scholarly journals Characterization of Ionospheric Scintillation Index over Low Latitude: Nepal Region

2020 ◽  
Author(s):  
Kutubuddin Ansari ◽  
Tae-Suk Bae ◽  
Punyawi Jamjareegulgarn ◽  
Shakera Khan ◽  
Soo-Hyeon Lim
Keyword(s):  
Satellite Communication ◽  
Scintillation Index ◽  
Ionospheric Scintillation ◽  
Small Scale ◽  
Low Latitude ◽  
Rapid Phase ◽  
Global Positioning ◽  
Low Latitudes ◽  
Communication Space

The ionospheric scintillation is a rapid phase and amplitude fluctuation of satellite signals due to the small-scale irregularity of electron density in the ionosphere. The characterization of the scintillation index in a proper way is a crucial aspect of the Global Positioning System (GPS) satellite signals for the purpose of space-based navigation, satellite communication, space weather as well as earth observation applications. In the current study, we analyzed the ionospheric scintillation index during the year of 2018 to 2019 over the Nepal region which locates itself almost being sandwiched between India and China and in the vicinity of low latitudes. The characteristic variations of scintillation occurrence are studied during the several geomagnetic storm and quiet days. The results show that the S4 indexes are varying from the 0.05 to 0.45 during the whole year. The S4 indexes behave higher variations during the whole day in the starting of the year and start to decrease at end of the day as well as at the ending months of the year 2019. The S4 values become completely less during the sunset time, while they have higher values during the sunrise. Especially, the S4 index during the storm days are larger than during the quiet days. It is worthy to note that the variations of S4 index studied in this current study do not follow the sunset property during the year of 2019. Consequently, the causes should be discovered and discussed additionally in the next research paper.

Global Positioning System (GPS) Positioning Errors During Ionospheric Scintillation Event

2014 ◽  
Vol 69 (2) ◽  
Author(s):  
Y. H. Ho ◽  
S. Abdullah ◽  
M. H. Mokhtar
Keyword(s):  
Global Positioning System ◽  
Financial Services ◽  
Scintillation Index ◽  
Ionospheric Scintillation ◽  
Primary Concern ◽  
Positioning System ◽  
Positioning Error ◽  
Amplitude Scintillation ◽  
Cycle Slips ◽  
Global Positioning

As technology advancement progresses throughout the years in this modern age, every technology has its part to play in that the world is moving towards a brighter future. GPS (Global Positioning System) has diverse application in current globalized world, its application has pervasive benefits not only to navigation and positioning, it is pivotal in industries like logistics, shipping, financial services and agriculture. Since the decision to shut down the Selectivity Availability (SA) by former U.S. President, Bill Clinton, ionospheric effect is now the primary concern of error contributing factors in GPS. Ionospheric scintillation induces rapid fluctuations in the phase and the amplitude of received Global Navigation Satellite System (GNSS) signals. These rapid fluctuations or scintillation potentially introduce cycle slips, degrade range measurements, and if severe enough lead to loss of lock in phase and code. Global Ionospheric Scintillation Model (GISM) was used to compute amplitude scintillation parameter for each GPS satellite visible from Melaka, Malaysia (Latitude 20 14’ N, Longitude 1020 16’ E) as its location has strong equatorial scintillation behavior. The output data from GISM was then used to calculate the positioning error where it is depends on the Dilution of Precision (DOP) and User Equivalent Range Error (UERE). There are two schemes that were used. First, the positioning error was calculated for all the visible satellites with better DOP but worse UERE due to scintillation event. Secondly, the positioning error was calculated for those satellites that have amplitude scintillation index, S4 < 0.7 which leads to worse DOP with better UERE. Comparison of results from the both schemes was then made.

Characterization of Equatorial Low Latitude Ionospheric Scintillation of GPS Signals: An E-POP Experiment

2020 ◽  
Author(s):  
Ali Mohandesi ◽  
David Knudsen ◽  
Susan Skone
Keyword(s):  
Signal Propagation ◽  
Equatorial Region ◽  
Point Of View ◽  
High Rate ◽  
Ionospheric Scintillation ◽  
Small Scale ◽  
High Temporal Resolution ◽  
Low Latitude ◽  
Ionospheric Scintillations ◽  
Navigation Signals

&lt;p&gt;Ionospheric irregularities are a major error source in GNSS positioning and navigation as they affect trans-ionospheric signal propagation. They cause random, rapid fluctuations in the intensity and phase of the received signal, referred to as ionospheric scintillations. From a global point of view, GNSS signal scintillations are more severe and frequent in the equatorial region and during post-sunset hours. Characterizing irregularities that interfere most with navigation signals requires high-temporal resolution of measurements. In this work we utilize high-rate upward-looking measurements accomplished by the GAP RO receiver on CASSIOPE (Swarm Echo) satellite to study GPS signal scintillations and irregularities associated with them. This was done by reorienting CASSIOPE by approximately 90 degrees for short periods during November and December, 2019 while it passed through low-latitude region during post-sunset hours local time. High-rate GAP RO measurements provide a unique opportunity to investigate small-scale irregularities that are responsible for signal scintillations.&lt;/p&gt;

scholarly journals Mesospheric gravity wave characteristics and identification of their sources around spring equinox over Indian low latitudes

2016 ◽  
Vol 9 (1) ◽  
pp. 93-102 ◽  
Author(s):  
M. Sivakandan ◽  
I. Paulino ◽  
A. Taori ◽  
K. Niranjan
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Longwave Radiation ◽  
Small Scale ◽  
Low Latitude ◽  
Wave Characteristics ◽  
Spring Equinox ◽  
Low Latitudes ◽  
Charged Couple Device ◽  
Wave Properties

Abstract. We report OI557.7 nm night airglow observations with the help of a charged-couple device (CCD)-based all-sky camera from a low-latitude station, Gadanki (13.5° N; 79.2° E). Based on the data collected during March and April over 3 years, from 2012 to 2014 (except March 2013), we characterize the small-scale gravity wave properties. During this period, 50 gravity wave events were detected. The horizontal wavelengths of the gravity waves are found to ranging from 12 to 42 km with the phase velocity 20–90 m s−1. In most cases, these waves were propagating northward with only a few occurrences of southward propagation. In the present novel investigation from the Indian sector, each of the wave events was reverse-ray-traced to its source. The outgoing longwave radiation (OLR) suggested that tropospheric convection was a possible source for generation of the observed waves. It was found that approximately 66 % of the events were triggered directly by the convection.

scholarly journals PERBANDINGAN KARAKTERISTIK AKTIVITAS SINTILASI IONOSFER DI ATAS MANADO, PONTIANAK DAN BANDUNG DARI DATA PENERIMA GPS (CHARACTERISTICS COMPARISON OF IONOSPHERIC SCINTILLATION ACTIVITIES OVER MANADO, PONTIANAK AND BANDUNG BASED ON GPS RECEIVER DATA)

2017 ◽  
Vol 14 (2) ◽  
pp. 1
Author(s):  
Sri Ekawati ◽  
Sefria Anggarani ◽  
Dessi Marlia
Keyword(s):  
Satellite Communication ◽  
Geomagnetic Latitude ◽  
Scintillation Index ◽  
Ionospheric Scintillation ◽  
Signal Quality ◽  
Gps Receiver ◽  
Band Frequency ◽  
Satellite Navigation System ◽  
Satellite Signal

Ionospheric scintillation activity on certain region need to be known its characteristics since its occurrence can degrade satellite signal quality of global satellite navigation system (GNSS) and also satellite communication that works at L-band frequency. The occurrence of ionospheric scintillation varies with location. Therefore, this paper aimed to determine comparative charasteristics of ionospheric scintillation activity over Manado, Pontianak and Bandung from amplitude scintillation index S4 data derived from GPS receiver. The data obtained from the GPS Ionospheric Scintillation and TEC Monitor (GISTM) at Manado station (1.48o N; 124.85oE geomagnetic latitude 7.7oS), at Pontianak station (0.03o S;109.33oE geomagnetic latitude 9.7oS) and at Bandung (-6.90oS;107.6oE geomagnetic latitude 16.54oS) on July 2014 to June 2015. The data were classified into three categores : quiet, moderate and strong based on s4 index. Then we calculated percentage occurrence of scintillation monthly from each observation stastions and mapping of S4 index over Manado, Pontianak and Bandung. The results show that the presentage of strong scintillation (S4>0.5) above Manado is always lower than the other stastions. Strong scintillation was detected at one stations may not also detected at other stations. For very strong scintillastion event, the occurrence of strong scintillation could be detected by all observation stastions but vary in duration. Duration of strong scintillation over Bandung was the longest (up to 4 hours) compared to Pontianak (less than 2 hours) and Manado (less than 1 hour). Based on map of distribution scintillastion occurrence, strong scintillation occurs more intensively over Bandung than over Pontianak and Manado.

scholarly journals Mitigation of Ionospheric Scintillation on Global Positioning System (GPS) Using Hamming and Convolutional Coding Techniques

2016 ◽  
Vol 1 (1) ◽  
Author(s):  
Festus K Ojo ◽  
Damilare O Akande ◽  
Babatunde S Daniel
Keyword(s):  
Global Positioning System ◽  
Satellite Communication ◽  
Signal To Noise Ratio ◽  
Power Level ◽  
Research Work ◽  
Ionospheric Scintillation ◽  
Error Correction Codes ◽  
Positioning System ◽  
Convolutional Coding ◽  
Global Positioning

The Global Positioning System (GPS) is a satellite-based system that can be used to locate positions anywhere on the earth surface. Any person with a GPS receiver can access the system, and it can be used for application that requires location coordinates. Currently, ionospheric scintillation is the largest error source in GPS. Scintillation causes some effects such as degradation of receiver tracking performance and in extreme cases, total loss of navigation capabilities.             Ionospheric scintillation is a problem for satellite communication because it affects the amplitude and phase of radio signals. A decrease in the amplitude of a radio signal reduces its power level which directly affects the signal to noise ratio, thus affecting a base station's ability to detect and receive the signal. Error correction codes techniques are applied in almost all digital systems as they provide better performance for dealing with the unwanted signal (noise). This research work has investigated the performance of hamming and convolutional coding techniques in mitigating error in GPS signal modeled in MATLAB/Simulink by transmitting randomly generated data through a Rayleigh fading channel. The performance metric employed in evaluating the system is Bit Error Rate (BER). The simulation results showed a comparison of the BER performance of the uncoded and coded signals (using Hamming and Convolutional coding techniques).

The characteristics of transforming coordinates from the geocentric system WGS-84 for the Mercator projection under low latitudes conditions

2018 ◽  
Vol 940 (10) ◽  
pp. 2-6
Author(s):  
J.A. Younes ◽  
M.G. Mustafin
Keyword(s):  
Coordinate System ◽  
Satellite System ◽  
Programming Algorithm ◽  
Low Latitude ◽  
Model Calculations ◽  
Mercator Projection ◽  
Low Latitudes ◽  
Rectangular Coordinates ◽  
Global Navigation Satellite ◽  
Coordination Methods

The issue of calculating the plane rectangular coordinates using the data obtained by the satellite observations during the creation of the geodetic networks is discussed in the article. The peculiarity of these works is in conversion of the coordinates into the Mercator projection, while the plane coordinate system on the base of Gauss-Kruger projection is used in Russia. When using the technology of global navigation satellite system, this task is relevant for any point (area) of the Earth due to a fundamentally different approach in determining the coordinates. The fact is that satellite determinations are much more precise than the ground coordination methods (triangulation and others). In addition, the conversion to the zonal coordinate system is associated with errors; the value at present can prove to be completely critical. The expediency of using the Mercator projection in the topographic and geodetic works production at low latitudes is shown numerically on the basis of model calculations. To convert the coordinates from the geocentric system with the Mercator projection, a programming algorithm which is widely used in Russia was chosen. For its application under low-latitude conditions, the modification of known formulas to be used in Saudi Arabia is implemented.

Optical and Chemical Characterization of Aerosols Emitted from Coal, Heavy and Light Fuel Oil, and Small-Scale Wood Combustion

2013 ◽  
Vol 48 (1) ◽  
pp. 827-836 ◽  
Author(s):  
Anna K. Frey ◽  
Karri Saarnio ◽  
Heikki Lamberg ◽  
Fanni Mylläri ◽  
Panu Karjalainen ◽  
...  
Keyword(s):  
Chemical Characterization ◽  
Fuel Oil ◽  
Small Scale ◽  
Wood Combustion

scholarly journals Multi-Scale Ionospheric Anomalies Monitoring and Spatio-Temporal Analysis during Intense Storm

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 215
Author(s):  
Na Cheng ◽  
Shuli Song ◽  
Wei Li
Keyword(s):  
Magnetic Storm ◽  
Large Scale ◽  
Temporal Dynamics ◽  
Ionospheric Disturbance ◽  
Ionospheric Scintillation ◽  
Small Scale ◽  
Electron Content ◽  
Total Electron ◽  
Multi Scale ◽  
Intense Storm

The ionosphere is a significant component of the geospace environment. Storm-induced ionospheric anomalies severely affect the performance of Global Navigation Satellite System (GNSS) Positioning, Navigation, and Timing (PNT) and human space activities, e.g., the Earth observation, deep space exploration, and space weather monitoring and prediction. In this study, we present and discuss the multi-scale ionospheric anomalies monitoring over China using the GNSS observations from the Crustal Movement Observation Network of China (CMONOC) during the 2015 St. Patrick’s Day storm. Total Electron Content (TEC), Ionospheric Electron Density (IED), and the ionospheric disturbance index are used to monitor the storm-induced ionospheric anomalies. This study finally reveals the occurrence of the large-scale ionospheric storms and small-scale ionospheric scintillation during the storm. The results show that this magnetic storm was accompanied by a positive phase and a negative phase ionospheric storm. At the beginning of the main phase of the magnetic storm, both TEC and IED were significantly enhanced. There was long-duration depletion in the topside ionospheric TEC during the recovery phase of the storm. This study also reveals the response and variations in regional ionosphere scintillation. The Rate of the TEC Index (ROTI) was exploited to investigate the ionospheric scintillation and compared with the temporal dynamics of vertical TEC. The analysis of the ROTI proved these storm-induced TEC depletions, which suppressed the occurrence of the ionospheric scintillation. To improve the spatial resolution for ionospheric anomalies monitoring, the regional Three-Dimensional (3D) ionospheric model is reconstructed by the Computerized Ionospheric Tomography (CIT) technique. The spatial-temporal dynamics of ionospheric anomalies during the severe geomagnetic storm was reflected in detail. The IED varied with latitude and altitude dramatically; the maximum IED decreased, and the area where IEDs were maximum moved southward.

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