scholarly journals An Efficient Conformal Stacked Antenna Array Design and 3D-Beamforming for UAV and Space Vehicle Communications

Sensors ◽  
2021 ◽  
Vol 21 (4) ◽  
pp. 1362
Author(s):  
Yasser Albagory
Keyword(s):  
Space Vehicle ◽  
Maximum Amplitude ◽  
Effective Area ◽  
Space Vehicles ◽  
Communication Performance ◽  
Amplitude Coefficient ◽  
3D Beamforming ◽  
Array Beamforming ◽  
Electronic Steering ◽  
Beamforming Technique

In this paper, a new conformal array structure and beamforming technique are proposed to provide efficient communication performance for unmanned aerial vehicles (UAVs) and space vehicles. The proposed array is formed by conformally stacking cylindrical, conical, and concentric circular (CSC4) arrays which are all coaxially aligned with the same axis of the conformed body and with uniform interelement spacing. The array elements are then fed by a weighting vector that has an adaptive cosine tapered profile where the maximum amplitude coefficient is oriented with the mainlobe direction to improve the scanning capabilities of the array and increase the array effective area. In addition, for very large, conformed body structures such as space vehicles, a frontal mainlobe-oriented partial CSC4 array beamforming technique is proposed to efficiently utilize the large CSC4 structure, reduce the processing requirements for mainlobe electronic steering, and to provide very low sidelobe levels with reduced backlobe levels. Simulation results show that the proposed CSC4 design can provide wide scanning angles of up to ±70° angular range in the θ-direction with only ±1° change in the beamwidth, without increasing array size and with achievable sidelobe level of −45 dB and backlobe levels less than −10 dB.

Relativistic synchronization of onboard clocks of navigation space vehicles with the aid of intersatellite measurements

2021 ◽  
pp. 56-66
Author(s):  
Nikolay N. Vasilyuk ◽  
Alexander P. Chervonkin
Keyword(s):  
Proper Time ◽  
Space Vehicle ◽  
Relativistic Correction ◽  
Point Of View ◽  
Space Vehicles ◽  
Satellite Measurements ◽  
Clock Drift ◽  
Coordinate Time ◽  
Upper Limit ◽  
Unambiguous Interpretation

The problem of the synchronization of onboard clocks of navigation satellites has considered from a relativistic point of view using the concept of “coordinate simultaneity”. This concept allows an unambiguous interpretation of the synchronization results within the framework of general relativity. The algorithm of intersatellite measurements processing has formulated in terms of a proper time of a space vehicle and the coordinate time of a reference frame. Rules of transformation between coordinate and proper time scales have indicated. An analytical expression has obtained for the periodic relativistic correction to the estimated value of the relative clock drift. This correction has expressed in terms of the coordinate time of a ground observer. The value of this correction exceeds the acceptable synchronization error and should be taken into account for the inter-satellite measurements processing. The error of the relativistic correction determination has calculated. This error provides an upper limit for the period of uploading of ephemeris data on the board of the space vehicle.

Observations of ELF (extremely low frequency) signatures arising from space vehicle disturbances of the ionosphere

1991 ◽  
Vol 69 (8-9) ◽  
pp. 959-965 ◽  
Author(s):  
Jack Y. Dea ◽  
William Van Bise ◽  
Elizabeth A. Rauscher ◽  
Wolfgang-M. Boerner
Keyword(s):  
Geomagnetic Field ◽  
San Diego ◽  
Low Frequency ◽  
Space Vehicle ◽  
Lower Ionosphere ◽  
Space Vehicles ◽  
Extremely Low Frequency ◽  
Evanescent Fields ◽  
Hydromagnetic Waves

We report on observations of extremely low-frequency (ELF) signatures during exit or reentry of space vehicles through the ionosphere. The two modes regularly observed gave signals that peaked at 5.6 and 11.2 Hz. The evidence points to the lower ionosphere, i.e., the D- and E-layers, as the generator of these signals. The measurements were performed using ground-based multiturn coil sensors located in Reno and San Diego. The nature of these signals is unclear at present but it is surmised that we are detecting either the evanescent fields of hydromagnetic waves traveling in the ionosphere or the oscillating geomagnetic field associated with these hydromagnetic waves.

Optimal Space Trajectories—A Review of Published Work

1968 ◽  
Vol 72 (686) ◽  
pp. 141-146 ◽  
Author(s):  
D. J. Bell
Keyword(s):  
Gravitational Field ◽  
General Theory ◽  
Optimal Trajectory ◽  
Space Vehicle ◽  
Two Dimensions ◽  
Performance Criteria ◽  
Space Vehicles ◽  
Optimal Space Trajectories ◽  
End Conditions ◽  
Optimal Space

The problem of transferring a space vehicle between two points in a given gravitational field such that the minimum amount of fuel is used has been called the fundamental navigational problem of astronautics. In such a problem it may be required to find the optimum thrust magnitude and thrust direction which yields a minimum fuel trajectory. Furthermore, certain end conditions may be specified which the optimal trajectory must satisfy. In a large number of published papers the velocity of the vehicle is supposed known both at the beginning of the transfer and at the end whereas the time taken to complete the manoeuvre may or may not be given. Also, other performance criteria have been chosen besides minimum fuel. For example, minimum time of transit or maximum orbital altitude at perigee. Papers mentioned in this review deal mainly with flight in two dimensions apart from those sections on general theory. Furthermore, all space vehicles considered are assumed to have a fixed exhaust velocity unless otherwise stated.

THE RESONANT FREQUENCIES OF CAVITIES IN A MAGNETOIONIC MEDIUM

1964 ◽  
Vol 42 (1) ◽  
pp. 90-102 ◽  
Author(s):  
K. G. Budden
Keyword(s):  
Plasma Frequency ◽  
Space Vehicle ◽  
Boundary Region ◽  
Plasma Sheath ◽  
Space Vehicles ◽  
Isotropic Plasma ◽  
Resonant Frequencies ◽  
Characteristic Frequencies ◽  
Spherical Mass ◽  
Electron Gyrofrequency

The resonant frequencies for a hollow cylindrical or spherical cavity in a magnetoionic medium are derived using a simple model in which the boundary of the cavity is sharp and the medium outside it is homogeneous and loss free, but anisotropic. The effects of electron temperature and of nonlinearity are ignored. The problem is complementary to a similar problem treated by Herlofsen (1951), who discussed the resonant frequencies of a uniform cylindrical or spherical mass of isotropic plasma surrounded by a vacuum. It is found that the resonant frequencies are not equal to the characteristic frequencies of the plasma as usually described by the formulae X = 1, X = 1 ± Y, but are more complicated functions of the plasma frequency and the electron gyrofrequency. It is concluded that, for a plasma sheath or cavity of any structure, with a sharp or gradual boundary region, the resonant frequencies will in general differ from the characteristic frequencies of the undisturbed plasma. For a cylindrical cavity the resonant frequencies depend upon the angle between the axis of the cavity and the constant magnetic field. The results may have applications to the interpretation of plasma "spikes" observed with space vehicles, and to the theory of the radar cross section of a space vehicle within the ionosphere.

Intelligent Techniques for Star-Pattern Recognition

2003 ◽  
Author(s):  
Lalitha Paladugu ◽  
Marco P. Schoen ◽  
Brian G. Williams
Keyword(s):  
Good Accuracy ◽  
Attitude Determination ◽  
Space Vehicle ◽  
Field Of View ◽  
Space Vehicles ◽  
Neural Network Approach ◽  
Star Pattern ◽  
The Neural Network ◽  
Star Pattern Recognition

This work presents the study of two different approaches for the attitude determination of space vehicles. The Neural Network approach is based on a simple Kohonen network, where the characteristics of a star distribution within the Field Of View (FOV) are matched against an on-board stored star map. The second approach utilizes a Genetic Algorithm (GA). The GA minimizes the discrepancy between the characteristics of the stars inside the FOV and a candidate FOV selected from the star map. Preliminary simulations indicate that both approaches work well and deliver good accuracy in determining the bore sight direction of the space vehicle with respect to the star map.

scholarly journals IMPLEMENTATION OF A SMALL SPACE VEHICLE DEVELOPMENT PROJECT AS AN ILLUSTRATION OF THE INNOVATIVE UNIVERSITY EVOLUTION

2017 ◽  
Vol 21 (4) ◽  
pp. 101-108 ◽  
Author(s):  
S. G. Yemelyanov ◽  
T. S. Kolmykova ◽  
P. G. Artemev ◽  
S. N. Samburov
Keyword(s):  
Russian Federation ◽  
Global Economy ◽  
Space Vehicle ◽  
Development Project ◽  
Commercial Application ◽  
Space Vehicles ◽  
Innovative Development ◽  
Small Space ◽  
Extensive Experience ◽  
The Russian Federation

Innovative development of the national economy, that has been declared in the Conception of long-term social and economic development of the Russian Federation, has become especially important in the modern situation characterized by geopolitical challenges and threats. Russia is looking for new possibilities to strengthen its competitive position in the global economy. One of the most promising innovative development areas is space science and technologies. Space technologies of manned flights developed in Russia have always been exceptionally competitive. However, in the last decade the onset of new aerospace industries in such countries as China, India or the USA has jeopardized the Russian Federation position of the world leader in this field. In this context such new trends in space technologies as the design, manufacture and launching of small-size space vehicles may be interesting both in terms of advanced engineering and technological solutions and in terms of commercial application of innovative low-cost space products. There are already several very positive practical examples of this engineering field development that involves the adoption of the so-called three-spiral theory describing the interaction between the state, science and business. One of such examples is the Southwest State University that has accumulated an extensive experience of long-time cooperation with Roscosmos (Russian Space Agency) core engineering businesses in the area of small space vehicle design and manufacture. This is a unique experience that has no parallels in Russia or abroad. In terms of economics such integration presents a good object for the investigation of system interaction between national authorities, businesses, educational and scientific institutions. It also makes a sound basis for the successful dissemination of the know-how.

scholarly journals Design of Partial Discharge Test Environment for Oil-Filled Submarine Cable Terminals and Ultrasonic Monitoring

Energies ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4774
Author(s):  
Yulong Wang ◽  
Xiaohong Zhang ◽  
Lili Li ◽  
Jinyang Du ◽  
Junguo Gao
Keyword(s):  
Partial Discharge ◽  
Maximum Amplitude ◽  
Signal Amplitude ◽  
Ultrasonic Signal ◽  
Signal Spectrum ◽  
Test Environment ◽  
Ultrasonic Signals ◽  
Amplitude Coefficient ◽  
Marine Cable ◽  
Submarine Cables

Based on the principle of operating an oil-filled-cable operation and the explanation of the oil-filling process provided in the cable operation and maintenance manual of submarine cables, this study investigated oil-pressure variation caused by gas generated as a result of cable faults. First, a set of oil-filled cables and their terminal oil-filled simulation system were designed in the laboratory, and a typical oil-filled-cable fault model was established according to the common faults of oil-filled cables observed in practice. Thereafter, ultrasonic signals of partial discharge (PD) under different fault models were obtained via validation experiments, which were performed by using oil-filled-cable simulation equipment. Subsequently, the ultrasonic signal mechanism was analyzed; these signals were generated via electric, thermal, and acoustic expansion and contraction, along with electric, mechanical, and acoustic electrostriction. Finally, upon processing the 400 experimental data groups, four practical parameters—maximum amplitude of the ultrasonic signal spectrum, Dmax, maximum frequency of the ultrasonic signals, fmax, average ultrasonic signal energy, Dav, and the ultrasonic signal amplitude coefficient, M—were designed to characterize the ultrasonic signals. These parameters can be used for subsequent pattern recognition. Thus, in this study, the terminal PD of an oil-filled marine cable was monitored.

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