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1

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

2

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

3

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

4

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

5

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

6

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

7

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

8

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

9

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

10

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

11

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

12

Ice sheet motion and topography from radar interferometry  

Microsoft Academic Search

Both topography and motion information are present in repeat pass ERS-1 interferograms over ice sheets. The authors demonstrate that the topography is separable from the surface displacement field when a sequence of radar images are available. If the velocity field is constant over the time span of observation, the topography can be derived from differential interferograms formed from sequential observations.

Ronald Kwok; Mark A. Fahnestock

1996-01-01

13

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

14

Shuttle radar topography mission accuracy assessment and evaluation for hydrologic modeling  

Microsoft Academic Search

Digital Elevation Models (DEMs) are increasingly used even in low relief landscapes for multiple mapping applications and modeling approaches such as surface hydrology, flood risk mapping, agricultural suitability, and generation of topographic attributes. The National Aeronautics and Space Administration (NASA) has produced a nearly global database of highly accurate elevation data, the Shuttle Radar Topography Mission (SRTM) DEM. The main

Pablo Alberto Mercuri

2005-01-01

15

Shuttle Radar Topography Mission - New Products in 2005  

USGS Publications Warehouse

In February 2000, the Shuttle Radar Topography Mission (SRTM) successfully collected Interferometric C-Band Synthetic Aperture Radar data over 80 percent of the Earth's land surface, for most of the area between 60?N and 56?S latitude. NASA and the National Geospatial-Intelligence Agency (NGA), formerly known as the National Imagery and Mapping Agency (NIMA), co-sponsored the mission. NASA's Jet Propulsion Laboratory (JPL) performed preliminary processing of SRTM data and forwarded partially finished data directly to NGA for finishing by NGA contractors and subsequent monthly deliveries to the NGA Digital Products Data Warehouse (DPDW). All data products delivered by the contractors conform to NGA SRTM Data Products and NGA Digital Terrain Elevation Data? (DTED?) specifications. The DPDW ingests the SRTM data products, checks them for formatting errors, loads the public SRTM DTED? into the NGA data distribution system, and ships them to the U.S. Geological Survey (USGS) Center for Earth Resources Observation and Science (EROS). In addition to NGA's SRTM DTED? format, USGS EROS has reformatted the data into a non-proprietary, generic raster binary SRTM format that is readable by most remote sensing software packages. The SRTM format is also publicly available from USGS EROS.

Geological Survey (U.S.)

2007-01-01

16

Scanning Radar Altimeter for Mapping Continental Topography.  

National Technical Information Service (NTIS)

Topographic information constitutes a fundamental data set for the Earth sciences. In the geological and geophysical sciences, topography combined with gravitational information provides an important constraint on the structure and rheologic properties of...

T. H. Dixon

1986-01-01

17

High spatial resolution radar altimetry for global Earth topography mapping  

Microsoft Academic Search

This paper summarises the work performed by Alenia Aerospazio in the design of new radar altimeter systems suitable for high spatial resolution Earth topography observation. The instrument concept proposed is based on the application of synthetic aperture processing and interferometric techniques to a conventional Ku band pulse limited system. The major design features and expected performance are briefly presented

G. Angino; F. Impagnatiello; C. Zelli

1997-01-01

18

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

19

Global Topography of Titan from Cassini RADAR Data (Invited)  

NASA Astrophysics Data System (ADS)

Cassini RADAR data are used to construct a global, albeit sparsely-sampled, topography map, and to generate a hypsometric profile to compare with other planetary bodies. Titan’s hypsogram is unimodal and strikingly narrow compared with the terrestrial planets. To investigate topographic extremes, a novel variant on the classic hypsogram is introduced, with a logarithmic abscissa to highlight mountainous terrain. In such a plot, the top of the terrestrial hypsogram is quite distinct from those of Mars and Venus due to the ‘glacial buzz-saw’ that clips terrestrial topography above the snowline. In contrast to the positive skew seen in other hypsograms, with a long tail of positive relief due to mountains, there is an indication (weak, given the limited data for Titan so far) that the Titan hypsogram appears slightly negatively skewed, suggesting a significant population of unfilled depressions. Limited data permit only a simplistic comparison of Titan topography with other icy satellites but we find that the standard deviation of terrain height (albeit at different scales) is similar to those of Ganymede and Europa. The topography of terrestrial planets is sampled with the same coverage that we have for Titan to gauge what as-yet-undiscovered topographic surprises may yet be hidden by Titan’s haze.

Lorenz, R. D.; Cassini RADAR Team

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

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

22

High-precision Ice Surface Topography Mapping Using Radar Interferometry  

NASA Astrophysics Data System (ADS)

In May 2009 a new radar technique for mapping ice surface topography was demonstrated in a Greenland campaign as part of the NASA International Polar Year activities. This was achieved with the airborne Glacier and Ice Surface Topography Interferometer (GLISTIN-A): a 35.6 GHz single-pass interferometer. Although the technique of using radar interferometry for mapping terrain has been demonstrated before, this is the first such application at millimeter-wave frequencies. Instrument performance indicates swath widths over the ice between 5-7km, with height precisions ranging from 30cm-3m at a posting of 3m x 3m. However, for this application the electromagnetic wave will penetrate an unknown amount into the snow cover thus producing an effective bias that must be calibrated. To evaluate this, GLISTIN-A flew a coordinated collection with the NASA Wallops Airborne Topographic Mapper (ATM) on a transect from Greenland’s Summit to its West coast. Two field calibration sites were established at Colorado Institute for Research in Environmental Science’s Swiss Camp and the National Science Foundation’s Summit station. Additional collections entailed flying a mosaic over Jakobshavn glacier which was repeated after 6 days to reveal surface dynamics. Through detailed calibration and inter-sensor comparisons we were able to observe penetration biases and compare them with theoretical expectations. We also demonstrated GLISTIN-A’s capability to measure the topography of large glacier systems in a seamless fashion and accurately measuring volume changes with a high level of spatial detail. In particular, repeating the airborne campaigns to observe elevation changes over time will allow very accurate volume change measurements. Not only is this very important for mass balance studies to have a precise mass-loss estimate, but the spatial pattern can reveal ice dynamics effects and surface mass balance effects. In this manner a high resolution, high-precision topographic mapping capability is an ideal complement to the ICESat, ICESat II and Cryosat altimeters. Interpolating between the high-accuracy elevation profiles from altimeters such as the ATM or ICESat II with the high-resolution GLISTIN-A swath will enable detailed ice-surface topography maps and extended spatial coverage. The result is the potential for higher fidelity mass-balance estimates and improved observational coverage. Upgrades are currently underway to improve the performance and portability of GLISTIN-A such that, onboard a long-range aircraft this radar can map Greenland’s significant glaciers in a few days. The upgraded GLISTIN-A will be compatible with GlobalHawk installation making, Antarctica basin and coastal mapping feasible. GLISTIN will make more topographic products available to glaciologists, initially through dedicated airborne campaigns or ultimately, perhaps, as a satellite mission.

Moller, D.; Hensley, S.; Michel, T.; Rignot, E. J.; Simard, M.; Krabill, W. B.; Sonntag, J. G.

2010-12-01

23

A new, earth-based radar technique for the measurement of lunar topography  

Microsoft Academic Search

Radio interferometry is a new technique for the measurement of the surface topography of the Moon. Elevation data may be obtained directly without regard for unambiguously-identified features, for any lunar surface element that yields a recognizable radar echo.

S. H. Zisk

1972-01-01

24

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

25

Topography adjacent to Signal Corps Radar (S.C.R.) 296 Station 5, ...  

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

Topography adjacent to Signal Corps Radar (S.C.R.) 296 Station 5, showing conditions before construction, May 28, 1943, this drawing shows the Bonita Ridge access road retaining wall and general conditions at Bonita Ridge before the construction of Signal Corps Radar (S.C.R.) 296 Station 5 - Fort Barry, Signal Corps Radar 296, Station 5, Transmitter Building Foundation, Point Bonita, Marin Headlands, Sausalito, Marin County, CA

26

Quality assessment and derivation of hydrological relevant parameters from Shuttle Radar Topography Mission data  

NASA Astrophysics Data System (ADS)

The aim of the paper is to demonstrate the value of Shuttle Radar Topography Mission (SRTM, X-Band) derived Digital Elevation Model (DEM) Data for hydrological applications. The quality assessment results are compared with other remote sensing derived elevation data, namely a photogrammetrically derived Digital Terrain Model (DTM) of the Thuringian Survey Agency, ERS Tandem Mission data (C-Band) and a high resolution Experimental SAR (E-SAR) DEM. The analysis carried out in three testsites in Thuringia (Biosphere Conservation Area Rhön Mountains, Ilm-Catchment and Zeulenroda Reservoir Area) comprises difference images between several DTMs and DEMs, statistical analysis and quality estimations as well as the derivation of secondary DEM products like slope, aspect, curvature, catchment area, river density, flow direction, flow accumulation, evaporation, transport capacity, etc. These parameters are used as spatial input for distributed hydrological models. Finally the suitability of the SRTM-DEMs for hydrological models (water balance and solute transport models) is assessed on the comparison of simulation results with measured runoff curves.

Hochschild, V.; Wolf, M.

2003-04-01

27

Global Land Topography and Ocean Bathymetry from Radar Altimetry  

NASA Astrophysics Data System (ADS)

A new Digital Elevation Model was compiled for ENVISAT with a 5*5' grid spacing. This Global Model was achieved by integrating a Bathymetry model built by Walter Smith from NOAA and David Sandwell from Scripps Institution of Oceanography, USA, with the Altimetry Corrected Elevations (ACE) produced by Philippa Berry of De Montfort University, UK. Both models present the advantage of associating satellite global altimetry grid with field data (depth sounding for the bathymetry and local DEM for the elevations). To take full advantage of the resolution of both input datasets, two other DEM were also produced with a respective grid spacing of 2' and 30". To obtain a final model with a full, dense and homogeneous coverage, that includes all the information from the initial models and preserves their accuracy, a merge of the data sets was performed carefully respecting the boundary between land and ocean because both original grids had different resolutions. Then, the entire dataset was divided in small geographical tiles that were separately triangulated and interpolated. Edge effects were avoided by taking in consideration an overlap boundary zone. Finally, three grids were obtained at different resolutions, 30 arcseconds, 2 arcminutes and 5 arcminutes (respectively, 1, 4 and 10 km approximately) to be used for applications requiring different scales. These grids are the first global models including essentially satellite radar altimeter measurements of land elevation and ocean bathymetry merged together, giving a unity and a complete, dense and homogeneous coverage of the world, with an unprecedented accuracy. This new global model at 5-arcminutes resolution will replace the previous model used in ENVISAT data processing and the model at 30-arcsecond resolution will be also used for MERIS and ASAR application projects.

Defrenne, D.; Benveniste, J.

28

Shuttle Radar Topography Mission (SRTM) flight system design and operations overview  

Microsoft Academic Search

This paper provides an overview of the Shuttle Radar Topography Mission SRTM), with emphasis on flight system implementation and mission operations from systems engineering perspective. Successfully flown in February, 2000, the SRTM's primary payload consists of several subsystems to form the first spaceborne dual-frequency (C- band and X-band) fixed baseline interferometric synthetic aperture radar (InSAR0 system, with the mission objective

Yuhsyen Shen; Scott J. Shaffer; Rolando L. Jordan

2000-01-01

29

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

30

A study of a potential venus radar topography mission  

Microsoft Academic Search

Radar has been shown to be the best way to view the surface of Venus as was demonstrated by Pioneer Venus Orbiter, Veneras 15 and 16, and Magellan Missions. Each of these missions progressively increased our knowledge of the surface and it has been nearly twenty years since Magellan covered nearly all the surface with SAR images from 120 to

W. Johnson; R. Jordan; L. Veilleux; R. Hodges; L. Giersch

2009-01-01

31

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

32

Modeling of fluidized ejecta emplacement over digital topography on Venus  

NASA Astrophysics Data System (ADS)

The FLOW computer model of McEwen and Malin (1989) modified for application to the study of Venus fluidized ejecta blankets (FEBs) demonstrates that relatively low viscosities, yield strengths, and initial velocities are required to duplicate the observed flow paths of the outflow materials. The model calculates the velocities and simulated flow paths of gravity flows over Magellan topography. The model is formulated to determine flow movements from initial conditions, gravitational acceleration, and resistance to motion as described by Coulomb, viscous, and turbulent resistance forces. Successful duplication of observed FEB flow paths has been achieved for the FEB craters Addams, Isabella, and Cochran. When used as a simple energy-line model, the model requires low coefficients of friction to extend FEBs to near their observed termini in the synthetic aperture radar (SAR) imagery, although the resulting straight flow lines do not follow the observed flow paths well. For Bingham flow, the model requires low values of viscosity and yield strength which are more similar to pyroclastic or debris flows than basaltic lavas. Flows of 100-m depth require 1 to 2 orders of magnitude higher values of both viscosity and yield strength than 10-m-deep flows. The complicated nature of the flow lines for the low velocity model suggests that FEBs were probably emplaced under variably laminar and turbulent flow conditions, where underlying topography influenced both the direction and energy of flow materials.

Johnson, Jeffrey R.; Gaddis, Lisa

33

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

34

Fractal mapping of digitized images - Application to the topography of Arizona and comparisons with synthetic images  

Microsoft Academic Search

The concept of fractal mapping is introduced and applied to digitized topography of Arizona. It is shown that the fractal statistics satisfy the topography of the state to a good approximation. The fractal dimensions and roughness amplitudes from subregions are used to construct maps of these quantities. It is found that the fractal dimension of actual two-dimensional topography is not

J. Huang; D. L. Turcotte

1989-01-01

35

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

36

Mapping the world's topography using radar interferometry: the TOPSAT mission  

Microsoft Academic Search

Global-scale topographic data are of fundamental importance to many Earth science studies, and obtaining these data is a priority for the Earth science community. Several groups have considered the requirements for such a data set, and a consensus assessment is that many critical studies would be enabled by the availability of a digital global topographic model with accuracies of 2

HOWARD A. ZEBKER; T. G. Farr; RONALD P. SALAZAR; TIMOTHY H. DIXON

1994-01-01

37

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

38

The Surface Water and Ocean Topography Mission: centimetric spaceborne radar interferometry  

NASA Astrophysics Data System (ADS)

Over the last two decades, several nadir profiling radar altimeters have provided our first global look at the ocean basinscale circulation and the ocean mesoscale at wavelengths longer than 100 km. Due to sampling limitations, nadir altimetry is unable to resolve the small wavelength ocean mesoscale and sub-mesoscale that are responsible for the vertical mixing of ocean heat and gases and the dissipation of kinetic energy from large to small scales. The Surface Water and Ocean Topography (SWOT) mission being considered by NASA has as one of its main goals the measurement of ocean topography with kilometer-scale spatial resolution and centimeter scale accuracy. In this paper, we provide an overview of all error sources that contribute to the SWOT mission for the ocean. This paper is a sequel to an earlier paper describing the SWOT mission, the science and its payload.

Esteban-Fernandez, D.; Rodriguez, Ernesto; Fu, Lee-Lueng; Alsdorf, Douglas; Vaze, Parag

2010-10-01

39

Extraction of Martian valley networks from digital topography  

NASA Astrophysics Data System (ADS)

We have developed a novel method for delineating valley networks on Mars. The valleys are inferred from digital topography by an autonomous computer algorithm as drainage networks, instead of being manually mapped from images. Individual drainage basins are precisely defined and reconstructed to restore flow continuity disrupted by craters. Drainage networks are extracted from their underlying basins using the contributing area threshold method. We demonstrate that such drainage networks coincide with mapped valley networks verifying that valley networks are indeed drainage systems. Our procedure is capable of delineating and analyzing valley networks with unparalleled speed and consistency. We have applied this method to 28 Noachian locations on Mars exhibiting prominent valley networks. All extracted networks have a planar morphology similar to that of terrestrial river networks. They are characterized by a drainage density of ~0.1 km-1, low in comparison to the drainage density of terrestrial river networks. Slopes of ``streams'' in Martian valley networks decrease downstream at a slower rate than slopes of streams in terrestrial river networks. This analysis, based on a sizable data set of valley networks, reveals that although valley networks have some features pointing to their origin by precipitation-fed runoff erosion, their quantitative characteristics suggest that precipitation intensity and/or longevity of past pluvial climate were inadequate to develop mature drainage basins on Mars.

Stepinski, T. F.; Collier, M. L.

2004-11-01

40

Shuttle radar topography mission accuracy assessment and evaluation for hydrologic modeling  

NASA Astrophysics Data System (ADS)

Digital Elevation Models (DEMs) are increasingly used even in low relief landscapes for multiple mapping applications and modeling approaches such as surface hydrology, flood risk mapping, agricultural suitability, and generation of topographic attributes. The National Aeronautics and Space Administration (NASA) has produced a nearly global database of highly accurate elevation data, the Shuttle Radar Topography Mission (SRTM) DEM. The main goals of this thesis were to investigate quality issues of SRTM, provide measures of vertical accuracy with emphasis on low relief areas, and to analyze the performance for the generation of physical boundaries and streams for watershed modeling and characterization. The absolute and relative accuracy of the two SRTM resolutions, at 1 and 3 arc-seconds, were investigated to generate information that can be used as a reference in areas with similar characteristics in other regions of the world. The absolute accuracy was obtained from accurate point estimates using the best available federal geodetic network in Indiana. The SRTM root mean square error for this area of the Midwest US surpassed data specifications. It was on the order of 2 meters for the 1 arc-second resolution in flat areas of the Midwest US. Estimates of error were smaller for the global coverage 3 arc-second data with very similar results obtained in the flat plains in Argentina. In addition to calculating the vertical accuracy, the impacts of physiography and terrain attributes, like slope, on the error magnitude were studied. The assessment also included analysis of the effects of land cover on vertical accuracy. Measures of local variability were described to identify the adjacency effects produced by surface features in the SRTM DEM, like forests and manmade features near the geodetic point. Spatial relationships among the bare-earth National Elevation Data and SRTM were also analyzed to assess the relative accuracy that was 2.33 meters in terms of the total standard deviation for flat areas of central Indiana with a positive bias for SRTM relative to the national elevation dataset. Physical watershed boundaries, streams vector files and topographic attributes have been produced to investigate the SRTM global coverage performance in watershed modeling applications. The verification of the precision of hydrologic delineations in Indiana with the availability of Hydrologic Units datasets at watershed and subwatershed levels showed very small differences in drainage areas calculated, even at subwatershed levels. The hydrologic boundaries and drainage network extraction for the Arrecifes basin in the Argentine Pampas was checked for quality assurance with Landsat data and georeferenced digital topographic quadrangles, demonstrating the feasibility of using the SRTM global coverage for water resources mapping. SRTM data presents unique challenges, but the results of this research have shown that high quality results can be obtained. However, there are numerous issues related to preprocessing of SRTM data for certain surface hydrology applications to be addressed regarding SRTM in such as watershed characterization, land use planning, hazards assessment, energy resources assessment and many other uses around the world.

Mercuri, Pablo Alberto

41

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

42

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

43

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

44

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

45

A novel digital x-ray topography system  

Microsoft Academic Search

X-ray topography (XRT) is recognized as being a powerful tool for directly imaging defects in single crystals, semiconductor wafers and epitaxially grown layers. The timely identification of defects can lead to increased yields and significant cost savings in wafer processing. The primary limitation to its general usage within the semiconductor community has been the difficulty in system use and difficulty

D. K. Bowen; M. Wormington; P. Feichtinger

2003-01-01

46

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

47

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

48

Application of digital image analysis techniques to the Geyser's data and topography  

Microsoft Academic Search

This paper describes the results of digital image analysis and techniques applied to acoustic sounder data and topographic relief in the Geyser's region. The two dimensional fast Fourier transform (2DFFT) represents the spacial variability of a photographic image. The spacial variability of topography in complex terrain can be represented in this way and insight into degree of complexity and dominating

Porch

1980-01-01

49

Variability in digital analysis of optic disc topography  

Microsoft Academic Search

We determined the magnitude of variability in optic disc topographical parameters on digital analysis of the optic disc using the IS 2000. The variability introduced by the system, the observer, the observer and patient, and by clinically different types of discs was assessed in the measurement of the vertical cup-to-disc ratio, horizontal cup-to-disc ratio, cup area-to-disc area, cup volume, neuroretinal

Rohit Varma; William C. Steinmann; George L. Spaeth; Richard P. Wilson

1988-01-01

50

Application of digital image analysis techniques to the Geyser's data and topography  

SciTech Connect

This paper describes the results of digital image analysis and techniques applied to acoustic sounder data and topographic relief in the Geyser's region. The two dimensional fast Fourier transform (2DFFT) represents the spacial variability of a photographic image. The spacial variability of topography in complex terrain can be represented in this way and insight into degree of complexity and dominating spacial wavelengths can be gained. This was performed for a 16 km square digitized topographic map of the Geyser's region with 63.5 m resolution. It was also of interest to compare facsimile recordings of acoustic sounder data to optical turbulence measurements.

Porch, W.M.

1980-05-05

51

Structural Analysis of Central Luzon, Philippines, Using Shuttle Radar Topography Mission DEM  

NASA Astrophysics Data System (ADS)

Central Luzon Island (13-16°N, 120-122°E), which is bounded to the east by Philippine Trench, to the west by Manila Trench, to the north by Digdig-Dingalan Fault (DDF) and to the south by Verde Island Passage Fault (VIPF), is one of the most seismically and volcanologically active regions in the Philippines. Active seismicity and violent earthquakes in the region are evidently related to the activities along the subduction zones and branches of the Philippine Fault system. Volcanic eruptions and periodic swarms of volcanic earthquakes were also observed in three active volcanoes, i.e., Pinatubo, Taal Volcano Island and Banahaw, while young calderas of Taal and Laguna de Bay are demonstrably fault-bounded. We use the Shuttle Radar Topography Mission (SRTM) data with 90 m spatial resolution to conduct regional mapping of the faults and volcanic structures in this region. Of particular interests are the NE-SW set of normal faults within the Macolod Corridor, the right-lateral Marikina Valley Fault System (MVFS), the prevalence of N-S trending structures and the series of NW-SE structures that parallel to sub-parallel the active branches of the Philippine Fault. Using ENVI software package, we processed the SRTM data into shaded relief images and examined the lineament features from different azimuth directions and angles of artificial illumination. The prominent NW-SE structures in this area revealed by SRTM data were formed as sinistral shears that parallel the seismically active DDF and VIPF. The N-S trending structures, including some segments of MVFS and N-S oriented fold axes, were apparently generated by an earlier E-W compression, but recently displayed dextral movement with localized vertical component and pull-apart zones. The overprinting of recent fault kinematics on previously formed structures suggest a dramatic shift of regional stress distribution in Central Luzon. The dextral movement along MVFS and the extensional NE-SW faults within the Macolod Corridor are consistent with the regional deformation due to coupling of DDF and VIPF movements. Similarly, the E-W to ENE-WSW and N-S to NNE-SSW structures probably formed as Riedel and anti-Riedel shears.

Torres, R.; Mouginis-Mark, P.; Garbeil, H.; Bautista, L.; Ramos, E.

2002-12-01

52

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

53

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

54

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

55

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

56

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

57

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

58

Classification of Martian Terrain Using Automated Discovery of Structure Algorithm Applied to Digital Topography  

NASA Astrophysics Data System (ADS)

The morphology of Martian landscape is of great interest because it helps to identify physical processes responsible for the observable topography. Traditionally, the descriptive method, applied to imagery data, has been used to study and categorize different types of Martian landscapes. We are developing a complementary approach, wherein a landscape is classified by a computer algorithm on the basis of digital topography provided by the Mars Orbiter Laser Altimeter data. We have adopted the automatic discovery of structure (ADOS) methodology, an unsupervised learning technique that classifies the data by grouping together similar cases. We use probabilistic algorithm that groups cases into classes by modeling each class through probability density function. Each case has a probability of class membership and is assigned to the class with highest posterior probability. The optimal number of classes is determined by cross-validation. The ADOS algorithm is applied to group pixels in a digital elevation model (DEM) of Tisia Valles, a typical Noachian Martian surface located at 46.13E, 11.83S. This terrain is heavily cratered, and shows presence of channels. An auxiliary DEM of the same size is calculated to contain an elevation field modified to make the landscape drainable. The DEM has 163240 pixels, each pixel carries its local topographical information encapsulated in a list of six quantities (h, ? h, s1, s2, a1, a2) which we call a topography descriptor. The components are: elevation, elevation difference between drainable and original DEMs, slopes in original and drainable DEMs, and contributing areas in original and drainable DEMs, respectively. Euclidean metric in space of topography descriptors is used to measure the ``closeness'' between pixels. The algorithm partitioned the pixels into 12 well-separated classes. Comparison of spatial distribution of these classes with visual rendering of digital topography reveals a geomorphic significance of obtained classification. Interiors of craters, ridges, inter-crater planes and channels are separated into different classes. Some subtle differences between otherwise similar terrain are picked up by our classification. Four classes represent crater interiors; they discriminate between different crater depths. Four classes represent inter-crater plains, they differ by actual elevation. Three classes represent ridges, they discriminate between different slopes. Finally, a single class represents channels. Using this classification we have constructed a thematic map of the Tisia Valles region that portrays spatial relations between various geomorphic features.

Vilalta, R.; Stepinski, T. F.

2003-12-01

59

Radar Seeker Based Autonomous Navigation Update System Using Topography Feature Matching Techniques.  

National Technical Information Service (NTIS)

The discussed navigation update system was designed for an unmanned platform with fire and forget capability. It meets the requirement due to fully autonomous operation. The system concept will be characterized by complementary use of the radar seeker for...

H. D. Lerche F. Tumbreagel

1992-01-01

60

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

61

Determination of Bedrock topography beneath the Greenland ice sheet by three-dimensional imaging of radar sounding data  

SciTech Connect

In the summer of 1987, approximately 42,600 radar reflections were obtained along 124 radial lines, 5 km long, centered at Dye 3 in southern Greenland. Processing of these data using a three-dimensional kinematic migration algorithm produces a high-resolution image of the rock surface topography beneath the ice sheet. Estimated uncertainties in the position of the rock surface increase where sampling is less dense, such as toward the edges of the survey, but are less than 5 m over most of the survey area. The main structure revealed is a northwest-southeast trending valley in the bedrock that crosses the westward regional dip of the rock surface. Ice thickness increases from approximately 1800 m in the east to approximately 2100 m in the west. copyright American Geophysical Union 1989

Fisher, E.; McMechan, G.A.; Gorman, M.R.; Cooper, A.P.R.; Aiken, C.L.V.; Ander, M.E.; Zumberge, M.A.

1989-03-10

62

Radar seeker based autonomous navigation update system using topography feature matching techniques  

Microsoft Academic Search

The discussed navigation update system was designed for an unmanned platform with fire and forget capability. It meets the requirement due to fully autonomous operation. The system concept will be characterized by complementary use of the radar seeker for target identification as well as for navigation function. The system works in the navigation mode during preprogrammable phases where the primary

H. D. Lerche; F. Tumbreagel

1992-01-01

63

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

64

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

65

Instruments and Methods Sub-ice topography in Patriot Hills, West Antarctica: first results of a newly developed high-resolution FM-CW radar system  

Microsoft Academic Search

We present a newly developed high-resolution frequency-modulated continuous-wave (FM- CW) radar system for sounding the sub-ice topography. The system, working in the frequency range from 200 to 400 MHz, was developed to measure thickness and internal layers in cold ice with a resolution better than 1 m. This system has the potential to measure accumulation rates, an important input for

Carlos A. CARDENAS MANSILLA; Martin JENETT; Klaus SCHUNEMANN; Jurgen WINKELMANN

2010-01-01

66

Mapping the mega paleodrainage basin using shuttle radar topography mission in Eastern Sahara and its impact on the new development projects in Southern Egypt  

Microsoft Academic Search

In the current study, the shuttle radar topography mission (SRTM) data, with ?90 m horizontal resolution, were used to delineate\\u000a the paleodrainage system and their mega basin extent in the East Sahara area. One mega-drainage basin has been detected, covering\\u000a an area of 256 000 km2. It is classified into two sub mega basins. The Uweinate sub mega basin, which

Ahmed Mohamed Youssef

2009-01-01

67

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

68

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

69

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

70

Cryovolcanism on Titan: Latest Evidence from Cassini RADAR Imagery and Topography  

NASA Astrophysics Data System (ADS)

Although not the pervasive agent of resurfacing in the Outer Solar System that it was once thought to be, cryovolcanism, the eruption of low-temperature fluids from the interior of icy worlds, appears to be an important phenomenon on several bodies. One of the icy worlds purported to be cryovolcanically active is Titan; its rich atmosphere contains non-primordial isotopic signatures and a methane abundance that cannot be sustained without active outgassing, and the presence of a subsurface ocean at depth provides a source for such materials. The dominant paradigm on Titan for many years has been one of a cryovolcanically resurfaced world with a magmatic chemistry that is principally ammonia-water. Owing to this, and the uniquely (for an icy world) high atmospheric pressure which suppresses explosivity, effusive eruptions with complex rheologies are expected, possibly akin to terrestrial basaltic eruptions, feeding flows and possibly domes. Cassini has observed several features proposed as cryovolcanic in origin on the basis of morphological consistency with expectations. However, an alternative paradigm of an endogenically-dead Titan has emerged recently, arguing for a crustal origin of atmosphere species, and suggesting that alternative exogenic (primarily erosional and fluvial) processes should be considered for most surface features. We present a critical re-assessment of interpretations of cryovolcanic landforms in the context of this new paradigm, on the basis of additional imagery and new topographic data. Some, such as Ganesa Macula and Tortola Facula, are no longer considered potential cryovolcanoes, mostly because the more recently measured topography contradicts the morphological inferences used as a basis for interpretation. However, observations of ˜200 m thick lobate forms in two locations, Hotei and Sotra, strengthen earlier cryovolcanic interpretations.

Mitchell, Karl L.; Kirk, R. L.; Lopes, R. M. C.; Radebaugh, J.; Lorenz, R. D.; Cassini RADAR Team

2010-10-01

71

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

72

Satellites images, digitized topography, and the recognition of the Xela Caldera, Quezaltenango Valley, Guatemala  

SciTech Connect

The authors propose, based on reconnaissance geology studies and interpretation of landforms as depicted by Landsat Thematic Mapper (TM) images combined with digitized topography, that the Quezaltenango basin of Guatemala is part of a caldera. The Quezaltenango basin is an elliptical depression, about 12 by 25 km and about 500 m deep. The proposed Xela Caldera extends beyond the basin more than 10 km to the north. The geomorphological features of the area that are typical of a geologically young large-scale caldera include bounding walls that have steep interior and gentle exterior slopes; broad flat areas at the base of the walls; at least one large block, about 3 by 12 km, that only partly floundered as the caldera collapsed; resurgence of a younger volcanic dome, flow and small-scale caldera complex (last active in 1818); younger volcanoes located along the structural margin of the major caldera (one of which is currently active) lobate features on the caldera margins that may indicate a multiple sequence of eruptions; and an active, high-temperature geothermal system. The valley is coincident with a gravity low. Extensive ash-flow tuff sheets that have no identified source are located north of the caldera, and may be the outflow deposits. The Xela caldera is similar in size to the Atitlan caldera, which lies about 50 km southeast of Quezaltenango. The Xela Caldera, if confirmed by future studies, may contain undiscovered geothermal resources, may present a significant geologic hazard to the more than 400,000 people who occupy the Quezaltenango valley, and may be a new member of the list of magmatic systems that have the capability to change global climate for several years.

Foley, D. (Pacific Lutheran Univ., Tacoma, WA (United States). Dept. of Earth Sciences); McEwen, A.; Duffield, W. (Geological Survey, Flagstaff, AZ (United States)); Heiken, G. (Los Alamos National Lab., NM (United States))

1992-01-01

73

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

74

Relationships between topography and precipitation at very high resolution in the tropics: insights from Tropical Rainfall Measuring Mission (TRMM) precipitation radar data (Invited)  

NASA Astrophysics Data System (ADS)

Interactions between spatial variability in precipitation and evolving topography have been proposed in several mountain ranges including the Himalaya and Andes. We present and evaluate precipitation data from the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) algorithm 2A25 version 6 and examine the spatial relationships between precipitation and topography. Ten years (1998-2007) of tropics-wide (±36° latitude) near-surface rain data are used to construct a high resolution (~10 km) map of average annual rainfall. An error model is developed by sub-sampling the TRMM Multi-satellite Precipitation Analysis as sampled by the PR. The error model predicts observed sampling error as a function of resolution, rain rate and sampling frequency with an r 2 of 0.82. This error model indicates that precipitation gradients at the 10 km scale are resolved in regions with large average daily rain totals including portions of the Andes, Himalaya and Western Ghats. Knowledge of the relationship between precipitation patterns and topography in these regions is crucial for evaluating the importance of orographic precipitation for landscape evolution.

Anders, A. M.; Nesbitt, S. W.

2009-12-01

75

Topography and Landforms of Ecuador  

USGS Publications Warehouse

EXPLANATION The digital elevation model of Ecuador represented in this data set was produced from over 40 individual tiles of elevation data from the Shuttle Radar Topography Mission (SRTM). Each tile was downloaded, converted from its native Height file format (.hgt), and imported into a geographic information system (GIS) for additional processing. Processing of the data included data gap filling, mosaicking, and re-projection of the tiles to form one single seamless digital elevation model. For 11 days in February of 2000, NASA, the National Geospatial-Intelligence Agency (NGA), the German Aerospace Center (DLR), and the Italian Space Agency (ASI) flew X-band and C-band radar interferometry onboard the Space Shuttle Endeavor. The mission covered the Earth between 60?N and 57?S and will provide interferometric digital elevation models (DEMs) of approximately 80% of the Earth's land mass when processing is complete. The radar-pointing angle was approximately 55? at scene center. Ascending and descending orbital passes generated multiple interferometric data scenes for nearly all areas. Up to eight passes of data were merged to form the final processed SRTM DEMs. The effect of merging scenes averages elevation values recorded in coincident scenes and reduces, but does not completely eliminate, the amount of area with layover and terrain shadow effects. The most significant form of data processing for the Ecuador DEM was gap-filling areas where the SRTM data contained a data void. These void areas are a result of radar shadow, layover, standing water, and other effects of terrain, as well as technical radar interferometry phase unwrapping issues. To fill these gaps, topographic contours were digitized from 1:50,000 - scale topographic maps which date from the mid-late 1980's (Souris, 2001). Digital contours were gridded to form elevation models for void areas and subsequently were merged with the SRTM data through GIS and remote sensing image-processing techniques. The data contained in this publication includes a gap filled, countrywide SRTM DEM of Ecuador projected in Universal Transverse Mercator (UTM) Zone 17 North projection, Provisional South American, 1956, Ecuador datum and a non gap filled SRTM DEM of the Galapagos Islands projected in UTM Zone 15 North projection. Both the Ecuador and Galapagos Islands DEMs are available as an ESRI Grid, stored as ArcInfo Export files (.e00), and in Erdas Imagine (IMG) file formats with a 90 meter pixel resolution. Also included in this publication are high and low resolution Adobe Acrobat (PDF) files of topography and landforms maps in Ecuador. The high resolution map should be used for printing and display, while the lower resolution map can be used for quick viewing and reference purposes.

Chirico, Peter G.; Warner, Michael B.

2005-01-01

76

Triangles: tangible interface for manipulation and exploration of digital information topography  

Microsoft Academic Search

This paper presents a system for interacting with digital information, called Triangles. The Triangles system is a physical\\/digital construction kit, which allows users to use two hands to grasp and manipulate complex digital information. The kit consists of a set of identical flat, plastic triangles, each with a microprocessor inside and magnetic edge connectors. The connectors enable the Triangles to

Matthew G. Gorbet; Maggie Orth; Hiroshi Ishii

1998-01-01

77

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

78

Gently dipping normal faults identified with Space Shuttle radar topography data in central Sulawesi, Indonesia, and some implications for fault mechanics  

USGS Publications Warehouse

Space-shuttle radar topography data from central Sulawesi, Indonesia, reveal two corrugated, domal landforms, covering hundreds to thousands of square kilometers, that are bounded to the north by an abrupt transition to typical hilly to mountainous topography. These domal landforms are readily interpreted as metamorphic core complexes, an interpretation consistent with a single previous field study, and the abrupt northward transition in topographic style is interpreted as marking the trace of two extensional detachment faults that are active or were recently active. Fault dip, as determined by the slope of exhumed fault footwalls, ranges from 4?? to 18??. Application of critical-taper theory to fault dip and hanging-wall surface slope, and to similar data from several other active or recently active core complexes, suggests a theoretical limit of three degrees for detachment-fault dip. This result appears to conflict with the dearth of seismological evidence for slip on faults dipping less than ~. 30??. The convex-upward form of the gently dipping fault footwalls, however, allows for greater fault dip at depths of earthquake initiation and dominant energy release. Thus, there may be no conflict between seismological and mapping studies for this class of faults. ?? 2011 Elsevier B.V.

Spencer, J. E.

2011-01-01

79

Gently dipping normal faults identified with Space Shuttle radar topography data in central Sulawesi, Indonesia, and some implications for fault mechanics  

NASA Astrophysics Data System (ADS)

Space-shuttle radar topography data from central Sulawesi, Indonesia, reveal two corrugated, domal landforms, covering hundreds to thousands of square kilometers, that are bounded to the north by an abrupt transition to typical hilly to mountainous topography. These domal landforms are readily interpreted as metamorphic core complexes, an interpretation consistent with a single previous field study, and the abrupt northward transition in topographic style is interpreted as marking the trace of two extensional detachment faults that are active or were recently active. Fault dip, as determined by the slope of exhumed fault footwalls, ranges from 4° to 18°. Application of critical-taper theory to fault dip and hanging-wall surface slope, and to similar data from several other active or recently active core complexes, suggests a theoretical limit of three degrees for detachment-fault dip. This result appears to conflict with the dearth of seismological evidence for slip on faults dipping less than ~ 30°. The convex-upward form of the gently dipping fault footwalls, however, allows for greater fault dip at depths of earthquake initiation and dominant energy release. Thus, there may be no conflict between seismological and mapping studies for this class of faults.

Spencer, Jon E.

2011-08-01

80

Model-Based Estimation of Forest Canopy Height in Red and Austrian Pine Stands Using Shuttle Radar Topography Mission and Ancillary Data: a Proof-of-Concept Study  

SciTech Connect

In this paper, accurate tree stand height retrieval is demonstrated using C-band Shuttle Radar Topography Mission (SRTM) height and ancillary data. The tree height retrieval algorithm is based on modeling uniform tree stands with a single layer of randomly oriented vegetation particles. For such scattering media, the scattering phase center height, as measured by SRTM, is a function of tree height, incidence angle, and the extinction coefficient of the medium. The extinction coefficient for uniform tree stands is calculated as a function of tree height and density using allometric equations and a fractal tree model. The accuracy of the proposed algorithm is demonstrated using SRTM and TOPSAR data for 15 red pine and Austrian pine stands (TOPSAR is an airborne interferometric synthetic aperture radar). The algorithm yields root-mean-square (rms) errors of 2.5-3.6 m, which is a substantial improvement over the 6.8-8.3-m rms errors from the raw SRTM minus National Elevation Dataset Heights.

Brown Jr., C G; Sarabandi, K; Pierce, L E

2007-04-06

81

Method for Crater Detection From Martian Digital Topography Data Using Gradient Value\\/Orientation, Morphometry, Vote Analysis, Slip Tuning, and Calibration  

Microsoft Academic Search

Recently, all the craters from the major currently available manually assembled catalogs have been merged into the catalog with 57 633 known Martian impact craters. This paper presents a new crater detection algorithm (CDA) for the search of still uncataloged impact craters. The CDA is based on fuzzy edge detectors and Radon\\/Hough transform and utilizes digital topography data instead of

Goran Salamuniccar; Sven Loncaric

2010-01-01

82

Tectonics, topography, climate, and erosion: Analysis of Himalayan digital elevation data and numerical modeling  

Microsoft Academic Search

Plate collision drives complex interactions among uplift, climate, and erosion involving feedbacks over many space and time scales. This dissertation investigates these processes and interactions through analysis of digital topographic data, imagery, and geologic data from the Himalayas, and through numerical modeling. A numerical model of continental collision and breakup is used to investigate properties of the global plate tectonic

Christopher Charles Duncan

1997-01-01

83

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

84

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

85

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.

86

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

87

The effect of topography on SAR calibration  

SciTech Connect

During normal synthetic aperture radar (SAR) processing, a flat earth is assumed when performing radiometric corrections such as antenna pattern and scattering area removal. Here the authors examine the effects of topographic variations on these corrections. Local slopes will cause the actual scattering area to be different from that calculated using the flat earth assumption. It is shown that this effect, which is present for both airborne and spaceborne SAR data, may easily cause calibration errors larger than a decibel. Ignoring the topography during antenna pattern removal is expected to be negligible for spaceborne SAR's. In this paper they show how these effects can be taken into account if a digital elevation model is available for the imaged area. It is also shown that not taking the topography into account during antenna pattern removal introduces polarimetric calibration errors.

Zyl, J.J. van; Chapman, B.D.; Dubois, P. (California Inst. of Tech., Pasadena, CA (United States). Jet Propulsion Lab.); Shi, Jiancheng (Univ. of California, Santa Barbara, CA (United States))

1993-09-01

88

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

89

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

90

Refinement of digital elevation models from shadowing cues  

Microsoft Academic Search

In this paper we derive formal constraints relating terrain elevation and observed cast shadows. We show how an optimisation framework can be used to refine surface estimates using shadowing constraints from one or more images. The method is particularly applicable to the digital elevation models produced by the Shuttle Radar Topography Mission (SRTM), which have an abundance of voids in

James Hogan; William A. P. Smith

2010-01-01

91

Georeferencing of continental-scale JERS-1 SAR mosaics based on matching homologous features with a digital elevation model: theory and practice  

Microsoft Academic Search

An effective method for a posteriori ortho-rectification of continental-scale synthetic aperture radar (SAR) mosaics using a digital elevation model (DEM) has been developed. The method is based on homologous feature matching between the DEM and a simulated SAR image. The simulated image is derived from the radar-viewing geometry, topographic information and contextual information provided by the Shuttle Radar Topography Mission

Jan Kropá?ek; Gianfranco De Grandi; Yrjö Rauste

2012-01-01

92

Georeferencing of continental-scale JERS-1 SAR mosaics based on matching homologous features with a digital elevation model: theory and practice  

Microsoft Academic Search

An effective method for a posteriori ortho-rectification of continental-scale synthetic aperture radar (SAR) mosaics using a digital elevation model (DEM) has been developed. The method is based on homologous feature matching between the DEM and a simulated SAR image. The simulated image is derived from the radar-viewing geometry, topographic information and contextual information provided by the Shuttle Radar Topography Mission

Jan Kropá?ek; Gianfranco De Grandi; Yrjö Rauste

2011-01-01

93

SRTM and Laser Altimeter Views of Western Washington State Topography  

NASA Astrophysics Data System (ADS)

Interferometric Synthetic Aperture Radar (InSAR) and laser altimeter measurements of topography provide complimentary approaches to characterize landforms. Results from the Shuttle Radar Topography Mission (SRTM) will provide an unprecedented, near-global, public-domain topography data set at 90 m resolution using a single pass C-band (5.6 cm wavelength) radar interferometer. In vegetated terrains, the C-band radar energy will penetrate part way into vegetation cover. The elevation of the resulting radar phase center, somewhere between the canopy top and underlying ground, will depend on the vegetation density, structure, and presence or absence of foliage. The high vertical accuracy and spatial resolution achieved by laser altimeters, and their capability to directly measure vegetation height and ground topography beneath vegetation cover, provides a method to evaluate InSAR representations of topography. Here a preliminary C-band SRTM digital elevation model (DEM) for a portion of western Washington State is evaluated using laser altimeter data to assess its elevation accuracy and the extent of vegetation penetration. The SRTM DEM extends from the Cascades Range westward to the Olympic Peninsula. The laser altimeter data includes two profiles acquired by the second flight of the Shuttle Laser Altimeter (SLA-02) in August, 1997, numerous transects acquired by the airborne Scanning Lidar Imager of Canopies by Echo Recovery (SLICER) in September, 1995, and comprehensive mapping in the Puget Lowland region acquired by Terrapoint, LLC for the Puget Sound Lidar Consortium in the winters of 2000 and 2001. SLA-02 and SLICER acquired waveforms that record the height distribution of illuminated surfaces within 120 m and 10 m diameter footprints, respectively. The Terrapoint elevations consist of up to four discrete returns from 1 m footprints spaced 1.5 apart, with all areas mapped twice. Methods for comparing laser altimeter and SRTM topography developed here will be applied on a global basis as Ice, Cloud and land Elevation Satellite and Vegetation Canopy Lidar laser altimeter waveform data and final SRTM products become available.

Harding, D. J.; Carabajal, C. C.

2001-12-01

94

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

95

On the use of the digital elevation model to estimate the solar radiation in areas of complex topography  

Microsoft Academic Search

The development of solar energy as a power source in the next few years requires reliable estimation of available solar energy resources. At local scales, topography is the most important factor in determining the distribution of solar radiation at the surface. Interpolation techniques are usually employed to estimate solar radiation where stations are not available, but their usefulness is limited

J. Tovar-Pescador; D. Pozo-Vázquez; J. A. Ruiz-Arias; J. Batlles; G. López; J. L. Bosch

2006-01-01

96

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

97

Gulf of Mexico Satellite Radar Altimetry.  

National Technical Information Service (NTIS)

The dynamic topography of the sea surface was measured. The radar altimeter measurements yield average ocean topographic data which are mapped. Seasonal deviations from a 3 year mean topography are presented. The altimeters are also instrumented with samp...

C. G. Parra R. G. Forsythe C. L. Parsons

1981-01-01

98

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

99

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

100

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

101

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

102

Soviet oceanographic synthetic aperture radar (SAR) research  

Microsoft Academic Search

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

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

1991-01-01

103

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

104

Meeting Gis Database Requirements For Natural Resource Management Through The Integration Of Digital Topography And Satellite Imagery  

Microsoft Academic Search

In order to be an effective tool for resource management, Geographic Information Systems (GIS's) require access to information that is not only comprehensive, standardized, digital, and current, but is also available Province-wide. Much of the existing provincial resource mapping fails to meet one or more of these criteria. In an attempt to overcome this lack of suitable data, a method

Malcolm Gray; Evert Kenk; Rostam Yazdani

1989-01-01

105

A comparison of stereoscopic and monoscopic evaluation of optic disc topography using a digital optic disc stereo camera  

PubMed Central

AIMS—To compare stereophotographic and monophotographic optic disc assessments made using a digital optic disc stereo camera.?METHODS—Stereo digital optic disc photographs of 150 selected patients who had presented to a glaucoma clinic were assessed by two masked observers on separate occasions using (1) the stereophotographs and a stereoviewer, (2) a single image from the same stereopair. Results were analysed for both right and left eyes separately. 95% tolerance limits for change (TC) and intraclass correlation coefficients (ICC) were calculated and a multivariate analysis using a general linear model for repeated measures was performed.?RESULTS—A total of 201 optic disc images of 150 patients (84 females, 108 left eyes) were analysed. Mean age of patients was 64 years. The results for right eyes are as follows (similar results were obtained for left eyes). Intraobserver (stereoscopic compared to monoscopic) measurements of: horizontal cup:disc ratios (CDR), ICC = 0.5995 and 0.7269, TC = 34% and 27%; vertical CDR, ICC = 0.8298 and 0.817, TC = 25% and 27%; area CDR, ICC = 0.7757 and 0.8259, TC = 28% and 25%; circumference CDR, ICC = 0.7618 and 0.8103, TC = 28% and 25%. Interobserver measurements of: horizontal CDR, ICC stereoscopic (SS) = 0.7287; monoscopic (MS) = 0.5030; TC SS = 30%; MS = 32%; vertical CDR, ICC SS = 0.8439; MS = 0.7106; TC SS = 25%; MS = 31%; area CDR, ICC SS = 0.8392; MS = 0.6276; TC SS = 26%; MS = 32%; circumference CDR, ICC SS = 0.8433; MS = 0.6438, TC SS = 26%; MS = 31%. Systematic bias between observers and between methods was within acceptable limits.?CONCLUSIONS—This study using a digital stereo camera indicates that there may be little benefit of stereoscopic imaging over monoscopic imaging despite demonstrating small but inconsistent differences between both observers and methods.??

Parkin, B.; Shuttleworth, G.; Costen, M.; Davison, C.

2001-01-01

106

Emerging Applications of Interferometric Synthetic Aperture Radar (InSAR) in Geomorphology and Hydrology  

Microsoft Academic Search

Interferometric synthetic aperture radar (InSAR) is a powerful geodetic tool used to construct digital elevation models of the earth’s topography and to image centimeter–scale displacements associated with crustal deformation and the flow of ice sheets. The past decade has seen significant improvements in our understanding of earthquakes, volcanoes, and glaciers as a direct result of this technology. Geomorphology and hydrology

Laurence C. Smith

2002-01-01

107

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

108

Applications of satellite imagery and digital topography to the construction of a crustal-scale transect across the central Andes at 20[degrees]S latitude  

SciTech Connect

The central Andean plateau is one of the Earth's most remote and poorly mapped regions. The plateau has an average elevation of 3.7 km, and extends from central Peru to at least 30[degrees]S latitude. The plateau and flanking Subandean foldthrust belt (FTB) reach their greatest width near 20[degrees]S, and at this latitude both the FTB and the basin within the plateau (Altiplano basin) are areas of active hydrocarbon exploration. We have used Landsat TM imagery, stereoscopic SPOT imagery, and digital topography to construct a crustal-scale transect across the central Andes in order to better understand Andean tectonics at this latitude. Beginning at the Peru-Chile trench and continuing to the east, the transect crosses the Coastal Cordillera, Longitudinal Valley, Active Magmatic Arc, Altiplano basin, Eastern Cordillera, Subandean fold-thrust belt, and Subandean foreland basin. A digital elevation model across the entire region illustrates that the magmatic arc, Altiplano basin, and Eastern cordillera all lie within the plateau region. Satellite imagery across the transect illustrates the characteristic geology, structure, and geomorphology of each of the major morphotectonic regions, as well as the nature of their boundaries. The transect has led us to a number of new insights on Andean tectonics at this latitude. Most importantly, it supports a two-stage model of Andean Cenozoic growth in which a widespread Oligocene to mid-Miocene compressional deformation in the Altiplano and Eastern Cordillera is followed in the late Miocene and Pliocene by thrusting localized east of the Eastern Cordillera, forming the Subandean fold-thrust belt.

Gubbels, T.L.; Isacks, B.L. (Cornell Univ., Ithaca, NY (United States)); Ellis, J.M. (Chevron Overseas Petroleum Inc., San Ramon, CA (United States))

1993-02-01

109

Method for crater detection from digital topography data: interpolation based improvement and application to Lunar SELENE LALT data  

NASA Astrophysics Data System (ADS)

Crater detection algorithms (CDAs) are an important subject of recent scientific research, as evident from the numerous recent publications in the field [ASR, 42 (1), 6-19]. In our previous work: (1) all the craters from the major currently available manually assembled catalogues have been merged into the catalogue with 57633 known Martian impact-craters [PSS, 56 (15), 1992-2008]; and (2) the CDA (developed to search for still uncatalogued impact-craters using 1/128° MOLA data) has been used to extend GT-57633 catalogue with 57592 additional craters resulting in GT-115225 catalog [GRS, 48 (5), in press, doi:10.1109/TGRS.2009.2037750]. On the other hand, the most complete catalog for Moon is the Morphological catalog of Lunar craters [edited by V. V. Shevchenko], which includes information on 14923 craters larger than 10km, visible on the lunar nearside and farside. This was the main motivation for application of our CDA to newly available Lunar SELENE LALT data. However, one of the main differences between MOLA and LALT data is the highest available resolution, wherein MOLA is available in 1/128° and LALT in 1/16° . The consequence is that only the largest craters can be detected using LALT dataset. However, this is still an excellent opportunity for further work on CDA in order to prepare it for forthcoming LRO LOLA data (which is expected to be in even better resolution than MOLA). The importance is in the fact that morphologically Martian and Lunar craters are not the same. Therefore, it is important to use the dataset for Moon in order to work on the CDA which is meant for detection of Lunar craters as well. In order to overcome the problem of currently available topography data in low resolution only, we particularly concentrated our work on the CDA's capability to detect very small craters relative to available dataset (up to the extreme case wherein the radius is as small as only two pixels). For this purpose, we improved the previous CDA with a new algorithm for sub-pixel interpolation of elevation samples, before subsequent computations. For elevation samples on larger distances from the crater's center, linear interpolation was used in order to speed-up the computations. For samples closer to the crater's center, the elevation value at the crater's center and relative sub-pixel distance to the selected elevation sample is additionally taken into account. The purpose is to compute the most realistic values for estimated elevation at a selected point. The results are, according to the initial visual evaluation, that numerous craters were successfully detected using SELENE LALT data.

Salamuni?car, Goran; Lon?ari?, Sven

110

The Application of RadarA~é Gauge Comparisons to Operational Precipitation Profile Corrections  

Microsoft Academic Search

The analyses of data recorded during the past eight years with two Swiss radars, a network of rain gauges, and river flow measurements have helped to quantify the vertical profile of reflectivity and the influences of topography, meteorology, and radar parameters on the precision of radar precipitation estimation. The influence of the topography around the radar, the width of the

Jürg Joss; Robert Lee

1995-01-01

111

The Surface Water and Ocean Topography Mission (SWOT): the Ka-band Radar Interferometer (KaRIn) for water level measurements at all scales  

NASA Astrophysics Data System (ADS)

The Surface Water and Ocean Topography (SWOT) mission will study ocean mesoscale and submesoscale phenomena and provide an inventory of storage change and discharge for fresh water bodies and rivers. In this paper, we examine the combination of measurements that will be used by SWOT to achieve a globally consistent data set. We introduce a new channel in the SWOT measurement that combines data transmitted by the interferometer antennas and received by the radiometer antenna allows the closing of the SWOT nadir coverage gap. This new mode also allows for improved calibration between the nadir altimeter and the interferometer, resulting in consistent range measurements. Consistency in the phase measurements is achieved using a mixture of cross-over calibration combined with optimal estimation of system error drift.

Rodriguez, Ernesto; Esteban-Fernandez, Daniel

2010-10-01

112

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

113

Venus topography - A harmonic analysis  

Microsoft Academic Search

A model of Venusian global topography has been obtained by fitting an eighteenth-degree harmonic series to Pioneer Venus orbiter radar altimeter data. The mean radius is (6051.45 + or - 0.04) km. The corresponding mean density is (5244.8 + or 0.5) kg\\/cu m. The center of figure is displaced from the center of mass by (0.339 + or - 0.088)

B. G. Bills; Michael Kobrick

1985-01-01

114

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

115

Backscaiter Analysis Of Airborne Radar: Implications For Background Geobotany  

Microsoft Academic Search

Multi-channel airborne radar data acquired by CCRS and INTERA Technologies Ltd. is assessed for its value in improving a TM-based geobotanical classification of the Mazinaw Lake area in central Ontario. Radar backscatter 'for each radar pass (total of three) is analyzed, with respect to surface parameters such as topography and to radar parameters such as incidence angle and look direction.

J. Harris; J. K. Hornsby

1989-01-01

116

Improved Accuracy for Interferometric Radar Images Using Polarimetric Radar and Laser Altimetry Data  

Microsoft Academic Search

The ability to measure land surface topography over large areas to assess natural hazard threats posed by seismic and flooding events is a critical, international need. Interferometric synthetic aperture radar (INSAR) has been used to map topography; however, accuracies are limited because observations are not measurements of true surface topography over vegetated areas. Instead, the measurements, which depend on the

K. Clint Slatton; Melba M. Crawford; Brian L. Evans

2000-01-01

117

Modeling the impact of topography on seismic amplification at regional scale  

NASA Astrophysics Data System (ADS)

The intensity of earthquake triggered ground shaking is influenced by the characteristics of earthquake source, medium and site effects. These site effects are often not included in the regional ground shaking models, especially the local topography. It is being experimentally proved and noticed during many previous earthquakes, that topography has significant impact on variation of ground shaking and subsequent building damages. Majority of the previous studies investigating the topographic impact on seismic response are limited to synthetic environments or isolated hills. This study deals with exploring the impact of topography on variation of ground shaking caused by the 2005 Kashmir earthquake, at a regional scale. With the proliferation of remote sensing technologies, digital elevation models (DEMs) are freely and readily available at medium resolution, and with global cover. DEMs derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), with 30m resolution, and Shuttle Radar Topography Mission (SRTM), with 90m resolution, can therefore be utilized to model and predict the impact of topography on seismic response, also quickly after a seismic event. The topography of the 2005 Kashmir earthquake affected area is derived from ASTER and SRTM DEMs and analyzed using a 3D spectral finite element code (SPECFEM3D). SPECFEM3D takes into account the seismic source parameters, medium and topography to generate shake maps and earthquake simulations. The ground shaking simulations and peak ground acceleration maps were generated initially assuming the homogenous ground surface and later by including the topography to assess the role of topography in seismic amplification. Topography derived from ASTER and SRTM DEMs were simulated separately to predict the impact of DEM resolution on computed ground shaking simulations and maps. The preliminary result from the model simulations shows that seismic waves were dispersed at topographic discontinuities, leading to intensification of seismic response at hill ridges. Comparing the simulations with and without topography confirmed that the ground shaking was intensified at the hill ridges and steep slopes upto 5 times. Therefore, this study shows the considerable impact of topography on variation of ground shaking and how seismic response modeling can benefit from the readily available global DEMs and SPECFEM3D in modeling earthquake impact more realistic and as early warning technique.

Shafique, Muhammad; Anggraeni, Dita; Bakker, Wim; van der Meijde, Mark

2010-05-01

118

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

119

Exploring scaling laws in surface topography  

Microsoft Academic Search

Surface topography affects many soil properties and processes, particularly surface water storage and runoff. Application of fractal analysis helps understand the scaling laws inherent in surface topography at a wide range of spatial scales and climatic regimes. In this research, a high resolution digital elevation model with a 3mm resolution on one side of the spectrum and large scale DEMs,

M. J. Abedini; M. R. Shaghaghian

2009-01-01

120

The Dawn Topography Investigation  

NASA Astrophysics Data System (ADS)

The objective of the Dawn topography investigation is to derive the detailed shapes of 4 Vesta and 1 Ceres in order to create orthorectified image mosaics for geologic interpretation, as well as to study the asteroids’ landforms, interior structure, and the processes that have modified their surfaces over geologic time. In this paper we describe our approaches for producing shape models, plans for acquiring the needed image data for Vesta, and the results of a numerical simulation of the Vesta mapping campaign that quantify the expected accuracy of our results. Multi-angle images obtained by Dawn’s framing camera will be used to create topographic models with 100 m/pixel horizontal resolution and 10 m height accuracy at Vesta, and 200 m/pixel horizontal resolution and 20 m height accuracy at Ceres. Two different techniques, stereophotogrammetry and stereophotoclinometry, are employed to model the shape; these models will be merged with the asteroidal gravity fields obtained by Dawn to produce geodetically controlled topographic models for each body. The resulting digital topography models, together with the gravity data, will reveal the tectonic, volcanic and impact history of Vesta, and enable co-registration of data sets to determine Vesta’s geologic history. At Ceres, the topography will likely reveal much about processes of surface modification as well as the internal structure and evolution of this dwarf planet.

Raymond, C. A.; Jaumann, R.; Nathues, A.; Sierks, H.; Roatsch, T.; Preusker, F.; Scholten, F.; Gaskell, R. W.; Jorda, L.; Keller, H.-U.; Zuber, M. T.; Smith, D. E.; Mastrodemos, N.; Mottola, S.

2011-12-01

121

Gallery of Virtual Topography  

NSDL National Science Digital Library

The Gallery of Virtual Topography features virtual depictions of topography, including 3D perspectives and QuickTime Virtual Reality (QTVR) movies, created from Digital Elevation Models (DEM's). The site showcases QTVR object movies where the user can spin a 3D terrain to view it from different perspectives. It also includes static 3D-perspective images (JPEG files) of the 3D terrains for those users with slower Internet connections. Some movies and images depict only the form of the landscape, but in others topographic contours are draped over the landscape to better illustrate how contours portray different types of topography (cliffs versus badlands, for example). Some animations illustrate the significance of contours, by allowing the user to progressively fill the landscape up with water to see the water interact with different topographic features. The site also contains a topographic contour map for each 3D terrain, so that instructors can develop student exercises, such as locating points on a map and constructing topographic profiles. Some QTVR movies contain numbered topographic features just for this purpose.

Reynolds, Stephen

122

Visualizing Topography  

NSDL National Science Digital Library

Topographic maps that display three-dimensional landscapes on two-dimensional surfaces can offer a great deal of spatial information in minimal space. However, it is often difficult for people to interpret the features on a topographic map. This interactive feature adapted from Stephen Reynolds's 'Visualizing Topography' website offers color-enhanced and three-dimensional visualizations to help interpret two-dimensional topographic maps. Users can introduce shading, tilt, and rotate the maps to better see the three dimensional feature being represented by the map.

Reynolds, Stephen J.

2010-09-27

123

Visualizing Topography  

NSDL National Science Digital Library

Topographic maps that display three-dimensional landscapes on two-dimensional surfaces can offer a great deal of spatial information in minimal space. However, it is often difficult for people to interpret the features on a topographic map. This interactive feature adapted from Stephen Reynolds's 'Visualizing Topography' website offers color-enhanced and three-dimensional visualizations to help interpret two-dimensional topographic maps. Users can introduce shading, tilt, and rotate the maps to better see the three dimensional feature being represented by the map.

Reynolds, Stephen

2006-01-01

124

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

125

Spatial relationship of groundwater arsenic distribution with regional topography and water-table fluctuations in the shallow aquifers in Bangladesh  

Microsoft Academic Search

The present study has examined the relationship of groundwater arsenic (As) levels in alluvial aquifers with topographic elevation,\\u000a slope, and groundwater level on a large basinal-scale using high-resolution (90 m × 90 m) Shuttle Radar Topography Mission\\u000a (SRTM) digital elevation model and water-table data in Bangladesh. Results show that high As (>50 ?g\\/l) tubewells are located\\u000a in low-lying areas, where mean surface elevation is approximately

M. Shamsudduha; L. J. Marzen; A. Uddin; M.-K. Lee; J. A. Saunders

2009-01-01

126

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

127

Radar imaging of submarine sand waves in tidal channels  

Microsoft Academic Search

The simple theoretical model of Alpers and Hennings describing the radar imaging of submarine bottom topography in coastal waters with strong unidirectional tidal currents is analytically extended to show the influence of advection. The theory applies for L band radar, where second-order terms in the hydrodynamic interaction can be neglected as a first approximation. If future imaging radars from satellites

Ingo Hennings

1990-01-01

128

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

129

Synthetic aperture radar and interferometry development at Sandia National Laboratories  

SciTech Connect

Environmental monitoring, earth-resource mapping, and military systems require broad-area imaging at high resolutions. Many times the imagery must be acquired in inclement weather or during night as well as day. Synthetic aperture radar (SAR) provides such a capability. SAR systems take advantage of the long-range propagation characteristics of radar signals and the complex information processing capability of modern digital electronics to provide high resolution imagery. SAR complements photographic and other optical imaging capabilities because of the minimum constrains on time-of-day and atmospheric conditions and because of the unique responses of terrain and cultural targets to radar frequencies. Interferometry is a method for generating a three-dimensional image of terrain. The height projection is obtained by acquiring two SAR images from two slightly differing locations. It is different from the common method of stereoscopic imaging for topography. The latter relies on differing geometric projections for triangulation to define the surface geometry whereas interferometry relies on differences in radar propagation times between the two SAR locations. This paper presents the capabilities of SAR, explains how SAR works, describes a few SAR applications, provides an overview of SAR development at Sandia, and briefly describes the motion compensation subsystem.

NONE

1993-04-01

130

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

131

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

132

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

133

Impacts of 21st century sea-level rise on a Danish major city - an assessment based on fine-resolution digital topography and a new flooding algorithm  

Microsoft Academic Search

This study examines the potential impact of 21st century sea-level rise on Aarhus, the second largest city in Denmark, emphasizing the economic risk to the city's real estate. Furthermore, it assesses which possible adaptation measures that can be taken to prevent flooding in areas particularly at risk from flooding. We combine a new national Digital Elevation Model in very fine

Jesper Erenskjold Moeslund; Peder Klith Bøcher; Jens-Christian Svenning; Thomas Mølhave; Lars Arge

2009-01-01

134

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

135

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

136

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

137

FFT implementation of Kirchhoff's migration for ground penetrating radar image focussing  

Microsoft Academic Search

GROUND-penetrating radar (GPR) is a mature remote sensing technique employed by engineers and scientists to obtain information from subsurface structures. It is often advantageous to estimate the ground surface topography from radar returns. In this letter, we propose a method to solve the diffraction problem and improve the accuracy of surface topography. A modified version of Kirchhoff's migration technique is

Shrikant Sharma; P Thangarasu; Paramananda Jena; Ramachandra Kuloor

2012-01-01

138

Quantitative Analysis of Venus Radar Backscatter Data in Arcgis.  

National Technical Information Service (NTIS)

Ongoing mapping of the Ganiki Planitia (V14) quadrangle of Venus and definition of material units has involved an integrated but qualitative analysis of Magellan radar backscatter images and topography using standard geomorphological mapping techniques. H...

S. M. Long E. B. Grosfils

2005-01-01

139

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

140

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

141

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

142

Spatial patterns of precipitation and topography in the Himalaya  

Microsoft Academic Search

Spatial variability in precipitation has received little attention in the study of connections between climate, erosion, and tectonics. However, long-term precipita- tion patterns show large variations over spatial scales of ~10 km and are strongly controlled by topography. We use precipitation rate estimates from Tropical Rainfall Measuring Mission (TRMM) satellite radar data to approximate annual precipita- tion over the Himalaya

Alison M. Anders; Gerard H. Roe; Bernard Hallet; David R. Montgomery; Noah J. Finnegan; Jaakko Putkonen

143

Topographies lacking tidal conversion  

Microsoft Academic Search

The consensus is that in a stratified sea a classical model of tidal flow over irregular\\u000abut smooth topography necessarily leads to the generation of internal tides, regardless\\u000aof the shape of the topography. This is referred to as tidal conversion. Here it is shown,\\u000ahowever, that there exists a large class of topographies for which there is neither tidal

Leo R. M. Maas

2011-01-01

144

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

145

Digital Globe  

NSDL National Science Digital Library

Visitors to the Digital Globe have a front seat view of Lisbon, Portugal and the Phillipine Trench. The site offers two MPEG videos which animate topographic seafloor images. The video clips were created by David Sandwell at the Scripps Institution of Oceanography. Also available are nine images of seafloor topography from around the globe. Note that the videos are very large files.

146

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

147

Impacts of 21st century sea-level rise on a Danish major city - an assessment based on fine-resolution digital topography and a new flooding algorithm  

NASA Astrophysics Data System (ADS)

This study examines the potential impact of 21st century sea-level rise on Aarhus, the second largest city in Denmark, emphasizing the economic risk to the city's real estate. Furthermore, it assesses which possible adaptation measures that can be taken to prevent flooding in areas particularly at risk from flooding. We combine a new national Digital Elevation Model in very fine resolution (~2 meter), a new highly computationally efficient flooding algorithm that accurately models the influence of barriers, and geospatial data on real-estate values to assess the economic real-estate risk posed by future sea-level rise to Aarhus. Under the A2 and A1FI (IPCC) climate scenarios we show that relatively large residential areas in the northern part of the city as well as areas around the river running through the city are likely to become flooded in the event of extreme, but realistic weather events. In addition, most of the large Aarhus harbour would also risk flooding. As much of the area at risk represent high-value real estate, it seems clear that proactive measures other than simple abandonment should be taken in order to avoid heavy economic losses. Among the different possibilities for dealing with an increased sea level, the strategic placement of flood-gates at key potential water-inflow routes and the construction or elevation of existing dikes seems to be the most convenient, most socially acceptable, and maybe also the cheapest solution. Finally, we suggest that high-detail flooding models similar to those produced in this study will become an important tool for a climate-change-integrated planning of future city development as well as for the development of evacuation plans.

Erenskjold Moeslund, Jesper; Klith Bøcher, Peder; Svenning, Jens-Christian; Mølhave, Thomas; Arge, Lars

2009-11-01

148

Challenges to Airborne and Orbital Radar Sounding in the Presence of Surface Clutter: Lessons Learned (so far) from the Dry Valleys of Antarctica  

NASA Astrophysics Data System (ADS)

The search for life and in-situ resources for exploration on Mars targets both liquid and solid water, whether distributed or in reservoirs. Massive surface ice may cover potential habitats or other features of great interest. Ice-rich layering in the high latitudes holds clues to the climatic history of the planet. Multiple geophysical methods will clearly be necessary to fully characterize these various states of water (and other forms of ice), but radar sounding will be a critical component of the effort. Orbital radar sounders are already being employed and plans for surface-based and suborbital, above-surface radar sounders are being discussed. The difficulties in interpreting data from each type of platform are quite different. Given the lack of existing orbital radar sounding data from any planetary body, the analysis of airborne radar sounding data is quite useful for assessing the advantages and disadvantages of above-surface radar sounding on Mars. In addition to over 300,000 line-km of data collected over the Antarctic ice sheet by airborne radar sounding, we have recently analyzed data from the Dry Valleys of Antarctica where conditions and features emulate Mars in several respects. These airborne radar sounding data were collected over an ice-free area of Taylor Valley, ice-covered lakes, Taylor Glacier, and Beacon Valley. The pulsed radar (52.5 - 67.5 MHz chirp) was coherently recorded. Pulse compression and unfocused SAR processing were applied. One of the most challenging aspects of above-surface radar sounding is the determination of echo sources. This can, of course, be problematic for surface-based radar sounders given possible subsurface scattering geometries, but it is most severe for above-surface sounders because echoes from cross-track surface topography (surface clutter) can have similar time delays to those from the subsurface. We have developed two techniques to accomplish the identification of this surface clutter in single-pass airborne radar sounding data. The first technique simulates radar data using a digital elevation model (DEM) of surface topography to predict the location and shape of surface echoes in the radar data. This is complemented by the cross-track migration of radar echoes onto the surface. These migrated echoes are superimposed on imagery in order to correlate them with potential surface sources. Using these techniques enabled us to identify a number of echoes in a 24-km segment of the Dry Valleys flight path as arising from the surface and to identify subsurface echoes under the main trunk of Taylor Glacier and possibly multiple reflectors beneath the toe of Taylor Glacier. Surface-based radar confirms the thickness of the glacier at three crossing points. In the ice-free section of the test segment no real subsurface reflectors were found, indicating that the electromagnetic properties of the ground there do not allow significant radar penetration at 60 MHz and/or no radar-significant subsurface interfaces exist. These results illustrate the importance of using complementary techniques, the usefulness of a DEM, and the limitations of single-pass radar sounding data. Advanced processing techniques utilizing radar phase information show promise for achieving better clutter removal for single-pass data. Multi-pass data that we recently collected in the Dry Valleys should allow for the development of techniques to reduce or eliminate the need for a surface elevation model.

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

2005-12-01

149

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

150

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

151

X Ray Topography  

ERIC Educational Resources Information Center

|Discusses some aspects in X-ray topography, including formation of dislocations, characteristics of stacking faults, x-ray contrast in defect inspection, Berg-Barrett technique, and Lang traversing crystal and Borrmann's methods. (CC)|

Balchin, A. A.

1974-01-01

152

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

153

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.

154

Topography-driven variations in backscatter strength and depth observed over the Greenland Ice Sheet with InSAR  

Microsoft Academic Search

ERS radar observations of the Greenland Ice Sheet have yielded images characterized by small-scale (~10 km) variations in backscatter. While these variations are associated with topography, they are not due to local incidence angle differences, since the undulations in topography are small enough (~tens of meters in height) that changes in slope amount to less than a degree; moreover the

E. Weber Hoen; Howard A. Zebker

2000-01-01

155

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

156

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

157

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

158

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

159

Object-based classification of vegetation and terrain topography in Southwestern Amazonia (Brazil) as a tool for detecting ancient fluvial geomorphic features  

NASA Astrophysics Data System (ADS)

Reconstructing the evolution of large tropical fluvial systems over the geological time is challenging, particularly in areas such as the Amazonian lowlands where basic geological and geomorphological data are still scarce relatively to the large dimension of the region. In such areas, remote sensing data are useful for detecting ancient morphological features that may reveal past fluvial dynamics. In this study, we explored object-based image analysis (OBIA) in the Madeira-Purus interfluve, Southwestern Brazilian Amazonia, integrating geospatial data including Landsat satellite multispectral images, the digital elevation model (DEM) acquired during the Shuttle Radar Topography Mission (SRTM), and stream channels digitized from topographic maps. This approach provided the basis to categorize automatically classes with contrasting vegetation and/or topographic characteristics within the dense tropical forest over an extensive and relatively flat forested area. The main goal was to use these classes as a surrogate for the recognition of ancient geomorphic features consisting mainly of paleochannels that may help reconstructing fluvial history in space and time. Landsat optical images with stream vector were appropriate to classify open vegetation areas that grow over paleochannels, but failed to identify these objects when they were located over forested areas. However, the digital elevation model (DEM) derived from the Shuttle Radar Topography Mission (SRTM) was successful to detect these objects even in forested areas. Topographic survey undertaken in the field increased the classification reliability by demonstrating true terrain variations along transects measured across the paleochannels. Based on this technique, networks of dendritic paleochannels were mapped and related to ancient tributaries of the Madeira River that had their courses flowing opposite to main modern streams. This denotes a significant change in fluvial dynamics over time, most likely resulting from tectonic tilting.

Bertani, Thiago de Castilho; Rossetti, Dilce de Fátima; Albuquerque, Paulo Cesar Gurgel

2013-10-01

160

Towards Mapping the Ocean Surface Topography at 1 KM Resolution  

NASA Astrophysics Data System (ADS)

We propose to apply the technique of synthetic aperture radar interferometry to the measurement of ocean surface topography at spatial resolu tion approaching 1 km . The measurement w ill have wide ranging applications in oceanography , hydrology , and marine geophysics. The oceanographic and related societal applications are briefly discussed in the paper. To meet the requirements for oceanographic application s, the in strument must be flown in an orbit w ith proper samp ling of ocean tides.

Fu, L. L.; Rodriguez, E.

2006-07-01

161

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

162

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.

163

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

164

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

165

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

166

Radar investigation of asteroids  

NASA Astrophysics Data System (ADS)

Radar investigations were conducted of selected minor planets, including: (1) observations during 1981-82 of 10 potential targets (2 Pallas, 8 Flora, 12 Victoria, 15 Eunomia, 19 Fortuna, 22 Kalliope, 132 Aethra, 219 Thusnelda, 433 Eros, and 2100 Ra-Shalom); and (2) continued analyses of observational data obtained during 1980-81 for 10 other asteroids (4 Vesta, 7 Iris, 16 Psyche, 75 Eurydike, 97 Klotho, 216 Kleopatra, 1685 Toro, 1862 Apollo, 1865 Cerberus, and 1915 Quetzalcoatl). Scientific objectives include estimation of echo strength, polarization, spectral shape, spectral bandwidth, and Doppler shift. These measurements: (1) yield estimates of target size, shape, and spin vector; (2) place constraints on topography, morphology, and composition of the planetary surface; (3) yield refined estimates of target orbital parameters; (4) reveal the presence of asteroidal satellites.

Ostro, S. J.

1981-07-01

167

Flow Interaction with Topography  

NSDL National Science Digital Library

This module explores the fundamental concepts used to determine how air flow interacts with topography. Using the simple analogy of a marble rolling over a hill, this module examines the relationship between wind speed and static stability of the atmosphere. These results are further extended to include three-dimensional terrain barriers as well as the evolution through time of the interaction.

Spangler, Tim

1999-05-01

168

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

169

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

170

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

171

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

172

Applications of imaging radar to geology  

NASA Astrophysics Data System (ADS)

Tone, texture, and features imaged by radars were studied. A variety of computer image processing techniques were developed to reveal characteristics of these scences. Field checking of sites suggests links between the geology and the images. Tonal studies examine the effects of varying frequency polarization, and illumination geometry. Most surficial geologic units in Death Valley, California, are distinguishable by use of multifrequency, multipolarization radar data. Quaternary basalt flows in Idaho are separable by changing illumination geometry in the vertical plane, whereas desert fans and dunes show little tonal variation as function of changing illumination aximuth. Topographic texture is strongly enhanced by radar's unusual imaging physics computer image processing techniques prove useful in classifying and enhancing image texture. The classification technique, yield results in good agreement with those of human interpreters. The enhancement technique resolves a plunging anticline that was not evident on unprocessed imagery. Identification of features such as lineaments and large topographic highs is critically dependent on radar system parameters. A mathematical model of topography-induced distortion provides insight into the relationship between a radar image and the illuminated terrain. Imaging radar is shown to be a useful sensor for geologic mapping, especially when complementary data are present. Careful image processing, field checking of interpretations, and an understanding of radar imaging physics are critical to effective utilization of this unusual sensor.

Daily, M. I.

173

Correction of Chandrayaan-1 M^3 Lunar Hyperspectral Image Data with Respect to Local Topography  

NASA Astrophysics Data System (ADS)

In this study we propose an empirical method to correct Chandrayaan-1 M³ hyperspectral image data with respect to the local topography based on a digital elevation model (DEM) of high lateral resolution.

Wöhler, C.; Grumpe, A.

2012-03-01

174

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

175

Surface Water and Ocean Topography (SWOT) mission  

NASA Astrophysics Data System (ADS)

The Surface Water Ocean Topography (SWOT) mission was recommended in 2007 by the National Research Council's Decadal Survey, "Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond", for implementation by NASA. The SWOT mission is a partnership between two communities, the physical oceanography and the hydrology, to share high vertical accuracy and high spatial resolution topography data produced by the science payload, principally a Ka-band radar Interferometer (KaRIn). The SWOT payload also includes a precision orbit determination system consisting of GPS and DORIS receivers, a Laser Retro-reflector Assembly (LRA), a Jason-class nadir radar altimeter, and a JASON-class radiometer for tropospheric path delay corrections. The SWOT mission will provide large-scale data sets of ocean sea-surface height resolving scales of 15km and larger, allowing the characterization of ocean mesoscale and submesoscale circulation. The SWOT mission will also provide measurements of water storage changes in terrestrial surface water bodies and estimates of discharge in large (wider than 100m) rivers globally. The SWOT measurements will provide a key complement to other NASA spaceborne global measurements of the water cycle measurements by directly measuring the surface water (lakes, reservoirs, rivers, and wetlands) component of the water cycle. The SWOT mission is an international partnership between NASA and the Centre National d'Etudes Spatiales (CNES). The Canadian Space Agency (CSA) is also expected to contribute to the mission. SWOT is currently nearing entry to Formulation (Phase A). Its launch is targeted for October 2020.

Neeck, Steven P.; Lindstrom, Eric J.; Vaze, Parag V.; Fu, Lee-Lueng

2012-09-01

176

Short contribution: Buried Canopic channel identified near Egypt's Nile delta coast with radar (SRTM) imagery  

Microsoft Academic Search

Shuttle Radar Topography Mission (SRTM) data, with ground-based geologic investigations, define the geographic position of the relict Canopic channel in Egypt's NW Nile delta. Two sinuous channel segments south of Abu Qir Bay are observed on a radar image: a more sinu- ous trace (36 km in length) west of Idku lagoon, and an eastern one (~20 km), reaching the

Jean-Daniel Stanley; Thomas F. Jorstad

2006-01-01

177

Venus topography and kilometer-scale slopes  

NASA Astrophysics Data System (ADS)

During the first 8 months of the Magellan mission, the radar altimeter has made some three million measurements of the surface of Venus covering the latitude range from 85 deg N to 80 deg S. Methods involving range correlation, Doppler filtering, multiburst summation, and range migration are used to focus the observations and to achieve high surface resolution. Results are presented as maps of the global distribution of topography, meter-scale roughness, and power reflection coefficient. The results are similar to those reported in previous experiments (surface heights exhibit a unimodal distribution with more than 80 percent of the surface lying within 1 km of the 6051.84-km mean radius) but the higher resolution of the Magellan altimeter has disclosed several surprisingly steep features, e.g., the southwest face of the Maxwell Montes, the southern face of the Danu Montes, and the chasmata to the east of Thetis Regio, where average kilometer-scale slopes of greater than 30 deg are not uncommon. This conclusion is corroborated by close inspection of synthetic aperture radar imagery.

Ford, Peter G.; Pettengill, Gordon H.

1992-08-01

178

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

179

Radar investigation of asteroids and planetary satellites  

Microsoft Academic Search

The aim is to make radar reconnaissance of near-Earth asteroids, mainbelt ateroids, the Galilean satellites, the Martian satellites, and the largest Saturnian satellites, using the Arecibo 13-cm and the Goldstone 3.5-cm systems. Measurements of echo strength, polarization, and delay\\/Doppler distribution of echo power provide information about dimensions, spin vector, large-scale topography, cm-to-m-scale morphology, and surface bulk density. The observations also

Steven J. Ostro

1988-01-01

180

Topography of Venus and earth - A test for the presence of plate tectonics  

Microsoft Academic Search

Comparisons of earth and Venus topography by use of Pioneer\\/Venus radar altimetry are examined. Approximately 93% of the Venus surface has been mapped with a horizontal resolution of 200 km and a vertical resolution of 200 m. Tectonic troughs have been indicated in plains regions which cover 65% of Venus, and hypsometric comparisons between the two planets' elevation distributions revealed

J. W. Head; S. E. Yuter; S. C. Solomon

1981-01-01

181

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

182

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

183

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

184

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

185

Ocean Surface Topography from Space  

NSDL National Science Digital Library

Interactive Flash Module about Ocean Surface Topography. Module includes sea surface observations and measurements as well as visuals explanations of the alimetry instruments used to detect surface changes.

Jet Propulsion Laboratory, California Institute of Technology, NASA

186

Mercury and Vesta - Preliminary shape and topography  

NASA Astrophysics Data System (ADS)

This year two spacecraft, MESSENGER and Dawn, were placed into orbit around Mercury and the asteroid Vesta, respectively. We have been using stereophotoclinometry (SPC) to analyze MESSENGER and Dawn images both for navigation and to determine the precise shapes and topography of these bodies. Because SPC requires images at different local Sun elevations and azimuths to distinguish between albedo and topographic variations, Mercury presents the challenges of a slow spin rate and a long solar day. Vesta, on the other hand, rotates more than four times per Earth day, allowing a given area of surface to be viewed under rapidly changing illumination and topographic information to be built up rapidly. The essence of SPC is that small pieces of surface called maplets and modeled with digital elevation and albedo are illuminated and correlated with images. Hundreds of these maplets are found in each image, providing a valuable data type for spacecraft navigation. Hundreds of images go into the construction of each maplet, and the resulting multi-image stereo over a wide range of viewing conditions provides a precise determination of the maplet's body-fixed position. The construction of topography with SPC uses each pixel, allowing resolutions comparable to the images themselves. Mercury's topography varies by about 5 km above and below that of a sphere of radius 2440 km. We compare the SPC-derived shape and topography with data from MESSENGER's Mercury Laser Altimeter (MLA). Vesta, although a tenth of Mercury's size, exhibits variations in elevation between 17 km below and 12 km above the equipotential that best matches its surface. The lowest areas lie on the floor of the south polar impact crater, and the highest points lie on the crater's rim.

Gaskell, R. W.; Palmer, E. E.; Mastrodemos, N.; Barnouin, O. S.; Jorda, L.; Taylor, A. H.

2011-12-01

187

Comparison of elevation derived from insar data with dem from topography map in Son Dong, Bac Giang, Viet Nam  

NASA Astrophysics Data System (ADS)

Digital Elevation Models (DEMs) are used in many applications in the context of earth sciences such as in topographic mapping, environmental modeling, rainfall-runoff studies, landslide hazard zonation, seismic source modeling, etc. During the last years multitude of scientific applications of Synthetic Aperture Radar Interferometry (InSAR) techniques have evolved. It has been shown that InSAR is an established technique of generating high quality DEMs from space borne and airborne data, and that it has advantages over other methods for the generation of large area DEM. However, the processing of InSAR data is still a challenging task. This paper describes InSAR operational steps and processing chain for DEM generation from Single Look Complex (SLC) SAR data and compare a satellite SAR estimate of surface elevation with a digital elevation model (DEM) from Topography map. The operational steps are performed in three major stages: Data Search, Data Processing, and product Validation. The Data processing stage is further divided into five steps of Data Pre-Processing, Co-registration, Interferogram generation, Phase unwrapping, and Geocoding. The Data processing steps have been tested with ERS 1/2 data using Delft Object-oriented Interferometric (DORIS) InSAR processing software. Results of the outcome of the application of the described processing steps to real data set are presented.

Nguyen, Duy

2012-07-01

188

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

189

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

190

Digital shaded-relief map of Venezuela  

USGS Publications Warehouse

The Digital Shaded-Relief Map of Venezuela is a composite of more than 20 tiles of 90 meter (3 arc second) pixel resolution elevation data, captured during the Shuttle Radar Topography Mission (SRTM) in February 2000. The SRTM, a joint project between the National Geospatial-Intelligence Agency (NGA) and the National Aeronautics and Space Administration (NASA), provides the most accurate and comprehensive international digital elevation dataset ever assembled. The 10-day flight mission aboard the U.S. Space Shuttle Endeavour obtained elevation data for about 80% of the world's landmass at 3-5 meter pixel resolution through the use of synthetic aperture radar (SAR) technology. SAR is desirable because it acquires data along continuous swaths, maintaining data consistency across large areas, independent of cloud cover. Swaths were captured at an altitude of 230 km, and are approximately 225 km wide with varying lengths. Rendering of the shaded-relief image required editing of the raw elevation data to remove numerous holes and anomalously high and low values inherent in the dataset. Customized ArcInfo Arc Macro Language (AML) scripts were written to interpolate areas of null values and generalize irregular elevation spikes and wells. Coastlines and major water bodies used as a clipping mask were extracted from 1:500,000-scale geologic maps of Venezuela (Bellizzia and others, 1976). The shaded-relief image was rendered with an illumination azimuth of 315? and an altitude of 65?. A vertical exaggeration of 2X was applied to the image to enhance land-surface features. Image post-processing techniques were accomplished using conventional desktop imaging software.

Garrity, Christopher P.; Hackley, Paul C.; Urbani, Franco

2004-01-01

191

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

192

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

193

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

194

Spacecraft studies of planetary surfaces using bistatic radar  

Microsoft Academic Search

Spaceborne transmitters have been used in bistatic geometries for a number of planetary surface studies including inference of topography, Fresnel reflectivity, and RMS surface slopes on the Moon, Mars, and Venus. For the Moon and Mars in particular, the bistatic geometry has enabled remote probing in regions and under conditions not obtainable with Earth-based radar systems, yielding information about surface

Richard A. Simpson

1993-01-01

195

Cave Detection in Limestone using Ground Penetrating Radar  

Microsoft Academic Search

Ground penetrating radar (GPR) is becoming a more common component of the standard array of geophysical techniques that are used by archaeologists. In this paper, we report on the use of GPR to survey an area of archaeologically important karst topography at Kitley Caves in Devon, U.K. We describe the use of GPR to detect voids within a limestone outcrop,

Andrew T. Chamberlain; William Sellers; Chris Proctor; Roslyn Coard

2000-01-01

196

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

197

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

198

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 ...

199

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

200

Gravity and topography  

NASA Astrophysics Data System (ADS)

The paper summarizes the fundamental gravity field constants for Mars and a brief historical review of early determinations and current-day accurate estimates. These include the planetary gravitational constant, global figure, dynamical oblateness, mean density, and rotational period. Topographic results from data acquired from the 1967 opposition to the most recent, 1988, opposition are presented. Both global and selected local topographic variations and features are discussed. The inertia tensor and the nonhydrostatic component of Mars are examined in detail. The dimensionless moment of inertia about the rotational axis is 0.4 for a body of uniform density and 0.37621 if Mars were in hydrostatic equilibrium. By comparing models of both gravity and topography, inferences are made about the degree and depth of compensation in the interior and stresses in the lithosphere.

Esposito, P. B.; Banerdt, W. B.; Lindal, G. F.; Sjogren, W. L.; Slade, M. A.; Bills, B. G.; Smith, D. E.; Balmino, G.

201

Dynamic topography in South America  

NASA Astrophysics Data System (ADS)

Supracrustal tectonics and mantle flow interact to create Earth's topography. While tectonics is associated with the isostatic components of topography, the deflections caused by mantle dynamics, or dynamic topography, represent the non-isostatic components. South America is an ideal natural laboratory to analyze these two contrasting components from the high Andes to the distal plains. Both regions are active and affected by complex geodynamic processes like the subduction of oceanic ridges, geometry and age of slabs, etc. These subducting anomalies affect not only the convergence dynamics and stresses along the entire margin, but also the distribution of mass anomalies in the mantle, which are the main cause of sublithospheric flow and dynamic topography. Here we revisited five examples from north to south, which demonstrate that, the Andes and the distal forelands have been uncompensated since the beginning of the Cenozoic and that additional forces, such as mantle downwellings and upwellings, are required to account for the observed topographies in basins and elevations.

Dávila, Federico M.; Lithgow-Bertelloni, Carolina

2013-04-01

202

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

203

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

204

Scale Dependencies of Vegetation and Topography in a Mountainous Environment of Montana  

Microsoft Academic Search

This research examines the effects of spatial scale on estimating the relationship between vegetation biomass and topography within a portion of Glacier National Park, Montana. The Reflectance\\/Absorptance vegetation index, developed from processed Landsat Thematic Mapper digital data, is related to three topographic variables obtained through processed Digital Elevation Models: elevation, slope angle, and slope aspect. R values between the vegetation

Ling Bian; Stephen J. Walsh

1993-01-01

205

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

206

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

207

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

208

Density, Isostasy, and Topography  

NSDL National Science Digital Library

Show caption HideA critical component of this activity involves sharing team data with the entire class, done the old-fashioned way on the chalkboard. Details This activity begins with an exploration of a topographic map of the earth, ending with the question: Why is the distribution of topography on the earth bimodal? The students then collect two forms of data. They measure the density of the most common rocks that make up oceanic crust (basalt), continental crust (granite), and the mantle (peridotite). They also measure the density of several different kinds of wood, and how high each kind floats in a tub of water. In each case, they work in teams of two or three and then the entire class shares their data. Based on the data from the wood, they derive an equation that relates the density of the wood to the height at which the block floats in the water - the isostasy equation. They then substitute density values for real rocks into their equation to derive thicknesses for average continental and oceanic crust, and apply their knowledge in order to draw a cross-section of the crust across South America. This activity gives students a real, hands-on and mathematical understanding of the principle of isostasy.

Egger, Anne

209

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

210

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

211

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

212

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

213

Rhythmic Patterns of Beach Topography.  

National Technical Information Service (NTIS)

Rhythmic patterns of topography may be apparent simultaneously in a longshore alternation of cuspate projections and arcuate embayments along the beach face, in a rhythmic longshore bar composed of an alternate series of arcs and cusps, and in longshore u...

J. L. van Beek

1974-01-01

214

The Glacier and Ice Sheet Topography Interferometer: An Update on a Unique Sensor for High Accuracy Swath Mapping of Land Ice  

NASA Astrophysics Data System (ADS)

We discuss the innovative concept and technology development of a Ka-band (35 GHz) radar for mapping the surface topography of glaciers and ice sheets. The "Glacier and Land Ice Surface Topography Interferometer" (GLISTIN) is a single-pass, single platform interferometric synthetic aperture radar (InSAR) with an 8mm wavelength, which minimizes snow penetration yet remains relatively impervious to atmospheric attenuation. Such a system has the potential for delivering topographic maps at high spatial resolution, high vertical accuracy, independent of cloud cover, with a subseasonal update and would greatly enhance current observational and modeling capabilities of ice mass-balance and glacial retreat. To enable such measurements, a digitally beamformed antenna array is utilized to provide a wide measurement swath at a technologically feasible transmit power. To prove this concept and advance the technology readiness of this design we are currently funded by the NASA Earth Science Technology Office (ESTO) Instrument Incubator Program (IIP) to build and test a 1m x 1m digitally-beamformed (DBF) Ka-band slotted waveguide antenna with integrated digital receivers. This antenna provides 16 simultaneous receive beams, effectively broadening the swath without reducing receive antenna gain. The implementation of such a large aperture at Ka-band presents many design, manufacturing and calibration challenges which are addressed as part of this IIP. The integrated DBF array will be fielded at the Jet Propulsion Laboratory's antenna range to demonstrate the overall calibration, beamforming and interferometric performance through creation of topographic imagery of the local Arroyo Seco. Currently entering the third year of the program, we will overview the system concept, array implementation and status of the technology. While the IIP addresses the development of the major technology challenges, an additional effort will demonstrate the phenomenology of the measurement by adapting the NASA ESTO-funded Uninhabited Aerial Vehicle - Synthetic Aperture Radar (UAVSAR) system for Ka-band single-pass interferometry. The conversion to Ka-Band will utilize the modular UAVSAR system originally designed for L-Band operation, retaining the radar control, data acquisition and processing infrastructure and requiring only minor pod and RF modifications. We will fly the Ka-Band interferometer aboard the UAVSAR platform over regions of Greenland, flying a grid over Jakobshavn glacier, then a transect from the coast to Swiss Camp ending at Greenland's Summit. Over a period of 4-5 weeks at the beginning of the melt season, these flight missions will be repeated in different snow/ice conditions. The flight data will be compared with airborne laser altimetry (Airborne Topographic Mapper lidar instrument, NASA GSFC/Wallops), field observations (GPS data at Swiss Camp, Summit), and climate data from the Automatic Weather Station (Colorado University) network (snowfall, corrected for densification) to estimate penetration and produce topographic surface maps. Topography is an essential piece of information for glaciology and a high-quality topographic map (tens of cm height accuracy over 10m pixels) will be produced. The experiment will pave the way to making more topographic products available to glaciologists and aid in the design a spaceborne mission capable of delivering similar products at the continental scale.

Moller, D.; Heavey, B.; Hensley, S.; Hodges, R.; Rengarajan, S.; Rignot, E.; Sadowy, G.; Simard, M.; Zawadzki, M.

2007-12-01

215

Hillslope Topography from Unconstrained Photographs  

Microsoft Academic Search

Quantifications of Earth surface topography are essential for modeling the connections between physical and chemical processes of erosion and the shape of the landscape. Enormous investments are made in developing and testing process-based landscape evolution models. These models may never be applied to real topography because of the difficulties in obtaining high-resolution (1–2 m) topographic data in the form of

Arjun M. Heimsath; Hany Farid

2002-01-01

216

Cassini radar : system concept and simulation results  

NASA Astrophysics Data System (ADS)

The Cassini mission is an international venture, involving NASA, the European Space Agency (ESA) and the Italian Space Agency (ASI), for the investigation of the Saturn system and, in particular, Titan. The Cassini radar will be able to see through Titan's thick, optically opaque atmosphere, allowing us to better understand the composition and the morphology of its surface, but the interpretation of the results, due to the complex interplay of many different factors determining the radar echo, will not be possible without an extensive modellization of the radar system functioning and of the surface reflectivity. In this paper, a simulator of the multimode Cassini radar will be described, after a brief review of our current knowledge of Titan and a discussion of the contribution of the Cassini radar in answering to currently open questions. Finally, the results of the simulator will be discussed. The simulator has been implemented on a RISC 6000 computer by considering only the active modes of operation, that is altimeter and synthetic aperture radar. In the instrument simulation, strict reference has been made to the present planned sequence of observations and to the radar settings, including burst and single pulse duration, pulse bandwidth, pulse repetition frequency and all other parameters which may be changed, and possibly optimized, according to the operative mode. The observed surfaces are simulated by a facet model, allowing the generation of surfaces with Gaussian or non-Gaussian roughness statistic, together with the possibility of assigning to the surface an average behaviour which can represent, for instance, a flat surface or a crater. The results of the simulation will be discussed, in order to check the analytical evaluations of the models of the average received echoes and of the attainable performances. In conclusion, the simulation results should allow the validation of the theoretical evaluations of the capabilities of microwave instruments, when considering topics like the surface topography, stratigraphy and identification of different materials.

Melacci, P. T.; Orosei, R.; Picardi, G.; Seu, R.

1998-10-01

217

Global Multi-Resolution Topography synthesis  

NASA Astrophysics Data System (ADS)

Seafloor bathymetric data acquired with modern swath echo sounders provide coverage for only a small fraction of the global seabed yet are of high value for studies of the dynamic processes of seafloor volcanism, tectonics, mass wasting, and sediment transport that create and shape the undersea landscape. A new method for compilation of global seafloor bathymetry that preserves the native resolution of swath sonars is presented. The Global Multi-Resolution Topography synthesis consists of a hierarchy of tiles with digital elevations and shaded relief imagery spanning nine magnification doublings from pole to pole (http://www.marine-geo.org/portals/gmrt). The compilation is updated and accessible as surveys are contributed, edited, and added to the tiles. Access to the bathymetry tiles is via Web services and with WMS-enabled client applications such as GeoMapApp®, Virtual Ocean, NASA World Wind®, and Google Earth®.

Ryan, William B. F.; Carbotte, Suzanne M.; Coplan, Justin O.; O'Hara, Suzanne; Melkonian, Andrew; Arko, Robert; Weissel, Rose Anne; Ferrini, Vicki; Goodwillie, Andrew; Nitsche, Frank; Bonczkowski, Juliet; Zemsky, Richard

2009-03-01

218

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

219

Precise integrated topography of Dokdo, East Sea, Korea, using LIDAR DEM and Multibeam echo sounding data  

Microsoft Academic Search

In this study, We created and analyzed Precise integrated topography of Dokdo, East Sea, Korea, using land data that were collected by airborne LIDAR(Light Detection and Ranging) DEM(Digital Elevation Model) and seafloor bathymetry data by Multi-beam echo sounder. Airborne LIDAR DEM represent more detailed topography of land than other DEM data. Composition of airborne LIDAR DEM and aerial photograph produced

C. Kim; H. Joo; E. Jeong; S. Lee; H. Kim

2009-01-01

220

Foldbelt exploration with synthetic aperture radar (SAR) in Papua New Guinea  

SciTech Connect

Synthetic aperture radar (SAR) is being successfully used within the southern fold and thrust belt of Papua New Guinea to map surface structure and stratigraphy and to help plan a hydrocarbon exploration program. The airborne SAR imagery, along with other surface data, is used as a primary exploration tool because acquisition of acceptable seismic data is extremely costly due to extensive outcrops of Tertiary Darai Limestone which develops rugged karst topography. Most anticlines in the licenses are capped with this deeply karstified limestone. The region is ideally suited to geologic analysis using remote sensing technology. The area is seldom cloud free and is covered with tropical rain forest, and geologic field studies are limited. The widespread karst terrain is exceedingly dangerous, if not impossible, to traverse on the ground. SAR is used to guide ongoing field work, modeling of subsurface structure, and selection of well locations. SAR provides their explorationists with an excellent data base because (1) structure is enhanced with low illumination, (2) resolution is 6 x 12 m, (3) digital reprocessing is possible, (4) clouds are penetrated by the SAR, and (5) the survey was designed for stereoscopic photogeology. Landsat images and vertical aerial photographs complement SAR but provide subdued structural information because of minimal shadowing (due to high sun angles) and the jungle cover. SAR imagery reveals large-scale mass wasting that has led to a reevaluation of previously acquired field data. Lithologies can be recognized by textural and tonal changes on the SAR images despite near-continuous canopy of jungle. Reprocessing and contrast stretching of the digital radar imagery provide additional geologic information.

Ellis, J.M.; Pruett, F.D.

1987-05-01

221

Surface Roughness of the Moon Derived from Multi-frequency Radar Data  

NASA Astrophysics Data System (ADS)

Surface roughness of the Moon provides important information concerning both significant questions about lunar surface processes and engineering constrains for human outposts and rover trafficabillity. Impact-related phenomena change the morphology and roughness of lunar surface, and therefore surface roughness provides clues to the formation and modification mechanisms of impact craters. Since the Apollo era, lunar surface roughness has been studied using different approaches, such as direct estimation from lunar surface digital topographic relief, and indirect analysis of Earth-based radar echo strengths. Submillimeter scale roughness at Apollo landing sites has been studied by computer stereophotogrammetry analysis of Apollo Lunar Surface Closeup Camera (ALSCC) pictures, whereas roughness at meter to kilometer scale has been studied using laser altimeter data from recent missions. Though these studies shown lunar surface roughness is scale dependent that can be described by fractal statistics, roughness at centimeter scale has not been studied yet. In this study, lunar surface roughnesses at centimeter scale are investigated using Earth-based 70 cm Arecibo radar data and miniature synthetic aperture radar (Mini-SAR) data at S- and X-band (with wavelengths 12.6 cm and 4.12 cm). Both observations and theoretical modeling show that radar echo strengths are mostly dominated by scattering from the surface and shallow buried rocks. Given the different penetration depths of radar waves at these frequencies (< 30 m for 70 cm wavelength, < 3 m at S-band, and < 1 m at X-band), radar echo strengths at S- and X-band will yield surface roughness directly, whereas radar echo at 70-cm will give an upper limit of lunar surface roughness. The integral equation method is used to model radar scattering from the rough lunar surface, and dielectric constant of regolith and surface roughness are two dominate factors. The complex dielectric constant of regolith is first estimated globally using the regolith composition and the relation among the dielectric constant, bulk density, and regolith composition. The statistical properties of lunar surface roughness are described by the root mean square (RMS) height and correlation length, which represent the vertical and horizontal scale of the roughness. The correlation length and its scale dependence are studied using the topography data from laser altimeter observations from recent lunar missions. As these two parameters are known, surface roughness (RMS slope) can be estimated by minimizing the difference between the observed and modeled radar echo strength. Surface roughness of several regions over Oceanus Procellarum and southeastern highlands on lunar nearside are studied, and preliminary results show that maira is smoother than highlands at 70 cm scale, whereas the situation turns opposite at 12 and 4 cm scale. Surface roughness of young craters is in general higher than that of maria and highlands, indicating large rock population produced during impacting process.

Fa, W.

2011-12-01

222

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

223

Radar images of the bed of the Greenland Ice Sheet  

NASA Astrophysics Data System (ADS)

In this paper, we apply radar tomography methods to very-high-frequency, airborne synthetic-aperture radar data to measure the ice thickness field and to construct three-dimensional basal image maps of a 5 × 20 km study area located along the southern flank of the Jakobshavn Glacier, Greenland. Unlike ice radar measurements typically made at nadir, our approach uses radar-echo phase and amplitude measured across an antenna array to determine the propagation angle and signal strength of pixel elements distributed on each side of the aircraft flight path. That information, combined with knowledge of aircraft position and the assumed dielectric properties of the glacier, can be used to measure ice thickness and radar reflectivity across a 3-km wide swath. Combining ice thickness and surface topography data, we estimate basal topography and basal drag. We conclude that the glacier is sliding over the bed. We use the three-dimensional image maps of the bed to inspect the modern subglacial geomorphology and find for the first time beneath the Greenland Ice Sheet assemblages of long ridge-groove landforms that are oriented in the direction of the ice flow. Spatial dimensions (10 to 30 m depths, 150 to 500 m spacing and lengths of 10 km or more) and correlation with the current ice flow direction suggest that these are glacial erosional features similar to mega-grooves observed on deglaciated terrain.

Jezek, Kenneth; Wu, Xiaoqing; Gogineni, Prasad; RodríGuez, Ernesto; Freeman, Anthony; Rodriguez-Morales, Fernando; Clark, Chris D.

2011-01-01

224

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

225

Analysis of 2001 US-ITASE Traverse Deep-Penetrating Radar Studies in West Antarctica  

Microsoft Academic Search

The 2001 US-ITASE traverse route covered 835 km from Byrd Surface Camp to Pine Island Glacier (PIG), crossing the Ross Sea\\/Amundsen Sea (RS\\/AS) divide and the PIG\\/ Rutford Ice Stream divide at two separate locations and recording bed topography and internal layers along most of the route. In regions where previous radar data have been available our bed topography corresponds

B. C. Welch; R. W. Jacobel; S. F. Harris; L. S. Smith

2002-01-01

226

MODIS observations of the bottom topography and its inter-annual variability of Poyang Lake  

Microsoft Academic Search

Using MODIS 250-m resolution data, we developed a novel approach to derive the bottom topography of Poyang Lake, the largest freshwater lake of China (>3000km2 at maximum inundation) for every year between 2000 and 2009. The approach differs from other traditional methods (sonar, Lidar, optical inversion, and Radar) but takes advantage of the fast-changing nature of the lake's inundation area.

Lian Feng; Chuanmin Hu; Xiaoling Chen; Rongfang Li; Liqiao Tian; Brock Murch

2011-01-01

227

Measured and Estimated Seafloor Topography: Land Topography from GTOPO30  

NSDL National Science Digital Library

This web site displays two "clickable" maps - one topographic, and the other a Ship Track Each of 16 regions on the maps displays measured and estimated seafloor topography. A poster of the images can be ordered for a fee. Links to related sites are also provided.

228

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

229

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

230

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

231

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

232

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

233

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

234

Numerical Methods in Understanding the Performances of Radar Sounding Techniques: Multiple low Frequency Approach for Unambiguous Identification of Subsurface Water Saturated Interfaces on Mars  

Microsoft Academic Search

Low frequency sounding radars can probes the subsurface layers of a planetary surface down to varying depths depending on the sounding frequency, geometry, surface topography, geoelectrical and geomagnetic properties of the sounded terrains. Hence a good understanding of the electric and magnetic wave interaction mechanisms between the radar waves and the rocks and sediments constituting the investigated media is crucial

J. Fernandez; E. Heggy; S. Khan

2004-01-01

235

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

236

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

237

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

238

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

239

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

240

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

241

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

242

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

243

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

244

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

245

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

246

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

247

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

248

Ground Penetrating Radar Advances in Subsurface Imaging for Archaeology  

Microsoft Academic Search

Advances in imaging software for Ground Penetrating Radar (GPR) have greatly enhanced the utility of this geophysical remote\\u000a sensing tool for archaeological discovery. Time-slice analysis, isosurface rendering, and “overlay analysis” are among several\\u000a image analyses used to identify subsurface archaeological remains. Static corrections, in which the tilt of the transmitting\\u000a antenna is accounted for over areas with significant topography, are

Dean Goodman; Kent Schneider; Salvatore Piro; Yasushi Nishimura; Agamemnon G. Pantel

249

X-ray Topography in Protein Crystals  

NASA Astrophysics Data System (ADS)

X-ray topography, especially synchrotron X-ray topography, provides a useful tool for the characterization of protein crystals in order to characterize the defects. We observed clear images of dislocations in hen-egg white lysozyme crystals. In this article we overviewed the research on crystal defects, especially dislocations of protein crystals by synchrotron X-ray topography.

Kojima, Kenichi; Tachibana, Masaru

250

The topography of Iapetus' leading side  

Microsoft Academic Search

We have used Cassini stereo images to study the topography of Iapetus' leading side. A terrain model derived at resolutions of 4–8 km reveals that Iapetus has substantial topography with heights in the range of ?10 km to +13 km, much more than observed on the other middle-sized satellites of Saturn so far. Most of the topography is older than

Bernd Giese; Tilmann Denk; Gerhard Neukum; Thomas Roatsch; Paul Helfenstein; Peter C. Thomas; Elizabeth P. Turtle; Alfred McEwen; Carolyn C. Porco

2008-01-01

251

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

252

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

253

Topography, Cell Response, and Nerve Regeneration  

PubMed Central

In the body, cells encounter a complex milieu of signals, including topographical cues. Imposed topography can affect cells on surfaces by promoting adhesion, spreading, alignment, morphological changes, and changes in gene expression. Neural response to topography is complex, and depends on the dimensions and shapes of physical features. Looking toward repair of nerve injuries, strategies are being explored to engineer guidance conduits with precise surface topographies. How neurons and other cell types sense and interpret topography remains to be fully elucidated. Studies reviewed here include those of topography on cellular organization and function as well as potential cellular mechanisms of response.

Hoffman-Kim, Diane; Mitchel, Jennifer A.; Bellamkonda, Ravi V.

2010-01-01

254

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

255

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

256

Stem Cell Interaction with Topography  

Microsoft Academic Search

\\u000a The growth and differentiation of stem cells are regulated by biochemical and biophysical cues in the extracellular microenvironment.\\u000a Increasing evidences have shown that substrate topography, one of the biophysical properties of the microenvironment, can\\u000a affect stem cell fate, such as the maintenance of embryonic stem cells and the differentiation of adult and embryonic stem\\u000a cells. The underlying mechanism of how

Benjamin K. K. Teo; Soneela Ankam; Evelyn K. F. Yim

257

Whitebeam X-ray topography  

Microsoft Academic Search

After radiography, white-beam X-ray topography (XRT) is the simplest X-ray imaging technique for crystals. An X-ray topograph is formed by a Bragg reflexion and is in effect a high-spatial-resolution Laue ‘spot’. Synchrotron radiation has given XRT additional powers, with its broad continuous spectrum, small beam divergence, high intensity, strong polarization and regular pulsed time structure. Each Laue image, however, may

Moreton Moore

2012-01-01

258

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

259

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

260

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

261

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

262

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

263

Urban topography: 3D database construction for propagation modeling in an urban environment  

NASA Astrophysics Data System (ADS)

Construction of digital elevation models (DEMs) for natural earth surfaces have now become common practice. What does one do when the topography is caused by the closely-spaced tall buildings of lower Manhattan, New York City. Although the DEM principles are applicable, special problems were encountered in this very exciting and innovative project, requiring unique solutions, which are all discussed in this article.

Goldsmith, Viktor; Williamson, Doug; Tobar, Juan; Becker, Mark

1998-01-01

264

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

265

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

266

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

267

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

268

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

269

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

270

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

271

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

272

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

273

Mapping and interpretation of Sinlap crater on Titan using Cassini VIMS and RADAR data  

Microsoft Academic Search

Only a few impact craters have been unambiguously detected on Titan by the Cassini-Huygens mission. Among these, Sinlap is the only one that has been observed both by the RADAR and VIMS instruments. This paper describes observations at centimeter and infrared wavelengths which provide complementary information about the composition, topography, and surface roughness. Several units appear in VIMS false color

Stéphane Le Mouélic; Philippe Paillou; Michael A. Janssen; Jason W. Barnes; Sébastien Rodriguez; Christophe Sotin; Robert H. Brown; Kevin H. Baines; Bonnie J. Buratti; Roger N. Clark; Marc Crapeau; Pierre J. Encrenaz; Ralf Jaumann; Dirk Geudtner; Flora Paganelli; Laurence Soderblom; Gabriel Tobie; Steve Wall

2008-01-01

274

Satellite radar altimetry from open ocean to coasts: challenges and perspectives  

Microsoft Academic Search

The history of satellite radar altimetry stems from the need to capture a global view of the surface topography of the oceans. As altimeters are specifically designed for global observations, they encounter major problems in coastal regions, such as relatively poor sampling and inaccuracy of the corrections, so measurements are generally discarded. Nevertheless, a global archive of 15 years of

Stefano Vignudelli; Helen M. Snaith; Florent Lyard; Paolo Cipollini; Fabio Venuti; Florence Birol; Jérôme Bouffard; Laurent Roblou

275

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

276

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

277

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

278

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

279

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

280

Topography of inner core boundary  

NASA Astrophysics Data System (ADS)

Precise determination of the topography of a major internal boundary of the Earth is difficult because of the trade-off with the unknown velocity structure above it. However, the discoveries of the inner core (IC) rotation and high-quality teleseismic waveform doublets make the precise mapping of the topography of the inner core boundary (ICB) possible, as demonstrated in recent studies. Here we examine IC refracted (PKP-DF) and reflected (PKP-CD) waves recorded at the Yellowknife Array and global stations from 13 high-quality doublets, among a large collection of doublets in S. Sandwich Islands that we have assembled. Our results show clear evidence for spatial and temporal variations of IC reflections in travel times and in waveforms. If the time separation (dT) between the two members of the doublet is less than 3 years, the IC arrivals show little temporal change in travel times or waveforms. If dT is greater than about 6 years, some doublets show large variations but some others do not. The ICB regions beneath Atlantic Ocean and Indian Ocean show little temporal change. The regions show large variations are beneath Africa and the Central America, which coincide with large seismic anomalies at the core-mantle boundary (CMB). Inside these two ICB regions, there are fine-scale (km scale) variations. The largest temporal changes of IC reflections are about 0.10 to 0.15 s, corresponding to a topographic variation of up to 3.7 to 5.6 km. The results suggest ICB topography of a few kms on fine to regional scales. Dynamical models include a bumpy ICB rotating with the IC itself or a transient slurry boundary sloshing about in the turbulence at the base of the convecting outer core. The geographical coincidence of the ICB and CMB anomalies may suggest strong thermal coupling of the mantle and the core.

Song, X.; Dai, W.

2007-12-01

281

Estimating lava volume by precision combination of multiple baseline spaceborne and airborne interferometric synthetic aperture radar: The 1997 eruption of Okmok Volcano, Alaska  

USGS Publications Warehouse

Interferometric synthetic aperture radar (InSAR) techniques are used to calculate the volume of extrusion at Okmok volcano, Alaska by constructing precise digital elevation models (DEMs) that represent volcano topography before and after the 1997 eruption. The posteruption DEM is generated using airborne topographic synthetic aperture radar (TOPSAR) data where a three-dimensional affine transformation is used to account for the misalignments between different DEM patches. The preeruption DEM is produced using repeat-pass European Remote Sensing satellite data; multiple interferograms are combined to reduce errors due to atmospheric variations, and deformation rates are estimated independently and removed from the interferograms used for DEM generation. The extrusive flow volume associated with the 1997 eruption of Okmok volcano is 0.154 ?? 0.025 km3. The thickest portion is approximately 50 m, although field measurements of the flow margin's height do not exceed 20 m. The in situ measurements at lava edges are not representative of the total thickness, and precise DEM data are absolutely essential to calculate eruption volume based on lava thickness estimations. This study is an example that demonstrates how InSAR will play a significant role in studying volcanoes in remote areas.

Lu, Z.; Fielding, E.; Patrick, M. R.; Trautwein, C. M.

2003-01-01

282

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.

283

Geologic Investigations of the Venusian Surface Using Magellan Radar Imagery, Altimetry, and Radiometry  

NASA Astrophysics Data System (ADS)

A comprehensive study of Magellan multiple-Cycle synthetic aperture radar (SAR) data from Venus reveals morphological, surface roughness, and dielectric variations valuable in understanding emplacement mechanisms of fluidized ejecta blanket (FEB) craters, nearby plains and lava flows. FEB deposits develop variable channel morphologies related to parameters such as crater diameter and flow length. This study develops new procedures of digital unit mapping and polygon-filling algorithms using Magellan SAR, altimetry, and radiometry data. These techniques allow the extraction of radiophysical information for geologic materials such as: (1) specific backscatter (sigma_ {rm O}) behavior; (2) average calculated values of emissivity, rms slopes, corrected reflectivity, and the diffuse component of reflectivity; and (3) variations in radar properties along longitudinal traverses that are best explained by surface roughness trends at several spatial scales and/or dielectric variations. Backscatter curve slopes of the FEBs studied here are consistent with surface textures that are either transitional between a'a and pahoehoe -like or more pahoehoe-like. Increasing FEB roughnesses downflow are interpreted to be associated with more lava -like flows, while decreasing roughnesses are more similar to trends typical of gravity (pyroclastic-like or debris -like) flows. Most commonly, FEB crater flow materials exhibit either gravity flow-like styles or transitions from proximal, lava/melt-like flow styles to distal, gravity flow-like styles. Some FEBs show more complicated behavior, however, or appear to be more dominated by dielectric differences downflow, as inferred from correlations between the data sets. Such transitions may result from changes in local topography or from overlapping of flow lobes during FEB emplacement. Computer modeling of FEB flows over topography was performed using modified programs previously applied to Mt. St. Helens' flows. These models demonstrate for the three FEB craters studied that the flows require relatively low initial velocities as well as low values of yield strength and viscosity. Geologic mapping of USGS quadrangle Barrymore (V59) shows evidence of an extensive plains formation event obscuring older local tectonic and volcanic structures, followed by regional and localized compression, forming wrinkle ridges and ridge belts. Application of terrestrial ERS-1 SAR data of the Channeled Scabland region shows backscatter values indicative of surfaces somewhat rougher than terrestrial a'a flows.

Johnson, Jeffrey Roy

1994-01-01

284

Plasma processing for nanostructured topographies  

NASA Astrophysics Data System (ADS)

Plasma and directed ion interactions with materials have been widely observed to create complex surface patterns on a micro- and nano- scale. Generally, these texturizations are byproducts of another intended application (such as a feature formation on a sputtering target) and patterning is considered inconsequential or even detrimental. This work examined the possibility of using these phenomena as primary methods for producing beneficial topographies. Specifically, investigations focused on the use of helium plasma exposure and directed ion etching to create nanostructured surfaces capable of affecting biological interactions with implanted materials. Orthogonal argon ion etching and low energy helium plasma texturization of titanium were considered for use on orthopedic and dental implants as a means of increasing osteoblast activity and bone attachment; and oblique angle etching was evaluated for its use in creating topographies with cell deterrent or anti-thrombogenic properties. In addition, the helium driven evolution of surface features on 6061 aluminum alloy was characterized with respect to ion energy and substrate temperature. These surfaces were then considered for ice phobic applications.

Riedel, Nicholas Alfred

285

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

286

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

287

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

288

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

289

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

290

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

291

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

292

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

293

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

294

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

295

Tectonics, Climate, and Mountain Topography  

NASA Astrophysics Data System (ADS)

By regressing simple, independent variables that describe climate and tectonic processes against measures of topography and relief of 69 mountain ranges worldwide, we quantify the relative importance of these processes in shaping observed landscapes. Climate variables include latitude (as a surrogate for mean annual temperature and insolation, but most importantly for the likelihood of glaciation) and mean annual precipitation. To quantify tectonics we use shortening rates across each range. As a measure of topography, we use mean and maximum elevations and relief calculated over different length scales. We show that the combination of climate (negative correlation) and tectonics (positive correlation) explain substantial fractions (> 25%, but < 50%) of mean and maximum elevations of mountain ranges, but that shortening rates account for smaller portions, <25%, of the variance in most measures of topography and relief (i.e. with low correlations and large scatter). Relief is insensitive to mean annual precipitation, but does depend on latitude, especially for relief calculated over small (~1 km) length scales, which we infer to reflect the importance of glacial erosion. Larger-scale (averaged over length scales of ~10 km) relief, however, correlates positively with tectonic shortening rate. Moreover, the ratio between small-scale and large-scale relief, as well as the relative relief (the relief normalized by the mean elevation of the region) varies most strongly with latitude (strong positive correlation). Therefore, the location of a mountain range on Earth and corresponding climatic conditions, not just tectonic forcing, appears to be a key factor in determining its shape and size. In any case, the combination of tectonics and climate, as quantified here, can account for approximately half of the variance in these measures of topography. The failure of present-day shortening rates to account for more than 25% of most measures of relief raises the question: Is active tectonics overrated in attempts to account for present-day relief and exhumation rates of high terrain? The following points are of particular importance: 1) Elevations of ranges directly reflect the interaction between tectonics, which thickens the crust, and therefore increases elevations, and climate (through erosion), which thins the crust, and hence decreases the elevation. The importance of tectonics appears to be modest in most cases, and suggests that although tectonics is obviously essential for mountain building, but the shapes of mature ranges appear to be controlled mostly by climate factors, that cause a large scatter. 2) Relief is not sensitive to mean annual precipitation amounts, but increases with shortening rates and latitude (hence glacial erosion). Relief averaged over large areas is not affected much by climatic factors, and more by tectonics, but relief measured on short distance scales correlates best with a combination of tectonics and latitude. Relief in high-latitude mountain ranges result largely from glacial excavation at valley scale of the topography created by tectonics. 3) The location of a mountain range on Earth appears to be an important factor in determining its elevation. Latitude also correlates with relief measured on short distance scales and the relative relief (the amount of relief scaled to the mean elevation of the range). Presumably, the climatic differences that vary with latitude, glaciers in particular, play a crucial role in shaping that relief.

Champagnac, J.-D.; Molnar, P.; Sue, C.; Herman, F.

2012-04-01

296

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

297

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

298

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

299

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

300

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.

301

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

302

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

303

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

304

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

305

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

306

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

307

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

308

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

309

Venus - Global gravity and topography  

NASA Astrophysics Data System (ADS)

A new gravity field determination that has been produced combines both the Pioneer Venus Orbiter (PVO) and the Magellan Doppler radio data. Comparisons between this estimate, a spherical harmonic model of degree and order 21, and previous models show that significant improvements have been made. Results are displayed as gravity contours overlaying a topographic map. We also calculate a new spherical harmonic model of topography based on Magellan altimetry, with PVO altimetry included where gaps exist in the Magellan data. This model is also of degree and order 21, so in conjunction with the gravity model, Bouguer and isostatic anomaly maps can be produced. These results are very consistent with previous results, but reveal more spatial resolution in the higher latitudes.

McNamee, J. B.; Borderies, N. J.; Sjogren, W. L.

1993-05-01

310

An Assessment of Global Digital Terrain Models Over Canada  

NASA Astrophysics Data System (ADS)

A variety of digital terrain models (DTMs) are nowadays available for use by the international scientific community. In terms of geodetic applications, such models are especially important for precise Stokesian geoid determinations, for geophysical and geodynamical studies related to the isostatic behaviour of the Earth's crust, and also for the development of realistic synthetic representations for the Earth's external gravitational field. However, the problem of which DTM should be chosen for such studies, as well as in other related applications of geo-sciences and engineering, is not a trivial question to answer. That is because most of the available global DTMs differ significantly in terms of their original data sources and their production technique, their accuracy and resolution levels and their actual spatial coverage. Furthermore, additional problems may arise from the fact that the accuracy characteristics within each DTM are not really homogeneous over the total coverage area, but they rather exhibit a spatially dependent behaviour which is often strongly correlated with the terrain morphology. Among the freely available DTMs covering Canada, the recently released SRTM30 model is of special interest for geodetic applications since it is based on the interferometric data gathered during NASA's Shuttle Radar Topography Mission (SRTM). The SRTM used space-borne radar interferometry sensors to produce a near global digital terrain model. The final SRTM30 model is thus primarily generated by a set of data which is consistent and of uniform quality over the entire coverage area. This is usually not the case for other global DTMs which are typically generated by merging existing topographic and/or cartographic data sources with varying (and often questionable) quality levels. This paper presents an initial assessment of the SRTM30 terrain model with respect to some other well known DTMs that are often used in practice, namely ETOPO2, GTOPO30 and the Canadian Digital Elevation Data (CDED) sets. The aforementioned models are evaluated and assessed through a statistical inter-comparison over various test areas representing typical Canadian landforms (e.g., mountain ranges along the Rockies in western Canada, flatter regions in the eastern Canada). A type of absolute comparison for all these models is also performed using as reference the orthometric, ellipsoidal and geoid height values at a set of nearly 1930 geodetic leveling benchmarks distributed throughout Canada.

Malmquist, C.; Kotsakis, C.; Sideris, M. G.

2004-05-01

311

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.

312

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

313

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

314

Topography, surface properties, and tectonic evolution  

Microsoft Academic Search

Differences in atmospheric composition, atmospheric and lithospheric temperature, and perhaps mantle composition, suggest that the rock cycle on Venus is not similar to the earth's. While radar data are not consistent with a thick, widespread and porous regolith like that of the moon, wind-transported regolith could be cemented into sedimentary rock that would be indistinguishable from other rocks in radar

G. E. McGill; J. L. Warner; M. C. Malin; R. E. Arvidson; E. Eliason; S. Nozette; R. D. Reasenberg

1983-01-01

315

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

316

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

317

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

318

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

319

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

320

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

321

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

322

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.

323

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

324

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.

325

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

326

Radar studies of the West Antarctic ice streams  

NASA Astrophysics Data System (ADS)

A collaboration has carried out measurements of ice thickness at the mouth of Ice Streams D and E, West Antarctica, using a surface-based impulse radar. These studies were undertaken as a part of the continuing effort to understand the state of the West Antarctic Ice Sheet and its response to climate change. Thickness measurements will be used in the mass balance calculation currently in progress and to better understand features in the surface topography seen at low-angle sun illumination in the satellite imagery. Results show that the discharge areas of Ice Streams D and E are thickening by approximately 1 meter per year, and thus that these ice streams are likely losing mass. Aperiodic wavelike features in the surface topography are described, which pose interesting questions about migration of the grounding line and ice-stream dynamics.

Jacobel, Robert W.

1993-07-01

327

Dunes on Titan observed by Cassini Radar  

NASA Astrophysics Data System (ADS)

Thousands of longitudinal dunes have recently been discovered by the Titan Radar Mapper on the surface of Titan. These are found mainly within ±30° of the equator in optically-, near-infrared-, and radar-dark regions, indicating a strong proportion of organics, and cover well over 5% of Titan's surface. Their longitudinal duneform, interactions with topography, and correlation with other aeolian forms indicate a single, dominant wind direction aligned with the dune axis plus lesser, off-axis or seasonally alternating winds. Global compilations of dune orientations reveal the mean wind direction is dominantly eastwards, with regional and local variations where winds are diverted around topographically high features, such as mountain blocks or broad landforms. Global winds may carry sediments from high latitude regions to equatorial regions, where relatively drier conditions prevail, and the particles are reworked into dunes, perhaps on timescales of thousands to tens of thousands of years. On Titan, adequate sediment supply, sufficient wind, and the absence of sediment carriage and trapping by fluids are the dominant factors in the presence of dunes.

Radebaugh, J.; Lorenz, R. D.; Lunine, J. I.; Wall, S. D.; Boubin, G.; Reffet, E.; Kirk, R. L.; Lopes, R. M.; Stofan, E. R.; Soderblom, L.; Allison, M.; Janssen, M.; Paillou, P.; Callahan, P.; Spencer, C.; the Cassini Radar Team

2008-04-01

328

A Study of Frequency-Dependent Seismic Wave Amplifications due to Topography Effects  

NASA Astrophysics Data System (ADS)

We present a study of the effects of free surface topography on the amplification of seismic waves. To this end we investigate a parameter space in which we systematically consider various frequencies of the incident wave, increasing roughness of the topography, and different spatial resolutions of the discrete topography model. We compare the ground motion at different topographic features, such as mountain peaks, elongated ridges, or valley floors in order to derive crest-to-base amplification factors of peak ground velocities and rotations. The study is mainly based on numerical simulations using the Discontinuous Galerkin method of high-order space and time accuracy that allows for an precise incorporation of real topography models given by high-resolution digital elevation models. Furthermore, we chose an area of investigation in southern Germany, where observational data is available to compare our numerical results with real measurements. Our results show at under which circumstances the incorporation of topography has important implications on the seismic wave field. We show possible consequences to consider in seismic hazard assessment and earthquake engineering.

Hermann, V. K.; Kaeser, M.; Wassermann, J. M.

2009-12-01

329

Interferometric synthetic aperture radar (InSAR) for fine-resolution basal ice sheet imaging  

NASA Astrophysics Data System (ADS)

This dissertation work was to examine the feasibility of InSAR through the ice sheets to create a fine resolution basal topography map and extraction of basal composition. InSAR was shown to be possible through the ice sheet, using data collected by the MCRDS radar around the NEEM drill site. Reflectivity maps were generated leading to the possibility of extracting useful basal composition data. Extraction of basal composition information was examined including estimating the roughness of basal topography and removing the effects of local slope.

Blake, William Arthur

330

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

331

Bistatic synthetic aperture radar imaging for arbitrary flight trajectories.  

PubMed

In this paper, we present an analytic, filtered backprojection (FBP) type inversion method for bistatic synthetic aperture radar (BISAR). We consider a BISAR system where a scene of interest is illuminated by electromagnetic waves that are transmitted, at known times, from positions along an arbitrary, but known, flight trajectory and the scattered waves are measured from positions along a different flight trajectory which is also arbitrary, but known. We assume a single-scattering model for the radar data, and we assume that the ground topography is known but not necessarily flat. We use microlocal analysis to develop the FBP-type reconstruction method. We analyze the computational complexity of the numerical implementation of the method and present numerical simulations to demonstrate its performance. PMID:18229806

Yarman, Can Evren; Yazici, Birsen; Cheney, Margaret

2008-01-01

332

Global Seafloor Topography from Satellite Altimetry  

NSDL National Science Digital Library

This site offers links to maps, posters, globes, and CD-ROMS showing seafloor topography, gravity anomalies, and bathymetry. The images were derived from GEOSAT and ERS satellite data and bathymetric surveys performed by the U.S. Navy.

333

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

334

Locating volcano-seismic signals in the presence of rough topography: wave simulations on Arenal volcano, Costa Rica  

Microsoft Academic Search

Quantifying the scattering effects of pronounced volcano topography on the seismic wavefield is an important component in locating and interpreting volcano seismic sources. In this study, we perform seismic wave simulations to quantify the scattering generated by a 3-D digital elevation map and 1-D velocity model of Arenal volcano, Costa Rica. Full waveform synthetic seismograms were generated using a 3-D

J. P. Métaxian; G. S. O'Brien; C. J. Bean; B. Valette; M. Mora

2009-01-01

335

Global mapping of topography on transition zone velocity discontinuities by stacking SS precursors  

Microsoft Academic Search

We stack long-period, transverse-component seismograms recorded by the Global Digital Seismograph Network (GDSN) (1976-1996), Incorporated Research Institutions for Seismology-International Deployment of Accelerometers (IRIS-IDA) (1988-1996), and Geoscope (1988-1996) networks to map large-scale topography on the 410- and 660-km seismic velocity discontinuities. Underside reflections from these discontinuities arrive as precursors to the SS phase, and their timing can be used to obtain

Megan P. Flanagan; Peter M. Shearer

1998-01-01

336

OneCleveland: Connecting the Digital City  

ERIC Educational Resources Information Center

|A new urban landscape characterizes cities around the globe, eclipsing the smokestacks of the 19th century and skyscrapers of the 20th century, yet the topography of the 21st century digital cityscape is almost invisible. In sharp contrast to the limits of interaction imposed by geography, architecture, and physical distances characteristic of…

Gonick, Lev; Junnar, Priya

2005-01-01

337

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

338

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

339

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

340

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

341

Genetic topography of brain morphology.  

PubMed

Animal data show that cortical development is initially patterned by genetic gradients largely along three orthogonal axes. We previously reported differences in genetic influences on cortical surface area along an anterior-posterior axis using neuroimaging data of adult human twins. Here, we demonstrate differences in genetic influences on cortical thickness along a dorsal-ventral axis in the same cohort. The phenomenon of orthogonal gradations in cortical organization evident in different structural and functional properties may originate from genetic gradients. Another emerging theme of cortical patterning is that patterns of genetic influences recapitulate the spatial topography of the cortex within hemispheres. The genetic patterning of both cortical thickness and surface area corresponds to cortical functional specializations. Intriguingly, in contrast to broad similarities in genetic patterning, two sets of analyses distinguish cortical thickness and surface area genetically. First, genetic contributions to cortical thickness and surface area are largely distinct; there is very little genetic correlation (i.e., shared genetic influences) between them. Second, organizing principles among genetically defined regions differ between thickness and surface area. Examining the structure of the genetic similarity matrix among clusters revealed that, whereas surface area clusters showed great genetic proximity with clusters from the same lobe, thickness clusters appear to have close genetic relatedness with clusters that have similar maturational timing. The discrepancies are in line with evidence that the two traits follow different mechanisms in neurodevelopment. Our findings highlight the complexity of genetic influences on cortical morphology and provide a glimpse into emerging principles of genetic organization of the cortex. PMID:24082094

Chen, Chi-Hua; Fiecas, Mark; Gutiérrez, E D; Panizzon, Matthew S; Eyler, Lisa T; Vuoksimaa, Eero; Thompson, Wesley K; Fennema-Notestine, Christine; Hagler, Donald J; Jernigan, Terry L; Neale, Michael C; Franz, Carol E; Lyons, Michael J; Fischl, Bruce; Tsuang, Ming T; Dale, Anders M; Kremen, William S

2013-09-30

342

Improved Lunar Control and Topography  

NASA Astrophysics Data System (ADS)

We are completing the Unified Lunar Control Network (ULCN) 2005, an update and combination of the ULCN (Davies and Colvin 1994) and the Clementine LCN (CLCN) (unpublished) on which USGS Clementine mosaics are based. The new network should correct for large ( 7 km average to > 15 km) errors in the CLCN by constraining ULCN positions and camera angles, and by solving for radii at all points rather than assuming a sphere. The result will be a 3-D network, including a globally complete and consistent topographic model for the Moon tied directly to horizontal control. The estimated horizontal accuracy of our current solution ranges from 1 km in the areas of ULCN points to 3 km outside these areas. The current ULCN has a vertical accuracy of a few hundred meters when compared to Clementine lidar. The true accuracy may be higher, due to interpolation and lidar positional errors involved in the comparison. The final version should be available at the time of the DPS. Our current solution includes 546,142 image measures of 272,949 points and 43,866 Clementine (mostly 750-nm) images. We will report the results in a peer-reviewed article and distribute the network data from our website (http://astrogeology.usgs.gov/Projects/ControlNetworks/). This solution will be useful for scientific study of lunar morphology and basins; and for operational uses in selecting and targeting landing sites and evaluating landing hazards due to topography. A future solution will include Lunar Orbiter, Mariner 10, and Galileo data. Additionally, it will serve as the basis for solutions with data from upcoming missions, thus placing all data in one consistent coordinate system. We acknowledge the initiation of this work by T. Colvin and (the late) M. Davies at RAND, and funding from the NASA PG&G program.

Archinal, B. A.; Rosiek, M. R.; Kirk, R. L.; Redding, B. L.

2005-08-01

343

Corneal topography measurements for biometric applications  

NASA Astrophysics Data System (ADS)

The term biometrics is used to describe the process of analyzing biological and behavioral traits that are unique to an individual in order to confirm or determine his or her identity. Many biometric modalities are currently being researched and implemented including, fingerprints, hand and facial geometry, iris recognition, vein structure recognition, gait, voice recognition, etc... This project explores the possibility of using corneal topography measurements as a trait for biometric identification. Two new corneal topographers were developed for this study. The first was designed to function as an operator-free device that will allow a user to approach the device and have his or her corneal topography measured. Human subject topography data were collected with this device and compared to measurements made with the commercially available Keratron Piccolo topographer (Optikon, Rome, Italy). A third topographer that departs from the standard Placido disk technology allows for arbitrary pattern illumination through the use of LCD monitors. This topographer was built and tested to be used in future research studies. Topography data was collected from 59 subjects and modeled using Zernike polynomials, which provide for a simple method of compressing topography data and comparing one topographical measurement with a database for biometric identification. The data were analyzed to determine the biometric error rates associated with corneal topography measurements. Reasonably accurate results, between three to eight percent simultaneous false match and false non-match rates, were achieved.

Lewis, Nathan D.

344

Shortwave radiation parameterization scheme for subgrid topography  

NASA Astrophysics Data System (ADS)

Topography is well known to alter the shortwave radiation balance at the surface. A detailed radiation balance is therefore required in mountainous terrain. In order to maintain the computational performance of large-scale models while at the same time increasing grid resolutions, subgrid parameterizations are gaining more importance. A complete radiation parameterization scheme for subgrid topography accounting for shading, limited sky view, and terrain reflections is presented. Each radiative flux is parameterized individually as a function of sky view factor, slope and sun elevation angle, and albedo. We validated the parameterization with domain-averaged values computed from a distributed radiation model which includes a detailed shortwave radiation balance. Furthermore, we quantify the individual topographic impacts on the shortwave radiation balance. Rather than using a limited set of real topographies we used a large ensemble of simulated topographies with a wide range of typical terrain characteristics to study all topographic influences on the radiation balance. To this end slopes and partial derivatives of seven real topographies from Switzerland and the United States were analyzed and Gaussian statistics were found to best approximate real topographies. Parameterized direct beam radiation presented previously compared well with modeled values over the entire range of slope angles. The approximation of multiple, anisotropic terrain reflections with single, isotropic terrain reflections was confirmed as long as domain-averaged values are considered. The validation of all parameterized radiative fluxes showed that it is indeed not necessary to compute subgrid fluxes in order to account for all topographic influences in large grid sizes.

Helbig, N.; LöWe, H.

2012-02-01

345

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

346

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

347

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

348

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).

349

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

350

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

351

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

352

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

353

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

354

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

355

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

356

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

357

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

358

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

359

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

360

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

361

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

362

Runoff Analysis Considering Orographical Features Using Dual Polarization Radar Rainfall  

NASA Astrophysics Data System (ADS)

Recently, the necessity for rainfall estimation and forecasting using the radar is being highlighted, due to the frequent occurrence of torrential rainfall resulting from abnormal changes of weather. Radar rainfall data represents temporal and spatial distributions properly and replace the existing rain gauge networks. It is also frequently applied in many hydrologic field researches. However, the radar rainfall data has an accuracy limitation since it estimates rainfall, by monitoring clouds and precipitation particles formed around the surface of the earth(1.5-3km above the surface) or the atmosphere. In a condition like Korea where nearly 70% of the land is covered by mountainous areas, there are lots of restrictions to use rainfall radar, because of the occurrence of beam blocking areas by topography. This study is aiming at analyzing runoff and examining the applicability of (R(Z), R(ZDR) and R(KDP)) provided by the Han River Flood Control Office(HRFCO) based on the basin elevation of Nakdong river watershed. For this purpose, the amount of radar rainfall of each rainfall event was estimated according to three sub-basins of Nakdong river watershed with the average basin elevation above 400m which are Namgang dam, Andong dam and Hapcheon dam and also another three sub-basins with the average basin elevation below 150m which are Waegwan, Changryeong and Goryeong. After runoff analysis using a distribution model, Vflo model, the results were reviewed and compared with the observed runoff. This study estimated the rainfall by using the radar-rainfall transform formulas, (R(Z), R(Z,ZDR) and R(Z,ZDR,KDP) for four stormwater events and compared the results with the point rainfall of the rain gauge. As the result, it was overestimated or underestimated, depending on rainfall events. Also, calculation indicates that the values from R(Z,ZDR) and R(Z,ZDR,KDP) relatively showed the most similar results. Moreover the runoff analysis using the estimated radar rainfall is performed. Then hydrologic component of the runoff hydrographs, peak flows and total runoffs from the estimated rainfall and the observed rainfall are compared. The results show that hydrologic components have high fluctuations depending on storm rainfall event. Thus, it is necessary to choose appropriate radar rainfall data derived from the above radar rainfall transform formulas to analyze the runoff of radar rainfall. The simulated hydrograph by radar in the three basins of agricultural areas is more similar to the observed hydrograph than the other three basins of mountainous areas. Especially the peak flow and shape of hydrograph of the agricultural areas is much closer to the observed ones than that of mountainous areas. This result comes from the difference of radar rainfall depending on the basin elevation. Therefore we need the examination of radar rainfall transform formulas following rainfall event and runoff analysis based on basin elevation for the improvement of radar rainfall application. Acknowledgment This study was financially supported by the Construction Technology Innovation Program(08-Tech-Inovation-F01) through the Research Center of Flood Defence Technology for Next Generation in Korea Institute of Construction & Transportation Technology Evaluation and Planning(KICTEP) of Ministry of Land, Transport and Maritime Affairs(MLTM)

Noh, Hui-seong; Shin, Hyun-seok; Kang, Na-rae; Lee, Choong-Ke; Kim, Hung-soo

2013-04-01

363

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.

364

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.

365

Effects of topography on the dune forming winds on Titan  

NASA Astrophysics Data System (ADS)

Cassini observed hundreds of dune fields on Titan, nearly all of which lie in the tropics and suggest westerly (from west to east) winds dominate at the surface. Most GCMs however have obtained easterly surface winds in the tropics, seemingly contradicting the wind direction suggested by the dunes. This has led to an active debate in the community about the origin of the dune forming winds on Titan and their direction and modality. This discussion is mostly driven by a study of Earth dunes seen as analogous to Titan. One can find examples of dunes on Earth that fit several wind regimes. To date only one GCM, that of Tokano (2008, 2010), has presented detailed analysis of its near surface winds and their dune forming capabilities. Despite the bulk of the wind being easterly, this GCM produces faster westerlies at equinox, thus transporting sand to the east. Our model, the Titan CAM (Friedson et al. 2009), is unable to reproduce the fast westerlies. Our GCM has been updated to include realistic topography released by the Cassini radar team. Preliminary results suggest our tropical wind regime now has net westerly winds in the tropics, albeit weak. References: Tokano, T. 2008. Icarus 194, 243-262. Tokano, T. 2010. Aeolian Research 2, 113-127. Friedson, J. et al. 2009. Planet. Sp. Sci., 57, 1931-1949.

Larson, Erik J.; Toon, O. B.; Friedson, A. J.

2013-10-01

366

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

367

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

368

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.

369

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

370

Evaluation of corneal thickness and topography in normal eyes using the Orbscan corneal topography system  

Microsoft Academic Search

AIMSTo map the thickness, elevation (anterior and posterior corneal surface), and axial curvature of the cornea in normal eyes with the Orbscan corneal topography system.METHODS94 eyes of 51 normal subjects were investigated using the Orbscan corneal topography system. The anterior and posterior corneal elevation maps were classified into regular ridge, irregular ridge, incomplete ridge, island, and unclassified patterns, and the

Zuguo Liu; Andrew J Huang; Stephen C Pflugfelder

1999-01-01

371

The geometric signature: Quantifying landslide-terrain types from digital elevation models  

Microsoft Academic Search

Topography of various types and scales can be fingerprinted by computer analysis of altitude matrices (digital elevation models, or DEMs). The critical analytic tool is the geometric signature, a set of measures that describes topographic form well enough to distinguish among geomorphically disparate landscapes. Different surficial processes create topography with diagnostic forms that are recognizable in the field. The geometric

Richard J. Pike

1988-01-01

372

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

373

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

374

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

375

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

376

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

377

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

378

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

379

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

380

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

381

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

382

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

383

3D Imaging Radar for Deep Ice Core Site Selection  

NASA Astrophysics Data System (ADS)

The site selection for a deep ice core is critical because of the high cost of drilling, extracting, and analyzing the ice cores. CReSIS has developed several multichannel radar systems which provide information at a much higher level of detail than was possible from previous radar surveys for ice core sites. Among the inputs used in site selection, depth sounding radars provide information about the internal stratigraphy, bed topography, and basal conditions. The internal stratigraphy and bed topography are ideally smooth and flat-lying - an indication that there are no ice flow disturbances. The chronological order must be preserved in the stratigraphy and lack of flow disturbances helps ensure that. Also, internal layers that can be traced to an existing ice core to be dated allow paleo-accumulation rates to be estimated when coupled with an ice flow model. Determining the basal conditions, specifically whether or not the bed is wet or dry, helps determine if the bottom layers (i.e. the oldest ice) are melting. In 2005 and 2008, CReSIS conducted two ground based radar surveys covering the GRIP, GISP2, and NEEM ice core sites. Unlike traditional depth sounders, these radar systems are multichannel making 3D imaging possible. In 2006 an airborne version of the ground based system was fielded for the first time and 3D tomographic images have been produced with that system as well. This work will present results from these ground and airborne surveys and how the information provided from these data can be used to enable optimal site selections in the future. Fig 1 shows an example of how 3D imaging resolves the englacial features that indicate the flow disturbances discovered by the GRIP and GISP2 ice core analysis. In Fig 1a, the bed is the bright mass of targets from 0-4 km along-track at the bottom of the image. Note the distinct change in texture of the englacial scatterers, from specular layers to point targets, around 2750 m and below. Fig 1b shows the cross-track position of the dominant englacial scatterers. The scattering centers for the flat internal layers above 2750 m are located directly beneath the platform while the disturbed layers below 2750 m are spread out. Similar englacial targets are seen at the GISP2 site. a) Radar profile with GRIP core high-lighted by vertical line. b) Cross-track position of the englacial scatterers.

Paden, J. D.; Blake, W.; Gogineni, P. S.; Leuschen, C.; Allen, C.; Dahl-Jensen, D.

2010-12-01

384

A correlation-based approach to modeling interferometric radar observations of the Greenland ice sheet  

Microsoft Academic Search

Interferometric synthetic aperture radar (InSAR) phase observations have greatly increased our understanding of the topography and motion of ice sheets, but yield little information on the sub-surface structure, a needed description for mass-balance estimates. Inversion of a diffuse volume scatter model shows that InSAR correlation values, rho, can be related to radiowave penetration depths, d, which depend on characteristics of

Edward Weber Hoen

2002-01-01

385

An iterative inverse method to estimate basal topography and initialize ice flow models  

NASA Astrophysics Data System (ADS)

We present and evaluate an inverse approach to reconstruct two-dimensional fields of bedrock topography and simultaneously initialize an ice flow model. The inverse method involves an iterative procedure in which an ice dynamical model (PISM) is run multiple times over a prescribed period, while being forced with space and time-dependent climate input. After every iteration bed heights are adjusted using information of the remaining misfit between observed and modeled surface topography. The inverse method is first applied in synthetic experiments with a constant climate forcing to verify convergence and robustness of the approach. In a next step, the inverse approach is applied to Nordenskiöldbreen, Svalbard, forced with height- and time-dependent climate input since 1300 AD. An L-curve stopping criterion is used to prevent overfitting. Validation against radar data reveals a high correlation (up to R = 0.89) between modeled and observed thicknesses. Remaining uncertainties can mainly be ascribed to inaccurate model physics, in particular uncertainty in the description of sliding. Results demonstrate the applicability of this inverse method to reconstruct the ice thickness distribution of glaciers and ice caps. In addition to reconstructing bedrock topography, the method provides a direct tool to initialize ice flow models for forecasting experiments. Application of the method is not constrained to a single model or glacier, indicating the potential to use the approach to compute the detailed thickness distribution of a single glacier, as well as the volume contained in a set of glaciers and ice caps.

van Pelt, W. J. J.; Oerlemans, J.; Reijmer, C. H.; Pettersson, R.; Pohjola, V. A.; Isaksson, E.; Divine, D.

2013-03-01

386

Surface undulations of Antarctic ice streams tightly controlled by bedrock topography  

NASA Astrophysics Data System (ADS)

Full Stokes flow-line models predict that fast-flowing ice streams transmit information about their bedrock topography most efficiently to the surface for basal undulations with length scales between 1 and 20 times the mean ice thickness. This typical behaviour is independent of the precise values of the flow law and sliding law exponents, and should be universally observable. However, no experimental evidence for this important theoretical prediction has been obtained so far, hence ignoring an important test for the physical validity of current-day ice flow models. In our work we use recently acquired airborne radar data for the Rutford Ice Stream and Evans Ice Stream, and we show that the surface response of fast-flowing ice is highly sensitive to bedrock irregularities with wavelengths of several ice thicknesses. The sensitivity depends on the slip ratio, i.e. the ratio between mean basal sliding velocity and mean deformational velocity. We find that higher values of the slip ratio generally lead to a more efficient transfer, whereas the transfer is significantly dampened for ice that attains most of its surface velocity by creep. Our findings underline the importance of bedrock topography for ice stream dynamics on spatial scales up to 20 times the mean ice thickness. Our results also suggest that local variations in the flow regime and surface topography at this spatial scale cannot be explained by variations in basal slipperiness.

De Rydt, J.; Gudmundsson, G. H.; Corr, H. F. J.; Christoffersen, P.

2013-03-01

387

Surface undulations of Antarctic ice streams tightly controlled by bedrock topography  

NASA Astrophysics Data System (ADS)

Full Stokes models predict that fast-flowing ice streams transmit information about their bedrock topography most efficiently to the surface for basal undulations with length scales between 1 and 20 times the mean ice thickness. This typical behaviour is independent on the precise values of the flow law and sliding law exponents, and should be universally observable. However, no experimental evidence for this important theoretical prediction has been obtained so far, hence ignoring an important test for the physical validity of current-day ice flow models. In our work we use recently acquired airborne radar data for the Rutford Ice Stream and Evans Ice Stream, and we show that the surface response of fast-flowing ice is highly sensitive to bedrock irregularities with wavelengths of several ice thicknesses. The sensitivity depends on the slip ratio, i.e. the ratio between mean basal sliding velocity and mean deformational velocity. We find that higher values of the slip ratio generally lead to a more efficient transfer, whereas the transfer is significantly dampened for ice that attains most of its surface velocity by creep. Our findings underline the importance of bedrock topography for ice stream dynamics on spatial scales up to 20 times the mean ice thickness. Our results also suggest that local variations in the flow regime and surface topography at this spatial scale cannot be explained by variations in basal slipperiness.

De Rydt, J.; Gudmundsson, G. H.; Corr, H. F. J.; Christoffersen, P.

2012-10-01

388

Surface undulations of Antarctic ice streams tightly controlled by bedrock topography  

NASA Astrophysics Data System (ADS)

Ice dynamics models predict that fast-flowing ice streams transmit information about their bedrock topography most efficiently to the surface for basal undulations with length scales between 1 and 20 times the mean ice thickness. This typical behaviour is independent on the precise values of the flow law and sliding law exponents, and should be universally observable. However, no experimental evidence for this important theoretical prediction has been obtained so far, hence ignoring an important test for the physical validity of current-day ice flow models. In our work we use recently acquired airborne radar data for the Rutford Ice Stream and Evans Ice Stream, and we show that the surface response of fast-flowing ice is highly sensitive to bedrock irregularities with wavelengths of several ice thicknesses. The sensitivity depends on the slip ratio, i.e., the ratio between mean basal sliding velocity and mean deformational velocity. We find that higher values of the slip ratio generally lead to a more efficient transfer, whereas the transfer is significantly dampened for ice that attains most of its surface velocity by creep. Our findings underline the importance of bedrock topography for ice stream dynamics on spatial scales up to 20 times the mean ice thickness. Our results also suggest that local variations in the flow regime and surface topography at this spatial scale cannot be explained by variations in basal slipperiness.

De Rydt, Jan; Hilmar Gudmundsson, G.; Corr, Hugh F. G.; Christoffersen, Poul

2013-04-01

389

Impact of topography and soil factors on crop suitability in two Mediterranean areas (Egypt and Spain)  

NASA Astrophysics Data System (ADS)

The aim of this research is to study the influence of topography and soil factors on crop suitability two Mediterranean areas: Sevilla (southern Spain) and El-Fayoum (northern Egypt). The Shuttle Radar Topography Mission (SRTM) images were processed using ENVI 4.7 software to extract elevation data, slope gradient and slope direction. North-south toposequences from both areas were extracted and studied using Arc-GIS 9.3 software. Soil characteristics along these toposequences were extracted from regional soil maps, as well as land surveying and laboratory analyses. The Almagra model (included in the agro-ecological system MicroLEIS DSS) was used to evaluate agricultural soil suitability using soil factors of useful depth, texture, drainage, carbonate content, salinity, sodium saturation, and degree of development of the profile. Changes of soil characteristics through the toposequences are discussed. The results of Almagra model indicate that the crop suitability main limiting factors are soil texture, drainage, soil salinity and sodium saturation percent and topography factors elevation, slope gradient, slope direction.

Abd-Elmabod, S. K.; Jordán, A.; Anaya-Romero, M.; Ali, R. R.; Muñoz-Rojas, M.; Zavala, L. M.; de la Rosa, D.

2012-04-01

390

Effects of topography on the interpretation of the deformation field of prominent volcanoes - Application to Etna  

USGS Publications Warehouse

We have investigated the effects of topography on the surface-deformation field of volcanoes. Our study provides limits to the use of classical half-space models. Considering axisymmetrical volcanoes, we show that interpreting ground-surface displacements with half-space models can lead to erroneous estimations of the shape of the deformation source. When the average slope of the flanks of a volcano exceeds 20??, tilting in the summit area is reversed to that expected for a flat surface. Thus, neglecting topography may lead to misinterpreting an inflation of the source as a deflation. Comparisons of Mogi's model with a three-dimensional model shows that ignoring topography may lead to an overestimate of the source-volume change by as much as 50% for a slope of 30??. This comparison also shows that the depths calculated by using Mogi's solution for prominent volcanoes should be considered as depths from the summit of the edifices. Finally, we illustrate these topographic effects by analyzing the deformation field measured by radar interferometry at Mount Etna during its 1991-1993 eruption. A three-dimensional modeling calculation shows that the flattening of the deflation field near the volcano's summit is probably a topographic effect.

Cayol, V.; Cornet, F. H.

1998-01-01

391

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

392

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

393

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

394

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

395

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

396

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

397

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

398

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

399

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

400

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

401

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

402

Topography of Martian central volcanoes  

NASA Astrophysics Data System (ADS)

Results are presented of the topographic mapping of six large central volcanoes on Mars. Stereo images of the volcanoes Olympus Mons, Elysium Mons, Albor Tholus, Ceraunius Tholus, Uranius Tholus and Uranius Patera were acquired by Viking Orbiter 1, and pairs of images were compiled into topographic maps through the use of digital image measurement techniques. Olympus Mons is found to have the general form of a terrestrial basaltic shield constructed almost entirely from lava flows, however with an altitude of 20-23 km and flank slopes averaging about 4 deg; a high nominal density indicates that anomalously dense lithosphere underlies the shield. Uranius Patera is observed to be a similar feature of present relief about 2 km, with its lower flanks buried by later lava flood deposits. Elysium Mons has about 13 km of local relief with average slopes of 4.4 deg, although its upper flank slopes are significantly steeper than those of Olympus Mons, suggesting a shield volcano modified by a terminal phase of mixed volcanic activity. Albor Tholus is found to be a partially buried 3-km shield-like construct, while Ceranius and Uranius Tholus are steeper cone-like features with reliefs of about 6 and 2 km, respectively, which may be lava shield constructs modified by a terminal stage of explosive activity.

Blasius, K. R.; Cutts, J. A.

1981-01-01

403

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

404

The evolution of topography on a comet  

NASA Astrophysics Data System (ADS)

The authors have developed a simple model of an infinite cylindrical trench on a comet. The energy balance equation has been modified to include physical processes which are relevant with topography present, and includes shadowing, radiative heating from the opposing walls, and the condensation energy of sublimed gas molecules striking the walls instead of escaping to space. The model is designed to indicate the general course of the evolution of topography on a comet, and is not intended as a complete model of a cometary nucleus. By running the model for trenches of different depths and at different solar distances, the authors draw conclusions about the evolution of topography through an orbit and the consequences this evolution has on the evolution of the nucleus as a whole over the course of several perihelion passages.

Colwell, J. E.; Jakosky, B. M.

1987-10-01

405

Topography of Earth's Inner Core Boundary  

NASA Astrophysics Data System (ADS)

Lateral variations in the structure and crystallization of the inner core will likely be associated with lateral variations in the topography of its boundary. Depending on liquid fraction and the ratio of solid over liquid viscosity, the process of compaction of solids and expulsion of fluids at the solidifying boundary can be dynamically unstable, resulting in small-scale corrugations of the boundary of 0.1 to 5 km height with a horizontal scale on the order of 1 to 10 km. Evidence of such ICB topography has been inferred from waveforms of PKiKP doublets (1). An additional observation consistent ICB topography includes the seismic wave diffracted around the top of the inner core (PKP-Cdiff), whose travel time agrees with that predicted by the AK135 Earth model, but whose amplitude decays more rapidly into the inner core shadow than is predicted by AK135 (2). These observations are modeled by synthesizing seismic body waves with a pseudospectral method (3) having a densified grid in the vicinity of a rough ICB. Validation of the forward modeling includes a comparison of results obtained with a boundary element method. Modeled spectra of ICB topography are used to constrain the parameters and processes that produce the topography. These include compaction length (assuming freezing upward from below), the structure of precipitated piles (assuming metallic snow falling from above), the sedimentary processes due to flow in the overlying F-layer of the outer core, and the relaxation of topography from viscous deformation of the inner core. 1. Cao, A., Y. Masson, and B. Romanowicz, PNAS, 104, 31-35, 2007. 2. Zou, Z., K. Koper, and V.F. Cormier, J. Geophys. Res., 113, 2008. doi: 10.1029/2007JB005316. 3. Furumura T., B.L.N. Kennett, and M. Furumura, Geophys. J. Int., 135, 845--860, 1998.

Cormier, V. F.; Zheng, Y.; Hernlund, J. W.

2011-12-01

406

Very high resolution precipitation climatologies from the Tropical Rainfall Measuring Mission precipitation radar  

NASA Astrophysics Data System (ADS)

To investigate processes related to the interaction of topography and precipitation, a tropics-wide (±36° latitude) high resolution (0.1°) ten year (1998-2007) rainfall climatology is presented from the Tropical Rainfall Measuring Mission (TRMM) precipitation radar (PR) using algorithm 2A25 version 6 near-surface rain. We observe a tight coupling between precipitation and topography with distinct precipitation-topography relationships present in northwest South America and South Asia. An error model is developed by subsampling the TRMM Multi-satellite Precipitation Analysis as sampled by the PR. The error model predicts observed sampling error as a function of resolution, rain rate and sampling frequency with an r 2 of 0.82. This error model indicates that the precipitation climatology at 0.1° resolution does resolve precipitation gradients in regions with large average daily rain totals including the Andes, Western Ghats, and Himalaya.

Nesbitt, Stephen W.; Anders, Alison M.

2009-08-01

407

Noninterferometric topography measurements of fast moving surfaces.  

PubMed

The topography of moving surfaces is recovered by noninterferometric measurements. The phase reconstruction is derived by measuring the intensities of a backscattered pulsed laser light and solving the transport intensity equation (TIE). The TIE is solved by expanding the phase into a series of Zernike polynomials, leading to a set of appropriate algebraic equations. This technique, which enables us to make a direct connection between experiments and the TIE, has been successfully tested in gas gun experiments. In particular, the topographies of a moving projectile and the free surface of a shocked target were recovered. PMID:21811317

Pinhasi, Shirly Vinikman; Eliezer, Shalom; Glam, Benny; Appelbaum, Gabi; Bakshi, Lior

2011-08-01

408

Effects of patterned topography on biofilm formation  

NASA Astrophysics Data System (ADS)

Bacterial biofilms are a population of bacteria attached to each other and irreversibly to a surface, enclosed in a matrix of self-secreted polymers, among others polysaccharides, proteins, DNA. Biofilms cause persisting infections associated with implanted medical devices and hospital acquired (nosocomial) infections. Catheter-associated urinary tract infections (CAUTIs) are the most common type of nosocomial infections accounting for up to 40% of all hospital acquired infections. Several different strategies, including use of antibacterial agents and genetic cues, quorum sensing, have been adopted for inhibiting biofilm formation relevant to CAUTI surfaces. Each of these methods pertains to certain types of bacteria, processes and has shortcomings. Based on eukaryotic cell topography interaction studies and Ulva linza spore studies, topographical surfaces were suggested as a benign control method for biofilm formation. However, topographies tested so far have not included a systematic variation of size across basic topography shapes. In this study patterned topography was systematically varied in size and shape according to two approaches 1) confinement and 2) wetting. For the confinement approach, using scanning electron microscopy and confocal microscopy, orienting effects of tested topography based on staphylococcus aureus (s. aureus) (SH1000) and enterobacter cloacae (e. cloacae) (ATCC 700258) bacterial models were identified on features of up to 10 times the size of the bacterium. Psuedomonas aeruginosa (p. aeruginosa) (PAO1) did not show any orientational effects, under the test conditions. Another important factor in medical biofilms is the identification and quantification of phenotypic state which has not been discussed in the literature concerning bacteria topography characterizations. This was done based on antibiotic susceptibility evaluation and also based on gene expression analysis. Although orientational effects occur, phenotypically no difference was observed between the patterned topography tested. Another potential strategy for biofilm control through patterned topography is based on the design of robust non-wetting surfaces with undercut feature geometries, characterized by 1) breakthrough pressure and 2) triple phase contact line model. It was found that height and presence of undercut had statistically significant effects, directly proportional to breakthrough pressures, whereas extent of undercut did not. A predictive triple phase contact line model was also developed. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html)

Vasudevan, Ravikumar

409

Comparative Ground-Penetrating Radar Stratigraphy: Differentiation of Lithologies and Depositional Environments Using Bedform Geometry and Radar Facies Analysis  

NASA Astrophysics Data System (ADS)

Ground-penetrating radar (GPR) profiles are valuable in the investigation of terrestrial subsurface stratigraphy at scales of cm to m, below the resolution of commonly-used acoustic profiling. One of the major benefits of GPR is its ability to characterize deposits non-invasively (without coring or trenching). Like nearly all efforts to invert true geology from geophysical data, attempts to derive lithology and depositional environment from radar-imaged layering provide non-unique solutions. However, we point out that qualitative and quantitative radar stratigraphy, including radar facies analysis, provides valuable information concerning depositional history in the shallow subsurface. Basic characteristics of any sedimentary deposit are generated by a combination of the depositional process and the nature of the particles themselves. For example, bedform height depends on the depth of the fluid in which it is created. Bedform steepness depends upon grain size, sorting, water velocity, and antecedent topography. Development of bedding depends upon grain size, sorting, and fluctuations in the transport capacity of the system. These characteristics can be understood from radar profiles in the absence of outcrop or core data. For example, properties of some clays cause energy absorption which decreases the depth of penetration. Extremely large grains, lateral heterogeneities, and irregular lithologic contacts cause EM energy to scatter, resulting in poorly resolved subsurface interfaces or chaotic reflector patterns. Analyses of radar wave velocity also yield information about water content, which is a function of grain size, sorting, and composition. Bedform geometry is often clearly visible in GPR profiles, and can be quantified after appropriate processing. GPR profiles from five different deposits accumulated during the past 18 ka in New Jersey are compared: fluvial deposits of the Delaware River; glacial outwash and an end moraine from the Wisconsinan glacial retreat; eolian sand deposited shortly after glacial retreat; and a migrating shoreline sand spit at Sandy Hook. Profiles from four of these settings show similarities in internal architecture due to comparable depositional processes in a moving fluid. The scale and shape of the bedforms seen in profiles varies as a function of grain size, velocity, and paleo-water depth. Differences in grain size, degree of sorting, and degree of heterogeneity of the deposits lead to markedly different radar facies. We describe and compare the radar facies and bedform geometries and scales of each environment to assist in the identification of ancient deposits of unknown origin using GPR profiling.

Bitting, K.; Earley, R.; Mountain, G.; Feibel, C.; Ashley, G.

2008-12-01

410

Plans for Radar Imaging of Asteroid 216 Kleopatra  

NASA Astrophysics Data System (ADS)

The available photometric, IRAS, occultation, and radar data suggest that Kleopatra's shape is extremely elongated, nonconvex, and possibly bifurcated, with a maximum dimension greater than 230 km. Kleopatra's radar albedo, the highest measured for a main-belt object, requires a very high surface bulk density that, given the asteroid's M classification, implies either a metallic composition and porosity typical of the lunar regolith or a regolith-free enstatite chondritic surface. The former is much more plausible; therefore Kleopatra may be a remnant of the core of a collisionally disrupted, differentiated asteroid. Kleopatra's fall 1999 opposition is the most favorable for radar until 2013. We plan an intensive campaign of delay-Doppler imaging to reconstruct the asteroid's detailed shape. The view will be a few tens of degrees from the pole, so the north/south ambiguity will be resolved easily and, given the anticipated echo strength, imaging with linear resolution of order 6 km should be possible. That level of geologic detail should define the asteroid's gross shape and also should reveal larger craters and any prominent topography. It also should define the radar scattering law, providing a very tight constraint on the Fresnel reflection coefficient and hence on the surface's bulk density and metal abundance. References Dunham, D. W. (1981). Recently-observed planetary occultations. Occultation Newsletter 2 (11), 139-143. Dunham, D. W. (1992). Planetary occultations of stars in 1992. Sky & Telescope, January 1992, pp. 72-73. Lagerkvist, C.-I., A. W. Harris, V. Zappala (1989). Asteroid lightcurve parameters. In Asteroids II (R. P. Binzel, T. Gehrels, M. S. Matthews, Eds.), pp. 1162-1179. Univ. Arizona Press, Tucson. Mitchell, D. L., et al. (1995). Radar observations of asteroids 7 Iris, 9 Metis, 12 Victoria, 216 Kleopatra, and 654 Zelinda. Icarus 118, 105-131.

Ostro, S. J.; Hudson, R. S.; Nolan, M. C.; Magri, C.; Campbell, D. B.; Giorgini, J. D.; Yeomans, D. K.

1999-09-01

411

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

412

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

413

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

414

Evaluating digital elevation models for glaciologic applications: An example from Nevado Coropuna, Peruvian Andes  

Microsoft Academic Search

This paper evaluates the suitability of readily available elevation data derived from recent sensors the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the Shuttle Radar Topography Mission (SRTM) for glaciological applications. The study area is Nevado Coropuna (6426 m), situated in Cordillera Ampato of Southern Peru. The glaciated area was 82.6 km2 in 1962, based on aerial photography.

Adina E. Racoviteanu; William F. Manley; Yves Arnaud; Mark W. Williams

2007-01-01

415

Evaluating digital elevation models for glaciologic applications: An example from Nevado Coropuna, Peruvian Andes  

Microsoft Academic Search

This paper evaluates the suitability of readily available elevation data derived from recent sensors – the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the Shuttle Radar Topography Mission (SRTM) – for glaciological applications. The study area is Nevado Coropuna (6426 m), situated in Cordillera Ampato of Southern Peru. The glaciated area was 82.6 km2 in 1962, based on aerial photography.

Adina E. Racoviteanu; William F. Manley; Yves Arnaud; Mark W. Williams

2007-01-01

416

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

417

The topography of multivariate normal mixtures  

Microsoft Academic Search

Multivariate normal mixtures provide a flexible method of fitting high-dimensional data. It is shown that their topography, in the sense of their key features as a density, can be analyzed rigorously in lower dimensions by use of a ridgeline manifold that contains all critical points, as well as the ridges of the density. A plot of the elevations on the

Surajit Ray; Bruce G. Lindsay

2005-01-01

418

THE TOPOGRAPHY OF MULTIVARIATE NORMAL MIXTURES1  

Microsoft Academic Search

Multivariate normal mixtures provide a flexible method of fitting high- dimensional data. It is shown that their topography, in the sense of their key features as a density, can be analyzed rigorously in lower dimensions by use of a ridgeline manifold that contains all critical points, as well as the ridges of the density. A plot of the elevations on

SURAJIT RAY; BRUCE G. LINDSAY

419

The topography of multivariate normal mixtures  

Microsoft Academic Search

Multivariate normal mixtures provide a flexible method of fitting high-dimensional data. It is shown that their topography, in the sense of their key features as a density, can be analyzed rigorously in lower dimensions by use of a ridgeline manifold that contains all critical points, as well as the ridges of the density. A plot of the elevations on the

Surajit Ray; Bruce G. Lindsay

2006-01-01

420

Bottom Topography Effects on Ocean Currents.  

National Technical Information Service (NTIS)

The effects of bottom topography on ocean currents are considered. it is shown that a laminar laboratory model with height to width ratio differing from that of large scale geophysical motions can be used to model topographic effects on ocean currents. Th...

J. R. Guala

1972-01-01

421

Ocean Surface Topography from Space - Science  

NSDL National Science Digital Library

This site, from the Jet Propulsion Laboratory at the California Institute of Technology, describes the scientific applications of ocean surface topography from missions such as TOPEX/Poseidon and Jason-1. Other topics include uses of the collected data, such as evaluations of ocean circulation, tides, weather and climate patterns, and other trends.

Laboratory, Jet P.; Nasa

422

The relationship between Martian gravity and topography  

Microsoft Academic Search

The relationship between gravity and topography of various regions of Mars is used to estimate their effective elastic thicknesses Te using direct measurements of line of sight velocity, rather than spherical harmonic coefficients. Estimates of Te vary from 70 km for Tharsis, 29 km for Elysium, to 14.5 km for the southern hemisphere, and show that the thickness of the

Dan McKenzie; David N. Barnett; Dah-Ning Yuan

2002-01-01

423

Shallow waters viscous flows for arbitrary topography  

Microsoft Academic Search

In this paper, we obtain new models for gravity driven shallow water laminar flows in several space dimensions over a general topography. These models are derived from the incompressible Navier Stokes equations with no-slip condition at the bottom and include capillary effects. No partic- ular assumption is made on the size of the viscosity and on the variations of the

Marc Boutounet; Laurent Chupin; Pascal Noble; Jean Paul Vila

424

Reconstructing ancient topography through erosion modelling  

Microsoft Academic Search

One of the main aims of geomorphology is to understand how geomorphic processes change topography over long time scales. Over the last decades several landscape evolution models have been developed in order to study this question. However, evaluation of such models has often been very limited due to the lack of necessary field data. In this study we present a

Iris Peeters; Tom Rommens; Gert Verstraeten; Gerard Govers; Anton Van Rompaey; Jean Poesen; Kristof Van Oost

2006-01-01

425

New boundary conditions for the West Antarctic Ice Sheet: Subglacial topography of the Thwaites and Smith glacier catchments  

NASA Astrophysics Data System (ADS)

Airborne radar sounding over the Thwaites Glacier (TG) catchment and its surroundings provides the first comprehensive view of subglacial topography in this dynamic part of the West Antarctic Ice Sheet (WAIS) and reveals that TG is underlain by a single, broad basin fed by a dendritic pattern of valleys, while Smith Glacier lies within an extremely deep, narrow trench. Subglacial topography in the TG catchment slopes inland from a broad, low-relief coastal sill to the thickest ice of the WAIS and makes deep connections to both Pine Island Glacier and the Ross Sea Embayment enabling dynamic interactions across the WAIS during deglaciation. Simple isostatic rebound modeling shows that most of this landscape would be submarine after deglaciation, aside from an island chain near the present-day Ross-Amundsen ice divide. The lack of topographic confinement along TG's eastern margin implies that it may continue to widen in response to grounding line retreat.

Holt, John W.; Blankenship, Donald D.; Morse, David L.; Young, Duncan A.; Peters, Matthew E.; Kempf, Scott D.; Richter, Thomas G.; Vaughan, David G.; Corr, Hugh F. J.

2006-05-01

426

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

427

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

428

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

429

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

430

Three-Dimensional Edge Waves on Curved Topographies.  

National Technical Information Service (NTIS)

Exact solutions are found to the linearized three dimensional equations for free surface gravity waves trapped against a straight coastline with a variable (perpendicular to the coastline) topography. Three families of topographies are found, one concave ...

R. P. Shaw

1979-01-01

431

Relations between heat flow, topography and Moho depth for Europe  

NASA Astrophysics Data System (ADS)

The relation between heat flow, topography and Moho depth for recent maps of Europe is presented. New heat flow map of Europe (Majorowicz and Wybraniec, 2010) is based on updated database of uncorrected heat flow values to which paleoclimatic correction is applied across the continental Europe. Correction is depth dependent due to a diffusive thermal transfer of the surface temperature forcing of which glacial-interglacial history has the largest impact. This explains some very low uncorrected heat flow values 20-30 mW/m2 in the shields, shallow basin areas of the cratons, and in other areas including orogenic belts were heat flow was likely underestimated. New integrated map of the European Moho depth (Grad et al., 2009) is the first high resolution digital map for European plate understand as an area from Ural Mountains in the east to mid-Atlantic ridge in the west, and Mediterranean Sea in the south to Spitsbergen and Barents Sea in Arctic in the north. For correlation we used: onshore heat flow density data with palaeoclimatic correction (5318 locations), topography map (30 x 30 arc seconds; Danielson and Gesch, 2011) and Moho map (longitude, latitude and Moho depth, each 0.1 degree). Analysis was done in areas where data from all three datasets were available. Continental Europe area could be divided into two large domains related with Precambrian East European craton and Palaeozoic Platform. Next two smaller areas correspond to Scandinavian Caledonides and Anatolia. Presented results show different correlations between Moho depth, elevation and heat flow for all discussed regions. For each region more detailed analysis of these relation in different elevation ranges is presented. In general it is observed that Moho depth is more significant to HF then elevation. Depending on region and elevation range HF value in mW/m2 is up to two times larger than Moho depth in km, while HF relation to elevation varies much more.

Polkowski, Marcin; Majorowicz, Jacek; Grad, Marek

2013-04-01

432

Topography and geomorphology of the Huygens landing site on Titan  

USGS Publications Warehouse

The Descent Imager/Spectral Radiometer (DISR) aboard the Huygens Probe took several hundred visible-light images with its three cameras on approach to the surface of Titan. Several sets of stereo image pairs were collected during the descent. The digital terrain models constructed from those images show rugged topography, in places approaching the angle of repose, adjacent to flatter darker plains. Brighter regions north of the landing site display two styles of drainage patterns: (1) bright highlands with rough topography and deeply incised branching dendritic drainage networks (up to fourth order) with dark-floored valleys that are suggestive of erosion by methane rainfall and (2) short, stubby low-order drainages that follow linear fault patterns forming canyon-like features suggestive of methane spring-sapping. The topographic data show that the bright highland terrains are extremely rugged; slopes of order of 30?? appear common. These systems drain into adjacent relatively flat, dark lowland terrains. A stereo model for part of the dark plains region to the east of the landing site suggests surface scour across this plain flowing from west to east leaving ???100-m-high bright ridges. Tectonic patterns are evident in (1) controlling the rectilinear, low-order, stubby drainages and (2) the "coastline" at the highland-lowland boundary with numerous straight and angular margins. In addition to flow from the highlands drainages, the lowland area shows evidence for more prolific flow parallel to the highland-lowland boundary leaving bright outliers resembling terrestrial sandbars. This implies major west to east floods across the plains where the probe landed with flow parallel to the highland-lowland boundary; the primary source of these flows is evidently not the dendritic channels in the bright highlands to the north. ?? 2007 Elsevier Ltd. All rights reserved.

Soderblom, L. A.; Tomasko, M. G.; Archinal, B. A.; Becker, T. L.; Bushroe, M. W.; Cook, D. A.; Doose, L. R.; Galuszka, D. M.; Hare, T. M.; Howington-Kraus, E.; Karkoschka, E.; Kirk, R. L.; Lunine, J. I.; McFarlane, E. A.; Redding, B. L.; Rizk, B.; Rosiek, M. R.; See, C.; Smith, P. H.

2007-01-01

433

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

434

3D Imaging Radar for Deep Ice Core Site Selection  

NASA Astrophysics Data System (ADS)

The site selection for a deep ice core is critical because of the high cost of drilling, extracting, and analyzing the ice cores. CReSIS has developed several multichannel radar systems which provide information at a much higher level of detail than was possible from previous radar surveys for ice-core sites. Among the inputs used in site selection, depth sounding radars provide information about the internal stratigraphy, bed topography, and basal conditions. The internal stratigraphy and bed topography are ideally smooth and flat-lying - an indication that there are no ice flow disturbances. The chronological order must be preserved in the stratigraphy and lack of flow disturbances helps ensure that. Also, internal layers that can be traced to an existing ice core to be dated allow paleo-accumulation rates to be estimated when coupled with an ice flow model. Determining the basal conditions, specifically whether or not the bed is wet or dry, helps determine if the bottom layers (i.e. the oldest ice) are melting. CReSIS has conducted several ground and airborne radar surveys around GRIP, GISP2, NGRIP, and NEEM ice core sites. Unlike traditional depth sounders, the radar systems are multichannel making 3D imaging possible. This work will present results from these ground and airborne surveys and how the information provided from these data can be used to enable optimal site selections in the future. Fig 1 shows an example of how 3D imaging resolves the englacial features that indicate the flow disturbances discovered by the GRIP and GISP2 ice core analysis. In Fig 1a, the bed is the bright mass of targets from 0-4 km along-track at the bottom of the image. Note the distinct change in texture of the englacial scatterers, from specular layers to point targets, around 2750 m and below. Fig 1b shows the cross-track position of the dominant englacial scatterers. The scattering centers for the flat internal layers above 2750 m are located directly beneath the platform while the disturbed layers below 2750 m are spread out. Similar englacial targets are seen at the GISP2 site.

Paden, J. D.; Li, J.; Gogineni, P. S.; Leuschen, C.; Dahl-Jensen, D.

2011-12-01

435

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

436

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

437

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

438

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

439

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

440

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

441

3-D topography simulator (3-D MULSS) based on a physical description of material topography  

Microsoft Academic Search

This paper presents a three-dimensional (3-D) topography simulator (3-D MULSS), and its applications. We focus on the description of the material surface and the algorithm of the surface advancement. Then we propose a 3-D topography simulation algorithm, with consideration of the probe size of observation, and based on the integration formula of the balance equation. Next, we show the simulation

Masato Fujinaga; Norihiko Kotani

1997-01-01

442

Continuum Statistics of the Bed Topography in a Sandy River  

NASA Astrophysics Data System (ADS)

Temporal and spatial variabilities in the bed geometry of sandy rivers contain information about processes of sediment transport that has not been fully appreciated. This is primarily due to a disparity between the dynamic nature of the sediment-fluid interface and the relatively static methods of surveying bed elevation, e.g. single profiles or point measurements. High resolution topographic data is paramount to understanding the dynamic behavior of sandy beds. We present and analyze a data set collected on a 2cm x 2cm grid at 1 minute intervals and with a vertical precision of ~1mm. This was accomplished by using Lambert-Beer's Law for attenuation of light to transform low-altitude aerial photographs into digital elevation models. Forty successive models were generated for a 20 m by 30 m section of channel bottom of the N. Loup River, Nebraska. To calculate the average, whole bed translation rate, or celerity, cross-correlations between a reference bed topography and its proceeding configurations were determined. Time differences between models were related to the shift lengths that produced correlation maxima for each model pair. The result is a celerity of ~3.8cm/s with a correlation coefficient of 0.992. Bed topography also deforms while it translates, and this can be seen as a secular decrease of correlation maxima. The form of this decrease in correlation is exponential, and from it an interface half-life is defined. In this case, the bed had become extensively reorganized within ~40 minutes, the time necessary to translate the bed one wavelength of the dominant roughness element. Although the bed is continuously deforming, its roughness is statistically stationary. Essentially, a mean roughness is maintained as the bed creates new realizations of itself. The dynamic nature of the whole bed and similarly transient behavior of individual elements suggests the utility of a holistic approach to studying the feedback between bed topography, fluid flow, and sediment transport. Furthermore, it raises questions about the usefulness of detailed analysis of flow and transport over individual forms.

McElroy, B.; Jerolmack, D.; Mohrig, D.

2005-12-01

443

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

444

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

445

Lunar South Pole Topography Derived from Clementine Imagery  

NASA Astrophysics Data System (ADS)

During the Clementine Mission both oblique and vertical multispectral images were collected. The oblique and vertical images from a single spectral band collected during the same orbit form a stereo pair that can be used to derive the topography. These stereo pairs are being used to derive the topography of an area (90 deg S to 650S latitude) surrounding the lunar south pole. Work on the lunar north pole topography will start after completion of the south pole topography. This report provides an update on the initial results for the lunar south pole topography. In 1994, the Clementine spacecraft acquired digital images of the Moon at visible and near-infrared wavelengths. Onboard there were four camera systems and a laser altimeter. During the first pass, periapsis was at 30S and the highest resolution images were obtained in the southern hemisphere. Over the northern polar area, a series of oblique and vertical images were obtained with the ultraviolet-visible (UV-VIS) camera on each orbit. During the second pass, periapsis was at 30N and the image acquisition strategy was reversed. The UV-VIS camera image size was 384 x 288 pixels with five spectral bands and one broad band. The 750-nm-band stereo pairs are the primary image source for this study. The ground sample distances (GSD) for oblique images range from 300 to 400m. The GSD for the vertical images, acquired at the end of an orbit, are slightly larger and range from 325 to 450 m. Using the formula for stereo-height accuracy, an estimate of height accuracy is 180m. This formula is IFOVMAX)/(K*B/H with IFOVMAX defined as Maximum Instantaneous Field of View; B/H is the base-to-height ratio and K is an estimate of pixel measurement accuracy on the imagery. The Clementine laser altimeter (LIDAR) data were used previously to produce a global topographic model of the Moon . The model has a vertical accuracy of about 100 m and a spatial resolution of 2.5 deg. Altimetry data were collected between 79S and 810N. These data were filtered and then interpolated to fill in the polar regions where the altimeter did not collect data. A global topography model was then derived based on spherical harmonic expansion. Image mosaic. A global image mosaic of the Moon was produced from the 750-nm. Clementine data . The mosaic includes high-resolution, oblique, and vertical images. Match points were picked to tie the imagery together, and the camera pointing angles were adjusted to align the imagery. This adjustment used a spherical surface, and the elevation of all points was held to a constant value, 1737.4 km. This produced a seamless image mosaic with latitude and longitude information but no information on the elevation. The imagery and support information were downloaded to our digital photogrammetric workstation from the Integrated Software for Imagers and Spectrometers (ISIS) system. The support data included the camera location and pointing angles. Match points used to, produce the image mosaic were also downloaded. The camera angles were adjusted to account for the elevation of the match points. This was accomplished with the Multi Sensor Triangulation (MST) software from LH Systems SOCET Set software package. The revised camera angles allowed for the derivation of a digital elevation model (DEM) from the stereo pairs. The match-point latitude and longitude from the global image mosaic are accurate and used for an initial estimate of the horizontal position. The elevations of the match points were estimated from the altimetry data. The camera angles used in the altimetry processing and in the creation of the image mosaic were adjusted independently. Hence, the horizontal position of the altimetry data and the image mosaic are not aligned correctly. Clementine was designed so the altimeter shared the optical system of the HIRES camera system. The HIRES and UV-VIS camera systems were aligned so the HIRES image was centered in the UV-VIS image. We therefore made an adjustment so that the altimetry points would fall near the centerline of the UV-VIS imagery. A DEM was created from

Rosiek, M. R.; Kirk, R.; Howington-Kraus, A.

1999-01-01

446

The effect of topography on SAR calibration  

Microsoft Academic Search

During normal synthetic aperture radar (SAR) processing, a flat Earth is assumed when performing radiometric corrections such as antenna pattern and scattering area removal. The authors examine the effects of topographic variations on these corrections. Local slopes will cause the actual scattering area to be different from that calculated using the flat Earth assumption. It is shown that this effect

Jakob J. van Zyl; Bruce D. Chapman; Pascale Dubois; Jiancheng Shi

1993-01-01

447

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

448

Wettability influences cell behavior on superhydrophobic surfaces with different topographies  

Microsoft Academic Search

Surface wettability and topography are recognized as critical factors influencing cell behavior on biomaterials. So far only few works have reported cell responses on surfaces exhibiting extreme wettability in combination with surface topography. The goal of this work is to study whether cell behavior on superhydrophobic surfaces is influenced by surface topography and polymer type. Biomimetic superhydrophobic rough surfaces of

B. N. Lourenco; G. Marchioli; W Song; R. L. Reis; Blitterswijk van C. A; H. B. J. Karperien; Apeldoorn van A. A; J. F. Mano

2012-01-01

449

Systematic error in topography-controlled groundwater models  

Microsoft Academic Search

The topography is often used as a boundary condition in groundwater flow models. This boundary condition is only valid if the groundwater table is a subdued exact replica of the topography. Since the water table never follows the topography exactly, applying this boundary condition induces a systematic error that overestimates the velocities of the top part of the saturated subsurface.

L. Marklund; A. Worman

2008-01-01

450

Feasibility of Intraoperative Corneal Topography Monitoring During Photorefractive Keratectomy  

Microsoft Academic Search

PURPOSE: We propose a feasibility study of new corneal topography technology with the aim of monitoring intraoperative corneal topography dur- ing excimer laser photorefractive keratectomy. The PAR system measures corneal topography with sin- gle grid projection and triangulation but requires fluorescent fluid to be deposited on the corneal sur- face for shape extraction. We propose and demon- strate a novel

Christophe Moser; Juergen Kampmeier; Peter McDonnell; D. Psaltis

451

A New Design for Digital Elevation Models of Bedrock Underlying Ice Sheets  

NASA Astrophysics Data System (ADS)

Proper knowledge of bedrock topography is an important prerequisite in order to model ice sheet behavior and estimate their future contribution to sea level rise. Today, 5-km resolution Digital Elevation Models are commonly used by modelers to obtain bedrock elevation on their grid nodes. This chosen resolution is questionable since most of the ice outflow goes through outlet glaciers whose size is of a similar order of magnitude, leading modelers to refine their grid with maximum mesh resolution of the order of 100 m. In this study we show that using current 5-km regular DEMs requires an 'undermeshing' interpolation that can locally lead to up to 100% relative error on the ice thickness value as well as opposite directions of the bedrock slope. The sensitivity of such changes on 3D dynamics is also investigated emphasizing the need to rely on more constrained dataset. We propose to modify the way DEMs are processed, moving from static DEMs with interpolated data on a regular mesh to more flexible ones that return a direct interpolation at the precise locations required by the user mesh. An illustration with the Astrolabe Glacier drainage basin (East Antarctica) is described, based on intensive ice thickness radar measurements that have been performed over the last 3 years. An application under the form of a web interface is proposed to demonstrate the feasibility of our procedure.

Drouet, A. S.; Durand, G.; Gillet-Chaulet, F.; Favier, L.; Le Meur, E.; Braun, J.; Sacchettini, M.; Young, D. A.; Blankenship, D. D.; Greenbaum, J. S.; Rignot, E.; Holt, J. W.; Siegert, M.; Kirchner, D.; Mouginot, J.; Gim, Y.; Scheuchl, B.

2012-04-01

452

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

453

Curvature sensor for the measurement of the static corneal topography and the dynamic tear film topography in the human eye  

NASA Astrophysics Data System (ADS)

A system to measure the topography of the first optical surface of the human eye noninvasively by using a curvature sensor is described. The static corneal topography and the dynamic topography of the tear film can both be measured, and the topographies obtained are presented. The system makes possible the study of the dynamic aberrations introduced by the tear film to determine their contribution to the overall ocular aberrations in healthy eyes, eyes with corneal pathologies, and eyes wearing contact lenses.

Gruppetta, Steve; Koechlin, Laurent; Lacombe, François; Puget, Pascal

2005-10-01

454

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

455

Radar Sounding of Mars with MARSIS  

NASA Astrophysics Data System (ADS)

MARSIS, the Mars Advanced Radar for Subsurface and Ionospheric Sounding, is a radar sounder that has been observing Mars from the Mars Express orbiter since June 2005. MARSIS works in the range of 1.3 to 5.5 MHz, and includes significant onboard data summing. MARSIS also operates in an Active Ionospheric Sounding mode down to 0.1 MHz to capture echoes from the topside of the ionosphere. MARSIS signals easily penetrate the polar layered deposits (PLD), usually to their basal contact with the substrate. The typically strong echo return from the lower interface of the PLD indicates that only minor attenuation of the radar signal is occurring within the PLD, implying a composition of nearly pure water ice. MARSIS data have been used to map the bed of the polar deposits to their maximum depth of over 3.5 km in the south. In the north, MARSIS delineates the extent of the “basal unit,” a sediment-laden icy layer that makes up more than a third of the total volume of the topographic cap. In both polar regions, the bed topography does not display a regional-scale deflection that might be expected from a flexural response to the PLD load, indicating a thick elastic lithosphere in these regions. Subsurface interfaces in the low latitudes of Mars are also being mapped by MARSIS, in the equatorial Medusae Fossae Formation. MARSIS has not detected any unambiguous evidence for sizable shallow aquifers. While it is possible that such features exist, the lack of detection more likely indicates that liquid water is not abundant in the shallow (< several km) subsurface of Mars. However, water ice is abundant in the polar regions, including a large area surrounding the polar layered deposits that is associated with the Dorsa Argentea Formation. In addition, analysis of the MARSIS surface echo strength suggests that a substantial fraction of the upper km of the subsurface of the northern plains may be ice-rich. In its ionospheric mode, MARSIS has characterized the complex structure of the topside ionosphere and documented the ionosphere’s behavior with changing solar zenith angle, crustal magnetic fields and solar activity.

Plaut, J. J.; Picardi, G.; Orosei, R.; Gurnett, D. A.

2009-12-01

456

Generation of a new Greenland Ice Sheet Digital Elevation Model  

NASA Astrophysics Data System (ADS)

Currently available Digital Elevation Models(DEMs) of the Greenland Ice Sheet (GrIS) were originally derived from radar altimetry data, e.g. Bamber (Bamber et al., 2001) and later improved by photoclinometry to fill the regions between orbits (Scambos and Haran, 2002). The elevation error of these DEMs is a few meters in the higher part (above 2000 m) of the ice sheet, but it can be as much as 50-100 meters in marginal regions. The relatively low resolution and accuracy poses a problem, especially for ice sheet modeling. Although accurate elevation data have been collected by airborne and spaceborne laser altimetry (airborne: Airborne Topographic Mapper (ATM) (1993-present), Laser Vegetation Imaging Sensor(LVIS) (2007,2009 and 2011); spaceborne: Ice, Cloud, and land Elevation Satellite (ICESat) (2003-2009)) and DEMs have been derived from stereo satellite imagery (e.g., SPOT (40 m), ASTER (15 m)), a high resolution, consistent DEM of GrIS is not yet available. This is due to various problems, such as different error sources in the data and different dates of data acquisition. In order to overcome these difficulties, we generated a multi-resolution DEM of GrIS, reflecting June 2008 conditions, by fusing a photoclinometry DEM, SPOT and ASTER DEMs as well as elevations from ICESat, ATM and LVIS laser altimetry. The new multi-resolution DEM has a resolution of 40 m x 40 m in the marginal ice sheet regions and 250 m elsewhere. The ice sheet margin is mapped from SPOT and Landsat imagery and SPOT DEMs are used to cover the complex topography of ice sheet marginal regions. The accuracy of SPOT DEMs is approximately ± 6 m except in the areas covered by clouds regions, where the SPOT elevations were replaced by ASTER DEMs. The ASTER DEMs were checked and improved by the DEM derived from aerial photography from the 1980s. A new photoclinometry DEM, derived from Advanced Very High Resolution Radiometer (AVHRR) and Moderate Resolution Imaging Spectroradiometer (MODIS) imagery provide a 250-meter resolution base topography at the higher elevations. ICESat and ATM and LVIS laser altimetry observations are used to improve the absolute elevation accuracy by computing the difference between the base DEM and point elevations, followed by 'distributing' the differences over the DEM using kriging interpolation. Adding these interpolated differences to the elevations at the grid posts results in an updated DEM. Finally, all elevations were corrected using elevation changes determined by SERAC (Surface Elevation Reconstruction And Change detection), to achieve a common reference date. Airborne laser altimetry elevations are used to evaluate the accuracy of the new GrIS DEM.

Nagarajan, S.; Csatho, B. M.; Schenk, A. F.; Babonis, G. S.; Scambos, T. A.; Haran, T. M.; Kjaer, K. H.; Korsgaard, N. J.

2011-12-01

457

Generation of Solitary Rossby Waves by Unstable Topography  

NASA Astrophysics Data System (ADS)

The effect of topography on generation of the solitary Rossby waves is researched. Here, the topography, as a forcing for waves generation, is taken as a function of longitude variable x and time variable t, which is called unstable topography. With the help of a perturbation expansion method, a forced mKdv equation governing the evolution of amplitude of the solitary Rossby waves is derived from quasi-geostrophic vorticity equation and is solved by the pseudo-spectral method. Basing on the waterfall plots, the generational features of the solitary Rossby waves under the influence of unstable topography and stable topography are compared and some conclusions are obtained.

Yang, Hong-Wei; Yin, Bao-Shu; Dong, Huan-He; Ma, Zhen-Dong

2012-03-01

458

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

459

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

460

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

461

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

462

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

463

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

464

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

465

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

466

Radar noise jamming calculations simplified  

Microsoft Academic Search

The ratio of radar jamming noise power to radar thermal noise power (J\\/N) is considered for a multiple noise jammer environment where jammer distances and energy levels vary. It is shown that the computation of J\\/N in a multiple noise jammer environment may be significantly simplified in several practical cases by reducing each case to that of a single equivalent

G. P. Kefalas

1981-01-01

467

Environment-adaptive radar techniques  

Microsoft Academic Search

This report describes the work performed in the first year of a contract to investigate the measurement and mitigation of environmental effects in a selected modern radar system. The baseline system is a mobile ground-based tactical radar system which performs wide-area surveillance for aircraft targets as well as multiple target tracking for eventual handover. The dominant technical problem is found

J. E. Howard; G. W. Lank; A. W. Rihaczek

1981-01-01

468

Automotive Radar - Status and Trends  

Microsoft Academic Search

The paper gives a brief overview of automo- tive radar. The status of the frequency regulation for short and long range radar is summarized because of its impor- tance for car manufacturers and their sensor suppliers. Front end concepts and antenna techniques of 24 GHz and 77 GHz sensors are briefly described. Their impact on the sensor's field of view

Martin Schneider

469

UWB radar for patient monitoring  

Microsoft Academic Search

During the last few years the Moscow Aviation Institute (Russia) and the Industrial Technology Research Institute (Taiwan) have worked jointly on the development of ultrawideband (UWB) medical radars for remote and contactiess monitoring of patients in hospitals. Preliminary results of these works were published in [1]. As of the present, several radars have been produced and tested in real conditions

Igor Immoreev; Teh-Ho Tao

2008-01-01

470

Radar Studies of Bird Migration.  

National Technical Information Service (NTIS)

Observations of bird migration with NASA radars were made at Wallops Island, Va. Simultaneous observations were made at a number of radar sites in the North Atlantic Ocean in an effort to discover what happened to those birds that were observed leaving th...

T. C. Williams J. M. Williams

1974-01-01

471

Microwave Emissions from Police Radar  

Microsoft Academic Search

This study evaluated police officers' exposures to microwaves emitted by traffic radar units. Exposure measurements were taken at approximated ocular and testicular levels of officers seated in patrol vehicles. Comparisons were made of the radar manufacturers' published maximum power density specifications and actual measured power densities taken at the antenna faces of those units. Four speed-enforcement agencies and one transportation

J. M. Fink; J. P. Wagner; J. J. Congleton; J. C. Rock

1999-01-01

472

Resolution independent radar target recognition  

Microsoft Academic Search

The value of Through the Wall Radar Imaging (TWRI) data collected with one system is limited when training the automatic target recognition classifier of a second system because of variation in the Point Spread Function (PSF). The target image is a function of both the scene reflectivity and the PSF, which is in turn a function of the imaging radar's

Graeme E. Smith; Bijan G. Mobasseri

2011-01-01

473

Millimeter radar improves target identification  

NASA Astrophysics Data System (ADS)

Recently developed millimeter wave radar has advantages for target identification over conventional microwave radar which typically use lower frequencies. We describe the pertinent features involved in the construction of the new millimeter wave radar, the pseudo-optical cavity source and the quasi-optical duplexer. The long wavelength relative to light allows the radar beam to penetrate through most weather because the wavelength is larger than the particle size for dust, drizzle rain, fog. Further the mm wave beam passes through an atmospheric transmission window that provides a dip in attenuation. The higher frequency than conventional radar provides higher Doppler frequencies, for example, than X-band radar. We show by simulation that small characteristic vibrations and slow turns of an aircraft become visible so that the Doppler signature improves identification. The higher frequency also reduces beam width, which increases transmit and receive antenna gains. For the same power the transmit beam extends to farther range and the increase in receive antenna gain increases signal to noise ratio for improved detection and identification. The narrower beam can also reduce clutter and reject other noise more readily. We show by simulation that the radar can be used at lower elevations over the sea than conventional radar.

McAulay, Alastair D.

2011-05-01