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  • 1
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    A SAR correlation algorithm which accommodates large-range migration (1984)
    Institute of Electrical and Electronics Engineers
    Details
    Publication Date: 1984-11-01
    Print ISSN: 0196-2892
    Electronic ISSN: 1558-0644
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Institute of Electrical and Electronics Engineers
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    PAPER CURRENT
  • 2
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    An analysis of the focusing performance of Magellan SAR image data (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Synthetic aperture radar (SAR) focusing can be achieved either based on accurate ephemeris data or on an autofocusing process. For the Magellan project, such a decision must be made in the early phase of Magellan SAR system design. The analysis of the emphemeris requirement is complicated. The analysis given by the author leads to the conclusion that empheris data obtained from the Magellan navigation system provide sufficient accuracy to meet the Magellan image resolution requirement.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 610-613.
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Effects of the ephemeris error on effective pointing for a spaceborne SAR (1989)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Both Magellan SAR data acquisition and image processing require the knowledge of both the ephemeris (spacecraft position and velocity) and the radar pointing direction. Error in the knowledge of the radar pointing direction results in a loss of SNR in the image product. An error in the ephemeris data has a similar effect. To facilitate SNR performance analysis, an effective pointing error is defined to characterize the effect of the ephemeris error. A systematic approach to relate the ephemeris error to the effective pointing errors is described. Result of this analysis has led to a formal accuracy requirement levied on the Magellan navigation system.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    An Efficient Image Recovery Algorithm for Diffraction Tomography Systems (1993)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: A diffraction tomography system has potential application in ultrasonic medical imaging area. It is capable of achieving imagery with the ultimate resolution of one quarter the wavelength by collecting ultrasonic backscattering data from a circular array of sensors and reconstructing the object reflectivity using a digital image recovery algorithm performed by a computer. One advantage of such a system is that is allows a relatively lower frequency wave to penetrate more deeply into the object and still achieve imagery with a reasonable resolution. An efficient image recovery algorithm for the diffraction tomography system was originally developed for processing a wide beam spaceborne SAR data...
    Type: NASA: Technology 2003 Conference; Anaheim, CA; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Radiometric Compensation and Calibration for Radarsat ScanSAR (1993)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: Due to lack of a standard for modeling the radar echo signal in terms of signal unit and coordinates as well as lack of a standard in designing the gain factors in each stage of a processor, absolute radiometric calibration of a SAR system is usually performed by treating the sensor and processor as one inseparable unit. This often makes the calibration procedure complicated and requiring the involvement of both radar system engineers and processor engineers in the whole process. This paper introduces a standard for modeling the radar echo signal and a standard in designing the gain factor of a ScanSAR processor. In this paper, the radar equation is derived based on the amount of energy instead of the power received from a backscatterer. These efforts lead to simple and easy-to-understand equations for radiometric compensation and calibration.
    Keywords: Communications and Radar
    Type: CEOS Calibration/Validation Working Group: SAR Calibration Workshop; Noordwijk; Netherlands
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
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    Optical Range and Doppler Centroid Estimation for a ScanSAR System (1994)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: This paper presents a new range and Doppler centroid estimation algorithm for a ScanSAR system. Its accurate range and Doppler centroid estimates lead to refined radar pointing angles, which enables the ScanSAR imagery meeting its radiometric reuirements. This algorithm attains an accuracy equal to the cramer Rao's lower bound for both the homogeneous and quasi-homogeneous targets. This algorithm is also efficient in computation and easy for implementation.
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    NASA TECHNICAL REPORTS
  • 7
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    Analysis and Simulation for a Spotlight-Mode Aircraft SAR in Circular Flight Path (1993)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: A wide azimuth beam SAR can offer higher resolution or wider azimuth viewing angle; two factors that help better characterize the backscattering property of targets for various science applications. One disadvantage of wide beam SAR is that a much higher pulse repetition frequency (PRF) is usually required since PRF is proportional to the radar beam angle. This problem can be resolved using a spotlight-mode concept: steering a narrow beam SAR to a fixed spot on the ground. The drawback of a spotlight-mode SAR is its limited coverage. A conventional spotlight-mode SAR operates along a straight line path as shown in Figure 1. It can be shown that spotlight-mode SAR that follows a straight line path has difficulty in achieving the ultimate resolution of lambda/4. It also cannot utilize the full 180 degree of azimuth viewing angle that can be attained only when the synthetic aperture length approaches infinity.
    Keywords: Earth Resources and Remote Sensing
    Type: IGARSS: Better Understanding of Earth Environment; Tokyo; Japan
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    PRF Ambiguity Detrmination for Radarsat ScanSAR System (1998)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: PRF ambiguity is a potential problem for a spaceborne SAR operated at high frequencies. For a strip mode SAR, there were several approaches to solve this problem. This paper, however, addresses PRF ambiguity determination algorithms suitable for a burst mode SAR system such as the Radarsat ScanSAR. The candidate algorithms include the wavelength diversity algorithm, range look cross correlation algorithm, and multi-PRF algorithm.
    Keywords: Communications and Radar
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    On Board Processor Development for NASA's Advanced Radar Technology Program (1996)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: This paper reports a preliminary study result of an on-board spaceborne SAR processor. It consists of a processing requirement analysis, functional specifications on custom hardware, and consideration on implementation approaches. Finally, a minimum version of this on-board processor designed for performance evaluation and for partial demonstration is illustrated.
    Keywords: Communications and Radar
    Type: DLR; Berlin-Adlershef; Germany
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    NASA TECHNICAL REPORTS
  • 10
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    Impulse Response Shaping for Ultra Wide Band SAR in a Circular Flight Path (1996)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: An ultra wide band SAR (synthetic aperture radar) has potential applications on imaging underground objects. Flying this SAR in a circular flight path is an efficient way to acquire high resolution images from a localized area. This paper characterizes the impulse response of sucha system. The results indicate that to achieve an image with a more uniformed resolution over the entire imaged area, proper weighting coeficients should be applied to both the principle aperture and the complimentary aperture.
    Keywords: Communications and Radar
    Format: text
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    NASA TECHNICAL REPORTS
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