (U.S. Navy, Naval Air Warfare Center, China Lake, CA (United States))

1992-08-01

281

CHIRP Doppler radar  

Microsoft Academic Search

The present investigation is concerned with the concept of a combination of the clinical procedure of reconstruction tomography with the radar processing for linear FM pulse compression. An approach based on such a combination is to be employed to map radar backscatter energy. Radar systems employing pulse compression of linear frequency modulated (CHIRP) pulses are considered along with the inversion

M. Bernfeld

1984-01-01

282

Aviation weather radar  

Microsoft Academic Search

The Federal Aviation Administration has established three ground-based weather radar programs. The terminal Doppler weather radar (TDWR) and weather system processor (WSP) provide wind shear detection capability for air traffic controllers in the terminal area. These systems also reduce weather related delays. The next generation weather radar (NEXRAD) is used by the FAA to improve safety and reduce weather related

D. H. Turnbull

1995-01-01

283

Ionospheric electron heating, optical emissions, and striations induced by powerful HF radio waves at high latitudes: Aspect angle dependence  

Microsoft Academic Search

In recent years, large electron temperature increases of 300% (3000 K above background) caused by powerful HF-radio wave injection have been observed during nighttime using the EISCAT incoherent scatter radar near Tromsø in northern Norway. In a case study we examine the spatial structure of the modified region. The electron heating is accompanied by ion heating of about 100 degrees

M. T. Rietveld; M. J. Kosch; N. F. Blagoveshchenskaya; V. A. Kornienko; T. B. Leyser; T. K. Yeoman

2003-01-01

284

Harmonic Radar Literature Harmonisk Radar - en Litteraturstudie.  

National Technical Information Service (NTIS)

A harmonic radar sends on a given frequency f sub o and receives on another frequency usually 3 f sub o. The overtone is generated on joints between the metal parts of the radar target. The generated high harmonic frequency is very weak, which is why this...

B. Jansson

1980-01-01

285

Performance of selected block and convolutional codes on a fading HF channel  

Microsoft Academic Search

This paper describes the application of selected block and convolutional coding techniques to digital transmission over an HF radio channel. Performance results are presented for interleaved binary Bose-Chaudhuri-Hocquenghem (BCH) codes, interleaved two-stage concatenated codes, and diffuse convolutional codes. The performance results are based upon raw error data recorded in transmission over a 640-km HF path, with various data runs representing

DAVID L. COHN; A. Levesque; J. Meyn; A. Pierce

1968-01-01

286

Radar image analysis utilizing junctive image metamorphosis  

NASA Astrophysics Data System (ADS)

A feasibility study was initiated to investigate the ability of algorithms developed for medical sonogram image analysis, to be trained for extraction of cartographic information from synthetic aperture radar imagery. BioComputer Research Inc. has applied proprietary `junctive image metamorphosis' algorithms to cancer cell recognition and identification in ultrasound prostate images. These algorithms have been shown to support automatic radar image feature detection and identification. Training set images were used to develop determinants for representative point, line and area features, which were used on test images to identify and localize the features of interest. The software is computationally conservative; operating on a PC platform in real time. The algorithms are robust; having applicability to be trained for feature recognition on any digital imagery, not just those formed from reflected energy, such as sonograms and radar images. Applications include land mass characterization, feature identification, target recognition, and change detection.

Krueger, Peter G.; Gouge, Sally B.; Gouge, Jim O.

1998-09-01

287

Delineate subsurface structures with ground penetrating radar  

SciTech Connect

High resolution ground penetrating radar (GPR) surveys were conducted at the Savannah River Site in South Carolina in late 1991 to demonstrate the radar techniques in imaging shallow utility and soil structures. Targets of interest at two selected sites, designated as H- and D-areas, were a buried backfilled trench, buried drums, geologic stratas, and water table. Multiple offset 2-D and single offset 3-D survey methods were used to acquire high resolution radar data. This digital data was processed using standard seismic processing software to enhance signal quality and improve resolution. Finally, using a graphics workstation, the 3D data was interpreted. In addition, a small 3D survey was acquired in The Woodlands, Texas, with very dense spatial sampling. This data set adequately demonstrated the potential of this technology in imaging subsurface features.

Wyatt, D.E. (Westinghouse Savannah River Co., Aiken, SC (United States)); Hu, L.Z. (New Wave Technology, Houston, TX (United States)); Ramaswamy, M. (Houston Advanced Research Center, Woodlands, TX (United States)); Sexton, B.G. (Microseeps, Inc., Pittsburgh, PA (United States))

1992-01-01

288

Delineate subsurface structures with ground penetrating radar  

SciTech Connect

High resolution ground penetrating radar (GPR) surveys were conducted at the Savannah River Site in South Carolina in late 1991 to demonstrate the radar techniques in imaging shallow utility and soil structures. Targets of interest at two selected sites, designated as H- and D-areas, were a buried backfilled trench, buried drums, geologic stratas, and water table. Multiple offset 2-D and single offset 3-D survey methods were used to acquire high resolution radar data. This digital data was processed using standard seismic processing software to enhance signal quality and improve resolution. Finally, using a graphics workstation, the 3D data was interpreted. In addition, a small 3D survey was acquired in The Woodlands, Texas, with very dense spatial sampling. This data set adequately demonstrated the potential of this technology in imaging subsurface features.

Wyatt, D.E. [Westinghouse Savannah River Co., Aiken, SC (United States); Hu, L.Z. [New Wave Technology, Houston, TX (United States); Ramaswamy, M. [Houston Advanced Research Center, Woodlands, TX (United States); Sexton, B.G. [Microseeps, Inc., Pittsburgh, PA (United States)

1992-10-01

289

Improved HF Manpack Antenna Systems.  

National Technical Information Service (NTIS)

The report describes the engineering changes made to a family of lightweight HF antennas (see AD-842 443). It also provides the acceptance tests, maintainability analysis, reliability analysis, and reliability demonstration tests which were performed. (Au...

R. A. Kneblik R. L. Bell

1970-01-01

290

Hf–W internal isochrons for ordinary chondrites and the initial 182 Hf\\/ 180 Hf of the solar system  

Microsoft Academic Search

Three ordinary chondrites, Forest Vale (H4), Ste. Marguerite (H4) and Richardton (H5) have been studied with 182Hf–182W system (t1\\/2=9 million years [m.y.]) in order to provide constraints on the initial 182Hf\\/180Hf for the chondritic parent body and the solar system. All three samples display positive correlations between 182W\\/184W and 180Hf\\/184W, providing confirmation that live 182Hf was present in these samples.

Der-Chuen Lee; Alex N Halliday

2000-01-01

291

Radar Meteorology Tutorial  

NSDL National Science Digital Library

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.

Mcnoldy, Brian

2007-08-16

292

Cloud and Precipitation Radar  

NASA Astrophysics Data System (ADS)

Precipitation or weather radar is an essential tool for research, diagnosis, and nowcasting of precipitation events like fronts or thunderstorms. Only with weather radar is it possible to gain insights into the three-dimensional structure of thunderstorms and to investigate processes like hail formation or tornado genesis. A number of different radar products are available to analyze the structure, dynamics and microphysics of precipitation systems. Cloud radars use short wavelengths to enable detection of small ice particles or cloud droplets. Their applications differ from weather radar as they are mostly orientated vertically, where different retrieval techniques can be applied.

Hagen, Martin; Höller, Hartmut; Schmidt, Kersten

293

Accuracy of topographic maps derived from ERS-1 interferometric radar  

Microsoft Academic Search

An interferometric radar technique for topographic mapping of surfaces promises a high-resolution approach to the generation of digital elevation models. The authors present analyses of data collected by the synthetic aperture radar instrument on-board the ERS-1 satellite on successive orbits. Use of a single satellite in a nearly repeating orbit is attractive for reducing cost and spaceborne hardware complexity; also

Howard A. Zebker; Charles L. Werner; Paul A. Rosen; Scott Hensley

1994-01-01

294

Weibull-distributed radar clutter reflected from sea ice  

Microsoft Academic Search

Sea-ice clutter was measured using an X-band radar which is located at the city of Mombetsu in Hokkaido. The pulse width of the radar was 80 ns. To sample at 40 ns and record digitally, an emitter-coupled logic (ECL) was used as a high-speed IC. The sampled data were first transferred to a 64-kbyte dynamic-memory board and then to a

Hiroshi Ogawa; Matsuo Sekine; Toshimitsu Musha; Masaaki Aota; Masayuki Ohi

1987-01-01

295

Terrain mapping by ground-based interferometric radar  

Microsoft Academic Search

The authors propose a ground-based interferometric synthetic aperture radar (SAR) technique for terrain mapping. It is based on a coherent continuous-wave step-frequency (CW-SF) radar moved along a linear horizontal rail. It works synthesising microwave holographic images taken from different points of view to obtain elevation maps by phase comparison. The focusing algorithm for imaging synthetic holograms and digital elevation models

Massimiliano Pieraccini; Guido Luzi; Carlo Atzeni

2001-01-01

296

Automated Oil Spill Detection with Ship Borne Radar  

Microsoft Academic Search

Abstract: This research outlines the need for a real-time, a ship borne radar facility SHIRA for the tracking ofnearby oil spills during oil containment and cleaning operations at sea with high quality imagery.SHIRA is imaging digital X-band radar, developed by TNO for the measurement of oceanographicfeatures. It was especially adapted for the imaging of oil slicks by implementing a number

Nasser Mostafa Saleh

2004-01-01

297

Half life of 175Hf.  

PubMed

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

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

2012-06-21

298

2. VIEW SOUTHWEST, prime search radar tower, height finder radar ...  

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

2. VIEW SOUTHWEST, prime search radar tower, height finder radar towards, height finder radar towers, and radar tower (unknown function) - Fort Custer Military Reservation, P-67 Radar Station, .25 mile north of Dickman Road, east of Clark Road, Battle Creek, Calhoun County, MI

299

Radar detection using Siegel distance between autoregressive processes, application to HF and X-band radar  

Microsoft Academic Search

In this paper, we present an original generalization of the CFAR technique . The technique of CFAR consists in testing two alternative assumptions ldquopresence of targetrdquo versus ldquoabsence of targetrdquo in a distance-azimuth cell called ldquocell under testrdquo. In the case where the noise is Gaussian and additive, one can show that the CFAR is equivalent to withdraw from the

J. Lapuyade-Lahorgue; F. Barbaresco

2008-01-01

300

Do you have a radar bill in your pocket?  

NSDL National Science Digital Library

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

National Council of Teachers of Mathematics (NCTM)

2002-01-01

301

Modeling of HF propagation and heating in the ionosphere  

SciTech Connect

A comprehensive numerical implementation of plasma geometric optics is being enhanced and adapted to the problem of self-consistent ionospheric propagation of high power, high frequency (HF) radar signals. The emphasis in this work is on realistic and rigorous description of the propagating waves so that geometric and spectral characteristics of nonlinear ionospheric effects can be predicted in detail. When improvements are complete, a plasma geometric optics code will be used in conjunction with an ionospheric transport code to determine self-consistently the HF radiation field and quasilinear modifications of ionospheric plasma properties due to ohmic dissipation of the HF radiation. This allows detailed study of nonlinear phenomena such as beam self-focusing, formation of large-scale density cavities and striations, and induced wave ducting. An overview of the theory underlying the modeling of radiation propagation and ohmic power deposition is given, and current results from the plasma geometric optics code together with associated ionospheric power deposition profiles are presented. Detailed structure of ordinary and extraordinary mode caustics formed in a manner consistent with a realistic antenna pattern and birefringence upon entrance into the ionosphere are evident.

Smith, T.M.; Shoucri, M.M.; Wagner, T.M.

1990-10-01

302

Nostradamus: The radar that wanted to be a seismometer  

NASA Astrophysics Data System (ADS)

Surface waves emitted after large earthquakes are known to induce, by dynamic coupling, atmospheric infrasonic waves propagating upward through the neutral and ionized atmosphere. Those waves have been detected in the past at ionospheric heights using a variety of techniques, such as HF Doppler sounding or GPS receivers. The HF Doppler technique, particularly sensitive to the ionospheric signature of Rayleigh waves is used here to show ionospheric perturbations consistent with the propagation of Rayleigh wave phases R1 and R2 following the Sumatra earthquake on the 28 March 2005 (M = 8.6). This is in our knowledge the first time that the phase R2 is detected by ionospheric sounding. In addition, we prove here that the ionospheric signature of R2 is also observed by over-the-horizon (OTH) Radar. The latter was never used before to detect seismic signature in the ionosphere. Adding the OTH Radar to the list of the “ionospheric seismometers” we discuss and compare the performances of the three different instruments mentioned above, namely HF Doppler sounding, GPS receivers and OTH radar.

Occhipinti, Giovanni; Dorey, Philippe; Farges, Thomas; Lognonné, Philippe

2010-09-01

303

Short--time-scale evidence for strong Langmuir turbulence during hf heating of the ionosphere  

SciTech Connect

Results of short-pulse, low--duty-cycle hf-heating experiments areshown to agree with predictions of a model of correlated, localized cavitonswhich undergo cycles of nucleation, collapse, and burnout. Predicted''free-mode'' spectral features associated with the radiation of Langmuir wavesfrom collapsing cavitons are observed. Single radar pulse data provide evidencethat temporal correlations between caviton events are present at early timesfollowing the onset of heating.

Cheung, P. Y.; Wong, A. Y.; Tanikawa, T.; Santoru, J.; DuBois, D. F.; Rose, H. A.; Russell, D.

1989-06-05

304

A simple digital TDPAC spectrometer  

NASA Astrophysics Data System (ADS)

We present a simplified digital time differential perturbed ? - ? angular correlation (TDPAC) spectrometer that demonstrates that such instruments can be built using primarily commercial components and with relatively modest coding effort. The system handles data rates of 70 kcps/detector with a timing resolution of better than 500 ps, and has been used with both 111In and 181Hf.

Webb, T. A.; Nikkinen, Leo; Gallego, Juan; Ryan, D. H.

2013-05-01

305

Correlation detection filter for imaging laser radar  

NASA Astrophysics Data System (ADS)

Laser radar can simultaneously produce the intensity and range images, and the space resolution is high, so the recognition performance is well, and it can choose the aim point of target. Laser radar is applied to many fields, such as guidance, navigation, and becomes the research hot point in recent years. In the vertical detection of laser radar, the algorithm is required not only solving in-plane rotation-invariant problem, also the distortion-invariant problem, and it must satisfied the real-time. Correlation algorithm is a parallel processing procedure, detecting many targets at one time, and its design can be implemented on the high speed digital signal processor. In the paper, a new filter named CHF-MACH filter is presented, which combine multiple circular harmonic expansions into one filter through MACH criteria. Because of the filter having the characters of the two filters, it can solve the problems of in-plane rotation-invariance and distortion-invariance simultaneously, and meet the real-time requirement. The simulated range image of laser radar is regarded as research target, and computing the PSR (peak to sidelobe ratio) values of correlation output of the different objects, and plotting the PSR curves of the different angles. Simulating the scene of laser radar which includes multiple objects, CHF-MACH filter performance is validated through testing with the different angles for the objects, and the non-training images can obtain the well correlation output.

Sun, Jianfeng; Li, Qi; Lu, Wei; Wang, Qi

2007-01-01

306

Rendezvous radar for the orbital maneuvering vehicle  

NASA Astrophysics Data System (ADS)

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.

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

307

A HWIL test facility of infrared imaging laser radar using direct signal injection  

Microsoft Academic Search

Laser radar has been widely used these years and the hardware-in-the-loop (HWIL) testing of laser radar become important because of its low cost and high fidelity compare with On-the-Fly testing and whole digital simulation separately. Scene generation and projection two key technologies of hardware-in-the-loop testing of laser radar and is a complicated problem because the 3D images result from time

Qian Wang; Wei Lu; Chunhui Wang; Qi Wang

2005-01-01

308

Nearshore Processes, Currents and Directional Wave Spectra Monitoring Using Coherent and Non-coherent Imaging Radars  

Microsoft Academic Search

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

D. Trizna; K. Hathaway

2007-01-01

309

Real-time beamforming synthetic aperture radar  

Microsoft Academic Search

This paper discusses the concept and design of a real-time Digital Beamforming Synthetic Aperture Radar (DBSAR) for airborne applications which can achieve fine spatial resolutions and wide swaths. The development of the DBSAR enhances important scientific measurements in Earth science, and serves as a prove-of-concept for planetary exploration missions. A unique aspect of DBSAR is that it achieves fine resolutions

Rafael Rincon; Peter Hildebrand; Lawrence Hilliard; Damon Bradley; Luko Krnan; Salman Sheikh; Jared Lucey

2006-01-01

310

3. VIEW NORTHWEST, height finder radar towers, and radar tower ...  

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

3. VIEW NORTHWEST, height finder radar towers, and radar tower (unknown function) - Fort Custer Military Reservation, P-67 Radar Station, .25 mile north of Dickman Road, east of Clark Road, Battle Creek, Calhoun County, MI

311

30. Perimeter acquisition radar building room #318, showing radar control. ...  

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

30. Perimeter acquisition radar building room #318, showing radar control. Console and line printers - Stanley R. Mickelsen Safeguard Complex, Perimeter Acquisition Radar Building, Limited Access Area, between Limited Access Patrol Road & Service Road A, Nekoma, Cavalier County, ND

312

Millimeter Wave Polarimetric Monopulse Radar Debugging System  

Microsoft Academic Search

For testing millimeter wave polarimetric monopulse radar and testing algorithms for polarimetric radar, millimeter wave polarimetric monopulse radar debugging system is proposed in this paper. Polarimetric radar, as a kind of radar with strong counter-countermeasure capability, is more and more popular used nowadays. The cost of polarimetric radar is more expensive than traditional single-polarimetric radar. Millimeter wave polarimetric monopulse radar

Jin Tao; Qi Xiaohui; Zhang Min; Qiao Xiaolin; Yuan Shuqing; Zhang Qunxing

2007-01-01

313

Basic characteristics of FM-CW radar systems  

NASA Astrophysics Data System (ADS)

Due to rapid technological progress in real-time signal processing, FM-CW radar systems are expected to become a more serious competitor to pulse radar systems. This paper deals with basic radar principles such as modulating waveforms and ambiguity functions characteristics. Advantages and disadvantages of FM-CW radar systems are compared to pulse radar systems. The inherent signal processing used in FM-CW radar systems allows a flexible choice of system parameters. In this context aspects like sensitivity, range and velocity resolution are discussed. It is elucidated that the use of digital processors for signal processing (frequency determination, filtering, etc.) offers the possibility to exchange dedicated hardware solutions with software implementations. Attention is paid to equipment like the antennas, diplexer, transmitter and receiver, and to isolation problems between transmitter and receiver. Results of an experimental FM-CW research radar are shown. In addition, the future prospects of FM-CW radar, with the aerial and solid-state R.F. head-end integrated, are indicated.

Ligthart, L. P.; Nieuwkerk, L. R.; Vansinttruyen, J. S.

1986-07-01

314

A short history of geophysical radar at Arecibo Observatory  

NASA Astrophysics Data System (ADS)

As Arecibo Observatory (AO) approaches its 50th anniversary, it is appropriate to review the many radars and ionospheric heaters that have been deployed on or near the 305 m dish and to summarize some of the innovative radar-based geophysical research that has resulted. The reasons William E. (Bill) Gordon developed the 305 m Arecibo dish are well known but are briefly reviewed. The early and then more recent radar/feed designs are reviewed as geophysical uses of Arecibo have evolved and as the full potential of the dish and nearby facilities was and is being realized from HF through S-band frequencies. This history surely has some gaps and there are a few mysteries. The community is encouraged to fill these gaps and to help complete the history.

Mathews, J. D.

2013-03-01

315

Design of the radar real-time simulation system joined with hardware  

Microsoft Academic Search

To improve the real-time property for typical Pulse Doppler radar simulation, an idea of signal-level simulation using hardware was proposed. The system framework and information flow was studied, then a host method of moving target echo simulation was given. Most of all, radar signal processing was realized by FPGA, which includes digital quadrature detection with IF sampling, pulse compression based

Yong Chen; Xinyu Yao; Wenbo Wu; Xiaofeng Tang

2011-01-01

316

FPGA-based Radar Signal Processing for Automotive Driver Assistance System  

Microsoft Academic Search

Safety and comfort applications are addressed using driver assistance (DA) systems like adaptive cruise control (ACC) system using long range radar (LRR) or short range radar (SRR) or both. Novel waveforms and functionalities applied to next generation DA multi-sensor systems and their corresponding complex algorithms require advanced digital hardware supporting high computation rate and severe real-time constraints. In this paper,

Jean Saad; Amer Baghdadi; Frantz Bodereau

2009-01-01

317

FPGA controlled DDS based frequency sweep generation of high linearity for FMCW radar systems  

Microsoft Academic Search

Two significant requirements in an FMCW radar system are linearity and low phase noise. Especially in range detection applications the achievable accuracy directly depends on the linearity of the modulated radar signal. In general PLL based systems with digital generated reference signals are used to meet this requirement. In this paper an FPGA controlled DDS based signal generator for highly

Serdal Ayhan; Viet Vu-Duy; Philipp Pahl; Steffen Scherr; Michael Hubner; Jurgen Becker; Thomas Zwick

2012-01-01

318

Direct Path Interference Cancellation in FM Radio-Based Passive Radar  

Microsoft Academic Search

In passive radar based on illuminators of opportunity, one of the key problems is the suppression of the direct path interference (DPI) from the illuminator. This paper analyzes the DPI and the effect of which on passive radar in practical application, and demonstrates the importance of the suppression of DPI prior to analog to digital converter (ADC). Based on which,

Hong Wan; Shentang Li; Zhigang Wang

2006-01-01

319

Research of CMLD-CFAR Detecting Algorithm in Radar Reconnaissance Receiver  

Microsoft Academic Search

In radar signal reconnaissance digital receiver based on DFT (Discrete Fourier Transform), automatic CFAR (Constant False Alarm Rate) detection in frequency domain is necessary in processing of peak-seek algorithm. A CMLD-CFAR (Censored Mean Level Detector CFAR) algorithm in frequency domain is presented. By researching the threshold generating algorithm of pulse radar signalspsila spectrum under clutter background, a threshold generating algorithm

Shuhua Wei; Xiaojun Wang

2009-01-01

320

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

Microsoft Academic Search

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,

Philip E. Zwicke; Imre Kiss

1983-01-01

321

Doppler Signal Analysis and Processing Techniques for Modified 'Porcupine' C-Band Pulse Doppler Radar.  

National Technical Information Service (NTIS)

The report deals primarily with various doppler signal processing techniques for the Porcupine Weather Radar System. Continuing emphasis is placed on digital data reduction techniques including the fast Fourier transform method of spectral analysis. Pract...

T. Berger E. G. Cox H. L. Groginsky J. M. Kovalik G. A. Works

1968-01-01

322

Laser radar in robotics  

SciTech Connect

In this paper the authors describe the basic operating principles of laser radar sensors and the typical algorithms used to process laser radar imagery for robotic applications. The authors review 12 laser radar sensors to illustrate the variety of systems that have been applied to robotic applications wherein information extracted from the laser radar data is used to automatically control a mechanism or process. Next, they describe selected robotic applications in seven areas: autonomous vehicle navigation, walking machine foot placement, automated service vehicles, manufacturing and inspection, automotive, military, and agriculture. They conclude with a discussion of the status of laser radar technology and suggest trends seen in the application of laser radar sensors to robotics. Many new applications are expected as the maturity level progresses and system costs are reduced.

Carmer, D.C.; Peterson, L.M. [Environmental Research Inst. of Michigan, Ann Arbor, MI (United States)

1996-02-01

323

Review of Radar Absorbing Materials.  

National Technical Information Service (NTIS)

Radar is a sensitive detection tool and since its development, methods for reducing microwave reflections have been explored. Radar absorbers can be classified as impedance matching or resonant absorbers. Radar absorbing materials are made from resistive ...

P. Saville

2005-01-01

324

Spaceborne Atmospheric Radar Technology  

Microsoft Academic Search

NASA is developing advanced instrument concepts and technologies for future spaceborne atmospheric radars, with the over-arching objectives 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

Eastwood Im; Stephen L. Durden

325

DORIS radar calibration method  

NASA Astrophysics Data System (ADS)

Following the interest expressed by ESA and FGAN, it was decided to realise some evaluation of the DORIS calibration method with the TIRA radar. This paper, organised in four parts, describes: - the importance of radar calibration in the space debris domain - the principle of the DORIS calibration method - the results obtained with the TIRA FGAN radar using the DORIS reference - the advantages of the DORIS calibration and the future uses of this method in an European exercise involving for the ESA benefit both French and German radars.

Ameline, P.

2001-10-01

326

The impact of technological evolution on radar systems  

NASA Astrophysics Data System (ADS)

It is possible to use surface acoustic wave devices having continually improving performance due to the possibilities of finer and finer engraving. In addition, the general evolution of silicon semiconductors has allowed the realization of efficient analog to digital encoding as well as the economic realization of dense digital memories which gave rise to digital solutions. Pulse compression was described before the end of WW II, but it was not truly developed in radar systems before the end of the 60's, due to the use of surface acoustic devices or of digital devices. Finally, radar systems will continue to benefit from new materials such as composites using carbon fiber, piezoelectric polymers, glass fibers, conductive polymers, PtSi, diamond thin films, compounds such as gallium arsenide, and possibly other materials such as high-temperature supraconducting materials.

Carpentier, Michel H.

327

EISCAT Svalbard radar  

Microsoft Academic Search

The main fields of interest of the Finnish scientists in EISCAT research are listed. Finnish interests in the Polar Cap Radar (PMR) and areas where the Finnish contribution could be important are addressed: radar techniques; sporadic E layers in the polar cap; atmospheric models; auroral studies in the polar cap; nonthermal plasmas in the F region; coordinated measurements with the

Markku Lehtinen; Jorma Kangas

1992-01-01

328

EISCAT Svalbard Radar.  

National Technical Information Service (NTIS)

The main fields of interest of the Finnish scientists in EISCAT research are listed. Finnish interests in the Polar Cap Radar (PMR) and areas where the Finnish contribution could be important are addressed: radar techniques; sporadic E layers in the polar...

M. Lehtinen J. Kangas

1992-01-01

329

Radar illusion via metamaterials  

NASA Astrophysics Data System (ADS)

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

Jiang, Wei Xiang; Cui, Tie Jun

2011-02-01

330

Doppler weather radar  

Microsoft Academic Search

The Doppler weather radar and its signals are examined from elementary considerations to show the origin and development of useful weather echo properties such as signal-to-noise ratio (SNR), range correlation, signal statistics, etc. We present a form of the weather radar equation which explicitly shows the echo power loss due to finite receiver bandwidth and how it is related to

RICHARD J. DOVIAK; DUSAN S. ZRNIC; DALE S. SIRMANS

1979-01-01

331

Advances in Radar Techniques  

NASA Astrophysics Data System (ADS)

Most of the clutter received by L, S, C, X, and Ku band radars obeys a Weibull ditribution. To suppress such Weibull-distributed sea and weather clutter, Weibull CFAR techniques are applied to data taken by an X-band radar using computer in real time. The results show the usefulness of Weibull CFAR.

Sekine, Matsuo

332

UWB radars in medicine  

Microsoft Academic Search

Applied research on biomedical applications of UWB radar is targeted to the identification of the possible new devices made possible by the technology, to the design and development of those devices, and to the clinical testing of the systems obtained. Applications can be divided into two main sectors according to the frequency range used. For the conventional UWB radar microwave

Enrico M. Staderini

2002-01-01

333

Stereo Radar Analysis.  

National Technical Information Service (NTIS)

The topographic accuracy of the AN/APQ-102(XA-2) side-looking radar and its specific applicability to 1:50,000 and 1:250,000 scale topographic mapping were tested using stereo radar techniques with real data. The two basic stereo configurations, opposite-...

G. Gracie R. K. Brewer J. W. Bricker R. A. Johnson

1970-01-01

334

Panchromatic and polypanchromatic radar  

Microsoft Academic Search

Application of broad-band (panchromatic) illumination in radar systems should permit improvement in image quality and reduction of tracking and detection problems due to fading. The effect of frequency averaging on radar return from a simple target array is demonstrated by numerical computation and on image quality by ultrasonic simulation. The required bandwidth for a slightly rough random surface is determined

RICHARD K. MOORE; WILLIAM P. WAITE

1969-01-01

335

Radar clutter classification  

Microsoft Academic Search

The problem of classifying radar clutter as found on air traffic control radar systems is studied, and an algorithm is developed to carry out this classification automatically. The basis for the algorithm is Bayes decision theory and the parametric maximum a posteriori probability (MAP) classifier. This classifier employs a quadratic discriminant function and is optimum for feature vectors that are

Wolfgang Stehwien

1990-01-01

336

Radar clutter classification  

Microsoft Academic Search

The problem of classifying radar clutter as found on air traffic control radar systems is studied. An algorithm based on Bayes decision theory and the parametric maximum a posteriori probability classifier is developed to perform this classification automatically. This classifier employs a quadratic discriminant function and is optimum for feature vectors that are distributed according to the multivariate normal density.

Wolfgang Stehwien

1989-01-01

337

4. VIEW NORTHEAST, radar tower (unknown function), prime search radar ...  

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

4. VIEW NORTHEAST, radar tower (unknown function), prime search radar tower, emergency power building, and height finder radar tower - Fort Custer Military Reservation, P-67 Radar Station, .25 mile north of Dickman Road, east of Clark Road, Battle Creek, Calhoun County, MI

338

5. VIEW EAST, height finder radar towers, radar tower (unknown ...  

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

5. VIEW EAST, height finder radar towers, radar tower (unknown function), prime search radar tower, operations building, and central heating plant - Fort Custer Military Reservation, P-67 Radar Station, .25 mile north of Dickman Road, east of Clark Road, Battle Creek, Calhoun County, MI

339

On radar polarimetry in FM-CW radar  

Microsoft Academic Search

This paper attempts to apply the principle of radar polarimetry to wideband synthetic aperture FM-CW radar and presents a basic polarimetric detection result of a linear target in a laboratory measurement. Although the principle of radar polarimetry has well been established for the completely polarized wave and for the monostatic case, it still needs to be extended to wideband radar

Y. Yamaguchi; T. Nishikawa; W.-M. Boerner; M. Sengoku; Hyo Joon Eom

1993-01-01

340

Time-frequency analysis of synthetic aperture radar signals  

SciTech Connect

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.

Johnston, B.

1996-08-01

341

Air traffic control radar tester  

Microsoft Academic Search

Our aim is to develop a radar tester equipment for commercial and military services. The task is to create one (or more) target or clutter on the radar screen with given distance, velocity and fluctuation. This equipment is placed within few hundred meters from the radar, so it is able to analyze the whole radar system from the antenna, via

Péter KOVÁCS; Levente DUDÁS; Rudolf SELLER; József ORBÁN

2008-01-01

342

Air traffic control radar tester  

Microsoft Academic Search

Our aim had been to develop a radar tester equipment for commercial and military services. The task is to create one (or more) target or clutter on the radar screen with given distance, velocity and fluctuation. This equipment is placed within few hundred meters from the radar, so it is able to analyze the whole radar system from the antenna,

Levente DUDÁS; Rudolf SELLER; Péter RENNER; József ORBÁN

2009-01-01

343

Acousto-optic correlator for radar report-track association  

NASA Astrophysics Data System (ADS)

An acousto-optic correlator has been developed for application to radar report-track association. This correlator employs a 2D, ferro-electric liquid crystal spatial light modulator for storage of track data while report data is input to the system's Bragg cell. Performance matches that of digital processing with the added capability of operation at much higher processing rates.

Abramowitz, I. J.; Malarkey, Edward C.; Oechsler, T.; Buechel, J.; Queeney, Tom; Wooton, A.

1994-06-01

344

Target Detection and Localization Using MIMO Radars and Sonars  

Microsoft Academic Search

In this paper, we propose a new space-time coding configuration for target detection and localization by radar or sonar systems. In common active array systems, the transmitted signal is usually coherent between the different elements of the array. This configuration does not allow array processing in the transmit mode. However, space-time coding of the transmitted signals allows to digitally steer

Ilya Bekkerman; Joseph Tabrikian

2006-01-01

345

Real-time adaptive radiometric correction for imaging radars systems  

NASA Astrophysics Data System (ADS)

A new solution is given of a real time radiometric image correction that also minimizes the quantization and saturation noise introduced by the process of analog-to-digital conversion of raw data of coherent and noncoherent imaging radar systems. The implementation of this procedure was successfully performed with the experimental SAR System (E-SAR) of the DLR.

Moreira, Joao R.; Poetzsch, Winfried

1989-10-01

346

Large Aperture Multi-Dimensional Laser Radar Testbed.  

National Technical Information Service (NTIS)

A 39 cm aperture multi-dimensional laser radar has been built and made operational. This sensor acquires pixel registered range, Doppler, 3-5 micrometer passive, and visible passive data. Range is digitized at 200 MHz for .75 m range resolution. Doppler i...

D. U. Fluckiger M. P. Boldue L. A. Prior

1988-01-01

347

Simulation of multistatic and backscattering cross sections for airborne radar  

Microsoft Academic Search

In order to determine susceptibilities of airborne radar to electronic countermeasures and electronic counter-countermeasures simulations of multistatic and backscattering cross sections were developed as digital modules in the form of algorithms. Cross section algorithms are described for prolate (cigar shape) and oblate (disk shape) spheroids. Backscattering cross section algorithms are also described for different categories of terrain. Backscattering cross section

Albert W. Biggs

1986-01-01

348

Incoherent scatter radar contributions  

NASA Astrophysics Data System (ADS)

The contributions of the incoherent scatter radar technique to knowledge of the neutral upper atmosphere of the earth in general and the development of the CIRA 1986 model in particular are discussed. Incoherent radar scattering involves the transmission of a radio wave into the atmosphere and the reception of the energy scattered by the free electrons illuminated by the wave. Attention is given to the chronology of radar contributions to the development of upper atmosphere models, the ion energy balance and continuity equations, exospheric temperatures, and studies of the lower thermosphere.

Oliver, W. L.; Alcayde, D.; Bauer, P.

349

Active radar jamming  

NASA Astrophysics Data System (ADS)

Active radar jammers are described. In confusion jammers the perturbing action is produced by thermal noise which is intensified, or by a carrier wave modulated by a noise signal, or by a carrier wave which is frequency modulated with a lot of sine waves of different frequencies. There are jammers to be used once, which are fired to the spot or hang from a parachute. Deception jammers (misleading jammers) emit false radar echoes, one or several produced by a repetition system, requiring a certain form of memory. It is shown how to emit varying false distance or velocities, and how to disturb angles in a radar used to guide artillery fire.

Jernemalm, Veine

1988-09-01

350

The 94 GHz MMW imaging radar system  

NASA Astrophysics Data System (ADS)

The 94 GHz MMW airborne radar system that provides a runway image in adverse weather conditions is now undergoing tests at Wright-Patterson Air Force Base (WPAFB). This system, which consists of a solid state FMCW transceiver, antenna, and digital signal processor, has an update rate of 10 times per second, 0.35x azimuth resolution and up to 3.5 meter range resolution. The radar B scope (range versus azimuth) image, once converted to C scope (elevation versus azimuth), is compatible with the standard TV presentation and can be displayed on the Head Up Display (HUD) or Head Down Display (HDD) to aid the pilot during landing and takeoff in limited visibility conditions.

Alon, Yair; Ulmer, Lon

1993-12-01

351

Current radar responsive tag development activities at Sandia National Laboratories.  

SciTech Connect

Over the past ten years, Sandia has developed RF radar responsive tag systems and supporting technologies for various government agencies and industry partners. RF tags can function as RF transmitters or radar transponders that enable tagging, tracking, and location determination functions. Expertise in tag architecture, microwave and radar design, signal analysis and processing techniques, digital design, modeling and simulation, and testing have been directly applicable to these tag programs. In general, the radar responsive tag designs have emphasized low power, small package size, and the ability to be detected by the radar at long ranges. Recently, there has been an interest in using radar responsive tags for Blue Force tracking and Combat ID (CID). The main reason for this interest is to allow airborne surveillance radars to easily distinguish U.S. assets from those of opposing forces. A Blue Force tracking capability would add materially to situational awareness. Combat ID is also an issue, as evidenced by the fact that approximately one-quarter of all U.S. casualties in the Gulf War took the form of ground troops killed by friendly fire. Because the evolution of warfare in the intervening decade has made asymmetric warfare the norm rather than the exception, swarming engagements in which U.S. forces will be freely intermixed with opposing forces is a situation that must be anticipated. Increasing utilization of precision munitions can be expected to drive fires progressively closer to engaged allied troops at times when visual de-confliction is not an option. In view of these trends, it becomes increasingly important that U.S. ground forces have a widely proliferated all-weather radar responsive tag that communicates to all-weather surveillance. The purpose of this paper is to provide an overview of the recent, current, and future radar responsive research and development activities at Sandia National Laboratories that support both the Blue Force Tracking and Combat ID application.

Plummer, Kenneth W.; Ormesher, Richard C.

2003-09-01

352

Digital Libraries  

NSDL National Science Digital Library

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 ...

Heather

2008-09-29

353

Introduction to special section: Science and technology of over-the-horizon radar  

NASA Astrophysics Data System (ADS)

The rationale for the development of over-the-horizon (OTH) radar systems operating at frequencies in the HF band arose out of a perceived need for an early-warning defense network. That need changed with the end of the Cold War; however, today OTH radars play a major role in the CounterDrug Program for the interdiction of drug-smuggling aircraft. This special section of Radio Science is devoted to a review of OTH radar technology, with emphasis on contemporary developments in this field. The collection of papers presented here has evolved largely from research and development efforts directed to improving the performance of OTH radar systems deployed both in the United States and in Australia.

Berkey, F. Tom

1998-07-01

354

System concept and analysis of an Artificial Ionospheric Mirror (AIM) radar  

NASA Astrophysics Data System (ADS)

Recognition of performance limitations associated with traditional skywave over-the-horizon (OTH) high frequency (HF) radars has led a number of investigators to propose the creation of an Artificial Ionospheric Mirror (AIM) in the upper atmosphere, in order to reflect ground-based radar signals for OTH surveillance. The AIM is produced by beaming sufficient electromagnetic power to the lower ionosphere (around 70 km) to enhance the in situ ionization level to 10(exp 7) to 10(exp 8) electrons/cu cm, thereby providing an ionized layer capable of reflecting radar frequencies of 30 to 90 MHz. This paper presents a baseline AIM system concept and an associated performance evaluation, based upon the relevant ionization and propagation physics and in the context of air surveillance for the cruise missile threat. Results of the subject study indicate that a system using this concept would both complement and enhance the performance of the existing skywave OTH radars.

Short, Robert D.; Stewart, Clayton V.; Wallace, Tom; Lallement, Pierre; Koert, Peter

1990-08-01

355

Generalized Radar Output Simulation.  

National Technical Information Service (NTIS)

Using the outputs from the simulation of overall body motion related to observations at a complex of earth stations, this report develops a model for generating the scattering matrix and radar output voltages. The general multistatic case is treated using...

J. F. A. Ormsby S. H. Bickel

1969-01-01

356

Multimode Radar Altimeter (MRA).  

National Technical Information Service (NTIS)

Multimode radar altimeter functions in the Comet Nucleus Sample Return mission are described. Range measurement gives distance information for navigation; angle tracking can be performed by optical systems. Velocity (three axes) can be obtained by Doppler...

G. Picardi C. Dai R. Seu A. Coradini

1988-01-01

357

Radar Techniques Program.  

National Technical Information Service (NTIS)

This is the fifth Quarterly Technical Summary covering the development of an airborne Multiple-Antenna Moving-Target Surveillance Radar (MASR) which employs special antenna and signal-processing techniques to provide continuous, wide-area surveillance of ...

C. E. Muehe

1974-01-01

358

Incoherent radar spectra  

Microsoft Academic Search

General expressions for the incoherent scatter spectra are presented. These are relevant for the UHF radar in the monostatic backscatter case (thus excluding only the effect of the magnetic field), based on the Nyquist approach.

Matti K. Vallinkoski

1987-01-01

359

Ultra-wideband radar  

Microsoft Academic Search

Here, we present a description of a block scheme, characteristics, specific features of design and results of testing for a prototype of the ultrawideband (UWB) radar, which has been developed by Russian UWB group researchers at Moscow Aviation Institute at \\

I. Immoreev; E. Ziganshin

2004-01-01

360

Radar investigation of asteroids  

NASA Astrophysics Data System (ADS)

For 80 Sappho, 356 Liguria, 694 Ekard, and 2340 Hathor, data were taken simultaneously in the same sense of circular polarization as transmitted (SC) as well as in the opposite (OC) sense. Graphs show the average OC and SC radar echo power spectra soothed to a resolution of EFB Hz and plotted against Doppler frequency. Radar observations of the peculiar object 2201 Oljato reveal an unusual set of echo power spectra. The albedo and polarization ratio remain fairly constant but the bandwidths range from approximately 0.8 Hz to 1.4 Hz and the spectral shapes vary dramatically. Echo characteristics within any one date's approximately 2.5-hr observation period do not fluctuate very much. Laboratory measurements of the radar frequency electrical properties of particulate metal-plus-silicate mixtures can be combined with radar albedo estimates to constrain the bulk density and metal weight, fraction in a hypothetical asteroid regolith having the same particle size distribution as lab samples.

Ostro, S. J.

361

Microprocessor-Based Data-Acquisition System for a Borehole Radar  

Microsoft Academic Search

An efficient microprocessor-based system has been implemented that permits real-time acquisition, stacking, and digital recording of data generated by a borehole radar system. Although the system digitizes, stacks, and records independently of a computer, it is interfaced to a desktop computer for program control over system parameters such as sampling interval, number of samples, number of times the data are

Jerry Bradley; David Wright

1987-01-01

362

Measurements of spatial and frequency coherence of an equatorial hf path during spread-F  

NASA Astrophysics Data System (ADS)

In August 1990, the authors set up an hf path on the equatorial path between Maloelap Atoll and Bikini Atoll. This path, which had a range of 702 km, reflected in the ionosphere approximately 100 km north of the Altair radar location on Kwajalein. Transmitters at Maloelap broadcasted four CW tones within bandwidth of either 4 kHz, 9 kHz, or 70 kHz to be used to determine frequency coherence and also a phase-coded pseudo random sequence with a bandwidth of 60 kHz (channel probe) to be used to determine time delay spread. A spatial array of antennas was deployed at Bikini to measure spatial and frequency coherence using the CW broadcasts. The system was run in the post-sunset time period over two weeks during which almost every night showed significant degradation due to spread F resulting in rapid fading, decreased spatial and frequency coherence, and increased time delay spread. Doppler spreads of greater than 20 Hz were not uncommon, and the spatial correlation distances and frequency coherence bandwidths became so small (50 meters and 1 kHz respectively) that the experiment had to be readjusted. Measurements taken by the Altair incoherent scatter radar and the CUPRI 50 MHz coherent scatter radar indicate that although the bistatic hf channel is affected by the large scale plume structures, most of the 'damage' is done by the bottomside spread F.

Fitzgerald, T. J.; Argo, P. E.; Carlos, R. C.

363

Measurements of spatial and frequency coherence of an equatorial hf path during spread-F  

SciTech Connect

In August 1990, the authors set up an hf path on the equatorial path between Maloelap Atoll and Bikini Atoll. This path, which had a range of 702 km, reflected in the ionosphere approximately 100 km north of the Altair radar location on Kwajalein. Transmitters at Maloelap broadcasted four cw tones within bandwidth of either 4 kHz, 9 kHz, or 70 kHz to be used to determine frequency coherence and also a phase-coded pseudo random sequence with a bandwidth of 60 kHz (channel probe) to be used to determine time delay spread. A spatial array of antennas was deployed at Bikini to measure spatial and frequency coherence using the cw broadcasts. The system was run in the post-sunset time period over two weeks during which almost every night showed significant degradation due to spread F resulting in rapid fading, decreased spatial and frequency coherence, and increased time delay spread. Doppler spreads of greater than 20 Hz were not uncommon, and the spatial correlation distances and frequency coherence bandwidths became so small (50 meters and 1 kHz respectively) that the experiment had to be readjusted. Measurements taken by the Altair incoherent scatter radar and the CUPRI 50 MHz coherent scatter radar indicate that although the bistatic hf channel is affected by the large scale plume structures, most of the [open quotes]damage[close quotes] is done by the bottomside spread F.

Fitzgerald, T.J.; Argo, P.E.; Carlos, R.C.

1993-01-01

364

An experimental adaptive radar MTI filter  

NASA Astrophysics Data System (ADS)

The theoretical and practical features of a self-adaptive filter designed to remove clutter noise from a radar signal are described. The hardware employs an 8-bit microprocessor/fast hardware multiplier combination along with analog-digital and digital-analog interfaces. The software here is implemented in assembler language. It is assumed that there is little overlap between the signal and the noise spectra and that the noise power is much greater than that of the signal. It is noted that one of the most important factors to be considered when designing digital filters is the quantization noise. This works to degrade the steady state performance from that of the ideal (infinite word length) filter. The principal limitation of the filter described here is its low sampling rate (1.72 kHz), due mainly to the time spent on the multiplication routines. The methods discussed here, however, are general and can be applied to both traditional and more complex radar MTI systems, provided that the filter sampling frequency is increased. Dedicated VLSI signal processors are seen as holding considerable promise.

Gong, Y. H.; Cooling, J. E.

365

Theory of Adaptive Radar  

Microsoft Academic Search

This paper reviews the principles of adaptive radar in which both the spatial (antenna pattern) and temporal (Doppler filter) responses of the system are controlled adaptively. An adaptive system senses the angular-Doppler distribution of the external noise field and adjusts a set of radar parameters for maximum signal-to-interference ratio and optimum detection performance. A gradient technique for control of the

L. E. Brennan; L. S. Reed

1973-01-01

366

Statistical observations of the MLT, latitude and size of pulsed ionospheric flows with the CUTLASS Finland radar  

Microsoft Academic Search

A study has been performed on the occurrence of pulsed ionospheric flows as detected by the CUTLASS Finland HF radar. These flows have been suggested as being created at the ionospheric footprint of newly-reconnected field lines, during episodes of magnetic flux transfer into the terrestrial magnetosphere (flux transfer events or FTEs). Two years of both high-time resolution and normal scan

G. Provan; T. K. Yeoman

1999-01-01

367

Assessing 4D-VAR for dynamical mapping of coastal high-frequency radar in San Diego  

NASA Astrophysics Data System (ADS)

The problem of dynamically mapping high-frequency (HF) radar radial velocity observations is investigated using a three-dimensional hydrodynamic model of the San Diego coastal region and an adjoint-based assimilation method. The HF radar provides near-real-time radial velocities from three sites covering the region offshore of San Diego Bay. The hydrodynamical model is the Massachusetts Institute of Technology general circulation model (MITgcm) with 1 km horizontal resolution and 40 vertical layers. The domain is centered on Point Loma, extending 117 km offshore and 120 km alongshore. The reference run (before adjustment) is initialized from a single profile of T and S and is forced with wind data from a single shore station and with zero heat and fresh water fluxes. The adjoint of the model is used to adjust initial temperature, salinity, and velocity, hourly temperature, salinity and horizontal velocities at the open boundaries, and hourly surface fluxes of momentum, heat and freshwater so that the model reproduces hourly HF radar radial velocity observations. Results from a small number of experiments suggest that the adjoint method can be successfully used over 10-day windows at coastal model resolution. It produces a dynamically consistent model run that fits HF radar data with errors near the specified uncertainties. In a test of the forecasting capability of the San Diego model after adjustment, the forecast skill was shown to exceed persistence for up to 20 h.

Hoteit, I.; Cornuelle, B.; Kim, S. Y.; Forget, G.; Köhl, A.; Terrill, E.

2009-10-01

368

Ultrawideband imaging radar based on OFDM: system simulation analysis  

NASA Astrophysics Data System (ADS)

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.

Garmatyuk, Dmitriy

2006-06-01

369

Bio-impedance signal processing using adaptive digital filter  

Microsoft Academic Search

Bio-impedance evaluation is one of the medicine diagnostic methods for the evaluation of tissue perfusion. The bioimpedance on the patient's body surface is evaluated by analogue HF-vector Z-meter. The Z signal is converted into a digital form and further digitally processed and filtered. Spurious disturbing signals distorting the bio-impedance signal are suppressed by adaptive FIR filter.

Vaclav Papez; Stanislava Papezova

2011-01-01

370

Fiber optic coherent laser radar 3d vision system  

SciTech Connect

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.

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

1994-12-31

371

Solvability of some inverse problems in radar polarimetry  

NASA Astrophysics Data System (ADS)

It is well known that, in the course of ionospheric propagation, the polarization state of radar signals is changed between transmitter and target, and again between target and receiver. For HF skywave radars, these changes may vary spatially and temporally in a quasi-random manner. When one wishes to determine the scattering matrix of a target, the presence of these unknown polarization transformations changes the nature of the inverse problem connecting received echoes with target scattering characteristics. Indeed, it is by no means obvious that the inverse problem is solvable. In this paper we demonstrate that, under certain realistic conditions, the scattering matrix can be estimated in the presence of a priori unknown polarization transformations in the propagation medium.

Anderson, Stuart J.; Abramovich, Yuri I.; Boerner, Wolfgang-Martin

1997-12-01

372

Can OTH Radar Help Tsunami Monitoring?  

NASA Astrophysics Data System (ADS)

Ionospheric anomalies following 2004 Sumatra tsunami have been detected and reported in the scientific literature (e.g., Liu et al. 2006; DasGupta et al. 2006; Occhipinti et al. 2006). Similar anomalies were also observed after the tsunamigenic earthquake in Peru in 2001 (Artru et al., 2005) and after earthquakes in Sumatra and Chile in 2007. All these anomalies show the signature in the ionosphere of tsunami-generated internal gravity waves (IGW) propagating in the neutral atmosphere over oceanic regions. Most of these ionospheric anomalies are deterministic and reproducible by numerical modeling (Occhipinti et al., 2006, 2008; Mai and Kiang, 2009; Hickey et al. 2009) via the coupling mechanism between ocean, neutral atmosphere and ionosphere. In addition, the numerical modeling supplies useful helps in the estimation of expected anomalies and to explore and identify new techniques to detect the ionospheric tsunami signature, other than GPS and altimeters. Here we present an overview of the physical coupling mechanism and the simulation environment that we developed to assess the capabilities of Over-The-Horizon (OTH) radars to detect these ionospheric anomalies. We use a full 3D approach, including empirical models of neutral atmosphere and ionosphere. Synthetic radar measurements are computed using HF numerical ray-tracing. The large coverage of OTH radar and its sensitivity to plasma anomalies open new perspectives in the future oceanic monitoring and tsunami warning system. [Artru et al., 2005] Geophys. J. Int., 160, 2005 [DasGupta et al., 2006] Earth Planet. Space, 35, 929-959. [Liu et al., 2006] J. Geophys. Res., 111, A05303. [Occhipinti et al., 2006] Geophys. Res. Lett., 33, L20104, 2006 [Occhipinti et al., 2008] Geophys. J. Int., 173, 3, 753-1135, 2008. [Mai and Kiang, 2009] Radio Sci., 44, RS3011 [Hickey et al., 2009] J. Geoophys. Res., 114, A08304

Coïsson, P.; Occhipinti, G.; Rolland, L. M.; Lognonne, P.

2009-12-01

373

Use of a weather radar for the hydrology of a mountainous area. Part I: radar measurement interpretation  

NASA Astrophysics Data System (ADS)

This paper addresses rainfall radar measurement in mountainous areas where numerous catchments subject to flash flooding are located. The main sources of error affecting the quantitative use of weather radar data are examined with special attention paid to the influence of topography and altitude. A radar in a mountainous region is affected by specific measurement errors such as beam blockage; other sources of error like bright band interception can be enhanced by the effect of altitude. This work is based on data collected during the 86-88 Cévennes Experiment conducted in a mountainous Mediterranean region in the south of France prone to flash floods. Analysis of the main sources of error leads to the following observations. Beam blockage can be corrected using digital terrain models with the correction efficiency depending on the accuracy of the radar antenna pointing direction. The influence of vertical variations in radar reflectivity is shown to be taken into account at an hourly time step in order to provide satisfactory range-dependent corrections. Additionally, the control of the stability of the radar signal using strong ground clutter is described. Because of attenuation effects, the use of a 10-cm wavelength is recommended for surveying intense rain events which regularly affect Mediterranean regions. The error due to an unadapted Z-R relationship is shown to depend on the statistical distribution of reflectivity over the catchment where the rainfall measurement is utilized.

Andrieu, H.; Creutin, J. D.; Delrieu, G.; Faure, D.

1997-06-01

374

Bistatic Radar In Space A New Dimension In Imaging Radar  

Microsoft Academic Search

Based on a set of examples, this paper shows that bistatic space radar systems can have important capabilities for special imaging radar applications. It explains' the different categories of bistatic space radars as there are single orbit systems, crossing orbit systems, tethered systems and systems with geostationary\\/ge osynchronous transmitters (GEO-BISAR). It discusses the ideas of mixed systems, where aircrafts are

Hans Martin Braun; Philipp Hartl

1989-01-01

375

Studies on Radar and Non-radar Sensor Networks.  

National Technical Information Service (NTIS)

During the period of 12/1/2005--5/30/2006, we expanded our research from generic wireless sensor networks to radar sensor networks. For radar sensor networks, we performed the following preliminary studies: (1) Waveform design and diversity in radar senso...

Q. Liang

2006-01-01

376

33. Perimeter acquisition radar building room #320, perimeter acquisition radar ...  

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

33. Perimeter acquisition radar building room #320, perimeter acquisition radar operations center (PAROC), contains the tactical command and control group equipment required to control the par site. Showing spacetrack monitor console - Stanley R. Mickelsen Safeguard Complex, Perimeter Acquisition Radar Building, Limited Access Area, between Limited Access Patrol Road & Service Road A, Nekoma, Cavalier County, ND

377

Microphysical cross validation of spaceborne radar and ground polarimetric radar  

Microsoft Academic Search

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

V. Chandrasekar; Steven M. Bolen; Eugenio Gorgucci

2003-01-01

378

Passive coherent location radar demonstration  

Microsoft Academic Search

This paper describes a passive coherent location (PCL) radar system developed by Dynetics, Inc. This system uses commercial FM broadcast signals for the radar waveform. This paper presents a technical description of the system and performance data.

C. L. Zoeller; M. J. Moody

2002-01-01

379

Terahertz radar cross section measurements  

Microsoft Academic Search

We present the result of terahertz radar cross section measurements on various objects including models of aircraft fighters. Application of a time domain system provides both values of radar cross section and ranging information.

Krzysztof Iwaszczuk; Henning Heiselberg; Peter Uhd Jepsen

2010-01-01

380

CFAR detection for multistatic radar  

Microsoft Academic Search

A multistatic radar system with n transmitters and one receiver is modelled. Several CFAR algorithms for detection are introduced. The proposed CFAR detectors are simulated and the performances are compared with the performance of a monostatic radar of higher power.

Vahideh Amanipour; Ali Olfat

2008-01-01

381

First observations from the new Rankin Inlet SuperDARN radar at high northern latitudes  

NASA Astrophysics Data System (ADS)

We present initial results from a new SuperDARN HF radar which became operational on May 11, 2006, at Rankin Inlet. This is the first of a new radar pair called PolarDARN, with radars at Rankin Inlet and Inuvik. The PolarDARN radars are designed to regularly monitor the ionospheric convection over the entire northern polar cap region. The data are obtained and processed with the standard SuperDARN data analysis and retrieval procedures. Located at 73.2 magnetic latitude in the poleward portion of the auroral zone, the Rankin Inlet radar is ideally located to monitor the dynamics of the polar cap and the open-closed field line boundary. Our initial results were obtained during summer conditions, when the polar cap was fully illuminated, and while the solar cycle was near its minimum. For these conditions, we find that the echo occurrence exceeds that of similar radars placed at lower auroral latitudes. In the near-half of the radar field of view, the new Rankin Inlet radar detects large amounts of scatter throughout the day. The new radar clearly captures the anti-sunward convection pattern over the polar cap, and it reveals that the polar cap remains very dynamic even during extremely quiet solar wind/IMF conditions. Another feature to emerge is a narrow spectral width region in the night-side polar cap echoes. This offers a vivid contrast with the large spectral widths on the day-side in the cusp region and in the nightside auroral zone. The radar can also detect echoes simultaneously on both sides of the polar cap, and we present an example of simultaneous data from both the Canadian midnight sector and a region near the European afternoon sector.

St. Maurice, J.; Sofko, G. J.; Wiid, J.; Andre, D.; Koustov, A. V.; McWilliams, K. A.; Choudhary, R. K.; Drayton, R.; Hussey, G. C.; Greenwald, R. A.

2006-12-01

382

Effect of powerful oblique HF waves on ionospheric D-layer absorption  

NASA Astrophysics Data System (ADS)

A simple model of D-layer ionospheric heating in the presence of strong, high frequency (HF) radio waves is used to predict the anomalous, nonlinear wave absorption due to collisional and recombination effects induced by the indirect signal. It is found that little anomalous absorption occurs until effective radiated power (ERP) approaches 100 dBW; further increases in power of several dB beyond this 100 dBW threshold are frustrated by a comparable increase in self-induced, one-way absorption. This trend of increasing absorption with increasing transmitter ERP has considerable implications for design of communication or radar systems that use ultra-powerful, high-gain HF transmitters.

Bloom, R. M.

1993-04-01

383

The new AIS-INGV digital ionosonde  

Microsoft Academic Search

A new digital ionosonde called AIS-INGV (Advanced Ionospheric Sounder) was designed both for research and for routine service of HF radio wave propagation forecast. Nearly the entire system was developed in the Laboratorio di Geofi sica Ambientale at the Istituto Nazionale di Geofi sica e Vulcanologia (INGV), Rome. It exploits advanced techniques for signal analysis, recent technological devices and PC

Baskaradas James Arokiasamy

2003-01-01

384

Aviation Digital Data Service (ADDS)  

NSDL National Science Digital Library

The Aviation Digital Data Service (ADDS) makes available to the aviation community digital and graphical analyses, forecasts and observations of meteorological variables in the United States. Analyses, forecasts, and observations are available for turbulence, icing, convection, wind speed, and temperature. You can even select the altitude of interest. Satellite and radar images are also available. Java tools to help with the analysis of the maps provided are available for download. Developed as the data distribution component of the Aviation Gridded Forecast System (AGFS), ADDS is a joint effort of NOAA Forecast Systems Laboratory (FSL), NCAR Research Applications Program (RAP), and the National Centers for Environmental Prediction (NCEP) Aviation Weather Center (AWC).

385

Superconductor Digital-RF Receiver Systems  

Microsoft Academic Search

Digital superconductor electronics has been experiencing rapid maturation with the emergence of smaller-scale, lower-cost communications applications which became the major technology drivers. These applications are primarily in the area of wireless communications, radar, and surveillance as well as in imaging and sensor systems. In these areas, the fundamental advantages of superconductivity translate into system benefits through novel Digital-RF architectures with

Oleg A. Mukhanov; Dmitri Kirichenko; Igor V. Vernik; Timur V. Filippov; Alexander Kirichenko; Robert Webber; Vladimir Dotsenko; Andrei Talalaevskii; Jia Cao Tang; Anubhav Sahu; Pavel Shevchenko; Robert Miller; Steven B. Kaplan; Saad Sarwana; Deepnarayan Gupta

2008-01-01

386

The Clementine Bistatic Radar Experiment  

Microsoft Academic Search

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

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

1996-01-01

387

Scanning ARM Cloud Radar Handbook.  

National Technical Information Service (NTIS)

The scanning ARM cloud radar (SACR) is a polarimetric Doppler radar consisting of three different radar designs based on operating frequency. These are designated as follows: (1) X-band SACR (X-SACR); (2) Ka-band SACR (Ka-SACR); and (3) W-band SACR (W-SAC...

K. Johnson K. Widener N. Bharadwaj

2012-01-01

388

The Venus Radar Mapper mission  

Microsoft Academic Search

The Venus Radar Mapper (VRM) mission is sponsored by NASA to put a single spacecraft in orbit around Venus to map the surface using a synthetic aperture mapping radar. This paper describes the VRM mission at its present state of design. The science objectives and project constraints are described. Key features of the spacecraft system and radar system are discussed.

E. Cutting; J. H. Kwok; S. N. Mohan

1984-01-01

389

Interception of LPI radar signals  

Microsoft Academic Search

Most current radars are designed to transmit short duration pulses with relatively high peak power. These radars can be detected easily by the use of relatively modest EW intercept receivers. Three radar functions (search, anti-ship missile (ASM) seeker, and navigation) are examined to evaluate the effectiveness of potential low probability of intercept (LPI) techniques, such as waveform coding, antenna profile

Jim P. Lee

1991-01-01

390

A radar tour of Venus  

Microsoft Academic Search

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

J. K. Beatty

1985-01-01

391

Radar model with terrain effects  

NASA Astrophysics Data System (ADS)

This thesis presents a novel naval radar model which computes radar detection in the presence of land masses. The model is an interactive computer program which accepts scenarios and radar parameters from the user and displays a map of the area indicating where targets can and cannot be detected. The resulting map can be displayed at the user's computer terminal or printed offline.

Meritt, J. W.

1982-03-01

392

Studies on Radar Sensor Networks.  

National Technical Information Service (NTIS)

During the period of 12/8/2006-6/30/2007, we performed the following studies in radar sensor network: (1) Sense-through-foliage target detection using UWB radar sensor network based on real-world data; (2) Foliage clutter modeling using UWB radars; (3) Ou...

Q. Liang

2007-01-01

393

Pulse-Doppler UWB Radar  

Microsoft Academic Search

The paper contains measurement results of moving targets by pulse-Doppler UWB radar. The description of a radar, principle of operation and technical specification are presented. Conditions and results of measurements are described. Feature of the presented measurements: Doppler signals of linear moving targets whose linear sizes exceed resolution of radar

A. Chernenko; E. Ziganshin

2006-01-01

394

Millimeter Radar Sea Return Study.  

National Technical Information Service (NTIS)

A site selection process was performed for a planned field exercise to measure radar sea clutter reflectivity at low grazing angles using several radar frequencies between 9.5 and 95 GHz. A detailed test plan was developed to collect calibrated radar cros...

R. N. Trebits

1979-01-01

395

Polarimetric Monopulse Radar Intelligent Emulator  

Microsoft Academic Search

For debugging polarimetric monopulse radar and testing polarization algorithms, a new polarimetric monopulse radar intelligent emulator is proposed and designed in this paper. The polarization information, as a basic character of the target echo, plays an important role in modern radar detection nowadays. The polarization algorithms are developed with rapid speed. It is not realistic to test all algorithms on

Jin Tao; Qi Xiaohui; Yuan Shuqing; Qiao Xiaolin; Zhang Min; Zhang Qunxing

2007-01-01

396

Synthetic Aperture Radar Signals: Formulations and Approaches for Data Analysis.  

National Technical Information Service (NTIS)

This report discusses principles of synthetic aperture radar, properties of radar targets, characteristics of radar imagery, statistical analysis of radar imagery, and the application of modern data analysis.

A. B. Lucero P. Swerling L. Breiman

1975-01-01

397

Instrumental Principles of MST Radars and Incoherent Scatter Radars and the Configuration of Radar System Hardware.  

National Technical Information Service (NTIS)

The principle of pulse modulation used in the case of coherent scatter radars (MST radars) is discussed. Coherent detection and the corresponding system configuration is delineated. Antenna requirements and design are outlined and the phase-coherent trans...

J. Roettger

1989-01-01

398

Coherent IR radar technology  

NASA Astrophysics Data System (ADS)

Recent progress in the development of coherent IR radar equipment is reviewed, focusing on the Firepond laser radar installation and the more compact systems derived for it. The design and capabilities of Firepond as a long-range satellite-tracking device are outlined. The technological improvements necessary to make laser radar mobile are discussed: a lightweight, stable 5-10-W transmitter laser for both CW and pulsed operation, a 12-element HgCdTe detector array, an eccentric-pupil Ritchey-Chretien telescope, and a combination of near-field phase modification and anamorphic expansion to produce a fan beam of relatively uniform intensity. Sample images obtained with a prototype system are shown, and the applicability of the mobile system to range-resolved coherent DIAL measurement is found to be similar to that of a baseline DIAL system.

Gschwendtner, A. B.; Harney, R. C.; Hull, R. J.

399

Ground based radar  

NASA Astrophysics Data System (ADS)

The current state of turmoil in the world of ballistic missile technology dictates that the U.S. be prepared to deal with a growing ballistic missile threat. To meet this challenge the U.S. Army is developing a new family of ground based radar to support both the Theater Missile Defense and the Strategic Defense Initiatives. This class of radar provides affordable, reliable tracking and discrimination based on mature technology and commonality of design. The commonality of design concept uses technology and components that can be scaled in number, size, and capability. This approach allows ground based radar to support the near term requirements of both tactical and strategic defense and also provide flexibility for more sophisticated future threats.

Ryan, William W.

400

HF equipment: Receivers, transmitters, synthesizers, and peripherals  

Microsoft Academic Search

Although long distance communications via satellites has dominated the last two decades of radio equipment development, high frequency (HF) radio equipment is experiencing a high technology renaissance. Satellite systems now transmit quality low data rate communications and navigation aids to mobile users, but the low cost and surviability attributes of HF radio are again being recognized. Emerging new systems automate

Q. C. Wilson

1983-01-01

401

Uninterrupted power supply with intermediate HF circuit  

Microsoft Academic Search

Contents This work presents an uninterrupted monophase power supply with IGBT transistors and HF intermediate circuit. Two three-phase UPS circuits with intermediate HF circuit are also presented, based on the suggested control method. All the suggested versions are characterized by small dimensions and a high fundamental content (0,995) of the alternating output voltages.

D. Alexa; M. Florea

1992-01-01

402

Flashlight radar: A three-dimensional imaging radar  

NASA Astrophysics Data System (ADS)

In support of several programs at Lincoln Laboratory, a small focused-beam polarimetric, millimeter-wave radar scatterometer (an instrument for measuring radar cross section) has been developed. An overview of the design of this Flashlight Radar is presented. Theoretical and empirical studies of antenna performance are discussed. The backscatter theory relating to the characteristics of the Flashlight Radar as a scatterometer is presented, and experimental RCS measurements are compared with theoretical predictions. The data processing steps (polarimetric calibration and compensation, signal processing, and image formation) are described. We show the results of two representative experiments using the Flashlight Radar. The first is a measurement of dihedral and trihedral reflectors with and without radar camouflage. The second is a faster scan of a truck tire, highlighting the radar's fine resolution and its ability to collect three-dimensional data.

Blejer, Dennis J.; Ferranti, Richard L.; Barnes, Richard M.; Irving, William W.; Verbout, Shawn M.

1989-08-01

403

Radar detection of phobos.  

PubMed

Radar echoes from the martian satellite Phobos provide information about that object's surface properties at scales near the 3.5-cm observing wavelength. Phobos appears less rough than the moon at centimeter-to-decimeter scales. The uppermost few decimeters of the satellite's regolith have a mean bulk density within 20% of 2.0 g cm(-3). The radar signature of Phobos (albedo, polarization ratio, and echo spectral shape) differs from signatures measured for small, Earth-approaching objects, but resembles those of large (>/=100-km), C-class, mainbelt asteroids. PMID:17847261

Ostro, S J; Jurgens, R F; Yeomans, D K; Standish, E M; Greiner, W

1989-03-24

404

Threat radar system simulations  

NASA Astrophysics Data System (ADS)

The capabilities, requirements, and goals of radar emitter simulators are discussed. Simulators are used to evaluate competing receiver designs, to quantify the performance envelope of a radar system, and to model the characteristics of a transmitted signal waveform. A database of candidate threat systems is developed and, in concert with intelligence data on a given weapons system, permits upgrading simulators to new projected threat capabilities. Four currently available simulation techniques are summarized, noting the usefulness of developing modular software for fast controlled-cost upgrades of simulation capabilities.

Miller, L.

405

Wavelets and impulse radar  

NASA Astrophysics Data System (ADS)

The signal generated by avalanche discharge circuitry that drives optical flash for cameras is ultra wideband and suitable as the excitation waveform for an Impulse Radar when transmitted through an appropriate antenna. In this paper, we experimentally and theoretically show that the Impulse Radar's radiated transmitted EM waves satisfy the admissibility condition of wavelets, i.e. (i) a finite power spectral density psd=<|S(f)|2>< and (ii) zero total area under the undulated wave amplitudes. If the radiated environment is linear (the natural scene), then the received signal also satisfies the admissibility condition.

Szu, Harold; Hsu, Charles; Scheff, Kim; Hansen, Peter; Willey, Jeff

2009-04-01

406

Development of a SAR digital system  

Microsoft Academic Search

A data acquisition system for an airborne SAR (Synthetic Aperture Radar) was designed and implemented. DSP is used for the first time in the implementation of a SAR data acquisition system. A novel precision programmable timer using the DDS (Direct Digital Synthesis) technique was designed, built, and successfully tested to provide increased flexibility, reliability and stability

T. S. Yeo; C. B. Zhang; Y. H. Lu; T. Ren

1999-01-01

407

Data acquisition system for Doppler radar vital-sign monitor.  

PubMed

Automatic gain control (AGC) units increase the dynamic range of a system to compensate for the limited dynamic range of analog to digital converters. This problem is compounded in wireless systems in which large changes in signal strength are effects of a changing environment. These issues are evident in the direct-conversion Doppler radar vital-sign monitor. Utilizing microwave radar signals reflecting off a human subject, a two-channel quadrature receiver can detect periodic movement resulting from cardio-pulmonary activity. The quadrature signal is analyzed using an arctangent demodulation that extracts vital phase information. A data acquisition (DAQ) system is proposed to deal with issues inherent in arctangent demodulation of a quadrature radar signal. PMID:18002443

Vergara, Alexander M; Lubecke, Victor M

2007-01-01

408

A study on Ganymede's surface topography: Perspectives for radar sounding  

NASA Astrophysics Data System (ADS)

Radar sounding of Jovian icy satellites has great potential to address specific science questions such as the presence of subsurface liquid water. Radargrams acquired over Mars polar caps allow observing clear echoes up to kilometers depth. However, Jovian icy satellites display dramatically different surface topographies. In order to assess possible issues arising from such surface topographies on radar sounding, we performed a study on different DEMs (Digital Elevation Models) obtained on Ganymede. Topographic data are derived using stereo and photoclinometric analysis of Galileo and Voyager images at resolutions of 16-629 m. Main results are presented in this paper. Overall we found that Ganymede's surface is quite rough, with mean slopes at 630 m scale varying from 3.5° to 8°, smoothest terrains being found within sulcii. This will be a major challenge for the design of radar sounders and parameters should be chosen accordingly in order to correctly sound this planetary body. Previous studies have shown similar concern for Europa.

Berquin, Y.; Kofman, W.; Herique, A.; Alberti, G.; Beck, P.

2013-03-01

409

Development of land based radar polarimeter processor system  

NASA Astrophysics Data System (ADS)

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.

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

1983-09-01

410

Detection of objects buried in wet snowpack by an FM-CW radar  

Microsoft Academic Search

A real-aperture FM-CW radar system was developed for the detection of objects buried in heavily wet snowpack. This radar uses the L-band microwave frequency with a maximum output power of 100 mW and utilizes digital signal processing techniques. A laboratory simulation and two field experiments were carried out to detect and map various objects embedded in the snowpack. It was

Yoshio Yamaguchi; Yasuichi Maruyama; Atsushi Kawakami; M. Sengoko; Takeo Abe

1991-01-01

411

Human body detection in wet snowpack by an FM-CW radar  

Microsoft Academic Search

An FM-CW radar system was applied to detect a human body buried in a very wet snowpack. This radar uses the L-band microwave frequency with a maximum output power of 100 mW, and utilizes digital signal processing techniques. Field experiments were carried out to detect and map a human body embedded at a depth of 125 cm in a natural

Yoshio Yamaguchi; Masashi Mitsumoto; Masakazu Sengoku; Takeo Abe

1992-01-01

412

Thickness profiling of freshwater ice using a millimeter-wave FM-CW radar  

Microsoft Academic Search

A prototype broadband millimeter wave (26.5 to 40 GHz) FM-CW radar employing digital signal processing techniques has been developed for profiling the thickness of freshwater ice. The radar was tested at elevations of up to 7 m above ice surfaces and at speeds up to 40 km\\/h both from a surface vehicle and a helicopter. The thickness of pond and

Norbert E. Yankielun; Steven A. Arcone; Robert K. Crane

1992-01-01

413

Implementation of radar CFAR-based target detection algorithm in a real-time multiprocessor environment  

Microsoft Academic Search

The implementation of radar CFAR-based target detection algorithm in a real-time multiprocessor environment is presented. For this purpose, a radar extractor has been developed. Two digital signal processors (DSPs), installed on a target board are used, with a PC computer as a host. The complete detection algorithm is divided into two parts and is being executed in real-time on the

D. D. Dimitrijevic; Miroslav M. Petrovic; Marko G. Hrasovec; Bozidar V. Damnjanovic

2001-01-01

414

Programmable AND-CFAR signal detector design and its FPGA prototyping for FMCW radar systems  

Microsoft Academic Search

This paper presents the digital signal processor design for constant-false-alarm-rate (CFAR) signal detection in a frequencymodulated-continuous-waveform (FMCW) radar system. It is capable of identifying the beat signal from the spectrum so as to calculate the distance between the radar and the ground. The proposed CFAR signal detection design is an enhancement of the basic AND-CFAR architecture, which combines the algorithms

Cheng-Ru Hong; Yin-Tsung Hwang; Wei-Chieh Hsu; Chi-Ho Chang; Jui-Chi Huang; Ho-En Liao

2011-01-01

415

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

416

A fully integrated 24GHz UWB radar sensor for automotive applications  

Microsoft Academic Search

Radar-based advanced safety systems are crucial to reduce road accidents caused by driver inattention. An actual and pervasive adoption of radar technology requires the development of low-cost Silicon-integrated sensors, including microwave, analog, and digital blocks on a single chip, able to replace existing discrete electronics based on compound semiconductors. Indeed, the considerable advantage of silicon lies in its natural capability

E. Ragonese; A. Scuderi; V. Giammello; E. Messina; G. Palmisano

2009-01-01

417

Collaborative experiments by Akebono satellite, Tromso ionospheric heater, and European incoherent scatter radar  

Microsoft Academic Search

Joint experiments using the Akebono satellite and the ionospheric heating facility and European incoherent scatter radar near Tromso were carried out in November 1990 and February 1991. In these experiments, Tromso HF transmissions were amplitude modulated at frequencies of 2.5 and 4.0 kHz. Signals radiated from the polar electrojet (PEJ) antenna in the heated ionosphere at these VLF frequencies were

I. Kimura; P. Stubbe; M. T. Rietveld; R. Barr; K. Ishida; Y. Kasahara; S. Yagitani; I. Nagano

1994-01-01

418

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

PubMed Central

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.

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

2013-01-01

419

Bistatic synthetic aperture radar  

Microsoft Academic Search

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

A. M. Horne; G. Yates

2002-01-01

420

Heat Resistant Radar Absorber.  

National Technical Information Service (NTIS)

A foamed ceramic slab is bonded to the three-layer polyimide RAM substrate to produce a radar absorbed capable of at least 10db absorptivity of the range 3 to at least 10 GHZ and of withstanding very high temperatures, for example, 3000 F for 80 seconds o...

W. P. Manning W. T. Passiuk

1978-01-01

421

Goldstone solar system radar  

Microsoft Academic Search

Information is provided about physical nature planetary surfaces and their topography as well as dynamical properties such as orbits and spin states using ground based radar as a remote sensing tool. Accessible targets are the terrestrial planets: the Earth's Moon, Mercury, Venus and Mars, the outer planets rings and major moons, and many transient objects such as asteroids and comets.

R. F. Jurgens; P. E. Clark; R. M. Goldstein; S. J. Ostro; M. A. Slade; T. W. Thompson; R. S. Saunders

1986-01-01

422

Airborne firefinder radar concept  

Microsoft Academic Search

An airborne firefinder radar (AFFR) is suggested for an upgraded version of the forthcoming Global Hawk Unmanned Aerial Vehicle (UAV). The AFFR could detect an artillery shell within 1 second of firing and, within a few seconds, determine its trajectory origin location (position of the gun) to a circular error probable (CEP) of less than 50 meters. The AFFR could

R. J. Sullivan; J. F. Nicoll; J. M. Ralston

1998-01-01

423

Doppler Radar System.  

National Technical Information Service (NTIS)

The radar system is utilized to guide a fused guided missile to an aircraft target. The secondary doppler effects are utilized between a moving object and a secondary reflecting surface to detect the presence of the object and indicate its point of closes...

A. E. Resnik

1964-01-01

424

Mars 96 subsurface radar  

Microsoft Academic Search

The Mars 96 International Scientific Mission to launch an aerostat that will drift in the Martian atmosphere for ten days is described. The stabilizing element of the aerostat (guiderope) will be dragged on the Martian surface every night. A ground penetrating radar will be installed within the guiderope. Its external surface will act as a transmit and receive antenna. A

Y. Barbin; W. Kofman; M. Elkine; M. Finkelstein; V. Glotov; V. Zolotarev

1991-01-01

425

Passive Radar Tracking Apparatus.  

National Technical Information Service (NTIS)

The radar system tracks a target whether it generates a signal of its own or not and may be used to sense noise energy radiated by the sun, other objects, or other celestial bodies. The system includes an antenna assembly of four horns arranged in a recta...

D. K. Barton W. J. Rose

1965-01-01

426

Comet radar explorer  

Microsoft Academic Search

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

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

2010-01-01

427

Pulse Doppler radar waveforms  

Microsoft Academic Search

Modern military airborne radars are highly sophisticated, multi-mode systems which are required to detect difficult targets in all aspects and over a large range\\/velocity detection space. There are particular difficulties associated with the airborne case such as the limited antenna aperture, high platform velocity and severe clutter levels which present difficult waveform design challenges. This tutorial will consider the design

C. M. Alabaster

2010-01-01

428

Laser Radar Development.  

National Technical Information Service (NTIS)

A range-gated imaging (RGI) laser radar system was constructed and field-tested at the Chesapeake Bay Division of the Naval Research Laboratories to evaluate the capability of RGI systems to provide extremely high contrast image displays. The system emplo...

J. A. Jenney

1968-01-01

429

Laser Imaging Radar System.  

National Technical Information Service (NTIS)

The simplicity, compactness, and reasonable cost of direct detection diode-laser range finders provide incentive for their use in laser imaging radar systems (LIRS). Efforts have been made to increase range performance of a diode-laser range finder by mea...

S. P. Yun R. A. Olson

1993-01-01

430

Stepped frequency ground penetrating radar  

DOEpatents

A stepped frequency ground penetrating radar system is described comprising an RF signal generating section capable of producing stepped frequency signals in spaced and equal increments of time and frequency over a preselected bandwidth which serves as a common RF signal source for both a transmit portion and a receive portion of the system. In the transmit portion of the system the signal is processed into in-phase and quadrature signals which are then amplified and then transmitted toward a target. The reflected signals from the target are then received by a receive antenna and mixed with a reference signal from the common RF signal source in a mixer whose output is then fed through a low pass filter. The DC output, after amplification and demodulation, is digitized and converted into a frequency domain signal by a Fast Fourier Transform. A plot of the frequency domain signals from all of the stepped frequencies broadcast toward and received from the target yields information concerning the range (distance) and cross section (size) of the target.

Vadnais, Kenneth G. (Ojai, CA); Bashforth, Michael B. (Buellton, CA); Lewallen, Tricia S. (Ventura, CA); Nammath, Sharyn R. (Santa Barbara, CA)

1994-01-01

431

The Fadeogram, A Sonogram-Like Display of the Time-Varying Frequency Response of HF-SSB Radio Channels  

Microsoft Academic Search

A method is presented for displaying the time-varying transfer characteristic of communication channels, and is illustrated by showing in detail the behavior of an HF-SSB radio channel during one minute periods, under the various fading characteristics classified by USAEL. It is also demonstrated how this method aided study of the causes of errors in data received by digital modems.

J. Filter; B. Arazi; R. Thomson

1978-01-01

432

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

Microsoft Academic Search

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.

G. Porter

1968-01-01

433

Ice Penetrating Radar Sounding Over Glaciers in Alaska and Greenland  

NASA Astrophysics Data System (ADS)

Using low-frequency (1-5 MHz) ice penetrating radar, we have measured the thickness of "warm" ice over outlet glaciers in Alaska and Greenland. The radar mainly consists of control software for National Instrument (NI) boards, a custom-made transmitter, a receiver, and an antenna towed at the back of an airplane. The radar can operate with either a short or a chirp exciter pulse. The same antenna receives echoes bounced from the surface and sub-surface ice layers. The echoes are digitized after being passed through a band-pass filter. We have run the radar in burst mode so that there is no pulse in air while receiving the echoes. To make a radar sounder image, multiple bursts are vertically stacked together in a 2-dimensional format named as echogram. The horizontal axis corresponds to aircraft motion, while the vertical axis corresponds to the arrival time inside a burst. Because the transmitted signal is reflected from various interfaces at different distances, the received echo has multiple peaks. The earliest and strongest peak is caused by the interface between the atmosphere and ice surface. It is very sharp for a flat surface, while becoming diffusive and relatively weak for a rough or sloped surface. After the initial rise, more complex and weak echoes follow. These are caused by various sources such as subsurface deposits, discontinuities in dielectric layers, and, most often, off-nadir surface reflections called surface clutter. We have applied an omega-k method to reduce the along-track surface clutter and thereby enhance the sub-surface features. In this way, we have been able to see 1.5 km deep ice bed at Jakobshavn glacier in Greenland and about 1 km deep glacier bed at Bering Glacier in Alaska. This radar is still in the development and improvement stage, and is expected to continue providing complementary data to existing airborne radar sounders.

Gim, Y.; Safaeinili1, A.; Rignot, E.; Kirchner, D.; Robison, W.

2008-12-01

434

EISCAT Incoherent Scatter Radars Probing High-Latitude Near-Earth Geospace for the EURIPOS Proposal  

NASA Astrophysics Data System (ADS)

EISCAT Scientific Association operates currently three incoherent scatter radars in Northern Scandinavia on behalf of its associate members in Finland, China, Germany, Japan, Norway, Sweden and United Kingdom, as well as currently supporting partners in France and Russia. The radar sites include transmitter/receiver site in Tromsø, Norway with a monostatic VHF radar and a tristatic UHF radar transmitter/receiver, UHF receiver sites in Kiruna, Sweden and Sodankylä, Finland and a 2-dish monostatic radar in Longyearbyen, Svalbard. Incoherent scatter radar method is known to be the most sophisticated radio method to remotely sense the ionosphere. The standard parameters analysed from the recorded scattered signals are the electron density, electron temperature, ion temperature, line-of-sight plasma velocity, ion-neutral collision frequency and ion mass. With more assumptions also information for example on neutral density and temperature, neutral velocity, Pedersen and Hall conductivities, electric current density and heat flux is available. Current applications of the radars include also interferometric applications for small-scale structures, mapping of meteroid orbits and monitoring space debris, as well as high-resolution mapping the radar reflectivity of the Moon surface. In addition to incoherent scatter radars, EISCAT also has a powerful HF heating facility for ionospheric modification experiments, and a dynasonde in Tromsø, as well as another dynasonde in Svalbard for routine ionospheric observations. All the current EISCAT facilities would serve the EURIPOS proposal quantifying the ionospheric variability and response to space weather events at high latitudes. Although the main ISR facilities cannot be run continuously, regular Common Programmes, measurement campaign modes - especially combined with coordinated satellite observations and specific model studies, and the continuous operation of supporting dynasondes, would greatly enhance the EURIPOS proposal. EISCAT real-time analysis of data is available and all measured data is accessible to researchers via the Madrigal database. In the near future, unprecedented science and technology application opportunities will open up with the construction of the new EISCAT 3D radar arrays. The new multiple site phased-array radar has a design goal of ten times higher temporal and spatial resolution than the present radars, a volumetric radar imaging capability in an extended spatial area with simultaneous full-vector drift velocities, avoiding spatial and temporal ambiguities, having continuous operation modes, short baseline interferometry capability for imaging sub-beamwidth scales, real-time data access for applications and extensive data archiving facilities. Some arrays are very large, in the scale of 30 000 individual antenna elements. The first design study is to be finished in 2009 and a modular construction of the facility would provide first measurements in 2013-2015.

Turunen, E.

2009-04-01

435

51. View of upper radar scanner switch in radar scanner ...  

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

51. View of upper radar scanner switch in radar scanner building 105 from upper catwalk level showing emanating waveguides from upper switch (upper one-fourth of photograph) and emanating waveguides from lower radar scanner switch in vertical runs. - 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

436

HF (High Frequency) absolute time of arrival sensing  

NASA Astrophysics Data System (ADS)

In late 1980 questions arose concerning whether the ionosphere was sufficiently stable to allow precisely measured time of arrival of skywave signals to be used for geolocation in the high frequency (HF) band between 2 and 32 MHz. The chief limitation in the accuracy of this type of system is the amount of uncertainty in the ionospheric height estimation and its temporal stability. Traditional ionospheric research resources did not address the issue in sufficient detail and time resolution to be of any assistance. In order to understand the exact nature of the ionospheric uncertainties and to quantify their extent, experimentation was proposed to sense the variation in the refraction height of the ionosphere as it relates to the time of arrival of the HF signal. The objective of this work was to determine the range of environmentally induced errors in a skywave Time Difference of Arrival (TDOA) measurement, thereby bounding the ultimate geolocation accuracy one could expect from this technique. The first experimental measurement system started operation in early 1981. This effort involved establishing a continuous absolute Time of Arrival (TOA) experiment over the one-hop midlatitude path between San Diego, California and Fort Collins, Colorado. The system is fully digital and stabilized with a cesium beam standard. This work was supplemented with vertical incidence sounder data at both ends of the path, a collateral Doppler sensing system, and coincident satellite solar data.

Rose, R. B.

1986-02-01

437

A 3D digital terrain model oriented to design a clutter predictor for the Mexican Republic  

Microsoft Academic Search

The variation of rainfall intensity with height makes mandatory to look at the rainfall as close to the ground as possible, when scanning the atmosphere by means of weather radars. Weather radar measurements contain many errors, which reduce the quality of the rainfall data. In particular, ground clutter has a strong relationship with the beam elevation angle and the Digital

E. Gonzalez-Ramirez; I. D. Cluckie; Margarita Tecpoyotl-Torres; M. A. Rico-Ramirez; G. Cerda-Villafana; Jesus Escobedo-Alatorre; Jose Javier Sanchez-Mondragon

2004-01-01

438

Application of SEASAT-1 Synthetic Aperture Radar (SAR) Data to Enhance and Detect Geological Lineaments and to Assist Landsat Landcover Classification Mapping.  

National Technical Information Service (NTIS)

Digital SEASAT-1 synthetic aperture radar (SAR) data were used to enhance linear features to extract geologically significant lineaments in the Appalachian region. Comparison of Lineaments thus mapped with an existing lineament map based on LANDSAT MSS im...

R. Sekhon

1981-01-01

439

Demonstration of HF Chain Reaction Laser.  

National Technical Information Service (NTIS)

A theoretical and experimental investigation was conducted to evaluate the performance potential of the HF/DF chain reaction laser. The program consisted of: theoretical calculations to aid in the selection of design conditions and laser operating conditi...

C. E. Kepler T. J. Sadowski R. Roback R. A. Meinzer

1974-01-01

440

Shuttle radar topography mapper (SRTM)  

NASA Astrophysics Data System (ADS)

The use of interferometric SAR (IFSAR) to measure elevation is one of the most powerful and promising capabilities of radar. A properly equipped spaceborne IFSAR system can produce a highly accurate global digital elevation map, including cloud-covered areas, in significantly less time and at significantly lower cost than with other systems. For accurate topography, the interferometric measurements must be performed simultaneously in physically sperate receive system, since measurements made at different times with the same system suffer significant decorrelation. The US/German/Italian spaceborne imaging radar C/X-band SAR (SIR-C/X-SAR), successfully flown twice in 1994 aboard the Space Shuttle Endeavor, offers a unique opportunity for global multifrequency elevation mapping by the year 2000. With appropriate augmentation, SIR-C/X-SAR is capable of producing an accurate elevation map covering 80 percent of the Earth's land surface in a single 10-day Shuttle flight. The existing US SIR-C SCANSAR mode provides a 225-km swath at C-band, which makes this coverage possible. Addition of a C-band receive antenna, extended from the Shuttle bay on a mast and operating in concert with the existing SIR-C antenna, produces an interferometric pair. Accuracy is enhanced by utilizing the SIR-C dual polarizations simultaneously to form separate SCANSAR beams. Due to the practical limitation of approximately 60 meters for the mast length, the longer SIR-C L-band wavelength does not produce useful elevation measurement accuracy. IFSAR measurements can also be obtained by the German/Italian X-SAR, simultaneously with SIR-C, by utilizing an added outboard antenna at X-band to produce a swath coverage of about 50 km. Accuracy can be enhanced at both frequencies by processing both ascending and descending data takes. It is estimated that the 90 percent linear absolute elevation error achievable is less that 16 meters for elevation postings of 30 meters. This will be the first use of spaceborne IFSAR to acquire accurate topographic data on a global scale.

Jordan, Rolando L.; Caro, Edward R.; Kim, Yunjin; Kobrick, Michael; Shen, Yuhsyen; Stuhr, Frederick V.; Werner, Marian U.

1996-12-01

441

Intermolecular Vibration-to-Vibration Energy Transfer in HF/DF(v=1) + HF/DF(v=1) yields HF/DF(v=0) + HF/DF(v=2) through the Formation of Dimers.  

National Technical Information Service (NTIS)

A theory of vibration-to-vibration energy transfer is developed for HF/DF(V=1) + HF/DF(V=1) yeilds HF/DF(V=0) + HF/DF(V=2) based on the model of dimer formation. This model is shown to be primarily responsible for the energy transfer below 500 K where a s...

H. K. Shin

1974-01-01

442

Improving intrusion detection radar  

Microsoft Academic Search

The first monostatic microwave intrusion detection sensor with range cutoff was introduced in 1984. This range cutoff circuit as used in the Model 375 and 385 has proven very effective in preventing nuisance alarms beyond a user-defined range. The Intrepid Digital Transceiver introduced in this paper builds upon this proven technology with the addition of a unique digital signal processing

E. Foley; K. Harman; J. Cheal

2002-01-01

443

An OTH radar clutter simulation  

NASA Astrophysics Data System (ADS)

A computer simulation is described which was developed with the objective of arriving at an understanding of OTH radar clutter originating in the equatorial ionosphere. This source of clutter is of particular interest in OTH radar, since all radar propagation paths must pass through the equatorial region, even if the desired targets are far removed from it. A central feature of the simulation is an ionospheric propagation model developed to synthesize OTH radar clutter by making use of state-of-the art models for global ionospheric structure, including small-scale irregularities, and combining these with efficient ray tracing procedures and a multiple phase-screen approach to computing the diffraction of radar energy by the irregular ionosphere. Simulated clutter data is compared to actual measurements using several radars, with generally satisfactory results.

Providakes, J.; Elkins, T. J.; Godwin, R. B.; Kelley, M. C.

1991-12-01

444

High spatial and temporal resolution observations of an impulse-driven field line resonance in radar backscatter artificially generated with the Tromsø heater  

Microsoft Academic Search

The CUTLASS Finland HF radar has been operated in conjunction with the EISCAT Tromsø RF ionospheric heater facility to examine a ULF wave characteristic of the development of a field line reso- nance (FLR) driven by a cavity mode caused by a magnetospheric impulse. When the heater is on, stria- ting the ionosphere with field-aligned ionospheric elec- tron density irregularities,

T. K. Yeoman; D. M. Wright; T. R. Robinson; J. A. Davies; M. Rietveld

1997-01-01

445

Super Dual Auroral Radar Network observations of fluctuations in the spectral distribution of near range meteor echoes in the upper mesosphere and lower thermosphere  

Microsoft Academic Search

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

N. F. Arnold; T. R. Robinson; M. Lester; P. B. Byrne; P. J. Chapman

2001-01-01

446

Radar Experiments Data Reduction, and Experimental Tests.  

National Technical Information Service (NTIS)

Work performed included software support for the evaluation and development of advanced radar antenna systems, development and maintenance of target identification databases, and the data reduction of raw radar data from field tests. Keywords: Radar anten...

W. O. Loescher

1990-01-01

447

Efficient nonchain discharge HF and DF lasers  

Microsoft Academic Search

Discharge and laser parameters in mixtures of SF6 with H2 and D2 are studied using inductive and LC-generators. Excitation pulse parameters providing ultimate performance of discharge non-chain HF- and DF-lasers are determined. Processes affecting efficiency of the lasers are discussed. Ultimate intrinsic efficiency etaint of the HF and DF lasers up to 10% and 7%, respectively, was realized in the

Victor F. Tarasenko; Alexei N. Panchenko; Viktor M. Orlovskii

2004-01-01

448

Advances in HF parallel tone modem technology  

Microsoft Academic Search

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

G. J. Luhowy

1988-01-01

449

Floor-plan radar  

NASA Astrophysics Data System (ADS)

Urban-warfare specialists, law-enforcement officers, counter-drug agents, and counter-terrorism experts encounter operational situations where they must assault a target building and capture or rescue its occupants. To minimize potential casualties, the assault team needs a picture of the building's interior and a copy of its floor plan. With this need in mind, we constructed a scale model of a single- story house and imaged its interior using synthetic-aperture techniques. The interior and exterior walls nearest the radar set were imaged with good fidelity, but the distal ones appear poorly defined and surrounded by ghosts and artifacts. The latter defects are traceable to beam attenuation, wavefront distortion, multiple scattering, traveling waves, resonance phenomena, and other effects not accounted for in the traditional (noninteracting, isotropic point scatterer) model for radar imaging.

Falconer, David G.; Ueberschaer, Ronald M.

2000-07-01

450

Ultrawideband radars: Features and capabilities  

Microsoft Academic Search

Features of ultrawideband (UWB) radars, which radiate signals whose spatial duration is substantially smaller than the antenna\\u000a dimensions and\\/or the longitudinal dimension of the illuminated target, are analyzed. It is shown that, during the radar observation\\u000a of the target, this signal changes its shape several times and enters the radar receiver as an unknown signal. In many cases,\\u000a this circumstance

I. Ya. Immoreev

2009-01-01

451

Algoritimos E Metodologia de Processamento Para Sintese de Imagens de Radar de Abertura Sintetica (SAR) (Algorithms and Methods for Processing Synthetic Aperture Radar (SAR) Images).  

National Technical Information Service (NTIS)

The Synthetic Aperture Radar (SAR) concepts is presented in this work, and describes a digital processing method to SAR system. The Doppler model is used to derive algorithms to the SAR processing. Matched Filters are used to range and azimuth compression...

J. C. Mura

1991-01-01

452

Imaging synthetic aperture radar  

DOEpatents

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.

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

1997-01-01

453

Radar techniques program  

Microsoft Academic Search

This is the fifth Quarterly Technical Summary covering the development of an airborne Multiple-Antenna Moving-Target Surveillance Radar (MASR) which employs special antenna and signal-processing techniques to provide continuous, wide-area surveillance of moving targets on or near the ground. Such a sensor, equipped with an appropriate data-reduction facility, can provide useful real-time information to a Tactical Air Control System. A DeHavilland

C. E. Muehe

1974-01-01

454

Radar detection of Iapetus  

NASA Astrophysics Data System (ADS)

We have obtained echoes from the bright, trailing hemisphere of Iapetus using the Arecibo Observatory's 13-cm radar system on three dates in January 2002. A circularly polarized signal was transmitted and an echo in the opposite circular (OC) sense to that transmitted was clearly received along with a much weaker detection of echo power in the same circular (SC) sense. Prior to this experiment, one expectation may have been that the radar scattering properties of Iapetus may behave like the similar atmosphere-less, icy surfaces of the Galilean satellites which, due to an efficient multiple scattering mechanism, are strong backscatterers with SC reflections stronger than their OC reflections. Instead we find that Iapetus' radar cross section and polarization properties are very different from those of the icy Galilean satellites, and more reminiscent of less efficient and less exotic scattering mechanisms such as dominate the echoes from inner Solar System targets. Thus these observations indicate that there is a significant difference between the surface properties of Iapetus and the icy Galileans despite their overall classification as low temperature, water ice surfaces. A plausible explanation for Iapetus' inefficient scattering is that contaminants in the water ice increase the absorption of the signal and suppress any multiple scattering. Likely contaminants on Iapetus are ammonia and the dark material from Cassini Regio embedded below the surface. Proposed observations will seek to measure Iapetus' radar scattering law and to detect the dark, leading side which was not targeted during this observing session. The Arecibo Observatory is part of the National Astronomy and Ionosphere Center, which is operated by Cornell University under a cooperative agreement with the National Science Foundation.

Black, G. J.; Campbell, D. B.; Carter, L. M.; Ostro, S. J.

2002-09-01

455

Tropopause detected by radar.  

PubMed

The tropopause has been detected by ultrasensitive, narrow-beam, microwave (10.7-centimeter) and ultrahigh-frequency (71.5-cm) radars. Its reflectivity is consistent with that expected theoretically for a refractively turbulent medium. Indications are that the layer is also mechanically turbulent, and that electromagnetic scatter techniques may be used to detect high-altitude clear-air turbulence. PMID:17737591

Atlas, D; Hardy, K R; Glover, K M; Katz, I; Konrad, T G

1966-09-01

456

Shuttle imaging radar experiment  

USGS Publications Warehouse

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.

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

457

Millimeter Wave Cloud Radar (MMCR) Handbook  

SciTech Connect

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.

KB Widener; K Johnson

2005-01-30

458

Comet radar explorer  

NASA Astrophysics Data System (ADS)

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

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

459

Radar clutter classification  

NASA Astrophysics Data System (ADS)

The problem of classifying radar clutter as found on air traffic control radar systems is studied. An algorithm based on Bayes decision theory and the parametric maximum a posteriori probability classifier is developed to perform this classification automatically. This classifier employs a quadratic discriminant function and is optimum for feature vectors that are distributed according to the multivariate normal density. Separable clutter classes are most likely to arise from the analysis of the Doppler spectrum. Specifically, a feature set based on the complex reflection coefficients of the lattice prediction error filter is proposed. The classifier is tested using data recorded from L-band air traffic control radars. The Doppler spectra of these data are examined; the properties of the feature set computed using these data are studied in terms of both the marginal and multivariate statistics. Several strategies involving different numbers of features, class assignments, and data set pretesting according to Doppler frequency and signal to noise ratio were evaluated before settling on a workable algorithm. Final results are presented in terms of experimental misclassification rates and simulated and classified plane position indicator displays.

Stehwien, Wolfgang

1989-11-01

460

Optimum frequency for subsurface-imaging synthetic-aperture radar  

SciTech Connect

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.

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

1993-05-01

461

Optimum frequency for subsurface-imaging synthetic-aperture radar  

SciTech Connect

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.

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

1993-05-01

462

Measurement of the nuclear magnetic dipole moments of 177Hf and 179Hf with the atomic beam magnetic resonance method  

Microsoft Academic Search

The nuclear ground-state magnetic dipole moments of 177Hf and 179Hf have been determined with the atomic beam magnetic resonance method. The results are: muI(177Hf = 0.7836(6)muN, muI(179Hf) = -0.6329(13) muN (uncorrected for diamagnetic shielding).

S. Büttgenbach; M. Herschel; G. Meisel; E. Schrödl; W. Witte

1973-01-01

463

Measurement of thermal neutron cross-sections and resonance integrals for 179Hf(n,gamma)180mHf and 180Hf(n,gamma)181Hf reactions at the Pohang neutron facility  

Microsoft Academic Search

The thermal-neutron cross-sections and the resonance integrals for the 179Hf(n,gamma)180mHf and the 180Hf(n,gamma)181Hf reactions have been measured by the activation method. The high purity Hf and Au metallic foils within and without a Cd shield case were irradiated in a neutron field of the Pohang neutron facility. The gamma-ray spectra from the activated foils were measured with a calibrated p-type

Van Do Nguyen; Duc Khue Pham; Tien Thanh Kim; Truong Son Le; Young Seok Lee; Guinyun Kim; Youngdo Oh; Hee-Seock Lee; Moo-Hyun Cho; In Soo Ko; Won Namkung

2008-01-01

464

Measurement of thermal neutron cross-sections and resonance integrals for 179Hf(n,?) 180mHf and 180Hf(n,?) 181Hf reactions at the Pohang neutron facility  

Microsoft Academic Search

The thermal-neutron cross-sections and the resonance integrals for the 179Hf(n,?)180mHf and the 180Hf(n,?)181Hf reactions have been measured by the activation method. The high purity Hf and Au metallic foils within and without a Cd shield case were irradiated in a neutron field of the Pohang neutron facility. The gamma-ray spectra from the activated foils were measured with a calibrated p-type

Van Do Nguyen; Duc Khue Pham; Tien Thanh Kim; Truong Son Le; Young Seok Lee; Guinyun Kim; Youngdo Oh; Hee-Seock Lee; Moo-Hyun Cho; In Soo Ko; Won Namkung

2008-01-01

465

Circular array radar technical and applications  

NASA Astrophysics Data System (ADS)

A new type circular array radar is introduced in this paper. First, the working theory of this radar is introduced, as well as the signal processing method. The characteristics and advancements of this type of radar are detailed analyzed, and the key technology of the circular array radar is proposed. Second, two applications of circular array radar are introduced; they are VHF circular array long-range surveillance radar and L band mini circular array radar. Finally, the potential prospect of this circular array radar is proposed.

Xu, Chengfa; Wang, Chonghui; Hong, Yongbin

2013-03-01

466

Nuclear shapes of highly deformed bands in {sup 171,172}Hf and neighboring Hf isotopes  

SciTech Connect

A Gammasphere experiment was carried out to search for triaxial strongly deformed (TSD) structures in {sup 171,172}Hf and the wobbling mode, a unique signature of nuclei with stable triaxiality. Three strongly deformed bands in {sup 172}Hf and one in {sup 171}Hf were identified through {sup 48}Ca({sup 128}Te, xn) reactions. Linking transitions were established for the band in {sup 171}Hf and, consequently, its excitation energies and spins (up to 111/2({Dirac_h}/2{pi})) were firmly established. However, none of the {sup 172}Hf sequences were linked to known structures. Experimental evidence of triaxiality was not observed in these bands. The new bands are compared with other known strongly deformed bands in neighboring Hf isotopes. Theoretical investigations within various models have been performed. Cranking calculations with the Ultimate Cranker code suggest that the band in {sup 171}Hf and two previously proposed TSD candidates in {sup 170}Hf and {sup 175}Hf are built on proton (i{sub 13/2}h{sub 9/2}) configurations, associated with near-prolate shapes and deformations enhanced with respect to the normal deformed bands. Cranked relativistic mean-field calculations suggest that band 2 in {sup 175}Hf has most likely a near-prolate superdeformed shape involving the {pi}i{sub 13/2} x {nu}j{sub 15/2} high-j intruder orbitals. It is quite likely that the bands in {sup 172}Hf are similar in character to this band.

Zhang, Y. C.; Ma, W. C.; Afanasjev, A. V.; Begnaud, J.; Ngijoi-Yogo, E.; Roux, D. G.; Yadav, R. B. [Department of Physics, Mississippi State University, Mississippi State, Mississippi 39762 (United States); Hagemann, G. B. [Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen (Denmark); Carpenter, M. P.; Janssens, R. V. F.; Khoo, T. L.; Lauritsen, T.; Moore, E. F.; Zhu, S. [Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Chowdhury, P. [Department of Physics, University of Massachusetts, Lowell, Massachusetts 01854 (United States); Cullen, D. M.; Rigby, S. V.; Scholes, D. T. [Schuster Laboratory, University of Manchester, Manchester M13 9PL (United Kingdom); Djongolov, M. K.; Riedinger, L. L. [Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996 (United States)] (and others)

2007-12-15

467

Modeling of HF propagation and heating in the ionosphere. Final report, Apr 89-Nov 91  

SciTech Connect

The purpose of the program of research reported here is to develop and demonstrate a realistic numerical model for self-consistent ionospheric propagation and heating of powerful frequency (HF) waves by conjoining existing, separate numerical models for high frequency wave propagation and ionospheric transport. A comprehensive numerical implementation of plasma geometric optics has been enhanced and adapted to the problem of self-consistent ionospheric propagation of high power, high frequency radar signals. The emphasis in this work is on the realistic and rigorous description of the propagation waves so that geometric and spectral characteristics of nonlinear ionospheric effects can be predicted in detail. The plasma geometric optics code has been used in conjunction with an ionospheric transport code to determine self-consistently the HF radiation field and quasilinear modifications of ionospheric plasma properties due to ohmic dissipation of the HF radiation. This allows detailed study of nonlinear phenomena such as beam self-focusing formation of large-scale density cavities and striations, and induced wave ducting. Overviews of the theory underlying the existing models of radiation propagation and ohmic power deposition are given, and enhancements to these models are described. New results achieved using the enhanced models are shown and the treatment of a self-consistent propagation and heating problem is presented.

Hinkel, D.; Shoucri, M.; Smith, T.; Wagner, T.

1992-02-01

468

Digital Collections, Digital Libraries & the Digitization of Cultural Heritage Information.  

ERIC Educational Resources Information Center

Discusses digital collections and digital libraries. Topics include broadband availability; digital rights protection; content, both non-profit and commercial; digitization of cultural content; sustainability; metadata harvesting protocol; infrastructure; authorship; linking multiple resources; data mining; digitization of reference works;…

Lynch, Clifford

2002-01-01

469

A search for the location of the HF excitation of enhanced ion acoustic and langmuir waves with eiscat and the tromsø heater  

Microsoft Academic Search

In an effort to understand the mechanisms which give rise to the enhanced ion acoustic and Langmuir waves in HF modification\\u000a experiments, we perform measurements with the EISCAT Troms? heater and the two incoherent scatter radars to locate the enhancement\\u000a regions in space. Simultaneous measurements of the enhancements were made with both the VHF (224 MHz) and the UHF (933

B. Isham; T. Hagfors; E. Mishin; M. T. Rietveld; C. Lahoz; W. Kofman; T. Leyser

1999-01-01

470

Digitizer Evaluation.  

National Technical Information Service (NTIS)

The report documents the acceptance tests conducted on the Gradicon digitizer manufactured by Instronics, Ltd. The digitizer was evaluated on the basis of its applicability to the area of cartography. Primary emphasis was placed on overall accuracy and re...

F. T. Kulon W. G. McLellan

1973-01-01

471

Resolute Bay CADI ionosonde drifts, PolarDARN HF velocities, and cross polar cap potential  

NASA Astrophysics Data System (ADS)

In this study, velocities measured by the Rankin Inlet and Inuvik PolarDARN HF radars over Resolute Bay (RB) are compared with measurements from the RB CADI ionosonde to investigate the consistency of the measurements. Two types of comparisons are performed: 1-D, where each PolarDARN radar line-of-sight velocity is plotted against CADI velocity projected onto appropriate radar beam, and 2-D, where the PolarDARN merged velocity is compared with the full CADI vector. In both cases, velocities were found to statistically agree. For the 1-D comparison, the velocities were comparable in ˜85% of cases. For the 2-D comparison, a minor tendency for larger PolarDARN merge velocities (˜60 m/s) was noticed. The second task performed is a comparison of the SuperDARN cross polar cap potential (CPCP) and the CADI-based CPCP and their dependence on the CADI velocity. Linear dependences were found allowing for inter-conversion between these parameters. For large plasma drifts, the SuperDARN CPCPs were found to be much smaller than the CADI-based CPCPs hinting that the separation between the foci of a large-scale convection pattern is often underestimated in the SuperDARN convection mapping.

Mori, D.; Koustov, A. V.; Jayachandran, P. T.; Nishitani, N.

2012-01-01

472

Lunar topography from earth-based radar interferometric mapping  

NASA Astrophysics Data System (ADS)

An incomplete knowledge of the topography of the Moon has hindered the solution to several problems in lunar science and comparative planetology. The lack of elevation data over the polar regions and the generally sparse coverage in non-equatorial areas have restricted investigations related to the global shape of the Moon, impact cratering processes, and the possible presence of water ice at the lunar poles. Three-dimensional maps of the nearside and polar regions of the Moon can be obtained with an Earth-based radar interferometer. This technique allows surface heights to be accurately measured from the relative phase between radar echoes recorded at two separate receiving stations. The 70 m antenna and several 34 m stations of the Deep Space Network in California were configured as a radar interferometer for a sequence of observations in 1997. This experiment provided the first detailed topographic maps of the lunar polar regions, with a coverage of 300 x 1200 km at each pole. Elevation maps and radar imagery were also obtained for a 200 x 200 km region centered on Tycho Crater, the freshest large crater on the Moon. With a surface resolution of 150 m and a height resolution of 50 m or better, the radar maps represent significant improvements compared to existing lunar topographic data sets. The digital elevation model of Tycho Crater was used to determine the fundamental parameters of the crater's shape. The data revealed an asymmetry in floor elevations, rim heights, and wall slump zones, which may be related to an oblique nature for the impact. The topographic maps of the polar areas were used to verify previous estimates of global shape parameters for the Moon, and to locate regions which are in permanent shadow from solar illumination. The actual locations of the cold traps, potential reservoirs of ice deposits, are delineated on radar images of the lunar polar areas.

Margot, Jean-Luc C.

1999-09-01

473

Topics in Mitigating Radar Bias  

Microsoft Academic Search

In this paper, we investigate two topics related to mitigating the effect of radar bias in ballistic missile tracking applications. We determine the absolute bias between two radars in polar coordinates when their relative bias is given in rectangular coordinates. Using this result, we then obtain the optimized steady-state filter to handle the random bias.

Demetrios Serakos; John E. Gray; Hazim Youssef

2008-01-01

474

Next Generation Incoherent Scatter Radars.  

National Technical Information Service (NTIS)

The 1990's promise to be an exciting time for users and practitioners of incoherent scatter radar as a new generation of radars is brought into operation at locations such as Svalbard, Resolute Bay, Alaska and Indonesia. Recent technological and theoretic...

J. M. Holt

1991-01-01

475

Radar Studies In Physical Volcanology  

Microsoft Academic Search

This paper discusses a number of projects currently underway at the University of Hawaii that involve airborne and orbital radar investigations of the styles of eruption and the geologic history of volcanoes on the Earth and Venus. The radar data have been derived from a NASA\\/JPL AIRSAR deployment to Hawaii in August 1990, the Magellan mission to Venus, and the

Peter J. Mouginis-Mark

1992-01-01

476

Decorrelation in interferometric radar echoes  

Microsoft Academic Search

A radar interferometric technique for topographic mapping of surfaces, implemented utilizing a single synthetic aperture radar (SAR) system in a nearly repeating orbit, is discussed. The authors characterize the various sources contributing to the echo correlation statistics, and isolate the term which most closely describes surficial change. They then examine the application of this approach to topographic mapping of vegetated

Howard A. Zebker; John Villasensor

1992-01-01

477

COBRA meteor radar antenna designs  

Microsoft Academic Search

A meteor radar system is one of the effective remote sensing techniques in measuring atmospheric parameters such as wind velocities, temperature, pressure and density which are essential in understanding the atmospheric dynamics in the Mesosphere Lower Thermosphere (MLT) region. Previous studies of very high frequency (VHF) meteors radar systems suggest that the minimum error for the estimation of the horizontal

Mohamad Zainuddin

2009-01-01

478

Imaging Radars for Geoscience Use  

Microsoft Academic Search

Properties of a side-looking airborne radar (SLAR) designed for geoscience rather than military use are presented. The speckled nature of usual single-frequency radar images may be reduced by averaging in azimuth and by averaging in range or transmitting excess range bandwidth. With synthetic aperture systems, averaging is possible in both range and azimuth, but only range averaging (excess bandwidth) is

R. K. Moore; G. C. Thomann

1971-01-01

479

Radar polarimetry for geoscience applications  

Microsoft Academic Search

The present volume on radar polarimetry for geoscience applications discusses wave properties and polarization, scattering matrix representation for simple targets, scattering models for point and distributed targets, polarimetric scatterometer systems and measurements, polarimetric radar system design, and polarimetric SAR applications. Attention is given to plane waves in a lossless homogeneous medium-wave polarization, polarization synthesis and response, and coordinate system transformations.

Fawwaz T. Ulaby; Charles Elachi; K. McDonald; K. Sarabandi; M. Whitt; H. Zebker; J. J. van Zyl

1990-01-01

480

A Multiband Passive Radar Demonstrator  

Microsoft Academic Search

Passive radar systems that exploit signals from the plethora of RF emissions that exist in the external environment offer a number of advantages over conventional active radar system, including procurement and operational cost saving. Each emitter has its own characteristics, including waveforms, which dictate system performance. BAE Systems Advanced Technology Centre has designed and built a demonstrator system to act

Dale Gould; Robert Pollard; Carlos Sarno; Paul Tittensor

2006-01-01

First Page Previous Page 1 2 3 4 5 6 7 8 9 10 <