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1

Radar image processing for the AFIT anechoic chamber  

NASA Astrophysics Data System (ADS)

The purpose of this study was to begin development of an Inverse Synthetic Aperature Radar imaging capability for the AFIT anechoic chamber. This began with an evaluation of the capabilities and limitations of the existing radar system and the chamber itself for this application. Then, after deciding on the image processing approach, software had to be written to collect the data necessary for image processing. This constituted the majority of this study, and resulted in a versatile, user-friendly program that automates the process of collecting data for high-resolution radar images. The program checks that the data to be collected will lead to a valid radar cross-section (RCS) image, but will allow data collection for general radar images. Finally, the image processing software was begun. This made use of commercially available software packages called PC-MATLAB and PRO-MATLAB. Further work is needed on the image processing software to generate calibrated images, and to perform focusing.

Sanders, Brian K.

1990-12-01

2

Multifrequency remote sensing radar images processing and analysis  

Microsoft Academic Search

The advantages of using multifrequency remote sensing for measuring underlying terrain parameters and radar data interpretation are discussed. Some important peculiarities of image processing and analysis are presented and novel algorithms of two-dimensional image filtering and transformation are proposed. Examples of their application to real data are given. Possible ways of using neural networks on different stages of radar data

V. V. Lukin; Miao Zhenjiang; Yuan Baozong

1993-01-01

3

Imaging Radar in Archaeological Investigations: An Image Processing Perspective  

Microsoft Academic Search

This paper provides a survey of the various ways researchers have used radar imagery in their particular studies. The early\\u000a studies were usually limited to single-band (gray-scale) imagery because little else was available in the public domain. In\\u000a the past few years, multi-polar, multi-frequency radar imagery has become available on an experimental basis (SIR-C and AirSAR).\\u000a This development has increased

Derrold W. Holcomb; Irina Lita Shingiray

4

Rain clouds tracking with radar image processing based on morphological skeleton matching  

Microsoft Academic Search

The aim of this study is to perform a short term forecasting of dynamic radar clutter evolution (shape and position). This dynamic clutter, like thunderstorms, can be tracked by means of adapted algorithms based on the matching of the morphological skeleton polygonal approximation by relaxation labeling processes. The efficiency of our methods is demonstrated on meteorological radar images. The objective

Fridiric BARBARESCO; Bernard MONNIER

2001-01-01

5

UWB Radar: Mechanical Scanning and Signal Processing for Through-the-Wall Imaging  

NASA Astrophysics Data System (ADS)

This chapter presents a state of the art of the UWB (ultra-wideband) radar for through-the-wall imaging, followed by a description of different methods to scan a scene situated through a wall using a UWB system. Principal attention of this chapter focuses on a mechanical scanning radar system and associated image processing to detect a human body through a wall and also the environment of a target.

Liebe, C.; Gaugue, A.; Khamlichi, J.; Menard, M.; Ogier, J.-M.

6

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

NASA Astrophysics Data System (ADS)

Two new radar systems have been developed for real-time measurement of near-shore processes, and results are presented for measurements of ocean wave spectra, near-shore sand bar structure, and ocean currents. The first is a non-coherent radar based on a modified version of the Sitex radar family, with a data acquisition system designed around an ISR digital receiver card. The card operates in a PC computer with inputs from a Sitex radar modified for extraction of analogue signals for digitization. Using a 9' antenna and 25 kW transmit power system, data were collected during 2007 at the U.S. Army Corps of Engineers Field Research Facility (FRF), Duck, NC during winter and spring of 2007. The directional wave spectrum measurements made are based on using a sequence of 64 to 640 antenna rotations to form a snapshot series of radar images of propagating waves. A square window is extracted from each image, typically 64 x 64 pixels at 3-m resolution. Then ten sets of 64 windows are submitted to a three-dimensional Fast Fourier Transform process to generate radar image spectra in the frequency-wavenumber space. The relation between the radar image spectral intensity and wave spectral intensity derived from the FRF pressure gauge array was used for a test set of data, in order to establish a modulation transfer function (MTF) for each frequency component. For 640 rotations, 10 of such spectra are averaged for improved statistics. The wave spectrum so generated was compared for extended data sets beyond those used to establish the MTF, and those results are presented here. Some differences between the radar and pressure sensor data that are observed are found to be due to the influence of the wind field, as the radar echo image weakens for light winds. A model is developed to account for such an effect to improve the radar estimate of the directional wave spectrum. The radar ocean wave imagery is severely influenced only by extremely heavy rain-fall rates, so that acceptable quality were assured for most weather conditions on a diurnal basis using a modest tower height. A new coherent microwave radar has recently been developed by ISR and preliminary testing was conducted in the spring of 2007. The radar is based on the Quadrapus four-channel transceiver card, mixed up to microwave frequencies for pulse transmission and back down to base-band for reception. We use frequency-modulated pulse compression methods to obtain 3-m spatial resolution. A standard marine radar pedestal is used to house the microwave components, and rotating radar PPI images similar to marine radar images are obtained. Many of the methods used for the marine radar system have been transferred to the coherent imaging radar. New processing methods applied to the coherent data allow summing of radial velocity images to map mean currents in the near shore zone, such as rip currents. A pair of such radars operating with a few hundred meter separation can be used to map vector currents continuously in the near shore zone and in harbors on a timely basis. Results of preliminary testing of the system will be presented.

Trizna, D.; Hathaway, K.

2007-05-01

7

Basics of Polar-Format algorithm for processing Synthetic Aperture Radar images.  

SciTech Connect

The purpose of this report is to provide a background to Synthetic Aperture Radar (SAR) image formation using the Polar Format (PFA) processing algorithm. This is meant to be an aid to those tasked to implement real-time image formation using the Polar Format processing algorithm.

Doerry, Armin Walter

2012-05-01

8

Wavefront curvature limitations and compensation to polar format processing for synthetic aperture radar images.  

SciTech Connect

Limitations on focused scene size for the Polar Format Algorithm (PFA) for Synthetic Aperture Radar (SAR) image formation are derived. A post processing filtering technique for compensating the spatially variant blurring in the image is examined. Modifications to this technique to enhance its robustness are proposed.

Doerry, Armin Walter

2006-01-01

9

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

10

Radar Images of the Earth: Volcanoes  

NSDL National Science Digital Library

This site features links to thirty-five NASA radar images of the world's volcanoes, including brief descriptions of the respective processes and settings involved. The images were created with the Spaceborne Imaging Radar-C and X-Band Synthetic Aperture Radar (SIR-C/X-SAR) as part of NASA's Mission to Planet Earth. The radar illuminates Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions.

11

Radar Images of the Earth: Oceans  

NSDL National Science Digital Library

This site features links to seven NASA radar images of the world's oceans, including brief descriptions of the respective processes and settings. The images were created with the Spaceborne Imaging Radar-C and X-Band Synthetic Aperture Radar (SIR-C/X-SAR) as part of NASA's Mission to Planet Earth. The radar illuminates Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions.

12

Radar Images of the Earth: Cities  

NSDL National Science Digital Library

This site features links to more than fifty NASA radar images of the world's cities, including brief descriptions of the respective processes and settings involved. The images were created with the Spaceborne Imaging Radar-C and X-Band Synthetic Aperture Radar (SIR-C/X-SAR) as part of NASA's Mission to Planet Earth. The radar illuminates Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions.

13

Space Radar Images of the Earth: Archaeology  

NSDL National Science Digital Library

This site features links to twelve NASA radar images of the world's famous archaeology sites, including brief descriptions of the respective processes and settings involved. The images were created with the Spaceborne Imaging Radar-C and X-Band Synthetic Aperture Radar (SIR-C/X-SAR) as part of NASA's Mission to Planet Earth. The radar illuminates Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions.

14

Radar Images of the Earth: Interferometry  

NSDL National Science Digital Library

This site features links to nineteen NASA radar images using interferometry to enhance details or measure changes in elevation. The image pages contain brief descriptions of the respective processes and settings. They were created with the Spaceborne Imaging Radar-C and X-Band Synthetic Aperture Radar (SIR-C/X-SAR) as part of NASA's Mission to Planet Earth. The radar illuminates Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions.

15

Array Processing for Radar Clutter Reduction and Imaging of Ice-Bed Interface  

NASA Astrophysics Data System (ADS)

A major challenge in sounding of fast-flowing glaciers in Greenland and Antarctica is surface clutter, which masks weak returns from the ice-bed interface. The surface clutter is also a major problem in sounding and imaging sub-surface interfaces on Mars and other planets. We successfully applied array-processing techniques to reduce clutter and image ice-bed interfaces of polar ice sheets. These techniques and tools have potential applications to planetary observations. We developed a radar with array-processing capability to measure thickness of fast-flowing outlet glaciers and image the ice-bed interface. The radar operates over the frequency range from 140 to 160 MHz with about an 800- Watt peak transmit power with transmit and receive antenna arrays. The radar is designed such that pulse width and duration are programmable. The transmit-antenna array is fed with a beamshaping network to obtain low sidelobes. We designed the receiver such that it can process and digitize signals for each element of an eight- channel array. We collected data over several fast-flowing glaciers using a five-element antenna array, limited by available hardpoints to mount antennas, on a Twin Otter aircraft during the 2006 field season and a four-element array on a NASA P-3 aircraft during the 2007 field season. We used both adaptive and non-adaptive signal-processing algorithms to reduce clutter. We collected data over the Jacobshavn Isbrae and other fast-flowing outlet glaciers, and successfully measured the ice thickness and imaged the ice-bed interface. In this paper, we will provide a brief description of the radar, discuss clutter-reduction algorithms, present sample results, and discuss the application of these techniques to planetary observations.

Gogineni, P.; Leuschen, C.; Li, J.; Hoch, A.; Rodriguez-Morales, F.; Ledford, J.; Jezek, K.

2007-12-01

16

Radar imaging and high-resolution array processing applied to a classical VHF-ST profiler  

NASA Astrophysics Data System (ADS)

Among the spaced antenna methods used in the field of atmospheric studies, radar interferometry has been of great interest for many authors. A first approach is to use the phase information contained in the cross-spectra between antenna output signals and to retrieve direction of arrival (DOA) of discrete scatterers. The second one introduces a phase shift between the antenna signals in order to steer the main beam of the antenna towards a desired direction. This paper deals with the later technique and presents a variant of postset beam steering (PBS) which does not require a multi-receiver system. Indeed, the data samples are taken alternately on each antenna by means of high-commutation-rate switches inserted before a unique receiver. This low-cost technique is called ``sequential PBS'' (SPBS) and has been implemented on two classical VHF-ST radars. The present paper shows that high flexibility of SPBS in angular scanning allows to perform radar imaging. Despite a limited maximum range due to the antennas' scanning, the collected data give a view of the boundary layer and the lower troposphere over a wide horizontal extent, with characteristic horizontally stratified structures in the lower troposphere. These structures are also detected by application of high-resolution imaging processing such as Capon's beamforming or Multiple Signal Classification algorithm. The proposed method can be a simple way to enhance the versatility of classical DBS radars in order to extend them for multi-sensor applications and local meteorology.

Hélal, D.; Crochet, M.; Luce, H.; Spano, E.

2001-01-01

17

Improving Ground Penetrating Radar Imaging in High Loss Environments by Coordinated System Development, Data Processing, Numerical Modeling, & Visualization  

SciTech Connect

Improving Ground Penetrating Radar Imaging in High Loss Environments by Coordinated System Development, Data Processing, Numerical Modeling, and Visualization Methods with Applications to Site Characterization EMSP Project 86992 Progress Report as of 9/2004.

Wright, David L.

2004-12-01

18

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

19

Spatial-spectral processing for imaging systems: Multibeam RF imaging and radar systems using spectral hole burning materials  

NASA Astrophysics Data System (ADS)

Systems which form many spatial beams (beamformers) for the RF and microwave spectral bands output either a few simultaneous spatial beams across a wide bandwidth---using true-time-delay beamformers---or many simultaneous spatial beams across a moderate bandwidth---using digital aperture synthesis imagers. The simultaneous spatial beams in true-time-delay beamformers require parallel hardware while digital aperture synthesis imagers requires both high speed digitizers and huge digital processors. Moreover; each output beam is typically processed further by a spectrum analyzer or a radar processor. Simultaneous formation and processing of all spatial beams is intractable for wide bandwidths and many beams. This dissertation develops and demonstrates a new class of photonic processing architectures which form and process many simultaneous, wide bandwidth spatial beams. These photonic architectures modulate RF signals from an emulated array of antennas onto an array of coherent optical carriers. I show the theory, the methods, and the results for systems which use Fourier optics and spectral hole burning (SHB) crystals; the demonstrated applications are: wideband RF imaging, Doppler radar, and multi-static radar applications. Proof-of-concept results show 20-beam RF images across a 1 GHz bandwidth and 20-beam radar correlations across bandwidths up to 150 MHz, but these systems can be scaled to process antenna arrays with thousands of beams across bandwidths up to 20 GHz. While these systems can process wide bandwidths for large antenna arrays, I also show an analysis that claims these systems can offer sensitivity levels comparable to other digital or analog beamformers.

Braker, Benjamin M.

20

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

21

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

22

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

23

Long-Wavelength Imaging Radar - A Window on Near-Surface Processes  

NASA Astrophysics Data System (ADS)

Radar observations of the terrestrial planets and the Galilean satellites have often been used to study the roughness and dielectric properties of their surfaces and near-surface environments. Longer radar wavelengths are most effective for deep probing, and can reveal subtle variations in bulk chemistry, the population of suspended rocks or voids, and sub-surface geologic features. We report here on applications of new L- and P-band (24-70 cm wavelength) radar observations of the Moon and Mars-analog terrestrial sites. The new 70-cm lunar observations have a spatial resolution of 300 m, representing a 10-fold improvement over previous maps. Images of the lunar poles do not support the existence of thick, Mercury-like deposits of ice in permanently shadowed craters. Any ice within the radar-observable areas must thus occur as disseminated grains or thin interbedded layers within the regolith. The new images also provide much greater spatial detail of geochemical differences among the mare basalt flows, and regional variations across the southern highlands that appear to correlate with large basin ejecta deposits. L- and P-band AIRSAR images and L-band SIR-C images, for a number of arid or semi-arid regions (Hawaii, Death Valley, Northern Arizona, Egypt), are being used to test theoretical predictions of backscatter from volume scatterers and buried surfaces. We are supporting these imaging radar studies with field topography measurements, ground-penetrating radar surveys, and laboratory sample analysis to constrain the sources and expected polarimetric properties of surface and sub-surface echoes. This work is an important step in refining the requirements on orbital radar systems for Mars and the Galilean satellites. Part of the research described in this paper was carried out by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA.

Campbell, B. A.; Campbell, D. B.; Freeman, A.

2003-12-01

24

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.

25

A radar image time series  

Microsoft Academic Search

A set of side-looking radar images has been collected over an area in the Sierrita Pediment, Arizona, U.S.A. The dates of image acquisition vary from 1965-1979 and the images are taken at various look angles, frequencies, flight directions and polarizations. The objective of the study is to demonstrate the photogrammetric orthophoto technique applied to radar images and at the same

F. Leberl; H. Fuchs; J. P. Ford

1981-01-01

26

Radar Images of the Earth: Ecology and Agriculture  

NSDL National Science Digital Library

This site features links to more than forty NASA radar images of areas of ecological or agricultural interest, including brief descriptions of the respective processes and settings. The images were created with the Spaceborne Imaging Radar-C and X-Band Synthetic Aperture Radar (SIR-C/X-SAR) as part of NASA's Mission to Planet Earth. The radar illuminates Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions.

27

Radar Images of the Earth: Snow, Ice, and Glaciers  

NSDL National Science Digital Library

This site features links to fourteen NASA radar images of the world's snow, ice, and glaciers, including brief descriptions of the respective processes and settings involved. The images were created with the Spaceborne Imaging Radar-C and X-Band Synthetic Aperture Radar (SIR-C/X-SAR) as part of NASA's Mission to Planet Earth. The radar illuminates Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions.

28

Radar images of Mars.  

PubMed

Full disk images of Mars have been obtained with the use of the Very Large Array (VLA) to map the radar reflected flux density. The transmitter system was the 70-m antenna of the Deep Space Network at Goldstone, California. The surface of Mars was illuminated with continuous wave radiation at a wavelength of 3,5 cm. The reflected energy was mapped in individual 12-minute snapshots with the VLA in its largest configuration; fringe spacings as small as 67 km were obtained. The images reveal near-surface features including a region in the Tharsis volcano area, over 2000 km in east-west extent, that displayed no echo to the very low level of the radar system noise. The feature, called Stealth, is interpreted as a deposit of dust or ash with a density less than about 0.5 gram per cubic centimeter and free of rocks larger than 1 cm across. The deposit must be several meters thick and may be much deeper. The strongest reflecting geological feature was the south polar ice cap, which was reduced in size to the residual south polar ice cap at the season of observation. The cap image is interpreted as arising from nearly pure CO(2) or H(2)O ice with a small amount of martian dust (less than 2 percent by volume) and a depth greater than 2 to 5 m. Only one anomalous reflecting feature was identified outside of the Tharsis region, although the Elysium region was poorly sampled in this experiment and the north pole was not visible from Earth. PMID:17784090

Muhleman, D O; Butler, B J; Grossman, A W; Slade, M A

1991-09-27

29

Applications of imaging radar to geology  

Microsoft Academic Search

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

M. I. Daily

1985-01-01

30

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

31

Radar images of Saturn's rings  

NASA Astrophysics Data System (ADS)

In October 1999 we obtained the first radar images of Saturn's rings, using the Arecibo telescope operating at a wavelength of 12.6 cm. The opening angle of the rings, B, was -19.9o, and dual-circular polarization data were collected over a period of 5 days, at ~22 min of receive time per day. We used a frequency-stepped technique similar to that used by Ostro et al. [Icarus, 49, 367 (1982)]. A train of sixteen 100 msec pulses was transmitted every 2.2 sec, an interval slightly longer than the delay depth of the rings, providing a range resolution of 15,000 km. The return echoes were processed to a frequency resolution of about 2 kHz, corresponding to a spatial resolution at the ring ansae of ~2000 km. In order to avoid return pulse overlap, the transmitter frequency was stepped by 800 kHz between pulses. Our observations yield a circular polarization ratio, ? C = 0.70 in the A ring and 0.78 in the B ring, intermediate between values obtained in the 1970s at B=-24.4o and -11.7o [Ostro & Pettengill IAU Colloq. No. 75 (1984)]. In agreement with earlier results [Ostro et al. (1982)], we find no detectable echo from the C ring. At the 3? level, we can set an upper limit of 0.06 on the ratio of its radar cross-section to that of the B Ring. The most striking feature of the new images is a very pronounced quadrupole azimuthal asymmetry in the brightness of the A Ring, seen in both circular polarizations, which is reminiscent of that seen in ground-based and Voyager images and more recently in HST images [French et al., BAAS 32, 864 (2000)]. By generating synthetic delay-Doppler images of the individual ring components and subtracting these piecewise from the Arecibo images, we find that the azimuthal asymmetry is concentrated in the A Ring, as in visible images, though there is also a suggestion of a much weaker asymmetry in the B ring. Fits of a dynamical model of gravitational wakes [Salo & Karjalainen BAAS 31, 1160 (1999)] to the data show that the asymmetry in the radar maps is over three times that measured in HST images obtained at 439 nm and the same opening angle. This work was supported by NASA's Planetary Geology & Geophysics Program.

Nicholson, P. D.; Campbell, D. B.; French, R. G.; Black, G. J.; Margot, J.-L.; Nolan, M.

2000-10-01

32

Region-Enhanced Passive Radar Imaging  

Microsoft Academic Search

Abstract We adapt and apply a recently-developed region-enhanced synthetic aperture radar (SAR) image reconstruction technique to the problem of passive radar imaging. One goal in passive radar imaging is to form images of aircraft using signals transmitted by commercial radio and television stations that are reflected from the objects of interest. This involves reconstructing an image from sparse samples of

Mujdat Cetin; Aaron D. Lanterman

2004-01-01

33

Radar imaging of Saturn's rings  

Microsoft Academic Search

We present delay–Doppler images of Saturn's rings based on radar observations made at Arecibo Observatory between 1999 and 2003, at a wavelength of 12.6 cm and at ring opening angles of 20.1°?|B|?26.7°. The average radar cross-section of the A ring is ?77% relative to that of the B ring, while a stringent upper limit of 3% is placed on the

Philip D. Nicholson; Richard G. French; Donald B. Campbell; Jean-Luc Margot; Michael C. Nolan; Gregory J. Black; Heikki J. Salo

2005-01-01

34

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

35

Short range tracking of rainy clouds by multi-image flow processing of X-band radar data  

NASA Astrophysics Data System (ADS)

Two innovative algorithms for motion tracking and monitoring of rainy clouds from radar images are proposed. The methods are generalizations of classical optical flow techniques, including a production term (modelling formation, growth or depletion of clouds) in the model to be fit to the data. Multiple images are processed and different smoothness constraints are introduced. When applied to simulated maps (including additive noise up to 10 dB of SNR) showing formation and propagation of objects with different directions and velocities, the algorithms identified correctly the production and the flow, and were stable to noise when the number of images was sufficiently high (about 10). The average error was about 0.06 pixels (px) per sampling interval (? T) in identifying the modulus of the flow (velocities between 0.25 and 2 px/? T were simulated) and about 1° in detecting its direction (varying between 0° and 90°). An example of application to X-band radar rainfall rate images detected during a stratiform rainfall is shown. Different directions of the flow were detected when investigating short (10 min) or long time ranges (8 h), in line with the chaotic behaviour of the weather condition. The algorithms can be applied to investigate the local stability of meteorological conditions with potential future applications in nowcasting.

Mesin, Luca

2011-12-01

36

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

37

Mercury Radar Imaging At Arecibo  

Microsoft Academic Search

The Arecibo telescope upgrade has enabled us to obtain radar images of Mercury of unprecedented quality. Here I report on results from Arecibo observations made dur- ing the period 1998-2001. The imaging was done using the delay-Doppler method in both its standard and long-code versions. The north polar \\

J. Harmon

2002-01-01

38

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

39

Mercury Radar Imaging At Arecibo  

NASA Astrophysics Data System (ADS)

The Arecibo telescope upgrade has enabled us to obtain radar images of Mercury of unprecedented quality. Here I report on results from Arecibo observations made dur- ing the period 1998-2001. The imaging was done using the delay-Doppler method in both its standard and long-code versions. The north polar "ice" features have been imaged at 1-km resolution. While these images strongly indicate radar backscatter- ing from volatile deposits in permanently shaded cold traps, the discovery of features in small craters and at relatively low (71-75) latitudes is difficult to reconcile with recent thermal modeling work. This suggests that our current understanding of the maintenance of water ice in the Mercurian environment is incomplete. Other (non- polar) regions have also been imaged, with the best results having come from long- code observations in the summer of 2001. These images are now indicating that all of the major radar features in the Mariner-unimaged hemisphere (including those earlier dubbed "A", "B", and "C") are associated with impact structures. Feature "A" shows a remarkable ejecta blanket and ray system as well as numerous secondary craters, all emanating from a central 85-km-diameter impact crater. Feature "B", earlier suggested as a possible volcano, now appears to be associated with an impact crater the same size as "A". Feature "C", though somewhat obscured by the Doppler equator, shows what appears to be a dense cluster of fresh craters, possibly an impactor swarm or secon- daries from a single (as yet unidentified) impact. A very large rayed impact feature has also been discovered to the south of "C". We have also obtained high-quality images over portions of the Mariner-imaged hemisphere. Here we find a strong correspon- dence between radar-bright craters and bright (and/or rayed) craters in the Mariner images. On the other hand, much of Caloris basin and its surrounding smooth plains appears radar-dark in depolarized radar images, suggesting surfaces that are smooth at wavelength scales. We conclude with a discussion of future plans for Mercury radar observations at Arecibo.

Harmon, J.

40

Survey of Radar Signal Processing.  

National Technical Information Service (NTIS)

During the last decade, considerable progress has been made in radar signal processing, and this report states its present status. The three broad areas of coherent processing, noncoherent detection, and track-while-scan systems are discussed. Specificall...

G. V. Trunk

1977-01-01

41

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

42

Long-Wavelength Imaging Radar - A Window on Near-Surface Processes  

Microsoft Academic Search

Radar observations of the terrestrial planets and the Galilean satellites have often been used to study the roughness and dielectric properties of their surfaces and near-surface environments. Longer radar wavelengths are most effective for deep probing, and can reveal subtle variations in bulk chemistry, the population of suspended rocks or voids, and sub-surface geologic features. We report here on applications

B. A. Campbell; D. B. Campbell; A. Freeman

2003-01-01

43

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

44

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

45

The evolution of the SEASAT imaging radar  

Microsoft Academic Search

The paper describes the design parameters and development of a synthetic aperture radar for use on the SEASAT spacecraft. This imaging radar is designed to operate at altitudes of 800 km with an orbital inclination of 108 deg, a nominal resolution of 25 m, and a swath width of 100 km. The design evolved from planetary imaging radar studies conducted

W. E. Brown Jr.

1975-01-01

46

Radar Imaging of Ocean Surface Patterns  

Microsoft Academic Search

Radar imagery of ocean surface patterns is presented and discussed. The imaging radar detects changes in ocean surface backscatter and yields imagery of deepwater gravity waves, oil slicks, island shadows, internal waves, coastal waves, and other features. The results of several observations suggest that the surface irregularities behave as iostropic scatterers for a radar wavelength of 25 cm. The popular

W. E. Brown; C. Elachi; T. W. Thompson

1976-01-01

47

Open Skies Treaty imaging radar technology issues  

NASA Astrophysics Data System (ADS)

This paper discusses the imaging radar technology requirements for the Open Skies regime, including the unresolved issues to be discussed at future Open Skies Consultative Commission (OSCC) meetings. Compliance with international rules on shared technology is addressed and some of the practical considerations for operational deployment of the radar imaging equipment in an Open Skies aircraft are presented. The Open Skies Treaty requirements and validation methodologies for imaging radars that were agreed on and those that will require future OSCC review are discussed.

Sandoval, M. B.

1992-06-01

48

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

49

SIR-B (Shuttle Imaging Radar) images  

NASA Astrophysics Data System (ADS)

Space Shuttle Mission 41G was launched from Kennedy Space Center on 5 October 1984. Aboard the instrument pallet was the 1.28 GHz (L-band) Shuttle Imaging Radar (SIR-B) intended to obtain SAR images for geology, agriculture, forestry, hydrology, and ocean sciences. Data were intended to be transmitted to earth via a Ku band communication link with the Tracking and Data Relay Satellite (TDRS). Unfortunately, the shuttle's trainable Ku communication antenna failed to lock onto the TDRS, making high rate data transmission impossible. A real-time-revised observation program, of much smaller scale than the original plan, was substituted making use of an onboard tape recorder. The flight crew recorded radar data on the recorder and then reoriented the shuttle itself, with the Ku antenna fixed, to point to TDRS and transmit the data. The revised plan eliminated about 80 percent of the planned data swaths and shortened the remainder. A number of errors crept into the SIR-B experiments as a result of the sudden and complete reprogramming as well as a problem in latching the radar antenna. Finally, an electrical problem in the radar caused an 8-10 dB reduction in signal-to-noise ratio.

1985-05-01

50

Difficulties in superresolving synthetic aperture radar images  

NASA Astrophysics Data System (ADS)

The ability to resolve Synthetic Aperture Radar (SAR) images to finer resolutions than the system bandwidths classically allow is a tantalizing prospect. Seemingly superresolution offers something for nothing, or at least something better than the system was designed for if only we process enough or right. Over the years this has proved to be a rather popular area of investigation, generating a wide variety of algorithms and corresponding claims of performance. Nevertheless, the literature on the fundamental underlying principles of superresolution as applied to SAR has been rather anemic. This paper addresses the following questions: What exactly is superresolution? and What is not really superresolution, but perhaps more aptly described as image enhancement? Is true superresolution possible? and to what degree? What constrains superresolution? and very importantly, How should we objectively test whether an image is in fact superresolved? Whereas superresolution concepts offer the potential of resolution beyond the classical limit, this great promise has not generally been realized. That is not to say that many reported algorithms have no useful effect on images. True superresolution is defined herein as the recovery of true scene spectrum, that allows more accurate scene rendering. The analytical basis for superresolution theory is outlined, and the application to SAR is then investigated as an operator inversion problem, which is generally ill posed. Noise inherent in radar data tends to severely inhibit significant enhancement of image resolution. A criterion for judging superresolution processing of an image is presented.

Doerry, Armin W.; Dickey, Fred M.; Romero, Louis A.; DeLaurentis, John M.

2002-08-01

51

Synthetic aperture radar processing with tiered subapertures  

SciTech Connect

Synthetic Aperture Radar (SAR) is used to form images that are maps of radar reflectivity of some scene of interest, from range soundings taken over some spatial aperture. Additionally, the range soundings are typically synthesized from a sampled frequency aperture. Efficient processing of the collected data necessitates using efficient digital signal processing techniques such as vector multiplies and fast implementations of the Discrete Fourier Transform. Inherent in image formation algorithms that use these is a trade-off between the size of the scene that can be acceptably imaged, and the resolution with which the image can be made. These limits arise from migration errors and spatially variant phase errors, and different algorithms mitigate these to varying degrees. Two fairly successful algorithms for airborne SARs are Polar Format processing, and Overlapped Subaperture (OSA) processing. This report introduces and summarizes the analysis of generalized Tiered Subaperture (TSA) techniques that are a superset of both Polar Format processing and OSA processing. It is shown how tiers of subapertures in both azimuth and range can effectively mitigate both migration errors and spatially variant phase errors to allow virtually arbitrary scene sizes, even in a dynamic motion environment.

Doerry, A.W. [Sandia National Labs., Albuquerque, NM (United States). Synthetic Aperture Radar Dept.

1994-06-01

52

Comparison of various enhanced radar imaging techniques  

NASA Astrophysics Data System (ADS)

Recently, many techniques have been proposed to enhance the quality of radar images obtained using SAR and/or ISAR. These techniques include spatially variant apodization (SVA), adaptive sidelobe reduction (ASR), the Capon method, amplitude and phase estimation of sinusoids (APES) and data extrapolation. SVA is a special case of ASR; whereas the APES algorithm is similar to the Capon method except that it provides a better amplitude estimate. In this paper, the ASR technique, the APES algorithm and data extrapolation are used to generate radar images of two experimental targets and an airborne target. It is shown that although for ideal situations (point targets) the APES algorithm provides the best radar images (reduced sidelobe level and sharp main lobe), its performance degrades quickly for real world targets. The ASR algorithm gives radar images with low sidelobes but at the cost of some loss of information about the target. Also, there is not much improvement in radar image resolution. Data extrapolation, on the other hand, improves image resolution. In this case one can reduce the sidelobes by using non-uniform weights. Any loss in the radar image resolution due to non-uniform weights can be compensated by further extrapolating the scattered field data.

Gupta, Inder J.; Gandhe, Avinash

1998-09-01

53

Comparison of monostatic and bistatic radar images  

Microsoft Academic Search

Relationships between monostatic and bistatic radar images are reviewed and discussed, both from the point of view of identical receiver locations, and from the conventional point of view where the monostatic radar is located at the angular bisector between the bistatic transmitter and receiver. Example images are computed using scattered fields from two three-dimensional (3D) body-of-revolution (BOR) geometries. A Method-of-Moments

R. J. Burkholder; L. J. Gupta; J. T. Johnson

2003-01-01

54

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

55

Doppler radar imaging of spherical planetary surfaces  

Microsoft Academic Search

A new approach to making radar reflectivity images of spherical planetary objects uses echo spectra acquired as a function of rotational phase and at an arbitrary number of subradar latitudes. If only equatorial views are used then the image will have a north-south ambiguity. If non-equatorial views are used than unambiguous images are possible. The technique is tailored for depolarized

R. Scott Hudson; Steven J. Ostro

1990-01-01

56

Spatial-spectral processing for imaging systems: Multibeam RF imaging and radar systems using spectral hole burning materials  

Microsoft Academic Search

Systems which form many spatial beams (beamformers) for the RF and microwave spectral bands output either a few simultaneous spatial beams across a wide bandwidth---using true-time-delay beamformers---or many simultaneous spatial beams across a moderate bandwidth---using digital aperture synthesis imagers. The simultaneous spatial beams in true-time-delay beamformers require parallel hardware while digital aperture synthesis imagers requires both high speed digitizers and

Benjamin M. Braker

2008-01-01

57

NASA Radar Images Asteroid Toutatis  

NASA Video Gallery

This 64-frame movie of asteroid Toutatis was generated from data by Goldstone's Solar System Radar on Dec. 12 and 13, 2012. In the movie clips, the rotation of the asteroid appears faster than it occurs in nature.

Anthony Greicius

2012-12-13

58

Programmable Radar Signal Processing Using the Rap  

Microsoft Academic Search

This paper describes the architecture of the Raytheon Associative\\/Array Processor (RAP) and its application to real-time radar signal processing. The nature of radar computations is analyzed and parallel processing requirements are characterized. The effects of these requirements upon the design of the RAP are described. Features of the operational RAP system are discussed. Finally, an implementation of a Constant False

George R. Couranz; Mark S. Gerhardt; Charles J. Young

1974-01-01

59

Spaceborne imaging radar: geologic and oceanographic applications.  

PubMed

Synoptic, large-area radar images of the earth's land and ocean surface, obtained from the Seasat orbiting spacecraft, show the potential for geologic mapping and for monitoring of ocean surface patterns. Structural and topographic features such as lineaments, anticlines, folds and domes, drainage patterns, stratification, and roughness units can be mapped. Ocean surface waves, internal waves, current boundaries, and large-scale eddies have been observed in numerous images taken by the Seasat imaging radar. This article gives an illustrated overview of these applications. PMID:17841450

Elachi, C

1980-09-01

60

Deconvolution techniques for passive radar imaging  

NASA Astrophysics Data System (ADS)

Forming images of aircraft using passive radar systems that exploit illuminators of opportunity, such as commercial television and FM radio systems, involves reconstructing an image from sparse samples of its Fourier transform. For a given flight path, a single receiver-transmitter pair produces one arc of data in Fourier space. Since the resulting Fourier sampling patterns bear a superficial resemblance to those found in radio astronomy, we consider using deconvolution techniques borrowed from radio astronomy, namely the CLEAN algorithm, to form images from passive radar data. Some deconvolution techniques, such as the CLEAN algorithm, work best on images which are well-modeled as a set of distinct point scatterers. Hence, such algorithms are well-suited to high-frequency imaging of man-made targets, as the current on the scatterer surface tends to collect at particular points. When using low frequencies of interest in passive radar, the images are more distributed. In addition, the complex-valued nature of radar imaging presents a complication not present in radio astronomy, where the underlying images are real valued. These effects conspire to present a great challenge to the CLEAN algorithm, indicating the need to explore more sophisticated techniques.

Lanterman, Aaron D.; Munson, David C.

2002-08-01

61

Deconvolution Techniques for Passive Radar Imaging  

Microsoft Academic Search

Forming images of aircraft using passive radar systems that exploit "illuminators of opportunity," such as commercial television and FM radio systems, involves reconstructing an image from sparse samples of its Fourier transform. For a given flight path, a single receiver-transmitter pair produces one arc of data in Fourier space. Since the resulting Fourier sampling patterns bear a superficial resemblance to

Aaron D. Lanterman; David C. Munson

62

Automatic signal processing of front monitor radar for tunneling machines  

SciTech Connect

It is planned to install a front monitoring impulse radar on the surface of the rotating drill of tunneling machines in order to detect obstacles such as casing pipes of vertical borings. The conventional aperture synthesis technique can no more be applied to such cases because the radar image of a pipe dies not constituent a hyperbola as is the case for linear scanning radars. The authors have developed a special purpose signal processing algorithm with the aid of the discrete model fitting method, which can be used for any pattern of scanning. The details of the algorithm are presented together with the results of numerical simulations and test site experiments.

Sato, Toru [Kyoto Univ. (Japan). Dept. of Electronics and Communication; Takeda, Kenya [NTT Co. Ltd., Chiba (Japan); Nagamatsu, Takashi [Mitsubishi Heavy Industries, Ltd., Tokyo (Japan); Wakayama, Toshio [Mitsubishi Electric Corp., Kamakura, Kanagawa (Japan); Kimura, Iwane [Osaka Inst. of Tech., Hirakata, Osaka (Japan); Shinbo, Tetsuya [Komatsu Co. Ltd., Kanagawa (Japan)

1997-03-01

63

Three-dimensional ground penetrating radar imaging using synthetic aperture time-domain focusing.  

National Technical Information Service (NTIS)

This paper discusses a three-dimensional synthetic aperture imaging technique based on time-domain focusing of pulse-echo radar data. We describe the basic image formation process, important data processing issues, and compensation for planar variations i...

E. M. Johansson J. E. Mast

1994-01-01

64

Radar transponder apparatus and signal processing technique  

DOEpatents

An active, phase-coded, time-grating transponder and a synthetic-aperture radar (SAR) and signal processor means, in combination, allow the recognition and location of the transponder (tag) in the SAR image and allow communication of information messages from the transponder to the SAR. The SAR is an illuminating radar having special processing modifications in an image-formation processor to receive an echo from a remote transponder, after the transponder receives and retransmits the SAR illuminations, and to enhance the transponder`s echo relative to surrounding ground clutter by recognizing special transponder modulations from phase-shifted from the transponder retransmissions. The remote radio-frequency tag also transmits information to the SAR through a single antenna that also serves to receive the SAR illuminations. Unique tag-modulation and SAR signal processing techniques, in combination, allow the detection and precise geographical location of the tag through the reduction of interfering signals from ground clutter, and allow communication of environmental and status information from said tag to be communicated to said SAR. 4 figs.

Axline, R.M. Jr.; Sloan, G.R.; Spalding, R.E.

1996-01-23

65

Radar transponder apparatus and signal processing technique  

DOEpatents

An active, phase-coded, time-grating transponder and a synthetic-aperture radar (SAR) and signal processor means, in combination, allow the recognition and location of the transponder (tag) in the SAR image and allow communication of information messages from the transponder to the SAR. The SAR is an illuminating radar having special processing modifications in an image-formation processor to receive an echo from a remote transponder, after the transponder receives and retransmits the SAR illuminations, and to enhance the transponder's echo relative to surrounding ground clutter by recognizing special transponder modulations from phase-shifted from the transponder retransmissions. The remote radio-frequency tag also transmits information to the SAR through a single antenna that also serves to receive the SAR illuminations. Unique tag-modulation and SAR signal processing techniques, in combination, allow the detection and precise geographical location of the tag through the reduction of interfering signals from ground clutter, and allow communication of environmental and status information from said tag to be communicated to said SAR.

Axline, Jr., Robert M. (Albuquerque, NM); Sloan, George R. (Albuquerque, NM); Spalding, Richard E. (Albuquerque, NM)

1996-01-01

66

Radar transponder apparatus and signal processing technique  

DOEpatents

An active, phase-coded, time-grating transponder and a synthetic-aperture radar (SAR) and signal processor means, in combination, allow the recognition and location of the transponder (tag) in the SAR image and allow communication of information messages from the transponder to the SAR. The SAR is an illuminating radar having special processing modifications in an image-formation processor to receive an echo from a remote transponder, after the transponder receives and retransmits the SAR illuminations, and to enhance tile transponder`s echo relative to surrounding ground clutter by recognizing special transponder modulations from phase-shifted from the transponder retransmissions. The remote radio-frequency tag also transmits information to the SAR through a single antenna that also serves to receive the SAR illuminations. Unique tag-modulation and SAR signal processing techniques, in combination, allow the detection and precise geographical location of the tag, through the reduction of interfering signals from ground clutter, and allow communication of environmental and status information from said tag to be communicated to said SAR.

Axline, R.M. Jr.; Sloan, G.R.; Spalding, R.E.

1994-12-31

67

Synthetic aperture radar imaging of a two-story building  

NASA Astrophysics Data System (ADS)

This paper investigates the expected performance of a ground-based, multi-story building imaging radar system through far-field and near-field computer models. We created a 3-D computer-aided design model of a complex two-story building, simulated the radar response from this complex structure for various geometries and applied synthetic aperture radar image formation algorithms consistent with the simulation scenarios. In this study, we employed the Finite Difference Time Domain method and the Xpatch software to compute the radar signatures. The numerical results give a better understanding of the phenomenology of the scattering and imaging processes and show that relying solely on the far-field scattering data at one elevation angle is not sufficient to obtain the multi-story building layout. Multiple elevation angle views are required in order to determine the location of imaged objects in the vertical direction. Xpatch simulation results in a near-field strip-map configuration suggest a way to achieve this goal within the constraints of a ground-based radar system.

Le, Calvin; Dogaru, Traian

2012-05-01

68

Biometric identification using holographic radar imaging techniques  

Microsoft Academic Search

Pacific Northwest National Laboratory researchers have been at the forefront of developing innovative screening systems to enhance security and a novel imaging system to provide custom-fit clothing using holographic radar imaging techniques. First-of-a-kind cylindrical holographic imaging systems have been developed to screen people at security checkpoints for the detection of concealed, body worn, non-metallic threats such as plastic and liquid

Douglas L. McMakin; David M. Sheen; Thomas E. Hall; Mike O. Kennedy; Harlen P. Foote

2007-01-01

69

Sub-canopy soil moisture inversion using repeat pass Shuttle Imaging Radar C polarimetric Synthetic Aperture Radar interferometric data  

Microsoft Academic Search

The advances in polarimetric synthetic aperture radar (SAR) interferometry techniques provide a promising way to extract sub-canopy surface parameters using processed SAR images. In this paper, we evaluate the fully maximum likelihood decomposition model of polarimetric SAR interferometry for sub-canopy soil moisture estimation. We further propose a methodology for sub-canopy soil estimation using repeat pass space-borne SIR-C (Shuttle Imaging Radar

Xinwu Li; Huadong Guo; Zhen Li; Huanyin Yue; Quan Chen

2009-01-01

70

Geodetic Imaging with Interferometric Airborne Radar  

NASA Astrophysics Data System (ADS)

Geodetic Imaging with Interferometric Airborne Radar Scott Hensley and Cathleen Jones Jet Propulsion Laboratory, California Institute of Technology 4800 Oak Grove Dr, Pasadena CA 91109. Unlike spaceborne sensors both revisit time and viewing geometry can be optimized to a particular application. Airborne sensors such as GeoSAR for topographic measurement and UAVSAR for deformation mapping are representative of the capabilities of airborne radar systems for making geodetically relevant measurements. We will provide a brief overview of the UAVSAR instrument and highlight the technical challenges in making airborne repeat pass measurements suitable for geodetic imaging. Several examples of geodetic imaging by UAVSAR will be presented showing the application or airborne repeat pass imaging to geodesy. The research described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

Hensley, S.; Jones, C. E.

2011-12-01

71

Coherent radar imaging using Capon's method  

NASA Astrophysics Data System (ADS)

A linearly constrained mathematical formulation is provided for the problem of coherent radar imaging. In contrast to studies of field-aligned irregularities in the ionosphere, where the technique has previously been applied, lower atmospheric imaging is complicated by the fact that the scattering structures are not aligned along any single baseline. As a result, a two-dimensional generalization of the brightness distribution was required. It is shown that Fourier-based imaging is a special case of this general formulation. Furthermore, an imaging technique based on constrained optimization is introduced and shown to exhibit higher resolution and resistance to interfering signals. These techniques were applied to data from the middle and upper atmosphere radar in Shigaraki, Japan. The experiment was conducted during the Baiu season, which is characterized by significant precipitation events.

Palmer, Robert D.; Gopalam, Sridhar; Yu, Tian-You; Fukao, Shoichiro

1998-11-01

72

Evidence for a large extended paleolake in the Eastern Sahara as revealed by spaceborne radar lab images  

Microsoft Academic Search

Recently processed radar images from the two flights of the space shuttle Endeavour by the spaceborne imaging radar-C\\/X-band synthetic aperture radar instrument in 1994 give a clear view, of widely distributed sediments of a palaeolake in today's hyperarid eastern Sahara (NW Sudan). Although a few of the sites of lacustrine sediments were previously examined in the field, their extent now

H.-J. Pachur; F. Rottinger

1997-01-01

73

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

74

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

75

Target detection during image formation for ultrawideband radar  

NASA Astrophysics Data System (ADS)

In this work, we introduce a detection scheme that is able to identify regions of interest during the intermediate stages of an image formation process for ultra-wideband (UWB) synthetic aperture radar. Traditional detection methods manipulate the data after image formation. However, this approach wastes computational resources by resolving to completion the entire scene including area dominated by benign clutter. As an alternative, we introduce a multiscale focus of attention (FOA) algorithm that processes intermediate radar data from a quadtree-based backprojection image formation algorithm. As the stages of the quadtree algorithm progress, the FOA thresholds a detection statistic that estimates the signal-to-background ratio for increasingly smaller subpatches. Whenever a subpatch fails a detection, the FOA cues the image formation processor to terminate further processing of that subpatch. We demonstrate that the FOA is able to decrease the overall computational load of the image formation process by a factor of two. We also show that the new FOA method provides fewer false alarms than the two-parameter CFAR FOA over a small database of UWB radar data.

Kaplan, Lance M.; Oh, Seung-Mok; McClellan, James H.; Murenzi, Romain; Namuduri, Kameswara R.

1999-09-01

76

Multistatic synthetic aperture radar image formation.  

PubMed

In this paper, we consider a multistatic synthetic aperture radar (SAR) imaging scenario where a swarm of airborne antennas, some of which are transmitting, receiving or both, are traversing arbitrary flight trajectories and transmitting arbitrary waveforms without any form of multiplexing. The received signal at each receiving antenna may be interfered by the scattered signal due to multiple transmitters and additive thermal noise at the receiver. In this scenario, standard bistatic SAR image reconstruction algorithms result in artifacts in reconstructed images due to these interferences. In this paper, we use microlocal analysis in a statistical setting to develop a filtered-backprojection (FBP) type analytic image formation method that suppresses artifacts due to interference while preserving the location and orientation of edges of the scene in the reconstructed image. Our FBP-type algorithm exploits the second-order statistics of the target and noise to suppress the artifacts due to interference in a mean-square sense. We present numerical simulations to demonstrate the performance of our multistatic SAR image formation algorithm with the FBP-type bistatic SAR image reconstruction algorithm. While we mainly focus on radar applications, our image formation method is also applicable to other problems arising in fields such as acoustic, geophysical and medical imaging. PMID:20051343

Krishnan, V; Swoboda, J; Yarman, C E; Yazici, B

2009-12-31

77

Radar Signal Processing Rulebase Partitioning.  

National Technical Information Service (NTIS)

This technical report addresses issues involved in the integration, enhancement and porting of two large knowledge-based systems, (1) Expert System Constant False Alarm Rate (ES-tFAR) and (2) The Integrated Multi-Domain Radar Demonstration (IMRD), to more...

M. Mehrotra

1995-01-01

78

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

79

Synthetic aperture radar (SAR) image focus performance during maneuvers  

NASA Astrophysics Data System (ADS)

Focus of a SAR image during maneuvers requires accurate estimates of the aircraft velocity vector. Velocity errors particularly along the radar line of sight (LOS) to the SAR map center cause LOS acceleration errors during an aircraft maneuver. This LOS acceleration results in defocused SAR images. Sensitivity to acceleration errors is greatest when mapping at small squint angles with respect to the aircraft velocity vector, i.e., at small angles with respect to the aircraft fore-aft axis. This paper shows the expected SAR map focus performance during maneuvers as a function of velocity errors. Simulation results showing expected focus performance using current and advanced processing techniques with background radar Doppler updates and with the use of Global Positioning System (GPS) are presented. With GPS aiding, velocity accuracy is improved by a factor of ten. The simulation results are compared to the flight test results performed with the APG-76 radar using both a gimbaled and a strapdown one nautical mile per hour class Inertial Navigation System with and without GPS aiding. The AN/APG-76 is a SAR radar with simultaneous Ground Moving Target Indication and is designed for `near the nose' imaging during aircraft maneuvers.

Ibsen, Paul M.; Guarino, Robert

1996-06-01

80

Models of radar imaging of the ocean surface waves  

Microsoft Academic Search

A number of models which would explain ocean wave imagery taken with a synthetic aperture imaging radar are analyzed analytically and numerically. Actual radar imagery is used to support some conclusions. The models considered correspond to three sources of radar backscatter cross section modulation:tilt modulation, roughness variation, and the wave orbital velocity. The effect of the temporal changes of the

CHARLES ELACHI

1977-01-01

81

UWB radar transceiver and measurement for medical imaging  

Microsoft Academic Search

Ultra-wideband radar has been considered as a good candidate for non invasive medical imaging of human body. This paper reports on prototyping, measurement methodology and results of UWB radar on phantoms and actual human body. The measurement experimentally verifies many claims made by previous papers. It sets qualifications on the performance of the UWB radar, and highlights the potential difficulties

Adrian E. C. Tan; Michael Y. W. Chia

2004-01-01

82

Ocean wind fields retrieved from radar-image sequences  

Microsoft Academic Search

The dependency of radar backscatter on the surface wind field is investigated using a nautical X-band radar operating at grazing incidence and horizontal polarization in transmit and receive. This resulted in development of an algorithm for wind retrieval from nautical radar image sequences. The algorithm consists of two parts: In the first part, wind directions are extracted from wind-induced streaks

H. Dankert; J. Horstmann; W. Rosenthal

2003-01-01

83

Two optronic identification techniques: lidar-radar and multispectral polarimetric imaging  

Microsoft Academic Search

We propose to review two concepts that can be used for target detection and identification in optronic systems: lidar-radar and multipectral polarimetric active imaging. The lidar-radar concept uses an optically pre-amplified intensity modulated lidar, where the modulation frequency is in the microwave domain (1-10 GHz). Such a system permits to combine directivity of laser beams with mature radar processing. As

Loic Morvan; Mehdi Alouini; Arnaud Grisard; Eric Lallier; Daniel Dolfi; Xavier Normandin; Anne M. Bouchardy; Gerard Berginc; G. Granger; Jean Chazelas

2004-01-01

84

A simulation study of coherent radar imaging  

NASA Astrophysics Data System (ADS)

Coherent radar imaging (CRI) is used in an attempt to overcome the angular resolution limitation of conventional single-station radars and is used to image the horizontal structure inside the resolution volume. This recently developed technique has been successfully applied to radar observations of the ionosphere as well as the lower atmosphere. However, no statistical analysis of the robustness of the various techniques has been presented to date. In this work, three CRI techniques are reviewed: Fourier-based, Capon's, and maximum entropy (MaxEnt) methods. The Fourier-based method is the simplest of the three algorithms but has inherent resolution limitations. Although quite different in nature and performance, both Capon's and MaxEnt methods can be posed as constrained optimization problems. A statistical comparison of performance of the three CRI techniques, using various receiver configurations and two distinct cases of scattering structure, is made using simulated data. The results show that the MaxEnt method exhibits the best performance in the case of aspect-sensitive scattering with a broad characteristic. In the localized scattering case, however, Capon's method shows superior performance for signals with high signal-to-noise ratio (SNR), but MaxEnt method outperforms all methods for low SNR. In general, both Capon's and MaxEnt methods are able to reproduce the gross characteristics of the scattering media under observation.

Yu, Tian-You; Palmer, Robert D.; Hysell, David L.

2000-09-01

85

Meteor radar signal processing and error analysis  

NASA Astrophysics Data System (ADS)

Meteor wind radar systems are a powerful tool for study of the horizontal wind field in the mesosphere and lower thermosphere (MLT). While such systems have been operated for many years, virtually no literature has focused on radar system error analysis. The instrumental error may prevent scientists from getting correct conclusions on geophysical variability. The radar system instrumental error comes from different sources, including hardware, software, algorithms and etc. Radar signal processing plays an important role in radar system and advanced signal processing algorithms may dramatically reduce the radar system errors. In this dissertation, radar system error propagation is analyzed and several advanced signal processing algorithms are proposed to optimize the performance of radar system without increasing the instrument costs. The first part of this dissertation is the development of a time-frequency waveform detector, which is invariant to noise level and stable to a wide range of decay rates. This detector is proposed to discriminate the underdense meteor echoes from the background white Gaussian noise. The performance of this detector is examined using Monte Carlo simulations. The resulting probability of detection is shown to outperform the often used power and energy detectors for the same probability of false alarm. Secondly, estimators to determine the Doppler shift, the decay rate and direction of arrival (DOA) of meteors are proposed and evaluated. The performance of these estimators is compared with the analytically derived Cramer-Rao bound (CRB). The results show that the fast maximum likelihood (FML) estimator for determination of the Doppler shift and decay rate and the spatial spectral method for determination of the DOAs perform best among the estimators commonly used on other radar systems. For most cases, the mean square error (MSE) of the estimator meets the CRB above a 10dB SNR. Thus meteor echoes with an estimated SNR below 10dB are discarded due to the potential of producing a biased estimate. The precision of the estimated parameters can then be computed using their CRB values as a proxy for the estimated variance. These errors propagate to form the instrumental errors on the height and horizontal wind measurements. Thirdly, the interferometer configuration of interferometric meteor radar system is studied. The interferometer uses the phase differences measured at different sensor pairs to determine the DOA of the meteor trail. Typically Jones cross is used in most of current meteor radar systems, such as MEDAC and SKYiMet. We have evaluated this configuration with other array geometries,such as 'T', 'L' and circular array to examine their performance on the precision of the DOA estimates. The results show that 'T' array has an overall better CRB than other geometries, while with the yagi antenna pattern as a course determination of the DOA range, the circular array performs the best with the lowest sidelobes on the spatial spectral. A Matlab based planar array design package designed for determination and visualization of the DOA estimation performance for a user designed antenna array was developed. Fourthly, based on the special configuration of the South Pole COBRA system, a low cost computational phase calibration method is proposed. Accurate knowledge of the receiver phase ofsets is another factor that can affect system performance. Lastly, the postprocessing results of the meteor echoes collected during 2005 from the South Pole COBRA system are presented. This radar system is shown to have a precision of 2m/s in the horizontal winds, an azimuth precision of 1o, and an elevation precision of 3o. Preliminary scientific results are presented to verify the effectiveness of our processing scheme, and include the seasonal variation of meteor rates as a function of height, and the vertical structure of large semidiurnal tide observed over the South Pole austral summer. The processing schemes and error analysis methods presented in this dissertation can be easily extended to other meteor radar

Kang, Chunmei

86

Synthetic aperture radar imaging with motion estimation and autofocus  

NASA Astrophysics Data System (ADS)

We introduce from first principles a synthetic aperture radar (SAR) imaging and target motion estimation method that is combined with compensation for radar platform trajectory perturbations. The main steps of the method are (a) segmentation of the data into properly calibrated small apertures, (b) motion or platform trajectory perturbation estimation using the Wigner transform and the ambiguity function of the data in a complementary way and (c) combination of small aperture estimates and construction of high-resolution images over wide apertures. The analysis provides quantitative criteria for implementing the aperture segmentation and the parameter estimation process. X-band persistent surveillance SAR is a specific application that is covered by our analysis. Detailed numerical simulations illustrate the robust applicability of the theory and validate the theoretical resolution analysis.

Borcea, L.; Callaghan, T.; Papanicolaou, G.

2012-04-01

87

Real-time windowing in imaging radar using FPGA technique  

NASA Astrophysics Data System (ADS)

The imaging radar uses the high frequency electromagnetic waves reflected from different objects for estimating of its parameters. Pulse compression is a standard signal processing technique used to minimize the peak transmission power and to maximize SNR, and to get a better resolution. Usually the pulse compression can be achieved using a matched filter. The level of the side-lobes in the imaging radar can be reduced using the special weighting function processing. There are very known different weighting functions: Hamming, Hanning, Blackman, Chebyshev, Blackman-Harris, Kaiser-Bessel, etc., widely used in the signal processing applications. Field Programmable Gate Arrays (FPGAs) offers great benefits like instantaneous implementation, dynamic reconfiguration, design, and field programmability. This reconfiguration makes FPGAs a better solution over custom-made integrated circuits. This work aims at demonstrating a reasonably flexible implementation of FM-linear signal and pulse compression using Matlab, Simulink, and System Generator. Employing FPGA and mentioned software we have proposed the pulse compression design on FPGA using classical and novel windows technique to reduce the side-lobes level. This permits increasing the detection ability of the small or nearly placed targets in imaging radar. The advantage of FPGA that can do parallelism in real time processing permits to realize the proposed algorithms. The paper also presents the experimental results of proposed windowing procedure in the marine radar with such the parameters: signal is linear FM (Chirp); frequency deviation DF is 9.375MHz; the pulse width T is 3.2?s taps number in the matched filter is 800 taps; sampling frequency 253.125*106 MHz. It has been realized the reducing of side-lobes levels in real time permitting better resolution of the small targets.

Ponomaryov, Volodymyr I.; Escamilla-Hernandez, Enrique

2005-02-01

88

Topographic mapping using radar interferometry: processing techniques  

Microsoft Academic Search

A new processing algorithm for the NASA JPL TOPSAR topographic radar mapper is described. It incorporates extensive motion compensation features as well as accurate three-dimensional target location algorithm. The processor applies an algorithm to resolving the absolute phase ambiguity. This allows rectified height maps to be generated without any use of ground reference points. The processor was tested using data

Smen N. Madsen; Howard A. Zebker; Jan Martin

1993-01-01

89

SIR-B-The Second Shuttle Imaging Radar Experiment  

Microsoft Academic Search

On October 5, 1984, the second Shuttle Imaging Radar (SIR-B) was launched into orbit aboard the space shuttle Challenger. SIR-B is part of an evolutionary radar program designed to progressively develop a multifrequency, multipolarization synthetic aperture radar with a variable Earth-imaging geometry. The SIR-B instrument is an upgraded version of SIR-A, with the additional capability of tilting the antenna mechanically

Jobea Cimino; Charles Elachi; Mark Settle

1986-01-01

90

Ultrawideband (UWB) Radar Imaging of Building Interior: Measurements and Predictions  

Microsoft Academic Search

In this paper, we explore using the ultrawideband radar technology for sensing through-the-wall imaging. We conducted a field experiment with our in-house designed impulse-based radar, in which a stripmap synthetic aperture radar (SAR) geometry was employed in mapping an abandoned army barrack building with a large footprint area. The images obtained from two sides of the building were combined in

Calvin Le; Traian Dogaru; Lam Nguyen; Marc A. Ressler

2009-01-01

91

Ocean surface winds retrieved from marine radar-image sequences  

Microsoft Academic Search

A new method for wind-field retrieval with spatially and temporally high-resolution using marine radar-image sequences is presented. The method is based on analyzing the movement of wind gusts, which become visible in radar image sequences after filtering. In contrast to previous methods, this new technique requires no calibration phase of the radar system. The retrieved wind directions are compared to

Heiko Dankert; Jochen Horstmann; Wolfgang Rosenthal

2004-01-01

92

Spaceborne Imaging Radar-C instrument  

NASA Astrophysics Data System (ADS)

The present discussion of the Spaceborne Imaging Radar-C (SIR-C) hardware design, subsystem functional design, and interfaces with the NASA Space Shuttle, gives attention to antenna characteristics and to instrument performance parameter characteristics in the C- and L-bands. The SIR-C antenna is a dual-frequency, dual-polarization distributed array antenna whose distribution of transmit/receive modules improves the system noise figure and eliminates the need for a single, high-power RF source. Phase shifters for individual subarrays allow electronic beam steering in elevation and azimuth.

Huneycutt, Bryan L.

93

Target Image Enhancement in Radar Imaging Using Fractional Fourier Transform  

NASA Astrophysics Data System (ADS)

This paper presents a new Range-Doppler Algorithm based on Fractional Fourier Transform (RDA-FrFT) to obtain High-Resolution (HR) images for targets in radar imaging. The performance of the proposed RDA-FrFT is compared with the classical RDA algorithm, which is based on the Fast Fourier Transform (FFT). A closed-form expression for the range and azimuth compression of the proposed RDA-FrFT is mathematically derived and analyzed from the HR Synthetic Aperture Radar (SAR) imaging point of view. The proposed RDA-FrFT takes its advantage of the property of the FrFT to resolve chirp signals with high precision. Results show that the proposed RDA-FrFT gives low Peak Side-Lobe (PSL) and Integrated Side-Lobe (ISL) levels in range and azimuth directions for detected targets. HR images are obtained using the proposed RDA-FrFT algorithm.

El-Mashed, M. G.; Dessouky, M. I.; El-Kordy, M.; Zahran, O.; Abd El-Samie, F. E.

2012-03-01

94

The first radar images of Saturn's rings.  

NASA Astrophysics Data System (ADS)

In October 1999 we obtained the first radar images of Saturn's rings, using the recently-upgraded Arecibo telescope operating at a wavelength of 12.6 cm. The opening angle of the rings was 19.9o, and dual-circular polarization data were collected over a period of 5 days. The resulting delay-Doppler maps have a range resolution of 100 msec and a frequency resolution of 2 kHz, corresponding to a spatial resolution cell of 15000 x 2000 km. Previous radar observations (e.g., Ostro et al. [1982] Icarus 49, 367) demonstrated the rings' high cross section and depolarization ratio, but did not yield 2-dimensional images. The most striking feature of the new maps is a very pronounced azimuthal asymmetry in the brightness of the A Ring, reminiscent of that seen in some ground-based and Voyager images, and more recently documented in HST images (see French et al., this meeting). In both circular polarizations, the rings are brighter on the far quadrant on the receding (western) ansa and on the near quadrant of the approaching (eastern) ansa. The asymmetry averages 25%, but appears to be greater on the eastern ansa. The azimuthal asymmetry is generally ascribed to small-scale trailing wakes generated by local gravitational instabilities in the rings, and as such may be expected to be more pronounced among the meter-sized particles which dominate the radar cross-section than for the cm-sized and smaller particles which contribute significantly to the rings' visible reflectivity. We have attempted to isolate the source of asymmetry by generating synthetic delay-Doppler images of the individual ring components and subtracting these piecewise from the Arecibo images. These models show that the azimuthal asymmetry is indeed concentrated in the A Ring, where it is at least twice as strong as that seen in nearly simultaneous HST images at 439 nm. The models also suggest a smaller asymmetry in the B Ring, with the same phase as that in the A Ring. Also noteworthy is the apparent absence of any detectable echo from the C Ring. At the 3? level, we can set an upper limit of 0.06 on the ratio of its cross-section to that of the B Ring, which may be compared to a reflectivity ratio of 0.2 at optical wavelengths and low phase angles.

Nicholson, P. D.; Campbell, D. B.; French, R. G.; Black, G. J.; Nolan, M.; Margot, J.-L.

2000-05-01

95

Investigation of topics in radar signal processing  

NASA Astrophysics Data System (ADS)

A promising image reconstruction algorithm proposed by W. Lawton for spotlight-mode synthetic aperture radar (SAR) is studied. The spatial domain image is produced through a series of convolutions and DFTs, all performed using FFTs. It is shown that the algorithm implements a form of trapezoidal-to-Cartesian interpolation followed by an FFT. A simplified back-projection algorithm is proposed for spotlight-mode SAR in which the filtered projections are obtained automatically by choosing the radar waveform to be the impulse response of the desired filter. The filtering is accomplished through the physical mechanism of the waveform reflecting off the target, which is described by a convolution. A parallel architecture is described for the back-projection of the filtered projections and its computational and memory requirements are analyzed. A basic derivation is given of bistatic spotlight-mode SAR (BSSAR). It is shown that BSSAR can be explained using the projection-slice theorem from computed tomography. The locations were found of the Fourier domain samples and examine the shape of the Fourier grid for several special cases of transmitter and receiver motions. The chirp-z interpolation algorithm, which is a promising approach to interpolation between two uniform grids with arbitrary spacings is considered. The least squares ambiguity function synthesis problem was studied, which has applications in range-Doppler radar imaging and time-frequency signal analysis. The solution is presented for least squares ambiguity function synthesis both in the continuous and discrete time-frequency domains.

Arikan, Orhan

96

Golay complementary waveforms for sparse delay-Doppler radar imaging  

Microsoft Academic Search

We present a new approach to radar imaging that exploits sparsity in the matched filter domain to enable high resolution imaging of targets in delay and Doppler. We show that the vector of radar cross-ambiguity values at any fixed test delay cell has a sparse representation in a Vandermonde frame that is obtained by discretizing the Doppler axis. The expansion

Yuejie Chi; Robert Calderbank; Ali Pezeshki

2009-01-01

97

Radar imaging through cinder block walls and other periodic structures  

Microsoft Academic Search

Through-wall radar imaging is a challenging area of research due to the complex multi-layer and inhomogeneous structure of building walls. The wall distorts and attenuates the radar signal in a way that is not easy to predict, except in the most simple of cases. In this paper a general periodic model is developed and applied to the imaging algorithm. Periodic

Robert J. Burkholder; Ronald J. Marhefka; John L. Volakis

2008-01-01

98

Ground Penetrating Radar Image Focusing using Frequency-Wavenumber based Synthetic Aperture Radar Technique  

Microsoft Academic Search

In the classical B-Scan ground penetrating radar (GPR), the collected data represented in the image domain, depict undesired hyperbolic effects and have low resolution features. In this work, we present frequency-wavenumber based Synthetic Aperture Radar (SAR) focusing technique to solve this problem. The formulation of algorithm is given and applied to both the simulation data obtained by a physical optics

Enes Yigit; Sevket Demirci; Caner Ozdemir

2007-01-01

99

Terrain Classification in Central Navarre (Spain) Using Polarimetric Radar Images  

NASA Astrophysics Data System (ADS)

Traditionally in Navarre, studies concerning remote sensing techniques have been carried out using optical sensor data. However, cloud cover frequently hampers the acquisition of optical data, causing limitations in its use. Radar sensors are not affected by clouds and, apart from that, the new generation of space-borne radar sensors available offer new capabilities such as the ability to operate with multiple polarizations simultaneously, acquiring polarimetric observations. The main objective of this study is to evaluate the feasibility of polarimetric radar observations for terrain classification in central Navarre. The use of radar images in Navarre is something new because until now these images only have been used to do doctoral thesis.

Larrañaga, A.; Álvarez-Mozos, J.; Albizua, L.; Barinagarrementeria, I.

2009-04-01

100

The development of two-dimensional target images from ultrawideband radar systems  

NASA Astrophysics Data System (ADS)

The development of ultrawideband radar systems has led to the production of echo waveforms with high resolution in range. The Valley Forge Research Center has studied the problem of extending this capability by adding the angular dimension to produce a 2-D image of the radar target. The system currently in use combines adaptive beamforming (ABF) phased array processing with a UWB radar to provide high resolution images of a variety of target configurations. The images were produced using the dominant scatterer ABF algorithm developed at VFRC over the past two decades. The tests were conducted at three frequencies (S, X and Ku bands) in order to allow diversity techniques to enhance the image quality. The formation of a monostatic synthetic aperture array with a 1 GHz bandwidth radar set allows the system to achieve a resolution of 15 cm. This permits fine detail to be observed on images of targets such as cars and trucks. Several examples are presented.

Carlson, Donald L.; Steinberg, Bernard D.

1992-05-01

101

28. Perimeter acquisition radar building room #302, signal process and ...  

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

28. Perimeter acquisition radar building room #302, signal process and analog receiver room - Stanley R. Mickelsen Safeguard Complex, Perimeter Acquisition Radar Building, Limited Access Area, between Limited Access Patrol Road & Service Road A, Nekoma, Cavalier County, ND

102

Radar data processing. Volume 2 - Advanced topics and applications  

Microsoft Academic Search

The design and implementation of the radar data processing (RDP) theory are discussed. Data processing for netted monostatic and bistatic radar systems and technical problems such as the misalignment between radars and target altitude uncertainty are examined. The organization and display of the data on a computer system are studied. The computer simulation of tracking algorithms for RDP performance evaluation

A. Farina; F. A. Studer

1986-01-01

103

Radar Interferometric Imaging of Near-Earth Objects  

Microsoft Academic Search

Very-Long-Baseline Interferometry (VLBI) provides the highest angular resolution of any astronomical imaging technique. VLBI radar imaging of asteroids can provide astrometry, relative orbits of binaries, unambiguous shapes, and maps of surface properties well beyond conventional delay-Doppler imaging. Interferometric radar imaging of asteroids is complicated by near-field optical effects, echo bandwidths that are miniscule compared to those of almost all radio

Michael W. Busch; S. J. Ostro; S. R. Kulkarni; W. F. Brisken; M. C. Nolan

2008-01-01

104

SMAP Radar Processing and Expected Performance  

NASA Astrophysics Data System (ADS)

This presentation will describe the processing algorithms being developed for the Soil Moisture Active Passive (SMAP) radar data and the expected characteristics of the measured backscattering cross sections. The SMAP radar combines some unique features such as a conically scanned antenna with SAR processing of the data. The rapidly varying squint angle gives the measurements variable resolution and noise characteristics and poses a challenge to the processor to maintain accuracy around the wide (1000 km) swath. Rapid variation of Doppler around the scan leads to a time domain azimuth correlation algorithm, and variation of the Doppler geometry will likely require varying the processing bandwidth to manage ambiguity contamination errors. The basic accuracy requirement is 1-dB (one-sigma) in the backscatter measurements at a resolution of 3 km. The main error contributions come from speckle noise, calibration uncertainty, and radio frequency interference (RFI). Speckle noise is determined by system design parameters and details of the processing algorithms. The calibration of the backscatter measurements will be based on pre-launch characterization of the radar components which allow corrections for short term (~1 month) variations in performance. Longer term variations and biases will be removed using measurements of stable reference targets such as parts of the Amazon rain forest, and possibly the oceans and ice sheets. RFI survey measurements will be included to measure the extent of RFI around the world. The SMAP radar is designed to be able to hop the operating frequency within the 80 MHz allocated band to avoid the worst RFI emitters. Data processing will detect and discard further RFI contaminated measurements. This work is supported by the SMAP project at JPL - CalTech. The SMAP mission has not been formally approved by NASA. The decision to proceed with the mission will not occur until the completion of the National Environmental Policy Act (NEPA) process. Material in this document related to SMAP is for information purposes only.

West, R. D.; Jaruwatanadilok, S.

2011-12-01

105

Automatic aircraft landing using interferometric inverse synthetic aperture radar imaging.  

PubMed

This paper presents an interferometric processing of an aircraft's monostatic and bistatic inverse synthetic aperture radar (ISAR) signatures for automatic landing. The aircraft's squint angle in this ISAR imaging problem is near 90 degrees . We show that this extreme squint angle does not pose any problem for the ISAR Fourier-based (wavefront) reconstruction algorithm. In fact, the aircraft can be imaged accurately, and without any erroneous shifts in the cross-range domain, within the imposed theoretical resolution. Moreover, the algorithm is accurate enough such that one can utilize the phase of the ISAR monostatic and bistatic measurements for interferometric processing. The resultant interferometric ISAR image is used to detect undesirable rotations in the aircraft's orientation. PMID:18285222

Soumekh, M

1996-01-01

106

Bistatic synthetic-aperture radar imaging of rotating objects  

Microsoft Academic Search

The imaging properties of a focused radar aperture synthesized by object rotation are considered. The ring-shaped aperture synthesized by the object rotation can provide high-resolution two-dimensional imaging using only monochromatic irradiation. The case of monochromatic irradiation is extended to the polychromatic case and to equivalent bistatic geometries. These techniques offer practical methods for radar imaging of rotating objects with scattering

D. Mensa; G. Heidbreder

1982-01-01

107

Ultrawideband radar imaging system for biomedical applications  

SciTech Connect

Ultrawideband (UWB) (3-10 GHz) radar imaging systems offer much promise for biomedical applications such as cancer detection because of their good penetration and resolution characteristics. The underlying principle of UWB cancer detection is a significant contrast in dielectric properties, which is estimated to be greater than 2:1 between normal and cancerous tissue, compared to a few-percent contrast in radiographic density exploited by x rays. This article presents a feasibility study of the UWB imaging of liver cancer tumors, based on the frequency-dependent finite difference time domain method. The reflection, radiation, and scattering properties of UWB pulses as they propagate through the human body are studied. The reflected and back-scattered electromagnetic energies from cancer tumors inside the liver are also investigated. An optimized, ultrawideband antenna was designed for near field operation, allowing for the reduction of the air-skin interface. It will be placed on the fat-liver tissue phantom with a malignant tumor stimulant. By performing an incremental scan over the phantom and removing early time artifacts, including reflection from the antenna ends, images based on the back-scattered signal from the tumor can be constructed. This research is part of our effort to develop a UWB cancer detection system with good detection and localization properties.

Jafari, H.M.; Liu, W.; Hranilovic, S.; Deen, M.J. [ECE Department, McMaster University, Hamilton, Ontario L8S 4K1 (Canada)

2006-05-15

108

Overview of results of Spaceborne Imaging Radar-C, X-Band Synthetic Aperture Radar (SIR-C\\/X-SAR)  

Microsoft Academic Search

The Spaceborne Imaging Radar-C, X-Band Synthetic Aperture Radar (SIR-C\\/X-SAR) was launched on the Space Shuttle Endeavour for two ten day missions in the spring and fall of 1994. Radar data from these missions are being used to better understand the dynamic global environment. During each mission, radar images of over 300 sites around the Earth were obtained, returning over a

Ellen R. Stofan; Diane L. Evans; Christianna Schmullius; Benjamin Holt; Jeffrey J. Plaut; Jakob van Zyl; Stephen D. Wall

1995-01-01

109

Radar beam- and range-weighting effects on three-dimensional radar imaging for the atmosphere  

NASA Astrophysics Data System (ADS)

Multiple-receiver and multiple-frequency radar imaging techniques used with VHF atmospheric radar can improve, respectively, angular and range resolutions of the atmospheric irregularity structure inside the radar volume. In addition to the imaging method itself, calibration of the imaging is also crucial to yield a better visualization of the irregularity structure. In this paper, the three-dimensional radar imaging using multiple receivers and multiple frequencies simultaneously is demonstrated on the basis of numerical simulation with the Capon method. More than previous works did, radar beam and range weighting effects on the imaging were examined in this study. Beam weighting effect on angular brightness distribution of the scattering region is apparent, but it gives different impacts on the range imaging as accompanying with the range weighting effect: the higher the range position of the scattering region is, the smaller the synthetic influence of both weighting effects will be. Beam weighting effect also causes a range-shortening effect for a localized scattering region, which should be considered in interpreting the shift of range brightness distribution with angular location of the target. Moreover, it is demonstrated that adaptable beam width is effectual to recover a two-blob structure and a wavy layer. An experimental case was also investigated to demonstrate the need of correcting beam weighting effect using adaptable beam width; meanwhile, it suggests that an adaptable range weighting function could be helpful to a further amendment of the three-dimensional imaging.

Chen, Jenn-Shyong; Chen, Chun-Hua; Furumoto, Jun-Ichi

2011-12-01

110

Computational Burden Resulting from Image Recognition of High Resolution Radar Sensors  

PubMed Central

This paper presents a methodology for high resolution radar image generation and automatic target recognition emphasizing the computational cost involved in the process. In order to obtain focused inverse synthetic aperture radar (ISAR) images certain signal processing algorithms must be applied to the information sensed by the radar. From actual data collected by radar the stages and algorithms needed to obtain ISAR images are revised, including high resolution range profile generation, motion compensation and ISAR formation. Target recognition is achieved by comparing the generated set of actual ISAR images with a database of ISAR images generated by electromagnetic software. High resolution radar image generation and target recognition processes are burdensome and time consuming, so to determine the most suitable implementation platform the analysis of the computational complexity is of great interest. To this end and since target identification must be completed in real time, computational burden of both processes the generation and comparison with a database is explained separately. Conclusions are drawn about implementation platforms and calculation efficiency in order to reduce time consumption in a possible future implementation.

Lopez-Rodriguez, Patricia; Fernandez-Recio, Raul; Bravo, Ignacio; Gardel, Alfredo; Lazaro, Jose L.; Rufo, Elena

2013-01-01

111

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

112

Landmine detection and imaging using Micropower Impulse Radar (MIR).  

National Technical Information Service (NTIS)

The Lawrence Livermore National Laboratory (LLNL) has developed radar and imaging technologies with potential applications in mine detection by the armed forces and other agencies involved in determining efforts. These new technologies use a patented ultr...

S. G. Azevedo D. T. Gravel J. E. Mast J. P. Warhus

1995-01-01

113

An Approach to Automatic Target Recognition in Radar Images Using SVM  

Microsoft Academic Search

This paper introduces an Automatic Target Recognition (ATR) method based on X Band Radar image processing. A software which\\u000a implements this method was developed following four principal stages: digital image formation, image preprocessing, feature\\u000a selection through a combination of C4.5 Decision Tree and PCA and classification using SVM. The automatic process was validated\\u000a using two images sets, one of them

Noslén Hernández-gonzález; José Luís Gil Rodríguez; Jorge A. Martin; Francisco Silva-mata; Ricardo González; Raúl Álvarez

2006-01-01

114

UWB array-based radar imaging using modified Kirchhoff migration  

Microsoft Academic Search

This paper presents a new modification of Kirchhoff migration algorithm for ultra-wideband (UWB) array-based radar imaging. The developed algorithm is evolved from traditional Kirchhoff migration which is based on the classical integral theorem of Helmholtz and Kirchhoff. The new algorithm is designed for array-based radar imaging with arbitrary multiple input multiple output (MIMO) configuration. The developed algorithm is compared with

X. Zhuge; T. G. Savelyev; A. G. Yarovoy; L. P. Ligthart

2008-01-01

115

Probabilistic fuzzy image fusion approach for radar through wall sensing.  

PubMed

This paper addresses the problem of combining multiple radar images of the same scene to produce a more informative composite image. The proposed approach for probabilistic fuzzy logic-based image fusion automatically forms fuzzy membership functions using the Gaussian-Rayleigh mixture distribution. It fuses the input pixel values directly without requiring fuzzification and defuzzification, thereby removing the subjective nature of the existing fuzzy logic methods. In this paper, the proposed approach is applied to through-the-wall radar imaging in urban sensing and evaluated on real multi-view and polarimetric data. Experimental results show that the proposed approach yields improved image contrast and enhances target detection. PMID:23996561

Seng, Cher Hau; Bouzerdoum, Abdesselam; Amin, Moeness G; Phung, Son Lam

2013-08-28

116

Aperture Synthesis Imaging at the EISCAT Svalbard radar  

NASA Astrophysics Data System (ADS)

The EISCAT incoherent radar on Svalbard has two dishes. In addition to this two dishes three smaller passive array antennas were built to attempt to implement radar aperture synthesis imaging. Limited to measurements of coherent backscatter the primary science goal of this new receiver system is to study so called naturally enhanced ion acoustic lines. In order to compare radar aperture synthesis images with optical data phase calibration of the interferometer system is needed. We present the phase calibration of the Svalbard interferometer system including the passive array antennas. The calibration was done using optical signatures of satellite transits and the coherent backscatter of the satellites. The optical signature provide accurate position of the satellites. Furthermore we will present sudo-3D aperture synthesis radar images from first observations of satellites conducted with this system.

Schlatter, N. M.; Goodbody, B. C.; Grydeland, T.; Ivchenko, N.; Gustavsson, B.; Belyey, V.; Lanchester, B. S.

2012-04-01

117

Meteor radar signal processing and error analysis  

Microsoft Academic Search

Meteor wind radar systems are a powerful tool for study of the horizontal wind field in the mesosphere and lower thermosphere (MLT). While such systems have been operated for many years, virtually no literature has focused on radar system error analysis. The instrumental error may prevent scientists from getting correct conclusions on geophysical variability. The radar system instrumental error comes

Chunmei Kang

2008-01-01

118

Automatic signal processing of front monitor radar for tunneling machines  

Microsoft Academic Search

It is planned to install a front monitor impulse radar on the surface of the rotating drill of tunneling machines in order to detect obstacles such as casing pipes of vertical borings. The conventional aperture synthesis technique can no more be applied to such cases because the radar image of a pipe does not constitute a hyperbola as is the

Toru Sato; Ken-ya Takeda; Takashi Nagamatsu; Toshio Wakayama; Iwane Kimura; Tetsuya Shinbo

1997-01-01

119

Clinical trials of a UWB imaging radar for breast cancer  

Microsoft Academic Search

This contribution presents a selection of phantom and clinical results from a prototype multistatic imaging radar designed and built at Bristol. Complex phantoms are employed in order to approximate the difficulty in imaging breast tissue, however, even so, imaging in a clinical environment poses particular challenges.

M. Klemm; I. J. Craddock; J. A. Leendertz; A. Preece; D. R. Gibbins; M. Shere; R. Benjamin

2010-01-01

120

47 CFR 15.509 - Technical requirements for ground penetrating radars and wall imaging systems.  

Code of Federal Regulations, 2010 CFR

...requirements for ground penetrating radars and wall imaging systems...requirements for ground penetrating radars and wall imaging systems. (a) The UWB bandwidth of an imaging system...paragraph (d) of this section, UWB transmitters operating...

2010-10-01

121

47 CFR 15.509 - Technical requirements for ground penetrating radars and wall imaging systems.  

Code of Federal Regulations, 2010 CFR

...requirements for ground penetrating radars and wall imaging systems...requirements for ground penetrating radars and wall imaging systems. (a) The UWB bandwidth of an imaging system...paragraph (d) of this section, UWB transmitters operating...

2009-10-01

122

Synthetic aperture radar imaging using a unique approach to frequency-modulated continuous-wave radar design  

Microsoft Academic Search

Synthetic-aperture-radar (SAR) imaging is an expensive endeavor. It can be difficult for universities, small business, or individuals to experiment with SAR imaging and algorithm development on a low budget. For this reason, a uniquely inexpensive solution to frequency-modulated continuous-wave (FMCW) radar was developed and then utilized as an ultra-low-cost SAR imaging system. This unique approach to FMCW radar used a

G. L. Charvat; Leo C. Kempel

2006-01-01

123

New sector imaging radar for enhanced vision: SIREV  

NASA Astrophysics Data System (ADS)

The DLR Radar-System SIREV is a forward looking airborne radar with a fixed mounted antenna at the fuselage of an aircraft or a helicopter. It is able to operate at different frequencies from L-band up to Ka-band and delivers high quality radar images of a flight sector ahead the airpath. The real time generated radar images look very similar to optical images. Depending from the application it can also include a 3D vision as well as information of ground elevation (e.g. obstacles). Due to the all-weather capability of the system and its ability to present radar images very similar to optical images either as top view (mapping mode) or as pilot view (central perspective), the system is especially qualified for: (1) navigation support to the pilot under IMC flight conditions; (2) autonomous landing approaches; (3) taxi support at the ground; (4) dropping of goods or airborne troops. Currently the system is under development. First simulations with data of the SAR system of DLR were performed. The expected image quality and the resolution of the SIREV system can presently not be achieved by any other system.

Witte, Franz; Sutor, Thomas; Scheunemann, Ruediger

1998-07-01

124

29. Perimeter acquisition radar building room #318, data processing system ...  

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

29. Perimeter acquisition radar building room #318, data processing system area; data processor maintenance and operations center, showing data processing consoles - Stanley R. Mickelsen Safeguard Complex, Perimeter Acquisition Radar Building, Limited Access Area, between Limited Access Patrol Road & Service Road A, Nekoma, Cavalier County, ND

125

Signal processing possibilities for pulse radars using polarimetric information  

Microsoft Academic Search

Radars using polarimetric signal information are different from most existing radars, which work on complex scalars and are only able to measure one element of the scattering matrix of a reflecting object. This paper addresses the use of the additional polarimetric information in signal processing. Signal processing problems, their grouping, and their structure are reviewed, and the generation of features

G. Wanielik

1987-01-01

126

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

127

Space-time adaptive processing bistatic airborne radar  

Microsoft Academic Search

In 1996, the United States Air Force initiated the Advanced Airborne Surveillance Program (AASP) to develop and demonstrate the detection performance of state-of-the-art multi-channel bistatic airborne radar technology. The AASP sensor utilizes a multi-channel, phased-array receiver, mounted on a BAC1-11 to collect and process bistatic radar returns from moving targets, clutter and jammers. The bistatic multi-channel airborne radar measurements (MCARM)

Probal K. Sanyal; Russell D. Brown; M. O. Little; R. A. Schneible; M. C. Wicks

1999-01-01

128

Estimation of significant wave height from X-band marine radar images  

Microsoft Academic Search

Radar images include abundant information about ocean waves. Sea state parameters and surface currents can be obtained by analyzing time series of radar images of the sea surface. Due to the non-linearity of the imaging mechanism of ocean waves, significant wave height (Hs) can not be determined directly from radar images. Applying a method to infer the Hs from synthetic

Feng Wang; Jian Wang; Shujuan Wang

2010-01-01

129

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

130

Pulse pair beamforming and the effects of reflectivity field variations on imaging radars  

NASA Astrophysics Data System (ADS)

Coherent radar imaging (CRI), which is fundamentally a beamforming process, has been used to create images of microscale, reflectivity structures within the resolution volume of atmospheric Doppler radars. This powerful technique has the potential to unlock many new discoveries in atmospheric studies. The Turbulent Eddy Profiler (TEP) is a unique 915 MHz boundary layer radar consisting of a maximum of 91 independent receivers. The TEP configuration allows sophisticated CRI algorithms to be implemented providing significant improvement in angular resolution. The present work includes a thorough simulation study of some of the capabilities of the TEP system. The pulse pair processor, used for radial velocity and spectral width estimation with meteorological radars, is combined with beamforming technique, in an efficient manner, to the imaging radar case. By numerical simulation the new technique is shown to provide robust and computationally efficient estimates of the spectral moments. For this study, a recently developed atmospheric radar simulation method is employed that uses the ten thousand scattering points necessary for the high resolution imaging simulation. Previous methods were limited in the number of scatterers due to complexity issues. Radial velocity images from the beamforming radar are used to estimate the three-dimensional wind field map within the resolution volume. It is shown that a large root mean square (RMS) error in imputed three-dimensional wind fields can occur using standard Fourier imaging. This RMS error does not improve even as SNR is increased. The cause of the error is reflectivity variations within the resolution volume. The finite beamwidth of the beamformer skews the radial velocity estimate, and this results in poor wind field estimates. Adaptive Capon beamforming consistently outperforms the Fourier method in the quantitative study and has been demonstrated to enhance the performance compared to the Fourier method.

Cheong, Boon Leng; Hoffman, Michael W.; Palmer, Robert D.; Frasier, Stephen J.; López-Dekker, F. J.

2004-06-01

131

Development and Application of Millimeter-Wave Imaging Radar  

Microsoft Academic Search

Significant advances in microwave and millimeter wave technology have enabled the development of a new generation of imaging diagnostics in this frequency region. Millimeter wave imaging radar is expected to be one of the most promising diagnostic methods for this purpose. It consists of a frequency-modulated continuous wave or pulsed wave as a probe beam and quasi-optical focusing optics followed

Atsushi Mase; Yuichiro Kogi; Akihide Yamamoto; Masamichi Ohashi; Shuhei Osako; Leonid G. Bruskin; Hitoshi Hojo

2002-01-01

132

Advances in radar imaging at Fraunhofer-FHR  

Microsoft Academic Search

The recent years mark a considerable progress in SAR techniques and systems. Radar imaging has been demonstrated at high frequencies and bandwidths never reached before. Miniaturized SAR systems have been developed which can be operated on board of small UAVs. Last but not least advanced imaging techniques have been demonstrated, e.g. bistatic SAR - even in a forward looking configuration,

Joachim H. G. Ender; Andreas R. Brenner; Helmut Essen; Helmut Wilden; Delphine Cerutti-Maori; Alfred Wahlen; Winfried Johannes

2011-01-01

133

Simulation of imaging radar for obstacle avoidance and enhanced vision  

NASA Astrophysics Data System (ADS)

One of the main advantages of millimeter wave (MMW) imaging radar systems result from the fact that their imaging performance does nearly not depend on atmospheric affects such as fog, rain and snow. That is the reason that MMW radar seems to be one of the most promising sensors for enhanced vision systems (EVS), which can aid the pilot during approach, landing and taxiing, especially under bad weather conditions. Compared to other imaging devices, MMW radar system deliver a lower image resolution and update rate, and have a worse signal to noise ratio. Moreover, the commonly proposed method of the perspective view projection in EVS applications results in some imaging errors and artifacts. These sensor specific effects should be taken into account during the presently conducted EVS research and development. To get the opportunity of studying imaging radar systems in ground based research environments, we have developed a new type of a MMW radar sensor simulator. Our approach is based on detailed terrain and/or airport databases, as they are available for normal visual simulations or VR applications. We have augmented these databases with some specific attributes which describe object surface properties with respect to MMW. Our approach benefits from the state of the art of high speed computer graphics hard- and software. It is implemented in C/C++ and uses the Open GL graphic standard and the SGI Performer database handler. It runs on every SGI graphic workstation, and achieves an image update rate of about 20 Hz, which is more than actual available radar systems deliver. One of the main advantages of our approach is, that it can be integrated easily in emergent multisensor based enhanced vision systems and it is a useful tool for EVS research and development.

Doehler, Hans-Ullrich; Bollmeyer, Dirk

1997-06-01

134

New sector imaging radar for enhanced vision: SIREV  

NASA Astrophysics Data System (ADS)

Recently the demand to supplement existing airborne radar systems with enhanced forward-looking abilities has increased considerably. Available radar systems are not able to fulfill the needed requirements. Here a new approach is been proposed to cover the forward lying sector with respect to the flight path. The new radar system has been denoted as SIREV (Sector Imaging Radar for Enhanced Vision) and is presently under development at DLR. Due to the all-weather capability of the system and its ability to produce high quality radar images either as top view (mapping mode) or as pilot view (central perspective mode) the system is especially qualified for navigation support, autonomous landing approaches or taxi support on the ground. In this paper the authors will especially investigate the azimuth properties of the new system. Azimuth bandwidth and resolution will be calculated and discussed as functions of an arbitrary illuminated sector. Finally a short compilation of the system parameters fixed on basis of these investigations will conclude the description of the new SIREV radar system.

Sutor, Thomas; Witte, Franz; Moreira, Alberto

1999-07-01

135

Combining magnetic resonance imaging and ultrawideband radar: A new concept for multimodal biomedical imaging  

Microsoft Academic Search

Due to the recent advances in ultrawideband (UWB) radar technologies, there has been widespread interest in the medical applications of this technology. We propose the multimodal combination of magnetic resonance (MR) and UWB radar for improved functional diagnosis and imaging. A demonstrator was established to prove the feasibility of the simultaneous acquisition of physiological events by magnetic resonance imaging and

F. Thiel; M. Hein; U. Schwarz; J. Sachs; F. Seifert

2009-01-01

136

Segmentation and cooperative fusion of laser radar image data  

SciTech Connect

In segmentation, the goal is to partition a given 2D image into regions corresponding to the meaningful surfaces in the underlying physical scene. Segmentation is frequently a crucial step in analyzing and interpreting image data acquired by a variety of automated systems ranging from indoor robots to orbital satellites. In this paper, we present results of a study of segmentation by means of cooperative fusion of registered range and intensity images acquired using a prototype amplitude-modulated CW laser radar. In our approach, we consider three modalities -- depth, reflectance and surface orientation. These modalities are modeled as sets of coupled Markov random fields for pixel and line processes. Bayesian inferencing is used to impose constraints of smoothness on the pixel process and linearity on the line process. The latter constraint is modeled using an Ising Hamiltonian. We solve the constrained optimization problem using a form of simulated annealing termed quenched annealing. The resulting model is illustrated in this paper in the rapid quenched, or iterated conditional mode, limit for several laboratory scenes.

Beckerman, M.; Sweeney, F.J.

1994-06-01

137

Validation of imaging Doppler interferometer winds using meteor radar  

NASA Astrophysics Data System (ADS)

There has been some debate over the years concerning the accuracy of mesospheric wind observations made using the imaging Doppler interferometer (IDI) technique. The high potential and increasing use of IDI wind data in joint studies with spaced-antenna MF and meteor radar systems make it important to quantify the IDI results. This paper presents a novel comparison of wind measurements between a dynasonde implementation of IDI and winds derived from an all-sky meteor radar system, a widely-accepted standard for such measurements. Both radars were located at the USU Bear Lake Observatory and operated almost continuously for a four-month period. The winds and tides derived from IDI were found to closely match those measured by meteor radar, not only during the day but also at night, and at all overlapping heights from 80-95 km.

Jones, G. O. L.; Berkey, F. T.; Fish, C. S.; Hocking, W. K.; Taylor, M. J.

2003-07-01

138

Precipitation processes as deduced by combining Doppler radar and disdrometer  

Microsoft Academic Search

Precipitation processes are investigated in stratiform and convective weather systems by combining Doppler radar and disdrometer measurements. Vertical scans are designed to measure the standard radar data fields and the power spectrum of the vertical Doppler velocities with high spatial and temporal resolution. A new method, based on iterative application of a disdrometer-determined Z-R relation, is developed to estimate vertical

Alan Douglas Thomson

1997-01-01

139

On joint phase-envelope use in radar CFAR processing  

Microsoft Academic Search

A method assuming linear phase drift is presented to improve radar detection performance. Its use is based on the assumption that the target illumination time comprises multiple coherent pulses or coherent processing intervals (CPI). For example in a conventional scanning radar, this often inaccurate information can be used for statistical data mapping to point out possible target presence. If coherent

Juho Vihonen; Timo Ala-Kleemola; Timo Hintikka; Juha Jylha; Ari Visa

2005-01-01

140

Winter and spring thaw as observed with imaging radar at BOREAS  

NASA Astrophysics Data System (ADS)

Measurements of the length of the growing season in the boreal regions, during which significant carbon exchange due to metabolic activity occurs, may improve current estimates of annual CO2 fluxes at high northern latitudes. For coniferous, evergreen forest species, the summer frost free period bounds the growing season length and period of net carbon uptake. Spring soil thaw bounds the period of soil respiration and decomposition and thus carbon release. The balance of these two exchanges determines whether the boreal region is a net carbon source or sink. Imaging radar data can potentially be used to monitor these periods of soil and canopy thaw due to the sensitivity of radar to surface freeze/thaw state. In considering the use of imaging radar, two issues must be addressed. First, the temporal relationship between the time of freezing and thawing of the forest canopy and soil and the periods of photosynthetic and respiration activity must be ascertained. Second, the sensitivity of imaging radar to freeze/thaw processes in each of the forest components must be assessed. Of particular interest is the extent to which radar is selectively sensitive to tree and soil thawing. In 1994, in situ soil, stem and root temperatures, and stem xylem flux were measured over a complete annual cycle at the Boreal Ecosystem-Atmosphere Study (BOREAS) test sites in Canada. Imaging radar data from the European Space Agency Remote Sensing (ERS-1) satellite were also acquired throughout 1994. The in situ temperature data show clear transitions in soil and stem thawing related to the start of soil respiration and canopy photosynthesis, respectively. The imaging radar data show clear shifts in backscatter related directly to soil thaw, and possibly to canopy thaw, as two independent transitions. These results are compared to seasonal ecosystem model results for carbon exchange.

Way, Jobea; Zimmermann, Reiner; Rignot, Eric; McDonald, Kyle; Oren, Ram

1997-12-01

141

Commanding Cassini Radar for the Imaging of Titan's Surface  

NASA Astrophysics Data System (ADS)

We have investigated the dependence of Cassini radar performance on pulse repetition frequency (PRF) and incidence angle for Synthetic Aperture Radar (SAR) imaging of Titan's surface. The Cassini radar has 5 beams which are used sequentially and whose 3dB beam widths are about 0.35 deg x 1.5 deg, except for the central beam of 0.38 deg x 0.38 deg. To make imaged areas of Titan's surface usable, it is necessary for each image pixel to have signal-to-noise ambiguity ratio higher than +14 dB and a thermal noise equivalent backscatter cross-section lower than -10 dB. Using the Doppler sharpening technique, we expect the Cassini radar to achieve an imaging resolution of 300 x 500 m2 in the along track and cross track dimensions at low altitudes (< 2000 km) and 600 x 1000 m2 at high altitudes (> 2000 km). For a typical Titan flyby pass for SAR imaging, the orbit of the Cassini spacecraft is hyperbolic with its lowest altitude of 950 km at the closest approach. As a result, the range from the Cassini radar to Titan's surface varies widely and continuously with time. This in turn requires PRF and incidence angle to be adjusted with time in order to maximize the usable area. We have simulated the performance of the Cassini radar by examining the contiguity of usable image area and by measuring the number of looks. Our preliminary studies show that at low altitudes incidence angle can be increased up to 30 deg and PRF up to 5-6 KHz while low incidence angles of less than 20 deg and low PRF of 3-4 KHz are preferred at high altitudes. The number of looks is 3-4 at low altitudes and approaches 10 at high altitudes. We will show the results of parameter studies and the resulting performance variation.

Gim, Y.; Stiles, B.; West, R.

2002-12-01

142

Imaging Doppler Interferometry using MU radar data  

NASA Astrophysics Data System (ADS)

Approximately 27 hours of observations were made from January 30 to 31, 1992 using the 46.5 MHz MU radar at Shigaraki, Japan. The results of the Space antenna (SA) apparent and true wind estimation, Doppler beam swinging (DBS), and the modified IDI (Ionospherics Dynamics Instrument) measurement are compared.

Chang, Yuli; Larsen, M. F.; Palmer, R. D.; Yamamoto, M.; Fukao, S.; Tsuda, T.; Kato, S.

1993-08-01

143

Sparsity and Compressed Sensing in Radar Imaging  

Microsoft Academic Search

Remote sensing with radar is typically an ill-posed linear inverse problem: a scene is to be inferred from limited measurements of scattered electric fields. Parsimonious models provide a compressed representation of the unknown scene and offer a means for regularizing the inversion task. The emerging field of compressed sensing combines nonlinear reconstruction algorithms and pseudorandom linear measurements to provide reconstruction

Lee C. Potter; Emre Ertin; Jason T. Parker; Müjdat Cetin

2010-01-01

144

Recognition of tanks using laser radar (LADAR) images  

NASA Astrophysics Data System (ADS)

Three-dimensional sensors based on Laser Radar (LADAR) technology possess vast potential for the future battlefield. This work presents an algorithm for the recognition of T62 and T72 tanks from 3D imagery. The algorithm consists of several stages: a) Pre-processing of LADAR images to remove range noise and to determine ground level. b) Segmentation to extract regions that fulfill certain pre-defined conditions. c) Extraction of specific tank features from each region. d) Applying a Fuzzy Logic classifier on the feature vector to discriminate between T62 or T72 tanks and other type of targets or natural clutter. A commercial airborne LADAR sensor was used to acquire images from an area of 40 square kilometers with a measurement density of 20 pixels per square meter and a range noise of 15 cm (1 sigma). The images included more than a hundred man-made objects (tanks, armored personnel carriers, trucks, cranes)along with natural clutter (vegetation and boulders). Among the targets were 18 tanks, two of which were covered with a camouflage net. The algorithm recognized the 16 uncovered tanks with a False Alarm Rate (FAR) of 0.025 per square kilometer. This FAR value is better than the respective FAR values derived for 2D Imaging where Automatic Target Recognition (ATR) techniques are applied. These results show promise for automatic recognition of various targets employing LADAR sensors.

Garten, Haim; Tal, Yoram; Swirski, Yoram; Imber, Amir

2004-12-01

145

Imaging radar simulation in realistic environment using shooting and bouncing rays technique  

Microsoft Academic Search

A three dimensional (3-D) realistic radar simulation package including imaging radar simulation concept applied to multisensor scenarios is under development as a project between the Electromagnetism and Radar Department of ONERA and the OKTAL SE Company. Taking advantage of various studies in the domain, this partnership associates the expertise of ONERA in radar phenomenology, wave interaction with targets and clutter,

Henri-Jose Mametsa; Frederic Rouas; Andre Berges; Jean Latger

2002-01-01

146

Extended radar observations with the frequency radar domain interferometric imaging (FII) technique  

NASA Astrophysics Data System (ADS)

In this paper, we present high-resolution observations obtained with the Middle and Upper Atmosphere (MU) radar (Shigaraki, Japan, /34.85°N, /136.10°E) using the frequency radar domain interferometric imaging (FII) technique. This technique has recently been introduced for improving the range resolution capabilities of the mesosphere-stratosphere-troposphere (MST) radars which are limited by their minimum pulse length. The Fourier-based imaging, the Capon method have been performed with 5 equally spaced frequencies between 46.25 and 46.75MHz and with an initial range resolution of 300m. These results have been compared firstly to results obtained using the frequency domain interferometry (FDI) technique with ?f=0.5MHz and, secondly, to results from a classical Doppler beam swinging (DBS) mode applied with a range resolution of 150m. Thin echoing structures could be tracked owing to the improved radar range resolution and some complex structures possibly related to Kelvin Helmholtz instabilities have been detected. Indeed, these structures appeared within the core of a wind shear and were associated with intense vertical wind fluctuations. Moreover, a well-defined thin echo layer was found in an altitude range located below the height of the wind shear. The radar observations have not been fully interpreted yet because the radar configuration was not adapted for this kind of study and because of the lack of complementary information provided by other techniques when the interesting echoing phenomena occurred. However, the results confirm the high potentialities of the FII technique for the study of atmospheric dynamics at small scales.

Luce, H.; Yamamoto, M.; Fukao, S.; Crochet, M.

2001-07-01

147

High-Resolution Radar Imaging of Mercury's North Pole  

Microsoft Academic Search

The recently upgraded Arecibo S-band (?12.6-cm) radar was used to make delay-Doppler images of Mercury's north polar region, where earlier observations had shown strong echoes from putative ice deposits in craters. The image resolution of 1.5–3 km is a substantial improvement over the 15-km resolution of the older Arecibo images (J. K. Harmon et al. 1994, Nature369, 213–215). The new

J. K. Harmon; P. J. Perillat; M. A. Slade

2001-01-01

148

Three-dimensional ground penetrating radar imaging using synthetic aperture time-domain focusing  

SciTech Connect

This paper discusses a three-dimensional synthetic aperture imaging technique based on time-domain focusing of pulse-echo radar data. We describe the basic image formation process, important data processing issues, and compensation for planar variations in the media. We present a high-resolution volumetric image reconstruction of a concrete test slab and show that we are able to identify steel reinforcing bars in the image. We conclude with a brief comparison of this imaging method with a technique based on diffraction tomography.

Johansson, E.M.; Mast, J.E.

1994-08-01

149

Three-dimensional ground-penetrating radar imaging using synthetic aperture time-domain focusing  

NASA Astrophysics Data System (ADS)

This paper discusses a three-dimensional synthetic aperture imaging technique based on time- domain focusing of pulse-echo radar data. We describe the basic image formation process, important data processing issues, and compensation for planar variations in the media. We present a high-resolution volumetric image reconstruction of a concrete test slab and show that we are able to identify steel reinforcing bars in the image. We conclude with a brief comparison of this imaging method with a technique based on diffraction tomography.

Johansson, Erik M.; Mast, Jeffrey E.

1994-09-01

150

Bistatic synthetic aperture radar inversion with application in dynamic object imaging  

Microsoft Academic Search

An inversion method is presented for bistatic synthetic aperture radar imaging. The method is based on a Fourier analysis (Doppler processing) of the bistatic synthesized array's data followed by a phase modulation analysis of the Doppler data. The approach incorporates the phase information of the wavefront curvature in the transmitted waves as well as the resultant echoed signals. The Doppler

Mehrdad Soumekh

1991-01-01

151

Feature-enhanced synthetic aperture radar image formation based on nonquadratic regularization  

Microsoft Academic Search

We develop a method for the formation of spotlight-mode synthetic aperture radar (SAR) images with enhanced features. The approach is based on a regularized reconstruction of the scattering field which combines a tomographic model of the SAR observation process with prior information regarding the nature of the features of interest. Compared to conventional SAR techniques, the method we propose produces

Müjdat Çetin; William Clement Karl

2001-01-01

152

Regolith Cover on Near-Earth Asteroids: Radar Polarimetric Imaging and Analysis  

Microsoft Academic Search

Asteroid regoliths can provide insight into the impact history, dynamical evolution, and surface processes on small objects. Infrared observations suggest that most asteroids, down to 1-2 km in size, have low thermal inertias consistent with the presence of regolith (e.g. Delbó et al., Icarus, 166, 116, 2003; Wolters et al., Icarus, 175, 92, 2005). Polarimetric radar imaging can be used

Lynn M. Carter; D. B. Campbell; M. C. Nolan

2006-01-01

153

Using Secondary Image Products to Aid in Understanding and Interpretation of Radar Imagery.  

National Technical Information Service (NTIS)

Radargrammetric exploitation of radar images as single images, stereo pairs, images combined with collateral data to from multisensor data sets, and as time series was reviewed. Secondary image products (ortho images, stereo ortho images, slope-effect red...

G. Domik F. Leberl

1986-01-01

154

Multicomponent Ground Penetrating Radar to Image Sedimentary Structures Exhibiting Directionality  

NASA Astrophysics Data System (ADS)

Ground penetrating radar (GPR) is often used in the study of sedimentary deposits because its resolution provides detail similar to outcrop studies. These studies often utilize only a single antenna configuration in a single orientation and use scalar processing techniques. However, the ability to excite and receive responses with GPR from geologic features that have high degrees of directionality, including faults, fractures, dipping beds, and cross-bedding, depends strongly on the polarization of the radar antennas with respect to the orientation or strike of subsurface features. Also, the received response of the subsurface strongly depends on the antenna configuration used. While these dependencies are often seen as problems, these issues can be used to advantage in the study of sedimentary deposits. By using a multicomponent GPR survey technique that utilizes to the vector nature of electromagnetic waves, received instantaneous amplitude signals can be represented by a second-rank tensor. Using Alford rotations it is possible to determine the strike of directional sedimentary features, and field studies show that is can be used to produce apparent images of the subsurface for any antenna orientation for co-polar and cross-polar antenna configurations. Cross-polarized configurations are sensitive to only depolarizing features such as dipping beds and rough surfaces, while co-polarized configurations are sensitive to both normal reflectors and depolarizing features. In field data, Alford rotations on multicomponent GPR data from point-bar deposits from the Brazos River in Texas were used to determine feature orientations and to produce migrated apparent images that provide insight into the overall architecture of the point-bar. From the multicomponent data sedimentary features are classified on the basis of orientation and the ability to depolarize the signal. This gives additional information that is used in the interpretation of the radar stratigraphy. This information is utilized to assess the flow direction, location relative to the channel, and the location within the point-bar. In some cases multicomponent GPR techniques can be used to identify and remove signals from faults and fractures that obscure sedimentary features.

Sassen, D. S.

2005-12-01

155

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

156

Quasi-optimal compression of noisy optical and radar images  

NASA Astrophysics Data System (ADS)

It is often necessary to compress remote sensing (RS) data such as optical or radar images. This is needed for transmitting them via communication channels from satellites and/or for storing in databases for later analysis of, for instance, scene temporal changes. Such images are generally corrupted by noise and this factor should be taken into account while selecting a data compression method and its characteristics, in the particular, compression ratio (CR). In opposite to the case of data transmission via communication channel when the channel capacity can be the crucial factor in selecting the CR, in the case of archiving original remote sensing images the CR can be selected using different criteria. The basic requirement could be to provide such a quality of the compressed images that will be appropriate for further use (interpreting) the images after decompression. In this paper we propose a blind approach to quasi-optimal compression of noisy optical and side look aperture radar images. It presumes that noise variance is either known a priori or pre-estimated using the corresponding automatic tools. Then, it is shown that it is possible (in an automatic manner) to set such a CR that produces an efficient noise reduction in the original images same time introducing minimal distortions to remote sensing data at compression stage. For radar images, it is desirable to apply a homomorphic transform before compression and the corresponding inverse transform after decompression. Real life examples confirming the efficiency of the proposed approach are presented.

Lukin, Vladimir V.; Ponomarenko, Nikolay N.; Zriakhov, Mikhail S.; Zelensky, Alexander A.; Egiazarian, Karen O.; Astola, Jaakko T.

2006-10-01

157

Radar data processing. Volume 2 - Advanced topics and applications  

NASA Astrophysics Data System (ADS)

The design and implementation of the radar data processing (RDP) theory are discussed. Data processing for netted monostatic and bistatic radar systems and technical problems such as the misalignment between radars and target altitude uncertainty are examined. The organization and display of the data on a computer system are studied. The computer simulation of tracking algorithms for RDP performance evaluation and the application of the simulation technique to monoradar and multiradar tracking algorithms are analyzed. The use of RDP in air-traffic control systems, maritime navigation surveillance, and defense systems is investigated. Computer requirements for the implementation of RDP algorithms are described.

Farina, A.; Studer, F. A.

158

Recent advances in 94 GHz FMCW imaging radar development  

Microsoft Academic Search

High resolution imaging radars have come a long way since the early 90's, starting with an FAA Synthetic Vision System program at 35\\/94 GHz. These systems were heavy and bulky, carried a price tag of about $500K, and were only suitable for larger aircrafts at very small quantity production. Size, weight, and power constraints make 94 GHz still a preferred

D. S. Goshi; Y. Liu; K. Mai; L. Bui; Y. Shih

2009-01-01

159

Multi-static synthetic aperture radar image formation  

Microsoft Academic Search

In this paper, we consider a multi-static synthetic aperture radar (SAR) imaging scenario where a swarm of airborne antennas, some of which are transmitting, receiving or both, are traversing arbitrary flight trajectories and transmitting arbitrary waveforms without any form of multiplexing. The received signal at each receiving antenna may be interfered by the scattered signals from multiple transmitters and the

V. P. Krishnan; J. Swoboda; C. E. Yarman; B. Yazici

2009-01-01

160

Application of ground penetrating radar imaging to deepwater (turbidite) outcrops  

Microsoft Academic Search

Ground Penetrating Radar (GPR) provides a high resolution image of bed-scale features within the interior of an outcrop. This geophysical technique has been used successfully in fluvial-deltaic sequences, but its successful use in deepwater deposits is less documented. The present paper demonstrates the ability of GPR to define the nature of channel margins and to distinguish internal channel facies at

R. A Young; R. M Slatt; J. G Staggs

2003-01-01

161

Application of neural networks to radar image classification  

Microsoft Academic Search

A number of methods have been developed to classify ground terrain types from fully polarimetric synthetic aperture radar (SAR) images, and these techniques are often grouped into supervised and unsupervised approaches. Supervised methods have yielded higher accuracy than unsupervised techniques, but suffer from the need for human interaction to determine classes and training regions. In contrast, unsupervised methods determine classes

Yoshihisa Hara; Robert G. Atkins; Simon H. Yueh; Robert T. Shin; J. A. Kong

1994-01-01

162

Imaging Radar Applications in the Death Valley Region.  

National Technical Information Service (NTIS)

Death Valley has had a long history as a testbed for remote sensing techniques (Gillespie, this conference). Along with visible-near infrared and thermal IR sensors, imaging radars have flown and orbited over the valley since the 1970's, yielding new insi...

T. G. Farr

1996-01-01

163

Chaos UWB radar for through-the-wall imaging.  

PubMed

In this paper, we propose to apply a novel chaos-based ultra-wide band (UWB) radar for through-the-wall imaging. The proposed chaos modulation offers superior resolution compared to conventional UWB radars when applied for through-the-wall imaging. A noncoherent receiver is designed based on expectation maximization (EM) algorithm. The theoretical detection performance is derived for through-the-wall detection in the presence and absence of room reverberations as a function of dielectric properties of walls, targets, and their geometry illustrating the robustness of the proposed modulation against room reverberations. The resolution of the proposed modulation is analyzed theoretically and verified through simulations for different wall materials. Numerical electromagnetic simulations using finite difference time domain (FDTD) method are performed to confirm the obtained theoretical results. From the theoretical and simulation analysis, we find that the proposed chaos-based pulse amplitude modulated ultra-wide band (CPAM-UWB) radar has better detection performance, penetrating ability and imaging performance compared to other conventional through-the-wall imaging radars. PMID:19403365

Venkatasubramanian, Vijayaraghavan; Leung, Henry; Liu, Xiaoxiang

2009-04-28

164

Optical processing for adaptive phased-array radar  

Microsoft Academic Search

Two architectural concepts for optical processors for adaptive phased-array radars (APAR) are discussed. A multichannel coherent correlator and a noncoherent optical vector-matrix processor are described, and their applications to APAR data processing are covered.

D. Casasent; D. Psaltis; B. V. K. Vijaha Kumar; M. Carlotto

1980-01-01

165

Radar Data Processing Using a Distributed Computational System.  

National Technical Information Service (NTIS)

This research specifies and validates a new concurrent decomposition scheme, called Confined Space Search Decomposition (CSSD), to exploit parallelism of Radar Data Processing algorithms using a Distributed Computational System. To formalize the specifica...

G. F. Mota

1992-01-01

166

An Approach for Sub-Second Imaging of Concealed Objects Using Terahertz (THz) Radar  

NASA Astrophysics Data System (ADS)

High-resolution, long-range detection of person-borne concealed weapons has recently been demonstrated using a terahertz imaging radar. However, the radar’s image acquisition time must be greatly shortened, from minutes to less than one second, before the system can be effectively deployed in a real-life threat environment. Here we analyze the major system modifications necessary for increasing the speed of a terahertz imaging radar by up to two orders of magnitude.

Cooper, K. B.; Dengler, R. J.; Llombart, N.; Bryllert, T.; Chattopadhyay, G.; Mehdi, I.; Siegel, P. H.

2009-12-01

167

Method for the processing of the reception signal of a deramp type synthetic aperture radar  

US Patent & Trademark Office Database

A Deramp type radar used in synthetic aperture radar for radar imaging transmits coherently repeated linear frequency-modulated pulses and carries out a sort of pulse compression in reception by demodulation of the echo signals received by means of a frequency ramp that reproduces all or part of a transmitted pulse, and by a Fourier transform performed in range. The application to a Deramp type radar signal of a standard SAR processing is disturbed by the fact that, in this signal, the effectively demodulated part of an echo signal due to a target has a position with respect to this echo signal and a duration that are variable as a function of the distance from the target to the radar. The proposed method makes it possible to eliminate this disturbance by means of a particular choice of a common temporal support used for the demodulation of the signals of all the targets of the useful swath and a phase correction applied to the level of the pulse response of the image focusing filter of the SAR processing. Secondarily, a second phase correction can be applied to the complex reflection coefficients obtained for the dots of the image at the end of the SAR processing.

2000-06-06

168

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

169

Three-Dimensional Imaging via Wideband MIMO Radar System  

Microsoft Academic Search

The 3-D inverse synthetic aperture radar imaging fast maneuvering targets is an active research area in the past decades. Planar antenna arrays are used to avoid the motion compensation algorithms but at the cost of increasing the hardware complexity. In this letter, to reduce the hardware complexity of the imaging system, a wideband multiple-input multiple-output system with two perpendicular linear

Guang Qing Duan; Dang Wei Wang; Xiao Yan Ma; Yi Su

2010-01-01

170

Cross-correlated back projection for UWB radar imaging  

Microsoft Academic Search

This paper presents a cross-correlated time-reversal algorithm for the reconstruction of UWB radar images. In comparison to a standard backprojection scheme, this algorithm produces images of superior quality with better cross-range resolution. Furthermore, by cross correlating the UWB array channels with a reference channel located appropriately away from the array center, this algorithm can improve the cross-range resolution of the

Senglee Foo; S. Kashyap

2004-01-01

171

UWB Tomographic Radar Imaging of Penetrable and Impenetrable Objects  

Microsoft Academic Search

In this paper, the capability of ultra-wide-band (UWB) sensor arrays for tomographic radar of electrically large objects is presented. The major concern when imaging is extended to real objects is to achieve a correct reconstruction of the object shape and its electric properties. A general framework based on a UWB bifocusing operator (UWB-BF) with good tomographic imaging capabilities is presented.

LluÍs Jofre; Antoni Broquetas; Jordi Romeu; SebastiÁn Blanch; Anna PapiÓ Toda; Xavier Fabregas; Angel Cardama

2009-01-01

172

Sector imaging radar for enhanced vision (SIREV): theory and applications  

NASA Astrophysics Data System (ADS)

The demand for supplementing existing airborne radar systems with enhanced forward looking abilities has considerably increased. Available radar systems are not able to accomplish the needed requirements for enhanced vision. Instead a new approach has to be taken to cover the forward lying sector with respect to the flight path. Presently a system called SIREV (Sector Imaging Radar for Enhanced Vision) is under development at DLR> Due to the all-weather capability of the system and its ability to present radar images very similar to optical images either as top view (mapping mode) or as pilot view (central perspective mode) the system is essentially qualified for navigation support, autonomous landing approaches or taxi support at the ground. IN this paper the authors will describe the idea the new SIREV system originates from and the relation of the SIREV principle to the SAR principle. Different modes of operation and thereby obtainable performance numbers will be discussed with regard to the special advantages of each sensor. Some potential applications of either sensor will be explained in detail. Finally a summarized overview of the system under development at DLR together with a description of a test field setup at Oberpfaffenhofen airfield will be given. The SIREV project at DLR was partially funded by STN Atlas Elektronik Bremen. This company also holds the SIREV license rights.

Sutor, Thomas; Buckreuss, Stefan; Wendler, Michael; Witte, Franz

2000-06-01

173

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

174

Radar imaging of equatorial F region irregularities with maximum entropy interferometry  

Microsoft Academic Search

Radar interferometry with multiple collinear antenna baselines has been performed at Jicarnarca, near Lima, Per6, and high-resolution images of plasma irregularities in equatorial spread F have been constructed from the data. The images represent the brightness distribution of the radar backscatter, which is the Fourier transform of the visibility or spatial cross correlation of the scattered radar signal on the

D. L. Hysell

1996-01-01

175

Adaptive space-time processing for interference suppression in phased array radar systems. I. Search radar  

Microsoft Academic Search

This paper presents an adaptive technique of filtering to suppress the interference in phased array search radar systems. This interference includes noise, clutter, and jamming signals. Unlike the time processing techniques, our filtering process is based upon the target Doppler shift as well as the interference spatial distribution to suppress adaptively the undesired signals. This can be achieved by estimating

H. H. M. Ghouz; F. I. A. Elghany; M. M. Qutb

2000-01-01

176

Radar Interferometric Imaging of Near-Earth Objects  

NASA Astrophysics Data System (ADS)

Very-Long-Baseline Interferometry (VLBI) provides the highest angular resolution of any astronomical imaging technique. VLBI radar imaging of asteroids can provide astrometry, relative orbits of binaries, unambiguous shapes, and maps of surface properties well beyond conventional delay-Doppler imaging. Interferometric radar imaging of asteroids is complicated by near-field optical effects, echo bandwidths that are miniscule compared to those of almost all radio astronomical sources, and rapid rotation rates. We can apply appropriate corrections in time delay and Doppler shift to remove the near-field effects over small fields of view, and installation of a software correlator has just brought 1 Hz bandwidths within the capabilities of the Very Long Baseline Array (VLBA). Rapid rotation limits the VLBA to short exposure `snapshot’ observations, and because of the limited number of VLBA stations ( 10) almost all potential targets larger than six resolution elements across are over-resolved and cannot be effectively imaged. In these cases, source modeling may still be effective. (4179) Toutatis will be a very strong radar target in November 2008. We will observe it with Arecibo transmitting and the VLBA receiving. Expectations for the VLBA data based on Toutatis’ known shape show that it can be reliably imaged, due to its slow rotation rate. These observations aim test the capabilities of the new correlator and the potential of radar-VLBI imaging, but may also refine our knowledge of Toutatis’ already well-known non-principal axis spin state. This material is based partially on work supported by NASA's Science Mission Directorate Research and Analysis Programs. The VLBA is operated by Associated Universities for the NSF. Arecibo Observatory is run by Cornell for the NSF. M.W. Busch was supported by the Hertz Foundation.

Busch, Michael W.; Ostro, S. J.; Kulkarni, S. R.; Brisken, W. F.; Nolan, M. C.

2008-09-01

177

340-GHz 3D radar imaging test bed with 10-Hz frame rate  

NASA Astrophysics Data System (ADS)

We present a 340 GHz 3D radar imaging test bed with 10 Hz frame rate which enables the investigation of strategies for the detection of concealed threats in high risk public areas. The radar uses a wideband heterodyne scheme and fast-scanning optics to achieve moderate resolution volumetric data sets, over a limited field of view, of targets at moderate stand-off ranges. The high frame rate is achieved through the use of DDS chirp generation, fast galvanometer scanners and efficient processing which combines CPU multi-threading and GPU-based techniques, and is sufficiently fast to follow smoothly the natural motion of people.

Robertson, Duncan A.; Marsh, Paul N.; Bolton, David R.; Middleton, Robert J. C.; Hunter, Robert I.; Speirs, Peter J.; Macfarlane, David G.; Cassidy, Scott L.; Smith, Graham M.

2012-05-01

178

Radar remote sensing for monitoring of dynamic ecosystem processes related to biogeochemical exchanges in tropical peatlands  

Microsoft Academic Search

Peatlands are an important multipurpose ecosystem, supporting huge quantities of biomass and peat soil carbon. A time series of Japanese Earth Resource Satellite-1 (JERS-1) L-band Synthetic Aperture Radar (SAR) data was employed to monitor two dynamic ecosystem processes; deforestation and inundation patterns. Using a change detection analysis for three images acquired during dry seasons of 1994, 1997 and 1998, we

Shakil Ahmad Romshoo

2004-01-01

179

Moving target imaging using ultrawideband synthetic aperture radar  

NASA Astrophysics Data System (ADS)

Moving Target High Resolution Imaging of Foliage Penetrate Ultra-Wide Band Synthetic Aperture Radar (FOPEN UWB SAR) is of great significance for battlefield awareness of concealed target. Great range migration and strong clutter make moving target detection and imaging difficult, especially the Signal to Clutter Ration(SCR) some times is so low that the moving targets is invisible in FOPEN UWB SAR imagery. To improve SCR, the clean technique is used in range compressed data domain. The clean technique and data reconstruction help single channel of FOPEN UWB SAR suppress strong tree clutter and stationary target signal from region of interest. A new definition called General Key-Stone Transform is given, which can correct any order of range migration. FOPEN UWB SAR has long integrated time. The plane and target moving in long time lead to complex range migration. To obtain high resolution imagery of moving target, General Key-Stone transform are applied to remove the range migration and realize multiple moving target data segment. Both General Key-Stone Transform and Clean Technique are applied in real data processing of FOPEN UWB SAR. The result shows that multiple moving targets in the trees are clearly detected and high resolution imagery is formed.

Guo, Hanwei; Liang, Diannong; Wan, Yan; Huang, Xiaotao; Dong, Zhen

2003-09-01

180

Parallel Distributed System for SAR Image Processing.  

National Technical Information Service (NTIS)

Synthetic Aperture Radar (SAR) image focusing involves the processing of a large amount of data, thus requiring a very high elaboration time if a sequential machine is used. Should high precision be desired on the final image, the computer time can increa...

G. Franceschetti A. Mazzeo N. Mazzoca V. Pascazio G. Schirinzi

1990-01-01

181

Models for synthetic aperture radar imaging of the Ocean: A comparison  

NASA Astrophysics Data System (ADS)

Theoretical comparisons are made of different models for synthetic aperture radar (SAR) imaging of ocean waves. The velocity bunching model, distributed surface model, Lyzenga model, Canadian Center for Remote Sensing/Radarsat (CCRS/RADARSAT) model, and the Ocean Research and Engineering (ORE) model are compared analytically with respect to their description of the SAR imaging process and the radar backscatter process. The study concentrates on the temporal description of the backscatter process and its impact on SAR imaging of the ocean. Sample simulations are conducted so as to quantify some of the similarities and differences of the aforementioned models. Other SAR imaging models are discussed, as they pertain to the comparisons noted above. The analytical and numerical simulations show that the Lyzenga model, the CCRS/RADARSAT, model and the ORE model are similar for most commonly occurring sea states. The velocity bunching model is similar to these models when the SAR integration time is small, but it tends to deviate for long integration times. The distributed surface model is shown to describe the imaging process adequately when the radar backscatter is highly correlated in space and time.

Kasilingam, Dayalan P.; Shemdin, Omar H.

1990-09-01

182

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

183

UWB Impulse Radar Characterization and Processing Techniques.  

National Technical Information Service (NTIS)

Ultra-Wideband (UWB) impulse radar is inherently a noise-limited technology. While sub-nanosecond pulses achieve good range resolution, the resultant extreme bandwidth exacts a toll on system performance in terms of noise power entering the receiver. Data...

G. Barrie

2004-01-01

184

Advances in Radar Signal Processing Techniques  

NASA Astrophysics Data System (ADS)

Weibull-distributed clutter are reviewed. Most of the clutter received by L, S, X and Ku band radars obeys a Weibull distribution when reflectors are terrain, sea, sea-ice and rain clouds. Clutter suppression techniques for Weibull clutter are also reviewed. Especially, Weibull CFAR is emphasized.

Sekine, Matsuo; Sayama, Shuji

185

Comparison of MESSENGER Optical Images with Thermal and Radar Data for the Surface of MERCURY  

NASA Astrophysics Data System (ADS)

Images collected by the MESSENGER spacecraft during its three Mercury flybys cover nearly the entire surface of the planet that was not imaged by Mariner 10. The MESSENGER data now allow us to observe features at optical wavelengths that were previously known only through remote sensing in other portions of the electromagnetic spectrum. For example, the Mariner 10 infrared (IR) radiometer made measurements along a track on the night side of Mercury during the spacecraft's first encounter in 1974. Analysis of the IR radiometer data identified several thermal anomalies that we have correlated to craters with extensive rays or ejecta deposits, including Xiao Zhao and Eminescu. The thermal properties are consistent with a greater exposure of bare rock (exposed in steep walls or as boulders and cobbles) in and around these craters compared with the lower-thermal-inertia, finer-grained regolith of the surrounding older surface. The portion of Mercury not viewed by Mariner 10 has also been imaged by Earth-based radar. The radar backscatter gives information on the wavelength-scale surface roughness. Arecibo S-band (12.6-cm wavelength) radar observations have produced images of Eminescu and also revealed two spectacular rayed craters (Debussy and Hokusai) that have since been imaged by MESSENGER. We are examining radial profiles for these craters, extracted from both the radar images and MESSENGER narrow-angle camera mosaics, that extend from the crater center outwards to a distance of several crater diameters. Comparison of optical and radar profiles for the craters, as well as similar profiles for lunar craters, can provide insight into ejecta deposition, the effect of surface gravity on the cratering process, and space weathering.

Blewett, D. T.; Coman, E. I.; Chabot, N. L.; Izenberg, N. R.; Harmon, J. K.; Neish, C.

2010-12-01

186

A comparison of spotlight synthetic aperture radar image formation techniques  

SciTech Connect

Spotlight synthetic aperture radar images can be formed from the complex phase history data using two main techniques: (1) polar-to-cartesian interpolation followed by two-dimensional inverse Fourier transform (2DFFT), and (2) convolution backprojection (CBP). CBP has been widely used to reconstruct medical images in computer aided tomography, and only recently has been applied to form synthetic aperture radar imagery. It is alleged that CBP yields higher quality images because (1) all the Fourier data are used and (2) the polar formatted data is used directly to form a 2D Cartesian image and therefore 2D interpolation is not required. This report compares the quality of images formed by CBP and several modified versions of the 2DFFT method. We show from an image quality point of view that CBP is equivalent to first windowing the phase history data and then interpolating to an exscribed rectangle. From a mathematical perspective, we should expect this conclusion since the same Fourier data are used to form the SAR image. We next address the issue of parallel implementation of each algorithm. We dispute previous claims that CBP is more readily parallelizable than the 2DFFT method. Our conclusions are supported by comparing execution times between massively parallel implementations of both algorithms, showing that both experience similar decreases in computation time, but that CBP takes significantly longer to form an image.

Knittle, C.D.; Doren, N.E.; Jakowatz, C.V.

1996-10-01

187

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

188

Ocean Waves Near Hurricane Josephine from SIR-B (Shuttle Imaging Radar-B).  

National Technical Information Service (NTIS)

Radar images of ocean surface waves near hurricane Josephine were acquired with the Shuttle Imaging Radar-B (SIR-B) system on October 12, 1984. Fast Fourier transform analyses of the images were performed along most of the 600-km image track. These data r...

B. Holt F. I. Gonzalez

1986-01-01

189

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

190

Investigation of ground target detection methods in fully polarimetric wide angle synthetic aperture radar images  

NASA Astrophysics Data System (ADS)

Target detection is a high priority of the Air Force for the purpose of reconnaissance and bombardment. This research investigates and develops methods to distinguish ground targets from clutter (i.e. foliage, landscape etc.) in Wide Angle Synthetic Aperture Radar (WASAR) images. WASAR uses multiple aspect angle SAR images of the same target scene. The WASAR data was generated from a pre-release software package (XPATCH-ES) provided by the sponsor (WL-AARA). A statistical analysis and feature extraction is performed on the XPATCH-ES data. Polarimetric and wide angle covariance matrices are estimated and analyzed. From an analysis of the wide angle covariance matrix it is shown that natural clutter has in general a uniform radar return for changing aspect angles, whereas the radar return for a target varies. Based on this analysis, two new wide angle algorithms, the WASAR Whitening Filter and the Adaptive WASAR Whitening Filter (AWWF) are developed. The target detection performance of polarimetric and multi aspect angle image combining algorithms are quantified using Receiver Operating Characteristic curves and target to clutter ratios. It is shown that wide angle processing provides superior target detection performance over polarimetric processing. Combinations of wide angle and polarimetric algorithms were used to achieve a 13.7 dB processing gain in target to clutter ratio when compared to unprocessed images of the target scene. This represents a significant improvement in target detection capabilities.

Laggan, Wayne B.

1995-03-01

191

Ground processing of Cassini RADAR imagery of Titan  

Microsoft Academic Search

The Cassini RADAR instrument onboard the Cassini Orbiter is currently collecting SAR imagery of the surface of Saturn's largest Moon, Titan. This paper describes the ground processing of Cassini SAR data. We focus upon the unusual features of the data and how these features impact the processing. We exhibit a data dependent mechanism we have implemented for eliminating artifacts due

Bryan W. Stiles; Yonggyu Gim; Gary Hamilton; Scott Hensley; William T. K. Johnson; J. Shimada; R. D. West; P. Callahan

2006-01-01

192

Holographic Radar Imaging Privacy Techniques Utilizing Dual-Frequency Implementation  

SciTech Connect

Over the last 15 years, the Pacific Northwest National Laboratory has performed significant research and development activities to enhance the state of the art of holographic radar imaging systems to be used at security checkpoints for screening people for concealed threats hidden under their garments. These enhancement activities included improvements to privacy techniques to remove human features and providing automatic detection of body-worn concealed threats. The enhanced privacy and detection methods used both physical and software imaging techniques. The physical imaging techniques included polarization-diversity illumination and reception, dual-frequency implementation, and high-frequency imaging at 60 GHz. Software imaging techniques to enhance the privacy of the person under surveillance included extracting concealed threat artifacts from the imagery to automatically detect the threat. This paper will focus on physical privacy techniques using dual-frequency implementation.

McMakin, Douglas L.; Hall, Thomas E.; Sheen, David M.

2008-04-18

193

Three-dimensional synthetic aperture radar imaging of a fir tree: first results  

Microsoft Academic Search

A three-dimensional (3D) inverse synthetic aperture radar (ISAR) imaging experiment on a fir tree is described. Radar measurements on single trees under laboratory conditions can be performed in the scatterometric, with no aperture synthesis, and in the imaging (SAR) mode. Imaging an entire tree requires the use of a wideband radar and a two-dimensional (2D) aperture which may be synthetic

Joaquim Fortuny; A. J. Sieber

1999-01-01

194

Optimum frequency for subsurface-imaging synthetic-aperture radar  

SciTech Connect

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

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

1993-05-01

195

Optimum frequency for subsurface-imaging synthetic-aperture radar  

SciTech Connect

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

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

1993-05-01

196

Standoff concealed weapon detection using a 350-GHz radar imaging system  

NASA Astrophysics Data System (ADS)

The sub-millimeter (sub-mm) wave frequency band from 300 - 1000 GHz is currently being developed for standoff concealed weapon detection imaging applications. This frequency band is of interest due to the unique combination of high resolution and clothing penetration. The Pacific Northwest National Laboratory (PNNL) is currently developing a 350 GHz, active, wideband, three-dimensional, radar imaging system to evaluate the feasibility of active sub-mm imaging for standoff detection. Standoff concealed weapon and explosive detection is a pressing national and international need for both civilian and military security, as it may allow screening at safer distances than portal screening techniques. PNNL has developed a prototype active wideband 350 GHz radar imaging system based on a wideband, heterodyne, frequency-multiplier-based transceiver system coupled to a quasi-optical focusing system and high-speed rotating conical scanner. This prototype system operates at ranges up to 10+ meters, and can acquire an image in 10 - 20 seconds, which is fast enough to scan cooperative personnel for concealed weapons. The wideband operation of this system provides accurate ranging information, and the images obtained are fully three-dimensional. During the past year, several improvements to the system have been designed and implemented, including increased imaging speed using improved balancing techniques, wider bandwidth, and improved image processing techniques. In this paper, the imaging system is described in detail and numerous imaging results are presented.

Sheen, David M.; Hall, Thomas E.; Severtsen, Ronald H.; McMakin, Douglas L.; Hatchell, Brian K.; Valdez, Patrick L. J.

2010-04-01

197

On joint phase-envelope use in radar CFAR processing  

NASA Astrophysics Data System (ADS)

A method assuming linear phase drift is presented to improve radar detection performance. Its use is based on the assumption that the target illumination time comprises multiple coherent pulses or coherent processing intervals (CPI). For example in a conventional scanning radar, this often inaccurate information can be used for statistical data mapping to point out possible target presence. If coherent integration is desired in a beam-agile system, the method should allow sequential detection. Discussion involves a pragmatic example on the echo phase progress utilization in the constant false alarm rate (CFAR) processing of a moving target indication (MTI) system. The detection performance is evaluated with scanning radar simulations. The method has been tested using real-world recordings and some observations are briefly outlined.

Vihonen, Juho; Ala-Kleemola, Timo; Hintikka, Timo; Jylha, Juha; Visa, Ari

2005-05-01

198

Contribution of radar images for grassland management identification  

NASA Astrophysics Data System (ADS)

This paper is concerned with the identification of grassland management using both optical and radar data. In that context, grazing, mowing and a mix of these two managements are commonly used by the farmers on grassland fields. These practices and their intensity of use have different environmental impact. Thus, the objectives of this study are, firstly, to identify grassland management practices using a time series of optical and radar imagery at high spatial resolution and, secondly, to evaluate the contribution of radar data to improve identification of farming practices on grasslands. Because of cloud coverage and revisit frequency of satellite, the number of available optical data is limited during the vegetation period. Thus, radar data can be considered as an ideal complement. The present study is based on the use of SPOT, Landsat and RADARSAT-2 data, acquired in 2010 during the growing period. After a pre-processing step, several vegetation indices, biophysical variables, backscattering coefficients and polarimetric discriminators were computed on the data set. Then, with the help of some statistics, the most discriminating variables have been identified and used to classify grassland fields. In addition, to take into account the temporal variation of variables, dedicated indexes as first and second order derivatives were used. Classification process was based on training samples resulting from field campaigns and computed according six methods: Decision Trees, K-Nearest Neighbor, Neural Networks, Support Vector Machines, the Naive Bayes Classifier and Linear Discriminant Analysis. Results show that combined use of optical and radar remote sensing data is not more efficient for grassland management identification.

Dusseux, P.; Gong, X.; Corpetti, T.; Hubert-Moy, L.; Corgne, S.

2012-09-01

199

Radar interferometric imaging of field-aligned plasma irregularities in the equatorial electrojet  

Microsoft Academic Search

A multiple-receiver radar technique for imaging the spatial distribution of ionospheric plasma irregularities is introduced and demonstrated with equatorial electrojet data obtained at the Jicamarca Radio Observatory. The images obtained with a few seconds time resolution enable the monitoring of the temporal evolution of the irregularity structures within the radar field of view. Daytime electroject images contain signatures of localized

Erhan Kudeki; Fahri Surucu

1991-01-01

200

Signal processing for through wall moving target tracking by M-sequence UWB radar  

Microsoft Academic Search

In this paper, through wall moving target tracking by UWB radar is described as a complex process with all required phases of radar signal processing. For particular phases of that process, i.e. for raw radar data preprocessing, background subtraction, detection, trace estimation, localization and tracking itself, the phase significance and its corresponding representative methods are outlined. The complete process is

J. Rovnakova; M. Svecova; D. Kocur; Trung Thanh Nguyen; J. Sachs

2008-01-01

201

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

202

Application of neural networks to radar image classification  

NASA Astrophysics Data System (ADS)

Classification of terrain cover using polarimetric radar is an area of considerable current interest and research. A number of methods have been developed to classify ground terrain types from fully polarimetric synthetic aperture radar (SAR) images, and these techniques are often grouped into supervised and unsupervised approaches. Supervised methods have yielded higher accuracy than unsupervised techniques, but suffer from the need for human interaction to determine classes and training regions. In contrast, unsupervised methods determine classes automatically, but generally show limited ability to accurately divide terrain into natural classes. In this paper, a new terrain classification technique is introduced to determine terrain classes in polarimetric SAR images, utilizin unsupervised neural networks to provide automatic classification, and employing an iterative algorithm to improve the performance. Several types of unsupervised neural networks are first applied to the classification of SAR images, and the results are compared to those of more conventional unsupervised methods. Results show that one neural network method, Learning Vector Quantization (LVQ), outperforms the conventional unsupervised classifiers, but is still inferior to supervised methods. To overcome this poor accuracy, an iterative algorithm is proposed where the SAR image is reclassified using Maximum Likelihood (ML) classifier. It is shown that this algorithm converges, and significantly improves classification accuracy. Performance after convergence is seen to be comparable to that obtained with a supervised ML classifier, while maintaining the advantages of an unsupervised technique.

Hara, Yoshihisa; Atkins, Robert G.; Yueh, Simon H.; Shin, Robert T.; Kong, J. A.

1994-01-01

203

Applications of neural networks to radar image classification  

SciTech Connect

Classification of terrain cover using polarimetric radar is an area of considerable current interest and research. A number of methods have been developed to classify ground terrain types from fully polarimetric synthetic aperture radar (SAR) images, and these techniques are often grouped into supervised and unsupervised approaches. Supervised methods have yielded higher accuracy than unsupervised techniques, but suffer from the need for human interaction to determine classes and training regions. In contrast, unsupervised methods determine classes automatically, but generally show limited ability to accurately divide terrain into natural classes. In this paper, a new terrain classification technique is introduced to determine terrain classes in polarimetric SAR images, utilizing unsupervised neural networks to provide automatic classification, and employing an iterative algorithm to improve the performance. Several types of unsupervised neural networks are first applied to the classification of SAR images, and the results are compared to those of more conventional unsupervised methods. Results show that one neural network method--Learning Vector Quantization (LVQ)--outperforms the conventional unsupervised classifiers, but is still inferior to supervised methods. To overcome this poor accuracy, an iterative algorithm is proposed where the SAR image is reclassified using Maximum Likelihood (ML) classifier. It is shown that this algorithm converges, and significantly improves classification accuracy. Performance after convergence is seen to be comparable to that obtained with a supervised ML classifier, while maintaining the advantages of an unsupervised technique.

Hara, Yoshihisa; Atkins, R.G.; Yueh, S.H.; Shin, R.T.; Kong, J.A. (Massachusetts Inst. of Tech., Cambridge, MA (United States))

1994-01-01

204

Ultra wide band radar holographic imaging of subsurface targets  

SciTech Connect

This report discusses ultra wide band (i.e., 60 ps impulse) radar holography which is a unique technique for imaging subsurface targets with extremely high lateral and depth resolution. The large frequency bandwidth, typically 100%, provides excellent depth resolution and the synthetic aperture optimum lateral resolution of one-half wavelength at the center pulse frequency. Radar impulse holography can simply be described as a multi-frequency detection and imaging technique where the target`s broadband time waveform signals are recorded over a defined aperture; decomposed into their discrete frequency components as single frequency holograms, and reconstructed into a composite image. Computer generated holograms are constructed for each frequency component in the 3-dB pulse bandwidth and plane wave angular spectrums computed to provide unique detection analysis with respect to target identification, etc. The hologram at each frequency component in the pulse can be thought of as a diffraction lens for each reflecting point on the target. A complex target consists, of a multitude of points, and the recorded hologram becomes the superposition of these individual diffraction lens. It is a unique diffraction pattern capable of defining the target`s image and scattering characteristics in the near- and far-field.

Collins, H.D.; Gribble, R.P.

1993-08-01

205

Geological analyses of the surface of Venus and Mars from lander spacecraft images and orbital radar observations  

Microsoft Academic Search

The association of observed local scale geologic structures with basic processes such as basaltic volcanism, and the extrapolation of larger regional scales in order to assess the relative importance of such processes on Venus and Mars is studied. The data considered are of two types: lander spacecraft digital images with centimeter resolution, and orbital radar measurements averaged over 30 to

J. B. Garvin

1984-01-01

206

EISCAT_3D: the European three-dimensional imaging radar for atmospheric and geospace research  

NASA Astrophysics Data System (ADS)

The EISCAT Scientific Association operates three incoherent scatter radars in Tromsø (Norway) and on Svalbard. The UHF radar, which operates at 930 MHz, is the only tristatic incoherent scatter radar in the world. The transmitter is located in Tromsø and additional receiver sites are in Kiruna (Sweden) and Sodankylü (Finland). However, due to interferences with mobile a communication, tristatic operation will come to an end in due time. In the future, EISCAT will build the next generation incoherent scatter radar, which will provide comprehensive 3D monitoring of the atmosphere and ionosphere above Northern Fenno-Scandinavia. The EISCAT 3D radar system will consist of multiple phased arrays, using the latest digital signal processing to achieve ten times higher temporal and spatial resolution than the present radars. The European Strategy Forum on Research Infrastructures (ESFRI) selected EISCAT 3D for the Roadmap 2008 for Large-Scale European Research Infrastructures for the next 20-30 years. The facility will be constructed as a modular system by 2015. EISCAT 3D will be a volumetric radar capable of imaging an extended spatial area with simul-taneous full-vector drift velocities, having continuous operation modes, short baseline interfer-ometry capability for imaging sub-beamwidth scales, real-time data access for applications and extensive data archiving facilities. The design of the antenna arrays will be modular at different scales allowing for mass-production of the components. Some arrays will be very large, in the scale of 32,000 individual antenna elements. The receiver arrays will be located at 50-150 km distance from the illuminators, and some smaller arrays closer by to support continuous interferometric observations. The total system will comprise 100,000 elements. The actual radar sites have to be carefully chosen. This new large-scale European research infrastructure has applications in a wide range of Eu-ropean research areas including Earth environment monitoring and technology solutions sup-porting sustainable development, well beyond atmospheric and space sciences. Here we will give an overview of this ambitious project, report on the current status of the preparatory phase, and invite interested parties to contribute to the planning of EISCAT 3D.

Ulich, Thomas; Aikio, Anita; McCrea, Ian; Turunen, Esa

207

Adaptive space-time processing for interference suppression in phased array radar systems. II. Tracking radar  

Microsoft Academic Search

For pt.I see ibid., p.B8\\/1-B8\\/8 (2000). In phased array radar systems, a tracking process is performed using an electronic scan of a predetermined sector to provide a continuous information about the detected targets. In practice, the presence of interference (noise, clutter, and jamming signals) either prevent or deceive the tracking circuit to follow the real targets, and consequently, the tracking

H. H. M. Ghouz; F. I. A. Elghany; M. M. Qutb

2000-01-01

208

Dynamic sector processing using 2D assignment for rotating radars  

NASA Astrophysics Data System (ADS)

Electronically scanned array radars as well as mechanically steered rotating antennas return measurements with different time stamps during the same scan while sweeping form one region to another. Data association algorithms process the measurements at the end of the scan in order to satisfy the common one measurement per track assumption. Data processing at the end of a full scan resulted in delayed target state update. This issue becomes more apparent while tracking fast moving targets with low scan rate sensors. In this paper, we present new dynamic sector processing algorithm using 2D assignment for continuously scanning radars. A complete scan can be divided into sectors, which could be as small as a single detection, depending on the scanning rate and sparsity of targets. Data association followed by filtering and target state update is done dynamically while sweeping from one end to another. Along with the benefit of immediate track updates, continuous tracking results in challenges such as multiple targets spanning multiple sectors and targets crossing consecutive sectors. Also, associations performed in the current sector may require changes in association done in previous sectors. Such difficulties are resolved by the proposed 2D assignment algorithm that implements an incremental Hungarian assignment technique. The algorithm offers flexibility with respect to assignment variables for fusing of measurements received in consecutive sectors. Furthermore the proposed technique can be extended to multiframe assignment for jointly processing data from multiple scanning radars. Experimental results based on rotating radars are presented.

Habtemariam, Biruk K.; Tharmarasa, R.; Pelletier, M.; Kirubarajan, T.

2011-09-01

209

The Calibration Processing for Impulse Ground Penetrating Radar  

Microsoft Academic Search

In order to meet the requirement of high measurement precision for ground penetrating radar (GPR), the geometrical calibration processing methods of the antenna are proposed to solve the measuring deflection problem and the antenna vibration problem for the bistatic impulse system. The calibration measurement method for the layer thickness is also presented to reduce the thickness measurement error. These calibration

Chunlin Huang; Min Lu; Su Yi

2006-01-01

210

A frequency domain radar interferometric imaging (FII) technique based on high-resolution methods  

NASA Astrophysics Data System (ADS)

In the present work, we propose a frequency-domain interferometric imaging (FII) technique for a better knowledge of the vertical distribution of the atmospheric scatterers detected by MST radars. This is an extension of the dual frequency-domain interferometry (FDI) technique to multiple frequencies. Its objective is to reduce the ambiguity (resulting from the use of only two adjacent frequencies), inherent with the FDI technique. Different methods, commonly used in antenna array processing, are first described within the context of application to the FII technique. These methods are the Fourier-based imaging, the Capon's and the singular value decomposition method used with the MUSIC algorithm. Some preliminary simulations and tests performed on data collected with the middle and upper atmosphere (MU) radar (Shigaraki, Japan) are also presented. This work is a first step in the developments of the FII technique which seems to be very promising.

Luce, H.; Yamamoto, M.; Fukao, S.; Helal, D.; Crochet, M.

2001-01-01

211

Digital Image Processing  

Microsoft Academic Search

This paper describes the basic technological aspects of Digital Image Processing with special reference to satellite image processing. Basically, all satellite image-processing operations can be grouped into three categories: Image Rectification and Restoration, Enhancement and Information Extraction. The former deals with initial processing of raw image data to correct for geometric distortion, to calibrate the data radiometrically and to eliminate

Minakshi Kumar

1981-01-01

212

Summary of science results from spaceborne imaging radar (SIR-C\\/X-SAR)  

Microsoft Academic Search

SIR-C\\/X-SAR (Spaceborne Imaging Radar-C\\/X-band Synthetic Aperture Radar) is the most advanced imaging radar system to fly in Earth orbit. Carried in the cargo bay of the Space Shuttle Endeavour in April and October, 1994, SIR-C\\/X-SAR simultaneously records SAR data at three wavelengths (L-, C-, and X-bands; 23.5, 5.8 and 3.1 cm, respectively). In addition, the full polarimetric scattering matrix may

Jeeffrey J. Plaut

1996-01-01

213

An Approach for Sub-Second Imaging of Concealed Objects Using Terahertz (THz) Radar  

Microsoft Academic Search

High-resolution, long-range detection of person-borne concealed weapons has recently been demonstrated using a terahertz imaging\\u000a radar. However, the radar’s image acquisition time must be greatly shortened, from minutes to less than one second, before\\u000a the system can be effectively deployed in a real-life threat environment. Here we analyze the major system modifications necessary\\u000a for increasing the speed of a terahertz

K. B. Cooper; R. J. Dengler; N. Llombart; T. Bryllert; G. Chattopadhyay; I. Mehdi; P. H. Siegel

2009-01-01

214

The Advanced Simulation System for MMW Imaging Radar Seeker onboard Air-to-air Missile  

Microsoft Academic Search

Millimeter wave (MMW) radar is booming in application to target seeker onboard the air-to-air missile (AAM), which has the capability to obtain all-weather radar images for auto target recognition (ATR) and intelligent active homing guidance. An advanced simulation system for MMW imaging radar seekers of AAM was introduced in this paper. The system is composed of parameter initialization module, signal

Sun Yumeng; C. Jie; G. Caihong; S. Bing; Z. Yinqing

2006-01-01

215

Fusion of magnetic resonance imaging and ultra-wideband-radar for biomedical applications  

Microsoft Academic Search

Due to the recent advances in ultra-wideband (UWB)-radar technologies, there has been widespread interest in medical applications of this technology. We propose the multimodal combination of magnetic resonance (MR) and UWB-radar for improved functional diagnosis and imaging. A demonstrator was established to prove the feasibility of simultaneous acquisition of physiological events by magnetic resonance imaging and UWB-radar.

Florian Thiel; Matthias Hein; Ulrich Schwarz; Jürgen Sachs; Frank Seifert

2008-01-01

216

Synthetic-aperture radar imaging through dispersive media  

NASA Astrophysics Data System (ADS)

In this paper we develop a method for synthetic-aperture radar (SAR) imaging through a dispersive medium. We consider the case when the sensor and scatterers are embedded in a known homogeneous dispersive material, the scene to be imaged lies on a known surface and the radar antenna flight path is an arbitrary but known smooth curve. The scattering is modeled using a linearized (Born) scalar model. We assume that the measurements are polluted with additive noise. Furthermore, we assume that we have prior knowledge about the power-spectral densities of the scene and the noise. This leads us to formulate the problem in a statistical framework. We develop a filtered-back-projection imaging algorithm in which we choose the filter according to the statistical properties of the scene and noise. We present numerical simulations for a case where the scene consists of point-like scatterers located on the ground, and demonstrate how the ability to resolve the targets depends on a quantity which we call the noise-to-target ratio. In our simulations, the dispersive material is modeled with the Fung-Ulaby equations for leafy vegetation. However, the method is also applicable to other dielectric materials where the dispersion is considered relevant in the frequency range of the transmitted signals.

Varslot, Trond; Héctor Morales, J.; Cheney, Margaret

2010-02-01

217

Real-time synthetic aperture radar (SAR) processing with a new subaperture approach  

Microsoft Academic Search

A time-domain subaperture approach that is suitable for real-time synthetic aperture radar (SAR) processing and that produces high-quality, full-resolution images is presented. The real-time subaperture algorithm is based on an approximation of the phase history correction in each subaperture with a simple linear correction, which can be carried out by an up\\/down-conversion of the received signal followed by a moving

A. Moreira

1992-01-01

218

Multiscale signal processing and shape analysis for an inverse SAR imaging system  

Microsoft Academic Search

The great challenge in signal processing is to devise computationally efficient and statistically optimal algorithms for estimating signals from noisy background and understanding their contents. This thesis treats the problem of multiscale signal processing and shape analysis for an Inverse Synthetic Aperture Radar (ISAR) imaging system. To address some of the limitations of conventional techniques in radar image processing, an

Yun He

2001-01-01

219

Marine radar imaging of nearshore bar structure: biases due to tidal and RMS wave height variations  

Microsoft Academic Search

We present results of an experiment using a marine radar to image the surface roughness patterns due to wave breaking and energy dissipation over coastal offshore sand bars. Data were collected at the US Army Coastal Engineer Field Research Facility research pier, Duck, NC. The experiment was designed to compare marine radar and video imaging mechanisms of wave breaking and

D. Trizna; K. Hathaway; J. McNinch

2004-01-01

220

Multistatic passive radar imaging using the smoothed pseudo Wigner-Ville distribution  

Microsoft Academic Search

We investigate passive radar imaging of aircraft using reflected TV signals. We apply a Smoothed Pseudo Wigner- Ville Distribution (SPWVD)-based SAR imaging algorithm to two different scenarios. In the first simulation, multi- static VHF-band dataset generated by Fast Illinois Solver Code (FISC) is used. In the second simulation, a more re- alistic simulated passive radar dataset is used. A set

Yong Wu; David C. Munson Jr.

2001-01-01

221

Reducing the effects of noise on atmospheric imaging radars using multilag correlation  

Microsoft Academic Search

Atmospheric imaging radars offer the capability to scrutinize structures within the illuminated volume at high temporal and spatial resolutions. The retrieval of the mean signal power using an imaging radar is obtained by subtracting the noise power from the covariance function at lag zero. The results obtained at low signal-to-noise ratio (SNR) are problematic when the noise power is unsuccessfully

K. D. Le; R. D. Palmer; B. L. Cheong; T.-Y. Yu; G. Zhang; S. M. Torres

2010-01-01

222

High-Resolution Inverse Synthetic Aperture Radar Imaging Based on the Shooting and Bouncing Ray Method  

Microsoft Academic Search

This paper concerns the simulation of inverse synthetic aperture radar (ISAR) image for radar targets based on the shooting and bouncing ray (SBR) method. Contrary to the conventional approach where the ISAR image is obtained by inverse Fourier transforming to the scattering field, we adopt a newly-developed method [8], where the Fourier transformation has been merged into the SBR algorithm.

X. B. Wang; X. Y. Zhou; T. J. Cui; Y. B. Tao; H. Lin

2008-01-01

223

Space Shuttle Radar Images of Terrestrial Impact Structures: SIR-C/X-SAR  

NASA Astrophysics Data System (ADS)

The Spaceborne Radar Laboratory (SRL) orbited Earth in April and October of 1994 operating two imaging radars: X-SAR, an X-band (3 cm lambda) instrument, and the polarimetric SIR-C, a combination L-band/C-band (24 cm and 5.6 cm lambda). More than 150 terrestrial meteorite craters and astroblemes are presently known. Three of these, Wolfe Creek in Australia; Roter Kamm in Namibia; and Zhamanshin in Kazakhstan, were planned targets and were imaged successfully with multiple passes and look directions. Several other impact sites were fortuitously imaged while radar data were being collected for other purposes. These sites include B.P. and Oasis structures in Libya, Aourounga multi-ring feature in Chad, Amguid crater in Algeria, and the Spider astrobleme and Henbury crater field in Australia. Wolfe Creek (19 degrees 10'S; 127 degrees 47'E; 875 m dia) Both the elevated rim and the inner floor of this crater appear as radar bright features. Strong radar returns are due to blocky rubble textures in the rim and desert vegetation within the central bowl. Associated linear sand dunes show differential penetration properties in the various radar wavelengths and polarization. Roter Kamm (27 degrees 46'S; 016 degrees 18'E; 2.5 km dia) This bowl-shaped crater is mostly buried by wind-blown sands. Comparison of differential radar penetration patterns due to changes in wavelength and look direction reveal concealed target rocks and a buried possible ejecta unit. Zhamanshin (48 degrees 24'N; 060 degrees 48'E; 14 km dia) This unusual impact structure, first detected by the presence of glassy impact melt products [1], has very little topographic relief and is nearly invisible on survey-quality radar imagery. Fully processed images, however, enhance subtle vegetation patterns which highlight regional streams. These drainage patterns are now being analyzed in detail to better delineate boundaries and internal structure of this feature. B.P. Structure (25 degrees 19'N; 024 degrees 20'E; 2.8 km dia) Wind-blown sands which cover much of this relatively small feature make it difficult to distinguish from numerous dark sandstone outcrops using only optical images. Radar, however, penetrates the shallow sand mantle to reveal a nearly complete radar-bright bullseye pattern typical of central-uplift style impact structure. Oasis Structure (24 degrees 35'N; 24 degrees 24'E; >11.5 km dia) Oasis astrobleme was originally described as an elevated ring of sandstone some 5.1 km wide in desert sands. Examination of optical satellite images detected subtle concentric patterns more than 11 km across [2]. SIR-C images reveal strong arcuate reflectors buried beneath the sand at an even larger diameter of greater than 17 km. Aurounga (19 degrees 06'N; 019 degrees 15'E; 12.6 km dia) Although this highly circular depression has been noticed in numerous remote sensing studies, eg.[3], it usually has been associated with a large volcanic field and attributed to endogenic forces. Recent reports of shatter cones [4] and microscopic shock metamorphic effects [5] now demonstrate an impact origin. The radar-dark ring is a sand-filled trough which interupts a regional pattern of yardangs, wind-cut parallel ridges and grooves, developed in surrounding sandstones. Amguid (26 degrees 05'N; 004 degrees 23'E; 450 m dia) Situated in elevated rocky highlands [6], the small Amguid crater is nearly overprinted by surrounding radar backscatter. A dry central bowl is partially filled with smoothly surfaced fine-grained playa deposits which absorb radar energy and/or reflect it away from the spacecraft. The result is a distinct radar-dark disk within a bright regional ground clutter. Spider (16 degrees 44'S; 126 degrees 05'E; 13 km dia) Named for a radially splayed fault system in its center, Spider is the exposed root structure of a central-uplift impact feature [7]. Radar slope effects on processed data clearly delineate its size and internal complexity. Henbury craters (24 degrees 35'S; 133 degrees 09'E; largest ca.150 m dia) Although quite small, Henbury crater field [8] app

McHone, J. F.; Blumberg, D. G.; Greeley, R.; Underwood, J. R., Jr.

1995-09-01

224

Radar Imaging of Binary Near-Earth Asteroid 2004 DC  

NASA Astrophysics Data System (ADS)

Arecibo S-band (2380 MHz, 13 cm) and Goldstone X-band (8560 MHz, 3.5 cm) radar observations on June 2-6, 2006 show that Apollo asteroid 2004 DC is a binary system [IAU CBET 535]. Preliminary estimates of the diameters, based on visible range extents in the delay-Doppler images, are 300 m for the primary and 60 m for the secondary. The motion of the secondary in the delay-Doppler images suggests an orbital period of roughly 23 hours and a maximum primary-to-secondary separation of at least 0.6 km. The bandwidth of the primary increases from May 29 to June 3, then decreases until the end of observations on June 6, implying 2004 DC was viewed closest to equatorial on June 3. Assuming an equatorial view, the bandwidth suggests a rotation period of about 2 hours, which is in agreement with lightcurve observations [R. Behrend, pers. comm.]. The radar albedo and circular polarization ratio are 0.4 and 0.8 at S-band and 0.3 and unity at X-band. The circular polarization ratios are larger than those of the majority of radar-observed asteroids and imply that 2004 DC has extreme decimeter-scale near-surface roughness. We will estimate the parameters of the mutual orbit and the shape of the primary, and will place the orbital and physical properties of the system into the context of the existing binary near-Earth asteroid population.

Taylor, Patrick A.; Margot, J. L.; Nolan, M. C.; Benner, L. A.; Ostro, S. J.; Giorgini, J. D.; Magri, C.

2006-09-01

225

Processing of wide-angle synthetic aperture radar signals for target detection  

NASA Astrophysics Data System (ADS)

This study investigated methods of targets detection using Wide-Angle Synthetic Aperture Radar (WASAR). WASAR uses multiple aspect angle Synthetic Aperture Radar (SAR) images of the same scene. The SAR images were generated using a pre-release software package from package from Loral Corporation. The software was able to generate 512 by 512 pixel SAR images that contained various vegetation return which for our purposes we classified as clutter. Within this clutter, targets (M35 trucks) could be placed at random location and orientations. The software also had the capability of generating fully-polarimetic WASAR images with multiple depression angles. This data was then processed and various detection algorithms tested to exploit the amount and diversity of information available from the multiple images. SAR images are generally known to contain large amounts of data, and WASAR images contain even more due to the multiple images. Various pre-processing filters were analyzed for detection optimization. These filters included: polarimetric averaging, polarimetric span, polarimetric optimal weighting, and polarimetric whitening filters. Simple classical detection (thresholding) algorithms were evaluated using these preprocessed data sets. The use of WASAR imagery improved detection by allowing thresholds to be set higher than for simple SAR thereby avoiding false alarms yet still allowing detection of the known targets.

Knurr, Kurt W.

1993-12-01

226

A flexible implementation for Doppler radar to verify various base-band array signal processing algorithms  

Microsoft Academic Search

We describe a flexible hardware system of the Doppler radar which is designed to verify various baseband array signal processing algorithms. In this work we design the Doppler radar system simulator for baseband signal processing in laboratory level. Based on this baseband signal processor, a PN-code pulse doppler radar simulator is developed. More specifically, this simulator consists of an echo

Eunjung Yang; Jonghyun Lee; Byungwook Jung; Joohwan Chun

2005-01-01

227

Improving Ground Penetrating Radar Imaging in High Loss Environments by Coordinated System Development, Data Processing, Numerical Modeling, and Visualization methods with Applications to Site Characterization  

SciTech Connect

The Department of Energy has identified the location and characterization of subsurface contaminants and the charcterization of the subsurface as a priority need. Many DOE facilities are in need of subsurface imaging in the vadose and saturated zones.

David Wright; Michael Powers / gary Olhoeft; Charles Oden; Craig Moulton

2006-10-07

228

Combining magnetic resonance imaging and ultrawideband radar: a new concept for multimodal biomedical imaging.  

PubMed

Due to the recent advances in ultrawideband (UWB) radar technologies, there has been widespread interest in the medical applications of this technology. We propose the multimodal combination of magnetic resonance (MR) and UWB radar for improved functional diagnosis and imaging. A demonstrator was established to prove the feasibility of the simultaneous acquisition of physiological events by magnetic resonance imaging and UWB radar. Furthermore, first in vivo experiments have been carried out, utilizing this new approach. Correlating the reconstructed UWB signals with physiological signatures acquired by simultaneous MR measurements, representing respiratory and myocardial displacements, gave encouraging results which can be improved by optimization of the MR data acquisition technique or the use of UWB antenna arrays to localize the motion in a focused area. PMID:19191450

Thiel, F; Hein, M; Schwarz, U; Sachs, J; Seifert, F

2009-01-01

229

Resampling methods for stretch processing in PCL radars  

NASA Astrophysics Data System (ADS)

The paper presents a study of effective resampling techniques to be used for stretch processing in Passive Coherent Location radars. In a typical PCL radar, two signals are correlated: one coming from a reference antenna pointed at a transmitter of opportunity, other coming from a search antenna pointed at the observed area, seeking the reflection of radio signal from a target. If the second antenna receives an echo from a moving target, the correlation of the two signals is disturbed by Doppler effect, consisting of frequency shift and envelope dilation. In order to compensate for this second effect, the reference signal has to be stretched (or dilated) by resampling. In the paper the review of applicable resampling methods is performed. The useful method should give results good enough for the correlation process, and it has to be very fast in the implementation, as the processing is to be done in real time.

Misiurewicz, Jacek

2008-01-01

230

Advanced ground-penetrating, imaging radar for bridge inspection  

SciTech Connect

Inspecting high-value structures, like bridges and buildings using Ground Penetrating Radar (GPR) is an application of the technology that is growing in importance. In a typical inspection application, inspectors use GPR to locate structural components, like reinforcing bars embedded in concrete, to avoid weakening the structure while collecting core samples for detailed inspection. Advanced GPR, integrated with imaging technologies for use as an NDE tool, can provide the capability to locate and characterize construction flaws and wear- or age-induced damage in these structures without the need for destructive techniques like coring. In the following sections, we discuss an important inspection application, namely, concrete bridge deck inspection. We describe an advanced bridge deck inspection system concept and provide an overview of a program aimed at developing such a system. Examples of modeling, image reconstruction, and experimental results are presented.

Warhus, J.P.; Mast, J.E.; Johansson, E.M.; Nelson, S.E. [Lawrence Livermore National Lab., CA (United States); Lee, Hua [California Univ., Santa Barbara, CA (United States). Dept. of Electrical and Computer Engineering

1993-08-01

231

A single chip VLSI architecture for radar signal processing  

NASA Astrophysics Data System (ADS)

The problem of how much radar signal processing one can achieve with a single chip signal processor is investigated through the design of a processor architecture suitable for single chip implementation using very large scale integration (VLSI) technology. The design of the single chip processor departs from existing processor designs both in the way it is structured and the manner in which it performs computations. Major emphasis is placed on taking advantage of the parallelism and pipelining inherent in radar signal processing functions, and on novel processor architecture capable of mapping high-level computations (i.e., complex primitives such as Fast Fourier Transform) directly into hardware. The single chip design is based on state-of-the-art technology and utilizes bit-serial arithmetic and externally supplied First-In First-Out memory.

Kanopoulos, N.

232

Principles and applications of imaging radar. Manual of remote sensing: Third edition, Volume 2  

SciTech Connect

This second volume in the Third Edition of the Manual of Remote Sensing offers a current and comprehensive survey of the theory, methods, and applications of imaging radar for geoscientists, engineers and application scientists interested in the advantages of radar remote sensing. Produced under the auspices of the American Society for Photogrammetry and Remote Sensing, it brings together contributions from experts around the world to discuss the basic principles of imaging radars and trace the research activity--past, present, and future--across the many sciences where radar remote sensing may be applied. This book offers an invaluable snapshot of radar remote sensing technology, including radargrammetry, radar polarimetry and interferometry and its uses. It combines technical and procedural coverage of systems, data interpretation, and other fundamentals with generous coverage of practical applications in agriculture; forestry; soil moisture monitoring; geology; geomorphology and hydrology; oceanography; land use, land cover mapping and archeology.

Henderson, F.M.; Lewis, A.J. [eds.

1998-12-31

233

An image-based approach for classification of human micro-doppler radar signatures  

NASA Astrophysics Data System (ADS)

With the advances in radar technology, there is an increasing interest in automatic radar-based human gait identification. This is because radar signals can penetrate through most dielectric materials. In this paper, an image-based approach is proposed for classifying human micro-Doppler radar signatures. The time-varying radar signal is first converted into a time-frequency representation, which is then cast as a two-dimensional image. A descriptor is developed to extract micro-Doppler features from local time-frequency patches centered along the torso Doppler frequency. Experimental results based on real data collected from a 24-GHz Doppler radar showed that the proposed approach achieves promising classification performance.

Tivive, Fok Hing Chi; Phung, Son Lam; Bouzerdoum, Abdesselam

2013-05-01

234

Automatic morphing using image registration: Application to continuous tracking of radar reflectivity and rain fields  

NASA Astrophysics Data System (ADS)

Rainfall is one of the most important natural phenomenon that influences human life. Accurate rainfall estimation and prediction are crucial for flood forecasting, flood control, climate diagnostics, and water resource management. Rain data may be collected from numerous sources. Conventional rain gauge networks or meteorological radars provide continuous coverage in time. Satellite observations provide snap-shots of precipitation fields at poor temporal resolution. While a number of spaceborne platforms have been deployed for rain observation, the development of continuous space/time rainfall remains a major challenge. This dissertation seeks alternative techniques to automatically generate continuous data streams of rainfall data from sparse or intermittent observations. In order to avoid human intervention in the process, an automatic procedure is needed for real-time operations. For this purpose, Automatic Morphing Using Image Registration (AMIR) model is developed by integrating automatic image registration and image morphing algorithm. The new AMIR technique uses automatic image registration as the basis for finding control points for the morphing process. In the study of data assimilation for weather forecasting, there is a need to generate continuous streams of rainfall data to alleviate the so-called "spin up" problem, or the inability to provide short-term forecasts [Road90]. The proposed algorithm has been tested using remote sensing images from Next Generation Weather Radars (NEXRAD) and Tropical Rainfall Measuring Mission (TRMM). Three cases of rainfall data have been used. These include the passage of a storm in Florida, hurricane Floyd, and scattered rain in the southwestern of the United States for the same period using NEXRAD radar data as surrogate for spaceborne observations. These cases have drastically different spatial and temporal characteristics and hence provide tests on the applicability of the AMIR method. Comparative experimental results have shown that AMIR advance the current state of the art as it is comparable to manual morphing and outperforms automatic morphing without control points proposed in literature.

Vongsaard, Jearanai

235

Range-imaging observations of cumulus convection and Kelvin-Helmholtz instabilities with the MU radar  

NASA Astrophysics Data System (ADS)

In the present work, we report observations of cumulus convection and Kelvin-Helmholtz (KH) instabilities in the troposphere at high vertical and time resolution with the middle and upper atmosphere (MU) radar (46.5 MHz, 34.85°N, 136.10°E, Japan). A detailed morphology of the structures could be obtained through application of range-imaging technique (called frequency radar interferometric imaging (FII) or range imaging (RIM)) with the Capon processing method. The usefulness of this work lies in the demonstration of the performance of the MU radar in range-imaging mode for investigating various atmospheric phenomena at small scales. As one case study, we describe the high-resolution echo pattern during a convective event. It is found that the convective cells formed in the early afternoon and reached a maximum altitude of about 3.5 km. The high-resolution images revealed thin layers above this altitude, unresolved at the standard 150-m low-resolution mode, associated with vertical oscillations possibly due to gravity waves generated by the convective cells through the mechanism of "obstacle effects." As a second case study, two clear images of KH billows and waves are shown. The KH billows were observed in the troposphere in regions of strong vertical shear of the horizontal wind and persisted for at least 20 min in both cases. The horizontal wavelengths of the KH waves were estimated to be about 2.5 and 5.7 km, according to the magnitude of the horizontal wind in the altitude range where the dynamic shear instabilities were observed.

Luce, H.; Hassenpflug, G.; Yamamoto, M.; Crochet, M.; Fukao, S.

2007-02-01

236

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

237

Wideband Radar for Ballistic Missile Defense and Range Doppler Imaging of Satellites  

Microsoft Academic Search

Lincoln Laboratory led the nation in the development of high-power wideband radar with a unique capability for resolving target scattering centers and producing three-dimensional images of individual targets. The Laboratory fielded the first wideband radar, called ALCOR, in 1970 at Kwajalein Atoll. Since 1970 the Laboratory has developed and fielded several other wideband radars for use in ballistic-missile-defense research and

William W. Camp; Joseph T. Mayhan; Robert M. O'Donnell

2000-01-01

238

Compact FMCW design for short range millimeter-wave radar imaging applications  

Microsoft Academic Search

This paper presents the design of a new compact, low- cost, FMCW millimeter-wave radar for high-resolution, short- range imaging applications. In this design, problems that have limited the performance of classical FMCW radars were solved. A W-band FMCW radar with better than 0.3 m range resolution, 1 o beamwidth, 25 kHz chirp rate, 19 dBm output power, and operating in

Adib Y. Nashashibi; Juseop Lee; Kamal Sarabandi

2011-01-01

239

Universal multifractal scaling of synthetic aperture radar images of sea-ice  

Microsoft Academic Search

Multifrequency, multipolarization imaging radar scattering coefficient data sets, acquired by synthetic aperture radar (SAR) over sea-ice, were studied in order to reveal their scale-invariant properties. Two distinct scenes were acquired at C-band (5.6 cm) and L-band (25 cm) wavelengths for three different linear polarizations (HH, VV, and HV). These sea-ice radar scattering coefficient fields were investigated by applying both Fourier

Tony Falco; Frkdkric Francis; Sham Lovejoy; Daniel Schertzer; Bryan Kerman; Mark Drinkwater

1996-01-01

240

Impact of frequency and polarization diversity on a terahertz radar's imaging performance  

Microsoft Academic Search

The Jet Propulsion Laboratory's 675 GHz, 25 m standoff imaging radar can achieve >1 Hz real time frame rates over 40x40 cm fields of view for rapid detection of person-borne concealed weapons. In its normal mode of operation, the radar generates imagery based solely on the time-of-flight, or range, between the radar and target. With good clothing penetration at 675

Ken B. Cooper; Robert J. Dengler; Nuria Llombart

2011-01-01

241

Geologic Studies of Planetary Surfaces Using Radar Polarimetric Imaging.  

National Technical Information Service (NTIS)

Radar is a useful remote sensing tool for studying planetary geology because it is sensitive to the composition, structure, and roughness of the surface and can penetrate some materials to reveal buried terrain. The Arecibo Observatory radar system transm...

B. A. Campbell D. B. Campbell L. M. Carter

2010-01-01

242

Improvements of radar clutter classification in air traffic control environment  

Microsoft Academic Search

The use of adaptive technologies may prove useful in the processing of radar signals. The proposed radar clutter classificator is aimed to improve the detection of snow clutter presence in data acquired by a ground radar system in an air traffic control environment. Each plot detected in the radar image is processed in order to extract a series of features

L. Pierucci; L. Bocchi

2007-01-01

243

Digital Imaging and Image Processing  

NSDL National Science Digital Library

The first site is an excellent introduction to digital imaging from the Eastman Kodak Company (1). There are five lessons with review questions and competency exams, covering fundamentals, image capture, and processing. A more technical introduction is found at the Digital Imaging Glossary (2). This educational resource has several short articles about compression algorithms and specific imaging techniques. The Hypermedia Image Processing Reference (3) goes into the theory of image processing. It describes operations involving image arithmetic, blending multiple images, and feature detectors, to name a few; and several of the sections have illustrative Java applets. The Center for Imaging Science at John Hopkins University (4) offers two chapters from a book on "metric pattern theory." A brief overview of the material is provided on the main page, and the chapters can be viewed on or offline with special plug-ins given on the Web site. The Journal of Electronic Imaging (5) is a quarterly publication with many papers on current research. The final issue of 2002 has a special section on Internet imaging that is quite interesting. A research project at the University of Washington (6) focuses on the role of mathematics in image processing. Besides a thorough description of the project, there is free software and documentation given on the Web site. Philips Research (7) is working on a product that seems like something from a science fiction movie. Three dimensional television and the technologies that make it possible are described on the site. Related to this is a November 2002 news article discussing holograms and 3-D video displays (8). The devices are being studied by the Spatial Imaging Group at the Massachusetts Institute of Technology Media Lab.

Leske, Cavin.

2002-01-01

244

wradlib - An Open Source Library for Weather Radar Data Processing  

NASA Astrophysics Data System (ADS)

Weather radar data is potentially useful in meteorology, hydrology, disaster prevention and mitigation. Its ability to provide information on precipitation with high spatial and temporal resolution over large areas makes it an invaluable tool for short term weather forecasting or flash flood forecasting. The indirect method of measuring the precipitation field, however, leads to a significant number of data artifacts, which usually must be removed or dealt with before the data can be used with acceptable quality. Data processing requires e.g. the transformation of measurements from polar to cartesian coordinates and from reflectivity to rainfall intensity, the composition of data from several radar sites in a common grid, clutter identification and removal, attenuation and VPR corrections, gauge adjustment and visualization. The complexity of these processing steps is a major obstacle for many potential users in science and practice. Adequate tools are available either only at significant costs with no access to the uncerlying source code, or they are incomplete, insufficiently documented and intransparent. The wradlib project has been initiated in order to lower the barrier for potential users of weather radar data in the geosciences and to provide a common platform for research on new algorithms. wradlib is an open source library for the full range of weather radar related processing algorithms, which is well documented and easy to use. The main parts of the library are currently implemented in the python programming language. Python is well known both for its ease of use as well as its ability to integrate code written in other programming languages like Fortran or C/C++. The well established Numpy and Scipy packages are used to provide decent performance for pure Python implementations of algorithms. We welcome contributions written in any computer language and will try to make them accessible from Python. We would like to present the current state of this library together with a few showcase examples.

Heistermann, M.; Pfaff, Th.; Jacobi, S.

2012-04-01

245

Two-dimensional imaging via a narrowband MIMO radar system with two perpendicular linear arrays.  

PubMed

This paper presents a system model and method for the 2-D imaging application via a narrowband multiple-input multiple-output (MIMO) radar system with two perpendicular linear arrays. Furthermore, the imaging formulation for our method is developed through a Fourier integral processing, and the parameters of antenna array including the cross-range resolution, required size, and sampling interval are also examined. Different from the spatial sequential procedure sampling the scattered echoes during multiple snapshot illuminations in inverse synthetic aperture radar (ISAR) imaging, the proposed method utilizes a spatial parallel procedure to sample the scattered echoes during a single snapshot illumination. Consequently, the complex motion compensation in ISAR imaging can be avoided. Moreover, in our array configuration, multiple narrowband spectrum-shared waveforms coded with orthogonal polyphase sequences are employed. The mainlobes of the compressed echoes from the different filter band could be located in the same range bin, and thus, the range alignment in classical ISAR imaging is not necessary. Numerical simulations based on synthetic data are provided for testing our proposed method. PMID:20040416

Wang, Dang-wei; Ma, Xiao-yan; Su, Yi

2009-12-28

246

EM-based measurement fusion for HRR radar centroid processing  

NASA Astrophysics Data System (ADS)

This paper develops a new algorithm for high range resolution (HRR) radar centroid processing for scenarios where there are closely spaced objects. For range distributed targets with multiple discrete scatterers, HRR radars will receive detections across multiple range bins. When the resolution is very high, and the target has significant extent, then it is likely that the detections will not occur in adjacent bins. For target tracking purposes, the multiple detections must be grouped and fused to create a single object report and a range centroid estimate is computed since the detections are range distributed. With discrete scatterer separated by multiple range bins, then when closely spaced objects are present there is uncertainty about which detections should be grouped together for fusion. This paper applies the EM algorithm to form a recursive measurement fusion algorithm that segments the data into object clusters while simultaneously forming a range centroid estimate with refined bearing and elevation estimates.

Slocumb, Benjamin J.; Blair, W. Dale

2002-08-01

247

The Processing of Altimetric Data (PAD) System for Cassini RADAR.  

NASA Astrophysics Data System (ADS)

This paper describes the Cassini RADAR PAD System, which has been designed and developed in the frame of Cassini-Huygens, a joint NASA/ESA/ASI mission to Saturn and its moons, responding to ASI request to process the data collected by the Cassini RADAR Altimeter. The PAD System contains the HW and SW operational tools necessary to evaluate the instrument performances, to process the raw data, and finally to visualize digital maps of Titan's surface by using the data acquired by the Cassini RADAR during close flybys of Titan. Titan, the largest moon of Saturn, is the only satellite in the solar system to host an appreciable atmosphere. The smoggy haze that completely envelops the satellite is composed mostly of nitrogen, aerosols and a variety of hydrocarbons, produced as atmospheric methane is destroyed by sunlight. To date, many scientists have speculated that the surface could probably contain solid, liquid and muddy material creating features such as lakes, seas, or rivers, and it should be mostly coated with sticky brown organic condensate rained down from the atmosphere. The PAD System, actually installed and operated at Alcatel Alenia Space Italia premises in Rome will be able to grant the provision of altimetric data for at least the nominal 4-years mission lifetime (i.e. 45 envisaged flybys of Titan).

Alberti, G.; Catallo, C.; Festa, L.; Flamini, E.; Orosei, R.; Papa, C.; Picardi, G.; Seu, R.; Spataro, F.; Vingione, G.

248

EISCAT_3D: A European Imaging Radar for Atmospheric and Geospace Research  

NASA Astrophysics Data System (ADS)

EISCAT_3D will be the next-generation radar for the high-latitude atmosphere and geospace, with capabilities going beyond anything currently available. The facility will consist of large phased arrays in three countries. Depending on funding, EISCAT_3D will comprise tens of thousands, up to more than 100 000, antenna elements. EISCAT_3D will combine capabilities for volumetric imaging, tracking and aperture synthesis imaging, realised by a multistatic configuration, with improved sensitivity and transmitter flexibility. At the passive sites, the design allows the full extent of the transmitted beam to be imaged using holographic techniques. EISCAT_3D will be modular, allowing an active array to be split into sections for imaging. The result will be a new data product, range-dependent images of small structures, with sizes down to tens of metres. EISCAT_3D will be the first multistatic phased array ISR. A minimum of five sites is envisaged, with receivers located around 120 km and 250 km from the active site, providing optimal geometry for vectors in the middle and upper atmosphere. The antenna gain and array size will deliver large increases in the figure-of-merit relative to EISCAT’s existing radars. An active site comprising 16,000 elements would exceed the sensitivity of the present VHF radar by an order of magnitude. Each transmitter will allow the generation and transmission of arbitrary waveforms. This permits the implementation of all currently used and envisaged modulation schemes and provides the possibility to adopt any future code. Our poster will summarise the technical specifications and science case for EISCAT_3D, including studies of the atmospheric energy budget, exploration of small-scale and large-scale processes, geospace environment monitoring and service applications. The timetable of future development activities will also be presented.

Turunen, E. S.; Eiscat 3D Project Team

2010-12-01

249

Distinguishing ability analysis of compressed sensing radar imaging based on information theory model  

NASA Astrophysics Data System (ADS)

Recent theory of compressed sensing (CS) has been widely used in many application areas. In this paper, we mainly concentrate on the CS in radar and analyze the distinguishing ability of CS radar image based on information theory model. The information content contained in the CS radar echoes is analyzed by simplifying the information transmission channel as a parallel Gaussian channel, and the relationship among the signal-to-noise ratio (SNR) of the echo signal, the number of required samples, the length of the sparse targets and the distinguishing level of the radar image is gotten. Based on this result, we introduced the distinguishing ability of the CS radar image and some of its properties are also gotten. Real IECAS advanced scanning two-dimensional railway observation (ASTRO) data experiment demonstrates our conclusions.

Jiang, Hai; Zhang, Bingchen; Lin, Yueguan; Hong, Wen; Wu, Yirong

2011-10-01

250

Multi focus millimeter-wave imaging radar using inline Tx\\/Rx printed antennas  

Microsoft Academic Search

Multi focus imaging radar using two pair of inline Tx\\/Rx printed antennas has been proposed. Antipodal Fermi antennas have been employed both for Tx\\/Rx antennas. Basic characteristics of the proposed imaging radar including the effect of offset of Tx\\/Rx antennas have been discussed by experiments. Imaging of conducting rods located on styrofoam with 250mm range, and scissors and gun have

Fuminori Sakai; Kiyozumi Chino; Hirosuke Suzuki; Hiroyasu Sato; Kunio Sawaya; Koji Mizuno

2008-01-01

251

Ground Penetrating Radar Imaging of Tephra Fallout and Surge Deposits  

NASA Astrophysics Data System (ADS)

GPR profiles on Cerro Negro volcano, Nicaragua, and Poás, Irazú, and Arenal volcanoes, Costa Rica, show this method has utility for mapping tephra blanket and surge deposit thicknesses, as well as ballistics distributions. These data are useful for estimating eruption volumes, particularly close to vents where deposits may be thicker than trenching depths. In the dry, highly resistive tephra of the Cerro Negro basaltic cinder cone, distinct deposits are clearly imaged between 2 and 20 m depth. The lowermost coherent reflection is presumed to be the contact with underlying pre-Cerro Negro lavas and weathered tephra deposits. Within the 2-20 m package, individual reflecting horizons are clearly resolved, and reflection attributes, particularly phase, may contain useful information on the nature of contacts, such as abrupt changes in granulometry. Because of the very high velocities at Cerro Negro (0.14 m/ns), even with 200 MHz antennas strata shallower than 2 m are difficult to resolve. In contrast, wetter ash, pumice, paleosol, and surge deposits on Irazú and Poás volcanoes show velocities as low as 0.045 m/ns. The corresponding shorter wavelengths permit strata as shallow as 40-70 cm to be imaged with 200 MHz antennas, with depth penetration typically 5 to 8 m. Comparison of trench observations and radar profiles indicates that strong radar reflections are produced by iron-rich zones at the water table and soil-ash contacts. Other features visible in the profiles are small (tens of cm) sub-vertical offsets of nearly horizontal units, and diffractions or disruptions in horizontal units presumed to reflect >30 cm blocks.

Kruse, S.; Martin, K.; Connor, C.; Mora, R.; Ramirez, C.; Alvarado, G.

2005-05-01

252

Classification of Weather Radar Images using Linguistic Decision Trees with Conditional Labelling  

Microsoft Academic Search

This paper focuses on the application of LID3 (Linguistic Decision Tree Induction Algorithm) to the classi- fication of weather radar images. In radar analysis a phe- nomenon known as Bright Band occurs. This essentially is an amplification in reflectivity due to melted snow and leads to overestimation of precipitation. It is therefore benefic ial to detect this Bright Band region

Daniel R. Mcculloch; Jonathan Lawry; Miguel A. Rico-ramirez; Ian D. Cluckie

2007-01-01

253

Characterization of the Attenuation due to Rain Cell Fields applying Cellular Automata to Weather Radar Images  

Microsoft Academic Search

A straightforward linkage between rain cell dynamics in terms of reflectivity Z (dBz) or its equivalent rain rate R (mm\\/h) and satellite or terrestrial radiolink attenuation can be performed. This work focuses on the presentation of an approach for assessing and characterizing rain cell dynamics based exclusively on the analysis of the radar reflectivity scans recorded in weather radar image,

A. Nunez; V. Pastoriza; P. Marino; F. P. Fontan; U.-C. Fiebig

2006-01-01

254

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

255

Microwave Penetration and Attenuation in Desert Soil: A Field Experiment with the Shuttle Imaging Radar  

Microsoft Academic Search

Receivers buried in the Nevada desert were used with the Shuttle Imaging Radar to measure microwave attenuation as a function of soil moisture in situ. Results agree closely with laboratory measureements of attenuation and suggest that penetration of tens of centimeters in desert soils is common for L-band (1.2-GHz) radar.

Tom Farr; Charles Elachi; Philip Hartl; K. Chowdhury

1986-01-01

256

The effect of vertical measurement resolution on the correlation structure of a ground penetrating radar reflection image  

Microsoft Academic Search

Geostatistical analysis of a ground penetrating radar reflection image can be used to quantify the maximum correlation direction and the range of horizontal and sub-horizontal radar reflections. A review of previous work, and an analysis of a photograph of layered sediments, suggest that the vertical resolution of a radar image strongly affects its lateral correlation structure. Numerical modeling was used

Rosemary Knight; Paulette Tercier; James Irving

2004-01-01

257

Image Processing Language.  

National Technical Information Service (NTIS)

This thesis introduces a new image processing language (IPL) which is based on the domains and operations required to express common image processing algorithms in a high-level language. IPL is independent of any particular computer architecture. Its impl...

R. C. Hood

1983-01-01

258

Image Processing Research.  

National Technical Information Service (NTIS)

The research program, Image Processing Research, has as its primary purpose the analysis and development of techniques and systems for efficiently generating, processing, transmitting, and displaying visual images and two dimensional data arrays. Research...

W. K. Pratt

1975-01-01

259

Sea surface monitoring with formation flying imaging radar altimeters  

NASA Astrophysics Data System (ADS)

Global sea-surface monitoring is crucial for studying and sensing the environment change of our planet. Radar altimeters have been played an unsubstituted role in this regard since later 1980s. However, traditional nadir-looking altimeters have some limitations on achieving wide swath, it means we are hard to get the required frequent revisit for meso-scale and large-scale ocean surveying and studying if just single satellite is available, even if we had wide swath altimeter, which has 100km-level swath. The idea of using coordinated multiple spaceborne sensors, which are distributed on a group of satellites in formation-flying, to complete one mission, or to enhance the sensing ability was proposed in the end of 1990s. Two famous missions, i.e. CartWheel project and TechSat-21 project were inaugurated since then, among which, CartWheel are ongoing well, but TechSat-21 was terminated in 2003. At the same time, the WITTEX was also proposed, which incorporates a group of altimeters. Unlike from CartWheel and TechSat-21, which adopted tight formation-flying geometries, the WITTEX adopted a loose formation-flying geometry. The "tight geometry" means the satellites are separated by hundred meters to several kilometers, and the satellites are synchronized by time, phase and beam steering with very high accuracy. The "loose geometry" means the satellites are separated by tens to hundreds of kilometers. In this paper we proposed a tight formation- flying geometry composed of two satellites, each boarded with an imaging radar altimeter. The aim is to provide a realistic technique for oceanic topography measurement with high accuracy in wide swath. Because the imaging altimeter has a pair of antennae, we can get interferometric measurements with short baseline and long baseline simultaneously when shoulder to shoulder flying is chosen. This will be helpful for overcome the problem of phase ambiguity. In another formation flying mode, i.e. two imaging altimeters fly in a forward-backward geometry along track, ocean current can be detected, because the imaging altimeter is of the imaging capability with 100m resolution. Several key issues, such as formation and orbit design were addressed and accompanied with simulations.

Zhang, Yunhua; Haiying, Cui; Zhang, Xiangkun; Jiang, Jingshan

260

Accurate Image Expansion Method Using Range Points Based Ellipse Fitting for UWB Imaging Radar  

NASA Astrophysics Data System (ADS)

Ultra-wideband (UWB) pulse radars have a definite advantage in high-range resolution imaging, and are suitable for short-range measurements, particularly at disaster sites or security scenes where optical sensors are rarely suitable because of dust or strong backlighting. Although we have already proposed an accurate imaging algorithm called Range Points Migration (RPM), its reconstructible area is too small to identify the shape of an object if it is far from the radar and the size of the aperture is inadequate. To resolve this problem, this paper proposes a novel image expansion method based on ellipse extrapolation; it enhances extrapolation accuracy by deriving direct estimates of the observed range points distributed in the data space. Numerical validation shows that the proposed method accurately extrapolates part of the target boundary, even if an extremely small region of the target boundary is obtained by RPM.

Abe, Yoriaki; Kidera, Shouhei; Kirimoto, Tetsuo

261

Model-supported exploitation of synthetic aperture radar images  

NASA Astrophysics Data System (ADS)

We address the application of model-supported exploitation techniques to synthetic aperture radar (SAR) imagery. The emphasis is on monitoring SAR imagery using wide area 2D and/or 3D site models along with contextual information. We consider here the following tasks useful in monitoring: (a) site model construction using segmentation and labeling techniques, (b) target detection, (c) target classification and indexing, and (d) SAR image-site model registration. The 2-D wide area site models used here for SAR image exploitation differ from typical site models developed for RADIUS applications, in that they do not model specific facilities, but constitute wide area site models of cultural features such as urban clutter areas, roads, clearings, fields, etc. These models may be derived directly from existing site models, possibly constructed from electro-optical (EO) observations. When such models are not available, a set of segmentation and labeling techniques described here can be used for the construction of 2D site models. The use of models can potentially yield critical information which can disambiguate target signatures in SAR images. We address registration of SAR and EO images to a common site model. Specific derivations are given for the case of registration within the RCDE platform. We suggest a constant false alarm rate (CFAR) detection scheme and a topographic primal sketch (TPS) based classification scheme for monitoring target occurrences in SAR images. The TPS of an observed target is matched against candidate targets TPSs synthesized for the preferred target orientation, inferred from context (e.g. road or parking lot targets). Experimental results on real and synthetic SAR images are provided.

Chellappa, Rama; Kuttikkad, Shyam; Meth, Reuven; Burlina, Philippe; Shekhar, Chandra S.

1996-02-01

262

A model for forming airborne synthetic aperture radar images of underground targets  

SciTech Connect

Synthetic Aperture Radar (SAR) from an airborne platform has been proposed for imaging targets beneath the earth`s surface. The propagation of the radar`s energy within the ground, however, is much different than in the earth`s atmosphere. The result is signal refraction, echo delay, propagation losses, dispersion, and volumetric scattering. These all combine to make SAR image formation from an airborne platform much more challenging than a surface imaging counterpart. This report treats the ground as a lossy dispersive half-space, and presents a model for the radar echo based on measurable parameters. The model is then used to explore various imaging schemes, and image properties. Dynamic range is discussed, as is the impact of loss on dynamic range. Modified window functions are proposed to mitigate effects of sidelobes of shallow targets overwhelming deeper targets.

Doerry, A.W.

1994-01-01

263

Real-time radar signal processing for autonomous aircraft landing  

NASA Astrophysics Data System (ADS)

Landing in poor weather is a crucial problem for the air transportation system. To aid the pilots for these conditions several solutions have been suggested and/or implemented including instrument landing systems (ILS) and microwave landing systems (MLS) that put the responsibility of the landing to a large extent in the hands of the airport facilities. These systems even though useful are not available due to their high costs even in a few major metropolitan airports. This shortcoming has generated interest in providing all weather capabilities not on the landing facility but on the vehicle itself. The Synthetic Vision System Technology Demonstration sponsored by the United States Federal Aviation Administration (FAA) and the U.S. Air Force represents an effort to respond to the above needs. In this paper we present a summary of a typical synthetic vision system. This system consists of a scanning 35 GHz radar, a scanning antenna, a signal/image processor and a head up display (HUD). The pilot is presented a final perspective image of the scene sensed by the radar with associated flight guidance symbology. This system is implemented in real time hardware and has been undergoing tower and flight testing under a variety of weather conditions since early 1992.

Sadjadi, Firooz A.; Helgeson, Michael A.; Radke, Jeffrey D.; Stein, Gunter

1993-11-01

264

Standoff concealed weapon detection using a 350 GHz radar imaging system  

SciTech Connect

The Pacific Northwest National Laboratory is currently developing a 350 GHz, active, wideband, three-dimensional, radar imaging system to evaluate the feasibility of active sub-mm imaging for standoff concealed weapon detection. The prototype radar imaging system is based on a wideband, heterodyne, frequency-multiplier-based transceiver system coupled to a quasi-optical focusing system and high-speed rotating conical scanner. The wideband operation of this system provides accurate ranging information, and the images obtained are fully three-dimensional. Recent improvements to the system include increased imaging speed using improved balancing techniques, wider bandwidth, and image display techniques.

Sheen, David M.; Hall, Thomas E.; Severtsen, Ronald H.; McMakin, Douglas L.; Hatchell, Brian K.; Valdez, Patrick LJ

2010-04-01

265

Determining Titan's Spin State from Cassini RADAR Images  

NASA Astrophysics Data System (ADS)

For some 19 areas of Titan's surface, the Cassini RADAR instrument has obtained synthetic aperture radar (SAR) images during two different flybys. The time interval between flybys varies from several weeks to two years. We have used the apparent misregistration (by 10-30 km) of features between separate flybys to construct a refined model of Titan's spin state, estimating six parameters: north pole right ascension and declination, spin rate, and these quantities' first time derivatives We determine a pole location with right ascension of 39.48 degrees and declination of 83.43 degrees corresponding to a 0.3 degree obliquity. We determine the spin rate to be 22.5781 deg day-1 or 0.001 deg day-1 faster than the synchronous spin rate. Our estimated corrections to the pole and spin rate exceed their corresponding standard errors by factors of 80 and 8, respectively. We also found that the rate of change in the pole right ascension is -30 deg century-1, ten times faster than right ascension rate of change for the orbit normal. The spin rate is increasing at a rate of 0.05 deg day-1 per century. We observed no significant change in pole declination over the period for which we have data. Applying our pole correction reduces the feature misregistration from tens of km to 3 km. Applying the spin rate and derivative corrections further reduces the misregistration to 1.2 km. The research described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

Stiles, Bryan W.; Kirk, Randolph L.; Lorenz, Ralph D.; Hensley, Scott; Lee, Ella; Ostro, Steven J.; Allison, Michael D.; Callahan, Philip S.; Gim, Yonggyu; Iess, Luciano; Perci del Marmo, Paolo; Hamilton, Gary; Johnson, William T. K.; West, Richard D.; Cassini RADAR Team

2008-05-01

266

Research on imaging simulation of airborne fire control radar for simulated training  

Microsoft Academic Search

A uniform simulation method was presented to realize ground imaging of RBM, DBS and Spotlight SAR for simulated training. The three imaging modes are widely used by modern airborne fire control radars. Considering the requirement of training real-time and the simulated images used for pilots observation, this method computed RCS images of ground based on the facet model and fused

Chen Yang; Ji Gang; Sun Wen-zhu; Sun Zhong-yun; Liu Yun-xiang

2010-01-01

267

Conventional and synthetic aperture processing for airborne ground-penetrating radar  

NASA Astrophysics Data System (ADS)

For the past four years Airborne Environmental Surveys, a division of Era Aviation, Inc., has used unique and patented airborne frequency modulated, continuous wave radars and processes for detection and mapping subsurface phenomena. Primary application has focused on the detection of manmade objects in landfills, hazardous waste sites (some of which contain unexploded ordnance), and subsurface plumes of refined free- floating hydrocarbons. Recently, MSB Technologies, Inc. has developed a form of synthetic aperture radar processing, called GPSAR, that is tailored especially for the AES radars. Used as an adjunct to more conventional airborne ground-penetrating radar data processing techniques, GPSAR takes advantage of the radars' coherent transmission and produces imagery that is better focused and more accurate in determining an object's range and true depth. This paper describes the iterative stages of data processing and analysis used with the radars and shows the added advantages that GPSAR processing offers.

Cameron, Robert M.; Simkins, William L.; Brown, Russell D.

1994-07-01

268

HERMES: a high-speed radar imaging system for inspection of bridge decks.  

National Technical Information Service (NTIS)

Corrosion of rebar in concrete bridges causes subsurface cracks and is a major cause of structural degradation that necessitates repair or replacement. A ground-penetrating radar imaging system has been designed and developed that performs the nondestruct...

S. G. Azevedo

1996-01-01

269

Statement of capabilities: Micropower Impulse Radar (MIR) technology applied to mine detection and imaging.  

National Technical Information Service (NTIS)

The Lawrence Livermore National Laboratory (LLNL) has developed radar and imaging technologies with potential applications in mine detection by the armed forces and other agencies involved in demining efforts. These new technologies use a patented ultra-w...

S. G. Azevedo D. T. Gavel J. E. Mast J. P. Warhus

1995-01-01

270

3D SAR image formation for underground targets using ultra-wideband (UWB) radar  

NASA Astrophysics Data System (ADS)

This paper analyzes the application of ultra-wideband ground-penetrating radar (GPR) in a down-looking configuration for the detection of buried targets. As compared to previous studies, where target detection algorithms have been developed based on the radar range profiles alone (pre-focus data), we investigate the potential performance improvement by forming synthetic aperture radar (SAR) images of the targets. This becomes important in scenarios with small signal-to-noise or signal-to-clutter ratios. Our three-dimensional (3-D) image formation algorithm is based on the backprojection technique. We apply this method to radar scattering data obtained through computer simulation by the finite-difference time-domain (FDTD) technique. Our analysis demonstrates the advantages of using focused SAR images versus the pre-focus range profiles. We also perform a parametric study of several physical factors that could affect the image quality.

Nguyen, Lam; Dogaru, Traian; Innocenti, Roberto

2009-05-01

271

Fast and Accurate 3-D Imaging Algorithm with Linear Array Antennas for UWB Pulse Radars  

NASA Astrophysics Data System (ADS)

Pulse radars with UWB signals are promising as a high-resolution imaging technique that can be used for the non-destructive measurement of surface details in industrial products such as antennas and aircraft. We have already proposed a fast 3-D imaging algorithm, SEABED, that utilizes a reversible transform between the time delay and the target boundary. However, data acquisition is time-consuming when obtaining an accurate image because it assumes a mono-static radar with 2-D scanning of an antenna. In this paper, we utilize linear array antennas and propose a fast and accurate imaging algorithm. We extend the reversible transform for mono-static radars to apply to bi-static radars to reduce the data acquisition time. The effectiveness of the proposed method is verified with numerical simulations and experiments.

Kidera, Shouhei; Kani, Yusuke; Sakamoto, Takuya; Sato, Toru

272

Imaging targets embedded in a lossy half space with Synthetic Aperture Radar.  

National Technical Information Service (NTIS)

This paper addresses theoretical aspects of forming images from an airborne Synthetic Aperture Radar (SAR) of targets buried below the earth's surface. Soil is generally a lossy, dispersive medium, with wide ranging variability in these attributes dependi...

A. W. Doerry B. Boverie B. C. Brock D. Cress

1994-01-01

273

Radar data processing using a distributed computational system  

NASA Astrophysics Data System (ADS)

This research specifies and validates a new concurrent decomposition scheme, called Confined Space Search Decomposition (CSSD), to exploit parallelism of Radar Data Processing algorithms using a Distributed Computational System. To formalize the specification, we propose and apply an object-oriented methodology called Decomposition Cost Evaluation Model (DCEM). To reduce the penalties of load imbalance, we propose a distributed dynamic load balance heuristic called Object Reincarnation (OR). To validate the research, we first compare our decomposition with an identified alternative using the proposed DCEM model and then develop a theoretical prediction of selected parameters. We also develop a simulation to check the Object Reincarnation Concept.

Mota, Gilberto F.

1992-06-01

274

Coherent radar imaging of mesosphere summer echoes: Influence of radar beam pattern and tilted structures on atmospheric echo center  

NASA Astrophysics Data System (ADS)

Multiple echo centers of a mesosphere-summer-echo layer (MSE) observed by the six-receiver OSWIN VHF radar (54.1°N, 11.8°E) were examined with the coherent radar imaging (CRI) technique. The data were collected by different observational modes: vertical and oblique radar beams with the receiving configurations of 3 × 2, 6 × 1 (meridional alignment) and 1 × 6 (zonal alignment) antenna groups. The unique receiving configurations of meridional and zonal aligned antenna groups reveal that the echo centers clustered in three distinct groups above the range height of ˜86 km. The central group of echo centers was around the direction of radar beam; however, the off-zenith angles of the two side groups, ranging between several and 20 degrees, increased with ascendant range height. Two potential causes of the echoes in the two side groups were examined on the basis of simulation calculation, namely, tilted structures in the layer and additionally, the influence of radar beam pattern. It is indicated that some echoes, originating from the lower part (<˜86 km) of the layer, can enter from the first and second sidelobes of the radar beam pattern and then be received at higher range gates (>˜86 km) at larger off-zenith angles. The tilted structures, which are considered to be related to wave activities, can also produce the features similar to the observations. This is demonstrated by simulation calculation with wavy reflecting layers, in which the waves are supposed to modulate the multiple reflecting layers, with increasing amplitudes, tilted shapes, asynchronous phases, and horizontal travel.

Chen, Jenn-Shyong; Hoffmann, Peter; Zecha, Marius; Hsieh, Cheng-Hsiung

2008-02-01

275

Digital image processing  

Microsoft Academic Search

The field of digital image processing is reviewed with reference to its origins, progress, current status, and prospects for the future. Consideration is given to the evolution of image processor display devices, developments in the functional components of an image processor display system (e.g. memory, data bus, and pipeline central processing unit), and developments in the software. The major future

B. R. Hunt

1981-01-01

276

Radar Signal Processing in Instrumentation and Measurement Technology  

NASA Astrophysics Data System (ADS)

It is reported that various radar clutter obey a Weibull distribution. To suppress such Weibull-distributed clutter, Weibull CFAR techniques are applied to data taken by an S-band radar. The results show the usefulness of Weibull CFAR.

Sekine, Matsuo

277

High-resolution imaging using a wideband MIMO radar system with two distributed arrays.  

PubMed

Imaging a fast maneuvering target has been an active research area in past decades. Usually, an array antenna with multiple elements is implemented to avoid the motion compensations involved in the inverse synthetic aperture radar (ISAR) imaging. Nevertheless, there is a price dilemma due to the high level of hardware complexity compared to complex algorithm implemented in the ISAR imaging system with only one antenna. In this paper, a wideband multiple-input multiple-output (MIMO) radar system with two distributed arrays is proposed to reduce the hardware complexity of the system. Furthermore, the system model, the equivalent array production method and the imaging procedure are presented. As compared with the classical real aperture radar (RAR) imaging system, there is a very important contribution in our method that the lower hardware complexity can be involved in the imaging system since many additive virtual array elements can be obtained. Numerical simulations are provided for testing our system and imaging method. PMID:20051345

Wang, Dang-wei; Ma, Xiao-yan; Chen, A-Lei; Su, Yi

2009-12-31

278

Impact of HRR radar processing on moving target identification performance  

Microsoft Academic Search

Airborne radar tracking in moving ground vehicle scenarios is impacted by sensor, target, and environmental dynamics. Moving targets can be assessed with 1-D High Range Resolution (HRR) Radar profiles with sufficient signal-to-noise (SNR) present which contain enough feature information to discern one target from another to help maintain track or to identify the vehicle. Typical radar clutter suppression algorithms developed

Bart Kahler; Erik Blasch

2009-01-01

279

CFAR processing for airborne pulse-Doppler radars  

Microsoft Academic Search

Constant false alarm rate (CFAR) processors which may be used in airborne pulse-Doppler radar systems are described. Using radar parameters selected for an aircraft flying at Mach 1 and at up to 10 km altitude, a simulation using the ABRSIM airborne radar simulator reveals that a 70 dB clutter peak appears across all of the range gates and many of

G. Vrckovnik; D. Faubert

1991-01-01

280

Geologic Studies of Planetary Surfaces Using Radar Polarimetric Imaging  

Microsoft Academic Search

Radar is a useful remote sensing tool for studying planetary geology because it is sensitive to the composition, structure, and roughness of the surface and can penetrate some materials to reveal buried terrain. The Arecibo Observa- tory radar system transmits a single sense of circular polari- zation, and both senses of circular polarization are received, which allows for the construction

Lynn M. Carter; Donald B. Campbell; Bruce A. Campbell

2011-01-01

281

Through-wall imaging and characterization of human activity using ultrawideband (UWB) random noise radar  

NASA Astrophysics Data System (ADS)

Recent terrorist activities and law-enforcement situations involving hostage situations underscore the need for effective through-wall imaging. Current building interior imaging systems are based on short-pulse waveforms, which require specially designed antennas to subdue unwanted ringing. In addition, periodically transmitted pulses of energy are easily recognizable by the intelligent adversary who may employ appropriate countermeasures to confound detection. A coherent polarimetric random noise radar architecture is being developed based on UWB technology and software defined radio, which has great promise in its ability to covertly image obscured targets. The main advantages of the random noise radar lie in two aspects: first, random noise waveform has an ideal "thumbtack" ambiguity function, i.e., its down range and cross range resolution can be separately controlled, thus providing unambiguous high resolution imaging at any distance; second, random noise waveform is inherently low probability of intercept (LPI) and low probability of detection (LPD), i.e., it is immune from detection, jamming, and interference. Thus, it is an ideal candidate sensor for covert imaging of obscured regions in hostile environments. The coherency in the system can be exploited to field a fully-polarimetric system that can take advantage of polarization features in target recognition. Moving personnel can also be detected using Doppler processing. Simulation studies are used to analyze backscattered signals from the walls, and humans and other targets behind the walls. Real-time data processing shows human activity behind the wall and human target tracking. The high resolution provides excellent multipath and clutter rejection.

Lai, Chieh-Ping; Narayanan, Ram M.

2005-05-01

282

Moving target detection in foliage using along track monopulse synthetic aperture radar imaging.  

PubMed

This paper presents a method for detecting moving targets embedded in foliage from the monostatic and bistatic synthetic aperture radar (SAR) data obtained via two airborne radars. The two radars, which are mounted on the same aircraft, have different coordinates in the along track (cross-range) domain. However, unlike the interferometric SAR systems used for topographic mapping, the two radars possess a common range and altitude (i.e., slant range). The resultant monopulse SAR images are used to construct difference and interferometric images for moving target detection. It is shown that the signatures of the stationary targets are weakened in these images. Methods for estimating a moving target's motion parameters are discussed. Results for an ultrawideband UHF SAR system are presented. PMID:18283004

Soumekh, M

1997-01-01

283

Technical Note: An open source library for processing weather radar data (wradlib)  

NASA Astrophysics Data System (ADS)

The potential of weather radar observations for hydrological and meteorological research and applications is undisputed, particularly with increasing world-wide radar coverage. However, several barriers impede the use of weather radar data. These barriers are of both scientific and technical nature. The former refers to inherent measurement errors and artefacts, the latter to aspects such as reading specific data formats, geo-referencing, visualisation. The radar processing library wradlib is intended to lower these barriers by providing a free and open source tool for the most important steps in processing weather radar data for hydro-meteorological and hydrological applications. Moreover, the community-based development approach of wradlib allows scientists to share their knowledge about efficient processing algorithms and to make this knowledge available to the weather radar community in a transparent, structured and well-documented way.

Heistermann, M.; Jacobi, S.; Pfaff, T.

2013-02-01

284

Atmospheric Radar Signal Processing using Bivariate Empirical Mode Decomposition  

NASA Astrophysics Data System (ADS)

This paper is based upon the analysis of real-time data collected from the MST radar, NARL, CityplaceGadanki, country-regionIndia. We apply a new method, Bivariate Empirical Mode Decomposition (BEMD), to the complex time series data for estimating the Doppler frequencies and thus find the parameters like zonal (u), meridonal (v) and Vertical Wind speed (w) etc. BEMD is an algorithm for the analysis of multicomponent signals that breaks them down into a number of amplitude and frequency modulated signals, termed as Intrinsic Mode Functions (IMFs), which are basis functions for representing the signal. In a noisy signal, decomposed IMFs are a combination of IMFs of both signal and noise. By comparing with the characteristics of noise-only IMFs, we will remove the noise-dominant IMFs from the noisy signal. We reconstruct the signal with remaining IMFs and thus denoising the signal. Due to the adaptive nature of the basis functions, EMD is ideally suited than any other method like the Spectrogram, Wavelet etc for analyzing nonlinear and non-stationary processes. Initially, we apply BEMD for simulated signals such as Doppler, Bumps etc. under various noise conditions and then apply the same for the radar data. Results have been validated using Global Positioning System Sonde data. Finally, we classify the noise as Gaussian or not associated with the radar signal received form vertical as well as non vertical directions in the higher bins of the atmosphere using different parameters like Skewness, Kurtosis, Negentropy (Syntropy) and incorporating some tests such as Autocorrelation test, Power Spectral Density test, Partial Autocorrelation test.

Sreenivasulu Reddy, Thatiparthi

2012-07-01

285

Impact of frequency and polarization diversity on a terahertz radar's imaging performance  

NASA Astrophysics Data System (ADS)

The Jet Propulsion Laboratory's 675 GHz, 25 m standoff imaging radar can achieve >1 Hz real time frame rates over 40x40 cm fields of view for rapid detection of person-borne concealed weapons. In its normal mode of operation, the radar generates imagery based solely on the time-of-flight, or range, between the radar and target. With good clothing penetration at 675 GHz, a hidden object will be detectable as an anomaly in the range-to-surface profile of a subject. Here we report on results of two modifications in the radar system that were made to asses its performance using somewhat different detection approaches. First, the radar's operating frequency and bandwidth were cut in half, to 340 GHz and 13 GHz, where there potential system advantages include superior transmit power and clothing penetration, as well as a lower cost of components. In this case, we found that the twofold reduction in range and cross-range resolution sharply limited the quality of through-clothes imagery, although some improvement is observed for detection of large targets concealed by very thick clothing. The second radar modification tested involved operation in a fully polarimetric mode, where enhanced image contrast might occur between surfaces with different material or geometric characteristics. Results from these tests indicated that random speckle dominates polarimetric power imagery, making it an unattractive approach for contrast improvement. Taken together, the experiments described here underscore the primary importance of high resolution imaging in THz radar applications for concealed weapons detection.

Cooper, Ken B.; Dengler, Robert J.; Llombart, Nuria

2011-05-01

286

Three-dimensional ground penetrating radar imaging using multi-frequency diffraction tomography  

SciTech Connect

In this paper we present results from a three-dimensional image reconstruction algorithm for impulse radar operating in monostatic pulse-echo mode. The application of interest to us is the nondestructive evaluation of civil structures such as bridge decks. We use a multi-frequency diffraction tomography imaging technique in which coherent backward propagations of the received reflected wavefield form a spatial image of the scattering interfaces within the region of interest. This imaging technique provides high-resolution range and azimuthal visualization of the subsurface region. We incorporate the ability to image in planarly layered conductive media and apply the algorithm to experimental data from an offset radar system in which the radar antenna is not directly coupled to the surface of the region. We present a rendering in three-dimensions of the resulting image data which provides high-detail visualization.

Mast, J.E.; Johansson, E.M.

1994-07-01

287

Radar Observations of Snowpack Changes from the Second Cold Land Processes Experiment  

NASA Astrophysics Data System (ADS)

To support the NASA Snow and Cold Land Processes (SCLP) and the ESA Cold Regions High-Resolution Hydrologic Observatory (CoRe-H2O) missions and advance observation of the global water cycle, NASA is supporting the second Cold Land Processes Experiment (CLPX-II). The experiment is being conducted in two parts over two winter seasons (Colorado 2006-2007, and Alaska 2007-2008). The focus of CLPX-II is on testing and development of advanced snow measurement using high-frequency radar through repeat observations of changing snow conditions using airborne and spaceborne radars and intensive in situ measurements. During 2006-2007 three field campaigns were conducted in a 90-km x 9-km study area in north-central Colorado. The campaigns were carried out in December, January and February to observe significant changes in snowpack characteristics. In each campaign, the Jet Propulsion Laboratory's conically scanning Ku- band polarimetric scatterometer (POLSCAT) was flown on a Twin Otter aircraft to collect radar data over the study area. Multiple complete images of the entire study area were acquired during each campaign, enabling examination of short-term changes in radar response as well as long-term changes between campaigns. In each campaign, intensive in situ observations of snow depth, water equivalent, stratigraphy, and grain size were made in each of 16 target sites. All of the target sites shared similar backgrounds (flat terrain with a ground cover of grasses and sedges) but exhibited a wide range of snowpack characteristics. Preliminary analyses of the POLSCAT data acquired from the CLPX-II in winter 2006-2007 are described. The data showed response of the Ku-band radar echoes to snowpack changes for various types of background vegetation. There was about 0.4 dB increase in backscatter for every 1 cm SWE accumulation for sage brush and pasture fields. The data also showed the impact of freeze/thaw cycles, which appeared to create depth hoar and ice lenses with large snow grain size, and consequently increased the radar signals by a few dBs.

Cline, D.; Yueh, S.; Elder, K.

2007-12-01

288

A fast level set method for synthetic aperture radar ocean image segmentation.  

PubMed

Segmentation of high noise imagery like Synthetic Aperture Radar (SAR) images is still one of the most challenging tasks in image processing. While level set, a novel approach based on the analysis of the motion of an interface, can be used to address this challenge, the cell-based iterations may make the process of image segmentation remarkably slow, especially for large-size images. For this reason fast level set algorithms such as narrow band and fast marching have been attempted. Built upon these, this paper presents an improved fast level set method for SAR ocean image segmentation. This competent method is dependent on both the intensity driven speed and curvature flow that result in a stable and smooth boundary. Notably, it is optimized to track moving interfaces for keeping up with the point-wise boundary propagation using a single list and a method of fast up-wind scheme iteration. The list facilitates efficient insertion and deletion of pixels on the propagation front. Meanwhile, the local up-wind scheme is used to update the motion of the curvature front instead of solving partial differential equations. Experiments have been carried out on extraction of surface slick features from ERS-2 SAR images to substantiate the efficacy of the proposed fast level set method. PMID:22399940

Huang, Xiaoxia; Huang, Bo; Li, Hongga

2009-02-03

289

A Fast Level Set Method for Synthetic Aperture Radar Ocean Image Segmentation  

PubMed Central

Segmentation of high noise imagery like Synthetic Aperture Radar (SAR) images is still one of the most challenging tasks in image processing. While level set, a novel approach based on the analysis of the motion of an interface, can be used to address this challenge, the cell-based iterations may make the process of image segmentation remarkably slow, especially for large-size images. For this reason fast level set algorithms such as narrow band and fast marching have been attempted. Built upon these, this paper presents an improved fast level set method for SAR ocean image segmentation. This competent method is dependent on both the intensity driven speed and curvature flow that result in a stable and smooth boundary. Notably, it is optimized to track moving interfaces for keeping up with the point-wise boundary propagation using a single list and a method of fast up-wind scheme iteration. The list facilitates efficient insertion and deletion of pixels on the propagation front. Meanwhile, the local up-wind scheme is used to update the motion of the curvature front instead of solving partial differential equations. Experiments have been carried out on extraction of surface slick features from ERS-2 SAR images to substantiate the efficacy of the proposed fast level set method.

Huang, Xiaoxia; Huang, Bo; Li, Hongga

2009-01-01

290

High resolution through-the-wall radar image based on beamspace eigenstructure subspace methods  

Microsoft Academic Search

Through-the-wall imaging (TWI) is a challenging problem, even if the wall parameters and characteristics are known to the system operator. Proper target classification and correct imaging interpretation require the application of high resolution techniques using limited array size. In inverse synthetic aperture radar (ISAR), signal subspace methods such as Multiple Signal Classification (MUSIC) are used to obtain high resolution imaging.

Yeo-Sun Yoon; Moeness G. Amin

2008-01-01

291

Passive Radar Imaging Algorithm Based on Subapertures Synthesis of Multiple Television Stations  

Microsoft Academic Search

In this paper, we presents a passive radar imaging algorithm based on signals received from multiple television stations at various aspect angles and bistatic equivalence theorem. The algorithm reconstructs a target image by synthesizing the subapertures of multiple television stations available into a large equivalent aperture. In addition to the high efficiency in imaging and low complexity in computation, the

Wang Jun; Zhang Xinwen; Bao Zheng

2006-01-01

292

A robust and fast imaging algorithm without derivative operations for UWB pulse radars  

Microsoft Academic Search

Target shape estimation with UWB pulse radars is promising as an imaging technique for household robots. We have already proposed a fast imaging algorithm, SEABED based on a reversible transform BST (Boundary Scattering Transform) between the received signals and the target shape. However the target image obtained by SEABED deteriorates in a noisy environment because it utilizes a derivative of

Shouhei Kidera; Takuya Sakamoto; Toru Sato

2006-01-01

293

Ultra-wideband antennas for combined magnetic resonance imaging and UWB radar applications  

Microsoft Academic Search

Magnetic resonance imaging (MRI) is one of the most highly appreciated medical diagnostic techniques worldwide. Recent developments aim at adding the capability of creating focused images of moving objects. Among the potential navigator techniques required for such an improved MRI is ultra-wideband (UWB) radar. We have studied the performance of UWB antennas for biomedical imaging inside the 3-Tesla MRI system

U. Schwarz; F. Thiel; F. Seifert; R. Stephan; M. Hein

2009-01-01

294

Imaging Simulation of Bistatic Synthetic Aperture Radar and Its Polarimetric Analysis  

Microsoft Academic Search

Employing the 3-D mapping and projection algorithm (MPA), an imaging simulation of bistatic synthetic aperture radar (BISAR) observation over a complex scenario is developed. Based on the explicit expression of the point target response of stripmap BISAR imaging, raw data are efficiently generated from the scattering map precalculated by MPA. Some examples of BISAR image simulation are studied. The polarimetric

Feng Xu; Ya-Qiu Jin

2008-01-01

295

Tomographic synthesis applied to radar \\/STAR  

Microsoft Academic Search

A real time radar target imaging procedure based on tomographic synthesis is discussed. The procedure, which can be used with an incoherent high range resolution radar (or a CW high Doppler resolution radar), employs a previously described (Le Chevalier et al., 1977) syntactic signal processing algorithm to detect and track a bright point on successive unit-impulse responses in real time.

F. Le Chevalier; C. Fugier-Garrel

1979-01-01

296

Synthetic aperture radar imaging of the sea surface during the PROMESS experiment  

NASA Astrophysics Data System (ADS)

The PROMESS experiment carried out wind and wave measurements on the sea surface with radars operating in the C-band, as with the Active Microwave Instrument aboard ERS-1. A good range of wave heights (ranging from 1 to 7 m) and wind speeds were encountered. The SAR 580 performed measurements with different azimuth angles in C and X-bands simultaneously. Images were obtained from a digital processor and from an optical one. The two sets of images were processed with Fourier and speckle removal technics. The wave length and direction of the long waves is determined with good accuracy. One day featured two wave systems at the same time with different wave lengths and directions. The two systems are well separated and measured by the SAR. The shape of the equivalent monodirectional wave spectrum obtained is very close to the one measured by the waverider.

Piau, P.; Gray, L.

1985-06-01

297

Research on harmonic radar's output data re-triggering DAQ and data processing technology  

NASA Astrophysics Data System (ADS)

Principle of harmonic radar system is introduced. Re-triggering DAQ(data acquisition) of harmonic radar's output data is studied based on NI(national instruments) M series device. Two re-triggering DAQ methods are presented. Time sequence of the two DAQ methods is interpreted. Program is provided to re-triggering acquire harmonic radar system's output data. Dynamic detecting trail of harmonic radar system installed on hauled vehicle is developed. The trail validates two DAQ methods. Data is replayed and processed using data processing Program. Some parameters of typical detecting curve are presented.

Song, Hai-feng; Zhang, Rong; Feng, Di-chao; Wang, Lei; Li, Xu

2013-08-01

298

The Rationale for a New High-resolution Imaging Radar Mission to Venus  

NASA Astrophysics Data System (ADS)

Magellan, NASA’s last geoscience mission to Venus, provided synthetic aperture radar (SAR) images at ~100-m resolution, topography at ~10-km resolution, and the gravity field at ~300-km resolution. Although that mission provided a major advance in our understanding of the planet, basic questions about the geologic history of Venus remain unresolved. For example, hypotheses on the planet’s surface evolution range from uniformitarian to catastrophic, and assessments of current geologic activity range from earth-comparable levels of volcanic and tectonic activity to a surface shaped only by occasional impact and eolian processes. It is now feasible to send a mission to Venus that could provide SAR imaging at 1-5-m resolution; topography with tens-of-meters spatial resolution by utilizing interferometric SAR (InSAR) and stereo radargrammetry; and surface deformation at centimeter-scale vertical resolution through InSAR. Such a mission would substantially further our understanding of Venus by means of: (1) assessing the fundamental framework of the planet's geologic history (e.g., catastrophic change, slow evolution, uniformitarian) by imaging key stratigraphic contacts; (2) expanding the global framework of geomorphic unit types and relative stratigraphy with reconnaissance surveys of large geographic provinces; (3) directly detecting volcanic and tectonic activity through imaging of flows and fault-related activities (e.g., landslides) that occur between imaging passes; (4) monitoring present-day volcanic and tectonic activity with repeat-pass InSAR deformation studies; (5) constraining the nature of Venusian geologic volcanic and tectonic processes, and their relationship to mantle convective processes; (6) understanding the role of eolian processes in modifying the surface and the use of eolian features as stratigraphic markers (e.g., parabolic features) through detailed examination; (7) constraining Venusian impact processes, particularly the role of the atmosphere in the ejecta emplacement process; (8) constraining the processes responsible for the abrupt decrease in emissivity at high altitudes; (9) selecting landing sites for future missions; and (10) identifying past landers/probes to place them in geologic context. Our state of knowledge about Venus is currently analogous to our knowledge of Mars in the post-Viking era, and a high-resolution imaging radar mission to Venus could revolutionize our understanding of Venus in the way that the Mars Global Surveyor mission did for Mars.

Herrick, R. R.; Sharpton, V. L.; Gens, R.; Ghent, R. R.; Gilmore, M. S.; Grimm, R. E.; Johnson, C. L.; McGovern, P. J.; Meyer, F.; Mouginis-Mark, P. J.; Plaut, J. J.; Sandwell, D. T.; Simons, M.; Solomon, S. C.

2009-12-01

299

Comparison of Simulated and Measured Synthetic Aperture Radar Image Spectra with Buoy-Derived Ocean Wave Spectra During the Shuttle Imaging Radar B Mission  

Microsoft Academic Search

During the SIR-B mission over the North Sea, two successful synthetic aperture radar (SAR) data takes with simultaneous buoy measurements of ocean wave spectra have been obtained on October 6 and 8, 1984. On October 6, the SAR imaging of ocean waves was predicted as strongly nonlinear and on October 8 as almost linear. The SIR-B experiment confirmed the theoretical

Werner Alpers; Claus Bruening; Karl Richter

1986-01-01

300

Volcanic and impact deposits of the Moon's Aristarchus Plateau: A new view from Earth-based radar images  

Microsoft Academic Search

Lunar pyroclastic deposits reflect an explosive stage of thebasaltic volcanism that filled impact basins across the nearside.These fine-grained mantling layers are of interest for theirassociation with early mare volcanic processes, and as possiblesources of volatiles and other species for lunar outposts. Wepresent Earth-based radar images, at 12.6 and 70 cm wavelengths,of the pyroclastic deposit that blankets the Aristarchus Plateau.The 70

Bruce A. Campbell; Lynn M. Carter; B. Ray Hawke; Donald B. Campbell; Rebecca R. Ghent

2008-01-01

301

Theory for Hybrid SAR/ISAR Radar Imaging.  

National Technical Information Service (NTIS)

A unified treatment of the SAR and ISAR imaging processes is presented in which each emerges as a special case of a more genera hybrid SAR/ISAR process. Several such special cases are considered, demonstrating the simplicity and flexibility of our analysi...

R. J. Tough K. D. Ward

1991-01-01

302

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

303

Radar imaging of concrete specimens for non-destructive testing  

Microsoft Academic Search

In this paper, the use of radar for non-destructive testing (NDT) of concrete is examined through radar measurements of laboratory size concrete specimens. In the measurements, the emphasis is given to the determination of the specimen thicknesses at three different microwave frequency ranges: 2 ? 3.4 GHz (S band), 3.4 ? 5.8 GHz (S\\/C band), and 8 ? 12 GHz

Oral Büyüköztürk; Hong C Rhim

1997-01-01

304

RADAR IMAGING OF CONCRETE SPECIMENS FOR NON.- DESTRUCTIVE TESTING  

Microsoft Academic Search

In this paper, the use of radar for non-destructive testing (NDT) of concrete is examined through radar measurements of laboratory size concrete specimens. In the measurements, the emphasis is given to the determination of the specimen thicknesses at three different microwave frequency ranges: 2 - 3.4 GHz 6 band), 3.4 - 5.8 GHz (S\\/C band), and 8 - 12 GHz

Hong C Rhim

1997-01-01

305

Acoustic micro-Doppler radar for human gait imaging.  

PubMed

A portable acoustic micro-Doppler radar system for the acquisition of human gait signatures in indoor and outdoor environments is reported. Signals from an accelerometer attached to the leg support the identification of the components in the measured micro-Doppler signature. The acoustic micro-Doppler system described in this paper is simpler and offers advantages over the widely used electromagnetic wave micro-Doppler radars. PMID:17407918

Zhang, Zhaonian; Pouliquen, Philippe O; Waxman, Allen; Andreou, Andreas G

2007-03-01

306

Knowledge-Based Radar Signal and Data Processing (Le traitement du signal et des donnees radar base sur la connaissance).  

National Technical Information Service (NTIS)

The objective of this Lecture Series was to present a state-of-the-art assessment of Knowledge-Based (KB) radar signal and data processing techniques, and thereby increase awareness of their value to the NATO scientific community. The Lecture Series cover...

2007-01-01

307

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

NASA Astrophysics Data System (ADS)

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

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

1985-12-01

308

EISCAT 3D: A European three-dimensional imaging radar for atmospheric and geospace research  

Microsoft Academic Search

(This talk is given on behalf of the EISCAT Scientific Association and the EISCAT_3D Design Team) EISCAT_3D is a new kind of three-dimensional imaging radar for high-latitude atmosphere and geospace studies, located in northern Scandinavia. The facility will consist of multiple large phased-array antenna transmitters\\/receivers in three countries, comprising some 100 000 individual antenna elements. The new radars will measure

Ian McCrea; Esa Turunen

2010-01-01

309

A study on fast imaging for walking human bodies by UWB radar with realistic model  

Microsoft Academic Search

UWB(Ultra Wide-Band) pulse radar is a promising candidate for surveillance systems used to prevent crimes and terror. The high-speed SEABED (Shape Estimation Algorithm based on BST and Extraction of Directly scattered waves) imaging algorithm, is deployed to apply UWB pulse radar in fields that require realtime operations. The SEABED algorithm assumes that omni-directional antennas are scanned to observe the scattered

Takuya Sakamoto; Toru Sato

2008-01-01

310

Thermal-wave radar: A novel subsurface imaging modality with extended depth-resolution dynamic range  

NASA Astrophysics Data System (ADS)

Combining the ideas behind linear frequency modulated continuous wave radars and frequency domain photothermal radiometry (PTR), a novel PTR method is introduced. Analytical solutions to the heat diffusion problem for both opaque and transparent solids are provided. Simulations and experimental results suggest a significant improvement in the dynamic range when using the thermal-wave radar (TWR) instead of conventional PTR. A practical TWR image resolution augmentation method is proposed.

Tabatabaei, Nima; Mandelis, Andreas

2009-03-01

311

Thermal-wave radar: a novel subsurface imaging modality with extended depth-resolution dynamic range.  

PubMed

Combining the ideas behind linear frequency modulated continuous wave radars and frequency domain photothermal radiometry (PTR), a novel PTR method is introduced. Analytical solutions to the heat diffusion problem for both opaque and transparent solids are provided. Simulations and experimental results suggest a significant improvement in the dynamic range when using the thermal-wave radar (TWR) instead of conventional PTR. A practical TWR image resolution augmentation method is proposed. PMID:19334943

Tabatabaei, Nima; Mandelis, Andreas

2009-03-01

312

What Can We Learn from Radar Images of Asteroids?  

NASA Astrophysics Data System (ADS)

Radar delay-doppler images are non-intuitive to interpret, but can be used to constrain a shape model of an asteroid (Hudson and Ostro, Science, 263:940 (1994). This modelling is complicated, and requires many observations; therefore, we investigate what can be learned about the shapes of asteroids from delay-doppler images. In this work, we examine synthetic images of an arbitrarily cratered model of Gaspra, in an attempt to measure the size-frequency distribution of craters from delay-doppler images and determine how well craters can be seen. These images are generated using a model developed by Black and Campbell (DPS 1993), who examined the overall shapes of synthetic d-d images of the Martian satellites and asteroid 951 Gaspra. We generated an exponential size/frequency distribution using four average crater sizes: 30 m, 100m, 300m, 1000m. The function fit random frequencies chosen within reasonable ranges for the largest and smallest craters. Angular positions were also generated randomly. We then deposited parabolic craters with cubic rims onto Gaspra according to the distribution, and fed the resulting coordinate file into the model discussed above. We assumed that the asteroid's maximum radius is 1.5 km and its rotation period is 5 hrs. First, we conducted a blind crater count on images made under the following distribution and compared the counts to the actual number visible within the limits of the delay-Doppler projection: SNR: 10^4 3 * 10^4 10^5 3 * 10^5 srlat: 0 30 60 srlon: 0 10 90 Averaging over the percentages counted for all subradar positions, we obtain: SNR: 10^4 3 * 10^4 10^5 3 * 10^5 percent counted: 15 36 41 52 Knowledge of the fraction of craters we are able to observe allows us to calculate the actual number of craters on the asteroid to within experimental errors. We find that a maximum number are counted at 30$^ subradar latitude due to optimization of the Doppler dispersion, and that observing two close phases results in higher counts because small features can be registered as craters. Finally, we looked at the size/frequency/position distribution and determined what SNR and resolution is needed to see the smallest craters. At an SNR of 3*10^4 and resolution of 0.1Hz x 32m, between 3% and 14% 30 m craters were consistently visible as a dim pixel followed by a bright one. At such low SNR and resolution, a small crater's visibility is highly dependent on the orientation of the local surface with respect to the beam. Arecibo can achieve resolutions approximately twice that used for this simulation. According to a list compiled by Greg Black, three targets in the next ten years will be observable with the upgraded Arecibo telescope at SNRs greater than 20000.

Nelson, K.; Nolan, M. C.

1995-12-01

313

Joseph F. Keithley Award For Advances in Measurement Science Lecture: Thermophotonic and Photoacoustic Radar Imaging Methods for Biomedical and Dental Imaging  

NASA Astrophysics Data System (ADS)

In the first part of this presentation I will introduce thermophotonic radar imaging principles and techniques using chirped or binary-phase-coded modulation, methods which can break through the maximum detection depth/depth resolution limitations of conventional photothermal waves. Using matched-filter principles, a methodology enabling parabolic diffusion-wave energy fields to exhibit energy localization akin to propagating hyperbolic wave-fields has been developed. It allows for deconvolution of individual responses of superposed axially discrete sources, opening a new field: depth-resolved thermal coherence tomography. Several examples from dental enamel caries diagnostic imaging to metal subsurface defect thermographic imaging will be discussed. The second part will introduce the field of photoacoustic radar (or sonar) biomedical imaging. I will report the development of a novel biomedical imaging system that utilizes a continuous-wave laser source with a custom intensity modulation pattern, ultrasonic phased array for signal detection and processing coupled with a beamforming algorithm for reconstruction of photoacoustic correlation images. Utilization of specific chirped modulation waveforms (``waveform engineering'') achieves dramatic signal-to-noise-ratio increase and improved axial resolution over pulsed laser photoacoustics. The talk will conclude with aspects of instrumental sensitivity of the PA Radar to optical contrast using cancerous breast tissue-mimicking phantoms, super paramagnetic iron oxide nanoparticles as contrast enhancement agents and in-vivo tissue samples.

Mandelis, Andreas

2012-02-01

314

Theory for synthetic aperture radar imaging of the ocean surface - With application to the Tower Ocean Wave and Radar Dependence experiment on focus, resolution, and wave height spectra  

NASA Astrophysics Data System (ADS)

A one-dimensional model for simulating azimuthal SAR imaging of the ocean surface is developed which can admit both the 'distributed surface' and 'velocity bunching' approaches. Computer simulations demonstrate that the time-dependent modulation patterns due to the radar cross section variation and the velocity bunching effects provide optimum focusing around half the phase velocity of the long wave. The results indicate that in the Tower Ocean Wave and Radar Dependence experiment, SAR imaging at L band is approximately linear.

Kasilingam, Dayalan P.; Shemdin, Omar H.

1988-11-01

315

Directional ocean wave measurements in a coastal setting using a focused array imaging radar  

SciTech Connect

A unique focused array imaging Doppler radar was used to measure directional spectra of ocean surface waves in a nearshore experiment performed on the North Carolina Outer Banks. Radar images of the ocean surface`s Doppler velocity were used to generate two dimensional spectra of the radial component of the ocean surface velocity field. These are compared to simultaneous in-situ measurements made by a nearby array of submerged pressure sensors. Analysis of the resulting two-dimensional spectra include comparisons of dominant wave lengths, wave directions, and wave energy accounting for relative differences in water depth at the measurement locations. Limited estimates of the two-dimensional surface displacement spectrum are derived from the radar data. The radar measurements are analogous to those of interferometric synthetic aperture radars (INSAR), and the equivalent INSAR parameters are shown. The agreement between the remote and in-situ measurements suggests that an imaging Doppler radar is effective for these wave measurements at near grazing incidence angles.

Frasier, S.J.; Liu, Y.; Moller, D.; McIntosh, R.E. [Univ. of Massachusetts, Amherst, MA (United States). Microwave Remote Sensing Lab.; Long, C. [Army Engineer Waterways Experiment Station, Duck, NC (United States)

1995-03-01

316

Directional ocean wave measurements in a coastal setting using a focused array imaging radar  

NASA Astrophysics Data System (ADS)

A unique focused array imaging Doppler radar was used to measure directional spectra of ocean surface waves in a nearshore experiment performed on the North Carolina Outer Banks. Radar images of the ocean surface's Doppler velocity were used to generate two dimensional spectra of the radial component of the ocean surface velocity field. These are compared to simultaneous in-situ measurements made by a nearby array of submerged pressure sensors. Analysis of the resulting two-dimensional spectral include comparisons of dominant wave lengths, wave directions, and wave energy accounting for relative differences in water depth at the measurement locations. Limited estimates of the two-dimensional surface displacement spectrum are derived from the radar data. The radar measurements are analagous to those of interferometric synthetic aperture radars (INSAR), and the equivalent INSAR parameters are shown. The agreement between the remote and in-situ measurements suggests that an imaging Doppler radar is effective for these wave measurements at near grazing incidence angles.

Frasier, Stephen J.; Liu, Yong; Moller, Delwyn; McIntosh, Robert E.; Long, Charles

1995-03-01

317

A method for retrieving the directional ocean wave spectra from synthetic aperture radar image  

NASA Astrophysics Data System (ADS)

Directional ocean wave spectra can describe the energy distribution of ocean wave and play an important role in oceanography. Synthetic aperture radar (SAR) can measure wave spectra based on a nonlinear mapping model between the image spectra (or cross spectra) and wave spectra. Due to the complexity of variable estimation and wave number cut off in azimuth direction in the mapping process, some scientists have been endeavoring to improve the retrieval of wave spectra. The paper proposes a method for the retrieval, which don't depend on any external information except wind direction. It separates into two parts. In part 1, the spectra for real image or the cross spectra for complex image are calculated. And the modulation transfer function (MTF) is estimated including real aperture radar (RAR) MTF and velocity bunching. Then the wave spectra are retrieved by direct dividing based on the quasi-linear relation. The 180° ambiguity is removed from the imaginary part of cross spectra or the wind direction. The significant wave height (Hs), peak wave wavelength (L) and peak wave direction (D) are extracted from the retrieval. If the angle between the D and the azimuth direction is higher than 45°, the retrieval is finished. If the angle is lower than 45°, we go on retrieving. In part 2, the first guess spectra are needed to compensate the lost wave information, which can be parametrically constructed based on the retrieved wave spectra in part 1. Finally the wave spectra are iteratively retrieved from the first guess spectra based on the nonlinear relation. The Envisat ASAR images are used to validate the method. In case 1, the RMSE between this method and SARTool on D, L, Hs is 7.6°, 19.7 m, 0.18 m respectively. In case 2, the RMSE between this method and Jason-1 on Hs is 0.5 m.

Ren, Lin; Yang, Jingsong; Chen, Peng

2012-09-01

318

A comparative study of algorithms for radar imaging from gapped data  

NASA Astrophysics Data System (ADS)

In ultra wideband (UWB) radar imagery, there are often cases where the radar's operating bandwidth is interrupted due to various reasons, either periodically or randomly. Such interruption produces phase history data gaps, which in turn result in artifacts in the image if conventional image reconstruction techniques are used. The higher level artifacts severely degrade the radar images. In this work, several novel techniques for artifacts suppression in gapped data imaging were discussed. These include: (1) A maximum entropy based gap filling technique using a modified Burg algorithm (MEBGFT); (2) An alternative iteration deconvolution based on minimum entropy (AIDME) and its modified version, a hybrid max-min entropy procedure; (3) A windowed coherent CLEAN algorithm; and (4) Two-dimensional (2-D) periodically-gapped Capon (PG-Capon) and APES (PG-APES) algorithms. Performance of various techniques is comparatively studied.

Xu, Xiaojian; Luan, Ruixue; Jia, Li; Huang, Ying

2007-10-01

319

Space Shuttle Columbia views the world with imaging radar: The SIR-A experiment  

Microsoft Academic Search

Images acquired by the Shuttle Imaging Radar (SIR-A) in November 1981, demonstrate the capability of this microwave remote sensor system to perceive and map a wide range of different surface features around the Earth. A selection of 60 scenes displays this capability with respect to Earth resources - geology, hydrology, agriculture, forest cover, ocean surface features, and prominent man-made structures.

J. P. Ford; J. B. Cimino; C. Elachi

1983-01-01

320

Achieving EMC in high frequency and high power switching environment on Radar Imaging Satellite  

Microsoft Academic Search

Satellite deck provides a challenging electro magnetic (EM) environment as the overall volume available is limited and a number of DC-DC converters and clocks are present. Add to this high frequency and high power switching the electro magnetic interference (EMI) scenario couldn't be worse. Radar imaging satellite (RISAT) India's first satellite with day night imaging capability, slated for launch by

G. V. C. Rajan; V. B. Pramod

2008-01-01

321

Tectonic Geomorphology of the Andes with SIR-A and SIR-B (Shuttle Imaging Radar).  

National Technical Information Service (NTIS)

Data takes from SIR-A and SIR-B (Shuttle Imaging Radar) crossed all of the principal geomorphic provinces of the central Andes between 17 and 34 S latitude. In conjunction with Thematic Mapping images and photographs from hand-held cameras as well as from...

A. L. Bloom E. J. Fielding

1986-01-01

322

Imaging targets embedded in a lossy half space with synthetic aperture radar  

Microsoft Academic Search

This paper addresses theoretical aspects of forming images from an airborne synthetic aperture radar (SAR) of targets buried below the Earth's surface. Soil is generally a lossy, dispersive medium, with wide ranging variability in these attributes depending on soil type, moisture content, and a host of other physical properties. Focussing a SAR subsurface image presents new dimensions of complexity relative

A. W. Doerry; B. C. Brock; B. Boverie; D. Cress

1994-01-01

323

Ocean wave extraction from RADARSAT synthetic aperture radar inter-look image cross-spectra  

Microsoft Academic Search

This study is concerned with the extraction of directional ocean wave spectra from synthetic aperture radar (SAR) image spectra. The statistical estimation problem underlying the wave-SAR inverse problem is examined in detail in order to properly quantify the wave information content of SAR. As a concrete focus, a data set is considered comprising six RADARSAT SAR images co-located with a

Michael Dowd; Paris W. Vachon; Fred W. Dobson; Richard B. Olsen

2001-01-01

324

Estimation of a Constant False Alarm Rate Processing Loss for a High- Resolution Maritime Radar System.  

National Technical Information Service (NTIS)

This report addresses a problem of estimation of a constant false alarm rate (CFAR) processing loss for a high-resolution maritime radar system on an example of a generic radar system Anti-Submarine Warfare mode and discusses approaches to modelling of th...

I. Antipov J. Baldwinson

2008-01-01

325

Tomographic imaging with ultra-wideband noise radar using time-domain data  

NASA Astrophysics Data System (ADS)

This paper investigates the feasibility of using a noise waveform in an ultra-wideband (UWB) radar system for two-dimensional tomographic imaging of a stationary object with a multistatic tomographic geometry. Multiple UWB transmitters and receivers are positioned along each side of the imaging area. We perform several numerical simulations in time-domain, and the successful imaging of the target is achieved by visual inspection of the formed images.

Shin, Hee Jung; Narayanan, Ram M.; Rangaswamy, Muralidhar

2013-05-01

326

Image Processing Software  

NASA Astrophysics Data System (ADS)

ABSTRACT: A brief description of astronomical image software is presented. This software was developed in a Digital Micro Vax II Computer System. : St presenta una somera descripci6n del software para procesamiento de imagenes. Este software fue desarrollado en un equipo Digital Micro Vax II. : DATA ANALYSIS - IMAGE PROCESSING

Bosio, M. A.

1990-11-01

327

HERMES: a high-speed radar imaging system for inspection of bridge decks  

SciTech Connect

Corrosion of rebar in concrete bridges causes subsurface cracks and is a major cause of structural degradation that necessitates repair or replacement. Early detection of corrosion effects can limit the location and extent of necessary repairs, while providing long-term information about the infrastructure status. Most current detection methods, however, are destructive of the road surface and require closing or restricting traffic while the tests are performed. A ground-penetrating radar imaging system has been designed and developed that will perform the nondestructive evaluation of road-bed cracking at traffic speeds; i.e., without the need to restrict traffic flow. The first-generation system (called the HERMES bridge inspector), consists of an offset-linear array of 64 impulse radar transceivers and associated electronics housed in a trailer. Computers in the trailer and in the towing vehicle control the data acquisition, processing, and display. Cross-road resolution is three centimeters at up to 30 cm in depth, while down-road resolution depends on speed; 3 cm below 20 mph up to 8 cm at 50 mph. A two-meter- wide path is inspected on each pass over the roadway. This paper, describes the design of this system, shows preliminary results, and lays out its deployment schedule.

Azevedo, S.G.

1996-10-26

328

Three radar imaging methods based on the one-dimensional laser range profile  

NASA Astrophysics Data System (ADS)

One-dimensional range profile is known as a simple radar imaging technology. Based on the imaging mechanism, the laser range profiles (LRPS) of the convex rotators in three different methods, which named as the Beam Scattering Method (BS method), Radar Cross Section Method (RCS method) and Surface Elements Method (SE method),were studied. In detail, BS method, which combined the laser beam pulse scattering theory and radar equation, is the very model that can be applied to the convex quadric rotary bodies, however, it may produce singular solutions in certain incident directions. The RCS method is just an extension of the theory of radar cross section theory and radar equation. According to the definition, the simplest forms of RCS which were then substituted into the radar equation were obtained, finally the one-dimensional range profiles were analytically resolved. The SE Method is a much more comprehensive theory to get the laser range profiles of arbitrary objects. The object should be first divided into numerous small triangle facets, and sum the backscattering power of these facets in the same distance, and in this way the final LRPS were deduced. In the meanwhile, the SE method is the most convenient way to evolve into the three-dimensional range profile. In the paper, the LRPS of a cone based on the three models above were simulated, it was found that the features and shape of each profiles were similar basically, but theoretical correction to SE method was still needed.

Mou, Yuan; Wu, Zhen-sen; Qu, Tan; Liao, Run-gui

2013-09-01

329

Methods in Astronomical Image Processing  

NASA Astrophysics Data System (ADS)

A Brief Introductory Note History of Astronomical Imaging Astronomical Image Data Images in Various Formats Digitized Image Data Digital Image Data Philosophy of Astronomical Image Processing Properties of Digital Astronomical Images Human Image Processing Astronomical vs. Computer Science Image Processing Basic Tools of Astronomical Image Processing Display Applications Calibration of Intensity Scales Calibration of Length Scales Image Re-shaping Feature Enhancement Noise Suppression Noise and Error Analysis Image Processing Packages: Design of AIPS and MIDAS AIPS MIDAS Reduction of CCD Data Bias Subtraction Clipping Preflash Subtraction Dark Subtraction Flat Fielding Sky Subtraction Extinction Correction Deconvolution Methods Rebinning/Combining Summary and Prospects for the Future

Jörsäter, S.

330

Atmospheric radar imaging using multiple-receiver and multiple-frequency techniques  

NASA Astrophysics Data System (ADS)

Atmospheric radar imaging techniques have shown promise in revealing the fine-scale structure of the atmosphere within the resolution volume of the radar. Enhanced resolution can be obtained in both angle and range by using spaced receivers and shifted frequencies, respectively. The distinct techniques have been termed coherent radar imaging (CRI) for angular resolution enhancement and range imaging (RIM) for radial resolution improvement. Because of the mathematical similarities between CRI and RIM it is possible to derive a generalization of both techniques. In this work, the three-dimensional (3-D) imaging technique, which uses multiple receivers and multiple frequencies simultaneously, is developed for the first time. Three-dimensional imaging has the advantage of mitigating the limitations of beam width as well as pulse width of a conventional radar to simultaneously improve both angular and range resolution. It is shown that CRI and RIM are special cases of 3-D imaging. The mathematical problem is formulated as an inverse problem with solutions provided by the Fourier, Capon, and maximum entropy (MaxEnt) methods. These three 3-D imaging methods are verified and statistically tested through numerical simulations.

Yu, Tian-You; Palmer, Robert D.

2001-01-01

331

Image quality analysis of the vibrating sparse MIMO antenna array of the airborne 3D imaging radar ARTINO  

Microsoft Academic Search

ARTINO1 is a new radar system, integrated in a small mobile and dismountable experimental UAV2. The side- looking geometry of usual SAR3 systems produces shading effects of the scene to be imaged. ARTINO overcomes this restriction with the ability to image the direct overflown area (Nadir looking) in three dimensions. The effects caused by vibrations of the used sparse MIMO4

Jens Klare; Delphine Cerutti-Maori; Andreas Brenner; Joachim Ender

2007-01-01

332

Integration of speckle de-noising and image segmentation using Synthetic Aperture Radar image for flood extent extraction  

NASA Astrophysics Data System (ADS)

Flood is one of the detrimental hydro-meteorological threats to mankind. This compels very efficient flood assessment models. In this paper, we propose remote sensing based flood assessment using Synthetic Aperture Radar (SAR) image because of its imperviousness to unfavourable weather conditions. However, they suffer from the speckle noise. Hence, the processing of SAR image is applied in two stages: speckle removal filters and image segmentation methods for flood mapping. The speckle noise has been reduced with the help of Lee, Frost and Gamma MAP filters. A performance comparison of these speckle removal filters is presented. From the results obtained, we deduce that the Gamma MAP is reliable. The selected Gamma MAP filtered image is segmented using Gray Level Co-occurrence Matrix (GLCM) and Mean Shift Segmentation (MSS). The GLCM is a texture analysis method that separates the image pixels into water and non-water groups based on their spectral feature whereas MSS is a gradient ascent method, here segmentation is carried out using spectral and spatial information. As test case, Kosi river flood is considered in our study. From the segmentation result of both these methods are comprehensively analysed and concluded that the MSS is efficient for flood mapping.

Senthilnath, J.; Shenoy, H. Vikram; Rajendra, Ritwik; Omkar, S. N.; Mani, V.; Diwakar, P. G.

2013-06-01

333

Image Processing REST Web Services.  

National Technical Information Service (NTIS)

In this report, we present a readily extensible architecture for image processing based on representational state transfer (REST) Web services. Relying on just two types of resources, images and collections of images, any number of new image processing al...

C. Schlesiger R. P. Winkler

2013-01-01

334

Revolutionising incoherent scatter science with EISCAT_3D: A European three-dimensional imaging radar for atmospheric and geospace research  

NASA Astrophysics Data System (ADS)

EISCAT_3D will be Europe's next-generation radar for the study of the high-latitude atmosphere and geospace, located in northern Fenno-Scandinavia, with capabilities going well beyond anything currently available to the international research community. The facility will consist of several very large active phased-array antenna transmitters/receivers, and multiple passive sites located in three countries. Depending on the available funding, EISCAT_3D will be comprised of tens of thousands, up to more than 100 000, individual antenna elements. EISCAT_3D combines several key attributes which have never before been available together in a single radar, such as volumetric imaging and tracking, aperture synthesis imaging, multistatic configuration, improved sensitivity and transmitter flexibility. The use of advanced beam-forming technology allows the beam direction to be switched in milliseconds, rather than the minutes which it can take to re-position dish-based radars. This allows very wide spatial coverage to be obtained, by interleaving multiple beam directions to carry out quasi-simultaneous volumetric imaging. It also allows objects such as satellites and space debris to be tracked across the sky. At the passive sites, the design allows for at least five simultaneous beams at full bandwidth, rising to over twenty beams if the bandwidth is limited to the ion line, allowing the whole range of the transmitted beam to be imaged from each passive site, using holographic radar techniques. EISCAT_3D has a modular configuration, which allows an active array to be split into smaller elements to be used for aperture synthesis imaging. The result will be an entirely new data product, consisting of range-dependent images of small sub-beamwidth scale structures, with sizes down to 20 m. EISCAT_3D will be the first phased array incoherent scatter radar to use a multistatic configuration. A minimum of five radar sites, consisting of two pairs located around 120 km and 250 km from the active site respectively, on baselines running East and South from the active core, is enivisaged. This provides an optimal geometry for calculation of vector velocities in the middle and upper atmosphere. The gain of the EISCAT_3D antennas and the large size of the active site arrays will deliver an enormous increase in the figure-of-merit relative to any of EISCAT's existing radars. An active site of 5,000 elements would already exceed the performance of the current EISCAT VHF system, while an active site comprising 16,000 elements, as suggested in the Design Study carried out from 2005 to 2009, will exceed the sensitivity of the present VHF radar by an order of magnitude. Each transmitter unit will have its own signal generator, allowing the generation and transmission of arbitrary waveforms, limited only by the available transmission bandwidth and spectrum allocation by the frequency management authorities. This unique innovation allows the implementation of all currently used and envisaged modulation schemes and antenna codings (such as polyphase alternating codes, array tapering, orbital angular momentum beams) and also provides the possibility to adopt any kind of future code. In addition, it will allow advanced clutter mitigation strategies such as adaptive null steering and null shaping. In this talk the upper atmosphere and geospace science case for EISCAT_3D is reviewed. Studies of the atmospheric energy budget, space plasma physics with both small-scale structures and large-scale processes, as well as geospace environment monitoring and possible service applications are reviewed, showing recent highlights from the current EISCAT incoherent scatter radars for comparison.

Turunen, Esa; McCrea, Ian; Kosch, Mike

2010-05-01

335

Bistatic Synthetic Aperture Radar Imaging for Arbitrary Flight Trajectories  

Microsoft Academic Search

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

Can Evren Yarman; Birsen Yazici; Margaret Cheney

2008-01-01

336

Classification of Radar Images in Polarimetric Remote Sensing  

Microsoft Academic Search

This paper describes the use of polarimetric data for Earth terrain classification. The Cloude (1992) target decomposition theorem is applied to classify the scene into several classes having each one a distinct physical interpretation. The implemented algorithm, under its new version, uses two parameters, not often exploited in radar remote sensing, namely the entropy and a parameter linked to scattering

Ziad Belhadj; Amel Benazza; Naceur Hidoussi

1998-01-01

337

Filtering of radar images based on blind evaluation of noise characteristics  

NASA Astrophysics Data System (ADS)

A common assumption concerning noise in radar images is that it is of multiplicative nature and spatially uncorrelated. Meanwhile, recent studies have shown that additive noise component cannot be neglected, especially for images formed by side look aperture radars (SLARs). Moreover, majority of radar image filtering techniques are designed under assumption that noise is i.i.d., i.e. spatially uncorrelated. However, in many practical situations the latter assumption is not true. Besides, spatial correlation properties of noise can be different and they are often a priori unknown. In this paper we demonstrate that complex statistical and spatial correlation characteristics of noise in radar images can and should be taken into consideration at image filtering stage. We design a modification of the denoising algorithm based on discrete cosine transform (DCT) that is able to easily incorporate a priori information or obtained estimates of noise statistical and spatial correlation characteristics. This can be done in automatic (blind) manner due to utilizing a sequence of blind estimation operations. We present simulation results that show appropriate accuracy and robustness of these operations. Finally, real life image filtering examples are given that confirm the effectiveness of the designed techniques.

Lukin, Vladimir V.; Ponomarenko, Nikolay N.; Abramov, Sergey K.; Vozel, Benoit; Chehdi, Kacem; Astola, Jaakko T.

2008-10-01

338

SHUTTLE IMAGING RADAR: PHYSICAL CONTROLS ON SIGNAL PENETRATION AND SUBSURFACE SCATTERING IN THE EASTERN SAHARA.  

USGS Publications Warehouse

It is found that the Shuttle Imaging Radar A (SIR-A) signal penetration and subsurface backscatter within the upper meter or so of the sediment blanket in the Eastern Sahara of southern Egypt and northern Sudan are enhanced both by radar sensor parameters and by the physical and chemical characteristics of eolian and alluvial materials. The near-surface stratigraphy, the electrical properties of materials, and the types of radar interfaces found to be responsible for different classes of SIR-A tonal response are summarized. The dominant factors related to efficient microwave signal penetration into the sediment blanket include 1) favorable distribution of particle sizes, 2) extremely low moisture content and 3) reduced geometric scattering at the SIR-A frequency (1. 3 GHz). The depth of signal penetration that results in a recorded backscatter, called radar imaging depth, was documented in the field to be a maximum of 1. 5 m, or 0. 25 times the calculated skin depth, for the sediment blanket. The radar imaging depth is estimated to be between 2 and 3 m for active sand dune materials.

Schaber, Gerald, G.; McCauley, John, F.; Breed, Carol, S.; Olhoeft, Gary, R.

1986-01-01

339

The detection of weak signal patterns in radar ocean intensity images  

SciTech Connect

Detection of weak patterns in radar ocean RCS images is complicated by the fact that signals and noise are interactive rather than additive and the ambient noise background is non Gaussian or even strongly non Gaussian at low grazing angles. This paper addresses this difficult problem with the aid of two simplifying assumptions: (1) the signal modulation is weak, and (2) departure from Gaussianity is small. In situations where this departure is large, an approach is suggested for reducing this non Gaussianity. The relevant weak signal detection theory, based on the Likelihood ratio, is reviewed and adapted for use in the analysis. The approach to this problem, similar to that previously used for complex images, is facilitated by approximating the multivariate probability distributions as a composite integral involving underlying processes which are assumed to be Gaussian. This formulation, subject to the approximations in the analysis, permits derivation of an ideal detection statistic (which determines the form of optimum receiver) and a signal/noise ratio which characterizes detection performance in the weak signal limit. Implications for image processing are discussed and directions for future analysis are suggested.

Manasse, R.

1996-06-15

340

Simulation of radar rainfall errors and their propagation into rainfall-runoff processes  

NASA Astrophysics Data System (ADS)

Radar rainfall data compared with rain gauge measurements provide higher spatial and temporal resolution. However, radar data obtained form reflectivity patterns are subject to various errors such as errors in Z-R relationship, vertical profile of reflectivity, spatial and temporal sampling, etc. Characterization of such uncertainties in radar data and their effects on hydrologic simulations (e.g., streamflow estimation) is a challenging issue. This study aims to analyze radar rainfall error characteristics empirically to gain information on prosperities of random error representativeness and its temporal and spatial dependency. To empirically analyze error characteristics, high resolution and accurate rain gauge measurements are required. The Goodwin Creek watershed located in the north part of Mississippi is selected for this study due to availability of a dense rain gauge network. A total of 30 rain gauge measurement stations within Goodwin Creak watershed and the NWS Level II radar reflectivity data obtained from the WSR-88dD Memphis radar station with temporal resolution of 5min and spatial resolution of 1 km2 are used in this study. Radar data and rain gauge measurements comparisons are used to estimate overall bias, and statistical characteristics and spatio-temporal dependency of radar rainfall error fields. This information is then used to simulate realizations of radar error patterns with multiple correlated variables using Monte Calro method and the Cholesky decomposition. The generated error fields are then imposed on radar rainfall fields to obtain statistical realizations of input rainfall fields. Each simulated realization is then fed as input to a distributed physically based hydrological model resulting in an ensemble of predicted runoff hydrographs. The study analyzes the propagation of radar errors on the simulation of different rainfall-runoff processes such as streamflow, soil moisture, infiltration, and over-land flooding.

Aghakouchak, A.; Habib, E.

2008-05-01

341

The Image Processing Data Manager.  

National Technical Information Service (NTIS)

The document describes a model of an image processing data management system called the Image Processing Data Manager. The Data Manager is an interactive program which, using a data base, aids the user in performing selective image processing. It answers ...

R. E. Nimensky J. Bebb

1973-01-01

342

UWB radar imaging system with two-element receiving array antenna  

Microsoft Academic Search

UWB signals can propagate in cluttered environment and opaque media that enables exploring hidden homogeneities through registering and processing backscattered signals. One of such an application is UWB through-wall vision radar (UWBR), Sostanovsky (2004), Radar Vision (2005). A prototype of low-complexity and low-cost portable UWBR sensor with a small receiving antenna array is presented. Several key implementation issues are discussed

Dmitriy L. Sostanovsky; A. O. Boryssenko; E. S. Boryssenko

2005-01-01

343

Image simulation of high resolution radar for polarimetric scattering from heterogeneous canopy surface  

Microsoft Academic Search

Polarimetric imaging of high resolution SAR is one of most important advances in microwave remote sensing. This paper, using fully polarimetric Mueller matrix solution and ray tracing method. Simulates radar images for fully polarimetric scattering from heterogeneous canopy surface. Non-uniform 3D structures and non-uniform distribution of multi-components of surface canopy are taken into account. Simulated image texture demonstrates spatial variation

Ya-Qiu Jin; Wei Zhang

2000-01-01

344

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

345

Automatic target classification of man-made objects in synthetic aperture radar images using Gabor wavelet and neural network  

NASA Astrophysics Data System (ADS)

Processing of synthetic aperture radar (SAR) images has led to the development of automatic target classification approaches. These approaches help to classify individual and mass military ground vehicles. This work aims to develop an automatic target classification technique to classify military targets like truck/tank/armored car/cannon/bulldozer. The proposed method consists of three stages via preprocessing, feature extraction, and neural network (NN). The first stage removes speckle noise in a SAR image by the identified frost filter and enhances the image by histogram equalization. The second stage uses a Gabor wavelet to extract the image features. The third stage classifies the target by an NN classifier using image features. The proposed work performs better than its counterparts, like K-nearest neighbor (KNN). The proposed work performs better on databases like moving and stationary target acquisition and recognition against the earlier methods by KNN.

Vasuki, Perumal; Roomi, S. Mohamed Mansoor

2013-01-01

346

Image sets for satellite image processing systems  

NASA Astrophysics Data System (ADS)

The development of novel image processing algorithms requires a diverse and relevant set of training images to ensure the general applicability of such algorithms for their required tasks. Images must be appropriately chosen for the algorithm's intended applications. Image processing algorithms often employ the discrete wavelet transform (DWT) algorithm to provide efficient compression and near-perfect reconstruction of image data. Defense applications often require the transmission of images and video across noisy or low-bandwidth channels. Unfortunately, the DWT algorithm's performance deteriorates in the presence of noise. Evolutionary algorithms are often able to train image filters that outperform DWT filters in noisy environments. Here, we present and evaluate two image sets suitable for the training of such filters for satellite and unmanned aerial vehicle imagery applications. We demonstrate the use of the first image set as a training platform for evolutionary algorithms that optimize discrete wavelet transform (DWT)-based image transform filters for satellite image compression. We evaluate the suitability of each image as a training image during optimization. Each image is ranked according to its suitability as a training image and its difficulty as a test image. The second image set provides a test-bed for holdout validation of trained image filters. These images are used to independently verify that trained filters will provide strong performance on unseen satellite images. Collectively, these image sets are suitable for the development of image processing algorithms for satellite and reconnaissance imagery applications.

Peterson, Michael R.; Horner, Toby; Temple, Asael

2011-05-01

347

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

348

Correlations between Cassini VIMS spectra and RADAR SAR images: Implications for Titan's surface composition and the character of the Huygens Probe Landing Site  

NASA Astrophysics Data System (ADS)

Titan's vast equatorial fields of RADAR-dark longitudinal dunes seen in Cassini RADAR synthetic aperture images correlate with one of two dark surface units discriminated as "brown" and "blue" in Visible and Infrared Mapping Spectrometer (VIMS) color composites of short-wavelength infrared spectral cubes (RGB as 2.0, 1.6, 1.3 ?m). In such composites bluer materials exhibit higher reflectance at 1.3 ?m and lower at 1.6 and 2.0 ?m. The dark brown unit is highly correlated with the RADAR-dark dunes. The dark brown unit shows less evidence of water ice suggesting that the saltating grains of the dunes are largely composed of hydrocarbons and/or nitriles. In general, the bright units also show less evidence of absorption due to water ice and are inferred to consist of deposits of bright fine precipitating tholin aerosol dust. Some set of chemical/mechanical processes may be converting the bright fine-grained aerosol deposits into the dark saltating hydrocarbon and/or nitrile grains. Alternatively the dark dune materials may be derived from a different type of air aerosol photochemical product than are the bright materials. In our model, both the bright aerosol and dark hydrocarbon dune deposits mantle the VIMS dark blue water ice-rich substrate. We postulate that the bright mantles are effectively invisible (transparent) in RADAR synthetic aperture radar (SAR) images leading to lack of correlation in the RADAR images with optically bright mantling units. RADAR images mostly show only dark dunes and the water ice substrate that varies in roughness, fracturing, and porosity. If the rate of deposition of bright aerosol is 0.001-0.01 ?m/yr, the surface would be coated (to optical instruments) in hundreds-to-thousands of years unless cleansing processes are active. The dark dunes must be mobile on this very short timescale to prevent the accumulation of bright coatings. Huygens landed in a region of the VIMS bright and dark blue materials and about 30 km south of the nearest occurrence of dunes visible in the RADAR SAR images. Fluvial/pluvial processes, every few centuries or millennia, must be cleansing the dark floors of the incised channels and scouring the dark plains at the Huygens landing site both imaged by Descent Imager/Spectral Radiometer (DISR).

Soderblom, Laurence A.; Kirk, Randolph L.; Lunine, Jonathan I.; Anderson, Jeffrey A.; Baines, Kevin H.; Barnes, Jason W.; Barrett, Janet M.; Brown, Robert H.; Buratti, Bonnie J.; Clark, Roger N.; Cruikshank, Dale P.; Elachi, Charles; Janssen, Michael A.; Jaumann, Ralf; Karkoschka, Erich; Mouélic, Stéphane Le; Lopes, Rosaly M.; Lorenz, Ralph D.; McCord, Thomas B.; Nicholson, Philip D.; Radebaugh, Jani; Rizk, Bashar; Sotin, Christophe; Stofan, Ellen R.; Sucharski, Tracie L.; Tomasko, Martin G.; Wall, Stephen D.

2007-11-01

349

Rapid beamsteering reflectarrays for mm-wave and submm-wave imaging radars  

NASA Astrophysics Data System (ADS)

Recent developments in millimetre to submillimetre-wave imaging radars with excellent ranging resolution provide an attractive route towards stand-off imaging of concealed explosives at ranges up to several tens of meters. Present systems typically rely on only one transceiver, coupled with an optomechanical scanning system for image formation. This limits the image acquisition speed to several seconds/frame. Frame rate can in principle be increased with increasing the channel count but this adds substantially to the system complexity and cost, while only providing a modest speed increase. In this paper we present preliminary designs for rapid electronic beam steering system that could provide a way towards real-time millimetre-wave to submillimetre-wave imaging radars.

Luukanen, Arttu; Ala-Laurinaho, Juha; Gomes Martins, David; Häkli, Janne; Koivisto, Päivi; Pursula, Pekka; Rantakari, Pekka; Säily, Jussi; Tamminen, Aleksi; Tuovinen, Reijo; Sipilä, Markku

2011-05-01

350

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

351

Polarimetric processing techniques for coherent stepped-frequency ground-penetrating radar systems: applications toward detection of buried utilities  

NASA Astrophysics Data System (ADS)

Stepped frequency radar systems are gaining popularity in ground penetrating radar applications since these can be designed to be phase coherent, thereby taking advantage of coherent processing techniques for target detection and clutter rejection. One such system is the GeoRadar model 1000B GPR system. This system operates over the 100 - 1000 MHz frequency range with a step size of 2 MHz and a modulation frequency of 500 kHz. The magnitudes of the in-phase (I) and the quadrature (Q) channels of the received radar return signal are combined vectorially to yield the amplitude, which is then fast Fourier transformed (FFT-ed) and displayed as the depth profile. The original design of the system used a pair of log-spiral antennas for transmit and receive functions. Although log-spiral antennas are broadband and frequency- independent, their polarization, although linear at each frequency, rotates as the frequency is stepped. The images acquired under these conditions are similar to those obtained by circularly polarized antennas, making it difficult to detect long slender objects, such as pipes and cables, which can be better detected by linearly polarized antennas oriented in the same direction. In order to enhance the performance of the system, a fully polarimetric processing technique has been implemented. A set of four wideband linearly polarized antennas is used, two for transmit and two for receive, each of the two being orthogonally polarized. The system sequentially transmits, orthogonal polarizations, while the receiver simultaneously measures both reflected polarizations. The transmit polarization switching rate is high enough to ensure that the successive pulses are correlated, thereby appearing as if taken from the same location. Reflected data from all four linear combinations of transmit and receive polarizations are then coherently processed to yield the polarimetric image of the target. Sandbox test results indicate that the system is better able to image pipes and utilities.

Narayanan, Ram M.; Becker, Randall T.; Bashforth, Michael B.

1999-10-01

352

Web Application System with Synthetic Aperture Rader Image Processing for Education  

Microsoft Academic Search

Remotely sensed images observed by synthetic aperture radar (SAR) become to be more significant for a variety of purposes. It is necessary to process and focus SAR images at a user's side for required precision. This paper presents a concept, a system structure, and an implementation method for a web application system with a SAR image processing for education. The

Yuuhei Teramoto; Yosuke Ito; Kenji Abe

2009-01-01

353

Titan's Surface: Distribution Of Endogenic And Exogenic Processes From Cassini Radar Data  

NASA Astrophysics Data System (ADS)

Cassini's Titan Radar Mapper has imaged the surface of Titan on six flybys to date, collecting Synthetic Aperture Radar (SAR) data at spatial resolution ranging from 300 m - 2km. These data reveal that Titan's surface has been modified by both endogenic (volcanism and tectonism) and exogenic (impact cratering and erosion) processes. Although only 10% of the surface of Titan has been imaged using SAR, the acquired swaths are distributed over a wide latitudinal range, enabling some preliminary conclusions to be drawn about the global distribution of processes. Cryovolcanic units have been identified mostly at mid-latitudes (40-60 N), though some depressions that may be calderas have been identified at high latitudes (> 75N, see Mitchell et al., this volume) and possible cryovolcanic features at lower latitudes have been suggested by VIMS data (e.g., Sotin et al., 2005, Science 435). Ridges and mountains that are probably of tectonic origin have been seen mostly at low latitudes, while drainage channels and candidate impact features have been identified in all swaths. Fields of dunes (Titan's "sand seas") are mostly equatorial, but extend as far as 60 degrees. In contrast, lakes and a shoreline feature have been seen at latitudes over 80 degrees. The distribution of lacustrine features is consistent with colder temperatures and more precipitation at high latitudes. The distribution of dunes is as expected from Titan's winds (Lorenz et al., 2006, Science 312; Radebaugh et al., this issue). Erosion by fluvial processes may have occurred on a global scale. Future data will allow us to further constrain the distribution of tectonism and volcanism, providing valuable input for models of Titan's interior.

Lopes, Rosaly M.; Stofan, E. R.; Mitchell, K. L.; Wall, S. D.; Wood, C. A.; Lorenz, R. D.; Paganelli, F.; Lunine, J.; Wall, E.; Radebaugh, J.; Cassini RADAR Team

2006-09-01

354

High power X-band monopulse tracking feed for the Lincoln Laboratory Long-Range Imaging Radar  

Microsoft Academic Search

The feed required for the 120-ft diameter M.I.T. Long Range Imaging Radar antenna must be capable of transmitting a power of 800 kW with a 50-percent duty cycle at 10 GHz. It must also provide very good amplitude and phase control for the radar signals over a 10-percent bandwidth. After installation in the radar, the feed will be used to

K. R. Goudey; A. F. Sciambi Jr.

1978-01-01

355

Real-Time Optical Processor for Synthetic Aperture Radar Image Formation.  

National Technical Information Service (NTIS)

An acousto-optic processor which forms synthetic aperture radar images in real-time is described. It employs a space and time integrating architecture to perform the required two dimensional matched filtering operation as a sequence of one dimensional pro...

K. T. Stalker P. A. Molley F. M. Dickey

1987-01-01

356

Implementation and Validation of Range Imaging on a UHF Radar Wind Profiler  

Microsoft Academic Search

The available range resolution of pulsed radar wind profilers is usually limited by bandwidth restrictions. Range imaging (RIM) has recently been developed as a means of mitigating these limitations by operating the wind profilers over a small set of distinct transmitter frequencies. A constrained optimization method can then be used to generate high-resolution maps of the reflectivity field as a

Phillip B. Chilson; Tian-You Yu; Richard G. Strauch; Andreas Muschinski; Robert D. Palmer

2003-01-01

357

Space Shuttle thermal protection system inspection by 3D imaging laser radar  

Microsoft Academic Search

NASA has developed a sensor suite to inspect the Space Shuttle Thermal Protection System while the Shuttle is flying in orbit. When the Space Shuttle returns to flight, it will carry a 3D Imaging Laser Radar as part of the sensor suite to observe the Thermal Protection System and indicate any damages that may need to be repaired before return

James C. Lamoreux; James D. Siekierski; J. P. N. Carter

2004-01-01

358

Imaging the subsurface stratigraphy in the Ubehebe hydrovolcanic field (Death Valley, California) using ground penetrating radar  

Microsoft Academic Search

Ground penetrating radar (GPR) surveys were carried out to collect subsurface images of the basaltic base surge deposits in the Ubehebe hydrovolcanic field, Death Valley National Park, California. Antennae with frequencies of 50, 100 and 200 MHz were used. This technique allowed the collection of useful geologic data, for example, the lower stratigraphic boundary of the pyroclastic deposits can be

B. Cagnoli; J. K Russell

2000-01-01

359

A photon counting 3-D imaging laser radar for advanced discriminating interceptor seekers  

Microsoft Academic Search

It is possible to produce a lightweight photon-counting laser radar which images targets in three spatial dimensions. In this paper, we illustrate as an example, the sensor parameters of an exoatmospheric interceptor seeker which, after radiometric bulk filtering, can perform discrimination and aim-point selection via 3D size, shape, and orientation measurements.

R. M. Marino; R. M. Spitzberg; M. J. Bohrer

1993-01-01

360

An Accurate Imaging Algorithm with Scattered Waveform Estimation for UWB Pulse Radars  

Microsoft Academic Search

SUMMARY UWB pulse radars that offer target shape estimation are promising as imaging techniques for household or rescue robots. We have already proposed an efficient algorithm for a shape estimation method SEABED which is a fast algorithm based on a reversible transform. SEABED extracts quasi wavefronts from received signals with the filter that matches the transmitted waveform. However, the scattered

Shouhei Kidera; Takuya Sakamoto; Satoshi Sugino; Toru Sato

2006-01-01

361

A High-Resolution Imaging Algorithm without Derivatives Based on Waveform Estimation for UWB Radars  

Microsoft Academic Search

SUMMARY UWB pulse radars enable us to measure a target location with high range-resolution, and so are applicable for measurement systems for robots and automobile. We have already proposed a robust and fast imaging algorithm with an envelope of circles, which is suitable for these applications. In this method, we determine time delays from received sig- nals with the matched

Shouhei Kidera; Takuya Sakamoto; Toru Sato

2007-01-01

362

Spectral signal to clutter and thermal noise properties of ocean wave imaging synthetic aperture radars  

Microsoft Academic Search

The high wavenumber detection cut-off is determined above which the spectrum of ocean waves imaged by a synthetic aperture radar (SAR) is lost in the background noise spectrum consisting of the clutter noise associated with the Rayleigh statistics of the backscattering surface and the thermal noise originating in the SAR system itself. For given power, the maximum detection cut-off wavenumber

Werner Alpers; Klaus Hasselmann

1982-01-01

363

Portable concealed weapon detection using millimeter-wave FMCW radar imaging  

NASA Astrophysics Data System (ADS)

Unobtrusive detection of concealed weapons on persons or in abandoned bags would provide law enforcement a powerful tool to focus resources and increase traffic throughput in high- risk situations. We have developed a fast image scanning 94 GHz radar system that is suitable for portable operation and remote viewing of radar data. This system includes a novel fast image-scanning antenna that allows for the acquisition of medium resolution 3D millimeter wave images of stationary targets with frame times on order of one second. The 3D radar data allows for potential isolation of concealed weapons from body and environmental clutter such as nearby furniture or other people. The radar is an active system so image quality is not affected indoors, emitted power is however very low so there are no health concerns for operator or targets. The low power operation is still sufficient to penetrate heavy clothing or material. Small system size allows for easy transport and rapid deployment of the system as well as an easy migration path to future hand held systems.

Johnson, Michael A.; Chang, Yu-Wen

2001-02-01

364

Improved Micro Rain Radar snow measurements using Doppler spectra post-processing  

NASA Astrophysics Data System (ADS)

The Micro Rain Radar 2 (MRR) is a compact Frequency Modulated Continuous Wave (FMCW) system that operates at 24 GHz. The MRR is a low-cost, portable radar system that requires minimum supervision in the field. As such, the MRR is a frequently used radar system for conducting precipitation research. Current MRR drawbacks are the lack of a sophisticated post-processing algorithm to improve its sensitivity (currently at +3 dBz), spurious artefacts concerning radar receiver noise and the lack of high quality Doppler radar moments. Here we propose an improved processing method which is especially suited for snow observations and provides reliable values of effective reflectivity, Doppler velocity and spectral width. The proposed method is freely available on the web and features a noise removal based on recognition of the most significant peak. A dynamic dealiasing routine allows observations even if the Nyquist velocity range is exceeded. Collocated observations over 115 days of a MRR and a pulsed 35.2 GHz MIRA35 cloud radar show a very high agreement for the proposed method for snow, if reflectivities are larger than -5 dBz. The overall sensitivity is increased to -14 and -8 dBz, depending on range. The proposed method exploits the full potential of MRR's hardware and substantially enhances the use of Micro Rain Radar for studies of solid precipitation.

Maahn, M.; Kollias, P.

2012-11-01

365

Improved Micro Rain Radar snow measurements using Doppler spectra post-processing  

NASA Astrophysics Data System (ADS)

The Micro Rain Radar (MRR) is a compact Frequency Modulated Continuous Wave (FMCW) system that operates at 24 GHz. The MRR is a low-cost, portable radar system that requires minimum supervision in the field. As such, the MRR is a frequently used radar system for conducting precipitation research. Current MRR drawbacks are the lack of a sophisticated post-processing algorithm to improve its sensitivity (currently at +3 dBz), spurious artefacts concerning radar receiver noise and the lack of high quality Doppler radar moments. Here we propose an improved processing method which is especially suited for snow observations and provides reliable values of effective reflectivity, Doppler velocity and spectral width. The proposed method is freely available on the web and features a noise removal based on recognition of the most significant peak. A dynamic dealiasing routine allows observations even if the Nyquist velocity range is exceeded. Collocated observations at 115 days of a MRR and a pulsed 35.2 GHz MIRA35 cloud radar show a very high agreement for the proposed method for snow, if reflectivities are larger than -5 dBz. The overall sensitivity is increased to -14 and -8 dBz, depending on range. The proposed method exploits the full potential of MRR's hardware and substantially enhances the use of Micro Rain Radar for studies of solid precipitation.

Maahn, M.; Kollias, P.

2012-07-01

366

Flight demonstration of image fix-taking with SAR.  

National Technical Information Service (NTIS)

Airborne Synthetic Aperture Radar (SAR) uses coherent radar processing techniques to image ground reflectors. After processing, range and Doppler can be associated with any feature of interest in the final image. The location of any imaged feature can be ...

R. Gibbs M. Bottkol T. Owen

1993-01-01

367

Image Processing for Teaching.  

ERIC Educational Resources Information Center

|The Image Processing for Teaching project provides a powerful medium to excite students about science and mathematics, especially children from minority groups and others whose needs have not been met by traditional teaching. Using professional-quality software on microcomputers, students explore a variety of scientific data sets, including…

Greenberg, R.; And Others

1993-01-01

368

Image processing and reconstruction  

SciTech Connect

This talk will examine some mathematical methods for image processing and the solution of underdetermined, linear inverse problems. The talk will have a tutorial flavor, mostly accessible to undergraduates, while still presenting research results. The primary approach is the use of optimization problems. We will find that relaxing the usual assumption of convexity will give us much better results.

Chartrand, Rick [Los Alamos National Laboratory

2012-06-15

369

Adaptive Compressive Sensing and Processing of Delay-Doppler Radar Waveforms  

Microsoft Academic Search

Compressive sensing and processing handles high-resolution delay-Doppler radar measurements using a low sampling rate, simple receiver design, and inexpensive processing when Nyquist rate sensing and processing becomes impractical. The benefits of compressive sensing and processing are, however, offset by an increase in estimation error that is introduced when processing compressed measurements versus measurements sampled at the Nyquist rate. In this

Ioannis Kyriakides

2012-01-01

370

An adaptive multimicroprocessor array computing structure for radar signal processing applications  

Microsoft Academic Search

This paper describes an array processor designed for signal processing in radar applications. The processor consists of a large number of microprocessor-based processing elements and is designed to be adaptive in real-time processing requirements. The processing problem has been considered to have a quite specific data organization and data rate which can be exploited in the architectural design. Parallel processing

C. V. W. Armstrong; H. M. Ahmed; N. A. Brans; E. Fathi

1979-01-01

371

High-resolution vertical imaging of the troposphere and lower stratosphere using the new MU radar system  

NASA Astrophysics Data System (ADS)

In the present paper, a new application of the range imaging technique called Frequency Interferometry Imaging (FII) or Range Imaging (RIM), performed in April 2005, is shown using the new 46.5-MHz Middle and Upper (MU) atmosphere radar system (Shigaraki, Japan). Height-time images of brightness distribution have been computed at the highest resolution ever obtained for imaging with VHF radars in the troposphere and, for the very first time, in the lower stratosphere, up to about 22 km. The images were produced by processing signals obtained with an initial range-resolution of ?r=150 m and five equally-spaced frequencies within ?f=1.0 MHz, with the adaptive Capon method. These values represent an improvement of a factor 2 over all the previous published experiments at VHF, which were performed with ?r=300 m and ?f=0.5 MHz. The Capon images present realistic and self-consistent features, and reveal many more organized structures than the height-time SNR plots at the initial range-resolution. For example, the Capon images show persistent enhanced brightness layers significantly thinner than 150 m in the stratosphere, which are impossible to track with the standard single-frequency mode owing to a lack of range resolution. These observations thus support the idea of strong stratification even at vertical scales much smaller than 100 m, as suggested by recent high-resolution temperature observations by balloons (Dalaudier et al., 1994). We also present comparisons of Capon images with patterns obtained from the dual-FDI technique and two parametric methods (the MUSIC algorithm and the newly-introduced Maximum Entropy Method based on an auto-regressive (AR) model). The comparisons confirm the insufficiencies of the dual-FDI technique and indicate that parametric methods such as MEM and the MUSIC algorithm can help to validate the Capon images when the parametric methods provide similar patterns.

Luce, H.; Hassenpflug, G.; Yamamoto, M.; Fukao, S.

2006-05-01

372

Standoff concealed weapon detection using a 350GHz radar imaging system  

Microsoft Academic Search

The sub-millimeter (sub-mm) wave frequency band from 300 - 1000 GHz is currently being developed for standoff concealed weapon detection imaging applications. This frequency band is of interest due to the unique combination of high resolution and clothing penetration. The Pacific Northwest National Laboratory (PNNL) is currently developing a 350 GHz, active, wideband, three-dimensional, radar imaging system to evaluate the

David M. Sheen; Thomas E. Hall; Ronald H. Severtsen; Douglas L. McMakin; Brian K. Hatchell; Patrick L. J. Valdez

2010-01-01

373

Atmospheric Fronts along the East Coast of Taiwan Studied by ERS Synthetic Aperture Radar Images  

Microsoft Academic Search

The existence of quasi-stationary alongshore atmospheric fronts typically located 30-70 km off the east coast of Taiwan is demonstrated by analyzing synthetic aperture radar (SAR) images of the sea surface acquired by the European Remote Sensing Satellites ERS-1 and ERS-2. For the data interpretation, cloud images from the Japanese Geostationary Meteorological Satellite GMS-4 and the American Terra satellite, rain-rate maps

Werner Alpers; Jen-Ping Chen; I.-I. Lin; Chun-Chi Lien

2007-01-01

374

Tutorial review of synthetic-aperture radar (SAR) with applications to imaging of the ocean surface  

Microsoft Academic Search

A synthetic aperture radar (SAR) can produce high-resolution two-dimensional images of mapped areas. The SAR comprises a pulsed transmitter, an antenna, and a phase-coherent receiver. The SAR is borne by a constant velocity vehicle such as an aircraft or satellite, with the antenna beam axis oriented obliquely to the velocity vector. The image plane is defined by the velocity vector

KIYO TOMIYASU

1978-01-01

375

3D characterization of radar targets by means of ISAR/SAR near field imaging techniques  

NASA Astrophysics Data System (ADS)

Inverse synthetic aperture radar (ISAR) imaging techniques based on indoor near field backscattering measurements turns out to be a powerful tool for diagnostic purposes in radar cross-section (RCS) reduction and for deriving RCS target models, viable for radar systems operating at larger distances, e.g. under far field conditions. This paper presents an advanced 3-D imaging approach, where in addition to the turntable rotation the antenna is moved along a linear path chosen in accordance with the geometry of the target and the aspect angle of interest. For reconstructing the reflectivity distribution a configuration-specific grid of spatial sampling points is employed which reduces the complexity of determining correct values for the scattering amplitudes. The reflectivity distribution reproduces the backscattering seen from an antenna moved along a finite surface (synthetic 2-D-aperture) in the scattering near field of the target, but is to be used to model backscattering for antennas at larger distances, e.g. in the far field. Therefore, the feasibility of this approach is discussed with respect to different applications, i.e. for the diagnostic of RCS reduction and for deterministic or statistical RCS models. Results obtained for a car as X-band radar target are presented in order to verify the features of the imaging system.

John, Marc-Andre; Aulenbacher, Uwe; Inaebnit, Christian

2007-04-01

376

An approach to forward looking FMCW radar imaging based on two-dimensional Chirp-Z transform  

Microsoft Academic Search

Airborne forward looking radar imaging, which is an important work mode of imaging radar system, has many advantages combined\\u000a with frequency modulated continuous wave (FMCW) technology. This paper studies the configuration with one central antenna\\u000a element for signal transmitting and other antenna elements for signal receiving. According to its imaging geometry, the analytical\\u000a expression of the received signal for forward

Yi Liang; HongXian Wang; Long Zhang; Zheng Bao

2010-01-01

377

A high-resolution 3-D imaging algorithm with linear array antennas for UWB pulse radar systems  

Microsoft Academic Search

UWB pulse radar systems have a great potential for a high-resolution imaging in indoor environments. For a real-time imaging, we have already proposed a fast 3-dimensional imaging algorithm called SEABED based on a reversible transform BST (boundary scattering transform) between the received signals and the target shape. SEABED can be applied only to a mono-static radar system. Therefore, the resolution

Shouhei KIDERA; Takuya SAKAMOTO; Toru SATO

2006-01-01

378

Bistatic Linear Antenna Array SAR for Moving Target Detection, Location, and Imaging With Two Passive Airborne Radars  

Microsoft Academic Search

In this paper, we propose a bistatic linear array synthetic aperture radar (BLA-SAR) system for moving target detection, location, and imaging. In the BLA-SAR system, a geostationary satellite is used as a transmitter, and two airborne linear array radars are used as passive receivers, where the transmitted waveforms from the geostationary satellite may have two different carrier frequencies, two linear

Gang Li; Jia Xu; Ying-Ning Peng; Xiang-Gen Xia

2007-01-01

379

High Rsolution Radar Polarimetric Imaging Of The Ocean Surface Due To Tilt Modulation - Unified Full Wave Approach  

Microsoft Academic Search

The unified full wave approach is used to simulate polarimetric images of composite rough surfaces illuminated by a high resolution radar (i.e. real or synthetic aperture radars with small effective footprints). The unified full wave solutions account for Bragg scattering and specular point scattering in a selfconsistent manner, therefore it is not necessary to decompose the surface into two surfaces

E. Bahar; R. D. Kubik

1991-01-01

380

Digital Image Processing: Binary Images.  

National Technical Information Service (NTIS)

The basic geometric concepts used to describe the spatial organization of the points on the support of the image are analyzed. The definitions include connectedness, connected components, interior and border, picture representation, structure representati...

J. M. Chassery

1986-01-01

381

Study of a method for 2-D imaging of simple-shaped targets with arbitrary motion using UWB radar with a small number of antennas  

Microsoft Academic Search

Ultra-wideband (UWB) pulse radar is an effective device as the basis for building a high-precision surveillance system. The fast SEABED (Shape Estimation Algorithm based on BST and Extraction of Directly scattered waves) imaging algorithm is capable of accurately estimating target shapes using UWB pulse radar. A new UWB radar imaging algorithm, based on an extension of the SEABED algorithm that

Yuji Matsuki; Takuya Sakamoto; Toru Sato

2010-01-01

382

The effects of snow on landmarks in K/sub u/ band SAR (Synthetic Aperture Radar) images  

SciTech Connect

This report documents research into the effects of snow on candidate landmarks for the TFS radar. It includes a discussion of a simple snow model, relevant backscatter data from previous ground based collections, predictions of the effects of snow coverage based on this data, a discussion of the snow data collection with the TFS radar, and an analysis of the results of that collection. All SAR images are for a K/sub u/ band radar, with HH polarization, and a 30/degree/ depression angle. The images have three meter resolution and a one kilometer swath. SAR images were collected of both rural and urban landmarks. 5 refs., 7 figs., 19 tabs.

Murrary, M.

1989-04-01

383

Retinomorphic image processing.  

PubMed

The present work is aimed at understanding and explaining some of the aspects of visual signal processing at the retinal level while exploiting the same towards the development of some simple techniques in the domain of digital image processing. Classical studies on retinal physiology revealed the nature of contrast sensitivity of the receptive field of bipolar or ganglion cells, which lie in the outer and inner plexiform layers of the retina. To explain these observations, a difference of Gaussian (DOG) filter was suggested, which was subsequently modified to a Laplacian of Gaussian (LOG) filter for computational ease in handling two-dimensional retinal inputs. Till date almost all image processing algorithms, used in various branches of science and engineering had followed LOG or one of its variants. Recent observations in retinal physiology however, indicate that the retinal ganglion cells receive input from a larger area than the classical receptive fields. We have proposed an isotropic model for the non-classical receptive field of the retinal ganglion cells, corroborated from these recent observations, by introducing higher order derivatives of Gaussian expressed as linear combination of Gaussians only. In digital image processing, this provides a new mechanism of edge detection on one hand and image half-toning on the other. It has also been found that living systems may sometimes prefer to "perceive" the external scenario by adding noise to the received signals in the pre-processing level for arriving at better information on light and shade in the edge map. The proposed model also provides explanation to many brightness-contrast illusions hitherto unexplained not only by the classical isotropic model but also by some other Gestalt and Constructivist models or by non-isotropic multi-scale models. The proposed model is easy to implement both in the analog and digital domain. A scheme for implementation in the analog domain generates a new silicon retina model implemented on a hardware development platform. PMID:18166395

Ghosh, Kuntal; Bhaumik, Kamales; Sarkar, Sandip

2008-01-01

384

The use of imaging radars for ecological applications—A review  

Microsoft Academic Search

At the behest of NASA's Mission to Planet Earth, the National Research Council recently conducted a review on the current status and future directions for earth science information provided by spaceborne synthetic aperture radars. As part of this process, a panel of 16 scientists met to review the utility of SAR for monitoring ecosystem processes. The consensus of this ecology

Eric S Kasischke; John M Melack; M Craig Dobson

1997-01-01

385

2D HRR Radar Data Modeling and Processing  

Microsoft Academic Search

High Range Resolution (HRR) -based Automatic Target Recognition (ATR) has attracted increasing attention due to a number of potential advantages over alternative radar techniques in moving target identification. Most current HRR-based ATR studies have been conducted using 1D HRR signatures. However, these 1D HRR signatures are generally plagued by scintillation effects, and thus demonstrate highly irregular behavior that dramatically degrades

Junshui Ma; Xun Du; Stanley C. Ahalt

2003-01-01

386

Adaptive radar CFAR detection in sea clutter using FFT processing  

Microsoft Academic Search

When a high-resolution radar is used to observe the sea surface, the sea clutter can be represented by a model comprising two components, one a slowly varying component associated with the undulating surface and the other a rapidly varying component caused by rapidly fluctuating capillary and short gravity waves, the latter having a probability density function approximating the Rayleigh distribution.

Ziyan Cui; D. C. Cooper

1986-01-01

387

Multichannel image storage with image processing capabilities  

NASA Astrophysics Data System (ADS)

We show that by trading light-throughput one can implement an optical technique for multiplexing storage, which allows image-processing operations at the retrieval stage. We illustrate our proposal by performing experimentally image subtraction and spatial differentiation.

Araiza-Esquivel, M.; Guel-Sandoval, S.; Ojeda-Castan~Eda, J.

2004-01-01

388

Image processing technology  

SciTech Connect

This is the final report of a two-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The primary objective of this project was to advance image processing and visualization technologies for environmental characterization. This was effected by developing and implementing analyses of remote sensing data from satellite and airborne platforms, and demonstrating their effectiveness in visualization of environmental problems. Many sources of information were integrated as appropriate using geographic information systems.

Van Eeckhout, E.; Pope, P.; Balick, L. [and others

1996-07-01

389

Goldstone Radar Imaging of Near-Earth Asteroid 2003 MS2  

NASA Astrophysics Data System (ADS)

We report delay-Doppler radar images of 2003 MS2 that were obtained at Goldstone (8560 MHz, 3.5 cm) on three dates during this object’s close Earth flyby in July of 2003 within 0.025 AU (9.7 lunar distances). The asteroid was a strong radar target and we obtained images with resolutions as high as 19 m/pixel. The radar images reveal an unusually angular object with pronounced facets. Our longest sequence of images was obtained on July 4 when the asteroid rotated at least several tens of degrees in 2.7 hours. During that interval, the bandwidths varied by a factor of about 1.5 and clearly establish that this is an elongated object. The rotation and bandwidth variations evident in the radar images are consistent with the 7 hour rotation period and 0.5 magnitude lightcurve amplitude reported by Muinonen et al. 2006[1]. If we adopt the 7 hour period, then the maximum and minimum bandwidths place lower bounds on the maximum pole-on dimensions of (0.35 x 0.23) km/cos ?, where ? is the (unknown) subradar latitude. These constraints are consistent with the range extents of 0.25 km visible in the images. We obtain a circular polarization ratio of 0.28+/-0.02 that is comparable to 25143 Itokawa and suggests a similar degree of near-surface roughness at decimeter spatial scales. [1] Muinonen, K. et al. (2006). Spins, shapes, and orbits for near-Earth objects by Nordic NEON. Proceedings of the International Astronomical Union, 2, pp 309-320 doi:10.1017/S1743921307003377.

Lawrence, Kenneth J.; Benner, L.; Ostro, S.; Giorgini, J.; Jurgens, R.; Brozovic, M.; Magri, C.; Margot, J. L.

2012-10-01

390

Multiple-frequency range imaging using the OSWIN VHF radar: Phase calibration and first results  

NASA Astrophysics Data System (ADS)

This paper demonstrates the multiple-frequency range imaging (RIM) which was implemented recently on the OSWIN VHF atmospheric radar (54.1°N, 11.8°E), Germany. A simple but practical phase calibration method is introduced. We validate the RIM technique and the proposed calibration method successfully by examining various radar experiments with different pulse lengths, mono and coded pulses, evenly and unevenly spaced frequencies, and receiver filter bandwidths. The proposed calibration method not only mitigates the phase imbalance between the echoes received at different transmitting frequencies, but also provides a likely value of standard deviation (?z) of the Gaussian range-weighting function for correcting the range-weighting effect. Moreover, it is found that ?z can be adaptive to signal-to-noise ratio when it is employed in practice; this procedure improves the continuity of the imaged powers of RIM around the boundaries of range gates, and an empirical expression has been proposed for this. With the improved power distribution around gate boundaries, we can obtain more available estimates of layer altitudes and exhibit the pass of the layer through gate boundaries clearly. Two observations are shown to demonstrate the maturation of the RIM technique used with the radar: convective cells and double-layer structures. These atmospheric structures cannot be seen clearly in the original presentation of signal-to-noise ratio (or height-time intensity) of the radar echoes having 150-m or 300-m range resolution.

Chen, Jenn-Shyong; Zecha, Marius

2009-02-01

391

Imaging topological radar for 3D imaging in cultural heritage reproduction and restoration  

NASA Astrophysics Data System (ADS)

We present the last results obtained by using our Imaging Topological Radar (ITR), an high resolution laser scanner aimed at reconstruction 3D digital models of real targets, either single objects or complex scenes. The system, based on amplitude modulation ranging technique, enables to obtain simultaneously a shade-free, high resolution, photographic-like picture and accurate range data in the form of a range image, with resolution depending mainly on the laser modulation frequency (current best performance are ~100?m). The complete target surface is reconstructed from sampled points by using specifically developed software tools. The system has been successfully applied to scan different types of real surfaces (stone, wood, alloy, bones) and is suitable of relevant applications in different fields, ranging from industrial machining to medical diagnostics. We present some relevant examples of 3D reconstruction in the heritage field. Such results were obtained during recent campaigns carried out in situ in various Italian historical and archaeological sites (S. Maria Antiqua in Roman Forum, "Grotta dei cervi" Porto Badisco - Lecce, South Italy). The presented 3D models will be used by cultural heritage conservation authorities for restoration purpose and will available on the Internet for remote inspection.

Poggi, Claudio; Guarneri, Massimiliano; Fornetti, Giorgio; Ferri de Collibus, Mario; De Dominicis, Luigi; Paglia, Emiliano; Ricci, Roberto

2005-10-01

392

Ground-based Mm-radar Imaging of Lava Domes and Flows.  

NASA Astrophysics Data System (ADS)

AVTIS (All-weather Volcano Topography Imaging Sensor) is a tripod-mounted imaging system, capable of both active (topography) and passive (temperature) imaging at 94 GHz. The use of these mm-wavelengths provides a high-resolution imaging capability from a portable instrument which can operate through cloud and aerosol. The instrument is designed to avoid the problem of obscuration by cloud which is common at many volcanoes and can prevent regular monitoring by most traditional measurement techniques (e.g. photogrammetry, lidar, thermal imaging). In its active (radar) mode, AVTIS acquires topographic data (in a manner similar to that of a terrestrial laser scanner) at a rate of 3 lines-of-sight per second, with a range resolution of less than 1 m and a maximum range of about 7 km. In its passive (radiometer) mode, a brightness temperature image is acquired with an apparent temperature resolution of about 5 K. AVTIS has been deployed to measure lava flows at Arenal volcano, Costa Rica and to the lava dome of Soufrière Hills volcano, Montserrat. At Arenal, topographic scans repeated every few days demonstrated the ability of AVTIS to detect changes associated with the advance of a lava flow, from a range of 3 km. The active lava flow was identified as a region of surface height increase (averaging about 10 m) and by its high reflectivity. Subtraction of acquired topographic surfaces indicated a flow advance rate of about 0.2 cubic metres per second. On Montserrat, opportunistic topographic scans of the lava dome from a distance of about 1 km have enabled extrusion rates to be calculated to an accuracy of about 0.1 cubic metres per second over several days. Equivalent radiometric scans recorded temperature images in cloudy conditions comparable to those attained using an infra-red camera during clear weather. Repeat imaging (up to three per hour) over several days from a distance of 6 km has provided information on the dynamics of dome growth. We discuss the data and the processing and registration procedures developed to extract this information. andrews.ac.uk/~mmwave/mmwave/avtis.shtml

Macfarlane, D. G.; Odbert, H. M.; Robertson, D. A.; James, M. R.; Wadge, G.; Pinkerton, H.

2006-12-01

393

Human Being Imaging with cm-Wave UWB Radar  

NASA Astrophysics Data System (ADS)

Possibilities of high-resolution human body imaging and concealed weapon detection using centimeter-wave microwave frequencies are investigated. Dependencies of the cross-range resolution of different imaging techniques on operational bandwidth, center frequency, imaging aperture size, and imaging topology have been studied. It has been demonstrated that the cross-range resolution of 2 cm can be achieved using frequencies below 10 GHz. These findings have been verified experimentally by producing high-resolution images of a foil-covered doll and some weapons.

Yarovoy, A.; Zhuge, X.; Savelyev, T.; Matuzas, J.; Levitas, B.

394

Key Techniques and Algorithms for the Development of an Air-to-Ground Bistatic Imaging Radar Simulation.  

National Technical Information Service (NTIS)

The following report describes and defines theoretical considerations necessary for the definition of an air-to-ground opposite side bistatic imaging radar simulation. Theoretical considerations include: range resolution, maximum and minimum range as func...

J. M. Henson

2001-01-01

395

Airborne and Spaceborne Radar Images for Geologic and Environmental Mapping in the Amazon Rain Forest, Brazil (Abstract Only).  

National Technical Information Service (NTIS)

Spaceborne and airborne radar image of portions of the Middle and Upper Amazon basin in the state of Amazonas and the Territory of Roraima are compared for purposes of geological and environmental mapping. The contrasted illumination geometries and imagin...

J. P. Ford J. J. Hurtak

1986-01-01

396

Coordinated optical and radar image measurements of noctilucent clouds and polar mesospheric summer echoes  

NASA Astrophysics Data System (ADS)

Novel coincident 3-D radar, lidar and optical image measurements of dynamical structures in polar mesosphere summer echoes (PMSE) and noctilucent clouds (NLC) are presented. Common volume mesospheric measurements were made over central Alaska using the new Poker Flat Incoherent Scatter Radar (PFISR), a co-located Rayleigh lidar and remote, two-station digital image observations, enabling the first detailed investigation of the horizontal and vertical structures of NLC and PMSE. Coincident measurements were made of an unusual NLC display recorded on 10-11 August 2007, characterized by a broad luminous band that contained several prominent wave forms. Concurrent lidar and image measurements established the presence of NLC within the radar volume from ~09:00 UT (01:00 LT), when the solar depression angle was 10.4°, until dawn. Strong but intermittent PMSE were detected by PFISR, with distinct patchy structures that exhibited a similar southward motion as the NLC. Detailed comparison of the 3-D PMSE structures and the NLC lidar and image data have revealed striking similarities when account was taken of the NLC layer altitude, suggesting a direct link between their small-scale spatial signatures (within the current resolution of the radar measurements). At the same time, the lidar detected a sustained increase in the backscatter signal, while the imagers revealed the development of copious short horizontal wavelength (4.9 km) billow waves. We conclude that strong wind shears associated with the Kelvin-Helmholtz billow instabilities played a key role in the development of a neutral turbulence layer in close proximity to the NLC layer resulting in the strong but intermittent PMSE detected at 450 MHz on this occasion.

Taylor, M. J.; Zhao, Y.; Pautet, P.-D.; Nicolls, M. J.; Collins, R. L.; Barker-Tvedtnes, J.; Burton, C. D.; Thurairajah, B.; Reimuller, J.; Varney, R. H.; Heinselman, C. J.; Mizutani, K.

2009-05-01

397

Processing of Indian Doppler Weather Radar data for mesoscale applications  

NASA Astrophysics Data System (ADS)

This paper demonstrates the usefulness of Indian Doppler Weather Radar (DWR) data for nowcasting applications, and assimilation into a mesoscale Numerical Weather Prediction (NWP) model. Warning Decision Support System Integrated Information (WDSS-II) developed by National Severe Storm Laboratory (NSSL) and Advanced Regional Prediction System (ARPS) developed at the Centre for Analysis and Prediction, University of Oklahoma are used for this purpose. The study reveals that the WDSS-II software is capable of detecting and removing anomalous propagation echoes from the Indian DWR data. The software can be used to track storm cells and mesocyclones through successive scans. Radar reflectivity mosaics are created for a land-falling tropical cyclone—Khaimuk of 14 November 2008 over the Bay of Bengal using observations from three DWR stations, namely, Visakhapatnam, Machilipatnam and Chennai. Assimilation of the quality-controlled radar data (DWR, Chennai) of the WDSS-II software in a very high-resolution NWP model (ARPS) has a positive impact for improving mesoscale prediction. This has been demonstrated for a land-falling tropical cyclone Nisha of 27 November 2008 of Tamil Nadu coast. This paper also discusses the optimum scan strategy and networking considerations. This work illustrates an important step of transforming research to operation.

Roy Bhowmik, S. K.; Sen Roy, Soma; Srivastava, Kuldeep; Mukhopadhay, B.; Thampi, S. B.; Reddy, Y. K.; Singh, Hari; Venkateswarlu, S.; Adhikary, Sourav

2011-03-01

398

Test results of an experimental autonomous aircraft landing system utilizing a 94 GHz FM-CW imaging radar  

Microsoft Academic Search

An experimental system capable of aiding a pilot during adverse weather landings, primarily dense fog, has been built and tested both on the ground and in flight. The system includes a 94-GHz FM-CW (frequency-modulation continuous-wave) radar as the front-end sensor and a back-end digital signal and image processor for image generation, enhancement, and transformation. The high-performance 94-GHz radar utilizes a

L. Q. Bui; D. Uecker; E. Loose; Y. Alon

1993-01-01

399

Calibration of polarimetric radar images using only image parameters and trihedral corner reflector responses  

Microsoft Academic Search

A technique that uses the radar return from natural targets and at least one trihedral corner reflector to calibrate compressed polarimetric radar data is described. Calibration for relative amplitude, relative phase, absolute amplitude, and system crosstalk is addressed. The crosstalk calibration method is based on the theoretical result that for natural targets with azimuthal symmetry the copolarized and crosspolarized components

J. J. van Zyl

1990-01-01

400

Image processing in precision agriculture  

Microsoft Academic Search

A brief review of our signal and image processing application in precision agriculture is presented. A method for determining sampling frequency for agriculture data is proposed, and some initial results based on data simulation and image processing are reported

Dragoljub Pokrajac; A. Lazarevic; S. Vucetic; T. Fiez; Z. Obradovic

1999-01-01

401

Spatial resolution enhancement of Cassini Titan Radar mapper data  

Microsoft Academic Search

Post processing reconstruction and resolution enhancement algorithms can be applied to Cassini Titan Radar Mapper data to improve the image resolution for scatterometermode imagery. Reconstruction algorithms can also yield enhanced resolution images when multiple passes are combined. This paper briefly describes the application of the AVE and the Scatterometer Image Reconstruction (SIR) algorithms to Cassini Radar data. Some sample results

David G. Long

2009-01-01

402

Ultra-wideband Radar Methods and Techniques of Medical Sensing and Imaging  

SciTech Connect

Ultra-wideband radar holds great promise for a variety of medical applications. We have demonstrated the feasibility of using ultra-wideband sensors for detection of internal injuries, monitoring of respiratory and cardiac functions, and continuous non-contact imaging of the human body. Sensors are low-power, portable, and do not require physical contact with the patient. They are ideal for use by emergency responders to make rapid diagnosis and triage decisions. In the hospital, vital signs monitoring and imaging application could improve patient outcomes. In this paper we present an overview of ultra-wideband radar technology, discuss key design tradeoffs, and give examples of ongoing research in applying ultra-wideband technology to the medical field.

Paulson, C N; Chang, J T; Romero, C E; Watson, J; Pearce, F J; Levin, N

2005-10-07

403

Ultra-wideband radar methods and techniques of medical sensing and imaging  

NASA Astrophysics Data System (ADS)

Ultra-wideband radar holds great promise for a variety of medical applications. We have demonstrated the feasibility of using ultra-wideband sensors for detection of internal injuries, monitoring of respiratory and cardiac functions, and continuous non-contact imaging of the human body. Sensors are low-power, portable, and do not require physical contact with the patient. They are ideal for use by emergency responders to make rapid diagnosis and triage decisions. In the hospital, vital signs monitoring and imaging application could improve patient outcomes. In this paper we present an overview of ultra-wideband radar technology, discuss key design tradeoffs, and give examples of ongoing research in applying ultra-wideband technology to the medical field.

Paulson, Christine N.; Chang, John T.; Romero, Carlos E.; Watson, Joseph; Pearce, Fred J.; Levin, Nathan

2005-11-01

404

Wide-Bandwidth Continuous-Wave Monostatic\\/Bistatic Synthetic Aperture Radar Imaging  

Microsoft Academic Search

Monostatic and bistatic synthetic aperture radar (SAR) imaging systems with wide-bandwidth continuous-wave (WB-CW) sources have been utilized for military reconnaissance. The WB-CW sources are less susceptible than FM-CW sources to electronic counter measures (ECM). The main shortcoming of the WB-CW microwave illumination is that its resultant SAR echoed signal is not composed of distinct Doppler spreadings around specific tones; this

Mehrdad Soumekh

1998-01-01

405

Near-Earth Asteroid 2005 CR37: Radar images and photometry of a candidate contact binary  

Microsoft Academic Search

Arecibo (2380 MHz, 13 cm) radar observations of 2005 CR37 provide detailed images of a candidate contact binary: a 1.8-km-long, extremely bifurcated object. Although the asteroid's two lobes are round, there are regions of modest topographic relief, such as an elevated, 200-m-wide facet, that suggest that the lobes are geologically more complex than either coherent fragments or homogeneous rubble piles.

Lance A. M. Benner; Michael C. Nolan; Steven J. Ostro; Jon D. Giorgini; Donald P. Pray; Alan W. Harris; Christopher Magri; Jean-Luc Margot

2006-01-01

406

A Volume-Imaging Radar Wind Profiler for Atmospheric Boundary Layer Turbulence Studies  

Microsoft Academic Search

This paper describes the turbulent eddy profiler (TEP), a volume-imaging, UHF radar wind profiler designed for clear-air measurements in the atmospheric boundary layer on scales comparable to grid cell sizes of large eddy simulation models. TEP employs a large array of antennas—each feeding an independent receiver—to simultaneously generate multiple beams within a 288 conical volume illuminated by the transmitter. Range

James B. Mead; Geoffrey Hopcraft; Stephen J. Frasier; Brian D. Pollard; Christopher D. Cherry; Daniel H. Schaubert; Robert E. McIntosh

1998-01-01

407

Novel guided-wave electro-optic processor for synthetic aperture radar imaging  

Microsoft Academic Search

We present the theoretical investigation of a novel architecture of a LiNbO3 guided-wave optical processor suitable for real-time microwave imaging in on-board synthetic aperture radar (SAR) applications, using a moving platform on either an aircraft or a spacecraft. The new configuration, which is basically interferometric, includes four Mach-Zehnder modulators, each characterized by an additional aperiodic phase-reversal traveling wave modulator. The

Mario N. Armenise; Vittorio M. Passaro

1994-01-01

408

Ground penetrating radar and imaging metal detector for antipersonnel mine detection  

Microsoft Academic Search

DeTeC (Demining Technology Center) is developing a sensor system for humanitarian demining enabling reduction in the number of false alarms and usable by a man or an autonomous robot (see http:\\/\\/diwww.epfl.ch\\/lami\\/detec\\/). We have chosen to concentrate our first experiments on a commercial impulse ground penetrating radar with a 1 GHz antenna and a metal detector used for imaging purposes. The

Claudio Bruschini; Bertrand Gros; Frédéric Guerne; Pierre-Yves Pièce; Olivier Carmona

1998-01-01

409

Nonlinear features of internal waves off Baja California as observed from the SEASAT imaging radar  

Microsoft Academic Search

The synthetic aperture radar (SAR) on SEASAT has yielded well-defined images of quasi-periodic internal waves in the waters on the west side of Baja California. These waves occur in groupings separated by 15-23 km, each group having 2-20 striations with wavelengths of the order of 300 m or longer. They appear in water approximately 200 m deep, shoreward of several

John R. Apel; Frank I. Gonzalez

1983-01-01

410

Radar Imaging and a Physical Model of Binary Asteroid 65803 Didymos  

Microsoft Academic Search

We report Arecibo (2380 MHz, 13 cm) and Goldstone (8560 MHz, 3.5 cm) delay-Doppler radar observations of binary near-Earth asteroid (NEA) 65803 Didymos (1996 GT) obtained on five dates between November 14-26, 2003 during the asteroid's approach within 0.048 AU. The images achieve resolutions as fine as 15 m in range and place hundreds of pixels on the primary. The

Lance A. M. Benner; J. Margot; M. C. Nolan; J. D. Giorgini; M. Brozovic; D. J. Scheeres; C. Magri; S. J. Ostro

2010-01-01

411

Segmentation and cooperative fusion of laser radar image data  

Microsoft Academic Search

In segmentation, the goal is to partition a given {2D} image into regions corresponding to the meaningful surfaces in the underlying physical scene. Segmentation is frequently a crucial step in analyzing and interpreting image data acquired by a variety of automated systems ranging from indoor robots to orbital satellites. In this paper, we present the results of a study of

Martin Beckerman; F. J. Sweeney

1994-01-01

412

Dynamic Experiment Design Regularization Approach to Adaptive Imaging with Array Radar/SAR Sensor Systems  

PubMed Central

We consider a problem of high-resolution array radar/SAR imaging formalized in terms of a nonlinear ill-posed inverse problem of nonparametric estimation of the power spatial spectrum pattern (SSP) of the random wavefield scattered from a remotely sensed scene observed through a kernel signal formation operator and contaminated with random Gaussian noise. First, the Sobolev-type solution space is constructed to specify the class of consistent kernel SSP estimators with the reproducing kernel structures adapted to the metrics in such the solution space. Next, the “model-free” variational analysis (VA)-based image enhancement approach and the “model-based” descriptive experiment design (DEED) regularization paradigm are unified into a new dynamic experiment design (DYED) regularization framework. Application of the proposed DYED framework to the adaptive array radar/SAR imaging problem leads to a class of two-level (DEED-VA) regularized SSP reconstruction techniques that aggregate the kernel adaptive anisotropic windowing with the projections onto convex sets to enforce the consistency and robustness of the overall iterative SSP estimators. We also show how the proposed DYED regularization method may be considered as a generalization of the MVDR, APES and other high-resolution nonparametric adaptive radar sensing techniques. A family of the DYED-related algorithms is constructed and their effectiveness is finally illustrated via numerical simulations.

Shkvarko, Yuriy; Tuxpan, Jose; Santos, Stewart

2011-01-01

413

Dynamic experiment design regularization approach to adaptive imaging with array radar/SAR sensor systems.  

PubMed

We consider a problem of high-resolution array radar/SAR imaging formalized in terms of a nonlinear ill-posed inverse problem of nonparametric estimation of the power spatial spectrum pattern (SSP) of the random wavefield scattered from a remotely sensed scene observed through a kernel signal formation operator and contaminated with random Gaussian noise. First, the Sobolev-type solution space is constructed to specify the class of consistent kernel SSP estimators with the reproducing kernel structures adapted to the metrics in such the solution space. Next, the "model-free" variational analysis (VA)-based image enhancement approach and the "model-based" descriptive experiment design (DEED) regularization paradigm are unified into a new dynamic experiment design (DYED) regularization framework. Application of the proposed DYED framework to the adaptive array radar/SAR imaging problem leads to a class of two-level (DEED-VA) regularized SSP reconstruction techniques that aggregate the kernel adaptive anisotropic windowing with the projections onto convex sets to enforce the consistency and robustness of the overall iterative SSP estimators. We also show how the proposed DYED regularization method may be considered as a generalization of the MVDR, APES and other high-resolution nonparametric adaptive radar sensing techniques. A family of the DYED-related algorithms is constructed and their effectiveness is finally illustrated via numerical simulations. PMID:22163859

Shkvarko, Yuriy; Tuxpan, José; Santos, Stewart

2011-04-27

414

Development of a high-resolution laser radar for 3D imaging in artwork cataloging  

NASA Astrophysics Data System (ADS)

A high resolution Amplitude Modulation Laser Radar (AM-LR) sensor has recently been developed, aimed at accurately reconstructing 3D digital models of real targets -- either single objects or complex scenes. The sensor sounding beam can be swept linearly across the object or circularly around it, by placing the object on a controlled rotation platform. Both intensity and phase shift of the back-scattered light are then collected and processed, providing respectively a shade-free photographic-like picture and accurate range data in the form of a range or depth image, with resolution depending mainly on the laser modulation frequency. Starting from the sample points, with an uncertainty that can be made as small as 100 ?m, the complete object surface can be reconstructed by using specifically developed software tools. The system has been successfully applied to scan different types of real surfaces (stone, wood, bones) and is expected to have significant applications in industrial machining, artwork cataloguing and medical diagnostics. Examples of 3D reconstructions are presented and the relevance of this technology for reverse engineering applied to artwork restoration and conservation is briefly discussed.

Bordone, Andrea; Ferri De Collibus, Mario; Fantoni, Roberta; Fornetti, Giorgio G.; Guarneri, Marianna; Poggi, Claudio; Ricci, Roberto

2003-04-01

415

Autofocus algorithm for synthetic aperture radar imaging with large curvilinear apertures  

NASA Astrophysics Data System (ADS)

An approach to autofocusing for large curved synthetic aperture radar (SAR) apertures is presented. Its essential feature is that phase corrections are being extracted not directly from SAR images, but rather from reconstructed SAR phase-history data representing windowed patches of the scene, of sizes sufficiently small to allow the linearization of the forward- and back-projection formulae. The algorithm processes data associated with each patch independently and in two steps. The first step employs a phase-gradient-type method in which phase correction compensating (possibly rapid) trajectory perturbations are estimated from the reconstructed phase history for the dominant scattering point on the patch. The second step uses phase-gradient-corrected data and extracts the absolute phase value, removing in this way phase ambiguities and reducing possible imperfections of the first stage, and providing the distances between the sensor and the scattering point with accuracy comparable to the wavelength. The features of the proposed autofocusing method are illustrated in its applications to intentionally corrupted small-scene 2006 Gotcha data. The examples include the extraction of absolute phases (ranges) for selected prominent point targets. They are then used to focus the scene and determine relative target-target distances.

Bleszynski, E.; Bleszynski, M.; Jaroszewicz, T.

2013-05-01

416

A two-level image pair simulator for interferometric synthetic aperture radar  

NASA Astrophysics Data System (ADS)

This paper presents a novel simulator to obtain single-look complex (SLC) image pair from the distributed target for interferometric synthetic aperture radar (InSAR). From conventional works, two simulation levels are derived: one is raw signal level (RSL) which means using raw signal to obtain SLC image pairs, the other is SLC image level (SIL) which means obtaining the SLC image pairs directly from existing SAR images. Conventional simulators only work on one simulation level, use complicated backscattering models, have high computational load on RSL and mismatch the real data on SIL. The novel simulator can robustly work on both RSL and SIL. It not only simplified the backscattering model, but also reduces the computational load on RSL. Moreover, the novel simulator creatively uses complex backscattering coefficient (CBC) pair to generate SLC image pair on SIL, which makes the result more accurately match real data. Finally, the improvements of this novel simulator are demonstrated by experimental results.

Chen, Wenxun; Xiang, Zheng; Liu, Xingzhao; Zhu, Mengmeng

2008-10-01

417

Tracking radar advanced signal processing and computing for Kwajalein Atoll (KA) application  

NASA Astrophysics Data System (ADS)

Two means are examined whereby the operations of KMR during mission execution may be improved through the introduction of advanced signal processing techniques. In the first approach, the addition of real time coherent signal processing technology to the FPQ-19 radar is considered. In the second approach, the incorporation of the MMW radar, with its very fine range precision, to the MMS system is considered. The former appears very attractive and a Phase 2 SBIR has been proposed. The latter does not appear promising enough to warrant further development.

Cottrill, Stanley D.

1992-11-01

418

Craters hosting radar-bright deposits in Mercury's north polar region: Areas of persistent shadow determined from MESSENGER images  

NASA Astrophysics Data System (ADS)

Radar-bright features near Mercury's poles were discovered in Earth-based radar images and proposed to be water ice present in permanently shadowed areas. Images from MESSENGER's one-year primary orbital mission provide the first nearly complete view of Mercury's north polar region, as well as multiple images of the surface under a range of illumination conditions. We find that radar-bright features near Mercury's north pole are associated with locations persistently shadowed in MESSENGER images. Within 10° of the pole, almost all craters larger than 10 km in diameter host radar-bright deposits. There are several craters located near Mercury's north pole with sufficiently large diameters to enable long-lived water ice to be thermally stable at the surface within regions of permanent shadow. Craters located farther south also host radar-bright deposits and show a preference for cold-pole longitudes; thermal models suggest that a thin insulating layer is required to cover these deposits if the radar-bright material consists predominantly of long-lived water ice. Many small (<10 km diameter) and low-latitude (extending southward to 66°N) craters host radar-bright material, and water ice may not be thermally stable in these craters for ~1 Gy, even beneath an insulating layer. The correlation of radar-bright features with persistently shadowed areas is consistent with the deposits being composed of water ice, and future thermal modeling of small and low-latitude craters has the potential to further constrain the nature, source, and timing of emplacement of the radar-bright material.

Chabot, Nancy L.; Ernst, Carolyn M.; Harmon, John K.; Murchie, Scott L.; Solomon, Sean C.; Blewett, David T.; Denevi, Brett W.

2013-01-01

419

High resolution through-the-wall radar image based on beamspace eigenstructure subspace methods  

NASA Astrophysics Data System (ADS)

Through-the-wall imaging (TWI) is a challenging problem, even if the wall parameters and characteristics are known to the system operator. Proper target classification and correct imaging interpretation require the application of high resolution techniques using limited array size. In inverse synthetic aperture radar (ISAR), signal subspace methods such as Multiple Signal Classification (MUSIC) are used to obtain high resolution imaging. In this paper, we adopt signal subspace methods and apply them to the 2-D spectrum obtained from the delay-andsum beamforming image. This is in contrast to ISAR, where raw data, in frequency and angle, is directly used to form the estimate of the covariance matrix and array response vector. Using beams rather than raw data has two main advantages, namely, it improves the signal-to-noise ratio (SNR) and can correctly image typical indoor extended targets, such as tables and cabinets, as well as point targets. The paper presents both simulated and experimental results using synthesized and real data. It compares the performance of beam-space MUSIC and Capon beamformer. The experimental data is collected at the test facility in the Radar Imaging Laboratory, Villanova University.

Yoon, Yeo-Sun; Amin, Moeness G.

2008-05-01

420

Mono-detection spatially super resolved microwave imaging for RADAR applications  

NASA Astrophysics Data System (ADS)

In this paper we present a novel RF photonic approach to radar scanning and imaging. The operating principle is based upon a system in which several (in our case two) radiating microwave sources generate and project at far field, a moving grating pattern over an object, e.g. by linearly modifying the relative phase between the microwave sources. Capturing a set of such integrated reflections (we work only with a mono detector) coming from the object at different radio frequencies (due to a simultaneously performed spectral scanning) can spatially reconstruct high resolution image of the object despite the fact that the sensing was performed with a small mono receiving antenna.

Shemer, Amir; Gabay, Isahar; Tur, Moshe; Boag, Amir; Kleinman, Haim; Zach, Shlomo; Zalevsky, Zeev

2012-05-01

421

Volcanic and impact deposits of the Moon's Aristarchus Plateau: A new view from Earth-based radar images  

NASA Astrophysics Data System (ADS)

Lunar pyroclastic deposits reflect an explosive stage of thebasaltic volcanism that filled impact basins across the nearside.These fine-grained mantling layers are of interest for theirassociation with early mare volcanic processes, and as possiblesources of volatiles and other species for lunar outposts. Wepresent Earth-based radar images, at 12.6 and 70 cm wavelengths,of the pyroclastic deposit that blankets the Aristarchus Plateau.The 70 cm data reveal the outlines of a lava-flow complex thatcovers a significant portion of the plateau and appears to haveformed by spillover of magma from the large sinuous rille VallisSchröteri. The pyroclastics mantling these flows are heavilycontaminated with rocks 10 cm and larger in diameter. The 12.6cm data confirm that other areas are mantled by 20 m or lessof material, and that there are numerous patches of 2 cm andlarger rocks associated with ejecta from Aristarchus crater.Some of the radar-detected rocky debris is within the mantlingmaterial and is not evident in visible-wavelength images. Theradar data identify thick, rock-poor areas of the pyroclasticdeposit best suited for resource exploitation.

Campbell, Bruce A.; Carter, Lynn M.; Hawke, B. Ray; Campbell, Donald B.; Ghent, Rebecca R.

2008-02-01

422

On the focusing issue of synthetic aperture radar imaging of ocean waves  

SciTech Connect

It is now widely accepted that the imaging of ocean surface waves by synthetic aperture radar (SAR) can be adequately described by velocity bunching theory in conjunction with the two-scale wave model. However, it has been conjectured that this theory is incapable of explaining why, under certain conditions, the image contrast of airborne SAR imagery of ocean waves can be enhanced by defocusing the SAR processor. It this were true it would raise serious doubts about the validity of the velocity bunching theory to describe the SAR imaging of ocean waves. In this paper the velocity bunching theory is defended. It is shown that image contrast enhancement by defocusing can also be obtained by this theory, which does not require the introduction of the phase or group velocity of the long ocean waves as a basic element of the SAR imaging theory.

Bruning, C. (Max-Planck-Inst. fuer Meterologie, Bundesstrasse 55, D-2000 Hamburg 13 (DE)); Alpers, W.R. (Univ. Hamburg, Inst. fuer Meereskunde, Troplowitzstrasse 7, D-2000 Hamburg 54 (DE)); Schroter, J.G. (Alfred-Wegener-Inst. fuer Polar-und Meeresforschung, D-2850 Bremerhaven (DE))

1991-01-01

423

Roles of equalization in radar imaging: modeling for superesolution in 3D reconstruction  

NASA Astrophysics Data System (ADS)

In radar imaging, resolution is generally dictated by its corresponding system point spread function, the response to a point source as a result of an external excitation. This notion of resolution turns out to be rather questionable, as the interpretation of echoes received from a range of continuous targets according to a linear model allows one to cast the imaging problem as a communication system that maps the target reflectivity function onto measurements, which in turn suggests that by virtue of sampling and equalization, one can achieve unlimited spatial resolution. This article reviews the fundamental problem inherent to pulse compression in a multistatic multi-input-multi-output (MIMO) scenario, from a communications viewpoint, in both focused and un-focused scenarios. We generalize the notion of 1D range compression and replace it by a more general 4D pulse compression. The process of focusing and scanning over a 3D object can be interpreted as a MIMO 4D convolution between a reflectivity tensor and a space-varying system, which naturally induces a 4D MIMO channel convolution model. This implies that several well-established block and linear equalization methods can be easily extended to a 3D scenario with the purpose of achieving exact reconstruction of a given reflectivity volume. That is, assuming that no multiple scattering occurs, resolution is only limited in range by the sampling device in the unfocused case, while unlimited in case of focusing at multiple depths. Exact reconstruction under a zero-forcing or least-squares criterion depends solely on the amount of diversity induced by sampling in both space (via scanning rate) and time (via sampling rate), which further allows for a tradeoff between range and cross-range resolution. For instance, the fastest scanning rate is achieved by steering non overlapping beams, in which case portions of the object can be reconstructed independently from each other.

Merched, Ricardo

2012-12-01

424

A new look at spotlight mode synthetic aperture radar as tomography: imaging 3-D targets.  

PubMed

A new 3D tomographic formulation of spotlight mode synthetic aperture radar (SAR) is developed. This extends the pioneering work of Munson et al. (1983), who first formally described SAR in terms of tomography but who made the simplifying assumption that the target scene was 2D. The present authors treat the more general and practical case in which the radar target reflectivities comprise a 3D function. The main goal is to demonstrate that the demodulated radar return data from a spotlight mode collection represent a certain set of samples of the 3D Fourier transform of the target reflectivity function and to do so using a tomographic paradigm instead of traditional range-Doppler analysis. They also show that the tomographic approach is useful in interpreting the reconstructed 2D SAR image corresponding to a 3D scene. Specifically, the well-known SAR phenomenon of layover is easily explained in terms of tomographic projections and is shown to be analogous to the projection effect in conventional optical imaging. PMID:18290021

Jakowatz, C V; Thompson, P A

1995-01-01

425

Radar target identification using an eigen-image approach  

Microsoft Academic Search

In order to maintain a high probability of correct classification the classifier must provide good separation between target classes and must be robust with respect to target variability. The authors have implemented a new target classifier based upon the eigen-image concept developed by Turk and Pentland (see Journal of Cognitive Neuroscience, vol.3, no.1, 1991) for automatic recognition of human faces.

Leslie M. Novak; G. J. Owirka

1994-01-01

426

Into the Cone: A Ground Penetrating Radar Investigation of Near Vent Processes at Cerro Negro Volcano  

NASA Astrophysics Data System (ADS)

Cinder cones are often assumed to grow via Strombolian activity as described by McGetchin et al (1974). Data with which to evaluate this and other models has historically been collected via eyewitness accounts, photography of eruptions, and mapping of exposed deposits. However, the dangerous nature of eruptions often prohibits near vent observations and accessible deposits are rare. Therefore, in order to gain a better understanding of near vent processes which may be used in volcanic modeling and hazard assessment, new data collection techniques must be implemented. Ground penetrating radar (GPR) imaging of tephra can reveal details of deposits at depths of approximately 2-20+ meters. Data collected in the fall of 2007 is here used to investigate the near vent processes of Cerro Negro, an active basaltic cinder cone in Nicaragua. Each of three GPR profiles begins at the crater rim and continues down the cone to the tephra blanket. One transect follows the prevailing wind direction (SW) while the other two head off at angles to the first: one to the NW and one to the SSW. The data display evidence of cone steepening over time, patterns of ballistic and tephra dispersal, and faulting within the cone, among other features.

Courtland, L. M.; Kruse, S. E.; Connor, C.

2009-12-01

427

Wideband Reception and Processing for Dual-Polarization Radars with Dual Transmitters  

SciTech Connect

Improving the estimation accuracy and reducing the time required for measurement are governing goals for any radar design. Polarimetric weather radar measures the polarization covariance matrix of the signal returns from precipitation volumes in addition to the Doppler parameters. Increasing the equivalent number of independent samples in any estimation process results in decrease in the standard deviation of estimates. Oversampling pulsed Doppler radar returns at a rate larger than the pulse bandwidth, whitening the range samples and subsequent averaging have been pursued as a potential way to decrease the measured standard deviation of signal parameters estimates. It has been shown that the application of oversampling, whitening and subsequent averaging improves the quality of reflectivity and mean velocity estimates in agreement with theory; Oversampled data collected from CSU-CHILL radar are analyzed to evaluate the performance of dual-polarization parameter estimators such as differential reflectivity and differential phase. The reasons that may limit the improvement in estimation quality of polarimetric parameters are investigated. It is demonstrated that the observation of the variability of range signals within subpulses is important for obtaining maximum variance reduction through whitening. Accurate measurement of the amplitude and phase of the transmitted pulse is critically important for effective whitening of the received waveform. The differential phase pattern between the transmit pulses is found to be critical for obtaining unbiased and accurate estimates of polarimetric parameters through whitening. CSU-CHILL radar's transmit pulse sampling capability is used to evaluate the impact of waveforms on oversampling and estimation.

Choudhury, Sutanay; Chandrasekar, V.

2007-01-01

428

Status of the ACRF Millimeter Wave Cloud Radars (MMCRs), the Path Forward for Future MMCR Upgrades, the Concept of 3D Volume Imaging Radar and the UAV Radar.  

National Technical Information Service (NTIS)

The United States (U.S.) Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) operates millimeter wavelength cloud radars (MMCRs) in several climatological regimes. The MMCRs, are the primary observing tool f...

K. B. Widener M. A. Mille P. Kollias R. T. Marchandr T. P. Ackerman

2005-01-01

429

Study of Tissue Phantoms, Tissues, and Contrast Agent with the Biophotoacoustic Radar and Comparison to Ultrasound Imaging for Deep Subsurface Imaging  

NASA Astrophysics Data System (ADS)

In this study, the imaging capability of our wide-spectrum frequency-domain photoacoustic (FD-PA) imaging alias "photoacoustic radar" methodology for imaging of soft tissues is explored. A practical application of the mathematical correlation processing method with relatively long (1 ms) frequency-modulated optical excitation is demonstrated for reconstruction of the spatial location of the PA sources. Image comparison with ultrasound (US) modality was investigated to see the complementarity between the two techniques. The obtained results with a phased array probe on tissue phantoms and their comparison to US images demonstrated that the FD-PA technique has strong potential for deep subsurface imaging with excellent contrast and high signal-to-noise ratio. FD-PA images of blood vessels in a human wrist and an in vivo subcutaneous tumor in a rat model are presented. As in other imaging modalities, the employment of contrast agents is desirable to improve the capability of medical diagnostics. Therefore, this study also evaluated and characterized the use of Food and Drug Administration (FDA)-approved superparamagnetic iron oxide nanoparticles (SPION) as PA contrast agents.

Alwi, R.; Telenkov, S.; Mandelis, A.; Gu, F.

2012-11-01

430

Signal Processing in Multisite UWB Radar Devices for Searching Survivors in Rubble  

Microsoft Academic Search

The use of ultra wideband multisite radar devices (UWB MSRDs) with two antennas separated by about 1...1.5 m for searching survivors in rubble is very prospective. Optimised signal processing in such UWB MSRD is considered, which has to solve two principal problems: 1) detection of very weak signals reflected from a moving human chest due to breathing against strong clutter

Victor Chernyak

2006-01-01

431

Dual Super-Systolic Core for Real-Time Reconstructive Algorithms of High-Resolution Radar/SAR Imaging Systems  

PubMed Central

A high-speed dual super-systolic core for reconstructive signal processing (SP) operations consists of a double parallel systolic array (SA) machine in which each processing element of the array is also conceptualized as another SA in a bit-level fashion. In this study, we addressed the design of a high-speed dual super-systolic array (SSA) core for the enhancement/reconstruction of remote sensing (RS) imaging of radar/synthetic aperture radar (SAR) sensor systems. The selected reconstructive SP algorithms are efficiently transformed in their parallel representation and then, they are mapped into an efficient high performance embedded computing (HPEC) architecture in reconfigurable Xilinx field programmable gate array (FPGA) platforms. As an implementation test case, the proposed approach was aggregated in a HW/SW co-design scheme in order to solve the nonlinear ill-posed inverse problem of nonparametric estimation of the power spatial spectrum pattern (SSP) from a remotely sensed scene. We show how such dual SSA core, drastically reduces the computational load of complex RS regularization techniques achieving the required real-time operational mode.

Atoche, Alejandro Castillo; Castillo, Javier Vazquez

2012-01-01

432

Dual super-systolic core for real-time reconstructive algorithms of high-resolution radar/SAR imaging systems.  

PubMed

A high-speed dual super-systolic core for reconstructive signal processing (SP) operations consists of a double parallel systolic array (SA) machine in which each processing element of the array is also conceptualized as another SA in a bit-level fashion. In this study, we addressed the design of a high-speed dual super-systolic array (SSA) core for the enhancement/reconstruction of remote sensing (RS) imaging of radar/synthetic aperture radar (SAR) sensor systems. The selected reconstructive SP algorithms are efficiently transformed in their parallel representation and then, they are mapped into an efficient high performance embedded computing (HPEC) architecture in reconfigurable Xilinx field programmable gate array (FPGA) platforms. As an implementation test case, the proposed approach was aggregated in a HW/SW co-design scheme in order to solve the nonlinear ill-posed inverse problem of nonparametric estimation of the power spatial spectrum pattern (SSP) from a remotely sensed scene. We show how such dual SSA core, drastically reduces the computational load of complex RS regularization techniques achieving the required real-time operational mode. PMID:22736964

Atoche, Alejandro Castillo; Castillo, Javier Vázquez

2012-02-24

433

Radar imaging of basement control on ice-sheet dynamics in West Antarctica  

NASA Astrophysics Data System (ADS)

Satellite remote sensing measurements show that ice streams draining the West Antarctic Ice Sheet (WAIS) to the Amundsen and Bellingshausen Sea Embayments are accelerating and thinning rapidly, contributing to ~10% of observed global sea-level rise. Losses are dominated by 'dynamic thinning,' the progressive acceleration, thinning and retreat of inland ice, likely forced by oceanic or atmospheric perturbations along the coastline. Recently highlighted as key to improving projections of future ice-sheet contributions to sea-level, the incorporation of dynamic thinning into numerical models has been restricted by lack of knowledge of basal topography so that, for much of the WAIS, the fundamental controls on its dynamic losses, hence the rate and ultimate extent of its potential retreat, remain difficult to quantify. Ice-penetrating radar systems offer the principal means by which we can acquire regional information on the basal conditions known theoretically to exert a strong control on dynamic thinning processes. Here we describe the detailed delineation, with radar, of a subglacial trench up to 2.5 km deep and 20 km wide, connecting the ice-sheet interior to the Bellingshausen margin, whose existence impacts profoundly on current ice-dynamic losses. We use ice-penetrating radar from 2 MHz oversnow radar (the British Antarctic Survey DELORES system) and airborne radar (from Operation IceBridge) in 2009/10 to map the geometry of the trench, and discuss its likely origins as a tectonic line of weakness. The trench represents a conduit through which a palaeo-ice stream was directed onto the continental shelf during glacial maxima, eroding the major Belgica Trough through Eltanin Bay, which today affords warm open-ocean water access to the ice front, promoting further dynamic thinning. We support recently reported findings from airborne geophysics over neighbouring Pine Island Glacier that the spatial configuration of West Antarctica's regions of inland dynamic thinning is strongly controlled by the locations of old faults and rift structures.

Bingham, R. G.; King, E. C.; Larter, R. D.; Ferraccioli, F.; Pritchard, H. D.; Smith, A.; Vaughan, D.

2011-12-01

434

Radar polarimetry for geoscience applications  

SciTech Connect

A source book for remote sensing and radar design engineers, this text covers wave polarization, polarization synthesis, scattering matrices, SAR polarization systems, and an array of applications It covers: an introduction to the different mathematical representations used to describe scattering properties, a review of scatterometer system design and calibration techniques for use in polarimetric measurements, a study of specific polarimetric radar systems, such as the shuttle imaging radar C (SIR-C), that includes calibration and compression techniques, data processing guidelines, and design approaches.

Elachi, C.; Kuga, Y.; McDonald, K.; Sarabandi, K.; Ulaby, F.T.; Whitt, M.; Zebker, H.; van Zyl, J.J.

1990-01-01

435

Advanced Radar Signal and Data Processing (Le traitement avance du signal et des donnees radar) (CD-ROM).  

National Technical Information Service (NTIS)

Radar is an important sensor characterized by day/night all-weather operation capability. A key feature of radar is the ability of reconnaissance, surveillance of a wide area with target acquisition (RSTA). In addition it offers the potential of moving ta...

2006-01-01

436

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

437

Multipath exploitation in through-wall radar imaging via point spread functions.  

PubMed

Due to several sources of multipath in through-wall radar sensing, such as walls, floors, and ceilings, there could exist multipath ghosts associated with a few genuine targets in the synthetic aperture beamformed image. The multipath ghosts are false positives and therefore confusable with genuine targets. Here, we develop a multipath exploitation technique using point spread functions, which associate and map back the multipath ghosts to their genuine targets, thereby increasing the effective signal-to-clutter ratio (SCR) at the genuine target locations. To do so, we first develop a multipath model advocating the Householder transformation, which permits modeling multiple reflections at multiple walls, and also allows for unconventional room/building geometries. Second, closed-form solutions of the multipath ghost locations assuming free space propagation are derived. Third, a nonlinear least squares optimization is formulated and initialized with these free space solutions to localize the multipath ghosts in through-wall radar sensing. The exploitation approach is general and does not require a priori assumptions on the number of targets. The free space multipath ghost locations and exploitation technique derived here may be used as is for multipath exploitation in urban canyons via synthetic aperture radar. Analytical expressions quantifying the SCR gain after multipath exploitation are derived. The analysis is validated with experimental EM results using finite-difference time-domain simulations. PMID:23568504

Setlur, Pawan; Alli, Giovanni; Nuzzo, Luigia

2013-04-04

438

Universal multifractal scaling of synthetic aperture radar images of sea-ice  

SciTech Connect

Multifrequency, multipolarization imaging radar scattering coefficient data sets, acquired by synthetic aperture radar (SAR) over sea-ice, were studied in order to reveal their scale-invariant properties. Two distinct scenes were acquired at C-band (5.6 cm) and L-band (25 cm) wavelengths for three different linear polarizations (HH, VV, and HV). These sea-ice radar scattering coefficient fields were investigated by applying both Fourier and multifractal analysis techniques. The (multi) scaling of the data is clearly exhibited in both scenes for all three polarizations at L-band and for the HV polarization at C-band. The fields presenting this symmetry were found to be well described by universal multifractals. The corresponding parameters {alpha}, C{sub 1}, and H were determined for all these fields and were found to vary little with only the parameter H (characterizing the degree of nonconservation) displaying some systematic sensitivity to polarization. The values found for the universal multifractal parameters are {alpha} {approx} 1.85 {+-} 0.05, C{sub 1} {approx} 0.0086 {+-} 0.0041, and H {approx} {minus}0.15 {+-} 0.05.

Falco, T.; Francis, F.; Lovejoy, S. [McGill Univ., Montreal, Quebec (Canada). Physics Dept.; Schertzer, D. [Univ. Pierre et Marie Curie, Paris (France). Lab. de Meteorologie Dynamique; Kerman, B. [Atmospheric Environment Service, Burlington, Ontario (Canada); Drinkwater, M. [Jet Propulsion Lab., Pasadena, CA (United States)

1996-07-01

439

Mapping of a major paleodrainage system in eastern Libya using orbital imaging radar: The Kufrah River  

NASA Astrophysics Data System (ADS)

Over the last few decades, remote sensing has revealed buried river channels in a number of regions worldwide, in many cases providing evidence of dramatic paleoenvironmental changes over Cenozoic time scales. Using orbital radar satellite imagery, we mapped a major paleodrainage system in eastern Libya, that could have linked the Kufrah Basin to the Mediterranean coast through the Sirt Basin, possibly as far back as the middle Miocene. Synthetic Aperture Radar images from the PALSAR sensor clearly reveal a 900 km-long river system, which starts with three main tributaries (north-eastern Tibesti, northern Uweinat and western Gilf Kebir/Abu Ras) that connect in the Kufrah oasis region. The river system then flows north through the Jebel Dalmah, and forms a large alluvial fan in the Sarir Dalmah. The sand dunes of the Calanscio Sand Sea prevent deep orbital radar penetration and preclude detailed reconstruction of any possible connection to the Mediterranean Sea, but a 300 km-long link to the Gulf of Sirt through the Wadi Sahabi paleochannel is likely. If this connection is confirmed, and its Miocene antiquity is established, then the Kufrah River, comparable in length to the Egyptian Nile, will have important implications for the understanding of the past environments and climates of northern Africa from the middle Miocene to the Holocene.

Paillou, Philippe; Schuster, Mathieu; Tooth, Stephen; Farr, Tom; Rosenqvist, Ake; Lopez, Sylvia; Malezieux, Jean-Marie