Station Receiver Research Articles

The connection between the critical frequency and the total electron content of the ionosphere at low and high solar activity period

Ionosonde-f0F2 measurements and corresponding GNSS TEC measurements have been analysed. Available f0F2 and TEC data respectively obtained from a pair of ionosonde and GNSS receiver stations of a mid-latitude station, named MO155, located in Moscow (55.8˚N, 37.2˚E), for 2010 and 2014 was used. Data for two years were respectively used in the study to represent years of low and high solar activity. A significant relation between the ionosonde-f0F2 measurements and the corresponding GNSS-VTEC measurements with correlation coefficients above 0.8 was observed for both periods. The f0F2/TEC ratios, for the MO155 station illustrated, are typically in the range of about 0.2 to 1.6 Mhz/TECU during the low solar activity period and 0.2 to 2.5 Mhz/TECU during the high solar activity period. The ratio is lower during the day-time, and higher during the nights and early mornings. The analysis of the four seasons for both periods (low solar activity and high solar activity) reveals a strong relationship between TEC and f0F2 in all the seasons. Significantly, summer season appear to have a different trend from all other seasons with a relatively low correlation. The relationship between TEC and f0F2 seem to be stronger during period of high solar activity than period of low solar activity. Results from the work indicate that the relationship between f0F2 and TEC is mostly dependent on the seasons, followed by the level of solar activity, and then the local time. It was shown that the relationship between f0F2 and TEC is not purely monotonic as suggested earlier; but that this relationship depends on factors like the season, level of solar activity, and local time. Considering the strong relationship between f0F2 and TEC, the study affirms the method of using TEC as a proxy for f0F2 estimation.

Broadband seismic source data acquisition and processing to delineate iron oxide deposits in the Blötberget mine‐central Sweden

ABSTRACTA prototype electromagnetic vibrator, referred to here as E‐Vib, was upgraded and developed for broadband hardrock and mineral exploration seismic surveys. We selected the iron oxide mine in Blötberget, central Sweden, for a test site in 2019 for the newly developed E‐Vib because of the availability of earlier seismic datasets (from 2015 to 2016) for verification of its performance for hardrock imaging purposes. The two‐dimensional data acquisition consisted of a fixed geometry with 550 receiver locations spaced at every 5 m, employing both cabled and wireless seismic recorders, along an approximately 2.7 km long profile. The E‐Vib operated at every second receiver station (i.e. 10 m spacing) with a linear sweep of 2–180 Hz and with a peak force of 7 kN. The processing workflow took advantage of the broadband signal generated by the E‐Vib in this challenging hardrock environment with varying ground conditions. The processed seismic section shows a set of reflections associated with the known iron oxide mineralization and a major crosscutting reflection interpreted to be from a fault system likely to be crosscutting the mineralization. The broadband source data acquisition and subsequent processing helped to improve signal quality and resolution in comparison with the earlier workflows and data where a drophammer seismic source was used as the seismic source. These results suggest new possibilities for the E‐Vib source for improved targeting in hardrock geological settings.

Constructing social networks from automated telemetry data: A worked example using within‐ and across‐group associations in cooperatively breeding birds

Abstract Advances in data‐logging technologies have provided a way to monitor the movement of individual animals at unprecedented spatial and temporal scales. When used in conjunction with social network analyses, these data can provide deep insight into the structure and dynamics of animal social systems. Emergence of these new technologies demands concomitant progress in workflows to translate data streams from automated systems to social networks, based on biologically relevant metrics. Here we outline key considerations for constructing social networks from automated telemetry data. We highlight the need for paying particular attention to the spatial arrangement of receiver stations with respect to the ecology of study system and developing appropriate criteria for quantifying associations. We provide a case study for constructing social networks from automated telemetry data collected over 1 month during a study of acorn woodpeckers Melanerpes formicivorus, a cooperatively breeding bird. The data consisted of detections of known birds near receiver stations placed within core areas of group territories. We use this system to demonstrate how to build social networks to investigate biological questions about patterns of associations between group members and territory visitors across the landscape.

Methodology for the remote transfer of GPS receiver station data through a GSM network

Coastline alterations severely impact the socio-economic conditions of populations living in coastal regions. Climate changes, together with land subsidence considerations, have increased recently according to high-accuracy fixed tide gauges and land subsidence sensors. In addition, networks of measurement devices are spread throughout the oceans, seas, and coastal areas to capture ongoing changes and to predict future impacts. However, some of these devices still require the in-situ extraction of data for postprocessing. This increases the cost, wastes time, and increases the probability of human errors leading to inaccurate results. This study presents a developed approach to remotely access the Trimble NetR9 GPS receiver device that is fixed at the Coastal Research Institute station in the city of Rosetta in Egypt. This will ease the remote retrieval of the station data for its processing and interpretation.

Low-Complexity Algorithm for Outage Optimal Resource Allocation in Energy Harvesting-Based UAV Identification Networks

We study an unmanned aerial vehicle (UAV) identification network equipped with an energy harvesting (EH) technique. In the network, the UAVs harvest energy through radio frequency (RF) signals transmitted from ground control stations (GCSs) and then transmit their identification information to the ground receiver station (GRS). Specifically, we first derive a closed-form expression of the outage probability to evaluate the network performance. Then we obtain the closed-form expression of the optimal time allocation when the bandwidth is equally allocated to the UAVs. We also propose a fast-converging algorithm for time and the bandwidth allocation, which is necessary for the UAV environment with high mobility, to optimize the outage performance of EH-based UAV identification network. Simulation results show that the proposed algorithm outperforms the conventional bisection algorithm and achieves near-optimal performance.

TEC Map Completion Through a Deep Learning Model: SNP‐GAN

AbstractThe limited availability of ground receiver stations causes an approximate 52% of data gaps in Massachusetts Institute of Technology (MIT)‐ total electron content (TEC) global maps. The completed TEC maps are highly desirable for both scientific research and space weather applications. Compared to the conventional image inpainting methods, the deep learning methods using generative adversarial networks (GANs) offer an effective image inpainting tool. We adapt the Spectrally Normalized Patch GAN (SNP‐GAN) for the TEC map completion using a traditional complete TEC data source, the International Global Navigation Satellite System TEC (IGS‐TEC) maps, as the training data. For 10‐fold cross‐validation of 20‐year IGS‐TEC data, SNP‐GAN reduces the root mean squared error (RMSE) by more than 30% compared to our previous model, the deep convolutional GAN with Poisson blending (DCGAN‐PB). Two case studies using MIT‐TEC data for 2013 and 2016 storms also demonstrate that SNP‐GAN outperforms DCGAN‐PB in terms of recovering equatorial and low latitude TEC structures. Meanwhile, the end‐to‐end styled generator of SNP‐GAN saves time in the map completion step by avoiding iterative mapping used in DCGAN‐PB. Both deep learning methods not only preserve the large‐scale TEC structures well, but also reveal mesoscale (100–1,000 km) TEC structures that are missing in IGS‐TEC. This work represents an important progress for efficient and automatic TEC map completion with high accuracy.

Evaluating the effects of controlled flows on historical spawning site access, reproduction and recruitment of lake sturgeon Acipenser fulvescens

Lake sturgeon Acipenser fulvescens spawn at the base of Kakabeka Falls, a 39 m waterfall on the Kaministiquia River, a tributary to Lake Superior. Access to this historical spawning site can be restricted or delayed due to hydroelectric flow fluctuations that coincide with the A. fulvescens spawning season. The objectives of this study were to determine (a) the necessary flow conditions that facilitate spawning site access; (b) quantity and duration of flow required for successful spawning and dispersal of larvae; and (c) evaluate recruitment of juvenile A. fulvescens in relation to flow. A. fulvescens spawning migrations were tracked using a stationary telemetry receiver that logged the movements of 166 A. fulvescens fitted with radio-transmitters. Unrestricted access to the spawning site was facilitated when spawning flow was controlled at 23 m3 s-1 in 2004 and 17 m3 s-1 in 2006. Fluctuating (0.5-8.5 m3 s-1 ) and delayed spawning flows resulted in restricted and delayed access to the spawning site. Flow duration for successful egg incubation, hatch and larval dispersal was determined by sampling larvae using drift nets and quantified using cumulative temperature units (CTU). Over 10 years, 10,083 larvae were captured between 31 May and 20 July with 97% of the drift occurring prior to 30 June. From the date of first spawning to the end of larval dispersal took an average of 38.6 days, and the mean CTU value was 398.6. In general, a minimum flow of approximately 14.5 m3 s-1 from the date of initial spawning to the accumulation of c. 400 CTU ensured successful hatch and larval dispersal. During the timeframe of this study, recruitment was variable. This study described the complex and variable reproductive life history of A. fulvescens and defined spawning flow requirements ecologically, which can be used to develop operational provisions at hydropower facilities to ensure successful reproduction.

Study on gas hydrate targets in the Danube Paleo-Delta with a dual polarization controlled-source electromagnetic system

The Black Sea is known to have extensive direct and indirect indicators of methane hydrates. Since the resistivity of the seafloor increases significantly in the presence of gas hydrates or free gas, marine controlled-source electromagnetics (CSEM) is a suitable method for the investigation of hydrates. We have collected CSEM data in a channel-levee system of the Danube paleo-delta (Bulgarian sector) at water depths of about 1500 m. The working area is within the gas hydrates stability zone and seismics suggests the presence of gas hydrates. The CSEM data were acquired with stationary receivers and a novel mobile, dual polarization transmitter system, and interpreted in terms of rotational invariants by means of 1-D inversions at common midpoints (CMP) to generate pseudo 2D resistivity sections. The inversion results reveal two resistive layers at shallow depths of 60–120 mbsf and greater depths of 270–400 mbsf. A comparison with seismics shows a good correlation of the shallow layer with high amplitude reflections and a velocity anomaly. The deeper layer can be tied to the current bottom simulating reflector (BSR). The comparison to a second CSEM experiment, which was conducted by the BGR (Federal Institute for Geosciences and Natural Resources, Germany) shows a good agreement of the derived sections down to a depth of about 350 m. Based on salinity and porosity models derived from boreholes in the Black Sea, we apply Archie's law to estimate potential gas hydrate saturations of up to 23% for the shallow resistor and up to 7% for the deeper layer. Differences are evident at depths greater than 450 m, where we see a conductive layer not evident in the BGR section. This deeper conductor could be evidence for increasing salinities of pore fluids at greater depths, which were previously found in DSDP drilling cores.

Design and implementation of DP-DQPSK DWDM transmission system by using direct detection

Designing a system that guarantees both the lower cost implantation, lower complexity on the receiver station side and higher data rate was an essential topic for several researchers recently, in which several methods and approaches were proposed to handle these problems individually and with the best overall outcome. In this work, these problems would be considered by designing and analyzing a novel system based on the combination of Dual Polarization Differential Quadrature Phase Shift Keying (DP-DQPSK) and Dense Wavelength Division Multiplexing (DWDM) technique and by using the Direct Detection (DD) technique. The system was designed with Optisystem software 18 and consist of 64 channels and each channel could transmit 14 Gbps of data rate. The channels 1,6,12,18,24,30,36,42,48,54,60 and 64 were selected as samples among all channels to be investigated and analyzed. Additionally, the proposed system was investigated based on different distances and different parameters of Quality Factor (QF) and Bit Error Rate (BER). The significant contribution of the proposed system is that using the DD would result in a no-required for reference wave and that will result in a less complex system and easier to implement. Results obtained indicate higher quality QF for the sampled channel and lower BER values. For instance, the average QF obtained were in the range of 6.75-8.36 dBm and 6.77-8.35 dBm for data 1 and 2 respectively, which indicates the reliability and efficiency of the proposed system by considering all results obtained from distance variation were above the minimum threshold

A Detection and Weakening Method for GNSS Time-Synchronization Attacks

In human society, the normal operation of important infrastructures, such as the power system, communication system, and computer network depend on the precise time provided by stationary satellite timing receivers, which are vulnerable to a kind of spoofing interference called time-synchronization attack. The aim of the attacks is to change the time provided by receivers to other systems, resulting in system disorders. This paper presents a time-synchronization attack detection and weakening method to solve this problem. The proposed method can estimate the binomial model parameters of receiver clock bias and the clock bias attack values at all observation instants by solving an optimization problem. Once the existence of the attacks is detected, the estimated clock bias attack values are used to correct the clock bias, so as to weaken the time-synchronization attacks. According to the numerical simulation results and analysis, we find that the proposed method outperforms other algorithms mentioned in this paper. Because it can not only realize real-time detection, but also greatly weaken the impact of time-synchronization attacks, making the attacks almost invalid.

On Russian Farms, the Robotic Revolution Has Begun: Hundreds of Aftermarket AIs are Harvesting Grain

THE FIELD OF AUTOMATED precision agriculture is based on one concept-autonomous driving technologies that guide vehicles through GPS navigation. Fifteen years ago, when high-accuracy GPS became available for civilian use, farmers thought things would be simple: Put a GPS receiver station at the edge of the field, configure a route for a tractor or a combine harvester, and off you go, dear robot! · Practice has shown, however, that this kind of carefree field cultivation is inefficient and dangerous. It works only in ideal fields, which are almost never encountered in real life. If there's a log or a rock in the field, or a couple of village paramours dozing in the rye under the sun, the tractor will run right over them. And not all countries have reliable satellite coverage-in agricultural markets like Kazakhstan, coverage can be unstable. This is why, if you want safe and efficient farming, you need to equip your vehicle with sensors and an artificial intelligence that can see and understand its surroundings instead of blindly following GPS navigation instructions.

Green morays (Gymnothorax funebris) have sedentary ways in mangrove bays, but also ontogenetic forays to reef enclaves

Surprisingly, little is known about basic life history of the largest moray eel species in the Caribbean region, the green moray eel (Gymnothorax funebris). Sixteen eels were captured from the mangrove fringe in multiple bays on St. Croix, USVI, implanted with coded acoustic transmitters, and their movements were tracked for up to 11 months using an array of 37 stationary acoustic receivers. They exhibited high site fidelity in the bays during their residence, using the same general parts of individual bays and did not switch bays except for one individual. There was no relationship between eel size (mean TL = 83 cm, range = 54–126 cm) and home range size (mean area of 95% KUD = 5.8 ha ± 0.7 SE). Most individuals were more frequently detected at night than during the day suggesting greater nocturnal activity. Several of the larger eels (mean TL = 93 cm ± 5.9 SE) showed clear and permanent emigration tracks out of the mangrove estuary to coral reef habitats offshore. For some individuals, these habitat shifts were preceded by exploratory movements away from the eel’s typical home range the night before emigration. All final emigration events took place nocturnally, happened during a single night, and occurred during months from December to May. Mean emigration speed was 3.4 km/h. This study is the first documentation of an ontogenetic habitat shift in moray eels, as well as the first determination of home range size for this species and their site fidelity in mangrove habitats.

Multi-run migratory behavior of adult male lake sturgeon in a short river

Lake sturgeon (Acipenser fulvescens) can migrate long distances to spawn, but many populations currently spawn in systems where the length of accessible riverine migratory habitat has been greatly reduced by dam construction. With the increased prevalence of shortened rivers, focusing on migratory dynamics in short rivers (<30 km) is beneficial to understanding the migratory needs of lake sturgeon populations. Here we document male lake sturgeon movements during the spawning period in the Winooski River, Vermont, USA; a river with only 17 km to the first natural upstream barrier. Male lake sturgeon were acoustically tagged (n = 25, 1215–1470 mm TL) and tracked using five to nine stationary receivers from 2017 to 2019. River discharge, temperature, the lagged effect of temperature (3-day), and time of day were significant factors describing upstream movements of tagged fish. Migrating male lake sturgeon (n = 10 in 2017, n = 18 in 2018, and n = 17 in 2019) displayed general movement patterns during the spawning period that included a single run upstream to the spawning site (60%), upstream and downstream movements throughout the river during the season (20%), or multiple runs made up the entire length of the spawning tributary to the spawning site (20%). No multi-run males were observed during 2018 when discharge was less flashy (i.e., fewer steep increases and declines in discharge) than in 2017 and 2019. These results suggest that the prevalence of multi-run spawning behavior of male lake sturgeon is related to flow conditions.

Conceptual scenarios for development of ground infrastructure for receiving mission payload data from a perspective Earth remote sensing satellite constellation

The paper addresses the problem of cooperative development of ground space infrastructure and orbital constellation of Earth remote sensing spacecraft (ERS). In view of the considerable number of elements in space and ground segments of a heterogenous space ERS system, a mechanism is required for developing its concepts involving acquiring updated inputs for determining measures to optimize the ERS ground segment configuration geography-wise and outfit receiving systems for receiving the mission payload data from high-performance ERS spacecraft. The paper describes trends in the development of equipment and technologies for transmitting ERS mission payload data, in particular, the current status of the high data rate optical backbone network in order to determine possible locations for ERS Ground Segment elements. It introduces indicators which provide system-level characterization of the capabilities for a distributed network of data receiving stations. Based on the obtained data, system-level patterns were determined in the development of the ground segment for receiving the ERS mission payload data depending on the state of the ERS orbital constellation, driving further development of growth strategy for the ERS ground space infrastructure. Key words: Earth remote sensing, concept, mission payload data, receiving system, data reception station.

Nonuniform SINR+Voronoi diagrams are effectively uniform

This paper concerns the behavior of an SINR diagram of wireless systems, composed of a set S of n stations embedded in Rd, when restricted to the corresponding Voronoi diagram imposed on S. The diagram obtained by restricting the SINR zones to their corresponding Voronoi cells is referred to hereafter as an SINR+Voronoi diagram.Uniform SINR diagrams, where all stations transmit with the same power, are simple and nicely structured, e.g., the station reception zones are convex and “fat”. In contrast, nonuniform SINR diagrams might be complex; the reception zones might be fractured and their boundaries might contain many singular points. In this paper, we establish the perhaps surprising fact that a nonuniform SINR+Voronoi diagram is topologically almost as nice as a uniform SINR diagram. In particular, it is convex and effectively5 fat. This holds for every power assignment, every path-loss parameter α and every dimension d≥1. The convexity property also holds for every SINR threshold β>0, and the effective fatness property holds for any β>1. These fundamental properties provide a theoretical justification to engineering practices basing zonal tessellations on the Voronoi diagram, and help to explain the soundness and efficacy of such practices.We also consider two algorithmic applications. The first concerns the Power Control with Voronoi Diagram (PCVD) problem, where given n stations embedded in some polygon P, it is required to find the power assignment that optimizes the SINR threshold of the transmission station si for any given reception point p∈P in its Voronoi cell ▪. The second application is approximate point location; we show that for SINR+Voronoi zones, this task can be solved considerably more efficiently than in the general non-uniform case.

Ramalan Pelemahan Hujan di Malaysia Menggunakan Data TRMM

Rainfall is observed as a main contributing factor in the degradation of electromagnetic signal for frequency above 10GHz through absorption and scattering, resulting a weak or fading signal. Broadcasting satellite service operates in Ku band (12GHz to 18GHz) is widely used has caused congestion, therefore Ka band is exploited to meet the customer demand. However, the rain attenuation effects on Ka band are higher than Ku band. In this study, the rain attenuation effects of Ka band downlink signal of the Measat-5 satellite are analysed to assess the rain fade properties using TRMM 3B42 data for eleven (11) years from January 2009 until December 2019 for fourteen study areas. All data are processed to obtain 1-minute integration data using Segal Model and the prediction of rain attenuation are implemented using ITU-R P.618-13 model. This study summarizes, there are three, (3) main factors that influence the impact of rain attenuation, namely the value of specific attenuation, receiver station altitude and elevation angle of the satellite signal receiver antenna. The signal availability impact on rain attenuation shows, eight (8) study areas could receive 99.90% of service readiness, while the rest at 99.00% to comply with the ITU unavailability requirements. Overall, the value of rain attenuation on the West Coast of Peninsular Malaysia is smaller than the East Coast of Peninsular Malaysia and the value of rain attenuation in the East Coast of Peninsular Malaysia is closer to the value of rain attenuation in Sabah and Sarawak.

Real-time frequency transfer system over ground-to-satellite link based on carrier-phase compensation at 10−16 level* *Project supported by the National Key Research and Development Program of China (Grant No. 2016YFA0302101) and the Initiative Program of State Key Laboratory of Precision Measurement Technology and Instruments.

We demonstrate a novel and stable frequency transfer scheme over ground-to-satellite link based on real-time carrier-phase detection and compensation. We performed a zero-baseline measurement with the designed system, an uninterrupted frequency standard signal is recovered in the reception station without additional post-correction of delay error caused in the route, which is because the phase error of the entire route is tracked and compensated continuously in real-time. To achieve this goal, we employed two carriers in the system and the differential signal is transferred in order to eliminate the instability results from the local oscillator at the satellite transponder as well as the common-mode noise induced in the transfer route and microwave components. The stability of 3 × 10−16 with an integration time of 1 day was achieved and the time fluctuation during one day was measured to be about ±20 ps. Error sources and possible solutions are discussed. Our zero-baseline method shows a promising result for real-time satellite-based time and frequency transfer and deserves further research to find whether it works between long-baseline stations.

Linear aplanatic Fresnel reflector for practical high-performance solar concentration

We propose the linear aplanatic Fresnel reflector (LAFR) as a novel optical design that is suitable for solar thermal power plants. It comprises a segmented primary reflector and a totally stationary secondary mirror and receiver. We show that it is capable of attaining the high intercept factors of conventional parabolic troughs at high concentration, while offering the practical and lower-cost benefits of linear Fresnel reflectors. The fact that dual-mirror Fresnel concentrators can be aplanatic had been overlooked, mainly due to the perception that Fresnel concentrators offer only one degree of design freedom (specifically, the shape of the secondary mirror). The problem is that the two leading orders of geometric aberration must be eliminated to achieve aplanatism, and hence two degrees of design freedom are necessary. After identifying the solar tracking strategy of the segmented primary reflector as the additional degree of design freedom, we derive analytic relations for its placement and curvature. The secondary mirror shape follows directly from the basic aplanatic formalism. We demonstrate that practical high-performance LAFR designs can achieve intercept factors as high as 0.84 at concentration values of ~26.

X-Ray Solar Flares Observed and Detected by The New Very-Low-Frequency Receiver in Nasiriyah City, South of Iraq

A receiver station was installed at Nasiriyah (Dhi Qar University - Faculty of Sciences) to receive very low frequency (VLF) radio signals from transmitters around the world. VLF waves are excellent probes of the sudden ionospheric disturbance (SID); they detect varying properties of the D layer presented as a lower region of the ionosphere when these waves propagate through the Earth-Ionosphere Waveguide. This study describes the set-up of our station system and it demonstrates its ability to detect sudden ionospheric disturbances caused by solar flares in May, June, July, August, and September 2017. We found out that the monitoring station is working successfully to receive FLV signals, and to detect sudden ionospheric disturbances. We detected 17 events resulting from solar flare C-class, 8 events from M-class, and 3 events from X-class that caused an increase in the received FLV amplitude.

Improving Accuracy of Source Localization Algorithms Using Kalman Filter Estimator

Passive geolocation of emitters provides benefits to military and civilian surveillance and in the field of aerospace. Passive geolocation can be done by exploiting some of the parameters of the signal transmitted by the source or emitter. In this paper the Time Difference Of Arrival (TDOA) of the signal at different receivers is used to estimate the position of the emitter. This paper aims at presenting the research for the development of an algorithm which can be used in a distributed network of acoustic sensors consisting of an emitter and five stationary receivers. By means of measurement of time difference of arrival of underwater acoustic signal the source position is estimated using three different algorithms. Taylor series, closed form and two stage weighted least square methods are used to estimate the stationary source location by TDOAmeasurements of received signal and compared on the basis of Cramer Rao Lower Bound (CRLB). Comparison of performance between these methods are done and analysed.Use of a kalman filter is proposed to improve the accuracy of all the three methods and the results are compared and analysed.