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Aerospace and Electronic Systems, IEEE Transactions on

Issue 3 • Date May 1978

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Displaying Results 1 - 21 of 21
  • Table of contents

    Publication Year: 1978 , Page(s): c1
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    Freely Available from IEEE
  • IEEE Aerospace and Electronic Systems Society

    Publication Year: 1978 , Page(s): c2 - 544b
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    Freely Available from IEEE
  • From the Editor-in-Chief

    Publication Year: 1978 , Page(s): 417
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    Freely Available from IEEE
  • State Estimation for Discrete Systems with Switching Parameters

    Publication Year: 1978 , Page(s): 418 - 425
    Cited by:  Papers (84)
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    The problem of state estimation for discrete systems with parameters which may be switching within a finite set of values is considered. In the general case it is shown that the optimal estimator requires a bank of elemental estimators with its number growing exponentially with time. For the Markov parameter case, it is found that the optimal estimator requires only N2 elemental estimators where N is the number of possible parameter values. View full abstract»

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  • Modeling the Superconducting Alternator with Thyristor Bridge

    Publication Year: 1978 , Page(s): 426 - 432
    Cited by:  Papers (1)
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    Steady state equations are derived for the superconducting alternator with a thyristor bridge (dc) output. This is accomplished by modification of a previous analysis for a machine with a diode bridge. The approach used avoids the need to numerically solve the differential equations for the system, and it is quite efficient in terms of computation time. Numerical simulations for both the diode and thyristor bridge circuits are included for comparison. View full abstract»

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  • A Sequential Approach to Target Discrimination

    Publication Year: 1978 , Page(s): 433 - 440
    Cited by:  Papers (10)
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    The Wald sequential probability ratio test is applied to the discrimination of targets observed by a radar or other sensor and a form for the classifier involving linear predictive filtering is developed. In this sequential approach, a target is illuminated with consecutive pulses until a classification of the target can be made to within a prescribed probability of error. Because of the linear-predictive formulation, the computational and storage requirements for the classifier are related only to the number of returns necessary to predict the target signature and not to the length of signature observed; a classifier with modest storage and computational requirements can be employed to process signatures consisting of an arbitrarily large number of returns. The classifier is based on some well-known results in mean-square filtering theory and has a simple intuitive interpretation. The classifier structure can also be related to autoregressive time series analysis and innovations process concepts and has an interpretation in the frequency domain in terms of the maximum entropy and maximum likelihood spectral estimates for the target signatures. View full abstract»

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  • Laser Velocimeter for Wind Tunnel Measurements

    Publication Year: 1978 , Page(s): 441 - 455
    Cited by:  Patents (3)
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    Laser velocimetry is an optical technique used to make local measurements of mean velocity and turbulence in fluid flows without disturbing them. Laser velocimetry principles are briefly recalled; the optical and mechanical elements making up a velocimeter are described. Their purpose is to create two laser beams of equal intensity which are focused and crossed in a probe volume ¿ where a fringe pattern is formed; the light scattered by submicron particles passing through ¿ is collected by an optics rigidly connected to the emitting optics and focused on a photomultiplier. Among the various signal processing techniques, counters are now widely used, in connection with minicomputers. The different means used to determine the velocity sign and to measure simultaneously two components of the velocity are described; the simultaneous measurement of the three velocity components is more a matter of technology and cost than a theoretical problem. The modular operational velocimeter developed at ONERA is described; as examples of application, some typical results obtained in different aerodynamic flows are reported. View full abstract»

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  • Instrument Fault Detection

    Publication Year: 1978 , Page(s): 456 - 465
    Cited by:  Papers (31)
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    The dedicated observer scheme (DOS) for detecting incipient instrument faults by functional redundancy is applied to a simulation of the lateral axis control system of a hydrofoil boat. Observer designs and detection logic are found for which 14 separate instrument faults are detected without false alarms. The scheme is shown to be robust with respect to variations in two significant physical parameters. View full abstract»

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  • Design of Satellite Constellations for Optimal Continuous Coverage

    Publication Year: 1978 , Page(s): 466 - 473
    Cited by:  Papers (15)  |  Patents (13)
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    A satellite-borne sensor can view a region at or above the Earth's surface. The size of this region depends on the satellite's altitude, the maximum range and scan angle of the sensor, the minimum above-the-horizon viewing angle required, the extent in altitude of the region to be viewed, and the maximum altitude of sensor obscuration by the atmosphere. Except for geosynchronous satellites this region moves relative to the Earth, so that constellations of satellites are generally necessary for continuous coverage. Satellite constellations which minimize the number of satellites required for continuous coverage are derived as a function of the angle subtended at the Earth's center by the coverage of a single satellite. This is done for single and triple continuous coverage of the entire Earth and of the polar regions extending to arbitrary latitude. Simple, cogent approximations for the configurations and numbers of satellites are found. Expressions which relate sensor capabilities and surveillance requirements to are presented. Examples are given to illustrate the use and accuracy of the results. View full abstract»

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  • Losses for Frequency Diversity Waveform Systems

    Publication Year: 1978 , Page(s): 474 - 486
    Cited by:  Papers (7)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2607 KB)  

    The use of a frequency diversity waveform to improve target detectability by reducing the fluctuation loss is a well-established technique. The diversity gain is commonly computed under the assumptions of a matched filter processor and the independent fluctuation of the target from channel to channel. Sometimes these conditions are not met and the full diversity gain cannot be obtained. In order to accurately compute the attainable diversity gain, it is necessary to calculate losses that occur only for diversity waveforms. The losses that have been considered are 1) unknown target velocity loss, 2) dependent samples due to small channel-to-channel frequency spacing, 3) linear envelope detector law loss, and 4) constant false alarm rate (CFAR) lpss. View full abstract»

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  • Image Correlation with Geometric Distortion Part 1: Acquisition Performance

    Publication Year: 1978 , Page(s): 487 - 493
    Cited by:  Papers (13)  |  Patents (4)
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    The degradation in acquisition probability that occurs when cross correlation is used to determine the offset of two images of the same scene that differ by a relative geometric distortion is presented. The geometric distortions considered can be represented by a general affine transformation of image coordinates. The analysis shows that for a given geometric distortion there is an image size and shape that minimizes the probability of false acquisition. The results are derived for images modeled as random patterns with arbitrary auto-correlation functions. The results are illustrated for images with Gaussian autocorrelation functions. View full abstract»

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  • Image Correlation with Geometric Distortion Part II: Effect on Local Accuracy

    Publication Year: 1978 , Page(s): 494 - 500
    Cited by:  Papers (15)  |  Patents (1)
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    The effect of geometric distortion on the local accuracy of the image registration algorithms using cross correlation is presented. Using a probabilistic model describing images as homogeneous random patterns, expressions for the mean and covariance of the local error vector in terms of image and noise autocorrelation functions, geometric distortion, and reference image area are derived. The geometric distortions considered are those represented by an affine transformation of image coordinates. It is shown that for a fixed geometric distortion there is an image size (integration area) that minimizes the local error. The optimum area decreases with increasing geometric distortion. View full abstract»

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  • A Unified Approach to Model-Reference Adaptive Systems Part I: Theory

    Publication Year: 1978 , Page(s): 501 - 513
    Cited by:  Papers (1)
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    A unified approach to model-reference adaptive control systems is presented. A linearized error equation for each adaptive system is derived about some operating point and converted into the standard form for plotting root loci. The contribution made here is to convert the selection of an adaptive technique and the choosing of adaptive coefficients for some desired system performance from a "mystical art" to standard control techniquess. View full abstract»

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  • A Unified Approach to Model-Reference Adaptive Systems Part II: Application of Conventional Design Techniques

    Publication Year: 1978 , Page(s): 514 - 524
    Cited by:  Papers (2)
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    The use of linearized error equations in the design of model-reference adaptive systems developed by Part I is illustrated. Using standard control specifications on the system error (e.g., percent overshoot, rise time, etc.), a set of desired root locations on the root loci can be obtained. Then constants in the adaptive scheme can be chosen to obtain the desired root locations. Simulation results are given to illustrate the validity of the linearized error characteristic equation design procedure. View full abstract»

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  • Control System Performance with Coded State Feedback

    Publication Year: 1978 , Page(s): 525 - 528
    Cited by:  Papers (2)
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    The error performance of a linear time-invariant plant, remotely controlled with constant-gain state feedback from a coded digital communications link, is considered. The effects of finite information rate, reliability, and delay are examined. While nonzero code transmission delay is generally deleterious to control system performance, it is shown that if the sampling period is specified, then block coding within each sample period may be beneficial. Numerical results are given for the case of a scalar plant View full abstract»

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  • Approximate Ellipsoidal-Earth Equations for Mapping and Fix-Taking Calculations

    Publication Year: 1978 , Page(s): 528 - 533
    Cited by:  Papers (1)
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    Approximate equations are developed for converting geodetic coordinates to a local north-east-down (NED) Cartesian coordinate system, and it is shown that good accuracy can be obtained if the ellipsoidal shape of the Earth is taken into account. View full abstract»

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  • Evaluation of Geometric Performance of Global Positioning System

    Publication Year: 1978 , Page(s): 533 - 539
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    The global positioning system (GPS) is a satellite-based radio navigation system to provide extremely accurate three-dimensional position fixes and system time to users anywhere on the Earth at any time regardless of weather conditions. The most significant performance parameter of the GPS is the degree of navigation accuracy which is strongly coupled to the choice of orbit configuration. The 3 X 8 orbit configuration has been considered as an operational GPS which consists of 24 satellites deployed in circular 63° inclined, subsynchronous 12-h orbits. In this paper, the geometric performance of several orbit configuration, including a 3 X 8 orbit configuration, is analyzed numerically by altering orbit period and elevation mask, respectively. It will be shown that 1) there are a few orbit configurations which are comparable to or better than the baseline 3 X 8 orbit configuration, and 2) for higher elevation mask, the geometric performance can be improved effectively by increasing orbit period to some extent. View full abstract»

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  • The Psi-Angle Error Equation in Strapdown Inertial Navigation Systems

    Publication Year: 1978 , Page(s): 539 - 542
    Cited by:  Papers (15)
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    A detailed development is presented of the psi-angle vector differential equation as applied to the error analysis of strapdown inertial navigation systems. The coordinate systems involved and the psi misalignment vector are clearly defined. It is proven that apart from a sign change the psi-angle differential equation in the error analysis of strapdown inertial navigation systems is identical to the one used in conventional gimbaled inertial navigation systems. View full abstract»

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  • Corrections to "Navigation Computation in Terrestrial Strapdown Inertial Navigation Systems"

    Publication Year: 1978 , Page(s): 542 - 544
    Cited by:  Papers (1)
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  • Corrections to "Multiple Gaussian Targets: The Track-On-Jam Problem"

    Publication Year: 1978 , Page(s): 544
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  • Corrections to "The Ratios of Functions of Random Variables"

    Publication Year: 1978 , Page(s): 544
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Aims & Scope

IEEE Transactions on Aerospace and Electronic Systems focuses on the equipment, procedures, and techniques applicable to the organization, installation, and operation of functional systems designed to meet the high performance requirements of earth and space systems.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Lance Kaplan
Army Research Laboratory