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  • Earth Resources and Remote Sensing  (5)
  • COMMUNICATIONS AND RADAR  (2)
  • Biochemistry and Biotechnology
  • GENERAL
  • 2015-2019
  • 1990-1994  (7)
  • 1993  (7)
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  • 2015-2019
  • 1990-1994  (7)
Year
  • 1
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    Development of SIR-C Ground Calibration Equipment (1993)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: SIR-C/X-SAR is currently scheduled for launch in April 1994. SIR-C is an L-Band and C-Band, multi-polarization spaceborne SAR system developed by NASA/JPL. X- SAR is an X-Band SAR system developed by DARA/ASI. One of the problems involved in calibrating the SIR-C instrument is to make sure that the horizontal (H) and vertical (V) polarized beams are aligned in the azimuth direction, i.e.. that they are pointing in the same direction. This is important if the polarimetric performance specifications for the system are to be met. To solve this problem, we have designed and built a prototype of a low-cost ground receiver capable of recording received power from two antennas, one H-polarized, the other V-polarized. The two signals are mixed to audio then recorded on the left and right stereo channels of a standard audio cassette player. The audio cassette recording can then be played back directly into a Macintosh computer, where it is digitized. Analysis of.
    Keywords: Earth Resources and Remote Sensing
    Type: IEEE, Geoscience and Remote Sensing; Tokyo; Japan
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    The Effects of Noise on Polarimetric SAR Data (1993)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: Polarimetric SAR data can provide a great deal of information about the scattering behavior of the surface under observation. Polarimetric SAR systems often measure the scattering matrices of the areas under observation in linear polarizations (H and V). From the scattering matrix commonly used forms such as the covariance matrix and the Stokes matrix can be easily derived. Other measures derived from polarimetric SAR data include the standard deviation of texture, correlation coefficients between scattering matrix terms, and the mode and variance of phase differences between scattering matrix terms. The effects of additive system noise on these measurements is not often considered in the literature on this subject.
    Keywords: Earth Resources and Remote Sensing
    Type: IEEE, Geoscience & Remote Sensing; Tokyo; Japan
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Calibration Results for J-ERS-1 SAR Data Produced by the Alaska SAR Facility (1993)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: The Alaska SAR Facility has been receiving and processing SAR data from the J-ERS-1 satellite since Spring 1992. Corner reflectors have been set up for J-ERS-1 SAR calibration at a site near Delta Junction, in central Alaska. Image quality and calibration analysis results from the Delta Junction site and others will be presented in this paper. The impact of the 3-bit Analog-to-Digital Converter and the automatic stepping of the gain as a function of range in the J-ERS-1 radar receiver on calibration performance has been assessed. Preliminary observations on J-ERS-1 SAR data are that the average Signal-to-Noise ratio is generally fairly low, in the range 5-6dB. Azimuth ambiguity levels are higher than preflight analysis indicated. Over land, the dynamic range in the backscatter at L-band for approximately 36 degree incidence angle is often fairly high.
    Keywords: Earth Resources and Remote Sensing
    Type: IEEE, Geoscience and Remote Sensing; Tokyo; Japan
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Unknown
    Calibration Results for J-ERS-1 SAR Data Produced by the Alaska SAR Facility (1993)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: The Alaska SAR Facility has been receiving and processing SAR data from the J-ERS-1 satellite since Spring 1992. Corner reflectors have been set up for J-ERS-1 SAR calibration at a site near Delta Junction, in central Alaska. Image quality and calibration analysis results from the Delta Junction site and others will be presented in this paper. The impact of the 3-bit Analog-to-Digital Converter and the automatic stepping of the gain as a function of range in the J-ERS-1 radar receiver on calibration performance has been assessed. Preliminary observations on J-ERS-1 SAR data are that the average Signal-to-Noise ratio is generally fairly low, in the range 5-6 dB. Azimuth ambiguity levels are higher than preflight analysis indicated. Over land, the dynamic range in the backscatter at L-band for approximately 36 degree incidence angle is often fairly high...
    Keywords: Earth Resources and Remote Sensing
    Type: IEEE, Geoscience & Remote Sensing; Tokyo; Japan
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Unknown
    The Effects of Noise on Polarimetric SAR Data (1993)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: Polarimetric SAR data can provide a great deal of information about the scattering behavior of the surface under observation. Polarimetric SAR systems often measure the scattering matrices of the areas under observation in linear polarizations (H and V). From the scattering matrix commonly used forms such as the covariance matrix and the Stokes matrix can be easily derived. Other measures derived from polarimetric SAR data include correlation coefficients between scattering matrix terms and the mode and variance of phase differences between scattering matrix terms. The effects of additive system noise on these measurements is not often considered in the literature on this subject. In this paper, the effects of additive system noise on measurements derived from polarimetric SAR data will be examined. It will be shown how first-order noise effects can be removed and how second-order noise effects can be reduced for some measurements...
    Keywords: Earth Resources and Remote Sensing
    Type: IEEE, Geoscience & Remote Sensing; Tokyo; Japan
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Determination of noise equivalent sigma(0) using highly correlated repeat-pass SAR images (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: Noise equivalent sigma(sup 0) is a fundamental parameter in any synthetic aperture radar (SAR) measurement. Knowledge of the noise equivalent sigma(sup 0) allows the radar application scientist to band the error contributions due to noise present in his/her data. In this paper, a novel technique for determining noise equivalent sigma(sup 0) is presented. It has been observed that a pair of images obtained by a SAR over the same area in a nearly repeating orbit can demonstrate a high degree of correlation, depending on the baseline. If noise independence and signal power invariance are assumed, an estimate for the noise equivalent sigma(sup 0) for each image can be determined without any known ground targets. We examine the application of this technique to several images of different backscatter obtained by ERS-1.
    Keywords: COMMUNICATIONS AND RADAR
    Type: gress In Electromagnetics Research Symposium (PIERS); p 168
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    Modifications to the three-component classification algorithm for SAR data (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Description: Previously, a scattering model was used to classify SAR data as due to three mechanisms: surface or odd-bounce scattering; double-bounce scattering; and volume scattering. A Bragg rough-surface model was used for odd-bounce scattering, and two reflecting surfaces, as in a dihedral corner reflector, represented the double-bounce scattering mechanism. A random collection of infinitely thin cylinders was used to model the volume scattering contribution. It was assumed that the cylinders are uniformly oriented in all directions. In this work, modifications are made to the above model, which include specifying a preferred orientation for the cylinders representing branches and using thin cylinders of finite thickness as opposed to infinitely thin ones. In the first case, the preferred orientation is represented by a probability density function in the form of a dirac delta function. For the second case, small argument asymptotic expansions of Bessel functions are used to express the volume scattering contributions in terms of quantities containing the average radius of the cylinders. Since in each case the number of unknowns exceeds that of equations, simplifying assumptions are made. The solutions are applied to multifrequency polarimetric SAR data to obtain the new unknowns in addition to the relative contributions of each scattering mechanism. Several results are presented. It is found that the calculated percentage of each mechanism does not change significantly compared to the original model; however, additional information is gained about the scatterers.
    Keywords: COMMUNICATIONS AND RADAR
    Type: gress In Electromagnetics Research Symposium (PIERS); p 164
    Format: text
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