scholarly journals Multi-Constellation Software-Defined Receiver for Doppler Positioning with LEO Satellites

Sensors ◽  
2020 ◽  
Vol 20 (20) ◽  
pp. 5866
Author(s):  
Farzan Farhangian ◽  
René Landry
Keyword(s):  
Line Element ◽  
Low Earth Orbit ◽  
Receiver Design ◽  
Orbital Elements ◽  
Doppler Shifts ◽  
Localization Algorithms ◽  
Adaptive Measurement ◽  
Doppler Tracking ◽  
Downlink Signal ◽  
Positioning Algorithm

A Multi-Constellation Software-Defined Receiver (MC-SDR) is designed and implemented to extract the Doppler measurements of Low Earth Orbit (LEO) satellite’s downlink signals, such as Orbcomm, Iridium-Next, Globalstar, Starlink, OneWeb, SpaceX, etc. The Doppler positioning methods, as one of the main localization algorithms, need a highly accurate receiver design to track the Doppler as a measurement for Extended Kalman Filter (EKF)-based positioning. In this paper, the designed receiver has been used to acquire and track the Doppler shifts of two different kinds of LEO constellations. The extracted Doppler shifts of one Iridium-Next satellite as a burst-based simplex downlink signal and two Orbcomm satellites as continuous signals are considered. Also, with having the Two-Line Element (TLE) for each satellite, the position, and orbital elements of each satellite are known. Finally, the accuracy of the designed receiver is validated using an EKF-based stationary positioning algorithm with an adaptive measurement matrix. Satellite detection and Doppler tracking results are analyzed for each satellite. The positioning results for a stationary receiver showed an accuracy of about 132 m, which means 72% accuracy advancements compared to single constellation positioning.

scholarly journals NLOS Identification and Positioning Algorithm Based on Localization Residual in Wireless Sensor Networks

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 2991 ◽  
Author(s):  
Jingyu Hua ◽  
Yejia Yin ◽  
Weidang Lu ◽  
Yu Zhang ◽  
Feng Li
Keyword(s):  
Hypothesis Test ◽  
Intermediate Position ◽  
Wireless Sensor ◽  
Line Of Sight ◽  
Localization Algorithm ◽  
Target Node ◽  
Localization Algorithms ◽  
Anchor Nodes ◽  
Positioning Algorithm ◽  
Non Line Of Sight

The problem of target localization in WSN (wireless sensor network) has received much attention in recent years. However, the performance of traditional localization algorithms will drastically degrade in the non-line of sight (NLOS) environment. Moreover, variable methods have been presented to address this issue, such as the optimization-based method and the NLOS modeling method. The former produces a higher complexity and the latter is sensitive to the propagating environment. Therefore, this paper puts forward a simple NLOS identification and localization algorithm based on the residual analysis, where at least two line-of-sight (LOS) propagating anchor nodes (AN) are required. First, all ANs are grouped into several subgroups, and each subgroup can get intermediate position estimates of target node through traditional localization algorithms. Then, the AN with an NLOS propagation, namely NLOS-AN, can be identified by the threshold based hypothesis test, where the test variable, i.e., the localization residual, is computed according to the intermediate position estimations. Finally, the position of target node can be estimated by only using ANs under line of sight (LOS) propagations. Simulation results show that the proposed algorithm can successfully identify the NLOS-AN, by which the following localization produces high accuracy so long as there are no less than two LOS-ANs.

scholarly journals Increasing the Accuracy of Orbital Elements for a Satellite in a Low Earth Orbit under the Influence of Atmospheric Drag Using Adams-Bashforth Method

2021 ◽  
pp. 81-90
Author(s):  
Rasha H. Ibrahim ◽  
Abdul-Rahman H. Saleh
Keyword(s):  
Integration Method ◽  
Major Axis ◽  
Low Earth Orbit ◽  
True Anomaly ◽  
Earth Orbit ◽  
Atmospheric Drag ◽  
Orbital Elements ◽  
Semi Major Axis ◽  
Literature Reviews ◽  
Perturbed Equation

The perturbed equation of motion can be solved by using many numerical methods. Most of these solutions were inaccurate; the fourth order Adams-Bashforth method is a good numerical integration method, which was used in this research to study the variation of orbital elements under atmospheric drag influence.  A satellite in a Low Earth Orbit (LEO), with altitude form perigee = 200 km, was selected during 1300 revolutions (84.23 days) and ASat / MSat value of 5.1 m2/ 900 kg. The equations of converting state vectors into orbital elements were applied. Also, various orbital elements were evaluated and analyzed. The results showed that, for the semi-major axis, eccentricity and inclination have a secular falling discrepancy, Longitude of Ascending Node is periodic, Argument of Perigee has a secular increasing variation, while true anomaly grows linearly from 0 to 360°. Furthermore, all orbital elements, excluding Longitude of Ascending Node, Argument of Perigee, and true anomaly, were more affected by drag than other orbital elements, through their falling as the time passes. The results illustrate a high correlation as compared with literature reviews in this field.

Perturbations Observed in The Orbital Elements of the Spectroscopic Binary 57 Cygni

2018 ◽  
Vol 125 (1-4) ◽  
pp. 1-11
Author(s):  
Kenneth W. McLaughlin ◽  
Janak Panthi
Keyword(s):  
Apsidal Motion ◽  
Mass Ratio ◽  
Orbital Elements ◽  
Third Body ◽  
Orbital Inclination ◽  
Doppler Shifts ◽  
Spectroscopic Binary ◽  
Type Assignment ◽  
Helium Line ◽  
Stellar Masses

We present spectroscopy that confirms periodic Doppler-shifts along with photometry that reinforces a lack of eclipsing in the double-lined spectroscopic binary 57 Cygni. Our spectroscopy concentrates on a range encompassing H-alpha and the helium 667.8 nm line, where we find Doppler-shifts of both stars resolved in the helium line but less so in the broader H-alpha profile. Although we find the radial velocities derived from both lines reasonably consistent, we retained only the helium-line derived velocities for sinusoidal curve-fits to the orbital dependence. The fit-amplitudes specify the ratio of the stellar masses as 1.03 ± 0.05, in agreement with previous assessments. We find an eccentricity of 0.028 ± 0.024 and a longitude of periastron of 163.5 ± 2.5°. The former is significantly lower than that previously reported, while the latter is in agreement but calls into question the apsidal motion predicted four decades ago. Our modeling suggests the presence of an external third body implicit in this previous apsidal motion, as well as the dominant mechanism for our reported change in eccentricity. Based upon the spectral type assignment, the near-circular orbit, and the well-established mass ratio, we can place restrictions on the orbital inclination from 51.5-to-53.0°, in reasonable agreement with previous estimates.

Advanced Sequence-Based Localization Algorithm in Wireless Sensor Networks

2014 ◽  
Vol 651-653 ◽  
pp. 387-390 ◽  
Author(s):  
Fu Bin Zhou ◽  
Shao Li Xue
Keyword(s):  
Wireless Sensor Networks ◽  
Sensor Networks ◽  
Large Scale ◽  
Sensor Nodes ◽  
Wireless Sensor ◽  
Localization Algorithm ◽  
Measuring Devices ◽  
Localization Algorithms ◽  
Positioning Algorithm ◽  
Range Free

As an important application of Internet of Things , Wireless Sensor Networks utilized in surveillance and other case.Localization of nodes in wireless sensor networks is the prerequisite and base of target tracking in some surveillance applications, so localization error of sensor nodes is a key. However, due to limited energy, unreliable link and limited communication ranges of sensor nodes, high accurate positioning is difficult to achieve, which made it hot and full of challenging for wireless sensor nodes to localize without any auxiliary facilities. Range-based localization algorithm , could achieve good accuracy but require measuring devices, thus it is not appropriate for large-scale wireless sensor networks.So range-free localization algorithms are more popular.This paper analyses the algorithms in range-free localization,and proposed Advanced Sequence-Based Localization algorithm to improve the performance of positioning algorithm in wireless sensor network.

The Effect of Atmospheric Drag Force on the Elements of Low Earth Orbital Satellites at Minimum Solar Activity

2021 ◽  
Vol 19 (9) ◽  
pp. 24-37
Author(s):  
Najlaa Ozaar Hasan ◽  
Wafaa Hasan Ali Zaki ◽  
Ahmed Kader Izzet
Keyword(s):  
Solar Activity ◽  
Low Earth Orbit ◽  
Atmospheric Drag ◽  
Size Parameter ◽  
Mass Ratio ◽  
Orbital Elements ◽  
Unperturbed Motion ◽  
Minimum Solar Activity ◽  
Low Earth Orbit Satellites ◽  
The Impact

Researching and modeling perturbations is essential in astrodynamics because it gives information on the deviations from the satellite's normal, idealized, or unperturbed motion. Examined the impact of non-conservative atmospheric drag and orbital elements of low-earth-orbit satellites under low solar activity. The study is consisting of parts, the first looks at the effects of atmospheric drag on LEO satellites different area to mass ratios, and the second looks at different inclination values. Modeling the impacts of perturbation is included in each section, and the final portion determines the effects of atmospheric drag at various node values. The simulation was run using the Celestial Mechanics software system's SATORB module (Beutler, 2005), which solves the perturbation equations via numerical integration. The findings were examined using Matlab 2012. Conclusion that the impacts are stronger for retrograde orbits, which is due to the fact that the satellite moves in the opposite direction. The atmospheric drag effects for all orbital elements were increased by increasing the area to mass ratio. When the node value rises, the size parameter changes slightly, but the other orbital elements change. At varying inclinations, it is found that the changes in orbital elements due to atmospheric drug.

scholarly journals PASSAGE OF TIME IN A PLANCK SCALE ROOTED LOCAL INERTIAL STRUCTURE

2004 ◽  
Vol 13 (06) ◽  
pp. 1037-1071 ◽  
Author(s):  
JOY CHRISTIAN
Keyword(s):  
Line Element ◽  
Planck Scale ◽  
Doppler Shifts ◽  
Internal Phase ◽  
The World ◽  
Flow Of Time ◽  
Structural Attribute ◽  
Γ Rays ◽  
Planck Energy

It is argued that the "problem of time" in quantum gravity necessitates a refinement of the local inertial structure of the world, demanding a replacement of the usual Minkowski line element by a (4+2n)-dimensional pseudo-Euclidean line element, with the extra 2n being the number of internal phase space dimensions of the observed system. In the refined structure, the inverse of the Planck time takes over the role of observer-independent conversion factor usually played by the speed of light, which now emerges as an invariant but derivative quantity. In the relativistic theory based on the refined structure, energies and momenta turn out to be invariantly bounded from above, and lengths and durations similarly bounded from below, by their respective Planck scale values. Along the external timelike world-lines, the theory naturally captures the "flow of time" as a genuinely structural attribute of the world. The theory also predicts expected deviations — suppressed quadratically by the Planck energy — from the dispersion relations for free fields in the vacuum. The deviations from the special relativistic Doppler shifts predicted by the theory are also suppressed quadratically by the Planck energy. Nonetheless, in order to estimate the precision required to distinguish the theory from special relativity, an experiment with a binary pulsar emitting TeV range γ-rays is considered in the context of the predicted deviations from the second-order shifts.

scholarly journals Satellite Constellation Orbit Design Optimization with Combined Genetic Algorithm and Semianalytical Approach

2017 ◽  
Vol 2017 ◽  
pp. 1-17 ◽  
Author(s):  
Tania Savitri ◽  
Youngjoo Kim ◽  
Sujang Jo ◽  
Hyochoong Bang
Keyword(s):  
Genetic Algorithm ◽  
Optimization Design ◽  
Semimajor Axis ◽  
Low Earth Orbit ◽  
Computational Time ◽  
Target Point ◽  
Target Area ◽  
Orbital Elements ◽  
Satellite Constellation ◽  
Fitness Value

This paper focuses on maximizing the percent coverage and minimizing the revisit time for a small satellite constellation with limited coverage. A target area represented by a polygon defined by grid points is chosen instead of using a target point only. The constellation consists of nonsymmetric and circular Low Earth Orbit (LEO) satellites. A global optimization method, Genetic Algorithm (GA), is chosen due to its ability to locate a global optimum solution for nonlinear multiobjective problems. From six orbital elements, five elements (semimajor axis, inclination, argument of perigee, longitude of ascending node, and mean anomaly) are varied as optimization design variables. A multiobjective optimization study is conducted in this study with percent coverage and revisit time as the two main parameters to analyze the performance of the constellation. Some efforts are made to improve the objective function and to minimize the computational load. A semianalytical approach is implemented to speed up the guessing of initial orbital elements. To determine the best parametric operator combinations, the fitness value and the computational time from each study cases are compared.

A Novel Navigation Approach of Low Earth Orbit Satellites Formation Based on Reduced Relative Orbital Elements

2021 ◽  
pp. 343-354
Author(s):  
Shengqing Yang ◽  
Yaoke Du ◽  
Wenyan Wang ◽  
Junli Chen ◽  
Jingyu Wu
Keyword(s):  
Low Earth Orbit ◽  
Earth Orbit ◽  
Orbital Elements ◽  
Low Earth Orbit Satellites
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