# IEEE Transactions on Aerospace and Electronic Systems

Published by Institute of Electrical and Electronics Engineers

Online ISSN: 0018-9251

Published by Institute of Electrical and Electronics Engineers

Online ISSN: 0018-9251

Publications

Article

This work intends to design, analyze and solve, from the systems control perspective, a complex, dynamic, and multiconstrained planning system for generating training plans for crew members of the NASA-led International Space Station. Various intelligent planning systems have been developed within the framework of artificial intelligence. These planning systems generally lack a rigorous mathematical formalism to allow a reliable and flexible methodology for their design, modeling, and performance analysis in a dynamical, time-critical, and multiconstrained environment. Formulating the planning problem in the domain of discrete-event systems under a unified framework such that it can be modeled, designed, and analyzed as a control system will provide a self-contained theory for such planning systems. This will also provide a means to certify various planning systems for operations in the dynamical and complex environments in space. The work presented here completes the design, development, and analysis of an intricate, large-scale, and representative mathematical formulation for intelligent control of a real planning system for Space Station crew training. This planning system has been tested and used at NASA-Johnson Space Center.

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Article

The major radio aids to air navigation are listed. Underlined are those whose signal format is standardized by the International Civil Aviation Organization (ICAO) and they have now all been the subject of the IEEE Aerospace and Electronic Systems Society Pioneer Award, as follows: airborne direction finder/nondirectional beacon (ADF/NDB), Busignies and Moseley, 1959; VHF omnidirectional range (VOR), Stuart, 1962; instrument landing system (ILS), Kramar 1964, Alford 1965; air traffic control radar beacon system (ATCRBS), Williams, Bowden, and Harris, 1973; distance measuring equipment (DME), Dodington, 1980. A brief history of the development of the distance measuring equipment, which also formed the basis for an IEEE National Aerospace Electronics Conference luncheon address, is given.

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Article

Best-known binary code autocorrelation peak sidelobe levels (PSLs) are updated for lengths 71 to 105. For lengths 71 to 82, codes with PSL 4 are found, establishing 4 as almost certainly the optimal value for these lengths. PSL-5 codes are produced for all lengths from 83 to 105, in many cases improving on best-known values.

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Article

The instrumentation on SNAP 10A, the world's first nuclear reactor space power system, was evaluated. Flight test information requirements, based on SNAPSHOT test experience, were summarized to provide criteria for judging instrument performance. Generally performance and reliability were good, but as with any initial flight test, instrumentation selected early in the program was not always optimum. These exceptions are emphasized. Larger flight test data errors caused changes in the relative usefulness of different types of instruments in flight compared to ground tests.

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Article

The AN/APS-116 Radar System was developed by the U.S. Navy for ocean surveillance and antisubmarine warfare patrol. The basic system requirement is to reliably detect small periscope-sized targets against strong interfering signals form sea clutter backscatter. The radar system design approach utilized very fine range resolution and a rapid scan antenna. A signal processing scheme was implemented using scan-to-scan decorrelation, with a M-out-of-N threshold for target detection. A brief description of each major unit of the radar is included, along with a summary of the evaluation tests that verified system performance.

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Article

Search and rescue satellite-aided tracking (SARSAT) has certain
shortcomings which could possibly be ameliorated by employing a more
extensive signal processing strategy. The approach proposed is based on
partially compensating for the Doppler shift, which then permits the
data processing windows to be increased significantly. Incorporating a
ranking technique with the conventional fast Fourier transform (FFT)
processor and implementing an autoregressive moving-average estimator
provides an optimal strategy that maximizes the probability of detecting
the emergency signals

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Article

In the SARSAT signal environment it is possible to receive many(5 to 20) simultaneous emergency beacon signals combined with voice and interference of various types, all simultaneously occupying essentially the same frequency-time space. The paper first provides a survey of the different sources of interference which occur in the 100 to 500 MHz frequency band. Then the paper examines those sources of interference which enter the 121.5/243 MHz frequency bands of the SARSAT system.

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Article

The COSPAS-SARSAT Mission Control Center (MCC) matches and merges
estimates of position and frequency of 121.5/243 MHz distress beacons
received from various ground stations and satellites. The matching and
merging are done sequentially as the estimates are received, and merges
are not reversed once sent out to search-and-rescue forces. A
sequential, irreversible match/merge algorithm is derived based on the
ratio of probabilities of the same beacon/different beacon hypotheses,
and it is tested using data received at the United States MCC. The total
number of mismatches based on tests for stability, correctness, and
completeness was less than 0.5% when the match parameters were properly
selected. The selected match parameters themselves were consistent with
previously published results

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Article

The 13/18-GHz COMSAT Propagation Experiment (CPE) is reviewed, the data acquisition and processing are discussed, and samples of preliminary results are presented. The need for measurements of both hydrometeor-induced attenuation statistics and diversity effectiveness is brought out The facilitation of the experiment-CPE dual frequency and diversity site location, the CPE ground transmit terminals, the CPE transponder on Applications Technology Satellite-6 (ATS-6), and the CPE receive and data acquisition system-is briefly examined. The on-line preprocessing of the received signal is reviewed, followed by a discussion of the off-line processing of this database to remove signal fluctuations not due to hydrometeors. Finally, samples of the results of first-level analysis of the resultant data for the 18-GHz diversity site near Boston, Mass., and for the dual frequency 13/18-GHz site near Detroit, Mich., are presented and discussed.

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Article

In this paper, a flight control law for a simplified F-14 aircraft model is designed based on variable structure control (VSC) theory. For m-input, q-output linear uncertain systems (q<m), a VSC law is derived. For the derivation of the control law, a choice of a sliding surface is made so that the zero dynamics of the system are stable. The linear lateral and longitudinal dynamics of the F-14 are decoupled. This allows design of lateral and longitudinal flight controllers separately. An application of variable structure system (VSS) theory to control of lateral dynamics is presented. A control law is derived for the control of roll angle, lateral velocity, and yaw rate. The chosen sliding surface for the controller design is a linear function of the tracking error, its derivative, and the integral of the tracking error. Simulation results are presented to show that in the closed-loop system, precise bank angle trajectory tracking and regulation of lateral velocity and yaw rate can be accomplished in spite of aerodynamic parameter uncertainty.

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Article

Data relay satellites are being developed to provide real-time data links between research satellites in low earth orbits and central data acquisition and processing facilities. Frequency assignments for data relay satellite links will be made in bands allocated internationally to the space research service. One of the bands which will be used lies between 14.5 and 15.35 GHz, where the space research service has had a frequency allocation as a secondary service since 1971. During the General World Administrative Radio Conference of the International Telecommunication Union, held in Geneva in 1979, a primary frequency allocation was made in the band 14.5-14.8 GHz to the fixed-satellite service, specifically for use by earth-to-space links of the broadcasting satellite service. The feasibility of shared band operation is evaluated between data relay satellite uplinks and broadcasting-satellite feeder links in the band 14.5-14.8 GHz. Relationships for predicting interference power levels are formulated, as functions of satellite separation and of earth station separation. Tradeoffs between satellite separation angle and earth station separation are explored, and conclusions are drawn regarding the feasibility of band sharing. Co-channel operation is demonstrated to be technically feasible for typical systems, provided appropriate separations are maintained.

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Article

A multiple model adaptive estimation (MMAE) algorithm is implemented with the fully nonlinear six-degree-of-motion, Simulation Rapid-Prototyping facility (SRF) VISTA F-16 software simulation tool. The algorithm is composed of a bank of Kalman filters modeled to match particular hypotheses of the real world. Each presumes a single failure in one of the flight-critical actuators, or sensors, and one presumes no failure. For dual failures, a hierarchical structure is used to keep the number of on-line filters to a minimum. The algorithm is demonstrated to be capable of identifying flight-critical aircraft actuator and sensor failures at a low dynamic pressure (20,000 ft, 0.4 Mach). Research includes single and dual complete failures. Tuning methods for accommodating model mismatch, including addition of discrete dynamics pseudonoise and measurement pseudonoise, are discussed and demonstrated. Scalar residuals within each filter are also examined and characterized for possible use as an additional failure declaration voter. An investigation of algorithm performance off the nominal design conditions is accomplished as a first step towards full flight envelope coverage.

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Conference Paper

Multiple model adaptive estimation (MMAE) is applied to the Variable Inflight Stability Test Aircraft (VISTA) F-16 flight control system at a low dynamic pressure flight condition (0.4M at 20000 ft). Single actuator and sensor failures are first, followed by dual actuator and sensor failures. The system is evaluated for complete or "hard" failures, patial or "soft" failures, and combinations of hard and soft actuator and sensor failures. Residual monitoring is discussed for single and dual failure scenarios. Performance is enhanced by the application of a modified Bayesian form of MMAE, scalar residual monitoring to reduce ambiguities, automatic dithering where advantageous, and purposeful commands.

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Article

A novel control technique, termed control redistribution, is
presented and applied in conjunction with multiple model adaptive
estimation (MMAE) to the variable in-night stability test aircraft
(VISTA) F-16, to detect and compensate for sensor and/or actuator
failures. This ad hoc method redistributes control commands (that would
normally be sent to failed actuators) to the nonfailed actuators,
accomplishing the same control action on the aircraft. Dither is
considered to help disambiguate failures in the longitudinal and
lateral-directional channels. Detection of both single-actuator and
single-sensor failures is considered. Failures are demonstrated
detectable in less than 1 s, with an aircraft output nearly identical to
that anticipated from a fully functional aircraft in the same
environment

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Article

A preliminary control system design for the YF-16 CCV aircraft in its longitudinal mode satisfying its flying qualities specifications is investigated. The design is shown to be robustly stable when the actuator model and the unstable pole in the airframe model of the aircraft are subjected to structured uncertainties. Very recent tools of robust stability analysis are utilized to accomplish this goal.< >

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Article

The AN/APG-66 is a digital, multimode, fire control radar that is the primary sensor for the F-16 air combat fighter. The detection and false alarm performance of this radar are described when it operates in its medium PRF pulse Doppler downlook mode. Descriptions are included of medium PRF clutter, the AN/APG-66 signal processing, the flight tests used to obtain performance data, a computer simulation of the radar, and the calibration of the simulation. The detection performance presented is based on both flight tests and the output of the flight test calibrated simulation. The false alarm performance is based on flight tests and is accompanied by a discussion of the sources of false alarms.

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Article

The development of pulse compression radar at MIT Lincoln
Laboratory is related on the basis of the author's personal
recollections. He describes the formation of the Radar Techniques Group,
the development of the concept, the first system constructed, and the
selection of an appropriate code for the transmitted waveform

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Article

Robust flight control laws based on variable structure control (VSC) theory and Lyapunov V-function method are designed for a simplified aircraft model F-18. A min-max control (MMC) and VSC laws are derived, for multi-input multi-output (MIMO) systems with plant uncertainties and input disturbance. Two types of robust feedback controllers MMC and VSC for uncertain MIMO systems are considered. For both cases the existence conditions of a stable sliding mode and the robust asymptotic stability in uncertain MIMO systems by MMC and VSC are investigated. For the design of an MMC and VSC, measurable states and sliding surface are chosen so that the zero dynamics of the system are stable. An application of tracking and positioning of VSC of longitudinal dynamics is presented. Finally, simulation results are presented to show the effectiveness of the design methods.

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Article

The question of inertial trajectory control of aircraft in the three-dimensional space is discussed. It is assumed that the nonlinear aircraft model has uncertain aerodynamic derivatives. The control system is decomposed into a variable structure outer loop and an adaptive inner loop. The outer-loop feedback control system accomplishes (x,y,z) position trajectory and sideslip angle control using the derivative of thrust and three angular velocity components (p,q,r) as virtual control inputs. Then an adaptive inner feedback loop is designed, which produces the desired angular rotations of aircraft using aileron, elevator, and rudder control surfaces to complete the maneuver. Simplification in the inner-loop design is obtained based on a two-time scale (singular perturbation) design approach by ignoring the derivative of the virtual angular velocity vector, which is a function of slow variables. These results are applied to a simplified F/A-18 model. Simulation results are presented which show that in the closed-loop system asymptotic trajectory control is accomplished in spite of uncertainties in the model at different flight conditions.

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Article

First Page of the Article

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Article

The Nimbus program is a major research effort in the development of satellite technology for meteorological purposes. Global cloudcover information is provided by sensors mounted on a 3-axis stabilized, earthoriented spacecraft. Electrical power for the spacecraft and sensors is provided by a solar-conversion energy-storage subsystem. This paper describes the evolution of the power supply subsystems designed for use on the Nimbus spacecraft. The original design, generated during the period 1961-1963, used dissipative regulation techniques and simple battery protection circuits. Battery overcharge protection was provided by ground control of special spacecraft loads. This type of system was successfully flown on Nimbus 1 in August 1964 and on Nimbus 2 in May 1966. The second generation design, currently being fabricated for test and evaluation, is intended for operational flight use in late 1967. The system concept, based on research and development effort in the period 1962-65, incorporates nondissipative regulation techniques and automatic battery overcharge control. A new concept, intended for use in a third generation Nimbus power system, is presently being explored. Recent advances in power conditioning technology will allow substantial gains in terms of extended spacecraft life or increased load capability. The new technology, called maximum power point tracking, assures more optimum source-to-load energy transfer. Thus, the increase in available solar cell energy caused by periodic, large, low-temperature excursions of the Nimbus solar array can be fully utilized.

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Article

Five basic needs for the improvement of system security are identified. Brief discussions are presented in the areas of system design, coordinated operation, more effective operation, and political- public relations problems. Recent results in the fifth basic need for system security, the development of more sophisticated approaches to the problems of system control, are presented. The results are in research areas sponsored by Electric Research Council Research Project RP90. Finally, several suggestions are offered for further research in this vital area of system control.

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Article

MILDATA was an Army-sponsored exploratory development study in the area of digital computer technology. Its objective was to explore and evaluate new organizational concepts for hardware and software in a tactical command control information system (CCIS) and to develop new measures of effectiveness and methods for evaluating system performance. It was assumed that the MILDATA system would be operational in the field army during the time frame 1975-1985. A unique feature of the MILDATA concept is an unprecedented degree of modularity which provides flexibility to fulfill a wide variety of tactical data processing requirements. This paper supplies necessary background on CCIS requirements and develops modular design criteria. It then summarizes MILDATA study requirements and the general nature of the results obtained and outlines a program of future work. Finally, an attempt is made to systematize the experience gained during MILDATA as an aid to the organization of future exploratory development studies.

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Article

This bibliography of Chinese radar papers was compiled by the PLA
Air Force Radar Institute under the sponsorship of the China Institute
of Electronics Radar Society. It covers the period from 1978 through
1987 and was prepared under the supervision of the Vice Chairman of the
CIE Radar Society. It follows the format of the IEEE AES Cumulative
Index on Radar Systems. Entries are listed chronologically under each
subject heading. All papers listed have been released for foreign
acquisition. Papers presented at the various conferences listed are
written in English; however, others are generally in Chinese, although
an abstract written in English is provided by some of them

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Article

Air surveillance radars for this decade will be required to provide reliable target location and trajectory information in height as well as the conventional geographical coordinates. These threedimensional radars will perform this task in spite of adverse environmental conditions such as ground, airborne clutter, and electromagnetic interference. The use of powerful false-alarm control processing allows automatic target detection and remoting of target information without overloading central processing capabilities. The technological evolution of the past decade has allowed sophisticated analysis, antenna/receiver/transmitter design, and signal/data processing techniques to be applied to the next generation of practical production radar systems. These radars will meet more severe performance requirements and will be significantly improved in terms of reliability, maintainability, and life cycle cost considerations. A candidate radar to fulfill the air surveillance role of this decade is the Series 320 radar manufactured by ITT Gilfillan.

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Article

This “second edition” is a continuation of the series
of National Cumulative Indexes on Radar Systems inaugurated in 1988.
These National series augment the periodic International Cumulative
Indexes on Radar Systems which are prepared by members of the IEEE AESS
Radar Systems Panel. Information on both series is contained in IEEE AES
Transactions vol. 27, no. 3 p. 581 (May 1991)

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Article

A comprehensive analysis reveals several drawbacks of the neural
network probabilistic data association (NPDA) algorithm, which is an
application of the Hopfield neural network to the data association
problem for multitarget tracking in clutter

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Conference Paper

This paper presents a single-phase three-wire (1φ3W) grid-connection photovoltaic (PV) power inverter with a feature of a partial active power filter (PAPF), which can not only deal with PV power but can filter current harmonics and improve power factor. Once the processed power exceeds the switch ratings, the inverter can reduce its output reactive power and harmonic power, while still can supply the maximum real power generated by the PV arrays. In derivation of control laws, a limit circle is defined to confine the output power of the inverter. To determine the power that the inverter can process, a criterion is proposed to find reactive power, which can avoid complex detections of phase angle and magnitude of the fundamental component of a nonlinear load current. Simulation results and experimental measurements have verified the proposed algorithm and the feasibility of the inverter.

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Article

This article is the culmination of research directed into finding a system to control the position of the focal spot of paraboloid concentrators for use in terrestrial and space solar concentration applications. After a brief introduction into the area of study, the article describes how a normal Shack-Hartmann wave front sensor is modified for use in detecting and tracking the focal spot. The paper details the analysis and development of the algorithms used in locating the focal spot on a thruster absorber utilizing a correlation method and an area centroid method. The article concludes with a paragraph on suitable future work.

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Article

The resource sharing experiment (RSE) of the DAVID (DAta and Video Interactive Distribution) multiexperiment mission of the Italian Space Agency (ASI) is described. The experiment envisages adaptively varying the robustness of signals down-transmitted, to a set (16) of Earth terminals by acting on their coding and spreading. During the DAVID satellite passes, each terminal determines autonomously its signal-to-noise ratio (SNR) and transmits it to a central station which, by using this information, works out the parameters for the global system optimization and indicates, in real time, to the terminals which code and despreading factor they must utilize to receive the part of the signal addressed to them.

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Article

This paper describes automatic monitoring equipment built in to a precision tracking radar system to detect and isolate faults. The purpose of the monitoring equipment is to minimize the mean time to repair faults and to exercise the overall system for pre-mission alignment and calibration. In addition, it is used to periodically check for performance degradation in key areas of the system. The paper describes the design approach used to meet the above requirements. Three types of signals are monitored: analog, digital, and switch closure. A list of each type is given and the technique used to monitor each is described. The design approach for pre-mission alignment and calibration is outlined. Tests performed are: RF alignment of the boresight axis, range tracking accuracy, angle servo calibration and accuracy, and receiver figure of merit measurements.

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Article

A 2D model-based generalization of the gradient step-track is introduced and simulation results are presented showing an overall tracking accuracy improvement and limit signal-to-noise ratio (SNR) advantage over the hill-climbing and the gradient procedures. At best, the new method is shown to allow a worse than 20 dB SNR in tracking a near geosynchronous satellite.

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Article

An effective compensation method for the mutual coupling effect in uniform circular arrays (UCAs) employed for two-dimensional (2D) direction-of-arrival (DOA) estimations is introduced. A new 2D DOA searching algorithm using the maximum likelihood technique optimized by the emperor selective genetic algorithm (ML-EMSGA) is introduced for use with UCAs. This method circumvents the difficulty of dealing with coherent signals in 2D DOA estimations. ML-EMSGA is less computationally demanding than the maximum likelihood method (MLM) and statistically more efficient. Our study shows that ML-EMSGA can be effectively combined with the proposed compensation method, which is based on the introduction of a new mutual impedance, to give very accurate and robust 2D DOA estimation results. The structure of mutual impedance matrix for UCAs under the compensation method is fully explained. The theory of the ML-EMSGA for the UCAs is formulated. Computer simulation examples on several synthetic scenarios are presented to demonstrate the effectiveness of the mutual coupling compensation method and the superior performance of the ML-EMSGA for UCAs.

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Article

Preliminary Applications Technology Satellite-6 (ATS-6) solar cell flight experiment data through the first 325 days in synchronous orbit is present. The experiment is transmitting data on 16 different solar cell/cover glass configurations. The experiment is designed to study the effect of this orbit on select solar cells and cover glass parameters such as solar cell thickness and base resistivity, cover glass thickness variation, new cover and adhesive processes and materials such as 7940 and 7070 integral covers and the fluorinated ethylene propylene (FEP) covers, the COMSAT "violet" cell, and backside irradiation effects. The in-spece solar cell data indicate short circuit currents are higher by 1 to 8 percent than measurements made with solar simulations; maximum power varied between -1 to +6 percent . Degradation of /sc due to ultraviolet effects was determined to be about 2 percent after 50 days in orbit. All cells performed well through 325 days in orbit, except the FEP-covered cells, which appear to have increased their rate of degradation during the first eclipse season.

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Article

An innovative Cassegrain antenna for spaceborne synthetic aperture radar (SAR) utilizes a reconfigurable feed array for scene grazing angles from 15° to 70° to produce the largest antenna beam footprints that are circular and to maintain high efficiency or the transmitter. The antenna has a beam waveguide input and the feed array is located in this waveguide. The feed array of transmit-receive modules is reconfigured to vary the illumination shape and area of the radiating portion of the antenna. Each transmit device operates at its full power for maximum efficiency, and the number of devices is determined by the required power. Single-point design for a 35 GHz SAR in a 700 km altitude orbit is presented to detect terrain with 0.1 m resolution. The antenna is a 19.6 m<sup>2</sup> elliptical reflector, the power density at the aperture is 25.5 W/m<sup>2</sup>, and 500 W maximum average power is required. Compared to X-band, 1) the 35 GHz design requires a much smaller antenna, 2) high resolution requires less percentage bandwidth, and 3) integration requirements are less demanding. For comparison, a 9 GHz SAR point design is included for grazing angles of 15° and 70°.

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Article

A -35kV power supply has been developed for a plasma experiment on the out-of-ecliptic mission. In addition, an isolation transformer has been developed to provide low voltage power at the -35kV potential. The design features incorporated to produce a spaceflight power supply housed within a 4 Ã 4 Ã 2.5 in package are discussed. The supply is powered from an unregulated spacecraft bus and provides a regulated output of -35kV Â± 5 percent with less than 0.5 percent ripple over a temperature range -20Â°C + 60Â°C. The unit serves as a bias supply with an output current less than 0.5 , Â¿A. With the supply essentially operating unloaded, 5 percent regulation is achieved by sensing and regulating the first stage of a 12-stage Cockcroft/Walton multiplier. Control of the ac voltage input to the multiplier stack provides the regulation. The isolation transformer utilizes a ferrite u-core with the primary and secondary windings placed on opposite legs for separation. The transformer is encapsulated with the power supply.

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Article

A circular prediction algorithm is proposed, which integrates the measured data into the filter and constrains the prediction to lie on a smooth curve modeled by an arc of a circle. The circular prediction is entirely defined in relation to three measurements in three-dimensional space. It is therefore not necessary to calculate the center and the radius of the circle. To obtain the statistics of the circular prediction, the unscented transformation has been utilized. The proposed hybrid filter combines the circular prediction and a constant velocity prediction by utilizing the covariance intersection (CI). This combined prediction can be updated with the subsequent measurement using a linear estimator. The proposed technique is compared with standard filters and the interacting multiple model (IMM) approach on a benchmark trajectory which includes coordinated turns and straight line maneuvers.

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Article

Reported here are the results of tests of five 3D image operators in eleven configurations to determine which is best for the enhancement of image sequences of rocket plumes. The operators enhance images both for visual inspection and for radiometric characterization. The tests used real and synthetic imagery to evaluate the operators under a variety of conditions. The results suggest the best choice of operator depends on the grayscale distribution of the noise in the image sequence. In terms of signal-to-noise ratio (SNR), long duration median filters with moderate spatial support appear to work best overall. The results show that successful enhancement for visual inspection requires the original image data to be remapped prior to filtering. This need not destroy the radiometric information in the imagery. Some attributes of rocket plume image time sequences and the noise in them are described. The remapping procedure is detailed and the operators tested are described. The methodology is explained and the results of the numerous tests on synthetic imagery are presented. The application of the procedures to two real rocket plume image sequences is described.

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Article

Proportional navigation (PN) guidance laws (GLs) have been widely
used and studied in the guidance literature. But most of the guidance
literature on PN has concentrated on the evaluation of empirical PNGLs
or GLs obtained from very specific optimality considerations. The
authors present a novel approach (called guidance laws modeling) to
derive new GLs. They consider the basic requirements of capture and
define a complete class of GLs that meet these requirements. It is shown
that PN is a natural candidate in this class. The main consequence of
this modeling process is the definition of two new GLs: one in 2D space
and the other in 3D space. These new GLs can be interpreted as new
generalizations of the true proportional navigation (TPN) GL. Moreover,
it is shown that these generalizations allow the TPNGL to match the
capturability performance of the pure proportional navigation (PPN) GL
in terms of initial conditions which allow the guided object to reach
its target

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Article

A novel Kalman filtering technique is presented that reduces the
mean-square-error (MSE) between three-dimensional (3D) actual angular
velocity values and estimated ones by an order of magnitude (when
compared with the MSE resulting from direct measurements) even under
extremely low signal-to-noise ratio conditions. The filtering problem is
nonlinear in nature because the dynamics of 3D angular motion are
described by Euler's equations. This nonlinear set of differential
equations state that the angular acceleration in one axis is
proportional to the torque applied to that axis, and to the products of
angular velocity components in the other two axes of rotation. Instead
of using extended Kalman filtering techniques to solve this complex
problem, the authors developed a new approach where the nonlinear
Euler's model is decomposed into two pseudolinear models (primary and
secondary). The first model describes the time progression of the state
vector containing the linear terms, while the other characterizes the
propagation of the state vector containing the nonlinearities. This
makes it possible to run two interlaced discrete-linear Kalman filters
simultaneously. One filter estimates the values of the state vector
containing the linear terms, while the other estimates the values of the
state vector containing the nonlinear terms in the system. These
estimates are then recombined, solving the nonlinear estimation process
without linearizing the system. Thus, the new approach takes advantage
of the simplicity, computational efficiency and higher convergence speed
of the linear Kalman filter form and it overcomes many of the drawbacks
typical of conventional extended Kalman filtering techniques. The high
performance and effectiveness of this method is demonstrated through a
computer simulation case study

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Article

We have developed a new formulation for three dimensional (3D)
radar imaging of inverse synthetic aperture radar (ISAR) data based on
recent developments in high resolution spectral estimation theory.
Typically for non real-time applications, image formation is a two step
process consisting of motion determination and image generation. The
technique presented focuses on this latter process, and assumes the
motion of the target is known. The new technique offers several
advantages over conventional techniques which are based on the
correlation imaging function. In particular, the technique provides for
a direct 3D estimate (versus back projection to a 3D target grid matrix)
of the locations of the dominant scattering centers using only a minimum
set of independent 2D range-Doppler ISAR “snapshots” of the
target. Because of the snapshot nature of the technique, it is
particularly applicable to 3D imaging of sectors of sparse-angle data,
for which the sidelobes of the correlation imaging integral become high.
Furthermore, the technique provides for an estimate of amplitude and
phase of each scattering center as a function of aspect angle to the
target, for those aspect angles which encompass the set of 2D
range-Doppler snapshots. Results illustrating the technique developed
are presented for both simulated and static range data

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Article

This paper develops three-dimensional (3D), bistatic parametric models that describe canonical radar scattering responses of several geometric objects. These models find use in inverse scattering-based processing of high-frequency radar returns. Canonical feature models are useful for extracting geometry from synthetic-aperture radar (SAR) scattering measurements and as feature primitives for automatic target recognition (ATR) and scene visualization. Previous work has considered monostatic feature models for two-dimensional (2D) radar processing; we extend this work to consider bistatic and 3D radar apertures. In the work presented here, we generalize geometric theory of diffraction (GTD) solutions for several scattering mechanisms in a plane. Products of these planar mechanisms in azimuth and elevation are used to produce 3D bistatic scattering models for six canonical shapes: a rectangular plate, dihedral, trihedral, cylinder, top-hat, and sphere. The derived models are characterized by a small number of parameters, and are shown to agree with results obtained from high-frequency, asymptotic scattering simulations.

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Article

The method for tracking based on Kalman filter with debiased
consistent converted 2D measurements was given and discussed by D. Lerro
et al. (1993) and Y. Bar-Shalom et al. (1993). In this work explicit
expressions for debiasing compensation terms and debiased covariance
statistics related to the 3D case are presented. The proposed procedure
can be employed in active sonar systems or long range radar systems
especially when the cross-range errors are significantly large relative
to the range errors

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Article

Since the proportional navigation guidance law was first introduced, many of the researchers had proposed different methodologies to investigate the corresponding performances of all the existing guidance laws. Even though a unified approach was proposed a few years ago, other authors found that under the proposed framework, all the existing guidance laws, namely ideal proportional navigation (IPN), true proportional navigation (TPN), and pure proportional navigation (PPN), were indeed special cases of the mentioned general guidance law. However, the results were restricted to two-dimensional space. In this paper, the author not only extends the results to three-dimensional space, but also to general IPN (GIPN), general TPN (GTPN), and PPN. Unlike conventional researchers, a modified polar coordinate (MPC) is adopted. It is shown that with the property of this MPC, for the line of sight (LOS) based guidance laws (GIPN and GTPN) the number of differential equations required to fully describe the relative dynamics can be reduced from six to three, however, for the missile's velocity-based guidance law, i.e., PPN, five differential equations are required. All the terms of differential equations involve only products and additions of variables. For all the mentioned guidance laws in this paper, only two transformed variables are required to describe the capture region, while the third variable is required to provide the condition of finite turn rate.

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