The short-term scenarios of high-throughput satellite systems foresee the exploitation of (currently commercially unused) extremely high frequency bands in the feeder link to support broadband user access services. In this context, spatial diversity plays a key role, considering that this is the only technique that can allow high link availability at frequency bands higher than the Ka-band without

We propose a compressive pulse-Doppler radar that works through one-bit quantization of the received noisy signal by comparing it with a time-varying reference level. Considering the sparsity of the targets in the range-Doppler domain, we solve the problem by sparse recovery methods in both the absence and presence of clutter. The proposed method leads to an optimization problem that can be tackled

We investigate the problem associated with the statistics of the product of two squared Shadowed Rician (SR) random variables (RVs). Both SR RVs are independent and nonidentically distributed. The distribution of the product of two squared SR RVs is very important from the satellite communication perspective. We derive approximate expressions of the probability density function (p.d.f.), the moment

The performance of a range-based indoor positioning system is severely degraded by non-line-of-sight (NLOS) propagation due to the offsets in range measurements (i.e., NLOS errors). It is difficult to predict or mitigate the NLOS errors since they are dependent on both the location and the environment. In this paper, we propose an accurate tracking scheme for NLOS environments by jointly estimating

In this paper, an integrated system health management oriented condition monitoring and maintenance decision-making model is proposed, which uses intelligent mobile agents to achieve real-time monitoring and to realize life cycle maintenance decision-making for multistate systems (MSSs). The model is applied to an aircraft engine system numerical example, the results of which illustrate that the proposed

Random jitter or offset between the transmitter/receiver clocks is an important parameter that has to be accurately estimated for optimal detection of pulse position modulation (PPM) symbols for high-data-rate optical communications. This parameter, in general, is modeled as an unknown random quantity that depends on the clock drift between the transmitter/receiver clocks and the random motion between

We present an optimal control method for distance-based formation control of multiagent systems with energy constraints. We combine the rigid graph theory and state-dependent Riccati equation method to develop a multiagent formation control scheme. We defined a normalized rigidity matrix and use it for the rigorous stability analysis. The proposed method asymptotically minimizes weighted cost functional

A new algorithm, the finite-difference algorithm, is proposed for single-component polynomial phase signal parameter estimation. The proposed algorithm takes advantage of the framework of the quasi-maximum-likelihood (QML) estimator but estimates the finite difference of the polynomial instead of the derivative. The algorithm is computationally simpler and has comparable performance to the QML algorithm

To compensate the range cell migration and Doppler frequency spread of a maneuvering target during the integration time, this paper proposes a new parameter estimation method based on sub-band dual-frequency conjugate (SDFC)–Radon chirp rate–quadratic chirp rate algorithm. In this method, SDFC process is first applied to reduce the equivalent frequency and Radon chirp rate–quadratic chirp rate algorithm

This paper presents a nonlinear tracking controller including the cutoff frequency adaptation algorithm for quadcopters without the use of true plant parameters. This study makes two contributions. First, an adaptation algorithm automatically updates the closed-loop cutoff frequency by updating the feedback gains. Second, a nonlinear control law renders the closed-loop system to guarantee the exponential

Reconfigurable avionics systems can tolerate faults by moving functionalities from failed components to another available system component. This paper proposes a distributed reconfigurable architecture for application migration from failed modules to working ones. The feasible system reconfiguration states are determined off-line to provide the expected configuration in foreseen situations. Model checking

In this paper, we present an expectation-maximization (EM) initialization method for estimation of unknown parameters in a radar noise model. We deal with radar based terrain referenced navigation (TRN) over vegetated areas, where the radar noise was modeled as a double-mode Gaussian mixture with two unknowns. The known parameters are used for EM initialization along with innovation samples. Through

This paper proposes an impulse radio ultrawideband (IR-UWB) wireless network channel model for next-generation wireless avionic system (NGWAS). Complexities such as poor network localization, redundant wiring, network security flaws, suitable physical proximity to the aircraft system's controller and need to guarantee scalable wireless network access have necessitated the adoption of wing system units

This paper proposes a channel model to be applied to the communications systems of CubeSats. The model considers the low earth orbit geometry when a satellite is passing over a ground station, and the propagation surrounding multiple paths of the ground station location in urban areas. The geometry was used to define the deterministic factors, which contribute to the fading of the communication signal

A reliable telemetry link is a key element to reduce reflies and to enhance test flight efficiency (i.e., real-time test point validation) and safety in flight test campaigns. However, the telemetry link undergoes losses owing to radio frequency noise and flight test maneuvers. In addition, the telemetry community has been facing a reduction of the available bandwidth owing to electromagnetic spectrum

This paper presents the thermal design of the electronics unit of the instrument Polarimetric Helioseismic Imager, onboard the European Space Agency mission Solar Orbiter. The thermal design procedure, along with the problems encountered during this design phase, and the solutions found to fix them are described, proving in this way the thermal feasibility and robustness of the unit. Its final thermal

By employing an expendable repeater-type decoy that is known as efficient electronic countermeasure device, the survivability of an airborne platform can be improved. To optimize the survivability of the aircraft by managing the active decoy, analyzing which factors critically affect to the survivability is very important. For its dynamic situation, where the motions and interaction of the decoy, platform

This paper presents a Poisson multi-Bernoulli mixture (PMBM) conjugate prior for multiple extended object filtering. A Poisson point process is used to describe the existence of yet undetected targets, while a multi-Bernoulli mixture describes the distribution of the targets that have been detected. The prediction and update equations are presented for the standard transition density and measurement

This paper is devoted to the estimation of target motion parameters with a forward scatter radar (FSR). To provide an upper bound for the estimation performance, a closed-form expression of the Cramér–Rao lower bound (CRLB) is provided for the main target signal parameters, namely Doppler rate, baseline crossing instant, and main lobe width parameter of the target amplitude modulation pattern. This

Modern aviation safety increasingly depends on reliable GPS services, while signal degrading effects such as multipath and masking often occur during critical flight phases, such as takeoff and landing. In this regard, we propose multireceiver direct position estimation (MR-DPE), which operates a network of DPE receivers to enhance GPS accuracy under degraded signal conditions. A DPE receiver directly

In this paper, we investigate the transmission schemes of space data systems for optimized network capacity in an integrated terrestrial-satellite network (ITSN) with a two-layered space segment. First, a theoretical model of the network capacity is developed to evaluate the strategy of utilizing both direct and relayed transmissions. Second, we consider the ideal and the resource-constrained scenarios

Aircraft are becoming increasingly connected to other systems or networks, introducing attack vectors and posing a threat to their operational effectiveness. Many military aircraft function using the MIL-STD-1553 protocol in order to communicate information across its systems. Previous intrusion detection research on this type of data bus is unable to detect spoofing attacks where only data words are

With sum throughputs exceeding 1 Tb/s, next-generation high throughput satellite will play a key role in 5G networks for applications including backhauling or broadband in-flight connectivity. Such satellites require the deployment of tens of $Q/V$ -band feeder links to support the data traffic in their uplink. Meanwhile, geographical restrictions and cost considerations significantly constrain the

Typically, near-Earth space objects are observable for a small fraction of the orbit revolution. In this paper, we consider the problem of identification and fusion of two short optical tracks of near-Earth space objects, as well as the problem of estimation of the parameters of the corresponding orbits directly from these tracks in the absence of a priori information. The popular approach to solving

This paper presents a learning approach to predict air-to-ground communication channel strength to support the communication-relay mission using the unmanned aerial vehicle (UAV) in complex urban environments. The knowledge of the air-to-ground communication channel quality between the UAV and ground nodes is essential for optimal relay trajectory planning. However, because of the obstruction by buildings

Aiming at the signal reconstruction problem for the conventional narrowband radar system, we propose a new statistical compressive sensing (SCS) method to achieve the reconstruction of superresolution time-frequency spectrum from the corrupted time-domain measurement. The proposed method assumes that the signal obeys complex Gaussian distribution and develops a hierarchical Bayesian model. Variational

In target tracking systems involving data fusion it is common to encounter sensor measurement biases that contribute to the tracking errors. There is extensive research into estimating sensor biases, but very little research into bias estimation in the dynamic case, meaning that biases that change over time are addressed. This paper investigates the means for and necessity of estimating bias rates

This paper deals with measurement extraction, from an optical sensor's Focal Plane Array (FPA), of a streaking target. We use a model that assumes pixels are separated by dead zones and model the streaking target's point spread function (PSF) as a Gaussian PSF that moves during the optical sensor's integration time. We make an assumption that the target has a constant velocity over the sampling interval

Safe landing site selection of a planetary lander is one of the most important technologies for the lander's mission success. In this paper, a new concept for safe landing site selection is proposed based on the digital terrain map and contour lines generated by light detection and ranging (LIDAR) measurements. The design parameters of the proposed approach are defined and systematically classified

With GPS/Global Navigation Satellite System (GNSS) receivers exposed to greater levels of Radio Frequency Interference (RFI), a potential problem is the saturation of the receiver front end (FE). This problem is further complicated in typical multifrequency receivers by the interfrequency saturation effect. Specifically, any inband RFI targeted to induce FE saturation at only one specific GPS/GNSS

In their previous work, the authors proposed a methodology for predicting and modeling electromagnetic emissions in case of shielded coaxial cable with respect to the ground dielectric properties. In that work, a shielded coaxial cable was treated as a travelling wave antenna and the decomposed contribution of each phenomenon was validated through extensive electric field measurements of the cable

Interplanetary networks are affected by long propagation delays, intermittent connectivity, possible packet losses due to residual errors, and other impairments. To cope with these challenges, the delay-/disruption-tolerant networking (DTN) architecture utilizes the Licklider transmission protocol (LTP) as convergence layer on space links. The LTP reliable service (red) relies on Automatic Repeat reQuest

A novel robust Rauch–Tung–Striebel smoothing framework is proposed based on a generalized Gaussian scale mixture (GGScM) distribution for a linear state-space model with heavy-tailed and/or skew noises. The state trajectory, mixing parameters, and unknown distribution parameters are jointly inferred using the variational Bayesian approach. As such, a major contribution of this paper is unifying results

A polarimetric scheme is presented for the detection of a range-spread target when the presumed target steering matrix is deviated from the actual one. Following the adaptive beamformer orthogonal rejection test model, the decision statistic of the proposed detector involves the polarimetric clutter-plus-noise covariance matrix, the target component after noise whitening and rotation, as well as the

To maximize file transfer from deep-space vehicles, a space-to-earth content-transfer protocol that combines turbo codes, RaptorQ codes, real-time channel prediction, and dynamic code-rate selection is proposed. The protocol features a signal-to-noise ratio prediction model that facilitates the periodic adjustment of turbo encoder to achieve adaptive-rate transmission, and fountain codes to eliminate

We propose a new compressive sensing scheme that enables fully polarimetric radar imaging from a subset of channel measurements. Previous sparse recovery methods for polarimetric radar have not modeled channel coupling. We recognize that mixing of information through coupling is key to dropping a channel. Our method complements fast and slow time sampling and may reduce hardware and communications

This paper presents a novel strategy to simultaneously estimate the direction of arrival (DOA) of a source signal and the phase error of a partly calibrated array with arbitrary geometry. We add up the snapshot data of two different sensors, and then extract a knowledge associated with the DOA and phase errors of these two elements by using singular value decomposition. In such a manner, we can establish

The relative pose (position and attitude) measurement of space noncooperative targets is very important for on-orbit servicing activities, such as target tracking, approaching, and capturing. The traditional methods rarely consider the instability of feature extraction and image blurring caused by target tumbling. In this paper, a method based on the maximum outer contour (MOC) recognition is proposed

In the fractional frequency reuse (FFR) system, the bandwidth is partitioned into orthogonal subbands such that users in the cell-center region use the subbands of a frequency reuse factor (FR factor) equal to 1, whereas users in the cell-edge region exploit the subbands of an FR factor larger than 1. The distance threshold, which is used to distinguish the cell-edge region from the cell-center region

In this paper, a new algorithm called blind star identification is presented to identify the stars in night sky images without using the intrinsic parameters of the star sensor camera (focal length, principal point, and pixel size), and in lost in space mode. The accuracy and reliability of the proposed algorithm were successfully validated by using the real night sky images and Monte Carlo simulations

We consider signal detection in subspace interference with partial prior knowledge of the subspace. The problem was recently considered by Li et al. , where a subspace knowledge with learning (SKL) Bayesian model was proposed to leverage partial and uncertain knowledge of the subspace bases. The SKL, however, is based on the assumption that the subspace bases are a subset of a known overdetermined

Radar with digitally generated orthogonal frequency division multiplexing (OFDM) signals is an emerging research field that has been studied for the past few years. Another trend for radar is the multiple-input multiple-output (MIMO) architecture used for an efficient direction-of-arrival estimation. These two technologies can be efficiently combined into an OFDM-MIMO radar with novel interleaving

This paper proposes a nonlinear discrete-time sliding mode based tension control for deployment of tethered space robot with only length and angle measurements. The discrete-time dynamics of deployment is uncovered based on discretization of Hamilton's principle. Taking into account the underactuated dynamics, the proposed discrete-time sliding surface can generate a specified reduced-order system

This paper is focused on noncooperative target position estimation via the joint use of two-dimensional (2-D) hyperbolic and elliptic passive location techniques based on time difference of arrival (TDOA) and passive coherent locator (PCL) measurements, respectively. A fusion strategy is laid down at the signal processing level to obtain a reliable estimate of the current target position. With reference

A new hierarchical method for fault detection, isolation, and identification of nonlinear systems with applications for in-orbit closed-loop controlled satellites is proposed where fault detection employs unscented Kalman filter and adaptive thresholds. Fault isolation employs multiple model approach in conjunction with Bayes’ probability theorem and adaptive window, and fault identification employs

Long-time integration is an effective method to improve target detection performance in a noisy background. However, when detecting high-speed and maneuvering targets by long-time integration, it is easy to encounter the across range unit and across Doppler unit effects, which deteriorate the detection performance of algorithms with low computational complexity, such as moving target detection and

This paper deals with a new modeling method and a powerful planning approach for deep space probes. The key technique is based on the concept of extended state model. Furthermore, extended state model planning (ESMP) algorithm is designed to be fully compliant with the model, and flaw selection strategies are proposed to avoid redundant work. Finally, we discuss the time complexity of ESMP, and computational

Next generation global navigation satellite systems (GNSSs) will embrace intersatellite links capability as an enabler of navigation and data transfer. However, platform restrictions will require of suitable contact plan design (CPD) schemes, which have been traditionally assumed centralized . After discussing the requirements of distributed CPD, we propose a first scheme in this class. Simulation

As bias estimation methods are developed, it becomes necessary to obtain the bound on bias estimation for more complex bias and sensor models. Three-dimensional (3-D) sensors, such as radars commonly used in applications, contain both scale and additive biases in sine space which result in a nonlinear estimation problem that may have poor observability and accuracy depending on the geometry of the

In helicopter satellite communication systems, the received signal is blocked by the helicopter rotor blades during propagation, incurring the unstableness of traditional methods of channel estimation due to unknown channel state. To this end, a joint occlusion detection and phase estimation algorithm is proposed by factor graph in this paper. For occlusion detection to acquire channel state, the occlusion

This study presents a method to adjust the waypoints of an unpowered air vehicle to compensate for the influence of wind on the trajectory. A framework combining preflight waypoint planning and inflight waypoint adjustment is proposed. In the offline planning phase, optimal trajectories under various wind profile combinations are generated by using a direct optimization method. Waypoints are extracted

The capturability of the two-dimensional (2-D) pure proportional navigation (PPN) guidance law against lower speed arbitrarily maneuvering target for homing phase had been thoroughly analyzed by using the nonlinear output regulation (NOR) method before. However, due to the complexity of the 3-D relative kinematics, the NOR method has not been applied to the capturability analysis of the 3-D PPN, which

In this paper, we demonstrate that the uncertainty of the dual-satellite ephemeris must be included in order for the geolocation covariance to be accurate. Without the inclusion of this additional error source, the covariance is no longer consistent with the true uncertainty and can convey misleading results. The larger the uncertainty associated with the dual-satellite ephemeris the larger the geolocation

An attitude control system (ACS) is one of the critical subsystems of any spacecraft and typically is in charge of de-tumbling, controlling, and orienting the satellite after initial deployment and during the satellite operations. The magnetorquer is a core magnetic attitude control actuator and, therefore, a good choice for nanosatellite attitude stabilization. There are various methods to achieve

Measuring the vibrating states of an artificial structure is an important approach to monitor the stability of the structure. However, the existing radar vibration measurement methods do not have enough azimuth resolution for measuring the vibrations in a relatively large scene, which contains multiple buildings or a large building. For such application scene, this paper proposes a vibration measurement

We tackle the problem of enhancing mobile ad-hoc networks (MANETs) coverage for emergency applications assisted by converged satellite–cloud networks. We propose the use of per-flow network coding (NC), which is provided by a NC function (NCF). We define NCFs with inputs available under 5G device-to-device assumption. Outputs are optimal coding rates balancing per-node computational resources and resulting

Space debris has become a great threat to space activities. We study and optimize space missions to remove multiple space debris. These missions are efficient and economical in stabilizing the orbital environment. In this paper, we propose an intelligent global optimization algorithm named the evolving elitist club algorithm (EECA), and we study its application in multiple debris removal missions.

For airborne-phased array radar systems, space-time adaptive processing (STAP) is supposed to be a crucial technique for improving target detection performance in the strong clutter background. However, practical application environments are always heterogeneous and have offered a severe challenge to the implementation of STAP. To address this reality, a data-dependent reduced dimension STAP approach

This paper proposes an autopilot design for an interceptor with thrust vector control that operates in the endo- and exoatmospheric regions. The main objective of the proposed autopilot design is to ensure control performance in both atmospheric regions, without changing the control mechanism. In this paper, the characteristics of the aerodynamic forces in both atmospheric regions are first investigated

In serial wireless sensor networks, nodes send their compact information (decisions) to a fusion center via multihop. Each node performs data fusion and transmits the result. We propose using the Plackett copula for resolving the correlation in heterogeneous serial networks. The proposed scheme improves detection performance with low computation burden.