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in subjects: "Synthetic-Aperture Radar"

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Development of a GPS-aided motion measurement, pointing, and stabilization system for a Synthetic Aperture Radar. [Global Positioning System (GPS)]

An advanced Synthetic Aperture Radar Motion Compensation System has been developed by Sandia National Laboratories (SNL). The system includes a miniaturized high accuracy ring laser gyro inertial measurement unit, a three axis gimbal pointing and stabilization assembly, a differential Global Positioning System (GPS) navigation aiding system, and a pilot guidance system. The system provides several improvements over previous SNL motion compensation systems and is capable of antenna stabilization… more

Date: January 1, 1991

Creator: Fellerhoff, J. R. & Kohler, S. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

SAR image registration in absolute coordinates using GPS carrier phase position and velocity information

It is useful in a variety of military and commercial application to accurately register the position of synthetic aperture radar (SAR) imagery in absolute coordinates. The two basic SAR measurements, range and doppler, can be used to solve for the position of the SAR image. Imprecise knowledge of the SAR collection platform`s position and velocity vectors introduce errors in the range and doppler measurements and can cause the apparent location of the SAR image on the ground to be in error by t… more

Date: September 1, 1994

Creator: Burgett, S. & Meindl, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Electromagnetic scattering from buried objects

Radar imaging and detection of objects buried in soil has potentially important applications in the areas of nonproliferation of weapons, environmental monitoring, hazardous-waste site location and assessment, and even archeology. In order to understand and exploit this potential, it is first necessary to understand how the soil responds to an electromagnetic wave, and how targets buried within the soil scatter the electromagnetic wave. We examine the response of the soil to a short pulse, and … more

Date: October 1, 1994

Creator: Brock, B. C. & Sorensen, K. W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Sensor feature fusion for detecting buried objects

Given multiple registered images of the earth`s surface from dual-band sensors, our system fuses information from the sensors to reduce the effects of clutter and improve the ability to detect buried or surface target sites. The sensor suite currently includes two sensors (5 micron and 10 micron wavelengths) and one ground penetrating radar (GPR) of the wide-band pulsed synthetic aperture type. We use a supervised teaming pattern recognition approach to detect metal and plastic land mines burie… more

Date: April 1, 1993

Creator: Clark, G. A.; Sengupta, S. K.; Sherwood, R. J.; Hernandez, J. E.; Buhl, M. R.; Schaich, P. C. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Synthetic aperture radar processing with polar formatted subapertures

Synthetic Aperture Radar (SAR) uses the motion of a small real antenna to synthesize a larger aperture, and thereby achieve very fine azimuth resolution. Efficient SAR image formation requires modelling the radar echo and compensating (focusing) the delay and phase for various positions in the target scene. Polar-Format processing is one successful algorithm developed to process large scenes at fine resolutions, but is still limited, especially at resolutions near a wavelength. This paper shows… more

Date: October 1, 1994

Creator: Doerry, A. W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Interferometric synthetic aperture radar terrain elevation mapping from multiple observations

All prior interferometric SAR imaging experiments to date dealt with pairwise processing. Simultaneous image collections from two antenna systems or two-pass single antenna collections are processed as interferometric pairs to extract corresponding pixel by pixel phase differences which encode terrain elevation height. The phase differences are wrapped values which must be unwrapped and scaled to yield terrain height. We propose two major classes of techniques that hold promise for robust multi… more

Date: July 1, 1994

Creator: Ghiglia, D. C. & Wahl, D. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Subsurface object position and image correction for standoff Ground Penetrating Radar

Present applications of standoff (airborne) Ground Penetrating SAR (Synthetic Aperture Radar) allows objects near the surface to be detected but only provides an approximation for the actual location and image. When single media models are employed the lack of correction for the phase velocity and refractive changes at the air/soil interface result in object distortions. Positional errors and image distortions comparable to the size of the object are possible. Correction is possible, if the med… more

Date: May 1, 1994

Creator: Kane, R. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Design and implementation of a Synthetic Aperture Radar for Open Skies (SAROS) aboard a C-135 aircraft

NATO and former Warsaw Pact nations have agreed to allow overflights of their countries in the interest of easing world tension. The United States has decided to implement two C-135 aircraft with a Synthetic Aperture Radar (SAR) that has a 3-meter resolution. This work is being sponsored by the Defense Nuclear Agency (DNA) and will be operational in Fall 1995. Since the SAR equipment must be exportable to foreign nations, a 20-year-old UPD-8 analog SAR system was selected as the front-end and r… more

Date: August 1, 1994

Creator: Cooper, D. W.; Murphy, M. & Rimmel, G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Synthetic aperture radar processing with tiered subapertures

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 algorithm… more

Date: June 1, 1994

Creator: Doerry, A. W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Developments in ground-penetrating radar at LLNL

Lawrence Livermore National Laboratory (LLNL) is developing a side-looking, ground-penetrating impulse radar system that will eventually be mounted on an airborne platform to locate buried minefields. Presently, the radar system is mounted on top of a 60-foot adjustable boom. Several unique as well as commercial antennas having bandwidths in the 200 to 2000 MHz range are being experimented with. Also, LLNL-developed monocycle pulse generators are tailored to be most efficient over this frequenc… more

Date: May 1, 1994

Creator: Sargis, P. D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

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

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 techni… more

Date: July 1, 1994

Creator: Mast, J. E. & Johansson, E. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Interferometric SAR phase difference calibration: Methods and results

This paper addresses the steps necessary to determine and maintain the phase calibration of a two-channel interferometric synthetic aperture radar (IFSAR). The method, setup, and accuracy of four different calibration techniques are compared. The most novel technique involves pointing the interferometric baseline at nadir and imaging a lake surface. The other techniques include measuring various flat surfaces in traditional side-looking IFSAR maps, in-flight closed-loop calibration path measure… more

Date: December 31, 1993

Creator: Bickel, D. L. & Hensley, W. H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Radially combined 30 W, 14-16 GHz amplifier

The paper describes a highly integrated 30 W power amplifier for a Synthetic Aperture Radar, operating in the 14--16 GHz band. The use of a waveguide radial combiner, a microstrip power divider and direct microstrip to waveguide miniaturized ceramic technology, leads to an unusually compact and accessible structure, well suited for commercial production.

Date: April 1, 1994

Creator: Sechi, F.; Bujatti, M.; Knudson, R. & Bugos, R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

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

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 to its surface-image counterpart, even when the soil`s properties are known. This paper … more

Date: May 1, 1994

Creator: Doerry, A. W.; Brock, B. C.; Boverie, B. & Cress, D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

New formulation for interferometric synthetic aperture radar for terrain mapping

The subject of interferometric synthetic aperture radar (IFSAR) for high-accuracy terrain elevation mapping continues to gain importance in the arena of radar signal processing. Applications to problems in precision terrain-aided guidance and automatic target recognition, as well as a variety of civil applications, are being studied by a number of researchers. Not unlike many other areas of SAR processing, the subject of IFSAR can at first glance appear to be somewhat mysterious. In this paper … more

Date: April 1, 1994

Creator: Jakowatz, C. V. Jr.; Wahl, D. E.; Eichel, P. H. & Thompson, P. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

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

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 gr… more

Date: January 1, 1994

Creator: Doerry, A. W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

New approach to strip-map SAR autofocus

Means for removing phase errors induced in spotlight mode synthetic aperture radar (SAR) imagery are now well-established. The Phase Gradient Autofocus (PGA) algorithm has been shown to be robust over a wide range of spotlight mode imagery and phase error functions. These phase errors could have their origin either in uncompensated platform motion or random propagation delays incurred, for example, from tropospheric turbulence. The PGA technique, however, cannot be directly applied to imagery f… more

Date: May 1, 1994

Creator: Wahl, D.; Jakowatz, C.; Thompson, P. & Ghiglia, D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Factors governing selection of operating frequency for subsurface- imaging synthetic-aperture radar

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, subsurface imaging is complicated by propagation loss in the soil and surface-clutter response. Both the loss and surface-clutter response depend on the operating frequency. This paper examines several factors which provide a basis for determining optimum frequencies and frequency ranges which will allow s… more

Date: December 31, 1993

Creator: Brock, B. C. & Patitz, W. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A SAR image-formation algorithm that compensates for the spatially-variant effects of antenna motion

A synthetic aperture radar (SAR) obtains azimuth resolution by combining data from a number of points along a specified path. Uncompensated antenna motion that deviates significantly from the desired path produces spatially-variant errors in the output image. The algorithm presented in this paper corrects many of these motion-related errors. In this respect, it is similar to time-domain convolution, but it is more computationally efficient. The algorithm uses overlapped subapertures in a three-… more

Date: March 1, 1994

Creator: Burns, B. L. & Cordaro, J. T.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Ground-penetrating radar for buried mine detection

Lawrence Livermore National Laboratory (LLNL) is developing an ultra-wideband, side-looking, ground-penetrating impulse radar system that can be mounted on an airborne platform for the purpose of locating buried mines. The radar system is presently mounted on an 18-meter boom. The authors have successfully imaged a minefield located at the Nevada Test Site. The minefield consists of real and surrogate mines of various materials and sizes placed in natural vegetation. Some areas have been cleare… more

Date: April 1, 1994

Creator: Sargis, P. D.; Lee, F. D.; Fulkerson, E. S.; McKinley, B. J. & Aimonetti, W. D.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

FESDIF -- Finite Element Scalar Diffraction theory code

This document describes the theory and use of a powerful scalar diffraction theory based computer code for calculation of intensity fields due to diffraction of optical waves by two-dimensional planar apertures and lenses. This code is called FESDIF (Finite Element Scalar Diffraction). It is based upon both Fraunhofer and Kirchhoff scalar diffraction theories. Simplified routines for circular apertures are included. However, the real power of the code comes from its basis in finite element meth… more

Date: September 1, 1992

Creator: Kraus, H. G.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Three-dimensional subsurface imaging synthetic aperture radar

The objective of this applied research and development project is to develop a system known as `3-D SISAR`. This system consists of a ground penetrating radar with software algorithms designed for the detection, location, and identification of buried objects in the underground hazardous waste environments found at DOE storage sites. Three-dimensional maps of the object locations will be produced which can assist the development of remediation strategies and the characterization of the digface d… more

Date: March 1, 1995

Creator: Moussally, G. J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Feature discovery in gray level imagery for one-class object recognition

Feature extraction transforms an object`s image representation to an alternate reduced representation. In one-class object recognition, we would like this alternate representation to give improved discrimination between the object and all possible non-objects and improved generation between different object poses. Feature selection can be time-consuming and difficult to optimize so we have investigated unsupervised neural networks for feature discovery. We first discuss an inherent limitation i… more

Date: December 31, 1993

Creator: Koch, M. W. & Moya, M. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A comparative evaluation of SAR and SLAR

Synthetic aperture radar (SAR) was evaluated as a potential technological improvement over the Coast Guard`s existing side-looking airborne radar (SLAR) for oil-spill surveillance applications. The US Coast Guard Research and Development Center (R&D Center), Environmental Branch, sponsored a joint experiment including the US Coast Guard, Sandia National Laboratories, and the Naval Oceanographic and Atmospheric Administration (NOAA), Hazardous Materials Division. Radar imaging missions were flow… more

Date: November 1, 1993

Creator: Mastin, G. A.; Manson, J. J.; Bradley, J. D.; Axline, R. M. & Hover, G. L.

Item Type: Article

Partner: UNT Libraries Government Documents Department