Pratt  G. W.  Arnaud  M.  Biviano  A.  Eckert  D.  Ettori  S.  Nagai  D.  Okabe  N.  Reiprich  T. H. 《Space Science Reviews》2019,215(2):1-19

Space Science Reviews - The QB50 mission is a satellite constellation designed to carry out measurements at between 200–380 km altitude in the ionosphere. The multi-needle Langmuir probe...  相似文献   

    

Hart  Walter G. McGowan  Gerald F. DuPont  T. E. 《IEEE transactions on aerospace and electronic systems》1968,(4):592-606

The design of an adaptive tracking filter control system and its application to large flexible booster vehicles is described. The problem of elastic vehicle stability is considered along with its solution by conventional and adaptive techniques. The improvement in vehicle stability, which may be achieved with the adaptive tracking filter technique as compared to conventional techniques, is shown. The control system evolved uses two adaptive tracking filters to phase stabilize the first and second bending modes, in addition to conventional compensation techniques. The application of this adaptive technique to a vehicle in which the modal frequencies are in close proximity (<2.5 percent separation) is discussed. The mechanization of the adaptive control system involves the selection of design techniques and components that are electrically and physically compatible with the intended airborne application. The development of a suitable frequency tracking technique and tracking filter is described, in addition to the electronic and mechanical design of the adaptive control system prototype.  相似文献   

    

Glisson  T.H. Black  C.I. Sage  A.P. 《IEEE transactions on aerospace and electronic systems》1970,(1):37-50

Systems which utilize acoustic energy to explore an undersea environment are called sonars. This introductory and tutorial paper presents a discussion of active sonar signal analysis concentrating upon sinusoidal, linear FM, and pseudorandom echolocation pulses. Many previously published results concerning sonar signals and their haracteristics are integrated, collected, and presented in a unified form such as to portray typical signal design considerations.  相似文献   

    

Albert T. Price 《Space Science Reviews》1969,9(2):151-197

The atmospheric dynamo theory of the daily magnetic variations (S) has received substantial support from recent observational and theoretical work. In particular, several features of the variations, such as their remarkable enhancement close to the dip equator and other effects indicating a strong control by the main geomagnetic field, are well explained by the dynamo theory. Also the detection of ionospheric currents by instrumental rockets has confirmed an essential part of the theory.Considerable impetus was given to their study by the acquirement of much new data on magnetic variations during the IGY-IQSY period. Additional observations in the Pacific area were obtained during the IQSY by the establishment of four island stations equipped with newly developed magnetometers. A major advance at other stations was the development of automatic standard observatories using nuclear magnetometers.Several methods for the world-wide analysis of the S-field have been developed. A possibility now being studied is the completely automatic evaluation and construction by computers of ionospheric current charts for any day and any epoch UT.Some theoretical and statistical papers are briefly reviewed. These include discussions of the day-to-day variability of S, seasonal changes of the S-field, the nature of the equatorial electrojet, the possibility of solar wind effects contributing to the daily variations, and the modification of the dynamo theory to take account of the possible flow of electric current from the ionosphere along magnetic lines of force in the magnetosphere.Finally, an attempt to extend the dynamo theory of S by treating the ionosphere as a three-dimensional medium, instead of regarding it as a thin shell, has revealed that, although the relations between the horizontal components of electric field and current density in the dynamo layer are given with reasonable accuracy by the well-known layer equations, the assumption, implicit in the thin shell treatment, that the horizontal currents are non-divergent is not in fact true. Hence a revision of some earlier theoretical work on S appears necessary.  相似文献   

    

Kaplan  L.J. Ormsby  J.F.A. Fowle  E.N. Johnson  K.R. Bates  R.H.T. Bickel  S.H. 《IEEE transactions on aerospace and electronic systems》1969,(4):654-660

A satellite has been designed for application to radar calibration. Electromagnetic and mechanical characteristics of the satellite and their influence on the selection of shape and other parameters are discussed. Theoretical and experimental scattering data are included.  相似文献   

    

Durrani  T.S. Greated  C. 《IEEE transactions on aerospace and electronic systems》1974,(4):418-428

The application of frequency-tracking systems to the analysis of laser doppler velocimeter (LDV) signals degraded by background noise has been studied both theoretically and experimentally. Expressions are derived for both the correlation function and the expected value of the phase derivative in the general case of noise off center from the Doppler frequency, and these results are specialized to specific cases of practical interest. Laboratory measurements of output signal-to-noise ratio (SNR) and dc error, for varying input SNR and noise center frequency offset, show good agreement with the theoretical predictions.  相似文献   

    

Hampton  R.L.T. Cooke  J.R. 《IEEE transactions on aerospace and electronic systems》1973,(2):197-207

The design of adaptive filters for the tracking of high-performance maneuvering targets is a fundamental problem in real-time surveillance systems. As is well known, a filter which provides heavy smoothing can not accurately track an evasive maneuver, and conversely. Consequently, one is led to the consideration of adaptive methods of filter design. This paper presents an improved self-adaptive filter algorithm for on-line solution of the above problem. Basically, this algorithm utilizes the orthogonality property of the residual time series to force the filter to automatically track the optimal gain levels in a changing environment.  相似文献   

    

Lee  F.C.Y. Wilson  T.G. Feng  S.Y.M. 《IEEE transactions on aerospace and electronic systems》1973,(4):571-584

A familiar two-transistor saturable-core parallel inverter is modeled as a nonlinear negative resistance in parallel with energy-storage elements. The techniques of singular-point analysis are combined with piecewise linear techniques to permit determination of solution trajectories on the phase plane. Clear insight is provided, not only into steady-state oscillation, but also into transient behavior of the circuit. Experimental results confirming the analytical model are included.  相似文献   

    

Jones  T. F. 《IEEE transactions on aerospace and electronic systems》1966,(2):140-142

Lifetime earnings of a high school graduate of $150 000 can be increased to $725 000 with a doctorate. Continued study is required to ?stand still? with an engineering half life of ten years. These points, among others, point to the value of investment in continued education.  相似文献   

    

Hawkes  T. A. Dupraz  J. 《IEEE transactions on aerospace and electronic systems》1967,(2):158-164

An improved method for frame synchronization of PCM telemetered data is described and performance analyses are presented. This method is based on the utilization of a threshold detector whose level is selfvarying according to the characteristics of the received data. It is simple to implement and simpler from an operational point of view than the frame synchronizers currently in use in that a threshold control is altogether eliminated. Analyses show, furthermore, that a synchronizer using a self-varying threshold always has a higher probability of detecting the synchronization code no matter what the frame length, sync code length, or error level.  相似文献