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  • 1
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    Vegetation canopy discrimination and biomass assessment using multipolarized airborne SAR (1985)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: Multipolarized airborne Synthetic Aperture Radar (SAR) data were acquired over a largely agricultural test site near Macomb, Illinois, in conjunction with the Shuttle Imaging Radar (SIR-B) experiment in October 1984. The NASA/JPL L-band SAR operating at 1.225 GHz made a series of daily overflights with azimuth view angles both parallel and orthogonal to those of SIR-B. The SAR data was digitally recorded in the quadpolarization configuration. An extensive set of ground measurements were obtained throughout the test site and include biophysical and soil measurements of approximately 400 agricultural fields. Preliminary evaluation of some of the airborne SAR imagery indicates a great potential for crop discrimination and assessment of canopy condition. False color composites constructed from the combination of three linear polarizations (HH, VV, and HV) were found to be clearly superior to any single polarization for purposes of crop classification. In addition, an image constructed using the HH return to modulate intensity and the phase difference between HH and VV returns to modulate chroma indicates a clear capability for assessment of canopy height and/or biomass. In particular, corn fields heavily damaged by infestations of corn borer are readily distinguished from noninfested fields.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA(JPL Aircraft SAR Workshop Proc.; p 67-75
    Format: text
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  • 2
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    CV-990 L-band SAR: A calibration experiment (1985)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: Calibrated image data is required by most users of synthetic aperture radar (SAR) data particularly those attempting to classify targets based upon their radar backscatter signature as a function of frequency polarization or incidence angle. In this experiment, the backscatter derived by calibrating the NASA/JPL CV-990 L-band SAR, and the backscatter reported from a pass of the NASA/JSC C-130 scatterometer as the two instruments flew over the same site at different times are compared.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA(JPL Aircraft SAR Workshop Proc.; p 17-20
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  • 3
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    Radar system description (1985)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: A brief overview is given of the hardware and software utilized to generate the CV-990 synthetic aperture radar's image products. The on-board hardware is described, then the operational processing software, and finally the image products that are routinely available.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA(JPL Aircraft SAR Workshop Proc.; p 5-12
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  • 4
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    Radio phase characteristics of terrain from multipolarized synthetic aperture radar data (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Recent advances in digital data acquisition and signal processing technology permit simultaneous measurement of the complex (amplitude and phase) radar backscatter from several polarization-diverse antennas. While absolute phase mesurements remain to be analyzed in detail. The differential phase of signals polarized parallel and perpendicular to the plane of incidence provide information on the scattering mechanisms that dominate the interaction of the radio waves with the terrain. Analysis of phase backscatter maps from a typical urban area yields a bimodal distribution with the two peaks separated by approximately 180 degrees, highly indicative of a dominant simple geometric one bounce-two bounce mechanism. Some maps of agricultural areas exhibit a similar distribution, however, other agricultural areas yield a distribution that, while still bimodal, consists of two peaks separated by about 110 deg. Still other agricultural areas exhibit a more complex distribution. All of the observed phase shifts appear to be independent of incidence angle from at least 20 deg to 55 deg, therefore the 110 degree shifts are inconsistent with both the geometric model used for the urban area and with common dielectric slab models.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
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  • 5
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    Radiometric calibration of Seasat SAR imagery (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A goal of future synthetic aperture radar (SAR) system design is to yield the radiometrically accurate imagery necessary for use in classification problems. To accomplish this, a reliable calibration technique must be developed. Many such techniques have been proposed (e.g., Stiles and Holtzman, 1982); however, until now, none have been tested on spaceborne SAR digital data. In this paper, a method of significantly increasing the reproducibility of several independent Seasat SAR data sets of a test site using an automated correction procedure is described.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
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  • 6
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    The NASA/JPL multipolarization SAR aircraft program (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The NASA/JPL aircrft program has been in existence for more than a decade. However, during the past two years, there has been a dramatic increase in the capability and scientific utility of this system as an L-band, 4-polarization synthetic aperture radar (SAR) system has become operational. The system is capable of simultaneously and coherently acquiring four independent complex polarization measurements for every pixel in the image. This capability has been exploited by a number of experimenters to generate several new data types that appear to contain significantly more information than was previously available from single or dual polarized SAR systems. The system will ultimately be capable of estimating the entire complex scattering matrix for every pixel on the ground. Within the next year the system will be extended to C-band so that it will be possible to simultaneously acquire 4-polarization imagery at L-band and C-band. This system will be the prototype for the SIR-C experiment that will have similar capabilities and be flown on the Space Shuttle in 1989.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
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  • 7
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    An adaptive quantization method for burst mode synthetic aperture radar data (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Synthetic aperture radar (SAR) has high data rate because it collects and processes the data coherently. The data rate limitation of the system has to be satisfied while maintaining good image quality. Thus, a quantizer with minimum data rate and high SNR should be employed. An adaptive quantization method is proposed for the burst mode SAR. This adaptive quantizer uses uniformly quantized data to select a subset of bits which is equivalent to changing the step size of the uniform quantizer. A simple implementation which uses the previous burst data to compute the local statistics for the bit selection is presented. The use of previous burst simplifies the implementation because it does not require storage or delay; however, an abrupt change in the terrain could result in incorrect bit selection. An error analysis of this implementation and comparison of two burst mode SAR images formed using the uniformly quantized and adaptively quantized data is presented.
    Keywords: COMMUNICATIONS AND RADAR
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  • 8
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    The NASA/JPL multifrequency, multipolarisation airborne SAR system (1988)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: Polarimetric synthetic aperture radars, operating at L-, C- and P-band, were designed to replace and upgrade a system destroyed in an aircraft accident. Ground and flight tests were conducted, and the radar was flown over a calibration site in a sequence of experiments designed to calibrate the system. The radar also took part in science campaigns.
    Keywords: COMMUNICATIONS AND RADAR
    Type: ESA, Proceedings of the 1988 International Geoscience and Remote Sensing Symposium (IGARSS 1988) on Remote Sensing: Moving Towards the 21st Century, Volume 1; p 345-349
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  • 9
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    SAR Speckle Noise Reduction Using Wiener Filter (1983)
    In:  CASI
    Details
    Publication Date: 2014-09-10
    Description: Synthetic aperture radar (SAR) images are degraded by speckle. A multiplicative speckle noise model for SAR images is presented. Using this model, a Wiener filter is derived by minimizing the mean-squared error using the known speckle statistics. Implementation of the Wiener filter is discussed and experimental results are presented. Finally, possible improvements to this method are explored.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: Texas A and M Univ. Proc. of the NASA Symp. on Math. Pattern Recognition and Image Analysis; p 295-310
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  • 10
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    Conversion loss and noise of microwave and millimeter-wave mixers. I - Theory. II - Experiment (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The conversion loss and noise of microwave and millimeter-wave mixers are analyzed. Nonlinear capacitance, arbitrary embedding impedances, as well as shot, thermal and scattering noise arising in the diode, figure in the analysis. The anomalous mixer noise noted in millimeter-wave mixers by Kerr (1975) is shown to be explainable in terms of the correlation of down-converted components of the time-varying shot noise. A digital computer analysis of the conversion loss, noise, and output impedance of an 80-120-GHz mixer is also conducted.
    Keywords: ELECTRONICS AND ELECTRICAL ENGINEERING
    Type: IEEE Transactions on Microwave Theory and Techniques; MTT-26; Feb. 197
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