Instrument Landing Research Articles

A Two-Way Split-Step Wavelet Scheme for Tropospheric Long-Range Propagation in Various Environments

In the context of improving the dimensioning of observation and telecommunication, the characterization of the propagation canal is very important. Thus, accurate models of propagation phenomenona in their environment and above a rough surface (maritime or terrestrial) are of major interest for many applications (such as radar, communications, and teledetection). To provide solutions to this problem, in this paper, we propose a fast, memory-efficient, and accurate asymptotic method for 2D tropospheric propagation for a large band of frequency that accounts for relief, as well as ground composition and roughness. This latter is a two-way split-step wavelet scheme with an intrinsic stopping criterion. For overseas propagation, roughness effects are considered through a hybrid method. A complete theoretical comparison with SSF in terms of memory and time efficiency is proposed. Simulations in various environments (ground, sea, and snow), as well as different frequencies (UHF, S, and X-band) are performed to validate the method and highlight its advantages. To highlight the interest of the developed methodology, this latter is applied to different real-life applications, such as the prediction of radar coverage and the optimization of an antenna location.

Routine Measurement of Water Vapour Using GNSS in the Framework of the Map-Io Project

The “Marion Dufresne Atmospheric Program-Indian Ocean” (MAP-IO) project is a research program that aims to collect long-term atmospheric observations in the under-instrumented Indian and Austral Oceans. As part of this project, a Global Navigation Satellite System (GNSS) antenna was installed on the research vessel (R/V) Marion Dufresne in October 2020. GNSS raw data is intended to be used to retrieve Integrated Water Vapour (IWV) content along the Marion Dufresne route, which cruises more than 300 days per year in the tropical and austral Indian Ocean. This paper presents a first assessment of this GNSS-based IWV retrieval, based on the analysis of 9 months of GNSS raw data acquired along the route of the R/V Marion Dufresne in the Indian Ocean. A first investigation of GNSS raw data collected during the first 5 months of operation has highlighted the bad positioning of the antenna on the R/V that makes it prone to interference. Changing the location of the antenna has been shown to improve the quality of the raw data. Then, ship-borne GNSS-IWV are compared with IWV estimates deduced using more conventional techniques such as European Centre for Medium-range Weather Forecasts (ECMWF) fifth reanalysis (ERA5), ground-launched radiosondes and permanent ground GNSS stations operating close to the route of the R/V Marion Dufresne. The rms difference of 2.79 kg m−2 shows a good match with ERA5 and subsequently improved after the change in location of the GNSS antenna (2.49 kg m−2). The match with ground-based permanent GNSS stations fluctuates between 1.30 and 3.63 kg m−2, which is also shown to be improved after the change in location of the GNSS antenna. However, differences with ground-launched radiosondes still exhibit large biases (larger than 2 kg m−2). Finally, two operational daily routine analyses (at day+1 and day+3) are presented and assessed: the rms of the differences are shown to be quite low (1 kg m−2 for the day+1 analyses, 0.7 kg m−2 for the day+3 analysis), which confirms the quality of these routine analysis. These two routine analyses are intended to provide a continuous monitoring of water vapour above the Indian Ocean and deliver ship-borne IWV with a low latency for the entire scientific community.

Atmospheric Propagation Studies and Development of New Instrumentation for Astronomy, Radar, and Telecommunication Applications in the Subterahertz Frequency Range

Current progress in the development of new subterahertz instruments discussed in this paper, including antennas, high-power gyrotrons, and low-noise receivers, provides a wide range of possible applications. Atmospheric absorption has now become a major limitation in the application of such high-performance subTHz systems, and the choice of the optimal location of antennas for astronomical, radar, and communication systems is important. The latest results of studying the microwave astroclimate in northern Eurasia are presented. Based on these studies, new perspectives and corrected plans for installing new antennas at the Suffa Plateau and in the Caucasus are formulated, and possible applications of new instruments such as radars for locating space debris and communication hubs for deep space communications, which are based on extremely-high-power gyrotrons and low-noise superconducting receivers, are discussed.

The PAPI Lights-Based Vision System for Aircraft Automatic Control during Approach and Landing

The paper presents the concept of a component of an aircraft’s automatic flight control system, controlling the airplane when in longitudinal motion (i.e., pitch angle, sink rate, airspeed channels) during automatic landing, from a final approach until a touchdown. It is composed of two key parts: a vision system and an automatic landing system. The first part exploits dedicated image-processing algorithms to identify the number of red and white PAPI lights appearing on an onboard video camera. Its output data—information about an aircraft’s position on a vertical profile of a landing trajectory—is used as one of the crucial inputs to the automatic landing system (the second part), which uses them to control the landing. The control algorithms implemented by the automatic landing system are based on the fuzzy logic expert system and were developed to imitate the pilot’s control actions during landing an aircraft. These two parts were teamed together as a component of a laboratory rig, first as pure software algorithms only, then as real hardware modules with downloaded algorithms. In two test campaigns (software in the loop and hardware in the loop) they controlled an aircraft model in a simulation environment. Selected results, presenting both control efficiency and flight precision, are given in the final section of the paper.

Positioning of aircraft relative to unknown runway with delayed image data, airdata and inertial measurement fusion

This work addresses the challenge of providing precise runway-relative position, velocity and orientation reference to a landing aircraft based on monocular camera and low-cost inertial sensor data complemented by barometric sensor readings. GPS information is excluded from this sensor set because it is intended to use the developed estimator for GPS and Instrumental Landing System fault detection. The characteristic size of the runway is assumed to be unknown and it is estimated run-time after verifying global observability of the nonlinear system. The delay caused by image processing is dealt with a delayed-Error-State Kalman Filter (ESKF). This algorithm considers dynamic propagation of the image information between acquisition and application forward in time thus the delay does not appear in the system dynamics. The first evaluation of the estimator is done for ideal simulated data to verify applicability of the delayed-ESKF and its flawless implementation. Then more realistic simulated data with sensor biases and noise is considered to verify closer to realistic performance and bias estimation precision. Finally, the estimator is tested with real flight data collected in the VISION EU H2020 research project. Estimation results are compared to GPS SBAS-based data and Airbus precision tolerances showing satisfactory performance. The methodological contribution of the paper is the unique combination of existing methods and ideas leading to a new solution proven to work satisfactorily even with real flight data.

공지통신 무전기 성능개량 간 안테나 추가에 따른 최적위치 설계 연구

In this study, we propose an antenna optimal positioning method for improving air-to-ground communication radios. To maximize the RF performance of communication radios and perform effective communication, a comprehensive and systematic process is developed by considering the structural impact, cable harness, and RF performance of additional antenna installation. The proposed method is applied to aircraft subjected to IFF performance improvement to optimally design IFF and GPS antennas. In addition, AIMS platform certification and development test evaluation are performed. Designing optimal antenna location is an effective method that can be applied to improve the performance of air-to-ground communication radios as well as to avionics equipment remodeling projects by reducing schedule and cost.

Visual Landing Based on the Human Depth Perception in Limited Visibility and Failure of Avionic Systems.

This paper introduces a novel visual landing system applicable to the accurate landing of commercial aircraft utilizing human depth perception algorithms, named a 3D Model Landing System (3DMLS). The 3DMLS uses a simulation environment for visual landing in the failure of navigation aids/avionics, adverse weather conditions, and limited visibility. To simulate the approach path and surrounding area, the 3DMLS implements both the inertial measurement unit (IMU) and the digital elevation model (DEM). While the aircraft is in the instrument landing system (ILS) range, the 3DMLS simulates more details of the environment in addition to implementing the DOF depth perception algorithm to provide a clear visual landing path. This path is displayed on a multifunction display in the cockpit for pilots. As the pilot's eye concentrates mostly on the runway location and touch-down point, “the runway” becomes the center of focus in the environment simulation. To display and evaluate the performance of the 3DMLS and depth perception, a landing auto test is also designed and implemented to guide the aircraft along the runway. The flight path is derived simultaneously by comparison of the current aircraft and the runway position. The Unity and MATLAB software are adopted to model the 3DMLS. The accuracy and the quality of the simulated environment in terms of resolution, the field of view, frame per second, and latency are confirmed based on FSTD's visual requirements. Finally, the saliency map toolbox shows that the depth of field (DOF) implementation increases the pilot's concentration resulting in safe landing guidance.

Justification of the choice of radiation sources for a computer vision system in the problem of automatic landing of unmanned aerial vehicles

An expedient spectral range of radiation sources for use in the automatic landing system of unmanned aerial vehicles has been substantiated. A method is proposed for synchronizing the photoexposure of the computer vision system and radiation from landmarks for the unambiguous determination of their mutual position. Results of the experimental studies are presented.

High-efficiency one-dimensional metalens for 3D focusing.

We demonstrate a high-efficiency on-chip one-dimensional metalens for three-dimensional (3D) light focusing. The metalens consists of a one-dimensional dielectric nano-antenna array, which scatters the evanescent wave of a nano-waveguide into free space and focuses this scattered light into a 3D ring. The corresponding phase profile of the metalens is controlled by the relative locations of antennas in the array. Through antenna-waveguide distance optimization, the designed metalens only scatters 1.5% of propagation light into free space and 55% of the scattered energy is focused into the 3D ring. When we use the antennas with an optimized shape, 50.18% of the focused energy is concentrated in a circular arc of the ring, which subtends an angle of 48°. This high-efficiency on-chip one-dimensional metalens is promising for non-invasive optical signal detection in photonic integrated chips.

Near‐ground propagation in automotive radar and communication obstructed deployments: Measurements and modelling

Wireless communication and radars will play a crucial role for autonomous vehicles in the nearest future. However, the blockage caused by surrounding cars can degrade communication performance, while automotive radars are never aimed to operate in such conditions. Therefore, in this paper, the authors propose the concept of near-ground propagation, reducing the blockage effect in the road traffic conditions. Specifically, the radio waves may freely propagate under the blocking car's bottom if the antennas are placed as low as possible to the road. Based on the measured and modelled results presented in the paper, it may be claimed that near-ground communication and radar sensing are feasible and may combat even heavily obstructed cases. Nevertheless, some challenges associated with antenna locations were encountered. For example, it was discovered that antenna height at 0.5 m acts less effectively against blockage than at 0.3 m. Next, the 27 dB excess loss at the 0.5 m antenna height in the radar deployment is larger than 17 dB at 0.3 m. In its turn, the higher ground clearance of the blocking vehicle positively affects the near-ground performance. Additionally, the signal propagation at the grazing angle crucially reduces the relevant losses.

Fault tolerant multi-sensor data fusion for autonomous navigation in future civil aviation operations

The problem addressed in this paper is that of fault-tolerant multi-sensor data-fusion for flight navigation during approach and landing of a civil jetliner. The work falls within the scope of a large collaborative project on future single pilot operations issues. The proposed methodology is based on a multi-layer hierarchical architecture which can integrate several heterogeneous information sources. The study is restricted to three classical information sources, namely, Inertial Reference System (IRS), Global Positioning System (GPS) and Instrument Landing System (ILS). The system is designed to meet the specified navigation performance requirements in terms of validity, accuracy, continuity and on-board implementation issues. The methodology takes advantage of recently developed set-membership tools, and paves the way toward a new and simple tuning of global merging filter.

Experimental and computational investigation of airwake aerodynamics of the generic aircraft carrier with ski-jump

A comprehensive experimental and computational investigation of flow past over a generic aircraft carrier with ski-jump is presented in this paper. The study has been performed to gain a deeper understanding of the airwake aerodynamics past such an aircraft carrier for different crosswind conditions. An experimental investigation is carried out in a wind tunnel on a prototype model of having a length of 1.1 m (1:250 scale). The prototype model was conceived from the various aircraft carriers existing in the world. A five-hole cobra probe is used to measure all the three velocity components along the 3° aircraft's landing slope for validation purposes. Reynolds-Averaged Navier-Stokes (RANS) based computational investigations are conducted to predict the overall airwake aerodynamics over the flight deck. Subsequently, a detailed parametric study has been conducted to examine the effect of relative wind conditions on the aircraft's landing slope. Detailed comparisons of velocity variations along the aircraft glide slope are discussed along with the experimental data. Results show that the top deck island structure and the oblique wind conditions are the two main contributors for adverse airwake aerodynamics over the flight deck.

A 3D Geometry-Based THz Channel Model for 6G Ultra Massive MIMO Systems

In this paper, a 3D geometry-based double-spherical terahertz (THz) channel model is proposed for ultra massive multiple-input multiple-output (MIMO) communications. To reflect real THz ultra massive MIMO communications, the characteristic of nano-material array antenna and the high loss of THz bands are considered in channel modeling. Based on the proposed geometry-based stochastic model (GBSM), power delay profile (PDP), space-time-frequency correlation function, and the Doppler power spectral density are derived and analyzed. Furthermore, the proposed model is validated by comparing the simulated results with the measurement reference. Influences of channel parameters, namely, antenna element spacing, carrier frequency, number and location of clusters, on the correlation functions are investigated. The results indicate that antenna element spacing and number of clusters have significant impacts on channel correlation, and the decreasing of correlation function becomes slower when antenna element spacing decreases. Moreover, location of clusters also affects the drop rate of correlation function. The influences of the number of clusters and concentration of intra-cluster multipath components (MPCs) on the Doppler power spectral density are analyzed. It is found that a larger number of clusters and a more concentrated distribution of intra-cluster MPCs increase the degree of Doppler spectrum variation. The proposed channel model and the corresponding statistical properties are insightful for designing and realizing THz ultra massive MIMO systems for 6G and beyond.

VR HMD 시뮬레이터를 활용한 조종사 시선 추적 및 착륙 절차 결과 분석

This study performed precision instrument landing procedures for pilots with a commercial pilot license using VR HMD flight simulators, and assuming that the center of the pilot's gaze is in the front, 3-D.O.F. head tracking data and 2-D eye tracking of VR HMD worn by pilots gaze tracking was performed through. After that, AOI (Area of Interesting) was set for the instrument panel and external field of view of the cockpit to analyze how the pilot's gaze was distributed before and after the decision altitude. At the same time, the landing results were analyzed using the Localizer and G/S data as the pilot's precision instrument landing flight data. As a result, the pilot was quantitatively evaluated by reflecting the gaze tracking and the resulting landing result using a VR HMD simulator.

ICEBEAR‐3D: A Low Elevation Imaging Radar Using a Non‐Uniform Coplanar Receiver Array for E Region Observations

AbstractThe Ionospheric Continuous‐wave E region Bistatic Experimental Auroral Radar (ICEBEAR) has been reconfigured using a phase error minimization and stochastic antenna location perturbation technique. The resulting 45‐baseline sparse non‐uniform coplanar T‐shaped array, ICEBEAR‐3D, is used for aperture synthesis radar imaging of low elevation targets. The reconfigured receiver antenna array now has a field of view ±45° azimuth and 0°–45° elevation at 0.1° angular resolution. Within this field of view no aliasing occurs. Radar targets are imaged using the Suppressed Spherical Wave Harmonic Transform (Suppressed‐SWHT) technique. This imaging method uses precalculated constant coefficient matrices to solve the integral transform from visibility to brightness through direct matrix multiplication. The method then suppresses image artefacts (dirty beam) due to undersampling by combining brightness maps of differing harmonic order. Measuring elevation angles of targets at low elevations with radar interferometers has been a long standing problem. ICEBEAR‐3D elucidates the underlying misinterpretations of the conventional geometry for vertical interferometry especially for low elevation angles. The proper phase reference vertical interferometry geometry is given which allows radar interferometers to unambiguously measure elevation angles from zenith to horizon without special calibration. The receiver antenna array reconfiguration, Suppressed‐SWHT imaging technique, and proper geometry for vertical interferometry are validated by showing agreement of the meteor trail altitude distribution with numerous data sets from other radars.

Finite horizon analysis of autolanded aircraft in final approach under crosswind

The paper presents a worst-case touchdown performance analysis of auto-landed aircraft under complex wind disturbance. It takes advantage of the fact that the approaching aircraft effectively follows a predefined trajectory provided by the instrument landing system. Thus, the aircraft dynamics’ linearization along the approach trajectory results in a finite horizon linear time-varying (LTV) representation. This naturally allows to include altitude triggered control law changes and changes in the flight dynamics, e.g., due to ground effect, in the analysis. To cover a broad range of environmental and aircraft parameter combinations in the worst-case analysis, a time-varying trajectory uncertainty description is introduced. The uncertainty’s input/output behavior is covered by integral quadratic constraints. Thus, recent advances on the worst-case gain analysis of finite horizon LTV systems can be used. The corresponding analysis condition is based on a parameterized Riccati differential equation’s solvability, which leads to a readily solvable nonlinear optimization problem. Applying the robust LTV framework, worst-cases for common touchdown criteria, such as vertical touchdown velocity, are calculated. These worst-cases cover the influence of complex wind fields and a large aircraft and environmental parameter set. The results are evaluated against corresponding Monte Carlo simulation on the original high fidelity, industry-sized nonlinear aircraft model.

INTERCOMPARISON OF DESIS, SENTINEL-2 (MSI) AND SENTINEL-3 (OLCI) DATA FOR WATER COLOUR APPLICATIONS

Abstract. In this work, we investigate the potential of DESIS hyperspectral data for water colour applications as preparation for the exploitation of data from the future EnMAP mission. We show results on the intercomparison of Level 2 data of the DESIS sensor, Sentinel-2 MultiSpectral Instrument (S2-MSI) and Sentinel-3 Ocean and Land Colour Instrument (S3-OLCI) processed with the Polymer atmospheric correction. Examples of mapping of water quality parameters in inland and coastal waters is provided for different ecosystems (e.g. lagoon, clear lakes, estuaries). First results of Polymer applied to DESIS data at different study regions show similar spatial distribution of chlorophyll-a concentration (Chl-a) to S2-MSI and S3-OLCI.

A fitness sharing based ant clustering method for multimodal optimization of the aircraft longitudinal automatic carrier landing system

With the flight envelope becoming larger and larger, the Automatic Carrier Landing System (ACLS) is becoming a complex large-scale system, and the corresponding control parameter design has been the most important key link to ensure the safety and flight quality of aircraft carrier landing missions. In this paper, a Fitness Sharing based Ant Clustering (FSAC) method is presented for use in multimodal optimization of the longitudinal ACLS and to reveal the hidden properties of the solution space. In doing so, first, the lattice rule based space sampling strategy is used to create the individual ant sequences. Then a fading memory fitness sharing function is applied to modify the clustering strategy and regroup the ants for multimodal optimization of the search space. An adaptive learning strategy is developed to dynamically adjust the search scope of the ant colony. Moreover, an online health monitor is used to replace the weak ants with new ones in a timely manner in order to keep robustness of the FSAC. Finally, the multimodal feasible solutions which are good candidates for the ACLS design are presented and the characteristics of the solution space are also analyzed. The result shows that many large solution sets are located at the bottom of the solution space, whereas on the upper side of the solution space, the number of feasible solutions decreases sharply. An F/A-18 model is used as a test bed and the simulations are carried out in various wind conditions to demonstrate the effectiveness and feasibility of the proposed method.

Numerical Modeling of Smartphones with WCDMA, LTE, and WLAN Bands for Epidemiological Studies

This paper presents the representative numerical modeling of smartphones with wideband code division multiple access (WCDMA), long-term evaluation (LTE), and wireless local area network (WLAN) bands for epidemiological studies. For this purpose, based on specific absorption rate (SAR) test reports for commercial smartphones released in South Korea from 2013 to 2019, we determined the smartphone size, frequency band categorization, antenna locations, and target 1-g peak-spatial SAR (psSAR) values for a specific anthropomorphic mannequin (SAM) phantom. Numerical results showed that the designed numerical smartphone models yielded good matching and radiation performance, and more importantly, their 1-g psSAR values were within ±16% of the target 1-g psSAR values.

Validation of a Flying Competence Scale for Aircraft Pilots

This study aims to validate a scale that evaluates the flying competence of aircraft pilots. The scale was developed by pilots in an aerospace university and was approved by the Civil Aviation Authority of the Philippines. To do so, the scale was administered to 288 pilots holding different levels of licenses. The data obtained were subjected to Exploratory Factor Analysis (EFA) and created a three-factor model. The factors are set of flying skills named as instrument flight (Factor 1), basic attitude flying (Factor 2), and instrument landing system (Factor 3). The model was confirmed utilizing the resulting values of five goodness of fit indices (GFIs) generated by the Confirmatory Factor Analysis (CFA). Only comparative fit index, Tucker–Lewis index, and Standardized Root Mean Squared Residual resulted to values falling within the thresholds. These three GFIs are already adequate to confirm that the model is relatively good fit. The standardized factor loadings (SFLs) and composite reliability (CR) were also excellent, thus, establishing convergent validity. Also, the estimated average variance extracted and Cronbach’s alpha of all factors provided evidence of discriminant validity and reliability, respectively. In conclusion, this scale is valid and reliable to evaluate the pilot’s performance in flying an aircraft.