The plasma mantle: Composition and other characteristics observed by means of the PROGNOZ-7 satellite

A brief summary of the main results of magnetospheric ion composition measurements in general is first presented. PROGNOZ-7 measurements in the nightside plasma mantle are then described and analyzed. Some of the results are the following: In the nightside mantle not too far from midnight the properties of the mantle are sometimes consistent with the open magnetosphere model. However during most magnetic storm situations O⁺ ions appear in the mantle in large proportions and with high energies. The acceleration process affecting the ions has been found in several cases to give equal amounts of energy to all ions independent of mass. Along the flanks of the magnetosphere the flow of the plasma is often low or absent. The O⁺ content is high (up to 20%) and the energy spectrum of both ions and electrons may be very hot, even up to the level of the ring current plasma in the keV range.The O⁺ content in the plasma mantle is positively correlated with the magnetospheric activity level. The mantle, however, does not appear to be the dominating source for the storm time ring current. Direct acceleration of ionospheric ions onto the closed field lines of the plasma sheet and ring current is most likely the main source. The magnetopause on the nightside and along the flanks of the magnetosphere appears to be a fairly solid boundary for mantle ions of ionospheric origin. This is especially evident during periods with high geomagnetic activity, when the mantle is associated with fairly strong fluxes of O⁺ ions.An interesting observation in most of the mantle passages during geomagnetically disturbed periods is the occurrence of intense, magnetosheath like, regions deep inside the mantle. In some cases these regions with strong antisunward flow and with predominant magnetosheath ion composition was observed in the innermost part of the mantle, i.e. marking a boundary region between the lobe and the mantle. These magnetosheath penetration events are usually associated with strong fluxes of accelerated ionospheric ions in nearby parts of the mantle. Evanescent penetration regions with much reduced flow properties are frequently observed in the flank mantle.     

Radar Identification of Naval Vessels

A scheme is presented for the identification of naval vessels via active multiple-frequency radar interrogation. A major virtue of the described method is the use of a response waveform synthesized using amplitude data only. A prediction correlation using natural resonances associated with substructures on the vessels is applied to synthetically generated matched-filter response waveforms. The identification scheme is tested using measured model data for 8 vessels on a simulated sea surface. A correct identification probability of roughly 77 percent is obtained.     

Hard Limiter Performance as a Polarity Detector for Extremely Polluted Signals

A hard limiter is a simple, yet highly efficient, RF signal sensor for VLF and LF navigation receivers. The observation reliability is used as the single quality criterion for the hard limiter if applied as a singlebit analog-to-digital converter (ADC). The effects of noise (Gaussian and atmospheric), nonsynchronous and synchronous interference, and dc offset on the observation reliability are described extensively. The single parameter determination Pobs is adequate for characterizing the polarity detector. This facilitates rank ordering of influences disturbing the signal and is a useful tool in optimizing digital tracking loops. The ?built-in? noise-censoring properties of the hard limiter in the presence of atmospheric noise are excellent. Therefore, three different atmospheric noise models are used in the determination of the observation reliability Pobs. Some ways for coping with other disturbances that potentially threaten the good performance of the hard limiter are suggested.     

Asymptotic Reproducibility in Nonlinear Systems and Attitude Control of Gyrostat

A control law is presented for asymptotic function reproducibility in a class of nonlinear-systems such that the output of the system asympotically tends to a given function. The controller consists of a prefilter and a servocompensator. Based on this result, a nonlinear feedback control law for the attitude control of a satellite containing symmetric rotors, in a circular orbit, is derived. In the closed-loop system, given trajectories of pitch, yaw, and roll angles are asymptotically followed, and set point control of attitude is accomplished. Digital simulation results are presented to show the capability of the nonlinear controller.     

Ambiguity Functions for Quadratic Phase-Coded Pulse Trains

The matched filter ambiguity function is presented for a burst waveform composed of repeated subbursts, each one of which consists of N pulses in which the phase is varied quadratically from pulse to pulse. The resulting ambiguity function exhibits small residual ambiguities along the delay axis separated by the reciprocal of the pulse repetition frequency (PRF). A cross-ambiguity function is derived which reduces these ambiguities to zero amplitude. A third cross-ambiguity function is presented for a receiver matched to a generalized Hamming weighted repeated quadratic burst. The location in the delay/Doppler plane of the waveform ambiguities for these waveforms is compared with that of an uncoded pulse burst.     

Advanced Aircraft Electric System

The topics, advanced aircraft electric system and all-electric airplane, inspire a broad range of concepts from the evolutionary to the revolutionary. The revolutionary developments are exciting to the research and development community but find little encouragement or acceptance from airframe developers whose objective is to build an advanced technology airplane using only-off-the-shelf, proven equipment. Their anthem rings "We know how bad the ___________ is, but we have learned to live with it. We have only your vision of how good an advanced system will be and fear to chance it. "However, the cost of living with these known systems combined with the escalating cost of fuel and the military need to address advanced mission capability demands more than a patch called improved reliability and maintainability. The time is at hand to demonstrate an evolutionary approach to achieve a revolutionary improvement. This paper describes an advanced electric system, the life cycle cost improvement anticipated, and the evolutionary means to implementation.     

Electromechanical Actuation Technology for the All-Electric Aircraft

Electromechanical actuation is a critical element that must be developed and verified to make the all-electric aircraft a viable concept. For several years the Flight Control Division of the Air Force Wright Aeronautical Laboratories has sponsored activities to demonstrate the credibility of electromechanical actuation systems (EMAS) for primary flight control actuation functions. The foundation for these EMAS activities and several electromechanical actuation development programs are described here. One involves the design, fabrication, and laboratory test of a rotary, hingeline electromechanical actuator. Another involves the development and flight test demonstration of a linear electromechanical actuator for controlling an aileron of a C-141 aircraft. A third involves the design and development of a linear electromechanical actuator for missiles having severe performance, temperature, and volumetric requirements. In addition, a brief summary of the results from two aircraft actuation trade studies compare the baseline (conventional) hydraulic flight control system with an all-electric airplane concept including quantitative comparisons of weight, reliability and maintainability, and life cycle costs.     

Extensions of the Discrete-Average Models for Converter Power Stages

An improved power converter model is developed by combining the average and discrete modeling techniques. The parameter determination of the proposed discrete-average model is shown to be dependent on the type of duty cycle control law and the nature of the error processor used in the feedback loop. Furthermore, the paper pinpoints deficiencies of the conventional loop gain measurement technique which is widely used in industries.     

State Estimation and Divergence Analysis

A growing memory discrete dynamic model for performing temporal extrapolations along a predetermined path in a random field is presented. This dynamic model is used to drive a linear system that is itself driven by discrete white noise. The coupled system is used to derive a state estimation scheme that recursively processes noisy measurements of the system. In addition, using the aforementioned dynamic model as a reference (truth) model, the authors develop a covariance analysis to measure the estimation errors that occur when the dynamics along the path through the field are modeled as a Markov linear model and state estimation is performed using discrete Kalman filtering. The performance evaluation of an inertial navigation system influenced by the Earth's gravity field aboard a maneuvering ship is provided as a specific illustrative example.     

Initial observations of low energy charged particles near the Earth's bow shock on ISEE-1

We report initial measurements from the ULECA sensor of the Max-Planck-Institut/University of Maryland experiment on ISEE-1. ULECA is an electrostatic deflection — total energy sensor consisting of a collimator, deflection analyzer and an array of solid state detectors. The position of a given detector, which determines the energy per charge of an incident particle, together with the measured energy determine the particle's charge state. We find that a rich variety of phenomena are operative in the transthermal energy regime (10 keV/Q to 100 keV/Q) covered by ULECA. Specifically, we present observations of locally accelerated protons, alpha particles, and heavier ions in the magnetosheath and upstream of the Earth's bow shock. Preliminary analysis indicates that the behavior of these locally accelerated particles is most similar at the same energy per charge.