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  Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 120 journals)
Showing 1 - 30 of 30 Journals sorted alphabetically
Acta Astronautica     Hybrid Journal   (Followers: 483)
Advances in Aerospace Engineering     Open Access   (Followers: 66)
Advances in Aerospace Science and Technology     Open Access   (Followers: 7)
Advances in Astronautics Science and Technology     Hybrid Journal  
Advances in Space Research     Full-text available via subscription   (Followers: 454)
Aeronautical Journal, The     Hybrid Journal   (Followers: 10)
Aerospace     Open Access   (Followers: 57)
Aerospace Medicine and Human Performance     Full-text available via subscription   (Followers: 14)
Aerospace Science and Technology     Hybrid Journal   (Followers: 422)
Aerospace Scientific Journal     Open Access   (Followers: 15)
Aerospace Systems     Hybrid Journal   (Followers: 3)
Aerospace technic and technology     Open Access   (Followers: 2)
Aerotecnica Missili & Spazio : Journal of Aerospace Science, Technologies & Systems     Hybrid Journal  
AIAA Journal     Hybrid Journal   (Followers: 1175)
Air Force Magazine     Full-text available via subscription   (Followers: 11)
Air Medical Journal     Hybrid Journal   (Followers: 8)
Annual of Navigation     Open Access   (Followers: 22)
Artificial Satellites     Open Access   (Followers: 23)
ASTRA Proceedings     Open Access   (Followers: 2)
Astrodynamics     Hybrid Journal   (Followers: 1)
Aviation     Open Access   (Followers: 15)
Aviation Advances & Maintenance     Open Access   (Followers: 3)
Aviation in Focus - Journal of Aeronautical Sciences     Open Access   (Followers: 10)
Aviation Psychology and Applied Human Factors     Hybrid Journal   (Followers: 26)
Aviation Week     Full-text available via subscription   (Followers: 438)
Canadian Aeronautics and Space Journal     Full-text available via subscription   (Followers: 33)
CEAS Aeronautical Journal     Hybrid Journal   (Followers: 29)
Chinese Journal of Aeronautics     Open Access   (Followers: 20)
Ciencia y Poder Aéreo     Open Access   (Followers: 2)
Civil Aviation High Technologies     Open Access   (Followers: 5)
Control Systems     Hybrid Journal   (Followers: 317)
Cosmic Research     Hybrid Journal   (Followers: 4)
COSPAR Colloquia Series     Full-text available via subscription   (Followers: 11)
Egyptian Journal of Remote Sensing and Space Science     Open Access   (Followers: 24)
Elsevier Astrodynamics Series     Full-text available via subscription   (Followers: 12)
Fatigue of Aircraft Structures     Open Access   (Followers: 15)
Frontiers in Astronomy and Space Sciences     Open Access   (Followers: 12)
Gyroscopy and Navigation     Hybrid Journal   (Followers: 255)
IEEE Aerospace and Electronic Systems Magazine     Full-text available via subscription   (Followers: 276)
IEEE Journal on Miniaturization for Air and Space Systems     Hybrid Journal   (Followers: 2)
IEEE Transactions on Aerospace and Electronic Systems     Hybrid Journal   (Followers: 383)
IEEE Transactions on Circuits and Systems I: Regular Papers     Hybrid Journal   (Followers: 39)
International Journal of Aeroacoustics     Hybrid Journal   (Followers: 39)
International Journal of Aerodynamics     Hybrid Journal   (Followers: 36)
International Journal of Aeronautical and Space Sciences     Hybrid Journal   (Followers: 2)
International Journal of Aerospace Engineering     Open Access   (Followers: 80)
International Journal of Aerospace Psychology     Hybrid Journal   (Followers: 23)
International Journal of Aerospace Sciences     Open Access   (Followers: 30)
International Journal of Applied Geospatial Research     Hybrid Journal   (Followers: 7)
International Journal of Aviation Management     Hybrid Journal   (Followers: 8)
International Journal of Aviation Technology, Engineering and Management     Full-text available via subscription   (Followers: 7)
International Journal of Aviation, Aeronautics, and Aerospace     Open Access   (Followers: 4)
International Journal of Crashworthiness     Hybrid Journal   (Followers: 12)
International Journal of Micro Air Vehicles     Full-text available via subscription   (Followers: 11)
International Journal of Satellite Communications Policy and Management     Hybrid Journal   (Followers: 13)
International Journal of Space Science and Engineering     Hybrid Journal   (Followers: 11)
International Journal of Space Structures     Full-text available via subscription   (Followers: 17)
International Journal of Space Technology Management and Innovation     Full-text available via subscription   (Followers: 10)
International Journal of Sustainable Aviation     Hybrid Journal   (Followers: 5)
International Journal of Turbo and Jet-Engines     Hybrid Journal   (Followers: 6)
Investigación Pecuaria     Open Access   (Followers: 3)
Journal of Aerodynamics     Open Access   (Followers: 17)
Journal of Aeronautical Materials     Open Access   (Followers: 9)
Journal of Aeronautics & Aerospace Engineering     Open Access   (Followers: 28)
Journal of Aerospace Engineering     Full-text available via subscription   (Followers: 68)
Journal of Aerospace Engineering & Technology     Full-text available via subscription   (Followers: 16)
Journal of Aerospace Information Systems     Hybrid Journal   (Followers: 20)
Journal of Aerospace Information Systems     Hybrid Journal   (Followers: 32)
Journal of Aerospace Technology and Management     Open Access   (Followers: 7)
Journal of Aircraft     Hybrid Journal   (Followers: 337)
Journal of Aircraft and Spacecraft Technology     Open Access   (Followers: 8)
Journal of Airline and Airport Management     Open Access   (Followers: 12)
Journal of Astrobiology & Outreach     Open Access   (Followers: 3)
Journal of Aviation Technology and Engineering     Open Access   (Followers: 11)
Journal of Aviation/Aerospace Education & Research     Open Access   (Followers: 2)
Journal of Engineering and Technological Sciences     Open Access   (Followers: 1)
Journal of Guidance, Control, and Dynamics     Hybrid Journal   (Followers: 204)
Journal of KONBiN     Open Access   (Followers: 3)
Journal of Navigation     Hybrid Journal   (Followers: 279)
Journal of Propulsion and Power     Hybrid Journal   (Followers: 610)
Journal of Space Safety Engineering     Hybrid Journal   (Followers: 7)
Journal of Space Weather and Space Climate     Open Access   (Followers: 27)
Journal of Spacecraft and Rockets     Hybrid Journal   (Followers: 770)
Journal of Spatial Science     Hybrid Journal   (Followers: 3)
Journal of the American Helicopter Society     Full-text available via subscription   (Followers: 7)
Journal of the Astronautical Sciences     Hybrid Journal   (Followers: 8)
Journal of the Australasian Society of Aerospace Medicine     Open Access   (Followers: 1)
Journal of Wind Engineering and Industrial Aerodynamics     Hybrid Journal   (Followers: 16)
Life Sciences in Space Research     Hybrid Journal   (Followers: 3)
MAD - Magazine of Aviation Development     Open Access   (Followers: 2)
Mekanika : Jurnal Teknik Mesin i     Open Access   (Followers: 1)
Microgravity Science and Technology     Hybrid Journal   (Followers: 2)
New Space     Hybrid Journal   (Followers: 6)
Nonlinear Dynamics     Hybrid Journal   (Followers: 19)
npj Microgravity     Open Access   (Followers: 3)
Open Aerospace Engineering Journal     Open Access   (Followers: 1)
Population Space and Place     Hybrid Journal   (Followers: 9)
Problemy Mechatroniki. Uzbrojenie, lotnictwo, inżynieria bezpieczeństwa / Problems of Mechatronics. Armament, Aviation, Safety Engineering     Open Access   (Followers: 3)
Proceedings of the Human Factors and Ergonomics Society Annual Meeting     Hybrid Journal   (Followers: 16)
Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering     Hybrid Journal   (Followers: 45)
Progress in Aerospace Sciences     Full-text available via subscription   (Followers: 79)
Propulsion and Power Research     Open Access   (Followers: 67)
REACH - Reviews in Human Space Exploration     Full-text available via subscription   (Followers: 5)
Research & Reviews : Journal of Space Science & Technology     Full-text available via subscription   (Followers: 17)
RocketSTEM     Free   (Followers: 6)
Russian Aeronautics (Iz VUZ)     Hybrid Journal   (Followers: 24)
Science and Education : Scientific Publication of BMSTU     Open Access   (Followers: 1)
Space and Polity     Hybrid Journal   (Followers: 4)
Space Policy     Hybrid Journal   (Followers: 30)
Space Research Today     Full-text available via subscription   (Followers: 48)
Space Safety Magazine     Free   (Followers: 51)
Space Science International     Open Access   (Followers: 192)
Space Science Reviews     Hybrid Journal   (Followers: 97)
SpaceNews     Free   (Followers: 824)
Spatial Information Research     Hybrid Journal   (Followers: 1)
Technical Soaring     Full-text available via subscription   (Followers: 1)
Transport and Aerospace Engineering     Open Access   (Followers: 1)
Transportmetrica A : Transport Science     Hybrid Journal   (Followers: 8)
Unmanned Systems     Hybrid Journal   (Followers: 5)
Вісник Національного Авіаційного Університету     Open Access   (Followers: 2)

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Similar Journals
Journal Cover
IEEE Transactions on Aerospace and Electronic Systems
Journal Prestige (SJR): 0.611
Citation Impact (citeScore): 3
Number of Followers: 383  
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0018-9251
Published by IEEE Homepage  [229 journals]
  • IEEE Aerospace and Electronic Systems Society
    • Abstract: Presents a listing of the editorial board, board of governors, current staff, committee members, and/or society editors for this issue of the publication.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • From the Editor-in-Chief
    • Pages: 4160 - 4160
      Abstract: Presents the introductory editorial for this issue of the publication.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • An Analysis of the Benefits and Difficulties of Aerial Magnetic Vector
    • Pages: 4161 - 4176
      Abstract: Recent successful flight tests have demonstrated scalar magnetic anomaly navigation to be a viable GPS-alternative navigation system. These flight tests matched magnetic field measurements to maps of the Earth's crustal magnetic field in order to navigate. Scalar magnetic navigation uses only the magnetic field intensity, not direction, in order to navigate. While it appears obvious to extend aerial magnetic navigation to use the full vector field, in practice there are substantial obstacles to doing so. This article explores the key challenges of magnetic vector navigation including current sensor limitations, lack of high frequency magnetic vector maps of the Earth's crust, and proper integration of the magnetic data with an inertial navigation system. In overcoming these challenges several key benefits of magnetic vector navigation over scalar magnetic navigation become apparent, including modestly improved navigation accuracy and greatly improved platform attitude.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Low-Computation GNSS Signal Acquisition Method Based on a Complex Signal
           Phase in the Presence of Sign Transitions
    • Pages: 4177 - 4191
      Abstract: During signal acquisition in a global navigation satellite system acquisition stage, a method of signal parameters estimation with low computational complexity is needed. However, due to the influence of sign transitions, the correct peak corresponding to the signal parameters is difficult to detect. For the estimation of the code phase of the received signal in the presence of sign transitions with low computational complexity, an acquisition method based on a complex signal phase (AMCSP) is proposed. The problem of estimating the sign transition position and the code phase is transformed into a problem of solving for a complex signal phase. Special block matrixes are constructed to obtain the complex signal phase, and integration processing is utilized to improve the detection probability performance. Based on an analysis of undesirable cases, a final code phase estimation process is proposed. Furthermore, expressions for the detection performance and computational complexity of AMCSP are derived. Simulation results demonstrate that the computational cost of AMCSP is much lower than that of a fast Fourier transform-based method.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Design of Parameter-Self-Tuning Controller Based on Reinforcement Learning
           for Tracking Noncooperative Targets in Space
    • Pages: 4192 - 4208
      Abstract: Tracking space noncooperative targets, including disabled and mobile spacecrafts, remains a challenging problem. This article develops two reinforcement-learning-based parameter-self-tuning controllers for the following two different tracking cases: case A, tracking a disabled target, and case B, tracking a mobile target. An adaptive controller consisting of five model uncertainties is adopted for case A, and a modified PD controller is derived for case B. The actor–critic framework is employed to reduce the initial control accelerations for case A and to improve the terminal tracking accuracy for case B. Relations between control parameters and tracking errors are found through the fuzzy inference system. Finally, the reinforcement learning is used to select suitable control parameters for achieving desired purposes. Numerical experimental results validate the effectiveness of the proposed algorithms on reducing initial control accelerations for case A and improving the terminal tracking accuracy for case B.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Doppler Sensitive Discrete-Phase Sequence Set Design for MIMO Radar
    • Pages: 4209 - 4223
      Abstract: We consider the design of sets of discrete-phase, including binary/quaternary, sequences for phase-modulated continuous-wave multiple-input multiple-output radar in the presence of nonnegligible Doppler shift. We consider the peak sidelobes of auto- and cross-correlations in a desired interval of the Doppler shift as the performance metric of the design. Then, the design problem is formulated via imposing the discrete-phase constraint for each element of the sequences, with emphasis on binary as well as quaternary cases. This problem is nonconvex and hence hard to solve. We introduce a method based on the block coordinate descent framework to solve the optimization problem. We also modify the proposed method to efficiently update the subproblem associated with each iteration. Also, we extend it to account for only a low-correlation zone in the presence of Doppler shift. Numerical examples are provided to illustrate the effectiveness and performance of the proposed algorithm in comparison with the existing methods.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • A GPS Spoofing Detection and Classification Correlator-Based Technique
           Using the LASSO
    • Pages: 4224 - 4237
      Abstract: This article proposes a global navigation satellite system (GNSS) spoofing detection and classification technique for single-antenna receivers. We formulate an optimization problem at the baseband correlator domain by using the Least Absolute Shrinkage and Selection Operator (LASSO). We model correlator tap outputs of the received signal to form a dictionary of triangle-shaped functions and leverage sparse signal processing to choose a decomposition of shifted matching triangles from said dictionary. The optimal solution of this minimization problem discriminates the presence of a potential spoofing attack peak by observing a decomposition of two different code-phase values (authentic and spoofed) in a sparse vector output. We use a threshold to mitigate false alarms. Furthermore, we present a variation of the minimization problem by enhancing the dictionary to a higher resolution of shifted triangles. The proposed technique can be implemented as an advanced fine-acquisition monitoring tool to aid in the tracking loops for spoofing mitigation. In our experiments, we are able to distinguish authentic and spoofer peaks from synthetic data simulations and from a real dataset, namely, the Texas spoofing test battery. The proposed method achieves 0.3% detection error rate for a spoofer attack in nominal signal-to-noise ratio conditions and an authentic-over-spoofer power of 3 dB.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Discrete Phase Coded Sequence Set Design for Waveform-Agile Radar Based on
           Alternating Direction Method of Multipliers
    • Pages: 4238 - 4252
      Abstract: With increased degrees of freedom of the transmitter, a coherent waveform-agile radar system can change its interpulse waveform to enhance the capability against increasingly sophisticated jamming and spoofing threats. Furthermore, radar agile waveform can provide better detection performance than a single waveform. In this article, we consider discrete phase coded sequence set design (DPCSSD) problem based on range-Doppler discrete ambiguity function for coherent waveform-agile radar system. DPCSSD problem for optimizing discrete phase coded sequence set under constant module constraint with desired minimized sidelobes on range-Doppler plane, is a quartic function and the constraint is nonconvex. To solve this quartic optimization problem, we propose an effective algorithm based on alternating direction method of multipliers (ADMM), which is a powerful mathematical tool of the augmented Lagrangian scheme for dealing with separable objective functions. As the quartic optimization problem is hard to solve, majorization–minimization (MM) is also considered to introduce a quadratic auxiliary function which is the upperbound of the original function. By minimizing the auxiliary function, the original DPCSSD optimization problem can be solved through MM in an iterative way. Meanwhile, the problem of minimizing the quadratic auxiliary function with constraints can be solved through ADMM algorithm. In particular, fast implementation for the most computationally demanding step of matrix inversion is investigated. The effectiveness of the proposed approach is demonstrated via computer simulations.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • A Machine Learning-Based Approach for Improved Orbit Predictions of LEO
           Space Debris With Sparse Tracking Data From a Single Station
    • Pages: 4253 - 4268
      Abstract: Accurate orbit prediction (OP) of space debris is vital in space situation awareness (SSA) related tasks, such as space collision warnings. However, owing to the sparse and low precision observations, unknown geometrical and physical features of debris, and effects of incomplete force models, OP based on the orbital mechanics theory or physics-based OP of space debris suffers from rapid error growth over a long duration, limiting the period of validity of debris OP for precise space applications. Considering that the tracking arcs of a debris object over a single station often share a similar temporal and spatial distribution in the inertial space, the resultant OP errors possibly have a coherent relationship with the temporal and spatial distribution of tracking arcs. This article proposes a machine learning (ML)-based approach to model the underlying pattern of debris OP errors from historical observations and apply it to modify the future physics-based OP results. The approach includes three steps: constructing a historical OP error set, training an ML model to fit the historical OP error set, and correcting the future physics-based OP with ML-predicted orbital errors. The ensemble learning algorithm of boosting tree is studied as the primary ML method for the error modeling and predicting process. Experiments with three low-Earth-orbit objects, tracked by a single radar station, demonstrate that the trained ML models can capture more than 80% of the underlying pattern of the historical OP errors. More importantly, the errors of physics-based OP over the future seven days reduce from thousands of meters to hundreds or even tens of meters through the error correction with the learned error pattern, achieving at least 50% accuracy improvement. Such dramatic OP improvements show the promising potential of ML for enhanced SSA capability.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Robust-Backstepping Missile Autopilot Design Considering Time-Varying
           Parameters and Uncertainty
    • Pages: 4269 - 4287
      Abstract: Missile autopilots for aerodynamic angle control and acceleration control are designed for fin-controlled missiles during the boost phase. In the boost phase, the speed change and the parameter variation of the missile are fast and large. To deal with the time-varying characteristics of the missile, the time-varying parameters are considered in nonlinear dynamics, and the parametric uncertainties are modeled. A state-feedback controller is designed for aerodynamic angle control based on a robust-backstepping scheme. Also, an output feedback controller is designed for acceleration control, where the acceleration dynamics are derived using input–output linearization. Numerical simulations are performed to demonstrate the performance of the proposed controllers.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Fast Nonsingular Terminal Sliding Mode Flight Control for Multirotor
           Aerial Vehicles
    • Pages: 4288 - 4299
      Abstract: This article is concerned with the robust flight control of multirotor aerial vehicles (MAVs) subject to bounded force and torque disturbances. The focus is on the entire class of MAVs containing an arbitrary even number (${geq}4$) of fixed (not vectoring) rotors. To deal with this problem, first, a ubiquitous hierarchical control architecture in which the attitude control loop is nested inside the position control loop is adopted and augmented with a control allocator which makes the design of the control laws themselves independent of the rotor arrangement. Specially, the control allocation problem is formulated as a quadratic program that minimizes the thrust commands and accounts for the thrust range and rate bounds. Second, geometric attitude and position control laws are designed separately using a multi-input fast nonsingular terminal sliding mode control (FNTSMC) strategy, which guarantees singularity-free finite-time stability and robustness. The main contributions are, first, the augmentation of the hierarchical control scheme for extending its applicability to any fixed-rotor MAV and, second, a detailed geometric design and finite-time stability analysis of the position and attitude control loops using the FNTSMC theory. The system is evaluated on computational simulations as well as on a hardware-in-the-loop experiment, showing that it is effective, simple to implement and adjust, and reliable to operate in nonlinear regimes as well as under bounded disturbances.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Aerodynamic Model-Aided Estimation of Attitude, 3-D Wind, Airspeed, AOA,
           and SSA for High-Altitude Long-Endurance UAV
    • Pages: 4300 - 4314
      Abstract: This article proposes a novel dynamic model-aided navigation filter to estimate the safety-critical states of an aircraft including the effect of wind. Aerodynamic coefficients and control signals are used to predict the angular rates. Experimental flight results of a high-altitude long-endurance unmanned aerial vehicle (UAV) demonstrated improvement in attitude estimation compared to a model-based navigation algorithm that does not consider wind, as well as accurate attitude estimation without using gyroscope signals, demonstrating its effectiveness for analytical redundancy.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Fusion of Multiple Mobility and Observation Models for Indoor Zoning-Based
           Sensor Tracking
    • Pages: 4315 - 4326
      Abstract: In this article, we propose a novel zoning-based tracking technique that combines the sensors’ mobility with a WiFi-based observation model in the belief functions framework to track the sensors in real time. The next possible destinations of the sensors are predicted, leading to a mobility model. The belief functions framework is used to propagate the previous step evidence till the current one. The mobility of the sensors, along with information from the network, is used to obtain an accurate estimation of their position. The contributions of this article are twofold. First, it proposes new mobility models based on the transition between zones and hidden Markov models to generate evidence on the zones of the sensors without the use of inertial measurement units. Second, it explores the fusion of evidence generated by the mobility models on one hand and the observation model on the other hand. The efficiency of the proposed method is demonstrated through experiments conducted on real data in two experimental scenarios.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • A Statistical Framework for Performance Analysis of Diversity Framed
           Slotted Aloha With Interference Cancellation
    • Pages: 4327 - 4337
      Abstract: As the Internet of Things (IoT)/machine-to-machine market is rapidly growing, a special role is expected to be played by satellite communications in that they offer ubiquitous coverage and therefore enable typical monitoring, telemetry, and control services also in areas with a poor terrestrial infrastructure. In this respect, the case of massive IoT devices deployment calls for random access solutions, which have been long analyzed by the scientific satellite community in the last ten years. This article further elaborates on the relation between the normalized offered load and the achievable performance in terms of packet loss rate, which was not much addressed so far at high loads. The proposed theoretical framework has been validated through extensive simulation campaigns, which show an excellent match at different loads and number of interfering packets configurations, by significantly improving the results achievable through other existing theoretical frameworks.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Fuel-Optimal Asteroid Descent Trajectory Planning Using a Lambert
           Solution-Based Costate Initialization
    • Pages: 4338 - 4352
      Abstract: This article presents a new and fast indirect method for solving fuel-optimal descent trajectories in the gravitational field of an irregularly-shaped asteroid. The costates associated with a two-impulse descent trajectory are used as approximate costates for the costate initialization of a finite-thrust fuel-optimal trajectory planning problem. The approximate solutions of the initial velocity and mass costates are given in analytical forms. A simple shooting equation is derived to solve the approximate position costates. The two-impulsive descent trajectory is solved by an irregular gravitational Lambert solver. Based on the Lambert solver and approximate costates, an algorithm is proposed for trajectory optimization with varying time of flight. The effectiveness and efficiency of the proposed method are tested through the simulation of landing on the asteroid 433 Eros. Additionally, a computationally efficient approximate model is employed to replace the polyhedral model, which greatly improves the computational speed and enhance the ability to address uncertainties.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Vector-Field-Based Guidance for Exoatmospheric Target Interception
    • Pages: 4353 - 4366
      Abstract: A homing guidance law against a high-speed target in the exoatmospheric area is proposed based on the vector field approach. The vector field is designed and utilized to achieve head-on hit-to-kill interception. The trajectory of the target is predicted using the gravity acceleration model. The vector-field-based guidance law makes the missile converge to the predicted trajectory of the target, and therefore, the missile can await the target by flying along the predicted trajectory. The shape of the vector field is designed with the consideration of the smooth convergence and finite-time convergence, and the corresponding bounding condition imposed by the lateral acceleration limit is derived. The feasible region for the parameters in the finite-time convergent vector field is analyzed, and the performance of the proposed guidance law is demonstrated using numerical simulations.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • A Sparse Learning Approach to the Detection of Multiple Noise-Like Jammers
    • Pages: 4367 - 4383
      Abstract: In this article, we address the problem of detecting multiple noise-like jammers (NLJs) through a radar system equipped with an array of sensors. To this end, we develop an elegant and systematic framework wherein two architectures are devised to jointly detect an unknown number of NLJs and to estimate their respective angles of arrival. The followed approach relies on the likelihood ratio test in conjunction with a cyclic estimation procedure, which incorporates at the design stage a sparsity promoting prior. As a matter of fact, the problem at hand owns an inherent sparse nature, which is suitably exploited. This methodological choice is dictated by the fact that, from a mathematical point of view, classical maximum likelihood approach leads to intractable optimization problems (at least to the best of authors’ knowledge) and, hence, a suboptimum approach represents a viable means to solve them. The performance analysis is conducted on simulated data and shows the effectiveness of the proposed architectures in drawing a reliable picture of the electromagnetic threats illuminating the radar system.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Detection in Sea Clutter Using Sparse Signal Separation
    • Pages: 4384 - 4394
      Abstract: Radar detection of small maritime targets can be difficult due to the dynamic motion of the sea. Airborne maritime surveillance platforms are also increasingly required to operate in environments where the sea clutter is strong with persistent breaking waves resembling targets. The focus of this article is to investigate three sparse signal separation formulations using the short time Fourier transform as a dictionary. This approach has been demonstrated as effective in separating both stationary and moving targets from sea clutter but relies on the tuning of different parameters. The first part of this article looks at how to select these parameters which are essential to achieve good separation. Then, a number of practical detection schemes are presented that allow control of the false alarm rate. The algorithm performance is demonstrated using Monte Carlo simulation with synthetic targets injected into the Ingara medium grazing angle sea-clutter data set.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • DOA Estimation Using Compressive Sampling-Based Sensors in the Presence of
    • Pages: 4395 - 4405
      Abstract: In this article, we propose a new compressive-sampling-based approach to detect a target and obtain its direction-of-arrival (DOA) by using samples collected by a set of sensor nodes. Since these sensors sample at a rate below Nyquist, instead of the Nyquist rate, the complexity, power consumption, memory requirement, and the volume of data that needs to be exchanged between sensors, are much lower than those of the existing approaches. The proposed scheme jointly estimates the DOA, the variance of the noise, and the covariance matrix of the interference. As a result, simulations have shown that this scheme significantly outperforms techniques that simply combine the noise and the interference.gg
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • State Estimation With Implicit Constraints of Circular Trajectory Using
    • Pages: 4406 - 4425
      Abstract: In some target tracking scenarios, tracking performance can be improved by the incorporation of a constraint imposed by a preset trajectory. When the complete information about the trajectory is known, the constraint can be formulated in an explicit way. However, in practical applications, only partial information about the trajectory may be available. This article deals with the modeling of implicit constraints, imposed by a circular trajectory, along with the constrained state estimation. First, constraint models for two kinds of representative implicit constraints, the destination constraint and the trajectory shape constraint, are proposed for various cases with different conditions of prior information. In the cases with destination constraints, the destination information and the trajectory shape information are assumed to be known a priori. For each case, two forms of constraint models are derived. One is a direct form model where the constraint relationships are used to eliminate the unknowns in the final model, whereas the other is a state augmentation form model, where the unknowns are augmented into the state vector being estimated along with the target state. In the cases with trajectory shape constraints, only the trajectory shape information is available. For each case, the state augmentation form models are formulated. Second, constrained state estimation methods are proposed by utilizing pseudomeasurement constructed based on the constraint models. Furthermore, an extension to the maneuvering target tracking by integrating the proposed constraint filters into an interacting multiple model estimator is also presented. Numerical simulations in two scenarios are provided to show the effectiveness of the proposed constraint models and state estimation methods.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Simulation of a Hybrid Energy System for Stratospheric Airships
    • Pages: 4426 - 4436
      Abstract: Effective energy management systems are critical for long endurance stratospheric airships. This article presents a hybrid energy system consisting of one renewable (photovoltaic) and two energy storage (lithium battery/regenerative fuel cell) systems. After examining different models of energy harvesting, balancing, and storage, we present the details of a rule-based energy management strategy. We further validate it by presenting the various power curves and state of charge (SOC) measurements. The results indicate that the strategy is effective for energy management planning.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Multiple Object Localization and Vital Sign Monitoring Using IR-UWB MIMO
    • Pages: 4437 - 4450
      Abstract: We consider 2-D localization and noncontact vital sign monitoring (i.e., determining the 2-D locations and estimating the rates of respiration and heartbeat) of multiple human objects via developing an impulse radio ultra-wideband (IR-UWB) distributed multi-input multi-output (MIMO) prototype radar system. A modified back projection algorithm is used to localize multiple objects. We also formulate the chest skin range displacement estimation problem caused by respiration and heartbeat into a sinusoidal frequency estimation problem, which can be solved efficiently via the fast Fourier transform method. Then, the robust, high resolution, and low sidelobe iterative adaptive approach (IAA) is adopted to obtain the IAA spectrum of the chest skin range displacement signal. Both respiration and heartbeat rates can be reliably determined from the IAA spectral estimates. Further, we solve the random body movement problem by developing a 2 × 2 IR-UWB distributed MIMO prototype radar system to obtain measurements from both the front and back of the human torso simultaneously. Finally, numerical and experimental results based on the prototype hardware radar systems we develop are presented to demonstrate the performances of the proposed 2-D localization and noncontact vital sign monitoring systems and the corresponding algorithms.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Application of an Efficient Graph-Based Partitioning Algorithm for
           Extended Target Tracking Using GM-PHD Filter
    • Pages: 4451 - 4466
      Abstract: One of the main tasks involving the extended target tracking is how to partition the measurement set accurately and efficiently. In this article, an efficient graph-based partitioning algorithm is introduced for extended target tracking. To reduce the computational load and the interference of clutter on the measurement set partition, a measurement set preprocessing method based on density-based clustering algorithm is presented. An intuitive directed $k$-nearest neighbor ($k$NN) graph model based on graph theory is established to represent the relationship between different measurements in the measurement set that needs to be segmented. In the framework of directed $k$NN graph, a novel similarity metric based on shared nearest neighbor (SNN) is used, and a pairwise similarity that integrates the number of elements in the set of SNN and the closeness of data points is constructed. The spectral clustering algorithm is used to process the multiway cut in the directed $k$NN graph. The graph-based partitioning algorithm is applied to the extended target Gaussian mixture probability hypothesis density filter. Simulation results illustrate the advantages of our proposed graph-based partitioning algorithm in performance and computational efficiency.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Artificial Collinear Lagrangian Point Maintenance With Electric Solar Wind
    • Pages: 4467 - 4477
      Abstract: This article discusses the maintenance of an $L_1$-type artificial equilibrium point in the Sun–[Earth+Moon] circular restricted three-body problem by means of an electric solar wind sail. The reference configuration instability is compensated for with a feedback control law that adjusts the grid voltage as a function of the distance from the natural $L_1$ point. Two different control strategies are analyzed assuming the solar wind fluctuations to be modeled through a statistical approach.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Warm-Start Multihomotopic Optimization for Low-Thrust Many-Revolution
    • Pages: 4478 - 4490
      Abstract: Traditionally, fuel-optimal problems for low-thrust spacecraft transfers are connected with energy-optimal problems to increase the convergence possibility of indirect methods. However, for low-thrust many-revolution missions, it is still hard to resolve the energy-optimal problems in a fast and reliable manner due to the strong nonlinearity. To address this issue, a warm-start multihomotopic optimization approach is proposed in this article, wherein the Sundman transformation and multihomotopic techniques are used to connect the energy-optimal problems to linear ones with analytical solutions. This article focuses on the following three contributions. First, the energy-optimal control problems are transformed into true longitude-depended energy-optimal problems based on the homotopy to dynamical model and Sundman transformation, and the equivalence relations of the solutions before and after transformation are obtained analytically. Second, the problems are further connected with time-free energy-optimal problems based on a homotopy to the time constraint. Third, the time-free problems are linearized near a nominal trajectory, and the corresponding analytical solutions are obtained. Starting with the analytical solutions, the algorithm can gradually iterate back to the solutions of the original energy- and fuel-optimal problems. Since the whole transformation process is lossless (optimality is preserved under the transformation process), the developed warm-start multihomotopic algorithm enjoys the advantages on reliable convergence and high computational efficiency. Numerical simulations of Earth-orbit transfer missions from GTO to GEO are conducted by comparing with traditional methods, and the results are given to substantiate the effectiveness of the proposed warm-start multihomotopic method.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Power Converter For 60 Hz-400 Hz Bilateral Power Conversion
    • Pages: 4491 - 4503
      Abstract: A power converter for 60–400 Hz bilateral power conversion (BPC) is proposed in this article. This power converter is composed of three power switch arms, a set of filter inductors, a frequency decoupling circuit, a 60 Hz ac capacitor and a 400 Hz ac capacitor. The proposed BPC has the salient feature that it has the function of 60–400 Hz bilateral power conversion using only one power electronic converter. Hence, the proposed BPC can simplify the power circuit. Both simulation and experimental results verify the performance of the proposed BPC is as expected.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Compressed-Domain Detection and Estimation for Colocated MIMO Radar
    • Pages: 4504 - 4518
      Abstract: This article proposes a compressed-domain signal processing (CSP) multiple-input multiple-output (MIMO) radar, a MIMO radar approach that achieves substantial sample complexity reduction by exploiting the idea of CSP. CSP MIMO radar involves two levels of data compression followed by target detection at the compressed domain. First, compressive sensing is applied at the receive antennas, followed by a Capon beamformer, which is designed to suppress clutter. Exploiting the sparse nature of the beamformer output, a second compression is applied to the filtered data. Target detection is subsequently conducted by formulating and solving a hypothesis testing problem at each grid point of the discretized angle space. The proposed approach enables an eightfold reduction of the sample complexity in some settings as compared to a conventional compressed sensing (CS) MIMO radar, thus enabling faster target detection. Receiver operating characteristic curves of the proposed detector are provided. Simulation results show that the proposed approach outperforms recovery-based CS algorithms.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Adaptive Compound Control of Air-Breathing Hypersonic Vehicles
    • Pages: 4519 - 4532
      Abstract: When working at extremely high altitude, aerodynamic surfaces of air-breathing hypersonic vehicles (AHVs) may not provide sufficient control authority. To remedy this shortage, we consider AHVs equipped with the auxiliary reaction control system (RCS), which utilize a set of control jets to compensate for ineffective aerodynamic surfaces. A novel longitudinal compound control is proposed to generate commands of aerodynamic surfaces and RCS, adaptively. Constrained angle-of-attack, uncertain parameters, and flexible dynamics are also considered.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Ultra-Wideband Air-to-Ground Propagation Channel Characterization in an
           Open Area
    • Pages: 4533 - 4555
      Abstract: This article studies the air-to-ground ultra-wideband channel through propagation measurements between 3.1 to 4.8 GHz using unmanned-aerial-vehicles (UAVs). Different line-of-sight (LOS) and obstructed-LOS scenarios and two antenna orientations were used in the experiments. Multipath channel statistics for different propagation scenarios were obtained, and the Saleh–Valenzuela model was found to provide a good fit for the statistical channel model. An analytical path loss model based on antenna gains in the elevation plane is provided for unobstructed UAV hovering and moving (in a circular path) propagation scenarios.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Omnidirectional Optical Crosslinks for CubeSats: Transmitter Optimization
    • Pages: 4556 - 4566
      Abstract: CubeSat swarm in low earth orbit is an attractive alternative to present-day expensive and bulky satellite-based remote sensing systems. This article presents the design and optimization rules to achieve omnidirectional, high speed, long-range (more than 100 km) data communication among CubeSats. The unprecedented size, weight, power, and cost constraints imposed by the CubeSat platform and the availability of the commercial-off-the-shelf components are considered in the analyses. Analytical studies related to the scanning mirror based beam steering system as well as scanning mirror's smallest step angle requirement are presented. In addition, we demonstrate the relations and dependencies among scanning mirror's smallest step angle, laser beam divergence, optics dimensions, communication distance, and scanning area filling efficiency, etc. Furthermore, the optimization challenges of the transmit laser beam size considering the interplay among beam divergence, beam clipping, and scattering are studied in detail. This article also presents the effect of laser peak power, initial beam size, and communication distance on effective communication beamwidth to maintain a long-distance (more than 100 km) communication with SNR ≥ 10 dB at a data rate greater than 500 Mb/s.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Real-Time Vision-Based Pose Tracking of Spacecraft in Close Range Using
           Geometric Curve Fitting
    • Pages: 4567 - 4593
      Abstract: This article presents a new framework of real-time vision-based pose tracking for spacecraft in close range using geometric fitting of the imaged geometric primitives (GPs) on the spacecraft. At the first time instant, the tracking is initialized with the template-based pose retrieval and GP-based pose determination. At each subsequent time instant, with the pose prediction from the extended Kalman filter (EKF) as initial value, the GPs are associated with the corresponding image data, and thereby the maximum-likelihood estimation (MLE) for spacecraft pose can be obtained in real time by geometrically fitting the GP projections over the corresponding image data with generalized expectation–maximization and M-estimation. Using the MLE, the EKF generates the final pose estimation and predicts the pose at the next time instant. The basic configurations of the GPs are investigated for the stability of tracking. Sufficient experiments validate the accuracy and the real-time performance of the proposed method.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • UAV Optimal Guidance in Wind Fields Using ZEM/ZEV With Generalized
           Performance Index
    • Pages: 4594 - 4605
      Abstract: This article presents an optimal guidance approach for unmanned aerial vehicle navigation between two given points in 3D considering the wind influence. The proposed cost function to be minimized involves the weighting of the travel time and the control energy. An analytical expression is derived for the optimal cost yielding a fourth-order polynomial, whose positive real roots correspond to the optimal travel times. The optimization problem is shown to be equivalent to the zero-effort-miss/zero-effort-velocity optimal guidance approach for the case of a constant wind acceleration. Case studies for rendezvous and intercept problems are shown through simulation examples for different wind conditions.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Antenna Placement in a Compressive Sensing-Based Colocated MIMO Radar
    • Pages: 4606 - 4614
      Abstract: Compressive sensing (CS) has been widely used in multiple-input–multiple-output (MIMO) radar in recent years. Unlike traditional MIMO radar, detection/estimation of targets in a CS-based MIMO radar is accomplished via sparse recovery. In this article, for a CS-based colocated MIMO radar with linear arrays, we attempt to improve the target detection performance by reducing the coherence of the associated sensing matrix. Our tool in reducing the coherence is the placement of the antennas across the array aperture. In particular, we choose antenna positions within a given grid. Initially, we formalize the position selection problem as finding binary weights for each of the locations. This problem is highly nonconvex and combinatorial in nature. Instead, we find continuous weight values for each location and interpret them as the probability of including an antenna at the given location. Next, we select antenna locations randomly according to the obtained probability distribution. We formulate the problem for the general case of a MIMO radar with independent transmit and receive arrays for which we propose an iterative algorithm. For the special case of a transceiver array, the solution is obtained through a convex optimization approach. Our experiments show that the proposed method achieves a superior detection performance compared to a uniform random placement of the antennas within the array aperture.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Spacecraft Autonomous Navigation Using the Doppler Velocity Differences of
           Different Points on the Solar Disk
    • Pages: 4615 - 4625
      Abstract: The solar differential rotation results in different velocities on the solar disk. The Doppler velocities of different points on the solar disk observed by the spacecraft are also different, which are functions of the current position of the spacecraft. Thus, using the velocities’ information or their differences, the position of the spacecraft can be estimated. The advantage of velocity difference measurement is that the influence of some systematic error, such as the spectrometer error and the periodic variation of the sun's velocity on the navigation performance, can be eliminated. In this article, a new autonomous navigation method using the Doppler velocity differences of different points on the solar disk is proposed. Taking solar explorer as an example, simulations show that the proposed method can effectively restrain systematic errors compared with the traditional Doppler velocity method.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Pursuit–Evasion Game for Satellites Based on Continuous Thrust
           Reachable Domain
    • Pages: 4626 - 4637
      Abstract: We investigate the pursuit–evasion differential game (PE Game) for satellites with continuous thrust from the viewpoint of reachable domain (RD). A concept of hyper-reachable domain (HRD) is introduced to help analyze the problem, and a sufficient condition for capture in a PE Game is proposed based on the players’ HRD. Meanwhile, to practically use the RD as a tool to analyze the PE Game, an analytical form of the satellite's reachable domain is deduced based on the Clohessy Wiltshire (CW) model. The simplicity and accuracy of the CW model in solving the RD render it practicable to apply the sufficient condition in studying the PE Game of continuous-thrust satellites.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Neural Network-Based Pose Estimation for Noncooperative Spacecraft
    • Pages: 4638 - 4658
      Abstract: This article presents the Spacecraft Pose Network (SPN), the first neural network-based method for on-board estimation of the pose, i.e., the relative position and attitude, of a known noncooperative spacecraft using monocular vision. In contrast to other state-of-the-art pose estimation approaches for spaceborne applications, the SPN method does not require the formulation of hand-engineered features and only requires a single grayscale image to determine the pose of the spacecraft relative to the camera. The SPN method uses a convolutional neural network (CNN) with three branches to solve the problem of relative attitude estimation. The first branch of the CNN bootstraps a state-of-the-art object detection algorithm to detect a 2-D bounding box around the target spacecraft in the input image. The region inside the 2-D bounding box is then used by the other two branches of the CNN to determine the relative attitude by initially classifying the input region into discrete coarse attitude labels before regressing to a finer estimate. The SPN method then estimates the relative position by using the constraints imposed by the detected 2-D bounding box and the estimated relative attitude. Further, with the detection of 2-D bounding boxes of subcomponents of the target spacecraft, the SPN method is easily generalizable to estimate the pose of multiple target geometries. Finally, to facilitate integration with navigation filters and perform continuous pose tracking, the SPN method estimates the uncertainty associated with the estimated pose. The secondary contribution of this article is the generation of the Spacecraft PosE Estimation Dataset (SPEED), which is used to train and evaluate the performance of the SPN method. SPEED consists of synthetic as well as actual camera images of a mock-up of the Tango spacecraft from the PRISMA mission. The synthetic images are created by fusing OpenGL-based renderings of the spacecraft's 3-D model with actual image- of the Earth captured by the Himawari-8 meteorological satellite. The actual camera images are created using a seven degrees-of-freedom robotic arm, which positions and orients a vision-based sensor with respect to a full-scale mock-up of the Tango spacecraft with submillimeter and submillidegree accuracy. The SPN method, trained only on synthetic images, produces degree-level relative attitude error and cm-level relative position errors when evaluated on the actual camera images with a different distribution not used during training.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Recognition of Multifunction Radars Via Hierarchically Mining and
           Exploiting Pulse Group Patterns
    • Pages: 4659 - 4672
      Abstract: Recognition of multifunction radar (MFR) is an open problem in the field of electronic intelligence. Parameters of MFR pulses are generally agile and difficult to distinguish statistically. A prospective way to realize credible MFR recognition is mining and exploiting more distinguishable high-dimensional patterns buried in pulse groups, which may be designed for implementing infrequently used radar modes such as target tracking. A high-dimensional pattern is defined according to the agile range and switching law of sequential pulse repetitive intervals within a pulse group. This article establishes deep recurrent neural networks (RNN) to discriminate and coarsely cluster different pulse groups hierarchically with respect to their sequential structures. Afterwards, RNN-based classifiers are trained to extract and exploit features within different pulse group clusters. Distinct degrees of confidence are then attached to these classifiers to indicate the discriminabilities of the corresponding pulse group clusters. The pulse group clustering and classifying models are finally cascaded to form an integrated classification model, which mines distinguishable patterns from sequentially arriving pulse groups of the same radar and accumulate them to realize MFR recognition. Simulation results demonstrate the much improved performance of the proposed method over existing counterparts in different scenarios.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Three-Dimensional Location Estimation Using Biased RSS Measurements
    • Pages: 4673 - 4688
      Abstract: Received signal strength (RSS)-based techniques are promising for location estimation because of low cost and easy implementation. RSS measurements can be used to determine the location of a receiver, given the positions of multiple emitters. In addition, RSS measurements at receivers with known positions can be used to determine the location of an emitter. This article investigates both 3-D receiver navigation and source localization using RSS measurements. In practice, sensor measurements are often biased owing to design problems or other effects. However, almost all existing methods deal with bias-free cases. In contrast, we focus on biased cases. For both receiver navigation and source localization, we propose united-RSS (URSS) and differential-RSS (DRSS) approaches, where URSS estimates the location and sensor bias together, while DRSS estimates the location by eliminating the effect of bias. They are based on semidefinite programming and constrained least squares, respectively. The proposed methods avoid the nonconvexity in the maximum likelihood method. Numerical examples verify the necessity for sensor registration in RSS-based location estimation and show better performance of the proposed methods.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Adaptive Internode Ranging for Coherent Distributed Antenna Arrays
    • Pages: 4689 - 4697
      Abstract: An adaptive ranging technique for maintaining high-accuracy ranging between nodes in coherent distributed antenna arrays is presented. Coherent distributed antenna arrays are networks of wireless systems coordinated coherently at the level of the wavelength of the wireless signal. Enabling coherent operation between separate mobile nodes for active and passive microwave remote sensing requires accurate knowledge of the relative positions of the nodes in the array. In this article, a novel adaptive ranging technique based on the near-optimal waveform for high-accuracy ranging, a two-tone waveform, is designed and demonstrated in software-defined radio platforms representing array nodes. Ranging accuracy is dependent on both signal-to-noise ratio and the separation of the two tones in the waveform; however, in realistic environments, factors such as attenuation or antenna misalignment are not easily predicted, which can lead to degradation of the ranging measurement. Selecting one appropriate waveform for range measurements is, thus, not feasible unless the bandwidth assigned to it is always higher than required for the needed range accuracy. Rather than allocating such an unnecessarily wide bandwidth, this article presents a controller that regulates the spectral resources adaptively to meet the desired reference accuracy while minimizing the total occupied bandwidth. The controller continuously monitors the statistical parameters of the received signal, such as signal-to-noise ratio, in a perception stage and adapts the spectral characteristics of the transmitted waveform in an action stage. The adaptive action, based on a Cramer–Rao lower bound analysis, maintains the signal statistical characteristics below a specified bound to maintain high coherent gain. Experimental results demonstrate the ability to maintain ranging standard deviation of 1.5 mm (standard deviation of time delay estimates equals
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Implementation of Mixing Sequence Optimized Modulated Wideband Converter
           for Ultra-Wideband Frequency Hopping Signals Detection
    • Pages: 4698 - 4710
      Abstract: Frequency hopping (FH) communications are widely used in Satcom systems. The latest FH systems have exceeded 3 GHz with hop rates up to 100 000 hops/s. Traditional spectrum sensing systems hardly monitor such signals. Modulated wideband converter (MWC) is an emerging compressive sampling structure applied to sample multiband signals. This article analyses the effects of the nonlinearity of analog devices and proposes an optimization method based on a greedy algorithm for mixing sequences to make reconstruction performance uniform across sub-bands. To correct the errors caused by the nonideality of analog front end circuits between the theoretical sensing matrix and the practical one, we also develop a calibrating method that obtains all the sensing matrix coefficients through a single measurement. In conventional MWC, out-band noise will be blended during reconstruction. Instead of matrix factorization, we reserve signal characters and designed sliding filters to improve narrowband signals reconstruction sensitivities. We produced a four-branch MWC principle prototype for FH signal detection. The sensing bandwidth is 3 GHz, and the sampling rate is 400 MHz, whereas the reconstruction sensitivity is as low as 13-dB in-band signal-to-noise.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Target Detection in Passive Radar Under Noisy Reference Channel: A New
           Threshold-Setting Strategy
    • Pages: 4711 - 4722
      Abstract: In the detection theory framework, it is customary to assign a bound to the false alarm probability and to attempt to maximize the detection probability subject to this constraint. In the problem of moving target detection in passive radar with a noisy reference channel, we formulate a detection problem as a composite hypothesis-testing problem and solve it with the likelihood ratio test (LRT) principle, which is known as generalized LRT in the electrical engineering works of literature. In such a problem, we show that any uncertainty in the value of the direct signal-to-noise ratio of the reference channel, abbreviated as $text{DNR}_r$, can result in excessive false alarm probability of the proposed noisy-reference-channel-based detector in the low-$text{DNR}_r$ regime. To facilitate efficient operation under uncertainty in $text{DNR}_r$, we propose a new threshold-setting strategy to adjust the level of the proposed detector. Through extensive Monte–Carlo simulations, we examine the above problem and investigate the efficiency of the proposed threshold-setting strategy. Besides, we apply the framework of the kernel theory to the target detection problem of a noisy and ideal reference channel passive radar to propose two new detectors. As such, we replace the inner products of the proposed tests with appropriate polynomial kernel functions allowing for richer feature space to be deployed in the detection, achieving better detection performance. In this case, our detection performance results show that the kernelized detectors offer more that 1-dB signal-to-noise ratio gain as compared to their conventional counterparts.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Implementation and Assessment of Jamming Effectiveness Against an FMCW
           Tracking Radar Based on a Novel Criterion
    • Pages: 4723 - 4733
      Abstract: The effect of jammer on radar or jamming performance has been and is being assessed on the basis of range reduction where consistency in tracking target ability is more important than range reduction in a tracking radar. A new criterion known as relative radar functionality destruction time is defined and introduced as the relative of functionality destruction time of radar to one period of jammer, where jammer signal and target echo power are of concern. The effective parameters in relative time of the receiver functioning destruction are assessed. Next, this criterion is applied in the assessment of simple conical scan radar receiver against a conventional jamming (sweep noise jamming). This criterion is modeled and simulated on a search radar in the jamming environment where the minimum required standard deviation of noise for destroying the radar function yields. By implementing the structure of a frequency modulated continuous wave tracking radar structure, a simple target based on digital radio frequency memory method and one type of jamming against this radar in a simultaneous manner, the functionality destruction is extracted for different radar parameters. This new criterion on outperforms its counterparts.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Joint Angle and Doppler Frequency Estimation for MIMO Radar with One-Bit
           Sampling: A Maximum Likelihood-Based Method
    • Pages: 4734 - 4748
      Abstract: We consider a multiple-input multiple-output (MIMO) radar that works through one-bit sampling of received radar echoes. The application of one-bit sampling significantly reduces the hardware cost, energy consumption, and systematic complexity, but it also poses serious challenges to extracting highly accurate target information from one-bit quantized data. In this article, we propose a maximum likelihood (ML)-based method that first iteratively maximizes the likelihood function to recover a virtual array data matrix and then jointly estimates the angle and Doppler parameters from the recovered matrix. Because the ML problem is convex, we can successfully apply a computationally efficient gradient descent algorithm to solve it. Based on our analysis of the Cram$acute{text{e}}$r–Rao bound of the ML-based method, a pre-estimation-assisted threshold (PET) strategy is developed to improve the estimation performance. Numerical experiments demonstrate that the proposed ML-based method, combined with the PET strategy, can provide highly accurate parameter estimation performance, close to that of the classic MIMO radar.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Spectrally Compatible MIMO Radar Beampattern Design Under Constant Modulus
    • Pages: 4749 - 4766
      Abstract: In this article, we propose a new algorithm that designs a transmit beampattern for multiple-input multiple-output (MIMO) radar considering coexistence with other wireless systems. This design process is conducted by minimizing the deviation of the generated beampattern (which in turn is a function of the transmit waveform) against an idealized one while enforcing the waveform elements to be constant modulus and in the presence of spectral restrictions. This leads to a hard nonconvex optimization problem primarily due to the presence of the constant modulus constraint (CMC). In this article, we exploit the geometrical structure of CMC, i.e., we redefine this constraint as an intersection of two sets (one convex and other nonconvex). This new perspective allows us to solve the nonconvex design problem via a tractable method called iterative beampattern with spectral design (IBS). In particular, the proposed IBS algorithm develops and solves a sequence of convex problems such that constant modulus is achieved at convergence. Crucially, we show that at convergence the obtained solution satisfies the Karush–Kuhn–Tucker conditions of the aforementioned nonconvex problem. Finally, we evaluate the proposed algorithm over challenging simulated scenarios, and show that it outperforms the state-of-the-art competing methods.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Deinterleaving of Pulse Streams With Denoising Autoencoders
    • Pages: 4767 - 4778
      Abstract: Analyzing radar signals is an important task in operating electronic support measure systems. The received signals in the real electromagnetic environment often originate from multiple emitters and must be separated for further processing. Pulses from important target emitters with known parameters should be picked out first. To solve the problem, time-of-arrival (TOA) deinterleaving may be performed to extract signals from a certain emitter by learning the pulse repetition interval (PRI) modulation that makes up the signal. However, conventional deinterleaving methods only work with simple PRI modulations; their performance degrades in noisy environments. A novel approach based on denoising autoencoders for TOA deinterleaving was developed in this article. The inner patterns of pulse-of-interest sequences were learned by the proposed denoising autoencoders to generate output sequences from well-trained autoencoders. Simulation results show that the proposed method outperforms conventional methods, especially in environments with high lost and spurious pulse ratios.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Distributed Fixed-Time Output-Feedback Attitude Consensus Control for
           Multiple Spacecraft
    • Pages: 4779 - 4795
      Abstract: This article investigates the problem of distributed fixed-time attitude consensus control for multiple spacecraft when only a subset of spacecraft has access to a common reference attitude and angular velocity. Two fixed-time sliding-mode observers are proposed to estimate the reference attitude and angular velocity in fixed time, respectively. Based on estimates of the reference attitude and angular velocity, two distributed fixed-time attitude consensus control schemes are proposed under the mild assumption that there exists a path from the virtual leader to any follower and the communication topology among followers is undirected. In the first control scheme, the measurement of angular velocity is required. However, this requirement is removed in the second control scheme by using a fixed-time state observer to estimate the angular velocity of spacecraft in fixed time. Only a subset of spacecraft is required to access a common reference attitude and angular velocity in the two proposed control schemes. The stability and convergence of the resulting closed-loop systems are guaranteed by the Lyapunov approach. Finally, simulation results validate the effectiveness of the proposed control schemes.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Comparison of Correlation-Based OFDM Radar Receivers
    • Pages: 4796 - 4813
      Abstract: Various correlation-based receivers have been proposed in passive bistatic and active monostatic radar exploiting orthogonal frequency-division multiplexing communications signals, but too little has been dedicated to establishing their relations and advantages over each other. Accordingly, this article provides an analytical comparison of the common filters in such waveform sharing scenarios, along with a performance analysis regarding three criteria: computational complexity, signal-to-interference-plus-noise-ratio, and resilience to ground clutter. The last two especially assess the possible detrimental effects of the random sidelobes (or pedestal) induced by the data symbols in the range-Doppler map. Although simulations show that none of the filters performs unanimously better, the ones employing circular correlations globally evidence attractive results.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Optimization-Based Autonomous Air Traffic Control for Airspace Capacity
    • Pages: 4814 - 4830
      Abstract: In order to handle increasing demand in air transportation, high-level automation support seems inevitable. This article presents an optimization-based autonomous air traffic control (ATC) system and the determination of airspace capacity with respect to the proposed system. We model aircraft dynamics and guidance procedures for simulation of aircraft motion and trajectory prediction. The predicted trajectories are used during decision process and simulation of aircraft motion is the key factor to create a traffic environment for estimation of airspace capacity. We define the interventions of an air traffic controller (ATCo) as a set of maneuvers that is appropriate for real air traffic operations. The decision process of the designed ATC system is based on integer linear programming (ILP) constructed via a mapping process that contains discretization of the airspace with predicted trajectories to improve the time performance of conflict detection and resolution. We also present a procedure to estimate the airspace capacity with the proposed ATC system. This procedure consists of constructing a stochastic traffic simulation environment that includes the structure of the evaluated airspace. The approach is validated on real air traffic data for enroute airspace, and it is also shown that the designed ATC system can manage traffic much denser than current traffic.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Nonlinear Suboptimal Guidance Law With Impact Angle Constraint: An
           SDRE-Based Approach
    • Pages: 4831 - 4840
      Abstract: In this article, a guidance law with impact angle constraint is developed using the state-dependent Riccati equation (SDRE) technique. First, the nonlinear guidance dynamics consisting of line-of-sight (LOS) angle rate and error is formulated under a planar engagement scenario. After the state-dependent coefficient parameterization, a nonlinear regulator problem is formed to concurrently zero LOS angle rate and error. Second, a preliminary guidance law is directly developed under the framework of the SDRE technique. By applying the Lyapunov stability analysis, a nonlinear suboptimal guidance law is obtained through further parameter modifications. Then, the proposed guidance law is extended to attack maneuvering targets. Finally, the effectiveness of the proposed guidance law is demonstrated through numerical simulations.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Optimal Concurrent Control for Space Manipulators Rendezvous and Capturing
           Targets Under Actuator Saturation
    • Pages: 4841 - 4855
      Abstract: This article proposes a control method for space manipulators rendezvousing with and capturing a target, involving concurrent operation of an optimal and a coordinated controller. The optimal controller drives the whole system to rendezvous with the target, which saves onboard fuel and satisfies obstacle avoidance constraint and base spacecraft thrust limits. The optimal control problem is solved using calculus of variations method, with state inequality constraints transformed into extended dynamical subsystems and thrust limits formulated as saturation functions. The coordinated controller is designed based on the dynamic equations of the space manipulator on a noninertial frame attached to the system center of mass, which drives the end-effector to approach the target along a desired trajectory while making the base attitude follow a desired profile. It also generates proper reaction moments on base through manipulator motions to ensure controlling the base attitude when base attitude actuators reach their torque limits. The solution optimality of the optimal controller and the stability of the coordinated controller are demonstrated. Numerical simulations verify the performance of the proposed concurrent control method.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Formulas for Source Depth Estimation From Multipath Arrivals in Deep Water
    • Pages: 4856 - 4871
      Abstract: This article presents formulas to calculate the source depth based on the arrival angle and time delay between the direct and surface-refracted arrivals measured in deep water from a broadband signal. Using the formulas, the data autocorrelation is transformed to a correlation sequence as a function of assumed source depth, which can be simply averaged over a long time to estimate the source depth in a noisy environment. Both the simulated and real data verify the effectiveness and efficiency of the proposed method.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Automatic Target Recognition Based on Alignments of Three-Dimensional
           Interferometric ISAR Images and CAD Models
    • Pages: 4872 - 4888
      Abstract: Inverse synthetic aperture radar (ISAR) is capable of producing 2-D and 3-D images of non-cooperative targets. Compared with 2-D ISAR images, 3-D ISAR reconstructions can provide not only range and cross-range information, but also the information about the third dimension of the target, which is of great significance for automatic target recognition (ATR) and even more specifically to the case of non-cooperative target recognition. The alignment between the point-like 3-D ISAR reconstructions of targets and the targets’ models, such as computer aided design (CAD) models, becomes one of the essential issues in ATR that uses 3-D ISAR reconstructions. In this article, we propose an approach to address the alignment problem. The alignment problem can be decomposed into two steps, a coarse alignment and an accurate alignment. The coarse alignment can be accomplished by means of the principal component analysis (PCA), whereas the accurate alignment can be achieved by iterative closest point algorithm. In this article, the 180° ambiguity issue in PCA is discussed, and a corresponding robust solution is proposed. Moreover, the k-d tree is utilized to accelerate the searching for the pairs of correspondences, both in coarse and accurate alignment steps. In order to simulate real radar scenarios, target self-occlusion is also taken into consideration. The experimental results based on target's scattering point model simulation as well as the electromagnetic simulation in different radar scenarios verify the validity of the proposed method.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Saturated Adaptive Relative Motion Coordination of Docking Ports in Space
           Close-Range Rendezvous
    • Pages: 4889 - 4898
      Abstract: An adaptive relative pose controller for docking ports of two uncertain spacecraft in autonomous rendezvous and docking is developed. A novel relative translational and rotational model represented in the chaser body-fixed frame is derived first based on the classical Newton–Euler equations. Based on the proposed model, a six-degrees-of-freedom adaptive control law is presented based on norm-wise estimations for the unknown parameters of two spacecraft to decrease the online computational burden. Meanwhile, an adaptive robust control input is designed by introducing an exponential function of states to improve the response performance with respect to the traditional adaptive robust control. Moreover, a linear antiwindup compensator is employed to ensure the bounded performance of the control inputs. The explicit tuning rules for designing parameters are derived based on the stability analysis of the closed-loop system. It is proved in Lyapunov framework that all closed-loop signals are always bounded and the pose tracking error ultimately converges to a small neighborhood of zero. Simulation results validate the performance of the proposed robust adaptive control strategy.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Underwater Target Tracking in Uncertain Multipath Ocean Environments
    • Pages: 4899 - 4915
      Abstract: In order to address the problem of 3-D localization of an underwater target using a 2-D active sonar with unknown oceanographic factors in a multipath environment with heavy clutter, a novel iterative framework based on Maximum Likelihood Probabilistic Data Association (ML-PDA), which considers ocean sound speed profile (SSP) uncertainty and utilizes multiple detections to realize 3-D position estimation with only bearing and time of flight (ToF) measurements, is proposed. ML-PDA is highly effective in low SNR target detection. However, it is limited by its assumption of at most one target-originated detection within a scan. To estimate the 3-D target state with multipath detections under weak observability conditions, we first extend the ML-PDA into a multipath ML-PDA by enumerating the combined association events formed from multiple detection patterns. In contrast to the situation in air target tracking, the water column is nonhomogeneous and the underwater sound speed profile varies, influenced by uncertain ocean factors, e.g., temperature, salinity, and pressure. The resultant acoustic signal travels in a curvilinear path instead of a straight line. In this article, an SSP-dependent ToF measurement model is derived for both the direct path and the surface-reflected path between two remote nodes, so that the SSP uncertainty can be addressed systematically. By adopting an iterative prediction-update methodology, we first propagate the SSP uncertainty into the modified measurement covariance with the help of the unscented sampling technique. Then, we formulate a new joint likelihood ratio (JLLR) function based on the modified measurement covariance within the multidetection ML-PDA framework. A hybrid optimization method with grid search and particle swarm optimization is applied to solve the complex JLLR objective function and to find the optimal target state estimate from a large surveillance region. Finally, a sequential update technique is used to update the S-P state with the estimated target state and sensor measurements. In subsequent iterations, a more accurate JLLR can be rebuilt based on the updated SSP state, which can help find a better parameter estimate eventually. In addition, the Cramér–Rao lower bound, which quantifies the best possible accuracy in the presence of SSP uncertainties, is derived and analyzed. Numerical simulations confirm the underwater target localization performance of the proposed method in the presence of heavy clutter in an unknown ocean environment with a realistic sound propagation model.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • An Information Elasticity Framework for the Adaptive Matched Filter
    • Pages: 4916 - 4929
      Abstract: The adaptive matched filter (AMF) uses a number of training samples observed by the radar to estimate the unknown disturbance covariance matrix of a cell under test. In general, as the number of homogeneous training samples increases, the detection performance of the AMF improves up to a theoretical limit (defined by the performance of a matched filter detector where the disturbance covariance is known). However, radar data are nonhomogeneous in practice. Consequently, a high number of training samples is typically undesirable, since nonhomogeneous training data cause detection performance to suffer. Thus, a decision maker (DM) must consider these tradeoffs when selecting this number of training samples, along with other decision parameters for the AMF. Using the concept of information elasticity, this tradeoff behavior is characterized for decisions that are relevant to a DM. A simple user defined constraint function is proposed, characterizing the relative cost of selecting different decisions. Using a multi-objective optimization (MOO) technique known as compromise programming, information overload is observed, in that increasing the cost of decisions improves performance up to a point, beyond which increasing the cost no longer provides meaningful benefit. Using this framework, a cost-efficient solution is selected.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Polarimetric Passive Radar: A Practical Approach to Parametric Adaptive
    • Pages: 4930 - 4946
      Abstract: Polarimetric diversity has been recently shown to significantly improve the target detection performance in the passive radar systems if properly exploited to mitigate the competing interference. An adaptive processing scheme is presented in this article, leveraging the information conveyed using multipolarized receiving antennas and modeling the disturbance as a multichannel autoregressive process. Despite the fact that this approach operates with a limited number of the adaptive degrees of freedom, the long integration time exploited by a passive radar typically requires a substantial computational cost and ad hoc expedients for its application. Therefore, a modified cost-effective implementation of the conceived solution is proposed in order to reduce the computational burden while controlling the resulting loss. The authors extensively demonstrate the effectiveness of the proposed solution against the experimental data collected by an FM radio-based passive coherent location system. The experimental results show that the proposed processing scheme yields a remarkable improvement with respect to both the conventional processing at the single polarimetric channel and the state-of-the-art strategies exploiting the polarization diversity in passive radars.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Anomaly Based Sea-Surface Small Target Detection Using K-Nearest Neighbor
    • Pages: 4947 - 4964
      Abstract: Sea-surface small target detection is always a difficult problem in high-resolution maritime ubiquitous radars for complex characteristics of sea clutter, weak target returns, and diversity of targets. Multiple features extracted from radar returns in different domains have ability but not enough to solely distinguish radar returns with target from sea clutter. Joint exploitation of multiple features becomes the key to improve detection performance. In this article, the K-nearest neighbor (KNN) algorithm and anomaly detection idea are cooperated to develop a novel sea-surface target detection method in the feature space spanned by the eight existing salient features. The detection is realized by the anomaly detection followed by a specially designed KNN-based classifier with a controllable false alarm rate. In the anomaly detection, a decision region is determined by the hyper-spherical coverage of the training set of sea clutter that is sufficient and ergodic in the feature space. The KNN-based classifier is designed based on the training sample set of sea clutter and the training sample set of simulated target returns plus sea clutter that is sufficient but nonergodic, by joint usage of feature weighting, neighbor weighting, and distance weighting. The novel method is validated by the two open and recognized IPIX and CSIR radar databases for sea-surface small target detection. The results show that it provides significant performance improvement in comparison with the existing multiple-feature-based detection methods, owing to the fact that the novel method avoids the dimension restriction and feature compression loss in the existing methods.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Joint DOA and Polarization Estimation With Crossed-Dipole and Tripole
           Sensor Arrays
    • Pages: 4965 - 4973
      Abstract: Electromagnetic vector sensor arrays can track both the polarization and direction of arrival (DOA) of the impinging signals. For linear crossed-dipole arrays, as shown by our analysis, due to inherent limitation of the structure, it can only track one DOA parameter and two polarization parameters. For full 4-D (two DOA, and two polarization parameters) estimation, we could extend the linear crossed-dipole array to the planar case. In this article, instead of extending the array geometry, we replace the crossed-dipoles by tripoles and construct a linear tripole array. Detailed proof shows that such a structure can estimate the 2-D DOA and 2-D polarization information effectively in general. A brief comparison between the planar crossed-dipole array and the linear tripole array is performed at last, showing that although the planar structure has a better performance, it is achieved at the cost of increased physical size.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Field-of-View Constrained Guidance Law for a Maneuvering Target With
           Impact Angle Control
    • Pages: 4974 - 4983
      Abstract: Most existing impact angle control guidance (IACG) laws that consider the reduced seeker field-of-view (FOV) focus only on a stationary or a nonmaneuvering moving target. In actual warfare, however, a number of targets are capable of maneuvering with lateral acceleration, which prohibits the existing FOV-constrained IACG laws from guaranteeing the reliable performance. In this article, we develop a guidance law that ensures the accurate IACG with obeying the FOV constraint against a maneuvering target. The proposed guidance law is based on the engagement kinematics against a maneuvering target and structured as a sliding mode controller to cope with unknown disturbance such as the normal acceleration of the target. The introduced sliding surface structure includes a sigmoid function of which output is limited in magnitude in order to restrict the missile look angle within the preset limits. In consequence, the proposed law has the capability to fulfill IACG without violating the FOV constraint against a maneuvering moving target. Numerical simulations that support the effectiveness of the proposed guidance law are also included in this article.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
  • Report on First Inflight Data of BepiColombo's Mercury Orbiter
           Radio Science Experiment
    • Pages: 4984 - 4988
      Abstract: BepiColombo's Mercury orbiter radio science experiment (MORE) was conceived to enable extremely accurate radio tracking measurements of the Mercury Planetary Orbiter to precisely determine the gravity field and the rotational state of Mercury, and to test theories of gravitation (e.g., Einstein's theory of general relativity). The design accuracy of the radio tracking data was 0.004 mm/s (at 1000 s integration time) for the range-rate measurements and 20 cm for the range (at a few seconds of the integration time). These accuracies are attained due to a combination of simultaneous two-way microwave links at X (7.2–8.4 GHz) and Ka-band (32–34 GHz) to calibrate the dispersive plasma noise component. In this letter, we present the first analysis of the range and range-rate data collected by ESA's deep-space antenna (DSA) during the initial cruise phase of BepiColombo. The novel 24 Mcps pseudonoise (PN) modulation of the Ka-band carrier, enabled by MORE's Ka-band transponder, built by Thales Alenia Space Italy, Rome, Italy, provided two-way range measurements to the centimeter-level accuracy, with an integration time of 4.2 s at 0.29 astronomical units. In tracking passes with favorable weather conditions, the range-rate measurements attained an average accuracy of 0.01 mm/s at 60 s integration time. Data from May 20–24, 2019 were combined in a multi-pass analysis to test the link stability on a longer timescale. The results confirm the noise level observed with the single-pass analysis and provide a preliminary indication that the MORE PN ranging system at 24 Mcps is compatible with the realization of an absolute measurement, where the need to introduce the range biases in the orbital fit is much more limited than in the past. We show that in the initial cruise test the BepiColombo ra-io link provided the range measurements of unprecedented accuracy for a planetary mission, and that, in general, all target accuracies for radio-metric measurements were exceeded.
      PubDate: Dec. 2020
      Issue No: Vol. 56, No. 6 (2020)
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