Scintillation Data Research Articles

SSLG4: A novel scintillator simulation library for Geant4

This study introduces a new Scintillator Simulation Library called SSLG4 for the Geant4 Monte Carlo simulation package. With SSLG4, we aim to enhance efficiency and accelerate progress in optical simulations within the Geant4 framework by simplifying scintillator handling and providing a rich repository of scintillators. The SSLG4 enables users to quickly include predefined scintillator materials in their simulations without requiring manual definition. The library initially contains 68 scintillators, consisting of 58 organic and 10 inorganic types. Most of these scintillators are selected from the catalogs of several scintillator manufacturers, notably Eljen and Luxium. Other scintillators are included based on their widespread use across various physics domains. The library stores optical data of scintillators in ASCII files with .mac and .txt extensions, enabling users to add, remove, or modify properties of scintillators at runtime of their applications. In addition, we made all the scintillator data available in the library on a dedicated page of our website to ensure convenient access for all users. Program summaryProgram title: SSLG4CPC Library link to program files:https://doi.org/10.17632/3zbwr5wf7z.1Developer's repository link:https://github.com/mkandemirr/SSLG4, https://neutrino.erciyes.edu.tr/SSLG4/Licensing provisions: GNU General Public License 3Programming language: C++External routines/libraries: Geant4, CMake, OPSimNature of problem: Defining a new scintillator in Geant4 is a cumbersome process for some users due to three main reasons: (1) It requires a lot of data input from users, (2) collecting the scintillator data requires an extensive literature review, and (3) the collected data needs to be converted into the desired format. In addition, the interfaces provided to define a scintillator direct users to embed scintillator data into their source code, resulting in increased code complexity, reduced code readability, and an inefficient working environment.Solution method: To solve the problems mentioned above, developing and introducing a new library consisting of fully parameterized and ready-to-use scintillators would greatly increase the useability of the Geant4 simulation package for scintillator studies and interest a wide range of scientific communities.

On the properties of lower mid-latitudes ionospheric scintillation observed over Chengdu, China

Low and high-latitude ionospheric scintillations are well-documented, but data on lower mid-latitude scintillations are scarce. Moreover, there is limited public reporting for the Chengdu station, which makes the data for the consecutive three years particularly valuable. This paper analyzes three years of ionospheric scintillation data from Chengdu and compares it with Chongqing. GNSS receivers in Chengdu (104.07°E, 30.67°N) and Chongqing (106.55°E, 29.57°N) recorded the data from 2018 to 2020. A custom data processing program for GPS/BDS/Galileo monitors was used. Results show diurnal and seasonal variations in the occurrence rate (OR) of scintillation events, with higher OR in spring and autumn, predominantly at night. There is a positive correlation between the annual OR of weak, moderate, and strong scintillations. Besides, moderate scintillation and strong scintillation events mainly occur at azimuth angles of 30°-90°, 150°-210°, and 300°-330° due to the aspect sensitivity of ionospheric irregularities. Solar activity, mesospheric winds, and ionospheric tides also influence scintillations. Notably, intense events were observed in May 2018(a year of low solar activity) due to post-sunset occurrences influenced by neutral wind and ionospheric tides, suggesting that in addition to solar radiation, neutral wind and ionospheric tides may serve as substantial driving mechanisms for ionospheric scintillation. This study provides a reference for the construction of a scintillation prediction in lower mid-latitudes.

GOLD plasma bubble observations comparison with geolocation of plasma irregularities by back propagation of the high-rate FORMOSA7/COSMIC 2 scintillation data

GOLD plasma bubble observations comparison with geolocation of plasma irregularities by back propagation of the high-rate FORMOSA7/COSMIC 2 scintillation data

On-Stream Pipe Scale Inspection Using Gamma-Ray Tomography Technique: Field Experiment in Karaha Geothermal Power Plant, Indonesia

Pipe scaling is a common problem in geothermal power plants. Currently, the pipeline withinside the Karaha Telaga Bodas geothermal subject is indicated to incorporate scale because of pressure anomalies. On-stream pipe scale inspection techniques are needed to maintain the production process. This research aims to apply the gamma-ray transmission tomography technique to pipelines in geothermal fields. The gamma-ray tomography system consists of a 137Cs (2.96 GBq) gamma radiation source, a scintillation detector, mechanical parts, control parts, and data acquisition. Scanning was performed at three predetermined points: brine pipe 1, two-phase pipe, and brine pipe 2. The system scans half of the pipe circumference (180°) and divides it into 32 projections (5.625°). Each projection performs a translational scan with a resolution of 4 mm. Three cross-sectional images of the pipe were obtained, showing the inside condition. Pipe scale was observed at three scanning points with a thickness of 12 mm-48 mm. Gamma tomography can potentially be a tool for examining pipe scale thickness in geothermal fields. The use of a single detector is a limitation that needs to be improved. Apart from that, the stability of the control and mechanical parts must also be improved.

Investigation of Ionospheric Small‐Scale Plasma Structures Associated With Particle Precipitation

AbstractWe investigate the role of auroral particle precipitation in small‐scale (below hundreds of meters) plasma structuring in the auroral ionosphere over the Arctic. In this scope, we analyze together data recorded by an Ionospheric Scintillation Monitor Receiver (ISMR) of Global Navigation Satellite System (GNSS) signals and by an All‐Sky Imager located in Longyearbyen, Svalbard (Norway). We leverage on the raw GNSS samples provided at 50 Hz by the ISMR to evaluate amplitude and phase scintillation indices at 1 s time resolution and the Ionosphere‐Free Linear Combination at 20 ms time resolution. The simultaneous use of the 1 s GNSS‐based scintillation indices allows identifying the scale size of the irregularities involved in plasma structuring in the range of small (up to few hundreds of meters) and medium‐scale size ranges (up to few kilometers) for GNSS frequencies and observational geometry. Additionally, they allow identifying the diffractive and refractive nature of fluctuations on the recorded GNSS signals. Six strong auroral events and their effects on plasma structuring are studied. Plasma structuring down to scales of hundreds of meters is seen when strong gradients in auroral emissions at 557.7 nm cross the line of sight between the GNSS satellite and receiver. Local magnetic field measurements confirm small‐scale structuring processes coinciding with intensification of ionospheric currents. Since 557.7 nm emissions primarily originate from the ionospheric E‐region, plasma instabilities from particle precipitation at E‐region altitudes are considered to be responsible for the signatures of small‐scale plasma structuring highlighted in the GNSS scintillation data.

Automatic GNSS Ionospheric Scintillation Detection with Radio Occultation Data Using Machine Learning Algorithm

Ionospheric scintillation often occurs in the polar and equator regions, and it can affect the signals of the Global Navigation Satellite System (GNSS). Therefore, the ionospheric scintillation detection applied to the polar and equator regions is of vital importance for improving the performance of satellite navigation. GNSS radio occultation is a remote sensing technique that primarily utilizes GNSS signals to study the Earth’s atmosphere, but its measurement results are susceptible to the effects of ionospheric scintillation. In this study, we propose an ionospheric scintillation detection algorithm based on the Sparrow-Search-Algorithm-optimized Extreme Gradient Boosting model (SSA-XGBoost), which uses power spectral densities of the raw signal intensities from GNSS occultation data as input features to train the algorithm model. To assess the performance of the proposed algorithm, we compare it with other machine learning algorithms such as XGBoost and a Support Vector Machine (SVM) using historical ionospheric scintillation data. The results show that the SSA-XGBoost method performs much better compared to the SVM and XGBoost models, with an overall accuracy of 97.8% in classifying scintillation events and a miss detection rate of only 12.9% for scintillation events with an unbalanced GNSS RO dataset. This paper can provide valuable insights for designing more robust GNSS receivers.

Equinoctial asymmetry of plasma bubble occurrence and electric field at evening: GPS and ionosonde measurements in Southeast Asia

We have investigated equinoctial asymmetry of scintillation occurrence and zonal irregularity drift velocity observed with closely-spaced GPS receivers at Kototabang (0.20°S, 100.32°E; geomagnetic latitude 10.6°S), Indonesia during a period from 2003 to 2016, and found that the scintillation occurrence rate is higher in Mar. equinox than in Sep. equinox, and that the eastward drift velocity at post-sunset is higher in Mar. equinox than in Sep. equinox. This result is consistent with previous work done by Otsuka et al. (2006), who have analyzed scintillation and zonal drift velocity data obtained at Kototabang in 2003–2004, and suggests that the eastward drift velocity corresponding to the downward electric field at post-sunset may be related to the pre-reversal enhancement of eastward electric field, which could play an important role in generating plasma bubble. In this study, we have investigated vertical drift velocity by analyzing the ionosonde data obtained near magnetic equator (Chumphon, Bac Lieu, and Cebu) during a period from 2003 to 2016, and found that the upward drift velocity at post-sunset is larger in Mar. equinox than Sep. equinox. We also find that solar activity dependence of the zonal and vertical drift velocities is more clearly seen in Mar. equinox than in Sep. equinox. In order to consider the mechanism causing the equinoctial asymmetry of the drift velocities, foF2 obtained by the ionosondes is also analyzed. We find that foF2 also depends on solar activity more clearly in Mar. equinox than in Sep. equinox, and that foF2 during high solar activity conditions is higher in Mar. equinox than in Sep. equinox. These results suggest that in Mar. equinox, due to high electron density, intense electric field could be generated through the F-region dynamo so that plasma bubble likely occurs.

Statistical Uncertainty in the Frequency Dependence of the Intensity Scintillation Index (S4)

AbstractThe intensity scintillation index (S4) exhibits a linear frequency dependence derived from a power law phase screen model, with the exponent determined by the phase spectral index (p). However, it is well known that a departure from linearity occurs as S4 increases and saturates under strong scatter conditions. Additionally, statistical errors over a finite time window can also cause the scintillation statistic to deviate from the power law dependence on frequency. This paper presents a parametric analysis on the deviation in the S4 frequency dependence from the power law form. This investigation focuses on the contribution of statistical uncertainty in S4 calculations to the deviation in the frequency dependence according to the selected parameters: S4 and Fresnel frequency (fF). The deviation is determined by comparing p estimates calculated from the power law relationship of S4 at different L‐band frequencies with those inferred from a model‐fitting method using a multi‐frequency global navigation satellite system scintillation data set. The results show the well‐known departure from linearity as S4 increases, and reveal increasing deviations with decreasing fF. The spectral analysis indicates that the variability at the lowest frequencies of intensity spectra contributes to the statistical errors in S4 calculations due to the finite time window, particularly when scintillations are dominated by low‐frequency contributions at low fF. Simulation results of scintillation realizations show much lower deviations with a 30‐min compared to 1‐min window. This suggests a 1‐min window can be too short for reliable S4 calculations due to statistical uncertainty, especially at low fF.

Turbulent fluxes at kilometer scale determined by optical-microwave scintillometry in a heterogeneous oasis cropland of the Heihe River Basin

Observations of kilometer-scale turbulent fluxes of sensible (H) and latent heat (LE) are required for the validation of flux estimate algorithms from satellite remote-sensing data and the development of parameterization schemes in the hydro-meteorological models. Since 2019, two sets of Optical and Microwave scintillometer (OMS) systems have been operated in the Heihe River Basin of northwestern China, one on an alpine grassland of upper reaches, another on an oasis cropland of middle reaches, to measure both the areal H and LE. Combined with the observations of eddy-covariance (EC) and meteorological tower systems in both sites, an improved procedure for OMS data processing is proposed. The newly proposed procedure especially improves the preprocessing of raw scintillation data, properly uses the current probably better Lüdi et al. (2005) method in deriving meteorological structure parameters, and chooses the coefficients of similarity functions by Kooijmans and Hartogensis (2016) in calculating fluxes. Evaluated with the results of rather homogeneous grassland, the area-averaged H and LE over the heterogeneous oasis are then determined. Estimates of H and LE agree reasonably well with those obtained from EC in most cases. However, the most interesting is that LE over the oasis during the early crop growing stages is clearly larger than that of EC; while both agree well during the longer crop grown periods. Footprint analysis shows that, compared with EC, the OMS has clearly larger source area that contains a slight area of orchard and shelterbelts distributed near the light path, leading to larger LE during the early stages of crop growth. The area-averaged evapotranspiration (ET) over the oasis is then analyzed more acceptably, which varies from 3 to 5 mm day−1 depending on meteorological conditions during the 39 days of the crop growing period. These results are used to validate the Penman-Monteith-Leuning Version 2 (PML-V2) scheme.

Irregularities Observed at the Edge of a Mid‐Latitude Ionospheric Depletion Following a Geomagnetic Storm

AbstractThis manuscript presents the analysis of data from multiple ground‐ and space‐based sensors in the North American region before, during, and after the 12 October 2021 geomagnetic storm. Total electron content (TEC) and electron density data show the formation and equatorward propagation of a mid‐latitude trough at ∼50°N followed by the appearance of a wider depletion region (∼15° in latitude) at lower latitudes. During the recovery phase on the 13th, the equatorward edge of this depletion region settled at around 30° latitude and exhibited a steep density gradient. By the 14th, this sharp boundary had disappeared. Near this edge on the 13th, small‐scale irregularities formed. The impact of these was observed within Global Positioning System data as elevated rate of TEC index (ROTI) and presented as strong 35 MHz scintillations of cosmic radio sources as well as spread‐F within ionograms from multiple digisonde systems. GPS and 35‐MHz data demonstrated that the irregularity region was narrowly confined (≲5° wide) near the edge of the depletion region. The 35‐MHz scintillation data also showed that the irregularities were moving relatively slowly at ∼7 m s−1, likely toward the southeast. Density and velocity measurements demonstrated that the conditions near the depletion boundary were highly favorable to the gradient drift instability (GDI) with the one‐dimensional growth rate estimated to be ∼0.01 s−1. Since these conditions persisted for many hours, this growth rate was more than sufficient for the GDI to be considered the primary driver of irregularity formation in this case.

Forecasting Heliospheric CME Solar-Wind Parameters Using the UCSD Time-Dependent Tomography and ISEE Interplanetary Scintillation Data: The 10 March 2022 CME

Remotely sensed interplanetary scintillation (IPS) data from the Institute for Space-Earth Environmental Research (ISEE), Japan, allows a determination of solar-wind parameters throughout the inner heliosphere. We show the 3D analysis technique developed for these data sets that forecast plasma velocity, density, and component magnetic fields at Earth, as well at the other inner heliospheric planets and spacecraft. One excellent coronal mass ejection (CME) example that occurred on the 10 March 2022 was viewed not only in the ISEE IPS analyses, but also by the spacecraft near Earth that measured the CME arrival at one AU. Solar Orbiter, that was nearly aligned along the Earth radial at 0.45 AU, also measured the CME in plasma density, velocity, and magnetic field. BepiColombo at 0.42 AU was also aligned with the STEREO A spacecraft, and viewed this CME. The instruments used here from BepiColombo include: 1) the European-Space-Agency Mercury-Planetary-Orbiter magnetic field measurements; 2) the Japan Aerospace Exploration Agency Mio spacecraft Solar Particle Monitor that viewed the CME Forbush decrease, and the Mercury Plasma Experiment/Mercury Electron Analyzer instruments that measured particles and solar-wind density from below the spacecraft protective sunshield covering. This article summarizes the analysis using ISEE, Japan real-time data for these forecasts: it provides a synopsis of the results and confirmation of the CME event morphology after its arrival, and discusses how future IPS analyses can augment these results.

Studies and optimization of scintillation light measurements for the development of the 3-gamma medical imaging XEMIS2 liquid xenon Compton camera

We report the studies and optimization of scintillation light measurements in an updated version of the XEMIS1 prototype for the development of the XEMIS2 camera. A novel monolithic liquid xenon Compton camera, named XEMIS2 (XEnon Medical Imaging System), attempts to achieve low-activity small-animal imaging using the 3-gamma imaging technique. This emerging detector relies on the time projection chamber technique: it will be able to perform a simultaneous detection of the three γ -rays emitted by a specific radionuclide, such as scandium-44, and to produce a good quality image with a remarkable diminution of radiopharmaceutical activity at the same time. Vacuum Ultraviolet (VUV) scintillation light and ionization charge carriers generated from the recoiling particles within the detector are detected and used to reconstruct the interaction position and deposited energy. A cost-effective self-triggering scintillation signal read-out and data acquisition (DAQ) system has been developed to achieve a continuous data read-out with negligible electronics dead time. The DAQ prototype has been installed and qualified in an updated version of the XEMIS1 detector. It reaches the performance specifications in scintillation light measurements. Moreover, scintillation signals can also be used for the virtual segmentation of the monolithic detection volume through the matching algorithm of the scintillation and ionization signals based on the light collection map (LCM). This spatial pre-localization of the physical events, called the virtual fiducialization of the active volume, is used to lower the detector occupancy rate when the administered activity is increased to lessen the examination time. The XEMIS1 experimental LCMs indicate that each PMT owns an individual field of view so as to segment the active volume virtually. The preparation work for the XEMIS2 camera operation has been completed in the updated XEMIS1 detector while the XEMIS2 scintillation light measurement system is under commissioning in Nantes Centre Hospitalier Universitaire. • The XEMIS2 camera oriented to the whole-body small animal 3-gamma medical imaging is presented. • The XEMIS2 system is a monolithic liquid xenon Compton camera with a 24 cm axial field of view. • A dedicated cost-effective 16-channel self-triggering scintillation signal front-end read-out electronics called XSRETOT is described. • The experimental light collection maps of an updated version of the XEMIS1 detector have been built, which can be used for the virtual segmentation of the monolithic detection volume to reduce the detector occupancy rate in the context of increasing the administered activity.

Ionospheric Scintillation Mitigation With Kalman PLLs Employing Radial Basis Function Networks

We investigate two adaptive Kalman phase locked loop (PLL) structures for ionospheric scintillation mitigation for global navigation satellite systems (GNSS) receivers, employing radial basis function (RBF) networks to model the scintillation phase and amplitude, instead of the typically employed autoregressive (AR) models. In the first structure, the Kalman filter innovations are computed by the arctangent phase discriminator, and the state estimates are directly employed in the carrier replica generation. In the second structure, the Kalman filter measurements are the prompt correlator outputs, and the error states are computed and used by a state feedback controller to provide a control signal to drive the carrier replica generation. The nonlinear RBFs provide more flexibility to capture nonlinear dynamics evolving with time, possibly present in the scintillation phase and amplitude. The weights of the RBF networks and the covariance matrices of the process and measurement noise of the Kalman filters are estimated online, in the adaptive Kalman PLL structures. Simulations with synthetic severe scintillation data show the capability of the proposed Kalman PLLs to improve robustness to scintillation effects in carrier synchronization, with performance similar to the corresponding structures employing AR scintillation models. Simulations using recorded scintillation data collected by a commercial receiver highlight the learning and generalization capability of the RBF networks to cope with evolving scintillation characteristics over time with possibly nonlinear effects. The Kalman PLL structures employing the RBF networks present reduced errors compared to the structures using AR models.

Analysis and Characterization of an Unclassified RFI Affecting Ionospheric Amplitude Scintillation Index Over the Mediterranean Area

Radio Frequency (RF) signals transmitted by Global Navigation Satellite Systems (GNSS) are exploited as signals of opportunity in many scientific activities, ranging from sensing waterways and humidity of the terrain to the monitoring of the ionosphere. The latter can be pursued by processing the GNSS signals through dedicated ground-based monitoring equipment, such as the GNSS Ionospheric Scintillation and Total Electron Content Monitoring (GISTM) receivers. Nonetheless, GNSS signals are susceptible to intentional or unintentional RF interferences (RFIs), which may alter the calculation of the scintillation indices, thus compromising the quality of the scientific data and the reliability of the derived space weather monitoring products. Upon the observation of anomalous scintillation indices computed by a GISTM receiver in the Mediterranean area, the study presents the results of the analysis and characterization of a deliberate, unclassified interferer acting on the L1/E1 GNSS signal bands, observed and captured through an experimental, software defined radio setup. The paper also highlights the adverse impacts of the interferer on the amplitude scintillation indices employed in scientific investigations, and presents a methodology to discriminate among regular and corrupted scintillation data. To support further investigations, a dataset of baseband signals samples affected by the RFI is available at IEEE DataPort.

Electron density fluctuations from Swarm as a proxy for ground-based scintillation data: A statistical perspective

The Swarm satellite mission has been used for numerous studies of the ionosphere. Here we use a global product, based on electron density measurements from Swarm that characterises ionospheric variability. The IPIR (Ionospheric Plasma IRregularities product) provides characteristics of plasma irregularities in terms of their amplitudes, gradients and spatial scales and assigns them to geomagnetic regions. Ionospheric irregularities and fluctuations are often the cause of errors in position, navigation, and timing (PNT) based on the Global Navigation Satellite Systems (GNSS), in which signals pass through the ionosphere. The IPIR dataset also provides an indication, in the form of a numerical value index (IPIR index), of the severity of irregularities affecting the integrity of trans-ionospheric radio signals and hence, the accuracy of GNSS positioning. We analysed datasets from Swarm A and ground-based scintillation receivers. Time intervals (when Swarm A passes over the field of view of the ground-based GPS receiver) are compared to ground-based scintillation data, collecting an azimuthal selection of the GNSS data relevant to the Swarm satellite overpass. We provide validations of the IPIR product against the ground-based measurements from 23 ground-based receivers, focusing on GPS TEC and scintillation data in low-latitude, auroral and polar regions, and in different longitudinal sectors. We have determined the median, mean, maximum and standard deviation of the parameter values for both datasets and each conjunction point. We found a weak correlation of the intensity of both phase and amplitude scintillation with the IPIR index.

Magnetohydrodynamic simulation of coronal mass ejections using interplanetary scintillation data observed from radio sites ISEE and LOFAR

Interplanetary scintillation (IPS) is a useful tool for detecting coronal mass ejections (CMEs) throughout interplanetary space. Global magnetohydrodynamic (MHD) simulations of the heliosphere, which are usually used to predict the arrival and geo-effectiveness of CMEs, can be improved using IPS data. In this study, we demonstrate an MHD simulation that includes IPS data from multiple stations to improve CME modelling. The CMEs, which occurred on 09–10 September 2017, were observed over the period 10–12 September 2017 using the Low-Frequency Array (LOFAR) and IPS array of the Institute for Space-Earth Environmental Research (ISEE), Nagoya University, as they tracked through the inner heliosphere. We simulated CME propagation using a global MHD simulation, SUSANOO-CME, in which CMEs were modeled as spheromaks, and the IPS data were synthesised from the simulation results. The MHD simulation suggests that the CMEs merged in interplanetary space, forming complicated IPS g-level distributions in the sky map. We found that the MHD simulation that best fits both LOFAR and ISEE data provided a better reconstruction of the CMEs and a better forecast of their arrival at Earth than from measurements when these simulations were fit from the ISEE site alone. More IPS data observed from multiple stations at different local times in this study can help reconstruct the global structure of the CME, thus improving and evaluating the CME modelling.

Long-term scintillation studies of EPTA pulsars

Context. Interstellar scintillation analysis of pulsars allows us to probe the small-scale distribution and inhomogeneities of the ionized interstellar medium. From the frequency scale of scintillation, one can estimate the geometric time delays from multipath propagation, a source of (typically) unmodeled, correlated noise in pulsar timing. Interstellar scintillation analysis of well-timed pulsars is useful to quantify the effects of time delays and may lead to improved timing precision, enhancing the probability of detecting gravitational waves. Aims. Our priority is to present the data set and the basic measurements of scintillation parameters of pulsars, employing long-term scintillation observations carried out from 2011 January to 2020 August by the European Pulsar Timing Array radio telescopes in the 21-cm and 11-cm bands. Additionally, we aim to identify future possible lines of study using this long-term scintillation data set. Methods. The autocorrelation function of dynamic spectra has been used to estimate the scintillation bandwidth vd and scintillation timescale τd. Results. We present the long-term time series of vd and τd for 13 pulsars. Sanity checks and comparisons indicate that the scintillation parameters of our work and previously published works are mostly consistent. For two pulsars, PSRs J1857+0943 and J1939+2134, we were able to obtain measurements of the vd at both bands, which allowed us to derive the time series of frequency scaling indices with a mean and a standard deviation of 2.82 ± 1.95 and 3.18 ± 0.60, respectively. We found some interesting features which will be studied in more detail in subsequent papers in this series: (i) in the time series of PSR J1939+2134, where vd and τd sharply decrease associated with a sharp increase in the dispersion measure; (ii) PSR J0613-0200 and PSR J0636+5126 show a strong annual variation in the time series of the τd; and (iii) PSR J1939+2134 shows a weak anticorrelation between the scintillation timescale and the dispersion in Westerbork Synthesis Radio Telescope data.

Scintillation Effects of Ka-band Frequency on Satellite Application

The satellite communication system is currently congested because of the high demand for data transmission. The Ka-band is a greater range band that can help to solve the issue. However, Ka-band is severely impacted by scintillation at its high frequency. One of the transmitting impairments is scintillation, a sudden fluctuation in the amplitude of the signal and electromagnetic waves, that generates signal attenuation and degradation. In the presence of rain and even under clear skies, scintillation affects the output of Ka-Band. The scintillation prediction model has mostly been evaluated and applied in countries with four-season climates. The objective of this study was to evaluate the Ka-band scintillation data and compare the findings with other existing scintillation models to validate the outcome. For data of one year (2016) at the Ka-Band frequency of 20.2 GHz, this research focused on analysing the tropospheric scintillation from the satellite data. The experimental data from MEASAT 5 were analysed to see the effect of tropospheric scintillation under clear-sky conditions using a dish antenna with a diameter of 7.3 metres and an elevation angle of 68.8°. The satellite signal measurement samples were gathered and filtered using MATLAB to provide clear-sky scintillation. Next, the obtained raw data was converted into readable data. The data was then plotted, and the experimental data was compared to the other models of scintillation. It was essential to evaluate the outcome of the comparison and address which model was most appropriate for tropical climates. Moreover, this project’s cutoff frequency was 0.023Hz, which was computed from the average cut-off frequencies of 12 months in 2016.

Testbed Emulator of Satellite-to-Ground FSO Downlink Affected by Atmospheric Seeing Including Scintillations and Clouds

Free Space Optics (FSO) technology enabling next-generation near-Earth communication is prone to severe propagation losses due to atmospheric-turbulence-induced fading and Mie scattering (clouds). As an alternative to the real-time evaluation of the weather effects over optical signal, a state-of-the-art laboratory testbed for verification of slant APD-based (Avalanche Photodiode) FSO links in laboratory conditions is proposed. In particular, a hardware channel emulator representing an FSO channel by means of fiber-coupled Variable Optical Attenuator (VOA) controlled by driver board and software is utilized. While atmospheric scintillation data are generated based on Radiosonde Observation (RAOB) databases combined with a statistical design approach, cloud attenuation is introduced using Mie theory together with empirical Log-Normal modeling. The estimation of atmospheric-turbulence-induced losses within the emulated optical downlink is done with an FSO IM/DD prototype (Intensity Modulation/Direct Detection) relying on two different data throughputs using a transmitter with external and internal modulation. Moreover, the receiver under-test is a high-speed 10 Gbps APD photodetector with integrated Transimpedance Amplifier (TIA) typically installed in OGSs (Optical Ground Stations) for LEO/GEO satellite communication. The overall testbed performance is addressed by a BER tester and a digital oscilloscope, providing BER graphs and eye diagrams that prove the applied approach for testing APD-TIA in the presence of weather-based disruptions. Furthermore, the testbed benefits from the used beam camera that measures the quality of the generated FSO beam.

Statistical Analysis of Refractive and Diffractive Scintillation at High Latitudes

AbstractA comprehensive statistical analysis was performed on Global Positioning System scintillation data acquired at high latitudes from 2014 to 2017 after separating phase scintillation events originating from refraction and/or diffraction. Events exceeding a prescribed threshold were identified and analyzed statistically as a function of time, latitude, and propagation angle. The statistical analysis indicates that at high latitudes phase scintillation, which occurs more frequently than amplitude scintillation, is generated through refractive processes which can typically be treated as a stochastic Total Electron Content effect at high latitudes for Global Navigation Satellite System frequencies, and have the highest probability around magnetic noon in the Cusp. On average the phase scintillation index values decrease as a function of latitude, particularly during the first 6 hr of the evening. In addition, irregularities on the poleward side of the aurora are predominantly smaller than the Fresnel scale, when amplitude scintillation events are observed. By comparison, the mean of the phase scintillations on the equatorial side of the aurora, when amplitude scintillations are also present, indicates the existence of irregularities which are larger and smaller than the Fresnel scale. We also found that, during the day and at dusk, the spectral content of the irregularities apparently changes with decreasing off‐B Angle. No such increase is readily apparent at night or at dawn.