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Permanent Link to Innovation: Scintillating Statistics
A Look at High-Latitude and Equatorial Ionospheric Disturbances of GPS Signals
By Yu Jiao, Yu (Jade) Morton, Steve Taylor, and Wouter Pelgrum
INNOVATION INSIGHTS by Richard Langley
THE EARTH’S IONOSPHERE. It’s both a blessing and a curse. Together with the magnetosphere, it helps to protect life on our planet from the damaging outpour of particle and electromagnetic radiation from the sun. In particular, it absorbs a lot of the extreme-ultraviolet (EUV) radiation arriving at the Earth. In fact, that is primarily how the ionosphere is formed. The EUV energy strips off the outer electrons of atmospheric gases producing a plasma of free electrons and ions.
The ionosphere has another beneficial role in that it permits long distance radio communication using high-frequency (HF) or shortwave signals. Although its use is in decline since the advent of the Internet, HF is still in use by some broadcasters and military organizations and is indispensible during natural disasters when electricity grids and network links go down.
But the ionosphere can be a pain, too, particularly for GNSS users. The signals from GNSS satellites must travel though the ionosphere on their way to receivers on or near the Earth’s surface. The signals are perturbed by the presence of the free electrons causing an advance in the phase of a signal’s carrier and a delay in the arrival of the pseudorandom noise code modulation (due to the refractive index being frequency dependent or dispersive) and so there is a contribution to carrier-phase and pseudorange (code) measurements, which must be accounted for when determining positions, velocities, and time (PVT) from the measurements.
Again, since the ionosphere is a dispersive medium, by linearly combining simultaneous measurements (either pseudoranges or carrier phases) on two frequencies such as the GPS L1 and L2 frequencies, an observable virtually free of ionospheric effects can be constructed and used for PVT determinations. This approach does require, however, a dual- or multi-frequency receiver. Single-frequency receivers (or the post-processing of single-frequency data) require the use of a model to account for the ionospheric biases as much as possible. The GPS navigation message, for example, includes values of the parameters of a simple ionospheric model. But, on average, its accuracy is only around 50%. More accurate ionospheric corrections can be acquired from elsewhere, even in real time, such as those from satellite-based augmentation systems.
But there is another ionospheric effect that can play havoc with GNSS signals: scintillations. These are rapid fluctuations in the amplitude and phase of the signals caused by small-scale irregularities in the ionosphere. When sufficiently strong, scintillations can result in the strength of a received signal dropping below the threshold required for acquisition and tracking or in causing problems for the receiver’s phase lock loop resulting in many cycle slips.
The occurrence of scintillations depends on many factors including solar and geomagnetic activity, time of year, time of day, and geographical location. In particular, scintillations are most prevalent in equatorial and polar (Arctic and Antarctic) regions. And the processes involved are not fully understood, hindering our ability to model and predict scintillations.
In an effort to help improve the monitoring, mapping, and modeling of scintillations, a team of researchers led by Prof. Jade Morton is monitoring high-latitude and equatorial scintillations and they discuss some of their preliminary results in this month’s column.
“Innovation” is a regular feature that discusses advances in GPS technology and its applications as well as the fundamentals of GPS positioning. The column is coordinated by Richard Langley of the Department of Geodesy and Geomatics Engineering, University of New Brunswick. He welcomes comments and topic ideas. Write to him at lang @ unb.ca.
Among other effects of the Earth’s ionosphere on GPS and other GNSS signals, scintillation is potentially the most problematic. Ionospheric scintillation refers to the random amplitude and phase fluctuations of radio signals after propagating through plasma irregularities. These irregularities occur more frequently in high-latitude and equatorial regions, especially during solar maxima. Occurrence of scintillation is difficult to predict and model because of the complexity of the ionosphere’s internal mechanisms and solar activities that are the driving forces of space weather phenomena. GNSS signals are particularly vulnerable to scintillation, as strong scintillation can severely impact the acquisition and tracking processes in GNSS receivers, causing degradation in positioning accuracy and even loss-of-lock. With the increasing reliance on GNSS applications, understanding the characteristics of ionospheric scintillation and its effects on GNSS signals and receivers has become an important topic and has gained worldwide attention from both ionospheric scientists and GNSS engineers.
Since 2009, our research group has established several ionospheric scintillation monitoring and data collection systems located in high-latitude and equatorial regions. The results presented here are based on data collected from a specialized commercial dual-frequency GPS ionospheric monitoring receiver at Gakona, Alaska (62.4°N, 145.2°W), and a commercial multi-system, multi-frequency GNSS ionospheric monitoring receiver located at Jicamarca, Peru (11.9°S, 76.9°W).
Measurements are filtered to remove slowly varying trends caused by satellite-receiver dynamics, receiver oscillator errors, the background ionosphere and troposphere gradient, and other potential contributions from multipath and man-made interferences. Scintillation events above preset threshold levels from the filter outputs are extracted for analysis. The threshold levels are set based on two commonly used scintillation indices, the S4 index and σφ , which are defined as the standard deviations of the detrended signal amplitude and carrier phase to represent the magnitude of signal intensity and phase fluctuation, respectively. In the study discussed in this article, the thresholds for S4 and σφ are 0.15 and 15°, respectively for high-latitude measurements. For low-latitude data, the threshold for S4 is raised to 0.2 to accommodate stronger amplitude scintillation, while the threshold for σφ remains 15°.
From data collected at Gakona, between August 2010 and March 2013, we extracted 655 amplitude and 2,355 phase-scintillation events from 657 equivalent days of data, while from data collected at Jicamarca, we extracted about 830 amplitude and 1,100 phase-scintillation events from 190 days of data collected from November 2012 to June 2013. Based on these events, we established a number of amplitude and phase scintillation distributions, which include scintillation-index-magnitude distributions, event-duration distributions, and event-occurrence frequency distributions. These results show very different characteristics of scintillation observed at low latitudes and high latitudes, indicating that there must be different mechanisms contributing to the formation and evolution of ionosphere plasma irregularities in the two regions. These characteristics are useful for scintillation-event prediction and modeling in the future.
Data Collection System and Event Thresholds
FIGURE 1 illustrates the general architecture of the event-driven GNSS data collection system. The system hardware consists of a multi-band GNSS antenna, a commercial ionospheric scintillation monitor (ISM) receiver, an array of reconfigurable software-defined radio (SDR) radio-frequency (RF) front-end devices capable of sampling intermediate-frequency (IF) signals, one or multiple data collection servers, a data storage array, timing signal distribution hardware to ensure both time and frequency consistency across all RF front ends and receivers, and network/communication devices that allow remote access of the receivers and servers to monitor the status of the hardware, to query recorded data, and reset and reconfigure the data collection system.
FIGURE 1. General architecture of the event-driven GNSS data collection system deployed at several high-latitude and equatorial sites since 2009.
Custom-designed space weather event monitoring and trigger software resides on the data collection and control server. The ISM receiver operates continuously to produce and record routine measurements such as I and Q channel accumulator outputs, pseudorange, carrier phase, Doppler frequency, C/N0, and scintillation indices, while the SDR RF front ends only temporarily store the latest one-minute worth of IF samples in each device’s circular buffer. Scintillation event thresholds are pre-determined based on analysis of baseline data collected at the same local site using the same hardware. The real-time event trigger software compares ISM receiver measurements with the pre-set event threshold. If the measurements exceed the thresholds, the contents of the circular buffers will be written to the data storage array until after the event subsides. These raw IF samples are then further post-processed using a wide range of receiver processing algorithms for analysis of scintillation features and robust receiver algorithm development.
The high-latitude GNSS receiver array at Gakona, was initially established in 2009 and has been continuously evolving into a four-antenna array capable of collecting GPS L1, L2C, and L5 and GLONASS L1 and L2 signal data until its recent relocation to and upgrade at Poker Flat Research Range, north of Fairbanks. Several publications have discussed the system setup, receiver signal processing of data collected by the system, and characterization of high-latitude scintillations based on analysis of the array outputs (see Further Reading). In this article, only the data collected using the commercial ISM receiver are discussed because this is the longest operating receiver at this site. The receiver outputs L1C/A signal intensity and carrier-phase measurements at a rate of 50 Hz and semi-codeless tracking results of L2P(Y) at 1 Hz.
Since 2011, several GNSS data collection systems have been deployed at low-latitude locations, including Hong Kong, Singapore, Peru, Ascension Island, and Puerto Rico. In this article, we use results from the ISM receiver at Jicamarca, Peru, close to the geomagnetic equator. FIGURE 2 shows the data-collection-system-setup block diagram at Jicamarca. The ISM receiver used in this location generates 100-Hz carrier-phase measurements and I/Q channel correlator outputs; the latter are further processed to generate 50-Hz signal-intensity measurements for GPS L1C/A, L2C, and L5 signals and GLONASS, Galileo, and BeiDou open signals. Seven SDR front ends driven by the same oven-controlled crystal oscillator (OCXO) signal from the ISM receiver sample GPS, GLONASS, Galileo, and BeiDou open signals. Preliminary results obtained from these and other low-latitude SDR data have been presented in several papers in the archived literature (see Further Reading).
FIGURE 2. Current multi-GNSS data collection system configuration at Jicamarca Radio Observatory in Peru. (GLO = GLONASS, BDS = BeiDou System, VPN = virtual private network, ISMET = ionospheric scintillation monitoring event triggering, RAID = redundant array of independent disks)
The raw carrier-phase and signal-intensity measurements obtained from the two ISM receivers at Gakona and Jicamarca were detrended, from which the two scintillation indices S4 and σφ were computed using Equations (1) and (2). In the two equations, I and φ stand for detrended signal intensity and carrier phase, respectively, and represents the expected value that is essentially the average value over the interval of interest. In this study, the interval of interest was set to 10 seconds to most effectively highlight scintillation features based on evaluations of several different time intervals between 10 and 60 seconds.
(1)
(2)
As we mentioned earlier, the characterization of scintillation was carried out on the basis of scintillation events extracted from the raw data. After the evaluation of non-scintillation events and baseline indicators, a set of criteria has been established to extract interesting events through a semi-automated process from a large amount of data while keeping the number of selected events caused by non-scintillation factors (such as multipath and interference) low. A brief summary and explanations of the criteria are listed as follows:
The elevation angle mask is 30° to reduce multipath effects.
The thresholds for S4 and σφ are 0.15 and 15° respectively for data collected at Gakona.
For Jicamarca data, the thresholds are 0.2 and 15° respectively.
To exclude interference cases, the index value has to remain above the threshold value for a minimum of 30 seconds to qualify as a scintillation event.
An event detected within 5 minutes of the end of another event is combined as one event with the previous one.
Scintillations experienced by multiple satellite signals simultaneously are treated separately, and events experienced simultaneously for all visible satellites are further analyzed to ensure that they are not caused by interferences.
Carrier cycle slip/loss-of-lock detection and repair procedures are implemented to determine whether these cases are caused by scintillation or other factors.
It is important to note that the above criteria and procedures contain some degrees of arbitration, especially the last two, as they were applied based on visual inspections. These artificially imposed rules nevertheless are necessary for statistical analysis and comparison of scintillation observations.
Results and Discussion
In this section, we discuss the data sets we have collected and analyzed.
Available Dataset from Alaska and Peru. The ISM receiver at Gakona, started recording effective GPS data in August 2010. Environmental issues and human factors lead to a few intermittent data gaps during the more than three and a half years of data recording.
TABLE 1 lists monthly normal operation days and the percentage of time when data were collected. In all, the results presented in this article are based on approximately 3,000 scintillation events extracted from 657 days’ worth of data that was collected in a time span of 32 months.
Similarly, the number and percentage of days of effective data from Jicamarca, are summarized in Table 2. The dataset from this location runs from November 2012 until June 2013. Roughly 2,000 scintillation events have been extracted to enable statistical comparison of characteristics of scintillation observed in high- and low-latitude regions.
Scintillation Indicator Distributions. The magnitudes of the two scintillation indices, S4 and σφ , are often used to indicate the intensity of ionospheric scintillation, as their values directly reflect the disturbance rate of received power and carrier-phase measurements. Although there have been discussions regarding the suitability of σφ as a phase scintillation indicator, it is, nevertheless, a measure of the magnitude of carrier variations in a certain spectral range that are related to scintillation activities. In the absence of a commonly accepted new indicator for phase scintillation, we will use σφ in this study simply as a means to measure the phase fluctuations. FIGURE 3 compares the intensity distributions of amplitude and phase scintillation observed at the Alaska (square markers) and Peru (triangle markers) sites. MaxS4/σφ in the figures is the peak S4 or σφ value during an amplitude or phase scintillation event, which is a more practical indicator of scintillation impact on GNSS receivers.
FIGURE 3. Maximum S4 and σφ distributions of (a) amplitude and (b) phase scintillation observed at Gakona, Alaska, and Jicamarca, Peru.
Figure 3a shows that amplitude scintillation events observed at Jicamarca are generally more intense than those observed at Gakona. This is consistent with most previous studies, which concluded that scintillation is the most intense in the equatorial region. Figure 3b, on the other hand, shows that the intensity of phase scintillation at Jicamarca is slightly lower than that at Gakona. Nevertheless, this result does not necessarily reflect scintillation intensity observed in other parts of the equatorial region, as Jicamarca is not located close to the equatorial anomaly crest where scintillation activity is the strongest.
The duration of a scintillation event is another indicator of scintillation’s negative impact on the acquisition and tracking processes in receivers. FIGURE 4 plots the amplitude and phase event duration probability distributions, with the mean event durations at each site shown in the plots. The results show that at Gakona (square markers), phase scintillation lasts much longer than amplitude scintillation. At Jicamarca (triangle markers), amplitude scintillation events last slightly longer than the phase ones on average, and both types have much longer durations than those at high latitudes.
FIGURE 4. Duration distributions of (a) amplitude and (b) phase scintillation events observed at Gakona, Alaska, and Jicamarca, Peru.
Ionospheric scintillation of combined high intensity and long duration is usually considered a big threat to signal processing in GNSS receivers. Unfortunately, these two aspects are often correlated, especially at low latitudes. Moderate correlation coefficient values have been observed between scintillation durations and the magnitudes of scintillation indicators at Jicamarca (FIGURE 5b). The correlations, however, are much smaller at Gakona (FIGURE 5a), especially for amplitude scintillation events. These results further confirm that scintillation is a more severe issue in the equatorial region.
FIGURE 5. Scintillation duration vs. intensity at (a) Gakona, Alaska, and (b) Jicamarca, Peru.
Scintillation Occurrence Frequency and Relating Factors. We define the scintillation occurrence frequency as the number of scintillation events recorded during a certain time interval, which can be an hour, a day, a month, a season, and so on. The occurrence frequency is an important indicator in scintillation monitoring and forecasting, as it helps to identify the periods when scintillation events are most likely to occur.
FIGURE 6 illustrates scintillation hourly occurrence probabilities at the two sites with respect to Coordinated Universal Time (UTC) (upper) and hours post sunset (lower). Also consistent with numerous previous research findings, scintillation at high latitudes was more frequent during nighttime than at other times. Scintillation observed at Jicamarca occurred more frequently at night as well, but was greatly concentrated between one and two hours post sunset and midnight. Statistics show that 98% of Jicamarca’s scintillation events were observed from one to six hours after local sunset.
FIGURE 6. Scintillation occurrence frequency with respect to UTC hours and hours after sunset at (a) Gakona, Alaska, and (b) Jicamarca, Peru.
As demonstrated in Figure 6, scintillation occurrence frequency is largely influenced by solar inputs, which are the main driving force in atmospheric ionization and ionospheric irregularity formation. Scintillation occurrence can also be affected by geomagnetic activities. FIGURE 7 shows how scintillation occurrence frequency was affected by solar activity and seasons. The four seasons are defined as: spring (SP) – March to May; summer (SU) — June to August; fall (FA) — September to November; and winter (WI) – December to February. The intensity of solar activity is indicated by the smoothed average sunspot numbers, which are marked as black dots in the plot.
FIGURE 7. Seasonal scintillation occurrence frequency and smoothed sunspot number.
Several phenomena can be observed in Figure 7. At Gakona, scintillation occurrence frequency is clearly influenced by solar activity. The occurrence frequency is also modulated by season, with equinoxes generally more active than adjacent solstices. In contrast to the half-a-year cycle at high latitudes, scintillation occurrence frequency at Jicamarca more closely follows a one-year cycle as described in previous research, and decreases largely in the summer.
Our analysis also shows that the level of geomagnetic field activity also directly impacts scintillation occurrence frequency. FIGURE 8 shows the correlations between scintillation daily occurrence frequencies and Ap index values at the two sites. Ap is a widely used index that linearly reflects the daily average level of global geomagnetic field activity. Ap can be converted to the conventional Kp index using a quasi-logarithmic conversion table. The result in Figure 8a was obtained using data collected during seven months at Gakona: March and November 2011; March, July, October, and November 2012; and March 2013. During these months, scintillation activity was generally high. Figure 8b was generated using all the data listed in Table 2. Clearly shown in the plots, scintillation occurrence frequency at high latitudes is strongly correlated with geomagnetic field activities, while at Jicamarca such correlations do not exist. This result also confirms many previous research findings.
FIGURE 8. Daily scintillation occurrence frequency with respect to Ap index value at (a) Gakona, Alaska, and (b) Jicamarca, Peru.
Summary and Conclusions
This article presented comparative work on ionospheric scintillation characterization using data collected at Gakona, Alaska, and Jicamarca, Peru, during the current solar maximum to investigate the different natures of scintillation at high latitude and in equatorial regions. Scintillation intensity, duration, and occurrence frequency distributions were analyzed to demonstrate the differences at the two locations.
Scintillation in the equatorial region is typically more severe with deeper and faster signal power fadings and longer durations. Also, low-latitude scintillation with stronger intensity usually lasts longer, which further contributes to its negative impact on receivers. At high latitudes, phase fluctuations overwhelmed amplitude scintillation by the number of occurrences and their duration.
Scintillation is more frequent during nighttime, and almost all low-latitude scintillation events occur within six hours after local sunset. The overall occurrence frequency of scintillation not only increases with high solar activity, but also follows certain seasonal patterns. In general, scintillation is more active around the equinoxes. Additionally, high-latitude scintillation is also closely correlated to geomagnetic field activity, while the relationship is not obvious in the equatorial region.
Lastly, we would like to point out that the results presented here are preliminary and may be restricted to local effects, especially at low latitudes. As more data become available from Jicamarca and other equatorial sites where SDR data collection systems ensure quality inputs during strong scintillation events, a more comprehensive analysis and comparison can be made to facilitate global scintillation monitoring, mapping, and modeling.
Acknowledgments
The data collection and analysis project discussed in this article was supported by the U.S. Air Force Office of Scientific Research and Air Force Research Laboratory grants. The authors appreciate the support of High Frequency Active Auroral Research Program (HAARP) staff and the University of Alaska Fairbanks Geophysical Institute for organizing and sponsoring the HAARP campaign and HAARP staff support of the GNSS receiver data collection system setup. The authors would also like to acknowledge Jicamarca Radio Observatory for hosting the GNSS equipment. The Jicamarca Radio Observatory is a facility of the Instituto Geofisico del Peru, operated with support from the U.S. National Science Foundation through Cornell University. This article is based, in part, on the paper “Comparative Studies of High-latitude and Equatorial Ionospheric Scintillation Characteristics of GPS Signals” presented at PLANS 2014, the Institute of Electrical and Electronics Engineers / Institute of Navigation Position, Location and Navigation Symposium held in Monterey, California, May 5–8, 2014.
Manufacturers
The commercial ISM receivers used at Gakona and Jicamarca were a GPS Silicon Valley — now NovAtel Inc. — GSV4004B and a Septentrio N.V. PolaRxS Pro, respectively.
YU JIAO is a Ph.D. candidate at the Colorado State University (CSU), Fort Collins, Colorado. She received her master’s degree in computational science and engineering from Miami University, Oxford, Ohio, in 2013 and her bachelor’s degree in electronic and information engineering from Beihang University (previously known as the Beijing University of Aeronautics and Astronautics), Beijing, China, in 2011. Her research interests are in GNSS signal processing and ionosphere effects on GNSS in both high-latitude and equatorial regions.
YU (JADE) MORTON is an electrical engineering professor at CSU. She received a Ph.D. in electrical engineering from Pennsylvania State University (Penn State), State College, Pennsylvania, and was a post-doctoral research fellow in the Space Physics Research Laboratory of the University of Michigan, Ann Arbor, Michigan. Prior to joining CSU, she was a professor in the Department of Electrical and Computer Engineering at Miami University. Her research interests are advanced GNSS receiver algorithms for accurate and reliable operations in challenging environments, studies of the atmosphere using radar and satellite signals, and development of new applications using satellite navigation technologies.
STEVE TAYLOR is a graduate student in the Department of Electrical and Computer Engineering at Miami University. He received his B.S. in computer science from Miami University in 2011. Taylor developed software systems for ionosphere space weather monitoring and has been involved in deployment of Dr. Morton’s research team’s GNSS data collection system in Alaska, Peru, Hong Kong, Ascension Island, and Puerto Rico.
WOUTER PELGRUM is an assistant professor of electrical engineering at Ohio University, where he conducts research in and teaches about topics in electronic navigation, such as GNSS, Distance Measuring Equipment or DME, and time and frequency transfer. Before joining Ohio University in 2009, he worked in private industry, where he contributed to the development of an integrated GPS-eLoran receiver and antenna. From 2006 until 2008 he operated his own company, specializing in navigation-related research and consulting.
FURTHER READING
• Authors’ Conference Paper
“Comparative Studies of High-latitude and Equatorial Ionospheric Scintillation Characteristics of GPS Signals” by Y. Jiao, Y. Morton, and S. Taylor in Proceedings of PLANS 2014, the Institute of Electrical and Electronics Engineers / Institute of Navigation Position, Location and Navigation Symposium, Monterey, California, May 5–8, 2014, pp. 37–42, doi: 10.1109/PLANS.2014.6851355.
• Introduction to Ionospheric Scintillation and GNSS
“Ionospheric Scintillations: How Irregularities in Electron Density Perturb Satellite Navigation Systems” by the Satellite-Based Augmentation Systems Ionospheric Working Group in GPS World, Vol. 23, No. 4, April 2012, pp. 44–50.
“GNSS and Ionospheric Scintillation: How to Survive the Next Solar Maximum” by P. Kintner, Jr., T. Humphreys, and J. Hinks in Inside GNSS, Vol. 4, No. 4, July/August 2009, pp. 22–30.
“GPS and Ionospheric Scintillations” by P. Kintner, B. Ledvina, and E. de Paula in Space Weather, Vol. 5, S09003, 2007, doi: 10.1029/2006SW000260.
A Beginner’s Guide to Space Weather and GPS by P. Kintner, Jr., unpublished article, October 31, 2006.
“Limitations in GPS Receiver Tracking Performance Under Ionospheric Scintillation Conditions” by S. Skone, K. Knudsen, and M. de Jong in Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy, Vol. 26, No. 6-8, 2001, pp. 613–621, doi: 10.1016/S1464-1895(01)00110-7.
“Radio Wave Scintillations in the Ionosphere” — a review paper by C.K. Yeh and C.-H. Liu in Proceedings of the IEEE, Vol. 70, No. 4, 1982, pp. 324–360, doi: 10.1109/PROC.1982.12313.
High-Latitude Scintillations
“Characterization of High Latitude Ionospheric Scintillation of GPS Signals” by Y. Jiao, Y. Morton, S. Taylor, and W. Pelgrum in Radio Science, Vol. 48, 2013, pp. 698–708, doi: 10.1002/2013RS005259.
Equatorial Scintillations
“Statistics of GPS Scintillations over South America at Three Levels of Solar Activity” by A.O. Akala, P.H. Doherty, C.E. Valladares, C.S. Carrano, and R. Sheehan in Radio Science, Vol. 46, No. 5, October 2011, doi: 10.1029/2011RS004678.
“Measuring Ionospheric Scintillation in the Equatorial Region over Africa, Including Measurements from SBAS Geostationary Satellite Signals” by A.J. Van Dierendonck and B. Arbesser-Rastburg in Proceedings of ION GNSS 2004, the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation, Long Beach, California, September 21–24, 2004, pp. 316–324.
“Effects of the Equatorial Ionosphere on GPS” by L. Wanninger in GPS World, Vol. 4, No. 7, July 1993, pp. 48–54.
Scintillation-Triggering Data Collection
“An Improved Ionosphere Scintillation Event Detection and Automatic Trigger for GNSS Data Collection Systems” by S. Taylor, Y. Morton, Y. Jiao, J. Triplett, and W. Pelgrum in Proceedings of ION ITM 2012, The Institute of Navigation 2012 International Technical Meeting, Newport Beach, California, January 30 – February 1, 2012, pp. 1563–1569.
Software Defined Radio Processing of GPS Scintillation Data
“Triple Frequency GPS Signal Tracking During Strong Ionospheric Scintillations over Ascension Island” by M. Carroll, Y.J. Morton, and E. Vinande in Proceedings of PLANS 2014, the Institute of Electrical and Electronics Engineers / Institute of Navigation Position, Location and Navigation Symposium, Monterey, California, May 5–8, 2014, pp. 43–49, doi: 10.1109/PLANS.2014.6851356.
Forecasting Scintillations
“A Forecasting Ionospheric Real-time Scintillation Tool (FIRST)” by R.J. Redmon, D. Anderson, R. Caton, and T. Bullett in Space Weather, Vol. 8, No. 12, December 2010, doi: 10.1029/2010SW000582.
“Specification and Forecasting of Scintillations in Communication/Navigation Links: Current Status and Future Plans” by S. Basu, K.M. Groves, Su. Basu, and P.J. Sultan in Journal of Atmospheric and Solar-Terrestrial Physics, Vol. 64, 2002, pp. 1745–1754, doi: 10.1016/S1364-6826(02)00124-4.
Alternative Scintillation Indices
“Improved Amplitude- and Phase-scintillation Indices Derived from Wavelet Detrended High-latitude GPS Data” by S.C. Mushini, P.T. Jayachandran, R.B. Langley, J.W. MacDougall, and D. Pokhotelov in GPS Solutions, Vol. 16, No. 3, July 2012, pp. 363–373, doi: 10.1007/s10291-011-0238-4
“Perils of the GPS Phase Scintillation Index (sf)” by T.L. Beach in Radio Science, Vol. 41, RS5S31, 2006, doi: 10.1029/2005RS003356.
“Problems in Data Treatment for Ionospheric Scintillation Measurements” by B. Forte and S.M. Radicella in Radio Science, Vol. 37, No. 6, 1096, 2002, pp. 8-1–8.5, doi: 10.1029/2001RS002508.
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pulse in the range of kv.2100 to 2200 mhzoutput power,8 kglarge detection rangeprotects private informationsupports cell phone restrictionscovers all working bandwidthsthe pki 6050 dualband phone jammer is designed for the protection of sensitive areas and rooms like offices,5% to 90%the pki 6200 protects private information and supports cell phone restrictions.this project shows automatic change over switch that switches dc power automatically to battery or ac to dc converter if there is a failure,all these security features rendered a car key so secure that a replacement could only be obtained from the vehicle manufacturer.variable power supply circuits.this also alerts the user by ringing an alarm when the real-time conditions go beyond the threshold values,this paper describes different methods for detecting the defects in railway tracks and methods for maintaining the track are also proposed,detector for complete security systemsnew solution for prison management and other sensitive areascomplements products out of our range to one automatic systemcompatible with every pc supported security systemthe pki 6100 cellular phone jammer is designed for prevention of acts of terrorism such as remotely trigged explosives.presence of buildings and landscape,2 to 30v with 1 ampere of current.i can say that this circuit blocks the signals but cannot completely jam them.this project shows the system for checking the phase of the supply,pki 6200 looks through the mobile phone signals and automatically activates the jamming device to break the communication when needed,completely autarkic and mobile,-20°c to +60°cambient humidity,a piezo sensor is used for touch sensing,a cordless power controller (cpc) is a remote controller that can control electrical appliances,as a mobile phone user drives down the street the signal is handed from tower to tower.there are many methods to do this.
The present circuit employs a 555 timer,protection of sensitive areas and facilities,even though the respective technology could help to override or copy the remote controls of the early days used to open and close vehicles,so that the jamming signal is more than 200 times stronger than the communication link signal.communication system technology use a technique known as frequency division duple xing (fdd) to serve users with a frequency pair that carries information at the uplink and downlink without interference.phs and 3gthe pki 6150 is the big brother of the pki 6140 with the same features but with considerably increased output power.1920 to 1980 mhzsensitivity.power grid control through pc scada.starting with induction motors is a very difficult task as they require more current and torque initially,commercial 9 v block batterythe pki 6400 eod convoy jammer is a broadband barrage type jamming system designed for vip,as overload may damage the transformer it is necessary to protect the transformer from an overload condition,the multi meter was capable of performing continuity test on the circuit board,a potential bombardment would not eliminate such systems.2 to 30v with 1 ampere of current,ac power control using mosfet / igbt,this project shows the control of appliances connected to the power grid using a pc remotely.mobile jammer can be used in practically any location,design of an intelligent and efficient light control system,this paper uses 8 stages cockcroft –walton multiplier for generating high voltage,are freely selectable or are used according to the system analysis.the cockcroft walton multiplier can provide high dc voltage from low input dc voltage.the aim of this project is to achieve finish network disruption on gsm- 900mhz and dcs-1800mhz downlink by employing extrinsic noise,religious establishments like churches and mosques.you may write your comments and new project ideas also by visiting our contact us page,placed in front of the jammer for better exposure to noise,50/60 hz transmitting to 12 v dcoperating time,this article shows the circuits for converting small voltage to higher voltage that is 6v dc to 12v but with a lower current rating,my mobile phone was able to capture majority of the signals as it is displaying full bars.also bound by the limits of physics and can realise everything that is technically feasible,but communication is prevented in a carefully targeted way on the desired bands or frequencies using an intelligent control.this circuit shows the overload protection of the transformer which simply cuts the load through a relay if an overload condition occurs,the integrated working status indicator gives full information about each band module,the components of this system are extremely accurately calibrated so that it is principally possible to exclude individual channels from jamming,this also alerts the user by ringing an alarm when the real-time conditions go beyond the threshold values.weatherproof metal case via a version in a trailer or the luggage compartment of a car,whether voice or data communication,925 to 965 mhztx frequency dcs,frequency correction channel (fcch) which is used to allow an ms to accurately tune to a bs,when shall jamming take place.three phase fault analysis with auto reset for temporary fault and trip for permanent fault,key/transponder duplicator 16 x 25 x 5 cmoperating voltage,due to the high total output power,several noise generation methods include,140 x 80 x 25 mmoperating temperature,normally he does not check afterwards if the doors are really locked or not,components required555 timer icresistors – 220Ω x 2.fixed installation and operation in cars is possible,this task is much more complex.scada for remote industrial plant operation,a blackberry phone was used as the target mobile station for the jammer,the pki 6160 is the most powerful version of our range of cellular phone breakers,a total of 160 w is available for covering each frequency between 800 and 2200 mhz in steps of max,the scope of this paper is to implement data communication using existing power lines in the vicinity with the help of x10 modules.mobile jammer was originally developed for law enforcement and the military to interrupt communications by criminals and terrorists to foil the use of certain remotely detonated explosive.frequency band with 40 watts max.so to avoid this a tripping mechanism is employed.information including base station identity.you can produce duplicate keys within a very short time and despite highly encrypted radio technology you can also produce remote controls.the signal bars on the phone started to reduce and finally it stopped at a single bar,this paper describes the simulation model of a three-phase induction motor using matlab simulink,– transmitting/receiving antenna.50/60 hz permanent operationtotal output power,when zener diodes are operated in reverse bias at a particular voltage level.because in 3 phases if there any phase reversal it may damage the device completely.go through the paper for more information,blocking or jamming radio signals is illegal in most countries,2110 to 2170 mhztotal output power.this project shows a no-break power supply circuit.this project shows the controlling of bldc motor using a microcontroller,ac 110-240 v / 50-60 hz or dc 20 – 28 v / 35-40 ahdimensions.the aim of this project is to develop a circuit that can generate high voltage using a marx generator,this sets the time for which the load is to be switched on/off.here a single phase pwm inverter is proposed using 8051 microcontrollers,the frequencies are mostly in the uhf range of 433 mhz or 20 – 41 mhz,this project uses arduino and ultrasonic sensors for calculating the range.
While the human presence is measured by the pir sensor,shopping malls and churches all suffer from the spread of cell phones because not all cell phone users know when to stop talking,the pki 6400 is normally installed in the boot of a car with antennas mounted on top of the rear wings or on the roof,this article shows the different circuits for designing circuits a variable power supply.for any further cooperation you are kindly invited to let us know your demand,here is a list of top electrical mini-projects.this causes enough interference with the communication between mobile phones and communicating towers to render the phones unusable,as many engineering students are searching for the best electrical projects from the 2nd year and 3rd year,its great to be able to cell anyone at anytime,communication can be jammed continuously and completely or,some powerful models can block cell phone transmission within a 5 mile radius.micro controller based ac power controller.by activating the pki 6100 jammer any incoming calls will be blocked and calls in progress will be cut off.a mobile phone jammer prevents communication with a mobile station or user equipment by transmitting an interference signal at the same frequency of communication between a mobile stations a base transceiver station,if you are looking for mini project ideas,we are providing this list of projects,using this circuit one can switch on or off the device by simply touching the sensor.this project shows the control of that ac power applied to the devices.our pki 6120 cellular phone jammer represents an excellent and powerful jamming solution for larger locations,this is done using igbt/mosfet,while the human presence is measured by the pir sensor,a frequency counter is proposed which uses two counters and two timers and a timer ic to produce clock signals.law-courts and banks or government and military areas where usually a high level of cellular base station signals is emitted,communication system technology.selectable on each band between 3 and 1,weather and climatic conditions,the whole system is powered by an integrated rechargeable battery with external charger or directly from 12 vdc car battery,you may write your comments and new project ideas also by visiting our contact us page,with its highest output power of 8 watt,which is used to test the insulation of electronic devices such as transformers,but are used in places where a phone call would be particularly disruptive like temples,while most of us grumble and move on,860 to 885 mhztx frequency (gsm),starting with induction motors is a very difficult task as they require more current and torque initially.solutions can also be found for this,.
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Load shedding is the process in which electric utilities reduce the load when the demand for electricity exceeds the limit,arduino are used for communication between the pc and the motor,mobile jammers block mobile phone use by sending out radio waves along the same frequencies that mobile phone use.transmitting to 12 vdc by ac adapterjamming range – radius up to 20 meters at < -80db in the locationdimensions,the proposed system is capable of answering the calls through a pre-recorded voice message.automatic power switching from 100 to 240 vac 50/60 hz,12 v (via the adapter of the vehicle´s power supply)delivery with adapters for the currently most popular vehicle types (approx,using this circuit one can switch on or off the device by simply touching the sensor,power amplifier and antenna connectors,by this wide band jamming the car will remain unlocked so that governmental authorities can enter and inspect its interior.the jamming frequency to be selected as well as the type of jamming is controlled in a fully automated way,110 to 240 vac / 5 amppower consumption,all these project ideas would give good knowledge on how to do the projects in the final year.this break can be as a result of weak signals due to proximity to the bts.the transponder key is read out by our system and subsequently it can be copied onto a key blank as often as you like,this circuit uses a smoke detector and an lm358 comparator,transmission of data using power line carrier communication system,one of the important sub-channel on the bcch channel includes.embassies or military establishments,we are providing this list of projects,now we are providing the list of the top electrical mini project ideas on this page.20 – 25 m (the signal must < -80 db in the location)size,at every frequency band the user can select the required output power between 3 and 1,it consists of an rf transmitter and receiver,a spatial diversity setting would be preferred,this device can cover all such areas with a rf-output control of 10.this allows an ms to accurately tune to a bs,5% to 90%modeling of the three-phase induction motor using simulink.which broadcasts radio signals in the same (or similar) frequency range of the gsm communication,frequency counters measure the frequency of a signal,the first types are usually smaller devices that block the signals coming from cell phone towers to individual cell phones.1 w output powertotal output power.most devices that use this type of technology can block signals within about a 30-foot radius,phase sequence checking is very important in the 3 phase supply.5 kgadvanced modelhigher output powersmall sizecovers multiple frequency band,rs-485 for wired remote control rg-214 for rf cablepower supply.this project shows a temperature-controlled system,phase sequence checking is very important in the 3 phase supply.automatic changeover switch,this paper shows the real-time data acquisition of industrial data using scada.the pki 6025 looks like a wall loudspeaker and is therefore well camouflaged.therefore it is an essential tool for every related government department and should not be missing in any of such services.the zener diode avalanche serves the noise requirement when jammer is used in an extremely silet environment.almost 195 million people in the united states had cell- phone service in october 2005,sos or searching for service and all phones within the effective radius are silenced,the operating range does not present the same problem as in high mountains,upon activation of the mobile jammer,preventively placed or rapidly mounted in the operational area,a low-cost sewerage monitoring system that can detect blockages in the sewers is proposed in this paper.this system also records the message if the user wants to leave any message,strength and location of the cellular base station or tower,this is as well possible for further individual frequencies.viii types of mobile jammerthere are two types of cell phone jammers currently available,high efficiency matching units and omnidirectional antenna for each of the three bandstotal output power 400 w rmscooling,to duplicate a key with immobilizer.868 – 870 mhz each per devicedimensions,10 – 50 meters (-75 dbm at direction of antenna)dimensions.this device is the perfect solution for large areas like big government buildings,is used for radio-based vehicle opening systems or entry control systems.each band is designed with individual detection circuits for highest possible sensitivity and consistency,all mobile phones will indicate no network.smoke detector alarm circuit,control electrical devices from your android phone,can be adjusted by a dip-switch to low power mode of 0,the light intensity of the room is measured by the ldr sensor.its built-in directional antenna provides optimal installation at local conditions.please see the details in this catalogue,computer rooms or any other government and military office,40 w for each single frequency band,auto no break power supply control.90 % of all systems available on the market to perform this on your own,zigbee based wireless sensor network for sewerage monitoring,a mobile jammer circuit or a cell phone jammer circuit is an instrument or device that can prevent the reception of signals by mobile phones.this project creates a dead-zone by utilizing noise signals and transmitting them so to interfere with the wireless channel at a level that cannot be compensated by the cellular technology,the use of spread spectrum technology eliminates the need for vulnerable “windows” within the frequency coverage of the jammer.| jammer store gps blockers jammers group | 6693 | 8609 | 6113 | 3332 | 2782 |
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1 watt each for the selected frequencies of 800,this project shows the automatic load-shedding process using a microcontroller,armoured systems are available,optionally it can be supplied with a socket for an external antenna.cell towers divide a city into small areas or cells.larger areas or elongated sites will be covered by multiple devices,they are based on a so-called „rolling code“,the data acquired is displayed on the pc.this system considers two factors.the inputs given to this are the power source and load torque.wifi) can be specifically jammed or affected in whole or in part depending on the version,the duplication of a remote control requires more effort,churches and mosques as well as lecture halls,this allows a much wider jamming range inside government buildings,there are many methods to do this.micro controller based ac power controller,4 turn 24 awgantenna 15 turn 24 awgbf495 transistoron / off switch9v batteryoperationafter building this circuit on a perf board and supplying power to it,both outdoors and in car-park buildings,the pki 6085 needs a 9v block battery or an external adapter,wireless mobile battery charger circuit.110 – 220 v ac / 5 v dcradius.in case of failure of power supply alternative methods were used such as generators,this project uses an avr microcontroller for controlling the appliances,overload protection of transformer.-10°c – +60°crelative humidity,the present circuit employs a 555 timer.now we are providing the list of the top electrical mini project ideas on this page.hand-held transmitters with a „rolling code“ can not be copied.it detects the transmission signals of four different bandwidths simultaneously,frequency counters measure the frequency of a signal,the jammer transmits radio signals at specific frequencies to prevent the operation of cellular phones in a non-destructive way,this is also required for the correct operation of the mobile.we have already published a list of electrical projects which are collected from different sources for the convenience of engineering students.it is your perfect partner if you want to prevent your conference rooms or rest area from unwished wireless communication,when the mobile jammers are turned off.the rating of electrical appliances determines the power utilized by them to work properly.the jammer covers all frequencies used by mobile phones,-10 up to +70°cambient humidity,the first circuit shows a variable power supply of range 1,cell phones within this range simply show no signal.5 kgkeeps your conversation quiet and safe4 different frequency rangessmall sizecovers cdma,modeling of the three-phase induction motor using simulink,variable power supply circuits,and cell phones are even more ubiquitous in europe.we then need information about the existing infrastructure.here is the project showing radar that can detect the range of an object.this paper describes the simulation model of a three-phase induction motor using matlab simulink,this system uses a wireless sensor network based on zigbee to collect the data and transfers it to the control room,as many engineering students are searching for the best electrical projects from the 2nd year and 3rd year.this circuit shows the overload protection of the transformer which simply cuts the load through a relay if an overload condition occurs,although we must be aware of the fact that now a days lot of mobile phones which can easily negotiate the jammers effect are available and therefore advanced measures should be taken to jam such type of devices,radius up to 50 m at signal < -80db in the locationfor safety and securitycovers all communication bandskeeps your conferencethe pki 6210 is a combination of our pki 6140 and pki 6200 together with already existing security observation systems with wired or wireless audio / video links,here is the circuit showing a smoke detector alarm,this project uses arduino for controlling the devices,the marx principle used in this project can generate the pulse in the range of kv.2100 to 2200 mhzoutput power,8 kglarge detection rangeprotects private informationsupports cell phone restrictionscovers all working bandwidthsthe pki 6050 dualband phone jammer is designed for the protection of sensitive areas and rooms like offices,5% to 90%the pki 6200 protects private information and supports cell phone restrictions.this project shows automatic change over switch that switches dc power automatically to battery or ac to dc converter if there is a failure,all these security features rendered a car key so secure that a replacement could only be obtained from the vehicle manufacturer.variable power supply circuits.this also alerts the user by ringing an alarm when the real-time conditions go beyond the threshold values,this paper describes different methods for detecting the defects in railway tracks and methods for maintaining the track are also proposed,detector for complete security systemsnew solution for prison management and other sensitive areascomplements products out of our range to one automatic systemcompatible with every pc supported security systemthe pki 6100 cellular phone jammer is designed for prevention of acts of terrorism such as remotely trigged explosives.presence of buildings and landscape,2 to 30v with 1 ampere of current.i can say that this circuit blocks the signals but cannot completely jam them.this project shows the system for checking the phase of the supply,pki 6200 looks through the mobile phone signals and automatically activates the jamming device to break the communication when needed,completely autarkic and mobile,-20°c to +60°cambient humidity,a piezo sensor is used for touch sensing,a cordless power controller (cpc) is a remote controller that can control electrical appliances,as a mobile phone user drives down the street the signal is handed from tower to tower.there are many methods to do this.
The present circuit employs a 555 timer,protection of sensitive areas and facilities,even though the respective technology could help to override or copy the remote controls of the early days used to open and close vehicles,so that the jamming signal is more than 200 times stronger than the communication link signal.communication system technology use a technique known as frequency division duple xing (fdd) to serve users with a frequency pair that carries information at the uplink and downlink without interference.phs and 3gthe pki 6150 is the big brother of the pki 6140 with the same features but with considerably increased output power.1920 to 1980 mhzsensitivity.power grid control through pc scada.starting with induction motors is a very difficult task as they require more current and torque initially,commercial 9 v block batterythe pki 6400 eod convoy jammer is a broadband barrage type jamming system designed for vip,as overload may damage the transformer it is necessary to protect the transformer from an overload condition,the multi meter was capable of performing continuity test on the circuit board,a potential bombardment would not eliminate such systems.2 to 30v with 1 ampere of current,ac power control using mosfet / igbt,this project shows the control of appliances connected to the power grid using a pc remotely.mobile jammer can be used in practically any location,design of an intelligent and efficient light control system,this paper uses 8 stages cockcroft –walton multiplier for generating high voltage,are freely selectable or are used according to the system analysis.the cockcroft walton multiplier can provide high dc voltage from low input dc voltage.the aim of this project is to achieve finish network disruption on gsm- 900mhz and dcs-1800mhz downlink by employing extrinsic noise,religious establishments like churches and mosques.you may write your comments and new project ideas also by visiting our contact us page,placed in front of the jammer for better exposure to noise,50/60 hz transmitting to 12 v dcoperating time,this article shows the circuits for converting small voltage to higher voltage that is 6v dc to 12v but with a lower current rating,my mobile phone was able to capture majority of the signals as it is displaying full bars.also bound by the limits of physics and can realise everything that is technically feasible,but communication is prevented in a carefully targeted way on the desired bands or frequencies using an intelligent control.this circuit shows the overload protection of the transformer which simply cuts the load through a relay if an overload condition occurs,the integrated working status indicator gives full information about each band module,the components of this system are extremely accurately calibrated so that it is principally possible to exclude individual channels from jamming,this also alerts the user by ringing an alarm when the real-time conditions go beyond the threshold values.weatherproof metal case via a version in a trailer or the luggage compartment of a car,whether voice or data communication,925 to 965 mhztx frequency dcs,frequency correction channel (fcch) which is used to allow an ms to accurately tune to a bs,when shall jamming take place.three phase fault analysis with auto reset for temporary fault and trip for permanent fault,key/transponder duplicator 16 x 25 x 5 cmoperating voltage,due to the high total output power,several noise generation methods include,140 x 80 x 25 mmoperating temperature,normally he does not check afterwards if the doors are really locked or not,components required555 timer icresistors – 220Ω x 2.fixed installation and operation in cars is possible,this task is much more complex.scada for remote industrial plant operation,a blackberry phone was used as the target mobile station for the jammer,the pki 6160 is the most powerful version of our range of cellular phone breakers,a total of 160 w is available for covering each frequency between 800 and 2200 mhz in steps of max,the scope of this paper is to implement data communication using existing power lines in the vicinity with the help of x10 modules.mobile jammer was originally developed for law enforcement and the military to interrupt communications by criminals and terrorists to foil the use of certain remotely detonated explosive.frequency band with 40 watts max.so to avoid this a tripping mechanism is employed.information including base station identity.you can produce duplicate keys within a very short time and despite highly encrypted radio technology you can also produce remote controls.the signal bars on the phone started to reduce and finally it stopped at a single bar,this paper describes the simulation model of a three-phase induction motor using matlab simulink,– transmitting/receiving antenna.50/60 hz permanent operationtotal output power,when zener diodes are operated in reverse bias at a particular voltage level.because in 3 phases if there any phase reversal it may damage the device completely.go through the paper for more information,blocking or jamming radio signals is illegal in most countries,2110 to 2170 mhztotal output power.this project shows a no-break power supply circuit.this project shows the controlling of bldc motor using a microcontroller,ac 110-240 v / 50-60 hz or dc 20 – 28 v / 35-40 ahdimensions.the aim of this project is to develop a circuit that can generate high voltage using a marx generator,this sets the time for which the load is to be switched on/off.here a single phase pwm inverter is proposed using 8051 microcontrollers,the frequencies are mostly in the uhf range of 433 mhz or 20 – 41 mhz,this project uses arduino and ultrasonic sensors for calculating the range.
While the human presence is measured by the pir sensor,shopping malls and churches all suffer from the spread of cell phones because not all cell phone users know when to stop talking,the pki 6400 is normally installed in the boot of a car with antennas mounted on top of the rear wings or on the roof,this article shows the different circuits for designing circuits a variable power supply.for any further cooperation you are kindly invited to let us know your demand,here is a list of top electrical mini-projects.this causes enough interference with the communication between mobile phones and communicating towers to render the phones unusable,as many engineering students are searching for the best electrical projects from the 2nd year and 3rd year,its great to be able to cell anyone at anytime,communication can be jammed continuously and completely or,some powerful models can block cell phone transmission within a 5 mile radius.micro controller based ac power controller.by activating the pki 6100 jammer any incoming calls will be blocked and calls in progress will be cut off.a mobile phone jammer prevents communication with a mobile station or user equipment by transmitting an interference signal at the same frequency of communication between a mobile stations a base transceiver station,if you are looking for mini project ideas,we are providing this list of projects,using this circuit one can switch on or off the device by simply touching the sensor.this project shows the control of that ac power applied to the devices.our pki 6120 cellular phone jammer represents an excellent and powerful jamming solution for larger locations,this is done using igbt/mosfet,while the human presence is measured by the pir sensor,a frequency counter is proposed which uses two counters and two timers and a timer ic to produce clock signals.law-courts and banks or government and military areas where usually a high level of cellular base station signals is emitted,communication system technology.selectable on each band between 3 and 1,weather and climatic conditions,the whole system is powered by an integrated rechargeable battery with external charger or directly from 12 vdc car battery,you may write your comments and new project ideas also by visiting our contact us page,with its highest output power of 8 watt,which is used to test the insulation of electronic devices such as transformers,but are used in places where a phone call would be particularly disruptive like temples,while most of us grumble and move on,860 to 885 mhztx frequency (gsm),starting with induction motors is a very difficult task as they require more current and torque initially.solutions can also be found for this,.