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Aerospace and Electronic Systems, IEEE Transactions on

Issue 3 • Date May 1977

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Displaying Results 1 - 22 of 22
  • Table of contents

    Page(s): c1
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  • IEEE Aerospace and Electronic Systems Society

    Page(s): c2 - 42c
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  • From the Editors

    Page(s): 225
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  • The Blind Road to the New Despotism

    Page(s): 226 - 229
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    First Page of the Article
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  • Practical Comparison of Iterative Matrix Orthogonalization Algorithms

    Page(s): 230 - 235
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    In previous work several algorithms for orthogonalizing the direction cosine matrix were introduced and their convergence rate and range were theoretically investigated. Three of the most promising algorithms are examined in this paper. lt is shown that the so-called Dual Algorithm is by far superior to the other two from the point of view of speed, computer memory, accuracy, and convergence rate. lt is therefore recommended that whenever the direction cosine matrix is computed by simple numerical integration of a matrix differential equation, the Dual Algorithm be used to orthogonalize the resultant matrix. View full abstract»

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  • Kalman Estimation and Control of Dual-Spin Satellites

    Page(s): 236 - 245
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    lt is necessary to maintain the spin axis of dual-spin geostationary communications satellites with nontracking ground antennas to within 0.1 degree of the orbit normal by periodic attitude corrections. Normally, the data for attitude estimation are determined from the analog sensor waveforms telemetered to the ground station. This information is supplied to the attitude determination program, which processes the data and outputs the right ascension and declination of the spin axis. An application of the extended Kalman/ filter in estimating the attitude of dual-spin geostationary satellites is presented. The precession of the angular momentum vector by the solar radia-tion torque is considered to be the only natural attitude perturbation. The orbital dynamics are considered to be known and are decoupled from the attitude dynamics. A periodic attitude control policy is then derived. View full abstract»

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  • Computerized Model Demonstrating Magnetic Submarine Localization

    Page(s): 246 - 254
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    A modet is described which consists of an aircraft with flux gate magnetometers mounted on the wing tips and a submarine containing a magnet to simulate the induced and permanent fields of an actual submarine. Equations are developed which enable a minicomputer sampling the magnetometers to calculate the location, depth, and heading of the submarine as the aircraft travels towards it. The real time plotted results are presented. View full abstract»

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  • Reliability of the Station-Keeping Activator Subsystem of a Geostationary Satellite

    Page(s): 255 - 263
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    The reliability of the station-keeping activator subsystem of a geostationary satellite using electric thrusters is analyzed by modeling the probabilistic behavior of the system as a homogeneous Markov process. The method is applied to the particular case of a 400-kg satellite using 1.5-mN cesium contact electric thrusters. lt is shown that certain system configurations offer a mass improvement without loss of reliability. View full abstract»

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  • A Distributed Intelligence Automatic Test System for PATRIOT

    Page(s): 264 - 272
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    An automatic test system supporting high volume production testing of diverse state-of-the-art electronic assemblies is described. The test complex consists of a centralized computer system communicating to a network of satellite stations, each structured as "Intelligent Test Centers" dedicated to a particular family of assemblies (e.g., analog, digital, microwave). Allocation of resources and tasks have been distributed for optimum efficiency of production testing. This paper describes the organization and characteristics of the test system. Test center operation is explained with emphasis given to unique man-machine interactive features designed for on-line generation, examination, and maintenance of Unit-Under-Test (UUT) programs. Details are presented of the test language, RATEL, used for UUT programming. Other aspects that are discussed include test data and UUT program characteristics. View full abstract»

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  • Adaptive Thresholding Systems

    Page(s): 273 - 280
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    The conditions under which adaptive thesholding should be employed are discussed. The three most important systems for accomplishing adaptive thresholding are the level adjuster, the constant-fraction discriminator, and the double differentiator. Practical implementations of these systems, including false alarm protection, are described in terms of subsystems. Approximate position variances associated with the three systems are derived. Relative advantages and disadvantages are discussed. View full abstract»

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  • Mean Power Estimation with a Recursive Filter

    Page(s): 281 - 289
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    Power estimates from smoothed detector outputs of stationary signals are analyzed for linear, square law, and logarithmic receiverdetectors. Smoothing is accomplished with a first-order recursive digital filter. lnput amplitude is assumed to be Rayleigh distributed and detector output samples independent. Expansion of results to other distributions is indicated. View full abstract»

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  • Performance of a Square Law Pseudonoise Ranging Time-of-Arrival Estimator

    Page(s): 290 - 301
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    The performance of a square law time-of-arrival (TOA) estimator that has been proposed for use in ASTRO-DABS, part of a possible satellite-based fourth generation air traffic control system is considered. The transmitted message consists of a pulse amplitude modulated (PAM) ranging sequence that, due to transmitter characteristics, is corrupted by an unknown frequency offset. The optimum TOA estimator, for the case of no frequency uncertainty, is first presented, together with a lower bound on the variance of the estimate generated. This is followed by the consideration of a suboptimum TOA estimator for which a high signal-to-noise ratio (SNR) performance analysis is carried out; here, the effects of frequency uncertainty are included. Next, the zero-crossing properties of the derivative of the (suboptimum) estimation statistic are presented and the results used to derive an upper bound to the TOA estimate variance that is valid for all SNR values. This latter result is significant because it displays the system threshold effect and complements performance lower bounds that may be derived via other methods. In addition, the method presented here may be applied to other optimum and suboptimum systems where a discrete set of parameters is to be estimated. View full abstract»

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  • Limit Cycle in a Four Sectors On-Off Tracking Loop

    Page(s): 302 - 309
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    A simplified model of a bidimensional on-off tracking loop is introduced. By using geometric analysis in the time domain, it is shown that there is a simple mode of limit cycle which is stable in the loop for finite disturbances and for a finite range of change of the loop parameters. The consideration of the unsymmetric general case covers a wide class of cases in which the loop is subjected to constant velocity inputs. A nonfiltering assumption is defined which is needed to establish the connection between the simplified loop and practical systems. The main results are applied to a conventional symmetric loop. The analytic approach developed here is applicable as weil to loops in which the number of sectors is different from four and also to loops containing nonlinearities more complex than simple on-off, like hysteresis. View full abstract»

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  • Maneuvering Target Tracking Using Adaptive State Estimation

    Page(s): 310 - 317
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    Two approaches to a nonlinear state estimation problem are presented. The particular problem addressed is that of tracking a maneuvering target in three-dimensional space using spherical observations (radar data). Both approaches rely on semi-Markov modeling of target maneuvers and result in effective algorithms that prevent the loss of track that often occurs when a target makes a sudden, radical change in its trajectory. Both techniques are compared using real and simulated radar measurements with emphasis on performance and computational burden. View full abstract»

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  • Phase Control in Multibeam Arrays

    Page(s): 318 - 321
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    The phases of the radiation fields in a multibeam antenna are analyzed and their relations to the feed network are established. A method of phase control is proposed and applied to the case of cophasal beams radiated from an array for which the feed network is a lossless Butler matrix. View full abstract»

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  • Correlation Effects of MTI Filters

    Page(s): 321 - 322
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    A frequency domain approach for determining the effective number of independent pulses at the output of a square law detector in a moving target indicator (MTI) system leads to a definition which gives the same asymptotic results as given by a previous definition. View full abstract»

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  • Frequency Domain Interpolation

    Page(s): 323 - 327
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    A formula is derived for interpolation between output samples of a fast Fourier transform (FFT), i.e., in the frequency domain. Such a formula is useful for obtaining greater frequency resolution when two coarse FFT outputs are available. Consideration is also given to the effect of such interpolation on a weighted FFT. View full abstract»

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  • Identification of a Ship or Submarine from its Magnetic Signature

    Page(s): 327 - 329
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    The relationship between the measured time fluctuations of the ambient magnetic field due to the passage of a ship or submarine and the characteristic magnetization properties of this vessel are derived. This relationship would be useful in identifying or classifying ships and submarines according to their magnetization properties. View full abstract»

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  • International Cumulative Index on Radar Systems: 1975-76 Update and Complete Author Index

    Page(s): i - 42
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  • Information for authors

    Page(s): 42a
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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.

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Meet Our Editors

Editor-in-Chief
Lance Kaplan
Army Research Laboratory